JP5687598B2 - Fuel supply device - Google Patents

Description

  The present invention relates to a fuel supply device that regulates the fuel stored in a fuel tank and supplies the fuel to a fuel consumption unit.

  2. Description of the Related Art Conventionally, a fuel supply device for an internal combustion engine mounted on a vehicle has a pressure control for adjusting the fuel supply pressure to the fuel consumption unit when the fuel stored in the fuel tank is supplied to the fuel consumption unit by a fuel pump. Equipment. This pressure control device regulates the fuel supply pressure from the fuel pump that pumps up the fuel in the fuel tank to the injector that constitutes the fuel consumption unit.

  In such a pressure control device, generally, a housing is divided into two chambers, and a diaphragm having a pressure regulating valve body at the center is provided. On one surface side of this diaphragm, the pressure regulating valve body is displaced in the valve opening direction and the valve closing direction by using the displacement of the diaphragm central portion in accordance with the fuel pressure in the pressure regulating chamber, while being installed on the other surface side of the diaphragm. The displacement of the diaphragm is suppressed by a compression coil spring. Thereby, the valve opening state of the pressure regulating valve body is maintained so that the fuel pressure in the pressure regulating chamber reaches the set pressure. Further, such a pressure control device is often arranged in a fuel tank together with a fuel pump.

  As such a pressure control device, there is a diaphragm partitioning the inside of the housing, a fuel introduction port for introducing pressurized fuel from a fuel pump, and a discharge port for discharging excess fuel, which are located on one surface side of the diaphragm. Displacement of the pressure adjusting chamber, a back pressure chamber that is located on the other side of the diaphragm, into which back pressure fluid is introduced, a plunger that forms an open chamber that is open to the atmosphere between the diaphragm and the back pressure chamber, and a displacement of the diaphragm A valve member mounted on the diaphragm so as to open and close the discharge port according to the pressure, a spring interposed between the diaphragm and the plunger to urge the valve member in the valve closing direction, and stopper means for defining a movable range of the plunger The thing provided with the variable fuel pressure regulating valve comprised by these is proposed (for example, refer patent document 1).

  The fuel supply device described in Patent Document 1 includes a variable fuel pressure adjustment valve that constitutes such a pressure control device, thereby switching the set load of the spring in two stages depending on whether or not the back pressure fluid is supplied. The set value of the fuel pressure to be regulated can be switched between low pressure and high pressure.

  However, although the fuel supply device described in Patent Document 1 can switch the fuel pressure by one variable fuel pressure adjusting valve, the variable fuel pressure adjusting valve is constituted by three chambers, so that it is difficult to reduce the size. In addition, since the pipes for supplying fuel to the pressure regulating chamber and the back pressure chamber are connected in opposite directions, there is a problem that the arrangement of the variable fuel pressure regulating valve is restricted.

  Furthermore, the fuel supply device described in Patent Document 1 is not limited to the deterioration or discharge of the fuel pump, even though the fuel pressure supplied to the fuel consumption unit changes according to the deterioration of the fuel pump or the variation in the discharge characteristics. It was not something that took into account variations in characteristics. Therefore, the actual fuel pressure deviates from the target fuel pressure, and the fuel injection amount to the cylinder is not appropriate. As a result, there is a problem that the air-fuel ratio may deviate from the target air-fuel ratio.

  Further, unlike the fuel supply device described in Patent Document 1, there is known a device that estimates the fuel pressure according to the stop period of the internal combustion engine, although it does not have a configuration for switching the fuel pressure between high pressure and low pressure. (For example, refer to Patent Document 2).

  The fuel supply device disclosed in Patent Document 2 includes a fuel supply unit that is driven by an internal combustion engine and a fuel pressure-containment unit that stores fuel from the fuel supply unit in a vehicle that does not include a fuel pressure sensor that detects fuel pressure. A fuel injection means for supplying the fuel of the fuel stock pressure means into the combustion chamber of the internal combustion engine, a fuel pressure estimation means for estimating the pressure of the fuel stored in the fuel stock pressure means, and a stop period for calculating the stop period of the internal combustion engine And a fuel pressure estimating means for setting an estimated fuel pressure value in accordance with a stop period of the internal combustion engine.

  By having such a configuration, the fuel supply device described in Patent Document 2 predicts the change in fuel pressure after the engine is stopped and sets the initial value of the estimated fuel pressure. It was supposed to be estimated.

JP 2009-144686 A JP-A-2005-330907

  However, although the fuel supply device described in Patent Document 2 described above estimates the fuel pressure without using the fuel pressure sensor regardless of the running state of the vehicle, individual differences in the discharge performance of the fuel pump It was not like estimating the aging itself.

  For this reason, it has not been possible to estimate how much the discharge performance of the fuel pump being used deviates from the average fuel pump or how much the fuel pump has deteriorated. Furthermore, the fuel supply device described in Patent Document 2 does not consider application to a fuel pressure adjusting valve that can set the fuel pressure between a high pressure and a low pressure. However, the fuel pump discharge performance and deterioration over time could not be obtained.

  Therefore, in a fuel supply device having a variable fuel pressure adjusting valve, such an amount of fuel pressure overshoot that occurs at the time of fuel pressure switching changes according to the discharge characteristics of the fuel pump or changes over time. We did not consider changes. Therefore, the fuel pressure until the fuel pressure switching converges cannot be accurately estimated, and the actual fuel injection amount may deviate from the desired fuel injection amount. For this reason, there has been a problem that the accuracy of the fuel injection control is lowered and the fuel efficiency cannot be improved.

  The present invention has been made to solve such problems. In a fuel supply apparatus having a variable fuel pressure adjusting valve, the timing for instructing the switching of the fuel pressure and the fuel injection time are optimized, and the fuel pressure is cut off. An object of the present invention is to provide a fuel supply device capable of improving fuel consumption by suppressing the actual fuel injection amount from deviating from a desired fuel injection amount even when the fuel injection is changed.

  In order to achieve the above object, a fuel supply apparatus according to the present invention is (1) a fuel supply apparatus that regulates fuel discharged from a fuel pump and supplies the fuel to a fuel consuming unit, and at least increases the fuel pressure of the fuel. A variable fuel pressure adjustment valve capable of taking either a high pressure supply state to be reduced or a low pressure supply state to be low pressure, an air / fuel ratio detection means for detecting an air / fuel ratio based on an exhaust component, and the variable fuel pressure adjustment valve The amount of fuel discharged from the variable fuel pressure regulating valve based on the voltage applied to the fuel pump and the air-fuel ratio detected by the air-fuel ratio detecting means on condition that the low-pressure supply state is established On the condition that the condition for switching the fuel pressure from the low pressure to the high pressure is satisfied, the fuel discharge amount estimated by the discharge amount estimation means is equal to or greater than a predetermined value. Yo Characterized in that it comprises a voltage control means for controlling a voltage applied to the fuel pump.

  With this configuration, if the amount of fuel discharged from the variable fuel pressure adjustment valve is equal to or greater than a predetermined value, the amount of overshoot that occurs when the fuel pressure is switched is constant, so the fuel pressure can be reduced even before the overshoot converges. It is possible to estimate. Therefore, the fuel pressure can be improved by optimizing the timing for instructing the switching of the fuel pressure and the fuel injection time, and suppressing the actual fuel injection amount from deviating from the desired fuel injection amount even when the fuel pressure is switched. Can be achieved.

  In the fuel supply apparatus described in (1) above, (2) the predetermined value is that the amount of overshoot that occurs when the fuel pressure is switched from low pressure to high pressure is substantially constant regardless of the change in the discharge amount. It is set to the area | region which becomes.

  With this configuration, when the discharge amount is set to a predetermined value or more, the overshoot amount at the time of fuel pressure switching can be estimated. Therefore, the timing for instructing the fuel pressure switching and the fuel injection time are optimized, and the fuel Even when the pressure is switched, the fuel consumption can be improved by suppressing the actual fuel injection amount from deviating from the desired fuel injection amount.

  In the fuel supply device described in the above (1) or (2), (3) the discharge amount estimation means changes the voltage applied to the fuel pump, and the air-fuel ratio detected by the air-fuel ratio detection means The lowest voltage that is the most lean is obtained, and the amount of the discharged fuel is estimated based on the difference between the lowest voltage and the initial voltage at which the air-fuel ratio becomes the leanest when the fuel pump is new. .

