JP2018112159A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine that can reduce the pressure in a negative pressure chamber of a brake booster even in the event of an abnormality of a vacuum pump.SOLUTION: A CPU 92 determines whether a vacuum pump 80 is abnormal on the basis of pressure Pb in a negative pressure chamber 52 of a brake booster 50. When determining that the vacuum pump 80 is abnormal, the CPU 92 performs following control: that is, in the operation of a fuel injection valve 16 to control an air-fuel ratio in a combustion chamber 24 to a target air-fuel ratio, a fuel injection period is shifted to a lag angle side so that it overlaps the valve opening period of an intake valve 18.SELECTED DRAWING: Figure 1

Description

  The present invention is equipped with an internal combustion engine equipped with a throttle valve, and sucks a portion of the intake passage of the internal combustion engine downstream of the throttle valve and air in the negative pressure chamber into the negative pressure chamber of the brake booster. The present invention relates to a control device for an internal combustion engine applied to a vehicle to which a vacuum pump is connected.

  For example, Patent Literature 1 below discloses a brake booster that includes an intake passage of an internal combustion engine connected to a negative pressure chamber of a brake booster and includes an electric vacuum pump that sucks air in the negative pressure chamber. ing. Further, in this document, when there is no abnormality in the vacuum pump, a lean air-fuel ratio control is executed to make the air-fuel ratio of the internal combustion engine lean. It is described. This is intended to reduce the pressure in the intake passage and sufficiently suck the air in the negative pressure chamber by the internal combustion engine.

JP 11-348768 A

  By the way, in recent years, an internal combustion engine set to reduce the pumping loss with the aim of reducing the fuel consumption has been developed. In such an internal combustion engine, even when the air-fuel ratio in the combustion chamber is controlled to the stoichiometric air-fuel ratio using a fuel injection valve that injects fuel into the intake passage, the air in the negative pressure chamber is sufficiently transferred to the intake passage. The inventor has found that there is a concern that suction cannot be performed.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a control device for an internal combustion engine that can reduce the pressure in the negative pressure chamber of a brake booster even when the vacuum pump is abnormal. There is to do.

  In order to solve the above-mentioned problems, an internal combustion engine control device is equipped with an internal combustion engine having a throttle valve, and a portion of the intake passage of the internal combustion engine on the downstream side of the throttle valve is installed in a negative pressure chamber of a brake booster. And a vacuum pump that sucks air in the negative pressure chamber, and the internal combustion engine includes a fuel injection valve that injects fuel into the intake passage, and whether or not the vacuum pump is abnormal When the fuel injection valve is operated to control the air-fuel ratio of the internal combustion engine to the target air-fuel ratio when the determination process determines that there is an abnormality, the injection by the fuel injection valve Overlapping processing that overlaps the opening period of the intake valve of the internal combustion engine and the injection period of fuel by the fuel injection valve by shifting the timing to the retard side. Row.

  In the above configuration, when it is determined that there is an abnormality in the vacuum pump, the overlapping process is performed when the fuel injection valve is operated to control the air-fuel ratio of the internal combustion engine to the target air-fuel ratio. Thereby, compared with the case where the overlapping process is not executed, the fuel injected from the fuel injection valve directly flows into the combustion chamber, so that the air-fuel mixture in the combustion chamber is further cooled. Accordingly, since the amount of air filled into the combustion chamber increases, the amount of injection required for achieving the target air-fuel ratio increases. For this reason, since the torque of the internal combustion engine increases, the torque becomes excessive to satisfy the required torque, and the opening degree of the throttle valve is reduced. For this reason, compared with the case where the overlapping process is not executed, the pressure in the intake passage downstream of the throttle valve is reduced, and as a result, the air in the negative pressure chamber can be sufficiently sucked. For this reason, in the said structure, the pressure in the negative pressure chamber of a brake booster can be made low also at the time of abnormality of a vacuum pump.

The figure which shows one Embodiment of the control apparatus of an internal combustion engine, an internal combustion engine, and the brake system of a vehicle. The flowchart which shows the process sequence of the fuel-injection control concerning the embodiment.

