JP2011032870A - Abnormality diagnostic device for fuel pressure holding mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abnormality diagnostic device for a fuel pressure holding mechanism capable of accurately diagnosing abnormality of a fuel pressure holding mechanism used in a fuel injection device of an engine. <P>SOLUTION: The abnormality diagnostic device for a fuel pressure holding mechanism is included in a fuel injection device having a high pressure pump 14 boosting a fuel pressure and supplying high pressure fuel delivered from the high pressure pump 14 to a fuel injection valve 34 via high pressure fuel piping 32, and it diagnoses whether or not there is abnormality in the fuel pressure holding mechanism holding a pressure of fuel in the high pressure fuel piping 32 at a holding fuel pressure higher than a pressure of fuel supplied to the high pressure pump 14 after stopping the engine. After stopping the engine, it is determined whether or not the pressure of fuel in the high pressure fuel piping 32 is within a normal fuel pressure range set on the basis of the holding fuel pressure (S31-S33), and it is diagnosed whether or not the fuel pressure holding mechanism is abnormal on the basis of a determination result (S34, S35). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an abnormality diagnosis device for a fuel pressure holding mechanism provided in a fuel injection device for an internal combustion engine.

  In-cylinder injection engines that inject fuel directly into the cylinder need to atomize the injected fuel by increasing the injection pressure, so the fuel pumped from the fuel tank by the low-pressure pump is supplied to the high-pressure pump. High-pressure fuel discharged from a pump is pumped to a fuel injection valve through a fuel manifold (for example, Patent Document 1).

  On the other hand, after the engine is stopped, the fuel pressure in the fuel manifold need not be as high as during engine operation. Therefore, in order to reduce the pressure load on the fuel manifold after the engine is stopped, Patent Document 1 includes a fuel passage for returning the fuel in the fuel manifold to the low pressure pump, and suppresses the pressure drop in the fuel manifold during engine operation. Therefore, a flow restrictor (pore) is arranged in the fuel passage. Moreover, in patent document 1, it is diagnosed whether the operation state of a flow restrictor is normal from the gradient of the fuel pressure fall when the high pressure pump is not operating.

  By the way, if the fuel pressure in the high-pressure fuel passage such as the fuel manifold is maintained at a high pressure even after the engine is stopped, the amount of fuel leaked from the fuel injection valve increases while the engine is stopped, and the leaked fuel stays in the cylinder. There is a problem that exhaust emission at the next start-up deteriorates. On the other hand, if the fuel pressure in the fuel manifold is lowered too much after the engine is stopped, it takes time to increase the fuel pressure in the fuel manifold to the fuel pressure necessary for restart at the time of restart, and the restartability deteriorates. To do.

  Therefore, it is conceivable to provide a fuel pressure holding mechanism that holds the fuel pressure when the high-pressure pump is not operating at a predetermined holding fuel pressure that is lower than the fuel pressure when the high-pressure pump is operating but higher than the feed pressure of the low-pressure pump.

US Pat. No. 7,171,952

  When the above-described fuel pressure holding mechanism is provided, it is necessary to diagnose whether or not the fuel pressure holding mechanism is normal. Here, in patent document 1, in order to diagnose whether the flow restrictor is operating normally, the gradient of the fuel pressure drop is used. Similarly, when diagnosing whether the operating state of the fuel pressure holding mechanism is normal from the gradient of the fuel pressure decrease, for example, even if the gradient of the fuel pressure decrease at the time of diagnosis is within an appropriate range, the fuel pressure further decreases. The diagnosis accuracy is not always sufficient, for example, when the pressure is lowered to the feed pressure by the low-pressure pump and the diagnosis is normal.

  The present invention has been made based on this situation, and an object of the present invention is to diagnose the abnormality of the fuel pressure holding mechanism that can accurately diagnose the abnormality of the fuel pressure holding mechanism used in the fuel injection device of the internal combustion engine. To provide an apparatus.