  With this configuration, it is possible to estimate the amount of fuel discharged from the variable fuel pressure adjustment valve in accordance with a change in the voltage applied to the fuel pump. As a result, the degree of deterioration of the fuel pump and the variation in the discharge characteristics can be obtained.

  In the fuel supply device described in (3) above, (4) the initial voltage is a substantially average value of voltages at which the air-fuel ratio becomes the leanest when a plurality of the fuel pumps are new.

  Here, the “substantially average value” in the present invention means a value by the fuel pump having an average discharge characteristic when the fuel pump is produced in large quantities, and may be a median value.

  With this configuration, if the initial voltage of the fuel pump having an average discharge characteristic is calculated in advance, the deterioration characteristic and discharge characteristic variation of the fuel pump are calculated without measuring the initial voltage for all the fuel pumps. It becomes possible to do. Therefore, each fuel pump can be maintained in an optimum state without reducing the production efficiency of the fuel supply device.

  In the fuel supply device described in (1) to (4) above, (5) the emission amount estimation unit corrects the estimated value of the emission amount according to the temperature of the fuel.

  With this configuration, even when the amount of fuel discharged from the variable fuel pressure regulating valve changes according to the temperature of the fuel, it is possible to accurately estimate the discharged amount.

  Further, in the fuel supply device described in (1) to (5) above, (6) the variable fuel pressure adjusting valve has a fuel introduction port through which the fuel is introduced and a fuel discharge port through which the fuel is discharged. A valve opening direction in which the pressure regulating chamber communicates with the fuel discharge port according to the fuel pressure in the pressure regulating chamber and a partition wall portion that forms a pressure regulating chamber communicating with the fuel introduction port between the housing and the housing A pressure adjusting member having a movable valve body portion that is displaced to the inside, and a discharge hole that communicates with the fuel discharge port inside the pressure regulating chamber and whose opening degree changes according to the displacement of the movable valve body portion A first valve seat portion that forms an operating pressure, and an operating pressure fuel introduction hole in which the opening degree changes according to the displacement of the movable valve body portion and fuel having an operating pressure is introduced inside the pressure regulating chamber. A second valve seat portion is provided in each housing, The area that member receives the fuel pressure in the opening direction, characterized in that changes in accordance with the operating pressure of the operating fuel introduction hole.

  With this configuration, the fuel pressure is regulated in two stages by making the area where the pressure regulating member receives the fuel pressure variable. Therefore, the fuel pressure supplied to the fuel consumption unit can be controlled in two stages without providing the variable fuel pressure adjusting valve with three chambers or providing two variable fuel pressure adjusting valves. For this reason, a fuel supply apparatus can be reduced in size.

  According to the present invention, in a fuel supply apparatus having a variable fuel pressure adjusting valve, the timing for instructing the switching of the fuel pressure and the fuel injection time are optimized, and the actual fuel injection amount is desired even when the fuel pressure is switched. By suppressing the deviation from the fuel injection amount, it is possible to provide a fuel supply device that can improve fuel efficiency.

It is a schematic block diagram which shows the fuel supply apparatus which concerns on embodiment of this invention, and its periphery. It is a schematic block diagram of the switching valve which concerns on embodiment of this invention. It is a schematic block diagram which shows the high voltage | pressure supply state of the fuel supply apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the low voltage | pressure supply state of the fuel supply apparatus which concerns on embodiment of this invention. It is a schematic block block diagram of the fuel supply apparatus which concerns on embodiment of this invention. It is a circuit diagram around a power supply unit according to an embodiment of the present invention. It is a timing chart of the fuel supply device concerning an embodiment of the invention. It is a graph which shows the relationship between the return flow volume and control pressure which concern on embodiment of this invention. It is a figure which shows the relationship between aged deterioration and the discharge amount of the fuel pump unit which concerns on embodiment of this invention. It is a flowchart which shows the return flow volume estimation control which concerns on embodiment of this invention. It is a graph which shows the discharge amount calculation map which concerns on embodiment of this invention. It is a graph which shows an example of change of the amount of overshoot to return flow volume concerning an embodiment of the invention. It is a graph which shows the relationship between the return flow volume and overshoot amount which concern on embodiment of this invention. It is a flowchart which shows the return flow rate control which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, the case where the fuel supply device according to the present invention is applied to a vehicle equipped with a four-cylinder gasoline engine will be described.

  First, the configuration will be described.

  As shown in FIG. 1, the fuel supply device 8 according to the present embodiment includes a fuel tank 2 that stores fuel consumed by the engine 1, and a plurality of fuels stored in the fuel tank 2. A fuel pumping mechanism 10 that pumps to the injector 3, a pressure regulator 20 that introduces fuel supplied from the fuel pumping mechanism 10 to the injector 3 and regulates the fuel pressure to a preset value, and a fuel that is regulated by the pressure regulator 20 And a switching valve 60 that controls the pressure regulator 20 so as to switch the pressure between the set pressure on the high pressure side and the set pressure on the low pressure side. Here, the pressure regulator 20 constitutes a variable fuel pressure regulating valve according to the present invention.

  The engine 1 is composed of a multi-cylinder internal combustion engine mounted on a vehicle. In the present embodiment, an internal combustion engine is constituted by a four-cycle gasoline engine having four cylinders 5. Here, the injector 3 and each cylinder 5 comprise the fuel consumption part which concerns on this invention. The injector 3 is installed in each cylinder 5 of the engine 1, and an end 3 a that forms an injection hole is exposed in the intake port 7.

  The fuel pumping mechanism 10 and the injector 3 are connected via a delivery pipe 4, and the fuel from the fuel pumping mechanism 10 is distributed to each injector 3 via the delivery pipe 4.

  The fuel pumping mechanism 10 pumps the fuel in the fuel tank 2 from the suction port, pressurizes it and discharges it from the discharge port, and is installed on the suction port side of the fuel pump unit 11 to the fuel pump unit 11. A suction filter 12 that prevents foreign matter from being sucked in, a fuel filter 13 that is installed on the discharge port side of the fuel pump unit 11 to remove foreign matters contained in the fuel discharged from the fuel pump unit 11, and an upstream side of the fuel filter 13 or And a check valve 14 installed on the downstream side.

  The fuel pump unit 11 is controlled by an ECU (Electronic Control Unit) 51, which will be described later, to energize a fuel pump 11p having an impeller for operating the pump and a pump drive motor 11m that is a built-in DC motor that rotationally drives the fuel pump 11p. To drive and stop.

  Further, the ECU 51 controls the voltage applied to the pump drive motor 11m of the fuel pump unit 11, thereby changing the rotational speed of the pump drive motor 11m, and changing the discharge amount D per unit time by the fuel pump unit 11. It can be made to. In the following description, for simplicity of explanation, it is assumed that a voltage is applied to the fuel pump unit 11. Further, the fuel pump unit 11 according to the present embodiment means a fuel pump according to the present invention.

  The check valve 14 opens in the direction of fuel supply from the fuel pump unit 11 to the injector 3 side, while the check valve 14 is closed in the reverse flow direction of fuel from the injector 3 side to the fuel pump unit 11 side, and pressurized supply It is designed to prevent fuel backflow.

  A fuel pump controller (hereinafter referred to as FPC) 17 for controlling the operation of the fuel pump unit 11 is provided at the upper part of the fuel tank 2, and this FPC 17 has a voltage detection for detecting the terminal voltage of the pump drive motor 11m. And a current detector for detecting a current flowing through the pump drive motor 11m.

  The FPC 17 controls the voltage applied to the fuel pump unit 11 according to the deviation between the pump control signal from the ECU 51 and the detection signal of the voltage detection unit that detects the terminal voltage of the pump drive motor 11m, or the fuel pumping mechanism. The ECU 51 is supplied with a diagnostic signal corresponding to the operating state of the pump drive motor 11m for 10 abnormality diagnosis. That is, in the present embodiment, the ECU 51 controls the voltage applied to the fuel pump unit 11 via the FPC 17.

  As shown in FIGS. 1 and 3, the pressure regulator 20 includes a housing 21 having a fluid inlet 21a through which fuel is introduced and a fluid outlet 21b through which the fuel is discharged. The housing 21 is formed by caulking and connecting a pair of concave housing members 18 and 19 at their outer peripheral portions.

