Fuel supply device

A fuel supply device includes a fuel injection valve, a delivery pipe, a relief passage, a first valve, and a second valve. The fuel injection valve injects gas fuel. The delivery pipe supplies the gas fuel to the fuel injection valve. The relief passage connects an intake passage of an internal combustion engine and the delivery pipe. The first valve is configured to supply the gas fuel in the delivery pipe to the relief passage. The second valve is arranged in the relief passage. The second valve opens when a downstream pressure becomes lower than an upstream pressure by an amount that is greater than or equal to a specified pressure determined in advance.

RELATED APPLICATION

The present application claims priority of Japanese Patent Application No. 2022-203310 filed on Dec. 20, 2022, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

The following description relates to a fuel supply device.

2. Description of Related Art

Japanese Laid-Open Patent Publication No. 2007-332879 describes a fuel supply device that includes a delivery pipe and a fuel injection valve. The fuel injection valve is supplied with gas fuel through the delivery pipe. Further, the fuel supply device includes a relief pipe and a relief valve. An upstream end of the relief pipe is connected to the delivery pipe. A downstream end of the relief pipe is connected to an intake passage of an internal combustion engine. If the pressure inside the delivery pipe is higher than an allowable limit pressure when the internal combustion engine is started, the relief valve is switched from a closed state to an open state. When the relief valve is in the open state, the gas fuel is discharged to the intake passage through the relief pipe. This lowers the pressure of the delivery pipe.

With the technique described in the above patent publication, if the pressure inside the delivery pipe is high when the internal combustion engine is started, a large amount of gas fuel flows into the intake passage. In contrast, an amount of intake air supplied to the internal combustion engine is relatively small when the internal combustion engine is started. This may unintendedly lead to a fuel-rich state upon the activation of the internal combustion engine.

SUMMARY

In one general aspect, a fuel supply device includes a fuel injection valve, a delivery pipe, a relief passage, a first value, and a second valve. The fuel injection valve is configured to inject gas fuel. The delivery pipe supplies the gas fuel to the fuel injection valve. The relief passage connects an intake passage of an internal combustion engine and the delivery pipe. The first valve is configured to open so that the gas fuel in the delivery pipe is supplied to the relief passage. The second valve is arranged in the relief passage. The delivery pipe, the first valve, the second valve, and the intake passage are arranged in this order. When a downstream pressure refers to a pressure of the relief passage at a side of the second valve toward the intake passage, and an upstream pressure refers to a pressure of the relief passage at a side of the second valve toward the delivery pipe, the second valve is configured to open when the downstream pressure becomes lower than the upstream pressure by an amount that is greater than or equal to a specified pressure determined in advance.

DETAILED DESCRIPTION

A fuel supply device according to one embodiment will now be described with reference to the drawings.

Structure of Internal Combustion Engine

As shown inFIG.1, a vehicle500includes an internal combustion engine10. The internal combustion engine10uses gas fuel, for example, hydrogen. The internal combustion engine10includes a crankshaft11, four cylinders12, four pistons13, four connecting rods14, and four ignition plugs15.FIG.1shows one of the four sets of the cylinder12, the piston13, the connecting rod14, and the ignition plug15.

The cylinder12is a space for burning air-fuel mixture of fuel and intake air. The piston13reciprocates in the cylinder12as the air-fuel mixture burns. The piston13is coupled to the crankshaft11by the connecting rod14. The connecting rod14transmits the reciprocating motion of the piston13as the rotation of the crankshaft11. The tip of the ignition plug15is located in the cylinder12. The ignition plug15ignites the air-fuel mixture in the cylinder12.

As shown inFIG.1, the internal combustion engine10includes an intake passage21and an exhaust passage31. The intake passage21is a flow passage for intake air. The intake passage21is connected to the cylinders12. The exhaust passage31is a passage for exhaust. The exhaust passage31is connected to the cylinders12.

The internal combustion engine10includes intake valves21A and exhaust valves31A.FIG.1shows only one of the intake valves21A and only one of the exhaust valves31A. The intake valves21A are provided on the respective cylinders12. The intake valve21A is located at a position where the intake passage21is connected to the cylinder12. The intake valve21A is actuated to open and close an open portion of the intake passage21at the side of the cylinder12. The exhaust valves31A are provided on the respective cylinders12. The exhaust valve31A is located at a position where the exhaust passage31is connected to the cylinder12. The exhaust valve31A is actuated to open and close an open portion of the exhaust passage31at the side of the cylinder12.

The internal combustion engine10includes an intercooler22, a throttle valve23, and a surge tank24. The intercooler22is located at an intermediate portion of the intake passage21. The intercooler22cools intake air. The throttle valve23is located at a downstream side of the intercooler22in the intake passage21. The throttle valve23is capable of adjusting a degree at which the throttle valve23is open. The throttle valve23adjusts the amount of intake air flowing into the cylinder12in accordance with the open degree. The surge tank24is located at a downstream side of the throttle valve23in the intake passage21. The surge tank24is capable of storing a certain volume of intake air.

