JP2013231373A - Fuel pressure control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel pressure control device which injects fuel less than the minimum fuel discharge amount corresponding to a lower-limit voltage, from a fuel injection valve, while keeping a voltage to be applied to an electric fuel pump at lower-limit voltage or higher.SOLUTION: A fuel pressure control device includes an electric fuel pump 21, a second return pipe 27 for causing part of fuel flowing in a fuel pipe 22 to flow back to a fuel tank 30, an electromagnetic reducing valve 29 provided in the second return pipe 27, and an ECU 100 for controlling the voltage to be applied to the fuel pump 21 and the opening/closing of the reducing valve 29. While the applied voltage is controlled at lower-limit voltage Vmin or higher to generate driving torque for keeping drive of the fuel pump 21 even if a foreign matter sticks to a sliding part of the fuel pump 21, the ECU 100 opens the reducing valve 29 on condition that a target fuel injection amount Q is smaller than the minimum fuel discharge amount of the fuel pump 21 when the lower-limit voltage Vmin is applied to the fuel pump 21 as the applied voltage.

Description

  The present invention relates to a fuel pressure control device, and more particularly to a fuel pressure control device that controls the pressure of fuel supplied to a fuel injection valve of an internal combustion engine mounted on a vehicle or the like.

  2. Description of the Related Art Conventionally, as this type of fuel pressure control device, a device including a motor-integrated electric pump that sucks fuel in a fuel tank and pumps the fuel into a delivery pipe is known (see, for example, Patent Document 1). . In this electric pump, the applied voltage is controlled by an electronic control unit so that the fuel pressure in the delivery pipe (hereinafter simply referred to as fuel pressure) becomes the target fuel pressure. Further, the fuel pressure control device has a function of an intake filter that removes relatively large foreign matters contained in the fuel and a function of a high-pressure filter that removes relatively small foreign matters and motor foreign matters contained in the fuel. An integrated filter is provided. This integrated filter is disposed upstream of the electric pump. This prevents small foreign matter from entering the electric pump.

  However, among the foreign matters contained in the fuel, there are small foreign matters that cannot be removed even if the integrated filter is used. When such foreign matter enters the electric pump, the foreign matter bites into the sliding portion of the electric pump, which may cause a load on the electric pump. Such a load due to foreign object biting is a factor that impairs the original discharge performance of the electric pump.

  For this reason, such an electric pump has a restriction that the applied voltage must be equal to or higher than a predetermined lower limit voltage so that the original discharge performance can be exhibited even when foreign matter biting occurs as described above. Therefore, the electric pump is not driven with an applied voltage lower than a predetermined lower limit voltage, and can exhibit its original discharge performance even if there is a slight foreign matter biting.

JP 2007-2733 A

  However, in the above-described conventional electric pump, the drive region is a region that is equal to or higher than the predetermined lower limit voltage, so that the fuel discharge amount supplied into the delivery pipe is limited to the minimum fuel discharge amount corresponding to the predetermined lower limit voltage. Will be. For this reason, such an electric pump cannot realize a fuel discharge amount lower than the minimum fuel discharge amount. Therefore, in the fuel pressure control device provided with such an electric pump, there has been a problem that the fuel injection amount injected from the fuel injection valve cannot be less than the minimum fuel discharge amount corresponding to the lower limit voltage.

  The present invention has been made in order to solve the above-described problems. The fuel injection amount injected from the fuel injection valve is set to the lower limit voltage while maintaining the applied voltage of the electric fuel pump at the lower limit voltage or higher. It is an object of the present invention to provide a fuel pressure control device that can be less than the minimum fuel discharge amount corresponding to the above.

  In order to achieve the above object, the fuel pressure control device according to the present invention is (1) an electric motor that pumps fuel stored in a fuel tank to a delivery pipe to which a fuel injection valve of an internal combustion engine is connected via a supply passage. A fuel pump of the type, a recirculation passage for recirculating part of the fuel branched from the supply passage and flowing in the supply passage to the fuel tank, an electromagnetic reduction valve provided in the recirculation passage, a target, Control means for controlling an applied voltage applied to the fuel pump so as to inject fuel for a target fuel injection amount to be injected from the fuel injection valve, and for controlling the opening and closing of the reduction valve. The means controls the applied voltage at a level equal to or higher than a lower limit voltage that generates a driving torque capable of maintaining the drive of the fuel pump even if foreign matter is caught in the sliding portion of the fuel pump, and the lower limit voltage is controlled. Said target fuel injection amount is small in the condition with respect to the fuel discharge amount of the fuel pump when the serial applied voltage is applied to the fuel pump, has a configuration which opens the reduction valve.

