JP4036165B2 - Auto-ignition engine - Google Patents

Description

  The present invention relates to an engine capable of compressing and igniting a fuel mixture in two cycles in a cylinder.

  This type of engine can improve fuel efficiency and suppress emission of air pollutants (especially NOx) by compressing the fuel mixture and autoigniting it so that the compression end temperature of the fuel in the combustion chamber is moderate. It is known that there is. Focusing on such characteristics, an engine capable of two-cycle operation having a multi-cylinder configuration is being mounted on a vehicle (for example, Patent Document 1).

JP 2001-280183 A

  The following proposals have also been made regarding the combustion state of fuel in a two-cycle compression ignition engine and combustion chamber.

JP-A-7-34958 Japanese Patent Laid-Open No. 7-119534 Japanese Patent Laid-Open No. 9-126041 JP 2001-152908 A Japanese Patent Laid-Open No. 2002-188445

  By the way, in the two-cycle engine, in the scavenging stroke, the intake of new air (fuel mixture) into the combustion chamber and the exhaust associated therewith are performed in parallel. The scavenging effect tends to be slightly different for each cylinder due to the influence of pressure pulsation in the supply pipe and exhaust pipe. For example, because there is too much exhaust gas remaining in the combustion chamber in one cylinder, there is less fresh air and a rich mixture, while in other cylinders there is too little residual exhaust gas and there is more fresh air. There may be a lean mixture.

  When such a situation occurs, when the required load (torque) of the engine is large, the fuel injection amount increases according to the load, and therefore, the rich cylinder is likely to increase combustion noise. Therefore, it is necessary to refrain from the self-ignition operation at a high load. On the other hand, when the required load of the engine is small, the fuel injection amount is small, and therefore, a lean cylinder may cause a torque drop or misfire, and the self-ignition operation is limited even at a low load side. In other words, if the combustion state of each cylinder (each combustion chamber) is different, the range of operating conditions in which self-ignition combustion is possible as a multi-cylinder engine is substantially due to the cylinder having a limited operation region in which self-ignition combustion can occur. There was a problem of being narrowed.

The following problems were also pointed out.
The self-ignition of a fuel mixture is not only the mixture temperature (compression end temperature), mixture concentration, and engine load (fuel injection amount) due to compression, but also the properties of the fuel used, such as the octane number and cetane number (light and heavy) It is also affected by such factors. In a vehicle, since the fuel supply area is not always constant due to its movement characteristics, it can be said that the vehicle is not supplied with uniform fuel properties depending on the fuel supply area, the season of fuel supply, and the like. In such a situation, the self-ignition of the fuel mixture becomes unstable, which may lead to engine misfire and increased combustion noise. This was one factor that substantially narrowed the range of conditions.

  In the technology described in the above-mentioned patent document, the amount of fuel supplied to the combustion chamber and the amount of residual gas are controlled to adjust the self-ignition timing (Patent Document 1). There is still room for improvement.

  When changes in engine components occur over time, fuel injection volume decreases, scavenging efficiency changes, etc. due to accumulation of combustion soot and equipment wear, etc. The point was not enough.

  It should be noted that coping with changes in fuel properties and aging can naturally occur even in a single cylinder engine.

  The present invention has been made to solve the above-described conventional problems, and in an engine capable of compressing and igniting a fuel mixture in two cycles, the range of operating conditions in which self-ignition combustion can be performed is more than conventional. Its purpose is to spread.

  In order to achieve at least a part of the above-described problems, the engine of the present invention uses a sensor provided in a cylinder when the fuel mixture is compressed and ignited in two cycles in a combustion chamber in the cylinder. A physical phenomenon reflecting the combustion state of the combustion chamber is detected, and a current combustion state parameter indicating the current combustion state of the combustion chamber is calculated based on the output transition of the physical phenomenon. The current combustion state parameter calculated in this way is compared with a reference combustion state parameter set and stored in advance in association with the operating state of the engine as a parameter indicating the combustion state of the combustion chamber. The engine of the present invention corresponds to the combustion device in the combustion chamber corresponding to the combustion state of the combustion chamber, such as a fuel injection valve for supplying fuel to the combustion chamber and a supply / exhaust valve provided at the head of the combustion chamber. When the control is performed based on the control parameter determined in advance according to the operation state of the engine, the control parameter is corrected according to the comparison result of the reference combustion state parameter and the current combustion state parameter, and the drive is performed using the parameter correction result. Control the equipment.

  As a result, the situation is such that the current combustion state parameter is different from the reference combustion state parameter assumed and stored in advance for the engine, that is, the influence of the difference in fuel properties and the aging of the equipment as described in the prior art. Even in the situation that appears, the current combustion state transition (current combustion state parameter transition) due to such a state transition is reflected in the control of the drive device such as the fuel injection valve through the correction of the control parameter, and these The device can be driven and controlled. For this reason, adverse effects (for example, misfires and increased noise described above) such as differences in fuel properties and aging of equipment can be suppressed, so even if such a situation changes, operation that allows autoignition combustion It can contribute to maintenance or expansion of the condition range.

  The above-mentioned present invention can also take the following aspects. That is, when comparing the current combustion state parameter with the reference combustion state parameter, the reference combustion state parameter is updated and corrected according to the transition state of the current combustion state parameter, and the updated reference combustion state parameter and the current operating state are corrected. Contrast with parameter. Then, parameter correction is performed according to the comparison result, and the drive device is controlled using the parameter correction result.

  In this way, not only the current combustion state parameter but also the reference combustion state parameter that is the object of comparison reflects the influence of the above-described situation change such as the difference in fuel properties and the secular change of equipment. Therefore, the comparison result of both parameters has a small degree of difference between the parameters. Therefore, the parameter correction according to the comparison reflects the influence of the above-mentioned situation in detail. For this reason, it becomes possible to raise the control precision of drive devices, such as a fuel injection valve. In addition, even in a transient state where the above situation transition starts to occur, for example, a transitional state immediately after refueling with different properties, such a transition is reflected in both the current and standard parameters. As a result, it is possible to suppress a situation in which the driving device is inadvertently driven too much, and to suppress misfire and increase in noise during the transition period, thereby enabling the self-ignition combustion to be maintained.

