JP2010249064A - Fuel injection control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device for an engine capable of suppressing a valve opening of a pressure limiter during the deceleration of a vehicle. <P>SOLUTION: The fuel injection control device for the engine 100 includes a fuel pump 53 for supplying fuel to a common rail 52 according to an engine operation state, and a fuel injection valve 51 for injecting fuel stored in the common rail 52 into a combustion chamber 13. The fuel injection control device further includes the pressure limiter 52A provided at the common rail 52 for performing the valve opening when rail pressure exceeds limit set pressure, a rail pressure determination means S102 for determining whether or not the rail pressure before a deceleration start is higher than the prescribed pressure at the deceleration start, and a fuel injection control means S105 for controlling a fuel injection amount during deceleration injected from the fuel injection valve 51 based on the rail pressure before the deceleration start so that the valve opening of the pressure limiter 52A is not performed during the deceleration when the rail pressure before the deceleration start is higher than the prescribed pressure. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an engine fuel injection control device.

  Conventionally, a common rail type fuel injection control device that injects high pressure fuel stored in a common rail from a fuel injection valve is widely known. In such a fuel injection control device, the target fuel injection amount is set to be small due to a decrease in the engine load when the vehicle is decelerated. Therefore, a torque shock may occur due to a change in the engine rotation speed accompanying a rapid decrease in engine output.

  In the fuel injection control device described in Patent Document 1, torque shock at the time of vehicle deceleration is suppressed by performing smoothed fuel injection that gradually reduces the fuel injection amount without rapidly decreasing the fuel injection amount at the time of vehicle deceleration. Or suppress the occurrence of knocking noise.

JP 2008-14207 A

  By the way, in the fuel injection control apparatus described above, it is important to maintain the fuel pressure in the common rail (hereinafter referred to as “rail pressure”) at the target rail pressure corresponding to the operating state. Generally, the fuel pressure on the high engine load side is set to a high pressure, but on the other hand, it is necessary to prevent an excessively high pressure. Therefore, the common rail is provided with a pressure limiter that suppresses an excessive increase in rail pressure. In the fuel injection control device, the rail pressure is adjusted by the high-pressure fuel pump so that the target rail pressure according to the engine operating state is obtained. During normal operation, since fuel injection is continued, when the fuel pressure is lowered, the rail pressure is reduced by reducing the supply of fuel from the high-pressure fuel pump. However, when the vehicle decelerates, the target rail pressure decreases because the driving state shifts to the low engine load side, but the fuel injection amount decreases, and the rotational speed of the high-pressure fuel pump does not decrease immediately. The pressure may increase. If the pressure limiter opens due to this rail pressure rise, the rail pressure is prevented from becoming excessively high, so the effect on the common rail parts can be reduced, but the engine control unit misdiagnoses the fuel system as having a high pressure abnormality. This may result in a fail mode that limits the engine output to the minimum necessary.

  Therefore, if the smoothed fuel injection is performed when the vehicle is decelerated, the above-described increase in rail pressure can be suppressed. However, in the fuel injection control device described in Patent Document 1, the opening of the pressure limiter due to the increase in rail pressure during vehicle deceleration Therefore, depending on the engine operating state before deceleration of the vehicle, there is a problem that the pressure limiter opens even if the smoothed fuel injection is performed.

  Therefore, the present invention has been made paying attention to such a problem, and an object thereof is to provide an engine fuel injection control device capable of suppressing the opening of the pressure limiter during deceleration of the vehicle.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention includes a fuel pump (53) for supplying fuel to a common rail (52) according to an engine operating state, and a fuel injection valve for injecting fuel stored in the common rail (52) into a combustion chamber (13). 51), a pressure limiter (52A) provided on the common rail (52) and opened when the rail pressure exceeds a limit set pressure, and a deceleration at the start of deceleration. If the rail pressure determination means (S102) for determining whether or not the rail pressure before the start is greater than the predetermined pressure, and the rail pressure before the start of deceleration is greater than the predetermined pressure, the pressure limiter (52A) is used during deceleration. Fuel injection control means (S105) for controlling the fuel injection amount at the time of deceleration injected from the fuel injection valve (51) based on the rail pressure before the start of deceleration so as not to open the valve; Characterized in that it comprises a.