  With this configuration, the fuel pressure control device according to the present invention is a drive capable of maintaining the drive of the fuel pump by the control means even when the applied voltage applied to the fuel pump causes a foreign matter to be caught in the sliding portion of the fuel pump. It is controlled above the lower limit voltage that generates torque. For this reason, it is possible to prevent the electric fuel pump from being stopped due to the foreign object biting as described above.

  The fuel pressure control device according to the present invention is an electromagnetic reduction valve on the condition that the target fuel injection amount is smaller than the fuel discharge amount of the fuel pump when the lower limit voltage is applied to the fuel pump as the applied voltage. Open the valve. As a result, the difference fuel between the fuel discharge amount of the fuel pump and the target fuel injection amount when the fuel pump is driven at the lower limit voltage is returned to the fuel tank through the supply passage. Therefore, the fuel injection amount injected from the fuel injection valve can be made less than the minimum fuel discharge amount corresponding to the lower limit voltage while maintaining the applied voltage of the electric fuel pump at or above the lower limit voltage.

  The fuel pressure control device according to the present invention is the fuel pressure control device according to the above (1), wherein (2) the control means is configured such that when the reduction valve is in a closed state, the fuel in the delivery pipe is The pressure reducing valve is configured to open on the condition that the pressure becomes equal to or higher than a predetermined upper limit threshold value.

  With this configuration, the fuel pressure control device according to the present invention is configured so that, when the reduction valve is in the closed state, the fuel pressure in the delivery pipe is equal to or higher than a predetermined upper limit threshold. Open the valve. For this reason, when the pressure of the fuel in the delivery pipe is too high, for example, with respect to the target fuel pressure, the excess fuel can be returned to the fuel tank by opening the reduction valve. The fuel pressure can be reduced. Therefore, the fuel pressure in the delivery pipe can be brought close to the target fuel pressure.

  The fuel pressure control device according to the present invention is the fuel pressure control device according to the above (1) or (2), wherein (3) the control means is configured to deliver the delivery when the reduction valve is in an open state. The reduction valve is closed on condition that the fuel pressure in the pipe is equal to or lower than a predetermined lower limit threshold value.

  With this configuration, the fuel pressure control device according to the present invention is configured so that when the reduction valve is in the open state, the fuel pressure in the delivery pipe is less than or equal to a predetermined lower limit threshold. Is closed. For this reason, when the pressure of the fuel in the delivery pipe is too low, for example, with respect to the target fuel pressure, the fuel that has been returned to the fuel tank is supplied into the delivery pipe by closing the reduction valve. Can do. Thereby, the pressure of the fuel in a delivery pipe can be raised. Therefore, the fuel pressure in the delivery pipe can be brought close to the target fuel pressure.

  According to the present invention, the fuel injection amount injected from the fuel injection valve is set to be less than the minimum fuel discharge amount corresponding to the lower limit voltage while maintaining the applied voltage of the electric fuel pump at or above the lower limit voltage. A fuel pressure control device that can be provided can be provided.

1 is a schematic configuration diagram of a vehicle to which a fuel pressure control device according to an embodiment of the present invention is applied. It is a flowchart which shows the opening / closing control of the weight reduction valve which concerns on embodiment of this invention. It is a flowchart which shows fuel pressure maintenance control when a reduction valve is in a valve closing state. It is a graph which shows the relationship between the difference of an actual fuel pressure when a real fuel pressure has deviated to the increase side with respect to a target fuel pressure, and a target fuel pressure, and the open / close state of a weight reduction valve. It is a flowchart which shows fuel pressure maintenance control when a reduction valve exists in a valve opening state. It is a graph which shows the relationship between the difference of an actual fuel pressure when a real fuel pressure deviates with respect to a target fuel pressure, and a target fuel pressure, and the open / close state of a reduction valve.

