JP2018076795A - Fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote the atomization of low pressure fuel to be injected from an injector at the time of the failure of a high pressure pump.SOLUTION: A fuel injection control device disclosed by this invention is applied for a fuel injection system in which fuel supplied from a low pressure pump is pressurized by the high pressure pump and the fuel supplied from the high pressure pump is injected from the injector into an internal combustion engine. In S400, a determination part determines the normality/failure of the high pressure pump. When the determination part determines the failure of the high pressure pump in S412, a control part executes at least either operation to set an injection timing for the injector to be closer to the top dead center side of an intake stroke than at the time of the normality of the high pressure pump or to advance a valve timing for an intake valve in S414.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a fuel injection control device when a high-pressure pump that supplies pressurized fuel to an injector that injects fuel into an internal combustion engine fails.

  There is known a fuel injection system in which fuel supplied from a low-pressure pump is pressurized by a high-pressure pump, and fuel supplied from the high-pressure pump is injected from an injector to an internal combustion engine. In such a fuel injection system, when the high-pressure pump fails, fuel injection from the injector may be cut off. However, if the fuel injection from the injector is cut, the retreat traveling that retreats the vehicle to a safe place cannot be performed.

  Therefore, in the technique disclosed in Patent Document 1, in a fuel injection system in which fuel supplied from a high-pressure pump is accumulated in a common rail and supplied to an injector, detour that supplies the fuel to the common rail by bypassing the high-pressure pump from the low-pressure pump There is a passage. A check valve that opens when the fuel pressure in the common rail falls below the discharge pressure of the low-pressure pump is installed in the bypass passage, and permits fuel supply from the low-pressure pump to the common rail through the bypass passage.

  With this technique, in the technology disclosed in Patent Document 1, when the fuel pressure in the common rail decreases because the high pressure pump fails and fuel cannot be supplied to the common rail, the fuel is supplied from the low pressure pump to the common rail through the bypass passage. Trying to supply.

JP-A-8-319871

  When the fuel supplied from the low-pressure pump is injected from the injector when the high-pressure pump fails, the injection pressure is lower than that when the injector injects the high-pressure fuel, and the atomization of the injected fuel becomes insufficient. If the atomization of the injected fuel is insufficient, good combustion of the injected fuel in the cylinder is hindered, so that there is a possibility that the internal combustion engine cannot generate the torque necessary for retreating the vehicle.

  One aspect of the present disclosure provides a technique for promoting atomization of low-pressure fuel injected from an injector when a high-pressure pump fails.

  One aspect of the present disclosure is a fuel injection in which fuel supplied from a low-pressure pump (30) is pressurized by a high-pressure pump (40), and fuel supplied from the high-pressure pump is injected from an injector (60) to an internal combustion engine (2). The fuel injection control device (70) applied to the system (10) includes a determination unit (S400) and a control unit (S412).

  The determination unit determines whether the high-pressure pump is normal or malfunctioning. When the determination unit determines that the high-pressure pump is out of order, the control unit advances the injection timing of the injector to the top dead center side of the intake stroke than when the high-pressure pump is normal.

  In this way, the fuel that is injected from the injector by the intake air that is sucked into the cylinder from the intake valve in the intake stroke is achieved by advancing the injection timing of the injector to the top dead center side of the intake stroke from the normal time of the high-pressure pump. The time for stirring is increased. Thereby, even if the fuel injected from the injector is low pressure, atomization of the injected fuel is promoted.

  In another aspect of the present disclosure, the fuel supplied from the low pressure pump (30) is pressurized by the high pressure pump (40), and the fuel supplied from the high pressure pump is injected from the injector (60) to the internal combustion engine (2). The fuel injection control device (70) applied to the injection system (10) includes a determination unit (S400) and a control unit (S414).

  The determination unit determines whether the high-pressure pump is normal or malfunctioning. When the determination unit determines that the high-pressure pump is out of order, the control unit advances the valve timing of the intake valve more than when the high-pressure pump is normal.

  Thus, by opening the valve timing of the intake valve from the normal time of the high pressure pump, the opening degree of the intake valve when starting fuel injection from the injector is increased in the intake stroke. As the opening of the intake valve increases, the amount of intake air taken into the cylinder increases and the flow of intake air in the cylinder becomes intense. By injecting the fuel into the cylinder in this state, atomization of the injected fuel is promoted even if the fuel injected from the injector has a low pressure.

  Note that the reference numerals in parentheses described in this column and in the claims indicate the correspondence with the specific means described in the embodiment described later as one aspect, and the technical scope of the present disclosure. It is not limited.

