JP4211610B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control device for an internal combustion engine.

  2. Description of the Related Art Conventionally, a pressure accumulation type fuel injection device that supplies high pressure fuel accumulated in a common rail as a pressure accumulation chamber from a injector to a diesel engine is known. In recent years, in this type of accumulator fuel injection system, so-called multi-injection, in which fuel is injected in multiple times during one combustion stroke, has been put into practical use due to the social demands for exhaust gas regulations and combustion noise reduction. Yes. A control device so-called ECU for driving and controlling the injector is composed of a heating element such as a power MOSFET as a switching element. The amount of heat generated by the heating element increases according to the number of injections per combustion stroke and the length of the injector drive time per injection, that is, the amount of injection, etc. If the temperature rises beyond the heat generation limit, the ECU malfunctions. There is a risk of failure.

Patent Document 1 discloses a technique for limiting the number of injections when it becomes impossible to maintain a predetermined temperature or less due to an increase in the amount of heat generated by the ECU or the like. As a temperature detection method for detecting the predetermined temperature, the temperature of the cooling medium (fuel) of the cooling mechanism that cools the ECU is detected.
JP-A-9-126044

  However, the conventional technology has a problem that exhaust gas, combustion noise, and the like deteriorate because all the multi-injections are limited to only the main injection.

  Also, the mounting position of the ECU is placed in a different mounting environment from that in the engine room or in the vehicle interior depending on the requirements of the vehicle. It was necessary to confirm by conducting an environmental test under different environmental conditions.

  The present invention has been made in consideration of such circumstances, and injects a plurality of times from one injector during one combustion stroke, and drives the injector with minimal influence on exhaust gas and combustion noise. It aims at preventing the temperature rise of the control apparatus to control.

  Another object is to inject a plurality of times from the injector during one combustion stroke, and to prevent an increase in the temperature of a control device that drives and controls the injector while minimizing the influence on exhaust gas and combustion noise. Another object of the present invention is to provide a fuel injection control device for an internal combustion engine that makes it easy to guarantee the operation of the control device and the injector.

According to a first aspect of the present invention, an injector for injecting fuel into the internal combustion engine and a control means for controlling the injector according to the operating state of the internal combustion engine are provided, and a plurality of injections are performed during one combustion stroke of the internal combustion engine. In the internal combustion engine fuel injection control apparatus, the control means outputs an injector drive circuit that outputs a drive signal for driving the injector to the injector, an ECU temperature detection means that detects or estimates the temperature of the injector drive circuit, When the temperature of the injector drive circuit detected or estimated by the ECU temperature detection means exceeds a predetermined temperature and the temperature rise within a predetermined period exceeds a predetermined value, Injection limiting means for limiting the injection of the injector in the specific injection of the multiple injections ,
The injection restricting means has a temperature rising determination means for determining whether or not the temperature of the injector drive circuit by the ECU temperature detecting means exceeds the predetermined temperature, and determines whether the temperature is rising. As an essential condition for restricting injection, the determination by means is an upward trend, and in accordance with the injection mode of multiple injections in one combustion stroke, reducing the injection amount in specific injection and changing the injection timing When at least one of the specific injections is corrected, and when the temperature is rising, the specific injection correction is maintained until the temperature drops below a predetermined temperature when the determination is made by the determination unit during temperature increase. It is characterized by.

  According to this, in the fuel injection control device for an internal combustion engine that performs injection a plurality of times during one combustion stroke of the internal combustion engine, the control means for controlling the injector according to the operating state of the internal combustion engine sends a drive signal to the injector. Since the injector drive circuit for outputting and the ECU temperature detecting means for detecting or estimating the temperature of the injector drive circuit are provided, the temperature of the injector drive circuit that rises according to the number of injections per combustion stroke, for example, control for controlling the injector It is possible to accurately detect or estimate the temperature of the ECU as a device.

  Further, when the ECU temperature detected or estimated by the ECU temperature detecting means exceeds a predetermined temperature and the increase in the ECU temperature within a predetermined period exceeds a predetermined value, multiple injections are performed during one combustion stroke. Because it includes an injection limiting means for limiting the injection of the injector in the specific injection of the exhaust gas by limiting only the injection in the specific injection without limiting all the multi-injection as in the prior art and only the main injection, It is possible to prevent the temperature of the ECU from rising by minimizing the influence on the combustion noise.

According to claim 2 of the present invention, an injector for injecting fuel into the internal combustion engine and a control means for controlling the injector in accordance with the operating state of the internal combustion engine are provided, and the internal combustion engine is controlled during one combustion stroke of the internal combustion engine. In a fuel injection control device for an internal combustion engine that performs main injection that forms main torque and multiple stages of injection other than main injection, the control means includes an injector drive circuit that outputs a drive signal for driving the injector to the injector; ECU temperature detection means for detecting or estimating the temperature of the injector drive circuit, and suppressing the amount of heat generated by the injector drive circuit according to the degree to which the temperature of the injector drive circuit detected or estimated by the ECU temperature detection means exceeds a predetermined temperature On the side, provided with injection limiting means for limiting the injection of a plurality of stages other than the main injection ,
The injection restricting means has a temperature rising determination means for determining whether or not the temperature of the injector drive circuit by the ECU temperature detecting means exceeds the predetermined temperature, and determines whether the temperature is rising. As an essential condition for limiting the injection, the determination by the means is an upward trend, and according to the injection mode of the multiple injections in one combustion stroke, the injection amount is determined in the specific injection of the multiple stages of injection other than the main injection. When at least one of the specific injection corrections of reducing the amount and changing the injection timing is performed, and the change from the rising tendency to the decreasing tendency is made by the determination during the temperature rising determination means, the predetermined temperature or less The correction of the specific injection is maintained until it becomes .

  According to this, in the fuel injection control device for an internal combustion engine that performs main injection that forms the main torque of the internal combustion engine during a single combustion stroke of the internal combustion engine and multiple stages of injection other than the main injection, The control means for controlling the injector accordingly has an injector drive circuit for outputting a drive signal to the injector and an ECU temperature detection means for detecting or estimating the temperature of the injector drive circuit, so that the temperature of the injector drive circuit is controlled. It is possible to accurately detect or estimate the temperature of the ECU as the control device.

  Further, an injection restricting means for restricting a plurality of stages of injection other than the main injection on the side of suppressing the heat generation amount of the injector drive circuit according to the degree to which the ECU temperature detected or estimated by the ECU temperature detecting means exceeds a predetermined temperature. Therefore, without restricting all the multi-injections and making only the main injections as in the past, for example, by restricting the specific injections in a plurality of stages other than the main injection according to the degree of exceeding a predetermined temperature Further, it is possible to prevent the temperature of the ECU from rising by minimizing the influence on exhaust gas and combustion noise.

