WO2013153611A1 - Internal combustion engine control device - Google Patents

Description

Control device for internal combustion engine

The present invention relates to a technical field of a control device for an internal combustion engine suitable for recovering an exhaust purification catalyst installed in an exhaust path from sulfur poisoning.

The exhaust purification catalyst installed in the exhaust path adsorbs sulfur contained as impurities in the fuel to the noble metal added to the catalyst and poisons the sulfur. In the state of sulfur poisoning, the activity of the catalyst is remarkably lost, and the original exhaust purification action of the catalyst cannot be obtained. Therefore, various sulfur poisoning recovery controls have been proposed for desorbing sulfur from the catalyst. Yes. In many cases, sulfur is oxidized inside the cylinder or in the exhaust path and is adsorbed to the catalyst as SOx (sulfur oxide), and the desorption of sulfur simply means reduction of sulfur.

For example, Patent Document 1 discloses sulfur poisoning recovery control in a lean NOx catalyst. The exhaust gas purification apparatus for an internal combustion engine disclosed in Patent Document 1 includes an H ₂ (hydrogen) sensor upstream of the lean NOx catalyst, and rich combustion in the cylinder is controlled based on the output value of the H ₂ sensor. It is the composition which becomes. That is, it is configured that the H ₂ concentration of the catalyst inflow gas is F / B controlled to a rich combustion control amount, and an appropriate amount of hydrogen can be supplied at the time of sulfur poisoning recovery.

Further, Patent Document 2 discloses a technique for raising the temperature of the catalyst by controlling some cylinders to be rich in the air-fuel ratio and the remaining cylinders to be air-fuel ratio lean.

Patent Document 3 discloses a configuration in which H ₂ is supplied by an H ₂ supply means mounted upstream of the catalyst when the amount of sulfur accumulated in the NOx catalyst exceeds a predetermined value.

Further, in Patent Document 4, a CO ₂ adsorbent, an H ₂ generation catalyst, and a NOx catalyst are arranged in an exhaust system of a lean combustion engine, and CO is supplied to the H ₂ generation catalyst, which is generated by an aquatic gas shift reaction. A configuration in which H ₂ is sent as a reducing agent to the NOx catalyst is disclosed.

Further, Patent Document 5 discloses a lean NOx catalyst system, and in an internal combustion engine capable of controlling in-cylinder combustion, when NOx catalyst is regenerated, post-injection timing is performed at a timing when the dehydrogenation reaction and cracking reaction repel each other. The structure to perform is disclosed.

JP 2006-242124 A JP 2004-218541 A JP 2002-235529 A JP-A-2005-090426 JP 2003-120369 A

As described above, there are various approaches to sulfur (S) desorption. Among them, the reduction of sulfur with hydrogen (H2) having a very high reducing ability is extremely effective in that it does not necessarily require a secondary process in which the catalyst is heated to promote the reduction reaction.

However, in order to recover sulfur poisoning, it is not desirable from the viewpoint of manufacturing cost to add a hydrogen supply means such as a hydrogen addition valve to the exhaust path separately.

In addition, even in a configuration in which hydrogen is generated by a catalyst using a reforming catalyst or the like, it is generally difficult to give controllability that can withstand actual use for the reforming reaction in the catalyst. In addition, the amount of hydrogen produced by the reforming reaction is limited, and there is no guarantee that the amount required at that time can be supplied. Even if the catalyst bed temperature is raised by some method (for example, a method of generating an air-fuel ratio imbalance between cylinders) for the purpose of promoting the reduction of sulfur, this does not change fundamentally.

On the other hand, as described above, in a configuration in which hydrogen is generated with a certain degree of controllability by rich combustion, a technical idea of providing a hydrogen concentration sensor upstream of the catalyst and supplying only a necessary amount of hydrogen to the catalyst is as follows: At first glance it is useful.

However, from a practical standpoint, there is no hydrogen sensor that can exhibit sufficient performance for this type of application when it is assumed that the vehicle is mounted with realistic constraints.

In addition, combustion on the rich side of the air-fuel ratio (rich combustion) is a disadvantageous control from the viewpoint of exhaust emission, apart from the reduction of sulfur and NOx, and is also economically disadvantageous in that it leads to a deterioration in fuel consumption. Control. Therefore, it is not reasonable to perform rich combustion in the dark cloud on the safe side (in this case, that is, on the side where the amount of hydrogen generated increases) for the purpose of reducing only sulfur.

Thus, even though various configurations or controls for recovering the catalyst from sulfur poisoning have been proposed in the past, each has its advantages and disadvantages, while satisfying various requirements including exhaust emission, fuel consumption, cost, etc. There is actually no control to recover from sulfur poisoning.

The present invention has been made in view of the above-described circumstances, and provides an internal combustion engine control device capable of recovering a catalyst from sulfur poisoning while suppressing an increase in cost and deterioration of exhaust emission and fuel consumption. This is the issue.

In order to solve the problems described above, an internal combustion engine control apparatus according to the present invention is capable of in-cylinder injection of a cylinder, an exhaust purification catalyst installed in an exhaust path connected to the cylinder, and fuel into the cylinder. A control device for an internal combustion engine that controls an internal combustion engine including an in-cylinder injection device, and in the case where sulfur accumulated in the catalyst is reduced, the homogeneity of the air-fuel mixture in the inside of the cylinder is reduced. A change means for changing the injection mode of the in-cylinder injection device and a first control means for controlling the in-cylinder injection device according to the changed injection mode (first item).

The internal combustion engine according to the present invention is a concept that encompasses an engine that can convert thermal energy generated when an air-fuel mixture containing fuel is burned into kinetic energy and take it out. A catalyst is provided, and at least an in-cylinder injection device is provided as a fuel injection device. Within the scope of the concept, in the internal combustion engine according to the present invention, the number of cylinders, the cylinder arrangement, the fuel type, the fuel injection mode, the intake / exhaust system configuration, the valve train configuration, the combustion system, the presence / absence of the supercharger, and the excess The manner of supply is not limited in any way.

The exhaust purification catalyst according to the present invention is a concept encompassing various types of catalysts that can be provided in the exhaust path of an internal combustion engine. As a suitable example, for example, a three-way catalyst, a lean NOx catalyst (also referred to as a NOx storage reduction catalyst). Practical forms such as oxidation catalyst.

The catalyst is poisoned by sulfur contained as an impurity in the fuel according to the actual operation period of the internal combustion engine. Since sulfur poisoning of the catalyst reduces the catalytic activity, it is necessary to desorb sulfur from the catalyst at the appropriate timing (that is, to recover the catalyst from sulfur poisoning). It should be noted that “appropriate timing” does not necessarily mean that a condition that defines such timing is determined in advance. In practice, it is effective to take this kind of recovery measure at a timing when the degree of sulfur poisoning can be considered to have exceeded the prescribed level, but there is no recovery measure for sulfur poisoning or measures to suppress sulfur poisoning. It is effective regardless of the level of sulfur poisoning.

In desorbing sulfur (or sulfur oxides) from a sulfur poisoned catalyst, hydrogen is known to be effective due to its extremely high reducing ability. The control device for an internal combustion engine according to the present invention promotes the generation of hydrogen in the cylinder by changing the injection mode of the in-cylinder injection device, so that recovery from sulfur poisoning of the catalyst, or sulfur of the catalyst It is configured to prevent adsorption.

That is, according to the control apparatus for an internal combustion engine according to the present invention, in the case of reducing the sulfur accumulated on the catalyst (including the case where the accumulated sulfur is desorbed and the adsorption is prevented), the in-cylinder injection device Is changed so that the homogeneity of the air-fuel mixture formed inside the cylinder is lowered. The first control means controls the in-cylinder injection device according to the changed injection mode.

