Internal combustion engine system and compressor

Abstract

In the present invention, an internal combustion engine system comprises: a fuel gas flow path that connects, to an internal combustion engine, a fuel storage source that stores fuel gas in a compressed state; and a compressor that pressurizes the fuel gas in the fuel gas flow path. The compressor has at least one reciprocating structure including: a cylinder having an intake port and a discharge port; a piston that is accommodated in the cylinder, and that defines a compression chamber facing the intake port and the discharge port; a rod protruding from the piston; and a cam that causes the rod to reciprocate.

Description

Internal combustion engine system and compressor

[0001] The present disclosure relates to internal combustion engine systems and compressors.

[0002] Patent Document 1 discloses an internal combustion engine system in which hydrogen gas supplied from a high-pressure hydrogen gas tank via a pressure reducing valve is burned as fuel in the internal combustion engine to generate driving force.

[0003] Japanese Patent Application Laid-Open No. 2021-173182

[0004] As the internal combustion engine continues to consume fuel gas in the fuel tank, the internal pressure of the fuel tank will eventually drop below a predetermined value. When this happens, the fuel gas in the fuel tank cannot be adequately supplied to the internal combustion engine, and the fuel tank will be treated as empty even though fuel gas remains.

[0005] Therefore, one aspect of the present disclosure aims to increase the amount of fuel gas that can be supplied to an internal combustion engine while preventing the system from becoming larger.

[0006] An internal combustion engine system according to one aspect of the present disclosure includes a fuel gas flow path connecting a fuel storage source that stores fuel gas in a compressed state to an internal combustion engine, and a compressor that compresses the fuel gas in the fuel gas flow path. The compressor has at least one reciprocating structure including a cylinder having an inlet port and a discharge port, a piston housed in the cylinder and defining a compression chamber facing the inlet port and the discharge port, a rod protruding from the piston, and a cam that reciprocates the rod.

[0007] A compressor according to one aspect of the present disclosure includes a cylinder having an inlet and an outlet, a piston housed in the cylinder and defining a compression chamber facing the inlet and the outlet, a rod protruding from the piston, a cam that reciprocates the rod, a camshaft that rotates the cam, and a ring that covers an outer peripheral surface of the cam and is rotatable relative to the cam. The outer peripheral surface of the cam has a perfect circular shape, the camshaft is eccentrically connected to the cam, and the cam presses the rod via the ring.

[0008] A compressor according to another aspect of the present disclosure includes a cylinder having an inlet and a discharge port, a piston housed in the cylinder and defining a compression chamber facing the inlet and the discharge port, a rod protruding from the piston, a first rod seal interposed between an outer circumferential surface of the rod and an inner circumferential surface of the cylinder, and a recompression chamber disposed between the piston and the first rod seal in the axial direction of the cylinder, the recompression chamber being defined by the outer circumferential surface of the rod and the inner circumferential surface of the cylinder, the volume of which decreases as the piston retracts, and the cylinder having an outlet fluidically connected to the recompression chamber.

[0009] According to an internal combustion engine system of one aspect of the present disclosure, it is possible to increase the amount of fuel gas supplied to the internal combustion engine while preventing the system from becoming larger. According to a compressor of one aspect of the present disclosure, it is possible to make the compressor more compact than a reciprocating compressor in which a piston is reciprocated by a crankshaft and a connecting rod. According to a compressor of another aspect of the present disclosure, it is possible to prevent leaked fuel gas from accumulating in the cylinder.

[0010] FIG. 1 is a schematic diagram of a mobile body equipped with an internal combustion engine system according to an embodiment. FIG. 2 is an enlarged schematic diagram of the compressor assembly of FIG. 1. FIG. 3 is a perspective view of the compressor of FIG. 2. FIG. 4 is a vertical cross-sectional view of the compressor of FIG. 3. FIG. 5 is a cross-sectional view taken along line V-V of FIG. 4. FIG. 6 is a horizontal cross-sectional view of the recompression chamber and re-leak chamber of the compressor of FIG. 5. FIG. 7 is a block diagram of an example arrangement of a reducer and an electric motor. FIG. 8 is a block diagram of another example arrangement of a reducer and an electric motor.

[0011] Hereinafter, an embodiment will be described with reference to the drawings.

[0012] FIG. 1 is a schematic diagram of a mobile body equipped with an internal combustion engine system according to an embodiment. As shown in FIG. 1 , in this embodiment, the internal combustion engine system 1 is installed in a mobile body V. The mobile body V may be a manned vehicle or an unmanned vehicle. The mobile body V is, for example, a vehicle equipped with drive wheels W. In the mobile body V, driving force generated by an internal combustion engine E of the internal combustion engine system 1 is transmitted to the drive wheels W via a transmission T. The mobile body V may be, for example, a two-wheeled vehicle, a three-wheeled vehicle, a four-wheeled vehicle, a railway vehicle, or the like. The drive wheels W are an example of a propulsion force generator that generates propulsion force using the driving force generated by the internal combustion engine E of the internal combustion engine system 1. The mobile body V may also be a ship, an aircraft, or the like. In this case, the propulsion force generator may be a propeller or a fan.

[0013] The internal combustion engine system 1 includes a fuel storage source 2. The fuel storage source 2 stores fuel gas in a compressed state. The fuel storage source 2 includes a plurality of fuel tanks. As an example, the fuel storage source 2 includes a first fuel tank 11, a second fuel tank 12, a third fuel tank 13, and a fourth fuel tank 14. These fuel tanks 11 to 14 store fuel gas in a compressed state. The internal pressure of the fuel tanks 11 to 14 when full is higher than standard atmospheric pressure (0.1 MPa), and specifically, is sufficiently higher than the fuel injection pressure required by the internal combustion engine E. The internal pressure of the fuel tanks 11 to 14 when full is, for example, 70 MPa. The fuel gas is, for example, hydrogen gas. Compared to carbon-based fuels, a larger amount of hydrogen gas is required to obtain the same output in the internal combustion engine E, and the remaining amount of fuel gas in each of the fuel tanks 11 to 14 tends to decrease more quickly. The fuel gas may be any other type of fuel gas such as a hydrocarbon fuel, as long as it contains fuel vaporized in a tank.

[0014] The internal combustion engine system 1 includes an internal combustion engine E. The internal combustion engine E combusts fuel gas supplied from a fuel storage source 2, converts the combustion energy into rotational energy, and outputs the rotational energy as driving force. The internal combustion engine E is, for example, a direct injection engine. In this embodiment, the internal combustion engine E is a reciprocating engine. In this case, the internal combustion engine E explodes fuel gas in a cylinder, causing reciprocating motion of a piston due to the expansion of the gas in the cylinder. This reciprocating motion of the piston is converted into rotational motion of a crankshaft of the internal combustion engine E and is output.

[0015] The internal combustion engine E is equipped with a fuel injection device 45. The internal combustion engine E needs to be supplied with fuel gas at a predetermined fuel injection pressure that is higher than standard atmospheric pressure (0.1 MPa). The required pressure of fuel gas supplied to a direct injection engine is higher than the required pressure of fuel gas supplied to a non-direct injection engine. In a direct injection engine, fuel gas is supplied directly to the combustion chamber when the gas in the combustion chamber of the cylinder is compressed by the piston. When a direct injection engine is used as the internal combustion engine E, the internal combustion engine E needs to be supplied with fuel gas having a pressure of, for example, 10 MPa or higher from the fuel storage source 2.

[0016] Therefore, if the flow path from the fuel storage source to the fuel injection device of the internal combustion engine is simple, when the pressure of the fuel gas in the fuel storage source falls below 10 MPa, the fuel gas cannot be injected from the fuel injection device in the internal combustion engine, and the fuel storage source is considered to be empty. In other words, if the flow path from the fuel storage source to the fuel injection device of the internal combustion engine is simple, a large amount of fuel gas remains in the fuel storage source when the fuel storage source is considered to be empty. However, according to the internal combustion engine system 1 of this embodiment, as described below, the fuel gas in the fuel storage source 2 is used as much as possible to supply to the internal combustion engine E. Therefore, when the fuel storage source 2 is considered to be empty, less fuel gas remains in the fuel storage source 2, and the fuel gas in the fuel storage source 2 is used efficiently.

