JP2016217263A - Controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for an internal combustion engine that can prevent erroneous determination that a fuel booster pump is abnormal.SOLUTION: An ECU 25 comprises: an abnormality determination part 25A which determines that a fuel booster pump 22 is abnormal on condition that when fuel injection is performed by an injector 23 while the fuel booster pump 22 is driven, fuel pressure Pr boosted by the fuel booster pump 22 becomes less than booster pump abnormality determination fuel pressure Perr; and an abnormality determination threshold setting part 25B which sets the booster pump abnormality determination fuel pressure Perr according to a state of an engine 2. The abnormality determination threshold setting part 25B sets the booster pump abnormality determination fuel pressure Perr according to a temperature of cooling water of the engine 2. The abnormality determination threshold setting part 25B sets the booster pump abnormality determination fuel pressure Perr lower as the temperature of the cooling water of the engine 2 is lower.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that determines an abnormality of a fuel boost pump that boosts fuel.

  In a cylinder injection internal combustion engine, fuel is boosted using a fuel booster pump driven by a camshaft, and the boosted fuel is injected into a combustion chamber by an injector.

  Conventionally, what was described in patent document 1 as a control apparatus of this kind of internal combustion engine is known. The device described in Patent Document 1 starts fuel injection when the internal combustion engine is started on the condition that the fuel pressure is increased to a predetermined start determination threshold value or more.

  In addition, since the fuel pressure fluctuates during fuel injection by repeating the increase of the fuel pressure by the fuel boost pump and the decrease of the fuel pressure by the fuel injection in the one described in Patent Document 1, the fuel pressure is increased. Accordingly, the fuel pressure fluctuation is suppressed by changing the fuel injection timing.

  Furthermore, in the device described in Patent Document 1, if the fuel pressure drops below the abnormality determination threshold after the fuel pressure has been increased above the start determination threshold and fuel injection has started, the fuel boost pump is abnormal. It comes to judge.

Japanese Patent No. 4126958

  Here, when the internal combustion engine is cold-started, the fuel injection amount is corrected to the increase side in order to ensure good startability, so the fuel pressure is increased due to the increase in the fuel injection amount after the start of fuel injection. descend.

  With such a fuel boost pump, if it is determined that the fuel pressure is lower than the abnormality determination threshold for determining that the fuel boost pump is abnormal, it is determined that the fuel boost pump is abnormal. Yes. However, when the internal combustion engine is cold-started under special conditions such as extremely low temperatures, the increase in the fuel injection amount is large, so that the fuel pressure after the fuel injection is greatly reduced, and the fuel pressure may fall below the abnormality determination threshold. there were. This phenomenon is derived from the performance of the fuel booster pump and is not an abnormality of the fuel booster pump.

  Therefore, there is a possibility that the fuel boost pump is erroneously determined to be abnormal although it is not abnormal.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a control device for an internal combustion engine that can prevent a fuel boost pump from being erroneously determined to be abnormal.

  An aspect of the present invention for solving the above-described problem is a control apparatus for an internal combustion engine, comprising: a fuel boost pump that boosts fuel; and an injector that injects fuel boosted by the fuel boost pump into a combustion chamber of the internal combustion engine. The fuel boosting is performed on the condition that the fuel pressure boosted by the fuel boosting pump is less than an abnormality determination threshold when the fuel boosting pump is driven and fuel injection is performed by the injector. An abnormality determination unit that determines that the pump is abnormal, and an abnormality determination threshold setting unit that sets the abnormality determination threshold according to the state of the internal combustion engine.

  According to the aspect of the present invention, the abnormality determination threshold value is set to a value corresponding to the state of the internal combustion engine instead of a fixed value. For this reason, when the fuel pressure is temporarily reduced due to the state of the internal combustion engine, the fuel pressure does not become less than the abnormality determination threshold value, so that the fuel boost pump is not determined to be abnormal. As a result, it can be prevented that the fuel boost pump is erroneously determined to be abnormal.