Here, the “injection mode” refers to, for example, the number of injections, the injection timing, the injection period, or the like, and a control amount that can change the homogeneity of the air-fuel mixture. In addition, as will be described later, if the internal combustion engine further includes a port injection device in addition to the in-cylinder injection device, it can suitably include an injection ratio between the in-cylinder injection amount and the port injection amount.

The in-cylinder injection device directly injects fuel into the cylinder, and therefore, compared with a port injection device that injects fuel into the intake port, for example, fuel loss due to port adhesion or the like does not occur, but more fuel and intake gas. Requires a long premixing period. For example, the fuel injection timing in the in-cylinder injection device is set between the intake top dead center and the bottom dead center as a preferred embodiment, although it depends on conditions. That is, by performing fuel injection before the start of the compression stroke, sufficient premixing of the fuel and the cylinder intake gas in the compression stroke is achieved.

Therefore, conversely, if the injection timing is controlled to the retard side, the homogeneity of the air-fuel mixture (which need not be detected as a clear quantitative index) can also be reduced. That is, the injection timing can be a suitable example of the “injection mode” according to the present invention.

Here, hydrogen generation in the cylinder (not all need to occur in the cylinder, and may include what is generated in the exhaust path after being discharged from the cylinder) is mainly a water gas shift reaction (CO + H ₂ O → H ₂ + CO ₂ ) And steam reforming reaction (HC + H ₂ O → H ₂ + CO). That is, by promoting the generation of unburned or incombustible substances such as CO or HC inside the cylinder, the generation of hydrogen in the cylinder or the exhaust path can be promoted. Therefore, by changing the mode of in-cylinder injection so as to reduce the homogeneity of the air-fuel mixture, the generation of hydrogen can be favorably promoted in the cylinder or the exhaust path.

Here, in particular, such a change in the injection mode requires a change in the fuel injection amount for each cylinder determined to maintain the theoretical air fuel ratio or the target air fuel ratio by, for example, various known air fuel ratio F / B controls. do not do. Therefore, the exhaust path and the air-fuel ratio of the catalyst are not greatly affected by such a change in the injection mode.

That is, according to the control device for an internal combustion engine according to the present invention, the catalyst is recovered from sulfur poisoning without increasing the cost and exhaust emission and fuel consumption are deteriorated, or the accumulation of sulfur on the catalyst is suppressed. Is possible.

In one aspect of the control apparatus for an internal combustion engine according to the present invention, the changing means changes the fuel injection timing to the retard side with respect to the standard time as the injection mode (second term).

According to this aspect, by changing the injection timing to the retard side with respect to the standard timing, the homogeneity of the air-fuel mixture can be reduced, and hydrogen generation inside the cylinder, the exhaust path or the catalyst can be favorably promoted. I can do it.

The “standard time” means the injection time under the same conditions when measures for recovery or suppression of such sulfur poisoning are not required. If the standard timing is determined so as to optimize the fuel consumption of the internal combustion engine, the retard of the injection timing, that is, the deterioration of the fuel consumption can be caused. Compared with the technical idea of generating hydrogen, the difference in the amount of fuel consumption occurs, but the effect is very small. In that sense, it can be said that deterioration of fuel consumption is sufficiently suppressed.

In another aspect of the control apparatus for an internal combustion engine according to the present invention, the internal combustion engine includes a port injection device capable of performing a port injection of fuel to the cylinder, and the changing means includes the port injection as the injection mode. The fuel injection amount and the fuel injection amount and ratio of the in-cylinder injection are changed so that the fuel injection amount of the in-cylinder injection increases, and the control means changes the changed injection ratio. The in-cylinder injection device and the port injection device are controlled according to (3rd item).

In the configuration provided with the port injection device as the fuel injection device, the port injection can maintain the homogeneity of the air-fuel mixture better than the in-cylinder injection. It is known that the cold startability can be improved by doing so.

Here, from the point that the mixability of the fuel and the intake gas can be different between the in-cylinder injection and the port injection, the ratio of the in-cylinder injection amount to the port injection amount with respect to a certain required injection amount, that is, The spray ratio can be a suitable control amount that gives controllability to the homogeneity.

According to this aspect, the injection ratio is controlled as an injection aspect of the in-cylinder injection device. More specifically, the injection ratio is changed so that the in-cylinder injection amount is larger than a standard value (for example, the in-cylinder injection amount under the same condition when S poison recovery is not considered). Accordingly, the generation of hydrogen in the cylinder or the exhaust path can be favorably promoted.

In another aspect of the control apparatus for an internal combustion engine according to the present invention, first estimation means for estimating the amount of sulfur accumulated in the catalyst, and for recovering the catalyst from the sulfur poisoning from the estimated amount of accumulation. Second estimating means for estimating a required amount or required concentration of hydrogen, and the changing means changes the injection mode in accordance with the estimated required amount or required concentration (fourth term).

According to this aspect, the amount of sulfur deposition on the catalyst is estimated by the first estimating means. Strictly speaking, the “deposition amount” means an accumulation amount. However, depending on the poisoning process of sulfur to the catalyst (which is not necessarily unambiguous depending on the catalyst), for example, the adhesion amount, the adsorption amount, and the deposition amount. You may replace it with a poisonous amount.

In estimating the amount of sulfur deposited on the catalyst, various known methods can be applied. For example, the accumulation amount is determined in advance experimentally with internal combustion engine operating parameters that may include at least part of the engine speed, intake pressure, accelerator opening, intake air amount, throttle opening, load factor, and fuel injection amount. It may be estimated based on the correlation between the operating parameter and the amount of sulfur production, which is established empirically or theoretically. At this time, the amount of sulfur or sulfur oxide (SOx) discharged per unit time in the exhaust path of the internal combustion engine may be integrated, and the accumulation amount may be estimated from this integrated value. In addition, when the relationship between the integrated value and the actual accumulation amount (that is, not all of the sulfur or sulfur oxide discharged from the cylinder is deposited on the catalyst) is clear, the relationship is further referred to. May be.

On the other hand, the second estimating means recovers the catalyst from sulfur poisoning from the amount of accumulation estimated by the first estimating means (including the concept of suppressing sulfur poisoning by suppressing the adsorption of sulfur to the catalyst). Estimate the required amount or concentration of hydrogen for It should be noted that such a required amount or required concentration does not necessarily have to be an amount capable of desorbing all of the sulfur deposited on the catalyst as long as it has an effect of considerably recovering the sulfur poisoning of the catalyst. However, it is possible to theoretically determine the amount of hydrogen required to remove all the sulfur corresponding to the estimated deposition amount, and among the hydrogen generated by changing the injection mode, The proportion of hydrogen that can be used for sulfur desorption can also be experimentally determined as a correction coefficient.

According to this aspect, it is possible to give a certain guideline during a period that requires the change of the injection mode, and to alleviate the concern that the hydrogen generated by the change of the injection mode is insufficient or excessive.

In the aspect provided with the first and second estimation means as described above, the apparatus further comprises third estimation means for estimating the amount of hydrogen generated in the cylinder, and the changing means includes the estimated required amount or A period for changing the injection mode may be determined based on the required concentration and the estimated generation amount (Section 5).

If the configuration is such that the amount of hydrogen produced by changing the injection mode is estimated in this way, it is possible to generate an appropriate amount of hydrogen according to the required amount or the required concentration estimated by the second estimating means. Therefore, sulfur poisoning of the catalyst or adsorption of sulfur to the catalyst can be efficiently prevented.

The estimation of the hydrogen generation amount by the third estimation means is preferably performed in advance experimentally, empirically, or theoretically for each injection mode changed by the changing unit. This can be suitably realized by associating the generation amount or the concentration of. In short, if such a relationship is held as a control map that can be referred to, the third estimation means can estimate the generation amount relatively easily.

In the aspect including the third estimating means, the cooling water temperature specifying means for specifying the cooling water temperature of the internal combustion engine is provided, and the third estimating means generates the estimated generation according to the specified cooling water temperature. The amount may be corrected (Section 6).