[0017] An intake passage 47 is connected to the intake port of the internal combustion engine E. A throttle valve 48 is provided in the intake passage 47. Outside air purified by the air cleaner 46 flows through the intake passage 47 and is supplied to the intake port of the internal combustion engine E to be used for combustion. The amount of intake air supplied to the internal combustion engine E is adjusted by the throttle valve 48.

[0018] The internal combustion engine system 1 includes a main flow path 3 that connects the fuel storage source 2 to the internal combustion engine E. Specifically, the main flow path 3 includes a first main flow path 15, a second main flow path 16, a third main flow path 17, and a fourth main flow path 18. The first main flow path 15 connects the first fuel tank 11 to the internal combustion engine E. The second main flow path 16 connects the second fuel tank 12 to the internal combustion engine E. The third main flow path 17 connects the third fuel tank 13 to the internal combustion engine E. The fourth main flow path 18 connects the fourth fuel tank 14 to the internal combustion engine E. In this embodiment, the first to fourth main flow paths 15 to 18 merge with each other on the way toward the internal combustion engine E. That is, the main flow path 3 has a common flow path portion 3a that makes the downstream portions of the first to fourth main flow paths 15 to 18 common and is connected to the internal combustion engine E.

[0019] The internal combustion engine system 1 includes a charge tank 4. The volume of the charge tank 4 is not particularly limited, but in this embodiment it is smaller than the volume of each of the fuel tanks 11 to 14. The maximum allowable internal pressure of the charge tank 4 is smaller than the maximum allowable internal pressure of each of the fuel tanks 11 to 14. Note that the maximum allowable internal pressure of the charge tank 4 may be the same as or larger than the maximum allowable internal pressure of each of the fuel tanks 11 to 14.

[0020] The internal combustion engine system 1 includes a charge path 5. The charge path 5 includes a first charge path 41, a second charge path 42, and a third charge path 43. The first charge path 41 connects the first fuel tank 11 to the charge tank 4. The second charge path 42 connects the second fuel tank 12 to the charge tank 4. The third charge path 43 connects the third fuel tank 13 to the charge tank 4. The fourth fuel tank 14 is not connected to the charge tank 4.

[0021] In this embodiment, the downstream portions of the first to third charge paths 41 to 43 are shared. The first to third charge paths 41 to 43 merge with each other on the way to the charge tank 4. That is, the charge path 5 shares the downstream portions of the first to third charge paths 41 to 43 and has a common path portion 5a connected to the charge tank 4. A compressor assembly 6 is provided in the common path portion 5a of the charge path 5. The compressor assembly 6 pressurizes the fuel gas flowing from the first to third fuel tanks 11 to 13 to the charge path 5, toward the charge tank 4. The fuel gas pressurized by the compressor assembly 6 is temporarily stored in the charge tank 4.

[0022] The compressor assembly 6 has an inlet port 6a, an outlet port 6b, and a leak port 6c. The inlet port 6a is a port into which fuel gas flows from an upstream portion of the common flow path portion 5a of the charge flow path 5. The outlet port 6b is a port from which fuel gas pressurized by the compressor assembly 6 is discharged to a downstream portion of the common flow path portion 5a of the charge flow path 5. The leak port 6c is a port from which blow-by gas generated in a compressor 60 (see FIG. 2 ) of the compressor assembly 6, which will be described later, is discharged. The leak port 6c is connected to the intake passage 47 via a blow-by gas flow path 49.

[0023] A cooler 28 is provided in the common flow path portion 5a of the charge flow path 5. The cooler 28 cools the fuel gas discharged from the outlet port 6b of the compressor assembly 6. That is, the fuel gas discharged from the outlet port 6b of the compressor assembly 6 is cooled by the cooler 28, thereby reducing its volume, and then supplied to the charge tank 4.

[0024] The internal combustion engine system 1 includes a secondary flow passage 7. The secondary flow passage 7 connects the charge tank 4 to the internal combustion engine E. Specifically, the secondary flow passage 7 includes a bridge flow passage 7a that connects the common flow passage portion 5a of the charge flow passage 5 to the common flow passage portion 3a of the main flow passage 3. A portion of the common flow passage portion 5a of the charge flow passage 5 downstream of a junction P1 between the bridge flow passage 7a and the common flow passage portion 5a of the charge flow passage 5 also serves as part of the secondary flow passage 7. A portion of the common flow passage portion 3a of the main flow passage 3 downstream of a junction P2 between the bridge flow passage 7a and the common flow passage portion 3a of the main flow passage 3 also serves as part of the secondary flow passage 7. Fuel gas from the charge tank 4 can be supplied to the internal combustion engine E via the portion of the common flow passage portion 5a of the charge flow passage 5 downstream of the junction P1, the bridge flow passage 7a, and the portion of the common flow passage portion 3a of the main flow passage 3 downstream of the junction P2.

[0025] The main flow path 3, the charge flow path 5, and the secondary flow path 7 are fuel gas flow paths that connect the fuel storage source 2 to the internal combustion engine E. The internal combustion engine system 1 includes a valve system 8 provided in the fuel gas flow paths. The valve system 8 opens and closes each of the main flow path 3, the charge flow path 5, and the secondary flow path 7. The configuration of the valve system 8 is not limited to a specific form. In other words, the valve system 8 can take various forms as long as it can open and close each of the main flow path 3, the charge flow path 5, and the secondary flow path 7.

[0026] For example, the valve system 8 includes a first fuel tank valve 21, a second fuel tank valve 22, a third fuel tank valve 23, a fourth fuel tank valve 24, a charge tank valve 25, check valves 26 and 27, shut-off valves 29 and 31, a pressure reducing valve 30, and a relief valve 32. The first to fourth fuel tank valves 21 to 24, the charge tank valve 25, and the shut-off valves 29 and 31 are, for example, electrically controllable solenoid valves.

[0027] The first fuel tank valve 21 operates between a closed state in which the port of the first fuel tank 11 is closed, a first open state in which the port of the first fuel tank 11 is connected to the first main flow path 15 but not connected to the first charge flow path 41, and a second open state in which the port of the first fuel tank 11 is connected to the first charge flow path 41 but not connected to the first main flow path 15.

[0028] The second fuel tank valve 22 operates between a closed state in which the port of the second fuel tank 12 is closed, a first open state in which the port of the second fuel tank 12 is connected to the second main flow path 16 but not connected to the second charge flow path 42, and a second open state in which the port of the second fuel tank 12 is connected to the second charge flow path 42 but not connected to the second main flow path 16.

[0029] The third fuel tank valve 23 operates between a closed state in which the port of the third fuel tank 13 is closed, a first open state in which the port of the third fuel tank 13 is connected to the third main flow path 17 but not connected to the third charge flow path 43, and a second open state in which the port of the third fuel tank 13 is connected to the third charge flow path 43 but not connected to the third main flow path 17.

[0030] The first to third fuel tank valves 21 to 23 may be, for example, three-way valves. The first fuel tank valve 21 may have an on-off valve that can connect the port of the first fuel tank 11 to the first main flow path 15, and an on-off valve that can connect the port of the first fuel tank 11 to the first charge flow path 41. Similarly, the second and third fuel tank valves 22 to 23 may each have two on-off valves.

[0031] The fourth fuel tank valve 24 operates between a closed state that closes the port of the fourth fuel tank 14 and an open state that connects the port of the fourth fuel tank 14 to the fourth main flow path 18. The charge tank valve 25 operates between a closed state that closes the port of the charge tank 4 and an open state that connects the port of the charge tank 4 to the charge flow path 5.

