hydrogen engine

Abstract

This hydrogen engine comprises: a cylinder; a piston reciprocatably provided inside the cylinder; an intake port provided on the cylinder to take air into a combustion room; an exhaust port provided on the cylinder to exhaust air from the combustion room; a hydrogen supply unit provided in the cylinder to supply hydrogen fuel into the cylinder; a crank case consecutively provided in the cylinder; an outlet port provided on the crank case to exhaust air from a crank room; a supercharger provided upstream of the intake port to supercharge intake air; and a switching unit switching supply of intake air supercharged by the supercharger between the crank room and at least the combustion room. When the hydrogen engine is a two-stroke hydrogen engine, a piston ring functions as the switching unit. When the hydrogen engine is a four-stroke hydrogen engine, an intake valve functions as the switching unit.

Description

[Technical Field]

[0001] The present invention relates to a hydrogen engine, and more particularly to a hydrogen engine used in transportation equipment and the like. [Background technology]

[0002] In a hydrogen engine, when hydrogen fuel is burned in the combustion chamber, water vapor (water) and unburned hydrogen fuel remain in the combustion chamber. The amount of water produced is greater than that produced by combustion in a gasoline engine. Some of the water vapor and unburned hydrogen fuel in the combustion chamber travel as blow-by gas between the cylinder and piston and into the crankcase. However, it is desirable to exhaust the blow-by gas from the crankcase to prevent emulsification of engine oil in the crankcase and embrittlement of components.

[0003] As an example of a conventional technique for discharging blow-by gas from a crankcase, a four-stroke engine is disclosed in Patent Document 1. This engine is capable of running on fuel containing hydrogen gas, and includes a crankcase with a ventilation port formed therein, a ventilation passage that connects the outside of the crankcase with the ventilation port, and a ventilation fan provided in the ventilation passage to forcibly discharge gas containing hydrogen gas from the inside of the crankcase to the outside. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-127704 Summary of the Invention [Problem to be solved by the invention]

[0005] The engine disclosed in Patent Document 1 requires an external ventilation fan to forcibly exhaust gas containing hydrogen gas from the inside of the crankcase to the outside, resulting in a complex structure.

[0006] SUMMARY OF THE INVENTION Therefore, a primary object of the present invention is to provide a hydrogen engine that can discharge blow-by gas from the crankcase with a simple structure. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a hydrogen engine comprising: a cylinder; a piston reciprocally disposed within the cylinder; an intake port disposed in the cylinder for drawing air into a combustion chamber defined by the cylinder and the piston; an exhaust port disposed in the cylinder for exhausting air from the combustion chamber; a hydrogen supply unit disposed in the cylinder for supplying hydrogen fuel into the cylinder; a crankcase connected to the cylinder; an exhaust port disposed in the crankcase for exhausting air from a crank chamber within the crankcase; a supercharger disposed upstream of the intake port for supercharging intake air into the combustion chamber or the crank chamber; and a switching unit for switching whether the intake air supercharged by the supercharger is supplied to the crank chamber or at least to the combustion chamber.

[0008] In this invention, intake air supercharged by a supercharger is supplied to either the combustion chamber or the crankcase by a switching unit. In the combustion chamber, a gas mixture containing oxygen contained in the supercharged intake air and hydrogen fuel supplied by the hydrogen supply unit is formed and used to drive the hydrogen engine. Meanwhile, by supplying the supercharged intake air to the crankcase, blow-by gas (including water vapor and unburned hydrogen fuel) in the crankcase is actively discharged from the exhaust port. In this way, by supplying the supercharged intake air not only to the combustion chamber but also to the crankcase, blow-by gas can be discharged from the crankcase with a simple configuration without using a ventilation fan or the like, and emulsification of engine oil in the crankcase and embrittlement of components can be suppressed.

