JP6094464B2 - Fuel injection control device - Google Patents

Description

  The present invention relates to a fuel injection control device that controls a fuel injection amount injected from a fuel injection valve into a cylinder of an internal combustion engine.

  In the common rail type fuel injection system, the fuel discharge amount of the fuel pump is feedback-controlled so that the detected value of the fuel pressure in the common rail by the fuel pressure sensor matches the target fuel pressure determined based on the operating state of the engine. Further, the fuel injection amount of the injector is determined based on the operating state of the engine, and the energization time of the injector is determined based on the detected value of the fuel pressure by the fuel pressure sensor. Therefore, when there is an abnormality in the fuel pressure sensor and the fuel pressure is not detected correctly, it becomes impossible to perform appropriate fuel injection control according to the operating state of the engine, so that abnormality determination of the fuel pressure sensor has been conventionally performed.

  In the technique described in Patent Document 1, the fuel injection valve is driven to the extent that fuel is not injected into the internal combustion engine, that is, so-called idle driving is performed, thereby repeatedly causing leakage of fuel returned from the fuel injection valve to the fuel tank. . Then, when the leak is repeated, the number of times the fuel injection valve is driven when the fuel pressure is greatly reduced, that is, the number of times the leak is performed is acquired as an index. When the difference between the index acquired this time and the index acquired in the past is greater than or equal to a predetermined value, it is determined that the fuel pressure sensor is abnormal.

JP 2012-87635 A

  By the way, when the type of fuel to be replenished to the fuel tank changes, its viscosity changes. Also, the viscosity of the same fuel can be changed according to the temperature change. Therefore, even if the opening degree and the opening / closing timing of the fuel injection valve are controlled to be constant in order to make the amount of leakage returned to the fuel tank due to the leak constant, the leakage is actually returned from the fuel injection valve to the fuel tank. The amount of fuel may include an error due to variations in fuel viscosity. Therefore, in the case of the technique described above, there is a possibility that the accuracy of the abnormality determination of the fuel pressure sensor cannot be obtained sufficiently.

  The abnormality determination of the fuel pressure sensor needs to be performed in a so-called idling state in which the fuel injection valve is driven in a time shorter than the time required to open the fuel injection valve.

  It is a technical object of the present invention to provide a fuel injection control device capable of suitably determining a fuel pressure detection abnormality.

  In the present invention, a fuel pump that increases the pressure of fuel in a fuel tank and discharges the fuel, a common rail that stores fuel pumped from the fuel pump, a fuel injection valve that supplies fuel accumulated in the common rail to an engine cylinder, A fuel pressure sensor for detecting the pressure of the fuel, and a control means for feedback-controlling the fuel discharge amount of the fuel pump based on a deviation between a detected value of the fuel pressure by the fuel pressure sensor and a target fuel pressure of the common rail; Based on the actual leak amount, the actual leak amount calculating means for calculating the actual leak amount that is the actual value of the fuel leak amount from the fuel injector from the difference between the fuel discharge amount and the fuel injection amount from the fuel injector Correction amount calculation means for calculating a correction amount of the fuel leak amount with respect to the viscosity of the fuel, and a reference fuel leak characteristic indicating a relationship between the fuel pressure and the fuel leak. In addition, an estimated leak amount calculating means for calculating an estimated leak amount that is an estimated value of the fuel leak amount from the detected fuel pressure value and the correction amount, and the detection of the fuel pressure based on the comparison result between the actual leak amount and the estimated leak amount Detecting abnormality determining means for determining presence or absence of abnormality.

  In the above invention, since the actual leak amount is calculated from the difference between the fuel discharge amount and the fuel injection amount, the actual fuel leak amount can be calculated correctly regardless of whether or not the fuel pressure is detected abnormally. In this case, the actual leak amount is in accordance with the actual fuel pressure. On the other hand, in the fuel leak characteristic, the leak amount has a correlation with the fuel viscosity and the fuel pressure. Therefore, if the parameter indicating the viscosity and the fuel pressure are known, the fuel leak amount can be estimated. However, if there is a fuel pressure detection abnormality, there will be a difference in the estimation of the leak amount. That is, there is a difference between the estimated leak amount calculated based on the correction amount of the fuel leak amount with respect to the viscosity and the fuel pressure, and the actual leak amount calculated based on the difference between the fuel discharge amount and the fuel injection amount. In this case, the estimated leak amount and the actual leak amount are compared, and if the difference between the two is large, it can be determined that the fuel pressure is erroneously detected. Further, when the abnormality determination is performed during the operation of the engine, it is not necessary to perform a special operation such as idling for the abnormality determination.