  Inside the housing 21, a partition-shaped pressure regulating member 22 that divides the inside of the housing 21 into two chambers is provided. The pressure regulating member 22 includes a partition wall portion 24 that forms a pressure regulating chamber 23 that communicates with the fluid introduction port 21a between the pressure regulating member 22 and the pressure regulating chamber 23 at an opening degree corresponding to the fuel pressure in the pressure regulating chamber 23. Is integrated with a movable valve body portion 25 that is displaced in the valve opening direction to communicate with the fluid discharge port 21b. The partition wall 24 always receives the fuel pressure in the pressure regulating chamber 23 on one surface side.

  Further, the partition wall portion 24 forms a back pressure chamber 26 that applies a back pressure to the pressure regulating chamber 23 side with the housing 21 on the other surface side, and the pressure regulating member 22 is provided in the back pressure chamber 26. A compression coil spring 27 is provided to urge the movable valve body portion 25 in the valve closing direction. Further, at least one atmospheric pressure introduction hole 19 a is formed in the other housing member 19 that forms the back pressure chamber 26 together with the pressure regulating member 22.

  Further, an outer cylindrical member 29 and an inner cylindrical member 30 having different diameters are installed inside the housing 21. A first valve seat portion 31 and a second valve seat portion 32 are formed at the ends of the inner cylindrical member 30 and the outer cylindrical member 29 on the movable valve body portion 25 side, respectively. Further, the outer cylindrical member 29 and the inner cylindrical member 30 form an operating pressure fuel introduction hole 32 h. The operation pressure fuel introduction hole 32h communicates with the inside of the switching valve 60 via the operation pressure outlet 21c.

  As shown in FIG. 2, the switching valve 60 is for switching the fuel pressure in the operation pressure fuel introduction hole 32h of the pressure regulator 20, and includes an electromagnetic coil 61, a compression coil spring 62, and a synthetic resin bobbin 63. And a valve 67 and a shield 65 that covers the outer periphery of the electromagnetic coil 61.

  The bobbin 63 includes a bobbin part 73, a cylinder part 74, and a fuel pipe part 75. An electromagnetic coil 61 is wound around the outer periphery of the bobbin portion 73. On the other hand, a compression coil spring 62 is accommodated inside the bobbin portion 73.

  The bobbin portion 73 and the cylinder portion 74 are formed so that their inner peripheral surfaces are the same surface, and the valve 67 is accommodated in the cylinder portion 74 so as to be capable of reciprocating.

  The fuel pipe portion 75 is formed at the end of the cylinder portion 74, and is used to return the fuel into the fuel tank 2 and the fuel inflow tube 77 through which the fuel flows in via the operation pressure outlet 21 c of the pressure regulator 20. The fuel outflow pipe 78 and an opening end portion 70 that forms an opening toward the inside of the cylinder portion 74 are provided.

  The valve 67 is made of a substantially cylindrical magnetic body, and has an armature portion 71 and a seal portion 64 provided on one end face. The valve 67 moves in the cylinder part 74 and the seal part 64 is pressed against the opening end part 70, so that the communication between the flow path in the fuel inflow pipe 77 and the flow path in the fuel outflow pipe 78 is prevented. It has become.

  The compression coil spring 62 biases the valve 67 in a direction that prevents communication between the flow path in the fuel inflow pipe 77 and the flow path in the fuel outflow pipe 78.

  When the switching valve 60 configured as described above is in an ON state in which the electromagnetic coil 61 is energized, the valve 67 resists the biasing force of the compression coil spring 62 by the electromagnetic coil 61 as shown in FIG. The flow path in the fuel inflow pipe 77 and the flow path in the fuel outflow pipe 78 are communicated. Therefore, the fuel that has flowed into the fuel inflow pipe 77 is discharged from the fuel outflow pipe 78 through the cylinder portion 74.

  On the other hand, when the electromagnetic coil 61 is not energized, as shown in FIG. 4, the valve 67 is urged by the compression coil spring 62 to flow in the fuel inflow pipe 77 and in the fuel outflow pipe 78. Block communication with the flow path. Therefore, the fuel flowing into the fuel inflow pipe 77 is prevented from flowing out to the fuel tank 2 by the valve 67.

  Next, the operation of the pressure regulator 20 in a high pressure supply state in which the fuel pressure is increased will be described.

  When the fuel pressure is set to a high pressure by the ECU 51 during operation of the fuel pump unit 11 (see FIG. 1), the switching valve 60 is controlled to be turned on by the ECU 51 as shown in FIG.

  At this time, the seal portion 64 of the valve 67 is separated from the opening end portion 70, and the flow path in the fuel inflow pipe 77 and the flow path in the fuel outflow pipe 78 communicate with each other. Therefore, the operation pressure fuel introduction hole 32h communicates with the inside of the fuel tank 2, and both the discharge hole 31h and the operation pressure fuel introduction hole 32h are at atmospheric pressure. Therefore, only the fuel inside the pressure regulating chamber 23 biases the pressure regulating member 22 in the valve opening direction. That is, the effective pressure receiving area of the pressure adjusting member 22 is only the annular pressure receiving surface 24 a of the partition wall portion 24. As a result, the thrust in the valve closing direction of the movable valve body 25 is increased, and the amount of deflection of the compression coil spring 27 that biases the movable valve body 25 in the valve closing direction is reduced, so that the movable valve body 25 is The first valve seat portion 31 and the second valve seat portion 32 are displaced in the valve closing direction.

  Due to the displacement of the movable valve body 25 in the valve closing direction, the amount of fuel supplied from the fuel passage 15 to the pressure regulating chamber 23 via the branch passage 15a is reduced, and as a result, the fuel flowing through the fuel passage 15 is reduced. Regulated to high pressure.

  On the other hand, the operation of the pressure regulator 20 in a low pressure supply state in which the fuel pressure is reduced will be described. When the fuel pressure is set to a low pressure by the ECU 51 during the operation of the fuel pump unit 11, the switching valve 60 is controlled to the OFF state by the ECU 51 as shown in FIG. 4.

  At this time, the seal portion 64 of the valve 67 contacts the opening end portion 70, and communication between the flow path in the fuel inflow pipe 77 and the flow path in the fuel outflow pipe 78 is prevented. Therefore, the fuel inflow pipe 77 and the operation pressure fuel introduction hole 32h of the pressure regulator 20 are closed at the downstream end of the fuel, so that the fuel pressure in the operation pressure fuel introduction hole 32h is in the pressure regulating chamber 23. It becomes equal to the fuel pressure. That is, only the discharge hole 31h becomes atmospheric pressure, and the fuel inside the pressure regulating chamber 23 and the fuel in the operation pressure fuel introduction hole 32h urge the pressure regulating member 22 in the valve opening direction. Therefore, the effective pressure receiving area of the pressure adjusting member 22 is expanded, and the substantially pressure receiving surface facing the annular pressure receiving surface 24a of the partition wall 24 and the operation pressure fuel introduction hole 32h is included. Therefore, the thrust in the valve opening direction of the movable valve body portion 25 increases, and the amount of deflection of the compression coil spring 27 that biases the movable valve body portion 25 in the valve opening direction increases, so that the movable valve body portion 25 becomes the first. The first valve seat portion 31 and the second valve seat portion 32 are displaced in the valve opening direction.

  Due to the displacement of the movable valve body 25 in the valve opening direction, the fuel supplied from the fuel passage 15 to the pressure regulating chamber 23 via the branch passage 15a increases, and as a result, the fuel flowing through the fuel passage 15 is increased. Regulated to low pressure.

  As shown in FIG. 5, a vehicle equipped with the engine 1 according to the present embodiment includes an engine speed sensor 41, an air flow meter 42, an intake air temperature sensor 43, a throttle opening sensor 44, a cooling water temperature sensor 45, an accelerator opening. A sensor 46, a wheel speed sensor 47, and an air-fuel ratio sensor 48 are provided. Each of these sensors outputs a signal representing a detection result to the ECU 51.

  The engine rotation speed sensor 41 detects the rotation speed of the crankshaft of the engine 1 and outputs it to the ECU 51 as the engine rotation speed Ne. The air flow meter 42 is arranged on the upstream side of intake air from a throttle valve (not shown), and outputs a detection signal corresponding to the intake air amount to the ECU 51. The intake air temperature sensor 43 is disposed in an intake manifold (not shown), and outputs a detection signal corresponding to the intake air temperature to the ECU 51. The throttle opening sensor 44 outputs a detection signal corresponding to the opening of the throttle valve to the ECU 51.