FIG. 1 is a schematic configuration diagram showing a main part of an engine of a vehicle equipped with a control device for an internal combustion engine according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the fuel boost pump of the control device for the internal combustion engine according to the embodiment of the present invention, showing a state where the plunger is lowered. FIG. 3 is a cross-sectional view of the fuel boost pump of the control device for an internal combustion engine according to the embodiment of the present invention, showing a state where the plunger is raised. FIG. 4 is a flowchart showing an engine start control process of the control device for the internal combustion engine according to the embodiment of the present invention. FIG. 5 is a time chart showing changes in fuel pressure and engine speed when engine start control processing is executed in the control apparatus for an internal combustion engine according to the embodiment of the present invention. FIG. 6 is a time chart showing changes in fuel pressure and engine speed when the engine is started in a conventional control device for an internal combustion engine.

  Hereinafter, an internal combustion engine control apparatus according to an embodiment in which an internal combustion engine control apparatus according to the present invention is applied to an engine 2 of a vehicle 1 will be described with reference to FIGS. 1 to 5.

  First, the configuration will be described. As shown in FIG. 1, the vehicle 1 includes an engine 2 as an internal combustion engine and a fuel tank 3. The vehicle 1 may be a hybrid vehicle including an engine and a motor serving as a power source.

  As shown in FIG. 1, the engine 2 includes a cylinder head 9, a cylinder block 11, a piston 12, a connecting rod 13, a crankshaft 14, an intake device 15, an exhaust device 16, an ignition device 17, A valve operating device 18 and an ignition switch 19 are included.

  The engine 2 is constituted by, for example, a four-cycle gasoline engine that performs a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

  The cylinder head 9 is formed with a combustion chamber 9n, an intake port 9k and an exhaust port 9h communicating with the combustion chamber 9n, and a water jacket 9w through which cooling water for cooling the engine 2 is passed.

  The cylinder block 11 is fastened by a fastener (not shown) and integrated with the cylinder head 9, and accommodates a piston 12, a connecting rod 13, and a crankshaft 14 inside. The piston 12, the connecting rod 13, and the crankshaft 14 are connected, and the reciprocating motion of the piston 12 is converted into the rotational motion of the crankshaft 14.

  A water jacket 11w is formed in the cylinder block 11, and the cylinder block 11 is cooled by cooling water flowing through the water jacket 11w. Cooling water flowing through the water jacket 11 w flows into the water jacket 9 w of the cylinder head 9.

  The intake device 15 includes an intake manifold 15m having an intake passage 15k that is connected to the cylinder head 9 and communicates with the intake port 9k, an intake pipe 15p, and a throttle valve 15s that adjusts the flow rate of intake air flowing through the intake pipe 15p. The intake air temperature sensor 15t detects the temperature of intake air (intake air temperature) flowing through the intake pipe 15p, and an air filter (not shown) that filters the intake air.

  The intake device 15 circulates the intake air into the combustion chamber 9n. The throttle valve 15s is connected to an ECU 25, which will be described later, and is driven and controlled by the ECU 25. The intake air temperature sensor 15t is also connected to the ECU 25, and the temperature information signal detected by the intake air temperature sensor 15t is sent to the ECU 25 and used for controlling the engine 2.

  The exhaust device 16 is connected to the cylinder head 9 and purifies the exhaust gas exhausted from the exhaust manifold 16m having an exhaust passage 16k communicating with the exhaust port 9h, the exhaust pipe 16p, and the combustion chamber 9n and flowing through the exhaust pipe 16p. An exhaust gas purification catalyst (not shown), and a muffler (not shown) that silences exhaust noise. The exhaust device 16 circulates exhaust gas, purifies and silences it, and exhausts it from the exhaust pipe 16p to the atmosphere.

  The ignition device 17 has an ignition plug 17p attached to the cylinder head 9 with the tip exposed to the combustion chamber 9n, and the ignition plug 17p ignites the mixture of intake air and fuel in the combustion chamber 9n. To start combustion.

