Internal combustion engine

Abstract

The present application relates to an internal combustion engine, comprising a tank for storing liquid fuel, a cylinder, an intake port connected to the cylinder, a port injection valve for injecting fuel into the intake port, a pressure device for pressurizing evaporated fuel in the tank, and a low-pressure passage connecting the pressure device and the port injection valve.

Description

Technical Field

[0001] This disclosure relates to internal combustion engines. Background Technology

[0002] Japanese Patent Application Publication No. 2024-125574 discloses a hydrogen supply device having a tank for storing liquid fuel and a vaporizer for converting the liquid hydrogen in the tank into gaseous hydrogen. Summary of the Invention

[0003] The problem that the invention aims to solve

[0004] Inside the tank, liquid fuel evaporates, producing vaporized fuel. As vaporized fuel is produced, the pressure inside the tank rises. When the pressure inside the tank exceeds a certain value, the vaporized fuel is released into the atmosphere. When vaporized fuel is released, the amount of fuel available to be supplied to the internal combustion engine decreases.

[0005] Methods for solving problems

[0006] In one aspect of this disclosure, an internal combustion engine is provided, comprising: a tank for storing liquid fuel; a cylinder; an air inlet connected to the cylinder; a port injection valve for injecting fuel into the air inlet; a pressurizer for pressurizing the evaporated fuel in the tank; and a low-pressure passage connecting the pressurizer to the port injection valve. Attached Figure Description

[0007] Figure 1 This is a schematic diagram illustrating the structure of one embodiment of an internal combustion engine.

[0008] Figure 2 This is a flowchart illustrating the processing steps of the fuel supply process performed by the control device. Detailed Implementation

[0009] Reference Figure 1 The structure of the internal combustion engine 1 will be described.

[0010] like Figure 1 As shown, the internal combustion engine 1 includes a cylinder 10, an intake passage 11, and a throttle valve 12 disposed in the intake passage 11. The intake passage 11 includes an intake port 13 connected to the cylinder 10. Air flows into the cylinder 10 through the intake passage 11. The amount of intake air flowing in the intake passage 11 is adjusted according to the opening of the throttle valve 12. In the cylinder 10, the air-fuel mixture introduced from the intake port 13 is combusted. Thus, the internal combustion engine 1 generates power.

[0011] [About gaseous fuels]

[0012] The internal combustion engine 1 includes a tank 14 for storing liquid fuel, a pump 16 for drawing liquid fuel from the tank 14, a vaporizer 18 for converting liquid fuel into gaseous fuel, and a liquid fuel passage 20 connecting the pump 16 and the vaporizer 18.

[0013] Pump 16 draws liquid fuel from tank 14 and supplies it to vaporizer 18 through liquid fuel passage 20. A portion of pump 16 may also be located within tank 14. Liquid fuel passage 20 has a shut-off valve 21. Shut-off valve 21 can cut off the supply of liquid fuel from pump 16 to vaporizer 18. An example of liquid fuel is hydrogen. Other examples of liquid fuels are liquefied natural gas and liquefied petroleum gas.

[0014] The vaporizer 18 vaporizes liquid fuel to convert it into gaseous fuel. The vaporizer 18 converts liquid fuel into gaseous fuel, for example, through heat exchange between the liquid fuel and a heat medium circulating between the vaporizer 18 and a heat source. The heat source can be cooling water from the internal combustion engine 1, or a heater capable of being heated by an electric current. The heat medium can be a gas such as helium, or a liquid such as water.

[0015] The internal combustion engine 1 includes a pressure reducing valve 22 for reducing the pressure of gaseous fuel and a vaporization passage 24 connecting a carburetor 18 to the pressure reducing valve 22. The vaporization passage 24 has an energy storage device 26. The energy storage device 26 stores the high-pressure gaseous fuel supplied from the carburetor 18. The pressure reducing valve 22 reduces the pressure of the gaseous fuel supplied from the carburetor 18 through the energy storage device 26.

