JP5905795B2 - Fuel pressure control device - Google Patents

Description

  The present invention relates to a fuel pressure control apparatus, and more particularly to a fuel pressure control apparatus that variably controls the fuel supply pressure in a system that supplies fuel to an internal combustion engine mounted on a vehicle.

  In an engine (internal combustion engine) mounted on a vehicle, since it is necessary to suppress exhaust emissions and meet advanced fuel consumption reduction requirements, the fuel injection amount is accurately controlled in a wide dynamic range according to the driving state. Is required. In addition, if fuel vapor is generated in the fuel, the fuel injection amount cannot be controlled with high accuracy. Therefore, in a system that supplies fuel to the engine, the fuel vapor is generated by increasing the fuel pressure when the fuel temperature is high. It is desirable to suppress this effectively. In view of this, a fuel pressure control device has been proposed that variably controls the pressure of fuel supplied to the engine (hereinafter also simply referred to as fuel pressure) in accordance with the operating state of the engine and a requested operation input from a driver.

  Such a fuel pressure control device includes a switching valve that can switch the fuel pressure to high or low by switching the fuel recirculation state from the fuel supply passage to the fuel tank (whether or not recirculation by a low-pressure pressure regulator), the fuel pump drive voltage And a fuel pump capable of changing the discharge pressure by variable control, and when switching the fuel pressure from low pressure to high pressure, a switch command is given to the switching valve after a predetermined time after raising the fuel pump drive voltage (for example, , See Patent Document 1). In this device, even when the load on the fuel pump suddenly increases when the fuel pressure is switched from the low pressure to the high pressure, the shortage of the fuel supply amount due to the load can be effectively suppressed.

  Also, by switching the back pressure of the pressure regulator between atmospheric pressure and intake negative pressure, the control fuel pressure can be switched between high and low, while the fuel pressure control device that switches the rotation speed of the fuel pump between the high speed side and the low speed side, When returning from a high fuel pressure state for high temperature restart etc. to a normal low fuel pressure state, there is one that sets a time difference between switching the fuel pump discharge amount to the low speed side and switching the pressure regulator to the low pressure side (for example, , See Patent Document 2). In this device, since the fuel pump discharge amount is switched to the low speed side and the pressure regulator is switched to the low pressure side step by step, the fuel injection amount from the fuel injection valve is reduced step by step and the air-fuel ratio is reduced. Can be prevented from thinning rapidly.

  Further, when a high fuel pressure command is output to the switching valve for switching the fuel recirculation state, the switching valve malfunctions based on the difference between the detected air-fuel ratio of the air-fuel ratio sensor installed in the engine and the target air-fuel ratio. If there is an abnormality in the switching valve and high fuel pressure cannot be obtained, the intake air amount is selectively limited based on the maximum fuel injection amount for each engine speed in the low fuel pressure state, and excessive lean Those that suppress the state are known (for example, see Patent Document 3).

JP 2010-024852 A JP-A-62-210255 JP 2010-038143 A

  However, in the conventional fuel pressure control device as described above, the load corresponding to the discharge pressure and the discharge amount of the fuel pump and the switching of the fuel pressure switching valve are executed exclusively based on the detected fuel pressure of the fuel pressure sensor. Basically, control was performed in which the load of the fuel pump did not change unless the fuel pressure changed.

  For this reason, normally, there is a delay in switching the discharge pressure and discharge amount of the fuel pump based on the detected fuel pressure of the fuel pressure sensor with respect to the switching of the fuel pressure by the fuel pressure switching valve, and fuel pressure fluctuations are likely to occur at the time of fuel pressure switching. As a result, fuel pressure overshoot and undershoot are likely to occur when the target fuel pressure is switched, fuel consumption (fuel consumption rate) and exhaust purification performance deteriorate, and drivability of vehicles equipped with the engine deteriorates. There was a possibility.

  In addition, when the engine stops at a high temperature and the fuel in the fuel pipe receives heat, the fuel vapor cannot be secured high enough to effectively suppress the generation of fuel vapor against the increase in fuel temperature. Could occur. When fuel vapor is generated, the fuel injection amount cannot be controlled accurately, so that engine stall may occur or the exhaust purification catalyst may overheat due to an increase in the amount of unburned fuel due to misfire. .

  In addition, the electric fuel pump requires a fuel pump drive voltage in terms of performance so that normal discharge performance of the fuel pump can be exhibited even if foreign matter that has passed through the suction side strainer or filter enters the pump operating part. In some cases, it may be necessary to exceed the lower limit voltage. In this case, for example, by providing a pressure reducing valve or the like that increases the amount of recirculation to the fuel tank, it is conceivable that the fuel supply amount is such that fine fuel injection control can be executed with a low injection amount. Since the fuel pressure fluctuation at the time of opening and closing of the valve becomes large, there is a possibility that the actual injection amount is deviated from the target injection amount of the engine.

  Therefore, the present invention provides a fuel pressure control device that can suppress unnecessary fluctuations in the fuel supply pressure when the fuel supply state to the fuel injection portion of the internal combustion engine is switched.

  In order to solve the above problems, the fuel pressure control device according to the present invention is capable of (1) changing the discharge capacity according to the drive voltage, and supplying the fuel in the fuel tank to the fuel injection unit of the internal combustion engine according to the drive voltage. It is possible to switch between an electric fuel pump that discharges to supply the fuel, a valve opening state that exhibits a pressure reducing function that reduces the pressure of fuel supplied to the fuel injection unit, and a valve closing state that stops the pressure reducing function. A pressure control valve that switches to an open / close state required by the switching control signal when the switching control signal is input, and a target pressure of the supplied fuel is variably set according to the operating state of the internal combustion engine, and the target pressure is set to In response, the control for executing the variable control of the drive voltage of the fuel pump that changes the discharge capacity in response to the switching control of the open / close state of the pressure control valve according to the target pressure by the switching control signal. A fuel pressure control device comprising: a mechanism, wherein when the open / close state of the pressure control valve is switched, the control mechanism discharges the fuel pump with respect to a direction in which the pressure of the supplied fuel increases or decreases due to the switching. The switching control signal for requesting the switching to the pressure control valve is changed to the pressure control valve after changing the driving voltage of the fuel pump so that the increase / decrease direction of the pressure of the supplied fuel due to the change in capacity is reversed. It is made to input into a valve, It is characterized by the above-mentioned.

  With this configuration, when the pressure control valve is switched, variable control of the discharge capacity of the fuel pump is started in advance, and switching control of the pressure control valve is started after that. Therefore, even if it takes time to change the supply fuel pressure due to the change in the discharge capacity of the fuel pump with respect to the change in the supply fuel pressure to the fuel injection unit due to the change in the pressure control valve, the pressure control valve is changed over. When a change in the supply fuel pressure due to the control occurs, a change in the supply fuel pressure in the reverse direction can be caused by a change in the discharge capacity of the fuel pump so as to suppress the change. As a result, these changes in the supply fuel pressure cancel each other, and an unnecessary change in the supply fuel pressure at the time of switching the fuel supply state to the fuel injection section is effectively suppressed.

  In the fuel pressure control device of the present invention, (2) the control mechanism lowers the drive voltage so as to reduce the discharge capacity when the pressure control valve is switched from the open state to the closed state. It is preferable that the switching control signal for requesting switching of the pressure control valve to the closed state is input to the pressure control valve.

  With this configuration, an unnecessary change in the supplied fuel pressure at the time of switching of the fuel supply state accompanied by switching of the pressure control valve from the open state to the closed state is effectively suppressed.

  In the fuel pressure control device having the configuration described in (2) above, (3) the control mechanism increases the discharge capacity when the pressure control valve is switched from the closed state to the open state. More preferably, after the drive voltage is increased, the switching control signal for requesting switching of the pressure control valve to the opened state is input to the pressure control valve.

  In this case, an unnecessary change in the supply fuel pressure at the time of switching of the fuel supply state accompanied by switching from the closed state to the open state of the pressure control valve is effectively suppressed.