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

  As shown in FIG. 1, the vehicle 1 includes an engine 10, a fuel supply mechanism 20, and an ECU (Electronic Control Unit) 100.

  The engine 10 is configured as an internal combustion engine that can output power using a hydrocarbon-based fuel such as gasoline or light oil. The fuel used for the engine 10 may be an alcohol fuel obtained by mixing alcohol such as ethanol and gasoline.

  In the present embodiment, the engine 10 is constituted by a so-called in-line 4-cylinder gasoline engine in which four cylinders 11 are arranged in series as indicated by # 1, # 2, # 3, and # 4. The engine 10 is not limited to an in-line four-cylinder engine, and is configured by various types of engines such as an in-line six-cylinder engine, a V-type six-cylinder engine, a V-type 12-cylinder engine, or a horizontally opposed six-cylinder engine. Also good.

  Further, in the present embodiment, the engine 10 is constituted by a four-cycle gasoline engine that performs a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke while a piston (not shown) reciprocates twice. Explain that it is.

  Furthermore, each of the four cylinders 11 indicated by # 1, # 2, # 3, and # 4 in the engine 10 is provided with an intake port 12 respectively. The engine 10 also includes a port injector 13 for injecting fuel into the intake port 12.

  The port injector 13 includes a solenoid coil controlled by an injection command signal Iq from the ECU 100, a needle valve, and a nozzle part. The port injector 13 is supplied with fuel at a predetermined pressure. When the solenoid coil is energized by the ECU 100, the port injector 13 opens the needle valve and injects fuel into the intake port 12. The port injector 13 in the present embodiment constitutes a fuel injection valve according to the present invention.

  The fuel supply mechanism 20 includes a fuel pump 21 that pressurizes and pumps fuel from the fuel tank 30, and a delivery pipe 23 that introduces the fuel pumped by the fuel pump 21 through the fuel pipe 22. A supply passage for supplying fuel from the fuel pump 21 to the delivery pipe 23 is formed in the fuel pipe 22.

  With this configuration, the fuel supply mechanism 20 supplies fuel to the plurality of port injectors 13 that respectively inject fuel into the plurality of intake ports 12 corresponding to the plurality of cylinders 11 in the intake passage 15 of the engine 10. It has become.

  The fuel pump 21 is an electric fuel pump that is driven in accordance with a control signal output from the ECU 100. The fuel pump 21 pumps up fuel stored in the fuel tank 30 and passes it through a supply passage in the fuel pipe 22. The port injection injector 13 is pressure-fed to a delivery pipe 23 to which the port injection injector 13 is connected.

  Specifically, the fuel pump 21 includes a motor whose rotational speed changes according to an applied voltage corresponding to a control signal output from the ECU 100, and an impeller that rotates by the rotational force of the motor. The fuel pump 21 pressurizes and pumps fuel from the fuel tank 30 by rotating the impeller. Therefore, in the fuel pump 21, the rotational force of the motor is adjusted according to the magnitude of the applied voltage applied to the motor, and the fuel discharge amount of the discharged fuel is variable.

  In addition, the fuel pump 21 is an integrated filter that has both a function of a suction filter that removes relatively large foreign matters contained in the fuel and a function of a fuel filter that removes relatively small foreign matters and motor foreign matters contained in the fuel. I have.

  The delivery pipe 23 is connected to the fuel pipe 22 at one end side in the series arrangement direction of the plurality of cylinders 11 and is configured to supply fuel to the plurality of port injectors 13 independently. The delivery pipe 23 is provided with a fuel pressure sensor 25 that detects the pressure of the fuel in the delivery pipe 23 (hereinafter referred to as fuel pressure).

  Further, the fuel supply mechanism 20 includes a first return pipe 26 and a first return pipe 26 formed therein, in which a recirculation passage is formed to return a part of the fuel branched from the fuel pipe 22 and flowing in the fuel pipe 22 to the fuel tank 30. 2 return pipes 27 are provided.

  The first return pipe 26 has a relief valve 28 for returning fuel from the fuel pipe 22 to the fuel tank 30 when the fuel pressure of the fuel pipe 22 exceeds a predetermined fuel pressure (for example, several hundred kPa). Is provided. The relief valve 28 is provided to prevent an abnormal increase in the fuel pressure of the fuel pipe 22.