The lineblock diagram showing the outline of a common rail type fuel injection system. The flowchart of detection abnormality determination of a fuel pressure. Explanatory drawing of the relationship between a fuel pressure and a fuel leak.

  Hereinafter, a fuel injection control device according to the present invention will be described with reference to the drawings. The fuel injection system is a common rail fuel injection system that injects fuel into, for example, a 4-cylinder diesel engine, and its operation is controlled by a fuel injection control device. FIG. 1 is a configuration diagram showing an outline of a fuel injection system. 1, the fuel injection system includes a fuel tank 10 in which fuel is stored, a fuel pump 11, a common rail 20, a fuel pressure sensor 21, an injector 23, a pressure limiter 30, and an ECU 50.

  The fuel pump 11 is connected to the fuel tank 10 through a fuel pipe 12 provided with a fuel filter 13. The fuel pump 11 sucks low-pressure fuel before pressurization pumped from the fuel tank 10 into a fuel pressurization chamber (not shown). Then, the high-pressure fuel that has been increased in pressure in the fuel pressurizing chamber is discharged as the plunger reciprocates in synchronization with the engine rotation. For example, the fuel pump 11 is a mechanical pump that is driven as the engine rotates and repeatedly performs intake and discharge of fuel. An electromagnetically driven suction metering valve (SCV) 14 is provided in the fuel suction portion of the fuel pump 11.

  The intake metering valve 14 is provided on the suction side of the fuel pump 11 and adjusts the fuel intake amount that the fuel pump 11 sucks in the suction process by current control. For example, as current control, duty ratio control of current for the intake metering valve 14 is performed. By controlling the fuel intake amount by the intake metering valve 14, the fuel discharge amount from the fuel pump 11 is metered.

  For example, when a normally open valve that is held in an open state (fully open state) of the electromagnetic solenoid is used as the intake metering valve 14, the opening area of the fuel intake passage is increased due to an increase in the indicated current value to the electromagnetic solenoid. When the fuel pump 11 is reduced, the fuel suction amount of the fuel pump 11 is reduced, and as a result, the fuel discharge amount by the fuel pump 11 is reduced. Note that a normally closed solenoid valve may be used as the suction metering valve 14.

  A common rail 20 is connected to the fuel pump 11 through a fuel discharge pipe 18. The high-pressure fuel discharged from the fuel pump 11 is sequentially fed to the common rail 20 through the fuel discharge pipe 18 so that the fuel in the common rail 20 is held in a high-pressure state.

  The common rail 20 is provided with a rail pressure sensor (hereinafter referred to as a fuel pressure sensor 21) that detects the fuel pressure in the common rail 20. In FIG. 1, the fuel pressure sensor 21 is provided on the fuel outlet side of the fuel pump 11 in the common rail 20, but the fuel pressure sensor 21 may be provided on a path from the fuel outlet of the fuel pump 11 to an injection port of an injector 23 described later. it can.

  The injector 23 is a known electromagnetically driven injection valve including, for example, a nozzle needle that opens and closes an injection hole, and is provided for each cylinder of the engine. High pressure fuel is supplied from the common rail 20 to the injector 23 through the high pressure fuel pipe 24, and fuel is injected and supplied to each cylinder of the engine by driving the injector 23. However, part of the high-pressure fuel supplied to the injector 23 is returned to the fuel tank 10 through the return pipe 25 due to leakage. Note that the amount of fuel returned to the fuel tank 10 due to a leak is referred to as a fuel leak amount. As the fuel injection valve, a piezo drive injector can be used instead of the electromagnetic drive injector.

  The common rail 20 is provided with a normally-closed pressure limiter 30 as a pressure release valve. The pressure limiter 30 basically has a mechanical check valve (check valve) structure, and when the rail pressure as the fuel pressure in the common rail rises excessively and exceeds the valve opening pressure of the pressure limiter 30. Open the valve. When the pressure limiter 30 is opened, the high pressure fuel is returned to the fuel tank 10 through the return pipe 25, and the rail pressure is reduced. Thereby, damage to high voltage parts, such as high voltage piping and common rail 20, is controlled.