  The cooling water temperature sensor 45 is disposed in a water jacket formed in the cylinder block of the engine 1, and outputs a detection signal corresponding to the cooling water temperature Tw of the engine 1 to the ECU 51. The accelerator opening sensor 46 outputs a detection signal corresponding to the amount of depression of the accelerator pedal to the ECU 51.

  The wheel speed sensor 47 outputs a detection signal corresponding to the rotational speed of a wheel (not shown) of the vehicle to the ECU 51. The air-fuel ratio sensor 48 outputs a voltage Vaf corresponding to the air-fuel ratio to the ECU 51 based on the oxygen concentration in the exhaust gas to be detected and the concentration of the unburned component of the fuel.

  As shown in FIG. 5, the ECU 51 constituting a part of the fuel supply device 8 includes a CPU (Central Processing Unit) 52, a RAM (Random Access Memory) 53, a ROM (Read Only Memory) 54, a backup memory 55, and the like. ing. The ECU 51 according to the present embodiment constitutes an air-fuel ratio detection unit, an emission amount estimation unit, and a voltage control unit according to the present invention.

  The ROM 54 stores various control programs including a control program for executing the fuel pressure switching control and the fuel injection control in the cylinder 5, and a map referred to when executing these various control programs. The CPU 52 executes various arithmetic processes based on various control programs and maps stored in the ROM 54. The RAM 53 temporarily stores the calculation results by the CPU 52, data input from the above-described sensors, and the like. The backup memory 55 is configured by a non-volatile memory, and stores, for example, data to be saved when the engine 1 is stopped.

  The CPU 52, RAM 53, ROM 54, and backup memory 55 are connected to each other via a bus 58, and are connected to an input interface 56 and an output interface 57.

  Connected to the input interface 56 are an engine speed sensor 41, an air flow meter 42, an intake air temperature sensor 43, a throttle opening sensor 44, a coolant temperature sensor 45, an accelerator opening sensor 46, a wheel speed sensor 47 and an air / fuel ratio sensor 48. ing. Further, the alternator 35 is connected to the input interface 56. Note that the vehicle may be mounted with an ECU other than the ECU 51, and signals output from at least some of these sensors may be input to the ECU 51 via the other ECU.

  The output interface 57 is connected to the injector 3, the spark plug 6, the switching valve 60, a throttle valve (not shown), and the like. Further, the output interface 57 is connected to the fuel pump unit 11 via the FPC 17 (see FIG. 1). The ECU 51 executes various controls including fuel pressure switching control and fuel injection control, return flow rate estimation control and overshoot calculation control, which will be described later, based on the outputs of the various sensors described above.

  In the present embodiment, the ECU 51 detects the electromotive force of the alternator 35. FIG. 6 is a circuit diagram around the power supply unit 34 in the present embodiment.

  The power supply unit 34 includes an alternator 35 that is mechanically connected to the engine 1 and a battery 37 that is electrically connected to the alternator 35. The alternator 35 is connected to the engine 1 by a belt 36, and a driving force is input from the engine 1 through the belt 36.

  The alternator 35 includes a stator stator coil (not shown), a rotor coil of a rotor, a rectifier, and a regulator. The rotor coil is connected to one terminal of the ignition switch 38 via a regulator. The other terminal of the ignition switch 38 is connected to the battery 37. When the ignition switch 38 shifts to the ON state, the rotor coil is energized from the battery 37 via the regulator, and the rotor coil is magnetized. The driving force generated by the engine 1 is input to the rotor coil. When the rotor coil rotates in conjunction with the rotation of the engine 1, an AC voltage is generated in the stator coil. The generated AC voltage is converted into a DC voltage by a rectifier, and this DC voltage is applied to the battery 37 as an electromotive voltage of the alternator 35.

  The electromotive force of the alternator 35 changes according to the engine speed Ne. When the engine speed Ne is high, the electromotive force of the alternator 35 is, for example, in the vicinity of 14 [V]. On the other hand, when the engine speed Ne is low, the electromotive force of the alternator 35 is, for example, in the vicinity of 8 [V].

  The alternator 35 is connected to the ECU 51, and the electromotive force of the alternator 35 is input to the ECU 51. Further, the electromagnetic coil 61 of the switching valve 60 is connected to the ECU 51, and a voltage corresponding to the electromotive force of the alternator 35 is applied to the electromagnetic coil 61. That is, the voltage applied to the electromagnetic coil 61 of the switching valve 60 is obtained by detecting the electromotive force of the alternator 35.

  Further, the ECU 51 has a transistor 69 controlled by the CPU 52 (see FIG. 5). The transistor 69 takes one of an ON state in which the electromotive force of the alternator 35 is applied to the electromagnetic coil 61 of the switching valve 60 and an OFF state in which the electromotive force of the alternator 35 is not applied to the electromagnetic coil 61 of the switching valve 60. It is like that.

  FIG. 7 is a timing chart showing the operation of the fuel supply device 8 configured as described above. First, in FIG. 7, a description will be given of a place where the fuel pressure is switched from a low pressure to a high pressure. The case where the electromotive force Eb of the alternator 35 is 12 [V] will be described as an example.

  First, the ECU 51 determines that a fuel pressure switching request for switching the fuel pressure from a low pressure to a high pressure has occurred before time T0 based on the traveling state of the vehicle. When the ECU 51 detects the electromotive force Eb of the alternator 35, the transistor is configured so that the electromotive force of the alternator 35 is applied to the electromagnetic coil 61 of the switching valve 60 at a time T0 set as described later, that is, at the switching timing. 69 is turned on (see solid line 81).

  When the transistor 69 is turned on, the voltage applied to the electromagnetic coil 61 is changed from 0 [V] to 12 [V] (see the solid line 82). At this time, when the voltage Eb is applied to the electromagnetic coil 61 of the switching valve 60, the current I supplied to the electromagnetic coil 61 of the switching valve 60 is expressed by the following equation (1).

I (t) = Eb / R (1-exp (−t / τ)) (1)
Here, Eb is an electromotive force of the alternator 35, and τ is a time constant represented by L / R. R represents the electric resistance of the electromagnetic coil 61, and L represents the inductance of the electromagnetic coil 61.

  For this reason, the current I supplied to the electromagnetic coil 61 rises according to the response characteristic represented by the equation (1) (see the solid line 83). When such a current I is supplied to the electromagnetic coil 61, the attractive force F applied to the valve 67 of the switching valve 60 is expressed by the following equation (2).

F = Φ ² / (2 · μ · S) (2)
In the formula (2), μ is a magnetic permeability and is obtained by a product of a vacuum magnetic permeability and a relative magnetic permeability. S represents the cross-sectional area of the magnetic path. Moreover, (PHI) is the magnetic flux in a magnetic gap, and is represented by the following formula | equation (3).

Φ = n · (I / R) (3)
In the formula (3), n represents the number of turns of the electromagnetic coil 61, I represents the current obtained by the above formula (1), and R represents the magnetic resistance.

  Therefore, when the current I supplied to the electromagnetic coil 61 increases according to the above equation (1), the attractive force of the electromagnetic coil 61 against the valve 67 increases according to the equation (2).

  At time T1, when the attractive force of the electromagnetic coil 61 with respect to the valve 67 becomes larger than the urging force of the compression coil spring 62 with respect to the valve 67, the seal portion 64 of the valve 67 is separated from the bottom dead center where it abuts against the opening end portion 70. The movement is started in the direction of the top dead center (see the solid line 84). As a result, the fuel pressure in the operating pressure fuel introduction hole 32h of the pressure regulator 20, that is, the pilot pressure is reduced from 300 [kPa] to the atmospheric pressure (see the solid line 85).

  As a result, the movable valve body 25 of the pressure regulator 20 is displaced in the valve closing direction via an overshoot (see the solid line 86), and accordingly, the fuel flowing through the fuel passage 15 is also temporarily at a high pressure at time T2. After that, a high pressure steady state is reached at time T3 after overshoot (see solid line 87).