[0009] Preferably, the hydrogen engine is a hydrogen two-stroke engine, the piston including a piston ring that can slide along the inner circumferential surface of the cylinder, the intake port being provided on the side surface of the cylinder within the range of motion of the piston ring, and the piston ring functioning as a switching unit that switches between supplying intake air supercharged by the supercharger to the crankcase via the intake port and supplying intake air supercharged by the supercharger to the combustion chamber via the intake port. In this case, in the hydrogen two-stroke engine, the piston ring functioning as a switching unit simply slides along the inner circumferential surface of the cylinder to switch between supplying intake air supercharged by the supercharger to the combustion chamber via the intake port and supplying intake air supercharged by the supercharger to the crankcase via the intake port. That is, when the piston ring is positioned below the intake port provided on the side surface of the cylinder, the intake air supercharged by the supercharger is supplied to the combustion chamber, whereas when the piston ring is positioned above the intake port provided on the side surface of the cylinder, the intake air supercharged by the supercharger is supplied to the crankcase.

[0010] Preferably, the exhaust port is located above the top dead center of the piston, and the hydrogen engine further includes an exhaust valve provided in the cylinder for opening and closing the exhaust port. In this case, regardless of the position of the piston, the exhaust port can be opened and closed by the exhaust valve, thereby allowing exhaust from the combustion chamber through the exhaust port at the desired timing.

[0011] More preferably, the hydrogen engine is a hydrogen four-stroke engine and further includes an intake passage connecting the intake port and the turbocharger, a bypass passage connecting the intake passage and the crankcase, and a switching valve that functions as a switching unit and switches between supplying supercharged intake air from the supercharger to the crankcase via the bypass passage or supplying it to the combustion chamber via at least the intake port.In this case, in the hydrogen four-stroke engine, the switching valve that functions as a switching unit easily switches between supplying the intake air supercharged by the supercharger to the combustion chamber via at least the intake port (supplying it to at least the combustion chamber out of the combustion chamber and the crankcase) or supplying it to the crankcase via the bypass passage.

[0012] Preferably, the switching valve includes an intake valve provided in the cylinder for opening and closing the intake port. In this case, by using the intake valve normally provided in a hydrogen four-stroke engine as the switching valve, a switching valve can be provided without a separate switching valve. Typically, while the piston is descending from top dead center to bottom dead center, the intake port is opened by the intake valve, and intake air supercharged by the supercharger is supplied to the combustion chamber through the intake port and also to the crankcase through the bypass passage. On the other hand, during other times, the intake port is closed by the intake valve, and intake air supercharged by the supercharger is supplied to the crankcase through the bypass passage without being supplied to the combustion chamber.

[0013] Preferably, the hydrogen engine further includes a spark plug provided in the cylinder above top dead center for igniting the combustion chamber, so that the gas mixture in the combustion chamber can be ignited at a desired timing regardless of the position of the piston.

[0014] More preferably, the spark plug is located at the top of the combustion chamber, which ensures that the gas mixture in the combustion chamber is ignited at the desired timing.

[0015] Preferably, the hydrogen supply unit includes a hydrogen injector provided above the top dead center of the piston for directly injecting hydrogen fuel into the combustion chamber, in which case hydrogen fuel can be directly injected into the combustion chamber at a desired timing regardless of the position of the piston.

[0016] The hydrogen engine according to the present invention does not contain carbon dioxide in its exhaust, and therefore can contribute to carbon neutrality of transportation equipment, and is suitable for use in transportation equipment.

