JP4488017B2 - Accumulated fuel injection device and accumulator fuel injection system - Google Patents

Description

  The present invention relates to an accumulator fuel injection device and an accumulator fuel injection system used in an internal combustion engine.

  Conventionally, for example, Patent Document 1 proposes an accumulator-type fuel injection device that detects a fuel leak when a fuel leak occurs due to a joint between components such as a fuel pipe or a malfunction of an injector in the accumulator-type fuel injector. Yes. Specifically, in Patent Document 1, a diesel engine, an injector for injecting and supplying fuel to each cylinder of the diesel engine, a common rail for accumulating high-pressure fuel to be supplied to the injector, and a fuel supply pump for pumping high-pressure fuel to the common rail And an accumulator fuel injection device that includes an ECU for driving and controlling the fuel supply pump based on the pressure in the common rail and the like.

  In such an accumulator fuel injection device, the ECU determines a fuel leak as follows. First, the target energization start timing TF used for actually driving the solenoid valve of the fuel supply pump is calculated, and the fuel discharge amount QT from the fuel supply pump is calculated based on the target energization start timing TF.

  Next, an arithmetic expression set in advance as a function of the fuel temperature THF detected by the fuel temperature sensor, the common rail pressure PA based on the detection signal from the common rail pressure sensor, and the engine rotational speed NE detected by the rotational speed sensor is used. An internal leak amount QI of the injector corresponding to the fuel amount leaking from the gap between the components while the injector is closed is calculated. Then, the switching leak amount QS of the injector corresponding to the amount of fuel released when the injector nozzle is opened is calculated from the fuel temperature THF and the common rail pressure PA.

Subsequently, a fuel amount QP corresponding to the change in the common rail pressure is calculated. Thereafter, the fuel leakage amount QL is calculated by an arithmetic expression {QL = QT− (QI + QS + QP + QF)}. QF is the current fuel injection amount. When the fuel leakage amount QL calculated in this way exceeds a threshold value indicating the occurrence of fuel leakage, it is determined that fuel leakage has occurred.
JP 9-177586 A

  However, the inventors have clarified that the conventional technique has a problem that fuel leakage cannot be determined or determination accuracy is low. Hereinafter, this will be described with reference to the drawings.

  FIG. 10 is a diagram illustrating the behavior of the common rail pressure and the fuel leakage amount QL calculated by the ECU in the accumulator fuel injection device. In FIG. 10, point A indicates normal control, point B indicates a high pressure abnormality, point C indicates fuel leakage, and point D indicates a fuel leakage state. FIG. 11 is a graph showing the increase and decrease of the fuel discharge amount QT delivered from the fuel supply pump to the common rail, the fuel amount Qx (= QI + QS + QP + QF) exiting from the common rail, and the fuel leakage amount QL.

  As shown in FIG. 10, in the behavior of the common rail pressure, it is preferable that the pressure in the common rail always follows the target common rail pressure. In the normal control state where there is no fuel leakage, the common rail pressure is almost the same as the target common rail pressure. It has become. In this case, the fuel leakage amount QL between A and B does not exceed the threshold value.

  However, when a high-pressure abnormal state occurs due to a malfunction of the intake metering valve that adjusts the fuel flow rate in the common rail, the fuel is continuously sent from the fuel supply pump, so the common rail pressure increases. In this case, as shown in FIG. 11, QT decreases because control is performed to reduce the amount of fuel supplied from the fuel supply pump to the common rail so that the actual common rail pressure follows the target common rail pressure. Further, since the actual common rail pressure increases, the fuel amount Qx that escapes from the common rail increases. As a result, the fuel leakage amount QL decreases between B and C. Since no fuel leakage occurs in the high pressure abnormality state, of course, the fuel leakage amount QL does not exceed the threshold value.

  When the high-pressure abnormal state continues on the common rail and the piping is damaged, fuel leakage occurs from the damaged portion. Therefore, the actual common rail pressure continues to decrease. In this case, in order to increase the pressure in the common rail, the amount of fuel supplied from the fuel supply pump to the common rail increases. Therefore, the supply amount from the fuel supply pump to the common rail and the amount of fuel leakage are constant, or the supply amount QT to the common rail is higher than the amount of fuel leakage. On the other hand, when the actual common rail pressure decreases, the amount of fuel leakage also decreases, so Qx decreases. As a result, the fuel leakage amount QL increases between CD.

  However, as shown in FIG. 10, the fuel leakage amount QL may not exceed the threshold value even in a fuel leakage state. That is, when the change in the fuel leakage amount QL is gradual, or when the threshold value is set to a large value indicating a large-scale fuel leakage in order to avoid erroneous determination, the fuel leakage amount QL is However, the fuel leak could not be determined reliably.

  In view of the above, the present invention makes it possible to reliably determine that fuel in a common rail is leaking in an accumulator fuel injection apparatus and an accumulator fuel injection system that supply fuel to a common rail with a fuel supply pump. For the purpose.