  Further, when the update correction of the reference combustion state parameter is accumulated and the cumulative number becomes a predetermined number, the reference combustion state parameter after the update correction is compared with the previously stored reference combustion state parameter, and the comparison result The stored reference combustion state parameter is updated and stored over the region of the operation state in which the reference combustion state parameter is prepared, and the comparison result between the reference combustion state parameter after the update storage and the current operation state parameter is stored. It is also possible to execute parameter correction according to the above.

This has the following advantages.
An engine is not operated constantly over its operable range, but is normally operated in a limited range. For example, in a vehicle, start and travel are repeated, but there are limited operating regions in which the driving region at the time of starting and the driving region at the time of traveling are regularly used. For this reason, it is possible to reflect the update correction of the reference combustion state parameter cumulatively performed during engine operation in such a limited operation region over the region of the operation state in which the reference combustion state parameter is prepared. it can. As a result, even when the engine is operated in a region outside the normal operation region, the drive device such as the fuel injection valve can be driven and controlled according to the above-described situation change such as the difference in fuel properties. Even in the operation region, the above-described effects such as avoidance of engine misfire can be achieved.

  Further, in an engine having a plurality of cylinders, the combustion state parameter is calculated based on the output transition of a sensor provided in a certain cylinder, and then the above-described parameter correction is performed. It can also be used for control.

This has the following advantages.
In the multi-cylinder engine, the combustion state for each cylinder is not uniform as described above, and therefore, the operating condition range in which self-ignition combustion is possible also differs for each cylinder. Therefore, if the operating condition range in which self-ignition combustion is possible is the narrowest in the cylinder to which the sensor is to be installed, the operating condition range for this cylinder can be expanded. This is useful for expanding the range of possible operating conditions.

  In addition, a sensor is provided for each cylinder of the multi-cylinder engine, and the current combustion state parameter calculation, reference combustion state parameter storage, and parameter correction are executed for each cylinder from the sensor output transition for each cylinder. It is also possible to perform drive device control for each of the plurality of cylinders using the parameter correction result performed for.

  In this way, the combustion state in the combustion chambers of all cylinders can be reflected in the equipment control in line with the respective combustion chambers. The operating range in which self-ignition combustion is possible can be expanded.

  Next, embodiments of the present invention will be described based on examples. FIG. 1 is an explanatory diagram conceptually showing the structure of a gasoline engine 100 as an embodiment of the present invention. FIG. 1 shows the structure of the combustion chamber when a cross section is taken at the center of the combustion chamber of the gasoline engine 100.

  The combustion chamber of the gasoline engine 100 includes a hollow cylindrical cylinder 142 provided in the cylinder block 140, a piston 144 that slides up and down in the cylinder 142, and a cylinder head 130 provided on the cylinder block 140. Is formed by. A cylindrical body constituted by both the cylinder block 140 and the cylinder head 130 is called a “cylinder” in a broad sense. Each combustion chamber is provided with an in-cylinder pressure sensor 36 (also referred to as “combustion pressure sensor”) for measuring the internal pressure (also referred to as “in-cylinder pressure”) of the combustion chamber.

  The cylinder head 130 includes an air supply valve 132 that opens and closes an opening of an air supply port through which intake air flows, an exhaust valve 134 that opens and closes an opening of an exhaust port through which exhaust gas flows out, a spark plug 136, a combustion A fuel injection valve 14 for injecting fuel into the room in a mist form is provided. The supply valve 132 and the exhaust valve 134 are driven by electric actuators 162 and 164, respectively. The electric actuators 162 and 164 can open and close the supply valve 132 and the exhaust valve 134 at an arbitrary timing. Note that the air supply valve 132 and the exhaust valve 134 may be driven by a hydraulic actuator or a cam mechanism instead of the electric actuator.

  An air supply passage 12 that guides intake air is connected to the air supply port, and an exhaust passage 16 through which exhaust gas passes is connected to the exhaust port. A catalyst 26 for purifying air pollutants contained in the exhaust gas and a turbine 52 of the supercharger 50 are provided downstream of the exhaust passage 16. Exhaust gas passing through the exhaust passage 16 is released into the atmosphere after rotating the turbine 52. The air supply passage 12 is provided with a compressor 54 for the supercharger 50. The compressor 54 is connected to the turbine 52 via a shaft 56, and the compressor 54 also rotates when the turbine 52 rotates by the exhaust gas. As a result, the compressor 54 pressurizes the air sucked from the air cleaner 20 and then pumps it toward the air supply port.

  Since air temperature rises when pressurized by the compressor 54, an intercooler 62 is provided downstream of the compressor 54 in order to cool the intake air. A surge tank 60 and a throttle valve 22 are also provided in the air supply passage 12. The surge tank 60 has a function of relaxing pressure waves generated when the combustion chamber sucks air, and the throttle valve 22 is set to an appropriate opening degree by the electric actuator 24 to adjust the intake air amount. It has a function to do.

  The piston 144 is connected to a crankshaft 148 via a connecting rod 146, and a crank angle sensor 32 that detects a crank angle is attached to the crankshaft 148.

  The operation of the gasoline engine 100 is controlled by an engine control unit (hereinafter referred to as ECU) 30. The ECU 30 detects the engine rotational speed Ne and the accelerator opening degree θac, and executes control of the opening degree of the throttle valve 22, ignition timing control of the spark plug 136, and control of the fuel injection valve 14 based on these. The engine speed Ne is detected by the crank angle sensor 32, and the accelerator opening degree θac is detected by an accelerator opening sensor 34 built in the accelerator pedal.

  The ECU 30 calculates the combustion state parameter indicating the combustion state of each combustion chamber based on the output transition of the pressure (internal pressure) accompanying the fuel combustion in each combustion chamber detected by the in-cylinder pressure sensor 36, and this combustion state parameter. Thus, the fuel injection valve 14, the air supply valve 132, the exhaust valve 134 and the like are driven and controlled. This function will be described later.

  FIG. 2 is a map showing an operation mode of the gasoline engine 100 of the embodiment. As shown in this map, the gasoline engine 100 of the embodiment can be switched between two-cycle operation and four-cycle operation. The horizontal axis in FIG. 2 is the engine speed, and the vertical axis is the load (torque). A two-cycle operation is executed when the engine speed is low, and a four-cycle operation is executed when the engine speed is high. The two-cycle operation region is divided into a spark ignition region at low load and high load and a self-ignition region at medium load. The self-ignition region is an operation region in which combustion is caused by self-ignition without performing spark ignition. In the spark ignition region, the engine is operated in a state where the excess air ratio is close to 1 (so-called “stoichi”). On the other hand, in the self-ignition region, the engine is operated in a lean state where the excess air ratio is large (for example, the excess air ratio is 2 or more). Note that self-ignition combustion can be performed even during four-cycle operation.