[0016] The internal combustion engine 1 includes a port injection valve 28 for injecting fuel into an intake port 13, an in-cylinder injection valve 30 for injecting fuel into a cylinder 10, and a gaseous fuel passage 32 connecting a pressure reducing valve 22 to the in-cylinder injection valve 30. The gaseous fuel passage 32 supplies gaseous fuel, pressurized by the pressure reducing valve 22, to the in-cylinder injection valve 30. The port injection valve 28 injects low-pressure (e.g., around several hundred kPa) fuel into the intake port 13. The in-cylinder injection valve 30 injects fuel at a higher pressure (e.g., around several MPa) than the fuel injection pressure of the port injection valve 28 into the cylinder 10.

[0017] [Regarding evaporative fuel]

[0018] The internal combustion engine 1 includes a pressurizer 34 for pressurizing evaporated fuel evaporating in a tank 14, an evaporated fuel passage 36 connecting the pressurizer 34 to the tank 14, a low-pressure passage 38 connecting the pressurizer 34 to a port injection valve 28, a high-pressure passage 40 connecting the pressurizer 34 to a cylinder injection valve 30, and a flow path switching valve 42. Although the tank 14 is insulated and kept at a low temperature, some of the fuel evaporates due to heat, liquid surface sloshing, etc. Evaporated fuel is supplied from the tank 14 to the pressurizer 34 through the evaporated fuel passage 36. The pressurizer 34 pressurizes the evaporated fuel to a pressure suitable for injection from the port injection valve 28 (hereinafter referred to as port injection pressure). Additionally, the pressurizer 34 pressurizes the evaporated fuel to a pressure suitable for injection from the cylinder injection valve 30 (hereinafter referred to as cylinder injection pressure).

[0019] Furthermore, both gaseous fuel and vaporized fuel are gases that have undergone a change of state from liquid fuel, and in this disclosure, they are distinguished as follows: Gaseous fuel is a gas produced by vaporizing liquid fuel through vaporizer 18. Vaporized fuel is a gas produced by evaporating liquid fuel within tank 14.

[0020] The low-pressure passage 38 includes a common passage 44 connecting the pressurizer 34 to the flow path switching valve 42 and a low-pressure branch passage 46 connecting the flow path switching valve 42 to the port injection valve 28. The high-pressure passage 40 includes a common passage 44, a high-pressure branch passage 48 connecting the flow path switching valve 42 and the gas fuel passage 32, and the gas fuel passage 32. Both the low-pressure passage 38 and the high-pressure passage 40 include the common passage 44. The flow path switching valve 42 branches the common passage 44 into the low-pressure branch passage 46 and the high-pressure branch passage 48.

[0021] The pressurized evaporating fuel from the pressurizer 34 is supplied to the flow path switching valve 42. The flow path switching valve 42 can be switched between a low-pressure position and a high-pressure position. In the low-pressure position, the pressurizer 34 is connected to the low-pressure passage 38, and the connection between the pressurizer 34 and the high-pressure passage 40 is cut off. In the high-pressure position, the pressurizer 34 is connected to the high-pressure passage 40, and the connection between the pressurizer 34 and the low-pressure passage 38 is cut off.

[0022] The flow path switching valve 42, by switching its position, can selectively supply evaporated fuel supplied from the pressurizer 34 to the low-pressure passage 38 and the high-pressure passage 40. When the flow path switching valve 42 is in the low-pressure position, evaporated fuel is supplied from the pressurizer 34 to the port injection valve 28 through the low-pressure passage 38. When the flow path switching valve 42 is in the high-pressure position, evaporated fuel is supplied to the in-cylinder injection valve 30 through the high-pressure passage 40. The in-cylinder injection valve 30 injects gaseous fuel that has been depressurized by the pressure reducing valve 22. The in-cylinder injection valve 30 also injects evaporated fuel that has been pressurized by the pressurizer 34.