  To achieve the above object, according to the present invention, in the accumulator fuel injection device, when fuel is supplied from the common rail (20) to the fuel inlet (41) of the injector (40) via the high-pressure pipe (65), The switching leak in which the fuel returns to the fuel tank (70) from the leak fuel outlet (42) of the injector (40) through the fuel pipe (63) during normal injection in the injector (40), and the fuel (40) ) From the leaked fuel outlet (42) of the injector (40) through the leaked fuel pipe (63) and the steady leak returning to the fuel tank (70), and the amount of leak in the injector (40) A leak amount calculation unit (51) that estimates the amount of fuel, and an injection amount calculation unit (5) that estimates the amount of fuel injected from the injector (40) into the combustion chamber ) And the pressure difference in the common rail (20) before and after the fuel is injected into the combustion chamber by the injector (40) and the amount of fuel supplied to the common rail (20) and the injector (40). The fuel outflow amount estimation value calculation unit (53) for estimating the fuel outflow amount estimation value that is the balance with the amount of fuel to be calculated, and the leak amount and injection amount calculation in the injector (40) acquired by the leak amount calculation unit (51) Based on the amount of fuel injected into the combustion chamber from the injector (40) acquired by the unit (52) and the estimated value of fuel outflow acquired by the fuel outflow amount estimated value calculation unit (53) A change amount calculation unit (55) for acquiring a post-filter fuel leak estimation amount that is a change amount of the fuel leak estimation amount input from the addition unit (54); Fuel leak after filter A determination unit (57) for determining that fuel in the common rail (20) is leaking when the estimated amount exceeds a fuel leakage determination threshold value indicating that fuel leakage has occurred in the common rail (20); It is characterized by that.

  Thereby, even if the estimated fuel leakage amount QL acquired by the adding unit (54) changes gradually with respect to time, the variation amount calculating unit (55) increases the variation amount of the estimated fuel leakage amount. Can be made. That is, when a fuel leak occurs, the amount of change in the estimated fuel leak amount can exceed the fuel leak determination threshold value indicating the fuel leak. In this way, fuel leakage in the common rail (20) can be reliably determined.

In such a case, as the change amount calculation unit (55), the estimated amount of fuel leak acquired by the addition unit (54) at the first timing and the addition unit at the second timing after the first timing. The difference value obtained by dividing the difference from the estimated fuel leak obtained in (54) by the time difference between the first timing and the second timing is used to obtain the differential value obtained as the post-filter fuel leak estimated amount. can do. Thereby, the variation | change_quantity of the fuel leak estimated amount with respect to time can be increased. Further, as the determination unit (57), when the estimated fuel leakage amount does not exceed the fuel leakage determination threshold value, but the post-filter fuel leakage estimation amount that is a differential value exceeds the fuel leakage determination threshold value, the common rail (20) What determines that the inside fuel is leaking can be adopted.

  The fuel leak determination threshold value calculation unit (56) that acquires a fuel leak determination threshold value based on the switching leak and the steady leak in the injector (40), and the fuel leak determination threshold value calculation unit (56) The fuel leak determination threshold value acquired in step S can be input to the determination unit (57).

  Thus, by calculating the fuel leakage determination threshold value in the fuel leakage determination threshold value calculation unit (56), the optimum fuel leakage determination threshold value according to the situation of the internal combustion engine, the common rail (20), or the like. Can be obtained. Therefore, the determination part (57) can determine the fuel leakage with higher accuracy.

  Further, when the determination unit (57) determines that the fuel in the common rail (20) is leaking, a treatment unit (58) that performs a notification process indicating that the fuel in the common rail (20) is leaking is provided. It can also be provided. Thereby, the user can be notified of fuel leakage in the common rail (20), and secondary damage due to fuel leakage can be prevented.

  Further, from the above-mentioned accumulator fuel injection device, a fuel supply pump (10) for pumping fuel from a fuel tank (70) via a suction pipe (61), and a fuel supply pump (10) via a supply pipe (62) A common rail (20) that stores the supplied high-pressure fuel, and an injector that injects high-pressure fuel supplied from the common rail (20) through the high-pressure pipe (65) into the combustion chamber of the internal combustion engine in accordance with a command from the pressure-accumulation fuel injection device (40) can also be configured as an accumulator fuel injection system.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The accumulator fuel injection system shown in the present embodiment is applied to an internal combustion engine such as a 4-cylinder diesel engine or a direct injection engine that accumulates gasoline and directly injects gasoline fuel into the internal combustion engine. In the following, a case where a regenerative fuel injection system is applied to a diesel engine will be described.

  FIG. 1 is an overall configuration diagram of an accumulator fuel injection system according to an embodiment of the present invention. As shown in FIG. 1, the accumulator fuel injection system 1 includes a fuel supply pump 10, a common rail 20, an EDU 30, an injector 40, and an engine ECU 50. The engine ECU 50 corresponds to the pressure accumulation type fuel injection device of the present invention.