The vehicle500includes a forced-induction device40. The forced-induction device40extends across the intake passage21and the exhaust passage31. The forced-induction device40includes a compressor wheel41, a turbine wheel42, a bypass passage43, and a wastegate valve44. The compressor wheel41is located at an upstream side of the intercooler22in the intake passage21. The turbine wheel42is located at an intermediate portion of the exhaust passage31. The turbine wheel42is rotated in response to the flow of exhaust. The compressor wheel41rotates integrally with the turbine wheel42. The compressor wheel41compresses intake air as it rotates and delivers the compressed air. That is, the rotation of the compressor wheel41supercharges the intake air. The bypass passage43connects an upstream section and a downstream section of the exhaust passage31with respect to the turbine wheel42. That is, the bypass passage43is a passage that bypasses the turbine wheel42. The wastegate valve44is located at the downstream end of the bypass passage43. The wastegate valve44is capable of adjusting a degree at which the wastegate valve44is open. A change in the opening degree of the wastegate valve44changes the amount of exhaust gas flowing through the bypass passage43.

Fuel Supply Device

As shown inFIG.1, the vehicle500includes a fuel supply device50. The fuel supply device50includes four fuel injection valves51and a delivery pipe52.FIG.1shows only one of the four fuel injection valves51.

The fuel injection valve51directly injects gas fuel into the cylinder12without using the intake passage21. That is, the fuel injection valve51is an in-cylinder injection valve. The delivery pipe52is a fuel circulation passage for supplying gas fuel to the fuel injection valve51. The delivery pipe52is connected to a fuel tank (not shown). That is, the delivery pipe52receives gas fuel from the fuel tank.

The fuel supply device50includes a relief passage60. The relief passage60includes a vacuum tank61, a first relief passage62, and a second relief passage63.

The pressure inside the vacuum tank61is lower than the atmospheric pressure. When the wastegate valve44is fully open, that is, when the internal combustion engine10is performing a non-supercharging operation, the air in the vacuum tank61is drawn into the surge tank24. In other words, the vacuum tank61stores the negative pressure of the surge tank24during the non-supercharging operation.

The vacuum tank61supplies a negative pressure to an actuator of the vehicle500. Specifically, the vacuum tank61supplies negative pressure to a brake booster of the vehicle500. Thus, the vacuum tank61has a sufficient volume to cause the actuator of the vehicle500to operate at a negative pressure.

The first relief passage62connects the delivery pipe52to the vacuum tank61. The second relief passage63connects the vacuum tank61to the surge tank24. Thus, the entire relief passage60connects the intake passage21of the internal combustion engine10to the delivery pipe52. This allows the gas fuel in the delivery pipe52to flow into the surge tank24through the first relief passage62, the vacuum tank61, and the second relief passage63.

The fuel supply device50includes a first valve64and a second valve65.

The first valve64is arranged at a position where the delivery pipe52is connected to the first relief passage62. The first valve64is an electronically controlled electromagnetic valve. The first valve64is normally closed. The first valve64is electrically switchable between an open state and a closed state. When the first valve64is open, the gas fuel in the delivery pipe52is supplied to the relief passage60.

The second valve65is arranged in the relief passage60. Specifically, the second valve65is located at an intermediate portion of the second relief passage63. The second valve65is a one-way valve. The second valve65only allows flow from the vacuum tank61to the surge tank24in the second relief passage63. Since the second valve65is located at an intermediate portion of the second relief passage63, the vacuum tank61is located at a side of the second valve65closer to the delivery pipe52. In other words, the delivery pipe52, the vacuum tank61, and the second valve65are arranged in this order.

Although the drawing does not show the detail, the second valve65includes a body and a valve member capable of opening and closing an open portion in the body. The valve member is pressed against the open portion of the body by a spring. The valve member closes the open portion of the body with the pressing force of the spring. Further, the valve member opens when a difference between the pressure at the downstream side of the valve member and the pressure at the upstream side of the valve member becomes greater than the pressing force of the spring. The pressure of the relief passage60at a side of the second valve65toward the intake passage21will be referred to as the downstream pressure. The pressure of the relief passage60at a side of the second valve65toward the delivery pipe52will be referred to as the upstream pressure.

The second valve65opens when the downstream pressure becomes lower than the upstream pressure by an amount that is greater than or equal to a specified pressure. Accordingly, the specified pressure is determined in advance as the pressure difference that allows the valve member to actuate against the pressing force of the spring.

Controller

The vehicle500includes a pressure sensor71and a controller72.

The pressure sensor71is located in the delivery pipe52. The pressure sensor71detects an in-pipe pressure P in the delivery pipe52.

The controller72controls the first valve64. The controller72obtains a signal indicating the in-pipe pressure P from the pressure sensor71. The controller72opens the first valve64in a case where the in-pipe pressure P is greater than or equal to a specified pipe pressure. The specified pipe pressure can be determined through experiments, simulations, or the like as the pressure that reduces leakage of gas fuel from the fuel injection valves51or the like to a permissible level.

