Fuel supply device of internal combustion engine

Abstract

To suppress an excessive increase in a fuel pressure inside a fuel injection valve when a fuel injection of the fuel injection valve is stopped.SOLUTION: A fuel supply device 200 of an internal combustion engine 10 includes: a tank 20 for storing gaseous fuel; a fuel injection valve 15 for supplying gaseous fuel to a cylinder 10a; a fuel pipe 40 for supplying gaseous fuel in the tank 20 to the fuel injection valve 15; a pressure relief valve 30 provided on a downstream of the tank 20 in the fuel pipe 40; a second cutoff valve 22 as a solenoid valve provided on a downstream of the pressure relief valve 30 in the fuel pipe 40 and that opens and closes the fuel pipe 40; and a control device 100. When the pressure after released by the pressure relief valve 30 is an outlet-side pressure, the pressure relief valve 30 is a valve having a valve body that opens and closes according to an increase and decrease of the outlet-side pressure. The control device 100 executes a close-valve process for closing the second cutoff valve 22 when a stop condition for stopping the fuel injection of the fuel injection valve 15 is satisfied.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fuel supply device for an internal combustion engine.

Background Art

[0002] For example, the internal combustion engine described in Patent Document 1 reduces the high-pressure gaseous fuel stored in a tank and supplies it to a fuel injection valve.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When reducing the high-pressure gaseous fuel, a pressure reducing valve is used. Here, in the case of a mechanical pressure reducing valve having a valve body that opens and closes as the outlet side pressure increases and decreases, assuming the pressure after being reduced by the pressure reducing valve as the outlet side pressure, the following inconveniences may occur.

[0005] That is, due to the response delay of the valve body when the fuel injection of the fuel injection valve is stopped, a temporary fuel pressure overshoot may occur in the fuel passage downstream of the pressure reducing valve. When such a fuel pressure overshoot is transmitted to the fuel injection valve, the pressure inside the fuel injection valve may become excessively high.

Means for Solving the Problems

[0006] The fuel supply device for an internal combustion engine that solves the above problems includes a tank for storing gaseous fuel, a fuel injection valve for supplying gaseous fuel to a cylinder, a fuel passage for supplying the gaseous fuel in the tank to the fuel injection valve, a pressure reducing valve provided downstream of the tank in the fuel passage, an electromagnetic valve provided downstream of the pressure reducing valve in the fuel passage for opening and closing the fuel passage, and a processing circuit. When the pressure after being reduced by the pressure reducing valve is defined as the outlet side pressure, the pressure reducing valve is a valve having a valve body that opens and closes in accordance with an increase or decrease in the outlet side pressure. And the processing circuit is configured to execute a valve closing process of closing the electromagnetic valve when a stop condition for stopping the fuel injection of the fuel injection valve is satisfied.

Advantages of the Invention

[0007] This fuel supply device for an internal combustion engine can suppress the fuel pressure in the fuel injection valve from becoming excessively high when the fuel injection of the fuel injection valve is stopped.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0009] Hereinafter, an embodiment in which the fuel supply device for an internal combustion engine is embodied will be described with reference to FIGS. 1 to 3. <Regarding the fuel supply device for an internal combustion engine> The internal combustion engine 10 shown in FIG. 1 is an internal combustion engine that uses hydrogen gas, which is a gaseous fuel, as fuel.

[0010] The fuel supply device 200 provided in the internal combustion engine 10 has a fuel injection valve 15, a tank 20, a fuel pipe 40, a first shut-off valve 21, a second shut-off valve 22, a pressure reducing valve 30, and a delivery pipe 60.

[0011] The fuel injection valve 15 supplies fuel to the cylinder 10a of the internal combustion engine 10. The tank 20 stores hydrogen gas, which is a gaseous fuel, in a compressed state. The fuel pipe 40 is a fuel passage through which fuel flows, and connects the tank 20 and the delivery pipe 60.

[0012] The fuel injection valve 15 is connected to the delivery pipe 60. The hydrogen gas stored in the tank 20 is supplied to the fuel injection valve 15 via the fuel pipe 40 and the delivery pipe 60.

[0013] In the fuel pipe 40, a first shut-off valve 21, a pressure reducing valve 30, and a second shut-off valve 22 are arranged in order in the fuel flow direction. The first shut-off valve 21 is an electromagnetic valve and is disposed near the outlet of the tank 20. When the first shut-off valve 21 is open, fuel is supplied from the tank 20 to the fuel pipe 40. When the first shut-off valve 21 is closed, the fuel supply from the tank 20 to the fuel pipe 40 is stopped.