  The fuel supply pump 10 pumps high-pressure fuel to the common rail 20. Specifically, the fuel supply pump 10 is supplied from the feed pump 11 to the pump cylinder in response to a control signal input from the engine ECU 50 and a feed pump 11 that pumps fuel from the fuel tank 70 via the suction pipe 61. A suction metering valve 12 that adjusts the fuel flow rate, a plunger 13 that slides in a liquid-tight state inside the pump cylinder when the cam rotates together with a camshaft that is rotated by the engine, and a check valve 14 that prevents backflow of fuel. And.

  In such a fuel supply pump 10, the fuel pumped up from the fuel tank 70 by the feed pump 11 is adjusted by the suction metering valve 12 and sucked into a pump chamber (not shown). Further, the fuel in the pump chamber is pressurized by the plunger 13 sliding in the pump cylinder according to the rotation of the cam. When the pressurized fuel pressure exceeds the valve opening pressure of the check valve 14, the pressurized fuel is supplied to the common rail 20 via the supply pipe 62.

  Further, the fuel supply pump 10 is provided with a temperature sensor 15 so that the temperature of the fuel pumped up from the fuel tank 70 is detected, and a signal corresponding to the temperature is input to the engine ECU 50. In FIG. 1, the temperature sensor 15 is depicted in a block diagram, but is actually attached to the fuel supply pump 10.

  Then, excess fuel in the fuel supply pump 10 is returned to the fuel tank 70 via the fuel pipe 63. Further, the suction pipe 61 is provided with a fail filter 64 that filters the fuel sucked from the fuel tank 70 and removes foreign matters.

  The common rail 20 is a livestock pressure means for storing high-pressure fuel supplied from the fuel supply pump 10 while maintaining the target rail pressure. This target rail pressure is determined by the engine ECU 50 based on the operation state of the diesel engine such as an accelerator opening signal and an engine speed signal, for example.

  Further, a pressure limiter 21 that opens when the fuel pressure in the common rail 20 exceeds a predetermined upper limit value and releases the fuel pressure in the common rail 20 is attached to the common rail 20. The fuel flowing out from the pressure limiter 21 is returned to the fuel tank 70 through the fuel pipe 63.

  Furthermore, a rail pressure sensor 22 is attached to the common rail 20, and a signal corresponding to the actual common rail pressure in the common rail 20 (hereinafter referred to as an actual rail pressure) is input to the engine ECU 50.

  The EDU 30 is a drive device that inputs an open / close signal for opening and closing the fuel injection valve of the injector 40 to the injector 40 based on a drive signal input from the engine ECU 50.

  The injector 40 is attached to a cylinder of the diesel engine, and injects fuel into the cylinder by opening and closing a fuel injection valve based on an open / close signal input from the EDU 30. In such an injector, a fuel inlet 41 into which high-pressure fuel from the common rail 20 is introduced via the high-pressure pipe 65 and a fuel that causes the fuel inside the injector 40 to flow out toward the fuel tank 70 via the fuel pipe 63. And an outlet 42.

  Such an injector 40 is provided in each cylinder according to the number of cylinders of the diesel engine, and high pressure fuel is supplied to each injector 40 through each high pressure pipe 65. In FIG. 1, only one cylinder is shown.

  The engine ECU 50 includes a microcomputer including a CPU, ROM, EEPROM, RAM, and the like (not shown), and performs arithmetic processing according to a program stored in the microcomputer. In the present embodiment, the engine ECU 50 performs a fuel leak determination process on the common rail 20 in the regenerative fuel injection system 1 shown in FIG.

  Here, when the fuel leakage occurs in the regenerative fuel injection system 1, for example, when the piping such as the supply piping 62 and the high-pressure piping 65 is damaged, a defect that causes fuel leakage occurs at the joint between each piping and the common rail 20. The case corresponds to a case where fuel leaks from the pressure limiter 21.

  In order to perform the process for detecting such fuel leakage, the engine ECU 50 receives a signal corresponding to the actual rail pressure in the common rail 20 from the rail pressure sensor 22 and a signal corresponding to the fuel temperature from the temperature sensor 15. In addition, a signal corresponding to the engine speed is also input from an engine speed sensor 80 that detects the engine speed provided in the diesel engine.

  In FIG. 1, the engine speed sensor 80 is depicted in a block diagram, but actually, in order to detect the passage of protrusions on a ring attached to the crankshaft of the diesel engine and acquire the engine speed, It is fixed to the engine housing.

  Various signals such as an accelerator pedal depression amount necessary for the engine ECU 50 (not shown) to control the fuel injection of the injector 40 are also input to the engine ECU 50. As described above, the engine ECU 50 is sequentially input with signals corresponding to the physical quantities detected by the sensors.

