JP2009270510A - Device and method for diagnosing abnormality of fuel system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately determine whether a pressure reducing valve for reducing the pressure of a fuel in a common rail is normal or abnormal. <P>SOLUTION: An ECU (electronic control unit) executes a program comprising a step (S102) of controlling an injector for stopping injection of a fuel, and a step (S108) of opening a pressure reducing valve if the number of rotation of the output shaft of an engine declines to a threshold (YES in S104). Whether the pressure reducing valve is abnormal or normal is diagnosed based on behavior of the pressure of the fuel in the common rail. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel system abnormality diagnosis device and abnormality diagnosis method, and more particularly to a technique for controlling a fuel system to diagnose whether a pressure reducing valve that reduces fuel pressure is abnormal or normal.

  Conventionally, diesel engines that inject high-pressure fuel stored in a common rail from an injector have been put into practical use. The pressure of the fuel in the common rail is controlled so as to be a target pressure determined according to the operating state of the engine and the vehicle.

  By the way, when the target pressure decreases, the fuel pressure in the common rail may increase with respect to the target pressure. Therefore, a pressure reducing valve is provided on the common rail in order to quickly reduce the fuel pressure in the common rail. When the pressure reducing valve is controlled to open, the pressure in the common rail is quickly reduced. Thereby, the difference between the fuel pressure in the common rail and the target pressure can be reduced.

  On the other hand, when the pressure reducing valve is abnormal, the pressure of the fuel in the common rail cannot be reduced unless the pressure reducing valve is opened. Therefore, it is necessary to diagnose whether or not the pressure reducing valve is abnormal in order to determine whether or not the pressure reducing valve needs to be repaired.

Japanese Unexamined Patent Application Publication No. 2007-1000062 (Patent Document 1) discloses a fuel injection control that diagnoses the presence or absence of an abnormality in a pressure reducing valve based on the behavior of the pressure of fuel in a pressure accumulation chamber (common rail) detected when the pressure reducing valve is operated. An apparatus is disclosed.
JP 2007-1000062 A

  However, even when the injector and the fuel pump are abnormal, the pressure of the fuel in the common rail can fluctuate. Therefore, it is difficult to specify which of the injector, the fuel pump, and the pressure reducing valve changes the pressure of the fuel in the common rail when the pressure reducing valve is operated. Therefore, it can be erroneously diagnosed whether or not the pressure reducing valve is abnormal.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel system abnormality diagnosis device and abnormality diagnosis method that can accurately determine whether or not a pressure reducing valve is abnormal. Is to provide.

  An abnormality diagnosis device for a fuel system according to a first invention includes a fuel injection valve that injects fuel, a storage unit that stores fuel to be supplied to the fuel injection valve, a fuel pump that supplies fuel to the storage unit, and an open state Is a fuel system abnormality diagnosis device provided with a pressure reducing valve for reducing the pressure of the fuel in the storage. This abnormality diagnosing device is configured so that the fuel injection valve is controlled so as to limit fuel injection, and the pressure reducing valve is changed from a closed state to an open state when the number of revolutions of the fuel pump is reduced to a threshold value. And a detecting means for detecting the pressure of the fuel in the storage section.

  According to this configuration, the fuel system includes a fuel injection valve that injects fuel, a storage unit that stores fuel to be supplied to the fuel injection valve, a fuel pump that supplies fuel to the storage unit, and an open state in the storage unit. A pressure reducing valve for reducing the pressure of the fuel is provided. When diagnosing whether or not there is an abnormality in the pressure reducing valve, the fuel injection valve is controlled so as to limit fuel injection, and the fuel pump speed is reduced to the threshold value. The abnormality diagnosis mode in which the pressure reducing valve is controlled so as to be in the state is executed, and the fuel pressure in the storage unit is detected. As a result, the fuel pressure in a state where the influence of the fuel injection valve and the fuel pump on the fuel pressure is small can be detected. If the fuel pressure decreases in this state, it can be said that the pressure of the fuel has decreased because the pressure reducing valve opened normally. Thereby, an operator or the like can diagnose whether or not the pressure reducing valve is abnormal based on the behavior of the pressure of the fuel by the operation of the pressure reducing valve. Therefore, it is possible to provide a fuel system abnormality determination device that can accurately determine whether or not the pressure reducing valve is abnormal.