  The second return pipe 27 is provided with an electromagnetic reduction valve 29. The reduction valve 29 can take a valve open state and a valve close state in response to a command signal from the ECU 100. When the reduction valve 29 is opened, a part of the fuel flowing in the fuel pipe 22, for example, surplus fuel is returned to the fuel tank 30 through the second return pipe 27 as described later. The weight reduction valve 29 in the present embodiment constitutes a weight reduction valve according to the present invention.

  The ECU 100 includes, for example, a microcomputer including a CPU, a RAM, a ROM, an input / output interface, and the like. The CPU uses a temporary storage function of the RAM and performs signal processing according to a program stored in advance in the ROM. It is like that. Various control constants and various maps are stored in advance in the ROM.

  Further, the ECU 100 is connected to various sensors such as the fuel pressure sensor 25, the rotational speed sensor 101, the intake air amount sensor 102, and the accelerator opening sensor 103, the port injector 13, the fuel pump 21, and the reduction valve 29 described above. ing.

  The fuel pressure sensor 25 detects the fuel pressure in the delivery pipe 23. The rotational speed sensor 101 detects the engine rotational speed Ne of the engine 10. The intake air amount sensor 102 detects the intake air amount GA. The accelerator opening sensor 103 detects an accelerator operation amount ACC corresponding to the depression amount of the accelerator pedal. Each of these sensors transmits a signal corresponding to the detection result to the ECU 100.

  The ECU 100 executes various calculations based on signals input from these various sensors, and executes various controls based on the calculation results.

  For example, the ECU 100 calculates the target fuel injection amount Q based on the intake air amount GA, the engine rotational speed Ne, the accelerator operation amount ACC, and the like. The ECU 100 sets a valve opening period of the port injector 13, that is, an injection period, based on the fuel pressure PF so that the calculated target fuel injection amount Q can be realized. ECU 100 individually outputs a valve opening command to each port injector 13 according to the set injection period. As a result, an amount of fuel commensurate with the operating state of the engine 10 is injected from each port injector 13. At this time, the ECU 100 controls the applied voltage applied to the fuel pump 21 so as to adjust the fuel discharge amount of the fuel pump 21 so that fuel for the target fuel injection amount Q is injected from the port injector 13. It has become. ECU 100 in the present embodiment constitutes a control means according to the present invention.

  Further, the ECU 100 applies the fuel pump 21 to the fuel pump 21 in accordance with the magnitude of the target fuel pressure PFt so that the minimum discharge capacity necessary for securing the target fuel pressure (hereinafter referred to as the target fuel pressure PFt) is obtained. Control the applied voltage. Here, the target fuel pressure PFt is an optimum fuel pressure according to, for example, the operating state of the engine 10 and the fuel injection amount.

  More specifically, the ECU 100 controls the applied voltage at a predetermined lower limit voltage Vmin or higher. The predetermined lower limit voltage Vmin generates a driving torque capable of maintaining the driving of the fuel pump 21 even if foreign matter is caught in a sliding portion of the fuel pump 21, for example, a gap portion between the impeller and the pump cover. The voltage that can be used. Therefore, it is possible to prevent the fuel pump 21 from being stopped due to the above-mentioned foreign matter being caught.

  Here, since the fuel pump 21 is limited by the above-described lower limit voltage Vmin, it cannot be driven with an applied voltage lower than the lower limit voltage Vmin. In this case, the minimum fuel discharge amount of the fuel pump 21 is a fuel discharge amount corresponding to the lower limit voltage Vmin. Therefore, the fuel pump 21 cannot discharge fuel with a fuel discharge amount less than the minimum fuel discharge amount according to the lower limit voltage Vmin. For this reason, for example, when the required fuel injection amount is small, such as during idle operation, the above-mentioned minimum fuel discharge amount becomes larger than the target fuel injection amount Q, and the desired fuel injection amount is reduced. There is a problem that cannot be obtained. As a result, the actual fuel pressure in the delivery pipe 23 (hereinafter referred to as the actual fuel pressure PFr) also rises above the target fuel pressure PFt, and the actual fuel pressure PFr cannot be maintained at the target fuel pressure PFt.

  Therefore, in the present embodiment, the above-described reduction valve 29 is provided in the fuel supply mechanism 20 in order to solve such a problem.

