Internal combustion engines and spark plugs

Abstract

To provide an internal combustion engine which can improve productivity while securing a stable fixed state between a housing and a plug cover, and a spark plug.SOLUTION: In an internal combustion engine 10 having a spark plug 1, the spark plug 1 has a cylindrical housing 2, and a plug cover 5 arranged at a tip part of the housing 2 so as to cover a sub-combustion chamber 50 in which a discharge gap G is arranged. The plug cover 5 has a base end hangout part 55 hanging out to an external peripheral side at a base end part. The housing 2 has a cover fixing part 25 for fixing the base end part of the plug cover 5 at the tip part. The cover fixing part 25 has an abutment part 26 on which a base end face 56 of the plug cover 5 abuts, and a tip protrusion 27 for covering the base end hangout part 55 from the external peripheral side and the tip side. The cover fixing part 25 is arranged at a base end side rather than a tip opening end 811 of a plug hole 81 of the internal combustion engine 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an internal combustion engine and a spark plug. [Background technology]

[0002] A spark plug equipped with an auxiliary combustion chamber is disclosed in, for example, Patent Document 1. In such a spark plug, a plug cover is welded to a housing. In order to ensure a stable fixed state of the plug cover to the housing, welding is performed over the entire circumferential direction of the plug. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-184433 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the process of welding the plug cover to the housing over the entire circumference takes time, and therefore there is room for improvement in terms of productivity of spark plugs.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide an internal combustion engine and a spark plug that can improve productivity while ensuring a stable fixed state between the housing and the plug cover. [Means for solving the problem]

[0006] A first aspect of the present invention is an internal combustion engine (10) having a spark plug (1), The above spark plugs are A cylindrical housing (2); a plug cover (5) provided at the tip of the housing so as to cover a sub-combustion chamber (50) in which a discharge gap (G) is arranged, The plug cover has a base end protruding portion (55) protruding outwardly from a base end thereof, The housing has a cover fixing portion (25) at a tip end portion for fixing a base end portion of the plug cover, the cover fixing portion has a contact surface (26) against which the base end surface of the plug cover contacts, and a tip protruding portion (27) that covers the base end protruding portion from an outer circumferential side and a tip side, The cover fixing portion is disposed on the base end side relative to a distal open end (811) of a spark plug hole (81) of the internal combustion engine. And, The contact surface of the cover fixing portion and the base end surface of the plug cover are inclined toward the tip side in the plug axial direction (Z) as they extend inward in the plug radial direction. , in internal combustion engines.

[0007] A second aspect of the present invention is a cylindrical housing (2), a plug cover (5) provided at a tip end of the housing so as to cover a sub-combustion chamber (50) in which a discharge gap (G) is arranged, The plug cover has a base end protruding portion (55) protruding outwardly from a base end thereof, The housing has a cover fixing portion (25) at a tip end portion for fixing a base end portion of the plug cover, the cover fixing portion has a contact surface (26) against which the base end surface of the plug cover contacts, and a tip protruding portion (27) that covers the base end protruding portion from an outer circumferential side and a tip side, In this spark plug, the abutment surface of the cover fixing portion and the base end surface of the plug cover are inclined toward the tip side in the plug axial direction (Z) as they extend radially inwardly. Effect of the Invention

[0008] In the internal combustion engine according to the first aspect, the housing has the cover fixing portion, and the cover fixing portion has the abutment surface and the tip projection. This makes it possible to fix the plug cover to the housing without welding or the like over the entire circumference. This improves the productivity of the spark plug.

[0009] In addition, the cover fixing portion is disposed closer to the base end than the tip opening end of the spark plug hole of the internal combustion engine. This makes it possible to prevent an excessive increase in temperature of the cover fixing portion. This makes it possible to prevent a decrease in strength of the tip protrusion of the housing and ensure a stable fixing state.

[0010] In the spark plug according to the second aspect, the housing has the cover fixing portion, and the cover fixing portion has the contact surface and the tip projection. This makes it possible to fix the plug cover to the housing without welding or the like over the entire circumference. This improves the productivity of the spark plug.

[0011] In addition, the abutment surface of the cover fastening portion and the base end surface of the plug cover are inclined so as to move inward in the plug radial direction and toward the tip side in the plug axial direction. This makes it possible to more firmly fasten the base end of the plug cover by the cover fastening portion, thereby ensuring a stable fastening state between the housing and the plug cover.

