JP5454522B2 - Engine abnormality detection device - Google Patents

Description

  The present invention relates to an engine abnormality detection device that detects, as an abnormality, closing of a pressure reducing valve that discharges fuel from an engine fuel system and lowers the fuel pressure of the fuel system.

  As is well known, a pressure accumulating diesel engine having a common rail for accumulating high-pressure fuel and injecting fuel to the engine through the common rail has been put into practical use. In recent years, in such an accumulator diesel engine, the pressure of fuel has been increased for the purpose of improving injection response and promoting atomization of spray. As the fuel pressure increases, it is desired to improve the control accuracy of the fuel pressure (rail pressure) accumulated in the common rail. The rail pressure is controlled through control of a pressure reducing valve that discharges fuel from the como rail, in addition to control of a pumping amount of a high-pressure fuel pump that pressurizes and supplies fuel to the common rail.

  By the way, as the pressure reducing valve, for example, a normally closed type valve that uses an electromagnetic attractive force generated by energizing a solenoid to open the inside of the common rail to the relief flow path is employed. In such a pressure reducing valve, even when the energization to the solenoid is interrupted, there may occur a valve closing operation abnormality in which the pressure reducing valve does not completely close. Conventionally, an apparatus described in Patent Document 1 is known as an engine abnormality detection device that detects such a valve closing operation abnormality of a pressure reducing valve. In the abnormality detection device described in the same document, the sum of the upper limit value of the performance standard for the fuel escape amount of the pressure reducing valve and the upper limit value of the performance standard for the fuel leak amount of the injector is set as a judgment pressure reducing amount, When the amount of decrease in the rail pressure after opening the valve is equal to or greater than the determined pressure reduction amount, it is determined that the pressure reducing valve is abnormally closed.

JP 2006-257883 A

  By the way, the abnormality of the pressure reducing valve includes, besides the above-described abnormal operation of closing the valve, there is an abnormality caused by the closed valve closing, in which the pressure reducing valve does not open even when the solenoid is energized by the fixing of the valve body or the like. Such a closed closing of the pressure reducing valve can be detected when the rail pressure does not decrease even when the opening of the pressure reducing valve is instructed after the engine is stopped. However, in addition to the opening of the pressure reducing valve, there are other factors that increase the amount of rail pressure drop, such as the inclusion of foreign matter into the valve part of the injector and the entry of foreign matter into the spill valve of the high-pressure fuel pump. There is a fuel leak from the rail, and when they occur, the rail pressure decreases even if the pressure reducing valve does not open. For this reason, when the valve closing sticking of the pressure reducing valve overlaps with another abnormality increasing the rail pressure drop, it becomes impossible to properly detect the valve closing sticking of the pressure reducing valve.

  The present invention has been made in view of such circumstances, and a problem to be solved is to provide an abnormality detection device for an engine that can more accurately detect sticking of a pressure reducing valve.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
In order to solve the above-mentioned problem, the invention according to claim 1 as an abnormality detection device for an engine for detecting a closed valve of a pressure reducing valve that discharges fuel from an engine fuel system and lowers the fuel pressure of the fuel system. In addition to commanding the opening of the pressure reducing valve after the engine is stopped , the amount of decrease in fuel pressure per unit time before the valve opening command from the time when the engine is stopped until the valve opening command is The amount of decrease in fuel pressure per unit time after the valve opening command until the time elapses is detected each time the valve opening command is issued after the engine stops , and the results of the detection are compared to close the pressure reducing valve. The presence or absence of sticking is determined.