  Next, the opening / closing control of the weight reduction valve 29 will be described with reference to FIG.

  The opening / closing control of the weight reduction valve 29 is executed by the ECU 100 at predetermined time intervals.

  As shown in FIG. 2, the ECU 100 first calculates a target fuel injection amount Q based on the intake air amount GA, the engine rotational speed Ne, the accelerator operation amount ACC, and the like (step S1).

  Next, the ECU 100 calculates a required voltage Vr for the fuel pump 21 corresponding to the fuel discharge amount of the fuel pump 21 required to obtain the target fuel injection amount Q calculated in step S1 (step S2). The required voltage Vr can be calculated, for example, by referring to a map or the like that is obtained by experimentally finding in advance a relationship between the fuel discharge amount of the fuel pump 21 and the required voltage Vr.

  Thereafter, the ECU 100 determines whether or not the required voltage Vr is less than the lower limit voltage Vmin (step S3). Here, the required voltage Vr and the target fuel injection amount Q have a correlation as described above. Therefore, determining whether or not the required voltage Vr is less than the lower limit voltage Vmin is determining whether or not the target fuel injection amount Q is smaller than the minimum fuel discharge amount corresponding to the lower limit voltage Vmin. The same.

  When the ECU 100 determines that the required voltage Vr is less than the lower limit voltage Vmin, the applied voltage of the fuel pump 21 is limited by the lower limit voltage Vmin, so that the fuel pump 21 is not the required voltage Vr but the lower limit voltage Vmin. Is driven (step S4). Then, the ECU 100 opens the reduction valve 29 (step S5) and ends this process.

  Thus, in the present embodiment, the reduction valve 29 has a target fuel injection amount Q that is smaller than the minimum fuel discharge amount of the fuel pump 21 when the lower limit voltage Vmin is applied to the fuel pump 21 as an applied voltage. Open the valve on the condition. As a result, the difference fuel (the surplus fuel) between the minimum fuel discharge amount and the target fuel injection amount Q at this time is returned from the fuel pipe 22 to the fuel tank 30 through the second return pipe 27. As a result, a desired fuel injection amount corresponding to the target fuel injection amount Q less than the minimum fuel discharge amount corresponding to the lower limit voltage Vmin is obtained.

  On the other hand, when it is determined in step S3 that the required voltage Vr is not less than the lower limit voltage Vmin, the ECU 100 drives the fuel pump 21 with the required voltage Vr (step S6). Then, the ECU 100 closes the reduction valve 29 (step S7) and ends this process.

  Next, fuel pressure maintenance control will be described with reference to FIGS.

  The actual fuel pressure PFr in the delivery pipe 23 is preferably maintained at the target fuel pressure PFt from the viewpoint of improving fuel consumption, exhaust emission, suppressing vapor generation, and the like. However, the actual fuel pressure PFr may deviate from the target fuel pressure PFt due to various factors such as a change in the discharge amount of the fuel pump. In the present embodiment, fuel pressure maintenance control using the weight reduction valve 29 is executed in order to suppress such a shift in fuel pressure.

  This fuel pressure maintenance control is executed by the ECU 100 at predetermined time intervals. Since the fuel pressure maintaining control is a process different depending on the open / close state of the weight reduction valve 29, the following description will be made separately for when the weight reduction valve 29 is in a closed state and when it is in a valve open state.

  First, with reference to FIG. 3, the fuel pressure maintenance control when the reduction valve 29 is in the closed state will be described. Note that this fuel pressure maintenance control is executed, for example, when the reduction valve 29 is closed (see step S7 in FIG. 2) executed in the opening / closing control shown in FIG.

  As shown in FIG. 3, the ECU 100 detects the actual fuel pressure PFr in the delivery pipe 23 based on an input signal from the fuel pressure sensor 25 (step S11).

  Next, the ECU 100 determines whether or not the difference ΔPF (= PFr−PFt) between the actual fuel pressure PFr detected in step S11 and the target fuel pressure PFt is greater than or equal to the threshold A (step S12). Here, the difference ΔPF is not an absolute value but a value including positive and negative signs. The threshold A is a positive value, and is experimentally obtained and stored in advance in consideration of fuel consumption, exhaust emission, and the like. The threshold A in the present embodiment corresponds to the upper limit threshold in the present invention.