[0012] As described above, according to the above aspects, it is possible to provide an internal combustion engine and a spark plug that can improve productivity while ensuring a stable fixed state between the housing and the plug cover. In addition, the symbols in parentheses described in the claims and the means for solving the problems indicate a correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present invention. [Brief description of the drawings]

[0013] [Figure 1]FIG. 4 is a cross-sectional explanatory view of the internal combustion engine according to the first embodiment, which is a cross-sectional view taken along line II in FIG. [Diagram 2] FIG. 2 is an explanatory sectional view of the spark plug according to the first embodiment, taken along line II-II in FIG. [Diagram 3] FIG. 3 is a cross-sectional view of the spark plug taken along line III-III in FIG. [Figure 4] FIG. 11 is an explanatory cross-sectional view of the first embodiment in a state immediately before the plug cover is attached to the housing. [Diagram 5] FIG. 11 is an explanatory cross-sectional view of the first embodiment, showing a state immediately before a base end portion of the plug cover is crimped by a cover fixing portion of a housing. [Figure 6] FIG. 6 is a cross-sectional view of a spark plug according to a second embodiment. [Figure 7] FIG. 11 is a cross-sectional view of a spark plug according to a third embodiment. [Figure 8] FIG. 13 is a cross-sectional view of a spark plug according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] ( Reference form 1 ) Related to internal combustion engines reference The configuration will be described with reference to FIGS. An internal combustion engine 10 of this embodiment is an internal combustion engine having a spark plug 1, as shown in FIG.

[0015] The spark plug 1 has a cylindrical housing 2 and a plug cover 5. The plug cover 5 is provided at the tip of the housing 2 so as to cover a pre-combustion chamber 50 in which a discharge gap G is arranged. The plug cover 5 has a base end protruding portion 55 that protrudes outwardly at a base end. The housing 2 has a cover fixing portion 25 at its tip to fix the base end of the plug cover 5.

[0016] The cover fixing portion 25 has an abutment surface 26 against which the base end surface 56 of the plug cover 5 abuts, and a tip protruding portion 27 that covers the base end overhanging portion 55 from the outer circumferential side and the tip side. The cover fixing portion 25 is disposed on the base end side relative to the distal open end 811 of the spark plug hole 81 of the internal combustion engine 10 .

[0017] The spark plug 1 can be used as an ignition means in an internal combustion engine of an automobile, a cogeneration system, or the like. One end of the spark plug 1 in the plug axial direction Z is disposed in a main combustion chamber 101 of an internal combustion engine 10. In the plug axial direction Z, the side exposed to the main combustion chamber 101 is referred to as the tip side, and the opposite side is referred to as the base side. Also, the direction perpendicular to the central axis of the spark plug 1 (i.e., the plug central axis) is referred to as the plug radial direction. Also, the direction along the circumference centered on the plug central axis is referred to as the plug circumferential direction.

[0018] 1 and 2, the spark plug 1 has a cylindrical insulator 3 on the inner periphery side of a housing 2, and a center electrode 4 held on the inner periphery side of the insulator 3. The center electrode 4 protrudes from the insulator 3 toward the tip side. The spark plug 1 also has a ground electrode 6 that forms a discharge gap G between itself and the center electrode 4. One end of the ground electrode 6, which is a fixed end 61, is fixed to the tip portion of the housing 2 by welding or the like.

[0019] 1 to 3, the plug cover 5 has a plurality of injection holes 51. The plug cover 5 has a generally cup shape, and its open end side corresponds to the base end side in the plug axial direction Z. The plug cover 5 has a cylindrical peripheral wall portion 53 along the open end. A base end protruding portion 55 that protrudes outwardly is formed at the base end (i.e., the portion on the open end side) of the peripheral wall portion 53.

[0020] The base end protruding portion 55 is formed over the entire circumference of the base end portion of the plug cover 5. The cover fixing portion 25 is formed over the entire circumference of the tip end portion of the housing 2.

[0021] A base end side surface of the base end overhanging portion 55 forms part of a base end surface 56 of the plug cover 5. In this embodiment, the base end surface 56 of the plug cover 5 is a flat surface perpendicular to the plug axial direction Z. A tip side surface 552 of the base end overhanging portion 55 forms a tapered surface that tapers toward the tip side in the plug axial direction Z as it moves inward in the plug radial direction.

