JP2005188308A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device for an internal combustion engine, for providing good startability, by appropriately controlling an air-fuel ratio in start of an engine, even if fuel biased to a property not susceptible to vaporization caused by vaporization of fuel along with increase in temperature of a fuel tank is supplied to the internal combustion engine. <P>SOLUTION: A fuel vaporizing condition in the fuel tank 2 is estimated based on a temperature THt in a tank and pressure Pt in the tank. If the fuel vaporizing condition is excessive (YES in a step S2), a fuel injection time Ti is multiplied by a correction coefficient Kf to perform increase correction (a step S4). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to fuel injection control at the time of engine start.

  When the internal combustion engine is stopped after the warm-up is completed, the fuel path may be heated due to radiant heat from the engine itself or the exhaust system, and vapor may be generated in the fuel. It becomes a factor which makes fuel supply amount short. As is well known, since the fuel injection amount at the time of engine start is controlled in an open loop, various measures can be taken because the startability is deteriorated by leaning the air-fuel ratio without being able to cope with the shortage of supply by vapor. It has been proposed (see, for example, Patent Document 1).

In the fuel injection control device disclosed in Patent Document 1, the fuel pressure supplied to the fuel injection valve is corrected to increase when the internal combustion engine is started at a high temperature, thereby preventing leaning due to the occurrence of vapor and improving startability. I am trying.
Japanese Patent No. 2722446

However, the factor that deteriorates the startability of the internal combustion engine at the time of high temperature start is not only the vapor generated in the fuel, but also the phenomenon that the fuel supplied from the fuel tank is biased to be difficult to vaporize. The inventor found out.
That is, the temperature of the fuel tank of the vehicle rises due to the influence of high outside air temperature, heat carried by the high-temperature fuel returned from the engine during operation, radiant heat from the exhaust system under the floor, etc. Fuel vaporization in the tank becomes active. Since the fuel vaporization at this time starts from a component that is easily vaporized in the fuel, as a result, the component that is difficult to vaporize is concentrated in the fuel remaining as a liquid in the fuel tank. Therefore, at the time of subsequent start-up, fuel that is difficult to vaporize is supplied to the internal combustion engine, causing the air-fuel ratio to become lean and worsening the startability.

  As described above, this phenomenon occurs due to the temperature rise in the fuel tank, and the deviation of the fuel property, not the vapor itself accompanying the fuel vaporization, is the cause of the lean air-fuel ratio, and mainly the fuel path, fuel injection valve, etc. The vapor itself generated in the fuel due to the temperature rise is completely different from the vapor generation phenomenon that causes leaning. Therefore, with the countermeasure of the above-mentioned Patent Document 1 assuming vapor, it is not possible to determine the occurrence of a deviation in the fuel property in the fuel tank, and the air-fuel ratio cannot be controlled appropriately, and as a result, the leanness of the air-fuel ratio cannot be prevented. However, the startability could not be improved sufficiently.

  The object of the present invention is to accurately control the air-fuel ratio when starting the engine, even in a situation where fuel that is biased to a property that is difficult to vaporize due to fuel vaporization accompanying the temperature rise in the fuel tank is supplied to the internal combustion engine. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine that can realize a good startability.

  In order to achieve the above object, according to the first aspect of the present invention, the fuel stored in the fuel tank is supplied to the fuel injection valve of the internal combustion engine through the fuel path, and the fuel injection valve is injected based on the operating state of the internal combustion engine. In a fuel injection control device for an internal combustion engine that controls the amount, an in-tank vaporization state estimation unit that estimates a fuel vaporization state in the fuel tank, and a fuel tank internal state estimated by the in-tank vaporization state estimation unit when the internal combustion engine is started And a first injection amount correcting means for correcting an increase in the injection amount of the fuel injection valve when it is determined that the fuel vaporization state is excessive.

  Accordingly, when the fuel vaporization state in the fuel tank estimated by the in-tank vaporization state estimation unit is excessive at the start of the internal combustion engine, the first injection amount correction unit corrects the injection amount of the fuel injection valve to be increased. Even in a situation where fuel that is biased to properties that are difficult to vaporize is supplied to the internal combustion engine as the fuel is vaporized in the fuel tank, it is possible to prevent the air-fuel ratio from becoming lean.