  When the ECU 100 determines that the difference ΔPF is not equal to or greater than the threshold A, that is, the difference ΔPF is less than the threshold A, the difference ΔPF is not limited even if the actual fuel pressure PFr matches or does not match the target fuel pressure PFt. It is determined that the amount is within the allowable range, the reduction valve 29 is closed (step S14), and the process is terminated. Specifically, the ECU 100 closes the reduction valve 29 when this process is performed again after the reduction valve 29 is opened in step S13 described later. Further, the ECU 100 maintains this when the reduction valve 29 is already closed at the time of shifting to step S14.

  On the other hand, if the ECU 100 determines that the difference ΔPF is equal to or greater than the threshold value A, the ECU 100 opens the reduction valve 29 (step S13) and ends the present process. Therefore, the reduction valve 29 opens on condition that the difference ΔPF is equal to or greater than the threshold value A. As a result, the actual fuel pressure PFr that has been excessively increased with respect to the target fuel pressure PFt can be reduced.

  Next, with reference to FIG. 4, the operation when the above-described fuel maintenance control is executed will be described.

  As shown in FIG. 4, first, the reduction valve 29 is maintained in a closed state. Thereafter, the difference ΔPF (indicated by a thick solid line in FIG. 4) starts to increase toward the positive side as time elapses. When the difference ΔPF is greater than or equal to the threshold value A, the reduction valve 29 is opened (step S13 in FIG. 3).

  In the present embodiment, the fuel pressure is reduced by opening the reduction valve 29 in addition to the adjustment of the applied voltage of the fuel pump 21. Therefore, the difference ΔPF is reduced earlier than in the prior art, that is, the actual fuel pressure that has increased too much. PFr can be brought close to the target fuel pressure PFt at an early stage. In FIG. 4, a difference ΔPF indicated by a thick broken line is a difference between the conventional actual fuel pressure and the target fuel pressure in which the fuel pressure control is performed only by the applied voltage of the fuel pump.

  Thereafter, when the difference ΔPF is less than the threshold A, the reduction valve 29 is closed (step S14 in FIG. 3). Thereafter, the difference ΔPF is reduced by adjusting the applied voltage of the fuel pump 21, and the actual fuel pressure PFr approaches the target fuel pressure PFt.

  Next, with reference to FIG. 5, the fuel pressure maintenance control when the weight reduction valve 29 is in the valve open state will be described. Note that this fuel pressure maintenance control is executed, for example, when the reduction valve 29 is opened (see step S5 in FIG. 2) executed in the opening / closing control shown in FIG.

  As shown in FIG. 5, the ECU 100 detects the actual fuel pressure PFr in the delivery pipe 23 based on an input signal from the fuel pressure sensor 25 (step S21).

  Next, the ECU 100 determines whether or not the difference ΔPF (= PFr−PFt) between the actual fuel pressure PFr detected in step S21 and the target fuel pressure PFt is equal to or less than a threshold value B (step S22). Here, the difference ΔPF is not an absolute value but a value including positive and negative signs. The threshold value B is a negative value, and is experimentally obtained and stored in advance in consideration of fuel consumption, exhaust emission, vapor generation, and the like. The threshold value B in the present embodiment corresponds to the lower limit threshold value in the present invention.

  When the ECU 100 determines that the difference ΔPF is not less than or equal to the threshold B, that is, the difference ΔPF is greater than the threshold B, the difference ΔPF is allowed even if the actual fuel pressure PFr matches or does not match the target fuel pressure PFt. Therefore, it is determined that the amount is within the range, the open state of the reduction valve 29 is maintained (step S27), and this process is terminated. Specifically, the ECU 100 opens the reduction valve 29 when this process is performed again after the reduction valve 29 is closed in step S23 described later. Further, the ECU 100 maintains this when the reduction valve 29 is already open at the time of transition to step S24.

  On the other hand, if the ECU 100 determines that the difference ΔPF is equal to or smaller than the threshold value B, the ECU 100 sets the reduction valve 29 to the closed state (step S23) and ends the present process. Therefore, the reduction valve 29 is closed on condition that the difference ΔPF is equal to or less than the threshold value B. As a result, the actual fuel pressure PFr that has been excessively decreased with respect to the target fuel pressure PFt can be increased.