[0014] The pressure reducing valve 30 is a mechanical pressure reducing valve, and is a valve that adjusts the fuel pressure, which is the pressure of the hydrogen gas supplied to the fuel injection valve 15, to a pressure corresponding to the engine operating state. The second shut-off valve 22 is an electromagnetic valve and is disposed near the delivery pipe 60. When the second shut-off valve 22 is open, fuel is supplied to the delivery pipe 60. When the second shut-off valve 22 is closed, the fuel supply to the delivery pipe 60 is stopped.

[0015] The first shut-off valve 21 and the second shut-off valve 22 are closed during the operation stop of the internal combustion engine 10. On the other hand, the first shut-off valve 21 and the second shut-off valve 22 are basically open during the operation of the internal combustion engine 10.

[0016] The first pressure sensor 81 provided in the fuel pipe 40 between the first shut-off valve 21 and the pressure reducing valve 30 detects the first pressure P1 which is the fuel pressure in the fuel pipe 40 between the first shut-off valve 21 and the pressure reducing valve 30.

[0017] The second pressure sensor 82 provided in the fuel pipe 40 between the pressure reducing valve 30 and the second shut-off valve 22 detects the second pressure P2 which is the fuel pressure in the fuel pipe 40 between the pressure reducing valve 30 and the second shut-off valve 22.

[0018] The third pressure sensor 83 provided in the delivery pipe 60 detects the third pressure P3 which is the fuel pressure of the delivery pipe 60. The control device 100 performs various controls such as fuel injection of the internal combustion engine 10 by controlling various controlled objects such as the fuel injection valve 15, the first shut-off valve 21, and the second shut-off valve 22. This control device 100 includes a CPU 110 and a memory 120 composed of a ROM and a RAM, etc. The CPU 110 executes the program stored in the memory 120 to perform various controls.

[0019] The control device 100 refers to various values necessary for the control of the internal combustion engine 10. For example, the control device 100 refers to the detection values of the first pressure sensor 81, the second pressure sensor 82, and the third pressure sensor 83. Further, the control device 100 refers to the detection signal of the accelerator position sensor 71 that detects the accelerator operation amount ACCP which is the operation amount of the accelerator pedal 27 operated by the driver of the vehicle equipped with the internal combustion engine 10. Also, the control device 100 refers to the detection signal of the speed sensor 72 that detects the vehicle speed SP of the vehicle equipped with the internal combustion engine 10. In addition, the control device 100 refers to the detection signal for calculating the engine rotation speed of the internal combustion engine 10, the detection signal of the intake air amount, etc.

[0020] When a stop condition for stopping the fuel injection of the fuel injection valve 15 is satisfied during the operation of the internal combustion engine 10, the control device 100 executes a fuel cut to stop the fuel injection of the fuel injection valve 15. Specific examples of the stop condition include that the accelerator pedal 27 is turned off during the operation of the internal combustion engine 10 and the accelerator operation amount ACCP becomes "0". That is, the stop condition includes that the output required for the internal combustion engine 10 becomes "0" during the operation of the internal combustion engine 10. Note that the stop of the fuel injection of the fuel injection valve 15 due to the satisfaction of the above stop condition does not include the stop of the fuel injection of the fuel injection valve 15 when the engine operation is stopped by turning off an ignition switch or the like.

[0021] <Structure of pressure reducing valve> Since the pressure reducing valve 30 is a well-known mechanical pressure reducing valve, a detailed description thereof will be omitted, and the outline is as follows.

[0022] As shown in FIG. 2, in the housing 31 of the pressure reducing valve 30, a first fuel chamber 32 into which fuel before pressure reduction flows, a second fuel chamber 33 from which fuel after pressure reduction flows out, and a communication hole 34 communicating the first fuel chamber 32 and the second fuel chamber 33 are formed.

[0023] The first fuel chamber 32 is connected to a fuel pipe 40 connected to the first shut-off valve 21. That is, the first fuel chamber 32 is connected to the tank 20 side. In the first fuel chamber 32, a valve body 35 for opening and closing the communication hole 34 and a spring 36 for biasing the valve body 35 in a direction to close the communication hole 34 are disposed.

[0024] The second fuel chamber 33 is connected to a fuel pipe 40 connected to the second shut-off valve 22. That is, the second fuel chamber 33 is connected to the delivery pipe 60 side. When the pressure after being reduced by the pressure reducing valve 30 is defined as the outlet side pressure Pout, the second fuel chamber 33 is provided with a cylinder 37 that is displaced in accordance with an increase or decrease in the outlet side pressure Pout, and a spring 38 that biases the cylinder 37 toward the valve body 35. A needle 37c that contacts the valve body 35 is fixed to the cylinder 37.