  The valve gear 18 is a cylinder that blocks and opens the intake valve 18k supported by the cylinder head so as to block and open between the intake port 9k and the combustion chamber 9n, and between the exhaust port 9h and the combustion chamber 9n. And an exhaust valve 18 h supported by the head 9. The valve operating device 18 is operated by power transmitted from the crankshaft 14.

  The ignition switch 19 includes a switch such as a key insertion type, a key rotation type, and a wireless authentication type carried by the user, and is connected to an ECU 25 described later. The ignition switch 19 is operated by a user to start and stop the engine 2 and output a signal indicating whether the ignition switch 19 is ON or OFF.

  In addition, the vehicle 1 includes a fuel pump 21, a fuel boost pump 22, an injector 23, a fuel supply pipe 24, a coolant temperature sensor 26, a fuel pressure sensor 27, an engine speed sensor 28, an internal combustion engine An ECU (Electronic Control Unit) 25 as a control device is included.

  The fuel pump 21 is provided in the fuel tank 3, sucks up the fuel in the fuel tank and sends it to the injector 23 via the fuel supply pipe 24 and the fuel booster pump 22.

  The fuel pump 21 is an electric pump and is driven by electric power supplied from a battery (not shown). The fuel pump 21 feeds fuel at a relatively low so-called feed pressure, for example, a pressure of about 300 kPa.

  The fuel pump 21 is connected to the ECU 25, and is driven and controlled by the ECU 25.

  The fuel booster pump 22 mechanically boosts the fuel sent from the fuel pump 21 through the fuel supply pipe 24 and sends it to the injector 23.

  The fuel booster pump 22 includes a housing 31, a pump body 32, an electromagnetic spill valve 33, a tappet 35, a tappet roller 36, a tappet spring 37, and a plunger 38.

  The housing 31 accommodates the tappet 35 so that the tappet 35 can be moved up and down, and accommodates the tappet spring 37 so that the tappet spring 37 presses the tappet 35 downward. The housing 31 is fastened to a pump mounting portion 2p provided in the engine 2 by a fastener (not shown).

  The pump main body 32 is fixed to the housing 31, and accommodates the electromagnetic spill valve 33 and accommodates the plunger 38 so as to be movable up and down. The pump body 32 has an intake port 32k connected to the upstream fuel supply pipe 24 through which fuel flows and sucks fuel, a discharge port 32t connected to the downstream fuel supply pipe 24 and discharging fuel, A boosting chamber 32s for boosting the fuel is formed.

  The electromagnetic spill valve 33 includes an electromagnet 33e, a valve 33v, a valve seat 33s, and a spring 33c that presses the valve 33v away from the valve seat 33s.

  The electromagnet 33e is connected to the ECU 25. When the electromagnet 33e is energized by the ECU 25, the valve 33v is attracted and the valve 33v is seated on the valve seat 33s to close the suction port 32k. That is, the electromagnetic spill valve 33 is a normally open valve that opens the valve 33v when not energized.

  On the contrary, when the energization to the electromagnet 33e is interrupted by the ECU 25, the valve 33v is separated from the valve seat 33s by the pressing force of the spring 33c, and the suction port 32k is opened.

  The tappet 35 rotatably supports the tappet roller 36, and is in contact with a substantially triangular pump cam 2 c provided on the exhaust camshaft 2 h of the engine 2 via the tappet roller 36. The tappet roller 36 is pressed against the tappet spring 37 via the tappet 35, and presses the pump cam 2c with a predetermined pressing force.

  The exhaust camshaft 2h is connected to the crankshaft 14 of the engine 2 shown in FIG. 1 by a power transmission member such as a chain (not shown), and is rotated once by two rotations of the crankshaft 14.

  Therefore, the pump cam 2c of the exhaust camshaft 2h rotates with the rotation of the crankshaft 14, and the tappet 35 is moved up and down three times via the tappet roller 36 by one rotation of the exhaust camshaft 2h.

  The end of the plunger 38 is connected to the tappet 35, and the plunger 38 moves up and down together with the tappet 35. As shown in FIG. 2, when the electromagnetic spill valve 33 is in an open state when the plunger 38 is lowered, the intake stroke is such that fuel is sucked into the pressurizing chamber 32s from the suction port 32k.