  Next, with reference to FIG. 6, the operation at the time of executing the fuel maintenance control described above will be described.

  As shown in FIG. 6, first, the weight reduction valve 29 is maintained in an open state. Thereafter, the difference ΔPF (indicated by a thick solid line in FIG. 6) starts to increase toward the negative side as time elapses. When the difference ΔPF is equal to or less than the threshold value B, the reduction valve 29 is closed (step S23 in FIG. 5).

  In the present embodiment, the fuel pressure is increased by closing the reducing valve 29 in addition to the adjustment of the applied voltage of the fuel pump 21. Therefore, the difference ΔPF is reduced earlier than in the prior art, that is, the actual fuel pressure has decreased too much. PFr can be brought close to the target fuel pressure PFt at an early stage. In FIG. 6, a difference ΔPF indicated by a thick broken line is a difference between the conventional actual fuel pressure and the target fuel pressure in which the fuel pressure control is performed only by the applied voltage of the fuel pump.

  Thereafter, when the difference ΔPF becomes larger than the threshold value B, the reduction valve 29 is opened (step S24 in FIG. 5). Thereafter, the difference ΔPF is reduced by adjusting the applied voltage of the fuel pump 21, and the actual fuel pressure PFr approaches the target fuel pressure PFt.

  As described above, in the fuel pressure control apparatus according to the present embodiment, the ECU 100 drives the fuel pump 21 even when the applied voltage applied to the fuel pump 21 causes foreign matter to be caught in the sliding portion of the fuel pump 21. Is controlled to be equal to or higher than the lower limit voltage Vmin for generating a driving torque capable of maintaining the above. For this reason, it is possible to prevent the electric fuel pump 21 from being stopped due to the foreign object biting as described above.

  Further, the fuel pressure control apparatus according to the present embodiment indicates that the target fuel injection amount Q is smaller than the minimum fuel discharge amount of the fuel pump 21 when the lower limit voltage Vmin is applied to the fuel pump 21 as the applied voltage. Under the condition, the electromagnetic reduction valve 29 is opened. Thereby, the difference fuel between the minimum fuel discharge amount of the fuel pump 21 and the target fuel injection amount Q when the fuel pump 21 is driven at the lower limit voltage Vmin is supplied to the fuel tank 30 via the second return pipe 27. To reflux. Therefore, while maintaining the applied voltage of the electric fuel pump 21 at or above the lower limit voltage Vmin, the fuel injection amount injected from the port injector 13 may be less than the minimum fuel discharge amount corresponding to the lower limit voltage Vmin. it can.

  Further, in the fuel pressure control device according to the present embodiment, when the reduction valve 29 is in the closed state, the difference ΔPF between the actual fuel pressure PFr in the delivery pipe 23 and the target fuel pressure PFt is predetermined threshold A. The weight reduction valve 29 is opened on condition that the above is satisfied. For this reason, when the actual fuel pressure PFr is too high with respect to the target fuel pressure PFt, the excess fuel can be recirculated to the fuel tank 30 by opening the reduction valve 29, and the actual fuel pressure PFr is lowered. be able to. Therefore, the actual fuel pressure PFr can be brought close to the target fuel pressure PFt.

  Further, in the fuel pressure control device according to the present embodiment, when the reduction valve 29 is in the open state, the difference ΔPF between the actual fuel pressure PFr in the delivery pipe 23 and the target fuel pressure PFt is set to a predetermined threshold B The weight reduction valve 29 is closed on condition that the following is true. Therefore, when the actual fuel pressure PFr is too low with respect to the target fuel pressure PFt, the fuel that has been recirculated to the fuel tank 30 can be supplied into the delivery pipe 23 by closing the reduction valve 29. . Thereby, the actual fuel pressure PFr can be raised. Therefore, the actual fuel pressure PFr can be brought close to the target fuel pressure PFt.

  Here, the fuel in the fuel pipe 22 and the delivery pipe 23 generally receives heat. For this reason, if the fuel pressure is not set to be equal to or higher than the predetermined pressure, vapor is generated, and there is a possibility that a fuel discharge failure such as a decrease in the discharge capacity of the fuel pump 21 or an inability to inject from the port injector 13 may occur. Such poor fuel discharge can cause engine stall or catalyst melting. However, in the present embodiment, as described above, when the actual fuel pressure PFr is excessively decreased, the actual fuel pressure PFr can be increased by closing the reduction valve 29, which causes a fuel discharge failure. Generation of the obtained vapor can be suppressed.