In order to achieve the object, the invention described in claim 1 includes a low-pressure pump that pumps up fuel in a fuel tank, a high-pressure pump that pressurizes fuel discharged from the low-pressure pump to high pressure, and pumps the fuel to a fuel injection valve; A low-pressure side fuel passage connecting the low-pressure pump and the high-pressure pump, a high-pressure side fuel passage connecting the high-pressure pump and the fuel injection valve, and detecting means for detecting the pressure of the fuel in the high-pressure fuel passage. An abnormality of a fuel pressure holding mechanism that is provided in the fuel injection device that holds the pressure of the fuel in the high pressure fuel passage at a holding fuel pressure higher than the pressure of the fuel in the low pressure side fuel passage after the internal combustion engine is stopped is diagnosed An abnormality diagnosis device for a fuel pressure holding mechanism,
After the internal combustion engine is stopped, it is determined whether or not the pressure of the fuel in the high pressure fuel passage detected by the detecting means is within a normal fuel pressure range set based on the holding fuel pressure, and the determination result An abnormality diagnosis means for diagnosing whether or not the fuel pressure holding mechanism is abnormal is provided.

  As described above, in the present invention, abnormality diagnosis of the fuel pressure holding mechanism is performed based on whether or not the pressure of the fuel in the high pressure fuel passage is within the normal fuel pressure range. Therefore, when the fuel pressure falls beyond the normal fuel pressure range, it can be diagnosed as an abnormality, so that an abnormality in the fuel pressure holding mechanism can be diagnosed with high accuracy.

  According to a second aspect of the present invention, the abnormality diagnosing means is configured so that the fuel pressure in the high pressure fuel passage is set based on the holding fuel pressure based on the fact that the diagnosis execution condition is satisfied after the internal combustion engine is stopped. It is characterized by determining whether it is in the range. In this way, although the fuel pressure holding mechanism is operating normally, it is possible to suppress the determination at the time when the fuel pressure in the high-pressure fuel passage has not yet dropped to the normal fuel pressure range.

  The diagnosis execution condition is, for example, that a predetermined time has elapsed since the internal combustion engine was stopped, as described in claim 3.

  According to a fourth aspect of the present invention, the predetermined time is set based on a fuel temperature related temperature which is a temperature that affects a temperature change of the fuel in the high pressure fuel passage. Between pressure and temperature, there is a relationship that the higher the temperature, the higher the pressure, and the lower the temperature, the lower the pressure. Therefore, the fuel pressure also changes due to the temperature change of the fuel in the high pressure fuel passage. Therefore, the time during which it can be estimated that the fuel pressure falls within the normal fuel pressure range is also affected by the change in the fuel temperature in the high-pressure fuel passage. Thus, in this way, by setting the predetermined time in the diagnosis execution condition based on the fuel temperature related temperature that affects the temperature change of the fuel in the high pressure fuel passage, the fuel pressure holding mechanism is normal, but the fuel pressure is still Can be more reliably prevented from making a diagnosis in a state that is not within the normal fuel pressure range. Therefore, more accurate diagnosis can be performed.

  By the way, when there is a request for restarting the internal combustion engine or when the fuel pressure in the high-pressure fuel passage is increased, the fuel pressure in the high-pressure fuel passage is increased. For this reason, if a diagnosis is made when a request is made to restart the internal combustion engine or after a request for increasing the fuel pressure in the high-pressure fuel passage is made, there is a high possibility that a correct diagnosis result cannot be obtained.

  Accordingly, in claim 5, the abnormality diagnosis means interrupts the diagnosis based on detecting at least one of a request for restarting the internal combustion engine and a request for increasing the fuel pressure in the high-pressure fuel passage. For this reason, it is possible to avoid making a diagnosis even though the pressure is increased, so that a decrease in diagnosis accuracy can be suppressed.

  According to a sixth aspect of the present invention, the fuel temperature related temperature is at least one of a fuel temperature in the fuel passage, an outside air temperature, an oil temperature of the internal combustion engine, and a cooling water temperature. Thus, the fuel temperature related temperature includes the outside air temperature, the oil temperature of the internal combustion engine, and the cooling water temperature in addition to the fuel temperature itself in the fuel passage. This is because the rate of decrease of the fuel temperature in the fuel passage also changes depending on the outside air temperature, the oil temperature of the internal combustion engine, and the cooling water temperature.

