hydrogen engine

Abstract

To reduce the possibility that an injector for injecting hydrogen gas is damaged by the influence of heat in a combustion chamber.SOLUTION: A hydrogen engine 1 which supplies hydrogen gas as fuel into a combustion chamber 7 includes an injector 51 for injecting the hydrogen gas, a pressure accumulation chamber 61 which is communicated with an injection hole 52 of the injector, a communication hole 62 which communicates the pressure accumulation chamber with the combustion chamber, and a pressure accumulation chamber defining part 63 which is provided between the injector and the combustion chamber so as to define the pressure accumulation chamber and the communication hole. The pressure accumulation chamber defining part is formed separately from the injector and has thermal conductivity equal to or higher than that of a combustion chamber wall defining the combustion chamber.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to hydrogen engines. [Background technology]

[0002] Conventionally, engines that directly inject gaseous fuel into the combustion chamber have been known (Patent Documents 1 and 2). In particular, Patent Document 1 discloses an engine that uses hydrogen gas as the gaseous fuel. Furthermore, in the rotary engine described in Patent Document 1, the hydrogen injector is positioned so that it faces the working chamber that is on the retard side of 100° of top dead center of compression. As a result, even if pre-ignition occurs in the working chamber, the hydrogen injector is positioned at the end of the flame and pressure wave, which is said to reduce damage to the hydrogen injector. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-162633 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-221037 Summary of the Invention [Problem to be solved by the invention]

[0004] However, hydrogen has a high combustion speed, low minimum ignition energy, and a wide flammable range depending on the mixture ratio with air, so the flame easily reaches the vicinity of the wall of the combustion chamber. Therefore, if the hydrogen injector is positioned facing the working chamber, even if it is located in a place where the flame and pressure waves cannot reach, the possibility of the hydrogen injector being damaged by the heat inside the combustion chamber cannot be sufficiently reduced.

[0005] In view of the above-mentioned problems, an object of the present disclosure is to reduce the possibility that an injector that injects hydrogen gas will be damaged by the influence of heat in the combustion chamber. [Means for solving the problem]

[0006] The gist of the present disclosure is as follows.

[0007] (1) A hydrogen engine that supplies hydrogen gas as fuel into a combustion chamber, an injector that injects hydrogen gas; a pressure accumulator chamber communicating with the nozzle hole of the injector; a communication hole communicating with the accumulator chamber and the combustion chamber; an accumulator chamber defining portion provided between the injector and the combustion chamber to define the accumulator chamber and the communication hole, A hydrogen engine, wherein the accumulator defining portion is formed separately from the injector and has thermal conductivity equal to or higher than that of a combustion chamber wall defining the combustion chamber. (2) One or more communication holes are provided, The hydrogen engine according to (1) above, wherein at least one of the communication holes is formed to have an axis that is angled with respect to the axis of the nozzle hole of the injector. (3) further comprising a piston reciprocating within a cylinder defining the combustion chamber; The hydrogen engine according to (2) above, wherein at least one of the communication holes is formed to have an axis that extends at an angle toward the piston in the injection direction relative to the axis of the nozzle hole of the injector. (4) further comprising a spark plug that is disposed so as to be exposed to the combustion chamber and that ignites the mixture of hydrogen gas and air; The hydrogen engine according to (2) or (3) above, wherein at least one of the communication holes is formed to have an axis that extends at an angle away from the ignition portion of the spark plug with respect to the axis of the nozzle hole of the injector. (5) Two or more of the communication holes are provided, A hydrogen engine as described in (4) above, wherein at least two of the communication holes are formed so as to have axes extending in directions that extend to both sides of the ignition portion of the spark plug when viewed in the axial direction of the combustion chamber. (6) The hydrogen engine according to any one of (1) to (5) above, wherein the accumulator chamber defining portion is configured as a part of a cylinder head defining the combustion chamber. (7) The hydrogen engine according to any one of (1) to (5) above, wherein the accumulator chamber defining portion is configured as a member separate from a cylinder head defining the combustion chamber. (8) A hydrogen engine according to any one of (1) to (7) above, wherein the communication holes are formed so that the total flow cross-sectional area thereof is smaller than the flow cross-sectional area of ​​the pressure accumulator chamber, so as to act as a throttle for the pressure accumulator chamber. (9) A hydrogen engine as described in (8) above, wherein the communication holes are formed so that the total flow path cross-sectional area thereof is larger than the flow path cross-sectional area of ​​the throttling portion of the injector so that the flow velocity of the hydrogen gas at the throttling portion of the injector becomes a predetermined flow velocity when the hydrogen gas is injected from the injector. (10) The hydrogen engine according to any one of (1) to (9) above, wherein the pressure accumulator is formed to have the same axis as the axis of the nozzle hole of the injector. (11) Further comprising a check valve provided in the pressure accumulator chamber, The hydrogen engine according to any one of (1) to (10) above, wherein the check valve allows fluid to flow from the injector to the communication hole and prohibits fluid from flowing from the communication hole to the injector. (12) The engine further includes a biasing member that biases the check valve toward the nozzle hole of the injector. The hydrogen engine according to (11) above, wherein the biasing member is fixed to the injector. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to reduce the possibility that the injector that injects hydrogen gas will be damaged by the influence of heat in the combustion chamber. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a partial cross-sectional view that schematically shows an engine according to a first embodiment. [Figure 2] FIG. 2 is a partial bottom view schematically showing the bottom surface of the cylinder head. [Figure 3] FIG. 3 is an enlarged cross-sectional view taken along line III-III in FIG. 2 showing a portion of the cylinder head around the spark plug and the injector. [Figure 4] FIG. 4 is an enlarged cross-sectional view of the cylinder head portion around the injector. [Figure 5] FIG. 5 is a cross-sectional view similar to FIG. 4, showing an enlarged view of a cylinder head portion around an injector according to one modification. [Figure 6] FIG. 6 is a cross-sectional view similar to FIG. 4, showing an enlarged view of a cylinder head portion around an injector according to another modified example. [Figure 7] FIG. 7 is a cross-sectional view similar to FIG. 4, showing an enlarged view of a cylinder head portion around an injector according to a second embodiment. [Figure 8] FIG. 8 is a cross-sectional view similar to FIG. 4, showing an enlarged view of a cylinder head portion around an injector according to a third embodiment. [Figure 9] FIG. 9 is a diagram illustrating the operation of a check valve. [Figure 10] FIG. 10 is a diagram schematically showing the configuration around the pressure accumulator chamber. [Figure 11] FIG. 11 is a diagram schematically showing the configuration around the pressure accumulator chamber. [Figure 12] FIG. 12 is a diagram schematically showing the configuration around the pressure accumulator chamber. [Figure 13] FIG. 13 is a cross-sectional view similar to FIG. 4, showing an enlarged view of a portion of a cylinder head around an injector when a pressure accumulator chamber defining member is provided. [Figure 14] FIG. 14 is a diagram similar to FIG. 12, which schematically shows the configuration around the pressure accumulator chamber. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the embodiments will be described in detail with reference to the drawings. In the following description, like components are designated by like reference numerals.