  In the abnormality diagnosis device for a fuel system according to the second invention, in addition to the configuration of the first invention, in the abnormality diagnosis mode, the fuel injection is limited after the pressure reducing valve is controlled to be in a closed state. The fuel injection valve is controlled.

  According to this configuration, the fuel injection valve is controlled to limit the fuel injection after the pressure reducing valve is controlled to be closed. If the fuel pressure does not drop in this state, it can be said that the pressure reducing valve is normally closed, and the fuel injection valve and the fuel pump can maintain the fuel pressure. Therefore, it can be determined whether or not the fuel pressure can be maintained.

  In addition to the configuration of the first or second invention, the abnormality diagnosis device for a fuel system according to a third aspect of the invention is configured such that the fuel injection valve is controlled so as to limit fuel injection instead of the abnormality diagnosis mode, and the fuel pump And a means for executing a diagnostic mode in which the pressure reducing valve is controlled to maintain a closed state in a state where the rotational speed of the engine is reduced to a threshold value.

  According to this configuration, instead of controlling the pressure reducing valve to open, the pressure reducing valve is controlled to remain closed. Thereby, it is possible to detect a pressure corresponding to the pressure of the fuel when the pressure reducing valve is not opened due to an abnormality. Therefore, based on the result of comparing the pressure of the fuel in the storage part when the pressure reducing valve is controlled to open and the pressure of the fuel in the storage part when controlled to maintain the closed state of the pressure reducing valve, An operator or the like can accurately diagnose whether or not is abnormal.

  An abnormality diagnosis method for a fuel system according to a fourth aspect of the present invention includes a fuel injection valve that injects fuel, a storage unit that stores fuel to be supplied to the fuel injection valve, a fuel pump that supplies fuel to the storage unit, and an open state Is a fuel system abnormality diagnosis method provided with a pressure reducing valve for reducing the pressure of the fuel in the storage. In this abnormality diagnosis method, the fuel injection valve is controlled so as to limit fuel injection, and the pressure reducing valve is changed from the closed state to the open state when the fuel pump speed is reduced to the threshold value. The method includes a step of executing an abnormality diagnosis mode in which is controlled, and a step of detecting the pressure of fuel in the storage unit.

  According to this configuration, the fuel system includes a fuel injection valve that injects fuel, a storage unit that stores fuel to be supplied to the fuel injection valve, a fuel pump that supplies fuel to the storage unit, and an open state in the storage unit. A pressure reducing valve for reducing the pressure of the fuel is provided. When diagnosing whether or not there is an abnormality in the pressure reducing valve, the fuel injection valve is controlled so as to limit fuel injection, and the fuel pump speed is reduced to the threshold value. The abnormality diagnosis mode in which the pressure reducing valve is controlled so as to be in the state is executed, and the fuel pressure in the storage unit is detected. As a result, the fuel pressure in a state where the influence of the fuel injection valve and the fuel pump on the fuel pressure is small can be detected. If the fuel pressure decreases in this state, it can be said that the pressure of the fuel has decreased because the pressure reducing valve opened normally. Thereby, an operator or the like can diagnose whether or not the pressure reducing valve is abnormal based on the behavior of the pressure of the fuel by the operation of the pressure reducing valve. Therefore, it is possible to provide a fuel system abnormality determination method capable of accurately determining whether or not the pressure reducing valve is abnormal.

  In the fuel system abnormality diagnosis method according to the fifth invention, in addition to the configuration of the fourth invention, in the abnormality diagnosis mode, the fuel injection is limited after the pressure reducing valve is controlled to be in a closed state. The fuel injection valve is controlled.

  According to this configuration, the fuel injection valve is controlled to limit the fuel injection after the pressure reducing valve is controlled to be closed. If the fuel pressure does not decrease in this state, it can be said that the pressure reducing valve is normally closed, and the fuel injection valve and the fuel pump can maintain the fuel pressure. Therefore, it can be determined whether or not the fuel pressure can be maintained.