  According to a second aspect of the present invention, there is provided an internal combustion engine that supplies fuel stored in a fuel tank to a fuel injection valve of an internal combustion engine through a fuel path and controls an injection amount of the fuel injection valve based on an operating state of the internal combustion engine. In the fuel injection control device, the vaporization state estimation means for estimating the vaporization state of the fuel in the fuel tank, and the fuel vaporization state in the fuel tank estimated by the tank vaporization state estimation means when the internal combustion engine is started are excessive. A first injection amount correction means for increasing and correcting the injection amount of the fuel injection valve, a vapor generation determination means for determining whether or not vapor is generated in the fuel supplied to the internal combustion engine, And a second injection amount correction means for increasing and correcting the injection amount of the fuel injection valve when the generation of vapor in the fuel is determined by the vapor generation determination means when the internal combustion engine is started.

  Accordingly, when the fuel vaporization state in the fuel tank estimated by the in-tank vaporization state estimation unit is excessive at the start of the internal combustion engine, the first injection amount correction unit corrects the injection amount of the fuel injection valve to be increased. Even in a situation where fuel that is biased to properties that are difficult to vaporize is supplied to the internal combustion engine as the fuel is vaporized in the fuel tank, leaning of the air-fuel ratio is prevented in advance. When the vapor generation determination means determines that the vapor generation in the fuel is started at the time of starting the internal combustion engine, the injection amount of the fuel injection valve is corrected to be increased by the second injection amount correction means, so that it is supplied to the internal combustion engine. Even in the situation where vapor is generated in the remaining fuel, leaning of the air-fuel ratio is prevented in advance.

  Preferably, the in-tank vaporization state estimating means is preferably configured to estimate the fuel vaporization state in the fuel tank based on at least one of temperature and pressure in the fuel tank. The fuel vaporization state in the fuel tank correlates with the temperature and pressure in the fuel tank. As the temperature in the fuel tank rises, the fuel vaporization in the fuel tank becomes more active and the fuel vaporization becomes more active. The pressure in the fuel tank rises. Therefore, the fuel vaporization state can be estimated with high reliability based on the temperature and pressure in these fuel tanks.

As described above, according to the fuel injection control device for an internal combustion engine of the first aspect of the present invention, in the situation where the fuel biased to the property that is difficult to vaporize due to the vaporization of the fuel accompanying the temperature rise in the fuel tank is supplied to the internal combustion engine. Even when the engine is started, the air-fuel ratio can be accurately controlled to achieve good startability.
According to the fuel injection control device for an internal combustion engine of the second aspect of the present invention, the situation where the fuel biased to the property which is hard to be vaporized due to the vaporization of the fuel accompanying the temperature rise in the fuel tank is supplied to the internal combustion engine, and the supply to the internal combustion engine Even in a situation where vapor is generated in the fuel to be produced, it is possible to achieve good startability by accurately controlling the air-fuel ratio when starting the engine.

[First Embodiment]
Hereinafter, a first embodiment of an internal combustion engine fuel injection control apparatus embodying the present invention will be described.
FIG. 1 is an overall configuration diagram showing a fuel injection control device for an internal combustion engine according to the present embodiment. A gasoline internal combustion engine 1 is mounted on the front of the vehicle, and the front wheels of the vehicle are rotationally driven by the internal combustion engine 1. A fuel tank 2 is mounted at the rear of the vehicle, and the fuel tank 2 is connected to the internal combustion engine 1 via a fuel supply path 3 and a fuel recovery path 4. The fuel stored in the fuel tank 2 is supplied to a regulator (not shown) of the internal combustion engine 1 through a fuel supply path 3 by a fuel supply pump 5 and further regulated to a predetermined pressure by the regulator, and then fuel injection of each cylinder (not shown). The surplus fuel that is supplied into the cylinder through the intake passage by the valve and is not consumed is recovered in the fuel tank 2 through the fuel recovery path 4.

On the other hand, an ECU 11 having an input / output device (not shown), a storage device (ROM, RAM, BURAM, etc.) used for storage of a control program, a control map, a central processing unit (CPU), a timer counter, etc. (Engine control unit) is installed. On the input side of the ECU 11, an intake air temperature sensor 12 for detecting the intake air temperature THa of the internal combustion engine 1, a water temperature sensor 13 for detecting the cooling water temperature THw of the internal combustion engine 1, and an exhaust system (not shown) of the internal combustion engine 1 are provided. An O ₂ sensor 14 that outputs a voltage according to the oxygen concentration, a tank pressure sensor 15 that detects the pressure in the fuel tank 1, a tank temperature sensor 16 that also detects the temperature in the fuel tank 1, and various other switches. And sensors are connected. Further, the fuel injection valve, spark plugs of each cylinder (not shown), and other devices are connected to the output side of the ECU 11.

