JP2005155415A - High-pressure fuel supply system enabling discrimination of abnormality of high-pressure fuel system and measure against abnormality - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-pressure fuel supply system capable of accurately detecting the trouble of a high-pressure fuel system. <P>SOLUTION: This high-pressure fuel supply system comprises a feed pump for feeding a fuel from a fuel tank, a high-pressure fuel pump receiving the fuel from the feed pump, a delivery pipe connected to the high-pressure fuel pump and feeding the fuel to a fuel injection device, a fuel pressure sensor detecting the pressure of the fuel in the delivery pipe, and an electronic control unit controlling, by feedback, the pressure of the fuel in the delivery pipe to a specified pressure based on the output of the pressure sensor. The electronic control unit is formed to determine the abnormality of the high-pressure fuel supply system based on the state of a feedback coefficient for feedback control. Since the abnormality of the high-pressure fuel supply system can be detected based on the state of the feedback coefficient used for the control of fuel pressure, a corrective action against trouble can be immediately taken. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a high-pressure fuel supply system capable of determining an abnormality of a high-pressure fuel system and taking countermeasures in a direct injection engine.

  In recent years, lean burn has been attracting attention in the field of engines from the viewpoint of fuel efficiency. However, the lean burn engine has problems that ignition and combustion are unstable and output torque is small. One method for solving such a problem is a direct injection engine.

  A direct injection engine directly injects fuel into the cylinder and forms an air-fuel mixture that easily burns around the spark plug, and an air layer that does not contain any other fuel. Combustion, so-called stratified combustion is realized. By this stratified combustion, reliable ignition and combustion and sufficient torque output can be realized even in a lean state, and also low fuel consumption can be realized.

  However, in a direct injection engine, the pressure of fuel to be ejected needs to be higher than usual. This is because fuel is ejected during the piston compression stroke, so that fuel cannot be injected unless a pressure higher than the compressed air inside the cylinder is applied. As a method for increasing the pressure of the fuel, for example, there is a method of pressurizing the fuel sent from the fuel tank with a high-pressure fuel pump.

Thus, in order to realize a stable operation of a direct injection engine, the function of a high-pressure fuel supply system such as a high-pressure fuel pump is indispensable. If any abnormality occurs in the high-pressure fuel supply system, a situation in which the fuel pressure does not increase sufficiently may occur. At this time, the fuel injection is insufficient and the stratified combustion of the engine is hindered. Therefore, when a problem occurs in the high-pressure fuel supply system, it is necessary to quickly detect the abnormality and take a countermeasure. In the prior art, for example, in Patent Document 1, the pressure of the fuel supplied to the fuel injection valve is detected, and it is determined whether or not the detected fuel pressure is lower than a predetermined required value. When it is determined that the fuel pressure is lower than the required value, the combustion method is set to homogeneous combustion and stratified combustion is stopped.
JP2000-145517

  In the prior art, the fuel pressure is maintained based on the output of the fuel pressure sensor, but sufficient measures are not taken to detect the failure of the high-pressure fuel system. The present invention provides a high-pressure fuel supply system that accurately detects a failure in a high-pressure fuel system. In addition, the present invention provides a measure corresponding to the occurrence of a failure in the high-pressure fuel system.

    A high-pressure fuel supply system provided by the present invention includes a feed pump for sending fuel from a fuel tank, a high-pressure fuel pump that receives fuel from the feed pump, and a delivery that is connected to the high-pressure fuel pump and supplies fuel to a fuel injection device. A pipe, a fuel pressure sensor for detecting the pressure of the fuel in the delivery pipe, and an electronic control unit for feedback-controlling the pressure of the fuel in the delivery pipe to a predetermined pressure based on the output of the pressure sensor. ing. The electronic control unit is configured to determine an abnormality in the high-pressure fuel supply system based on the state of the feedback coefficient of the feedback control.

  According to the present invention, since it is possible to detect an abnormality in the high-pressure fuel supply system based on the state of the feedback coefficient used for fuel pressure control, it is possible to quickly take a countermeasure for failure.

  The feedback coefficient is a correction amount calculated from the deviation between the detected value of the fuel pressure sensor and the target pressure value. In one form, when this feedback coefficient reaches the upper limit value or the lower limit value, the electronic control unit determines an abnormality in the high pressure fuel supply system.