  In addition to the configuration of the fourth or fifth invention, the fuel system abnormality diagnosis method according to the sixth aspect of the invention is configured such that the fuel injection valve is controlled so as to limit fuel injection instead of the abnormality diagnosis mode, and the fuel pump The method further includes the step of executing a diagnostic mode in which the pressure reducing valve is controlled to maintain the closed state in a state where the rotational speed of the motor is reduced to a threshold value.

  According to this configuration, instead of controlling the pressure reducing valve to open, the pressure reducing valve is controlled to remain closed. Thereby, it is possible to detect a pressure corresponding to the pressure of the fuel when the pressure reducing valve is not opened due to an abnormality. Therefore, based on the result of comparing the pressure of the fuel in the storage part when the pressure reducing valve is controlled to open and the pressure of the fuel in the storage part when controlled to maintain the closed state of the pressure reducing valve, An operator or the like can accurately diagnose whether or not is abnormal.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  With reference to FIG. 1, an engine 100 for a vehicle equipped with an abnormality diagnosis apparatus according to an embodiment of the present invention will be described. The engine 100 is a diesel engine. An internal combustion engine other than the diesel engine may be used. Engine 100 is provided with a plurality of cylinders.

  Air sucked into the engine 100 is filtered by an air cleaner 102 and compressed by a compressor 104 of a turbocharger. The compressed air is cooled by heat exchange with the outside air by the intercooler 106, passes through the intake pipe 108 and the intake manifold 110, and is introduced into the combustion chamber. Of the air introduced into the combustion chamber, the amount of fresh air is controlled by the throttle valve 112. The opening degree of the throttle valve 112 is controlled by an ECU (Electronic Control Unit) 200. Note that the throttle valve 112 may not be provided.

  Fuel that is pressurized by the supply pump 114 and stored in the common rail 116 is injected into the combustion chamber by the injector 118. The engine 100 generates a driving force by burning the air-fuel mixture in the combustion chamber.

  Supply pump 114 is connected to an output shaft (crankshaft) of engine 100 and is driven by the rotation of the output shaft. Fuel is supplied from the supply pump 114 to the common rail 116. The flow rate of the fuel supplied from the supply pump 114 to the common rail 116 is controlled according to the opening degree of the suction control valve provided in the supply pump 114. Therefore, fuel supply from the supply pump 114 to the common rail 116 can be stopped in a state where the output shaft of the engine 100 is rotating. A supply pump driven by an electric motor may be used.

  An injector 118 is provided for each cylinder. The target fuel injection timing is determined according to a map having, for example, the accelerator opening, the output shaft speed of the engine 100, the vehicle speed, and the like as parameters. In addition, since the method of setting the target injection timing should just use a known general technique, the further description is not repeated here.

  The amount of fuel injected from injector 118 is determined according to a map having, for example, the accelerator opening, the output shaft speed of engine 100, the vehicle speed, and the like as parameters. During idling, the fuel injection amount is determined by ISC (Idle Speed Control) so that the output shaft rotational speed of the engine 100 becomes a predetermined target rotational speed. In addition, since the method of setting the injection amount of fuel should just use a known general technique, the further description is not repeated here.

  The air-fuel mixture after combustion, that is, exhaust gas, is guided to the exhaust manifold 120, passes through the turbine 122 of the turbocharger, is purified by the catalyst 124, and is discharged outside the vehicle.

  A part of the exhaust gas is recirculated via an EGR (Exhaust Gas Recirculation) pipe 126 connected to the exhaust manifold 120. Exhaust gas flowing through the EGR pipe 126 passes through the oxidation catalyst 128 and is cooled by heat exchange with the cooling water by the EGR cooler 130. The cooled exhaust gas is recirculated to the intake side downstream of the throttle valve 112 via the EGR valve 132.