  According to claim 3 of the present invention, it is preferable that the ECU temperature detection means includes a temperature sensor provided in the injector drive circuit, which directly or indirectly detects the temperature of the injector drive circuit.

  According to this, since the temperature sensor provided in the injector drive circuit is used as the ECU temperature detection method, for example, the temperature of the injector drive circuit that rises according to the number of injections per combustion stroke can be accurately determined. it can. For example, as an environmental condition for mounting an ECU as a control device, whether it is mounted in an engine room or mounted in a vehicle, the heat generation state of the injector drive circuit, which is the main cause of the temperature rise of the ECU, is used as a temperature sensor. Therefore, it is possible to accurately determine a change point (when the ECU temperature exceeds a predetermined temperature and a limiting condition where the temperature increase for a predetermined period exceeds a predetermined value is satisfied) for suppressing the temperature increase of the ECU. Is possible. Furthermore, since this change point can be detected with high accuracy, it is easy to guarantee the operation of the ECU regardless of the environmental conditions in the engine room or the vehicle compartment in which the ECU is mounted.

  According to claim 4 of the present invention, in the multi-injection in which the number of injections during one combustion stroke is N, the injection limiting means is the fifth injection in the injection order when N = 5, and the first when N = 4. , And when N = 3, there is provided an injection amount correction means for reducing the injection amount of either the first injection or the third injection.

  According to this, as a method of limiting the specific injection among the plural (N) injections in the injection limiting means, N = 5 is the fifth injection in the injection order, N = 4 is the first injection, and N = 3. Then, since the injection amount of either the first injection or the third injection is reduced by the injection amount correction means, it is possible to minimize the influence on the exhaust gas and the combustion noise and to prevent the ECU temperature from rising.

  According to claim 5 of the present invention, in the first injection and the third injection at N = 3, the injection restricting means can change the injection timing of each of the first injection and the third injection. Preferably means are provided.

  According to this, when the specific injection is the first injection and the third injection at N = 3 as the method of limiting the specific injection among the plural (N) injections in the injection limiting means, the respective injection timings Can be adjusted by the injection timing correction means to the optimal injection timing according to the driver's request or driving condition.

  According to claim 6 of the present invention, the number of times of injection during one combustion stroke is N, and the injection limiting means is the fifth injection in the injection order when N = 5, and when N = 4 In the first injection and N = 3, there is provided drive signal correcting means for correcting a drive signal in either the first injection or the third injection.

  According to this, in the multi-injection in which the number of injections during one combustion stroke is N, the injection limiting means is the fifth injection in the injection order when N = 5, the first injection when N = 4, and N When = 3, the drive signal in either the first injection or the third injection is corrected by the drive signal correcting means, so that the amount of heat generated by the injector drive circuit that outputs the drive signal can be suppressed.

  According to claim 7 of the present invention, the drive signal correcting means reduces the initial maximum current value of the energization current supplied to the injector by correcting the drive signal.

  According to this, as a method of correcting the drive signal to the side that suppresses the heat generation amount of the injector drive circuit, the initial maximum current value is generated because the correction is made so that the initial maximum current value of the energization current supplied to the injector is decreased. Therefore, heat generation in a heat generating circuit such as a so-called charge circuit can be suppressed.

  According to an eighth aspect of the present invention, the injector drive circuit includes a charge circuit that increases and stores a power supply voltage from the on-vehicle power supply, a discharge control switching element, and a discharge control circuit that intermittently controls the discharge control switching element. It is suitable for application to a fuel injection control device for an internal combustion engine. For example, even if the device has a charge circuit as a heat generating circuit or a discharge control switching element such as a MOSFET as a heat generating element, it is possible to prevent the ECU temperature from increasing due to heat generated by the heat generating circuit or the heat generating element. it can.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments in which a fuel injection control device for an internal combustion engine according to the present invention is applied to an accumulator fuel injection control device will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a configuration diagram showing the overall configuration of the fuel injection system of the present embodiment. FIG. 2 is a schematic diagram illustrating a schematic configuration of the ECU in FIG. 1. FIG. 3 is a flowchart showing a control process related to injection control of the injector in the ECU shown in FIG. FIG. 4 is a graph illustrating an example of the relationship among the engine speed, the injection amount, and the number of injections per combustion stroke. FIG. 5 is a timing chart showing an injection state of the fuel injection system.

  As shown in FIG. 1, an accumulator fuel injection control device includes an operation state or an operation condition of a multi-cylinder (for example, four-cylinder) diesel engine (hereinafter referred to as an engine) 1 mounted on a vehicle such as an automobile. The driving state of the vehicle and the operation amount (will) of the driver are detected by various sensors, and are transmitted to an engine control unit (engine control unit) (hereinafter referred to as ECU) 100, which is optimized by sensor signals from the various sensors. Multiple target injection amounts (command injection amounts), target injection timings (command injection timings), target injection periods (command injection periods) and target injection pressures (command injection pressures), which are controlled respectively. 4) injectors (electromagnetic fuel injection valves) 2, high pressure supply pump (fuel supply pump) (hereinafter referred to as supply pump) 3, etc. It is configured.

  The engine 1 is a four-cycle four-cylinder engine that includes a cylinder, a cylinder head, an oil pan, and the like. The intake port of each cylinder of the engine 1 is opened and closed by an intake valve (intake valve) 11, and the exhaust port is opened and closed by an exhaust valve (exhaust valve) 12. In each cylinder, a piston 14 connected to the crankshaft 13 via a connecting rod is slidably disposed.

  The injector 2 is attached to the cylinder head of the engine 1 corresponding to each cylinder. These injectors 2 include a fuel injection nozzle in which a nozzle needle for opening and closing the injection hole is slidably accommodated in a nozzle body in which the injection hole is formed, and an electromagnetic valve (needle drive means, Solenoid actuator) and needle biasing means such as a spring for biasing the nozzle needle in the valve closing direction.

  The fuel injection from the injector 2 to the engine 1 energizes and energizes a solenoid valve (not shown) that controls the fuel pressure in the back pressure control chamber (pressure control chamber) of the command piston connected to the nozzle needle. Electronically controlled by stopping (ON / OFF). While the solenoid valve of the injector 2 of each cylinder is open, the high-pressure fuel accumulated in the common rail 17 as the pressure accumulation chamber is injected into the combustion chamber of each cylinder of the engine 1. In addition, the fuel leaked from the internal leak of the injector 2 or the fuel discharged from the pressure control chamber (the fuel used to open the injector 2) is returned to the fuel tank 15 via the return pipe 33.