水 素 Hydrogen generated in the cylinder under one injection mode change condition varies depending on the engine warm-up state of the internal combustion engine. In short, the combustion state of the cylinder worsens as engine warm-up becomes insufficient, such as during cold start. That is, even if the uniformity of the air-fuel mixture is constant, the amount of hydrogen produced tends to increase by the amount that the engine is in a relatively cooled state.

Therefore, by correcting the hydrogen generation amount estimated by the third estimation means in accordance with the cooling water temperature specified by the cooling water temperature specifying means, it becomes possible to estimate the hydrogen generation amount more accurately.

The “specific” according to the present invention is comprehensive including not only detection by a detection unit such as a sensor but also acquisition of a sensor value from this type of detection unit or estimation based on an operating condition of the internal combustion engine. It is a concept.

In another aspect of the control apparatus for an internal combustion engine according to the present invention, the control apparatus includes catalyst temperature specifying means for specifying the temperature of the catalyst, and air-fuel ratio specifying means for specifying an air-fuel ratio in the exhaust path, wherein the changing means includes When the specified air-fuel ratio is richer than the stoichiometric air-fuel ratio by a predetermined value or more and the temperature of the specified catalyst is lower than the predetermined value, the homogeneity inside the cylinder is reduced. The injection mode of the in-cylinder injection device is changed (Seventh Item).

According to this aspect, the catalyst temperature (in short, the catalyst bed temperature) is specified by the catalyst temperature specifying means. The air-fuel ratio in the exhaust path is specified by the air-fuel ratio specifying means.

The air-fuel ratio of the internal combustion engine is often F / B controlled to the theoretical air-fuel ratio or a target air-fuel ratio in the vicinity thereof by air-fuel ratio F / B control as described above, for example, power performance is required. In many cases, the air-fuel ratio is controlled to be rich for promoting the temperature rise of the catalyst or for other reasons.

On the other hand, in a temperature range where the catalyst bed temperature is lower than a predetermined value (for example, approximately around 500 to 600 ° C.) under a rich air-fuel ratio, the amount of sulfur adsorbed on the catalyst becomes high. From the viewpoint of actively avoiding sulfur poisoning of the catalyst, it is effective to actively generate hydrogen under such conditions.

According to this aspect, when the air-fuel ratio is richer than the predetermined value and the catalyst bed temperature is lower than the predetermined value, the changing means changes the injection mode of the in-cylinder injection device so that the homogeneity inside the cylinder is lowered. It is the composition to do. In other words, such a condition is adopted as an example of “when reducing sulfur deposited on the catalyst” according to the present invention.

Therefore, it is possible to actively avoid sulfur adsorption on the catalyst, prevent sulfur poisoning of the catalyst, or delay its progress.

Such an operation and other advantages of the present invention will be clarified from embodiments described below.

1 is a schematic configuration diagram conceptually showing a configuration of an engine system according to an embodiment of the present invention. It is a schematic block diagram which represents notionally the structure of the fuel supply apparatus in the engine system of FIG. It is a schematic block diagram which represents notionally the structure of the high pressure pump in the fuel supply apparatus of FIG. 2 is a flowchart of S poison recovery control executed by an ECU in the engine system of FIG. 1. FIG. 5 is a conceptual diagram of an H2 request amount map referred to in S poison recovery control of FIG. 4. It is a figure which illustrates the relationship between the injection ratio and the amount of H2 generation in the engine system of FIG. It is a conceptual diagram of the correction coefficient in the S poison recovery control of FIG. It is a flowchart of S poison recovery control which concerns on 2nd Embodiment of this invention. It is a figure which illustrates the relationship between the in-cylinder injection timing and H2 production | generation amount in the engine system of FIG. It is a flowchart of S adsorption | suction suppression control which concerns on 3rd Embodiment of this invention. It is a figure which illustrates the relationship between the catalyst bed temperature Tcat in the rich air fuel ratio, and the S adsorption amount of a three way catalyst. It is a flowchart of S adsorption | suction suppression control which concerns on 4th Embodiment of this invention.

<Embodiment of the Invention>
Hereinafter, various embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
<Configuration of Embodiment>
First, the configuration of an engine system 10 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram conceptually showing the configuration of the engine system 10.

1, an engine system 10 is mounted on a vehicle (not shown) and includes an ECU 100 and an engine 200.

The ECU 100 is an electronic control unit that includes a CPU, a ROM, a RAM, and the like and is configured to be able to control the operation of the engine system 10, and is an example of the “control device for an internal combustion engine” according to the present invention. The ECU 100 is configured to be able to execute S poisoning recovery control described later in accordance with a control program stored in the ROM.

The ECU 100 is an example of each of “changing means”, “first control means”, “first estimating means”, “second estimating means”, “third estimating means”, and “specifying means” according to the present invention. Although it is an integrated electronic control unit that can function, the physical, mechanical, and electrical configuration of each means according to the present invention is not limited to this, and each means includes, for example, a plurality of ECUs, You may comprise as various computer systems, such as various processing units, various controllers, or a microcomputer apparatus.

Engine 200 is an in-line four-cylinder gasoline engine that is an example of an “internal combustion engine” according to the present invention.

1, the engine 200 includes a plurality of cylinders 201 accommodated in a cylinder block CB. In FIG. 1, the cylinders 201 are arranged in the depth direction of the drawing, and only one cylinder 201 is shown in FIG. 1.

In the engine 200, the combustion chamber formed in the cylinder 201 is provided with a piston 202 that reciprocates in the vertical direction in the figure in accordance with the explosive force accompanying the combustion of the air-fuel mixture. The reciprocating motion of the piston 202 is converted into the rotational motion of the crankshaft 204 via the connecting rod 203 and is used as power for the vehicle on which the engine 200 is mounted.

In the vicinity of the crankshaft 204, a crank position sensor 205 capable of detecting the rotational position (ie, crank angle) of the crankshaft 204 is installed. The crank position sensor 205 is electrically connected to the ECU 100, and the detected crank angle is referred to the ECU 100 at a constant or indefinite period. For example, the crank position sensor 205 is used for calculation of the engine speed NE or other control. It becomes the composition which is done.

In the engine 200, air sucked from the outside is purified by a cleaner (not shown) and then guided to a common intake pipe 206 for each cylinder. The intake pipe 206 is provided with a throttle valve 207 that can adjust the amount of intake air that is the amount of intake air. The throttle valve 207 is configured as a kind of electronically controlled throttle valve whose driving state is controlled by a throttle valve motor (not shown) electrically connected to the ECU 100.

The ECU 100 basically drives and controls the throttle valve motor so as to obtain a throttle opening corresponding to an accelerator opening Ta detected by an unillustrated accelerator position sensor. However, the ECU 100 can also adjust the throttle opening without intervention of the driver's intention through the operation control of the throttle valve motor.

The intake air appropriately adjusted by the throttle valve 207 is sucked into the cylinder through the intake port 208 corresponding to each cylinder 201 when the intake valve 209 is opened. The intake valve 209 is configured such that its opening / closing timing is defined according to the cam profile of a cam 210 having a substantially elliptical shape in cross section as shown in the figure.

On the other hand, the cam 210 is fixed to an intake camshaft (reference number omitted) connected to the crankshaft 204 via power transmission means such as a cam sprocket or a timing chain. Therefore, the opening / closing phase of the intake valve 209 is uniquely related to the rotation phase of the crankshaft 204 (ie, the crank angle) in one fixed state.

Here, the fixed state between the intake cam 210 and the intake camshaft varies depending on the hydraulic pressure of the control oil supplied by the hydraulic drive device 211. More specifically, the intake cam 210 is connected to the intake cam shaft via a wing-like member called a vane, and the rotational phase between the vane and the intake cam shaft is applied to the hydraulic chamber of the hydraulic drive device 211. The configuration changes according to the hydraulic pressure applied. Therefore, the rotational phase between the intake cam 210 fixed to the vane and the intake camshaft also changes according to the hydraulic pressure. The hydraulic drive device 211 is in a state of being electrically connected to the ECU 100, and the ECU 100 can change the opening / closing timing of the intake valve 209 through the control of the hydraulic drive device 211.