[0017] The hydrogen engine of this invention does not contain carbon dioxide in its exhaust and can improve power and torque even with small exhaust, so it can contribute to carbon neutrality in small mobility vehicles and improve power and torque, and is suitable for use in small mobility vehicles. [Effects of the Invention]

[0018] According to this invention, a hydrogen engine can be obtained that has a simple structure and can exhaust from the crankcase. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram showing a hydrogen engine according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating the operation of the hydrogen engine of FIG. 1. [Figure 3] FIG. 2 is a schematic diagram showing a small mobility vehicle equipped with the hydrogen engine shown in FIG. 1. [Figure 4] FIG. 10 is a schematic diagram showing a hydrogen engine according to another embodiment of the present invention. [Figure 5] FIG. 5 is a diagram illustrating the operation of the hydrogen engine of FIG. 4. [Figure 6] FIG. 6 is an illustrative view showing a continuation of the operation of FIG. 5; DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] Referring to FIG. 1, a hydrogen engine 10 according to one embodiment of the present invention is a uniflow hydrogen two-stroke engine and includes a cylinder 12. A crankcase 14 is connected to the cylinder 12. A piston 16 is provided reciprocally within the cylinder 12. A crankshaft 18 is housed within the crankcase 14. The piston 16 and the crankshaft 18 are connected by a connecting rod 20. The piston 16 includes a piston ring 22 that is slidable along the inner circumferential surface of the cylinder 12. The piston ring 22 is provided near the upper end of the piston 16. Here, the upper end of the piston 16 refers to the end of the piston 16 on the combustion chamber 24 side. The piston ring 22 functions as a switching unit, switching whether intake air supercharged by a supercharger 30 (described below) is supplied to a crank chamber 50 (described below) via an intake port 26 (described below) or to the combustion chamber 24 via the intake port 26.

[0022] An intake port 26 is provided on the side of the cylinder 12 to introduce air into a combustion chamber 24 defined by the cylinder 12 and the piston 16. An exhaust port 28 is provided in the cylinder 12 above the intake port 26 to exhaust air from the combustion chamber 24.

[0023] The intake port 26 is located above the bottom dead center of the piston 16 and below the top dead center (see FIGS. 2(b) and 2(d)). That is, the intake port 26 is located between the top dead center and bottom dead center of the piston 16, in other words, within the range of motion of the upper end of the piston 16. The intake port 26 is also located within the range of motion of the piston ring 22. Therefore, the intake port 26 is located above the upper end of the piston 16 when the piston 16 is at the bottom dead center, and below the upper end of the piston 16 when the piston 16 is at the top dead center. The exhaust port 28 is located above the top dead center of the piston 16.

[0024] A supercharger 30 is provided upstream of the intake port 26 to supercharge the intake air from the intake port 26 to the combustion chamber 24 or the crankcase 50, and the intake port 26 and the supercharger 30 are connected via an intake pipe 32 that serves as an intake path. Either a turbocharger or a supercharger may be used as the supercharger 30. A throttle valve 34 for adjusting the amount of intake air supplied is disposed in the intake pipe 32. In this embodiment, the intake air is constantly supercharged by the supercharger 30.

[0025] An exhaust pipe 36 is attached to the exhaust port 28 to exhaust gas from the combustion chamber 24. A front catalyst 38 is provided in the exhaust pipe 36 to purify the exhaust gas. An exhaust valve 40 is provided in the cylinder 12 to open and close the exhaust port 28. In this embodiment, the exhaust valve 40 is a poppet valve.

[0026] To ignite the combustion chamber 24, a spark plug 42 is provided in the cylinder 12 above the top dead center of the piston 16. The spark plug 42 is located at the top of the combustion chamber 24.

[0027] A hydrogen injector 44 is provided in the cylinder 12 to directly inject hydrogen fuel into the combustion chamber 24. The hydrogen injector 44 functions as a hydrogen supply unit for supplying hydrogen fuel into the cylinder 12. The hydrogen injector 44 is located above the top dead center of the piston 16. A hydrogen tank 48 is connected to the hydrogen injector 44 via a regulator 46. The hydrogen injector 44 directly injects hydrogen fuel, which is supplied from the hydrogen tank 48 and has its injection pressure adjusted by the regulator 46, into the combustion chamber 24.

[0028] In order to exhaust gas from a crank chamber 50 inside the crankcase 14, an exhaust port 52 is provided in the crankcase 14, and an exhaust pipe 54 is attached to the exhaust port 52. From the exhaust pipe 54, for example, blow-by gas present in the crank chamber 50 is exhausted to the outside.