  As shown in FIG. 3, if the electromagnetic spill valve 33 is in a closed state when the plunger 38 is raised, the fuel in the pressure raising chamber 32 s is in a pressure raising stroke in which the pressure is increased by the raising of the plunger 38. When the fuel pressure is increased in the pressure increasing stroke, the discharge stroke is discharged into the fuel supply pipe 24 from the discharge port 32t.

  On the other hand, if the electromagnetic spill valve 33 is in the open state when the plunger 38 is raised, the fuel in the boosting chamber 32s is not boosted and returned to the fuel supply pipe 24 from the suction port 32k or the discharge port 32t. And is discharged into the fuel supply pipe 24.

  If the electromagnetic spill valve 33 is in an open state when the plunger 38 is raised, a so-called idling state occurs, and the feed pressure sent by the fuel pump 21 is applied to the injector 23.

  The fuel boosting pump 22 boosts the sucked fuel to a high pressure in the boosting chamber 32 s, for example, about several MPa to several tens of MPa at the maximum by the ascending of the plunger 38 in the aforementioned boosting stroke. The boosted fuel flows through the fuel supply pipe 24 through the discharge stroke discharged from the discharge port 32t and is supplied to the injector 23.

  In the fuel boost pump 22, the plunger 38 moves up and down as the pump cam 2c provided on the exhaust camshaft 2h rotates. That is, the plunger 38 smoothly moves up and down from time 0 to the maximum lift amount over time.

  The amount of pressure increase of the fuel by raising the plunger 38 is controlled by adjusting the opening / closing timing of the electromagnetic spill valve 33 with respect to the raising / lowering timing of the plunger 38.

  The injector 23 has an electromagnetic coil (not shown) connected to the ECU 25 and a nozzle 23n that injects fuel. One end of the injector 23 is connected to the fuel supply pipe 24, and the other end is the intake air of the cylinder head 9. A nozzle 23n is attached to the cylinder head 9 below the port 9k so as to be exposed in the combustion chamber 9n.

  The injector 23 is configured to switch between a valve opening state and a holding state by a drive current flowing in the electromagnetic coil, and injects fuel toward the upper portion of the piston 12 when the piston 12 moves up in the compression stroke of the engine 2. Atomize. When the drive time (sec) of the injector 23 is corrected by the ECU 25, the injector 23 injects fuel with the corrected drive time.

  The drive time of the injector 23 refers to the time from when the nozzle 23n of the injector 23 is opened to when the nozzle 23n is closed and held. If the pressure of the fuel supplied to the injector 23 is constant, the fuel injection amount increases as the drive time increases, and the injection amount decreases as the drive time decreases.

  If the driving time is the same, the fuel injection amount increases as the fuel pressure supplied to the injector 23 increases, and the fuel injection amount decreases as the fuel pressure decreases.

  The fuel supply pipe 24 is connected between the fuel pump 21 and the injector 23, and is constituted by a hollow pipe that circulates the fuel discharged from the fuel pump 21 and sends it to the injector 23. The fuel supply pipe 24 is provided with a fuel boost pump 22 and a fuel pressure sensor 27.

  The fuel supply pipe 24 may include a delivery pipe that is connected to the injector 23 and supplies a stable fuel pressure to the injector 23. In this case, the fuel pressure sensor 27 detects the pressure in the delivery pipe. Further, a fuel pressure regulator may be provided so as to obtain a stable fuel injection while keeping the pressure in the delivery pipe constant.

  The cooling water temperature sensor 26 includes a temperature detecting element such as a thermistor, and detects the temperature of the cooling water flowing through the water jacket 9w of the cylinder head 9 as the starting water temperature Ts.

  The cooling water temperature sensor 26 is connected to the ECU 25 and outputs the detected starting water temperature Ts to the ECU 25. The cooling water temperature sensor 26 may detect the temperature of the cooling water flowing through the water jacket 11 w of the cylinder block 11.