It is a schematic structure figure of the whole fuel supply system in one embodiment of the present invention. It is a block diagram of a fuel pressure holding mechanism and a high pressure pump. It is a figure explaining the control method of the fuel pressure control valve after an engine stop. It is a flowchart explaining the flow of the abnormality diagnosis process of a fuel pressure holding mechanism. It is a flowchart which shows step S3 of FIG. 4 in detail. It is a graph which shows the engine speed Ne, the fuel pressure in the high pressure fuel piping 32, and the change of an engine stall flag from the time of an ignition switch being turned off.

  Hereinafter, an embodiment of the present invention will be described. First, a schematic configuration of the entire fuel supply system of an in-cylinder injection engine (internal combustion engine) will be described with reference to FIG.

  A low pressure pump 12 that pumps up the fuel in the fuel tank 11 is installed in the fuel tank 11 that stores the fuel. The low-pressure pump 12 is driven by an electric motor (not shown) that uses a battery (not shown) as a power source. The fuel discharged from the low-pressure pump 12 is supplied to the high-pressure pump 14 through the fuel pipe 13 (low-pressure side fuel passage). A pressure regulator 15 is connected to the fuel pipe 13, and the discharge pressure of the low-pressure pump 12 (fuel supply pressure to the high-pressure pump 14) is adjusted to a predetermined pressure by the pressure regulator 15, and surplus fuel exceeding that pressure Is returned to the fuel tank 11 by the fuel return pipe 16.

  The high-pressure pump 14 pressurizes the fuel supplied from the low-pressure pump 12 via the fuel pipe 13 to a high pressure and sends it to the fuel injection valve 34. The configuration of the high-pressure pump 14 is shown in FIG. As shown in FIG. 2, the high-pressure pump 14 is a piston pump that sucks / discharges fuel by reciprocating a piston 19 in a cylindrical pump chamber 18. The piston 19 is fitted to a camshaft 20 of the engine. It is driven by the rotational movement of the cam 21. A fuel pressure control valve 23 is provided on the suction port 22 side of the high-pressure pump 14. The fuel pressure control valve 23 is a normally open type electromagnetic valve, and a valve body 24 that opens and closes the suction port 22, a spring 25 that biases the valve body 24 in the valve opening direction, and a valve body 24 in the valve closing direction. And a solenoid 26 that is electromagnetically driven.

  During the intake stroke of the high-pressure pump 14 (when the piston 19 is lowered), the fuel pressure control valve 23 is opened and fuel is sucked into the pump chamber 18, and during the discharge stroke (when the piston 19 is raised), the fuel pressure control valve. By controlling the valve closing time 23 (the valve closing state time from the valve closing start time to the top dead center of the piston 19), the discharge amount of the high-pressure pump 14 is controlled to control the fuel pressure (discharge pressure).

  That is, when increasing the fuel pressure, the valve closing start timing (energization timing) of the fuel pressure control valve 23 is advanced, thereby extending the valve closing time of the fuel pressure control valve 23 and increasing the discharge amount of the high pressure pump 14. Conversely, when lowering the fuel pressure, the valve closing start timing (energization timing) of the fuel pressure control valve 23 is retarded, thereby shortening the valve closing time of the fuel pressure control valve 23 and reducing the discharge amount of the high pressure pump 14. .

  On the other hand, a check valve 28 for preventing the backflow of discharged fuel is provided on the discharge port 27 side of the high-pressure pump 14. The check valve 28 includes a valve body 29 that opens and closes the discharge port 27 and a spring 30 that biases the valve body 29 in the valve closing direction. Further, an orifice 31 having a minute hole diameter (for example, a hole diameter of several tens of μm) is provided at the center of the valve body 29, and the fuel pressure in the pump chamber 18 is lower than the fuel pressure in the high pressure fuel pipe 32 (high pressure fuel passage). At times, the fuel in the high-pressure fuel pipe 32 gradually returns to the pump chamber 18 through the orifice 31.