[0011] First embodiment <Overall engine configuration> First, the overall configuration of a hydrogen engine (hereinafter also simply referred to as "engine") 1 according to a first embodiment will be described with reference to Figures 1 and 2. In a hydrogen engine, hydrogen gas is directly injected into a combustion chamber as fuel. Figure 1 is a partial cross-sectional view that schematically shows the engine 1 according to this embodiment. As shown in Figure 1, the engine 1 includes a cylinder block 2, a cylinder head 3, a piston 4, and a connecting rod 5.

[0012] The cylinder block 2 has a plurality of cylinders 6 arranged side by side. The cylinder head 3 is arranged to abut against the cylinder block 2 at an abutment plane A, and is arranged to close one end of the cylinders 6 formed in the cylinder block 2. The cylinder block 2 and the cylinder head 3 are made of metal such as aluminum alloy or cast iron.

[0013] Pistons 4 are arranged to reciprocate within cylinders 6 formed within the cylinder block 2. The pistons 4 are connected to connecting rods 5 via piston pins. The connecting rods 5 are connected to a crankshaft (not shown) via crank pins. The connecting rods 5 act to convert the reciprocating motion of the pistons 4 into the rotational motion of the crankshaft. The walls of the cylinders 6 of the cylinder block 2, the cylinder head 3, and the pistons 4 define combustion chambers 7 in which a mixture of air and hydrogen gas is burned. Within the combustion chamber 7, a swirling flow of the mixture is generated in the direction indicated by the arrows in FIG. 1.

[0014] Fig. 2 is a partial bottom view that schematically shows the bottom surface of the cylinder head 3. In particular, Fig. 2 schematically shows a portion of the cylinder head 3 that is positioned to cover one cylinder 6. Fig. 2 also shows an injector 51, an accumulator chamber 61, and a communication hole 62, which will be described later. These are located inside the cylinder head 3 and therefore would not normally be visible from the bottom side of the cylinder head 3, but are shown here to make the explanation easier to understand.

[0015] 1 and 2, an intake port 11 and an exhaust port 12 are formed in the cylinder head 3. The intake port 11 faces the combustion chamber 7 and communicates with the combustion chamber 7 via an intake opening 13 formed in the cylinder head 3. Similarly, the exhaust port 12 faces the combustion chamber 7 and communicates with the combustion chamber 7 via an exhaust opening 14 formed in the cylinder head 3.

[0016] As shown in Figure 2, in this embodiment, two intake openings 13 and two exhaust openings 14 are provided for each combustion chamber 7. The two intake openings 13 are arranged side by side in the same direction as the direction in which the multiple cylinders 6 are arranged side by side (hereinafter also referred to as the "cylinder alignment direction"). Similarly, the two exhaust openings 14 are arranged side by side in the same direction as the cylinder alignment direction. The two intake openings 13 are arranged on one side of a midplane C that passes through the center of each cylinder 6 and extends in the cylinder alignment direction, and the two exhaust openings 14 are arranged on the other side.

[0017] As shown in Figure 1, the cylinder head 3 is formed so that the upper surface of the combustion chamber 7 has two inclined surfaces: an intake-side inclined surface 17 and an exhaust-side inclined surface 18. The intake-side inclined surface 17 is formed so that its height from the abutment plane A (the length from the abutment plane A in the direction of the axis Z of the cylinder 6) increases from the edge on the intake opening side toward the central plane C. The exhaust-side inclined surface 18 is formed so that its height from the abutment plane A increases from the edge on the exhaust opening side toward the central plane C. Therefore, the upper surface of the combustion chamber 7 is inclined so that it is highest at the central plane C.

[0018] The cylinder head 3 is also provided with an intake valve 21 that opens and closes the intake opening 13, an exhaust valve 31 that opens and closes the exhaust opening 14, an ignition plug 41 that ignites the air-fuel mixture in the combustion chamber 7, and an injector 51 that directly injects hydrogen gas into the combustion chamber 7.

[0019] The intake valve 21 includes a valve stem 22 and a valve body 23 fixed to one end of the valve stem 22. The intake valve 21 is disposed in the cylinder head 3 so as to be slidable in the direction in which the valve stem 22 extends, i.e., in the axial direction of the intake valve 21. The intake valve 21 is lifted in its axial direction by an intake valve train (not shown).