  The amount of exhaust gas to be recirculated (EGR amount) is adjusted by the opening degree of the EGR valve 132. The EGR valve opening degree is controlled by the EGR valve linear solenoid 134. Normally, the EGR valve opening is controlled so that the EGR valve 132 is closed as the torque of the engine 100 increases, that is, the EGR amount decreases. Specifically, the EGR valve lift is set so that the intake oxygen concentration changed by EGR becomes a target value corresponding to the state of the engine 100 (engine speed, supercharging pressure, temperature of each part, load, intake air amount). The EGR valve opening detected using the sensor 136 is input to the ECU 200, and the EGR valve opening is feedback controlled. The operation method of the EGR valve 132 may be a negative pressure type or a motor type other than the method using the EGR valve linear solenoid 134.

  The common rail 116 is provided with a pressure reducing valve 138. When the pressure reducing valve 138 opens, the fuel in the common rail 116 is discharged, and the pressure of the fuel in the common rail 116 decreases. The fuel discharged from the pressure reducing valve 138 is returned to the fuel tank.

  The ECU 200 receives signals from an output shaft rotation speed sensor (crank position sensor) 202, an accelerator opening sensor 204, a vehicle speed sensor 206, a pressure sensor 208, and the like.

  Output shaft speed sensor 202 detects the output shaft speed of engine 100. The accelerator opening sensor 204 detects the opening of the accelerator pedal. The vehicle speed sensor 206 detects the speed of the vehicle on which the engine 100 is mounted. For example, the vehicle speed is detected from the output shaft speed of a transmission connected to engine 100.

  The pressure sensor 208 detects the pressure of the fuel in the common rail 116. The pressure detected by the pressure sensor 208 is stored in a RAM (Random Access Memory) 210 of the ECU 200.

  ECU 200 performs arithmetic processing based on signals transmitted from these sensors, programs stored in memory, maps, and the like. Thereby, ECU 200 controls engine 100.

  With reference to FIG. 2, the function of ECU 200 in the present embodiment will be described. Note that the functions of the ECU 200 described below may be realized by software, or may be realized by hardware.

  ECU 200 includes a closing control unit 300, a stop control unit 302, and an opening / closing control unit 304.

  The closing control unit 300 controls the pressure reducing valve 138 to be closed when an operator diagnoses whether the pressure reducing valve 138 is abnormal or normal in an automobile repair shop or the like. For example, when the operator receives a command signal from the diagnostic device in a state where a diagnostic device (diagnostic tool) designed for an abnormality diagnosis of the pressure reducing valve 138 is connected to the ECU 200, the closing control unit 300 receives the pressure reducing valve. 138 is forcibly controlled to close.

  The stop control unit 302 controls the injector 118 so as to stop the fuel injection after the pressure reducing valve 138 is closed, and the supply pump so as to stop the fuel supply from the supply pump 114 to the common rail 116. 114 is controlled.

  After stopping fuel injection, the opening / closing control unit 304 opens the pressure reducing valve 138 when the output shaft rotational speed of the engine 100 decreases to a threshold value, that is, when the output shaft rotational speed of the engine 100 falls below the threshold value. To force control. For example, a value at which the influence of the supply pump 114 on the fuel pressure in the common rail 116 is almost eliminated is set as the threshold value.

  Further, the open / close control unit 304 forces the pressure reducing valve 138 to remain closed instead of controlling the pressure reducing valve 138 to open when the output shaft rotational speed of the engine 100 decreases to a threshold value. To control.

  In other words, in the present embodiment, when it is diagnosed whether the pressure reducing valve 138 is abnormal or normal, the ECU 200 maintains the first diagnosis mode in which the pressure reducing valve 138 is opened and the state in which the pressure reducing valve 138 is closed. 2 Execute diagnosis mode. For example, after one of the first diagnosis mode and the second diagnosis mode is executed, the other diagnosis mode is executed.

  In the present embodiment, when the output shaft rotational speed of engine 100 decreases to the threshold value, it is determined that the rotational speed of supply pump 114 has decreased to the threshold value. That is, whether or not the rotation speed of supply pump 114 has decreased to a threshold value is indirectly determined by whether or not the output shaft rotation speed of engine 100 has decreased to a threshold value. The rotation speed of the supply pump 114 may be directly detected.