  The high-pressure pump 14 configured as described above has a fuel pressure holding function for holding the fuel pressure in the high-pressure fuel pipe 32 at the holding fuel pressure after the engine is stopped. The fuel pressure control valve 23, which is a valve, and the check valve 28 having an orifice 31 constitute a fuel pressure holding mechanism. The fuel pressure holding operation by this fuel pressure holding mechanism will be described later.

  As shown in FIG. 1, the fuel discharged from the high-pressure pump 14 is sent to a delivery pipe 33 through a high-pressure fuel pipe 32 (high-pressure fuel passage), and attached to the cylinder head of the engine from the delivery pipe 33 for each cylinder. High pressure fuel is distributed to the fuel injection valve 34. The high pressure fuel pipe 32 is provided with a fuel pressure sensor 35 (detection means) for detecting the fuel pressure in the high pressure fuel pipe 32, and the engine cylinder block is provided with a coolant temperature sensor 36 for detecting the coolant temperature. The fuel supply system further includes a fuel temperature sensor 39 that detects the temperature of the fuel in the high-pressure fuel pipe 32, an outside air temperature sensor 40 that detects the outside air temperature, and an engine oil temperature sensor 41 that detects the engine oil temperature. .

  Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 37. The ECU 37 is mainly composed of a microcomputer, and has a high pressure so that the fuel pressure in the high-pressure fuel pipe 32 (pressure of fuel supplied to the fuel injection valve 34) detected by the fuel pressure sensor 35 during engine operation matches the target fuel pressure. The discharge amount of the pump 14 (the energization timing of the fuel pressure control valve 23) is feedback controlled.

  Further, the ECU 37 holds the fuel pressure in the high-pressure fuel pipe 32 at the holding fuel pressure after the engine is stopped by executing the post-stop fuel pressure holding control. Further, the ECU 37 diagnoses whether or not the fuel pressure holding mechanism is operating normally by executing abnormality diagnosis processing of the fuel pressure holding mechanism. That is, the ECU 37 also functions as abnormality diagnosis means in the claims.

  First, the post-stop fuel pressure holding control will be described. In the post-stop fuel pressure holding control, it is first determined whether or not the engine has stopped. In order to execute the fuel pressure holding control after the stop, the main relay of the power supply line is maintained in the on state for a while (for example, a predetermined time such as 120 seconds) even after the ignition switch 38 is turned off. It is assumed that energization to the ECU 37 is continued.

  If it determines with the engine having stopped, the electricity supply to the fuel pressure control valve 23 will be stopped, and the fuel pressure control valve 23 will be in a valve opening state. FIG. 3A shows this state. By opening the fuel pressure control valve 23, the suction port 22 of the pump chamber 18 is opened, and is in communication with the fuel pipe 13 on the low pressure side. Therefore, the fuel pressure in the pump chamber 18 becomes lower than the fuel pressure in the high pressure fuel pipe 32, and the fuel in the high pressure fuel pipe 32 returns to the pump chamber 18 through the orifice 31. As a result, the fuel pressure in the high pressure fuel pipe 32 gradually decreases.

  When the fuel pressure in the high-pressure fuel pipe 32 detected by the fuel pressure sensor 35 drops to the holding fuel pressure or the valve closing fuel pressure set near the holding fuel pressure, the fuel pressure control valve 23 is energized as shown in FIG. This closes the fuel pressure control valve 23 and closes the suction port 22 of the pump chamber 18.

  As a result, the fuel pressure in the high-pressure fuel pipe 32 decreases, while the fuel pressure in the pump chamber 18 increases. When the fuel pressure in the pump chamber 18 and the fuel pressure in the high-pressure fuel pipe 32 become substantially equal, the flow of fuel from the high-pressure fuel pipe 32 to the pump chamber 18 through the orifice 31 stops, and the fuel pressure in the high-pressure fuel pipe 32 Is maintained near the holding fuel pressure. The holding fuel pressure is the lowest restartable fuel pressure or a slightly higher fuel pressure, and the valve closing fuel pressure is the pressure fluctuation in the pump chamber 18 until the fuel pressure stabilizes after the fuel pressure control valve 23 is closed. This is the pressure corrected for the holding fuel pressure.