  By the way, the characteristics of convergence of the overshoot amount and displacement pulsation of the movable valve body 25 can be obtained by the return flow rate control process as described later. On the other hand, the time T1 when the valve 67 of the switching valve 60 starts to move from the bottom dead center to the top dead center is electromagnetic according to the voltage Eb applied to the electromagnetic coil 61 as shown in the above equation (1). Since the current I supplied to the coil 61 changes, the value changes each time. That is, the time t1 from time T0 to time T2 varies depending on the electromotive force Eb and the overshoot characteristic of the alternator 35.

  Therefore, when the fuel pressure is switched from the low pressure to the high pressure, the ECU 51 according to the present embodiment detects the electromotive force Eb of the alternator 35 and obtains the overshoot amount and the overshoot duration, thereby delaying the switching. The time t1 is calculated, and the fuel pressure switching timing T0 is controlled based on the calculated switching delay time t1 and the pulsation time t2 obtained in advance.

  Next, referring to FIG. 7, a description will be given of the location where the fuel pressure is switched from high pressure to low pressure. The ECU 51 reduces the fuel pressure from a high pressure to a low pressure when the warming up of the vehicle is finished or the fuel temperature is lowered while the fuel pressure is set to a high pressure when the vehicle is warming up or when the fuel temperature is high. Fuel pressure switching control is executed.

  The ECU 51 switches the fuel pressure from the high pressure to the low pressure when the warming up of the vehicle is finished or the fuel temperature is lowered while the fuel pressure is set to a high pressure when the vehicle is warming up or when the fuel temperature is high. It is determined that a fuel pressure switching request has occurred.

  Then, the ECU 51 switches the transistor 69 from the ON state at time T0 ′ set as described later, that is, at the switching timing, so that the electromotive force of the alternator 35 applied to the electromagnetic coil 61 of the switching valve 60 is cut off. Transition to the OFF state (see solid line 81).

  When the transistor 69 is turned off, the voltage applied to the electromagnetic coil 61 is changed from 12 [V] to 0 [V] (see the solid line 82). At this time, the voltage applied to the electromagnetic coil 61 of the switching valve 60 changes from Eb to 0, and the current I (t) supplied to the electromagnetic coil 61 of the switching valve 60 is expressed by the following equation (4). The

I (t) = Eb / R · exp (−t / τ) (4)
Therefore, the current I supplied to the electromagnetic coil 61 decreases according to the response characteristic represented by the equation (4) (see the solid line 83).

  Further, the suction force F applied to the valve 67 of the switching valve 60 is expressed by the above-described equations (2) and (3). Therefore, when the current I supplied to the electromagnetic coil 61 decreases according to the above equation (4), the attractive force of the electromagnetic coil 61 against the valve 67 decreases according to the equation (2).

  At time T 1 ′, when the attractive force of the electromagnetic coil 61 to the valve 67 becomes smaller than the biasing force of the compression coil spring 62 to the valve 67, the top dead center at which the seal portion 64 of the valve 67 is separated from the opening end portion 70. The movement starts in the direction of the bottom dead center (see the solid line 84).

  At time T2 ′, when the seal portion 64 of the valve 67 comes into contact with the opening end portion 70 (see the solid line 84), the fuel pressure in the operating pressure fuel introduction hole 32h of the pressure regulator 20, that is, the pilot pressure is reduced from the atmospheric pressure. It rises to 300 [kPa] (see solid line 85).

  As a result, the fuel pressure of the fuel flowing in the fuel passage 15 once exceeds the target low pressure at time T3 ′ according to the displacement of the movable valve body 25 of the pressure regulator 20 in the valve opening direction. After passing through the chute (see solid line 87), the pressure becomes low at time T4 ′ (see solid line 87).

  Further, since the convergence of the overshoot amount and displacement pulsation of the movable valve body 25 has a correlation with the return flow rate Q at the time of low pressure setting, this correlation should be obtained in advance by experimental measurement. Thus, it can be calculated from the return flow rate Q. Further, the time (time T1 ′ to T2 ′) required for the valve 67 of the switching valve 60 to reach the bottom dead center from the top dead center can also be obtained in advance by experimental measurement. On the other hand, the time T1 ′ at which the valve 67 starts moving from the top dead center to the bottom dead center is equal to the voltage Eb applied to the electromagnetic coil 61 at the start of switching, as shown in the above equation (4). Accordingly, the current I supplied to the electromagnetic coil 61 changes and varies. That is, the switching delay time t1 varies depending on the electromotive force and overshoot characteristics of the alternator 35.

  Therefore, the ECU 51 according to the present embodiment detects the electromotive force Eb of the alternator 35 when switching the fuel pressure from the high pressure to the low pressure, and obtains the overshoot amount and the overshoot duration, thereby delaying the switching. The time t1 is predicted, and the fuel pressure switching timing T0 ′ is controlled based on the predicted switching delay time t1.

  The electromotive force Eb of the alternator 35 and the switching delay time t1 are associated in advance as a switching delay time map. The ECU 51 stores in advance in the ROM 54 a switching delay time map used when switching to high pressure and switching to low pressure. When the ECU 51 acquires a signal representing the electromotive force Eb of the alternator 35, the switching delay is delayed. The switching delay time t1 is calculated with reference to the time map.

  When the fuel pressure is switched from low pressure to high pressure, the smaller the electromotive force Eb of the alternator 35 is, the longer the time from when the transistor 69 is turned on to when the valve 67 starts to move is longer. Therefore, the ECU 51 advances the timing for turning off the transistor 69 as the electromotive force Eb of the alternator 35 is smaller. On the other hand, when the fuel pressure is switched from high pressure to low pressure, the larger the electromotive force Eb of the alternator 35, the longer the time from when the transistor 69 is turned off until the valve 67 starts to move. Therefore, the ECU 51 advances the timing for turning off the transistor 69 as the electromotive force Eb of the alternator 35 increases.

  In the fuel supply device 8 configured as described above, the pressure regulator 20 needs to always fill at least the pressure regulation chamber 23 with fuel in order to operate so as to switch the fuel pressure between the high pressure and the low pressure. Therefore, the ECU 51 controls the fuel pump unit 11 so that more fuel than the amount of fuel necessary for the operation of the pressure regulator 20 is introduced from the fluid introduction port 21a and excess fuel is discharged from the fluid discharge port 21b. It has become.

  Here, when the pressure regulator 20 sets the fuel pressure to a low pressure, the fuel pressure (control pressure) P regulated by the pressure regulator 20 and the amount of fuel discharged from the fluid discharge port 21b (hereinafter referred to as return flow rate Q). ) Has the correspondence shown in FIG.

  In general, when the return flow rate Q decreases according to the decrease in the discharge amount D by the fuel pump unit 11, the control pressure P also decreases. However, when the return flow rate Q decreases to a predetermined value, the fuel pressure in the operation pressure fuel introduction hole 32h does not increase, and as a result, the pressure receiving area in the movable valve body 25 decreases. Therefore, when the return flow rate Q is lower than the predetermined value, the pressure regulator 20 approaches the high pressure supply state as the return flow rate Q is lower, and the control pressure P increases. In other words, the pressure regulator capable of adjusting the fuel pressure to a high pressure and a low pressure, like the pressure regulator 20 according to the present embodiment, sets the bending point at which the control pressure P is minimum with respect to the return flow rate Q as the predetermined pressure. Has as a value.

  Therefore, the ECU 51 maintains the function that the pressure regulator 20 switches the fuel pressure between the high pressure and the low pressure, and the return flow rate at the bending point, that is, the predetermined flow rate so that an excessive voltage is not applied to the fuel pump unit 11. The value is set as the minimum required amount of the return flow rate Q, and the voltage applied to the fuel pump unit 11 is controlled so that the return flow rate Q is maintained above the minimum required amount.

  The amount of fuel injected from the injector 3 per unit time is proportional to the square root of the fuel pressure. Therefore, when the fuel injection time by the injector 3 is constant, the amount of fuel supplied into the combustion chamber of each cylinder 5 increases as the control pressure P increases. That is, the higher the control pressure P, the lower the air-fuel ratio, that is, the richer. The air-fuel ratio sensor 48 indicates that the air-fuel mixture burned in the combustion chamber of each cylinder 5 is rich based on the exhaust gas component described above. The signal to represent is transmitted to ECU51.