[0020] Similarly, the exhaust valve 31 includes a valve stem 32 and a valve body 33 fixed to one end of the valve stem 32. The exhaust valve 31 is arranged in the cylinder head 3 so as to be slidable in the direction in which the valve stem 32 extends, i.e., in the axial direction of the exhaust valve 31. The exhaust valve 31 is lifted in its axial direction by an exhaust valve mechanism (not shown).

[0021] The spark plug 41 is attached to the cylinder head 3 so as to be located on the upper surface of the combustion chamber 7, approximately in the center of the combustion chamber 7 when viewed in the Z direction of the axis of the cylinder 6 (i.e., the axis of the combustion chamber 7). Therefore, the spark plug 41 is positioned so as to be exposed to the combustion chamber 7. The spark plug 41 has an electrode 42 at its end that functions as an ignition part that ignites the air-fuel mixture. Therefore, the electrode 42 of the spark plug 41 is located near the upper surface of the combustion chamber 7, approximately in the center of the combustion chamber 7 when viewed in the Z direction of the axis of the cylinder 6.

[0022] <Injector peripheral configuration> Next, the configuration of the cylinder head 3 around the injector 51 will be described with reference to Figures 3 and 4 in addition to Figures 1 and 2. Figure 3 is a cross-sectional view taken along line III-III in Figure 2, showing an enlarged view of the portion of the cylinder head 3 around the spark plug 41 and the injector 51. Figure 4 is an enlarged cross-sectional view of a portion of Figure 3, showing an enlarged view of the portion of the cylinder head 3 around the injector 51. Note that in Figure 4, only the tip of the injector 51 is depicted in cross section.

[0023] 2, the injector 51 is disposed closer to the intake openings than the central plane C. In particular, in this embodiment, the injector 51 is disposed between the two intake openings 13 and in the vicinity of the outer periphery of the cylinder 6 so as to inject hydrogen gas. Note that the injector 51 does not necessarily have to be disposed between the intake openings 13, and may be disposed in the cylinder head 3 between the exhaust openings 14 or near the center of the combustion chamber 7.

[0024] 4, the injector 51 has a nozzle hole 52 at its tip for injecting hydrogen gas. The nozzle hole 52 is formed so that its axis coincides with the axis of the injector 51 (in the drawing, the axis of the injector 51 and the axis of the nozzle hole 52 are both indicated by X). In this embodiment, the nozzle hole 52 is formed so that the flow path cross-sectional area in a cross section perpendicular to the main flow direction of the hydrogen gas is the smallest in the injector 51. Therefore, in this embodiment, the nozzle hole 52 functions as a throttle for the flow of hydrogen gas in the injector 51. Note that the nozzle hole 52 may be formed so that its axis faces in a direction different from the axis X of the injector 51. The injector 51 may also be formed so that the flow path cross-sectional area around a valve element such as a needle valve that opens and closes the nozzle hole 52 is the smallest in the injector 51. In this case, the area around the valve element such as the needle valve functions as a throttle for the flow of hydrogen gas.

[0025] 3 and 4, the injector 51 is disposed in a hole 45 formed in the cylinder head 3. The hole 45 is open to the outside of the cylinder head 3 so that the injector 51 can be inserted therein. The hole 45 is formed so that its cross-sectional shape perpendicular to its axial direction is substantially the same as or slightly larger than the cross-sectional shape of the injector 51. In addition, the hole 45 is formed so that the axial length of the portion of the hole 45 having substantially the same cross-sectional shape (circular in this embodiment) as the cylindrical portion 53, which has a circular cross-section that is thinner than the other portion of the tip end of the injector 51, is longer than the axial length of the cylindrical portion 53. The injector 51 is fixed in the hole 45 by any method, for example, by supporting its rear portion with another member fixed to the cylinder head 3.

[0026] 3 and 4, an accumulator chamber 61, a communication hole 62, and a pressure-accumulator-chamber defining portion 63 that defines the accumulator chamber 61 and the communication hole 62 are provided between the injector 51 and the combustion chamber 7. As shown in FIG. 4, the accumulator chamber 61 communicates with the injection hole 52 of the injector 51 and also communicates with the communication hole 62. The communication hole 62 also communicates with the accumulator chamber 61 and the combustion chamber 7. In particular, in this embodiment, the communication hole 62 is formed so as to open to an end face of the accumulator chamber 61 opposite to the injector 51 side. However, the communication hole 62 may be formed so as to open to an annular side surface of the accumulator chamber 61 in addition to the end face of the accumulator chamber 61 opposite to the injector 51 side.

[0027] The accumulator chamber 61 is formed to have the same axis as the axis X of the injection hole 52 of the injector 51. Therefore, the annular side wall that defines the accumulator chamber 61 is prevented from acting as a flow resistance for the hydrogen gas injected from the injector 51. In addition, in the present embodiment, the accumulator chamber 61 has a cross-sectional shape in a cross section perpendicular to the axis X that is substantially the same as the cross-sectional shape of the tip of the injector 51 where the injection hole 52 is provided (i.e., the cross-sectional shape of the tubular portion 53). Therefore, in the present embodiment, the accumulator chamber 61 has a circular cross-sectional shape. In addition, the flow cross-sectional area of ​​the accumulator chamber 61 (i.e., the cross-sectional area in the cross section perpendicular to the axis X) is substantially the same as the cross-sectional area of ​​the tip of the injector 51. Therefore, the accumulator chamber 61 has a flow cross-sectional area that is larger than the flow cross-sectional area of ​​the injection hole 52 by the thickness of the wall portion around the injection hole 52 of the injector 51. In this embodiment, the accumulator chamber 61 is formed in the hole 45 of the cylinder head 3, and is formed by the axial length of a portion of the hole 45 having substantially the same cross-sectional shape as the cylindrical portion 53 of the injector 51 being longer than the length of the cylindrical portion 53 in the direction of the axis X. The accumulator chamber 61 may have a cross-sectional shape other than a circle, such as a polygonal shape or an elliptical shape.