  When the fuel pressure in the high-pressure fuel pipe 32 and the fuel pressure in the pump chamber 18 become substantially equal, the fuel pressure control valve 23 is energized by the force generated by the pressure difference between the fuel pressure in the pump chamber 18 and the pressure in the fuel pipe 13. Even when stopped, the fuel pressure control valve 23 can be kept closed. Further, when the fuel pressure in the high pressure fuel pipe 32 and the fuel pressure in the pump chamber 18 are substantially equal, the fuel pressure in the high pressure fuel pipe 32 detected by the fuel pressure sensor 35 is also stabilized.

  Therefore, as shown in FIG. 3C, the energization of the fuel pressure control valve 23 is stopped when the fuel pressure detected by the fuel pressure sensor 35 is stabilized. Even when the energization is stopped, as described above, the fuel pressure control valve 23 is kept closed by the pressure difference between the fuel pressure in the pump chamber 18 and the pressure in the fuel pipe 13.

  With the post-stop fuel pressure holding control described above, the fuel pressure after engine stop is held at the hold fuel pressure. However, when there is an abnormality in the fuel pressure holding mechanism such as a failure of the fuel pressure control valve 23, the fuel pressure after the engine is stopped is not held at the holding fuel pressure. Therefore, the ECU 37 executes an abnormality diagnosis process for the fuel pressure holding mechanism. Next, this abnormality diagnosis processing will be described using the flowchart shown in FIG.

  FIG. 4 is a flowchart for explaining the flow of the abnormality diagnosis process of the fuel pressure holding mechanism. This process is executed at a predetermined cycle while the ECU 37 is powered on, for example.

  In step S1, it is determined whether or not the engine has stopped. This determination is made based on the state of the engine stall flag, for example. This engine stall flag is, for example, a flag that is “1” when the engine rotation speed becomes 0 (or less than a predetermined rotation speed close thereto). Further, the engine stall flag may be “1” when the ignition switch is turned off, and among these two conditions and other conditions (for example, fuel injection stop, ignition stop, etc.) The state may change based on a plurality of conditions.

  If step S1 is negative, step S1 is repeated. On the other hand, if step S1 is positively determined, that is, if it is determined that the engine has stopped, the process proceeds to step S2.

  In step S2, it is determined whether a predetermined time has elapsed after the engine is stopped. This predetermined time is set based on the time that can be estimated to decrease to the above-mentioned holding fuel pressure after the engine is stopped. The time that can be estimated to decrease to the holding fuel pressure is determined based on an experiment using an actual vehicle equipped with this fuel supply system. The predetermined time thus determined may be a constant value independent of the temperature, but is preferably set based on the temperature as follows.

  That is, the holding fuel pressure is the lowest restartable fuel pressure or a slightly higher fuel pressure as described above, but the lowest restartable fuel pressure generally varies depending on the engine temperature at the start. Therefore, since the holding fuel pressure also changes according to the engine temperature, the differential pressure between the holding fuel pressure and the fuel pressure in the high-pressure fuel pipe 32 when the engine is stopped also changes according to the engine temperature. Therefore, the predetermined time is preferably set by a map or a relational expression (hereinafter referred to as a map or the like) based on the holding fuel pressure or the engine temperature for determining the holding fuel pressure.

  Furthermore, not only the magnitude of the differential pressure is affected by temperature, but also the fuel pressure reduction rate is affected by temperature. More specifically, the temperature and the pressure have a relationship such that the higher the temperature, the higher the pressure, and the lower the temperature, the lower the pressure. Therefore, the faster the fuel temperature decreases, the faster the fuel pressure decreases. Therefore, the predetermined time is preferably set by a map or the like based on the fuel temperature related temperature which is a temperature that affects the temperature change of the fuel in the high pressure fuel pipe 32. The fuel temperature related temperature includes the outside air temperature, engine oil temperature, cooling water temperature, etc., in addition to the fuel temperature itself in the high-pressure fuel pipe 32. When a map or the like is used for setting the predetermined time, the map or the like has a relationship that the predetermined time is shortened as the temperature difference between the fuel temperature in the high-pressure fuel pipe 32 and the temperature around the high-pressure fuel pipe 32 is large. The temperature around the high-pressure fuel pipe 32 may be any one of the outside air temperature, the engine oil temperature, and the cooling water temperature, or may be estimated using a plurality of these. The map or the like may be such that the fuel temperature in the high-pressure fuel pipe 32 is regarded as constant, and the predetermined time is set by using only the temperature around the high-pressure fuel pipe 32 as an input variable. The predetermined temperature may be set with only the fuel temperature in the high-pressure fuel pipe 32 as an input variable. From the above, it can be said that the map using the fuel temperature related temperature may be any map using any one of the fuel temperature related temperatures, and it is more preferable to use a plurality of fuel temperature related temperatures.