  In the fuel pressure control apparatus of the present invention, (4) the control mechanism sends the switching control signal to the pressure control valve when a preset delay time has elapsed since the drive voltage of the fuel pump was changed. The delay time is determined by the change in the open / close state of the pressure control valve due to a change in the pressure of the supply fuel to one side in the increase / decrease direction accompanying a change in the discharge capacity of the fuel pump. It is preferable that the pressure is set within a time range in which a change in the fuel pressure to the other side in the increase / decrease direction is suppressed.

  In this case, when a change in the supply fuel pressure due to the switching control of the pressure control valve occurs, a change in the supply fuel pressure in the reverse direction due to a change in the discharge capacity of the fuel pump occurs so as to suppress the change.

  In the fuel pressure control device having the configuration described in (4) above, (5) a variable width of the drive voltage of the fuel pump by the control mechanism when the open / close state of the pressure control valve is switched is the fuel Change of the pressure of the supplied fuel to the other side of the increase / decrease direction accompanying switching of the open / close state of the pressure control valve due to a change of the pressure of the supplied fuel to the one side of the increase / decrease direction due to the change of the discharge capacity of the pump Is preferably set to a value that substantially cancels.

  In this case, when a change in the supply fuel pressure occurs due to the switching control of the pressure control valve, the change is offset by a change in the supply fuel pressure in the reverse direction due to a change in the discharge capacity of the fuel pump. Unnecessary changes in the supply fuel pressure at the time of switching are accurately suppressed.

  In the fuel pressure control device of the present invention, (6) the pressure control valve has a throttle portion that allows a part of the fuel discharged from the fuel pump to pass through when the valve is open, It is preferable to recirculate the fuel that has passed through the throttle portion into the fuel tank.

  With this configuration, the pressure control valve can have a simple configuration that establishes a return passage with a throttle when the valve is opened. Further, the fuel discharged from the fuel pump when the pressure control valve is opened is fueled to the fuel injection unit while being adjusted to the target pressure according to the discharge capacity of the fuel pump and the strength of the throttle in the throttle unit. , Excess fuel returns to the fuel tank. Therefore, only by variably controlling the drive voltage of the fuel pump while the pressure control valve is open, the pressure can be controlled with high accuracy while keeping the fuel supplied to the fuel injection portion at a minute flow rate.

  According to the present invention, when a change in the supply fuel pressure due to the switching control of the pressure control valve occurs, it is possible to cause a change in the reverse direction of the supply fuel pressure due to a change in the discharge capacity of the fuel pump. As a result, it is possible to provide a fuel pressure control device that can suppress unnecessary fluctuations in the fuel supply pressure when the fuel supply state is switched.

It is a schematic block diagram of the fuel supply system of the internal combustion engine for vehicles equipped with the fuel pressure control apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the procedure of the necessity determination process of the reduction valve switching performed with the fuel pressure control apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the procedure of the switching control of the weight reduction valve performed with the fuel pressure control apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the schematic procedure of the fuel pressure feedback control performed with the fuel pressure control apparatus which concerns on one Embodiment of this invention. FIG. 5A shows the switching timing of the reducing valve opening / closing state and pump applied voltage and the switching timing when the reducing valve is switched from the open state to the closed state in the fuel pressure control device according to the embodiment of the present invention. 5 is a timing chart showing a fuel pressure fluctuation suppressing action due to the difference between the two. FIG. 5B is a timing chart showing the switching timing of the reduction valve opening / closing state and the pump application voltage when the reduction valve is switched from the closed state to the opened state, and the fuel pressure fluctuation suppressing action due to the difference in the switching timing. It is. FIG. 6A is a graph for explaining the expansion effect of the control range of the injection amount by switching the fuel pressure supplied to the fuel injection unit in the fuel pressure control apparatus according to the embodiment of the present invention, and the vertical axis represents the injection. The quantity and the horizontal axis show the injection time. FIG. 6 (b) shows the switching control of the open / close state of the reduction valve and the feed pump drive voltage for performing the variable control of the fuel pressure supplied to the fuel injection section in the fuel pressure control apparatus according to one embodiment of the present invention. 6 is a graph for explaining a fuel pressure control mode that is used in combination with the variable control of the supplied fuel pressure by the variable control of FIG. 5, wherein the vertical axis indicates the drive voltage and the horizontal axis indicates the discharge capacity. FIG. 7A shows the switching timing of the reducing valve opening / closing state and pump applied voltage when switching the reducing valve in the fuel pressure control device of the comparative example from the open state to the closed state, and problems of the switching control. It is a timing chart which shows. FIG. 7B shows the switching timing of the reducing valve opening / closing state and the pump applied voltage when switching the reducing valve from the closed state to the opened state in the fuel pressure control device of the comparative example, and the problems of the switching control. It is a timing chart which shows.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram of a fuel supply system for a vehicle internal combustion engine equipped with a fuel pressure control apparatus according to an embodiment of the present invention.

  First, the configuration will be described.

  As shown in FIG. 1, the fuel supply system includes a fuel supply mechanism 20 that supplies fuel from a fuel tank 30 to a fuel injection unit 15 of an engine 10 mounted on a vehicle, and a control that controls the fuel supply mechanism 20. The mechanism 40 is comprised. The control mechanism 40 includes an electronic control unit (hereinafter referred to as ECU) 41 that generates a fuel pressure command signal, and a pressure of fuel supplied to the fuel injection unit 15 (hereinafter referred to as supply fuel pressure) Pf in accordance with the fuel pressure command signal from the ECU 41. And a fuel pressure control circuit (hereinafter referred to as FPC) 42 that variably controls the engine.

  The engine 10 is a multi-cylinder internal combustion engine mounted on an automobile, for example, an in-line 4-cylinder 4-cycle gasoline engine. The engine 10 can output rotational power from a crankshaft (not shown) while consuming fuel in each cylinder 11. A piston (not shown) is accommodated in each cylinder 11 to define a combustion chamber 12, and an intake valve and an exhaust valve (not shown) are mounted to open and close at the operation timing. Further, the engine 10 is provided with a plurality of spark plugs corresponding to the plurality of cylinders 11 so as to be exposed in the corresponding combustion chambers 12, respectively, and an ignition device having an ignition coil for igniting these spark plugs, An electronically controlled throttle motor that variably controls the throttle opening is equipped.

  The engine 10 has an intake passage 14 that branches into a plurality of intake ports 13 corresponding to the plurality of cylinders 11, and fuel can be injected into the plurality of intake ports 13 in the order of combustion of the plurality of cylinders 11. A fuel injection unit 15 is provided. The fuel injection unit 15 includes a plurality of port injection injectors 16 corresponding to the plurality of intake ports 13 and a delivery pipe 17 to which the plurality of injectors 16 are connected by piping.

  The plurality of injectors 16 are provided corresponding to the plurality of cylinders 11 and the intake ports 13, and end portions on the side of the respective injection holes (not shown) are exposed in the corresponding intake ports 13. Although not shown in detail, each injector 16 is driven by a solenoid coil that is excited and controlled by an injection command signal Iq (only one cylinder is shown in FIG. 1), which will be described later, and the solenoid coil. It has a needle valve and a nozzle part. The plurality of injectors 16 are wired to a driver circuit (not shown) on the ECU 41 side so as to be valve-open driven in accordance with an injection command signal Iq from the ECU 41. When these injectors 16 are driven by the injection drive signal Iq for a required injection time in a predetermined order, the fuel accumulated and stored in the delivery pipe 17 is supplied to the intake ports corresponding to the injectors 16 that are sequentially opened. 13 is injected in an amount corresponding to the fuel injection time corresponding to the injection command signal Iq and the fuel pressure in the delivery pipe 17.

  The delivery pipe 17 is made of metal that introduces fuel supplied from the fuel supply mechanism 20 through a fuel pipe 22 (fuel supply passage) and stores a predetermined amount of fuel, and bends according to the pressure of the fuel. Thus, both the function of absorbing the pulsation of the supply fuel pressure Pf and the function of accumulating the fuel pressure necessary for port injection from the injector 16 are provided.