  The reason why the 2-cycle operation and the 4-cycle operation are properly used is as follows. In general, in a two-cycle operation, an explosion occurs once per rotation of the crankshaft. Therefore, under the same fuel injection amount, approximately twice the torque of a four-cycle operation can be obtained. Therefore, when the same torque is output, two-cycle operation requires less fuel injection than four-cycle operation, allowing operation under leaner conditions (conditions with a larger excess air ratio). It is. By operating the gasoline engine under leaner conditions, it is possible to improve fuel consumption and reduce the concentration of pollutants in the exhaust gas. Furthermore, it is known that if self-ignition operation is performed, the effects of improving fuel consumption and significantly reducing the concentration of pollutants in exhaust gas are further enhanced. However, in the two-cycle operation, so-called scavenging (operation of pushing out exhaust gas by supplying air) is performed, but scavenging may not be sufficiently performed at high speed. Therefore, four-cycle operation is more suitable for high-speed operation conditions.

  FIG. 3 is an explanatory view showing the state of self-ignition combustion in the two-cycle operation. 3 (a) to 3 (c) show the expansion / exhaust / first scavenging stroke (lowering stroke) in the two-cycle operation, and FIGS. 3 (d) to (f) show the second scavenging / intake / compression. The process (up process) is shown. FIG. 4 schematically shows the opening / closing period of the supply valve (IN valve) and the exhaust valve (EX valve) during the two-cycle operation.

  FIG. 3A shows a state in which the air-fuel mixture in the combustion chamber has started combustion by self-ignition. When the air-fuel mixture burns, high-pressure combustion gas is generated in the combustion chamber and pushes down the piston 144. When the piston 144 is lowered to a certain extent, the exhaust valve 134 is opened at an appropriate timing (FIG. 3B). In the example of FIG. 4, the exhaust valve 134 is opened at a timing of about 70 ° before the bottom dead center (BDC) of the piston.

  When the supply valve 132 is opened at a timing when the combustion gas flows out from the exhaust valve to some extent, air flows in from the supply port (FIG. 3C). Since the air in the air supply passage 12 is pressurized to a predetermined pressure by the supercharger 50, the combustion gas in the combustion chamber can be scavenged by the fresh air flowing from the air supply valve 132. In the example of FIG. 4, the supply valve 132 is opened at a timing of about 60 ° before the bottom dead center (BDC) of the piston.

  During the scavenging period and when the piston 144 is in the vicinity of bottom dead center, the fuel injection valve 14 injects fuel spray into the combustion chamber (FIGS. 3D and 4). Since the exhaust valve 134 is closed soon after the bottom dead center, if the fuel spray is injected in the vicinity of the bottom dead center, the injected fuel spray is hardly discharged from the exhaust valve 134, and the fuel and fresh air Can be mixed well.

  After the fuel is injected, after closing the exhaust valve 134 at a predetermined timing, as shown in FIG. 3E, the pressurized air flows from the air supply valve 132 into the combustion chamber. In the example of FIG. 4, the timing for closing the exhaust valve 134 is set to about 50 ° after the bottom dead center of the piston. The fuel spray injected during the scavenging period is dispersed in the combustion chamber by the flow of intake air and mixed with the intake air.

  After the air supply valve 132 is closed, the air-fuel mixture in the combustion chamber is compressed as the piston 144 rises. While the air supply valve 132 is open, the air-fuel mixture in the combustion chamber cannot be compressed even if the piston rises. Therefore, in the two-cycle operation, the substantial compression ratio of the air-fuel mixture is determined by the timing at which the air supply valve 132 is closed. In the example of FIG. 4, the timing for closing the air supply valve 132 is set to about 60 ° after the bottom dead center of the piston.

  When the piston 144 is raised after the air supply valve 132 is closed, the air-fuel mixture is compressed in the combustion chamber and self-ignited near the top dead center of the piston 144 as shown in FIG. As a result, the air-fuel mixture formed in the combustion chamber can be burned quickly.

  As described above, in the two-cycle self-ignition operation, the lean air-fuel mixture having a large excess air ratio is compressed and self-ignited, so that the fuel consumption can be reduced and the emission amount of air pollutants can be greatly reduced. . In addition, since the fuel injection amount increases at a high load and the excess air ratio decreases, knocking tends to occur during compression. In view of this, it is preferable to set the compression ratio slightly low at the time of high load and to burn the air-fuel mixture by igniting with a spark plug. On the other hand, when the load is extremely low, the self-ignition may become unstable because the fuel injection amount is small. Therefore, the air-fuel mixture may be burned by igniting with an ignition plug even at an extremely low load.

  FIG. 5 is an explanatory diagram illustrating a configuration related to combustion state control in the embodiment. The ECU 30 includes a combustion state parameter calculation unit 42, a parameter correction & device control unit 44, a device control parameter map 46, and a combustion state parameter map 48. The functions of the combustion state parameter calculation unit 42 (hereinafter simply referred to as “calculation unit”) and the parameter correction & device control unit 44 (hereinafter simply referred to as “correction / control unit”) are stored in a memory in the ECU 30. Realized by a computer program. Both the device control parameter map 46 and the combustion state parameter map 48 are stored in advance in a nonvolatile memory in the ECU 30, but the contents can be updated as will be described later and are retained even after the power is turned off.

  The calculation unit 42 calculates the current combustion state parameter (indicating the combustion state of each combustion chamber) from the output transition of the pressure accompanying the fuel combustion in each combustion chamber detected by the in-cylinder pressure sensor 36 and the crank angle output of the crank angle sensor 32. The current combustion state parameter) is calculated. Various parameters can be used as the present combustion state parameters. For example, the pressure increase rate dP / dθ, the heat generation rate dQ / dθ, and the heat generation amount Q shown in FIG. 6 can be calculated from the relationship between the in-cylinder pressure P and the crank angle θ. A specific value associated with can be used as the combustion state parameter. More specifically, for the kth combustion chamber, any one of the maximum pressure increase rate dPk, the maximum heat generation rate dQk, and the ignition timing Xk can be used as the current combustion state parameter of the combustion chamber. Here, the ignition timing Xk is defined as the time when the heat generation amount Q reaches 2% of the final generation amount. However, the ignition timing Xk may be a parameter that quantitatively indicates the timing of actual ignition in the combustion chamber, and other definitions may be used.