[0029] Such a hydrogen engine 10 operates, for example, as follows.

[0030] First, as shown in Figure 2(a), the piston 16 descends, and when the piston 16 reaches bottom dead center as shown in Figure 2(b), the exhaust valve 40 opens the exhaust port 28. Then, as shown by the arrows in Figure 2(b), the turbocharger 30 supercharges intake air from the intake port 26 into the combustion chamber 24, and scavenges the combustion chamber 24. In other words, exhaust gas containing water vapor is discharged from the combustion chamber 24 by uniflow. This replaces the gas in the combustion chamber 24, and intake air (air) containing oxygen is introduced into the combustion chamber 24.

[0031] Thereafter, as the piston 16 rises, the exhaust port 28 is closed by the exhaust valve 40. As shown in FIG. 2(c), when the piston ring 22 moves above the intake port 26 and is unable to take air into the combustion chamber 24, the exhaust port 28 is completely closed by the exhaust valve 40, forming a closed combustion chamber 24. At this time, the supply destination of the supercharged intake air is switched by the piston ring 22, and the intake air supercharged by the supercharger 30 is supplied to the crank chamber 50. Then, the blow-by gas in the crank chamber 50 is discharged to the outside from the exhaust port 52 through the exhaust pipe 54.

[0032] In this state, as the piston 16 continues to rise toward top dead center, the combustion chamber 24 is compressed. When hydrogen fuel is directly injected into the combustion chamber 24 by the hydrogen injector 44 at a predetermined timing, a gas mixture of compressed hydrogen and oxygen is formed in the combustion chamber 24. Furthermore, as shown in Figure 2(d), the combustion chamber 24 is ignited by the spark plug 42 near the point when the piston 16 reaches top dead center, and combustion (explosion) occurs in the combustion chamber 24.

[0033] This pushes the piston 16 downward (towards bottom dead center), and the hydrogen engine 10 returns to the state shown in Figure 2(a). Here, the supply of intake air to the crankcase 50 continues until the piston ring 22 descends and passes the intake port 26, after which the supply of intake air switches to the combustion chamber 24.

[0034] The above-mentioned operation is then repeated. In this way, in the hydrogen engine 10, intake, compression, combustion, and exhaust are completed during one reciprocating motion of the piston 16. The hydrogen engine 10 is suitable for use in a small mobility vehicle 1 as shown in FIG. 3.

[0035] In this hydrogen engine 10, intake air supercharged by the supercharger 30 is supplied to either the combustion chamber 24 or the crankcase 50 by a switching unit. In the combustion chamber 24, a gas mixture containing oxygen contained in the supercharged intake air and hydrogen fuel supplied by the hydrogen injector 44 is formed and used to drive the hydrogen engine 10. Meanwhile, by supplying the supercharged intake air to the crankcase 50, blow-by gas (including water vapor and unburned hydrogen fuel) within the crankcase 50 is actively discharged from the exhaust port 52. In this way, by supplying the intake air supercharged by the supercharger 30 not only to the combustion chamber 24 but also to the crankcase 50, blow-by gas can be discharged from the crankcase 50 with a simple configuration without using a ventilation fan or the like, and emulsification of engine oil within the crankcase 50 and embrittlement of components can be suppressed.

[0036] The spark plug 42 is located above top dead center in the cylinder 12, so that the mixture in the combustion chamber 24 can be ignited at the desired timing regardless of the position of the piston 16.

[0037] The spark plug 42 is located at the top of the combustion chamber 24, so that the gas mixture in the combustion chamber 24 can be reliably ignited at the desired timing.

[0038] The hydrogen injector 44 is provided above the top dead center of the piston 16, so that hydrogen fuel can be directly injected into the combustion chamber 24 at a desired timing regardless of the position of the piston 16.

