Spark plug assembly and hydrogen engine

Abstract

This spark plug assembly is attached to a cylinder head having a plug hole connected to a combustion chamber. The spark plug assembly comprises: a plug pipe that includes a base end part, a leading end part on the opposite to the base end part, and a flange part provided between the base end part and the leading end part, that can be inserted into the plug hole, and in which the leading end part abuts the cylinder head when the plug pipe is inserted into the plug hole; and a spark plug disposed in the plug pipe. The flange part has a pressed surface that receives a force pressing the plug pipe toward a combustion chamber.

Description

Spark plug assembly and hydrogen engine

[0001] The present disclosure relates to a spark plug assembly and a hydrogen engine.

[0002] Hydrogen engines, which use hydrogen as fuel and burn it mixed with air, are attracting attention as a zero-emission power source that does not emit harmful substances such as carbon dioxide.However, the huge cost required to develop a new hydrogen engine is a factor hindering the widespread adoption of hydrogen engines.

[0003] In order to reduce the development costs of hydrogen engines, attempts have been made to convert cylinder heads for commonly used diesel engines into hydrogen engines. One known technique for converting diesel engine cylinder heads into engines with other combustion systems is described in, for example, Patent Document 1.

[0004] Patent Document 1 describes a method in which a plug pipe containing an ignition plug is inserted into a space in which a diesel fuel injector is disposed, and a screw provided at the tip of the plug pipe is threaded into a screw hole on the cylinder head side to fix the plug pipe to the cylinder head.

[0005] JP 2016-130485 A

[0006] In Patent Document 1, a screw provided at the tip of the plug pipe is threaded into a threaded hole in the cylinder head, but the cylinder head may not have a threaded hole that communicates with the combustion chamber. In such cases, it is necessary to process the cylinder head to form a threaded hole in order to thread the plug pipe into the cylinder head. However, this process is time-consuming and causes a decrease in engine production efficiency.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present disclosure to provide a spark plug assembly that can be attached to a cylinder head without requiring special processing.

[0008] A spark plug assembly according to one aspect of the present invention is mounted in a cylinder head having a plug hole communicating with a combustion chamber. The spark plug assembly comprises a plug pipe that is insertable into the plug hole and includes a base end, a tip end opposite the base end, and a flange portion provided between the base end and the tip end, the tip end of which abuts against the cylinder head when the plug pipe is inserted into the plug hole, and an ignition plug disposed within the plug pipe, the flange portion having a pressing surface that receives a force pressing the plug pipe toward the combustion chamber.

[0009] With the tip of the plug pipe abutting the cylinder head, the plug pipe is pressed against the cylinder head by the pressing surface of the flange, and is fixed in the plug hole. Therefore, with this spark plug assembly, the spark plug assembly can be attached to the cylinder head without any special processing of the cylinder head.

[0010] The spark plug assembly may further include a fixing device that fixes the plug pipe to the cylinder head by pressing the pressing surface toward the combustion chamber. By fixing the plug pipe to the cylinder head with this fixing device, the spark plug assembly can be attached to the cylinder head without any special processing of the cylinder head.

[0011] The fixing device may include a clamp member that clamps the plug pipe between the flange portion and the base end portion, and a fastening member that is fastened to the cylinder head, and the clamp member may apply a pressing force toward the combustion chamber to a pressing surface when the fastening member is fastened to the cylinder head. By applying a pressing force toward the combustion chamber from the clamp member to the pressing surface, the plug pipe can be pressed against the cylinder head and fixed in the plug hole.

[0012] The plug pipe may have an internal thread on its inner surface, and the spark plug may have an external thread that screws into the internal thread. The spark plug is fixed to the plug pipe by screwing the external thread of the spark plug into the internal thread of the plug pipe.

[0013] The cylinder head may have a guide pipe that defines the plug hole and provides a butting surface against which the tip of the plug pipe butts, and the spark plug assembly may further include a first seal member disposed between the tip and the butt surface. By disposing the first seal member between the tip and the butt surface, the gap between the plug pipe and the guide pipe is sealed, preventing combustible gas from entering the gap from the combustion chamber.