[0028] The accumulator chamber 61 may be formed to have an axis different from the axis X of the injection hole 52. The accumulator chamber 61 may have a cross-sectional shape different from the cross-sectional shape of the tip of the injector 51, and the flow path cross-sectional area of ​​the accumulator chamber 61 may be larger or smaller than the cross-sectional area of ​​the tip of the injector 51.

[0029] In this embodiment, two communication holes 62 are provided. In particular, in this embodiment, as can be seen from FIG. 2, the communication holes 62 are arranged side by side when viewed in the axial Z direction of the cylinder 6. Furthermore, the cross-sectional shape of the communication holes 62 in a cross section perpendicular to the main flow direction of the hydrogen gas is formed to be approximately circular. Additionally, in this embodiment, the two communication holes 62 are formed so that their cross-sectional shapes are the same, and therefore their flow path cross-sectional areas are the same. Note that the communication holes 62 may have cross-sectional shapes other than circular, such as polygonal or elliptical.

[0030] The two communication holes 62 are formed so that the total flow path cross-sectional area thereof is smaller than the flow path cross-sectional area of ​​the pressure accumulator chamber 61. As a result, the communication holes 62 act as a throttle for the flow of hydrogen gas in the pressure accumulator chamber 61.

[0031] In addition, the two communication holes 62 are formed so that their total flow path cross-sectional area is larger than the flow path cross-sectional area of ​​the throttle portion of the injector 51 so that the flow velocity of the hydrogen gas at the throttle portion (injection hole 52 in this embodiment) of the injector 51 becomes a predetermined flow velocity (sonic velocity in this embodiment) when the hydrogen gas is injected from the injector 51. Specifically, for example, the two communication holes 62 are formed so that their total flow path cross-sectional area is, for example, 1.75 times or more the flow path cross-sectional area of ​​the throttle portion of the injector 51. In this way, by making the hydrogen gas at a predetermined flow velocity (for example, sonic velocity) when injected from the injector 51, the amount of hydrogen gas supplied to the combustion chamber 7 can be adjusted based only on the time that the injector 51 is open, thereby making it easier to control the amount of hydrogen gas supplied to the combustion chamber 7.

[0032] 2 and 4, in this embodiment, each of the two communication holes 62 is formed to have an axis Y that is angled with respect to the axis X of the nozzle hole 52 of the injector 51. In particular, in this embodiment, as shown in FIG. 4, the axis Y of the two communication holes 62 extends at an incline toward the piston 4 (the direction from the cylinder head 3 toward the cylinder block 2 in the direction of the axis Z of the cylinder 6) with respect to the axis X of the nozzle hole 52 of the injector 51 in the injection direction of hydrogen gas from the nozzle hole 52. That is, as shown in FIG. 4, the axis Y of the two communication holes 62 extends at an incline with respect to the axis X of the injector 51 in a cross section including the axis Z of the cylinder 6 and the axis X of the injector 51. The inclination angle α in this case is, for example, 5 to 30°, 7 to 20°, or 10 to 15°.

[0033] Furthermore, in this embodiment, as shown in FIG. 2, the axes Y of the two communication holes 62 extend at an incline with respect to the axis X of the nozzle hole 52 of the injector 51 so as to move away from the electrode 42 of the spark plug 41. That is, as shown in FIG. 2, the axes Y of the two communication holes 62 extend at an incline with respect to the axis X of the nozzle hole 52 that passes through the spark plug 41, when viewed in the direction of the axis Z of the cylinder 6. The inclination angle β in this case is, for example, 5 to 45°, 7 to 35°, or 10 to 20°. Also, as shown in FIG. 2, the axes Y of the two communication holes 62 extend at an incline in opposite directions with respect to the axis X of the nozzle hole 52, when viewed in the direction of the axis Z of the cylinder 6. Therefore, in this embodiment, as shown in Figure 2, the axes Y of the two communication holes 62 extend in directions that widen on both sides across the electrode 42 of the spark plug 41 when viewed in the direction of the axis Z of the cylinder 6.

[0034] The accumulator defining portion 63 is located around the injector 51, the accumulator 61, and the communication hole 62. In particular, in this embodiment, the accumulator defining portion 63 is configured as a part of the cylinder head 3. Therefore, the accumulator defining portion 63 is a part of the cylinder head 3 that is located around the accumulator 61 and the communication hole 62. Therefore, the accumulator defining portion 63 is formed of the same material as the cylinder head 3 (i.e., the combustion chamber wall that defines the combustion chamber 7). Therefore, the accumulator defining portion 63 has the same thermal conductivity as the cylinder head 3. On the other hand, the cylinder head 3 is formed as a separate body from the injector 51, and therefore the accumulator defining portion 63 is formed as a separate body from the injector 51.

[0035] In the hydrogen engine 1 configured as described above, when hydrogen gas is injected from the nozzle hole 52 of the injector 51, the injected hydrogen gas passes through the pressure accumulator chamber 61 and the communication hole 62 and is injected from the communication hole 62 into the combustion chamber 7. As described above, the hydrogen gas is injected from the nozzle hole 52 at a flow velocity such that the flow velocity reaches the speed of sound at the throttling portion of the injector 51, and then flows through the pressure accumulator chamber 61 and the communication hole 62 at a speed slower than the speed of sound and is injected into the combustion chamber 7. When injected from the communication hole 62, the hydrogen gas is injected into the combustion chamber 7 mainly in the direction of the axis Y of the communication hole 62.