[0032] The check valves 26, 27 allow a flow in the main flow path 3 toward the internal combustion engine E and block a flow in the reverse direction. Specifically, the check valve 26 allows a flow in the main flow path 3 from the first fuel tank 11 and the second fuel tank 12 toward the internal combustion engine E and blocks a flow in the main flow path 3 toward the first fuel tank 11 and the second fuel tank 12. The check valve 27 allows a flow in the main flow path 3 from the third fuel tank 13 and the fourth fuel tank 14 toward the internal combustion engine E and blocks a flow in the main flow path 3 toward the third fuel tank 13 and the fourth fuel tank 14.

[0033] The shutoff valve 29 opens and closes the bridge flow passage 7a of the secondary flow passage 7. That is, when the shutoff valve 29 is open, the fuel gas in the charge tank 4 can be supplied to the common flow passage portion 3a of the main flow passage 3 via the secondary flow passage 7.

[0034] The pressure reducing valve 30 is provided in the common flow path portion 3a of the main flow path 3. Specifically, the pressure reducing valve 30 is provided downstream of the confluence P2 of the bridge flow path 7a of the sub-flow path 7 and the common flow path portion 3a of the main flow path 3. The pressure reducing valve 30 reduces the pressure of the fuel gas in the main flow path 3 to a predetermined pressure suitable for the internal combustion engine E. The pressure reducing valve 30 maintains the pressure of the main flow path 3 downstream of the pressure reducing valve 30 at a predetermined fuel injection pressure (e.g., 10 MPa) of the internal combustion engine E. The pressure reducing valve 30 opens a bypass passage connecting the upstream and downstream sides of the internal flow path when the pressure downstream of the internal flow path falls below the fuel injection pressure. The pressure reducing valve 30 closes the bypass passage when the pressure exceeds the fuel injection pressure. In this way, the pressure of the fuel gas flowing downstream of the pressure reducing valve 30 is reduced compared to the pressure of the fuel gas flowing upstream of the pressure reducing valve 30 so as to maintain the pressure of the fuel gas supplied from the main flow path 3 to the internal combustion engine E at the predetermined fuel injection pressure.

[0035] The shutoff valve 31 opens and closes a portion of the common flow path portion 3a of the main flow path 3 downstream of the pressure reducing valve 30. The shutoff valve 31 is capable of cutting off the supply of fuel gas from the main flow path 3 to the internal combustion engine E in an emergency or the like, and is disposed in a portion of the main flow path 3 downstream of the pressure reducing valve 30. The relief valve 32 discharges fuel gas from the common flow path portion 3a of the main flow path 3 when the pressure in the portion of the common flow path portion 3a of the main flow path 3 between the pressure reducing valve 30 and the shutoff valve 31 exceeds a predetermined relief pressure.

[0036] The first fuel tank pressure sensor 35 detects the pressure of the fuel gas stored in the first fuel tank 11. The second fuel tank pressure sensor 36 detects the pressure of the fuel gas stored in the second fuel tank 12. The third fuel tank pressure sensor 37 detects the pressure of the fuel gas stored in the third fuel tank 13. The fourth fuel tank pressure sensor 38 detects the pressure of the fuel gas stored in the fourth fuel tank 14. The charge tank pressure sensor 39 detects the pressure of the fuel gas stored in the charge tank 4.

[0037] The internal combustion engine system 1 has a configuration for replenishing fuel gas to the first to fourth fuel tanks 11 to 14. Specifically, a first replenishing flow path 51 is connected to a portion upstream of the check valve 26 in the shared portion of the first main flow path 15 and the second main flow path 16. A replenishing port 52 is provided at an end of the first replenishing flow path 51. A check valve 53 is provided in the first replenishing flow path 51, which allows a flow from the replenishing port 52 toward the first fuel tank 11 and the second fuel tank 12 and prevents a flow in the opposite direction.

[0038] A second supply flow path 54 is connected to a portion upstream of the check valve 27 in the shared portion of the third main flow path 17 and the fourth main flow path 18. A supply port 55 is provided at an end of the second supply flow path 54. The second supply flow path 54 is provided with a check valve 56 that allows flow from the supply port 55 toward the third fuel tank 13 and the fourth fuel tank 14 and prevents flow in the reverse direction. Note that a configuration may be adopted in which fuel gas can be supplied from a single supply port to the first to fourth fuel tanks 11 to 14, or a supply port may be provided corresponding to each of the fuel tanks 11 to 14.

[0039] The internal combustion engine system 1 includes a controller 9. The controller 9 controls the valve system 8 and an electric motor 61 (described later) based on detection signals from the sensors 35 to 39. The controller 9 has a processing circuit 19. The controller 9 includes, for example, a processor, a system memory, and a storage memory. The processor includes, for example, a central processing unit (CPU). The system memory is, for example, a RAM. The storage memory may include a ROM. The storage memory may include a hard disk, a flash memory, or a combination thereof. The storage memory stores a program. A configuration in which the processor executes a program read into the system memory is an example of the processing circuit 19.

[0040] The processing circuit 19 controls the valve system 8 to supply fuel gas from at least one of the fuel tanks 11 to 14 to the internal combustion engine E. The processing circuit 19 controls the electric motor 61 (described later) to compress the fuel gas from at least one of the fuel tanks 11 to 13 using the compressor assembly 6. The processing circuit 19 controls the valve system 8 to supply fuel gas from the charge tank 4 to the internal combustion engine E.

[0041] In this way, even if the pressure of the fuel gas in the fuel storage source 2 drops, the fuel gas can be compressed by the compressor assembly 6, and the pressurized fuel gas can be supplied to the internal combustion engine E. Therefore, the amount of fuel gas that can be supplied to the internal combustion engine E can be increased without increasing the size of the fuel storage source 2.

[0042] Fig. 2 is an enlarged schematic diagram of the compressor assembly 6 of Fig. 1. As shown in Fig. 2, the compressor assembly 6 includes a compressor 60, an electric motor 61, and a flow path group 62. The compressor 60 will be described later with reference to Figs. 3 to 5. The electric motor 61 drives the compressor 60. The flow path group 62 will be described after the compressor 60 has been described in detail with reference to Figs. 3 to 5. In this embodiment, the compressor 60 is driven by the driving force of the electric motor 61, but it may also be driven by utilizing energy generated by the internal combustion engine E.

[0043] Figure 3 is a perspective view of the compressor 60 of Figure 2. As shown in Figure 3, the compressor 60 is a reciprocating pump type compressor. The number of cylinders in the compressor 60 is not particularly limited, but in this embodiment, it is two cylinders. The compressor 60 includes a cylinder head 64, a cylinder block 65, and a cam case 66. The cylinder head 64, the cylinder block 65, and the cam case 66 are each separate pieces and are fastened together with a plurality of through bolts B. Each of the plurality of through bolts B is inserted through the cylinder head 64, the cylinder block 65, and the cam case 66 in order.

[0044] The cylinder head 64 and the cylinder block 65 are formed of a material different from that of the cam case 66. The cylinder head 64 and the cylinder block 65 are formed of a metal material that is less susceptible to embrittlement by fuel gas than the cam case 66. For example, when the fuel gas is hydrogen gas, the cylinder head 64 and the cylinder block 65 are formed of stainless steel. The cam case 66 is formed of an aluminum alloy. In other words, the cylinder block 65 and the cylinder head 64, which are exposed to high-pressure hydrogen, are formed of a material that is more resistant to hydrogen embrittlement than the cam case 66. This prevents a decrease in strength of the compressor 60 due to hydrogen when the fuel gas is hydrogen, and increases the flexibility in selecting the material for the cam case 66. For example, using an aluminum alloy as the material for the cam case 66 reduces the weight and manufacturing costs of the compressor 60 as a whole. Note that the cylinder block 65 and the cylinder head 64 may be formed of the same material as the cam case 66.