Hereinafter, an embodiment of a control device for an internal combustion engine will be described with reference to the drawings.
As shown in FIG. 1, the intake passage 12 of the internal combustion engine 10 is provided with an electronically controlled throttle valve 14 that adjusts the cross-sectional area of the passage. A fuel injection valve 16 for injecting fuel into the intake passage 12 is provided downstream of the throttle valve 14 in the intake passage 12. A mixture of the fuel injected into the intake passage 12 and the air taken into the intake passage 12 flows into the combustion chamber 24 defined by the cylinder 20 and the piston 22 when the intake valve 18 is opened. The air-fuel mixture flowing into the combustion chamber 24 is used for combustion by the spark discharge of the ignition device 26, and the combustion energy is converted into rotational energy of the crankshaft 28 via the piston 22. On the other hand, the air-fuel mixture subjected to combustion in the combustion chamber 24 is discharged into the exhaust passage 32 as exhaust when the exhaust valve 30 is opened.

  A portion of the intake passage 12 downstream of the throttle valve 14 is connected to a brake booster 50 via a negative pressure introduction passage 40. Specifically, the brake booster 50 includes a negative pressure chamber 52 and an atmospheric pressure chamber 54, and the negative pressure introduction path 40 is connected to the negative pressure chamber 52. The brake booster 50 assists in driving the master cylinder 60 by amplifying the pedaling force input to the brake pedal 56 by the user.

  An electric hydraulic actuator 62 is connected to the master cylinder 60. The hydraulic actuator 62 can control the oil supply to each of the wheel cylinders 64 to 70 corresponding to each wheel of the vehicle.

  The negative pressure introduction passage 40 is provided with check valves 42 and 44 that are opened on condition that the pressure on the intake passage 12 side is lower than the pressure on the reverse side. Is provided with an electric vacuum pump 80 for sucking air in the negative pressure chamber 52. The vacuum pump 80 is an actuator for compensating for a case where the suction of air in the negative pressure chamber 52 by the intake passage 12 is insufficient. Here, as a factor in the present embodiment in which the suction of the air in the negative pressure chamber 52 by the intake passage 12 is insufficient, the intake valve 18 is opened on the retard side from the top dead center and is delayed from the bottom dead center. The valve may be closed on the corner side. This setting of the intake valve 18 has the effect of selectively lowering the compression ratio and making the expansion ratio higher than the compression ratio. On the other hand, compared with the case where such a setting is not made, the opening degree of the throttle valve 14 is reduced. The amount of air charged into the combustion chamber 24 is reduced, making it difficult to generate torque. For this reason, compared with the case where this setting is not performed, the opening degree of the throttle valve 14 tends to be a large value, and as a result, the pressure in the intake passage 12 tends to increase.

  The control device 90 controls the internal combustion engine 10 and controls the control amounts (torque, exhaust components). When controlling the control amount, the control device 90 detects the accelerator pedal operation amount (accelerator operation amount ACCP) detected by the accelerator sensor 100, the intake air amount Ga detected by the air flow meter 102, and the negative pressure sensor 104. The pressure Pb in the negative pressure chamber 52 is taken in. The control device 90 operates the opening degree of the throttle valve 14 in accordance with the accelerator operation amount ACCP in order to control the torque of the internal combustion engine 10. Further, in order to control the exhaust component of the internal combustion engine 10, the fuel injection valve 16 is operated in order to control the air-fuel ratio of the air-fuel mixture in the combustion chamber 24 to a target air-fuel ratio (for example, theoretical air-fuel ratio). In addition, when the pressure Pb in the negative pressure chamber 52 is not sufficiently low, the control device 90 operates the vacuum pump 80 to suck air in the negative pressure chamber 52 and control the pressure Pb to be lowered. The control device 90 includes a central processing unit (CPU 92), a ROM 94, and a RAM 96.