  The fuel supply mechanism 20 includes a feed pump 21, a fuel pipe 22 that connects the discharge port portion (not shown) of the feed pump 21 and the delivery pipe 17, and a fuel provided on the suction port portion (not shown) of the feed pump 21. A filter 23, a relief valve 24 for limiting the pressure of fuel in the fuel pipe 22 to a set upper limit pressure, and an electromagnetic open / close reduction valve capable of returning a part of the fuel in the fuel pipe 22 to the fuel tank 30 25.

  The feed pump 21 is a non-volumetric electric fuel pump that is controlled by the ECU 41 via a fuel pressure control circuit (indicated as FPC in FIG. 1) 42 of the control mechanism 40. For example, a circumferential flow pump (rotary type) Pump).

  Although not shown in detail, this feed pump 21 has an impeller for operating the pump and a built-in motor that drives the pump operating part, and the pump according to the drive voltage and load torque of the built-in motor. By changing at least one of the rotational speed [rpm] and the rotational torque of the impeller for operation, the pressure [kPa] and the flow rate of the discharged fuel per unit time can be changed. That is, when the drive voltage Vp is applied by the FPC 42, the feed pump 21 changes the discharge capacity (discharge pressure and discharge amount) by rotating the impeller for operating the pump according to the drive voltage Vp. This is a variable discharge capacity type fuel pump.

  The fuel filter 23 is composed of a filter medium capable of capturing foreign matters in the fuel sucked into the feed pump 21.

  The relief valve 24 opens when the pressure of the fuel discharged from the feed pump 21 into the fuel pipe 22 rises to reach a preset upper limit pressure, and limits the supply fuel pressure Pf to be lower than the preset upper limit pressure. It has a safety valve function. The set upper limit pressure here is a fuel pressure that is high enough to easily induce fuel leakage from the injector 16, for example, and this set upper limit fuel pressure that is the valve opening set pressure of the relief valve 24 is, for example, It is set to 600 kPa.

  The relief valve 24 is a well-known valve, the details of which are not shown, but a valve seat that forms a discharge port through which a part of the fuel in the fuel pipe 22 can be recirculated into the fuel tank 30, and the valve It has a relief valve element that can open and close the discharge port by engaging and disengaging from the seat, and a valve spring that normally biases the relief valve element in the valve closing direction. When the fuel pressure in the fuel pipe 22 reaches the set upper limit pressure, the urging force in the valve opening direction acting on the relief valve body of the relief valve 24 corresponds to the built-in load of the valve spring that has closed the relief valve body The relief valve 24 is opened by overcoming the urging force.

  The reduction valve 25 has a valve open state in which the fuel from the fuel pipe 22 can be recirculated into the fuel tank 30 through the throttle portion 25a to reduce the flow rate and pressure of the fuel supplied to the fuel injection portion 15, and the fuel. It is an electromagnetic type that can be switched to a closed state that prevents recirculation of the gas. The reduction valve 25 is opened when the amount of fuel consumption is small, such as at least when the engine 10 is idling, and the amount of discharge from the feed pump 21 is larger than the amount of fuel consumption of the engine 10. In addition, surplus fuel (a part of pump discharge fuel; hereinafter referred to as surplus fuel) can be returned to the fuel tank 30. In other words, the reduction valve 25 is configured to stop or reduce the valve opening state in which a decompression function for reducing the fuel pressure Pf supplied to the delivery pipe 17 is exhibited by returning excess fuel into the fuel tank 30 and the decompression function. The pressure control valve is switchable to a closed state in which the fuel pressure Pf supplied to the delivery pipe 17 can be raised and returned.

  The reduction valve 25 includes, for example, a valve body 25v including at least a part of a magnetic material, and a holding cylinder portion that holds the valve body 25v in a movable state in the axial direction and introduces fuel from the fuel pipe 22 side. 25b, a throttle part 25a provided on the fuel discharge port side of the holding cylinder part 25b, and a coil 25c supported by the holding cylinder part 25b and capable of biasing the valve body 25v away from the throttle part 25a. Have. Further, an annular valve seat (not shown in detail) on which the valve body 25v can be seated is formed in the holding cylinder portion 25b. When the valve body 25v is seated on the valve seat, the valve body is closed, and the valve body When 25v separates from the valve seat, the fuel discharge passage 26 whose partial passage sectional area is reduced by the throttle portion 25a is opened.

  The reduction valve 25 is configured to selectively excite the coil 25c in accordance with a voltage signal supplied as a switching control voltage Vs from the FPC 42, and to switch to an open / closed state requested by the switching control signal Vs. Here, when the feed pump 21 is operated, the valve body 25v is urged in a valve closing direction in which the valve seat 25v is seated on the valve seat by a fuel pressure or the like from the inside of the fuel pipe 22 (a valve spring for valve closing may be provided separately) Although the description will be made assuming that the valve body 25v is urged by the coil 25c in the valve opening direction so as to separate from the valve seat, the valve 25v is constantly urged in the valve opening direction by an elastic member such as a coil spring. The electromagnetic force that urges the valve body 25v in the valve closing direction may be generated by the coil 25c.

  The fuel tank 30 has a predetermined volume and can be replenished with fuel from the outside.

  The control mechanism 40 variably sets the target fuel pressure Pc (target pressure of fuel supplied to the fuel injection unit 15) according to the operating state of the engine 10, and changes the discharge capacity of the feed pump 21 according to the target fuel pressure Pc. The variable control of the drive voltage Vp and the switching control of the open / close state of the reduction valve 25 according to the target fuel pressure Pc by the switching control signal Vs are executed.

  Specifically, the ECU 41 of the control mechanism 40 calculates the target fuel pressure Pc based on the operation state of the vehicle and the engine 10 and the requested operation input from the driver. Further, a fuel pressure control circuit (referred to as FPC in FIG. 1) 42 of the control mechanism 40 cooperates with the ECU 41 to discharge the feed pump 21 by the variable control of the drive voltage Vp (discharge pressure and discharge pressure). In addition to variably controlling the discharge amount), feedback control is performed to cause the fuel pressure in the delivery pipe 17 to follow the target fuel pressure Pc required by the ECU 41 by executing switching control of the opening / closing state of the reduction valve 25. It is like that.

  The ECU 41 captures an actual fuel pressure signal corresponding to an actual fuel pressure Pr (hereinafter referred to as an actual fuel pressure) Pr in the delivery pipe 17 from a fuel pressure sensor 51 mounted on the delivery pipe 17 and is installed in the vehicle or the engine 10. The sensor information of the other sensor groups is taken in, and the fuel injection amount of the engine 10 corresponding to the operating state of the engine 10 and the requested operation input from the driver is calculated with reference to a map or the like, and the fuel injection amount corresponds The target fuel pressure Pc is calculated.

  The fuel pressure sensor 51 detects the fuel pressure (Pf in FIG. 1) in the delivery pipe 17 on the low pressure side. Further, the other sensor group mentioned here includes, for example, an accelerator opening sensor 52, an air flow meter 53, a crank angle sensor 54, a water temperature sensor 55, and the like. The accelerator opening sensor 52 detects the depression rate of an accelerator pedal (not shown) mounted on the vehicle as the accelerator opening (Accp in FIG. 1), and the air flow meter 53 detects the intake air amount (in FIG. 1). Qa) is detected. The crank angle sensor 54 detects a crank angle (CA in FIG. 1) from which the engine rotation speed of the engine 10 can be calculated, and the water temperature sensor 55 detects the coolant temperature (Thw in FIG. 1) of the engine 10. . It goes without saying that the other sensor group may include a known intake air temperature sensor, throttle opening sensor, air-fuel ratio sensor, oxygen sensor, intake cam angle sensor, exhaust cam angle sensor, and the like.

  The fuel pressure control device in the present embodiment includes a feed pump 21, a relief valve 24 and a reduction valve 25 of the fuel supply mechanism 20, an ECU 41 and an FPC 42 of the control mechanism 40, a fuel pressure sensor 51, and other sensor groups. Has been.