[0022] The cover fixing portion 25 of the housing 2 has an abutment surface 26 that abuts against the base end surface 56 of the plug cover 5. In this embodiment, the abutment surface 26 is a flat surface perpendicular to the plug axial direction Z. The tip protrusion 27 of the cover fixing portion 25 protrudes from the outer circumferential side of the abutment surface 26 toward the tip side in the plug axial direction Z. Both the abutment surface 26 and the tip protrusion 27 are formed over the entire circumferential direction of the plug.

[0023] Tip protrusion 27 is provided in a state of contact with outer peripheral surface 551 and tip side surface 552 of base end overhang 55. Tip protrusion 27 is bent with base end overhang 55 crimped from the outer peripheral side and the diagonal tip side.

[0024] The plug cover 5 has a larger linear expansion coefficient than the housing 2. In this embodiment, the plug cover 5 is made of nickel or an alloy mainly composed of nickel. The housing 2 is made of an alloy mainly composed of iron. More specifically, the plug cover 5 is made of, for example, a nickel alloy. The housing 2 is made of, for example, low carbon steel. The ground electrode 6 is made of, for example, a nickel alloy.

[0025] The housing 2 has an attachment thread portion 23 on its outer circumferential surface. The spark plug 1 is attached to the internal combustion engine 10 by screwing the attachment thread portion 23 into a female thread portion 82 formed in a plug hole 81 of the internal combustion engine 10, as shown in FIG.

[0026] Next, a method for manufacturing the spark plug 1 of this embodiment will be described. As shown in Fig. 4, a housing 2 is prepared with a cover fixing portion 25 at its tip before bending deformation. That is, at this stage, the tip protrusion 27 of the cover fixing portion 25 protrudes cylindrically parallel to the plug axial direction Z. In addition, a sub-assembly is prepared inside the housing 2, in which the center electrode 4, the insulator 3, and the ground electrode 6 are assembled. The fixed end 61 of the ground electrode 6 is joined to the tip of the housing 2 by laser welding or the like.

[0027] Next, the plug cover 5 is attached to the housing 2. That is, as shown in Fig. 4 and Fig. 5, the base end of the plug cover 5 is inserted into the inner periphery of the tip protruding portion 27 of the cover fixing portion 25 of the housing 2. Then, the base end surface 56 of the plug cover 5 is brought into contact with the contact surface 26 of the housing 2.

[0028] From this state, by bending the tip protruding portion 27 of the housing 2 inward, the base end of the plug cover 5 is crimped together with the base end overhanging portion 55, as shown in Figures 1 and 2. At this time, the base end surface 56 of the plug cover 5 is in pressure contact with the abutment surface 26 of the housing 2, and the tip protruding portion 27 of the housing 2 is in pressure contact with the outer circumferential surface 551 and the tip side surface 552 of the base end overhanging portion 55. This results in a state in which the cover fixing portion 25 of the housing 2 fixes the base end of the plug cover 5.

[0029] Note that, in order to further improve the fixed state between the housing 2 and the plug cover 5 from this state, welding such as laser welding may be performed. However, welding does not need to be performed along the entire circumference of the plug, and welding can be performed only at some locations, for example, welding can be performed at four locations at 90° intervals.

[0030] In this manner, the spark plug 1 shown in FIGS. 1 to 3 can be obtained. Then, by mounting the spark plug 1 in a plug hole 81 of an internal combustion engine 10 as shown in FIG. 1, the internal combustion engine 10 of this embodiment can be obtained.

[0031] When the spark plug 1 is attached to the plug hole 81, the mounting screw portion 23 provided on the outer peripheral surface of the housing 2 is screwed into the female screw portion 82 formed on the inner peripheral surface of the spark plug hole 81. Then, the cover fixing portion 25 of the spark plug 1 is arranged closer to the base end in the plug axial direction Z than the opening end of the plug hole 81 on the main combustion chamber 101 side, i.e., the leading opening end 811. More specifically, the leading-end side portion of the portions where the cover fixing portion 25 and the plug cover 5 are in pressure contact with each other is arranged closer to the base end than the leading opening end 811.

[0032] Next, the effects of this embodiment will be described. In the above-described internal combustion engine 10, the housing 2 has a cover fixing portion 25, and the cover fixing portion 25 has an abutment surface 26 and a tip protrusion 27. This allows the plug cover 5 to be fixed to the housing 2 without welding or the like over the entire circumference. This allows the productivity of the spark plug 1 to be improved.