  FIG. 2 shows one procedure of processing executed by the control device 90. The processing shown in FIG. 2 is realized by the CPU 92 repeatedly executing the program stored in the ROM 94 at a predetermined cycle. In the following, the step number is represented by a number with “S” at the beginning.

  In the series of processes shown in FIG. 2, the CPU 92 first diagnoses whether there is a history of abnormality determination of the vacuum pump 80 (S10). When determining that there is no history (S10: NO), the CPU 92 determines whether or not the vacuum pump 80 is abnormal (S12). Here, when the pressure Pb in the negative pressure chamber 52 is high (close to atmospheric pressure), it may be diagnosed that there is an abnormality.

  When determining that there is no abnormality (S12: NO), the CPU 92 operates the fuel injection valve 16 as usual (S14). That is, the fuel injection period by the fuel injection valve 16 is set to a period before the opening period of the intake valve 18, and the intake valve 18 is opened after the fuel injection by the fuel injection valve 16 is completed. In FIG. 2, the injection period is expressed as “TQ”, and this period does not overlap with the valve opening period of the intake valve 18 (indicated as “IN valve open” in FIG. 2).

  On the other hand, when determining that there is an abnormality in the vacuum pump 80 (S12: YES), the CPU 92 notifies the user that there is an abnormality (S16). When the process of S16 is completed or when an affirmative determination is made in S10, the CPU 92 executes an overlapping process for overlapping the fuel injection period of the fuel injection valve 16 with the valve opening period of the intake valve 18 (S18). The overlapping process is a fail-safe process for traveling until the user brings the vehicle to the dealer. The overlapping process is aimed at increasing the amount of air filled in the combustion chamber 24 even if the opening degree of the throttle valve 14 is the same. That is, compared with the case where fuel is injected from the fuel injection valve 16 when the intake valve 18 is closed, when the fuel is injected from the fuel injection valve 16 when the intake valve 18 is open, the injected fuel is There is a tendency to flow directly into the combustion chamber 24, thereby realizing a state close to fuel injection by an in-cylinder injection valve that directly injects fuel into the combustion chamber 24. In that case, the temperature of the air-fuel mixture in the combustion chamber 24 can be further reduced as compared with the case where fuel is injected from the fuel injection valve 16 with the intake valve 18 closed, and the combustion chamber 24 is filled. The amount of air that is produced can be increased.

Note that when the processes of S14 and S18 are completed, the CPU 92 once ends the series of processes shown in FIG.
Here, the operation of the present embodiment will be described.

  The internal combustion engine 10 according to the present embodiment has a tendency that the force for sucking the air in the negative pressure chamber 52 tends to be insufficient. For this reason, when the pressure Pb in the negative pressure chamber 52 does not sufficiently decrease, the pressure Pb in the negative pressure chamber 52 is decreased by driving the vacuum pump 80. Here, when an abnormality occurs in the vacuum pump 80, the CPU 92 executes an overlapping process in which the fuel injection period by the fuel injection valve 16 overlaps the valve opening period of the intake valve 18. As a result, the amount of air charged in the combustion chamber 24 increases as compared with the case where the overlapping process is not performed, and thus the intake air amount Ga detected by the air flow meter 102 increases. For this reason, when the CPU 92 operates the fuel injection valve 16 in order to control the air-fuel ratio to the target air-fuel ratio, the torque generated by the internal combustion engine 10 becomes larger than when the overlap processing is not executed. For this reason, compared with the case where a user does not perform duplication processing, even if the output calculated | required from the internal combustion engine 10 is the same, the operation amount of an accelerator pedal comes to be made small. As a result, the CPU 92 obtains a smaller value as the accelerator operation amount ACCP than when the overlap processing is not executed, and controls the opening degree of the throttle valve 14 to a smaller value. For this reason, the pressure on the downstream side of the throttle valve 14 in the intake passage 12 is lower than when the overlapping process is not performed. Therefore, the air in the negative pressure chamber 52 is compared with the case where the overlapping process is not performed. Is sucked more strongly into the intake passage 12 side. For this reason, the drive of the master cylinder 60 by the user depressing the brake pedal 56 can be sufficiently assisted.

