JP2018178978A - Fuel injection control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control system capable of precisely detecting last injection and current injection being joined together in multi-stage injection.SOLUTION: A fuel injection control system comprises: a fuel pressure sensor which detects the pressure of fuel being introduced into an injector; a determination value setting part (S130) which sets, when letting the injector perform fuel injection a plurality of times, a determination value based upon fuel pressure detected by the fuel pressure sensor before the plurality of times of fuel injection; an abnormality detection part (S100, S110, S140, S150, and S160) which detects such abnormality that two arbitrary successive fuel injection actions are joined together if it is determined, based upon the fuel pressure detected by the fuel pressure sensor, that the fuel pressure having dropped in the last fuel injection further drops in the current fuel injection without rising up to the determination value when the fuel injection is performed successively a plurality of times.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fuel injection control system capable of performing multiple fuel injections by an injector during one combustion cycle of an internal combustion engine.

  For example, Patent Document 1 relates to a combustion control device for an internal combustion engine capable of optimally controlling the timings of multiple fuel injections when performing multiple fuel injections during one fuel cycle of the internal combustion engine. It is disclosed.

  In the combustion control device of Patent Document 1, when the rotation fluctuation rate of the engine is equal to or more than a predetermined value set according to the operation range, the pilot injection timing for the main injection is retarded and the rotation fluctuation rate is less than the predetermined value In this case, the pilot injection timing relative to the main injection is advanced. That is, when the engine rotation fluctuation rate is large, the engine rotation fluctuation rate is reduced by controlling the pilot injection timing so as to narrow the interval between the pilot injection and the main injection. On the other hand, when the rotation fluctuation rate is small, the generation of smoke is suppressed by controlling the pilot injection timing so as to widen the interval between the pilot injection and the main injection.

JP 2012-154180 A

  However, as in the case of Patent Document 1 described above, there is a possibility that two injections that should be separately injected may be coupled, such as when the injection timing is controlled so as to narrow the interval between successive fuel injections. . For example, it may be considered that the needle valve in the injector becomes difficult to close due to the deterioration with age of the injector, the machine difference variation, the property of the fuel, and the like. In such a case, when the interval between successive fuel injections is set narrow, the next injection is started before the needle valve of the injector is completely closed after the previous injection is finished. As a result, the earlier injection and the later injection are combined. When the first injection and the second injection are combined, the effects of the respective injections can not be sufficiently exhibited, which may affect the operating state of the internal combustion engine.

  The present invention has been made in view of the above-described point, and an object of the present invention is to provide a fuel injection control system capable of accurately detecting that a preceding injection and a subsequent injection are coupled.

In order to achieve the above object, a fuel injection control system (50) according to the present invention is capable of performing a plurality of fuel injections by an injector (20) during one combustion cycle of an internal combustion engine. ,
A fuel pressure sensor (20a) for detecting the pressure of fuel introduced into the injector;
A determination value setting unit (S130) configured to set a determination value based on the fuel pressure detected by the fuel pressure sensor before the plurality of fuel injections when causing the injector to perform the fuel injection a plurality of times;
With regard to any two fuel injections which are injected in succession in a plurality of fuel injections, the fuel pressure decreased by the previous fuel injection is decreased by the later fuel injection without rising to the judgment value And an abnormality detection unit (S100, S110, S140) for detecting that an abnormality has occurred in which two fuel injections injected before and after the fuel pressure are combined based on the fuel pressure detected by the fuel pressure sensor. , S150, S160).

  When the previous injection and the subsequent injection performed one after another are separated, the injector is once completely closed after the previous injection. Therefore, when the injector is closed, the flow of fuel injected from the injector is shut off, and the pressure of the fuel introduced into the injector rises sharply due to so-called water hammer phenomenon. As a result, the fuel pressure rises to a pressure exceeding the determination value set based on the fuel pressure before fuel injection.

  On the other hand, when the preceding injection and the subsequent injection performed one after another are combined, the injector starts the valve opening operation for the subsequent injection without completely closing the valve after the preceding injection. Become. If the injector starts to open before the valve is completely closed, the increase in fuel pressure introduced into the injector also decreases and starts to decrease with the subsequent injection without rising to the judgment value. Therefore, based on such a change in fuel pressure, it is possible to accurately detect that an abnormality has occurred in which two fuel injections performed in succession are combined.