[0033] That is, as described above, the plug cover 5 can be fixed to the housing 2 by bending the tip protrusion 27 and crimping the base end overhanging portion 55 of the plug cover 5. Therefore, the plug cover 5 can be fixed to the housing 2 without welding the entire circumference in the plug circumferential direction. As a result, the spark plug 1 can be manufactured with good productivity. Furthermore, the productivity of the internal combustion engine 10 can be improved.

[0034] Moreover, the cover fixing portion 25 is disposed closer to the base end than the tip opening end 811 of the spark plug hole 81 of the internal combustion engine 10. This makes it possible to suppress an excessive temperature rise in the cover fixing portion 25. This therefore makes it possible to suppress a decrease in the strength of the cover fixing portion 25. Furthermore, it makes it possible to suppress the occurrence of excessive thermal stress in the cover fixing portion 25. In particular, it makes it possible to suppress the tensile stress in the plug circumferential direction from acting excessively on the tip protruding portion 27. This therefore makes it possible to suppress a decrease in the strength of the tip protruding portion 27 of the housing 2 and ensure a stable fixed state.

[0035] The plug cover 5 has a linear expansion coefficient larger than that of the housing 2. The environment in which the spark plug 1 is used is a high-temperature environment, and both the plug cover 5 and the housing 2 thermally expand from their assembled states. Here, since the linear expansion coefficient of the plug cover 5 is larger than that of the housing 2, the plug cover 5 thermally expands more than the housing 2 when the spark plug 1 is used. As a result, the pressure contact force between the plug cover 5 and the housing 2 becomes stronger at the cover fixing portion 25. Therefore, the fitting strength between the plug cover 5 and the housing 2 can be made stronger during use than when assembled, and vibration resistance and the like can be improved. In addition, the heat dissipation of the plug cover 5 is improved, and therefore the temperature rise of the plug cover 5 during use of the spark plug 1 can be more easily suppressed.

[0036] Moreover, the base end overhang 55 is formed around the entire circumference of the base end of the plug cover 5. And the cover fixing portion 25 is formed around the entire circumference of the tip end of the housing 2. This makes it possible to improve the fitting strength between the housing 2 and the plug cover 5 and further improve the heat dissipation properties of the plug cover 5. Also, it is possible to eliminate the need for circumferential alignment of the plug when assembling the plug cover 5 to the housing 2. This makes it even easier to manufacture the spark plug 1.

[0037] As described above, according to the present embodiment, it is possible to provide an internal combustion engine and a spark plug that can improve productivity while ensuring a stable fixed state between the housing and the plug cover.

[0038] (Embodiment 2) In this embodiment, as shown in FIG. 6, the contact surface 26 of the cover fixing portion 25 and the base end surface 56 of the plug cover 5 are inclined surfaces. That is, the abutment surface 26 and the base end surface 56 are inclined toward the tip side in the plug axial direction Z as they move toward the inside in the plug radial direction.

[0039] The inclination angle of the abutment surface 26 and the base end surface 56 with respect to the plug axial direction Z may be, for example, about 50 to 70°. Others: Reference form 1 In addition, among the symbols used in the second and subsequent embodiments, the symbols already mentioned Form The same symbols as those used in Form It represents the same components as those in.

[0040] In this embodiment, when the cover fixing portion 25 of the housing 2 crimps the base end protruding portion 55 of the plug cover 5, the direction of the force acting from the tip protruding portion 27 to the base end protruding portion 55 can be easily brought closer to the normal direction of the abutment surface 26. This can improve the fixing strength of the plug cover 5 by the cover fixing portion 25.

[0041] In addition, since the pressing force between the abutment surface 26 and the base end surface 56 tends to be high, the thermal resistance between the plug cover 5 and the housing 2 can be reduced. As a result, the temperature rise of the plug cover 5 can be suppressed. In addition, since the areas of the abutment surface 26 and the base end surface 56 tend to be large, the heat dissipation properties of the plug cover 5 can be improved from this viewpoint as well. others, Reference form 1 It has the same effect as above.

[0042] ( Reference form 3 ) In this embodiment, as shown in FIG. 7, a discharge gap G is provided between the center electrode 4 and the plug cover 5. That is, in this embodiment, the spark plug 1 does not have a ground electrode that is a separate member from the plug cover 5. However, by bringing the tip of the center electrode 4 close to a part of the plug cover 5, a discharge gap G is formed between the part of the plug cover 5 and the tip of the center electrode 4. The part of the plug cover 5 functions as the ground electrode 6.