  More specifically, the ECU 41 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a backup memory (for example, a backup RAM or a nonvolatile memory). In addition, an input interface circuit and an output interface circuit are included.

  The input interface circuit of the ECU 41 captures an ON / OFF signal of an ignition switch of the vehicle and captures sensor information from the various sensors 51 to 55 described above. The output interface circuit of the ECU 41 is connected to an injector 16, an electronic throttle motor, the above-described ignition device, and the like via a driver circuit (not shown) and an FPC 42.

  The ECU 41 can execute known electronic throttle control, fuel injection amount control, ignition timing control, fuel cut control, and the like by executing a control program stored in the ROM. For example, the ECU 41 calculates the basic injection amount required for each combustion based on the intake air amount detected by the air flow meter and the engine speed detected by the crank angle sensor, and further according to the operating state of the engine 10. The fuel injection amount subjected to various corrections, air-fuel ratio feedback correction, and the like can be calculated, and the injector 16 corresponding to the injection time corresponding to the fuel injection amount can be driven to open.

  Further, the ECU 41 sets the target fuel pressure at a high temperature restart when the engine 10 is started in a state where the coolant temperature of the engine 10 is higher than a predetermined temperature, or when returning from the fuel cut state to the normal operation state. Pc is set to a high-pressure side target fuel pressure value PH (see FIG. 6A), for example, 530 kPa.

  When the engine 10 is restarted from a so-called idling stop state in which the engine 10 is automatically stopped when the vehicle is temporarily stopped, for example, when the engine is restarted at a high temperature, the power unit is a vehicle equipped with a hybrid traveling drive unit. For example, when the engine 10 is temporarily stopped and then restarted. The fuel cut state refers to a fuel injection from the injector 16 in a predetermined operating state of the engine 10, for example, when the accelerator opening is substantially zero when the vehicle is decelerated or downhill, and the engine 10 is in a crank rotation state. Is temporarily stopped, and the fuel cut is executed while the ECU 41 determines that the fuel cut is possible based on various sensor information.

  When the engine 10 is in the idling stop state, the cooling of the engine 10 by cooling water or cooling air is stopped, so that the temperature of the fuel in the fuel supply path such as the delivery pipe 17 on the low pressure side becomes high and depends on the temperature. Since the saturated vapor pressure of the fuel increases, fuel vapor is likely to occur. Even in the fuel cut state, the fuel flow is stopped in the fuel supply path such as the delivery pipe 17 and the low temperature fuel from the fuel tank 30 side is not introduced. It becomes higher, the saturated vapor pressure of the fuel depending on the temperature becomes higher, and fuel vapor tends to be generated. If fuel vapor is generated in the fuel in the fuel supply path, normal fuel injection amount control cannot be performed, and the exhaust emission of the engine 10 may deteriorate or the operating state of the engine 10 may deteriorate. is there. Therefore, in the present embodiment, when the saturated vapor pressure of the fuel becomes high, the ECU 41 sets the target fuel pressure Pc on the high pressure side to suppress the generation of fuel vapor.

  The target fuel pressure value PH on the high pressure side is used to ensure the required fuel supply pressure or to inject fuel when the engine 10 is restarted at a high temperature, when returning from a fuel cut state for a long time, or during high-load operation. This is the fuel pressure that can bias the control range of the amount toward the high fuel injection amount side.

  On the other hand, when the engine 10 is in an operation region where the engine 10 is exclusively in partial load operation, for example, the ECU 41 has a low pressure side that can suppress the generation of fuel vapor in the fuel supply path due to heat generation of the engine 10 in the operation region. A target fuel pressure value PL (see FIG. 6A), for example, 300 kPa is set.

  The target fuel pressure value PL on the low pressure side is a fuel pressure that can suppress the power consumption of the feed pump 21 during the operation period of the mode region described above and can bias the control range of the fuel injection amount toward the low fuel injection amount.

  The ECU 41 sets the target fuel pressure Pc as described above to the operating state of the engine 10, an acceleration request from the driver, a shift operation, and other required operation inputs during a predetermined period of time during the operation period of the engine 10 or under the ignition ON state. And the target fuel pressure Pc is output to the FPC 42.

  The FPC 42 to which the target fuel pressure Pc from the ECU 41 is input is a deviation between the fuel pressures Pc and Pr so that the input target fuel pressure Pc and the actual fuel pressure Pr in the delivery pipe 17 detected by the fuel pressure sensor 51 coincide. Accordingly, the drive voltage Vp of the feed pump 21 is feedback controlled. Then, according to the change of the driving voltage Vp from the FPC 42, the rotational speed and rotational torque (of course, both speed and torque may be sufficient) of the impeller for pump operation of the feed pump 21 change, and the discharge of the feed pump 21 By changing the capacity, the actual fuel pressure Pr in the delivery pipe 17 on the low pressure side changes in a direction to follow the target fuel pressure Pc.

  As shown in FIG. 6A, when the supply fuel pressure Pf is controlled to the high target fuel pressure value PH, and when the supply fuel pressure Pf is controlled to the low target fuel pressure value PL, the injector 16 is set. Even if the injection time τ to be opened is the same, the fuel injection amount is different. For example, the supply fuel pressure Pf is lower than the minimum fuel injection amount qb when the injection time τ is controlled to the minimum injection time τ1 while the supply fuel pressure Pf is controlled to the high-pressure side target fuel pressure value PH. The minimum fuel injection amount qa when the injection time τ is controlled to the minimum injection time τ1 while being controlled to the value PL is a minute amount. Further, the maximum fuel injection amount qd when the injection time τ is controlled to the maximum injection time τ2 in a state where the supply fuel pressure Pf is controlled to the target fuel pressure value PH on the high pressure side is the target fuel pressure value on which the supply fuel pressure Pf is the low pressure side. In the state controlled by PL, the injection time τ becomes sufficiently larger than the maximum fuel injection amount qc when the injection time τ is controlled to the maximum injection time τ2. Therefore, the fuel injection amount is changed to the minimum fuel injection amount qa by switching the target fuel pressure Pc from the high pressure side to the low pressure side or vice versa between the fuel injection amounts qb and qc in FIG. To a maximum fuel injection amount qd.

  On the other hand, the drive voltage of the feed pump 21 is controlled within a voltage variable range that is not less than a preset lower limit voltage Vmin for preventing lock. The lower limit voltage Vmin referred to here is sufficient rotation to prevent the impeller for pump operation of the feed pump 21 from being locked even if foreign matter passing through the fuel filter 23 is sucked into the feed pump 21. This is a drive voltage that can generate torque. That is, the lower limit voltage Vmin is set to a voltage value that can prevent the rotation of the feed pump 21 due to the suction of the solid matter in the fuel. The upper limit voltage Vmax is set based on the maximum discharge amount and the maximum fuel pressure required for the feed pump 21.

  As described above, since the variable range of the drive voltage Vp of the feed pump 21 is limited, and particularly the lower limit voltage Vmin for preventing lock is set, the lower limit of the discharge capacity of the feed pump 21 cannot be set small. Therefore, if the drive voltage Vp of the feed pump 21 is only variably controlled so that the actual fuel pressure Pr follows the target fuel pressure Pc, the drive voltage Vp falls outside the voltage variable range before the actual fuel pressure Pr reaches the target fuel pressure Pc. May occur.

  Therefore, the ECU 41 remains in the closed state of the reducing valve 25 even when the drive voltage Vp of the feed pump 21 is controlled to the lower limit voltage Vmin side in the voltage variable range and the discharge pressure of the feed pump 21 becomes relatively low. Then, when the drive voltage Vp can reach the lower limit voltage Vmin before the actual fuel pressure Pr reaches the target fuel pressure Pc, the control for switching the reduction valve 25 from the closed state to the open state is executed. Further, the ECU 41 remains in the open state of the reduction valve 25 even when the drive voltage Vp of the feed pump 21 is controlled to the upper limit voltage Vmax side within the voltage variable range and the discharge pressure of the feed pump 21 becomes relatively high. Then, when the drive voltage Vp can reach the upper limit voltage Vmax before the actual fuel pressure Pr reaches the target fuel pressure Pc, the switching control of the reduction valve 25 from the open state to the closed state is executed. Yes.