  The reference numerals in the parentheses above merely show an example of the correspondence with specific configurations in the embodiments to be described later so as to facilitate understanding of the present invention, and it is intended to limit the scope of the present invention in any way. It is not intended.

  The technical features described in the claims of the claims other than the features described above will be apparent from the description of the embodiments to be described later and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the whole structure of the fuel-injection control system by embodiment. It is a schematic sectional drawing for demonstrating the structure of an injector. It is a flowchart which shows the coupling abnormality detection process performed in the control apparatus of a fuel injection control system. It is a timing chart which shows operation of each part at the time of two injections which go near each other combine.

  Hereinafter, an embodiment of a fuel injection control system according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of a fuel injection control system according to the present embodiment. FIG. 1 shows the configuration in the case where the fuel injection control system 50 according to the present embodiment is applied to a four-cylinder diesel engine. Further, the fuel injection control system 50 according to the present embodiment is a common rail fuel injection system, and directly applies high-pressure fuel (for example, light oil with an injection pressure of “1000 atm” or more) directly into the combustion chamber of each cylinder of a diesel engine. It is possible to inject.

  As shown in FIG. 1, the fuel injection control system 50 of the present embodiment adds the common rail 12 for holding (accumulating) the fuel injected and supplied to each cylinder of the diesel engine at high pressure, and adding the fuel drawn from the fuel tank 10. The fuel pump 11 pressure-feeds the common rail 12 via the fuel supply pipe, and a plurality of (four in this embodiment) injectors for injecting and supplying high pressure fuel in the common rail 12 into the combustion chamber of each cylinder of the diesel engine An electronic control unit (hereinafter referred to as an ECU) 30 for electronically controlling the fuel pump 11 and the plurality of injectors 20 is provided.

  The fuel pump 11 is connected to the fuel tank 10 via a pipe 10a provided with a fuel filter 10b. The fuel pump 11 has a high pressure pump 11a and a low pressure pump 11b which functions as a feed pump for the high pressure pump 11a. The low pressure pump 11 b pumps the fuel from the fuel tank 10, and pumps the pumped fuel to the high pressure pump 11 a. The high pressure pump 11a further pressurizes the fuel pressure-fed by the low pressure pump 11b and discharges it. The high-pressure pump 11a and the low-pressure pump 11b are both driven by a drive shaft 11d driven and rotated by a diesel engine.

  A suction control valve (SCV: Suction Control Valve) 11 c whose opening degree is controlled by the ECU 30 is provided on the fuel suction side of the fuel pump 11. The amount of fuel drawn into the fuel pump 11 is adjusted by the suction adjusting valve 11 c. As a result, the pressure feeding amount of the fuel from the low pressure pump 11b to the high pressure pump 11a and hence the fuel discharge amount of the fuel pump 11 are regulated. Therefore, the ECU 30 can control the pressure of the high pressure fuel stored in the common rail 12 to coincide with the target pressure through the opening control of the suction adjusting valve 11c.

  Among the two types of pumps constituting the fuel pump 11, the low pressure pump 11b can be configured as, for example, a trochoid feed pump. On the other hand, the high-pressure pump 11a is, for example, a plunger pump, and reciprocates the plunger in the axial direction by an eccentric cam (not shown) to pressurize and feed the fuel introduced into the pressure chamber. As a result, the fuel pressure in the common rail 12 is gradually increased each time the fuel is delivered from the high pressure pump 11a.

  The common rail 12 stores fuel under high pressure through high-pressure pipes 14 provided for each cylinder, and injectors 20 (# 1) to 20 (#) for the first cylinder (# 1) to the fourth cylinder (# 4). Supply to 4). Between the common rail 12 and each high pressure pipe 14, an orifice 12a is provided, which attenuates pressure pulsation of the fuel propagating from the common rail 12 to the high pressure pipe 14, respectively. Further, the common rail 12 is provided with a fuel pressure sensor (not shown) for measuring the fuel pressure accumulated in the common rail 12.