  In the present embodiment, when the actual fuel pressure PFr is too high or too low with respect to the target fuel pressure PFt, the fuel pressure maintenance control can be executed to bring the actual fuel pressure PFr closer to the target fuel pressure PFt. It is possible to prevent the actual air-fuel ratio from being excessively rich or leanly displaced with respect to the air-fuel ratio. As a result, fuel consumption, exhaust emission and drivability can be prevented from deteriorating.

  In the present embodiment, the engine 10 is configured by an internal combustion engine that performs only port injection for injecting fuel into the intake port. However, the present invention is not limited to this, and a cylinder that directly injects fuel into the combustion chamber in the cylinder. You may comprise with the internal combustion engine of the dual injection system which uses together internal injection and port injection which injects a fuel in the intake port corresponding to a cylinder.

  In the present embodiment, in the fuel pressure maintenance control, the open / close state of the weight reduction valve 29 is controlled based on the comparison between the difference ΔPF between the actual fuel pressure PFr and the target fuel pressure PFt and the threshold value A or the threshold value B. However, the open / close state of the weight reduction valve 29 may be controlled based on a comparison between the actual fuel pressure PFr and a predetermined threshold C or a predetermined threshold D. Specifically, the reduction valve 29 is opened on the condition that the actual fuel pressure PFr is equal to or higher than a predetermined threshold C set higher than the target fuel pressure PFt. On the other hand, the reduction valve 29 is closed on condition that the actual fuel pressure PFr becomes equal to or less than a predetermined threshold D set lower than the target fuel pressure PFt. The predetermined thresholds C and D are preferably set to a value higher or lower than the target fuel pressure PFt by a predetermined amount.

  As described above, the fuel pressure control device according to the present invention corresponds to the lower limit voltage for the amount of fuel injected from the fuel injection valve while maintaining the applied voltage of the electric fuel pump at the lower limit voltage or higher. It can be less than the minimum fuel discharge amount, and is useful for a fuel pressure control device that controls the pressure of fuel supplied to a fuel injection valve of an internal combustion engine mounted on a vehicle or the like.

1 vehicle 10 engine (internal combustion engine)
13 port injector (fuel injection valve)
20 Fuel supply mechanism 21 Fuel pump 22 Fuel piping (supply passage)
23 Delivery Pipe 25 Fuel Pressure Sensor 26 First Return Pipe 27 Second Return Pipe (Reflux Path)
28 Relief valve 29 Reduction valve (Reduction valve)
30 Fuel tank 100 ECU (control means)

Claims (3)

An electric fuel pump that pumps fuel stored in a fuel tank to a delivery pipe to which a fuel injection valve of an internal combustion engine is connected via a supply passage;
A return passage for branching off from the supply passage and returning a part of the fuel flowing in the supply passage to the fuel tank;
An electromagnetic reduction valve provided in the reflux passage;
Control means for controlling an applied voltage to be applied to the fuel pump so that fuel corresponding to a target fuel injection amount as a target is injected from the fuel injection valve, and controlling opening and closing of the reduction valve;
The control means controls the applied voltage at or above a lower limit voltage that generates a driving torque capable of maintaining the drive of the fuel pump even if foreign matter is caught in the sliding portion of the fuel pump, and the lower limit voltage is controlled. The pressure reducing valve is opened on the condition that the target fuel injection amount is small with respect to the fuel discharge amount of the fuel pump when the voltage is applied to the fuel pump as the applied voltage. apparatus.   The control means opens the reduction valve on the condition that when the reduction valve is in a closed state, the pressure of the fuel in the delivery pipe becomes equal to or higher than a predetermined upper limit threshold value. The fuel pressure control device according to claim 1, wherein   The control means closes the reduction valve on the condition that when the reduction valve is in an open state, the pressure of the fuel in the delivery pipe is equal to or lower than a predetermined lower limit threshold value. The fuel pressure control device according to claim 1 or 2, wherein the fuel pressure control device is a fuel pressure control device.

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