  Furthermore, it can be said that the predetermined time is more preferably set based on the retained fuel pressure or the engine temperature for determining the retained fuel pressure and the fuel temperature related temperature. However, the engine temperature can be estimated from the fuel temperature related temperature. Therefore, by preparing a map etc. that uses the fuel noise related temperature for estimation of the holding fuel pressure or the engine temperature for determining the holding fuel pressure, and setting the holding time from the map etc. and the fuel temperature related temperature. Even when only the fuel temperature related temperature is used, the holding time based on the engine temperature and the fuel temperature related temperature for determining the holding fuel pressure or the holding fuel pressure can be set substantially. In addition, when setting holding time based on fuel temperature related temperature, the holding time setting step which sets holding time from the temperature measured by the temperature measurement step and the temperature measurement step between step S1 and step S2, for example And provide.

  If the determination in step S2 is negative, step S2 is repeated. On the other hand, when it becomes affirmation determination, it progresses to step S3. In step S3, a fuel pressure comparison process is performed. The fuel pressure comparison process in step S3 is shown in detail in FIG.

  In FIG. 5, first, in step S <b> 31, the fuel pressure is measured by the fuel pressure sensor 35. In subsequent step S32, it is determined whether or not the fuel pressure measured in step S31 is higher than the Min guard value. If this determination is negative, that is, if the fuel pressure is equal to or less than the Min guard value, the process proceeds to step S35, where it is determined that the fuel pressure holding mechanism is abnormal.

  On the other hand, if step S32 is affirmative, the process proceeds to step S33. In step S33, it is determined whether or not the fuel pressure measured in step S31 is lower than the Max guard value. If this determination is negative, that is, if the fuel pressure is greater than or equal to the Max guard value, the process proceeds to step S35 as in the case where negative determination is made in step S32, and it is determined that the fuel pressure holding mechanism is abnormal.

  On the other hand, if step S33 is also affirmative, the process proceeds to step S34. In this case, the fuel pressure is between the Min guard value and the Max guard value. The Min guard value and the Max guard value respectively indicate a lower limit value and an upper limit value of the normal fuel pressure range determined in consideration of the fuel pressure fluctuation range at the time of fuel pressure measurement confirmed by an actual vehicle experiment. Therefore, if the determination in step S33 is also affirmative, it can be estimated that the fuel pressure holding mechanism is normal. Therefore, in step S34, it is determined that the fuel pressure holding mechanism is normal.

  Returning to FIG. 4, in step S <b> 4, based on which of steps S <b> 34 and S <b> 35 of FIG.

  FIG. 6 shows changes in the engine speed Ne (solid line in the upper diagram), the fuel pressure in the high-pressure fuel pipe 32 (broken line and alternate long and short dash line in the upper diagram), and the engine stall flag (lower diagram) from when the ignition switch is turned off. It is a graph which shows. The broken line is an example of a change in fuel pressure when the fuel pressure holding mechanism is normal, and the one-dotted line is an example of a change in fuel pressure when the fuel pressure holding mechanism is abnormal.