[0036] <Effects> As described above, hydrogen has a high burning speed, a low minimum ignition energy, and a wide flammable range at various mixture ratios with air. Therefore, the quenching distance is short, and the flame reaches the vicinity of the wall surface of the combustion chamber 7. Therefore, the temperature of components exposed to the combustion chamber 7 tends to become relatively high. Additionally, because hydrogen has a low minimum ignition energy, it is prone to abnormal combustion, such as pre-ignition. When such abnormal combustion occurs, the components exposed to the combustion chamber 7 are exposed to high temperatures.

[0037] In contrast, in this embodiment, the accumulator defining portion 63 provided between the injector 51 and the combustion chamber 7 is part of the cylinder head 3 and has the same thermal conductivity as the cylinder head 3. Therefore, it is cooled together with the cylinder head 3 by the cooling water flowing through the cylinder head 3. In addition, the accumulator 61 and the communication hole 62 are provided between the injector 51 and the combustion chamber 7. Therefore, the injector 51 is disposed at a position set back from the other wall surfaces that define the combustion chamber 7. For this reason, it is difficult for the flame in the combustion chamber 7 to reach the tip of the injector 51. Therefore, the injector 51 is steadily maintained at a high temperature, which prevents the injector 51 from being damaged, and also prevents the injector 51 from being damaged in the event of, for example, pre-ignition.

[0038] In this embodiment, the communication holes 62 are formed so that the total flow path cross-sectional area thereof is smaller than the flow path cross-sectional area of ​​the pressure accumulator chamber 61. As such, the small flow path cross-sectional area of ​​the communication holes 62 makes it difficult for the flame in the combustion chamber 7 to reach the inside of the pressure accumulator chamber 61. Therefore, this also prevents the injector 51 from being maintained at a high temperature and prevents the injector 51 from being damaged.

[0039] Furthermore, in this embodiment, the communication hole 62 has an axis Y that is angled at an arbitrary angle with respect to the axis X of the nozzle hole 52 of the injector 51. Therefore, while the injector 51 can be disposed at a position recessed from other wall surfaces that define the combustion chamber 7, it is possible to inject hydrogen gas in a desired direction specified by the axis Y, other than the direction of the axis X of the nozzle hole 52 of the injector 51. Furthermore, because the stoichiometric air-fuel ratio of a hydrogen gas mixture is low, it is necessary to supply a large amount of hydrogen gas into the combustion chamber 7. Therefore, it is preferable to make the cross-sectional area of ​​the nozzle hole 52 of the injector 51 as large as possible. However, it is difficult to orient and shape the nozzle hole 52 in an optimal injection direction. In contrast, in this embodiment, because the communication hole 62 injects hydrogen into the combustion chamber 7 in the optimal injection direction, the nozzle hole 52 of the injector 51 can be formed to extend in the direction of the axis X of the injector 51, allowing the flow path cross-sectional area of ​​the injector 51 to be large.

[0040] In this embodiment, the axis Y of the communication hole 62 extends at an inclination angle α toward the piston 4 (downward in FIGS. 1 and 4) with respect to the axis X of the nozzle hole 52 of the injector 51. This prevents the hydrogen gas injected into the combustion chamber 7 through the communication hole 62 from coming into contact at an early stage with uneven portions on the underside of the cylinder head 3 that tend to become hot, thereby preventing abnormal combustion such as pre-ignition.

[0041] Furthermore, in this embodiment, the axis Y of the communication hole 62 extends at an inclination angle β with respect to the axis X of the nozzle hole 52 of the injector 51, inclining away from the electrode 42 of the spark plug 41. This prevents the concentration of the air-fuel mixture near the electrode 42 of the spark plug 41, which becomes hot, from becoming too high, thereby preventing pre-ignition near the spark plug 41. Also, in this embodiment, the axes Y of the two communication holes 62 extend in directions widening on both sides of the electrode 42 of the spark plug 41. This prevents the concentration of the air-fuel mixture near the electrode 42 of the spark plug 41 from becoming too high, while still allowing a certain amount of air-fuel mixture to be formed around the electrode 42 of the spark plug 41, thereby enabling the spark plug 41 to ignite the mixture.

[0042] <Modification> In the above embodiment, the engine 1 is provided with two communication holes 62. However, any number of communication holes may be provided as long as it is one or more. Therefore, the engine 1 may be provided with one or more communication holes 62, and therefore the engine 1 may be provided with only one communication hole 62, or with three or more communication holes 62.

[0043] Additionally, in the above embodiment, each communication hole 62 is formed so that its axis Y extends at an angle with respect to the axis X of the injection hole 52 of the injector 51. However, all or some of one or more communication holes 62 may be formed so that their axis Y extends in the same direction as the axis X of the injection hole 52. Furthermore, at least some of the communication holes 62 may extend so that their axis Y does not deviate from the electrode 42 of the spark plug 41 with respect to the axis X of the injection hole 52.

[0044] Furthermore, in the above embodiment, the axes Y of the two communication holes 62 are both inclined in the direction of the axis Z of the cylinder 6 at the same inclination angle α with respect to the axis X of the injection hole 52. However, the axes Y of the two communication holes 62 may be inclined in the direction of the axis Z of the cylinder 6 (i.e., upward or downward in FIG. 4 ) at different inclination angles with respect to the axis X of the injection hole 52. In addition, in the above embodiment, the axes Y of the two communication holes 62 are both inclined in opposite directions with respect to the axis X of the injection hole 52 at the same inclination angle β with respect to the axis X of the injection hole 52 when viewed in the direction of the axis Z of the cylinder 6. However, the axes Y of the two communication holes 62 may be inclined in the same direction with respect to the axis X of the injection hole 52 at the same inclination angle with respect to the axis X of the injection hole 52 when viewed in the direction of the axis Z of the cylinder 6 (i.e., they may both be inclined upward or downward in FIG. 2 ). Alternatively, the axes Y of the two communication holes 62 may be inclined in opposite directions or in the same direction with respect to the axis X of the injection hole 52 at different inclination angles when viewed in the direction of the axis Z of the cylinder 6.