[0023] [Regarding the control device]

[0024] The internal combustion engine 1 includes a control device 50. The control device 50 is configured to control the pressurizer 34 and the flow path switching valve 42. The control device 50 is capable of obtaining the load state of the internal combustion engine 1. The internal combustion engine 1 has a measuring device 52. The control device 50 is capable of obtaining the state quantities of the gaseous fuel and the vaporized fuel from the measuring device 52. State quantities include, for example, at least one of the pressure, temperature, and flow rate of the gaseous fuel and the vaporized fuel flowing in the high-pressure passage 40 and the low-pressure passage 38, respectively. The measuring device 52 is, for example, respectively installed in the high-pressure passage 40 and the low-pressure passage 38. The measuring device 52 for measuring the state quantity of the vaporized fuel may also be installed in the tank 14 or the pressurizer 34.

[0025] The control device 50 controls the pressurizer 34 and the flow path switching valve 42 based on the obtained load state of the internal combustion engine 1 and the state quantity of the evaporated fuel. The control device 50 controls the pressurizer 34, adjusting the pressure of the evaporated fuel supplied from the pressurizer 34 to the high-pressure passage 40 and the low-pressure passage 38. The control device 50 switches the valve position of the flow path switching valve 42 to a low-pressure position and a high-pressure position. When the valve position of the flow path switching valve 42 is in the low-pressure position, the evaporated fuel pressurized by the pressurizer 34 is supplied to the port injection valve 28 through the low-pressure passage 38. When the valve position of the flow path switching valve 42 is in the high-pressure position, the evaporated fuel pressurized by the pressurizer 34 is supplied to the in-cylinder injection valve 30 through the high-pressure passage 40. The control device 50 can control the flow path switching valve 42 to change the destination of the evaporated fuel supply.

[0026] <The Role of the Implementation Method>

[0027] Next, refer to Figure 2 The processing steps of the evaporative fuel supply process performed by the control device 50 are explained.

[0028] When the evaporative fuel supply process begins, the control device 50 determines in step S101 whether the internal combustion engine 1 is operating under high load. For example, the control device 50 determines that the internal combustion engine 1 is operating under high load if the load rate of the internal combustion engine 1 is above a predetermined value. The load rate, for example, is the ratio of the actual amount flowing into the cylinder 10 to the maximum amount when the throttle valve 12 is fully open, as determined in step S101. If the control device 50 determines that the internal combustion engine 1 is not operating under high load (S101: No), since the internal combustion engine 1 is operating under low load, the process proceeds to step S102. If the internal combustion engine 1 is operating under high load (S101: Yes), the control device 50 proceeds to step S104.

[0029] In step S102, the control device 50 controls the pressurizer 34 in such a way that the pressure of the evaporated fuel becomes the port injection pressure. Then, the control device 50 causes the process to proceed to step S103.

[0030] In step S103, the control device 50 controls the flow path switching valve 42 to set its valve position to the low-pressure position. As a result, the pressurizer 34 is connected to the port injection valve 28, and vaporized fuel is supplied to the port injection valve 28.

[0031] When the internal combustion engine 1 is under high load (S101: Yes), in step S104, the control device 50 controls the pressurizer 34 in a manner that makes the pressure of the evaporated fuel equal to the in-cylinder injection pressure. Afterwards, the control device 50 causes the process to proceed to step S105.

[0032] In step S105, the control device 50 controls the flow path switching valve 42 to set its valve position to the high-pressure position. As a result, the pressurizer 34 connects to the in-cylinder injection valve 30, and vaporized fuel is supplied to the in-cylinder injection valve 30. In summary, the control device 50 controls the pressurizer 34 such that, during high-load operation of the internal combustion engine 1, the pressure of the vaporized fuel pressurized by the pressurizer 34 is higher than during low-load operation. Furthermore, the control device 50 controls the flow path switching valve 42 to set its valve position to the high-pressure position.

[0033] Upon completion of step S103 or step S105, a series of evaporative fuel supply processes are completed. Furthermore, the order of steps S102 and S103 can be reversed or performed simultaneously. Similarly, the order of steps S104 and S105 can be reversed or performed simultaneously.

[0034] <Effects of this implementation method>

[0035] (1) After the internal combustion engine 1 of this disclosure pressurizes the evaporated fuel in the tank 14 by the pressurizer 34, it is supplied to the port injection valve 28 through the low-pressure passage 38. By injecting the evaporated fuel from the port injection valve 28 into the intake port 13, it can be used as fuel for the internal combustion engine 1.