  The correction / control unit 44 drives and controls the fuel injection valve 14 and the like based on the comparison between the current combustion state parameter given from the calculation unit 42 and the parameters stored in the device control parameter map 46 and the combustion state parameter map 48. The fuel injection valve 14 and the like are driven and controlled while correcting the control parameters for the operation. As control parameters, the opening / closing timing of the air supply valve 132, the opening / closing timing of the exhaust valve 134, the fuel injection amount from the fuel injection valve 14, the presence or absence of ignition of the spark plug 136, the valve opening of a throttle valve (not shown), and the like are used. Is possible. This control parameter is set in advance in the form of a map in association with the operating state defined by the engine speed and load (fuel injection amount), and is stored in the device control parameter map 46.

  The parameters stored in the combustion state parameter map 48 are to be compared with the current combustion state parameters given from the calculation unit 42, and include the same quality as the current combustion state parameters and indicate the combustion state of the combustion chamber. Contains parameters. This parameter is stored in the combustion state parameter map 48 for each combustion chamber (cylinder) as a reference combustion state parameter set in advance in association with the operating state defined by the engine speed and load (fuel injection amount). Has been. As described above, when the ignition timing Xk is used as the current combustion state parameter, the combustion state parameter map 48 stores the reference ignition timing Yk as the reference combustion state parameter and the like in association with the operation state in a map form.

  FIG. 7 is a flowchart showing a procedure of combustion state control in the embodiment. This procedure is a control procedure for the kth combustion chamber, and the control of each combustion chamber is executed in this procedure. The parameters used below (for example, Xijk) are subscripts “ijk” that are associated with the operating state of the engine and the combustion chamber number (cylinder number), where “i” represents the engine speed, “ “j” means an engine load (fuel injection amount), and “k” means a parameter value relating to the kth combustion chamber.

  The combustion state control of FIG. 7 is repeatedly executed for each combustion chamber (cylinder) at predetermined time intervals. First, for the kth combustion chamber, the current ignition timing Xijk (FIG. 6) and the combustion state parameter are set. The reference ignition timing Yijk stored in the map 48 is compared (step S100). Here, the current ignition timing Xijk represents the current ignition timing calculated and calculated as shown in FIG. 6 for the kth combustion chamber at the current rotational speed i and engine load j. The reference ignition timing Yijk is determined by referring to the map stored in the combustion state parameter map 48 for the kth combustion chamber and determined by the current rotational speed i and engine load j, and is read from the combustion state parameter map 48. The calculated current ignition timing Xijk is a map-like data associated with the current rotational speed i and the engine load j each time the combustion state control of FIG. The parameter map 48 is updated and stored.

  If it is determined in step S100 that the absolute value of the difference between the current ignition timing Xijk and the reference ignition timing Yijk is within the allowable ignition timing difference Mijk as a result of parameter comparison in step S100, the subsequent processing is performed once. This control is terminated. In this case, the fuel injection valve 14, the air supply valve 132, the exhaust valve 134, and the like are driven and controlled based on the control parameters (fuel injection amount, valve opening timing, etc.) stored in the device control parameter map 46. The ignition timing difference Mijk is set in advance, and is stored in the combustion state parameter map 48 as map-like data associated with the rotational speed i and the engine load j. The ignition timing difference Mijk is read from the combustion state parameter map 48 when comparing the ignition timing. The ignition timing difference Mijk can be changed and set.

  On the other hand, as a result of parameter comparison in step S100, if it is determined that the difference between the current ignition timing Xijk and the reference ignition timing Yijk exceeds the allowable ignition timing difference Mijk, the current ignition timing Xijk is separated from the reference ignition timing Yijk. If so, the process proceeds to step S110 and subsequent steps. Following the affirmative determination in step S100, the ignition timing is learned by the following equation 1 in accordance with the transition status of the current ignition timing Xijk, and the learned ignition timing Gijk is calculated (step S110).

  Gijk <-(Gijk '* Nijk + Xijk) / (Nijk + 1) ... Formula 1

  Here, Gijk represents the learning ignition timing learned in step S110 in the current processing, and Gijk ′ represents the learning ignition timing learned in step S110 in the previous processing. Nijk is a counter value of the number of times of learning at the ignition timing.

  As is apparent from Equation 1, in step S110, the previous learning ignition timing Gijk ′ calculated by learning the previous time and the current current ignition timing Xijk are weighted and averaged, and the calculated value is used as the current learning ignition timing Gijk. . In step S110, along with this learning, the number of learnings Nijk is incremented by 1 and the number of learning times is also counted. The learning ignition timing Gijk is updated and stored in the combustion state parameter map 48 as the map-like data in which the current and previous values are associated with the current rotational speed i and the engine load j.

  Next, the number of times of ignition timing is compared with a predetermined value (in this embodiment, value 10000) based on the value of the number of times of learning Nijk (step S120). If an affirmative determination is made that the number of learnings has reached a predetermined value, the process proceeds to step S130. If a negative determination is made, the process proceeds to step S140 without performing a correction process described later in step S130.

  In step S130, since the ignition timing is learned a predetermined number of times, the following ignition timing correction is performed to reflect the learning result. First, the learning ignition timing Gijk is set to the learning correction ignition timing Zijk, and the value zero is set to the learning number Nijk and the learning ignition timing Gijk. At the same time, the number of corrections NHijk indicating the number of times of learning correction of the ignition timing is incremented by 1 and the number of learning corrections is also counted. Further, the fuel correction amount QHijk of the fuel injection amount of the fuel injection valve 14 is also calculated from the following equation 2 by reflecting this learning correction ignition timing Zijk.

  QHijk ← QHijk + (Zijk−Yijk) * Hijk ... Equation 2

  Here, Hijk is a fuel correction coefficient when the fuel correction amount QHijk is obtained by reflecting the learning correction ignition timing Zijk, and is multiplied by the difference (ignition timing difference) between the learning correction ignition timing Zijk and the reference ignition timing Yijk. Thus, a unit corresponding to the value corresponding to the fuel injection correction amount can be calculated. Further, the fuel correction coefficient Hijk is set as data having a property that a multiplication value (a fuel injection correction amount equivalent amount) with the ignition timing difference reduces the ignition timing difference. The fuel correction coefficient Hijk is preset and stored in the combustion state parameter map 48 as map-like data associated with the rotational speed i and the engine load j. Read out.