[0045] FIG. 5 is a cross-sectional view similar to FIG. 4 , but showing an enlarged view of a portion of the cylinder head 3 around the injector 51 according to one modification. In the example shown in FIG. 5 , the engine 1 is provided with four communication holes 62. As shown in FIG. 5 , two communication holes 62 are provided side by side in the axial direction Z of the cylinder 6, and these communication holes 62 are inclined at different inclination angles relative to the axis X of the injection hole 52. In particular, in this modification, the inclination angle of the communication hole 62 provided on the side opposite the piston 4 (upper side in the drawing) is smaller than the inclination angle of the communication hole 62 provided on the piston 4 side (lower side in the drawing). Furthermore, in this modification, when viewed in the axial direction Z of the cylinder 6, two communication holes 62 are inclined at the same inclination angle β in opposite directions relative to the axis X of the injection hole 52. By forming the communication holes 62 in this manner, hydrogen gas can be widely diffused within the combustion chamber 7.

[0046] Fig. 6 is a cross-sectional view similar to Fig. 4, showing an enlarged view of the cylinder head 3 around the injector 51 according to another modified example. In the example shown in Fig. 6, the engine 1 is provided with only one communication hole 62. In addition, the communication hole 62 is formed so that its axis Y extends on the axis X of the injection hole 52 of the injector 51. By configuring the communication hole 62 in this way, the formation and processing of the communication hole 62 becomes easier.

[0047] In the above embodiment, the flow path cross-sectional area of ​​the pressure accumulator chamber 61 is larger than the flow path cross-sectional area of ​​the injection hole 52 of the injector 51. However, the flow path cross-sectional area of ​​the pressure accumulator chamber 61 may be substantially the same as the flow path cross-sectional area of ​​the injection hole 52 of the injector 51. In addition, in the above embodiment, the total flow path cross-sectional area of ​​the multiple communication holes 62 is smaller than the flow path cross-sectional area of ​​the pressure accumulator chamber 61. However, when multiple communication holes 62 are provided, the multiple communication holes 62 may be formed so that the total flow path cross-sectional area is substantially the same as the flow path cross-sectional area of ​​the pressure accumulator chamber 61. In addition, in the present embodiment, the communication holes 62 are formed so that the total flow path cross-sectional area is larger than the flow path cross-sectional area of ​​the throttle portion of the injector 51. However, the communication holes 62 may be formed so that the flow path cross-sectional area is substantially the same as the flow path cross-sectional area of ​​the throttle portion of the injector 51.

[0048] Furthermore, in the above embodiment, the hydrogen engine 1 only has the injector 51 that directly injects hydrogen gas into the combustion chamber 7. However, the hydrogen engine 1 may also have an injector that injects hydrogen gas or other fuel into an intake passage such as the intake port 11, in addition to the injector 51 that directly injects hydrogen gas into the combustion chamber 7.

[0049] Second embodiment Next, a hydrogen engine 1 according to a second embodiment will be described with reference to Figure 7. The configuration of the hydrogen engine 1 according to the second embodiment is basically the same as the configuration of the hydrogen engine 1 according to the first embodiment. Therefore, the following description will focus on the parts that are different from the configuration of the hydrogen engine 1 according to the first embodiment.

[0050] FIG. 7 is a cross-sectional view similar to FIG. 4 , showing an enlarged view of a portion of the cylinder head 3 around an injector 51 according to the second embodiment. As shown in FIG. 7 , the hole 45 formed in the cylinder head 3 is formed so that its cross-sectional shape perpendicular to the axial direction is larger than the cross-sectional shape of the tubular portion 53 of the injector 51. In this embodiment, a pressure accumulator chamber defining member 63′ is provided between the inner surface of the hole 45 and the outer surface of the tubular portion 53 of the injector 51, near the tip end of the tubular portion 53. The pressure accumulator chamber defining member 63′ is provided between the injector 51 and the combustion chamber 7, and functions as a pressure accumulator chamber defining portion that defines the pressure accumulator chamber 61 and the communication hole 62. Therefore, in this embodiment, the pressure accumulator chamber defining portion is configured as a member separate from the cylinder head 3 that defines the combustion chamber 7.

[0051] In this embodiment, the accumulator chamber defining member 63' is formed of the same material as the cylinder head 3, namely, a metal such as an aluminum alloy or cast iron. Therefore, in this embodiment, the accumulator chamber defining member 63' has the same thermal conductivity and corrosion resistance as the cylinder head 3. However, the accumulator chamber defining member 63' may be formed of another material having thermal conductivity equal to or higher than that of the cylinder head 3 used as the combustion chamber wall. Furthermore, the accumulator chamber defining member 63' may be formed of another material having corrosion resistance equal to or higher than that of the cylinder head 3. Specifically, the accumulator chamber defining member 63' may be formed of, for example, beryllium copper or the like.

[0052] 7, the accumulator chamber defining member 63' has a hole 64 into which the injector 51 is inserted. The hole 64 is formed so that its cross-sectional shape perpendicular to the axial direction is substantially the same as or slightly larger than the cross-sectional shape of the tubular portion 53 of the injector 51. The accumulator chamber defining member 63' is press-fit into the hole 45 of the cylinder head 3, and is configured so that when the injector 51 is inserted, the tip of the injector 51 does not reach the bottom surface of the hole 64 of the accumulator chamber defining member 63'. As a result, the accumulator chamber 61 is formed between the tip of the injector 51 and the bottom surface of the hole 64 of the accumulator chamber defining member 63'.