  Each injector 20 is attached to the cylinder head of each cylinder of a diesel engine. Each injector 20 is an electromagnetic fuel injection valve provided with a solenoid valve that injects high pressure fuel into the combustion chamber of each cylinder according to a drive signal (injection command pulse signal) from the ECU 30. The fuel injection from these injectors 20 is achieved, for example, by injecting and supplying high pressure fuel accumulated in the common rail 12 while the solenoid valve is open. In this case, as the valve opening time of the solenoid valve of the injector 20 is longer, the amount of fuel injected is larger, and as the valve opening time of the solenoid valve is shorter, the amount of fuel injected is smaller.

  Each injector 20 is provided with a fuel pressure sensor 20 a on the fuel inlet side connected to the high pressure pipe 14. In addition, each injector 20 has a fuel outlet 21 which is connected to a pipe 18 connected to the fuel tank 10. An example of the structure of these injectors 20 is demonstrated based on FIG. The four injectors 20 all have the same structure.

  As shown in FIG. 2, a needle housing portion is provided in a body housing 20 e of the injector 20, and an axially displaceable needle valve 20 c is housed in the needle housing portion. The needle accommodating portion mainly includes a tip on the injection hole side, a rear end on the solenoid valve side, and an intermediate portion formed between the tip and the rear end.

  The high pressure fuel from the common rail 12 is supplied to the tip end portion of the needle accommodating portion via the internal fuel passage 25 formed in the body housing 20 e. In addition, high pressure fuel is also supplied to the hydraulic pressure chamber Cd formed at the rear end of the needle housing through an orifice. A return spring 20d is disposed at an intermediate portion of the needle accommodating portion. The return spring 20d biases the needle valve 20c in the valve closing direction.

  The needle valve 20c is seated on the seat portion formed in the tip end portion of the needle storage portion, thereby blocking the flow path connected to the injection hole 20f (needle valve closed state). On the other hand, the needle valve 20c separates the seat from the seat to connect the tip end of the needle housing and the injection hole 20f, and injects high pressure fuel from the injection hole 20f (needle valve open state).

  A leak hole 24 connected to the fuel discharge port 21 is formed in the hydraulic pressure chamber Cd. The leak hole 24 is opened and closed by a valve body 23 of a solenoid valve. That is, when the solenoid coil 20b of the solenoid valve is energized and the valve body 23 is attracted in the direction of the solenoid coil 20b, the valve body 23 opens the leak hole 24. When the electromagnetic coil 20b is not energized, the valve body 23 closes the leak hole 24 by the biasing force of the spring.

  When the valve body 23 opens the leak hole 24 by energizing the electromagnetic coil 20b of the solenoid valve, the high pressure fuel in the hydraulic chamber Cd is returned from the leak hole 24 to the fuel tank 10 through the fuel discharge port 21. As a result, the fuel pressure in the hydraulic pressure chamber Cd is reduced. Since the back pressure of the needle valve 20c decreases with the decrease of the fuel pressure in the hydraulic chamber Cd, the needle valve 20c moves in the direction of the solenoid valve, and the needle is opened.

  When energization of the electromagnetic coil 20b of the solenoid valve is stopped, the valve body 23 of the solenoid valve returns to the state of closing the leak hole 24. As a result, the high pressure fuel from the common rail 12 flows into the hydraulic chamber Cd, so the pressure in the hydraulic chamber Cd gradually rises. Due to the pressure increase in the hydraulic pressure chamber Cd, the force that biases the needle valve 20c in the valve closing direction by the back pressure from the hydraulic pressure chamber Cd also becomes strong. Therefore, the needle valve 20c is moved in the direction of the injection hole 20f in conjunction with the biasing force of the return spring 20d, and the needle is closed.

  The fuel pressure sensor 20 a provided in the injector 20 outputs a detected pressure signal according to the fuel pressure introduced into the injector 20. As for the installation position of the fuel pressure sensor 20a, for example, as shown in FIG. 2, the fuel pressure sensor is connected to the fuel inlet 22 formed in the body housing 20e and the high pressure pipe 14 by the jig 20j. 20a can be provided. However, the fuel pressure sensor 20a may be provided inside the injector 20, or may be provided at an arbitrary position of the high pressure pipe 14 closer to the injector 20 than the orifice 12a. With the high pressure pipe 14 closer to the injector 20 than the orifice 12a, it is possible to detect with high accuracy the fluctuation of the fuel pressure accompanying the injection operation of the injector 20.