  The ECU 50 is an electronic control device having a known microcomputer comprising a CPU, ROM, RAM, flash memory, etc., and detects a fuel pressure sensor 21, a rotation speed sensor 51 for detecting the rotation speed of the engine, and an accelerator operation amount. The engine operation state is detected by taking in signals from various sensors such as an accelerator sensor 52 that performs the operation and a water temperature sensor 53 that detects the temperature of the engine cooling water. The engine operating state is controlled by executing a control program stored in a ROM or the like.

  Specifically, the ECU 50 performs feedback control of the common rail pressure. That is, the ECU 50 calculates the target fuel pressure of the common rail pressure based on the engine operating state. The target fuel pressure is set to a relatively low value when the engine is in a low load state such as during idle operation, and to a relatively high value when the engine is in a high load operation such as at full load. Then, the drive current for driving the intake metering valve 14 is feedback-controlled based on the deviation between the detected value of the fuel pressure and the target fuel pressure so that the detected value of the fuel pressure by the fuel pressure sensor 21 matches the target fuel pressure.

  Further, the ECU 50 controls the energization of the injector 23 based on the engine operating state. That is, the fuel injection amount, that is, the command injection amount is set according to the operating state of the engine, and the energization time of the injector 23 based on the command injection amount is calculated based on the fuel pressure detected by the fuel pressure sensor 21. Control for driving the injector 23 according to the energization time is performed.

  As described above, the fuel discharge amount and the fuel injection amount are obtained based on the detected value of the fuel pressure. Therefore, when there is an abnormality in detection of the fuel pressure, when the fuel pressure of the common rail 20 is not correctly controlled, there may be a problem associated with the fact that appropriate fuel injection control according to the operating state of the engine is not performed.

  For example, when the lead wire of the fuel pressure sensor 21 is disconnected or short-circuited, the voltage level of the fuel pressure sensor 21 becomes smaller than the minimum value of the voltage range in the normal state, or the voltage range in the normal state. A fuel pressure detection error occurs when the value is larger than the maximum value of. Further, although the fuel pressure sensor 21 is normal, a fuel pressure detection error occurs even when the detection signal of the fuel pressure sensor 21 is not correctly converted due to distortion of the arithmetic circuit of the ECU 50 due to engine vibration or the like. In the present embodiment, the occurrence of a fuel pressure detection error due to such a fuel pressure sensor 21 and the ECU 50 is regarded as a fuel pressure detection abnormality.

  For example, it is assumed that the detected value of the fuel pressure is recognized as a value lower than the actual fuel pressure of the common rail 20 due to an abnormality in the detection of the fuel pressure. In this case, since the actual fuel pressure accumulated in the common rail 20 is maintained at a value higher than the target fuel pressure, the injection pressure of the injector 23 is increased, and the actual commanded injection amount is increased. In this case, a problem associated with the engine not being correctly controlled occurs.

  Therefore, the ECU 50 determines the presence or absence of a fuel pressure detection abnormality as a detection abnormality determination means. Incidentally, the leak amount (hereinafter referred to as the actual leak amount) that is the actual value of the fuel returned to the fuel tank 10 is obtained from the difference between the fuel discharge amount and the fuel injection amount. Since the actual leak amount is calculated from the actual amount of fuel entering and exiting, it can be correctly calculated as the actual leak amount regardless of the presence or absence of fuel pressure detection abnormality.

  Note that the amount of leakage returned from the injector 23 to the fuel tank 10 varies depending on the viscosity of the fuel. That is, if the viscosity is different, the amount of fuel returned from the injector 23 (the gap between the injectors 23) to the fuel tank 10 changes due to leakage.

  That is, in the fuel leak characteristic, the leak amount has a correlation with the viscosity of the fuel and the fuel pressure. Therefore, if the parameter indicating the viscosity and the fuel pressure are known, the fuel leak amount can be estimated. However, if there is a detection abnormality in the fuel pressure, there will be a difference in the leak amount estimation. That is, there is a difference between the fuel leak amount correction value for the viscosity and the estimated fuel leak amount calculated based on the fuel pressure (hereinafter referred to as the estimated leak amount) and the actual leak amount. In this case, when there is a fuel pressure detection abnormality and the correct fuel pressure is not recognized, the difference between the estimated leak amount and the actual leak amount becomes large.

  Therefore, in this embodiment, fuel pressure detection abnormality is determined by comparing the estimated leak amount and the actual leak amount using the fuel leak characteristic indicating the relationship between the fuel pressure and the fuel leak determined according to the viscosity. In this case, since the difference in the estimated leak amount due to the difference in viscosity is taken into account, the accuracy of detecting the abnormality in the fuel pressure can be increased.