[0014] The plug pipe may have a stepped surface that provides a step on the inner surface of the plug pipe, and the spark plug assembly may further include a second seal member disposed between the spark plug and the stepped surface. By disposing the second seal member between the spark plug and the stepped surface, the gap between the spark plug and the plug pipe is sealed, preventing combustion gas from the combustion chamber from entering the gap.

[0015] The first seal member and the second seal member may be made of copper or aluminum. Because copper and aluminum are relatively soft metals, making the first seal member and the second seal member from copper or aluminum can achieve high sealing performance. Furthermore, by making the first seal member and the second seal member from a conductive material, the spark plug is electrically grounded to the cylinder head via the first seal member and the second seal member. Grounding the spark plug allows for stable operation of the spark plug.

[0016] The outer diameter of the plug pipe may be gradually reduced toward the tip end thereof. In this case, the plug pipe can be inserted deep into the plug hole even if the inner diameter of the plug hole is gradually reduced toward the combustion chamber.

[0017] A hydrogen engine according to one aspect of the present invention comprises a cylinder that defines a combustion chamber, a piston that reciprocates within the cylinder, a cylinder head having an intake port for intake air, an exhaust port for exhaust air, and a spark plug hole that communicates with the combustion chamber, a hydrogen injector that adds hydrogen fuel to the intake air, and a spark plug assembly that ignites combustible gas containing hydrogen fuel, the spark plug assembly being a plug pipe that is inserted into the plug hole and includes a base end, a tip end opposite the base end, and a flange portion provided between the base end and the tip end, the tip end being abutted against the cylinder head, and the spark plug arranged within the plug pipe, the flange portion having a pressing surface that receives a force pressing the plug pipe toward the combustion chamber.

[0018] According to the present disclosure, the spark plug assembly can be attached to the cylinder head without any special processing being performed on the cylinder head.

[0019] FIG. 2 is a side view of an ignition plug assembly according to one embodiment. FIG. 3 is a partial cross-sectional view of a plug pipe along the axial direction. (a) is a cross-sectional view taken along line A-A in FIG. 2, and (b) is a cross-sectional view taken along line B-B in FIG. 2. FIG. 3 is a plan view of a clamp member. FIG. 4 is a partial cross-sectional view showing the spark plug assembly attached to a cylinder head. FIG. 5 is a schematic view of a hydrogen engine having an ignition plug assembly. FIG. 6 is a partial cross-sectional view showing a modified example of the plug pipe.

[0020] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate explanations will be omitted. In the drawings, some parts may be simplified or exaggerated for ease of understanding, and the dimensional ratios, angles, etc. are not limited to those shown in the drawings.

[0021] 1 is a side view of a spark plug assembly 1 according to one embodiment. The spark plug assembly 1 is used to convert a cylinder head 50 for a diesel engine into a hydrogen engine. As will be described later, the cylinder head 50 has a space for installing an injector that injects diesel fuel. When the cylinder head 50 is converted into a hydrogen engine, the injector for diesel fuel is no longer necessary. The spark plug assembly 1 is installed in the space in place of the injector and is used to ignite hydrogen fuel mixed with air.

[0022] As shown in Figure 1, the spark plug assembly 1 includes a plug pipe 2, an ignition plug 3, and a retainer 4. The plug pipe 2 is a hollow cylinder that includes a base end 11 and a tip end 12 and extends along an axis Z between the base end 11 and the tip end 12. The plug pipe 2 is a metallic cylinder made of, for example, austenitic stainless steel that is resistant to hydrogen embrittlement. Examples of austenitic stainless steel that is resistant to hydrogen embrittlement include SUS304, SUS316, and SUS316L.

[0023] Figure 2 is a partial cross-sectional view of the plug pipe 2 taken along the axis Z. As shown in Figure 2, an internal space 2s for accommodating the spark plug 3 is formed inside the plug pipe 2. The internal space 2s extends in a direction along the axis Z (hereinafter referred to as the "axial direction"). In the following description, the direction from the base end 11 to the tip end 12 in the axial direction may be referred to as "downward," and the direction from the tip end 12 to the base end 11 may be referred to as "upward."