The block diagram which shows the fuel-injection system by this embodiment. The flowchart which shows the control processing by this embodiment. Explanatory drawing explaining injection timing. The schematic diagram explaining the injection timing. The time chart which shows valve timing.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
[1. Constitution]
A fuel injection system 10 shown in FIG. 1 is for, for example, injecting fuel into a direct injection gasoline engine 2 for an automobile as an internal combustion engine. Hereinafter, the gasoline engine is also simply called an engine. The fuel injection system 10 includes a fuel tank 20, a low pressure pump 30, a high pressure pump 40, a delivery pipe 50, an injector 60, and an ECU 70. ECU is an abbreviation for Electronic Control Unit.

The low pressure pump 30 is an electric pump driven by a motor. The low pressure pump 30 sucks up the fuel in the fuel tank 20 and supplies it to the high pressure pump 40.
The high-pressure pump 40 pressurizes the fuel supplied from the low-pressure pump 30 to the pressurizing chamber by a reciprocating movement of a plunger (not shown) driven by a cam. A check valve is installed on the fuel outlet side for supplying fuel from the pressurizing chamber to the delivery pipe 50. The check valve opens when the difference between the fuel pressure in the pressurizing chamber and the fuel pressure in the delivery pipe 50 exceeds a predetermined pressure. When the check valve is opened, the fuel in the pressurizing chamber is supplied to the delivery pipe 50.

  A metering valve (not shown) for metering the discharge amount of the high-pressure pump 40 is installed on the fuel inlet side of the pressurizing chamber of the high-pressure pump 40 to which fuel is supplied from the low-pressure pump 30. The metering valve is an electromagnetically driven valve that closes when energized and opens when energized. The ECU 70 controls energization to the metering valve.

  The ECU 70 opens the metering valve in the intake stroke of the high-pressure pump 40 that lowers the plunger and sucks the fuel supplied from the low-pressure pump 30 into the pressurizing chamber. The ECU 70 closes the metering valve at a predetermined timing in the pressurization stroke of the high-pressure pump 40 in which the plunger moves up. In the pressurization stroke, the metering valve is closed to pressurize the fuel in the pressurizing chamber, and the high-pressure pump 40 discharges the high-pressure fuel. By controlling the timing of closing the metering valve, the discharge amount of the high-pressure pump 40 is metered.

  The delivery pipe 50 is a hollow member that accumulates fuel supplied from the high-pressure pump 40 and supplies the fuel to the injector 60. The pressure sensor 52 is installed in the delivery pipe 50 and detects the fuel pressure in the delivery pipe 50.

  The injector 60 is installed in each cylinder of the engine 2, and a fuel inlet is inserted into the delivery pipe 50. The injector 60 directly injects fuel supplied from the delivery pipe 50 into the cylinder of the engine 2 by controlling energization.

  The ECU 70 is mainly configured of a microcomputer including a CPU 72 and a semiconductor memory 74 such as a RAM, a ROM, and a flash memory. Hereinafter, the semiconductor memory is also simply referred to as a memory. The number of microcomputers constituting the ECU 70 may be one or more.

  Various functions of the ECU 70 are realized by the CPU 72 executing a program stored in a non-transitional physical recording medium. In this example, the memory 74 corresponds to a non-transitional tangible recording medium that stores a program. When the CPU 72 executes this program, a method corresponding to the program is executed.

  The method for realizing various functions of the ECU 70 is not limited to software, and hardware in which some or all of the elements are combined with a logic circuit, an analog circuit, or the like may be used.

The ECU 70 executes various controls of the fuel injection system 10 as described below based on detection signals acquired from various sensors including the pressure sensor 52.
The ECU 70 controls the injection amount and injection timing of the injector 60. Further, the ECU 70 instructs a valve timing adjusting device 80 that adjusts the valve timing of an intake valve (not shown) to determine how much the valve timing of the intake valve is advanced or retarded. Further, the ECU 70 controls the discharge amount of the high-pressure pump 40 by controlling the metering valve so that the pressure in the delivery pipe 50 acquired from the pressure sensor 52 becomes the target pressure.

[2. processing]
Control processing executed by the CPU 72 will be described with reference to the flowchart of FIG. The flowchart of FIG. 2 is always executed.

  In S <b> 400, the CPU 72 determines whether the high-pressure pump 40 is faulty or normal rather than faulty. The CPU 72 determines that the high-pressure pump 40 is in failure when at least one of the following conditions (1) and (2) is satisfied.