  The fuel pressure sensor 27 is provided between the fuel boost pump 22 and the injector 23, and is a so-called piezoelectric element or variable resistor that detects the pressure of fuel sent from the fuel boost pump 22 to the injector 23. It consists of a fuel pressure sensor. The fuel pressure sensor 27 is connected to the ECU 25, and the detected pressure information signal is sent to the ECU 25.

  The engine speed sensor 28 detects the engine speed Nr of the engine 2 by detecting the rotation angle of the crankshaft 14. The rotational speed sensor 28 is connected to the ECU 25 and outputs the detected engine rotational speed Nr to the ECU 25.

  The fuel tank 3 is constituted by a hollow container that stores the fuel of the engine 2, and is fixed to a vehicle body (not shown) of the vehicle 1.

  The ECU 25 is configured by a microcomputer. The microcomputer includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), a flash memory, an input port, an output port, and a network module.

  The ECU 25 controls the engine 2 by executing arithmetic processing based on data and programs stored in the ROM.

  The ECU 25 performs fuel injection by the injector 23 while driving the fuel boost pump 22 when the engine 2 is started.

  When starting the engine 2, the ECU 25 calculates the start-up injection time as the fuel injection time at start-up. The start-up injection time is obtained by multiplying the start-up basic injection time determined by the cooling water temperature by the intake air temperature correction coefficient determined by the intake air temperature, and further adding the voltage correction time determined by the battery voltage. It is calculated by.

  Here, the starting injection time is set to be longer as the temperature of the cooling water is lower. The intake air temperature correction coefficient is determined so as to increase as the intake air temperature decreases. For this reason, the fuel injection amount at the start of the engine 2 increases as the temperature of the cooling water (starting water temperature Ts) and the intake air temperature decrease.

  In the present embodiment, when starting the engine 2, the ECU 25 starts the engine 2 by either high fuel pressure start or low fuel pressure start. The high fuel pressure start is to start the engine 2 by injecting fuel boosted by the fuel boost pump 22 from the injector 23. In the high fuel pressure start, the opening and closing of the electromagnetic spill valve 33 is controlled according to the raising and lowering of the plunger 38.

  The low fuel pressure start is to start the engine 2 by injecting fuel from the injector 23 at the fuel pressure (feed pressure) supplied by the fuel pump 21 without operating the fuel boost pump 22.

  In the low fuel pressure start, the electromagnetic spill valve 33 is kept open so that the fuel supplied by the fuel pump 21 passes through the fuel boost pump 22 and is supplied to the injector 23.

  In the low fuel pressure start, since the fuel pressure supplied to the injector 23 is lower than that in the high fuel pressure start, fuel is injected in the first half of the exhaust stroke, the intake stroke, or the compression stroke.

  The ECU 25 compares the current fuel pressure with the high fuel pressure start determination fuel pressure Ph when the engine 2 is started. If the fuel pressure is less than the high fuel pressure start determination fuel pressure Ph, the ECU 25 starts the engine 2 with the low fuel pressure start. It is like that.

  Further, when starting the engine 2, the ECU 2 starts the engine 2 by starting the low fuel pressure if the fuel boost pump 22 is in an abnormal state even if the fuel pressure is equal to or higher than the high fuel pressure start determination fuel pressure Ph. It has become.

  On the other hand, when the fuel pressure is equal to or higher than the high fuel pressure start determination fuel pressure Ph and the state of the fuel boost pump 22 is not abnormal, the ECU 25 starts the engine 2 by high fuel pressure start.

  As described above, the low fuel pressure start is performed as a fail-safe function when the high fuel pressure start is impossible due to an abnormal state of the fuel boost pump 22 or the like. When the engine 2 is started by the low fuel pressure start, fuel consumption may deteriorate or soot in the exhaust gas may increase.

  For this reason, it is accurately determined whether or not the fuel boost pump 22 is abnormal, and it is erroneously determined that the fuel boost pump 22 is abnormal although the fuel boost pump 22 is not abnormal, so that the low fuel pressure start is performed. Need to avoid.