  FIG. 2 is a specific configuration diagram of engine ECU 50 shown in FIG. As shown in this figure, the engine ECU 50 includes a leak amount calculation unit 51, an injection amount calculation unit 52, a fuel outflow amount estimated value calculation unit 53, an addition unit 54, a differential amount calculation unit 55, and a fuel leakage. A determination threshold value calculation unit 56, a determination unit 57, and a treatment unit 58 are provided.

  The leak amount calculation unit 51 calculates the leak amount in the injector 40. In the present embodiment, the leak amount is the amount of fuel that exits from the fuel outlet 42 to the fuel pipe 63 during normal injection of the injector 40 (hereinafter referred to as switching leak), and the injector 40 is configured in a steady manner. This is equivalent to the total amount of fuel leaking from each part (hereinafter referred to as steady leak).

  Such a leak amount calculation unit 51 inputs parameters such as engine speed, actual rail pressure, command injection amount, and fuel temperature, and based on these parameters and a map stored in the engine ECU 50 in advance, switching leak and The leak amount QINJ in the injector 40 is estimated by acquiring the steady leak.

  Here, the command injection amount is an injection amount calculated in accordance with the accelerator depression amount, and is a parameter acquired in advance by the engine ECU 50 based on the accelerator depression amount input to the engine ECU 50.

  The injection amount calculation unit 52 calculates the amount of fuel injected from the injector 40 into the cylinder. Such an injection amount calculation unit 52 inputs parameters of engine speed, actual rail pressure, and command torque, and fuel injected from the injector 40 based on these parameters and a map stored in the engine ECU 50 in advance. The quantity QTotal is estimated.

  Here, the command torque is a parameter acquired from the map in accordance with the accelerator depression amount, and is a parameter acquired in advance based on the accelerator depression amount input to the engine ECU 50.

  The fuel outflow amount estimated value calculation unit 53 determines the amount of fuel supplied to the common rail 20 and the injector based on the pressure difference in the common rail 20 before and after fuel injection by the injector 40 at a predetermined crank angle of the diesel engine. The fuel outflow amount estimated value QPC, which is a balance with the amount of fuel supplied to 40, is estimated. In the present embodiment, the predetermined crank angle is, for example, −BTDC 54 ° CA and ATDC 54 ° CA (5 cyl), −BTDC 60 ° CA and ATDC 30 ° CA (4 cyl).

  The fuel outflow amount estimated value calculation unit 53 receives parameters of the actual rail pressure, the crank angle range start, and the crank angle range end, and the injector is based on these parameters and a map stored in the engine ECU 50 in advance. A fuel outflow estimation value QPC at 40 is estimated.

  Specifically, the fuel outflow amount estimated value QPC will be described with reference to FIG. FIG. 3 is a diagram showing a change in the actual fuel pressure in the common rail 20. As shown in this figure, the pressure in the common rail 20 increases or decreases according to the rotation of the crankshaft of the diesel engine due to the supply of fuel from the fuel supply pump 10 and the discharge of fuel to the injector 40.

  If the pressure in the common rail 20 in the crank angle range start is the pre-injection common rail pressure NPCBIJLK, and the pressure in the common rail 20 in the crank angle range end is the post-injection common rail pressure NPCAIJLK, the estimated fuel outflow amount QPC is ([NPCBIJLK ]-[NPCAIJLK]) × [KCRVOL] / [EPC].

  Here, KCRVOL refers to the high-pressure fuel piping system volume, and is the total volume of fuel in the common rail 20 and the high-pressure piping 65. EPC refers to a body elastic coefficient, and is a correction coefficient for a volume difference between when pressure is applied to fuel and when it is not applied. The volume KCRVOL and the coefficient EPC are stored in advance in the engine ECU 50 and are used in the above arithmetic expression.

  In this manner, the fuel outflow amount estimated value calculation unit 53 estimates the fuel outflow amount estimated value QPC based on the pressure difference in the common rail 20 before and after injection by the injector 40.

  The addition unit 54 performs addition and subtraction operations for each input parameter, and outputs the calculation result as the fuel leakage estimation amount QL. Specifically, the adding unit 54 inputs the leak amount QINJ from the leak amount calculating unit 51, the fuel amount QTotal from the injection amount calculating unit 52, and the fuel outflow amount estimated value QPC from the fuel outflow amount estimated value calculating unit 53, respectively. The calculation of [QL] = [QPC]-[QINJ]-[QTotal] is performed to obtain the estimated fuel leak amount QL.

  The differential amount calculation unit 55 is a filter that calculates a change amount of the fuel leakage estimation amount QL input from the addition unit 54, that is, a differential value. The steeper the slope of the input signal with respect to time, the greater the change of the output signal relative to the input signal, and the slower the slope of the input signal with respect to time, the more the output signal The change is smaller than that. Therefore, the change amount of the estimated amount QL can be amplified by acquiring the differential value of the estimated fuel leakage amount QL. Such a differential amount calculation unit 55 outputs a value obtained by differentiating the estimated amount QL as a post-filter fuel leak estimated amount QL ′. The differential amount calculation unit 55 corresponds to the change amount calculation unit of the present invention.