[0025] <Opening and closing operation of pressure reducing valve> When the second pressure P2 decreases due to fuel injection from the fuel injection valve 15, the outlet side pressure Pout decreases. When the outlet side pressure Pout decreases, the fuel pressure in the second fuel chamber 33 decreases, so the force Pcl that displaces the cylinder 37 in the direction away from the valve body 35 decreases. When the force Pcl decreases, the force resisting the force Pop of the spring 38 that biases the cylinder 37 toward the valve body 35 decreases, so the cylinder 37 displaces in the direction approaching the valve body 35. When the cylinder 37 displaces in the direction approaching the valve body 35, the needle 37c pushes down the valve body 35 in the direction away from the communication hole 34. Then, when the pushed-down valve body 35 separates from the valve seat of the communication hole 34, the valve body 35 opens.

[0026] When the valve body 35 opens, fuel flows from the first fuel chamber 32 where high-pressure fuel before pressure reduction flows in, through the communication hole 34, into the second fuel chamber 33. When the outlet side pressure Pout increases due to the fuel flowing into the second fuel chamber 33, the force Pcl increases, so the force resisting the force Pop of the spring 38 that biases the cylinder 37 toward the valve body 35 increases. Therefore, the cylinder 37 displaces in the direction away from the valve body 35. When the cylinder 37 displaces in the direction away from the valve body 35, the valve body 35 that has been pushed down by the needle 37c is pushed up in the direction approaching the communication hole 34 by the biasing force of the spring 36. Then, when the pushed-up valve body 35 hits the valve seat of the communication hole 34, the valve body 35 closes.

[0027] In this way, the pressure reducing valve 30 is a valve having a valve body 35 that opens and closes as the outlet side pressure Pout increases and decreases. <Overshoot of fuel pressure> Here, when the fuel injection amount of the fuel injection valve 15 is large, the degree of decrease in the outlet pressure Pout is greater than when the fuel injection amount is small. When the degree of decrease in the outlet pressure Pout increases, the amount of movement of the valve body 35 in the valve opening direction increases, so the amount of fuel passing through the communication hole 34, that is, the amount of fuel passing through the pressure reducing valve 30, increases. When the amount of fuel passing through the pressure reducing valve 30 is large, for example, when fuel cut or the like is performed and the fuel injection of the fuel injection valve 15 stops, the decrease in the outlet pressure Pout stops, and the valve body 35 moves in the valve closing direction. However, since the amount of movement of the valve body 35 in the valve opening direction is large, the response delay time from when the fuel injection of the fuel injection valve 15 stops until the valve body 35 closes becomes long. During this response delay time, fuel flows from the first fuel chamber 32 toward the second fuel chamber 33. Therefore, as the response delay time becomes long, the amount of fuel flowing into the second fuel chamber 33 increases. When the amount of fuel flowing into the second fuel chamber 33 becomes excessively large, the outlet pressure Pout is likely to overshoot. When the outlet pressure Pout overshoots, such overshoot of the fuel pressure is transmitted to the fuel injection valve 15 as well, and there is a risk that the fuel pressure in the fuel injection valve 15 becomes excessively high. When the fuel pressure in the fuel injection valve 15 becomes excessively high, there may be inconveniences such as difficulty in opening the fuel injection valve 15 or a decrease in the accuracy of the fuel injection amount when the fuel injection is restarted.

[0028] <Processing executed by the control device> The control device 100 suppresses the occurrence of the above-mentioned inconveniences by executing the processing shown in FIG. 3.

[0029] FIG. 3 shows the procedure of the processing executed by the control device 100. The processing shown in FIG. 3 is implemented by the CPU 110 executing a program stored in the memory 120 of the control device 100. Note that the processing shown in FIG. 3 starts when the above-mentioned stop condition for stopping the fuel injection of the fuel injection valve 15 is satisfied during the operation of the internal combustion engine 10. Also, hereinafter, the step numbers are represented by numbers with "S" attached at the beginning.

[0030] When this process starts, the control device 100 determines whether the fuel injection amount QOF is equal to or greater than the determination value QOFref (S100). The fuel injection amount QOF is the fuel injection amount instructed to the fuel injection valve 15 at the time when the above stop condition for stopping the fuel injection of the fuel injection valve 15 is satisfied. The determination value QOFref is the minimum value of the fuel injection amount at which the above-mentioned overshoot occurs and is preset.

[0031] In the process of S100, when it is determined that the fuel injection amount QOF is equal to or greater than the determination value QOFref (S100: YES), the control device 100 executes a valve closing process of closing the second shut-off valve 22 by outputting a valve closing command to the second shut-off valve 22 (S110).