  By the way, the fuel pump unit 11 has individual differences in the discharge amount D even if the same voltage is applied due to variations in characteristics at the time of manufacture and deterioration over time. FIG. 9 is a graph showing a change in the discharge amount D by the fuel pump unit 11 according to the characteristic variation and deterioration. The horizontal axis indicates the aging deterioration according to the travel distance, and the vertical axis indicates the fuel discharge amount D by the fuel pump unit 11. Further, the amount of fuel consumed in the combustion chamber of the engine 1 among the fuel discharged from the fuel pump unit 11 is defined as an engine consumption amount A. Therefore, the fuel amount D discharged from the fuel pump unit 11 is a total value of the engine consumption A and the return flow rate Q from the pressure regulator 20.

  When the travel distance of the vehicle is 0, the discharge amount D of the fuel pump unit 11 is distributed between the points a and b due to characteristic variations. Hereinafter, when the travel distance is 0, the fuel pump unit 11 at which the discharge amount D is a point a is referred to as an upper limit product, and the fuel pump unit 11 at which the discharge amount D is a point b is referred to as a lower limit product.

  The discharge amount D of the fuel pump unit 11 decreases along the deterioration curve as the travel distance of the vehicle increases. For example, when reaching 200,000 km, even if a voltage equal to that when the travel distance is 0 is applied. The upper limit product drops to point a ′, and the lower limit product drops to point b ′.

  At this time, if the return flow rate Q of the lower limit product is lower than the minimum required amount Qmin, the fuel pressure on the low pressure side increases as shown in FIG.

  Therefore, conventionally, when the fuel pump unit 11 is installed in a vehicle, even if the fuel pump unit 11 is a lower limit product, the return flow rate Q is the minimum required amount when the travel distance reaches 200,000 km. In order not to fall below Qmin, a higher voltage was applied from the time of the new article, and this voltage was maintained.

  However, when the voltage applied to the fuel pump unit 11 is set in this way, the ECU 51 does not include an expensive sensor for detecting the return flow rate Q, and the return flow rate Q regardless of the discharge performance or the travel distance. Can be maintained at the minimum required amount Qmin or more, but in the fuel pump unit 11 other than the lower limit product whose mileage has reached 200,000 [km], the fuel exceeding the minimum required amount Qmin is a pressure regulator. 20 will continue to be discharged. In other words, the conventional ECU 51 continues to apply more voltage than necessary to the fuel pump unit 11, causing a decrease in fuel consumption and an accelerated deterioration of the fuel pump unit 11.

  Therefore, the ECU 51 according to the present embodiment estimates the return flow Q in a vehicle that does not include a sensor that detects the return flow Q, and the voltage applied to the fuel pump unit 11 based on the estimated return flow Q. In addition, the variation in the discharge performance of the fuel pump unit 11 and the aging deterioration are obtained.

  The ECU 51 is configured to execute return flow rate estimation control in order to calculate the return flow rate Q. FIG. 10 is a flowchart showing return flow rate estimation control according to the present embodiment. The following processing is executed at a predetermined timing by the CPU 52 constituting the ECU 51 and realizes a program that can be processed by the CPU 52.

  The ECU 51 first determines whether or not the fuel is in a low pressure supply state (step S11). Specifically, the ECU 51 determines, based on a signal input from the coolant temperature sensor 45, whether or not the vehicle is warming up or in a high fuel temperature when the fuel is in a high pressure supply state. When the ECU 51 determines that the fuel is in a low pressure supply state (YES in step S11), the ECU 51 proceeds to step S12. On the other hand, when the ECU 51 determines that the fuel is in a high pressure supply state (NO in step S11), the ECU 51 proceeds to END.

  Next, the ECU 51 determines whether or not the fuel injection amount is constant (step S12). Specifically, the ECU 51 detects the engine speed, the throttle opening, and the accelerator opening for a predetermined time based on signals input from the engine speed sensor 41, the throttle opening sensor 44, and the accelerator opening sensor 46. . The ECU 51 determines that the fuel injection amount is constant when these values are within a predetermined range.

  When the ECU 51 determines that the fuel injection amount is constant (YES in step S12), the ECU 51 proceeds to step S13. On the other hand, when the ECU 51 determines that the fuel injection amount is not constant (NO in step S12), the ECU 51 proceeds to END.

  Next, the ECU 51 determines whether or not the fuel temperature can be estimated based on a signal input from a known sensor such as the coolant temperature sensor 45 (step S13). Specifically, the ECU 51 determines whether or not the vehicle is in a traveling state in which the fuel temperature can be estimated from a sensor such as the cooling water temperature sensor 45. Various conditions representing the traveling state are determined in advance according to the sensor to be used.

  If the ECU 51 determines that the fuel temperature can be estimated (YES in step S13), the ECU 51 proceeds to step S14. On the other hand, if the ECU 51 determines that the fuel temperature cannot be estimated (NO in step S13), the ECU 51 proceeds to END. When the vehicle includes a fuel temperature sensor for detecting the fuel temperature, information representing the fuel temperature may be directly acquired based on a signal input from the fuel temperature sensor.

  Next, the ECU 51 decreases the voltage applied to the fuel pump unit 11 by a predetermined value (step S14). In the present embodiment, the ECU 51 reduces the predetermined value by 0.5 [V]. Then, the ECU 51 stores the voltage currently applied to the fuel pump unit 11 in the RAM 53 (step S15).

  Next, the ECU 51 determines whether or not the air-fuel ratio fluctuates in the lean direction based on the signal input from the air-fuel ratio sensor 48 (step S16).

  When the ECU 51 determines that the air-fuel ratio fluctuates in the lean direction by reducing the voltage applied to the fuel pump unit 11 (YES in step S16), the ECU 51 returns to step S14 and applies to the fuel pump unit 11. The applied voltage is further reduced by 0.5 [V]. As an example, when the relationship between the return flow rate Q and the control pressure P in the fuel pump unit 11 is from the point 2 to the point 5 shown in FIG. 8, the air-fuel ratio is reduced by reducing the voltage by 0.5 [V]. Therefore, the ECU 51 lowers the voltage again by 0.5 [V] in step S16.

  On the other hand, when the ECU 51 determines that the air-fuel ratio does not swing in the lean direction, that is, it swings in the rich direction (NO in step S16), the ECU 51 acquires the voltage stored in the RAM 53 (step S17). As an example, when the relationship between the return flow rate Q and the control pressure P in the fuel pump unit 11 is at point 6 shown in FIG. 8, the air-fuel ratio is rich by reducing the voltage by 0.5 [V]. The ECU 51 obtains the voltage at the point 6 from the RAM 53 in step S <b> 17 because it swings in the direction.

Since the air-fuel ratio fluctuates most leanly when the voltage higher by 0.5 [V] than the voltage value acquired from the RAM 53 is applied to the fuel pump unit 11, the ECU 51 uses this voltage as the most lean voltage Vaf. And stored in the backup memory 55. As an example, the ECU 51 defines V ₇ (see FIG. 8) obtained by adding 0.5 [V] to the voltage acquired from the RAM 53 as the most lean voltage Vaf. Note that the ECU 51 may always execute this return flow rate estimation control, or may execute it for every predetermined travel distance or travel time. Here, the leanest voltage Vaf according to the present embodiment means the lowest voltage according to the present invention.

  Further, the ECU 51 calculates the return flow rate Q as described below based on the most lean voltage Vaf (step S18).

  Even if the same voltage is applied to the fuel pump unit 11, the return flow rate Q varies depending on the degree of deterioration of the fuel pump unit 11 and individual differences in discharge characteristics. Therefore, when the ECU 51 calculates the most lean voltage Vaf, the fuel pump that estimates the most lean voltage Vaf (hereinafter referred to as the initial voltage Vini) and the return flow rate when the fuel pump unit 11 having an average discharge characteristic is new. Based on the difference from the most lean voltage Vaf of the unit 11, the discharge characteristic corresponding to the individual difference of the fuel pump unit 11 is calculated.

  The difference between the initial voltage Vini and the most lean voltage Vaf and the amount of change in the discharge amount D by the fuel pump unit 11, that is, the amount of change in the return flow rate Q, are expressed uniformly regardless of individual differences. Therefore, the ECU 51 previously stores a discharge amount calculation map in which the difference between the initial voltage Vini and the most lean voltage Vaf applied to the fuel pump unit 11 and the change amount of the discharge amount D corresponding to the voltage difference are associated with each other. It is stored in the ROM 54. As shown in FIG. 11, the discharge amount calculation map is represented by a graph in which the slope α is constant. The ECU 51 determines the voltage between the leanest voltage Vaf and the initial voltage Vini obtained in the return flow rate estimation control. The difference in the return flow rate Q is calculated by calculating the difference and referring to the discharge amount calculation map. In addition, this inclination (alpha) is computable with the well-known voltage equation in the pump drive motor 11m. In addition, the slope α may be obtained in advance by experimental measurement.