In the present embodiment, the differential amount calculation unit 55 uses the fuel leakage estimation amount QL acquired by the addition unit 54 at the first timing and the addition unit 54 at the second timing after the first timing. The differential value obtained by dividing the difference from the acquired estimated fuel leak amount QL by the time difference between the first timing and the second timing is acquired as the estimated post-filter fuel leak amount QL ′. Then, the estimated amount QL ′ is obtained by the arithmetic expression y (i) = a × u (i) + b × u (i−1) −d × y (i−1). Here, u (i) is the estimation amount QL input this time, u (i-1) is the estimation amount QL input last time, y (i) is the estimation amount QL 'output last time, and y (i-1) is the previous time. The output estimated quantities QL ′, a, b, and d are coefficients.

  The amount of change in differentiation can be adjusted by the values of the coefficients a, b, and d. In this embodiment, for example, a = 2, b = −1.5, and d = −0.5. Each numerical value is experimentally obtained by the inventors as an optimum value that can reliably determine whether fuel leakage has occurred in an abnormal state where fuel leakage has occurred, and can reliably determine that fuel leakage has not occurred in normal times when no fuel leakage has occurred. It is what was done.

  Such a differential amount calculation unit 55 is schematically shown in FIG. The arithmetic expression is y (i) = 2 × u (i) −1.5 × u (i−1) + 0.5 × y (i−1) depending on each coefficient. Therefore, as shown in FIG. 4, the estimated fuel leakage amount QL input to the differential amount calculation unit 55 passes through the filter 55a that can realize the above calculation, and is calculated as a post-filter fuel leak estimation amount QL ′. Is output from the unit 55.

  FIG. 5 is a diagram for explaining the effect of the filter 55 a of the differential amount calculation unit 55. As shown in this figure, when the accumulator fuel injection system 1 is in the normal control state, the behavior of the fuel leak estimation amount QL and the behavior of the post-filter fuel leak estimation amount QL ′ indicate fuel leakage between A and B. Below the threshold.

  Then, when the accumulator fuel injection system 1 is in a high-pressure abnormal state, the estimated amounts QL and QL 'decrease together between B and C. In this case, since the post-filter fuel leak estimated amount QL ′ is a differential value of the estimated amount OL, the amount of change is larger than the estimated amount QL.

  Subsequently, when a fuel leak occurs in the accumulator fuel injection system 1 at the point C, the actual rail pressure decreases along with the fuel leak. The fuel leak estimation amount QL starts to increase, but exhibits a behavior that does not exceed the threshold value. This is the same as the behavior in the conventional apparatus. However, since the estimated amount QL ′ that has passed through the filter 55a has the effect of increasing the change in the estimated amount QL, the slope of the post-filter fuel leak estimated amount QL ′ becomes larger than the estimated amount QL, and between C and D The estimated amount QL ′ exceeds the threshold value indicating fuel leakage.

  In this way, the estimated fuel amount QL ′, which is a differential value, is obtained by passing the estimated fuel leakage amount QL through the filter 55a, so that it is possible to reliably determine when the fuel leakage has occurred in the accumulator fuel injection system 1. I have to.

  The fuel leakage determination threshold value calculation unit 56 calculates a threshold value indicating that fuel leakage has occurred in the common rail 20. Such a fuel leak determination threshold value calculation unit 56 inputs parameters of steady leak, switching leak, and fuel temperature in the injector 40, and based on these parameters and an arithmetic expression stored in advance in the engine ECU 50, the fuel leak determination threshold value calculation unit 56 The leakage determination threshold value QIjda is estimated.

  For each parameter of the steady leak and the switching leak input to the fuel leak determination threshold value calculation unit 56, values acquired by the leak amount calculation unit 51 and stored in the engine ECU 50 are used.

  The determination unit 57 inputs the post-filter fuel leak estimation amount QL ′ from the differential amount calculation unit 55 and also inputs the fuel leak determination threshold value QIjda from the fuel leak determination threshold value calculation unit 56, so that the estimation amount QL ′ is calculated. It is determined whether or not the threshold value QIjda is exceeded. Then, when the estimated amount QL ′ exceeds the threshold value QIjda, the determination unit 57 sets a determination flag and outputs the result. When the estimated amount QL ′ does not exceed the threshold value QIjda, the determination unit 57 does not set the determination flag. The result is output to.

  When the determination flag input from the determination unit 57 is set, the treatment unit 58 performs a notification process such as turning on a warning lamp in the meter, limiting the fuel injection amount from the injector 40, stopping the diesel engine, and the like. It is. If the determination flag is not set, it is determined that no fuel leakage has occurred, and thus the treatment unit 58 does not perform the treatment. The above is the overall configuration of the accumulator fuel injection system 1 according to the present embodiment.