[0053] According to this embodiment, the pressure accumulator chamber defining portion is configured as a member separate from the cylinder head 3, which facilitates the processing of forming the communication hole 62 and thereby improves the processing accuracy of the communication hole 62. Furthermore, the pressure accumulator chamber defining portion can be formed from a material that has higher thermal conductivity and corrosion resistance than the cylinder head 3, which improves the cooling performance around the tip end of the injector 51 and also makes it possible to suppress deformation of the communication hole 62, clogging, and the like due to corrosion resistance.

[0054] Third embodiment Next, a hydrogen engine 1 according to a third embodiment will be described with reference to Figures 8 to 12. The configuration of the hydrogen engine 1 according to the third embodiment is basically the same as the configuration of the hydrogen engine 1 according to the first embodiment. Therefore, the following description will focus on the parts that are different from the configuration of the hydrogen engine 1 according to the first embodiment.

[0055] 8 is a cross-sectional view similar to FIG. 4, showing an enlarged view of the cylinder head 3 around the injector 51 according to the third embodiment. As shown in FIG. 8, the engine 1 according to this embodiment has a spherical check valve 65 and a coil spring 66 that biases the check valve 65 toward the nozzle hole 52 of the injector 51.

[0056] The check valve 65 and the coil spring 66 are provided in the pressure accumulator chamber 61. The check valve 65 and the coil spring 66 are arranged so that their axes coincide with the axis X of the injection hole 52 of the injector 51. The coil spring 66 is arranged so as to rest on the end face of the pressure accumulator chamber 61 where the communication hole 62 opens. The check valve 65 is arranged between the coil spring 66 and the injector 51.

[0057] 9A and 9B are diagrams schematically illustrating the operation of the check valve 65. FIG. 9A shows a state in which hydrogen gas is not injected from the injector 51 and no combustion of the air-fuel mixture occurs in the combustion chamber 7. FIG. 9B shows a state in which hydrogen gas is injected from the injector 51. In addition, FIG. 9C shows a state in which combustion of the air-fuel mixture occurs in the combustion chamber 7.

[0058] As shown in FIG. 9A, when hydrogen gas is not being injected from the injector 51 and no combustion of the air-fuel mixture is occurring in the combustion chamber 7, the check valve 65 is urged toward the nozzle hole 52 of the injector 51 by the coil spring 66 to close the nozzle hole 52. As shown in FIG. 9B, when hydrogen gas is being injected from the injector 51, the check valve 65 is opened by the pressure of the hydrogen gas. In other words, when hydrogen gas is injected from the nozzle hole 52, the coil spring 66 urges the check valve 65 toward the nozzle hole 52 with such a force that the check valve 65 is opened by the pressure of the hydrogen gas. As a result, hydrogen gas flows from the injector 51 toward the communication hole 62. On the other hand, as shown in FIG. 9C, when combustion of the air-fuel mixture is occurring in the combustion chamber 7, the check valve 65 is closed by the pressure within the combustion chamber 7. As a result, gas generated by combustion in the combustion chamber 7 is prevented from flowing into the nozzle hole 52 of the injector 51 via the communication hole 62 and the pressure accumulator chamber 61. That is, in this embodiment, the check valve 65 is configured to permit the flow of hydrogen gas (fluid) from the injector 51 to the communication hole 62 and to prohibit the flow of combustion gas (fluid) from the communication hole 62 to the injector 51.

[0059] According to this embodiment, the check valve 65 prevents the combustion gas from flowing back from the combustion chamber 7 through the nozzle hole 52 into the injector 51. Therefore, the durability of the injector 51 can be improved.

[0060] In the third embodiment, the check valve 65 is a spherical valve, and the coil spring 66 is used as a biasing member that biases the check valve 65 toward the nozzle hole 52 of the injector 51. However, the check valve 65 may be a valve of any shape other than a spherical valve, such as a plate valve or a cylindrical valve. Furthermore, the biasing member may be any elastic member, such as a disc spring or a leaf spring.

[0061] 10 to 12 are diagrams that schematically show the configuration around the pressure accumulator chamber 61. In particular, Fig. 10 to 12 show the configuration around the pressure accumulator chamber 61 in which the check valve 65 and the biasing member have mutually different configurations.

[0062] FIG. 10 shows an example in which a plate valve 65a is used as the check valve and a conically shaped coil spring 66a is used as the biasing member. FIG. 10(A) shows a cross-sectional view of the accumulator 61 and its surroundings, and FIG. 10(B) shows a cross-sectional view of the accumulator 61 and its surroundings taken along line BB in FIG. 10(A). As shown in FIG. 10(B), the plate valve 65a is configured so that its outer periphery partially contacts the inner surface of the accumulator-chamber defining portion 63. This limits movement of the plate valve 65a in a direction perpendicular to the main flow direction of hydrogen gas. In addition, the plate valve 65a is configured so that its outer periphery is partially separated from the inner surface of the accumulator-chamber defining portion 63. This allows hydrogen gas to flow between the plate valve 65a and the inner surface of the accumulator-chamber defining portion 63.

[0063] FIG. 11 also shows an example in which a cylindrical valve 65b is used as the check valve and a disc spring 66b is used as the biasing member. FIG. 11(A) shows a cross-sectional view of the pressure accumulator 61 and its surroundings, and FIG. 11(B) shows a cross-sectional view of the pressure accumulator 61 and its surroundings taken along line BB in FIG. 11(A). FIG. 11(C) is a plan view of the disc spring 66b. As shown in FIG. 11(C), the disc spring 66b has an annular portion 67 that contacts the inner surface of the pressure accumulator defining portion 63 and is placed on the end face where the communication hole 62 of the pressure accumulator 61 opens, and multiple elastic portions 68 that extend inward from the annular portion 67. The multiple elastic portions 68 bias the cylindrical valve 65b and are spaced apart from one another in the circumferential direction, allowing hydrogen gas to flow between these elastic portions 68.