  The fuel injection control system 50 shown in FIG. 1 includes, in addition to the fuel pressure sensor 20a, a crank angle sensor 43 for detecting a crank position and a rotational speed of a diesel engine, an accelerator sensor 44 for detecting an opening degree of an accelerator pedal, A cylinder discrimination sensor for discriminating a cylinder to be injected, a fuel pressure sensor for detecting the fuel pressure in the common rail 12, a vehicle speed sensor, a cooling water temperature sensor, and various sensors for detecting the operating state of the diesel engine There is.

  The crank angle sensor 43 includes a signal rotor (rotating body that rotates one revolution while the crankshaft rotates one rotation) 41 that rotates corresponding to the crankshaft of the diesel engine and a protrusion formed on the outer periphery of the signal rotor 41. And an electromagnetic pickup 42 for outputting a signal according to the approach and the separation. A large number (e.g., 36 teeth) of teeth (protrusions) for detecting a crank angle are formed on the outer periphery of the signal rotor 41. Due to the approach and separation of the teeth, the electromagnetic pickup 42 outputs a plurality of crank angle signals while the signal rotor 41 makes one rotation (one rotation of the crankshaft). The specific crank angle signal corresponds to the position of the top dead center (TDC) of the # 1 to # 4 cylinders. Then, the ECU 30 detects the engine rotational speed by measuring the interval time of the crank angle signal.

  Similarly to the crank angle sensor 43, the cylinder discrimination sensor is also formed on the outer periphery of the signal rotor, which rotates in correspondence with the camshaft of a diesel engine (a rotating body that rotates one revolution while the crankshaft rotates twice). And an electromagnetic pickup for outputting a signal according to the approach and separation of the projection. On the outer periphery of the signal rotor, cylinder teeth (projections) corresponding to each cylinder are formed. The electromagnetic pickup outputs a cylinder discrimination signal by the approach and separation of these cylinder teeth.

  The detection results of the various sensors described above are taken into the ECU 30 of the fuel injection control system 50. The ECU 30 includes a CPU for performing arithmetic processing, a RAM for temporarily storing data necessary for the CPU to perform arithmetic processing, a microcomputer including a ROM for storing various programs and data, and the like, each component in the ECU 30 A power supply circuit for supplying an operating voltage, an injector drive circuit for outputting an injection command pulse signal to the injector 20, and the like are provided. Furthermore, the ECU 30 includes an A / D converter, and the detected pressure signal from the fuel pressure sensor 20a and sensor signals from various other sensors are A / D converted by the A / D converter and then incorporated in the ECU 30. Is input to the microcomputer.

  The ECU 30 executes processing for operating various actuators of the diesel engine, such as the fuel pump 11 and the injector 20, based on detection results of various sensors. For example, the ECU 30 calculates a target fuel injection pressure from engine operation information such as an engine rotational speed, an accelerator opening degree, and an engine load. Then, the ECU 30 controls the driving state of the fuel pump 11 so that the fuel pressure in the common rail 12 becomes the target fuel injection pressure.

  Further, the ECU 30 controls the fuel injection amount injected from the injector 20 of each cylinder. Here, in the fuel injection control system 50 of the present embodiment, the ECU 30 can drive the injectors 20 of each cylinder so as to inject fuel multiple times during one combustion cycle consisting of suction, compression, explosion, and exhaust. It is configured (multistage injection). For example, the multistage injection includes a main injection in which the injection amount of fuel is set to the largest, and a pilot injection in which a small amount of fuel is injected before the main injection. The main injection and the pilot injection may be performed multiple times as split injections, respectively. Furthermore, after injection may be performed after the main injection to inject a small amount of fuel. The pilot combustion related to the pilot injection can reduce NOx, and the after combustion related to after injection can reduce the amount of black smoke emission.