  The supply pump 3 is a high-pressure supply pump that pressurizes sucked fuel and pumps high-pressure fuel from the discharge port to the common rail 17, and includes a feed pump (low-pressure supply pump) 6 that pumps fuel from the fuel tank 15. The fuel path from the feed pump 6 to the pressurization chamber of the supply pump 3 is adjusted by adjusting the degree of opening of the fuel path (valve opening or opening area) so that the amount of fuel discharged from the supply pump 3 to the common rail 17 ( A suction metering valve (linear solenoid actuator) 7 is attached as an electromagnetic actuator for changing the pump discharge amount and the pump pumping amount.

  The intake metering valve 7 is electronically controlled by a pump drive signal from the ECU 100 via a pump drive circuit 122 (see FIG. 2), so that the fuel sucked into the pressurized chamber of the supply pump 3 from the feed pump 6 is controlled. A solenoid valve for adjusting the intake amount, which adjusts the intake amount, and changes the fuel injection pressure (hereinafter referred to as common rail pressure) supplied from each injector 2 into each cylinder of the engine 1. The supply pump 3 sucks fuel from the fuel tank 15 and pressurizes it, and pumps the fuel discharge amount commanded by the ECU 100 to the common rail 17. The common rail pressure in the common rail 17 is measured by a fuel pressure sensor 18 as a fuel pressure detecting means, and a pump drive command value (pump drive current value) and an injection amount command value (pulsed injector drive current, injector injection command pulse). ) Is calculated by the ECU 100.

  The common rail 17 continuously supplies high-pressure fuel corresponding to the fuel injection pressure, and high-pressure fuel stored in the common rail 17 is supplied from the support pump 3 via a supply pipe (hereinafter referred to as high-pressure pipe) 20. The A return pipe 21 for returning fuel from the common rail 17 to the fuel tank 15 is provided. The common rail 17 is provided with a normally closed pressure reducing valve 22 that can adjust the degree of opening of the return pipe 21. The pressure reducing valve 22 is electronically controlled by a pressure reducing valve driving current value applied from the ECU 100 via the pressure reducing valve driving circuit, so that the common rail pressure in the common rail 17 is quickly reduced from a high pressure to a low pressure when the engine is decelerated or the engine is stopped, for example. It has a function to reduce pressure. Instead of the pressure reducing valve 22, a pressure limiter for releasing the fuel pressure in the common rail 17 between the common rail 17 and the return pipe 21 so that the common rail pressure in the common rail 17 does not exceed the limit set pressure. May be attached.

  Here, the injector 2, the supply pump 3 and the common rail 17 constitute fuel injection means for supplying fuel to the engine 1.

  The ECU 100 includes a CPU that performs control processing, arithmetic processing, a storage device (memory such as ROM and RAM) that stores various programs and data, an input circuit, an output circuit, a power supply circuit, an injector drive circuit, a pump drive circuit, and the like. A microcomputer having a known structure configured to include functions is provided. As shown in FIG. 2, the ECU 100 includes a control unit 110, a fuel injection system drive circuit 120 (specifically, an ejector drive circuit 121 and a pump drive circuit 122), an engine control actuator circuit 130, and a sensor receiving circuit 140. With. The control unit 110 is an essential part of the control that the CPU and the storage device have. The CPU injects fuel from the injector 2 in accordance with the program written in the ROM and the operating state of the internal combustion engine or the like read into the RAM. Various calculation processes such as calculation of the amount, injection timing, etc., and calculation of the amount of high-pressure fuel supplied from the supply pump 3 to the common rail 17 are performed. The fuel injection system drive circuit 120 includes an injector drive circuit 121 that supplies a drive signal for opening the solenoid valve of the injector 2 in accordance with a command value from the control unit 110, and an intake control in accordance with the command value from the control unit 110. The quantity valve 7 is provided with a pump drive circuit 122 that provides a drive signal for closing the valve. The engine control actuator circuit 130 provides drive signals to actuators such as the actuator 40 of the throttle valve 39 and the EGR valve 42 in accordance with the command value of the control unit. The sensor receiving circuit 140 is a circuit that processes output signals of various sensors connected via a connector (not shown), such as accelerator, rotational speed, water temperature, intake air temperature, atmospheric pressure, intake air pressure, fuel temperature, and the like. Sensing.

  The ECU 100 detects the detection signal (voltage signal) output from the fuel pressure sensor 18, the detection signal output from the fuel temperature sensor 34, and sensor signals from other various sensors by using an A / D converter. After the conversion, it is configured to be input to a microcomputer built in the ECU 100. Further, when the engine key is set to the IG position and an ignition switch (not shown) is turned on (ON), the ECU 100 controls, for example, the solenoid valve of the injector 2 and the suction metering of the supply pump 3 based on the control program stored in the memory. The actuator of each control component such as the valve 7, the actuator 40 that drives the throttle valve 39, and the EGR valve 42 that adjusts the exhaust gas recirculation amount (EGR amount) is electronically controlled.

  The ECU 100 receives the crankshaft rotation pulse and the camshaft rotation pulse from the crank angle sensor 4 attached to the crankshaft (crankshaft) 13 and the cam angle sensor 5 attached to the camshaft (camshaft) 23. The actual fuel pressure in the common rail 17 (actual common rail pressure) is held at the command injection pressure by determining the injection timing of the injector 2 and the pumping period of the supply pump 3 for each cylinder based on the signal. The crank angle sensor 4 includes a magnetic timing rotor (signal rotor) 24 fixed to the crankshaft 13 of the engine 1, an electromagnetic pickup coil disposed so as to face the peripheral surface of the timing rotor 24, and a magnetic flux. It is an electromagnetic rotation sensor composed of a permanent magnet (magnet) to be generated, and detects the rotation angle of the crankshaft 13. The ECU 100 detects the engine rotation speed (NE) by measuring the interval time of the crank angle signal (NE pulse signal). A plurality of convex teeth are formed on the timing rotor 24 at predetermined angles (for example, 10 °). When the timing rotor 24 rotates, the convex teeth approach and move away from the electromagnetic pickup coil, so that a crank angle signal (NE pulse signal) is output from the electromagnetic pickup coil by electromagnetic induction. The cam angle sensor 5 includes a magnetic timing rotor (signal rotor) 27 fixed to the cam shaft 23 of the engine 1, an electromagnetic pickup coil disposed so as to face the peripheral surface of the timing rotor 27, and An electromagnetic rotation sensor composed of a permanent magnet (magnet) or the like that generates magnetic flux, and detects the rotation angle of the cam shaft 23. In the timing rotor 27, a plurality of convex teeth are arranged for each predetermined angle.