  As shown by the broken line in FIG. 6, when the fuel pressure holding mechanism is normal, after the ignition is turned off, the fuel pressure quickly decreases for about 10 seconds (about 5 seconds after the engine stall flag becomes “1”). S), the fuel pressure drops to a holding fuel pressure (4 MPa) and stabilizes. Since the diagnosis may be performed after the fuel pressure is stabilized in this manner, for example, the diagnosis may be performed at the time of 20 seconds shown in FIG. Assuming that diagnosis is performed at the time point of 20 seconds shown in FIG. 6, at this time point, the alternate long and short dash line still shows a high pressure of 12 MPa or more. Therefore, it will be out of the normal fuel pressure range. Therefore, it can be diagnosed that the fuel pressure holding mechanism is abnormal when the fuel pressure decrease rate is significantly slower than the normal fuel pressure decrease curve, as indicated by the alternate long and short dash line.

  As described above, according to the present embodiment, whether or not the fuel pressure holding mechanism is abnormal is determined based on whether or not the fuel pressure in the high-pressure fuel pipe 32 is within the normal fuel pressure range. Therefore, not only when the fuel pressure does not drop to the normal fuel pressure range as shown in FIG. 6, but also when the fuel pressure falls beyond the normal fuel pressure range, it can be diagnosed as abnormal, so the abnormality of the fuel pressure holding mechanism can be accurately detected. Can be diagnosed.

  Further, according to the present embodiment, since the diagnosis is performed when a predetermined time has elapsed since the engine was stopped, the fuel pressure holding mechanism is operating normally, but the fuel pressure in the high-pressure fuel pipe 32 is still normal. It is possible to prevent the determination from being made when the fuel pressure range has not been reduced.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, The following embodiment is also contained in the technical scope of this invention, and also the summary other than the following is also included. Various modifications can be made without departing from the scope.

  For example, in the above-described embodiment, the diagnosis is performed when a predetermined time has elapsed after the engine is stopped, and the abnormality diagnosis process shown in FIG. 4 is not interrupted, such as resetting the time count of the predetermined time. However, when at least one of an engine restart request and a fuel pressure increase request in the high-pressure fuel pipe 32 is detected, the processing shown in FIG. 4 may be interrupted. By doing so, it is possible to avoid making a diagnosis even though the pressure is boosted, so that a reduction in diagnosis accuracy can be suppressed. The engine restart request is determined based on, for example, an ignition switch ON signal, and the fuel pressure increase request in the high-pressure fuel pipe 32 is, for example, a hybrid vehicle including an engine and a motor as driving force sources. In a vehicle that does not start the engine at the start of travel, the determination is made based on a signal indicating the start of travel (for example, the power supply position is on).

  Further, the fuel pressure holding mechanism is not limited to that of the above-described embodiment. In the above-described embodiment, after stabilizing at the holding fuel pressure, the fuel pressure control valve 23 is held in the closed state by the pressure difference between the fuel pressure in the pump chamber 18 and the pressure in the fuel pipe 13. For example, an electromagnetically driven relief valve is provided as a fuel pressure holding mechanism between the high-pressure pump and the high-pressure fuel pipe, and relief is performed only during the period until the fuel pressure in the high-pressure fuel pipe drops to the holding fuel pressure after the engine stops. The valve may be opened.

  In the description of FIG. 6, an example is described in which diagnosis is performed during a period in which the main relay after the ignition is turned off. However, the present invention is not limited to this, and the predetermined time is longer than the period in which the main relay after the ignition is turned off. A long time may be set. In this case, diagnosis is performed at the next engine restart.

  In the above-described embodiment, the diagnosis execution condition is that a predetermined time has elapsed after the engine is stopped. However, the present invention is not limited to this, and the fuel pressure holding mechanism is in a fuel pressure holding state (for example, in the above embodiment, FIG. The state of c) may be used as a diagnosis execution condition. Further, the time point when the fuel pressure holding mechanism is in the fuel pressure holding state may be set as the time measurement start time point, and the diagnosis execution condition may be that a predetermined time has passed thereafter.

  In the above-described embodiment, the fuel pressure is measured only once. However, the fuel pressure may be measured a plurality of times, and the diagnosis may be performed based on the measurement results obtained a plurality of times. In this case, a change tendency of the fuel pressure may be determined from the fuel pressure measured a plurality of times, and the diagnosis may be performed using the tendency of the fuel pressure change in addition to whether or not the fuel pressure is in the normal fuel pressure range.