  When there is a fuel leak from the fuel system due to the foreign matter biting into the injector valve or the foreign matter biting into the spill valve of the high-pressure fuel pump, the fuel system A drop in fuel pressure occurs. In such a case, the fuel pressure is reduced due to the fuel leak before the pressure reducing valve is opened. After the pressure reducing valve is opened, the fuel pressure is reduced due to the fuel leak and the fuel pressure is reduced due to the opening of the pressure reducing valve. A decrease. Therefore, even when the fuel pressure has decreased due to factors other than the opening of the pressure reducing valve, the amount of decrease in fuel pressure per unit time before the opening command of the pressure reducing valve and the unit time after the opening command Compared with the amount of decrease in the fuel pressure per contact, whether or not the increase in the amount of decrease in fuel pressure accompanying the opening of the pressure reducing valve has occurred, that is, the pressure reducing valve is actually opened according to the valve opening command. It can be confirmed whether or not. Therefore, according to the above-described configuration, it is possible to more accurately detect the closing of the pressure reducing valve.

In order to solve the above-mentioned problem, the invention according to claim 2 as an abnormality detection device for an engine, which detects closing of a pressure reducing valve that discharges fuel from an engine fuel system and lowers the fuel pressure of the fuel system. In addition to commanding the opening of the pressure reducing valve after the engine is stopped , the amount of decrease in fuel pressure per unit time before the valve opening command from the time when the engine is stopped until the valve opening command is detecting a decrease in the fuel pressure per unit time after opening instruction to definitive until time elapses every time a valve-opening command after stopping the engine, reduction of the fuel pressure per unit were they detected time vacuo When there is no change before and after the valve opening command, it is determined that the pressure reducing valve is stuck closed.

  When there is a fuel leak from the fuel system due to foreign object biting into the injector valve or foreign object biting into the spill valve of the high-pressure fuel pump, the fuel system The fuel pressure has decreased. Even in such a case, if the pressure reducing valve is actually opened according to the command, the rate of decrease of the fuel pressure, that is, the amount of decrease of the fuel pressure per unit time should increase. Therefore, even if the opening of the pressure reducing valve is commanded, if the amount of decrease in fuel pressure per unit time does not change, the pressure reducing valve has not been opened regardless of the valve opening command. Can be determined to be stuck closed. Therefore, according to the above-described configuration, it is possible to more accurately detect the closing of the pressure reducing valve.

Incidentally, the abnormality detecting device for an engine of this invention, such as by claim 3, the pressure reducing valve as a valve for discharging the fuel from the common rail of the accumulator type diesel engine can be applied to an engine that is configured.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic which shows typically the structure of the fuel system of the pressure accumulation type diesel engine used as the application object about one Embodiment of the abnormality detection apparatus of the engine of this invention. The flowchart which shows the process sequence of the valve closing sticking determination routine employ | adopted as the embodiment. The time chart which shows an example of the control aspect at the time of valve-closing sticking determination of the embodiment when there is no fuel leak. The time chart which shows an example of the control aspect at the time of valve-closing sticking determination of the embodiment when there exists a fuel leak.

  Hereinafter, an embodiment of an engine abnormality detection device according to the present invention will be described in detail with reference to FIGS. In addition, the abnormality detection apparatus of this Embodiment is applied to a pressure accumulation type diesel engine.

First, with reference to FIG. 1, the structure of the fuel system of the pressure accumulation type diesel engine used as the application object of the abnormality detection apparatus of this Embodiment is demonstrated.
The fuel in the fuel tank 1 is pumped up by the high-pressure fuel pump 2. The high-pressure fuel pump 2 driven by the crankshaft pressurizes and discharges the fuel pumped from the fuel tank 1. The high pressure fuel discharged from the high pressure fuel pump 2 is pumped to the common rail 4. The high-pressure fuel pump 2 is provided with a spill valve, and surplus fuel is returned to the fuel tank 1 through the check valve 3 by the spill valve.

  The common rail 4 that is an accumulator pipe is provided with a rail pressure sensor 5 that detects the fuel pressure inside the common rail 4, that is, the rail pressure. The common rail 4 is provided with a pressure reducing valve 6, and the fuel discharged from the common rail 4 in response to the opening of the pressure reducing valve 6 is returned to the fuel tank 1 through the check valve 3.