[0039] The hydrogen engine 10 does not contain carbon dioxide in its exhaust and can improve power and torque even with small exhaust, so it can contribute to making the compact mobility 1 carbon neutral and improving power and torque, and is therefore suitable for use in the compact mobility 1.

[0040] The above-mentioned effects can also be achieved in the hydrogen engine 100 described later.

[0041] Furthermore, with the hydrogen engine 10, the piston ring 22, which functions as a switching unit, simply slides against the inner circumferential surface of the cylinder 12 to easily switch between supplying the intake air supercharged by the supercharger 30 to the combustion chamber 24 via the intake port 26 and supplying it to the crank chamber 50 via the intake port 26. That is, when the piston ring 22 is positioned below the intake port 26 provided on the side surface of the cylinder 12, the intake air supercharged by the supercharger 30 is supplied to the combustion chamber 24, while when the piston ring 22 is positioned above the intake port 26 provided on the side surface of the cylinder 12, the intake air supercharged by the supercharger 30 is supplied to the crank chamber 50.

[0042] Since the exhaust port 28 is located above the top dead center of the piston 16, air can be exhausted from the combustion chamber 24 through the exhaust port 28 at the desired timing by opening and closing the exhaust port 28 with the exhaust valve 40, regardless of the position of the piston 16.

[0043] Next, a hydrogen engine 100 according to another embodiment of the present invention will be described.

[0044] Referring to FIG. 4, the hydrogen engine 100 is a hydrogen four-stroke engine and includes a cylinder 102. A crankcase 104 is connected to the cylinder 102. A piston 106 is provided in the cylinder 102 so that it can reciprocate. A crankshaft 108 is housed in the crankcase 104. The piston 106 and the crankshaft 108 are connected by a connecting rod 110. The piston 106 includes a piston ring 112 that is slidable against the inner circumferential surface of the cylinder 102. The piston ring 112 is provided near the upper end of the piston 106. Here, the upper end of the piston 106 refers to the end of the piston 106 on the combustion chamber 114 side.

[0045] An intake port 116 is provided at the top of the cylinder 102 for admitting air into a combustion chamber 114 defined by the cylinder 102 and the piston 106. An exhaust port 118 is provided at the top of the cylinder 102 for exhausting air from the combustion chamber 114.

[0046] A supercharger 120 is provided upstream of the intake port 116 to supercharge the intake air from the intake port 116 to the combustion chamber 114 or the crankcase 142, and the intake port 116 and the supercharger 120 are connected via an intake pipe 122, which serves as an intake path. Either a turbocharger or a supercharger may be used as the supercharger 120. A throttle valve 124 is provided in the intake pipe 122 to adjust the amount of intake air supplied. In this embodiment, the intake air is constantly supercharged by the supercharger 120. An intake valve 126 is provided in the cylinder 102 to open and close the intake port 116. In this embodiment, the intake valve 126 is a poppet valve. The intake valve 126 functions as a switching unit (switching valve) by switching between supplying the supercharged intake air from the supercharger 120 to a crank chamber 142 (described later) via a bypass passage 144 (described later) or supplying the supercharged intake air to the crank chamber 142 via the bypass passage 144 and also supplying the supercharged intake air to the combustion chamber 114 via the intake port 116.

[0047] An exhaust pipe 128 is attached to the exhaust port 118 to exhaust gas from the combustion chamber 114. A front catalyst 130 is provided in the exhaust pipe 128 to purify the exhaust gas. An exhaust valve 132 is provided in the cylinder 102 to open and close the exhaust port 118. In this embodiment, the exhaust valve 132 is a poppet valve.

[0048] To ignite the combustion chamber 114, a spark plug 134 is provided in the cylinder 102 above the top dead center of the piston 106. The spark plug 134 is located at the top of the combustion chamber 114.

