JP2015059471A - Control device for common rail type fuel injection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce a common rail pressure during a failure of a pressure reducing valve in a control device for a common rail type fuel injection system.SOLUTION: A control device for a common rail type fuel injection system includes a pressure reducing valve 15. The pressure reducing valve 15 injects a pressure accumulated fuel in a common rail 14 from an injector 16 into a cylinder of an engine 10, and also reduces a common rail pressure. The control device includes a pressure reducing valve failure determination section 41 that determines a failure of the pressure reducing valve 15, and a reduced pressure injection control section 43 that causes the injector 16 to perform a fuel injection when the pressure reducing valve failure determination section 41 determines the failure of the pressure reducing valve 15.

Description

  The present invention relates to a control device for a common rail fuel injection system, and more particularly to fail-safe control when a pressure reducing valve fails.

  In general, a common rail fuel injection system is configured to pressurize fuel pumped up from a fuel tank by a feed pump with a high pressure pump and to pressurize the pressurized fuel into the common rail. In such a common rail type fuel injection system, one having a pressure reducing valve for reducing the pressure in the common rail (hereinafter referred to as common rail pressure) is known (for example, see Patent Document 1).

JP 2004-169633 A

  By the way, the amount of static leak in which livestock pressure fuel in the common rail leaks into the cylinder from the injection hole of the injector is very small. If the pressure reducing valve stops functioning due to a failure or the like, the common rail pressure may not be reduced. .

  If the pressure reducing valve breaks down, a large amount of fuel is injected from the injector into the cylinder, which may cause excessive combustion noise. In addition, the increase in the common rail pressure may cause damage to the fuel injection system, such as fuel leaking from joint portions such as the common rail and piping. Furthermore, there is a problem that fuel may be blown out due to residual pressure in the common rail at the time of disassembly and maintenance in which replacement of the failed pressure reducing valve or the like is performed, and there is a problem in that workability is deteriorated.

  An object of the present invention is to provide a control device for a common rail fuel injection system that can effectively reduce the common rail pressure when a pressure reducing valve fails.

  In order to achieve the above-described object, a control device for a common rail fuel injection system according to the present invention includes a common rail provided with a pressure reducing valve that injects the stock pressure fuel in the common rail into the cylinder of the engine from the injector, and reduces the common rail pressure. And a pressure reduction control means for causing the injector to perform fuel injection when the failure determination means determines a failure of the pressure reducing valve. And.

  The decompression control means preferably causes the injector to perform the fuel injection at an injection timing that does not cause torque in the engine.

  In addition, pressure detecting means capable of detecting a common rail pressure is further provided, and the pressure reducing control means is configured such that the failure determining means determines a failure of the pressure reducing valve, and the detected value of the pressure detecting means avoids damage to the common rail. When the pressure is higher than a predetermined upper limit pressure, it is preferable to cause the injector to perform the fuel injection.

  Further, it is preferable that the pressure reduction control means sets the fuel injection amount to be larger as the differential pressure increases based on the differential pressure between the detected value of the pressure detection means and the upper limit pressure.

  Further, the pressure reduction control means, when the injection amount set based on the differential pressure is larger than a predetermined upper limit injection amount vaporized in the cylinder, the fuel injection is performed for each cycle of the engine. It is preferable that the injection is performed in a plurality of times with a small injection amount smaller than the injection amount.

  Further, it is preferable that the pressure reduction control means prohibits the fuel injection until the detection value of the pressure detection means exceeds the upper limit pressure even when the failure determination means determines a failure.

  According to the control device for the common rail fuel injection system of the present invention, the common rail pressure can be effectively reduced when the pressure reducing valve fails.

It is a typical whole lineblock diagram showing the common rail type fuel injection device concerning one embodiment of the present invention. It is a figure which shows an example of the decompression injection amount setting map which concerns on one Embodiment of this invention. It is a figure explaining the injection timing of the pressure reduction injection which concerns on one Embodiment of this invention. It is a figure explaining the case where the decompression injection which concerns on one Embodiment of this invention is divided and performed in multiple times. It is a flowchart explaining the fail safe control which concerns on one Embodiment of this invention.