  Next, the fuel leakage determination process in the engine ECU 50 will be described with reference to the drawings. FIG. 6 is a flowchart showing the contents of the fuel leakage determination process performed by the engine ECU 50. The flow shown in FIG. 6 starts after cranking and the engine is started and the idling speed is stabilized. Signals are always input from the engine speed sensor 80, the temperature sensor 15, and the rail pressure sensor 22 to the engine ECU 50.

  In step 100, the leak amount QINJ of the injector 40 is calculated. That is, the leak amount calculation unit 51 shown in FIG. 2 obtains the leak amount QINJ based on the engine speed, actual rail pressure, command injection amount, fuel temperature parameters and a map stored in the engine ECU 50 in advance. Is done. The leak amount QINJ is input to the adder 54.

  In step 110, the fuel amount QTotal injected from the injector 40 is calculated. That is, the injection amount calculation unit 52 shown in FIG. 2 acquires the fuel amount QTotal based on the parameters of the engine speed, the actual rail pressure, and the command torque and the map stored in the engine ECU 50 in advance. The fuel amount QTotal is input to the adding unit 54.

  In step 120, an estimated fuel outflow amount QPC is calculated. That is, the fuel outflow amount estimated value calculation unit 53 shown in FIG. 2 is based on the engine speed, the actual rail pressure, the crank angle range start, the crank angle range end, and a map stored in the engine ECU 50 in advance. Thus, the estimated fuel outflow amount QPC is obtained. The estimated fuel outflow amount QPC is input to the adding unit 54.

  In step 130, a fuel leak determination threshold value QIjda is calculated. That is, the fuel leak determination threshold value calculation unit 56 shown in FIG. 2 determines the fuel leak determination threshold value based on the steady leak, switching leak, and fuel temperature parameters and the calculation formula stored in the engine ECU 50 in advance. QIjda is acquired. The fuel leak determination threshold value QIjda is input to the determination unit 57.

  In step 100 to step 130, the latest parameter input to engine ECU 50 or the latest parameter acquired by engine ECU 50 is used when the processing in each step is executed.

  In step 140, an estimated fuel leakage amount QL is calculated. Specifically, the estimated fuel leakage amount QL = QPC−QINJ−QTotal is calculated using each of the leakage amount QINJ, the fuel amount QTotal, and the fuel outflow amount estimated value QPC input to the adding unit 54 to estimate the fuel leakage. A quantity QL is obtained. The estimated fuel leak amount QL is input to the differential amount calculation unit 55.

  In step 150, a post-filter fuel leak estimation amount QL 'is calculated. That is, the estimated fuel leakage amount QL input to the differential amount calculation unit 55 is applied to the filter 55a shown in FIG. Thereby, the estimated amount QL is differentiated to increase the amount of change with respect to time. The post-filter fuel leak estimation amount QL ′ thus acquired by the differential amount calculation unit 55 is input to the determination unit 57.

  In step 160, the determination unit 57 determines whether or not the post-filter fuel leak estimation amount QL 'exceeds the fuel leak determination threshold value QIjda. If it is determined that the estimated amount QL ′ does not exceed the threshold value QIjda, it is determined that no fuel leakage has occurred in the accumulator fuel injection system 1, and the process returns to step 100. In addition, a result that the determination flag is not raised is input from the determination unit 57 to the treatment unit 58. Therefore, no treatment is performed in the treatment unit 58.

  Then, the fuel leak determination threshold value QIjda and the post-filter fuel leak estimation amount QL ′ are obtained and determined again using new parameters such as the engine speed input to the engine ECU 50. As long as the post-filter fuel leak estimation amount QL ′ does not exceed the fuel leak determination threshold value QIjda, the flow shown in FIG. 6 is repeated.

  On the other hand, when it is determined by the determination unit 57 that the post-filter fuel leak estimation amount QL ′ exceeds the fuel leak determination threshold value QIjda, it is determined that a fuel leak has occurred in the accumulator fuel injection system 1, and the process proceeds to step 170. .

  In step 170, the determination unit 57 sets a determination flag indicating that a fuel leak has occurred. As a result, the determination unit 57 inputs the result of setting the determination flag to the treatment unit 58. The fuel leak determination process ends here. Thereafter, the following processing is continued unless the processing is reset.

  That is, the treatment unit 58 performs a treatment for notifying that a fuel leak has occurred. FIG. 7 is a diagram illustrating the treatment of the treatment unit 58 with respect to the determination result of the determination unit 57. As shown in this figure, if the determination unit 57 determines that no fuel leakage has occurred, no action is taken. However, if the determination unit 57 determines that fuel leakage has occurred, the treatment unit 58 performs measures such as lighting the lamp, limiting the injection amount of the injector 40, and stopping the engine.

  Here, the lamp lighting refers to, for example, lighting a warning lamp indicating that a fuel leak has occurred in the meter. That is, for example, the treatment unit 58 outputs a warning signal for lighting the warning lamp to the meter ECU, thereby performing a treatment for lighting the warning lamp on the meter.