  For example, in the present embodiment, it is assumed that the fuel leak characteristic at a predetermined viscosity is stored in the ROM of the ECU 50 as shown in the example of FIG. In this case, the fuel leak characteristic is calculated using the viscosity calculated based on the actual leak amount. Then, an estimated leak amount is obtained by associating the fuel leak characteristic with the fuel pressure Pc detected by the fuel pressure sensor 21. Then, the difference between the actual leak amount and the estimated leak amount is calculated to determine whether or not there is a fuel pressure detection abnormality.

  That is, when there is no abnormality in detecting the fuel pressure, the difference between the actual leak amount and the estimated leak amount is relatively small. On the other hand, when there is a fuel pressure detection abnormality, the difference between the actual leak amount and the estimated leak amount becomes relatively large. A fuel pressure detection abnormality is determined using the difference depending on whether or not there is a fuel pressure detection abnormality.

  In addition, as a case where a predetermined difference occurs between the actual leak amount and the estimated leak amount, there is a leak abnormality in which the fuel leak amount becomes excessive in addition to a fuel pressure detection abnormality. Regarding a fuel leak, if there is a leak abnormality in which the leak amount becomes excessively large, it is impossible to correctly determine a fuel pressure detection abnormality. Therefore, in the present embodiment, it is also determined whether or not there is a leakage abnormality, and the leakage abnormality and the fuel pressure detection abnormality are distinguished. In this case, since it is determined that a leak abnormality has occurred, the detection abnormality determination of the fuel pressure is not performed, thereby suppressing the inconvenience that the detection abnormality of the fuel pressure is erroneously determined due to the occurrence of the leak abnormality. As a result, the accuracy of fuel pressure detection abnormality can be increased.

  FIG. 2 shows a flowchart of fuel pressure detection abnormality determination performed by the ECU 50. The following processing is repeatedly performed at a predetermined cycle while the engine is being driven.

  First, in step S10, the fuel pressure Pc of the common rail 20 is obtained. The fuel pressure Pc is obtained from the detection result of the fuel pressure sensor 21. In the subsequent step S11, it is determined whether the fuel pressure Pc is the fuel pressure Pc1 in a predetermined low pressure state. For example, it is determined that the fuel pressure Pc is the fuel pressure Pc1 in the low pressure state when the fuel pressure Pc is within the target fuel pressure range set in the engine idling operation state. If the determination is affirmative, in the subsequent step S12, the actual leak amount QL1 in the low pressure state is calculated. The actual leak amount QL1 is calculated using Expression (1).

QL1 = Qsp−Qinj Expression (1)
In Expression (1), Qinj is the fuel injection amount from the injector 23, and Qsp is the fuel discharge amount from the fuel pump 11. The fuel discharge amount is calculated from the drive current of the intake metering valve (SCV) 14 based on the IQ characteristics. Note that when the fuel pressure Pc is relatively small, the variation in the fuel injection amount is small, which is advantageous in calculating the actual leak amount.

  In a succeeding step S13, it is determined whether or not the actual leak amount QL1 in the low pressure state is less than the leak abnormality determination value QLJD. Note that the determination value QLJD is set by obtaining an allowable leak value in an idle operation state of the engine through experiments or the like. When the actual leak amount QL1 is less than the determination value QLJD, the process proceeds to step S14. When the actual leak amount QL1 is greater than or equal to the determination value QLJD, the process proceeds to step S22, and it is determined that there is a leak abnormality. At this time, a predetermined warning is output to notify the driver that there is a leak abnormality.

  In step S13, when the target fuel pressure is set high with an increase in engine load or the like, the fuel pressure Pc of the common rail 20 does not change, or the fuel pressure Pc is greatly reduced with respect to the fuel discharge amount. Alternatively, it may be determined that there is a leak abnormality. In any case, it may be determined that there is a leak abnormality when a fuel leak occurs in an unacceptable range.

  In step S14, the current estimated leak amount Qc is obtained. Here, using the reference leak characteristic Lbase shown in FIG. 3, the reference leak amount QLbase is calculated from the fuel pressure Pc1 acquired in step S10. Then, a correction amount ΔQc of the fuel leak amount with respect to the viscosity is obtained from the difference between the actual leak amount QL1 calculated in step S12 and the reference leak amount QLbase. Then, the current estimated leak amount Qc = QLbase + ΔQc is calculated from the reference leak amount QLbase and the correction amount ΔQc. In the subsequent step S15, a fuel leak characteristic determined according to the estimated leak amount Qc is obtained.