Specifically, the ECU 41 sets the drive voltage Vp of the feed pump 21 to the lower limit voltage Vmin side from the center voltage in the variable range when the reduction valve 25 is closed, as indicated by the dashed arrow in FIG. when lowered to the judges whether the driving voltage Vp prior further lowering the driving voltage Vp remains closed weight loss valve 25 to reach the target fuel pressure Pc is obtained will reach the lower limit voltage Vmin. The decreased driving voltage Vp to a predetermined voltage value Va, the driving voltage Vp of the feed pump 21 is obtained will reach the lower limit voltage Vmin determination result, the switching control from the closed state of the reduction valve 25 to the open state Run.

  In the open state of the reduction valve 25, the fuel pressure Pf supplied to the fuel injection unit 15 is relatively lower than when the reduction valve 25 is in the closed state, and the delivery pipe 17 with respect to the change in the drive voltage Vp. The rate of change of the fuel pressure P that can be supplied to the fuel becomes small. Therefore, the fuel injection amount control by the opening and closing of the injector 16 in the fuel injection unit 15 can be executed finely and with high accuracy.

Further, as indicated by a two-dot chain line in FIG. 6B, the ECU 41 increases the drive voltage Vp of the feed pump 21 from the center voltage to the upper limit voltage Vmax side in the variable range when the reduction valve 25 is opened. In some cases, it is determined whether or not the drive voltage Vp can reach the upper limit voltage Vmax before the target fuel pressure Pc is reached if the drive voltage Vp is further increased while the reduction valve 25 is still open. Then, it increases the driving voltage Vp to a predetermined voltage value Vb, and the driving voltage Vp of the feed pump 21 is obtained will reach the upper limit voltage Vmax determination result, the switching control from the open state of the reduction valve 25 to the closed state Run.

  In the closed state of the reducing valve 25, the fuel pressure Pf supplied to the fuel injection unit 15 is relatively increased as compared to when the reducing valve 25 is in the opened state, and the delivery pipe 17 is changed with respect to the change in the driving voltage Vp. The rate of change of the fuel pressure P that can be supplied to the fuel increases. Therefore, the fuel injection amount in the fuel injection unit 15 can be sufficiently increased when necessary.

  Further, when the ECU 41 executes the switching control from the open state to the closed state of the reduction valve 25, first, as shown in FIG. 5A, the ECU 41 is driven to reduce the discharge capacity of the feed pump 21. Voltage switching for lowering the voltage Vp is executed. Then, at the time tb when a preset delay time Td1 has elapsed from the switching time ta of the drive voltage Vp, voltage switching of the switching control signal Vs that requests switching of the reduction valve 25 to the closed state (for example, the voltage is set to OFF). The switching control signal Vs is input to the reduction valve 25. The switching width ΔV1 (variable width of the driving voltage) of the driving voltage Vp here can be offset against the fuel pressure increase (deviation from the target fuel pressure Pc) accompanying the switching of the reduction valve 25 to the closed state. Is set to a differential voltage value that lowers the discharge capacity of the feed pump 21 so as to cause a change in the fuel pressure in the depressurizing direction.

  In addition, when the ECU 41 executes the switching control from the closed state to the open state of the reduction valve 25, first, as shown in FIG. 5B, the ECU 41 is driven to increase the discharge capacity of the feed pump 21. The voltage switching for increasing the voltage Vp is executed. Then, the ECU 41 switches the voltage of the switching control signal Vs for requesting switching to the valve open state of the reduction valve 25 at the time tb when a preset delay time Td2 has elapsed from the switching time ta of the drive voltage Vp (for example, voltage The switching control signal Vs is input to the reduction valve 25. The switching width ΔV2 (variable width of the driving voltage) of the driving voltage Vp here can be offset with respect to the fuel pressure drop (deviation from the target fuel pressure Pc) accompanying the switching of the reduction valve 25 to the valve open state. Is set to a differential voltage value that increases the discharge capacity of the feed pump 21 so as to cause a change in fuel pressure in the boosting direction.

  As described above, when the ECU 41 and the FPC 42 of the control mechanism 40 switch the opening / closing state of the reduction valve 25, the increase or decrease in the supply fuel pressure due to the change in the discharge capacity of the feed pump 21 with respect to the increase or decrease direction of the supply fuel pressure due to the switching. The switching control signal is input to the reduction valve 25 after the drive voltage Vp of the feed pump 21 is changed in advance so that the direction is reversed.

  The time point tb when the delay time Td has elapsed from the switching time point ta of the drive voltage Vp can be detected by the timer function of the ECU 41. Further, the delay time Td may be set as different delay times Td1 and Td2 that are optimal for the respective switching directions of the reduction valve 25, or may be set as the same delay time Td. In the former case, the optimum delay times Td1 and Td2 for switching the reduction valve 25 are preferably set as delay times with a high probability that the fluctuation range of the actual fuel pressure Pr at the time of switching is the smallest.

  Here, the ECU 41 and the FPC 42 of the control mechanism 40 cause the switching control signal to be input to the reduction valve 25 when a preset delay time Td1 or Td2 elapses after the drive voltage Vp of the feed pump 21 is changed. It has become. In addition, the delay time Td1 or Td2 is used to switch the opening / closing state of the reduction valve 25 by changing the supply fuel pressure to one side (for example, increasing or decreasing) in accordance with the change in the discharge capacity of the feed pump 21. Accordingly, the pressure is set within a time range in which the change of the pressure of the supplied fuel to the other side (for example, the decrease side or the increase side) is suppressed. Further, the variable widths V1 and V2 of the drive voltage of the feed pump 21 by the control mechanism 40 when switching the opening / closing state of the reduction valve 25 are changed to one side in the increase / decrease direction of the supply fuel pressure accompanying the change in the discharge capacity of the feed pump 21. Due to the change, the value is set such that the change in the increase / decrease direction of the supplied fuel pressure accompanying the switching of the open / close state of the reduction valve 25 is substantially offset.

  As described above, when the engine 10 is operated in a state where the coolant temperature of the engine 10 is higher than the predetermined temperature, the control mechanism 40 sets the fuel pressure Pf supplied to the delivery pipe 17 from the above-described set upper limit pressure. The pressure can be changed within a low-pressure fuel pressure control range (here, a fuel pressure range of 300 kPa to 530 kPa), and the relief valve 24 is maintained in a closed state exclusively during such operation of the engine 10.

  Further, the ECU 41 determines the sensor information during operation of the engine 10 based on sensor information from the various sensors 51 to 55 and setting values or map information stored in advance in a ROM or backup memory (hereinafter referred to as ROM). The load state is repeatedly determined, and the target fuel pressure is set to a target fuel pressure value PL on the low pressure side or a fuel pressure close thereto in the normal partial load operation state. On the other hand, the ECU 41 sets the target fuel pressure to the target fuel pressure value PH on the high-pressure side or a fuel pressure close thereto when the engine 10 is restarted at a high temperature, returned from the fuel cut state, or immediately before the engine 10 is stopped. It has become. For this reason, the set values stored in the ROM or the like of the ECU 41 include at least the set values of the target fuel pressure value PH on the high pressure side and the target fuel pressure value PL on the low pressure side that define the fuel pressure control range by the control mechanism 40. The map information stored in includes a map for determining the operating load and controlling the fuel pressure according to the determination result.

  In addition, when the feed pump 21 is controlled to the specific voltage value Va, the FPC 42 has surplus fuel other than the fuel injected from the fuel injection unit 15 among the fuel discharged from the feed pump 21 (pump discharge amount and fuel injection unit). The valve opening time of the reducing valve 25 is controlled so that the difference in fuel consumption at 15) is recirculated into the fuel tank 30.