  As is apparent from Equation 2, in step S130, a value (corrected amount calculated value) obtained by multiplying the difference (ignition timing difference) between the learning corrected ignition timing Zijk and the reference ignition timing Yijk by the fuel correction coefficient Hijk is calculated. In addition to the correction amount QHijk, the result is set to the fuel correction amount QHijk. In this case, since the current ignition timing Xijk is reflected through the learning ignition timing Gijk in the learning correction ignition timing Zijk, the current ignition timing Xijk is also reflected in the fuel correction amount QHijk calculated from Equation 2. . Since the learning ignition timing Gijk is a learning value that has undergone a weighted average of the current ignition timing Xijk, the learning correction ignition timing Zijk reflected by the learning ignition timing is used for calculating the fuel injection correction amount. For this reason, coupled with the fact that the fuel correction coefficient Hijk is data having a property of reducing the ignition timing difference, the control intention that the deviation of the ignition timing is small appears in the fuel correction amount QHijk obtained by Equation 2. .

  Since step S130 is performed when the ignition timing is learned a predetermined number of times, when learning of the ignition timing is small, the learning correction ignition timing Zijk set and the fuel correction amount QHijk are not calculated.

  Even in the learning correction ignition timing Zijk and the fuel correction amount QHijk determined as described above, the data is updated and stored in the combustion state parameter map 48 as map-like data associated with the current rotational speed i and the engine load j. The Note that the above calculation is performed with the initial value of the learning correction ignition timing Zijk being the reference ignition timing Yijk and the initial value of the fuel correction amount QHijk being zero.

  Following the processing in step S130 or the negative determination in step S120, the current ignition timing Xijk is compared with the learning correction ignition timing Zijk set in step S130, and the absolute value of the difference is an allowable ignition timing. It is determined whether the difference is within the difference Mijk (step S1140). In this case, if the process is subsequent to the negative determination in step S120, the learning correction ignition timing Zijk calculated in the main control up to the previous time is used.

  If a negative determination is made in step S140, the process proceeds to step S150, the final fuel injection amount QFijk is calculated, and this control is temporarily terminated. In step S150, the map stored in the device control parameter map 46 for the kth combustion chamber is referred to, and the fuel injection amount Qijk is read based on the current rotational speed i and engine load j, and obtained in step S130. The fuel correction amount QHijk is added and set to the final fuel injection amount QFijk. Thus, the fuel injection valve 14 is driven and controlled based on the calculated final fuel injection amount QFijk.

  In step S150 following the negative determination in step S140, the current ignition timing Xijk obtained when the current main control is executed is compared with the learning correction ignition timing Zijk obtained by the previous control execution. It is the case when it has not changed beyond. Therefore, in the calculation of the final fuel injection amount in step S150, the fuel correction amount QHijk reflected by the current ignition timing Xijk through the learning ignition timing Gijk (step S110) and the learning correction ignition timing Zijk (step S130) is used as the fuel injection amount Qijk. Take into account.

  On the other hand, if it is determined that the difference between the current ignition timing Xijk and the learning corrected ignition timing Zijk exceeds the allowable ignition timing difference Mijk as a result of the parameter comparison in step S140, the current ignition timing Xijk becomes the learning corrected ignition timing Zijk. Since the distance is too far, the process proceeds to step S160 and subsequent steps. Following the affirmative determination in step S140, the number of times of learning correction of the ignition timing is compared with a predetermined value (in this embodiment, value 100) based on the value of the number of corrections NHijk (step S160). If an affirmative determination is made that the number of learning corrections has reached a predetermined value, the process proceeds to step S170, and if a negative determination is made, the process proceeds to step S190 described later without performing a correction process described later from step S170.

  If the determination in step S160 is affirmative, the set of the learning correction ignition timing Zijk in step S130 based on the current ignition timing Xijk being separated from the reference ignition timing Yijk and the fuel correction amount QHijk using the learning correction ignition timing Zijk. Is calculated cumulatively. Moreover, it means that the current ignition timing Xijk is also separated from the learning corrected ignition timing Zijk (Yes determination in step S140). As described above, the phenomenon in which the current ignition timing Xijk is separated from the reference ignition timing Yijk and the learning corrected ignition timing Zijk is the combustion before the combustion state in the combustion chamber causes such a setting of the learning corrected ignition timing Zijk. It is expected to appear when it changes from the situation.

  For example, in an engine mounted on a vehicle, the properties of fuel to be used (heavy / light, octane number, cetane number, etc.) are not uniform and often differ depending on the fueling area, the fueling timing, and the like. Alternatively, there may be a case where light oil is erroneously supplied to the gasoline engine due to human error during refueling. However, since the reference ignition timing Yijk is determined by a method such as an experiment assuming a predetermined fuel, it cannot be said that such a difference in fuel properties is planned. Therefore, even in the fuel correction amount QHijk calculated using the reference ignition timing Yijk and the learning correction ignition timing Zijk (step S130), it is difficult to reflect the difference in fuel properties.

  The same can be said for changes over time in the engine components. For example, in the initial state of operation and the state in which the usage time has elapsed, the fuel injection amount at the fuel injection valve 14 may slightly change due to adhesion of fuel combustion residue to the valve mechanism. Various phenomena involving not only the fuel injection valve 14 but also the air supply valve 132 and the exhaust valve 134 (such as misalignment of the supply / exhaust timing, air amount due to leakage, scavenging efficiency, etc.) may also change, and the combustion state of the combustion chamber Can affect.

  In other words, if there is no change in fuel properties or change over time, it can be said that the phenomenon that the current ignition timing Xijk is separated from the reference ignition timing Yijk and the learning corrected ignition timing Zijk is unlikely to occur, but such a phenomenon has occurred. Therefore (the affirmative determination in step S100 and step S140 and its continuation), the processing after step S170 is executed in order to cope with the change in fuel properties and the change with time.