  (1) The output of the pressure sensor 52 is fixed at a high level or a low level. In this case, since the fuel pressure supplied from the delivery pipe 50 to the injector 60 cannot be detected, it is determined that the high-pressure pump 40 has failed.

  (2) The fuel pressure of the delivery pipe 50 detected from the output of the pressure sensor 52 is continuously lower or higher than the pressure control range by the CPU 72. In this case, the discharge amount of the high-pressure pump 40 is abnormal, and it is determined that the high-pressure pump 40 has failed.

  If the determination in S400 is No and the high-pressure pump 40 is normal rather than malfunctioning, the CPU 72 sets the injection timing of the injector 60 based on the engine speed and the intake air flow rate in S402. In S404, the CPU 72 sets the valve timing of the intake valve based on the engine operating state, and ends this process.

  If the determination in S400 is Yes and the high-pressure pump 40 is faulty, in S406, the CPU 72 cuts off the power supply to the metering valve of the high-pressure pump 40 and opens the metering valve even in the pressurization stroke. Thereby, the fuel supplied by the low pressure pump 30 is not pressurized by the high pressure pump 40.

  When the difference between the fuel pressure supplied to the pressurizing chamber by the low pressure pump 30 and the fuel pressure of the delivery pipe 50 exceeds a predetermined pressure, the check valve opens, and the fuel supplied to the pressurizing chamber by the low pressure pump 30 is increased. Supplied to delivery pipe 50.

  In S408, the CPU 72 determines whether or not to limit the engine speed to a low speed. The engine speed is limited to a low speed when the injector 60 injects low-pressure fuel supplied by the low-pressure pump 30 due to a failure of the high-pressure pump 40, so that the time of the intake stroke is lengthened and the fuel is discharged during the intake stroke. This is to end the injection. By limiting the engine speed to a low speed, the vehicle performs evacuation.

  On the other hand, if there is no control for limiting the engine speed to a low speed, the intake stroke time is short even if the injector 60 injects the low-pressure fuel supplied by the low-pressure pump 30 due to the failure of the high-pressure pump 40. Therefore, there exists an engine speed region in which injection cannot be completed during the intake stroke. In this case, the CPU 72 determines that it is difficult to perform the retreat travel, and performs fuel cut. That is, the CPU 72 determines No in S408.

  If the determination in S408 is No and there is no control to limit the engine speed to a low speed, the CPU 72 executes fuel cut in S410, stops fuel injection from the injector 60, and ends this process.

  When the determination in S408 is Yes and the engine speed is limited to a low speed, the CPU 72 limits the engine speed to a low speed that is slightly higher than the idle speed, for example. In S412, the CPU 72 advances the injection start timing at which the injector 60 starts fuel injection to the top dead center side of the intake stroke in comparison with the normal time of the high-pressure pump 40 in the intake stroke, as shown in FIG.

  When the injection start timing of the injector 60 is advanced to the top dead center side of the intake stroke from the normal time of the high pressure pump 40, the injection start timing in the cylinder 4 is higher than the normal injection start timing of the high pressure pump 40 as shown in FIG. When the lift position of the piston 6 is large, fuel is injected from the injector 60.

  As a result, the amount of movement by which the piston 6 descends after the injector 60 injects fuel increases. As a result, the time during which the fuel 100 injected from the injector 60 is agitated by the intake air sucked into the cylinder 4 becomes longer, and the momentum of the intake flow sucked into the cylinder 4 increases as the piston 6 descends. Therefore, atomization of the injected fuel is promoted.

  Further, in S414, the CPU 72 instructs the valve timing adjusting device 80 that adjusts the valve timing of the intake valve to indicate the valve timing at which the intake valve starts to open when the high-pressure pump 40 is normal, indicated by the dotted line 310 in FIG. Rather than as shown by the solid line 300.

  When the valve timing of the intake valve is advanced, the opening degree of the intake valve at the injection timing increases regardless of whether or not the injection timing of the injector 60 is advanced when the high-pressure pump 40 is abnormal. Intake flow increases. Thereby, since the fuel is injected from the injector 60 in a state where the momentum of the intake flow sucked into the cylinder 4 is large, atomization of the fuel injected into the cylinder 4 is promoted.

[3. effect]
In the embodiment described above, the following effects can be obtained.
(1) When the high-pressure pump 40 fails, the injection timing of the injector 60 is advanced to the top dead center side of the intake stroke, and the valve timing of the intake valve is advanced, so that only low-pressure fuel can be supplied to the injector 60. The atomization of the injected fuel can be promoted. Thereby, even the low-pressure injected fuel is atomized and burns well, so that the engine 2 can generate torque necessary for the retreat travel.