[0032] Next, the control device 100 determines whether the valve closing time TCL is equal to or greater than the determination value TCLref (S120). The valve closing time TCL is the elapsed time since the valve closing command was output to the second shut-off valve 22 in S110 and is measured by the control device 100. Also, the determination value TCLref is the time required for the above-mentioned overshoot to subside after the valve closing command is output to the second shut-off valve 22 and is preset.

[0033] And until it is determined that the valve closing time TCL is equal to or greater than the determination value TCLref, the control device 100 repeats the process of S120. In the process of S120, when it is determined that the valve closing time TCL is equal to or greater than the determination value TCLref (S120: YES), the control device 100 executes an opening process of opening the second shut-off valve 22 by outputting an opening command to the second shut-off valve 22 (S130).

[0034] And when the control device 100 finishes the process of S130 or makes a negative determination in the process of S100, this process ends. <Actions and Effects of this Embodiment> (1) When the stop condition for stopping the fuel injection of the fuel injection valve 15 is satisfied, the control device 100 executes a valve closing process of closing the second shut-off valve 22, which is a solenoid valve provided downstream of the pressure reducing valve 30 in the fuel pipe 40. Therefore, the fuel pressure overshoot that occurs in the fuel pipe 40 downstream of the pressure reducing valve 30 when the fuel injection of the fuel injection valve 15 is stopped is not transmitted to the fuel pipe 40 downstream of the second shut-off valve 22. Therefore, it is possible to suppress the fuel pressure in the fuel injection valve 15 from becoming excessively high when the fuel injection of the fuel injection valve 15 is stopped.

[0035] (2) There is a time difference between when the stop condition for stopping the fuel injection of the fuel injection valve 15 is satisfied and when the fuel injection of the fuel injection valve 15 is actually stopped. In this regard, in the present embodiment, when the stop condition for stopping the fuel injection of the fuel injection valve 15 is satisfied, the process shown in FIG. 3 is started to close the second shut-off valve 22. Therefore, the second shut-off valve 22 can be closed before the fuel pressure overshoot generated upstream of the second shut-off valve 22 reaches the second shut-off valve 22.

[0036] (3) The temporary fuel pressure overshoot that occurs in the fuel pipe 40 downstream of the pressure reducing valve 30 when the fuel injection of the fuel injection valve 15 is stopped is likely to occur when the injection amount of the fuel injection valve 15 at the time of stopping the fuel injection is large.

[0037] In this regard, in the present embodiment, the process shown in FIG. 3 is started when the stop condition for stopping the fuel injection of the fuel injection valve 15 is satisfied. And in the process of S100 shown in FIG. 3, when the control device 100 determines that the fuel injection amount QOF of the fuel injection valve 15 is equal to or greater than a predetermined determination value QOFref, the valve closing process is executed. That is, when the stop condition for stopping the fuel injection of the fuel injection valve 15 is satisfied and the injection amount of the fuel injection valve 15 when the stop condition is satisfied is equal to or greater than the determination value QOFref, the control device 100 executes the valve closing process of the second shut-off valve 22. Therefore, the valve closing process of the second shut-off valve 22 can be executed when the above-mentioned fuel pressure overshoot is likely to occur.

[0038] (4) The above-mentioned fuel pressure overshoot subsides after a certain period of time. In this regard, when the valve closing time TCL of the second shut-off valve 22 becomes equal to or greater than a predetermined determination value TCLref due to the execution of the valve closing process of the second shut-off valve 22, the control device 100 of the present embodiment executes an opening process for opening the second shut-off valve 22. Therefore, since it becomes possible to open the second shut-off valve 22 after the fuel pressure overshoot has subsided, the second shut-off valve 22 can be opened at an appropriate timing.

[0039] <Modified Example> Note that each of the above embodiments can be modified and implemented as follows. Each of the above embodiments and the following modified examples can be implemented in combination with each other as long as there is no technical contradiction.

[0040] · In the above embodiment, when the valve closing time TCL of the second shut-off valve 22 becomes equal to or greater than the determination value TCLref, an opening process for opening the second shut-off valve 22 is executed. In addition, after the valve closing process of the second shut-off valve 22 is executed, an opening process for opening the second shut-off valve 22 may be executed when the overshoot of the fuel pressure detected by the second pressure sensor 82 has subsided.

[0041] FIG. 4 shows the procedure of the process executed by the control device 100 to implement this modified example. As shown in FIG. 4, after executing the process of S110 shown in FIG. 3, the control device 100 executes the process of S200.