  The ECU 21 executes various controls for operating the internal combustion engine 1 including fuel injection control and ignition timing control based on each detection information described above. As for fuel injection control, fuel injection control according to the general operating state of the internal combustion engine 1 is executed, and when the internal combustion engine 1 is started, the fuel injection valve is operated according to the deviation of the fuel property accompanying the temperature rise in the fuel tank 2. The fuel injection control at the start will be described below.

FIG. 2 is a flowchart showing a fuel injection control subroutine executed by the ECU 11 when the internal combustion engine 1 is started. This subroutine is executed when the engine is started. At this time, the fuel injection time Ti is corrected to be increased based on the coolant temperature THw by a main routine (not shown).
First, the ECU 11 determines whether or not fuel vaporization in the fuel tank 2 is excessive in step S2 (tank vaporization state estimation means). Here, excessive fuel vaporization refers to a situation in which the fuel remaining in the fuel tank 2 as a liquid in the fuel tank 2 is liable to vaporize and influences the air-fuel ratio of the internal combustion engine 1 as the fuel vaporizes. This phenomenon causes the startability of the internal combustion engine 1 to deteriorate due to the lean air-fuel ratio, similar to the vapor generation phenomenon noted in the prior art patent document 1, but the two phenomena are completely different. is there.

  That is, the deviation of the fuel property occurs due to the temperature increase of the fuel tank 2, and at this time, vapor is generated in the fuel tank 2 due to fuel vaporization, but the vapor itself does not cause the air-fuel ratio to become lean, The fuel vaporization starts from components that are easily vaporized in the fuel, and the components that are difficult to vaporize are concentrated in the fuel remaining in the fuel tank 2 as a liquid, and the fuel is supplied to the internal combustion engine 1. On the other hand, the vapor | steam which patent document 1 assumes mainly originates in temperature rises of the fuel supply path 3 from the fuel tank 2 to the internal combustion engine 1, a fuel injection valve, etc., and vapor is internal combustion with a fuel. Generated by being supplied to the engine 1. In the present embodiment, after paying attention to the fact that such a deviation in fuel properties affects the air-fuel ratio of the internal combustion engine 1, fuel injection is performed in advance as a value that can prevent leaning of the air-fuel ratio due to the deviation in fuel properties. A correction coefficient Kf (> 1.0) for the time Ti is set.

  The fuel vaporization state in the fuel tank 2 determined in step S2 correlates with the tank temperature THt and the tank pressure Pt. For example, the fuel tank 2 passes through the fuel recovery path 4 from the engine during operation at a high outside temperature. The fuel vaporization in the fuel tank 2 becomes more active as the temperature in the tank THt rises due to the heat carried by the high-temperature fuel collected in the tank, the radiant heat from the exhaust system under the floor, etc., and the fuel vaporization becomes more active in the tank. The pressure Pt increases. Accordingly, in step S2, the vaporization state of the fuel is determined from the tank internal pressure Pt detected by the tank internal pressure sensor 15 and the tank internal temperature THt detected by the tank internal temperature detection sensor 16 based on a preset map. Yes.

  This determination may be performed based on either the tank internal temperature THt or the tank internal pressure Pt. Further, in the present embodiment, an existing sensor for diagnosing an evaporative smoke for suppressing exhaust gas transpiration is used as the tank pressure sensor 15. However, in a vehicle not equipped with the tank pressure sensor 15, the tank pressure Pt is used. Instead of this, the fuel vaporization state may be estimated based on the intake air temperature THa or the coolant temperature THw at the time of starting.

  When the determination in step S2 is NO, the routine is temporarily terminated. That is, the fuel in the fuel tank 2 at this time is vaporized within a normal range, and the fuel property remaining as a liquid in the fuel tank 2 is not biased so as to affect the air-fuel ratio of the internal combustion engine 1. Therefore, the increase correction of the fuel injection time Ti with respect to the deviation of the fuel property is not executed, and only the general start-up correction in the main routine is executed, and the internal combustion engine 1 is started.

On the other hand, when the determination in step S2 is YES, it is considered that the fuel property in the fuel tank 2 is biased to affect the air-fuel ratio, the process proceeds to step S4, and the correction coefficient Kf is set to the injection time Ti of the fuel injection valve. Multiply (first injection amount correction means). In the next step S6, it is determined whether or not the exhaust air-fuel ratio AF of the engine calculated from the detection information from the O ₂ sensor 14 has reached a preset target air-fuel ratio tgtAF. If the determination is NO, the process of step S6 is performed. repeat. The target air-fuel ratio tgtAF is set as the exhaust air-fuel ratio when the combustion of the internal combustion engine 1 is stable. When the determination in step S6 becomes YES, the combustion of the internal combustion engine 1 is stable and the fuel property is biased. Assuming that it is not necessary to correct the increase in the fuel injection time Ti as a countermeasure, the routine is terminated after the increase correction of the fuel injection time Ti based on the correction integer Kf is stopped in the subsequent step S8.