[0036] (2) After the internal combustion engine 1 of this disclosure pressurizes the evaporated fuel in the tank 14 by the pressurizer 34, it supplies the fuel to the cylinder injection valve 30 through the high-pressure passage 40. By injecting the evaporated fuel from the cylinder injection valve 30 into the cylinder 10, it can be used as fuel for the internal combustion engine 1.

[0037] (3) The internal combustion engine 1 of this disclosure can selectively use the evaporative fuel injected by the port injection valve 28 and the evaporative fuel injected by the in-cylinder injection valve 30 as fuel for the internal combustion engine 1 by switching the valve position of the flow path switching valve 42.

[0038] (4) When the internal combustion engine 1 is operating under high load, more fuel is required compared to the low load operation state, and the time available for fuel injection is shorter. The port injection pressure is lower than the in-cylinder injection pressure. As a result, if fuel is to be injected from the port injection valve 28 during high load operation, the fuel injection time is insufficient, and the fuel injection quantity may be insufficient.

[0039] In this regard, the control device 50 of the internal combustion engine 1 of this disclosure pressurizes the evaporated fuel to a high pressure and supplies it to the in-cylinder injection valve 30 during high-load operation. When fuel is injected from the in-cylinder injection valve 30, the in-cylinder injection pressure is higher than the port injection pressure, thus injecting a larger amount of fuel in the same time compared to when fuel is injected from the port injection valve 28. As a result, even when the internal combustion engine 1 is operating at high load, the evaporated fuel can be used as fuel for the internal combustion engine 1.

[0040] On the other hand, if the vaporized fuel is pressurized to a high pressure and supplied to the in-cylinder injection valve 30 regardless of the load condition of the internal combustion engine 1, the work done by the pressurizer 34 when pressurizing the vaporized fuel increases. In this regard, the control device 50 of the internal combustion engine 1 of this disclosure supplies vaporized fuel to the port injection valve 28 when operating at low load. As a result, the work done by the pressurizer 34 required to pressurize the vaporized fuel decreases.

[0041] <Example of Change>

[0042] The above embodiments can be implemented by modification as follows. The above embodiments and the following modifications can be combined with each other within the scope of technical inconsistency.

[0043] A structure without a high-pressure passage 40 can be used. In this structure, the internal combustion engine 1 supplies the vaporized fuel pressurized by the pressurizer 34 only to the port injection valve 28. Moreover, the control device 50 only needs to be able to pressurize the vaporized fuel to the port injection pressure by controlling the pressurizer 34.

[0044] A structure without a flow path switching valve 42 can be used. One example of this structure is that a common passage 44 is connected to both the low-pressure passage 38 and the high-pressure passage 40, and a backflow prevention valve is provided in the high-pressure passage 40. When the pressure in the portion of the high-pressure passage 40 upstream of the backflow prevention valve rises to the in-cylinder injection pressure, the backflow prevention valve opens, connecting the common passage 44 to the gaseous fuel passage 32. As a result, the vaporized fuel, pressurized to the in-cylinder injection pressure by the pressurizer 34, is supplied to the in-cylinder injection valve 30 and then injected into the cylinder 10 from the in-cylinder injection valve 30.

[0045] When the pressure in the portion of high-pressure passage 40 downstream of the backflow prevention valve is higher than the pressure in the portion of high-pressure passage 40 upstream of the backflow prevention valve, the backflow prevention valve closes to cut off communication with the common passage 44 and the gas fuel passage 32. As a result, vaporized fuel pressurized to the port injection pressure by the pressurizer 34 is injected from the port injection valve 28 into the inlet 13 after being supplied to the port injection valve 28.

[0046] With the pressure booster 34 having a built-in flow path switching valve 42, a structure that omits the common passage 44 can be used. In this structure, the low-pressure passage 38 connects the pressure booster 34 to the port injection valve 28. The high-pressure passage 40 includes a high-pressure branch passage 48 and a gas fuel passage 32. The high-pressure passage 40 connects the pressure booster 34 to the in-cylinder injection valve 30.