Moreover, the situation where the learning correction of the ignition timing and the calculation of the fuel correction amount occur cumulatively due to the positive determination in step S160 can be considered as follows.
When the driver drives the vehicle, it is difficult to say that the engine is operated evenly over the entire allowable rotational speed range, and the engine is operated in a limited region within the rotational speed range. . Therefore, it is considered that the learning correction of the ignition timing and the calculation of the fuel correction amount occurred cumulatively in this limited operation region. Then, in the engine operation region other than this limited region, the learning correction of the ignition timing and the fuel correction amount calculation are not performed, but even in such a region, the same measures as in a certain limited region should be taken. Is desirable.

  In consideration of these matters, in step S170 following the affirmative determination in step S160, a difference correction amount A used for fuel injection amount correction described later is obtained by the following equation 3.

  A ← (Zijk−Yijk) * Lijk ... Equation 3

  Here, Lijk is a correction coefficient set in advance, and is set and stored in advance in the combustion state parameter map 48 as map-like data associated with the rotational speed i and the engine load j. Then, the correction coefficient Lijk is read from the device control parameter map 46 in the calculation of Expression 3. Even with this correction coefficient Lijk, there is a unit that enables the calculation of the difference correction amount A at the time of fuel injection amount correction by multiplication with the ignition timing difference (Zijk−Yijk), similarly to the fuel correction coefficient Hijk described above. The calculated difference correction amount A is set as data having a property of reducing the ignition timing difference (Zijk−Yijk).

  After the calculation of the difference correction amount A, the learning correction ignition timing Zijk and the fuel correction amount QHijk are corrected for the entire map as described below (step S180). As a result, the map data is corrected not only for the normal operation region of the engine but also for other regions.

In this map correction, the engine speed (fuel injection amount) is set to 4 mm ³ over a range of zero to 60 mm ³ / st with respect to the engine load (fuel injection amount) every 400 rpm over a range of zero to 6000 rpm. / St is performed from the first cylinder (fuel chamber) to each of the third cylinders. The correction target is the learning correction ignition timing Zijk and the fuel correction amount QHijk. For the learning correction ignition timing Zijk, the difference correction amount A in step S170 is added to the reference ignition timing Yijk, and this is the learning correction ignition timing. Set to Zijk. Thus, the learning correction ignition timing Zijk is updated and corrected for each rotation speed and engine load described above, and this update correction is performed for each combustion chamber. This update result is rewritten and stored in the combustion state parameter map 48 as map-like data associated with the rotational speed i and the engine load j.

  As for the fuel correction amount QHijk, a value obtained by multiplying the difference between the learning correction ignition timing Zijk and the reference ignition timing Yijk by the fuel correction coefficient Hijk is set to the fuel correction amount QHijk. Thus, the fuel correction amount QHijk is updated and corrected for each rotation speed and engine load described above, and this update correction is performed for each combustion chamber. This update result is rewritten and stored in the combustion state parameter map 48 as map-like data associated with the rotational speed i and the engine load j. The fuel correction amount QHijk updated in this way is used for the processing of step S130 and step S150 described above in the next and subsequent main control.

  When calculating the fuel correction amount QHijk, the fuel correction coefficient Hijk described in step S130 is used, and the learning correction ignition timing Zijk reflecting the learning ignition timing Gijk is also used. Therefore, the correction in step S180 is performed. The control intention that the deviation of the ignition timing is reduced also in the quantity.

  In addition to the above correction, in step S180, a value of zero is set in the correction number NHijk indicating the learning correction number of the ignition timing, and the correction number is reset.

  Following the processing in step S180 or the negative determination in step S160, the final fuel injection amount QFijk is calculated from the following equation 4 in step S190, and this control is temporarily terminated.

  QFijk ← Qijk + QHijk + (Xijk−Zijk) * Hijk ... Equation 4

  The fuel injection amount Qijk is read based on the current rotational speed i and engine load j with reference to the map stored in the device control parameter map 46 for the kth combustion chamber. The learning correction ignition timing Zijk and the fuel correction amount QHijk are the steps after the update correction in step S180 if step S190 is a process following step S180, and the previous steps if the negative correction in step S160 is followed. What was obtained in S130 is used.

  Note that since the fuel correction coefficient Hijk and the learning correction ignition timing Zijk are also used in step S190, the control intention that the deviation of the ignition timing is small appears in the calculated correction amount of fuel injection.

  When the final fuel injection amount QFijk is thus calculated, the fuel injection valve 14 is driven and controlled based on the calculated final fuel injection amount QFijk.

  As described above, according to the gasoline engine 100 of the embodiment, the pressure (internal pressure) associated with fuel combustion is detected by the in-cylinder pressure sensor 36 for each combustion chamber, and based on the detection output transition, as shown in FIG. The current ignition timing Xijk indicating the current combustion state of each combustion chamber is calculated, and the fuel injection valve 14 is driven and controlled using the current ignition timing Xijk as follows.

  First, the current ignition timing Xijk and the reference ignition timing Yijk are compared (step S100), and if the difference is large, the fuel injection amount (final fuel injection amount QFijk) that is a control parameter for driving the fuel injection valve 14 is controlled. ) Is corrected for each combustion chamber (steps S130 and S180), and the fuel injection valve 14 is driven and controlled with this final fuel injection amount QFijk. For this reason, a situation where the current ignition timing Xijk changes from the ignition timing (reference ignition timing Yijk) assumed at the time of designing and manufacturing the gasoline engine 100, that is, fuel having a property different from the assumed fuel described above is used. Even in such a situation or a situation where the influence of aging of the device appears, the fuel injection valve 14 can be driven by reflecting the change in the ignition timing due to such a change in the situation. The misfire and noise increase described above can be suppressed. In addition, since such device control is performed for each combustion chamber, the combustion state in all the combustion chambers can be reflected in device control in accordance with each combustion chamber, so that the gasoline engine 100 as a whole can perform self-ignition combustion. There is an effect that the range can be expanded.

  Further, if the current ignition timing Xijk is separated from the reference ignition timing Yijk, the learning ignition timing Gijk (learning corrected ignition timing Zijk) according to the transition status of the current ignition timing Xijk is subjected to learning calculation (steps S110 and 130). In addition, the final fuel injection amount QFijk is corrected and calculated for each combustion chamber by reflecting this learned ignition timing Gijk (learned corrected ignition timing Zijk) (step S190). For this reason, if the situation surrounding the engine changes (fuel property change / aging change, etc.), such situation change is learned and the result is reflected in the final fuel injection amount QFijk. Can be controlled. Moreover, even during the transition period of the situation transition, the equipment can be controlled following the situation transition, so the fuel injection amount correction can be prevented from increasing carelessly even during the transition period immediately after refueling. This is useful for avoiding misfires and noise during the transition period.