[0024] As shown in FIG. 2 , the plug pipe 2 includes a first flange portion 13 and a second flange portion 14. The first flange portion 13 is disposed axially between the base end portion 11 and the tip end portion 12 and protrudes radially (perpendicular to the axis Z) outward from the outer surface of the main body portion 2 a of the plug pipe 2. The second flange portion 14 is disposed axially between the base end portion 11 and the first flange portion 13 and protrudes radially (perpendicular to the axis Z) outward from the outer surface of the main body portion 2 a of the plug pipe 2. The first flange portion 13 and the second flange portion 14 are spaced apart in the axial direction. Therefore, a fitting portion 16 having an outer diameter smaller than the radial widths of the first flange portion 13 and the second flange portion 14 is formed between the first flange portion 13 and the second flange portion 14.

[0025] Fig. 3(a) is a cross-sectional view taken along line A-A in Fig. 2, and Fig. 3(b) is a cross-sectional view taken along line B-B in Fig. 2. As shown in Fig. 3(a), the first flange portion 13 has a generally rectangular outline when viewed from the axial direction. The first flange portion 13 has an upper surface 13a facing upward and a lower surface 13b facing downward. The upper surface 13a and the lower surface 13b are surfaces perpendicular to the axis Z. As will be described later, the upper surface 13a of the first flange portion 13 forms a pressing surface that receives a force that presses the plug pipe 2 toward the combustion chamber.

[0026] As shown in Figure 3(b), the second flange portion 14 has a circular outline when viewed in the axial direction. The second flange portion 14 has an upper surface 14a facing upward and a lower surface 14b facing downward. The upper surface 14a and the lower surface 14b are surfaces perpendicular to the axis Z. The maximum width of the first flange portion 13 in the direction perpendicular to the axial direction is greater than the outer diameter of the second flange portion 14.

[0027] 2, the outer diameter of the plug pipe 2 may be gradually reduced toward the tip end 12. The inner diameter of the plug pipe 2 is gradually reduced toward the tip end 12 in accordance with the outer diameter. In particular, the inner surface of the tip end 12 of the plug pipe 2 has the smallest inner diameter of all the inner surfaces of the plug pipe 2. A female thread 15 for fixing the spark plug 3 is formed on the inner surface of the tip end 12.

[0028] The inner diameter of the plug pipe 2 is reduced in stages, forming a stepped surface 11a on the inner surface of the plug pipe 2. That is, the stepped surface 11a provides a step on the inner surface of the plug pipe 2. The stepped surface 11a is an annular flat surface facing upward, and is connected to the inner surface of the tip portion 12. The stepped surface 11a supports a metal fitting 24 of the spark plug 3.

[0029] The spark plug 3 is disposed in the internal space 2s of the plug pipe 2. As shown in Fig. 2, the spark plug 3 has a terminal 21, a center electrode 22, a ground electrode 23, a metal fitting 24, and a male thread portion 25. The terminal 21 is disposed at the upper end of the spark plug 3 and supplies power received from an external power source to the center electrode 22. The ground electrode 23 is disposed at the lower end of the spark plug 3 and is disposed outside the plug pipe 2. When power is supplied to the terminal 21, a high-voltage current is discharged between the center electrode 22 and the ground electrode 23, generating a spark in the combustion chamber 60. This spark ignites combustible gas in the combustion chamber 60.

[0030] The metal fitting 24 is provided between the terminal 21 and the ground electrode 23 in the axial direction, and is provided along the outer periphery of the spark plug 3. The metal fitting 24 is electrically connected to the ground electrode 23. The male thread portion 25 is provided between the ground electrode 23 and the metal fitting 24 in the axial direction, and can be threaded into the female thread portion 15. When the male thread portion 25 is threaded into the female thread portion 15, the spark plug 3 is fixed to the plug pipe 2.