The determination in step S6 can also be performed based on the rotational fluctuation of the internal combustion engine 1 instead of the exhaust air-fuel ratio. In this case, combustion is performed when the amount of change in the engine rotational speed Ne becomes smaller than a predetermined value. Consider stable.
The enrichment process in step S4 was open roof correction by multiplication of the correction coefficient Kf. For example, as indicated by a broken line in the figure, the process in step S4 is repeated until YES is determined in step S6. In step S4, the correction coefficient Kf may be fed back so that the actual exhaust air-fuel ratio AF becomes the target air-fuel ratio tgtAF.

  As described above, in the fuel injection control device for the internal combustion engine of the present embodiment, the fuel property in the fuel tank 2 is determined based on the tank temperature THt and the tank pressure Pt that correlate with the fuel vaporization state in the fuel tank 2. The deviation is determined, and when there is a deviation in fuel properties, the fuel injection time Ti is increased and corrected by the correction coefficient Kf set as a countermeasure. Therefore, even in a situation where fuel that is hardly vaporized due to excessive fuel vaporization is supplied to the internal combustion engine 1 at the time of starting, the fuel injection amount is accurately increased by the correction coefficient Kf accordingly. It is possible to prevent a situation where the air-fuel ratio becomes lean due to the deviation of the above, and to realize good startability with certainty.

  Moreover, after the engine is started, the combustion state of the internal combustion engine 1 is determined based on the exhaust air-fuel ratio AF, and the increase correction of the fuel injection time Ti based on the correction coefficient Kf is stopped when the combustion is stabilized. If the correction stop timing is too early, the startability deterioration due to the fuel biased to be difficult to vaporize cannot be sufficiently eliminated, while if the correction stop timing is too late, the air-fuel ratio enrichment is not possible. Unnecessary continuation deteriorates the exhaust gas characteristics of the internal combustion engine 1 and may cause over-rich engine stall, but the effect of preventing these problems can also be obtained.

  By the way, in this embodiment, the deterioration of the startability due to the deviation of the fuel property is solved only by increasing the fuel injection amount. However, another measure may be implemented in addition to the increase of the fuel injection amount. Specifically, the radiator fan of the vehicle is operated for a predetermined time after the engine is stopped, and the temperature of the fuel recovered in the fuel tank 2 via the fuel recovery path 4 is lowered, or provided around the fuel tank 2 The fuel tank 2 may be forcibly cooled by a cooling fan. By taking these measures, the fuel vaporization can be suppressed to some extent by suppressing the temperature rise in the fuel tank 2, so that the correction coefficient Kf of the fuel injection time Ti can be reduced, and the deterioration of the fuel consumption due to the increase in the fuel injection amount can be minimized. be able to.

[Second Embodiment]
Next, a description will be given of a second embodiment of a fuel injection control device for an internal combustion engine that embodies the present invention. The fuel injection control device of this embodiment has the same basic configuration as that described in the first embodiment, and the difference is in the fuel injection control executed by the ECU 11 when the engine is started. Therefore, description of common parts is omitted, and processing of the ECU 11 which is a difference will be described according to the flowchart shown in FIG.

  In step S12, the ECU 11 determines whether or not vapor is generated in the fuel supplied to the internal combustion engine 1 (vapor generation determination means). The vapor in the fuel is more likely to be generated as the outside air temperature is higher, and is likely to be generated as the temperature of the internal combustion engine 1 is higher and the fuel supply path 3 or the fuel injection valve is heated by radiant heat. The determination in step S12 is performed based on the intake air temperature THa at the start and the coolant temperature THw at the start that correlates with the engine temperature. When the determination in step S12 is NO, the routine is temporarily terminated. When the determination is YES, the fuel injection time Tf is multiplied by a preset correction coefficient Kv (> 1.0) in step S14. The correction coefficient Kv is set as a countermeasure against vapor, and the fuel injection time Ti is increased and corrected by multiplication of the correction coefficient Kv (second injection amount correction means).