[0049] A hydrogen injector 136 is provided in the cylinder 102 to directly inject hydrogen fuel into the combustion chamber 114. The hydrogen injector 136 functions as a hydrogen supply unit for supplying hydrogen fuel into the cylinder 102. The hydrogen injector 136 is located above the top dead center of the piston 106. A hydrogen tank 140 is connected to the hydrogen injector 136 via a regulator 138. The hydrogen injector 136 directly injects hydrogen fuel, which is supplied from the hydrogen tank 140 and has its injection pressure adjusted by the regulator 138, into the combustion chamber 114.

[0050] The intake pipe 122 and a crank chamber 142 in the crankcase 104 are connected by a bypass passage 144. In order to exhaust gas from the crank chamber 142 in the crankcase 104, an exhaust port 146 is provided in the crankcase 104, and an exhaust pipe 148 is attached to the exhaust port 146. From the exhaust pipe 148, for example, blow-by gas present in the crank chamber 142 is exhausted to the outside.

[0051] Such a hydrogen engine 100 operates, for example, as follows.

[0052] First, as shown in Figure 5(a), when the piston 106 moves from top dead center to bottom dead center, the intake valve 126 opens the intake port 116, and the turbocharger 120 draws air into the combustion chamber 114 through the intake port 116, as shown by the arrow. As shown in Figure 5(b), when the piston 106 reaches bottom dead center, the intake valve 126 completely closes the intake port 116, forming a closed combustion chamber 114, which is filled with intake air (air) containing oxygen. By closing the intake valve 126 in this way, the intake air supercharged by the turbocharger 120 is not supplied to the combustion chamber 114, but is supplied only to the crank chamber 142 via the bypass path 144.

[0053] In this state, as the piston 106 rises toward top dead center, the combustion chamber 114 is compressed, as shown in Figure 5(c). When hydrogen fuel is directly injected into the combustion chamber 114 by the hydrogen injector 136 at a predetermined timing, a gas mixture of compressed hydrogen and oxygen is formed in the combustion chamber 114. Furthermore, as shown in Figure 5(d), the combustion chamber 114 is ignited by the spark plug 134 around the time the piston 106 reaches top dead center, and combustion (explosion) occurs in the combustion chamber 114.

[0054] Then, the piston 106 is pushed downward (towards the bottom dead center), passes through the state shown in FIG. 6(a), and reaches the bottom dead center as shown in FIG. 6(b).

[0055] Then, as shown in FIG. 6(c), as the piston 106 moves from bottom dead center to top dead center, the exhaust port 118 is opened by the exhaust valve 132, and exhaust gas containing water vapor is discharged from the combustion chamber 114 as shown by the arrow.

[0056] As shown in FIG. 6(d), when the piston 106 reaches the top dead center, the exhaust port 118 is completely closed by the exhaust valve 132, and then the state returns to that of FIG. 5(a).

[0057] In this embodiment, intake air supercharged by the supercharger 120 is always supplied to the crank chamber 142 via a bypass passage 144. Then, the blow-by gas in the crank chamber 142 is always discharged to the outside from an exhaust port 146 through an exhaust pipe 148.

[0058] The above-mentioned operation is then repeated. In this way, in the hydrogen engine 100, intake, compression, combustion, and exhaust are completed during two reciprocating motions of the piston 106. The hydrogen engine 100 is also suitable for use in a small mobility vehicle 1 such as that shown in FIG. 3.

[0059] According to this hydrogen engine 100, the intake valve 126 that is normally provided in hydrogen four-stroke engines is used as a switching valve, thereby eliminating the need for a separate switching valve. Typically, while the piston 106 is descending from top dead center to bottom dead center, the intake valve 126 opens the intake port 116, and intake air supercharged by the turbocharger 120 is supplied to the combustion chamber 114 via the intake port 116 and also supplied to the crankcase 142 via the bypass passage 144. On the other hand, during other times, the intake valve 126 closes the intake port 116, and intake air supercharged by the turbocharger 120 is supplied to the crankcase 142 via the bypass passage 144 without being supplied to the combustion chamber 114.