[0064] Furthermore, Fig. 12 shows an example in which a spherical valve 65 is used as the check valve and a disc spring 66b is used as the biasing member. Fig. 12(A) shows a cross-sectional view of the periphery of the pressure accumulator chamber 61, and Fig. 12(B) is a plan view of the disc spring 66b.

[0065] Furthermore, in the third embodiment, the accumulator chamber defining portion 63 is formed as a part of the cylinder head 3, similar to the first embodiment. However, the accumulator chamber defining portion may be configured as a accumulator chamber defining member 63' separate from the cylinder head 3, similar to the second embodiment. FIG. 13 is a cross-sectional view similar to FIG. 4, showing an enlarged view of a portion of the cylinder head 3 around the injector 51 when the accumulator chamber defining member 63' is provided. In the example shown in FIG. 13, the accumulator chamber defining member 63' is disposed in the hole 45 of the cylinder head 3, and a spherical check valve 65 and a coil spring 66 are disposed in the accumulator chamber 61 defined by the accumulator chamber defining member 63'.

[0066] Furthermore, in the third embodiment, the coil spring 66 serving as the biasing member is placed on the end surface of the pressure accumulator chamber 61 where the communication hole 62 opens. However, the biasing member may be fixed to the injector 51. FIG. 14 is a diagram similar to FIG. 12, schematically illustrating the configuration around the pressure accumulator chamber 61. As shown in FIG. 14, the biasing member 66' has a cylindrical annular portion 67' and a plurality of elastic portions 68 extending inward from the end of the annular portion 67' opposite the injector 51 side. The end of the annular portion 67' facing the injector 51 is press-fitted onto the outer surface of the injector 51, and is thereby fixed to the injector 51. Therefore, in the example shown in FIG. 14, the biasing member 66' is fixed to the injector 51. Fixing the biasing member to the injector 51 in this manner facilitates the assembly of the check valve and the biasing member.

[0067] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims. [Explanation of symbols]

[0068] 1 Hydrogen engine 2 Cylinder block 3. Cylinder head 6 cylinders 7. Combustion chamber 41 Spark plug 42 electrodes 45 Hole 51 Injector 52 nozzle 61 Pressure accumulator 62 Communication hole 63 Accumulator chamber defining section

Claims

1. A hydrogen engine that supplies hydrogen gas as fuel into a combustion chamber, an injector that injects hydrogen gas; a pressure accumulator chamber communicating with the nozzle hole of the injector; a communication hole communicating with the accumulator chamber and the combustion chamber; an accumulator chamber defining portion provided between the injector and the combustion chamber to define the accumulator chamber and the communication hole; a piston reciprocating within a cylinder defining the combustion chamber; the accumulator chamber defining portion is formed separately from the injector and has thermal conductivity equal to or greater than that of a cylinder head defining the combustion chamber, One or more communication holes are provided, At least one of the communication holes is formed to have an axis that is angled with respect to an axis of the injection hole of the injector, A hydrogen engine, wherein at least one of the communication holes is formed to have an axis that extends at an angle toward the piston in the injection direction with respect to the axis of the nozzle hole of the injector.

2. a spark plug disposed in the combustion chamber and configured to ignite the mixture of hydrogen gas and air; 2. The hydrogen engine according to claim 1, wherein at least one of the communication holes is formed to have an axis that extends at an angle away from the ignition portion of the spark plug with respect to the axis of the nozzle hole of the injector.

3. A hydrogen engine that supplies hydrogen gas as fuel into a combustion chamber, an injector that injects hydrogen gas; a pressure accumulator chamber communicating with the nozzle hole of the injector; a communication hole communicating with the accumulator chamber and the combustion chamber; an accumulator chamber defining portion provided between the injector and the combustion chamber to define the accumulator chamber and the communication hole; a spark plug disposed in the combustion chamber and configured to ignite a mixture of hydrogen gas and air; the accumulator-chamber defining portion is formed separately from the injector and has thermal conductivity equal to or higher than that of a combustion chamber wall defining the combustion chamber, One or more communication holes are provided, At least one of the communication holes is formed to have an axis that is angled with respect to an axis of the injection hole of the injector, A hydrogen engine, wherein at least one of the communication holes is formed to have an axis that extends at an angle away from the ignition portion of the ignition plug with respect to the axis of the nozzle hole of the injector.

4. Two or more of the communication holes are provided, 4. The hydrogen engine according to claim 2, wherein at least two of the communication holes are formed so as to have axes extending in directions that diverge on both sides of an ignition portion of the spark plug when viewed in the axial direction of the combustion chamber.

5. 4. The hydrogen engine according to claim 1, wherein the pressure accumulator defining portion is configured as a part of a cylinder head that defines the combustion chamber.

6. 4. The hydrogen engine according to claim 1, wherein the accumulator chamber defining portion is configured as a member separate from a cylinder head defining the combustion chamber.

7. 4. The hydrogen engine according to claim 1, wherein the communication holes are formed so that a total flow cross-sectional area thereof is smaller than a flow cross-sectional area of ​​the pressure accumulator chamber, so as to act as a throttle with respect to the pressure accumulator chamber.

8. 4. The hydrogen engine according to claim 1, wherein the pressure accumulator is formed to have the same axis as the axis of the nozzle hole of the injector.

9. Further, a check valve is provided in the pressure accumulator chamber, 4. The hydrogen engine according to claim 1, wherein the check valve allows fluid to flow from the injector to the communication hole and prohibits fluid to flow from the communication hole to the injector.

10. a biasing member that biases the check valve toward the nozzle hole of the injector; 10. The hydrogen engine according to claim 9, wherein the biasing member is fixed to the injector.

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