[0045] A plurality of heat dissipation fins are integrally provided on the cylinder block 65 as a heat sink 67. The cam case 66 has a shaft through-hole 66a. A camshaft 70 housed in the cam case 66 passes through the shaft through-hole 66a and protrudes to the outside. The driving force of the electric motor 61 (see FIG. 2) is input to the end of the camshaft 70 protruding from the cam case 66 to the outside.

[0046] Figure 4 is a vertical cross-sectional view of the compressor 60 of Figure 3. Figure 5 is a cross-sectional view taken along line V-V of Figure 4. As shown in Figures 4 and 5, the compressor 60 is a reciprocating pump having two cylinders. That is, the compressor 60 has two reciprocating structures 72. Each of the two reciprocating structures 72 includes a cylinder 80, a piston 81, a rod 82, a linear bushing 83, a cam 84, a cam bearing 85, a spring 86, a rider ring 87, a piston seal 88, a first rod seal 89, a second rod seal 90, a compression chamber 91, a recompression chamber 92, and a re-leak chamber 93.

[0047] The cylinder 80 has a suction port 80a connected to the inlet port 6a (see FIG. 2) of the compressor assembly 6, and a discharge port 80b connected to the outlet port 6b (see FIG. 2) of the compressor assembly 6. A check valve 97 communicating with the suction port 80a is attached to the cylinder 80. A check valve 98 communicating with the discharge port 80b is attached to the cylinder 80.

[0048] The check valve 97 allows flow from the inlet port 6a (see FIG. 2) of the compressor assembly 6 through the suction port 80a toward the compression chamber 91, and blocks flow from the compression chamber 91 through the suction port 80a toward the inlet port 6a (see FIG. 2) of the compressor assembly 6. The check valve 98 allows flow from the compression chamber 91 through the discharge port 80b toward the outlet port 6b (see FIG. 2) of the compressor assembly 6, and blocks flow from the outlet port 6b (see FIG. 2) of the compressor assembly 6 toward the compression chamber 91 through the discharge port 80b.

[0049] The cylinder 80 has a first inner circumferential surface 80c, a second inner circumferential surface 80d, and a third inner circumferential surface 80e. That is, the inner circumferential surface of the cylinder 80 has multiple steps aligned in the reciprocating direction of the piston 81. The first inner circumferential surface 80c, the second inner circumferential surface 80d, and the third inner circumferential surface 80e are aligned in this order in the axial direction X of the cylinder 80 from the piston 81 toward the cam 84. The first inner circumferential surface 80c defines a space in which the piston 81 is accommodated. The second inner circumferential surface 80d and the third inner circumferential surface 80e define a space in which the rod 82 is accommodated. The inner diameter of the second inner circumferential surface 80d is smaller than the inner diameter of the first inner circumferential surface 80c. The inner diameter of the third inner circumferential surface 80e is smaller than the inner diameter of the second inner circumferential surface 80d.

[0050] The cylinder 80 has a first opposing surface 80f that connects the first inner circumferential surface 80c to the second inner circumferential surface 80d in a stepped manner. The first opposing surface 80f extends in a radial direction R that is perpendicular to the axial direction X of the cylinder 80 and faces the back surface of the piston 81 in the axial direction X. The cylinder 80 has a second opposing surface 80g that connects the second inner circumferential surface 80d to the third inner circumferential surface 80e in a stepped manner. The second opposing surface 80g extends in the radial direction R that is perpendicular to the axial direction X of the cylinder 80.

[0051] The piston 81 is housed in the cylinder 80 in a space defined by the first inner circumferential surface 80c. The piston 81, together with the cylinder 80, defines a compression chamber 91 facing the suction port 80a and the discharge port 80b. A rider ring 87 and a piston seal 88 are fitted onto the outer circumferential surface of the piston 81. The rider ring 87 is a sliding member that prevents axial wobble of the piston 81. The piston seal 88 serves to seal the gap between the first inner circumferential surface 80c of the cylinder 80 and the outer circumferential surface of the piston 81.

[0052] The rod 82 protrudes from the back surface of the piston 81. The back surface of the piston 81 faces away from the compression chamber 91 in the axial direction X. The rod 82 has a first rod portion 82a and a second rod portion 82b. The first rod portion 82a protrudes from the back surface of the piston 81 and has a smaller diameter than the piston 81. The first rod portion 82a has a first outer peripheral surface 82c that slides against the second inner peripheral surface 80d of the cylinder 80. The outer diameter of the first rod portion 82a is substantially the same as the inner diameter of the second inner peripheral surface 80d of the cylinder 80. The second rod portion 82b protrudes from the back surface of the first rod portion 82a and has a smaller diameter than the first rod portion 82a. In other words, the outer peripheral surface of the rod 82 has steps aligned in the reciprocating direction of the piston 81. The back surface of the first rod portion 82a faces away from the compression chamber 91 in the axial direction X. The second opposing surface 80g of the cylinder 80 faces the back surface of the second rod portion 82b in the axial direction X.

[0053] The first rod portion 82a passes through a space defined by the second inner circumferential surface 80d of the cylinder 80. A first rod seal 89 is fitted onto the outer circumferential surface of the first rod portion 82a. That is, the first rod seal 89 is interposed between the outer circumferential surface of the first rod portion 82a and the second inner circumferential surface 80d of the cylinder 80. The first rod seal 89 serves to seal the gap between the second inner circumferential surface 80d of the cylinder 80 and the outer circumferential surface of the first rod portion 82a. The outer circumferential surface of the first rod portion 82a corresponds to the first outer circumferential surface 82c of the rod 82.

[0054] The second rod portion 82b passes through a space defined by the third inner circumferential surface 80e of the cylinder 80. A second rod seal 90 is fitted onto the outer circumferential surface of the second rod portion 82b. That is, the second rod seal 90 is interposed between the outer circumferential surface of the second rod portion 82b and the third inner circumferential surface 80e of the cylinder 80, between the first rod seal 89 and a cam chamber 66b (described later) in the axial direction X. The second rod seal 90 serves to seal the gap between the third inner circumferential surface 80e of the cylinder 80 and the outer circumferential surface of the second rod portion 82b. The outer circumferential surface of the second rod portion 82b corresponds to the second outer circumferential surface 82d of the rod 82.

[0055] The linear bushing 83 is supported by the cylinder 80 between the second rod seal 90 and the cam 84 in the axial direction X. The linear bushing 83 supports the second rod portion 82b so as to be slidable in the axial direction X.

[0056] The cam 84 and camshaft 70 are housed in a cam chamber 66b, which is the internal space of the cam case 66. The cam 84 presses the end face of the rod 82 in the axial direction X, causing the rod 82 to reciprocate in the axial direction X. The camshaft 70 is eccentrically connected to each cam 84 of the two reciprocating structures 72. When the camshaft 70 rotates, the cam 84 rotates integrally with the camshaft 70 around the axis of the camshaft 70. The camshaft 70 is rotatably supported by the cam case 66 via a shaft bearing 71.

[0057] The cam bearing 85 is, for example, a rolling bearing. In this embodiment, the cam bearing 85 is a ball bearing. The outer peripheral surface of the cam 84 has a perfect circular shape. The cam bearing 85 is fitted onto the cam 84 so as to cover the outer peripheral surface of the cam 84. The cam bearing 85 has an inner ring 94, an outer ring 95, and a plurality of balls 96. The inner ring 94 and the outer ring 95 have perfect circular shapes. The inner ring 94 is fitted onto the outer peripheral surface of the cam 84. The plurality of balls 96 are interposed between the inner ring 94 and the outer ring 95. The plurality of balls 96 are held in a predetermined position by a cage, but the cage is not shown in the drawing.