  According to the present invention, since fuel injection is performed with the fuel injection amount at the time of vehicle deceleration calculated based on the rail pressure before deceleration operation, even if the rail pressure increases after deceleration, the pressure limiter valve opening pressure may be exceeded. Without opening the pressure limiter during deceleration.

It is a schematic block diagram of the fuel-injection control apparatus of the engine of 1st Embodiment. It is a flowchart which shows the main routine of the fuel injection control at the time of deceleration which a controller performs. It is a timing chart explaining the effect | action of fuel injection control at the time of deceleration. It is a timing chart explaining how to obtain the rail pressure in the fuel injection control device of the engine of the second embodiment.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic configuration diagram of a fuel injection control device for an engine 100 for a vehicle.

  An engine 100 shown in FIG. 1 is an in-line four-cylinder diesel engine, and includes a cylinder block 10 and a cylinder head 20 disposed above the cylinder block 10.

  A cylinder 11 is formed in the cylinder block 10. A piston 12 is slidably fitted into the cylinder 11. A combustion chamber 13 is formed by the wall surface of the cylinder 11, the crown surface of the piston 12, and the lower surface of the cylinder head 20.

  The cylinder head 20 is formed with an intake port 30 through which fresh air flows into the combustion chamber 13 and an exhaust port 40 through which exhaust from the combustion chamber 13 flows.

  The intake port 30 is provided with an intake valve 31. The intake valve 31 is driven by an intake cam provided on the intake camshaft. The intake valve 31 opens and closes the intake port 30 according to the vertical movement of the piston 12.

  The exhaust port 40 is provided with an exhaust valve 41. The exhaust valve 41 is driven by an exhaust cam provided on the exhaust camshaft. The exhaust valve 41 opens and closes the exhaust port 40 according to the vertical movement of the piston 12.

  Fuel is supplied to the engine 100 by the fuel injection system 50. The fuel injection system 50 includes a fuel injection valve 51, a common rail 52, a high-pressure fuel pump 53, and a fuel tank 54.

  The fuel injection valve 51 is provided in the cylinder head 20 for each cylinder of the engine 100. The fuel injection valve 51 directly injects the fuel stored in the common rail 52 into the combustion chamber 13 at a predetermined timing. The fuel supplied to the fuel injection valve 51 is stored in the fuel tank 54.

  The fuel stored in the fuel tank 54 is supplied to the high-pressure fuel pump 53 via the fuel pipe 55 by a feed pump (not shown) provided in the fuel tank 54.

  The high-pressure fuel pump 53 is driven to rotate as the crankshaft of the engine 100 rotates to further pressurize the fuel supplied from the feed pump. The high-pressure fuel discharged from the high-pressure fuel pump 53 is supplied to the common rail 52 through the fuel pipe 55.

  The leaked fuel from the high-pressure fuel pump 53 that is not supplied to the common rail 52 is returned to the fuel tank 54 via the return pipe 56.

  The common rail 52 is a pressure accumulation tank that stores high-pressure fuel. The common rail 52 is provided with a pressure limiter 52 </ b> A that allows fuel to escape to the return pipe 56 so that the rail pressure does not exceed the limit set pressure.

  The pressure limiter 52A is a pressure relief valve that is opened when the rail pressure exceeds the limit set pressure and suppresses the rail pressure to be equal to or lower than the limit set pressure. The pressure limiter 52A has a pressure regulating function. The pressure regulating function is a function of securing a minimum rail pressure necessary for continuously running the vehicle when the pressure limiter 52A is opened and the limp home mode for retracting the vehicle is set.

  The fuel injection valve 51 and the high-pressure fuel pump 53 of the fuel injection system 50 are controlled by the controller 60.

  The controller 60 is configured by a microcomputer including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface).

  The controller 60 includes a crank angle sensor 61 that generates a crank angle signal for each predetermined crank angle, an accelerator pedal sensor 62 that detects the amount of depression of the accelerator pedal, and a pressure sensor 63 that detects the actual rail pressure of the common rail 52. The detection data from are respectively input as signals. The crank angle signal is used as a signal representative of the engine rotation speed of engine 100. The amount of depression of the accelerator pedal is used as a signal representative of the engine load of engine 100.

  The controller 60 adjusts the fuel injection amount and fuel injection timing of the fuel injection valve 51 based on the above-described input signal and the like. Further, the controller 60 adjusts the fuel discharge amount of the high-pressure fuel pump 53 so that the rail pressure of the common rail 52 becomes a target rail pressure set according to the engine operating state.