  Further, the ECU 100 inputs sensor signals from an accelerator opening sensor 30 that measures the amount of depression of the accelerator pedal (accelerator operation amount, accelerator opening), a cooling water temperature sensor 31 that detects the cooling water temperature of the engine 1, and the like. It is configured. Then, the ECU 100 calculates an optimal command injection pressure (= target fuel pressure: PFIN) according to the operating conditions of the engine 1 and discharges the intake metering valve 7 of the supply pump 3 via the pump drive circuit 122. It has quantity control means. Specifically, the ECU 100 calculates the target fuel pressure (PFIN) according to the engine speed (NE) and the command injection amount (QFIN), and in order to achieve the target fuel pressure (PFIN), The pump drive signal (pump drive current value) to the suction metering valve 7 of the supply pump 3 is adjusted to control the pumping amount (pump discharge amount) of fuel discharged from the supply pump 3.

  The ECU 100 has a function of individually controlling the fuel injection amount injected from the injector 2 of each cylinder. Specifically, ECU 100 includes basic injection amount determination means, command injection amount determination means, injection timing determination means, injection period determination means, and injector drive means. The basic injection amount determination means has a function of calculating an optimum basic injection amount (Q) based on the engine speed (NE), the accelerator opening (ACCP), and a characteristic map created by measurement in advance through experiments or the like. The command injection amount determination means takes into account the cooling water temperature (THW) detected by the cooling water temperature sensor 31 or the fuel leak temperature (fuel temperature: THF) detected by the fuel temperature sensor 34 in the basic injection amount (Q). It has a function of calculating the command injection amount (QFIN) in consideration of the injection amount correction amount. The injection timing determining means has a function of calculating a command injection timing (TFIN) from a command injection amount (QFIN), an engine rotation speed (NE), and a characteristic map created by measurement in advance through experiments or the like. The injection period determining means calculates the common pulse pressure (NPC), the command injection amount (QFIN), and the energization pulse time (injection command pulse time: TQ) to the injector 2 from the characteristic map created by measurement in advance through experiments or the like. Have The injector drive means applies a pulsed injector drive current (injector injection command pulse) to the solenoid valve of the injector 2 of each cylinder until the injection command pulse time (TQ) elapses from the command injection timing (TFIN). It has the function to do.

Here, the accumulator type fuel injection control device is in one cycle of the combustion cycle of the engine 1 (intake stroke-compression stroke-expansion stroke (explosion stroke) -exhaust stroke) for each injector 2 of each cylinder of the engine 1 (hereinafter referred to as the following). Multi-stage injection (multi-injection), in which fuel is injected in a plurality of times within one injection stroke while the crankshaft 13 of the engine 1 rotates twice (720 ° CA). It is configured to be possible. Here, for example, what is injected twice during one combustion stroke is called two-stage injection, and what is injected three times, four times, and five times below are respectively three-stage injection, four-stage injection, and five-stage injection. Call it. Incidentally, details, in addition to the normal injection mode of only the main injection Q _M into a time of injection stroke, the pilot injection mode for performing one minute injection (pilot injection) Q _P before the main injection Q _M, the main multiple multi-injection mode for performing a plurality of minute injection after the multi-injection mode or the main injection Q _M for performing a minute injection before and after the injection Q _M (after injection form) is configured to be implemented. The main injection Q _M (C injection in FIG. 5) is mainly injection that forms the torque of the engine 1, and any other injection (in FIG. 5) injected during one combustion stroke in pilot injection or multi-injection. , A, B, D and E injections).

  Therefore, the ECU 100 is configured to determine the injection mode according to the operating state of the engine 1. More specifically, an injection mode determining means for determining an optimal injection mode based on an engine speed (NE), an accelerator opening (ACCP), and a characteristic map (not shown) created by measurement in advance through experiments or the like is provided.

  In the following description of multi-stage injection, the injection mode is described as a 5-stage injection mode (see FIG. 5). According to the order of injection during one combustion stroke, they are called A injection, B injection, C injection, D injection, and E injection as shown in FIG.

  The ECU 100 includes multi-stage injection calculation means for calculating the pilot injection amount and the main injection amount according to the operating state of the engine 1 when implementing the pilot injection mode. In detail, when implementing the pilot injection mode, the ECU 100 performs pilot injection from the engine rotation speed (NE) and the target injection amount QFIN) and a characteristic map (not shown) created by measurement in advance through experiments or the like. Means is provided for obtaining the main injection amount QM by obtaining the amount QP and subtracting the pilot injection amount QP from the target injection amount QFIN).

Moreover, ECU 100 is carrying out the multi-injection (at least 3 times or more injection) form, depending on the operating condition of the engine 1, as later injection to subsequent injection and pilot injection Q _P as before injection for injecting previously It comprises interval calculating means for calculating the distance (interval) INT of the fuel injection between the main injection Q _M. In detail, when implementing the pilot injection mode, the ECU 100 performs pilot injection from the engine rotation speed (NE) and the target injection amount QFIN) and a characteristic map (not shown) created by measurement in advance through experiments or the like. It means for determining Q _P and injection interval INT between the main injection Q _M, in the practice of multi-injection mode, characteristics created by measuring by experiment such as the engine rotational speed (NE) and the target injection amount QFIN) and map means for determining the injection interval of the pilot injection Q _P is injected a plurality of times from a (not shown), in carrying out after-injection mode, the engine rotational speed (NE) and the target injection amount QFIN) in advance experimentally or the like Means for determining an injection interval of after-injection multiple times from a characteristic map (not shown) created by measurement.

  For the purpose of improving the control accuracy of the fuel injection amount, the common rail pressure (NPC) in the common rail 17 detected by the fuel pressure sensor 18 is a target fuel pressure (PFIN) set according to the operating state of the engine 1. It is preferable to perform feedback control of the pump drive current value to the supply pump 3 so as to substantially match. The pump drive current value to the intake metering valve 7 is preferably controlled by duty (DUTY) control. For example, by adjusting the pump drive signal ON / OFF ratio (energization time ratio, duty ratio) per unit time according to the deviation (ΔP) between the common rail pressure (NPC) and the target fuel pressure (PFIN) High-precision digital control is possible by using duty control that changes the valve opening of the quantity 7.

  Further, exhaust gas combusted in each cylinder during operation of the engine 1 passes through an exhaust pipe 35 and becomes a driving source of a turbine of a variable nozzle turbo (VNT) 36, and then a catalyst (not shown), a muffler It is discharged through (not shown). The variable nozzle turbo 36 is controlled based on the signal from the intake pressure sensor 47 and the signal from the VNT drive amount sensor 37. The supercharged intake air is introduced into each cylinder through the intake pipe 38. A throttle valve (throttle valve) 39 is disposed in the middle of the intake pipe 38, and the opening degree of the throttle valve 39 is adjusted by an actuator 40 that is actuated by a signal from the ECU 100.