[0058] The outer ring 95 is rotatable relative to the inner ring 94 via balls 96. That is, the outer ring 95 is a ring that covers the outer peripheral surface of the cam 84 and is rotatable relative to the cam 84. The outer ring 95 abuts against the end face 82e of the rod 82 in the axial direction X. The end face 82e of the rod 82 is a surface that faces away from the compression chamber 91 in the axial direction X. The cam 84 presses the end face 82e of the rod 82 in the axial direction X via a cam bearing 85. The spring 86 biases the rod 82 in a direction in which the rod 82 moves toward the cam 84.

[0059] This relative rotation of the outer ring 95 with respect to the cam 84 reduces the sliding resistance that the cam 84 receives from the rod 82. Furthermore, the force in the radial direction R that is applied from the cam 84 to the rod 82 is reduced, and the sliding resistance between the piston 81 and the cylinder 80 is also reduced.

[0060] Because the compression chamber 91 is connected to the fuel tanks 11 to 14, the cam chamber 66b is set to a pressure lower than the internal pressure of the compression chamber 91, even when the piston 81 has moved to bottom dead center. In this embodiment, the cam case 66 has a communication hole that communicates with the space outside the cam case 66. In other words, the cam chamber 66b is open to the atmosphere. Therefore, the pressure difference between the compression chamber 91 and the cam chamber 66b can generate a force that presses the piston 81 toward the cam 84. Therefore, a spring 86 with a small elastic modulus can be used.

[0061] The cams 84 of the two reciprocating structures 72 are offset in phase from each other by an equal interval. That is, when the piston 81 of one reciprocating structure 72 is at top dead center, the piston 81 of the other reciprocating structure 72 is at bottom dead center. When it is necessary to rotate the cam 84 in one reciprocating structure 72 to exert a force compressing the fuel gas in the compression chamber 91, the pressure of the fuel gas flowing into the compression chamber 91 of the other reciprocating structure 72 moves the piston 81 backward, rotating the corresponding cam 84. That is, the operation of one reciprocating structure 72 is assisted by the operation of the other reciprocating structure 72. This reduces the driving force required for the electric motor 61 (see FIG. 2 ) that rotates the camshaft 70, and allows the spring 86 to be made lighter and more compact.

[0062] Two gaskets G are sandwiched between the cylinder head 64 and the cylinder block 65 to surround the internal spaces of the cylinders 80 of the two reciprocating structures 72. Similarly, two gaskets G are sandwiched between the cylinder block 65 and the cam case 66 to surround the internal spaces of the cylinders 80 of the two reciprocating structures 72. Lubricating oil can be stored in the cam chamber 66b of the cam case 66. This allows the shaft bearing 71 and the cam bearing 85 to be lubricated with oil.

[0063] The recompression chamber 92 is disposed between the piston 81 and the first rod seal 89 in the axial direction X. The recompression chamber 92 is defined by the outer peripheral surface of the first rod portion 82a of the rod 82, the first inner peripheral surface 80c of the cylinder 80, the back surface of the piston 81, and the first opposing surface 80f of the cylinder 80. The recompression chamber 92 has an annular shape when viewed from the axial direction X. When the piston 81 retreats to approach the cam chamber 66b, the distance between the back surface of the piston 81 and the first opposing surface 80f of the cylinder 80 decreases. Therefore, the volume of the recompression chamber 92 decreases as the piston 81 retreats.

[0064] The cylinder 80 has an outlet 80h that is fluidly connected to the recompression chamber 92. A check valve 99 that is connected to the outlet 80h is attached to the cylinder 80. The check valve 99 protrudes to the outside from the cylinder 80. It is preferable that the heat sink 67 protrudes at least in the direction in which the check valve 99 protrudes. This limits the amount of protrusion of the check valve 99 from the cylinder 80, including the heat sink 67, in the outer shape of the compressor 60.

[0065] The check valve 99 allows flow from the recompression chamber 92 to the outside of the recompression chamber 92 through the outlet 80h, and prevents flow from the outside of the recompression chamber 92 to the recompression chamber 92 through the outlet 80h.

[0066] If fuel gas in the compression chamber 91 leaks past the piston seal 88 into the recompression chamber 92, the leaked fuel gas is recompressed in the recompression chamber 92 as the piston 81 moves backward. This recompressed leaked gas is discharged to the outside from the outlet 80h of the cylinder 80 via the check valve 99. The fuel gas discharged from the outlet 80h is supplied again to the suction port 80a through the return flow path 62c (see FIG. 2) and the inlet flow path 62a (see FIG. 2).

[0067] The outlet 80h is disposed at a position offset from the recompression chamber 92 in the direction in which the suction port 80a is offset from the center of the compression chamber 91 in the radial direction R of the cylinder 80. This allows the check valve 97 provided at the suction port 80a and the check valve 99 provided at the outlet 80h to be closer to each other, thereby shortening the length of the flow path from the return flow path 62c to the junction with the inlet flow path 62a.

[0068] The re-leak chamber 93 is disposed between the first rod seal 89 and the second rod seal 90 in the axial direction X. The re-leak chamber 93 is defined by the outer circumferential surface of the second rod portion 82b of the rod 82, the second inner circumferential surface 80d of the cylinder 80, the back surface of the first rod portion 82a of the rod 82, and the second opposing surface 80g of the cylinder 80. The re-leak chamber 93 has an annular shape when viewed from the axial direction X. When the rod 82 retracts toward the cam chamber 66b, the distance between the back surface of the first rod portion 82a and the second opposing surface 80g of the cylinder 80 decreases. Therefore, the volume of the re-leak chamber 93 decreases as the rod 82 retracts. In other words, the first rod portion 82a acts as a piston that reduces the volume of the re-leak chamber 93.

[0069] The cylinder 80 has an exhaust port 80i fluidly connected to the re-leak chamber 93. The exhaust port 80i is connected to the leak port 6c (see FIG. 2) of the compressor assembly 6. If fuel gas from the re-compression chamber 92 leaks past the first rod seal 89 into the re-leak chamber 93, the leaked fuel gas is discharged from the re-leak chamber 93 to the outside through the exhaust port 80i as the rod 82 retracts. This prevents the leaked fuel gas from traveling toward the cam chamber 66b. The fuel gas discharged from the exhaust port 80i flows through the exhaust passage 62d (see FIG. 2) and the blow-by gas passage 49 (see FIG. 1) and is supplied to the intake passage 47. This allows the leaked fuel gas to mix with air and contribute to combustion in the internal combustion engine E.

[0070] Because the re-leak chamber 93 is connected to the intake passage 47, the internal pressure of the re-leak chamber 93 is set to a pressure lower than the internal pressure of the compression chamber 91, even when the piston 81 moves from top dead center to bottom dead center. This allows the force pressing the rod 82 against the cam 84 to be further increased, making it possible to use a spring 86 with a small elastic modulus.

[0071] Because the re-leak chamber 93 is connected to the intake passage 47 where negative pressure is generated during the intake stroke of the internal combustion engine E, the internal pressure of the re-leak chamber 93 is set lower than the internal pressure of the cam chamber 66b during the intake stroke of the internal combustion engine E. This effectively prevents fuel gas from leaking from the re-leak chamber 93 to the cam chamber 66b.

[0072] 6 , the distance in the radial direction R from the first inner circumferential surface 80c of the cylinder 80 to the first outer circumferential surface 82c of the first rod portion 82a in the recompression chamber 92 is smaller than the distance in the radial direction R from the second inner circumferential surface 80d of the cylinder 80 to the second circumferential surface 82d of the second rod portion 82b in the re-leak chamber 93. In this embodiment, with respect to a cross section of the compressor 60 cut in the radial direction R, the cross-sectional area of ​​the recompression chamber 92 is approximately the same as the cross-sectional area of ​​the re-leak chamber 93, but is not limited to this.