  Further, the FPC 42 is provided with a voltage detection unit that detects a terminal voltage of the built-in motor of the feed pump 21 and a current detection unit that detects a current flowing through the built-in motor of the feed pump 21. The FPC 42 controls the drive voltage Vp applied to the built-in motor of the feed pump 21 according to the deviation between the target fuel pressure Pc from the ECU 41 and the actual fuel pressure Pr detected by the fuel pressure sensor 51, or for abnormality diagnosis. A diagnostic signal (Diag signal in FIG. 1) corresponding to the operating state of the built-in motor of the feed pump 21 can be supplied to the ECU 41.

  The FPC 42 is supplied with power from a battery, and an ECU 41 is communicably connected thereto. Further, the FPC 42 incorporates a switching element (not shown) or the like for variably controlling the drive voltage Vp applied to the built-in motor of the feed pump 21 or the energy supplied to the built-in motor of the feed pump 21.

  Next, the fuel pressure control in this embodiment and the effect | action by it are demonstrated.

  In the present embodiment configured as described above, the target fuel pressure Pc is calculated by the control mechanism 40 according to the operation state of the vehicle and the engine 10 and the requested operation input from the driver, and is detected by the fuel pressure sensor 51. In order to control the actual fuel pressure Pr to the target fuel pressure Pc, variable control of the drive voltage Vp of the feed pump 21 is repeatedly executed, and switching control of the reduction valve 25 is executed when necessary.

  2 to 4 show a plurality of control programs executed for such fuel pressure control. These processes are repeatedly executed at respective control cycles set in advance during operation of the engine 10.

  In the first control program shown in FIG. 2, first, the fuel consumption per predetermined time of the engine 10 according to the operating state of the engine 10 and the requested operation input from the driver (the required discharge capacity of the feed pump 21 may be used. ) Is calculated based on the detection information of the various sensors 51 to 55, the map information, and the like (step S11).

  Next, after the target fuel pressure Pc corresponding to the required fuel consumption is calculated (step S12), it is determined whether or not the target fuel pressure Pc is less than the switching fuel pressure Pth that requires switching of the open / close state of the reduction valve 25. It is determined (step S13).

At this time, if the calculated target fuel pressure Pc is less than the switching fuel pressure Pth (YES in step S13 ), then , when the drive voltage Vp is changed to a voltage value necessary to obtain the target fuel pressure Pc, It is determined whether or not the specific voltage value Vb on the upper limit voltage Vmax side is reached (Vp = Vb and the voltage cannot be increased any more) (step S14). When the drive voltage Vp reaches the specific voltage value Vb (YES in step S14), a switch request flag from the open state to the closed state of the reduction valve 25 is set (step S15).

On the other hand, if the target fuel pressure Pc is not less than the switching fuel pressure Pth (NO in step S13), it is first determined whether or not the target fuel pressure Pc is the switching fuel pressure Pth (step S16) .

At this time, if the target fuel pressure Pc is the switching fuel pressure Pth (YES in step S16), since the switching control of the reduction valve 25 is being performed, the current process is terminated.

If the target fuel pressure Pc is not the switching fuel pressure Pth (NO in step S16), then when the drive voltage Vp is changed to a voltage value necessary to obtain the target fuel pressure Pc, the specific voltage value on the lower limit voltage Vmin side It is determined whether or not Va is reached (Vp = Va and the voltage cannot be further reduced) (step S17). When the drive voltage Vp reaches the specific voltage value Va (YES in step S17), after a flag for requesting switching from the closed state to the open state of the reducing valve 25 is set (step S18), This process is terminated.

  In other cases, that is, when the target fuel pressure Pc is less than the switching fuel pressure Pth but the driving voltage Vp does not reach the specific voltage value Vb, or when the target fuel pressure Pc exceeds the switching fuel pressure Pth but the driving voltage Vp becomes the specific voltage value Va. If not, switching of the reduction valve 25 is not necessary, and after the switching request flag is reset (step S19), the current process ends.

  Here, when the switching request flag is set, it means that the switching request flag is set to 1 (or ON), for example, and when the switching request flag is reset, the switching request flag is 0 (or OFF). ) Is set.

  In the second control program shown in FIG. 3, first, it is determined whether or not the switching request flag is set (step S21), and the switching request flag that requires switching of the open / close state of the reduction valve 25 is set. If this is the case (YES in step S21), it is then determined whether or not switching of the reduction valve 25 from the open state to the closed state is necessary (step S22).

  At this time, if it is necessary to switch the reducing valve 25 from the open state to the closed state (YES in step S22), the drive voltage Vp is then plotted so as to reduce the discharge capacity of the feed pump 21 by a predetermined amount. The variable voltage control for reducing the switching width ΔV1 shown in FIG. 5A is executed (step S23).

  Next, the ECU 41 uses the timer function to wait until a delay time Td set in advance from the switching time ta of the drive voltage Vp, for example, a delay time Td1 optimum for switching the valve 25 from the open state to the closed state elapses. It becomes. Then, at the time tb when the delay time Td1 elapses, voltage switching of the switching control signal Vs that requests switching of the reducing valve 25 to the closed state (for example, switching to turn off the voltage) is executed, thereby reducing the reducing valve. 25 is switched from the open state to the closed state (step S24). It should be noted that immediately after switching of the drive voltage Vp, until the delay time Td1 elapses, the determination process of whether or not the delay time Td1 has elapsed is repeated, and when the determination result is YES, the voltage of the switching control signal Vs is switched. Needless to say, it may be executed.

  On the other hand, if the determination result in step S22 is NO, that is, if it is necessary to switch the reduction valve 25 from the closed state to the open state, the discharge capacity of the feed pump 21 in the next step S25. The variable voltage control is executed to increase the drive voltage Vp by the switching width ΔV2 shown in FIG. Next, the ECU 41 uses the timer function to wait until a preset delay time Td from the switching time ta of the drive voltage Vp, for example, the optimum delay time Td2 for switching the valve 25 from the closed state to the open state has elapsed. It becomes. Then, at the time tb when the delay time Td2 elapses, voltage switching (for example, switching to voltage ON) of the switching control signal Vs that requests switching of the reducing valve 25 to the valve open state is executed, thereby reducing the reducing valve 25. Is switched from the closed state to the open state (step S26).

  If it is in the reset state of the switching request flag that does not require switching of the opening / closing state of the reduction valve 25 in the first switching request flag determination step S21 (in the case of NO in step S21), FIG. (Step S27), and the current process is terminated.

  The third control program shown in FIG. 4 executes fuel pressure feedback control.

  In this control, first, the actual fuel pressure Pr is detected based on the detection signal from the fuel pressure sensor 51 (step S31).

  Next, the fuel pressure error ΔPe (= Pc−Pr) that is the deviation between the actual fuel pressure Pr and the target fuel pressure Pc is 0 [kPa] or a preset 0 [kPa] in the nearby dead zone region, or the fuel pressure It is determined whether the error ΔPe becomes a significant positive or negative pressure value (step S32).

  When the fuel pressure error ΔPe is a significant positive pressure value (ΔPe> 0 [kPa]), voltage control for increasing the drive voltage Vp of the feed pump 21 according to the fuel pressure error ΔPe is performed (step S33). When the fuel pressure error ΔPe is a significant negative pressure value (ΔPe <0 [kPa]), voltage control is performed to reduce the drive voltage Vp of the feed pump 21 according to the fuel pressure error ΔPe (step S34). On the other hand, when the fuel pressure error ΔPe is within 0 [kPa] or a preset dead zone in the vicinity of 0 [kPa], voltage control for holding the drive voltage Vp of the feed pump 21 is performed (step S35).

  The drive voltage Vp of the feed pump 21 is thus feedback-controlled so that the fuel pressure error ΔPe approaches 0 [kPa] and the actual fuel pressure Pr in the delivery pipe 17 follows the target fuel pressure Pc.

