Internal combustion engine

Abstract

The generation of evaporated fuel reduces the amount of fuel available for supply to the internal combustion engine. [Solution] The internal combustion engine 1 comprises a tank 14 for storing liquid fuel, a cylinder 10, an intake port 13 connected to the cylinder 10, a port injection valve 28 for injecting fuel into the intake port 13, a pressurizer 34 for pressurizing the evaporated fuel in the tank 14, and a low-pressure passage 38 connecting the pressurizer 34 and the port injection valve 28.

Description

Technical Field

[0001] The present invention relates to an internal combustion engine.

Background Art

[0002] Patent Document 1 describes 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.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a tank for storing liquid fuel, the liquid fuel evaporates to generate evaporated fuel. The pressure in the tank rises due to the generation of the evaporated fuel. When the pressure in the tank exceeds a certain value, the evaporated fuel is released into the atmosphere. When the evaporated fuel is released, the fuel available for supply to the internal combustion engine decreases.

Means for Solving the Problems

[0005] The internal combustion engine that solves the above problems includes 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 pressurizer for pressurizing the evaporated fuel in the tank, and a low-pressure passage connecting the pressurizer and the port injection valve.

Effects of the Invention

[0006] The evaporated fuel evaporated in the tank can be used as fuel for the internal combustion engine.

Brief Description of the Drawings

[0007] [Figure 1]Figure 1 is a schematic diagram showing the configuration of one embodiment of an internal combustion engine. [Figure 2] Figure 2 is a flowchart showing the processing steps of the fuel supply process performed by the control unit. [Modes for carrying out the invention]

[0008] The configuration of the internal combustion engine 1 will be explained with reference to Figure 1. As shown in Figure 1, the internal combustion engine 1 comprises a cylinder 10, an intake passage 11, and a throttle valve 12 installed in the intake passage 11. The intake passage 11 includes an intake port 13 connected to the cylinder 10. Air flows through the intake passage 11 into the cylinder 10. The throttle valve 12 adjusts the amount of intake air flowing through the intake passage 11 according to its opening. The internal combustion engine 1 generates power when the mixture of air and fuel introduced into the cylinder 10 from the intake port 13 is burned.

[0009] [Regarding gaseous fuels] The internal combustion engine 1 includes a tank 14 for storing liquid fuel, a pump 16 for drawing out the liquid fuel from the tank 14, a vaporizer 18 for converting the liquid fuel into gaseous fuel, and a liquid fuel passage 20 connecting the pump 16 and the vaporizer 18.

[0010] Pump 16 draws liquid fuel from tank 14 and supplies it to vaporizer 18 through liquid fuel passage 20. Part of pump 16 may be located inside tank 14. Liquid fuel passage 20 has a shut-off valve 21. The shut-off valve 21 can shut off the supply of liquid fuel from pump 16 to vaporizer 18. An example of liquid fuel is hydrogen. Other examples of liquid fuel are liquefied natural gas and liquefied petroleum gas.

[0011] The vaporizer 18 vaporizes the liquid fuel and converts it into a gaseous fuel. The vaporizer 18 is a device that converts liquid fuel into a gaseous fuel by heat exchange between the liquid fuel and a heat transfer medium that circulates between the vaporizer 18 and a heat source. The heat source may be the cooling water of the internal combustion engine 1, or it may be a heater that can be heated by electric current. The heat transfer medium may be a gas such as helium, or a liquid such as water.

[0012] The internal combustion engine 1 includes a pressure reducing valve 22 for reducing the pressure of gaseous fuel, and a vaporization passage 24 connecting the vaporizer 18 and the pressure reducing valve 22. The vaporization passage 24 has an accumulator 26. The accumulator 26 stores the high-pressure gaseous fuel supplied from the vaporizer 18. The pressure reducing valve 22 reduces the pressure of the gaseous fuel supplied from the vaporizer 18 through the accumulator 26.

[0013] The internal combustion engine 1 includes a port injection valve 28 that injects fuel into the intake port 13 of the internal combustion engine 1, an in-cylinder injection valve 30 that injects fuel into the cylinder 10 of the internal combustion engine 1, and a gaseous fuel passage 32 that connects the pressure reducing valve 22 and the in-cylinder injection valve 30. The gaseous fuel passage 32 supplies the gaseous fuel, which has been depressurized by the pressure reducing valve 22, to the in-cylinder injection valve 30. The port injection valve 28 injects low-pressure fuel (for example, several hundred kPa) into the intake port 13. The in-cylinder injection valve 30 injects fuel at a pressure higher than the fuel injection pressure of the port injection valve 28 (for example, several MPa) into the cylinder 10.