  In one aspect of the present invention, when an abnormality of the high pressure fuel supply system is determined, the electronic control unit stops the high pressure fuel pump, prohibits stratified combustion, or causes the fuel cut to be executed at a relatively low engine speed. Take corrective actions such as.

  FIG. 1 is a schematic view of a high-pressure fuel supply system. The system includes a feed pump 41 for delivering fuel from a fuel tank, a high-pressure fuel pump 47 for receiving fuel from the feed pump 41, a delivery pipe 31 connected to the high-pressure fuel pump and supplying fuel to the fuel injection device 35. , A fuel pressure sensor 33 for detecting the pressure of the fuel in the delivery pipe 31, and an electronic control unit (feedback control) based on the output of the fuel pressure sensor 33 so that the pressure of the fuel in the delivery pipe 31 becomes a predetermined pressure. ECU) 20 and a relief valve 37 for releasing a pressure equal to or higher than a predetermined value.

  The fuel discharged from the feed pump 41 is introduced into the pressure regulator 43. The pressure regulator 43 is connected to the high-pressure pump 47 by the low-pressure fuel passage 44, and the fuel that has passed through the pressure regulator 43 is introduced to the high-pressure pump 47 by the low-pressure fuel passage 44. The pressure of the fuel passing through the low pressure fuel passage 44 is adjusted to a substantially constant pressure by the pressure regulator 43.

  The high-pressure fuel pump 47 includes a plunger 51 that reciprocates based on the rotation of the cam 53, and a pressurizing chamber 49 whose volume changes as the plunger 51 reciprocates. As the plunger 51 moves in the direction of reducing the volume of the pressurizing chamber 49, the fuel introduced into the pressurizing chamber is pressurized to a high pressure.

  The high-pressure fuel pump 47 includes a solenoid valve 48 that opens and closes the spill valve 46 according to a voltage applied to the solenoid 45. The solenoid valve 48 is disposed between the low-pressure fuel passage 44 and the pressurizing chamber 49, and communicates and blocks between the two. In the solenoid valve 48, when the plunger 51 moves in the direction of increasing the volume of the pressurizing chamber 49, the energization to the solenoid 45 is stopped, the spill valve 46 is opened, and the low pressure fuel passage 44 and the pressurizing chamber 49 are communicated. . Further, when the plunger 51 moves in a direction to reduce the volume of the pressurizing chamber 49, the solenoid valve 48 is energized to the solenoid 45 to close the spill valve 46, and the low pressure fuel passage 44 and the pressurizing chamber 49 are closed. The interval is interrupted.

  The high-pressure fuel pump 47 can control the fuel pressure by controlling the opening and closing of the solenoid valve 48. That is, the fuel pressure in the high-pressure fuel passage 57 and the delivery pipe 31 is adjusted by changing the timing of opening and closing the solenoid valve 48 and adjusting the amount of fuel supplied from the high-pressure fuel pump 47 to the delivery pipe 31. Specifically, when the plunger 51 moves in the direction in which the volume of the pressurizing chamber 49 decreases, the pressure of the fuel supplied to the delivery pipe 31 decreases as the timing for closing the solenoid valve 48 is delayed. The amount is also reduced. The opening / closing control of the solenoid valve 48 is executed by using the ECU 20 and will be described in detail later.

  The fuel whose pressure has been increased by the high-pressure fuel pump 47 passes through the pressure regulator 55 and is introduced into the delivery pipe 31 through the high-pressure fuel passage 57. The pressure of the fuel in the high-pressure fuel passage 57 and the delivery pipe 31 is regulated almost uniformly by the pressure regulator 55.

  The delivery pipe 31 includes a fuel injection device 35 that injects high-pressure fuel into the engine 10 and a fuel pressure sensor 33 that detects the fuel pressure in the pipe. A detection signal of the fuel pressure sensor 33 is sent to the ECU 20. The ECU 20 corrects the pressure of the high-pressure pump based on this detection signal, and generates a control input for opening / closing control of the solenoid valve 48 so as to realize an optimum fuel pressure. The delivery pipe 31 further includes a relief valve 37. When the pressure in the pipe exceeds a predetermined value, the relief valve 37 is opened to reduce the pressure in the pipe to a predetermined value. The high-pressure fuel discharged from the relief valve 37 is reduced in pressure while passing through the passage 39 and returned to the fuel tank 40.