[0073] 2 , the flow passage group 62 of the compressor assembly 6 includes an inlet flow passage 62a, an outlet flow passage 62b, a return flow passage 62c, and a discharge flow passage 62d. The inlet flow passage 62a connects the inlet port 6a of the compressor assembly 6 to the suction port 80a of the compressor 60 via a check valve 97. The outlet flow passage 62b connects the discharge port 80b of the compressor 60 to the outlet port 6b of the compressor assembly 6 via a check valve 98. The return flow passage 62c connects the outlet 80h of the recompression chamber 92 of the compressor 60 to the inlet flow passage 62a.

[0074] The fuel gas recompressed in the recompression chamber 92 of the compressor 60 is supplied again to the suction port 80a of the compressor 60 through the check valve 99 and the return flow path 62c. Therefore, the fuel gas leaking from the compression chamber 91 and recompressed in the recompression chamber 92 is supplied to the fuel injection device 45 of the internal combustion engine E. The discharge flow path 62d connects the discharge port 80i of the re-leak chamber 93 of the compressor 60 to the leak port 6c of the compressor assembly 6. Therefore, the fuel gas leaking from the compression chamber 91 and the recompression chamber 92 and reaching the re-leak chamber 93 is used for combustion as intake air for the internal combustion engine E.

[0075] 3 to 5 , in this embodiment, a plurality of through-bolts B are arranged around the reciprocating structure 72 as viewed from the axial direction X of the cylinder 80. As a result, even if resistance to the compressive force occurs in the compressor 60, the through-bolts B maintain a strong fastening of the cylinder head 64, the cylinder block 65, and the cam case 66. Specifically, the plurality of through-bolts B are arranged side by side in the axial direction of the camshaft 70. The plurality of through-bolts B are also arranged side by side in a direction perpendicular to both the axial direction of the camshaft 70 and the axial direction X of the cylinder 80.

[0076] Furthermore, because the multiple through-bolts B are arranged in the same direction as the check valves 97, 98, the through-bolts B can be arranged without interfering with the check valves 97, 98. Furthermore, because the through-bolts B are offset in the axial direction of the camshaft 70 with respect to the suction port 80a, the discharge port 80b, and the discharge port 80i, interference with the suction port 80a, the discharge port 80b, and the discharge port 80i can be prevented. In other words, the suction port 80a, the discharge port 80b, and the discharge port 80i in one reciprocating structure 72 of interest are preferably arranged along an imaginary plane perpendicular to the camshaft 70.

[0077] FIG. 7 is a block diagram of an example of the arrangement of the reducer 100 and the electric motor 61. As shown in FIG. 7, the driving force of the electric motor 61 may be input to the camshaft 70 of the compressor 60 via the reducer 100. This allows the electric motor 61 to be made smaller. The electric motor 61 may be arranged alongside the compressor 60 in the direction in which the camshaft 70 of the compressor 60 extends. Specifically, the camshaft 70 of the compressor 60 and the drive shaft 61a of the electric motor 61 may be arranged coaxially with each other. The reducer 100 is not particularly limited and may be, for example, a planetary gear mechanism.

[0078] 8 is a block diagram of another example of the arrangement of the reducer 200 and the electric motor 61. As shown in FIG. 8, the driving force of the electric motor 61 may be input to the camshaft 70 of the compressor 60 via the reducer 200. The electric motor 61 may be aligned with the compressor 60 in a direction perpendicular to the direction in which the camshaft 70 of the compressor 60 extends. Specifically, the camshaft 70 of the compressor 60 and the drive shaft 61 a of the electric motor 61 may be arranged parallel to each other. The reducer 200 is not particularly limited and may be, for example, a pulley-belt mechanism or a chain-sprocket mechanism.

[0079] According to the configuration described above, the compressor 60 reciprocates the piston 81 using the cam 84, and therefore can be made more compact than a reciprocating compressor in which the piston is reciprocated using a crankshaft and a connecting rod. For example, when the piston is not at top dead center or bottom dead center, the connecting rod is inclined with respect to the piston reciprocation direction, protruding in a direction perpendicular to the piston reciprocation direction, which increases the size of the compressor case. In contrast, in this embodiment, the extension direction of the rod 82 is maintained in the same direction as the piston 81 reciprocation, allowing the size of the compressor case to be reduced. Therefore, due to the reduced size of the compressor 60, it is possible to increase the amount of fuel gas that can be supplied to the internal combustion engine E while preventing the system 1 from becoming larger.

[0080] The technology of the present disclosure is not limited to the above-described embodiment. For example, the present system can be suitably applied to a mobile body that requires miniaturization, but is not limited thereto and may also be mounted on a non-mobile body. For example, the internal combustion engine system 1 may be used as a driving source for a transportable power generation device. In this case, the internal combustion engine system 1 serves as a driving source for rotating a power generation generator. The present system may also be applied to a fixed object such as a fixed facility. In the above-described embodiment, there are multiple fuel tanks 11 to 14, but there may be only one fuel tank. If the fuel tank is detachable, the internal combustion engine system 1 sold, etc., does not need to include a fuel tank.

[0081] The multiple cylinders 80 do not have to be arranged in parallel, but may be horizontally opposed or V-shaped. The orientation of the cylinders 80 does not have to be vertical, but may be horizontal, for example. The configuration of the flow path and valve system in the embodiment is merely an example. The spring 86 may be omitted. The number of cylinders in the compressor assembly 6 may be one, three or more. The outlet 80h of the recompression chamber 92 does not have to be connected to the suction port 80a, but may be connected to the charge flow path 5 or the sub-flow path 7 downstream of the discharge port 80b. The first opposing surface 80f and the second opposing surface 80g may be inclined with respect to the radial direction R.

[0082] Although the outer ring 95 covering the cam 84 is rotatable relative to the cam 84 via the balls 96 in the above description, it may be rotatable via cylindrical rollers or cones instead of the balls 96. In this way, it is preferable to use a rolling bearing. The cam bearing 85 may be a plain bearing or a fluid bearing instead of a rolling bearing. When the cam bearing 85 is a plain bearing or a fluid bearing, a cylindrical body fitted onto the outside of the cam 84 is a ring that covers the outer peripheral surface of the cam 84 and is rotatable relative to the cam 84.

[0083] A plurality of recompression chambers 92 may be provided. In the cross section cut in the radial direction R of the compressor 60, the cross-sectional area of ​​the recompression chamber 92 is smaller than the cross-sectional area of ​​the re-leak chamber 93, but this is not limited to this. The cross-sectional area of ​​the recompression chamber 92 may be the same as the cross-sectional area of ​​the re-leak chamber 93, or may be larger than the cross-sectional area of ​​the re-leak chamber 93. One or both of the recompression chamber 92 and the re-leak chamber 93 may not be provided.

[0084] When the compressor 60 has a plurality of reciprocating structures 72, the reciprocating structures 72 may be arranged along the axis of the camshaft 70, or the reciprocating structures 72 may be arranged around the axis of the camshaft 70. By arranging the reciprocating structures 72 along or around the camshaft 70, the camshaft 70 can be shared for each reciprocating structure 72, making it easier to make the compressor more compact.

[0085] When the compressor has a plurality of reciprocating structures 72, it is preferable that the eccentric directions of the cams 84 corresponding to the respective reciprocating structures 72 are different from one another. For example, when the number of reciprocating structures 72 is N, it is preferable that the phases of the cams 84 are shifted around the axis of the cam 70 shaft by an angle obtained by dividing 360° by N (360° / N). This makes it possible to suppress fluctuations in the rotational resistance of the camshaft 70 due to changes in the rotation angle of the camshaft 70.

[0086] The compressor 60 may have a relief valve that maintains the pressure in the cam chamber 66b higher than atmospheric pressure and prevents the pressure from approaching the internal pressure of the compression chamber 91. Increasing the pressure in the cam chamber 66b makes it easier to prevent fuel gas from leaking into the cam chamber 66b.