In addition, the form which a variable valve apparatus can take is not limited to the thing of this embodiment. For example, the intake valve 209 may be a so-called electromagnetically driven valve (cam-by-wire) that is electromagnetically driven by a solenoid actuator or the like.

The intake pipe 206 is provided with an air flow meter 212 capable of detecting the intake air amount Ga. The air flow meter 212 is electrically connected to the ECU 100, and the detected intake air amount Ga is referenced by the ECU 100 at a constant or indefinite period.

The intake air guided to the intake port 208 is mixed with the port injection fuel injected from the PFI (Port Fuel Injector) 342 in which a part of the injection valve is exposed to the intake port 208 and mixed with the above-described fuel. It becomes a mixture. The PFI 342 is one element that constitutes the fuel supply device 300 described later with reference to FIG.

In the combustion chamber of the engine 200, a part of a spark plug (not shown) of an ignition device 213 that is a spark ignition device is exposed. The air-fuel mixture compressed in the compression stroke of the engine 200 is ignited and burned by the ignition operation of the spark plug. The ignition device 213 is electrically connected to the ECU 100, and the ignition timing of the ignition device 213 is controlled by the ECU 100.

On the other hand, the air-fuel mixture that has undergone a combustion reaction in the combustion chamber is opened and closed by an exhaust valve 215 that is driven to open and close by the cam profile of the exhaust cam 214 that is indirectly connected to the crankshaft 204 in the exhaust stroke following the combustion stroke. The exhaust port 216 is discharged.

The exhaust port 216 is connected to one end of an EGR pipe 217. The other end of the EGR pipe 217 is connected to an intake manifold (reference numeral omitted) located on the upstream side of the intake port 208, and a part of the exhaust can be returned to the intake system as EGR gas.

The EGR amount that is the supply amount of EGR gas is controlled by an EGR valve 218 installed in the EGR pipe 217. The EGR valve 218 is an electromagnetically driven valve that controls the opening and closing of the valve by the electromagnetic force of the solenoid, and the valve opening degree is controlled by the control of the ECU 100 electrically connected to the drive device that controls the excitation state of the solenoid. It becomes the composition which is done. In FIG. 1, the EGR pipe 217 is connected to the exhaust port 216. However, the EGR pipe 217 collects exhaust ports 216 of a plurality of cylinders 201 on the downstream side of the exhaust port 216, and will be described later. It may be connected to an exhaust manifold leading to 219.

In this embodiment, the EGR pipe 217 and the EGR valve 218 constitute an HPL (High Pressure Pressure Loop) EGR device. However, the configuration of the EGR device is not limited to this, and for example, a three-way catalyst 220 described later is used. It may be an LPL (Low Pressure Loop) EGR device that extracts exhaust gas from the downstream side.

The exhaust pipe 219 is connected to the exhaust port 216 of each cylinder. The exhaust pipe 214 is an example of an “exhaust path” according to the present invention.

The exhaust pipe 219 is provided with a three-way catalyst 220 as an example of the “exhaust purification catalyst” according to the present invention. The three-way catalyst 215 is a known catalyst device in which a noble metal such as platinum is supported on a catalyst carrier. The three-way catalyst 215 emits exhaust gas by causing the oxidative combustion reaction of HC and CO and the reduction reaction of nitrogen oxide NOx to proceed substantially simultaneously. It can be purified.

On the upstream side of the three-way catalyst 220 in the exhaust pipe 219, an air-fuel ratio sensor 221 capable of detecting the input side air-fuel ratio A / Fin that is the air-fuel ratio of the catalyst inflow gas flowing into the three-way catalyst 220 is installed. The air-fuel ratio sensor 221 is, for example, a limiting current type wide-area air-fuel ratio sensor provided with a diffusion resistance layer.

The air-fuel ratio sensor 221 is a sensor that outputs an output voltage value Vafin corresponding to the input-side air-fuel ratio A / Fin that is the air-fuel ratio of the exhaust (catalyst inflow gas) upstream of the three-way catalyst 220. That is, the air-fuel ratio sensor 221 employs a configuration in which the input-side air-fuel ratio A / Fin is indirectly detected by a voltage value having a unique relationship with the input-side air-fuel ratio A / Fin.

The output voltage value Vafin matches the reference output voltage value Vst when the input side air-fuel ratio A / Fin is the stoichiometric air-fuel ratio. The output voltage value Vafin is lower than the reference output voltage value Vst when the input side air-fuel ratio A / Fin is on the air-fuel ratio rich side, and when the input-side air-fuel ratio A / Fin is on the air-fuel ratio lean side. It becomes higher than the reference output voltage value Vst. That is, the output voltage value Vafin continuously changes with respect to the change of the input side air-fuel ratio A / Fin. The air-fuel ratio sensor 221 is electrically connected to the ECU 100, and the detected output voltage value Vafin is referred to by the ECU 100 at a constant or indefinite period.

On the downstream side of the three-way catalyst 220 in the exhaust pipe 219, an O ₂ sensor 222 that can detect the downstream oxygen concentration Coxs that is the oxygen concentration of the catalyst exhaust gas that has passed through the three-way catalyst 220 is installed. The O ₂ sensor 222 is a known electromotive force type oxygen concentration sensor (that is, a concentration cell type oxygen concentration sensor using stabilized zirconia).

The O ₂ sensor 222 is a sensor that outputs an output voltage value Voxs corresponding to the downstream oxygen concentration Coxs. That is, the O ₂ sensor 222 adopts a configuration in which the oxygen concentration is indirectly detected by a voltage value having a unique relationship with the oxygen concentration.

The output voltage value Voxs of the O ₂ sensor 222 is a reference when the air-fuel ratio of the catalyst exhaust gas is the stoichiometric air-fuel ratio (in other words, when the downstream oxygen concentration Coxs is the reference oxygen concentration Coxsb corresponding to the stoichiometric air-fuel ratio). It corresponds to the output voltage value Voxsb (for example, about 0.5V). The output voltage value Voxs is higher than the reference output voltage value Voxsb when the air-fuel ratio of the catalyst exhaust gas is on the air-fuel ratio rich side with respect to the stoichiometric air-fuel ratio, and when the air-fuel ratio is also on the air-fuel ratio lean side. It becomes lower than the reference output voltage value Voxsb.

Specifically, when the air-fuel ratio of the catalyst exhaust gas is between the stoichiometric air-fuel ratio and the rich detection limit air-fuel ratio, the output voltage value Voxs of the O ₂ sensor 222 is a decrease in the air-fuel ratio (ie, oxygen concentration). With a decrease in Coxs), it increases relatively linearly and substantially linearly to a maximum output voltage value Voxsmax (for example, about 0.9 V) corresponding to the rich-side detection limit air-fuel ratio. In the air-fuel ratio region on the rich side with respect to the rich-side detection limit air-fuel ratio, the output voltage value Voxs is substantially constant at the maximum output voltage value Voxsmax.

When the air-fuel ratio of the catalyst exhaust gas is between the stoichiometric air-fuel ratio and the lean side detection limit air-fuel ratio, the output voltage value Voxs of the O ₂ sensor 222 increases the air-fuel ratio (that is, the oxygen concentration Coxs increases). ) To a minimum output voltage value Voxsmin (for example, about 0.1 V) corresponding to the lean-side detection limit air-fuel ratio, it decreases relatively linearly and substantially linearly. In the air-fuel ratio region leaner than the lean-side detection limit air-fuel ratio, the output voltage value Voxs is substantially constant at the minimum output voltage value Voxsmin.

The O ₂ sensor 222 is electrically connected to the ECU 100, and the detected output voltage value Voxs is referred to by the ECU 100 at a constant or indefinite period.