  The ECU 20 is a device for controlling the operating state of the engine 10 such as fuel injection amount control, fuel injection timing control, fuel pressure control, and combustion mode switching control. The ECU 20 includes a central processing unit that performs the control as described above, a memory for storing function data or calculation results, and the like. In the present invention, the ECU 20 calculates a correction amount so that the pressure in the delivery pipe 31 approaches the target value, and performs feedback control of the solenoid valve 48, and system abnormality based on the correction amount of the feedback control. Processing system to determine.

  FIG. 2 is a flowchart of the abnormality detection method for the high-pressure fuel supply system of the present invention. The feedback control of the present invention performs PID control based on the deviation between the detection signal of the fuel pressure sensor in the delivery pipe and the target pressure value. The correction amount of the input signal by this PID control, that is, the feedback amount is defined as a “feedback coefficient”. In one embodiment of the present invention, an upper limit value and a lower limit value of the feedback coefficient are set, and an abnormality is determined when the feedback coefficient reaches the upper limit value or the vicinity of the lower limit value. This will be described in detail with reference to the flowchart of FIG.

  Steps S101 to S107 are steps for determining whether or not the engine is in an appropriate state for executing fuel pressure abnormality detection. If it is determined that each step is inappropriate, the process proceeds to step S102, and a loop is formed by removing the processing step that is the core of the abnormality detection processing.

  In step S101, the monitor permission flag is confirmed. If the engine operating state is not in a state of permitting monitoring of the feedback coefficient for determining fuel pressure abnormality (flag is 0), the process proceeds to step S102, and if monitoring is permitted (flag is 1), step is performed. Proceed to 103.

  In step S103, the failure detection execution completion flag is confirmed. The failure detection executed flag is 1 when it is determined that the fuel pressure is abnormal, and 0 otherwise. Once this flag becomes 1 (failure detection), it does not return to 0 in the processing routine of the present invention, and is reset to 0 at the service factory when the failure location is repaired. If failure detection has been performed (flag is 1), the process proceeds to step S102, and if failure detection has not yet been performed (flag is 0), the process proceeds to step S105.

  In step S105, it is confirmed whether a predetermined time has elapsed after the engine is started. This is because at the time of start-up, the load is large and the fuel pressure is unstable, so that abnormality determination is not performed. If the predetermined time has not elapsed, the process proceeds to step S102, and if the predetermined time has elapsed, the process proceeds to step S107.

  In step S107, it is confirmed whether the ECU is performing feedback control of fuel pressure based on the detection value of the fuel pressure sensor. This is because if the feedback control process is not executed, the feedback coefficient does not fluctuate and an abnormality cannot be determined. When the feedback control is not executed, the process proceeds to step S102, and when the feedback control is being executed, the process proceeds to step S109.

  Here, a loop including step S102 that proceeds when it is determined in steps S101 to S107 that the fuel pressure abnormality is not suitable will be described. In step S102, the delay timer is returned to a predetermined value. The value of the delay timer is sequentially subtracted from a predetermined value to 0. Examples of the subtraction method include a method of subtracting a fixed number for each cycle of the method shown in this flowchart, and a method of subtracting according to real time. . That is, if it is determined in any step up to step S107 that the fuel pressure abnormality is not suitable, the value of the cycle delay timer is returned to a predetermined value. In step S104, the high pressure abnormality determination timer, the low pressure abnormality determination timer, and the normality determination timer are returned to predetermined values. The values of these timers are also sequentially subtracted from a predetermined value to 0, like the delay timer.

  Returning to the original loop and continuing the description, it is confirmed in step S109 whether the value of the delay timer is zero. This is because the abnormality detection determination process is executed after a predetermined time has elapsed after it is confirmed that the fuel pressure feedback control is being executed. If the value is other than 0, the process proceeds to step S104, and if the value is 0, the process proceeds to step S111.