  As an example in the present embodiment, it is assumed that the voltage difference between the most lean voltage Vaf and the initial voltage Vini obtained in the return flow rate estimation control is 0.6 [V] and the slope α = 30. Also, consider a case where the discharge amount D of the fuel pump unit 11 having an average discharge characteristic (point c in FIG. 9) is 80 [L / h] when a voltage of 8 [V] is applied when new. . Further, Vaf when the fuel pump unit 11 having the average discharge characteristic is new is set to 7 [V].

  The ECU 51 calculates the change amount of the discharge amount D as 18 [L / h] from the product of the difference 0.6 [V] between the initial voltage Vaf and the most lean voltage Vaf and the inclination α = 30. Accordingly, when the ECU 51 applies a voltage of 8 [V] to the fuel pump unit 11, the current return flow rate Q is discharged from the discharge amount 80 [L / h] to the engine consumption amount 16 [L / h]. It is estimated that 46 [L / h] is obtained by subtracting the change amount 18 [L / h] of the amount D.

  Further, the ECU 51 may correct the calculated return flow rate Q according to the fuel temperature T. The correction amount for the return flow rate Q is stored in advance in the ROM 54 as a correction amount map associated with the fuel temperature T. The correction amount in the correction amount map is defined so that the return flow rate Q decreases as the fuel temperature T decreases, and is obtained in advance by experimental measurement. The ECU 51 may store an equation for calculating the correction amount in accordance with the fuel temperature T in the ROM 54 instead of the correction amount map.

  Further, the ECU 51 adjusts the voltage applied to the fuel pump unit 11 based on the most lean voltage Vaf calculated. In this case, the ECU 51 suppresses applying an unnecessarily high voltage by applying a voltage slightly higher than the leanest voltage Vaf to the fuel pump unit 11 and returns the return flow rate until the next return flow rate estimation control is executed. Even if Q varies, it is possible to prevent the return flow rate Q from falling below the minimum required amount Qmin.

  Here, when the ECU 51 switches the fuel pressure from the low pressure to the high pressure, the fuel pressure approaches the high set pressure via the overshoot. For this reason, when fuel injection is performed during overshoot, a state occurs in which the actual fuel pressure and the target fuel pressure are different. In addition, when fuel injection is performed after the overshoot ends, if the overshoot end timing is not accurately predicted, the fuel injection may be performed even though the overshoot has not ended yet. Sex also occurs.

  Therefore, the ECU 51 in the present embodiment predicts the overshoot amount OS so that the state of the fuel pressure is accurately predicted even during the overshoot in order to suppress the actual air / fuel ratio from deviating from the target air / fuel ratio. The overshoot duration Tos is calculated.

  As shown in FIG. 12, the overshoot amount OS changes in accordance with the return flow rate Q at low pressure in the region around the minimum required amount Qmin. For example, it is assumed that the overshoot characteristic for a certain return flow rate Q is represented by a solid line 91. When the return flow rate Q at the time of the low pressure increases, as shown by a broken line 92, the overshoot amount OS and the overshoot duration Tos are also increased. On the other hand, when the return flow rate Q is decreased, the overshoot amount OS and the overshoot duration Tos are also reduced as indicated by the broken line 93.

  For this reason, if the ECU 51 tries to accurately calculate the fuel injection amount after the fuel pressure is switched in the region of the return flow Q, it is necessary to accurately grasp the return flow Q before the fuel pressure is switched. The correspondence between the flow rate Q and the overshoot characteristic needs to be stored in the ROM 54 one by one, which may increase the cost.

  On the other hand, as shown in FIG. 13, when the return flow rate Q at the time of low pressure becomes equal to or greater than a predetermined value Qa, the overshoot amount OS and the time Tos required for convergence of the overshoot become substantially constant. Therefore, the ECU 51 in the present embodiment stores in advance the overshoot characteristics such as the overshoot amount OS and the overshoot duration Tos in the ROM 54 when the return flow rate Q is equal to or greater than the predetermined value Qa. When a fuel pressure switching request is generated, the ECU 51 controls the voltage applied to the fuel pump unit 11 so that the return flow rate Q is equal to or higher than the predetermined value Qa before switching the fuel pressure. It has become.

  Further, the ECU 51 switches the fuel pressure from the low pressure to the high pressure when the return flow rate Q becomes equal to or greater than the predetermined value Qa. At this time, the fuel injection control is executed based on the overshoot characteristic stored in the ROM 54 in advance.

  Next, the return flow rate control process according to the present embodiment will be described with reference to FIG. The following processing is executed at a predetermined timing by the CPU 52 constituting the ECU 51 and realizes a program that can be processed by the CPU 52.

  First, the ECU 51 determines whether or not a switching request for switching the fuel pressure from a low pressure to a high pressure has occurred (step S21). Specifically, the ECU 51 determines, based on a signal input from the coolant temperature sensor 45, whether or not the vehicle is warmed up or at a high fuel temperature when the vehicle is in a high pressure supply state.

  When the ECU 51 determines that this switching request has occurred (YES in step S21), the ECU 51 proceeds to step S22. On the other hand, if it is determined that a switching request has not occurred (NO in step S21), the process proceeds to END.

  Next, the ECU 51 determines whether or not the engine consumption A of fuel is equal to or less than a predetermined value (step S22). Specifically, the ECU 51 acquires data representing the fuel injection amount per unit time set by the fuel injection control, and compares this fuel injection amount with the predetermined value. If the ECU 51 determines that the fuel injection amount is less than or equal to the predetermined value (YES in step S22), the ECU 51 proceeds to step S23, and if it determines that the fuel injection amount exceeds the predetermined value (NO in step S22). ) And END.

  The predetermined value is set to include, for example, the fuel consumption per unit time during idle operation. Note that the ECU 51 determines whether or not the fuel consumption amount of the engine is equal to or less than a predetermined value depending on whether or not the engine is idling instead of acquiring data representing the fuel consumption amount per unit time. You may make it judge.

  Next, the ECU 51 estimates the return flow rate Q at low pressure (step S23). As described above, the return flow rate Q is estimated by executing the return flow rate estimation control based on the calculated leanest voltage Vaf, the initial voltage Vini, and the like.

  Next, the ECU 51 determines whether or not the return flow rate Q estimated in step S23 is greater than or equal to a predetermined value Qa (step S24). As described above, the predetermined value Qa is a minimum value in a region where the overshoot amount OS and the overshoot duration time Tos are constant regardless of the return flow rate Q when the fuel pressure is switched from low pressure to high pressure. It is obtained in advance by experimental measurement.

  If the ECU 51 determines that the estimated return flow rate Q is equal to or greater than the predetermined value Qa (YES in step S24), the ECU 51 proceeds to step S26. On the other hand, when it is determined that the estimated return flow rate Q is smaller than the predetermined value Qa (NO in step S24), the process proceeds to step S25.

  When the process proceeds to step S25, the ECU 51 increases the voltage applied to the fuel pump unit 11 so that the return flow rate Q is equal to or greater than the predetermined value Qa. In this case, the ECU 51 stores in advance the relationship between the voltage applied to the fuel pump unit 11 as shown in FIG. 8 and the return flow rate Q, and is applied to the current return flow rate Q and the fuel pump unit 11. The voltage for making the return flow rate Q equal to or higher than the predetermined value Qa is calculated from the existing voltage. It is preferable that the ECU 51 controls the voltage applied to the fuel pump unit 11 so that the return flow rate Q is slightly higher than the predetermined value Qa. As a result, even if the return flow rate Q fluctuates, the actual return flow rate Q can be suppressed from falling below the return flow rate Qa, and an excessive voltage can be applied to the fuel pump unit 11 to reduce fuel consumption or reduce the fuel pump unit 11. It is possible to suppress the consumption of the constituent parts.

  Next, the ECU 51 switches the fuel pressure from the low pressure to the high pressure by energizing the electromagnetic coil 61 and controlling the switching valve 60 to the ON state (step S26).