  The common rail 4 is connected to an injector 7 for each cylinder, and high-pressure fuel accumulated in the common rail 4 is distributed and supplied to the injector 7 for each cylinder. From the injector 7, fuel is injected and supplied to the combustion chamber of the diesel engine. The surplus fuel in the injector 7 is returned to the fuel tank 1 via the check valve 3.

  An accumulator diesel engine having such a fuel system is controlled by an electronic control unit 8 for engine control. The electronic control unit 8 is provided in a central processing unit (CPU) that performs various arithmetic processes related to engine control, a read-only memory (ROM) that stores engine control programs and data, CPU calculation results, and engine parts. A random access memory (RAM) for temporarily storing detection results of the detected sensors. Then, the electronic control unit 8 adjusts the fuel pumping amount of the high-pressure fuel pump 2 based on the detection result of the rail pressure sensor 5 and also adjusts the fuel amount discharged from the common rail 4 through the pressure reducing valve 6. The rail pressure is controlled to be a value. The electronic control unit 8 controls the fuel injection timing and the fuel injection amount by sending a command signal to the solenoid valve of the injector 7.

  In the pressure accumulating diesel engine configured as described above, the electronic control unit 8 detects whether or not the pressure reducing valve 6 is firmly closed when the engine is stopped. This detection is performed through the processing of the valve closing sticking determination routine shown in FIG. Note that the processing of this routine is started from the time when the ignition switch is turned off by the electronic control unit 8. Note that the pressure reducing valve 6 at the time when the ignition switch is turned off is closed.

  When the processing of this routine is started, first, in step S101, the amount of decrease in fuel pressure (rail pressure) per unit time, that is, the rate of decrease in fuel pressure is detected. When the detection is completed, a valve opening command is output to the pressure reducing valve 6 in step S102. In step S103, after the valve opening command is output, the decrease amount of the fuel pressure (rail pressure) per unit time, that is, the decrease speed is detected again.

  When the detection of the fuel pressure decrease rate before and after the valve opening command is completed in this way, it is confirmed in step S104 whether or not a change has been recognized in the fuel pressure decrease rate before and after the valve opening command. Whether there is a change in the fuel pressure decrease rate before and after the valve opening command is, for example, whether the difference in the fuel pressure decrease rate before and after the valve open command is greater than or equal to a predetermined judgment value, This can be confirmed by checking whether or not the rate of decrease rate is equal to or higher than a predetermined determination value.

  If no change is observed in the rate of decrease in the fuel pressure before and after the valve opening command (S104: YES), it is determined in step S105 that the pressure reducing valve 6 is firmly closed, and then the process of this routine is performed. Is terminated. On the other hand, if there is a significant change in the rate of decrease in the fuel pressure before and after the valve opening command (S104: NO), it is determined in step S106 that the pressure reducing valve 6 is not closed, and the process of this routine is performed. Is terminated.

Then, the effect | action of this Embodiment comprised as mentioned above is demonstrated.
First, referring to FIG. 3, there is no fuel leakage from the fuel system due to foreign matter biting into the valve portion of the solenoid valve of the injector 7 or foreign matter biting into the spill valve of the high-pressure fuel pump 2. The control mode will be described.

  When the ignition switch (IG switch) is turned off at time t0 in FIG. 3, the fuel pressure per unit time is calculated from the decrease ΔPref of the fuel pressure (rail pressure) until the predetermined time TA elapses from that time. The amount of decrease, that is, the decrease rate ΔPref / TA is measured. When the ignition switch is turned off, the pressure reducing valve 6 is closed, and if there is no fuel leak, the fuel pressure in the common rail 4 is maintained. Accordingly, the fuel pressure decrease amount ΔPref and the decrease rate ΔPref / TA at this time are both “0”.

  At time t1 after the measurement, a valve opening command is output to the pressure reducing valve 6. Then, the amount of decrease in fuel pressure per unit time, that is, the rate of decrease ΔP / TA, is measured from the amount of decrease ΔP in fuel pressure (rail pressure) until the predetermined time TB elapses from that point.