[0031] The spark plug assembly 1 further includes a first seal member 41 and a second seal member 42. The first seal member 41 is a packing such as an O-ring, and is provided outside (below) the plug pipe 2 so as to surround the spark plug 3. The second seal member 42 is a packing such as an O-ring, and is disposed between the metal fitting 24 of the spark plug 3 and the stepped surface 11a of the plug pipe 2 so as to surround the spark plug 3.

[0032] The first seal member 41 and the second seal member 42 are made of a conductive metal material such as copper or aluminum. Copper and aluminum are relatively soft metal materials, so by making the first seal member 41 and the second seal member 42 from copper or aluminum, high sealing performance is achieved.

[0033] The fixing device 4 functions to fix the plug pipe 2 to the cylinder head 50. The fixing device 4 is originally a device used to fix a diesel fuel injector. Therefore, as will be described later, the cylinder head 50 is formed with a screw hole 50a for fastening the fixing device 4 (see FIG. 5). The spark plug assembly 1 is designed so that the plug pipe 2 can be fixed to the cylinder head 50 using the fixing device 4 for a diesel engine.

[0034] As shown in FIG. 1 , the fixing device 4 includes a clamp member 31 and a fastening member 32. FIG. 4 is a top view of the clamp member 31. As shown in FIG. 4 , the clamp member 31 has a base 33 having a through hole and a pair of arm portions 34 extending in a bifurcated manner from the base 33. The base 33 and the pair of arm portions 34 are integrally formed from a metal material. As shown in FIG. 1 , the pair of arm portions 34 are fitted into the fitting portion 16 so as to sandwich the plug pipe 2 between the first flange portion 13 and the second flange portion 14 in the radial direction. Typically, the pair of arm portions 34 are arranged in the fitting portion 16 so as to face each other in the long side direction of the first flange portion 13.

[0035] The fastening member 32 has a head 35 and a shank 36 that is connected to the head 35 and extends in the axial direction. Typically, the fastening member 32 is a hexagon bolt. The shank 36 is inserted into a through hole formed in the base 33 of the clamp member 31. The through hole has a diameter that is smaller than the maximum width of the head 35 and larger than the diameter of the shank 36. A male thread 36a is formed at the tip of the shank 36 to be fastened to a threaded hole 50a in the cylinder head 50.

[0036] As will be described later, when the fastening member 32 is fastened to the cylinder head, the clamp member 31 is pressed downward together with the head portion 35, and the upper surface 13a of the first flange portion 13 is pressed toward the combustion chamber 60 side.

[0037] Figure 5 is a partial cross-sectional view showing the spark plug assembly 1 attached to a cylinder head 50. The cylinder head 50 shown in Figure 5 is a diesel engine cylinder head that has been converted for use in a hydrogen engine. The cylinder head 50 is a structure that defines the combustion chamber 60 from above, and has a guide pipe 52 that defines a spark plug hole 51, and a water jacket 53 through which cooling water flows.

[0038] The spark plug hole 51 is originally a space for accommodating a diesel fuel injector and communicates with the combustion chamber 60. The spark plug hole 51 has, for example, a circular cross-sectional shape, and the inner diameter of the spark plug hole 51 gradually decreases toward the combustion chamber 60. As the inner diameter of the spark plug hole 51 gradually decreases, an abutment surface 52a is formed on the inner surface of the guide pipe 52. The abutment surface 52a is an upward-facing, annular flat surface, and has an inner diameter smaller than the outer diameter of the tip end 12. Therefore, when the plug pipe 2 is inserted into the spark plug hole 51, the tip end 12 of the plug pipe 2 abuts against the abutment surface 52a. The first seal member 41 described above is disposed between the tip end 12 of the plug pipe 2 and the abutment surface 52a.

[0039] The cylinder head 50 has a screw hole 50a for fastening the fastening member 32 of the fixing device 4. The screw hole 50a is formed in a position adjacent to the spark plug hole 51 in a top view.