  In order to execute such multistage injection, the ECU 30 calculates various target values related to the injection state control amount of the fuel based on the engine speed, the engine load, and the like. The injection state control amount includes the injection timing, the injection amount, the number of multistage injections, and the interval. For example, the target value of the injection timing can be calculated as follows. First, the relationship between the engine speed and the engine load, and the optimum value of the injection timing is acquired through a test, and the acquired optimum value is mapped to be associated with the engine speed and the engine load. Then, the map (injection timing map) is stored in the memory of the ECU 30. The ECU 30 acquires the optimal value of the injection timing corresponding to the current engine speed and the engine load from the injection timing map, and sets it as the target injection timing. Similarly, the ECU 30 sets the injection amount, the number of multistage injections, and the target value of the interval, and generates an injection command pulse signal based on those target values.

  Thus, when performing multistage injection, the interval between the injections in multistage injection is also controlled. Therefore, when the interval between injections is set relatively narrow, there is a possibility that two injections to be separately injected may be combined. That is, after the injection command pulse signal for the first injection is finished, the injection command pulse for the next injection is output while the needle valve 20c of the injector 20 is not completely closed. When 20c starts the valve opening operation, the previous injection and the subsequent injection may be combined. When the first injection and the second injection are combined, the effects of the respective injections are not sufficiently exhibited, which may affect the operating state of the diesel engine, the exhaust gas purification performance, and the like.

  Therefore, in the fuel injection control system according to the present embodiment, when an abnormality occurs in which two consecutive injections precede or follow each other when multistage injection is performed, the coupling abnormality is accurately detected. I was able to Hereinafter, the process executed by the ECU 30 to detect the coupling abnormality will be described in detail based on the flowchart of FIG. The process shown in the flowchart of FIG. 3 is repeatedly executed in a predetermined cycle.

  First, in step S100, the fuel pressure introduced into the injector 20 is detected based on the detected pressure signal output from the fuel pressure sensor 20a. In the following step S110, the differential value of the fuel pressure detected in step S100 is calculated.

  Then, in step S120, it is determined whether it is before the start of multistage injection. As described above, since the ECU 30 calculates the target value of each injection timing in the multistage injection, it determines whether or not it is before the start of the multistage injection based on the target value of the injection timing of the first injection. be able to. If it is determined that the multistage injection has not been started, the process proceeds to step S130. On the other hand, if it is determined that the multistage injection has been started, the process proceeds to step S140.

  In step S130, a determination value is set based on the fuel pressure detected in the process of step S100. When the fuel pressure introduced into the injector 20 is changed by multistage injection, this judgment value indicates that the change is a combination of two injections, or the two injections are separated and the injection is separated It is used to determine whether it is an indication of what has been done. The determination value is set to, for example, a constant value corresponding to the fuel pressure before multistage injection, and is used continuously during the corresponding multistage injection.

  Here, a method of determining the coupling abnormality of the two injections and the normal injection using the determination value in the present embodiment will be described based on the waveform diagram of FIG. 4. Note that, in FIG. 4, a change in fuel pressure and the like when a coupling abnormality occurs is indicated by a solid line, and a state of a change in the case of normal injection is indicated by a dotted line.

  In the multistage injection, when the previous injection and the subsequent injection that are performed one after another are separated, the injector 20 is once completely closed after the previous injection. That is, as shown by a dotted line in FIG. 4, the lift position of the needle valve 20c reaches the valve closed position and is held. As a result, the injection rate of the injector 20 becomes zero, and the flow of fuel injected from the injector 20 is shut off. As a result, the pressure of the fuel introduced into the injector 20 sharply decreases and largely rises due to the so-called water hammer phenomenon. Due to the increase in fuel pressure, the fuel pressure after the previous injection exceeds the fuel pressure before injection.

  On the other hand, in the multistage injection, when the preceding injection and the subsequent injection performed one after another are combined, the injector 20 does not completely close the valve after the previous fuel injection and opens for the later fuel injection. It will start the valve operation. That is, as indicated by the solid line in FIG. 4, the lift position of the needle valve 20c starts to move in the valve opening direction for the subsequent injection without reaching the valve closing position. In this case, since the injection rate of the injector 20 after the previous injection does not become zero, the first injection and the subsequent injection are combined.