  Here, when the engine 2 is started at an extremely low temperature, conventionally, since the temperature of the cooling water is low and the fuel injection amount is increased, the fuel pressure is lowered and the fuel boost pump 22 is erroneously determined to be abnormal. There was a risk.

  Therefore, in the present embodiment, as will be described in detail later, the ECU 25 sets the booster pump abnormality determination fuel pressure Perr for determining whether or not the fuel booster pump 22 is abnormal to the engine 2 without setting a fixed value. It is set according to the state.

  In the present embodiment, the ECU 25 includes an abnormality determination unit 25A and an abnormality determination threshold setting unit 25B.

  The abnormality determination unit 25A, when driving the fuel boost pump 22 and performing fuel injection by the injector 23, the fuel pressure boosted by the fuel boost pump 22 is less than the boost pump abnormality determination fuel pressure Perr as an abnormality determination threshold. As a condition, the fuel boost pump is determined to be abnormal.

  The abnormality determination threshold value setting unit 25B is configured to set the booster pump abnormality determination fuel pressure Perr according to the state of the engine 2.

  Specifically, the abnormality determination threshold value setting unit 25B is configured to set the boost pump abnormality determination fuel pressure Perr according to the coolant temperature (starting water temperature Ts) as the state of the engine 2.

  A booster pump abnormality determination fuel pressure setting table (not shown) is stored in the ROM of the ECU 25. In the booster pump abnormality determination fuel pressure setting table, a correlation between the coolant temperature and the booster pump abnormality determination fuel pressure Perr is defined.

  In the booster pump abnormality determination fuel pressure setting table, the booster pump abnormality determination fuel pressure Perr is determined to be lower as the coolant temperature of the engine 2 is lower. For this reason, the abnormality determination threshold value setting unit 25B sets the booster pump abnormality determination fuel pressure Perr to be lower as the coolant temperature of the engine 2 is lower.

  Further, the booster pump abnormality determination fuel pressure Perr is determined even when the fuel pressure is lowered due to the low coolant temperature at the start of the engine 2 and the increased fuel injection amount. The value is set so as not to fall below the fuel pressure Perr.

  In the booster pump abnormality determination fuel pressure setting table, correlations between the coolant temperature, the intake air temperature, and the booster pump abnormality determination fuel pressure Perr are determined, and either the coolant temperature or the intake air temperature is low. The boost pump abnormality determination fuel pressure Perr may be set to a lower value. That is, the booster pump abnormality determination fuel pressure Perr is a value determined according to the state of the engine 2.

  When the ignition switch 19 is turned on and power is supplied to the ECU 25, the ECU 25 executes an engine start control process described later.

  Next, an engine start control process executed in the ECU 25 will be described with reference to FIG. The fuel injection control process described below is executed when the ECU 25 detects that the ignition switch 19 is on.

  First, when the ignition switch 19 is turned on and the power supply to the ECU 25 is started, the ECU 25 detects the starting water temperature Ts by the cooling water temperature sensor 26 and the fuel pressure sensor 27 in step S1. The pressure Pr is detected.

  Further, the ECU 25 refers to the booster pump abnormality determination fuel pressure table and starts calculating the booster pump abnormality determination fuel pressure Perr in accordance with the starting water temperature Ts.

  Next, the ECU 25 starts cranking (step S2). Here, the ECU 25 operates a starter (not shown) to rotate the crankshaft 14 by this starter.

  When the crankshaft 14 rotates, the fuel booster pump 22 is driven via the exhaust camshaft 2h, so that the fuel pressure Pr increases.

  Next, the ECU 25 compares the current fuel pressure Pr and the high fuel pressure start determination fuel pressure Ph to determine whether or not the fuel pressure Pr is equal to or higher than the high fuel pressure start determination fuel pressure Ph (step S3). The process of step S3 is performed after a lapse of a predetermined time from the process of step S2. This predetermined time is a time when the fuel pressure Pr is normally equal to or higher than the high fuel pressure start determination fuel pressure Ph after the process of step S2, and is a preset time.