[0087] As described above, the above-described embodiments have been described as examples of the technology disclosed in this application. However, the technology of the present disclosure is not limited to these embodiments and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. Furthermore, the components described in the above-described embodiments can be combined to create new embodiments. Some configurations in the embodiments can be separated from other configurations in the embodiment and extracted as desired. Furthermore, the components described in the accompanying drawings and detailed description include not only components essential for solving the problem, but also components that are not essential for solving the problem and are used to illustrate the technology.

[0088] Each of the following sections is a disclosure of a preferred embodiment.

[0089] [Item 1] An internal combustion engine system comprising: a fuel storage source including at least one fuel tank that stores fuel gas in a compressed state; a fuel gas flow path that connects the fuel storage source to an internal combustion engine; and a compressor that compresses the fuel gas in the fuel gas flow path, wherein the compressor has at least one reciprocating structure that includes a cylinder having an intake port and a discharge port, a piston that is housed in the cylinder and defines a compression chamber facing the intake port and the discharge port, a rod that protrudes from the piston, and a cam that reciprocates the rod.

[0090] With this configuration, even if the pressure of the fuel gas in the fuel storage source drops, the fuel gas can be compressed by the compressor and the pressurized fuel gas can be supplied to the internal combustion engine. Therefore, the amount of fuel gas that can be supplied to the internal combustion engine can be increased without increasing the size of the fuel storage source. Furthermore, because the compressor reciprocates the pistons using a cam, it can be made more compact than a reciprocating compressor, which reciprocates the pistons using a camshaft and a connecting rod. Therefore, due to the compact compressor, it is possible to increase the amount of fuel gas that can be supplied to the internal combustion engine without increasing the size of the system.

[0091] [Item 2] The internal combustion engine system described in Item 1, wherein the reciprocating structure further includes: a first rod seal interposed between an outer peripheral surface of the rod and an inner peripheral surface of the cylinder; and a recompression chamber arranged between the piston and the first rod seal in the axial direction of the cylinder, wherein the recompression chamber is defined by the outer peripheral surface of the rod and the inner peripheral surface of the cylinder, and a volume of the recompression chamber decreases as the piston retracts, and the cylinder has an outlet fluidically connected to the recompression chamber.

[0092] With this configuration, if fuel gas in the compression chamber leaks past the piston into the space where the rod is located, the leaked fuel gas is recompressed in the recompression chamber as the piston moves back. This recompressed leaked gas is then discharged to the outside through the cylinder outlet, thereby preventing the leaked fuel gas from accumulating inside the cylinder.

[0093] [Item 3] The internal combustion engine system according to Item 2, wherein the reciprocating structure further includes a check valve that allows a flow from the recompression chamber toward the outside of the recompression chamber through the outlet and inhibits a flow from the outside of the recompression chamber toward the recompression chamber through the outlet, and the outlet is fluidly connected to a flow path that is fluidly connected to the internal combustion engine via the check valve.

[0094] According to this configuration, the leaked fuel gas recompressed in the recompression chamber can be used to supply to the internal combustion engine.

[0095] [Item 4] The internal combustion engine system according to item 2 or 3, wherein the inner circumferential surface of the cylinder has a first inner circumferential surface that defines a space in which the piston is accommodated and a second inner circumferential surface that defines a space in which the rod is accommodated, an inner diameter of the second inner circumferential surface is smaller than an inner diameter of the first inner circumferential surface, and the cylinder further has an opposing surface that extends radially to connect the first inner circumferential surface to the second inner circumferential surface and that faces the piston in the axial direction, and the recompression chamber is defined between the piston and the opposing surface of the cylinder.

[0096] With this configuration, when fuel gas enters the compression chamber through the cylinder inlet and the piston retracts, the distance between the piston and the opposing surface of the cylinder in the axial direction of the cylinder is reduced, so that leaked fuel gas that has passed over the piston and entered the recompression chamber can be suitably compressed by the retraction of the piston.

[0097] [Item 5] The internal combustion engine system according to any one of items 2 to 4, wherein the compressor further includes a cam case defining a cam chamber in which the cam is housed, and the reciprocating structure further includes: a second rod seal interposed between the outer peripheral surface of the rod and the inner peripheral surface of the cylinder, between the first rod seal and the cam chamber in the axial direction of the cylinder; and a re-leak chamber arranged between the first rod seal and the second rod seal in the axial direction of the cylinder, wherein the re-leak chamber is defined by the outer peripheral surface of the rod and the inner peripheral surface of the cylinder, and a volume of the re-leak chamber decreases as the rod retracts, and the cylinder has an outlet fluidically connected to the re-leak chamber.

[0098] With this configuration, if fuel gas leaking from the compression chamber past the piston into the recompression chamber further leaks past the first rod seal, the leaked fuel gas is pressurized in the re-leak chamber as the rod moves backward, and can be discharged from the exhaust port, thereby more effectively preventing the leaked fuel from heading toward the cam chamber.

[0099] [Item 6] The internal combustion engine system according to Item 5, wherein the outlet communicating with the recompression chamber is fluidly connected to a flow path that supplies fuel gas to a fuel injection device of the internal combustion engine, and the exhaust port of the re-leak chamber is fluidly connected to an intake passage that is fluidly connected to the internal combustion engine.

[0100] With this configuration, the leaked fuel gas can be easily used for combustion in the internal combustion engine.

[0101] [Item 7] The internal combustion engine system according to any one of Items 1 to 6, wherein the compressor further has a cam chamber in which the cam is housed, and the internal pressure of the cam chamber is set lower than the internal pressure of the compression chamber during a stroke in which the piston moves from top dead center to bottom dead center.

[0102] With this configuration, a force acting on the rod toward the cam is generated due to the pressure difference, making it easier to maintain contact between the cam and the rod.

[0103] [Item 8] The internal combustion engine system according to any one of items 1 to 7, wherein the compressor further includes a camshaft that rotates the cam, the reciprocating structure further includes a ring that covers an outer peripheral surface of the cam and is rotatable relative to the cam, the outer peripheral surface of the cam has a perfect circular shape, the camshaft is eccentrically connected to the cam, and the cam presses the rod via the ring.

[0104] With this configuration, the ring rotates relative to the cam, reducing the sliding resistance that the rod exerts on the cam. This reduces the energy required to drive the compressor. It also reduces the radial force that the cam exerts on the rod, perpendicular to the axial direction of the cylinder. This reduces the radial force transmitted from the piston to the cylinder, reducing the sliding resistance between the piston and the cylinder.

[0105] [Item 9] The internal combustion engine system according to any one of items 1 to 8, wherein the reciprocating structure further includes: a check valve that allows a flow from the charge passage through the suction port toward the compression chamber and blocks a flow from the compression chamber toward the charge passage through the suction port; and a check valve that allows a flow from the compression chamber toward the charge passage through the discharge port and blocks a flow from the charge passage toward the compression chamber through the discharge port.

[0106] According to this configuration, the fuel gas can be smoothly sucked into the compression chamber and discharged from the compression chamber without any special control.

[0107] [Item 10] The internal combustion engine system according to any one of Items 1 to 9, wherein the at least one reciprocating structure includes a plurality of reciprocating structures, and the cams of the plurality of reciprocating structures have phases that are shifted at equal intervals from one another.

[0108] With this configuration, when one reciprocating mechanism needs to rotate a cam to generate a force that compresses fuel gas in a compression chamber, the pressure of fuel gas flowing into the compression chamber of another reciprocating mechanism causes the piston to move backward, rotating the corresponding cam. In other words, the operation of one reciprocating mechanism is assisted by the operation of the other reciprocating mechanism. This prevents the maximum value of the driving force required to drive the camshaft from increasing.

[0109] [Item 11] The fuel engine system according to any one of Items 1 to 10, further comprising a cooler that cools the fuel gas discharged from the discharge port of the compressor.