  The fuel pressure detected by the pressure sensor 208 in each diagnostic mode is input to the diagnostic device via the ECU 200, for example. The operator determines whether the pressure reducing valve 138 is abnormal or normal based on the behavior (transition) of the pressure of the fuel displayed on the display of the diagnostic apparatus. Note that the ECU 200 may diagnose whether the pressure reducing valve 138 is abnormal or normal.

  With reference to FIG. 3, a control structure of a program executed by ECU 200 in the present embodiment will be described. The program described below is executed when an operator diagnoses whether or not the pressure reducing valve 138 is abnormal. The program executed by the ECU 200 may be recorded on a recording medium such as a CD (Compact Disc) or a DVD (Digital Versatile Disc) and distributed to the market. Further, a program may be stored in the diagnostic device instead of the ECU 200, and the diagnostic device may execute the program.

  In step (hereinafter, step is abbreviated as S) 100, ECU 200 performs control so that pressure reducing valve 138 is closed. In S102, ECU 200 controls injector 118 so as to stop fuel injection, and also controls supply pump 114 so as to stop fuel supply from supply pump 114 to common rail 116.

  In S104, ECU 200 determines whether or not the output shaft rotational speed of engine 100 has decreased to a threshold value, that is, whether or not the rotational speed of supply pump 114 has decreased to the threshold value. When output shaft speed of engine 100 decreases to the threshold value (YES in S104), the process proceeds to S106. If not (NO in S104), the process returns to S104.

  In S106, ECU 200 determines whether control is performed so that pressure reducing valve 138 is opened or control is performed so that pressure reducing valve 138 is kept closed. If control is performed to open pressure reducing valve 138 (open in S106), the process proceeds to S108. When controlling to maintain the pressure reducing valve 138 in the closed state (closed in S106), the process proceeds to S110.

  In S108, ECU 200 controls pressure reducing valve 138 to open. In S110, ECU 200 controls so that pressure reducing valve 138 is kept closed.

  An operation of the abnormality diagnosis apparatus according to the present embodiment based on the above-described structure and flowchart will be described.

  When the abnormality diagnosis of the pressure reducing valve 138 is performed, the pressure reducing valve 138 is controlled to close at time T1 in FIG. 4 (S100). Thereafter, at time T2, the injector 118 is controlled to stop fuel injection, and the supply pump 114 is controlled to stop fuel supply from the supply pump 114 to the common rail 116 (S102).

  In a state where the pressure reducing valve 138 is closed and fuel injection and fuel supply are stopped, as shown by a one-dot chain line in FIG. 4, when the fuel pressure rapidly decreases, the injector 118, the supply pump 114, and the pressure reducing valve 138 It can be said that fuel is leaking from at least one of them.

  On the other hand, when the pressure is maintained as shown by the solid line in FIG. 4 or when the pressure gradually decreases, the pressure reducing valve 138 operates normally and the injector 118 and the supply pump 114 can maintain the fuel pressure. It can be said that it is in a state.

  At time T3 in FIG. 4, when output shaft speed of engine 100 decreases to a threshold value (YES in S104), control is performed so that pressure reducing valve 138 is opened, or pressure reducing valve 138 is kept closed. It is determined whether or not to control (S106). When controlling so that the pressure reducing valve 138 is kept closed (closed in S106, S110), if the pressure reducing valve 138 is normal, the fuel pressure gradually decreases as shown by a two-dot chain line in FIG. descend.

  When control is performed so that the pressure reducing valve 138 is opened (open in S106, S108), as shown by the solid line in FIG. It can be said that the pressure dropped.

  On the other hand, if the pressure of the fuel gradually decreases as in the case of controlling so that the pressure reducing valve 138 is kept closed, it can be said that the pressure reducing valve 138 remains closed. In this case, it can be said that the pressure reducing valve 138 is abnormal.