  The intake pipe 38 is connected to an exhaust gas recirculation pipe 41 that guides an exhaust gas recirculation gas (EGR gas) that is part of the exhaust gas flowing through the exhaust pipe 35 to the intake pipe 38. An exhaust gas recirculation device valve (EGR valve) 42 is installed at the connection port between the exhaust gas recirculation pipe 41 and the suction pipe 38, and EGR gas for cooling the EGR gas is provided in the middle of the exhaust gas recirculation pipe 41. A gas cooler 43 is provided.

  The EGR amount of the EGR gas is determined by the intake air amount sensor (air flow meter: AFM) 44 that detects the intake air amount as a voltage ratio by a potentiometer, the intake air temperature sensor 45 that detects the intake air temperature, and the lift amount of the EGR valve 42. The EGR valve opening degree sensor (a signal from the EGR valve lift sensor 46 is feedback-controlled so as to be able to maintain a predetermined value. Intake that is sucked into each cylinder of the engine 1 and passes through the intake pipe 38 The valve opening (lift amount) of the EGR valve 42 is linearly controlled so that the air has an exhaust gas recirculation amount (EGR amount) set for each operating state of the engine 1 in order to reduce emissions, and the exhaust pipe 35 and the exhaust gas are mixed.

  Here, the injector drive circuit 121 of the ECU 100 includes, as shown in FIG. 2, a charge circuit 121a for increasing and storing a battery voltage from an in-vehicle battery (not shown) as an in-vehicle power source, and a discharge control switching element. 121b and a discharge control circuit 121c for intermittently controlling the discharge control switching element 121b. These configurations constitute an initial maximum current generating circuit that instantaneously applies a high voltage and a large current to the solenoid valve of the injector 2. As shown in FIG. 7, this initial maximum current generation circuit is a drive signal (drive current) supplied to the injector 2 in response to each injection that is divided and injected during one combustion stroke. A current portion that forms the maximum current is formed. Specifically, when the discharge control circuit 121c is given a drive signal from the control unit 110, the discharge control switching element 121b is turned on, and then the drive current value of the injector 2 posted by a current detection unit (not shown) is predetermined. When the threshold value (for example, 17A: discharge stop threshold value) is reached, the discharge control switching element 121b is turned off. Also, as shown in FIG. 7, in order to switch the current value held in the constant current state in the drive current to two stages, the injector drive circuit 121 is configured to switch the current value of the drive current applied to the injector 2 (not shown) to two stages. A current control circuit is provided. The constant current control circuit includes a constant current control switching element (not shown) to which a battery voltage is supplied, and a two-stage current control circuit (not shown) for intermittently controlling the constant current control switching element. It is what is done.

  Here, the charge circuit 121a includes a coil (not shown), a charge control switching element that performs intermittent connection of the coil, and a charge capacitor that stores a voltage generated by the intermittent connection of the coil, and constitutes a heat generating circuit. The switching element for discharge control 121b and the switching element for constant current control that are intermittently controlled are made of semiconductor elements such as MOSFETs, and constitute heating elements.

  Therefore, a temperature sensor 60 is installed in the injector drive circuit 121 as temperature detection means (hereinafter referred to as ECU temperature detection means) for detecting the temperature of the heat generating circuit and the heat generating element. The temperature sensor 60 may be provided so as to be in direct contact with the injector drive circuit 121, or an indirect range in which the temperature of a specific circuit or element in the injector drive circuit 121 can be directly detected (in the injector drive circuit 121). It may be provided in the vicinity).

  As a method for detecting the temperature of the injector 2 (specifically, the solenoid valve to which the drive current is supplied), the ECU 100 detects, for example, the resistance value of the solenoid valve (solenoid), and estimates the injector heat generation amount or temperature. It has a temperature estimation means. The injector temperature estimation means is not limited to the one that detects the resistance value of the injector 2, but the temperature signal output from the fuel temperature sensor 34 (see FIG. 1) installed in the return pipe 33 that discharges the internal leak fuel of the injector 2. It may be detected.

  Note that there are cases where the ECU 100 is mounted in the engine room or in the cabin (cabin), depending on the requirements of the vehicle or the like, as mounting environment conditions for the ECU 100. When mounted in the engine room, the amount of heat generated by the injector factor that generates heat according to the injection mode (number of injections) of the injector 2 and the length of the drive time (injection amount), and the intake air that is led to the engine The heat generation factor of the ECU 100 is the intake air temperature and the vehicle speed that guides outside air as a cooling medium into the engine room according to the vehicle running state. When mounted in the vehicle compartment, the main factor is the amount of heat generated by the injector according to the injection mode of the injector 2 and the size of the injection amount.

  In the following embodiments, the ECU 100 will be described as being mounted in the engine room.

Next, the injection control method of the present embodiment having the above-described configuration will be described with reference to FIGS. In FIG. 4, the horizontal axis represents the engine rotation speed, the vertical axis represents the injection amount, and the injection characteristic corresponding to the torque performance of the engine 1. The solid line represents the maximum injection amount for each engine rotation speed. Indicates. In the high load region surrounded by FULL Q in FIG. 4, a three-stage injection mode is desired for the purpose of reducing smoke by premixed combustion due to a torque increase request and the like. In the MAX ENGINE SPEED CONTROL side according to the output performance is limited only to the main injection _{Q M} for the injection time reduction in a conventional manner. This injection mode, the method comprising injecting three times per combustion stroke, the main injection Q _M from becoming a high injection quantity (specifically, the injector drive circuit 121) ECU 100 increases the heating value of a concern. In addition, it is also an area | region severe to the heat_generation | fever of the solenoid of the injector 2. FIG.

  When the engine is used in this region and generates heat, for example, when the internal combustion engine is in an operating state (vehicle traveling state) in the region of low rotational speed and low injection amount indicated by the dashed line arrow in FIG. The injection mode in FIG. 5 performs five-stage injection, and a temperature increase due to heat generation of the ECU 100 is expected. Further, since the vehicle speed is low, the air flow rate of the outside air introduced into the engine room is reduced, so that the cooling effect by the outside air corresponding to the vehicle speed that suppresses the heat generation of the ECU 100 is reduced, and the heat generation of the ECU 100 is severe. It is expected that the engine 1 will be in an operating state.