In the engine 200, a water temperature sensor 223 capable of detecting a cooling water temperature Tw, which is a temperature of cooling water (LLC) circulated and supplied to cool the engine 200, is installed in a water jacket installed so as to surround the cylinder block CB. It is arranged. The water temperature sensor 223 is electrically connected to the ECU 100, and the detected cooling water temperature Tw is referred to by the ECU 100 at a constant or indefinite period.

Engine 200 includes DFI (Direct Fuel Injector) 362 capable of in-cylinder fuel injection in addition to PFI 342. A part of the injection valve of the DFI 362 is exposed to the combustion chamber of the cylinder 201. The DFI 362 and the PFI 342 constitute a fuel supply device 300.

Here, the configuration of the fuel supply apparatus 300 will be described with reference to FIG. Here, FIG. 2 is a schematic configuration diagram conceptually showing the fuel supply device 300. In addition, in the same figure, the same code | symbol shall be attached | subjected about the location which overlaps with each figure mentioned above, and the description shall be abbreviate | omitted suitably.

3, the fuel supply apparatus 300 includes a fuel tank 310, a feed pipe 320, a feed pump 330, a port injection system 340, a high-pressure pump 350, and an in-cylinder injection system 360.

The fuel tank 310 is a tank for storing fuel (in this embodiment, gasoline).

The feed pipe 320 is a metal tubular member having one end connected to the fuel tank 310 and the other end connected to the port injection system 340 and the in-cylinder injection system 360. The feed pump 330 is provided in the vicinity of the fuel tank 310 in the feed pipe 320.

The feed pump 330 is an electric pump device configured to pump fuel from the fuel tank 310 and supply the fuel to the feed pipe 320 at a desired fuel discharge speed (discharge amount per hour). The fuel discharged from the feed pump 330 is a low-pressure fuel having a predetermined feed pressure Pfd. The fuel discharge speed of the feed pump 330 is controlled by a drive device (not shown) that is electrically connected to the ECU 100. The feed pump 330 can variably control the feed pressure Pfd that is the fuel pressure in the feed pipe 320 through the control of the fuel discharge speed.

The port injection system 340 includes a low pressure delivery 341, a plurality of PFIs 342, and a feed pressure sensor 343.

The low pressure delivery 341 is a buffer configured to accumulate a certain amount of low pressure fuel having a feed pressure Pfd.

The PFI 342 is a fuel injection device as an example of the “port injection device” according to the present invention connected to the low pressure delivery 341. As described above, the fuel injection valve of the PFI 342 is exposed to the intake port 208 of each cylinder, and an amount of port injection fuel Fpi determined by the valve opening period of the fuel injection valve and the feed pressure Pfd is injected into the intake port 208 as spray. It is configured to be possible.

The feed pressure sensor 343 is a sensor configured to be able to detect the feed pressure Pfd of the low-pressure fuel described above. The feed pressure sensor 343 is electrically connected to the ECU 100, and the detected feed pressure Pfd is referred to by the ECU 100 at a constant or indefinite period.

The high-pressure pump 350 is a mechanical pump device interposed between the feed pump 330 and the in-cylinder injection system 360.

Here, the configuration of the high-pressure pump 350 will be described with reference to FIG. FIG. 3 is a schematic configuration diagram conceptually showing the configuration of the high-pressure pump 350. In addition, in the same figure, the same code | symbol shall be attached | subjected about the location which overlaps with each figure mentioned above, and the description shall be abbreviate | omitted suitably.

3, the high-pressure pump 350 includes an electromagnetic metering valve 351, a suction valve 352, a cylinder 353, a plunger 354, a pressurizing chamber 355, a cam 356, a discharge valve 357, and a high-pressure pipe 358.

The electromagnetic metering valve 351 is an electromagnetic on-off valve that is provided on the feed pipe 320 connected to the feed pump 330 and adjusts the flow rate of the low-pressure fuel delivered by the feed pump 320. The flow rate of the low-pressure fuel pumped up from the fuel tank 310 by the feed pump 320 is adjusted by the electromagnetic metering valve 351 and supplied to the pressurizing chamber 355 to which one end of the feed pipe 320 is connected. The electromagnetic metering valve 351 is electrically connected to the ECU 100, and the drive duty that defines the valve opening period is controlled by the ECU 100.

Plunger 354 is a pressurizing member installed in cylinder 353, and a rod-like member connected to the lower end is fixed to intake camshaft ICS of engine 200 and rotates in conjunction with the rotation of intake camshaft ICS. As the above-described cam profile of the intake cam 210 reciprocates in the vertical direction in the drawing, the upper end portion thereof is shown in the figure TDC (Top Death Center) and shown in the figure BDC (Bottom Death ： Center: bottom dead center) It is the structure which reciprocates between.

The pressurizing chamber 355 is a space defined by the inner wall portion of the cylinder 353 and the upper end portion of the plunger 354, and is a space whose volume changes in accordance with the reciprocation of the plunger 354 described above.

The fuel metered by the electromagnetic metering valve 351 is sucked into the pressurizing chamber by pushing the suction valve 352 open when the plunger 354 moves from the TDC to the BDC in the cylinder 353 (that is, during the decompression period). The Thereafter, when the plunger 354 moves from the BDC toward the TDC in the cylinder 353 (ie, during the pressurization period), the fuel inside the pressurizing chamber 355 is compressed (ie, pressurized) by the plunger 354. The pressurized fuel is configured to push open the discharge valve 357 to be supplied to the high-pressure pipe 358 and to be pumped to the high-pressure delivery 361 connected to the high-pressure pipe 358.

Here, in the mechanical pump device in which the pressurizing operation is performed in conjunction with the engine motion of the engine 200 as described above, the driving load is uniquely related to the open state of the electromagnetic metering valve 351. That is, if the valve opening period of the electromagnetic metering valve 351 is long, more fuel is introduced into the pressurizing chamber 355, and the driving load of the high pressure pump 350 is increased accordingly.

The high-pressure pump 350 exemplified here is an example of a high-pressure pump device in a cylinder injection system that directly injects fuel into the cylinder, and of course, other known modes can be adopted.

2, the in-cylinder injection system 360 includes a high-pressure delivery 361, a plurality of DFIs 362, and a high-pressure sensor 363.

The high-pressure delivery 361 is a buffer configured to be able to store a certain amount of high-pressure fuel having a fuel pressure Ph (Ph> Pfd).

The DFI 362 is a fuel injection device that is connected to the high pressure delivery 361 and is an example of the “in-cylinder injection device” according to the present invention. As described above, the fuel injection valve of the DFI 362 is exposed to the combustion chamber of each cylinder, and the amount of in-cylinder injection fuel Fdi determined by the opening period of the fuel injection valve and the fuel pressure Ph is sprayed into the combustion chamber of the cylinder 201. It is configured to be jettable.

Here, we will supplement the configuration of DFI362. The DFI 362 includes an electromagnetic valve that operates based on a command supplied from the ECU 100, and a nozzle (both not shown) that injects fuel when the electromagnetic valve is energized. The solenoid valve is configured to be able to control the communication state between the pressure chamber to which the high-pressure fuel accumulated in the high-pressure delivery 361 is applied and the low-pressure passage connected to the pressure chamber. The pressure chamber and the low-pressure passage are sometimes communicated with each other, and the pressure chamber and the low-pressure passage are shut off from each other when energization is stopped.

On the other hand, the nozzle has a built-in needle that opens and closes the nozzle hole, and the fuel pressure in the pressure chamber urges the needle in the valve closing direction (direction in which the nozzle hole is closed). Accordingly, when the pressure chamber communicates with the low pressure passage by energizing the electromagnetic valve and the fuel pressure in the pressure chamber decreases, the needle rises in the nozzle and opens (opens the nozzle hole), thereby causing the high pressure delivery 361. High-pressure fuel supplied from the nozzle is injected from the injection hole. Further, when the pressure chamber and the low pressure passage are cut off from each other by stopping energization of the solenoid valve and the fuel pressure in the pressure chamber rises, the needle is lowered in the nozzle and closed, thereby terminating the injection.