The controller72can be circuitry including one or more processors that execute various processes in accordance with computer programs (software). Alternatively, the controller72may be circuitry including one or more exclusive hardware circuits, such as an application specific integrated circuit (ASIC), to execute at least part of various processes. Further, the controller72may be circuitry including a combination of the above. The processor includes a computer processing unit (CPU) and a memory, such as a random-access memory (RAM) and a read-only memory (ROM). The memory stores program codes or commands that are configured to have the CPU execute a process. The memory, which is a computer readable medium, may be any available medium that is accessible by a versatile or dedicated computer.

Operation of Present Embodiment

When the in-pipe pressure P of the pipe is greater than or equal to a specified pipe pressure, the controller72opens the first valve64. When the first valve64opens, the gas fuel in the delivery pipe52is stored in the vacuum tank61through the first relief passage62. This reduces the in-pipe pressure P.

When the internal combustion engine10is in a stopped state, the pressure inside the surge tank24is substantially equal to the atmospheric pressure. Thus, the pressure of the relief passage60at a side of the second valve65toward the intake passage21is higher than the pressure at a side of the second valve65toward the delivery pipe52. Therefore, the second valve65is closed. That is, when the internal combustion engine10is in a stopped state, the gas fuel that has flowed into the vacuum tank61from the delivery pipe52remains stored in the vacuum tank61.

When the internal combustion engine10is activated, the pressure of the intake passage21, including the surge tank24, decreases as the piston13and the intake valve21A operate. However, immediately after the internal combustion engine10is started, the amount of intake air flowing through the intake passage21is relatively small. Thus, the pressure of the surge tank24is not significantly reduced. Thus, even if the pressure of the surge tank24is smaller than the pressure of the vacuum tank61, the second valve65remains closed if the differential pressure is less than the specified pressure. Thus, in this case, the gas fuel remains stored in the vacuum tank61.

An example assumes that the amount of intake air in the internal combustion engine10increases while the internal combustion engine10is in a non-supercharging operation state after the internal combustion engine10is started. This significantly reduces the pressure of the intake passage21. The second valve65opens when the pressure of the relief passage60at a side of the second valve65toward the intake passage21becomes lower than the pressure of the relief passage60at a side of the second valve65toward the delivery pipe52by an amount that is greater than or equal to the specified pressure. As a result, the gas fuel that has flowed into the vacuum tank61from the delivery pipe52flows into the surge tank24. The gas fuel that has flowed into the surge tank24is introduced to the cylinder12and burned.

An example assumes that the internal combustion engine10performs a supercharging operation as the required torque of the internal combustion engine10increases. In this case, the pressure of the surge tank24is greater than the atmospheric pressure. Thus, the pressure of the relief passage60at a side of the second valve65toward the intake passage21is higher than the pressure at a side of the second valve65toward the delivery pipe52. Therefore, the second valve65is closed. That is, when the internal combustion engine10is performing the supercharging operation, the gas fuel remains stored in the vacuum tank61even if the gas fuel is flowing into the vacuum tank61from the delivery pipe52.

Advantages of Present Embodiment

(1) As described above, when the pressure of the relief passage60at a side of the second valve65closer to the intake passage21is low enough, the second valve65is opened. When the pressure of the relief passage60at a portion closer to the intake passage21is low, a large amount of intake air is supplied to the internal combustion engine10. Therefore, in the above-described embodiment, even if the second valve65opens and the gas fuel flows into the surge tank24, the internal combustion engine10is unlikely to be in a state in which fuel is excessively rich.(2) In the above-described embodiment, the vacuum tank61can be used as a supply destination of gas fuel from the first valve64. Since the vacuum tank61has a sufficient volume, the pressure of the vacuum tank61is unlikely to vary greatly even if gas fuel is supplied. In addition, since the volume of the vacuum tank61is relatively large, the concentration of the gas fuel is significantly decreased when the gas fuel is supplied from the first valve64. Thus, even if air containing gas fuel is supplied from the vacuum tank61to the surge tank24, the influence on the air-fuel ratio of the gas fuel is relatively small.(3) In the above-described embodiment, the existing vacuum tank61for supplying negative pressure to the actuator is used as a supply destination of gas fuel from the first valve64. Accordingly, it is not necessary to newly install a member having a large volume as a supply destination of gas fuel from the first valve64.

Modified Examples

The present embodiment may be modified as follows. The present embodiment and the following modifications can be combined as long as the combined modifications remain technically consistent with each other.

The configuration of the vehicle500is not limited to that described in the above-described embodiment. For example, the configuration related to the forced-induction device40may be omitted from the vehicle500. The vehicle500only needs to include the configuration related to at least the fuel supply device50and the combustion of the internal combustion engine10.

In the above-described embodiment, the vacuum tank61may be omitted from the relief passage60. When the vacuum tank61is omitted, the relief passage60does not have to include the first relief passage62and the second relief passage63, and may be a single pipe. Also, the relief passage60may further include a tank or the like differing from the vacuum tank61.

In the above-described embodiment, the first valve64and the second valve65may be electromagnetic valve or mechanical valves. The second valve65may have any configuration as long as the second valve65is open when the pressure of the relief passage60at a side of the second valve65closer to the intake passage21becomes lower than the pressure of the relief passage60at a side of the second valve65closer to the delivery pipe52by the specified pressure or greater.