As shown in FIG. 3, in S201 (S is a step), the ECU 100 receives a signal output from the ECU temperature sensor 60, and detects the temperature T _ECU of the _ECU 100 (specifically, the injector drive circuit 121). Specifically, the ECU 100 receives the output signal of the ECU temperature sensor 60 periodically (for example, 0.5 second interval: measurement interval), and continuously detects the temperature of the ECU 100 (hereinafter referred to as ECU temperature). Measure the transition. The ECU temperature T _ECU detected this time is also represented in detail by T _ECU (j), and the previous measurement is represented by T _ECU (j-1). Then, it is determined whether or not the detected ECU temperature T _ECU {specifically, T _ECU (j)} exceeds a predetermined temperature T _SET . If the ECU temperature T _ECU has not reached the predetermined temperature T _SET , the process proceeds to S202, where the ECU 100 performs injection in the optimal injection mode according to the operating state of the engine 1 (referred to as a normal mode), and the control processing Exit. On the contrary, if the ECU temperature T _ECU exceeds the predetermined temperature T _SET , the process proceeds to S203.

Here, the predetermined temperature T _SET is a temperature that is arbitrarily set in order to perform the injection restriction control described later before reaching the heat generation limit of the ECU 100. The predetermined temperature T _SET is set at a temperature (Tk−Δt) that allows for a margin value Δt in the heat generation limit temperature Tk of the ECU 100 or a temperature (Tk / K) that allows for a margin coefficient K (K> 1). Also good.

In S203, it is determined whether or not the ECU temperature T _ECU measured at this time {specifically, T _ECU (j)} is higher than the ECU temperature T _ECU (j-1) measured last time. If the ECU temperature T _ECU (j) measured this time is not larger than the ECU temperature T _ECU (j-1) measured last time, the process proceeds to S204, where the current injection control (normal mode injection control or previous control processing is performed). Continued injection restriction control). Conversely, if the ECU temperature T _ECU (j) measured this time is higher than the ECU temperature T _ECU (j-1) measured last time, the process proceeds to S205.

Note that the difference (temperature rise) between the ECU temperature T _ECU measured this time {specifically, T _ECU (j)} and the ECU temperature T _ECU (j-1) measured last time is a predetermined value ΔT (in this embodiment, ΔT = 0) may be determined. ΔT that satisfies T _ECU (j) −T _ECU (j−1) = ΔT may be zero or any positive number. Note that ΔT is preferably set to a predetermined value greater than the temperature Δtt of the ECU temperature estimation error in consideration of variations in the output signal of the ECU temperature sensor 60 and the calculation error of the ECU 100 that receives this output signal and estimates the ECU temperature. .

S201 and S203 monitor a change point for suppressing the ECU temperature rise (when the ECU temperature T _ECU exceeds the predetermined temperature T _SET and the temperature rise for a predetermined period exceeds the predetermined value Δtt is satisfied). The ECU temperature monitoring means is configured. S201 and S203 constitute ECU heat generation determination means for determining that the ECU temperature T _ECU exceeds the predetermined temperature T _SET and the temperature is rising.

If it is determined from the determination by the control processing in S201 and S203 that the temperature exceeds the predetermined temperature T _SET and the temperature is still rising, it is determined in S205 whether the current multi-injection mode is five-stage injection. If the current multi-injection mode is five-stage injection, the process proceeds to S206. Conversely, if the current multi-injection mode is not a five-stage injection, the process proceeds to S207.

  In S206, the injection restriction of the injection form of the five-stage injection is examined. The E injection is for the purpose of supplying unburned hydrocarbons together with exhaust gas to the catalyst without burning in the cylinder. In order to give priority to the protection of the ECU over the regeneration of the catalyst, first, the amount of E injection related to the E injection (the fifth injection in the order of the five-stage injection) is reduced. Specifically, the target injection command value in E injection or the drive time of the drive signal (drive pulse) for driving the injector 2 is reduced by a predetermined amount.

Even if the predetermined amount is reduced, the control process in S201 and S203 as the ECU temperature monitoring means determines that the predetermined temperature T _SET is exceeded and the temperature is still rising (hereinafter referred to as a temperature rising determination). When E is repeated, the E injection amount to be reduced finally becomes zero, and as a result, the injection of E injection itself is limited (the E injection disappears).

  In S207, it is determined whether or not the current multi-injection mode is four-stage injection. If the current multi-injection mode is four-stage injection, the process proceeds to S208. Conversely, if the current multi-injection mode is not four-stage injection, the process proceeds to S209.

  In S208, the injection restriction of the injection form of the four-stage injection is examined. In the operating region of the engine 1 using this injection mode, exhaust gas due to exhaust gas regulations becomes a problem (specifically, there is an exhaust gas evaluation mode). The A and B injections are performed before the C injection, and are intended to reduce combustion noise while minimizing deterioration of HC and fuel consumption. Since the A injection mainly contributes to the combustion noise, the amount of A injection related to the A injection (the first injection in the injection order of the four-stage injection) is reduced here. Specifically, the target injection command value in the A injection or the drive time of the drive signal (drive pulse) for driving the injector 2 is reduced by a predetermined amount. Even if the predetermined amount is reduced, if the ECU temperature monitoring means S201 and S203 repeat the determination during the temperature rise, the A injection amount to be reduced finally becomes zero, and as a result, the injection of the A injection itself is limited. (A injection disappears).

  In S209, it is determined that the current multi-injection form is a three-stage injection form, and the process proceeds to S210.

  In S210, the injection restriction of the injection form of the three-stage injection is examined. This injection form of the three-stage injection is mainly used in a region of a high injection amount and high speed (specifically, medium speed and high speed side). In this region, the noise generated by the drive system or structure of the engine itself is larger than the combustion noise. Moreover, it is away from the above mode of current exhaust gas regulation. D injection is aimed at reducing smoke, HC, and fuel consumption by injecting unburned gas immediately after C injection, and to protect the minimum exhaust gas and combustion noise along with B injection. Leave until the end. For this reason, the B injection amount and the D injection amount relating to the B injection and the D injection of the three-stage injection (the first injection and the third injection in the injection order of the three-stage injection) are respectively reduced.

The B and D injections also contribute to the torque, and eliminating them creates a torque step, causing a shock to the driver. At this time, it is preferable to correct the injection timing of the C injection amount, the injection amount, and the injection timing of the B injection and the D injection, with the first priority being that no torque step is generated. Reducing B injection amount and D injection quantity, respectively, some degree of the exhaust gas, even if the influence of the combustion sound occurs, by correcting for example the injection timing to the retard side, reduction and combustion noise of the NO _X in the exhaust gas Can be relaxed. In this correction method, the correction amount is adjusted to the optimal injection timing according to the driver's request or driving state.