  By the way, when the vehicle is decelerated, the target fuel injection amount is set small due to a rapid decrease in engine load, and the target rail pressure is also set small. However, since the rail pressure is less likely to decrease as the fuel injection amount decreases, and the rotational speed of the high-pressure fuel pump 53 does not decrease immediately, the rail pressure of the common rail 52 increases after vehicle deceleration. In particular, when the rail pressure in the common rail 52 before deceleration is set high, the pressure limiter 52A may open due to the increase in rail pressure after deceleration. When the pressure limiter 52A is opened, an excessive increase in rail pressure is suppressed, but the engine output is limited due to the fail mode. Thus, when the vehicle decelerates, there is a problem that the pressure limiter 52A opens due to an increase in rail pressure, although there is no abnormality in the high-pressure fuel pump 53 and the like.

  Therefore, in the present embodiment, the smoothed fuel injection is performed without rapidly decreasing the fuel injection amount when the vehicle is decelerated, thereby preventing the pressure limiter 52A from opening during the deceleration.

  The deceleration fuel injection control will be described with reference to FIG. FIG. 2 is a flowchart showing a main routine of the fuel injection control during deceleration executed by the controller 60. This main routine is repeatedly executed at regular intervals, for example, 20 milliseconds while the engine 100 is operating.

  In step S101, the controller 60 determines whether or not the vehicle has started to decelerate based on the detection value of the accelerator pedal sensor 62.

  If it is determined that the vehicle has started to decelerate, the controller 60 executes the process of step S102. In other cases, the controller 60 ends the process.

In step S102, the controller 60 determines whether the actual rail pressure P before the vehicle deceleration detected by the pressure sensor 63 is greater than the predetermined pressure P _0.

  The rail pressure detection routine for detecting the rail pressure P by the pressure sensor 63 is executed separately from the deceleration fuel injection control routine, and is repeatedly executed at intervals of 20 milliseconds. The rail pressure P before deceleration in step S102 uses the previous value read in the routine one time before the vehicle deceleration determination time.

The predetermined pressure P ₀ is a value smaller than the pressure limiter valve opening pressure, and is set as a value with which it can be determined whether or not the pressure limiter 52A is opened due to an increase in rail pressure during vehicle deceleration.

When the rail pressure P is greater than the predetermined pressure P ₀ , it is determined that the pressure limiter 52A may open due to the increase in rail pressure during vehicle deceleration, and the controller 60 executes the process of step S103. On the other hand, if the rail pressure P is smaller than the predetermined pressure P ₀ , it is determined that the pressure limiter 52A will not open even if the rail pressure increases during vehicle deceleration, and the controller 60 performs the process of step S106. Execute.

In step S103, the controller 60, first smoothing calculates the injection quantity Q ₁ based on the rail pressure P before the vehicle deceleration detected by the pressure sensor 63. Smoothing injection quantity Q ₁ First, rail pressure during deceleration is calculated as a fuel injection amount that is lower than the pressure limiter valve opening pressure.

In step S104, the controller 60, the second smoothing calculates the injection quantity Q ₂ based on the engine operating state before the vehicle deceleration. The engine operating state is determined from the engine speed and the engine load.

When the vehicle decelerates, the pressure limiter 52A opens due to an increase in rail pressure, and the fuel injection amount suddenly decreases with the shift to the low engine load side of the operating region, thereby generating a torque shock. There is a possibility. The second smoothing injection amount Q ₂ is calculated as a fuel injection amount that suppresses the occurrence of torque shock when the vehicle is decelerated based on the demand from such drivability.

When the vehicle is an AT vehicle, a torque shock due to a sudden decrease in the fuel injection amount at the time of deceleration of the vehicle becomes a problem in the operation state in which the lockup clutch is engaged. Such torque shock is not a problem. Therefore, at the time of the lock-up clutch engagement to set the second smoothing injection quantity Q ₂ to which according to engine operating conditions at the time of the lock-up clutch release and close the Shi injection quantity Q ₂ raw second to zero.

In step S105, the controller 60, first smoothing injection quantity Q ₁ and the larger of the second smoothing injection quantity Q ₂ and fuel injection quantity Q, performs graded fuel injection by the fuel injection valve 51, the process Exit.