[0014] [About evaporative fuels] The internal combustion engine 1 includes a pressurizer 34 for pressurizing the evaporated fuel evaporated in the tank 14, an evaporated fuel passage 36 connecting the pressurizer 34 and the tank 14, a low-pressure passage 38 connecting the pressurizer 34 and the port injection valve 28, a high-pressure passage 40 connecting the pressurizer 34 and the in-cylinder injection valve 30, and a flow path switching valve 42. Although the tank 14 that stores the liquid fuel is insulated and kept at a low temperature, some of it evaporates due to heat, fluctuations in the liquid level, etc. The 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 fuel injection from the port injection valve 28 (hereinafter referred to as the port injection pressure). The pressurizer 34 also pressurizes the evaporated fuel to a pressure suitable for fuel injection from the in-cylinder injection valve 30 (hereinafter referred to as the in-cylinder injection pressure).

[0015] Although both gaseous fuel and evaporated fuel are liquid fuels that have undergone a state change from liquid to gas, they are distinguished in this disclosure as follows: Gaseous fuel is the gas generated when liquid fuel is vaporized by the vaporizer 18, and evaporated fuel is the gas generated when liquid fuel evaporates in the tank 14.

[0016] The low-pressure passage 38 includes a common passage 44 connecting the pressurizer 34 and the flow path switching valve 42, and a low-pressure branch passage 46 connecting the flow path switching valve 42 and the port injection valve 28. The high-pressure passage 40 includes the common passage 44, a high-pressure branch passage 48 connecting the flow path switching valve 42 and the gaseous fuel passage 32, and the gaseous 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.

[0017] The evaporative fuel pressurized by the pressurizer 34 is supplied to the flow path switching valve 42. The valve position of the flow path switching valve 42 can be switched between a low-pressure position that connects the pressurizer 34 to the low-pressure passage 38 and blocks communication between the pressurizer 34 and the high-pressure passage 40, and a high-pressure position that connects the pressurizer 34 to the high-pressure passage 40 and blocks communication between the pressurizer 34 and the low-pressure passage 38.

[0018] The flow path switching valve 42 can selectively supply the evaporated fuel supplied from the pressurizer 34 to the low-pressure passage 38 and the high-pressure passage 40 by switching the valve position. When the valve position of the flow path switching valve 42 is the low-pressure position, the evaporated fuel is supplied from the pressurizer 34 to the port injection valve 28 through the low-pressure passage 38. When the valve position of the flow path switching valve 42 is the high-pressure position, the evaporated fuel is supplied to the in-cylinder injection valve 30 through the high-pressure passage 40. The in-cylinder injection valve 30 injects the gaseous fuel depressurized by the pressure reducing valve 22. The in-cylinder injection valve 30 injects the evaporated fuel pressurized by the pressurizer 34.

[0019] [Regarding the control device] The internal combustion engine 1 includes a control device 50. The control device 50 is configured to be able to control the pressurizer 34 and the flow path switching valve 42. The control device 50 can acquire the load state of the internal combustion engine 1. The internal combustion engine 1 has a measuring instrument 52. The control device 50 can acquire the state quantities of the gaseous fuel and the evaporated fuel from the measuring instrument 52. The state quantities include at least one of the pressure, temperature, and flow rate of the gaseous fuel and the evaporated fuel flowing through the high-pressure passage 40 and the low-pressure passage 38, respectively. The measuring instrument 52 is installed in the high-pressure passage 40 and the low-pressure passage 38, respectively, for example. Among the measuring instruments 52, the measuring instrument 52 for measuring the state quantity of the evaporated fuel may be installed in the tank 14 and the pressurizer 34.

[0020] The control device 50 controls the pressurizer 34 and the flow path switching valve 42 based on the acquired load state of the internal combustion engine 1 and the state quantity of the evaporated fuel. The control device 50 controls the pressurizer 34 and can adjust 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 between the low-pressure position and the high-pressure position. When the valve position of the flow path switching valve 42 is 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 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 controls the flow path switching valve 42 and can change the supply destination of the evaporated fuel.

[0021] <Operation of the Embodiment> Next, referring to FIG. 2, the processing procedure of the evaporated fuel supply process executed by the control device 50 will be described.