  Here, if there is no abnormality in the pressure reducing valve 6 and the pressure reducing valve 6 is opened in response to the valve opening command, fuel is discharged from the common rail 4 and the fuel pressure (rail pressure) in the common rail 4 decreases. To go. Therefore, at this time, a significant difference occurs in the rate of decrease in the fuel pressure before and after the valve opening command, and as a result, the electronic control unit 8 determines that the pressure reducing valve 6 is not closed. .

  On the other hand, when the pressure reducing valve 6 is stuck closed, even if a valve opening command is issued, the pressure reducing valve 6 remains closed, and fuel is not discharged from the common rail 4, and the fuel pressure inside the same is reduced. (Rail pressure) is maintained as it is. Accordingly, at this time, the rate of decrease in fuel pressure remains “0” even after the valve opening command, and there is no significant difference in the rate of decrease in fuel pressure before and after the valve opening command. Therefore, at this time, the electronic control unit 8 determines that the pressure reducing valve 6 is firmly closed.

  Next, referring to FIG. 4, a fuel leak from the fuel system occurs due to the entry of foreign matter into the valve portion of the solenoid valve of the injector 7 or the entry of foreign matter into the spill valve of the high-pressure fuel pump 2. A control mode when the vehicle is in operation will be described.

  When the ignition switch (IG switch) is turned off at time t0 in FIG. 4, in this case as well, from the amount ΔPref of decrease in fuel pressure (rail pressure) until the predetermined time TA elapses from that time, the unit time The amount of decrease in the fuel pressure per contact, that is, the decrease rate ΔPref / TA is measured. In this case, the fuel pressure (rail pressure) in the common rail 4 decreases with time due to fuel leakage in the injector 7 and the high-pressure fuel pump 2. Therefore, the fuel pressure decrease rate ΔPref / TA at this time takes a positive value.

  At time t1 after the measurement, a valve opening command is output to the pressure reducing valve 6. Then, the amount of decrease in fuel pressure per unit time, that is, the rate of decrease ΔP / TA, is measured from the amount of decrease ΔP in fuel pressure (rail pressure) until the predetermined time TB elapses from that point.

  Here, if there is no abnormality in the pressure reducing valve 6 and the pressure reducing valve 6 is opened in response to the valve opening command, fuel is discharged from the common rail 4. In this case, since the fuel discharge from the pressure reducing valve 6 is added to the fuel leak in the injector 7 and the high pressure fuel pump 2, the rate of decrease in the fuel pressure becomes higher than before the opening command of the pressure reducing valve 6. Therefore, at this time, a significant difference occurs in the rate of decrease in the fuel pressure before and after the valve opening command, and as a result, the electronic control unit 8 determines that the pressure reducing valve 6 is not closed. .

  On the other hand, when the pressure reducing valve 6 is stuck closed, the pressure reducing valve 6 remains closed even when a valve opening command is issued, and fuel is not discharged from the common rail 4. Therefore, in this case, even after the valve opening command, the fuel pressure is reduced only by the fuel leak in the injector 7 and the high-pressure fuel pump 2, and even after the valve opening command, the fuel pressure decrease rate is the same as that before the valve opening command. Will not change. Therefore, at this time, there is no significant difference in the rate of decrease of the fuel pressure before and after the valve opening command, and as a result, the electronic control unit 8 determines that the pressure reducing valve 6 is firmly closed. .