  In addition, in this embodiment, when the learning calculation number of the learning ignition timing Gijk (learning correction ignition timing Zijk) according to the transition state of the current ignition timing Xijk reaches a predetermined number (step S160), the learning correction ignition timing Zijk The correction is made for the entire map (that is, for almost the entire region of the engine operating state), and the corrected fuel correction amount Qijk is calculated using the corrected learning correction ignition timing Zijk and the current ignition timing Xijk. (Xijk−Zijk) * Hijk) is calculated (step S180), and the final fuel injection amount QFijk is corrected and calculated for each combustion chamber (step S190). Therefore, as described above, the result of learning correction performed when the engine is operated in a certain operation state can be reflected in the operation state in almost the entire region. For this reason, even when the engine is operated in a region outside the normal operation region, the drive control of the fuel injection valve 14 can be performed according to the above-described situation change surrounding the engine. However, the above-described effects such as avoidance of engine misfire can be achieved.

Next, a modification of the above embodiment will be described.
In the above embodiment, the in-cylinder pressure sensor 36 is provided in each cylinder (each combustion chamber), and the fuel injection correction described above is performed for each cylinder from the transition thereof. However, the following modifications may be made.

  First, the in-cylinder pressure sensor 36 is installed in one cylinder. The cylinder to be installed has the narrowest operating condition range in which self-ignition combustion explained in FIG. 2 is possible. The sensor installation target cylinder can be determined from a combustion state monitor or the like after completion of the engine. Then, the combustion state control shown in FIG. 7 is executed for the sensor installation target cylinder based on the sensor output transition, and the drive control of the fuel injection valve 14 for each cylinder is performed using the obtained final fuel injection amount QFijk. Do.

  According to this modification, since the operating condition range can be expanded for a cylinder having a narrow operating condition range in which self-igniting combustion is possible, the operating condition range in which self-igniting combustion is possible can be expanded as the entire engine. .

Further, the sensor to be used is not limited to the in-cylinder pressure sensor 36, and can be modified as follows.
FIG. 8 is an explanatory view conceptually showing the configuration of the engine of a modified example in which the ignition timing is detected by the temperature sensor 200 provided in the cylinder, and FIG. It is explanatory drawing which showed notionally the structure of the engine of the modification about the principal part.

  As shown in these drawings, the temperature sensor 200 is incorporated facing the inside of the combustion chamber, and outputs the temperature transition in the combustion chamber to the ECU 30 through the temperature converter 210. As a specific configuration of such a temperature sensor, a thermocouple can be exemplified, and a gas seal is applied to the sensor mounting portion for installation. In this case, the thermocouple as the temperature sensor 200 has its detection end positioned slightly inside the combustion chamber wall surface, and detects the heat flux flowing through the combustion chamber wall surface. The ECU 30 processes this sensor output in synchronization with the crank angle from the crank angle sensor 32, and calculates the combustion chamber temperature for each crank angle. And the present ignition timing Xijk is calculated | required from the calculation result. Thereafter, the combustion state control shown in FIG. 7 is executed, and drive control of the fuel injection valves 14 for each cylinder is performed using the obtained final fuel injection amount QFijk.

  According to the above-described modification, since the temperature in the combustion chamber can be directly obtained, the current ignition timing Xijk can be easily calculated, and the engine system can be obtained by using the temperature sensor 200 (thermocouple) having a simple configuration. As a result, the cost can be reduced.

  In this modification, the thermocouple as the temperature sensor 200 is preferably a low heat mass having a sheath outer diameter of about 0.1 mm from the viewpoint of responsiveness. Moreover, it is preferable that the detection single position is a place where gas flow such as squish is not so intense in the combustion chamber.

  FIG. 10 is an explanatory view conceptually showing the configuration of the engine of a modified example in which the ignition timing is detected by the ion probe 220 provided in the cylinder, and FIG. 11 is an optical diagram in which the ignition timing is provided in the cylinder. It is explanatory drawing which showed notionally the structure of the engine of the modification which deform | transformed so that it might detect with the sensor 240 about the principal part.

  The modification shown in FIG. 10 utilizes the phenomenon that when a flame reaches between electrodes having a potential difference, an ionic current flows between the electrodes, and the ionic current value is determined by the state of the flame (combustion state). . The ion probe 220 includes a center electrode at the center thereof, and is in a state of being incorporated with the center electrode facing the inside of the combustion chamber, and the center electrode is insulated from the combustion chamber wall functioning as a ground electrode. The ion probe 220 receives a voltage of about 5 to 50 V from the ion current detector 230 to the center electrode, and converts the ion current corresponding to the flame state (combustion state) associated with the fuel combustion in the combustion chamber to the ion current. Output to the ECU 30 through the detector 230. Note that the ion probe 220 can also be on the top side of the combustion chamber, similar to the temperature sensor 200.

  The ECU 30 processes this sensor output (ion current value) in synchronization with the crank angle from the crank angle sensor 32, and obtains the current ignition timing Xijk based on the transition of the ion current value. Thereafter, the combustion state control shown in FIG. 7 is executed, and drive control of the fuel injection valves 14 for each cylinder is performed using the obtained final fuel injection amount QFijk.

  According to this modification, as in the modification of FIG. 9, the cost of the engine system can be reduced through the simplification of the sensor configuration.

  In the modification shown in FIG. 11, the detection end of the optical sensor 240 containing sapphire glass is incorporated facing the inside of the combustion chamber, and the optical sensor 240 allows the combustion light accompanying the combustion of fuel in the combustion chamber to be emitted. The state (combustion state) is detected, and the output is output to the ECU 30 through the light intensity detector 250. Note that the optical sensor 240 can also be the top side of the combustion chamber, similar to the temperature sensor 200.

  The ECU 30 processes this sensor output (combustion light amount) in synchronization with the crank angle from the crank angle sensor 32, and obtains the current ignition timing Xijk based on the transition of the combustion light amount. Thereafter, the combustion state control shown in FIG. 7 is executed, and drive control of the fuel injection valves 14 for each cylinder is performed using the obtained final fuel injection amount QFijk.