  If the determination in step S3 is NO (the fuel pressure Pr is less than the high fuel pressure start determination fuel pressure Ph), the ECU 25 proceeds to step S7 and starts the low fuel pressure start of the engine 2.

  On the other hand, if the determination in step S3 is YES (the fuel pressure Pr is equal to or higher than the high fuel pressure start determination fuel pressure Ph), the ECU 25 proceeds to step S4.

  In step S4, the ECU 25 compares the current engine speed Nr with the complete explosion determination engine speed Np, and determines whether or not the engine speed Nr is equal to or greater than the complete explosion determination engine speed Np.

  Here, the complete explosion determination engine speed Np is an engine speed at which the engine 2 can operate independently.

  If the determination in step S4 is YES (the engine speed Nr is equal to or greater than the complete explosion determination engine speed Np), the ECU 25 proceeds to step S8 and starts the high fuel pressure start of the engine 2.

  On the other hand, if the determination in step S4 is NO (the engine speed Nr is less than the complete explosion determination engine speed Np), the ECU 25 proceeds to step S5, where the current fuel pressure Pr is less than the boost pump abnormality determination fuel pressure Perr. It is determined whether or not there is.

  If the determination in step S5 is NO (the fuel pressure Pr is equal to or higher than the booster pump abnormality determination fuel pressure Perr), the ECU 25 returns to step S4.

  On the other hand, if the determination in step S5 is YES (the fuel pressure Pr is less than the boost pump abnormality determination fuel pressure Perr), the ECU 25 determines that the fuel boost pump 22 is abnormal and cancels the high fuel pressure start of the engine 2.

  After step S6, the ECU 25 starts the low fuel pressure start of the engine 2 in step S7, and ends the flowchart of FIG.

  Next, an example of a change in the fuel pressure Pr when the engine start control process is executed will be described with reference to FIG.

  In the timing chart shown in FIG. 5, the horizontal axis represents time, and the vertical axis represents the engine speed Nr and the fuel pressure Pr.

  In FIG. 5, when the starter starts cranking of the engine 2 due to the ignition switch 19 being turned on at time t11, the engine speed Nr increases from 0 to the speed by cranking.

  When the engine 2 is cranked, the fuel boost pump 22 is driven via the exhaust camshaft 2h, and the fuel pressure Pr increases.

  Thereafter, at time t12, the fuel injection Pr is started by the injector 23 because the fuel pressure Pr becomes equal to or higher than the high fuel pressure start determination fuel pressure Ph. That is, at time t12, the fuel boost pump 22 is being driven and fuel injection is performed by the injector 23.

  In addition, at time t12, fuel injection Pr is started by the injector 23, so that the fuel pressure Pr starts to decrease. At this time, the lower the coolant temperature, the larger the correction amount of the fuel injection amount to the increase side, and thus the decrease amount of the fuel pressure Pr also increases.

  Thereafter, at time t13, the engine speed Nr becomes equal to or higher than the complete explosion determination engine speed Np, and the high fuel pressure start is completed. Further, at time t13, the engine speed Nr becomes equal to or higher than the complete explosion determination engine speed Np, so that the fuel boosting capability of the fuel boost pump 22 increases and the fuel pressure Pr begins to rise.

  Here, the boost pump abnormality determination fuel pressure Perr is set to be lower as the cooling water temperature is lower by the abnormality determination threshold setting unit 25B of the ECU 25, so that the engine speed Nr is determined to be the complete explosion determination engine rotation at time t13. The fuel pressure Pr does not fall below the boost pump abnormality determination fuel pressure Perr before it reaches several Np or more.

  For this reason, when the engine 2 is cold-started in a state where the coolant temperature is low, the fuel pressure Pr is increased due to the increase in the fuel injection amount even though the fuel boost pump 22 is not abnormal. It is prevented that the fuel boost pump 22 is erroneously determined to be abnormal because the pump abnormality determination fuel pressure has fallen below the Perr.