  Hereinafter, based on an accompanying drawing, a control device of a common rail type fuel injection system concerning one embodiment of the present invention is explained. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  As shown in FIG. 1, the common rail fuel injection system of the present embodiment includes a fuel tank 11 that stores fuel, a feed pump 12 that pumps fuel from the fuel tank 11, a high-pressure pump 13 that pressurizes the fuel, and a high-pressure fuel. A common rail 14 for stocking pressure, a pressure reducing valve 15 provided on the common rail 14, a plurality of injectors 16 for injecting fuel into each cylinder # 1 to 4 of a diesel engine (hereinafter simply referred to as an engine) 10, and an electronic control unit (Hereinafter referred to as ECU) 40. In FIG. 1, the engine 10 is shown as a four-cylinder engine, but it may be a single-cylinder or a multi-cylinder engine other than the four-cylinder engine.

  The high pressure pump 13 pressurizes the fuel pumped up by the feed pump 12 and pumps the pressurized high pressure fuel to the common rail 14. More specifically, the high-pressure pump 13 includes a pump drive shaft that is rotated by the power of the engine 10, a plunger that reciprocates in the cylinder by the rotation of the pump drive shaft, a flow rate adjustment valve that adjusts the fuel discharge amount, and the like. Has been. The drive and discharge amount of the high-pressure pump 13 are feedback-controlled by the ECU 40 so that a sensor value of a common rail pressure sensor 20 described later becomes a predetermined target pressure.

  The common rail 14 stocks the high-pressure fuel supplied from the high-pressure pump 13 and distributes the high-pressure fuel to each injector 16 via the supply pipe 17. Further, the common rail 14 is provided with a common rail pressure sensor 20 capable of detecting a common rail pressure corresponding to the fuel injection pressure. The common rail pressure detected by the common rail pressure sensor 20 is input to the electrically connected ECU 40. The common rail pressure sensor 20 is preferable as an example of the pressure detection means of the present invention.

  The pressure reducing valve 15 reduces the common rail pressure, and is interposed between the common rail 14 and the discharge pipe 18. In other words, when the pressure reducing valve 15 is opened, the high pressure fuel stored in the common rail 14 is returned to the fuel tank 11 via the discharge pipe 18. The opening of the pressure reducing valve 15 is executed by applying an electric current from the ECU 40 to an electromagnetic drive unit including a solenoid or the like when the sensor value of the common rail pressure sensor 20 rises above a predetermined target pressure.

  The injectors 16 are provided corresponding to the cylinders # 1 to # 4 of the engine 10, respectively, and directly inject the high-pressure fuel supplied from the common rail 14 into the cylinders # 1 to # 4. As for the fuel injection amount and injection timing of the injector 16, a predetermined instruction signal (pulse current) corresponding to the operating state of the engine 10 is applied from the ECU 40 to the electromagnetic solenoid, and the injection hole at the nozzle tip is opened and closed by the lift of the core valve. It is controlled by that.

  The ECU 40 performs various controls of the engine 10 and includes a known CPU, ROM, RAM, input port, output port, and the like. In order to perform these various controls, the ECU 40 is connected to the common rail pressure sensor 20 and various sensors such as an engine rotation sensor and an accelerator opening sensor (not shown).

  Further, the ECU 40 includes a pressure reducing valve failure determination unit 41, a high pressure pump drive control unit 42, and a pressure reducing injection control unit 43 as some functional elements. In the present embodiment, each of these functional elements is described as being included in the ECU 40, which is an integral piece of hardware. However, any one of these functional elements may be provided in separate hardware.

  The pressure reducing valve failure determination unit 41 is an example of a failure determination unit of the present invention, and determines a failure of the pressure reducing valve 15 caused by disconnection or short circuit of the drive circuit, valve body sticking, or the like. More specifically, when the current amount input from the ECU 40 to the drive circuit does not reach the target current amount, the drive circuit may be disconnected or short-circuited. Further, when the sensor value of the common rail pressure sensor 20 does not decrease despite the output of current to the drive circuit, the valve body of the pressure reducing valve 15 may be fixed. The pressure reducing valve failure determination unit 41 determines that the pressure reducing valve 15 is in failure when such a state is detected. In order to notify the driver of the failure of the pressure reducing valve 15, the failure determination result is displayed on a display device or the like in a driver's cab (not shown).

  The high-pressure pump drive control unit 42 feedback-controls the drive and discharge amount of the high-pressure pump 13 based on the sensor value of the common rail pressure sensor 20 so that the common rail pressure becomes a predetermined target pressure. The high-pressure pump drive control unit 42 stops driving the high-pressure pump 13 when the pressure reducing valve failure determination unit 41 determines that the pressure reducing valve 15 is in failure. Thereby, the rise of the common rail pressure when the pressure reducing valve 15 fails is effectively suppressed.