  Thereafter, the process is the same as in the first embodiment. In step S2, it is determined whether the fuel vaporization in the fuel tank 2 is excessive. If the determination is YES, the fuel injection time Ti based on the correction coefficient Kf is determined in step S4. When the exhaust air-fuel ratio AF reaches the target air-fuel ratio tgtAF in step S6, the increase correction of the fuel injection time Ti (in this case, correction based on the correction coefficients Kv and Kf) is stopped in step S8. Even if the determination in step S2 is NO and the correction process based on the correction coefficient Kf in step S4 is not performed, in the present embodiment, the correction process based on the correction coefficient Kv in step S14 is performed. Since it is necessary to determine the processing stop timing, the process proceeds to step S6 unlike the first embodiment in which the determination in step S2 is NO and the routine is ended.

  As described above, in the fuel injection control device for an internal combustion engine according to the present embodiment, in addition to the increase correction of the fuel injection time Ti based on the correction coefficient Kf as a countermeasure against the deviation of the fuel property described in the first embodiment, the vapor is contained in the fuel. When this occurs, the fuel injection time Ti is increased and corrected by the correction coefficient Kv set as a countermeasure against vapor. Therefore, not only can the deterioration of the startability due to the deviation of the fuel properties be prevented, but also the vapor is generated in the fuel supplied to the internal combustion engine 1 due to the temperature rise of the fuel supply path 3 and the fuel injection valve. However, since the fuel injection amount is accurately increased by the correction coefficient Kv accordingly, it is possible to prevent a situation in which the air-fuel ratio is made lean by vapor and to realize a good startability with certainty.

In this embodiment, the fuel vaporization state is determined only when vapor is generated (YES in step S12) (step S2). However, it is not always necessary to determine in this order. For example, the determination in step S12 is NO. However, the determination in step S2 may be performed.
This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in each of the above embodiments, the fuel injection control device of the gasoline internal combustion engine 1 is embodied. However, since the same fuel property bias occurs in the fuel tank 2 with other fuels such as light oil, for example, light oil is used. You may apply to a diesel internal combustion engine. Moreover, you may apply to a gasoline type cylinder injection type internal combustion engine.

  In each of the above embodiments, the fuel injection amount is increased by correcting the injection time Ti of the fuel injection valve to be increased when the fuel vaporization in the fuel tank 2 is excessive or when vapor is generated in the fuel. However, other methods may be used. For example, the fuel injection amount may be increased by increasing the discharge pressure or the discharge amount of the fuel supply pump 5. In a cylinder injection type internal combustion engine, the discharge amount of a high-pressure fuel pump provided on the downstream side of the fuel supply pump 5 may be increased, or the adjustment pressure of the regulator may be variable.

It is a whole block diagram which shows the fuel-injection control apparatus of the internal combustion engine of 1st and 2nd embodiment. 4 is a flowchart showing a fuel injection control subroutine executed by the ECU according to the first embodiment when the engine is started. It is a flowchart which shows the subroutine of the fuel-injection control which ECU of 2nd Embodiment performs at the time of engine starting.

Explanation of symbols

1 Internal combustion engine 2 Fuel tank 3 Fuel supply path (fuel path)
11 ECU (tank vaporization state estimation means, vapor generation determination means, first injection amount correction means, second injection amount correction means)
12 Intake air temperature sensor (vapor generation judging means)
13 Water temperature sensor (vapor generation judgment means)
15 Tank pressure sensor (Evaporation state estimation means in tank)
16 Tank temperature sensor (Evaporation state estimation in tank)

Claims (2)

In a fuel injection control device for an internal combustion engine that supplies fuel stored in a fuel tank to a fuel injection valve of the internal combustion engine via a fuel path and controls an injection amount of the fuel injection valve based on an operating state of the internal combustion engine ,
A tank vaporization state estimation means for estimating a fuel vaporization state in the fuel tank;
A first injection for increasing the injection amount of the fuel injection valve when it is determined that the fuel vaporization state in the fuel tank estimated by the tank vaporization state estimation means is excessive when the internal combustion engine is started. And a fuel injection control device for an internal combustion engine. In a fuel injection control device for an internal combustion engine that supplies fuel stored in a fuel tank to a fuel injection valve of the internal combustion engine via a fuel path and controls an injection amount of the fuel injection valve based on an operating state of the internal combustion engine ,
A tank vaporization state estimating means for estimating the vaporization state of the fuel in the fuel tank;
A first injection for increasing the injection amount of the fuel injection valve when it is determined that the fuel vaporization state in the fuel tank estimated by the tank vaporization state estimation means is excessive when the internal combustion engine is started. An amount correction means;
Vapor generation determining means for determining whether or not vapor is generated in the fuel supplied to the internal combustion engine;
And a second injection amount correcting means for increasing and correcting the injection amount of the fuel injection valve when the generation of vapor in the fuel is determined by the vapor generation determining means when the internal combustion engine is started. A fuel injection control device for an internal combustion engine.

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