[0022] When starting the evaporated fuel supply process, the control device 50 determines, in step S101, whether the internal combustion engine 1 is in a high load operation state. For example, the control device 50 determines that the internal combustion engine 1 is in a high load operation state when the load factor of the internal combustion engine 1 is equal to or greater than a predetermined value. The load factor is, for example, the ratio of the amount actually flowing into the cylinder 10 to the maximum amount when, at the time of determination in step S101, assuming that the throttle valve 12 is fully open, the amount flowing into the cylinder 10 is the maximum amount. If the control device 50 determines that the internal combustion engine 1 is not in a high load operation state (S101: NO), since the internal combustion engine 1 is in a low load operation state, the process proceeds to step S102. If the control device 50 determines that the internal combustion engine 1 is in a high load operation state (S101: YES), the process proceeds to step S104.

[0023] In step S102, the control device 50 controls the pressurizer 34 so that the pressure of the evaporated fuel becomes the port injection pressure. Thereafter, the control device 50 proceeds to step S103.

[0024] In step S103, the control device 50 controls the flow path switching valve 42 so that the valve position of the flow path switching valve 42 becomes the low pressure position. As a result, the pressurizer 34 and the port injection valve 28 communicate with each other, and the evaporated fuel is supplied to the port injection valve 28.

[0025] If the control device 50 determines that the internal combustion engine 1 is in a high load state (S101: YES), in step S104, the control device 50 controls the pressurizer 34 so that the pressure of the evaporated fuel becomes the in-cylinder injection pressure. Thereafter, the control device 50 proceeds to step S105.

[0026] In step S105, the control device 50 controls the flow path switching valve 42 so that its valve position is set to the high-pressure position. As a result, the pressurizer 34 and the in-cylinder injection valve 30 are connected, and evaporated fuel is supplied to the in-cylinder injection valve 30. In summary, the control device 50 controls the pressurizer 34 so that, during high-load operation of the internal combustion engine 1, the pressure of the evaporated 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 so that its valve position is set to the high-pressure position.

[0027] The series of evaporative fuel supply processes is completed upon completion of step S103 or step S105. Note that the order of steps S102 and S103 may be reversed or performed simultaneously. Similarly, the order of steps S104 and S105 may be reversed or performed simultaneously.

[0028] <Effects of this embodiment> (1) The internal combustion engine 1 of this disclosure pressurizes the evaporated fuel in the tank 14 with a pressurizer 34 and then supplies it to the port injection valve 28 through a low-pressure passage 38. The evaporated fuel can be used as fuel for the internal combustion engine 1 by injecting it from the port injection valve 28 into the intake port 13.

[0029] (2) The internal combustion engine 1 of this disclosure pressurizes the evaporated fuel in the tank 14 with a pressurizer 34 and then supplies it to the in-cylinder injection valve 30 through a high-pressure passage 40. The evaporated fuel can be used as fuel for the internal combustion engine 1 by injecting it into the cylinder 10 from the in-cylinder injection valve 30.

[0030] (3) The internal combustion engine 1 of this disclosure can selectively use the evaporated fuel injected by the port injection valve 28 and the evaporated 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.

[0031] (4) When the internal combustion engine 1 is operating under high load conditions, more fuel is required and the time available for fuel injection is shorter than when it is operating under low load conditions. Port injection pressure is lower than in-cylinder injection. As a result, when attempting to inject fuel from the port injection valve 28 during high-load operation, there is a possibility that the fuel injection time will be insufficient.

[0032] In this regard, the control device 50 of the internal combustion engine 1 of this disclosure pressurizes 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, so more fuel is injected in the same amount of 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 a high load, evaporated fuel can be used as fuel for the internal combustion engine 1.

[0033] On the other hand, if the evaporated fuel is to be 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 amount of work done by the pressurizer 34 when pressurizing the evaporated fuel becomes large. In this regard, the control device 50 of the internal combustion engine 1 of this disclosure supplies the evaporated fuel to the port injection valve 28 during low-load operation. As a result, the amount of work done by the pressurizer 34 required to pressurize the evaporated fuel is reduced.

[0034] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0035] A configuration without a high-pressure passage 40 can be adopted. In this configuration, the internal combustion engine 1 supplies the evaporated fuel pressurized by the pressurizer 34 only to the port injection valve 28. Furthermore, the control device 50 only needs to be able to pressurize the evaporated fuel to the port injection pressure by controlling the pressurizer 34.

[0036] A configuration without a flow path switching valve 42 can be adopted. One example of this configuration is to connect the common passage 44 to the low-pressure passage 38 and the high-pressure passage 40, respectively, and to provide a backflow prevention valve in the high-pressure passage 40. The backflow prevention valve opens when the pressure in the part of the high-pressure passage 40 upstream of the backflow prevention valve rises to the in-cylinder injection pressure, connecting the common passage 44 and the gaseous fuel passage 32. As a result, the evaporated fuel pressurized by the pressurizer 34 to the in-cylinder injection pressure is supplied to the in-cylinder injection valve 30 and then injected into the cylinder 10 from the in-cylinder injection valve 30.