The decompression injection control unit 43 is an example of a decompression control unit of the present invention, and controls decompression injection that injects fuel from the injector 16 to reduce the common rail pressure. More specifically, the ECU 40 stores an upper limit pressure P _{MAX that} is obtained in advance through experiments or the like and that avoids damage to the common rail 14. Further, the ECU 40 stores a reduced pressure injection amount setting map (see FIG. 2) showing the relationship between the fuel injection amount and the reduced amount of the common rail pressure, which is obtained in advance through experiments or the like.

Vacuum injection control unit 43, the pressure reducing valve failure determining unit 41 pressure reducing valve 15 is determined to fail, and, if the sensor value P _ACT common rail pressure sensor 20 is higher than the upper limit pressure P _MAX, run the vacuum injection control To do. Vacuum injection control, along with reading the injection amount corresponding to the differential pressure between the sensor value P _ACT and the upper limit pressure P _MAX of the common rail pressure sensor 20 from the vacuum injection amount setting map as vacuum injection amount Q _DEP, the vacuum injection amount Q _DEP Is applied to the electromagnetic solenoid of the injector 16.

  Note that if torque is generated in the engine 10 due to the reduced pressure injection, there is a possibility that a driving force unexpected by the driver may be transmitted to the driving system of the vehicle. For this reason, the decompression injection control unit 43 performs the decompression injection at an injection timing at which no torque is generated in the engine 10 (for example, the exhaust stroke top dead center from the advance side slightly indicated by the reference symbol A in FIG. It is configured to be executed in the period until. As the injection timing at which no torque is generated, for example, substantially the same timing as the post injection performed at the time of forced regeneration of the DPF provided in the exhaust system is suitable.

Even if the injection timing does not generate torque, if a large amount of decompression injection is performed in one injection, a large amount of the fuel flows into the exhaust system without being vaporized in each cylinder # 1 to # 4. It becomes a factor that generates smoke. Therefore, the reduced pressure injection control unit 43 presets an upper limit injection amount Q _MAX for vaporizing the injected fuel in the cylinder, and the reduced pressure injection amount Q _DEP read from the reduced pressure injection amount setting map is set to the upper limit injection amount Q _MAX. 4, as shown in FIG. 4, the engine 10 is configured to inject a plurality of times (three times in the illustrated example) with a minute injection amount smaller than the upper limit injection amount Q _{MAX for} each cycle of the engine 10. ing. Here, one cycle of the engine 10 refers to one combustion stroke including each stroke of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke.

  Next, the flow of fail-safe control according to the present embodiment will be described based on FIG.

  In step (hereinafter, step is simply referred to as “S”) 100, the pressure reducing valve failure determination unit 41 determines a failure of the pressure reducing valve 15. If disconnection / short circuit of the drive circuit, sticking of the valve body, or the like is confirmed, it is determined that the pressure reducing valve 15 has failed, and the present control proceeds to S110. On the other hand, if no failure is confirmed, the present control is returned. In S110, the high pressure pump drive control unit 42 stops the drive of the high pressure pump 13.

In S120, by vacuum injection control unit 43, sensor value P _ACT common rail pressure sensor 20 whether higher than the upper limit pressure P _MAX is confirmed. If the sensor value P _ACT is higher than the upper limit pressure P _MAX (YES), while the control proceeds to S130, if the sensor value P _ACT is equal to or smaller than the upper limit pressure P _MAX (NO), the control is returned to S110. That is, even if the pressure reducing valve 15 breaks down, it does not proceed to S130 until the common rail pressure exceeds the upper limit pressure P _MAX (the pressure reducing injection control is prohibited).

In S130, setting of the pressure reducing injection quantity Q _DEP to read the injection amount corresponding to the differential pressure between the sensor value P _ACT and the upper limit pressure P _MAX of the common rail pressure sensor 20 from the vacuum injection amount setting map (see FIG. 2) is executed .

In S140, vacuum injection amount Q _DEP set in S130 whether exceeds the upper-limit injection amount Q _MAX is confirmed. When the reduced pressure injection amount Q _DEP is less than or equal to the upper limit injection amount Q _MAX (NO), the reduced pressure injection is executed only once at a timing at which no torque is generated in the engine 10 in S150. On the other hand, if the reduced pressure injection amount Q _DEP exceeds the upper limit injection amount Q _MAX (YES), the reduced pressure injection is executed in a plurality of times with a minute injection amount for each cycle of the engine 10 in S160.

In S170, the sensor value P _ACT common rail pressure sensor 20 whether or not reduced to the upper limit pressure P _MAX is confirmed. If the sensor value P _ACT is reduced to the upper limit pressure P _MAX (YES), the control is returned. On the other hand, if the sensor value P _ACT is not reduced to the upper limit pressure P _MAX (NO), the control is returned to S130 in order to continue the vacuum injection. Thereafter, each control step from S100 to S170 is repeatedly executed until the engine 10 is stopped.