  On the other hand, in the conventional control device for an internal combustion engine, as shown in FIG. 6, cranking is started at time t21, and at time t22, the fuel pressure starts to decrease after reaching the high fuel pressure start determination fuel pressure. Since the boost pump abnormality determination fuel pressure is a fixed value, the fuel pressure falls below the boost pump abnormality determination fuel pressure at time t23 before the engine speed becomes equal to or higher than the complete explosion determination engine speed. For this reason, it is erroneously determined that the fuel boost pump is abnormal. Further, when it is determined that the fuel boost pump is abnormal, the operation of the fuel boost pump is stopped. In this case, a low fuel pressure start without using the fuel boost pump 22 is started, and the engine 2 is started by increasing the engine speed Nr to a complete explosion determination engine speed Np or higher.

  Since the control apparatus for an internal combustion engine of the present embodiment is configured as described above, the following effects can be obtained.

  In the present embodiment, when the ECU 25 performs fuel injection by the injector 23 while driving the fuel boost pump 22, the fuel pressure Pr boosted by the fuel boost pump 22 becomes less than the boost pump abnormality determination fuel pressure Perr. Provided that the fuel boost pump 22 is abnormal, and an abnormality determination threshold setting unit 25B that sets the boost pump abnormality determination fuel pressure Perr according to the state of the engine 2. ing.

  With this configuration, the booster pump abnormality determination fuel pressure Perr is set to a value corresponding to the state of the engine 2 instead of a fixed value. For this reason, when the fuel pressure Pr temporarily decreases due to the state of the engine 2, the fuel pressure Pr does not become lower than the booster pump abnormality determination fuel pressure Perr. It is not determined to be.

  As a result, it can be prevented that the fuel boost pump 22 is erroneously determined to be abnormal.

  In the present embodiment, the abnormality determination threshold setting unit 25B sets the booster pump abnormality determination fuel pressure Perr according to the temperature of the cooling water of the engine 2.

  With this configuration, since the booster pump abnormality determination fuel pressure Perr is set to a value corresponding to the temperature of the cooling water, it is possible to more reliably prevent erroneous determination that the fuel booster pump 22 is abnormal.

  In the present embodiment, the abnormality determination threshold value setting unit 25B sets the booster pump abnormality determination fuel pressure Perr lower as the cooling water temperature of the engine 2 is lower.

  With this configuration, the lower the cooling water temperature, the lower the boost pump abnormality determination fuel pressure Perr is set. Therefore, the engine 2 is started when the temperature of the cooling water is low, and the fuel injection amount is increased due to the increase correction at the time of starting. As a result, when the fuel pressure Pr temporarily decreases, the fuel boost pump 22 is not determined to be abnormal. For this reason, it can prevent erroneous determination that the fuel boost pump 22 is abnormal.

  While embodiments of the invention have been disclosed, it will be apparent to those skilled in the art that changes may be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims.

2 Engine (Internal combustion engine)
9n Combustion chamber 20 Control device for internal combustion engine 22 Fuel boost pump 23 Injector 25 ECU (control device for internal combustion engine)
25A abnormality determination unit 25B abnormality determination threshold setting unit

Claims (3)

A control device for an internal combustion engine, comprising: a fuel boost pump that boosts fuel; and an injector that injects fuel boosted by the fuel boost pump into a combustion chamber of the internal combustion engine,
When fuel injection is performed by the injector while driving the fuel boost pump, the fuel boost pump is abnormal on condition that the fuel pressure boosted by the fuel boost pump is less than an abnormality determination threshold. An abnormality determination unit that determines that there is,
A control device for an internal combustion engine, comprising: an abnormality determination threshold value setting unit that sets the abnormality determination threshold value according to a state of the internal combustion engine.   The control apparatus for an internal combustion engine according to claim 1, wherein the abnormality determination threshold value setting unit sets the abnormality determination threshold value in accordance with a temperature of cooling water of the internal combustion engine. The control apparatus for an internal combustion engine according to claim 2, wherein the abnormality determination threshold value setting unit sets the abnormality determination threshold value lower as the temperature of the cooling water is lower.

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