[0037] The check valve closes when the pressure downstream of the check valve in the high-pressure passage 40 is higher than the pressure upstream of the check valve, thereby blocking communication with the common passage 44 and the gaseous fuel passage 32. As a result, the evaporated fuel, pressurized by the pressurizer 34 to the port injection pressure, is supplied to the port injection valve 28 and then injected from the port injection valve 28 into the intake port 13.

[0038] • If the pressurizer 34 incorporates a flow path switching valve 42, a configuration omitting the common passage 44 can be adopted. In this configuration, the low-pressure passage 38 connects the pressurizer 34 and the port injection valve 28. The high-pressure passage 40 includes the high-pressure branch passage 48 and the gaseous fuel passage 32. The high-pressure passage 40 connects the pressurizer 34 and the in-cylinder injection valve 30.

[0039] • A configuration with multiple pressurizers can be adopted. One example of this configuration includes, for instance, 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 configuration, the first pressurizer pressurizes the evaporated fuel supplied from the 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 the tank 14 to the in-cylinder injection pressure and supplies it to the in-cylinder injection valve 30.

[0040] A configuration can be adopted that includes a port fuel passage connecting the pressure reducing valve 22 and the port injection valve 28. In this configuration, a flow path switching valve is included. 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 and the in-cylinder injection valve 30. The port fuel passage includes a common passage and a passage connecting the flow path switching valve and the port injection valve 28. By switching the valve position, the flow path switching valve can selectively supply the gaseous fuel supplied from the pressure reducing valve 22 to the gaseous fuel passage 32 and the port fuel passage. The pressure reducing valve 22 reduces the gaseous fuel to the in-cylinder injection pressure and supplies it to the in-cylinder injection valve 30 through the gaseous fuel passage 32. The pressure reducing valve 22 reduces the gaseous fuel to the port injection pressure and supplies it to the port injection valve 28 through the port fuel passage. [Explanation of Symbols]

[0041] 1...Internal combustion engine 10...Cylinders 11...Intake passage 12...Throttle valve 13…Intake port 14…Tank 16…Pump 18…Vaporizer 20…Liquid fuel passage 21…Shut-off valve 22…Pressure reducing valve 24…Vaporization passage 26…Accumulator 28...Port injection valve 30...In-cylinder injection valve 32...Gaseous fuel passage 34...Pressurizer 36... Evaporation fuel passage 38... Low-pressure passage 40... High-pressure passage 42... Flow path switching valve 44...Common passage 46...Low-voltage branch passage 48...High-voltage branch passage 50...Control device 52… Measuring instruments

Claims

1. A tank for storing liquid fuel, Cylinders and, An intake port connected to the cylinder, A port injection valve that injects fuel into the intake port, A pressurizer for pressurizing the evaporated fuel in the tank, A low-pressure passage connecting the pressurizer and the port injection valve is provided. Internal combustion engine.

2. An in-cylinder injection valve for injecting fuel into the cylinder of the internal combustion engine, A vaporizer that converts the aforementioned liquid fuel into a gaseous fuel, A pressure reducing valve for reducing the pressure of the gaseous fuel, A gaseous fuel passage connecting the pressure reducing valve and the in-cylinder injection valve, The system further comprises a high-pressure passage connecting the pressurizer and the in-cylinder injection valve. The internal combustion engine according to claim 1.

3. The internal combustion engine is equipped with a flow path switching valve, The valve position of the aforementioned flow path switching valve is A low-pressure position that connects the pressurizer and the low-pressure passage, and blocks communication between the pressurizer and the high-pressure passage, It is possible to switch between a high-pressure position that connects the pressurizer and the high-pressure passage, and a high-pressure position that blocks communication between the pressurizer and the low-pressure passage. The internal combustion engine according to claim 2.

4. The internal combustion engine is equipped with a control device, The control device is During low-load operation of the internal combustion engine, the flow path switching valve is controlled so that its valve position becomes the low-pressure position. During high-load operation of the internal combustion engine, the pressurizer is controlled so that the pressure of the evaporated fuel pressurized by the pressurizer is higher than during low-load operation, and the flow path switching valve is controlled so that the valve position of the flow path switching valve is the high-pressure position. The internal combustion engine according to claim 3.

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