  In step S111, a feedback coefficient upper limit value for determining abnormality of the fuel pressure system is determined based on the engine speed NE. For the upper limit value, a map is prepared for each rotation speed in advance, and the map is searched based on the rotation speed. Next, in step S113, it is confirmed whether or not the feedback coefficient exceeds the upper limit value. If it is less than or equal to the upper limit value, the process proceeds to step S115, and if it exceeds the upper limit value, the process proceeds to step S125.

  Here, a loop including step S125 that proceeds when the upper limit value is exceeded will be described. The state where the feedback coefficient upper limit value is exceeded is a state where the fuel pressure raised by the high pressure pump is lower than the target pressure. If such a state continues for a certain period of time (predetermined value of the low-pressure abnormality determination timer) in spite of feedback control of the pressure, it is determined that there is some abnormality in the fuel pressure system. In step S125, the high pressure abnormality determination timer and the normality determination timer are returned to predetermined values. In step S127, it is confirmed whether the low-pressure abnormality determination timer is zero. If the value is other than 0, the loop is terminated as it is, and the next cycle is started. When the determination of exceeding the upper limit limit for each cycle is continued in step S113 for a predetermined time of the low-pressure abnormality determination timer, the low-pressure abnormality determination timer becomes 0, and the process proceeds to step S129. In step S129, the normal flag is 0, in step S131, the low-pressure abnormality flag is 1, and in step S133, the failure detection executed flag is 1. Steps S129 to S133 indicate that the ECU has detected a low pressure abnormality in the fuel pressure system.

  Returning to the original loop again and continuing the description, in step S115, a feedback coefficient lower limit value for determining abnormality of the fuel pressure system is determined. Similar to step S111, the map is searched based on the engine speed. Next, in step S117, it is confirmed whether the feedback coefficient is below the lower limit value. If it is greater than or equal to the lower limit, the process proceeds to step S119, and if it is less than the lower limit, the process proceeds to step S135.

  Here, a loop including step S119 that proceeds when the value is less than the lower limit will be described. The state where the feedback coefficient is lower than the lower limit is a state where the fuel pressure by the high-pressure pump is higher than the target pressure. Even if the amount of feedback is small, this state continues for a certain period of time (predetermined value of the high-pressure abnormality determination timer). If this state continues, it means that the high pressure is maintained despite the suppression of the operation of the high-pressure pump. To do. Therefore, it is determined that there is some abnormality in the fuel pressure system. The following processing is the same as the upper limit passing loop of steps S125 to S133 described above. In step S135, the low-pressure abnormality determination timer and the normality determination timer are returned to predetermined values. In step S137, it is confirmed whether the high-pressure abnormality determination timer is zero. If the value is other than 0, the loop is terminated as it is, and the next cycle is started. If the timer is 0, the process proceeds to step S139. In step S139, the normal flag is 0, in step S141, the high-pressure abnormality flag is 1, and in step S143, the failure detection executed flag is 1. Steps S139 to S143 indicate that the ECU has detected a high pressure abnormality in the fuel pressure system.

  Returning to the original loop again and continuing the description, in step S119, the high pressure abnormality determination timer and the low pressure abnormality determination timer are returned to predetermined values. After a predetermined time (predetermined value of normality determination timer) has elapsed, if the value of the normality determination timer is 0 in step S121, the process proceeds to step S123. In step S123, the normal flag is set to 1. That is, the feedback coefficient is between the lower limit value and the upper limit value, indicating that the ECU has determined that the fuel pressure system is normal.

  As described above, the ECU detects the abnormality of the fuel pressure system by the method described so far. Then, when the low pressure or high pressure abnormality flag is 1 and it is determined that the system is abnormal, an action as a countermeasure is generated.

  FIG. 3 is a flowchart of the high pressure pump stop action shown as an example of the action. In step S201, a crank failure is confirmed. If a failure is confirmed, the process proceeds to step S215, and if there is no failure, the process proceeds to step S205. Similarly, in step S205, the fuel pressure sensor characteristic abnormality is detected, in step S207, the fuel pressure sensor abnormality is detected, in step S209, the spill valve failure is confirmed, in step S211, the fuel pressure system abnormality is confirmed, and if applicable, the process proceeds to step S215. In step S215, the high-pressure pump stop flag becomes 1. This indicates that the pump is stopped because a failure has been confirmed in any part of the high-pressure pump. On the other hand, if any failure from S201 to S211 cannot be confirmed, the process proceeds to step S213, and the high-pressure pump stop flag becomes zero. This indicates that the pump was not stopped because there was no failure in the high-pressure pump.