[0047] A structure with multiple pressurizers can be employed. One example of this structure includes a first pressurizer that pressurizes the evaporated fuel to the port injection pressure and a second pressurizer that pressurizes the evaporated fuel to the in-cylinder injection pressure. In this structure, the first pressurizer pressurizes the evaporated fuel supplied from tank 14 to the port injection pressure and supplies it to the port injection valve 28. The second pressurizer pressurizes the evaporated fuel supplied from tank 14 to the in-cylinder injection pressure and supplies it to the in-cylinder injection valve 30.

[0048] A structure can be adopted that includes a port fuel passage connecting the pressure reducing valve 22 to the port injection valve 28. This structure includes a flow path switching valve. The gaseous fuel passage 32 includes a common passage connecting the pressure reducing valve 22 and the flow path switching valve, and a passage connecting the flow path switching valve to the in-cylinder injection valve 30. The port fuel passage includes a common passage and a passage connecting the flow path switching valve to the port injection valve 28. The flow path switching valve, by switching its position, can selectively supply gaseous fuel supplied from the pressure reducing valve 22 to both the gaseous fuel passage 32 and the port fuel passage. The pressure reducing valve 22 reduces the gaseous fuel pressure to the in-cylinder injection pressure and supplies it to the in-cylinder injection valve 30 via the gaseous fuel passage 32. The pressure reducing valve 22 also reduces the gaseous fuel pressure to the port injection pressure and supplies it to the port injection valve 28 via the port fuel passage.

[0049] The control device 50 includes a CPU and a ROM, and is not limited to having a processing circuit configured to perform software processing. That is, the control device 50 can be any of the structures in (a) to (c) below.

[0050] (a) The control device 50 includes one or more processors that perform various processes according to a computer program. The processor includes a CPU and memories such as RAM and ROM. The memories store program code or instructions configured to cause the CPU to perform processes. Memory, or computer-readable medium, includes all available media that can be accessed by a general-purpose or special-purpose computer.

[0051] (b) The control device 50 has one or more dedicated hardware circuits for performing various processes. Examples of dedicated hardware circuits include application-specific integrated circuits, i.e., ASICs or FPGAs. ASIC is an abbreviation for "Application-Specific Integrated Circuit", and FPGA is an abbreviation for "Field-Programmable Gate Array".

[0052] (c) The control device 50 has a processor that performs a portion of the various processes according to a computer program and dedicated hardware circuitry that performs the remaining processes in the various processes.

Claims

1. An internal combustion engine, comprising: Tanks for storing liquid fuels; cylinder; The air inlet is connected to the cylinder; Port injection valve, injecting fuel into the air intake; A pressurizer is used to pressurize the evaporated fuel in the tank; as well as A low-pressure passage connects the pressurizer to the port injection valve.

2. The internal combustion engine according to claim 1, further comprising: The in-cylinder injection valve injects fuel into the cylinder of the internal combustion engine; A vaporizer converts the liquid fuel into a gaseous fuel; A pressure reducing valve is used to reduce the pressure of the gaseous fuel; A gaseous fuel passage connects the pressure reducing valve to the in-cylinder injection valve; and A high-pressure passage connects the pressurizer to the in-cylinder injection valve.

3. The internal combustion engine according to claim 2, The internal combustion engine is equipped with a flow path switching valve. The valve position of the flow path switching valve can be switched to a low-pressure position that connects the pressurizer to the low-pressure passage and disconnects the pressurizer from the high-pressure passage, and a high-pressure position that connects the pressurizer to the high-pressure passage and disconnects the pressurizer from the low-pressure passage.

4. The internal combustion engine according to claim 3, The internal combustion engine is equipped with a control device. The control device performs: When the internal combustion engine is operating at low load, the flow path switching valve is controlled in such a way that its valve position is the low-pressure position; and When the internal combustion engine is operating under high load, the pressurizer is controlled in such a way that the pressure of the vaporized fuel pressurized by the pressurizer is higher than that when operating under low load, and the flow path switching valve is controlled in such a way that the valve position of the flow path switching valve is the high-pressure position.

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