  Then, the ECU 51 executes fuel injection control based on the overshoot characteristic stored in advance in the ROM 54 (step S27).

  In this step, the ECU 51 selects and executes, for example, one of the following fuel injection controls based on the fuel injection time, the injection interval, the overshoot amount OS stored in the ROM 54, the duration Tos, and the like.

  First, as a first example, the ECU 51 interrupts fuel injection while the fuel pressure is being switched, including during overshoot. Then, the fuel injection control is resumed after the continuation time Tos has elapsed.

  Further, as a second example, the ECU 51 is configured so that the deviation from the target value of the fuel injection amount is offset by the portion where the overshoot is positive and the portion where the overshoot is negative. The fuel injection control is executed so that this time coincides with the timing of the duration time Tos.

  Further, as a third example, the ECU 51 compares the duration Tos with the fuel injection time, and if the duration Tos is sufficiently shorter than the fuel injection time, the variation in the fuel injection amount is within one fuel injection. Since the deviation from the target fuel injection amount is suppressed, the fuel injection is executed regardless of the occurrence of the overshoot.

  Further, the ECU 51 may adjust the fuel injection time based on the overshoot amount OS and the duration time Tos stored in the ROM 54 so that the actual fuel injection amount approaches the target fuel injection amount.

  Further, the ECU 51 may execute any fuel injection control for reducing the difference between the actual fuel injection amount and the target fuel injection amount based on the overshoot amount OS and the duration time Tos stored in the ROM 54. .

  As described above, in the fuel supply device 8 according to the embodiment of the present invention, if the return flow rate Q in the pressure regulator 20 is equal to or greater than a predetermined value, the overshoot amount OS generated when the fuel pressure is switched is constant. Thus, the fuel pressure can be estimated even before the overshoot converges. Therefore, the fuel pressure can be improved by optimizing the timing for instructing the switching of the fuel pressure and the fuel injection time, and suppressing the actual fuel injection amount from deviating from the desired fuel injection amount even when the fuel pressure is switched. Can be achieved.

  Further, the return flow rate Q from the pressure regulator 20 can be estimated in accordance with the change in the voltage applied to the fuel pump unit 11. As a result, the degree of deterioration of the fuel pump unit 11 and the variation in the discharge characteristics can be obtained.

  Further, if the initial voltage Vini of the fuel pump unit 11 having an average discharge characteristic is calculated in advance, the deterioration characteristics of the fuel pump unit 11 can be measured without measuring the initial voltage Vini for all the fuel pump units 11. It is possible to calculate the variation in the ejection characteristics. Therefore, each fuel pump unit 11 can be maintained in an optimum state without reducing the production efficiency of the fuel supply device 8.

  Further, even when the amount of fuel discharged from the pressure regulator 20 changes according to the temperature of the fuel, the estimated value of the return flow rate Q is corrected according to the temperature of the fuel, so that the return flow rate Q can be estimated accurately. Is possible.

  In the above description, the configurations of the pressure regulator 20 and the switching valve 60 are examples. Therefore, although there is a high possibility that the fuel supply device 8 according to the present embodiment is reduced in terms of downsizing, cost reduction, or fuel pressure switching response, for example, the pressure regulator 20 is replaced with a known one. Also good.

  In the above description, when the ECU 51 estimates the return flow rate Q, the case where the voltage is decreased by 0.5 V until the air-fuel ratio swings in the rich direction has been described. However, the present invention is not limited to this. May be decreased by 0.5 V until the air-fuel ratio swings in the rich direction, and if the air-fuel ratio swings in the rich direction, the voltage may be increased again by 0.5 V. In this case, the voltage immediately before the air-fuel ratio swings again in the rich direction by raising the voltage becomes the leanest voltage Vaf. Further, the ECU 51 decreases the voltage by 0.5 V in order to decrease the voltage in order to obtain the most lean voltage Vaf, and increases the voltage again when the voltage is increased again due to the air-fuel ratio swinging in a rich direction. You may make it raise 0.1V at a time. In this case, the leanest voltage Vaf can be obtained more accurately.

  As described above, the fuel supply device according to the present invention can improve fuel consumption by suppressing the actual fuel injection amount from deviating from the desired fuel injection amount even when the fuel pressure is switched. This is advantageous in that it is useful for a fuel supply device that regulates the fuel stored in the fuel tank and supplies the fuel to the fuel consumption unit.

1 Engine 2 Fuel tank 3 Injector (Fuel consumption part)
5 cylinders (fuel consumption part)
7 Intake port 8 Fuel supply device 10 Fuel pressure feeding mechanism 11 Fuel pump unit 15 Fuel passage 15a Branch passage 19a Atmospheric pressure introduction hole 20 Pressure regulator (variable fuel pressure adjusting valve)
21 Housing 21a Fluid inlet 21b Fluid outlet 21c Operation pressure outlet 22 Pressure regulating member 23 Pressure regulating chamber 24 Partition portion 24a Annular pressure receiving surface 25 Movable valve body portion 26 Back pressure chamber 31 First valve seat portion 31h Discharge hole 32 2nd Valve seat portion 32h Operation pressure fuel introduction hole 35 Alternator 41 Engine speed sensor 42 Air flow meter 44 Throttle opening sensor 45 Cooling water temperature sensor 47 Wheel speed sensor 48 Air fuel ratio sensor 51 ECU (Air fuel ratio detection means, discharge amount estimation means, voltage Control means)
60 switching valve 61 electromagnetic coil 67 valve 69 transistor 70 open end 75 fuel pipe 77 fuel inflow pipe 78 fuel outflow pipe

Claims (6)

A fuel supply device that regulates fuel discharged from a fuel pump and supplies the fuel to a fuel consumption unit,
A variable fuel pressure regulating valve capable of taking at least one of a high pressure supply state in which the fuel pressure of the fuel is high and a low pressure supply state in which the fuel pressure is low;
Air-fuel ratio detecting means for detecting the air-fuel ratio based on the exhaust component;
Based on the voltage applied to the fuel pump and the air-fuel ratio detected by the air-fuel ratio detecting means, on the condition that the variable fuel pressure adjusting valve is in the low-pressure supply state, the variable fuel pressure adjusting valve Emission estimation means for estimating the amount of fuel discharged;
On the condition that the condition for switching the fuel pressure from a low pressure to a high pressure is satisfied, a voltage to be applied to the fuel pump is set so that the fuel discharge amount estimated by the discharge amount estimating means is not less than a predetermined value. And a voltage control means for controlling the fuel supply device.   2. The predetermined value is set in a region where an overshoot amount generated when the fuel pressure is switched from a low pressure to a high pressure is substantially constant regardless of a change in the discharge amount. Fuel supply system.   The discharge amount estimation means changes the voltage applied to the fuel pump to obtain the lowest voltage at which the air-fuel ratio detected by the air-fuel ratio detection means becomes the leanest, and the air-fuel ratio when the fuel pump is new 3. The fuel supply device according to claim 1, wherein the amount of discharged fuel is estimated based on a difference from an initial voltage at which the fuel cell becomes the leanest.   4. The fuel supply device according to claim 3, wherein the initial voltage is a substantially average value of voltages at which the air-fuel ratio becomes the leanest when a plurality of the fuel pumps are new. 5.   The fuel supply device according to any one of claims 1 to 4, wherein the discharge amount estimation unit corrects the estimated value of the discharge amount according to the temperature of the fuel. The variable fuel pressure regulating valve forms a pressure regulating chamber communicating with the fuel inlet between the housing having a fuel inlet into which the fuel is introduced and a fuel outlet through which the fuel is discharged, and the housing. A pressure regulating member having a partition wall portion and a movable valve body portion that is displaced in a valve opening direction to communicate the pressure regulating chamber with the fuel discharge port according to the fuel pressure in the pressure regulating chamber,
A first valve seat portion that communicates with the fuel discharge port inside the pressure regulating chamber and forms a discharge hole whose opening degree changes according to the displacement of the movable valve body portion, and the pressure regulating chamber inside the pressure regulating chamber A second valve seat part that forms an operating pressure fuel introduction hole into which fuel having an operating pressure is introduced while the opening degree changes according to the displacement of the movable valve body part is provided in the housing,
The area according to claim 1, wherein an area where the pressure adjusting member receives fuel pressure in the valve opening direction changes according to an operating pressure in the operating pressure fuel introduction hole. The fuel supply device described in 1.

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