  In addition, the treatment unit 58 is a part of the engine ECU 50 that performs a process of limiting the injection amount of the injector 40 by inputting a command signal indicating the injection amount restriction to a part that adjusts the injection amount of the injector 40, or a part that drives the engine. The engine is stopped by inputting a command signal for stopping the engine itself. For example, the treatment unit 58 performs any or all of these treatments.

  The inventors performed a simulation to obtain the post-filter fuel leak estimation amount QL ′ by applying the fuel leak estimation amount QL estimated according to the situation to the filter 55 a of the differential amount calculation unit 55. The results are shown in FIGS. 8 and 9, the fuel leak estimated amount QL is indicated by a solid line, and the filtered fuel leak estimated amount QL 'is indicated by a broken line. In addition, the above-described a = 2, b = −1.5, and d = −0.5 were applied to the calculation formula in the differential amount calculation unit 55.

  FIG. 8 (a) shows a case where there is a fuel leak, FIG. 8 (b) shows a case where the accelerator is released from a state where the accelerator is depressed, and FIG. 8 (c) shows a case where the accelerator is depressed in a normal operation. The results are shown. The fuel leak determination threshold value QIjda is, for example, Output = 1.5.

  As shown in FIG. 8 (a), when fuel leakage occurs, the actual rail pressure of the common rail 20 decreases rapidly, so the fuel leakage estimation amount QL increases rapidly with time. By differentiating the quantity QL, it is possible to obtain an estimated quantity QL ′ that changes more greatly. In this case, the estimated amount QL ′ exceeds the value of Output = 1.5 which is the fuel leakage determination threshold value QIjda, and it is determined in step 160 that fuel leakage has occurred.

  On the other hand, as shown in FIGS. 8B and 8C, when there is no fuel leakage, the estimated amount of fuel leakage QL changes gradually with time. The slope of a certain post-filter fuel leakage estimation amount QL ′ does not increase. Therefore, in these cases, the post-filter fuel leak estimation amount QL ′ does not exceed the fuel leak determination threshold value QIjda, and it is determined in step 160 that no fuel leak has occurred.

  FIG. 9 shows the result of simulation for the case where the vehicle has accelerated although no fuel leakage has occurred. 9A shows the simulation results when the accelerator is suddenly depressed, FIG. 9B shows the simulation results when the vehicle suddenly accelerates, and FIG. 9C shows the acceleration results during normal operation. is there.

  As shown in FIG. 9, in the case of vehicle acceleration, each fuel leak estimated amount QL is convex downward, and the filtered fuel that is a differential value of the estimated amount QL according to the slope of the estimated amount QL. The estimated leak amount QL ′ is obtained. In these cases, the estimated amount QL ′ obtained is convex downward, and therefore the estimated amount QL ′ does not exceed Output = 1.5, which is the threshold value QIjda.

  As described above, when the fuel leakage occurs, the post-filter fuel leakage estimated amount QL ′ obtained by the differential amount calculating unit 55 exceeds the fuel leakage determination threshold value QIjda, and in other cases, the estimated amount QL ′. Obtained a result that does not exceed the threshold value QIjda.

  As described above, according to the present embodiment, after obtaining the fuel leakage estimated amount QL, the differential value of the estimated amount QL is obtained, thereby increasing the amount of change of the fuel leakage estimated amount QL with respect to time. It has become. Thus, even if the fuel leak is occurring and the estimated fuel leak amount QL shows a gradual change with respect to time, the amount of change of the estimated amount QL is increased by the differential amount calculation unit 55, The estimated amount QL ′ after the differentiation can be made to exceed a fuel leakage determination threshold value QIjda indicating fuel leakage. In this way, fuel leakage in the common rail 20 can be reliably determined.

(Other embodiments)
In the above embodiment, the case where the heat storage type fuel injection system 1 is applied to a diesel engine has been described. However, the present invention can also be applied to a case where gasoline is stored and the gasoline fuel is directly injected into the internal combustion engine.

  In the above embodiment, the change in the estimated amount QL is increased by differentiating the estimated fuel leak amount QL acquired by the adding unit 54 by the derivative amount calculating unit 55. May increase the change in the estimated amount QL.

  In the above embodiment, when the notification process is performed in the treatment unit 58, the warning lamp is turned on by the meter, the fuel injection amount from the injector 40 is limited, and the diesel engine is stopped. However, other means may be adopted as long as it is a means that can notify the user that fuel leakage has occurred.

  Each step shown in FIG. 6 shows the flow of the fuel leakage determination process executed by each component of the engine ECU 50.