[0040] Next, a procedure for attaching the spark plug assembly 1 to the cylinder head 50 will be described. When attaching the spark plug assembly 1 to the cylinder head 50, first, the spark plug 3 is inserted into the plug pipe 2, and the second seal member 42 is interposed between the metal fitting 24 of the spark plug 3 and the stepped surface 11a, and the male thread portion 25 is threaded onto the female thread portion 15 to fasten the spark plug 3 to the plug pipe 2. At this time, the second seal member 42 is compressed between the spark plug 3 and the stepped surface 11a, sealing the gap between the plug pipe 2 and the spark plug 3. As a result, combustible gas is prevented from entering the internal space 2s of the plug pipe 2 from the combustion chamber 60.

[0041] Next, the first seal member 41 is attached to the tip end of the spark plug 3, and the plug pipe 2 is inserted into the spark plug hole 51. At this time, the pair of arms 34 of the clamp member 31 are fitted into the fitting portion 16 of the plug pipe 2 above the first flange portion 13, more specifically, between the first flange portion 13 and the second flange portion 14. When the plug pipe 2 is inserted all the way into the plug hole 51, the tip end 12 of the plug pipe 2 abuts against the abutment surface 52a of the guide pipe 52, as shown in FIG. 5 . This positions the ground electrode 23 of the spark plug 3 in the combustion chamber 60.

[0042] Next, the male thread portion 36a of the fastening member 32 is screwed into the threaded hole 50a of the cylinder head 50. This presses down the clamp member 31 connected to the fastening member 32, applying a downward (toward the combustion chamber 60) pressing force F to the upper surface 13a of the first flange portion 13. This pressing force F presses and fixes the plug pipe 2 against the cylinder head 50. This pressing force F also crushes the first seal member 41 between the tip end 12 of the plug pipe 2 and the abutment surface 52a. As a result, the gap between the plug pipe 2 and the guide pipe 52 is sealed, preventing combustible gas from entering the gap from the combustion chamber 60.

[0043] As described above, in the spark plug assembly 1, when the fastening member 32 of the fixing device 4 is fastened to the cylinder head 50, the clamp member 31 is pressed down, and a pressing force toward the combustion chamber 60 is applied to the upper surface 13a of the first flange portion 13. This pressing force presses the plug pipe 2 against the cylinder head 50, so that the plug pipe 2 is fixed together with the spark plug 3 in the plug hole 51 of the cylinder head 50. By fixing the plug pipe 2 by pressing the first flange portion 13, the spark plug assembly 1 can be attached to the cylinder head 50 without any special processing such as forming a screw hole in the cylinder head. Furthermore, employing such a structure makes it easier to attach and detach the spark plug assembly 1, which also contributes to improved maintainability.

[0044] Next, a cylinder head cover 55 that covers the cylinder head 50 is attached to the top of the cylinder head 50. For example, as shown in FIG. 5 , the cylinder head cover 55 is provided so as to surround the outer periphery of the second flange portion 14 via a packing 56. As a result, the base end 11 of the plug pipe 2 is located outside (above) the cylinder head cover 55. Note that the cylinder head cover 55 may also be located above the base end 11 of the plug pipe 2.

[0045] Next, a hydrogen engine 100 equipped with the spark plug assembly 1 will be described. Figure 6 is a diagram schematically showing the hydrogen engine 100 according to one embodiment. The hydrogen engine 100 is equipped with the spark plug assembly 1, a cylinder block 40, a cylinder head 50, and a hydrogen injector 62. The cylinder block 40 is equipped with a cylinder 71 that defines a combustion chamber 60.

[0046] A piston 72 is provided in the cylinder 71. The piston 72 is connected to a crank 74 via a connecting rod 73. When fuel is combusted in the combustion chamber 60, the piston 72 reciprocates within the cylinder 71, causing the crank 74 to rotate.

[0047] The cylinder head 50 has a spark plug hole 51, an intake port 75, and an exhaust port 76. The spark plug assembly 1 described above is disposed in the spark plug hole 51. The intake port 75 opens to the combustion chamber 60 and supplies intake air (combustible gas) containing hydrogen fuel supplied through an intake passage 78 to the combustion chamber. The intake port 75 is provided with an intake valve 81 that controls the supply of intake air to the combustion chamber 60. The intake valve 81 is opened and closed by controlling the drive of a camshaft 83.