  Incidentally, instead of the fail-safe process according to the present embodiment, when dealing with a rich target air-fuel ratio when an abnormality occurs in the vacuum pump 80, the disadvantage is that the combustion efficiency decreases and the fuel consumption rate increases. In addition, there is a demerit that the amount of HC in the exhaust increases and the exhaust characteristics deteriorate.

According to the embodiment described above, the following effects can be obtained.
(1) The closing timing of the intake valve 18 is retarded from the bottom dead center. In this case, the pressure in the intake passage 12 is likely to be higher than in the case where the angle is not retarded. Therefore, if an abnormality occurs in the vacuum pump 80, the pressure Pb in the negative pressure chamber 52 tends to increase. For this reason, the utility value of duplication processing is especially great.

<Correspondence>
The correspondence relationship between the items in the above embodiment and the items described in the column “Means for Solving the Problems” is as follows. The determination process corresponds to the process of S12, and the duplication process corresponds to the process of S18.

<Other embodiments>
In addition, you may change at least 1 of each matter of the said embodiment as follows.
The vacuum pump is not limited to the electric vacuum pump 80, and may be an engine driven vacuum pump driven by the rotational power of the crankshaft 28, for example.

  In the above embodiment, the operating state of the internal combustion engine 10 is not specified for retarding the closing timing of the intake valve 18 from the bottom dead center. The valve closing timing of the intake valve 18 may be retarded from the bottom dead center outside the load operation region. However, it is not essential to delay the closing timing of the intake valve 18 from the bottom dead center. Depending on the operating state of the internal combustion engine 10, it is effective to execute the overlapping process if there is a possibility that the negative pressure in the negative pressure chamber 52 is insufficient when the brake pedal 56 is depressed.

  In the above embodiment, the intake passage 12 and the vacuum pump 80 are connected to the common negative pressure introduction passage 40, but the present invention is not limited to this. Alternatively, an electronically controlled valve that selectively connects either the intake passage 12 or the vacuum pump 80 to the negative pressure chamber 52 may be used.

  The control device is not limited to one that includes the CPU 92 and the ROM 94 and executes software processing. For example, a dedicated hardware circuit (for example, an ASIC) that performs hardware processing on at least a part of the software processed in the above embodiment may be provided.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 12 ... Intake passage, 14 ... Throttle valve, 16 ... Fuel injection valve, 18 ... Intake valve, 20 ... Cylinder, 22 ... Piston, 24 ... Combustion chamber, 26 ... Ignition device, 28 ... Crankshaft, 30 ... exhaust valve, 32 ... exhaust passage, 40 ... negative pressure introduction path, 42,44 ... check valve, 50 ... brake booster, 52 ... negative pressure chamber, 54 ... atmospheric pressure chamber, 56 ... brake pedal, 60 ... master cylinder 62 ... Hydraulic actuator, 64, 66, 68, 70 ... Wheel cylinder, 80 ... Vacuum pump, 90 ... Control device, 92 ... CPU, 94 ... ROM, 96 ... RAM, 100 ... Accelerator sensor, 102 ... Air flow meter, 104 ... negative pressure sensor.

Claims (1)

An internal combustion engine having a throttle valve is mounted, a vacuum pump for sucking air in the negative pressure chamber, a portion of the intake passage of the internal combustion engine on the downstream side of the throttle valve, and a negative pressure chamber of the brake booster Applies to connected vehicles,
The internal combustion engine includes a fuel injection valve that injects fuel into the intake passage,
A determination process for determining the presence or absence of abnormality of the vacuum pump;
When it is determined by the determination processing that there is an abnormality, when operating the fuel injection valve to control the air-fuel ratio of the internal combustion engine to the target air-fuel ratio, the injection timing by the fuel injection valve is shifted to the retard side Thus, the control device for the internal combustion engine that performs the overlapping process of overlapping the valve opening period of the intake valve of the internal combustion engine and the fuel injection period of the fuel injection valve.

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