In the fuel supply device 300, as will be described later, the injection ratio Rinj, which is the ratio of the port injection fuel Fpi and the in-cylinder injection fuel Fdi, can be freely controlled between the PFI 342 and the DFI 362.

<Operation of Embodiment>
<Outline of air-fuel ratio F / B control>
In the engine 200, the fuel injection amount Q of one cylinder 201 is the sum of the port injection amount Qpfi that is the fuel injection amount of the PFI 342 and the in-cylinder injection amount Qdfi that is the fuel injection amount of the DFI 362. The fuel injection amount Q is controlled by the ECU 100 by air-fuel ratio F / B control that is always executed during the operation period of the engine 200. The air-fuel ratio F / B control according to the present embodiment includes a main F / B control and a sub F / B control.

The main F / B control is control of the fuel injection amount so that the input side air-fuel ratio A / Fin obtained based on the output voltage value Vafin of the air-fuel ratio sensor 221 converges to the input side target air-fuel ratio A / Fintg. is there.

The sub F / B control is a control for correcting the output voltage value Vafin of the air-fuel ratio sensor 221 or the input side target air-fuel ratio A / Fintg so that the output voltage value Voxs of the O ₂ sensor 222 converges to the target output voltage value Voxstg. is there.

When the air-fuel ratio F / B control including the main F / B control and the sub F / B control is executed, the air-fuel ratio inside the three-way catalyst 220 can be converged to the target air-fuel ratio. The target air-fuel ratio is an air-fuel ratio that optimizes the exhaust purification action of the three-way catalyst 220, and is, for example, a theoretical air-fuel ratio. Of course, this target air-fuel ratio may be changed as appropriate according to the required performance of the engine 200, etc., as long as it is allowed in consideration of emissions and fuel consumption, and may be changed as appropriate.

Various types of feedback control based on the values corresponding to the air / fuel ratios upstream and downstream of the catalyst have been proposed in the past. Here, further details are omitted for the purpose of preventing complication of explanation. And

In the air-fuel ratio F / B control, when the fuel injection amount Q is determined for each cylinder 201, the ECU 100 determines the above-described injection division ratio Rinj according to a predetermined standard. Note that the injection ratio Rinj is usually a value experimentally, empirically, or theoretically determined in advance so that the fuel consumption of the engine 200 is best (this value is appropriately referred to as “standard injection ratio Rinjb” thereafter). Control).

<Details of S poison recovery control>
The gasoline used for the engine 200 often contains sulfur. The sulfur in the fuel is likely to be combined with oxygen in the cylinder 201 or in the exhaust pipe 219 to become sulfur oxide (SOx). The sulfur oxide is easily chemically combined with the noble metal of the three-way catalyst 220, and the three-way catalyst 220 is gradually sulfur poisoned (S poison) during the operation period of the engine 200. In the engine system 10, S (sulfur) poisoning recovery control is executed by the ECU 100 in order to recover the three-way catalyst 220 from sulfur poisoning.

Here, the details of the S poison recovery control will be described with reference to FIG. FIG. 4 is a flowchart of the S poison recovery control.

In FIG. 4, the ECU 100 acquires the S accumulation amount Dsf of the three-way catalyst 220 (step S101). The S deposition amount Dsf is the amount of sulfur deposited on the three-way catalyst 220 during the period from the end of the previous S poison recovery control to the present, and “the amount of sulfur deposition on the catalyst” according to the present invention. It is an example.

The S accumulation amount Dsf is repeatedly calculated by the ECU 100 in a control routine different from the S poison recovery control, and stored in a rewritable memory such as a RAM with appropriate updating. That is, in the process of executing the S accumulation amount Dsf, the ECU 100 functions as an example of the “first estimation unit” according to the present invention.

The ECU 100 estimates the S accumulation amount Dsf from the accumulated fuel consumption amount ΣQ, which is a value obtained by accumulating the fuel injection amount Q, which is the sum of the port injection amount Qpfi and the in-cylinder injection amount Qdfi, for each cycle of each cylinder. It is assumed that the sulfur content in the unit fuel is given as an initial value in advance. The ECU 100 calculates the S accumulation amount Dsf by multiplying the accumulated fuel consumption amount ΣQ at that time by a predetermined accumulation rate σ.

This deposition rate σ is a correction coefficient that represents the ratio of sulfur deposited on the three-way catalyst 220 out of the sulfur discharged to the exhaust pipe 219, and experimentally, empirically, or theoretically, engine speed NE in advance. And the load factor KL (that is, the ratio of the amount of fresh air sucked into the cylinder 201 to the physical maximum value) is stored in the control map as a parameter. Qualitatively, the higher the engine speed NE and the larger the load factor KL, the weaker the accumulation rate σ tends to decrease. Note that such an estimation mode of the S accumulation amount Dsf is an example, and various known modes can be applied to the calculation of the S deposition amount.

ECU100 determines whether the acquired S accumulation amount Dsf is larger than the reference value Dsfth (step S102). The reference value Dsfth is determined in advance experimentally, empirically, or theoretically as a value that reduces the purification efficiency of the three-way catalyst 220 to a predetermined level or more due to S poisoning. When the S accumulation amount Dsf is equal to or less than the reference value Dsfth (step S102: NO), the ECU 100 returns the process to step S101.

On the other hand, when the S accumulation amount Dsf is larger than the reference value Dsfth (step S102: YES), the ECU 100 executes the processing after step S103, assuming that the three-way catalyst 220 needs to be recovered from sulfur poisoning.

In step S103, the ECU 100 calculates an H2 (hydrogen) demand amount Nh2. The required H2 amount Nh2 is a required amount of hydrogen that needs to be generated in each cylinder 201 in order to recover the sulfur poisoning of the three-way catalyst 220, and according to the present invention, “for recovering the catalyst from sulfur poisoning” This is an example of “required amount of hydrogen”.

The ECU 100 refers to the H2 request amount map stored in the ROM when calculating the H2 request amount Nh2. Here, the H2 request amount map will be described with reference to FIG. FIG. 5 is a conceptual diagram of the H2 request amount map.

In FIG. 5, the H2 requirement amount Nh2 and the S deposition amount Dsf are represented on the vertical axis and the horizontal axis, respectively. As shown in the figure, the H2 requirement amount Nh2 has a linear relationship with the S deposition amount Dsf. The relationship illustrated in FIG. 5 is digitized and stored in the H2 request amount map, and when calculating the H2 request amount Nh2, the ECU 100 acquires the S accumulation acquired in step S101 from the H2 request amount map. A value corresponding to the amount Dsf is selected (note that such a selection process is also an example of calculation).

Returning to FIG. 4, when the required H2 amount Nh2 is calculated, the ECU 100 changes the injection division ratio Rinj from the above-described standard injection ratio Rinjb to the injection division ratio Rinjh2 for sulfur poisoning recovery (step S104).

Here, with reference to FIG. 6, the relationship between the injection ratio Rinj and the H2 generation amount of the cylinder 201 will be described. FIG. 6 is a diagram illustrating the relationship between the ejection division ratio Rinj and the H2 generation amount Gh2.

6, the vertical axis and the horizontal axis respectively represent the H2 generation amount Gh2 and the spray distribution ratio Rinj. The injection ratio Rinj in the present embodiment is defined as Qpfi / (Qpfi + Qdfi). The larger the value (left side in the figure), the larger the port injection amount Qpfi, and the smaller the value (right side in the figure), the in-cylinder injection. The quantity Qdfi increases.

As illustrated, the H2 generation amount Gh2 increases in a quadratic function as the injection ratio Rinj decreases (that is, the in-cylinder injection amount Qdfi increases). Note that the characteristics shown in the figure are characteristics when the air-fuel ratio of the cylinder is the stoichiometric air-fuel ratio (14.6).