[0048] The exhaust port 76 opens to the combustion chamber 60 and discharges exhaust gas generated in the combustion chamber 60 by combustion of combustible gas into an exhaust passage 79. The exhaust port 76 is provided with an exhaust valve 82 that controls the discharge of exhaust gas from the combustion chamber 60. The exhaust valve 82 is opened and closed by controlling the drive of a camshaft 84.

[0049] The hydrogen injector 62 injects hydrogen fuel into the intake passage 78 to add hydrogen fuel to the intake air. Combustible gas containing hydrogen fuel is supplied to the combustion chamber 60 via the intake port 75. The spark plug assembly 1 activates the spark plug 3 to ignite the combustible gas in the combustion chamber 60. Exhaust gas generated by the combustion of the combustible gas is discharged from the exhaust port 76.

[0050] The spark plug assembly 1 according to various embodiments has been described above, but the invention is not limited to the above-described embodiments and various modifications can be made without departing from the spirit of the invention. The above-described various embodiments can be combined within a consistent range.

[0051] For example, the spark plug assembly 1 does not necessarily have to include the fixing device 4 as long as the plug pipe 2 can be pressed toward the combustion chamber 60. For example, the plug pipe 2 may be fixed to the cylinder head 50 by pressing the upper surface 14a of the second flange portion 14 downward from above the cylinder head cover 55 using bolts or the like to press the plug pipe 2 against the cylinder head 50. Furthermore, the outer diameter of the plug pipe 2 may be constant in the axial direction except for the positions where the first flange portion 13 and the second flange portion 14 are formed. The spark plug assembly 1 can also be applied to engines that use gases other than hydrogen gas as fuel.

[0052] In one embodiment, the plug pipe 2 does not have to have the second flange portion 14. For example, as shown in FIG. 7 , the plug pipe 2 may not include the second flange portion 14, and the base end portion 11 of the plug pipe 2 may be disposed in the same plane as the upper surface 13a of the first flange portion 13. In this embodiment, the first flange portion 13 is disposed below the cylinder head cover 55, and the upper surface 13a of the first flange portion 13 receives a pressing force from the fixing device 4 toward the combustion chamber 60. As a result, the plug pipe 2 is pressed against and fixed to the cylinder head 50.

[0053] The present disclosure includes the following: [1] A spark plug assembly to be attached to a cylinder head having a plug hole communicating with a combustion chamber, comprising: a plug pipe insertable into the plug hole, the plug pipe including a base end, a tip end opposite the base end, and a flange portion; and a spark plug arranged in the plug pipe, wherein the tip end abuts against the cylinder head when the plug pipe is inserted into the plug hole, and the flange portion has a pressing surface that receives a force pressing the plug pipe toward the combustion chamber.

[0054] [2] The spark plug assembly according to [1], further comprising a fixing device that fixes the plug pipe to the cylinder head by pressing the pressing surface toward the combustion chamber.

[0055] [3] The spark plug assembly according to [2], wherein the fixing device includes a clamp member disposed above the flange portion and a fastening member fastened to the cylinder head, and the clamp member applies a pressing force toward the combustion chamber to the pressing surface when the fastening member is fastened to the cylinder head.

[0056] [4] The spark plug assembly according to any one of [1] to [3], wherein the inner surface of the plug pipe is provided with a female thread portion, and the spark plug is provided with a male thread portion that screws into the female thread portion.

[0057] [5] The spark plug assembly according to any one of [1] to [4], wherein the cylinder head has a guide pipe that defines the plug hole and provides an abutment surface against which the tip end of the plug pipe abuts, and the spark plug assembly further includes a first seal member disposed between the tip end and the abutment surface.

[0058] [6] The spark plug assembly according to [5], wherein the plug pipe has a stepped surface that provides a step on an inner surface of the plug pipe, and the spark plug assembly further includes a second seal member disposed between the spark plug and the stepped surface.