  (2) The advancement of the injection timing of the injector 60 to the top dead center side of the intake stroke and the advancement of the valve timing of the intake valve can be realized by control by software, so there is no need to add new parts.

  In the above embodiment, the engine 2 corresponds to the internal combustion engine, the cylinder 4 corresponds to the cylinder, the fuel injection system 10 corresponds to the fuel injection system, the low pressure pump 30 corresponds to the low pressure pump, and the high pressure pump 40 corresponds to the high pressure pump. The injector 60 corresponds to the injector, and the ECU 70 corresponds to the fuel injection control device.

Moreover, in the said embodiment, S400 respond | corresponds to the process of a determination part, and S412 and S414 respond | correspond to the process of a control part.
[4. Other Embodiments]
(1) In the above embodiment, when the high-pressure pump 40 fails, the process of advancing the injection timing of the injector 60 toward the top dead center side of the intake stroke than when the high-pressure pump 40 is normal, and the valve timing of the intake valve are advanced. Both processing and executed. On the other hand, only one of the processes may be executed.

  (2) When the injection timing of the injector 60 is advanced to the top dead center side of the intake stroke when the high-pressure pump 40 fails, the injection timing may be set to the top dead center of the intake stroke. When the valve timing of the intake valve is advanced at the time of failure of the high-pressure pump 40, the valve timing of the intake valve may be set to the most advanced angle within the control range.

  (3) The internal combustion engine is not limited to the direct injection type as long as the fuel supplied from the low pressure pump is pressurized by the high pressure pump and the fuel supplied from the high pressure pump is injected from the injector to the internal combustion engine.

  (4) A plurality of functions of one constituent element in the above embodiment may be realized by a plurality of constituent elements, or a single function of one constituent element may be realized by a plurality of constituent elements. Further, a plurality of functions possessed by a plurality of constituent elements may be realized by one constituent element, or a single function possessed by a plurality of constituent elements may be realized by one constituent element. Moreover, you may abbreviate | omit a part of structure of the said embodiment. Further, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects contained in the technical thought specified only by the wording described in the claim are embodiment of this indication.

  (5) In addition to the fuel injection control device described above, a fuel injection system including the fuel injection control device as a constituent element, a fuel injection control program for causing a computer to function as the fuel injection control device, and the fuel injection control program are recorded. The present disclosure can also be realized in various forms such as a recording medium and a fuel injection control method.

2: engine (internal combustion engine), 4: cylinder, 10: fuel injection system, 30: low pressure pump, 40: high pressure pump, 60: injector, 70: ECU (fuel injection control device)

Claims (5)

The fuel supplied from the low pressure pump (30) is pressurized by the high pressure pump (40) and applied to the fuel injection system (10) for injecting the fuel supplied from the high pressure pump from the injector (60) to the internal combustion engine (2). In the fuel injection control device (70)
A determination unit (S400) for determining whether the high-pressure pump is normal or malfunction;
When the determination unit determines that the high-pressure pump is out of order, a control unit (S412) that advances the injection timing of the injector to the top dead center side of the intake stroke from the normal time of the high-pressure pump;
A fuel injection control device comprising: The fuel injection control device according to claim 1,
Further, the control unit (S414) advances the valve timing of the intake valve more than when the high pressure pump is normal when the determination unit determines that the high pressure pump is in failure.
Fuel injection control device. The fuel supplied from the low pressure pump (30) is pressurized by the high pressure pump (40) and applied to the fuel injection system (10) for injecting the fuel supplied from the high pressure pump from the injector (60) to the internal combustion engine (2). In the fuel injection control device (70)
A determination unit (S400) for determining whether the high-pressure pump is normal or malfunction;
When the determination unit determines that the high-pressure pump is out of order, a control unit (S414) that advances the valve timing of the intake valve from the normal time of the high-pressure pump;
A fuel injection control device comprising: The fuel injection control device according to claim 2 or 3,
When the determination unit determines that the high-pressure pump is in failure, the control unit causes the valve timing of the intake valve to advance most within a control range,
Fuel injection control device. The fuel injection control device according to claim 4, wherein the fuel injection control device refers to claim 1 or 2 or claim 2.
When the determination unit determines that the high-pressure pump is out of order, the control unit sets the injection timing of the injector at the top dead center of the intake stroke.
Fuel injection control device.

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