  Next, functions and effects of the control device for the common rail fuel injection system according to the present embodiment will be described.

  In the present embodiment, when the pressure reducing valve 15 breaks down due to disconnection of the drive circuit or the like, the valve body is fixed, etc., the pressure reducing injection for reducing the common rail pressure by injecting fuel from the injector 16 is executed. That is, even if the pressure reducing valve 15 falls into a state where it does not function due to a failure, the increase in the common rail pressure is surely suppressed by executing the pressure reducing injection.

  Therefore, according to this embodiment, it is possible to reliably prevent damage to the fuel injection system due to an increase in common rail pressure and excessive combustion noise due to a large amount of fuel injection. Furthermore, the workability at the time of disassembly and maintenance can be effectively ensured by removing the residual pressure in the common rail by the reduced pressure injection.

Further, in the present embodiment, even when the pressure reducing valve 15 is determined to be a failure, until the sensor value P _ACT common rail pressure sensor 20 exceeds the upper limit pressure P _MAX is configured not to perform the vacuum injection ing.

  Therefore, according to the present embodiment, unnecessary reduction of the common rail pressure is suppressed, and the vehicle can travel to some extent even after the pressure reducing valve 15 has failed.

  Further, in the present embodiment, the decompression injection is configured to be executed at an injection timing that does not cause torque in the engine 10 (for example, substantially the same timing as the post injection at the time of DPF forced regeneration).

  Therefore, according to the present embodiment, it is possible to effectively suppress the generation of torque of the engine 10 due to the reduced pressure injection, and reliably prevent the driver's unexpected driving force from being transmitted to the driving system of the vehicle. can do.

Further, in the present embodiment, when the reduced pressure injection amount Q _DEP exceeds the upper limit injection amount Q _MAX that is vaporized in the cylinder, the reduced pressure injection is a minute injection smaller than the upper limit injection amount Q _{MAX for} each cycle of the engine 10. The injection is divided into a plurality of times (three times in the illustrated example).

  Therefore, according to the present embodiment, the fuel injected by the reduced pressure injection can be surely vaporized in each of the cylinders # 1 to # 4, and the generation of black smoke or the like can be effectively suppressed.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

  For example, the engine 10 is not limited to a diesel engine, but can be applied to other engines such as a gasoline engine.

DESCRIPTION OF SYMBOLS 11 Fuel tank 12 Feed pump 13 High pressure pump 14 Common rail 15 Pressure reducing valve 16 Injector 17 Supply piping 18 Discharge piping 20 Common rail pressure sensor 40 ECU
41 Pressure reducing valve failure determination unit 42 High pressure pump drive control unit 43 Pressure reducing injection control unit

Claims (6)

A control device for a common rail fuel injection system including a pressure reducing valve for reducing the common rail pressure while injecting the stock pressure fuel in the common rail into the cylinder of the engine from the injector,
Failure determination means for determining failure of the pressure reducing valve;
A control device for a common rail fuel injection system, comprising: a pressure reduction control unit that causes the injector to perform fuel injection when the failure determination unit determines a failure of the pressure reducing valve. 2. The control device for a common rail fuel injection system according to claim 1, wherein the pressure reduction control unit causes the injector to execute the fuel injection at an injection timing that does not generate torque in the engine. It further comprises pressure detection means capable of detecting the common rail pressure,
The pressure reduction control means determines whether the failure determination means determines a failure of the pressure reducing valve, and the detected value of the pressure detection means is higher than a predetermined upper limit pressure that avoids damage to the common rail. The control device for a common rail fuel injection system according to claim 1 or 2, wherein fuel injection is executed. 4. The common rail fuel according to claim 3, wherein the depressurization control unit sets the fuel injection amount to be larger as the differential pressure increases based on a differential pressure between the detected value of the pressure detection unit and the upper limit pressure. Control device for injection system. When the injection amount set based on the differential pressure is larger than a predetermined upper limit injection amount that is vaporized in a cylinder, the decompression control means performs the fuel injection for each cycle of the engine. The control device for a common rail fuel injection system according to claim 4, wherein the injection is performed in a plurality of times with a smaller minute injection amount. The pressure reduction control means prohibits the fuel injection until the detection value of the pressure detection means exceeds the upper limit pressure even when the failure determination means determines a failure. The control apparatus for a common rail fuel injection system according to claim 1.

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