  According to this modification, since the sensor sensitivity is high, more accurate device control is possible.

  The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

  In the above embodiment and its modification, the ignition timing Xk is used as the current combustion state parameter indicating the current combustion state of the combustion chamber, but the maximum pressure increase rate dPi and the maximum heat generation rate dQi as described in FIG. Etc. may be used.

  The drive device control based on the parameter correction includes correction control of the fuel injection amount of the fuel injection valve 14 and correction control of the valve opening timing of the air supply / exhaust valves (the air supply valve 132 and the exhaust valve 134) (actual compression thereby) Rate adjustment) and correction control of the valve opening of the throttle valve may be performed. For example, the scavenging period is reduced by the delay of the opening timing of the supply valve 132 and / or the advancement of the closing timing of the exhaust valve 134, the advancement of the opening timing of the supply valve 132, and / or the closing timing of the exhaust valve 134. In addition to increasing the scavenging period due to the retarded angle, air-fuel ratio correction after correction of the intake air amount can be used.

  In the above embodiment, the engine capable of switching between the 2-cycle operation and the 4-cycle operation has been described. However, the present invention can also be applied to an engine that performs only the 2-cycle operation. It can also be applied to a single cylinder engine.

It is explanatory drawing which showed notionally the structure of the gasoline engine 100 as an Example of this invention. It is a map which shows the operation mode of the gasoline engine 100 of an Example. It is explanatory drawing which shows the mode of the self-ignition combustion of 2 cycle operation. It is explanatory drawing which shows typically the opening / closing period of an air supply valve (IN valve) and an exhaust valve (EX valve) at the time of 2 cycle operation | movement. It is explanatory drawing which shows the structure relevant to the combustion state control in an Example. 6 is a graph showing a pressure increase rate dP / dθ, a heat generation rate dQ / dθ, and a heat generation amount Q calculated from an output transition of the in-cylinder pressure sensor 36. It is a flowchart which shows the procedure of the combustion state control in an Example. It is explanatory drawing which showed notionally the structure of the engine of the modification which deform | transformed so that an ignition timing might be detected with the temperature sensor 200 provided in the cylinder about the principal part. It is explanatory drawing which showed notionally the structure of the engine of the modification which changed the installation position of the temperature sensor 200 about the principal part. It is explanatory drawing which showed notionally the structure of the engine of the modification which deform | transformed so that ignition timing might be detected with the ion probe 220 provided in the cylinder about the principal part. It is explanatory drawing which showed notionally the structure of the engine of the modification which deform | transformed so that an ignition timing might be detected with the optical sensor 240 provided in the cylinder about the principal part.

Explanation of symbols

12 ... Air supply passage 14 ... Fuel injection valve 16 ... Exhaust passage 20 ... Air cleaner 22 ... Throttle valve 24 ... Electric actuator 26 ... Catalyst 32 ... Crank angle sensor 34 Accelerator opening sensor 36 Cylinder pressure sensor 42 Combustion state parameter calculation unit 44 Parameter correction & device control unit 46 Device control parameter map 48 Combustion state parameter map 50 ... supercharger 52 ... turbine 54 ... compressor 56 ... shaft 60 ... surge tank 62 ... intercooler 100 ... gasoline engine 130 ... cylinder head 132 ... supply Gas valve 134 ... Exhaust valve 136 ... Ignition plug 140 ... Cylinder block 142 ... Cylinder 144 ... Piston 146 ... Connecting rod 148 ... Crankshaft 162,164 ... Electric actuator 220 ... Ionop Lobe 240 ... Optical sensor 230 ... Ion current detector 250 ... Light intensity detector 200 ... Temperature sensor 210 ... Temperature converter

Claims (4)

An engine capable of compressing and igniting a fuel mixture in two cycles in a combustion chamber in a cylinder,
A fuel injection valve for supplying fuel to the combustion chamber;
An intake valve and an exhaust valve provided at the head of the combustion chamber;
Control means for controlling a drive device that is drive-controlled during operation of the engine and includes the fuel injection valve and the supply / exhaust valve, based on a predetermined control parameter in accordance with the engine operating state corresponding to the combustion state of the combustion chamber; ,
A sensor provided in the cylinder for detecting a physical phenomenon reflecting the combustion state of the combustion chamber;
The control means includes
Based on the output transition of the physical phenomenon detected by the sensor, a calculation unit that calculates a current combustion state parameter indicating a current combustion state of the combustion chamber;
A storage unit that presets a parameter indicating a combustion state of the combustion chamber in association with the operation state of the engine, and stores the parameter as a reference combustion state parameter;
Necessity of parameter correction for correcting the control parameter when controlling the drive device according to the degree of difference between the reference combustion state parameter corresponding to the current engine operating state and the calculated current combustion state parameter Determining means for determining
If necessary the determination of the parameter correction by said determining means reaches a predetermined number of times, before SL computed current combustion state parameter current combustion state in which the learning calculation combustion state parameter calculated was the arithmetic by learning arithmetic in response to the transition situation of correcting the previous SL control parameter by the correction calculation using the difference parameter, an engine and a correction unit to reduce the difference by controlling the driving device by using the control parameters after the correction. The engine according to claim 1,
The correction unit is
When the cumulative number of calculation calculations of the learning calculation combustion state parameter by the learning calculation becomes a predetermined number, each reference combustion stored in the storage unit for the region of the operating state in which the reference combustion state parameter is prepared the state parameter is corrected using the difference of the learning calculation combustion state parameter reference combustion state parameter already stored in the storage unit for the operating state when performing the calculation of the learning calculation combustion state parameter, after the correction engine you said learning calculation combustion state parameter using the reference combustion state parameter in the correction calculation. An engine according to claim 1 or claim 2,
A cylinder having a plurality of cylinders and having the sensor as a monitoring target,
The control means includes
An engine that controls the drive device for the plurality of cylinders using the parameter correction result performed by the correction unit for the cylinder to be monitored. An engine according to claim 1 or claim 2,
It has a plurality of cylinders, each sensor is provided with the sensor,
The control means includes
The present combustion state parameter calculation by the calculation unit, the reference combustion state parameter storage by the storage unit, and the parameter correction by the correction unit are executed for each cylinder, and the parameter correction result performed for each cylinder is obtained. And an engine for controlling the driving device for the plurality of cylinders.

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