[0110] According to this configuration, the volume of the fuel gas can be reduced by cooling, and the filling amount, i.e., density, of the fuel gas supplied to the internal combustion engine can be increased.

[0111] [Item 12] A compressor comprising: a cylinder having an inlet and an outlet; a piston housed in the cylinder and defining a compression chamber facing the inlet and the outlet; a rod protruding from the piston; a cam that reciprocates the rod; a camshaft that rotates the cam; and a ring that covers an outer circumferential surface of the cam and is rotatable relative to the cam, wherein the outer circumferential surface of the cam has a perfect circular shape, the camshaft is eccentrically connected to the cam, and the cam presses the rod via the ring.

[0112] According to this configuration, the compressor reciprocates the pistons using the cams, and therefore can be made more compact than a reciprocating compressor in which the pistons are reciprocated by a camshaft and a connecting rod.

[0113] [Item 13] A compressor comprising: a cylinder having an inlet and a discharge port; a piston housed in the cylinder and defining a compression chamber facing the inlet and the discharge port; a rod protruding from the piston; a first rod seal interposed between an outer circumferential surface of the rod and an inner circumferential surface of the cylinder; and a recompression chamber disposed between the piston and the first rod seal in the axial direction of the cylinder, wherein the recompression chamber is defined by the outer circumferential surface of the rod and the inner circumferential surface of the cylinder, and a volume of the recompression chamber decreases as the piston retracts, and the cylinder has an outlet fluidically connected to the recompression chamber.

[0114] With this configuration, if fuel gas in the compression chamber leaks past the piston into the space where the rod is located, the leaked fuel gas is recompressed in the recompression chamber as the piston moves back. This recompressed leaked gas is then discharged to the outside through the cylinder outlet, thereby preventing the leaked fuel gas from accumulating inside the cylinder.

[0115] 1 Internal combustion engine system 2 Fuel storage source 11 to 14 Fuel tank 28 Cooler 45 Fuel injection device 47 Intake passage 60 Compressor 66 Cam case 66b Cam chamber 70 Camshaft 72 Reciprocating structure 80 Cylinder 80a Intake port 80b Discharge port 80c First inner circumferential surface 80d Second inner circumferential surface 80e Third inner circumferential surface 80f First opposing surface 80h Outlet port 80i Discharge port 81 Piston 82 Rod 82a First rod portion 82c First outer circumferential surface 82b Second rod portion 82d Second outer circumferential surface 84 Cam 89 First rod seal 91 Compression chamber 92 Recompression chamber 93 Re-leak chamber 95 Outer ring (ring) 97 to 99 Check valve E Internal combustion engine R Radial direction X Axial direction

Claims

1. An internal combustion engine system comprising: a fuel gas flow path connecting a fuel storage source that stores fuel gas in a compressed state to an internal combustion engine; and a compressor that pressurizes the fuel gas in the fuel gas flow path, wherein the compressor has at least one reciprocating structure including a cylinder having an intake port and a discharge port, a piston housed in the cylinder and defining a compression chamber facing the intake port and the discharge port, a rod protruding from the piston, and a cam that reciprocates the rod.

2. The internal combustion engine system of claim 1, wherein the reciprocating structure further includes: a first rod seal interposed between an outer peripheral surface of the rod and an inner peripheral surface of the cylinder; and a recompression chamber disposed between the piston and the first rod seal in the axial direction of the cylinder, the recompression chamber being defined by the outer peripheral surface of the rod and the inner peripheral surface of the cylinder, the volume of which decreases as the piston retracts, and the cylinder having an outlet fluidically connected to the recompression chamber.

3. The internal combustion engine system according to claim 2, wherein the reciprocating structure further includes a check valve that allows a flow from the recompression chamber toward the outside of the recompression chamber through the outlet and inhibits a flow from the outside of the recompression chamber toward the recompression chamber through the outlet, and the outlet is fluidly connected to a flow path that is fluidly connected to the internal combustion engine through the check valve.

4. An internal combustion engine system as described in claim 2 or 3, wherein the inner circumferential surface of the cylinder has a first inner circumferential surface that defines a space in which the piston is accommodated and a second inner circumferential surface that defines a space in which the rod is accommodated, an inner diameter of the second inner circumferential surface is smaller than an inner diameter of the first inner circumferential surface, the cylinder further has an opposing surface that extends radially to connect the first inner circumferential surface to the second inner circumferential surface and faces the piston in the axial direction, and the recompression chamber is defined between the piston and the opposing surface of the cylinder.

5. An internal combustion engine system according to any one of claims 2 to 4, wherein the compressor further comprises a cam case defining a cam chamber in which the cam is housed, and the reciprocating structure further comprises: a second rod seal interposed between the outer peripheral surface of the rod and the inner peripheral surface of the cylinder between the first rod seal and the cam chamber in the axial direction of the cylinder; and a re-leak chamber arranged between the first rod seal and the second rod seal in the axial direction of the cylinder, wherein the re-leak chamber is defined by the outer peripheral surface of the rod and the inner peripheral surface of the cylinder, and a volume of the re-leak chamber is reduced by the retraction of the rod, and the cylinder has an exhaust port fluidically connected to the re-leak chamber.

6. An internal combustion engine system as set forth in claim 5, wherein the outlet communicating with the recompression chamber is fluidly connected to a flow passage that supplies fuel gas to a fuel injection device of the internal combustion engine, and the exhaust port of the re-leak chamber is fluidly connected to an intake passage that is fluidly connected to the internal combustion engine.

7. An internal combustion engine system according to any one of claims 1 to 6, wherein the compressor further has a cam chamber in which the cam is housed, and the internal pressure of the cam chamber is set lower than the internal pressure of the compression chamber during the stroke in which the piston moves from top dead center to bottom dead center.

8. An internal combustion engine system as claimed in any one of claims 1 to 7, wherein the compressor further comprises a camshaft that rotates the cam, the reciprocating structure further includes a ring that covers an outer peripheral surface of the cam and is rotatable relative to the cam, the outer peripheral surface of the cam has a perfect circular shape, the camshaft is eccentrically connected to the cam, and the cam presses the rod via the ring.

9. An internal combustion engine system as claimed in any one of claims 1 to 8, wherein the reciprocating structure further includes: a check valve that allows flow from the charge passage through the suction port toward the compression chamber and blocks flow from the compression chamber toward the charge passage through the suction port; and a check valve that allows flow from the compression chamber toward the charge passage through the discharge port and blocks flow from the charge passage toward the compression chamber through the discharge port.

10. The internal combustion engine system according to any one of claims 1 to 9, wherein the at least one reciprocating structure includes a plurality of reciprocating structures, and the cams of the plurality of reciprocating structures have phases that are shifted at equal intervals from each other.

11. The internal combustion engine system according to any one of claims 1 to 10, further comprising a cooler for cooling the fuel gas discharged from the discharge port of the compressor.

12. A compressor comprising: a cylinder having an inlet and a discharge port; a piston housed in the cylinder and defining a compression chamber facing the inlet and the discharge port; a rod protruding from the piston; a cam which reciprocates the rod; a camshaft which rotates the cam; and a ring which covers the outer peripheral surface of the cam and is rotatable relative to the cam, wherein the outer peripheral surface of the cam has a perfect circular shape, the camshaft is eccentrically connected to the cam, and the cam presses the rod via the ring.

13. A compressor comprising: a cylinder having an inlet and a discharge port; a piston housed in the cylinder and defining a compression chamber facing the inlet and the discharge port; a rod protruding from the piston; a first rod seal interposed between an outer circumferential surface of the rod and an inner circumferential surface of the cylinder; and a recompression chamber disposed between the piston and the first rod seal in the axial direction of the cylinder, wherein the recompression chamber is defined by the outer circumferential surface of the rod and the inner circumferential surface of the cylinder, and a volume of the recompression chamber is reduced by the retraction of the piston, and the cylinder has an outlet fluidically connected to the recompression chamber.

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