1 is an overall configuration diagram of a pressure accumulation fuel injection system according to an embodiment of the present invention. It is a specific block diagram of engine ECU shown by FIG. It is a figure for demonstrating the fuel outflow amount estimated value QPC, and is a figure which showed the change of the actual fuel pressure in a common rail. FIG. 3 is a diagram schematically illustrating a differential amount calculation unit illustrated in FIG. 2. It is a figure for demonstrating the effect of the filter of the derivative calculation part shown by FIG. It is the flowchart which showed the content of the fuel leak determination process which engine ECU shown by FIG. 2 performs. It is the figure which showed the treatment of the treatment part with respect to the determination result of the determination part shown by FIG. It is the figure which showed the simulation result about the post-filter fuel leak estimated amount QL 'when the fuel leak estimated amount QL estimated when there is a fuel leak, etc. is applied to the filter of the differential amount calculation unit. It is the figure which showed the simulation result about the fuel leak estimated amount QL 'after filtering when the fuel leak estimated amount QL estimated about the case of acceleration of a vehicle is applied to the filter of the differential amount calculating part. It is the figure which showed the behavior of the common rail pressure in the conventional accumulator fuel injection device, and the fuel leak amount QL calculated by ECU, respectively. In the conventional accumulator fuel injection device, the fuel discharge amount QT delivered from the fuel supply pump to the common rail, the fuel amount Qx (= QI + QS + QP + QF) exiting from the common rail, and the fuel leakage amount QL are respectively shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Fuel supply pump, 20 ... Common rail, 40 ... Injector, 41 ... Fuel inlet part, 42 ... Fuel outlet part, 50 ... Engine ECU, 51 ... Leak amount calculating part, 52 ... Injection amount calculating part, 53 ... Fuel outflow amount Estimated value calculation unit 54... Addition unit 55. Differentiation amount calculation unit 56. Fuel leak determination threshold value calculation unit 57. Determination unit 58. Treatment unit 63. Fuel piping 65 65 High-pressure piping 70. Fuel tank.

Claims (4)

High pressure fuel in a common rail (20) for storing fuel supplied from a fuel supply pump (10) is injected into a combustion chamber of an internal combustion engine by an injector (40),
When the fuel is supplied from the common rail (20) to the fuel inlet (41) of the injector (40) via the high-pressure pipe (65), the fuel is injected into the fuel pipe ( 63) and the switching leak returning from the fuel outlet (42) of the injector (40) to the fuel tank (70) through the steady leak in which the fuel constantly leaks from the injector (40). A leak amount calculation unit (51) for estimating a leak amount in the injector (40);
An injection amount calculation unit (52) for estimating the amount of fuel injected from the injector (40) into the combustion chamber;
The amount of fuel supplied to the common rail (20) and the injector (40) based on the pressure difference in the common rail (20) before and after the fuel is injected into the combustion chamber by the injector (40). A fuel outflow amount estimated value calculation unit (53) for estimating a fuel outflow amount estimated value that is a balance with the amount of fuel supplied to
The amount of leak in the injector (40) acquired by the leak amount calculator (51), the amount of fuel injected into the combustion chamber from the injector (40) acquired by the injection amount calculator (52), An accumulator fuel injection device comprising: an addition unit (54) that acquires an estimated fuel leakage amount based on the estimated fuel outflow amount obtained by the estimated fuel outflow amount calculation unit (53);
A change amount calculation unit (55) that acquires a post-filter fuel leak estimation amount that is a change amount of the fuel leak estimation amount input from the addition unit (54);
Judgment that the fuel in the common rail (20) is leaking when the estimated amount of fuel leak after filtering exceeds a fuel leak judgment threshold value indicating that fuel leak is occurring in the common rail (20). Part (57) ,
The change amount calculation unit (55) includes the estimated fuel leak amount acquired by the addition unit (54) at a first timing, and the addition unit at a second timing after the first timing. A differential value obtained by dividing the difference from the estimated fuel leak obtained in (54) by the time difference between the first timing and the second timing is obtained as the post-filter fuel leak estimated amount. Is supposed to
The determination unit (57), when the estimated fuel leakage amount does not exceed the fuel leakage determination threshold value, but the filtered fuel leakage estimation amount that is the differential value exceeds the fuel leakage determination threshold value, It is determined that fuel in the common rail (20) is leaking . A fuel leak determination threshold value calculation unit (56) that acquires the fuel leak determination threshold value based on the switching leak and the steady leak in the injector (40) is provided, and the fuel leak determination threshold value is provided. The accumulator fuel injection device according to claim 1, wherein the fuel leakage determination threshold value acquired by the calculation unit (56) is input to the determination unit (57). When the determination unit (57) determines that the fuel in the common rail (20) is leaking, the treatment unit (58) performs a notification process indicating that the fuel in the common rail (20) is leaking. accumulator fuel injection device according to claim 1 or 2, characterized in that is provided. An accumulator fuel injection device according to any one of claims 1 to 3 ,
A fuel supply pump (10) for pumping fuel from the fuel tank (70) via the suction pipe (61);
A common rail (20) for storing high-pressure fuel supplied from the fuel supply pump (10) via a supply pipe (62);
An injector (40) for injecting high-pressure fuel supplied from the common rail (20) through the high-pressure pipe (65) into the combustion chamber of the internal combustion engine in accordance with a command from the accumulator fuel injection device; An accumulator fuel injection system.

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