If it is determined in step S102 that the pressure limiter 52A does not open even when the vehicle is decelerating, in step S106, the controller 60 determines the second smoothed injection amount Q ₂ based on the engine operating state before vehicle deceleration. Is calculated. Second smoothing injection quantity Q ₂ in step S106 is calculated as in step S104.

In step S107, the controller 60, the second smoothing injection quantity Q ₂ to which calculated in step S106 and the fuel injection amount Q, by performing the fuel injection has such a fuel injection valve 51, the process ends.

With reference to the timing charts of FIGS. 3A to 3E, the operation of the fuel injection control during deceleration will be described. 3A to 3E, the first smoothing injection amount Q ₁ is larger than the second smoothing injection amount Q _2, and the fuel injection amount from the fuel injection valve 51 during deceleration is the first. This is an example of a case where the better injection amount Q ₁ is set.

As shown in FIG. 3 (A), the accelerator pedal depression amount decreases at time t _1, the vehicle begins to decelerate. When the accelerator pedal depression amount decreases, the target rail pressure in the common rail 52 is set small as shown in FIG. As shown in FIG. 3E, the actual rail pressure before vehicle deceleration is greater than a predetermined pressure P ₀ , and further, the first smoothed injection amount Q ₁ is greater than the second smoothed injection amount Q _2. The fuel injection during deceleration is controlled so as to become the first smoothing injection amount Q ₁ as shown in FIG.

Thus, since fuel injection is performed at the first smoothing injection amount Q ₁ during vehicle deceleration, the pressure limiter valve opening pressure P ₁ is exceeded even if the rail pressure increases during vehicle deceleration as shown in FIG. 3 (E). There is nothing. Further, the smoothed fuel injection at the first smoothed injection amount Q ₁ suppresses a rapid decrease in the fuel injection amount as shown in FIG. 3 (B), and changes in the engine speed as shown in FIG. 3 (C). Since the torque becomes smooth, the occurrence of torque shock during deceleration is suppressed.

  As described above, the fuel injection control device for the engine 100 of the first embodiment can obtain the following effects.

When the vehicle decelerates, since the smoothed fuel injection is performed with the first smoothed injection amount Q ₁ calculated based on the rail pressure P before deceleration, it is avoided that the pressure limiter 52A opens due to the increase in rail pressure after deceleration. Is done. Moreover, the graded fuel injection in Shi injection amount Q ₁ first raw, since rapid decrease of the fuel injection amount during deceleration is suppressed, it is possible to suppress the occurrence of torque shock.

Since the smoothed fuel injection is performed with the first smoothed injection amount Q ₁ only when the rail pressure P before deceleration is higher than the predetermined pressure P ₀ , deterioration of fuel consumption during deceleration can be suppressed.

During deceleration of the vehicle, if the rail pressure P before deceleration is greater than the predetermined pressure P ₀ , the first smoothed injection amount Q ₁ and the second smoothed injection amount Q ₂ calculated from the engine operating state Since the smoother fuel injection is performed with the larger one as the fuel injection amount, it is possible to efficiently suppress the occurrence of torque shock while preventing the opening of the pressure limiter 52A after deceleration.

(Second Embodiment)
The fuel injection control device for the engine 100 in the second embodiment has substantially the same configuration as that in the first embodiment, but differs in the method of obtaining the rail pressure P used in step S102 of the fuel injection control during deceleration. Hereinafter, the difference will be mainly described.

  With reference to FIGS. 4 (A) to 4 (D), a method of obtaining the rail pressure P in the fuel injection control device of engine 100 will be described.

In the fuel injection control apparatus for an engine 100, as shown in FIG. 4 (A), the vehicle is at a time t ₁ to initiate the deceleration, implementing the smoothed fuel injection based on the rail pressure P before deceleration.

Since the deceleration fuel injection control routine is executed at intervals of 20 milliseconds as shown in FIG. 4B, in the first embodiment, the rail read in the routine 20 milliseconds before the vehicle deceleration determination time. adopted pressure P _a as a rail pressure P, the rail pressure P is determined whether larger or not than the predetermined pressure P _0.