  In the above-described embodiment, the fuel pressure is measured when a predetermined time has elapsed after the engine is stopped, that is, when the diagnosis execution condition is satisfied. (Determining whether or not it is normal) may be performed after the diagnosis execution condition is satisfied. In addition, in this manner, the fuel pressure measurement itself may be performed sequentially after the engine is stopped. As a condition for performing the diagnosis, time (for example, just before the main relay is turned off) may be used, but the fuel pressure is stable. Alternatively, the diagnosis execution condition may be that the degree of change in the fuel pressure is small. When it is determined that the fuel pressure is stable or the degree of change in the fuel pressure is small, if the fuel pressure does not decrease while being high, it can be quickly determined that the fuel pressure is abnormal.

11: Fuel tank, 12: Low pressure pump, 13: Fuel pipe (low pressure side fuel passage), 14: High pressure pump, 15: Pressure regulator, 16: Fuel return pipe, 18: Pump chamber, 19: Piston, 20: Cam shaft 21: Cam, 22: Suction port, 23: Fuel pressure control valve, 24: Valve body, 25: Spring, 26: Solenoid, 27: Discharge port, 28: Check valve, 23, 28: Fuel pressure holding mechanism, 29: Valve body 30: Spring 31: Orifice 32: High pressure fuel pipe (high pressure side fuel passage) 33: Delivery pipe 34: Fuel injection valve 35: Fuel pressure sensor (detection means) 36: Cooling water temperature sensor 37 : ECU (abnormality diagnosis means), 38: Ignition Pitch, 39: fuel temperature sensor, 40: outside air temperature sensor, 41: engine oil temperature sensor

Claims (6)

A low pressure pump that pumps fuel in a fuel tank, a high pressure pump that pressurizes fuel discharged from the low pressure pump to a high pressure and pumps it to a fuel injection valve, and a low pressure side fuel passage that connects the low pressure pump and the high pressure pump; A fuel injection device having a high pressure side fuel passage connecting the high pressure pump and the fuel injection valve, and a detecting means for detecting the pressure of the fuel in the high pressure fuel passage, and after the internal combustion engine is stopped, An abnormality diagnosing device for a fuel pressure holding mechanism for diagnosing an abnormality in a fuel pressure holding mechanism for holding a fuel pressure in a high pressure fuel passage at a holding fuel pressure higher than a fuel pressure in the low pressure side fuel passage,
After the internal combustion engine is stopped, it is determined whether or not the pressure of the fuel in the high pressure fuel passage detected by the detecting means is within a normal fuel pressure range set based on the holding fuel pressure, and the determination result An abnormality diagnosis device for a fuel pressure holding mechanism, comprising abnormality diagnosis means for diagnosing whether or not the fuel pressure holding mechanism is abnormal. In claim 1,
The abnormality diagnosis means determines whether the pressure of the fuel in the high pressure fuel passage is within a normal fuel pressure range set based on the holding fuel pressure based on the fact that the diagnosis execution condition is satisfied after the internal combustion engine is stopped. An abnormality diagnosis device for a fuel pressure retention mechanism, characterized by determining whether or not. In claim 2,
The abnormality diagnosis device for a fuel pressure holding mechanism, wherein the diagnosis execution condition is that a predetermined time has elapsed since the internal combustion engine was stopped. In claim 3,
The abnormality diagnosis device for a fuel pressure holding mechanism, wherein the predetermined time is set based on a fuel temperature related temperature which is a temperature that affects a temperature change of the fuel in the high pressure fuel passage. In any one of Claims 1 thru | or 4,
The abnormality diagnosis means interrupts the diagnosis based on detecting at least one of a request for restarting the internal combustion engine and a request for increasing the fuel pressure in the high-pressure fuel passage. Abnormality diagnosis device. In claim 4,
The abnormality diagnosis device for a fuel pressure holding mechanism, wherein the fuel temperature related temperature is at least one of a fuel temperature in the fuel passage, an outside air temperature, an oil temperature of the internal combustion engine, and a cooling water temperature.

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