According to the engine abnormality detection device of the present embodiment described above, the following effects can be obtained.
(1) In this embodiment, after the engine is stopped, the opening of the pressure reducing valve 6 is commanded, the amount of decrease in the fuel pressure per unit time before the valve opening command, and the unit time after the valve opening command The amount of decrease in the fuel pressure is detected, and whether or not the pressure reducing valve 6 is stuck closed is determined based on the detection results. More specifically, the amount of decrease in fuel pressure per unit time before the valve opening command and the amount of decrease in fuel pressure per unit time after the valve opening command are detected, and the detected fuel pressure per unit time is detected. When the amount of decrease does not change before and after the opening of the pressure reducing valve, it is determined that the pressure reducing valve is firmly closed. Therefore, regardless of whether or not a fuel leak has occurred from the fuel system due to the foreign matter biting into the valve portion of the solenoid valve of the injector 7 or the foreign matter biting into the spill valve of the high-pressure fuel pump 2. Whether or not the pressure reducing valve 6 is stuck closed can be accurately determined. Therefore, according to the present embodiment, it is possible to more accurately detect the closure of the pressure reducing valve.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the rate of decrease in fuel pressure is calculated from the amount of decrease in fuel pressure. However, if the amount of decrease in fuel pressure during the same length of time before and after the valve opening command is measured, the amount of decrease Is directly compared, it is possible to determine whether or not the pressure reducing valve 6 is closed. That is, when the times TA and TB in FIGS. 3 and 4 are the same length, the amount of decrease in fuel pressure during that period can be used as it is as the amount of decrease in fuel pressure per unit time. Calculation can be omitted.

  In the above embodiment, the rail pressure is used as the fuel pressure of the fuel system, but the pressure reducing valve 6 can be closed even if the fuel pressure of other parts of the fuel system, for example, the fuel pressure in the injector 7 is used. Determination of the presence or absence of valve sticking can be performed similarly.

  In the above embodiment, the pressure reducing valve 6 is configured as a valve for discharging fuel from the common rail 4 of the pressure accumulating diesel engine. However, the pressure reducing valve for discharging fuel from the fuel system and reducing the fuel pressure of the fuel system. If so, the abnormality detection device of the present invention can be applied to an engine provided with a pressure reducing valve provided in another part of the fuel system.

  In the above embodiment, the case where the abnormality detection device of the present invention is applied to a pressure accumulating diesel engine has been described. However, a pressure reducing valve that discharges fuel from the fuel system and lowers the fuel pressure of the fuel system is provided. As long as the engine has a fuel system, the present invention can be similarly applied to other engines.

  DESCRIPTION OF SYMBOLS 1 ... Fuel tank, 2 ... High pressure fuel pump, 3 ... Check valve, 4 ... Common rail, 5 ... Rail pressure sensor, 6 ... Pressure reducing valve, 7 ... Injector, 8 ... Electronic control unit.

Claims (3)

In an engine abnormality detection device that detects closing of a pressure reducing valve that discharges fuel from an engine fuel system and lowers the fuel pressure of the fuel system,
A command to open the pressure reducing valve after the engine is stopped, and a decrease amount of the fuel pressure per unit time before the valve opening command from the time when the engine is stopped to the valve opening command time , and the valve opening command time The amount of decrease in the fuel pressure per unit time after the valve opening command until a predetermined time elapses after the valve opening command is detected each time the valve opening command is issued after the engine is stopped, and the results of the pressure reduction are compared with each other. An engine abnormality detection device characterized by determining whether or not a valve is stuck closed. In an engine abnormality detection device that detects closing of a pressure reducing valve that discharges fuel from an engine fuel system and lowers the fuel pressure of the fuel system,
A command to open the pressure reducing valve after the engine is stopped, and a decrease amount of the fuel pressure per unit time before the valve opening command from the time when the engine is stopped to the valve opening command time , and the valve opening command time predetermined time and a decrease amount of the fuel pressure per unit time after the opening command definitive until elapse detected every time a valve-opening command after stopping the engine, decrease in the fuel pressure per unit were those detection time from An engine abnormality detection device, characterized in that it is determined that the pressure reducing valve is closed and closed when the amount does not change before and after the opening command of the pressure reducing valve. The pressure reducing valve, the abnormality detecting apparatus for an engine according to claim 1 or claim 2 comprising configured as a valve for discharging the fuel from the common rail pressure accumulator type diesel engine.

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