[0059] [7] The spark plug assembly according to [6], wherein the first seal member and the second seal member are made of copper or aluminum.

[0060] [8] The spark plug assembly according to any one of [1] to [7], wherein the outer diameter of the plug pipe is gradually reduced toward the tip end.

[0061] [9] A hydrogen engine comprising: a cylinder that defines a combustion chamber; a piston that reciprocates within the cylinder; a cylinder head having an intake port for intake, an exhaust port for exhaust, and a spark plug hole that communicates with the combustion chamber; a hydrogen injector that adds hydrogen fuel to the intake air; and a spark plug assembly that ignites combustible gas containing the hydrogen fuel, wherein the spark plug assembly comprises: a plug pipe that is inserted into the plug hole and includes a base end, a tip end opposite the base end, and a flange portion; and an ignition plug arranged within the plug pipe, wherein the tip end is abutted against the cylinder head within the plug hole, and the flange portion has a pressing surface that receives a force that presses the plug pipe toward the combustion chamber.

[0062] 1...spark plug assembly, 2...plug pipe, 3...spark plug, 4...fixing device, 11...base end, 11a...step surface, 12...tip end, 15...female thread portion, 25...male thread portion, 31...clamp member, 32...fastening member, 41...first seal member, 42...second seal member, 50...cylinder head, 51...plug hole, 52...guide pipe, 52a...butting surface, 60...combustion chamber, 62...hydrogen injector, 71...cylinder, 72...piston, 75...intake port, 76...exhaust port, 100...hydrogen engine, F...pressing force.

Claims

1. A spark plug assembly to be attached to a cylinder head having a plug hole communicating with a combustion chamber, comprising: a plug pipe insertable into the plug hole, the plug pipe including a base end, a tip end opposite the base end, and a flange portion; and an ignition plug disposed within the plug pipe, wherein the tip end is abutted against the cylinder head when the plug pipe is inserted into the plug hole, and the flange portion has a pressing surface that receives a force pressing the plug pipe towards the combustion chamber.

2. The spark plug assembly according to claim 1, further comprising a fixing device for fixing said plug pipe to said cylinder head by pressing said pressing surface against said combustion chamber side.

3. The spark plug assembly according to claim 2, wherein the fixing device includes a clamp member disposed above the flange portion and a fastening member fastened to the cylinder head, and the clamp member applies a pressing force toward the combustion chamber to the pressing surface when the fastening member is fastened to the cylinder head.

4. The spark plug assembly according to claim 1, wherein the inner surface of the plug pipe is provided with a female thread portion, and the spark plug is provided with a male thread portion that screws into the female thread portion.

5. The spark plug assembly according to claim 1, wherein said cylinder head has a guide pipe that defines said plug hole and provides a butt surface against which said tip end of said plug pipe is butted, and said spark plug assembly further comprises a first seal member disposed between said tip end and said butt surface.

6. The spark plug assembly according to claim 5, wherein the plug pipe has a stepped surface providing a step on an inner surface of the plug pipe, and the spark plug assembly further comprises a second seal member disposed between the spark plug and the stepped surface.

7. The spark plug assembly according to claim 6, wherein said first seal member and said second seal member are constructed of copper or aluminum.

8. The spark plug assembly according to claim 1, wherein the outer diameter of said plug pipe is gradually reduced toward said tip end.

9. A hydrogen engine comprising: a cylinder defining a combustion chamber; a piston reciprocating within the cylinder; a cylinder head having an intake port for intake, an exhaust port for exhaust, and a plug hole communicating with the combustion chamber; a hydrogen injector for adding hydrogen fuel to the intake air; and an ignition plug assembly for igniting combustible gas containing the hydrogen fuel, wherein the ignition plug assembly comprises: a plug pipe inserted into the plug hole, the plug pipe including a base end, a tip end opposite the base end, and a flange portion; and an ignition plug disposed within the plug pipe, wherein the tip end is abutted against the cylinder head within the plug hole, and the flange portion has a pressing surface that receives a force pressing the plug pipe towards the combustion chamber.

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