  As described above, if the needle valve 20c moves in the valve opening direction before reaching the valve closing position, the resistance to the flow of fuel injected from the injector 20 only increases, and it is not completely shut off. The increase in fuel pressure introduced is also reduced. In other words, even if the fuel pressure rises, as shown by the solid line in FIG. 4, the fuel pressure starts to decrease due to the later injection without reaching the fuel pressure before the injection.

  Therefore, based on whether or not the fuel pressure shows a change that reaches the pre-injection pressure as the judgment value, whether or not the coupling abnormality of two fuel injections performed one after another occurs or is separated and normal It can be accurately determined whether the fuel has been injected.

  As described above, the determination value may be a value other than the constant value corresponding to the fuel pressure before the start of multistage injection. For example, the determination value may be a fixed value obtained by discounting the fuel pressure before the start of multistage injection at a predetermined rate. Alternatively, since the fuel pressure in the injector 20 is decreased each time the injection is performed, it may be set as a fluctuation value which decreases each time the injection is performed in anticipation of the decrease.

  In step S140 executed after step S120 or step S130, it is determined whether the differential value of the fuel pressure calculated in step S110 crosses zero and changes from plus to minus. As shown in FIG. 4, when the fuel pressure rises and reaches its peak, the derivative value of the fuel pressure changes so as to zero-cross from plus to minus. In other words, the value of the fuel pressure when the derivative value of the fuel pressure changes from positive to negative indicates the peak of the rising fuel pressure. Therefore, if it is determined in step S140 that the differential value of the fuel pressure has changed from positive to negative, the process proceeds to step S150, and the fuel pressure detected at that time is compared with the determination value as the peak fuel pressure, Determine their magnitude relationship.

  The fuel pressure may not change smoothly as in the example shown in FIG. In such a case, the derivative value of the fuel pressure may also change from positive to negative multiple times. Therefore, when the ECU 30 detects that the derivative value of the fuel pressure changes from positive to negative multiple times within a predetermined time, the maximum value among the fuel pressures corresponding to each is selected, and the selected maximum The value may be compared with the determination value.

  If it is determined in step S150 that the detected fuel pressure is less than the determination value, the process proceeds to step S160, and it is determined that two consecutive injections are coupled. Thereby, in the multistage injection, when an abnormality occurs in which any two adjacent injections are coupled, it is possible to accurately detect the coupling abnormality. In the subsequent step S170, in the subsequent multistage injection, a correction instruction is issued to make the interval between the injections wider than the interval between the two corresponding injections. For example, in step S170, a correction amount for making the interval between two coupled successive injections coincide with the target multistage injection interval is calculated, and the interval between injections is corrected by the correction amount. Make correction instructions. As a result, even if the needle valve in the injector 20 is difficult to close due to the aged deterioration of the injector 20, the machine difference variation, the property of the fuel, etc., the two injections before and after are coupled. It is possible to suppress the occurrence of an abnormality.

  On the other hand, if it is determined in step S150 that the detected fuel pressure is equal to or higher than the determination value, it is determined in step S180 that the two injections are not coupled, and the process shown in the flowchart of FIG.

  Although the preferred embodiments of the present invention have been described above, the present invention can be variously modified and practiced without departing from the spirit of the present invention without being limited to the above-described embodiments. .

  For example, as described above, the fuel pressure of the common rail 12 is increased by the pumping of the fuel by the fuel pump 11. The increase in fuel pressure in the common rail 12 also affects the pressure of fuel introduced into each injector 20. Therefore, in the flowchart of FIG. 3, a correction pressure is calculated to calculate a correction pressure obtained by subtracting a fuel pressure increase caused by fuel delivery by the fuel pump 11 from the fuel pressure detected by the fuel pressure sensor 20a when performing multistage injection. A step may be provided. As a result, it is possible to calculate the change in the net fuel pressure due to each fuel injection in the multistage injection in the injector 20 to be processed and compare it with the determination value. The amount of increase in fuel pressure caused by pumping of the fuel by the fuel pump 11 can be calculated from the fuel pressure detected by the fuel pressure sensor 20a provided in the other injectors 20 that are not targets of multistage injection.