Referring back to FIG. 4, as an extreme case, the injection ratio Rinjh2 for recovery from sulfur poisoning may be a value smaller than the standard injection ratio Rinjb, and there is no need to have a clear guideline for the determination. However, if the H2 generation amount Gh2 is not sufficiently large, the time during which the ejection ratio Rinj deviates from the standard ejection ratio Rinjb becomes longer, and thus is set to an appropriate value experimentally in advance. At this time, a configuration in which one ejection ratio Rinjh2 is selected from a plurality of options according to the magnitude of the H2 request amount Nh2 may be adopted.

On the other hand, when the injection division ratio Rinjh2 for recovery from sulfur poisoning is determined, the ECU 100 acquires a correction coefficient for the H2 generation amount Gh2 (step S105). Here, the correction coefficient will be described with reference to FIG. FIG. 7 is a conceptual diagram of the correction coefficient.

In FIG. 7, the correction coefficient is a function of the cooling water temperature Tw. That is, the correction coefficient is set to be larger than 1 in the temperature region where the coolant temperature Tw is lower than the warm-up completion determination value Tww. This is because in the unwarmed state, the combustion in the cylinder 201 is worse than after the warm-up is completed.

Returning to FIG. 4, when the correction coefficient for the H2 generation amount Gh2 is acquired, the ECU 100 determines the basic H2 generation amount according to the injection ratio Rinjh2 for recovery from sulfur poisoning, the correction coefficient, and the engine of the engine 200. The instantaneous H2 generation amount Gh2m is calculated based on the rotational speed NE and the load factor KL (that is, has a unique relationship with the gas discharge amount per unit time), and the instantaneous H2 generation amount Gh2m is integrated ( Step S106).

Subsequently, the ECU 100 acquires the time integration value ΣGh2m of the instantaneous H2 generation amount Gh2m (step S107). The time integrated value ΣGh2m means the amount of hydrogen produced up to the present after the change of the injection ratio Rinj.

When the time integration value ΣGh2m is acquired, the ECU 100 determines whether or not the acquired time integration value ΣGh2m is larger than the previously calculated H2 request amount Nh2 (step S108). If ΣGh2m is equal to or less than Nh2 (step S108: NO), the process returns to step S105.

When it is determined in step S108 that ΣGh2m is larger than Nh2 (step S108: YES), the ECU 100 clears the S accumulation amount Dsf (step S109), and returns the injection division ratio Rinj to the standard injection division ratio Rinjb. (Step S110), the process returns to Step S101. The S poison recovery control is executed as described above.

Thus, according to the S poison recovery control according to the present embodiment, when the S accumulation amount Dsf of the three-way catalyst 220 exceeds the reference value Dsfth, the injection as the injection mode of the DFI 362 that is the in-cylinder injection device The division ratio Rinj is changed from the standard injection division ratio Rinjb for optimally maintaining fuel efficiency to the injection division ratio Rinjh2 for recovery from sulfur poisoning.

The injection ratio Rinjh2 for recovery from sulfur poisoning is an injection ratio in which the in-cylinder injection amount Qdfi is larger than the standard injection ratio Rinjb. In the three-way catalyst 220 in which the homogeneity of the air-fuel mixture in the engine is reduced and the combustion state is relatively deteriorated to generate hydrogen in the cylinder 201, the desorption of sulfur is promoted by the H2 generated in the cylinder 201. .

On the other hand, the injection ratio Rinj does not affect the fuel injection amount Q required for each cylinder. Therefore, for the engine 200 as a whole, the fuel injection amount is maintained at the required value, and fuel consumption does not deteriorate. That is, according to the S poisoning recovery control according to the present embodiment, the three-way catalyst 220 can be recovered from sulfur poisoning without causing an increase in cost and deterioration of emission and fuel consumption.
<Second Embodiment>
Next, S poison recovery control according to the second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a flowchart of the S poison recovery control according to the second embodiment of the present invention. In the figure, the same reference numerals are given to the same portions as those in FIG. 4, and the description thereof will be omitted as appropriate.

In FIG. 8, when the required H2 amount Nh2 is calculated (step S103), the ECU 100 changes the in-cylinder injection timing Tdfi from the standard in-cylinder injection timing Tdfi to the in-cylinder injection timing Tdfih2 for sulfur poisoning recovery (step S103). S201).

Here, the relationship between the in-cylinder injection timing Tdfi and the H2 generation amount of the cylinder 201 will be described with reference to FIG. FIG. 9 is a diagram illustrating the relationship between the in-cylinder injection timing Tdfi and the H2 generation amount Gh2.

9, the vertical axis and the horizontal axis represent the H2 generation amount Gh2 and the in-cylinder injection timing Tdfi, respectively. The in-cylinder injection timing Tdfi is a crank angle at which the DFI 362 starts fuel injection.

As shown in the figure, the H2 generation amount Gh2 increases as the in-cylinder injection timing Tdfi moves toward the retard side (the right side in the figure). Note that the illustrated characteristics are characteristics after the engine 200 is completely warmed up.

The standard in-cylinder injection timing Tdfib is between the intake top dead center TDCi and the intake bottom dead center BDCi, and the end of the intake stroke and the entire compression stroke are provided for premixing of fuel and intake gas. Yes. On the other hand, if the in-cylinder injection timing Tdfi is changed to the retarded angle side, it is difficult to ensure a period during which the in-cylinder injected fuel is sufficiently mixed with the intake gas, and the homogeneity of the air-fuel mixture decreases. As a result, the H2 generation amount Gh2 increases as in the case of the spray distribution ratio Rinj.

Returning to FIG. 8, in an extreme case, the in-cylinder injection timing Tdfi for recovery from sulfur poisoning may be a value retarded from the standard in-cylinder injection timing Tdfib. It is not necessary. However, if the H2 generation amount Gh2 is not sufficiently large, the time during which the in-cylinder injection timing Tdfi deviates from the standard in-cylinder injection timing Tdfi becomes long, and thus is set to an appropriate value experimentally in advance. At this time, one in-cylinder injection timing Tdfih2 may be selected from a plurality of options according to the magnitude of the H2 request amount Nh2.

When the in-cylinder injection timing Tdfih2 for sulfur poisoning recovery is determined in this way, the instantaneous H2 generation amount Gh2m is integrated (step S106) in the same way as when the injection ratio Tinj is switched. In this case, the H2 generation amount Gh2 that is a calculation reference of the instantaneous H2 generation amount Gh2m is different from the case where the injection ratio Rinj is switched.

Step S106 and subsequent steps are the same as in the first embodiment up to step S109. When the S accumulation amount Dsf is cleared (step S109), the in-cylinder injection timing Tdfi is returned to the standard in-cylinder injection timing Tdfib (step S202). ), The process returns to step S101. The S poison recovery control according to the second embodiment is executed as described above.

As described above, according to the S poison recovery control according to the present embodiment, the hydrogen in the cylinder 201 is controlled by the retard control of the in-cylinder injection timing Tdfi, similarly to the injection ratio Rinj according to the first embodiment. Generation | occurrence | production can be accelerated | stimulated and S poisoning of the three-way catalyst 220 can be recovered suitably.
<Third Embodiment>
In the first and second embodiments, when the S accumulation amount Dsf of the three-way catalyst 220 exceeds a predetermined value, that is, when the three-way catalyst 220 has been poisoned to some extent by S, the S poison recovery control is executed. It was. However, if the conditions under which S adsorption to the three-way catalyst 220 is likely to occur are known in advance, it is also effective to positively suppress this S adsorption separately from the control according to the S accumulation amount of the catalyst. In the third embodiment, the S adsorption suppression control based on such a purpose will be described with reference to FIG. FIG. 10 is a flowchart of the S adsorption suppression control according to the third embodiment. In the figure, the same reference numerals are given to the same portions as those in FIG. 4, and the description thereof will be omitted as appropriate.