  On the other hand, if a negative determination is made in step S11, the process proceeds to step S16 to determine whether the fuel pressure Pc is the high-pressure fuel pressure Pc2. For example, when the fuel pressure Pc is within the range of the target fuel pressure set during high-load operation of the engine, it is determined that the fuel pressure Pc2 is in a high pressure state.

  When there is a fuel pressure detection abnormality, particularly when the fuel pressure sensor 21 has a detection abnormality, the difference between the actual leak amount and the estimated leak amount tends to increase as the fuel pressure Pc increases. For this reason, a state in which the fuel pressure Pc is relatively high is advantageous in making an abnormality determination of the fuel pressure detection, and when the fuel pressure Pc is in a high pressure state, the determination of an abnormality in the detection of the fuel pressure can be more suitably performed.

  If a negative determination is made in step S16, this process is terminated. If the determination is affirmative, the process proceeds to step S17, and the estimated leak amount QLes2 of the leak amount is obtained using the fuel leak characteristic determined according to the current estimated leak amount Qc.

  In the subsequent step S18, the actual leak amount QL2 in the high pressure state is calculated. The actual leak amount QL2 is also calculated using equation (1). In the subsequent step S19, it is determined whether or not the difference ΔC between the actual leak amount QL2 and the estimated leak amount QLes2 in the high pressure state is less than the threshold value C. For example, the threshold value C is determined by obtaining in advance an experiment or the like the difference between the actual leak amount and the estimated leak amount when there is a fuel pressure detection abnormality. If the difference ΔC is less than the threshold C and an affirmative determination is made, the process proceeds to step S20, and it is determined that there is no abnormality in detection of fuel pressure (normal). If the difference ΔC is equal to or greater than the threshold value C and a negative determination is made, the process proceeds to step S21, and it is determined that there is a fuel pressure detection abnormality (abnormal). In the case of FIG. 3, since the difference ΔC is equal to or greater than the threshold value C, it is determined that there is a fuel pressure detection abnormality.

  According to the above, the following excellent effects can be obtained.

  (1) Since the actual leak amount is calculated from the difference between the fuel discharge amount and the fuel injection amount, the actual fuel leak amount can be correctly calculated regardless of whether or not the fuel pressure is detected abnormally. In this case, the actual leak amount is in accordance with the actual fuel pressure. On the other hand, in the fuel leak characteristic, the leak amount has a correlation with the fuel viscosity and the fuel pressure. Therefore, if the parameter indicating the viscosity and the fuel pressure are known, the fuel leak amount can be estimated. However, if there is a fuel pressure detection abnormality, there will be a difference in the estimation of the leak amount. That is, there is a difference between the estimated leak amount calculated based on the correction amount of the fuel leak amount with respect to the viscosity and the fuel pressure, and the actual leak amount calculated based on the difference between the fuel discharge amount and the fuel injection amount. In this case, the estimated leak amount and the actual leak amount are compared, and if the difference between the two is large, it can be determined that the fuel pressure is erroneously detected. Further, when the abnormality determination is performed during the operation of the engine, it is not necessary to perform a special operation such as idling for the abnormality determination.

  (2) When the engine is in a predetermined low pressure state such as an idle operation state, the number of sampling of the actual leak amount can be increased, and the calculation accuracy of the correction amount of the fuel leak amount with respect to the fuel viscosity can be increased.

  (3) The amount of fuel leakage increases in a quadratic function as the fuel pressure increases. Therefore, when there is a fuel pressure detection abnormality, the difference between the actual leak amount and the estimated leak amount tends to increase as the target fuel pressure determined based on the operating state of the engine increases. Therefore, by determining whether or not there is a fuel pressure detection abnormality when the engine is in a predetermined high pressure state such as a high load operation state, the accuracy of the fuel pressure detection abnormality can be increased.

  (4) A state where the fuel pressure is relatively small is advantageous in calculating the actual leak amount because the variation in the fuel injection amount is small, and a state where the fuel pressure is relatively high is an error in estimating the leak amount due to the fuel pressure error. Since it becomes large, it becomes advantageous when performing abnormality determination of detection of fuel pressure. Therefore, according to the above configuration, it is possible to realize highly accurate abnormality determination of the fuel pressure.