[0043] In this embodiment, the tip end portion of the center electrode 4 is disposed to face the inner surface of the bottom wall portion 52 of the plug cover 5 . Others: Reference form 1is the same as:

[0044] In the case of this embodiment, since there is no need to provide the ground electrode 6 as a separate member, it is possible to reduce the number of parts and the number of assembly steps. others, Reference form 1 It has the same effect as above.

[0045] ( Reference form 4 ) In this embodiment, a discharge gap G is also provided between the center electrode 4 and the plug cover 5, as shown in FIG. In this embodiment, a raised portion 54 is provided by raising a part of the plug cover 5 toward the auxiliary combustion chamber 50. The raised portion 54 rises from the bottom wall portion 52 of the plug cover 5 toward the base end side in the plug axial direction Z. The tip end of the center electrode 4 faces the base end of the raised portion 54. A discharge gap G is formed between the tip end of the center electrode 4 and the base end of the raised portion 54. In this embodiment, the raised portion 54 functions as the ground electrode 6. Others: Reference form 3 is the same as:

[0046] In the present embodiment, the discharge gap G can be separated from the bottom wall portion 52, so that, from the viewpoint of ignition performance, Reference form 3 is more advantageous than others, Reference form 3 It has the same effect as above.

[0047] In the above embodiment, the base end overhanging portion 55 is formed around the entire circumference of the base end of the plug cover 5, and the cover fixing portion 25 is formed around the entire circumference of the front end of the housing 2. However, the base end overhanging portion may be formed only on a portion of the base end of the plug cover in the circumferential direction of the plug. In this case, the base end overhanging portions are provided at a plurality of locations (preferably three or more locations) in the circumferential direction of the plug. The cover fixing portion may be formed only on a portion of the front end of the housing in the circumferential direction of the plug. In this case, the cover fixing portion is provided at a plurality of locations (preferably three or more locations) in the circumferential direction of the plug.

[0048] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the gist of the present invention. [Explanation of symbols]

[0049] 1...spark plug, 10...internal combustion engine, 2...housing, 25...cover fixing portion, 26...contact surface, 27...tip protruding portion, 5...plug cover, 50...auxiliary combustion chamber, 55...base end protruding portion, 56...base end surface, G...discharge gap, 81...spark plug hole, 811...tip opening end

Claims

1. An internal combustion engine (10) having a spark plug (1), The above spark plugs are A cylindrical housing (2); a plug cover (5) provided at the tip of the housing so as to cover a sub-combustion chamber (50) in which a discharge gap (G) is arranged; The plug cover has a base end protruding portion (55) protruding outwardly from a base end thereof, The housing has a cover fixing portion (25) at a tip portion for fixing a base end portion of the plug cover, the cover fixing portion has an abutment surface (26) against which the base end surface (56) of the plug cover abuts, and a tip protruding portion (27) that covers the base end protruding portion from the outer circumferential side and the tip side, the cover fixing portion is disposed on the base end side relative to a tip opening end (811) of a spark plug hole (81) of the internal combustion engine, the contact surface of the cover fixing portion and the base end surface of the plug cover are inclined so as to move inward in the plug radial direction and toward the tip side in the plug axial direction (Z).

2. 2. The internal combustion engine according to claim 1, wherein the base end projection is formed around the entire circumference of the base end of the plug cover, and the cover fixing portion is formed around the entire circumference of the tip end of the housing.

3. 3. The internal combustion engine according to claim 1, wherein the plug cover has a linear expansion coefficient greater than that of the housing.

4. A cylindrical housing (2); a plug cover (5) provided at the tip of the housing so as to cover a sub-combustion chamber (50) in which a discharge gap (G) is arranged, The plug cover has a base end protruding portion (55) protruding outwardly from a base end thereof, The housing has a cover fixing portion (25) at a tip portion for fixing a base end portion of the plug cover, the cover fixing portion has an abutment surface (26) against which the base end surface (56) of the plug cover abuts, and a tip protruding portion (27) that covers the base end protruding portion from the outer circumferential side and the tip side, the contact surface of the cover fixing portion and the base end surface of the plug cover are inclined toward the tip side in the plug axial direction (Z) as they extend inward in the plug radial direction.

5. 5. The spark plug according to claim 4, wherein the base end overhanging portion is formed around the entire periphery of the base end portion of the plug cover, and the cover fixing portion is formed around the entire periphery of the tip end portion of the housing.

6. 6. The spark plug according to claim 4, wherein the plug cover has a linear expansion coefficient greater than that of the housing.

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