[0060] In the hydrogen engine 100, a switching valve functioning as a switching unit may be provided at the branch point between the intake pipe 122 and the bypass passage 144. By using this switching valve, it is possible to easily switch between supplying the supercharged intake air from the supercharger 120 to the crank chamber 142 via the bypass passage 144 or to the combustion chamber 114 via the intake port 116.

[0061] The hydrogen engines 10 and 100 according to the present invention can be used in any transportation equipment, not just the compact mobility 1. Because the hydrogen engines 10 and 100 do not contain carbon dioxide in their exhaust, they can contribute to carbon neutrality of transportation equipment and are therefore suitable for use in transportation equipment.

[0062] While the preferred embodiment of the present invention has been described above, it will be apparent that various modifications can be made without departing from the scope and spirit of the present invention, which is limited only by the appended claims. [Explanation of symbols]

[0063] 1. Small mobility 10,100 Hydrogen engine 12,102 cylinders 14,104 Crankcase 16,106 pistons 18,108 crankshaft 20,110 Connecting Rod 22,112 Piston rings 24,114 combustion chambers 26,116 Intake port 28,118 Exhaust port 30,120 Turbocharger 32,122 Intake pipe 36,128 exhaust pipe 40,132 Exhaust valve 42,134 spark plugs 44,136 Hydrogen injector 50,142 crankcase 52,146 outlet 54,148 Discharge pipe 126 Intake valve 144 Bypass Road

Claims

1. A cylinder; a piston reciprocally disposed within the cylinder; an intake port provided in the cylinder for inletting air into a combustion chamber defined by the cylinder and the piston; an exhaust port in the cylinder for exhausting air from the combustion chamber; a hydrogen supply unit provided in the cylinder for supplying hydrogen fuel into the cylinder; a crankcase connected to the cylinder; an exhaust port provided in the crankcase for exhausting air from a crank chamber within the crankcase; a supercharger provided upstream of the intake port to supercharge intake air into the combustion chamber or the crank chamber; a switching unit that switches whether the intake air supercharged by the supercharger is supplied to the crank chamber or at least to the combustion chamber.

2. The hydrogen engine is a hydrogen two-stroke engine, the piston includes a piston ring that is slidable against an inner circumferential surface of the cylinder, the intake port is provided on a side surface of the cylinder within a range of motion of the piston ring, 2. The hydrogen engine according to claim 1, wherein the piston ring functions as the switching unit by switching whether the intake air supercharged by the supercharger is supplied to the crank chamber via the intake port or to the combustion chamber via the intake port.

3. The exhaust port is located above the top dead center of the piston, 3. The hydrogen engine according to claim 1, further comprising an exhaust valve provided in the cylinder for opening and closing the exhaust port.

4. The hydrogen engine is a hydrogen four-stroke engine, an intake passage communicating the intake port with the turbocharger; a bypass passage that connects the intake passage and the crank chamber; 2. The hydrogen engine according to claim 1, further comprising a switching valve that functions as the switching unit and switches between supplying the supercharged intake air from the supercharger to the crankcase via the bypass passage or supplying the supercharged intake air to the combustion chamber via at least the intake port.

5. 5. The hydrogen engine according to claim 4, wherein the switching valve includes an intake valve provided in the cylinder for opening and closing the intake port.

6. 6. A hydrogen engine according to claim 1, further comprising a spark plug provided in said cylinder above the top dead center of said piston for igniting said combustion chamber.

7. 7. The hydrogen engine of claim 6, wherein the spark plug is located at the top of the combustion chamber.

8. 6. The hydrogen engine according to claim 1, wherein the hydrogen supply unit includes a hydrogen injector provided above the top dead center of the piston for directly injecting the hydrogen fuel into the combustion chamber.

9. 6. The hydrogen engine according to claim 1, 2, 4 or 5, which is used in transportation equipment.

10. The hydrogen engine of claim 9 , wherein the transportation device comprises a small mobility vehicle.

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