  (5) In the case of a fuel leak, if there is a leak abnormality in which the amount of leak becomes excessively large, a fuel pressure detection abnormality cannot be correctly determined. In this regard, when it is determined that a leak abnormality has occurred, the fuel pressure detection abnormality determination is not performed, so that the inconvenience that a fuel pressure detection abnormality is erroneously determined due to the occurrence of a leakage abnormality is suppressed. it can.

  (6) Since the fuel pressure is low during idle operation, fuel leakage is unlikely to occur, and the allowable amount of fuel leakage is relatively small. For this reason, it is advantageous to determine the leakage abnormality during idle operation in order to increase the determination accuracy.

  (7) Since the fuel leak amount increases in a quadratic function as the fuel pressure increases, when the fuel pressure sensor 21 is abnormal, the difference between the actual leak amount and the estimated leak amount may increase as the fuel pressure increases. Is expensive. Therefore, a threshold value is set according to the detected value of the fuel pressure by the fuel pressure sensor 21. That is, when the detected value of the fuel pressure is low, the determination value QLJD for comparing the difference between the actual leak amount and the estimated leak amount is set small, and when the detected value of the fuel pressure is high, the determination value QLJD is set large. So that In this case, abnormal detection of the fuel pressure can be suitably performed according to the state of the fuel pressure of the common rail 20.

  The present invention is not limited to the description of the above embodiment, and may be implemented as follows.

  In the above, the fuel pressure Pc may be set to a low pressure state (for example, an idle state) at a predetermined timing in order to calculate the estimated leak amount Qc. Alternatively, the estimated leak amount Qc may be calculated when it is determined that the engine operating state is the low pressure state.

  In the above, the threshold value C may be adjusted according to the fuel pressure Pc. When there is a detection abnormality in the fuel pressure, particularly when there is an abnormality in the fuel pressure sensor 21, the higher the fuel pressure Pc, the higher the possibility that the difference between the actual leak amount and the estimated leak amount will increase. Therefore, the threshold value C is corrected to the increase side according to the fuel pressure Pc. In this case, according to the difference in the fuel pressure Pc, it is possible to increase the determination accuracy of the fuel pressure detection abnormality.

  In the above description, the correction amount ΔQc of the fuel leak amount with respect to the viscosity is calculated in the low pressure state, that is, the idle state. However, even if the correction amount ΔQc is calculated in the high pressure state, that is, the high load operation state of the engine. Good. In this case, it is preferable that the correction amount ΔQc is calculated when it is determined that the steady state of the engine, for example, the rate of change of the rotational speed is equal to or less than a predetermined value and the rotational speed is constant.

  In the above description, the calculation of the fuel leak correction amount ΔQc with respect to the viscosity and the determination of the abnormality in detecting the fuel pressure are performed at different fuel pressures Pc1 and Pc2. In addition to this, the calculation of the correction amount ΔQc and the determination of abnormality in detection of the fuel pressure may be performed at the same fuel pressure.

  When the fuel tank 10 is refilled with fuel, the fuel leak amount correction amount ΔQc with respect to the viscosity may change due to refilling with a different type of fuel. When the correction amount ΔQc changes, the fuel leak amount with respect to the predetermined fuel pressure Pc changes. Therefore, when the ECU 50 determines that the fuel has been replenished in the fuel tank 10, the processing for calculating the correction amount ΔQc may be performed. For example, a sensor for detecting the amount of fuel is provided in the fuel tank 10, and it is determined whether or not fuel has been replenished based on the detection result of the sensor. In this case, the fuel pressure detection abnormality can be suitably implemented using the fuel leak characteristic based on the correction amount ΔQc after refueling.

  ・ Viscosity of fuel varies with temperature. Therefore, the estimated leak amount may be corrected in consideration of the temperature change of the viscosity of the fuel. For example, a temperature sensor for detecting the temperature of the fuel is provided, and the estimated leak amount is corrected using the temperature detection value by the temperature sensor. In this case, the estimated leak amount can be obtained more accurately, and as a result, the accuracy of fuel pressure detection abnormality can be increased.

  In the above, an example is shown in which the pressure limiter 30 that is a pressure reducing valve is provided on the common rail 20, but the configuration of the present invention can also be applied to a fuel control device that does not include the pressure limiter 30.