  In the present embodiment in which the control as described above is executed, when the reduction valve 25 is switched from the open state to the closed state, as shown in FIG. When the delay time Td1 elapses after the drive voltage Vp is lowered so as to reduce the discharge capacity, the switching control signal Vs for switching the reduction valve 25 to the closed state is input to the reduction valve 25. Therefore, when it is difficult to make the actual fuel pressure Pr follow the target fuel pressure Pc quickly and accurately by only the fuel pressure feedback control at the time of switching of the weight reducing valve 25, the speed is quickly increased by increasing or decreasing the pump load prefetching the effect of switching the weight reducing valve 25. It is possible to perform switching control such as adding feedforward control. As a result, the increase ΔPsw of the actual fuel pressure Pr caused by the switching of the reduction valve 25 and the decrease ΔPmd of the actual fuel pressure Pr caused by the switching to the discharge capacity lowering side of the feed pump 21 cancel each other. It is possible to perform switching control that effectively suppresses the change in the actual fuel pressure Pr accompanying switching of the open / close state.

  Further, when the reduction valve 25 is switched from the closed state to the open state, the drive voltage Vp is first raised to increase the discharge capacity of the feed pump 21 as shown in FIG. 5B. At the time tb when the delay time Td2 elapses from the time ta, the switching control signal Vs for switching the reduction valve 25 to the open state is input to the reduction valve 25. Therefore, by increasing the drive voltage Vp of the feed pump 21 first and delaying the switching of the reducing valve 25 to the opened state, the switching of the reducing valve 25 from the opened state to the closed state is performed. Similarly, switching control can be performed in which feed-forward control for quickly suppressing the influence of switching of the reduction valve 25 is added. As a result, the decrease ΔPsw of the actual fuel pressure Pr caused by the switching of the reduction valve 25 and the increase ΔPmd of the actual fuel pressure Pr caused by the switching to the discharge capacity increase side of the feed pump 21 cancel each other. The change in the actual fuel pressure Pr accompanying the switching of the open / close state is effectively suppressed.

  Thus, in the present embodiment, when the pressure control valve is switched, variable control of the discharge capacity of the feed pump 21 is started in advance, and switching control of the reduction valve 25 is started later than that. Therefore, it takes time for the change in the actual fuel pressure Pr caused by the change in the discharge capacity of the feed pump 21 to the change in the supply fuel pressure (actual fuel pressure Pr) to the fuel injection unit 15 caused by the change of the reduction valve 25. Even so, the change in the actual fuel pressure Pr due to the switching control of the reduction valve 25 is substantially canceled and suppressed by the change in the supply fuel pressure in the reverse direction due to the change in the discharge capacity of the feed pump 21.

  5A and 5B, when the fuel supply state is switched with the switching of the reduction valve 25, regardless of the switching direction of the opening / closing state of the reduction valve 25, as shown by the fuel pressure Pr indicated by a solid line in FIG. It is possible to quickly and accurately suppress the change in the supplied fuel pressure Pf and sufficiently suppress the change in the actual fuel pressure Pr. Therefore, for example, even when the target fuel pressure Pc is switched between the target fuel pressure values PH and PL on the high pressure side and the low pressure side, overshoot and undershoot are less likely to occur when the actual fuel pressure Pr is changed, and fuel consumption (fuel) Consumption rate) and exhaust purification performance can be prevented, and the drivability of a vehicle equipped with the engine 10 can be prevented from deteriorating.

  In particular, in the present embodiment, the delay times Td1 and Td2 are associated with the switching of the open / close state of the reduction valve 25 due to a change in the supply actual fuel pressure Pr in the increasing direction or decreasing direction accompanying the change in the discharge capacity of the feed pump 21, respectively. It is set within a time range in which a change in the decreasing direction or increasing direction of the supplied actual fuel pressure Pr is suppressed. Therefore, when a change in the supply fuel pressure due to the switching control of the reduction valve 25 occurs, a change in the supply fuel pressure in the reverse direction due to a change in the discharge capacity of the feed pump 21 occurs so as to suppress the change.

  In addition, the variable widths V1 and V2 of the drive voltage of the feed pump 21 by the control mechanism 40 when the open / close state of the reduction valve 25 is switched are increased in the supply actual fuel pressure Pr accompanying the change in the discharge capacity of the feed pump 21 or The change in the decreasing direction is set to a value that substantially offsets the change in the decreasing or increasing direction of the actual fuel pressure Pr that accompanies switching of the open / close state of the reduction valve 25. As a result, when the change in the actual fuel pressure Pr due to the switching control of the reduction valve 25 is about to occur, the change is offset by the change in the fuel pressure in the reverse direction due to the change in the discharge capability of the feed pump 21. Unnecessary changes in the supply fuel pressure at the time of switching the state are accurately suppressed.

  Incidentally, the change in the fuel pressure when the switching of the driving voltage Vp and the voltage switching of the switching control signal Vs of the reduction valve 25 corresponding to the switching so as to reduce the discharge capacity of the feed pump 21 are performed at the same timing is shown in FIG. It will fluctuate as illustrated in a) and FIG. 7 (b).

  As shown in FIGS. 7A and 7B, when the opening / closing state of the reducing valve 25 is switched, the driving voltage Vp and the voltage switching of the switching control signal Vs of the reducing valve 25 corresponding thereto are switched. Are executed at the same timing, the actual fuel pressure Pr starts to change suddenly in a short time due to the switching of the reduction valve 25, but it is based on the switching of the discharge capacity accompanying the switching of the drive voltage Vp of the feed pump 21 and the fuel pressure feedback control. It takes a relatively long time to change the fuel pressure. Therefore, the actual fuel pressure Pr temporarily increases when the reduction valve 25 is switched to the closed state, and the actual fuel pressure Pr decreases temporarily when the reduction valve 25 is switched to the valve open state. The fuel pressure is likely to fluctuate.

  As described above, in the present embodiment, even when the drive voltage Vp of the feed pump 21 is controlled to the lower limit voltage Vmin side in the voltage variable range and the discharge pressure of the feed pump 21 is relatively low, If the drive voltage Vp can reach the lower limit voltage Vmin before the target fuel pressure Pc is reached with the reduction valve 25 closed, switching control from the closed state to the open state of the reduction valve 25 is executed. Is done. Accordingly, in the opened state of the reduction valve 25, the fuel pressure Pf supplied to the fuel injection unit 15 is relatively decreased as compared with when the reduction valve 25 is in the closed state. The injection amount control can be executed finely and with high accuracy.

  In addition, even when the drive voltage Vp of the feed pump 21 is controlled to the upper limit voltage Vmax side in the voltage variable range and the discharge amount of the feed pump 21 becomes a relatively high flow rate, the reduction valve 25 is in the open state. If the drive voltage Vp can reach the upper limit voltage Vmax before reaching the target fuel pressure Pc, the control for switching the reduction valve 25 from the opened state to the closed state is executed. Therefore, in the closed state of the reduction valve 25, the supply fuel pressure Pf and the supply flow rate to the fuel injection unit 15 are relatively increased as compared to when the reduction valve 25 is in the open state. The fuel injection amount at 15 can be increased sufficiently.

  In addition, in the present embodiment, the reduction valve 25 can be simply configured to open and establish the throttled return passage 26 when the reduction valve 25 is opened. When the reduction valve 25 is in the open state, the discharge from the feed pump 21 is possible. A part of the fuel to be recirculated into the fuel tank 30 with a recirculation amount corresponding to the discharge capacity of the feed pump 21 and the strength of the throttling in the throttling portion 25a. Therefore, the supply fuel pressure Pf to the fuel injection unit 15 is adjusted according to the discharge capacity of the feed pump 21 and the throttle strength in the throttle unit 25a.

  In particular, in the present embodiment, when the fuel injection amount in the fuel injection unit 15 is small relative to the discharge amount of the feed pump 21 controlled to the specific voltage value Va on the lower limit voltage Vmin side, the surplus is reduced by the reduction valve 25. By recirculating the fuel into the fuel tank 30, the fuel supply amount to the fuel injection unit 15 can be adjusted to a sufficiently low fuel pressure while being limited to an appropriate amount. Therefore, when the fuel injection amount in the fuel injection unit 15 is increased, the fuel pump can be operated at a high discharge capacity, but the feed pump 21 is driven on the lower limit voltage Vmin side. The flow rate and pressure of the fuel supplied to the section 15 can be sufficiently reduced. In addition, it is possible to eliminate the need to recirculate the fuel that has been supplied to the fuel injection unit 15 and whose temperature has risen to the fuel tank 30.