In FIG. 10, the ECU 100 detects that the input side air-fuel ratio A / Fin detected by the air-fuel ratio sensor 221 is shifted to a rich side by a predetermined amount or more with respect to the theoretical air-fuel ratio (hereinafter, such an air-fuel ratio is referred to as “rich air-fuel ratio”. It is determined whether the catalyst bed temperature Tcat, which is the temperature of the three-way catalyst 220, is less than the reference value Tcatth (referred to as “fuel ratio”) (step S301).

When the input side air-fuel ratio A / Fin is a rich air-fuel ratio and the catalyst bed temperature Tcat is lower than the reference value Tcatth (step S301: YES), the ECU 100 generates the injection ratio Rinj as H2 as in the first embodiment. It changes to the injection division ratio Rinjh2 for use (step S104).

When the spray distribution ratio Rinj is changed, the process returns to step S301. The change of the injection ratio Rinj is continued until the input side air-fuel ratio A / Fin is no longer the rich air-fuel ratio or the catalyst bed temperature Tcat becomes equal to or higher than the reference value Tcatth.

When the input side air-fuel ratio A / Fin is no longer the rich air-fuel ratio or the catalyst bed temperature Tcat becomes equal to or higher than the reference value Tcatth (step 301: NO), the ECU 100 returns the injection ratio Rinj to the standard injection ratio Rinjb ( In step S110, the process returns to step S301. The S adsorption suppression control is executed as described above.

Here, the significance of such S adsorption suppression control will be described with reference to FIG. FIG. 11 is a diagram illustrating the relationship between the catalyst bed temperature Tcat and the S adsorption amount of the three-way catalyst 220 under a rich air-fuel ratio. FIG. 11 is a characteristic diagram when the air-fuel ratio is a rich air-fuel ratio.

As shown in FIG. 11, under the rich air-fuel ratio, when the catalyst bed temperature Tcat is lower than the reference value in the vicinity of 500 to 600 ° C., a high S adsorption amount is shown. Therefore, if the injection ratio Rinj is changed to the injection ratio Rinjh2 for generating H2 and the amount of H2 generation is increased under such conditions, it is possible to prevent sulfur from being deposited on the three-way catalyst 220 itself. I can do it. That is, the S poisoning of the catalyst can be actively recovered.

In step S301, the catalyst bed temperature Tcat is acquired, and the catalyst bed temperature Tcat is calculated after the latest IG on timing in a control routine different from the S poison recovery control. Is estimated based on Specifically, a control map indicating the relationship between the accumulated fuel consumption and the catalyst bed temperature Tcat is stored in advance in the ROM, and the ECU 100 acquires a temperature value corresponding to the accumulated fuel consumption from the control map. As a result, the catalyst bed temperature Tcat is estimated. In addition, when a temperature sensor is arrange | positioned at the three-way catalyst 220, the detected value of the said temperature sensor may be used.
<Fourth embodiment>
The S adsorption suppression control according to the third embodiment can be realized by changing the in-cylinder injection timing Tdfi, similarly to the relationship between the first embodiment and the second embodiment. Here, with reference to FIG. 12, such S adsorption suppression control will be described as a fourth embodiment of the present invention. FIG. 12 is a flowchart of the S adsorption suppression control according to the fourth embodiment. In the figure, the same reference numerals are given to the same portions as those in FIGS. 8 and 10, and the description thereof is omitted as appropriate.

In FIG. 12, when the input side air-fuel ratio A / Fin is a rich air-fuel ratio and the catalyst bed temperature Tcat is lower than the reference value Tcatth (step S301: YES), in-cylinder injection is performed as in the second embodiment. The timing Tdfi is changed to the in-cylinder injection timing Tdfih2 for generating H2 (step S201).

When the in-cylinder injection timing Tdfi is changed, the process returns to step S301. The change in the in-cylinder injection timing Tdfi is continued until the input side air-fuel ratio A / Fin is no longer the rich air-fuel ratio or the catalyst bed temperature Tcat becomes equal to or higher than the reference value Tcatth.

When the input side air-fuel ratio A / Fin is not a rich air-fuel ratio or the catalyst bed temperature Tcat becomes equal to or higher than the reference value Tcatth (step 301: NO), the ECU 100 returns the in-cylinder injection time Tdfi to the standard time Tdfib (step step (S202), the process returns to step S301. The S adsorption suppression control according to the fourth embodiment is executed as described above.

In the fourth embodiment, the in-cylinder injection timing Tdfi is changed to the in-cylinder injection timing Tdfih2 for generating H2 in the same manner as the injection dividing ratio Rinj for changing the injection ratio Rinjh2 for generating H2 in the third embodiment. As a result, the amount of H2 generated in the cylinder is increased. If the amount of H2 generated increases, it is possible to prevent sulfur from being deposited on the three-way catalyst 220 itself. That is, the S poisoning of the catalyst can be actively recovered.

The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and the control of the internal combustion engine accompanying such a change. The apparatus is also included in the technical scope of the present invention.

The present invention can be applied to sulfur poisoning recovery control of a catalyst in an internal combustion engine.

10 ... engine system, 100 ... ECU, 200 ... engine, CB ... Cylinder block, 201 ... cylinder, 212 ... intake port injector, 219 ... exhaust pipe, 220 ... three-way catalyst, 221 ... air-fuel ratio sensor, 222 ... _{O 2} sensor .

Claims (7)

Cylinders,
An exhaust purification catalyst installed in an exhaust passage connected to the cylinder;
A control device for an internal combustion engine, comprising: an in-cylinder injection device capable of in-cylinder injection of fuel into the cylinder;
Change means for changing the injection mode of the in-cylinder injection device so as to reduce the homogeneity of the air-fuel mixture inside the cylinder when reducing sulfur accumulated in the catalyst;
A control device for an internal combustion engine, comprising: first control means for controlling the in-cylinder injection device in accordance with the changed injection mode. The control device for an internal combustion engine according to claim 1, wherein the changing means changes the fuel injection timing to a retard side with respect to a standard timing as the injection mode. The internal combustion engine includes a port injection device capable of port injection of fuel to the cylinder,
The changing means changes, as the injection mode, an injection ratio that is a ratio of the fuel injection amount of the port injection and the fuel injection amount of the in-cylinder injection so that the fuel injection amount of the in-cylinder injection increases. ,
The control device for an internal combustion engine according to claim 1 or 2, wherein the control means controls the in-cylinder injection device and the port injection device in accordance with the changed injection ratio. First estimating means for estimating the amount of sulfur deposited on the catalyst;
Second estimation means for estimating a required amount or a required concentration of hydrogen for recovering the catalyst from the sulfur poisoning from the estimated amount of deposition, and
The control device for an internal combustion engine according to claim 1, wherein the changing means changes the injection mode according to the estimated required amount or required concentration. Further comprising third estimating means for estimating the amount of hydrogen produced in the cylinder;
5. The internal combustion engine according to claim 4, wherein the changing unit determines a period for changing the injection mode based on the estimated required amount or concentration and the estimated generated amount. Engine control device. Comprising cooling water temperature specifying means for specifying the cooling water temperature of the internal combustion engine,
The control apparatus for an internal combustion engine according to claim 5, wherein the third estimating means corrects the estimated generation amount in accordance with the specified cooling water temperature. A catalyst temperature specifying means for specifying the temperature of the catalyst;
Air-fuel ratio specifying means for specifying the air-fuel ratio in the exhaust path,
The changing means has a degree of homogeneity inside the cylinder when the specified air-fuel ratio is richer than a stoichiometric air-fuel ratio by a predetermined value or more and the temperature of the specified catalyst is less than a predetermined value. The control device for an internal combustion engine according to claim 1, wherein the injection mode of the in-cylinder injection device is changed so as to decrease.

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