  Another example of the action is a method of prohibiting stratified combustion in response to abnormality determination. Stratified combustion is a method of realizing stable combustion even with a lean mixture as a whole by forming an air-fuel mixture around the spark plug during the compression stroke of the engine. Since the method is performed during the compression stroke, it is necessary to inject the fuel at a higher pressure than the compressed air inside the engine. That is, stratified combustion is not performed by weakening the function of the high-pressure pump and suppressing the high-pressure fuel. It can be said that it is an effective treatment when any abnormality is confirmed in the fuel pressure system by the abnormality determination according to the present invention.

  FIG. 4 is a flowchart of the fuel cut action at the time of high pressure fuel failure, shown as still another example of the action. In step S231, the high-pressure pump failure flag is confirmed. The high-pressure pump failure flag is a flag that is set to 1 when either the low-pressure abnormality flag or the high-pressure abnormality flag is 1 described in S131 and S141 of FIG. When the high pressure pump failure flag is 0, the process proceeds to step S237, and when the flag is 1, the process proceeds to step S233.

  In step S233, it is confirmed whether the engine speed NE exceeds a predetermined value (for example, 1500 rpm). If it is less than the predetermined value, the process proceeds to step S237, and if it is greater than the predetermined value, the process proceeds to step S235.

  In step S237, the failure time fuel cut flag becomes zero. This processing is performed when no abnormality is confirmed in the high-pressure pump, or when a failure is confirmed in the high-pressure pump but the engine speed is low. In these states, if the fuel is cut, the driving is disturbed, so the fuel cut action is not executed.

  In step S235, the fuel cut flag at failure is set to 1. When a failure is confirmed in the high-pressure pump, normal operation of the in-cylinder direct injection engine is not possible, and it is desired to repair the cylinder immediately. For this reason, a fuel cut is executed so that the vehicle speed does not increase, and the driver is informed of the engine malfunction.

  In this way, the failed vehicle is brought to the service factory for repair.

  As mentioned above, although this invention was described about the specific Example, this invention is not limited to such an Example.

Schematic of a high pressure fuel supply system. The flowchart of the abnormality detection method of a high pressure fuel supply system. High-pressure pump stop action flowchart Fuel cut action flowchart

Explanation of symbols

20 Electronic control unit (ECU)
31 Delivery pipe 33 Fuel pressure sensor 35 Fuel injection device 37 Relief valve 40 Fuel tank 41 Feed pump 49 High pressure fuel pump

Claims (6)

A high pressure fuel supply system for an in-cylinder direct injection engine,
A feed pump for delivering fuel from the fuel tank;
A high pressure fuel pump that receives fuel from the feed pump;
A delivery pipe connected to the high pressure fuel pump for supplying fuel to the fuel injection device;
A fuel pressure sensor for detecting the pressure of the fuel in the delivery pipe;
An electronic control unit that feedback-controls the pressure of the fuel in the delivery pipe to be a predetermined pressure based on the output of the pressure sensor;
And the electronic control unit is configured to determine an abnormality of the high-pressure fuel supply system based on a state of a feedback coefficient of the feedback control.   The high-pressure fuel supply system according to claim 1, configured to stop the high-pressure fuel pump in response to the determination of the abnormality.   The high-pressure fuel supply system according to claim 2, wherein the high-pressure fuel supply system is configured to prohibit stratified combustion in response to the determination of the abnormality.   The high pressure fuel supply system according to claim 2, wherein the fuel cut is executed at a relatively low engine speed in response to the determination of the abnormality.   The high-pressure fuel supply system according to claim 1, wherein the delivery pipe includes a relief valve for releasing a pressure equal to or higher than a predetermined value.   The feedback coefficient is a correction amount calculated from a deviation between a detected value of the fuel pressure sensor and a target pressure value, and an abnormality is determined when the feedback coefficient sticks near an upper limit value or a lower limit value. The high-pressure fuel supply system according to 1.

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