  In the present embodiment, the lower limit voltage Vmin of the drive voltage Vp of the feed pump 21 is set to a voltage value that can prevent the rotation of the feed pump 21 due to the suction of solid matter in the fuel. Even if foreign matter that has passed through and the like increases the driving load of the pump rotor of the feed pump 21, the rotation of the feed pump 21 can be prevented and the power consumption of the feed pump 21 can be kept low. become.

  Further, in the present embodiment, variable control of the drive voltage Vp of the feed pump 21 and switching control of the open / close state of the reduction valve 25 are performed so that the actual fuel pressure Pr detected by the fuel pressure sensor 51 follows the target fuel pressure Pc. Is done. Therefore, not only the discharge capacity of the feed pump 21 is controlled by the variable control of the drive voltage Vp of the feed pump 21, but also the pressure of the supplied fuel can be changed by the switching control of the open / close state of the reduction valve 25. The variable range of the supply fuel pressure can be made sufficiently large, and the control range of the fuel injection amount in the fuel injection section 15 can be made sufficiently wide.

  Thus, according to the present embodiment, when switching the reduction valve 25, the variable control of the discharge capacity of the feed pump 21 is started prior to the switching control of the reduction valve 25. Therefore, the reduction valve 25 The change in the supply fuel pressure Pf due to the change in the discharge capacity of the feed pump 21 can be caused at a suitable timing so as to suppress the change in the supply fuel pressure Pf due to the switching control. As a result, it is possible to provide a fuel pressure control device that can suppress unnecessary fluctuations in the fuel supply pressure when the fuel supply state is switched.

  In the above-described embodiment, the engine 10 is configured by an internal combustion engine that performs only port injection for injecting fuel into the intake port 13. However, the present invention is not limited thereto, and the engine 10 is directly connected to the combustion chamber 12 in the cylinder 11. It may be a dual injection internal combustion engine that uses both in-cylinder injection for injecting fuel and port injection for injecting fuel into an intake port corresponding to the cylinder, or as a direct injection internal combustion engine that performs only in-cylinder injection. Also good.

  In the above-described embodiment, the reduction valve 25 is opened when the coil 25c is energized. However, the valve may be opened when the coil 25c is not energized. The pressure reducing valve 25 has a sufficiently lower set pressure than the relief valve 24 and opens / closes even at the target fuel pressure value PL on the low pressure side, and connection / cutoff of such a pressure control valve to the fuel pipe 22. And a valve for switching between.

  In the above-described embodiment, the specific voltage value Va on the lower limit voltage Vmin side is exemplified as a voltage value larger than the lower limit voltage Vmin, and the specific voltage value Vb on the upper limit voltage Vmax side is exemplified as a voltage value smaller than the upper limit voltage Vmax. However, the specific voltage value Va on the lower limit voltage Vmin side may be a voltage value equal to the lower limit voltage Vmin, or the specific voltage value Vb on the upper limit voltage Vmax side may be a voltage value equal to the upper limit voltage Vmax. Needless to say.

  Furthermore, although the opening / closing state of the reduction valve 25 is switched only once within the variable range of the supply fuel pressure P, the supply is performed using a plurality of reduction valves (which may be pressure reducing valves, etc.) having different reduction degrees and throttle strengths. It is also possible to switch the open / close states of the plurality of reduction valves within the variable range of the fuel pressure P.

  As described above, according to the present invention, when a change in the supply fuel pressure occurs due to the switching control of the pressure control valve, a change in the reverse direction of the supply fuel pressure due to a change in the discharge capacity of the fuel pump can be generated in a timely manner. it can. As a result, it is possible to sufficiently suppress unnecessary fluctuations in the fuel supply pressure when the fuel supply state is switched. The present invention as described above is useful for all fuel pressure control devices that variably control the fuel supply pressure in a system that supplies fuel to an internal combustion engine mounted on a vehicle.

DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 11 ... Cylinder, 13 ... Intake port, 15 ... Fuel-injection part,
DESCRIPTION OF SYMBOLS 16 ... Injector, 17 ... Delivery pipe, 20 ... Fuel supply mechanism, 21 ... Feed pump (fuel pump), 22 ... Fuel piping (fuel supply passage), 24 ... Relief valve, 25 ... Reduction valve (pressure control valve), 25a ... throttle part, 25c ... coil, 25v ... valve body, 26 ... fuel discharge passage, 30 ... fuel tank, 40 ... control mechanism, 41 ... ECU (electronic control unit), 42 ... FPC (fuel pressure control circuit), 51 ... fuel pressure Sensor: 52 ... Accelerator opening sensor, 53 ... Air flow meter, 54 ... Crank angle sensor, 55 ... Water temperature sensor, Pc ... Target fuel pressure (target pressure), Pr ... Actual fuel pressure, Td, Td1, Td2 ... Delay time, ΔPe ... Fuel pressure error, ΔV1, ΔV2 ... switching width, τ ... injection time, τ1 ... minimum injection time, τ2 ... maximum injection time

Claims (6)

An electric fuel pump that can change the discharge capacity according to the drive voltage, and discharges the fuel in the fuel tank according to the drive voltage to be supplied to the fuel injection part of the internal combustion engine;
The switching control signal can be switched between a valve opening state that exhibits a pressure reducing function for reducing the pressure of fuel supplied to the fuel injection unit and a valve closing state that stops the pressure reducing function. A pressure control valve that switches to the open / close state required by
A variable control of the drive voltage of the fuel pump that variably sets a target pressure of the supplied fuel according to the operating state of the internal combustion engine, and changes the discharge capacity according to the target pressure, and the switching control signal A fuel pressure control device comprising: a control mechanism that executes switching control of the open / close state of the pressure control valve according to a target pressure,
When the open / close state of the pressure control valve is switched, the control mechanism has an increase / decrease direction of the supply fuel pressure due to a change in the discharge capacity of the fuel pump with respect to an increase / decrease direction of the supply fuel pressure due to the switch. A fuel pressure control device that causes the pressure control valve to input the switching control signal that requests the switching after changing the driving voltage of the fuel pump so as to be in the reverse direction. .   When the pressure control valve is switched from the open state to the closed state, the control mechanism lowers the drive voltage to reduce the discharge capacity and then switches the pressure control valve to the closed state. The fuel pressure control device according to claim 1, wherein the switching control signal for requesting switching is input to the pressure control valve.   When the pressure control valve is switched from the closed state to the open state, the control mechanism increases the drive voltage so as to increase the discharge capacity and then changes the pressure control valve to the open state. The fuel pressure control device according to claim 1 or 2, wherein the switching control signal for requesting switching is input to the pressure control valve. The control mechanism causes the switching control signal to be input to the pressure control valve when a preset delay time elapses after the drive voltage of the fuel pump is changed,
The delay time is determined based on a change in the pressure of the supplied fuel accompanying the switching of the open / closed state of the pressure control valve due to a change in the pressure of the supplied fuel to the one side in the increase / decrease direction accompanying a change in the discharge capacity of the fuel pump. The fuel pressure control device according to any one of claims 1 to 3, wherein the fuel pressure control device is set within a time range in which a change to the other side in the increase / decrease direction is suppressed.   The variable width of the drive voltage of the fuel pump by the control mechanism when the open / close state of the pressure control valve is switched is one side of the increase / decrease direction of the pressure of the supplied fuel accompanying a change in the discharge capacity of the fuel pump The change in the pressure control valve is set to a value that substantially cancels out the change in the increase / decrease direction of the pressure of the supplied fuel accompanying the switching of the open / close state of the pressure control valve. 5. The fuel pressure control device according to 4.   The pressure control valve has a throttle part that allows a part of the fuel discharged from the fuel pump to pass through when the valve is open, and the fuel that has passed through the throttle part is returned to the fuel tank. The fuel pressure control device according to any one of claims 1 to 5, wherein the fuel pressure control device is a fuel pressure control device.

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