  Therefore, if the pressure of the fuel when the pressure reducing valve 138 is controlled to be opened and the pressure of the fuel when the pressure is controlled to maintain the closed state of the pressure reducing valve 138 are substantially the same, the pressure reducing valve 138 is abnormal. Can be determined.

  On the other hand, if the pressure of the fuel when the pressure reducing valve 138 is controlled to open is lower than the pressure of the fuel when the pressure reducing valve 138 is controlled to maintain the closed state, the pressure reducing valve 138 opens normally. It can be said that the pressure of the fuel decreased. Therefore, it can be determined that the pressure reducing valve 138 is normal.

  As described above, according to the abnormality diagnosis device in accordance with the present embodiment, when performing abnormality diagnosis of the pressure reducing valve, the injector is controlled so as to stop fuel injection. Thereafter, when the output shaft speed of the engine decreases to a threshold value, the pressure reducing valve is controlled to open. Thereby, the pressure of the fuel in a state where the influence of the injector and the supply pump is small can be detected. If the fuel pressure decreases in this state, it can be said that the pressure of the fuel has decreased due to the normal opening of the pressure reducing valve. Therefore, the operator can diagnose whether or not the pressure reducing valve is abnormal based on the behavior of the pressure of the fuel due to the operation of the pressure reducing valve. As a result, it can be accurately determined whether or not the pressure reducing valve is abnormal.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic block diagram of an engine. It is a functional block diagram of ECU. It is a flowchart which shows the control structure of the program which ECU performs. It is a timing chart which shows changes, such as fuel pressure.

Explanation of symbols

  100 Engine, 114 Supply pump, 116 Common rail, 118 Injector, 138 Pressure reducing valve, 200 ECU, 208 Pressure sensor, 300 Close control unit, 302 Stop control unit, 304 Open / close control unit

Claims (6)

A fuel injection valve for injecting fuel, a storage section for storing fuel to be supplied to the fuel injection valve, a fuel pump for supplying fuel to the storage section, and a decompression for reducing the pressure of the fuel in the storage section in an open state An abnormality diagnosis device for a fuel system provided with a valve,
The fuel injection valve is controlled so as to limit fuel injection, and the pressure reducing valve is controlled so as to change from a closed state to an open state when the rotational speed of the fuel pump is reduced to a threshold value. Execution means for executing the abnormal diagnosis mode,
An abnormality diagnosis device for a fuel system, comprising: detecting means for detecting a pressure of fuel in the storage unit.   2. The fuel system abnormality diagnosis device according to claim 1, wherein in the abnormality diagnosis mode, the fuel injection valve is controlled to limit fuel injection after the pressure reducing valve is controlled to be in a closed state. 3. .   Instead of the abnormality diagnosis mode, the fuel injection valve is controlled so as to limit fuel injection, and the closed state is maintained in a state where the rotation speed of the fuel pump is reduced to the threshold value. 3. The fuel system abnormality diagnosis device according to claim 1, further comprising means for executing a diagnosis mode in which the pressure reducing valve is controlled. A fuel injection valve for injecting fuel, a storage section for storing fuel to be supplied to the fuel injection valve, a fuel pump for supplying fuel to the storage section, and a decompression for reducing the pressure of the fuel in the storage section in an open state An abnormality diagnosis method for a fuel system provided with a valve,
The fuel injection valve is controlled so as to limit fuel injection, and the pressure reducing valve is controlled so as to change from a closed state to an open state when the rotational speed of the fuel pump is reduced to a threshold value. Executing the abnormal diagnosis mode,
And detecting a fuel pressure in the storage unit.   5. The fuel system abnormality diagnosis method according to claim 4, wherein, in the abnormality diagnosis mode, the fuel injection valve is controlled to limit fuel injection after the pressure reducing valve is controlled to be in a closed state. .   Instead of the abnormality diagnosis mode, the fuel injection valve is controlled so as to limit fuel injection, and the closed state is maintained in a state where the rotation speed of the fuel pump is reduced to the threshold value. The fuel system abnormality diagnosis method according to claim 4, further comprising executing a diagnosis mode in which the pressure reducing valve is controlled.

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