  -After determining with the step S11 of FIG. 2 being a low pressure state, you may determine the presence or absence of completion of warming-up of an engine. In this case, if it is determined affirmatively that the warm-up of the engine has been completed, the process proceeds to step S12. If a negative determination is made, this process ends. When determination of abnormality in detection of fuel pressure is performed in a state where engine warm-up is complete and engine operation is stable, determination of abnormality in detection of fuel pressure can be suitably performed.

  DESCRIPTION OF SYMBOLS 10 ... Fuel tank, 11 ... Fuel pump, 20 ... Common rail, 21 ... Fuel pressure sensor, 23 ... Injector, 50 ... ECU.

Claims (9)

A fuel pump (11) for controlling the fuel intake amount by an intake metering valve and increasing the pressure of the fuel in the fuel tank (10);
A common rail (20) for storing fuel pumped from the fuel pump;
A fuel injection valve (23) for supplying fuel accumulated in the common rail to a cylinder of the engine;
A fuel pressure sensor (21) for detecting the pressure of the fuel in the common rail, and a fuel injection device comprising:
Control means for feedback-controlling the fuel discharge amount of the fuel pump based on a deviation between a detected value of the fuel pressure by the fuel pressure sensor and a target fuel pressure of the common rail;
From the difference between the fuel discharge amount calculated based on IQ characteristics from the drive current of the intake metering valve and the fuel injection amount from the fuel injection valve determined based on the operating state of the engine, the fuel from the fuel injection valve An actual leak amount calculating means for calculating an actual leak amount which is an actual value of the leak amount;
A leakage abnormality determination unit that determines that a leakage abnormality has occurred when the actual leakage amount calculated by the actual leakage calculation unit is greater than a predetermined leakage allowable value;
Correction amount calculating means for calculating a correction amount of the fuel leak amount with respect to the viscosity of the fuel based on the actual leak amount;
Estimated leak amount calculation means for calculating an estimated leak amount that is an estimated value of the fuel leak amount from the detected value of the fuel pressure and the correction amount, using a reference fuel leak characteristic indicating a relationship between the fuel pressure and the fuel leak;
Based on the comparison result between the actual leak amount and the estimated leak amount, the detection error of the fuel pressure is determined as the fuel pressure detection error, and it is determined that a leak abnormality has occurred by the leak abnormality determination means. Detection abnormality determination means that does not determine that the detection abnormality of the fuel pressure has occurred ,
A fuel injection control device comprising:   The fuel injection control device according to claim 1, wherein the correction amount calculating means calculates the correction amount when the engine is in a predetermined low pressure state.   The fuel injection control device according to claim 1, wherein the detection abnormality determination unit determines whether or not the fuel pressure is detected abnormally when the engine is in a predetermined high pressure state. When the fuel pressure is the first pressure, the actual leak amount calculating means calculates the actual leak amount from the fuel discharge amount and the fuel injection amount at that time,
The estimated leak amount calculation means estimates based on the correction amount calculated by the correction amount calculation means and the fuel pressure detected by the fuel pressure sensor when the fuel pressure is a second pressure greater than the first pressure. The fuel injection control apparatus according to any one of claims 1 to 3, wherein a leak amount is calculated. Leak abnormality determination means for determining that a leak abnormality has occurred when the actual leak amount calculated by the actual leak amount calculation means is greater than a predetermined allowable leak value,
The detection abnormality determination means is configured not to determine that the fuel pressure detection abnormality has occurred when the leakage abnormality determination means determines that a leakage abnormality has occurred. The fuel injection control device according to any one of the above.   The leak abnormality determining means determines the leak allowable value in the idle operation state of the engine, and the estimated leak amount estimated in the idle operation state is larger than the leak allowable value in the idle operation state. The fuel injection control device according to claim 5, wherein it is determined that a leak abnormality has occurred.   The detection abnormality determination means sets a determination value for comparing the difference between the actual leak amount and the estimated leak amount in accordance with a detected value of fuel pressure by the fuel pressure sensor. The fuel injection control device described. A fuel replenishment determining means for determining whether or not fuel has been replenished in the fuel tank;
The fuel injection control device according to any one of claims 1 to 7, wherein the correction amount calculation means calculates the correction amount when it is determined that the fuel is replenished.   The fuel injection control apparatus according to any one of claims 1 to 8, wherein the estimated leak amount calculation means corrects the estimated leak amount based on a temperature change of the viscosity.

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