It should be noted that the control processing from S205 to S210 is performed during one combustion stroke when a change point (temperature rising exceeding the predetermined temperature T _SET ) is detected by the ECU heat generation determination means (ECU temperature monitoring means) S201 and S203. An injection restricting means for restricting the injection of the injector in the specific injection among the plural injections to be injected is configured. Note that S205, S207, and S209 constitute an injection mode specifying unit that determines the number of injections (number of stages) of the multi-injection mode when it is determined that the ECU temperature T _ECU exceeds the predetermined temperature and the temperature is rising. To do.

Next, the operation and effect of the present embodiment will be described. (1) Since the ECU 100 includes the temperature sensor 60 that detects or estimates the temperature of the exothermic circuit and the injector drive circuit 121 having the exothermic element, the multi-injection mode It is possible to accurately detect or estimate the temperature of the injector drive circuit 121 that rises according to the number of injections (the number of injection stages) (specifically, the number of injections per combustion stroke), that is, the temperature T _ECU of the _ECU . Further, when the ECU temperature T _ECU detected or estimated by the temperature sensor 60 exceeds the predetermined temperature and the temperature is rising, the injection of the injector in the specific injection among the multiple injections injected during one combustion stroke is performed. Since the injection limiting means S205 to S210 for limiting are provided, the influence on exhaust gas and combustion noise is minimized by limiting only the injection in the specific injection without limiting all the multi-injections and limiting only the main injection as in the past. It is possible to prevent the temperature of the ECU from rising.

(2) In the injection limiting means S205 to S210 of the present embodiment described above, the injection amount of the specific injection is reduced by a predetermined amount. By reducing the injection amount, the drive time of the injector drive signal (drive pulse) in the specific injection can be reduced, so that the amount of heat generated by the ECU 100 (specifically, the injector drive circuit 121) can be reduced. Further, only a predetermined amount with a reduced injection amount of the specific injection, even if the effect of reducing the amount of heat generated ECU100 is small, since the regularly ECU temperature _{T ECU} is monitored by the ECU temperature monitoring means S201 and S203, the specific It is also possible to limit the injection of the specific injection specific injection by repeatedly reducing the injection amount of the injection.

(3) Furthermore, in the injection restriction means S205 to S210 of the present embodiment described above, the specification for performing the injection restriction for each number of injection stages (number of injections) of the multi-injection form monitored by the ECU temperature monitoring means S201 and S203. Decided to spray. Therefore, as a result of reduced repeating the injection amount of the specific injection, even if the injection stage number has decreased, the heat generation ECU temperature monitoring means S201 and ECU temperature _{T ECU} by S203 the temperature rising above a predetermined temperature (for ECU100 As long as it is determined that the effect of reducing the amount is insufficient), it is possible to take countermeasures to reduce the injection amount or limit the injection itself.

  (4) Even if the engine environment is disadvantageous as a mounting environment, and the engine operating state is in an unfavorable driving state such as rapid deceleration (vehicle traveling state in the direction of the dashed line in FIG. 4), the heat generation of the ECU 100 is suppressed. The temperature increase of the ECU 100 can be prevented.

(5) In addition, injection limiting means S205~S210, it N times the injection number of the multi-injection mode when the ECU temperature _{T ECU} is judged to be in a temperature rise above a predetermined temperature (stage number), N = 5 E injection (fifth injection in injection order), N = 4 A injection (first injection in injection order), and N = 3 B injection and E injection (first injection in injection order). Since the reduction process of the injection amount of the third injection) is performed, the influence on the exhaust gas and the combustion noise can be minimized to prevent the ECU 100 from rising in temperature.

  (6) In the B injection and the D injection at N = 3, it is preferable that the injection restricting means S205 to S210 include an injection timing correcting means capable of changing the injection timings of the B injection and the D injection. The injection timing correction means can adjust the optimal injection timing according to the driver's request or driving state.

(7) Furthermore, as an environmental condition for mounting the ECU 100, the ECU temperature detecting means such as the temperature sensor 60 that can accurately detect the ECU temperature T _ECU regardless of whether the ECU 100 is mounted in the engine room or in the vehicle. Therefore, it is possible to monitor the heat generation state of the injector drive circuit 121, which is the main cause of the temperature increase of the ECU 100. Therefore, it is possible to accurately determine a change point (when the ECU temperature exceeds a predetermined temperature and a limiting condition where the temperature increase for a predetermined period exceeds a predetermined value is satisfied) for suppressing the temperature increase of ECU 100. Furthermore, since this change point can be detected with high accuracy, it is easy to guarantee the operation of the ECU regardless of the environmental conditions in the engine room or the vehicle compartment in which the ECU is mounted.

(Second Embodiment)
Hereinafter, other embodiments to which the present invention is applied will be described. In the following embodiments, the same or equivalent components as those in the first embodiment are denoted by the same reference numerals, and description thereof will not be repeated.

  In the second embodiment, as shown in FIG. 6, the current waveform of the drive signal (drive current) output to the injector 2 is corrected. FIG. 6 is a flowchart showing a control process of the injection control of the injector according to the present embodiment. As a method for limiting the specific injection in the multi-injection mode recognized by the injection mode specification S205, S207, and S209, the specific injection in S206, S208, and S210 is reduced as in the first embodiment. It may be. Further, as shown in FIG. 6, the specific injection itself in S506 and S508 may be restricted. In this case, in S510, the initial maximum current value in the initial state of energization rising of the drive current in the B injection and the E injection is reduced so that the restriction on the B injection and the E injection is not limited to the main injection, and the low current value is used. A drive current waveform is formed (hereinafter referred to as low current control). Specifically, the ECU 100 controls the injector drive circuit 121 to lower the discharge stop threshold from, for example, 17A to a low current value of the drive current. The injection form remains three-stage injection.

  As a result, the drive signal (drive current) can be corrected so as to suppress the amount of heat generated by the injector drive circuit 121. More specifically, since the correction is made so that the initial maximum current value of the energization current supplied to the injector 2 is decreased, the heat generation of the heating circuit such as the charge circuit 121a for generating the initial maximum current value can be suppressed. .

  In the present embodiment described above, the low current control may be performed in the same manner as in S510, except that the control process in S506 and S508 is limited to the specific injection itself. In this case, in addition to the process of storing COUNT = 4 and COUNT = 3 in the control processes of S506 and S508, respectively, for example, in the process of S207, in addition to the method of determining the multi-injection mode from the arithmetic process in the ECU 100, etc. Thus, if COUNT = 4, even if it is actually a 5-stage injection, it is regarded as a 4-stage injection. Even in the embodiment having such a configuration, it is possible to obtain the same effect as that of the first embodiment.