By the way, the rail pressure detection routine for detecting the rail pressure by the pressure sensor 63 is performed separately from the deceleration fuel injection control routine, as shown in FIG. 4C, and is also related to other control routines. It may be repeatedly executed in about 8 milliseconds, which is shorter than the fuel injection control routine during deceleration. Therefore, as shown in FIG. 4 (D), the rail pressure P _C which is detected between the previous and current deceleration fuel injection routine is also contemplated that exceeds the predetermined pressure P _0. In such a case, than adopting a rail pressure P _A in the previous routine as a rail pressure P as in the first embodiment, it may be opened inhibitory effect of pressure limiter 52A can not be obtained after reduction.

Therefore, in the second embodiment, the rail pressure P _A read in the previous deceleration fuel injection control routine is not set to the rail pressure P as in the first embodiment, but before the current deceleration fuel injection control routine. It adopts the maximum value among the detected three times the rail pressure P _a to P _C as a rail pressure P, and executes the processing of S102 in FIG. The other processes of the deceleration fuel injection control routine in the second embodiment are the same as those in the first embodiment.

  As described above, the following effects can be obtained in the fuel injection control device for the engine 100 of the second embodiment.

In the second embodiment, since employing the maximum value of the rail pressure P _A to P _C of 3 times of the previously deceleration as a rail pressure P, the repetition time of the rail pressure detecting routine than deceleration fuel injection control routine Even when it is short, the opening of the pressure limiter 52A after deceleration can be suppressed, and the occurrence of torque shock can be further suppressed.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

In the second embodiment, the maximum is value was configured to employ as the rail pressure P, the rail pressure rail pressure circuit number to be read before the deceleration of the rail pressure P _A to P _C of 3 times of the previously deceleration A determination may be made based on the repetition time of the detection routine and the deceleration control routine, and the maximum value of the determined number of rail pressures may be adopted as the rail pressure P.

DESCRIPTION OF SYMBOLS 100 Engine 13 Combustion chamber 30 Intake port 40 Exhaust port 51 Fuel injection valve 52 Common rail 52A Pressure limiter 53 High pressure fuel pump 60 Controller 61 Crank angle sensor 62 Accelerator pedal sensor 63 Pressure sensor S102 Rail pressure determination means S105 Fuel injection control means

Claims (6)

In an engine fuel injection control device comprising a fuel pump that supplies fuel to a common rail according to an engine operating state, and a fuel injection valve that injects fuel stored in the common rail into a combustion chamber,
A pressure limiter provided on the common rail and opened when the rail pressure exceeds a limit setting pressure;
Rail pressure determining means for determining whether the rail pressure before starting deceleration is greater than a predetermined pressure at the start of deceleration;
When the rail pressure before the start of deceleration is greater than the predetermined pressure, during deceleration to inject from the fuel injection valve based on the rail pressure before the start of deceleration so that the pressure limiter does not open during deceleration Fuel injection control means for controlling the fuel injection amount of
An engine fuel injection control device comprising: The fuel injection control means further includes means for controlling a fuel injection amount at the time of deceleration injected from the fuel injection valve so as to suppress a torque shock generated during a deceleration operation,
The larger one of the fuel injection amount calculated so as not to open the pressure limiter and the fuel injection amount calculated so as to suppress the torque shock is adopted, and fuel is injected from the fuel injection valve. ,
The engine fuel injection control device according to claim 1. The fuel injection amount calculated so as to suppress the torque shock is calculated based on the engine rotation speed and the engine load before starting deceleration so as to reduce the torque shock during deceleration.
The fuel injection control device for an engine according to claim 2. The rail pressure determination means employs, as the detected rail pressure, a maximum value among a plurality of times of rail pressure detected before the start of deceleration in the rail pressure detected at a predetermined cycle.
The engine fuel injection control device according to any one of claims 1 to 3, wherein The predetermined pressure is a value that is smaller than the pressure limiter valve opening pressure, and is set as a value that can determine whether or not the pressure limiter opens due to an increase in rail pressure during vehicle deceleration.
The fuel injection control device for an engine according to any one of claims 1 to 4, wherein the fuel injection control device is used. Applies to engines with automatic transmission with lock-up clutch,
The fuel injection control means has a larger one of a fuel injection amount calculated not to open the pressure limiter and a fuel injection amount calculated to suppress the torque shock when the lockup clutch is engaged. And injecting fuel from the fuel injection valve,
The fuel injection control device for an engine according to claim 2.

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