  Further, the correction target of the fuel pressure increase due to the pressure feeding of the fuel by the fuel pump 11 may be a determination value instead of the fuel pressure detected by the fuel pressure sensor 20a. In this case, if a correction determination value calculation step is performed to calculate a correction determination value obtained by adding the increase in fuel pressure caused by the fuel pump 11 to the set determination value in the flowchart of FIG. good. Even in this case, the same effect as described above can be obtained.

10: Fuel tank 11: Fuel pump 12: Common rail 20: Injector 20a: Fuel pressure sensor 30: ECU
50: Fuel injection control system

Claims (10)

A fuel injection control system (50) capable of causing a plurality of fuel injections to be performed by an injector (20) during one combustion cycle of an internal combustion engine, comprising:
A fuel pressure sensor (20a) for detecting the pressure of fuel introduced into the injector;
A determination value setting unit (S130) configured to set a determination value based on the fuel pressure detected by the fuel pressure sensor before the plurality of fuel injections when the injector performs the fuel injections a plurality of times;
With regard to any two fuel injections injected in succession in the plurality of fuel injections, the fuel pressure decreased by the previous fuel injection is decreased by the subsequent fuel injection without rising to the determination value An abnormality detection unit (S100, which detects that an abnormality has occurred in which two fuel injections injected before and after the fuel pressure are combined, when it is determined based on the fuel pressure detected by the fuel pressure sensor S110, S140, S150, S160).   When it is detected by the abnormality detection unit that an abnormality has occurred, in the next plurality of fuel injections, the injection is performed more than the interval between two fuel injections that were injected immediately before and after the abnormality was detected. The fuel injection control system according to claim 1, further comprising a correction unit (S170) instructing correction to widen the interval.   The fuel injection control system according to claim 2, wherein the correction unit instructs correction so that an interval of fuel injection injected before and after the next plurality of fuel injections coincides with a target injection interval. .   The fuel injection control system according to any one of claims 1 to 3, wherein the judgment value setting unit uses a constant value for the plurality of fuel injections as the judgment value.   The fuel injection control system according to claim 4, wherein the constant value corresponds to a fuel pressure detected by the fuel pressure sensor before the plurality of fuel injections.   The fuel injection control system according to any one of claims 1 to 3, wherein the judgment value setting unit uses, as the judgment value, a fluctuation value that decreases as the number of injections increases with respect to the plurality of fuel injections. The abnormality detection unit
A detection unit (S100) that repeatedly detects the fuel pressure using the fuel pressure sensor while the plurality of fuel injections are performed;
A differential value calculation unit (S110) that differentiates the fuel pressure calculated by the detection unit to calculate a differential value of the fuel pressure;
When the differential value of the fuel pressure changes from positive to negative, the fuel pressure detected by the fuel pressure sensor is compared with the determination value, so that the fuel pressure decreased by the previous fuel injection is The fuel injection control system according to any one of claims 1 to 6, further comprising: a determination unit (S140, S150) that determines whether or not the determination value has risen before the decrease in fuel injection.   When the differential value of the fuel pressure changes from positive to negative a plurality of times within a predetermined time, the determination unit selects the maximum value among the fuel pressures corresponding to each, and selects the selected maximum value. The fuel injection control system according to claim 7, wherein the fuel injection control system is compared with the determination value. The fuel pressurized by the fuel pump (11) is introduced into the injector,
The fuel pressure detection apparatus further includes a correction pressure calculation unit that calculates a correction pressure obtained by subtracting a fuel pressure increase due to fuel delivery by the fuel pump from the fuel pressure detected by the detection unit.
The fuel injection control system according to claim 7 or 8, wherein the determination unit uses the correction pressure calculated by the correction pressure calculation unit as the fuel pressure to be compared with the determination value. Fuel pressurized by a fuel pump is introduced into the injector,
A correction determination value calculation unit configured to calculate a correction determination value obtained by adding a fuel pressure increase due to fuel delivery by the fuel pump to the determination value set by the determination value setting unit;
The fuel injection control system according to claim 7 or 8, wherein the determination unit uses the correction determination value calculated by the correction determination value calculation unit as the determination value to be compared with the fuel pressure.

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