(Other embodiments)
In the present embodiment described above, the injector drive circuit 121 is described as being mounted in the ECU 100 as the control device. However, as shown in FIG. 8, the injector drive circuit 121 is arranged as an EDU separately from the ECU 100. You may do it. Moreover, the injector drive circuit 121 may be incorporated in the casing of the ECU 100 (not shown).

  In the present embodiment described above, the mounting condition of the ECU 100 is set in the engine room, but it may be mounted in the vehicle. Further, it may be mounted in the engine room and directly mounted on the engine 1.

In the present embodiment described above, the injection limiting means for preventing the ECU temperature T _ECU from rising beyond the heat generation limit of the ECU 100 has been described. However, the main cause of heat generation of the ECU temperature is the solenoid valve (solenoid) of the injector 2. Therefore, by applying the present embodiment, it is possible to prevent a decrease in the amount of heat generated by the injector 2, that is, an increase in the temperature of the injector 2.

  In the present embodiment described above, in a fuel injection control device for an internal combustion engine that performs main injection that forms the main torque of the internal combustion engine during one combustion stroke of the internal combustion engine and multiple stages of injection other than the main injection, As described above, exhaust gas, combustion noise can be reduced by limiting any specific injection from a plurality of stages other than the main injection according to the degree of exceeding the predetermined temperature without limiting all the multi-injections to only the main injection. An increase in the temperature of the ECU is prevented by minimizing the influence on the ECU.

1 is a configuration diagram illustrating an overall configuration of a fuel injection system according to a first embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a schematic configuration of an ECU in FIG. 1. It is a flowchart which shows the control processing regarding the injection control of the injector in ECU in FIG. It is a graph explaining one Example of the relationship between an engine speed, the injection quantity, and the frequency | count of injection per combustion stroke. It is a timing chart which shows the injection state of a fuel injection system. It is a flowchart which shows the control processing of the injection control of the injector concerning 2nd Embodiment. It is a graph explaining the relationship between an injection rate and an injector drive current. It is a schematic diagram showing schematic structure of ECU concerning other embodiment.

Explanation of symbols

1 engine (internal combustion engine)
2 Injector (fuel injection valve, electromagnetic fuel injection valve)
3 Supply pump (high pressure supply pump, fuel supply pump)
100 ECU (engine control unit, control means, correction means)
DESCRIPTION OF SYMBOLS 120 Fuel-injection-system drive circuit 121 Injector drive circuit 121a Charge circuit 121b Discharge control switching element 121c Discharge control circuit 122 Pump drive circuit 17 Common rail (pressure accumulation chamber)
60 Temperature sensor (ECU temperature detection means)

Claims (8)

An internal combustion engine comprising: an injector that injects fuel into an internal combustion engine; and a control unit that controls the injector in accordance with an operating state of the internal combustion engine, wherein a plurality of injections are performed during one combustion stroke of the internal combustion engine In the fuel injection control device,
The control means includes
An injector driving circuit for outputting a driving signal for driving the injector to the injector;
ECU temperature detecting means for detecting or estimating the temperature of the injector drive circuit;
When the temperature of the injector drive circuit detected or estimated by the ECU temperature detection means exceeds a predetermined temperature, and the temperature rise within a predetermined period exceeds a predetermined value, the amount of heat generated by the injector drive circuit is suppressed. An injection restricting means for restricting the injection of the injector in the specific injection of the plurality of injections ,
The injection limiting means is
When the temperature of the injector drive circuit by the ECU temperature detection means exceeds the predetermined temperature, it has a temperature rise determination means for determining whether or not the temperature tends to increase,
Decrease the injection amount in the specific injection according to the injection mode of the multiple injections in the one combustion stroke, as an indispensable condition for limiting the injection that the determination by the determination means during the temperature increase is an upward trend And correction of at least one specific injection of changing the injection timing,
The fuel injection control device for an internal combustion engine , wherein the correction of the specific injection is maintained until the temperature becomes equal to or lower than the predetermined temperature when the temperature rising is determined by the determination means during the determination. . An injector for injecting fuel into the internal combustion engine; and control means for controlling the injector in accordance with an operating state of the internal combustion engine, and forming a main torque of the internal combustion engine during one combustion stroke of the internal combustion engine In a fuel injection control device for an internal combustion engine that performs injection and multiple-stage injection other than the main injection,
The control means includes
An injector driving circuit for outputting a driving signal for driving the injector to the injector;
ECU temperature detecting means for detecting or estimating the temperature of the injector drive circuit;
According to the degree to which the temperature of the injector drive circuit detected or estimated by the ECU temperature detection means exceeds a predetermined temperature, the amount of heat generated by the injector drive circuit is suppressed.
Injection limiting means for limiting a plurality of stages of injection other than the main injection ,
The injection limiting means is
When the temperature of the injector drive circuit by the ECU temperature detection means exceeds the predetermined temperature, it has a temperature rise determination means for determining whether or not the temperature tends to increase,
As an essential condition for limiting the injection, the determination by the determination means during the temperature rise is an upward trend, and according to the injection mode of the multiple injections in the one combustion stroke, the injection of multiple stages other than the main injection is performed. Of at least one of the specific injections of reducing the injection amount and changing the injection timing in the specific injection,
The fuel injection control device for an internal combustion engine , wherein the correction of the specific injection is maintained until the temperature becomes equal to or lower than the predetermined temperature when the temperature rising is determined by the determination means during the determination. . 3. The ECU temperature detecting means according to claim 1, further comprising a temperature sensor provided in the injector driving circuit and detecting the temperature of the injector driving circuit directly or indirectly. The fuel injection control device for an internal combustion engine as described. A multi-injection in which the number of injections during the one combustion stroke is N times,
The injection limiting means sets the injection amount of any of the fifth injection in the injection order when N = 5, the first injection when N = 4, and the first injection and the third injection when N = 3. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 3, further comprising an injection amount correction means for reducing the injection amount. In the first injection and the third injection at the N = 3,
5. The fuel injection for an internal combustion engine according to claim 4, wherein the injection limiting unit includes an injection timing correcting unit capable of changing an injection timing of each of the first injection and the third injection. Control device. A multi-injection in which the number of injections during the one combustion stroke is N times,
The injection restricting means is configured such that the driving signal in any one of the fifth injection in the injection order when N = 5, the first injection when N = 4, and the first injection and the third injection when N = 3. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 3, further comprising drive signal correction means for correcting The internal combustion engine fuel according to claim 6, wherein the drive signal correction unit reduces an initial maximum current value of an energization current supplied to the injector by correcting a current value of the drive signal. Injection control device. The injector drive circuit includes a charge circuit that increases and stores a power supply voltage from an in-vehicle power supply, a discharge control switching element, and a discharge control circuit that intermittently controls the discharge control switching element. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 7.

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