[0042] In the process of S200, the control device 100 acquires the second pressure P2, which is the fuel pressure detected by the second pressure sensor 82. Next, the control device 100 determines whether or not the overshoot of the second pressure P2, which is the fuel pressure, has subsided (S210). The determination of whether or not the overshoot of the second pressure P2 has subsided can be made as appropriate. For example, when the second pressure P2 exceeds a predetermined first determination pressure and then continues to be in a state where it is equal to or lower than a second determination pressure lower than the first determination pressure, it can be determined that the overshoot of the second pressure P2 has subsided.

[0043] Then, the control device 100 repeats the process of S210 until it is determined that the overshoot of the second pressure P2 has subsided. In the process of S210, when it is determined that the overshoot of the second pressure P2 has subsided (S210: YES), the control device 100 executes the process of S130. That is, the control device 100 outputs an open valve command to the second shut-off valve 22 to execute an open valve process of opening the second shut-off valve 22. Then, when the control device 100 finishes the process of S130, this process ends.

[0044] In this modification example, after the closing process of the second shut-off valve 22 is executed, the second shut-off valve 22 opens after the overshoot of the fuel pressure subsides, so the second shut-off valve 22 can open at an appropriate timing.

[0045] · The process of S100 shown in FIG. 3 may be omitted. In this case, the timing of starting the closing process of the second shut-off valve 22 can be advanced compared to the case where the process of S100 is executed.

[0046] · The gaseous fuel was hydrogen gas, but other gaseous fuels such as compressed natural gas may also be used. · The control device 100 includes a CPU 110 and a memory 120, and executes software processing. However, this is merely an example. The control device 100 may include, for example, a dedicated hardware circuit (such as an ASIC, etc.) that processes at least a part of the software processing executed in the above-described embodiment. That is, the control device 100 may have any of the following configurations (a) to (c). (a) It includes a processing device that executes all of the above processing according to a program, and a program storage device such as a memory that stores the program. (b) It includes a processing device and a program storage device that execute a part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) It includes a dedicated hardware circuit that executes all of the above processing. Here, there may be a plurality of software circuits including a processing device and a program storage device, and dedicated hardware circuits. That is, the above processing may be executed by a processing circuit including at least one of one or more software circuits and one or more dedicated hardware circuits. The program storage device, that is, the computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer.

Explanation of Signs

[0047] 10... Internal combustion engine 10a... Cylinder 15... Fuel injection valve 20... Tank 21... First shut-off valve 22... Second shut-off valve 30... Pressure reducing valve 31... Housing 32... First fuel chamber 33... Second fuel chamber 34... Communication hole 35... Valve body 36... Spring 37... Cylinder 37c... Needle 38... Spring 40... Fuel pipe 60... Delivery pipe 71... Accelerator position sensor 72…Speed sensor 81…First pressure sensor 82…Second pressure sensor 83…Third pressure sensor 100…Control device 200…Fuel supply device

Claims

1. A fuel supply device for an internal combustion engine, wherein the fuel supply device comprises a tank for storing gaseous fuel, a fuel injection valve for supplying gaseous fuel to a cylinder, a fuel passage for supplying the gaseous fuel in the tank to the fuel injection valve, a pressure reducing valve provided downstream of the tank in the fuel passage, an electromagnetic valve provided downstream of the pressure reducing valve in the fuel passage for opening and closing the fuel passage, and a processing circuit; when the pressure after being reduced by the pressure reducing valve is taken as the outlet side pressure, the pressure reducing valve is a valve having a valve body that opens and closes in accordance with an increase or decrease in the outlet side pressure; the processing circuit is configured to execute a valve closing process of closing the electromagnetic valve when a stop condition for stopping fuel injection of the fuel injection valve is satisfied. A fuel supply device for an internal combustion engine.

2. The processing circuit is configured to execute the valve closing process when the stop condition for stopping fuel injection of the fuel injection valve is satisfied and the injection amount of the fuel injection valve when the stop condition is satisfied is equal to or greater than a predetermined determination value. The fuel supply device for an internal combustion engine according to Claim 1.

3. The processing circuit is configured to execute a valve opening process of opening the electromagnetic valve when the valve closing time of the electromagnetic valve due to the execution of the valve closing process is equal to or greater than a predetermined determination value. The fuel supply device for an internal combustion engine according to Claim 1.

4. The fuel supply device has a sensor for detecting the fuel pressure in the fuel passage between the pressure reducing valve and the electromagnetic valve, and the processing circuit is configured to execute a valve opening process of opening the electromagnetic valve when an overshoot of the fuel pressure detected by the sensor has subsided after the valve closing process is executed. The fuel supply device for an internal combustion engine according to Claim 1.

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