Seal member, and plug tube seal structure for engine

A seal member (3) is disposed between a cylinder head cover (1) in which an ignition plug mounting hole (1a) is formed and a plug tube (2) which is inserted in the ignition plug mounting hole (1a). The seal member (3) is provided with: a base section (31) configured to be elastically deformable and inserted into the ignition plug mounting hole (1a); a protrusion section (32) formed so as to protrude outward in the radial direction from the outer peripheral surface of the base section (31) and engaging with a groove (12b) formed in the inner peripheral surface of the ignition plug mounting hole (1a); a seal lip section (33) in elastic contact with the outer peripheral surface of the plug tube (2); and a grip section (34) formed between the base section (31) and the seal lip section (33) and protruding downward from the ignition plug mounting hole (1a).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage entry of International Application No. PCT/JP2012/058885, filed Apr. 2, 2012, which claims priority to Japanese Application No. 2011-084156, filed Apr. 6, 2011. The disclosures of the prior applications are hereby incorporated in their entirety by reference.

TECHNICAL FIELD

The present invention relates to a seal member, and a plug tube seal structure for an engine.

BACKGROUND ART

Conventionally, a cylinder head cover is provided with a spark plug fitting hole for inserting a plug tube in which a spark plug is housed. Further, a seal member is arranged between the inner circumferential surface of the spark plug fitting hole and the outer circumferential surface of the plug tube, wherein sealing with airtightness and liquid tightness is made between the cylinder head cover and the plug tube.

For example, Patent Document 1 discloses an invention wherein there are provided a cylinder head cover having a flange portion protruding from the lower part of the inner circumferential surface of a spark plug fitting hole inward along the axial direction, a plug tube inserted in the spark plug fitting hole, and an annular seal member disposed between the cylinder head cover and the plug tube, pressure fitted inside the spark plug fitting hole, and supported by and in contact with the upper surface of the flange portion.

BACKGROUND ART DOCUMENT

Patent Document

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

However, by the invention disclosed in Patent Document 1, as the seal member is pressure-fitted in the spark plug hole, in removing the seal member from the cylinder head cover, it is necessary to forcibly remove the seal member from the cylinder head cover, using a tool, which requires a lot of work for removing the seal member.

The present invention has been developed in this point of view, and an object of the invention is to provide a seal member and a plug tube seal structure for an engine, which improve the work efficiency in removing the seal member.

Means for Solving the Problem

In order to solve the above-described problems, according to the invention, provided is a seal member that is elastically deformable, fitted to a fitting hole formed through a base member, and disposed between a cylindrical member inserted in the fitting hole and the base member, the seal member including: a base portion inserted in the fitting hole; a first engaging portion that is formed protruding outward in a radial direction from an outer circumferential surface of the base portion and engages with a first engaged portion formed on an inner circumferential surface of the fitting hole; a seal lip portion that elastically contacts an outer circumferential surface of the cylindrical member; and a handling portion formed between the base portion and the seal lip portion, protruding from one end side of the fitting hole.

According to the present invention, the elastically deformable seal member has a handling portion protruding from one end side of the fitting hole, and thereby, when the handling portion is pressed toward the other end side of the fitting hole, the handling portion elastically deforms such as to shrink inward in the radial direction, the engagement state between the first engaging portion and the first engaged portion of the base member is released, and it is thereby possible to easily remove off the seal member from the base member without using a tool. Accordingly, the work efficiency during removing the seal member is improved.

Further, the handling portion is preferably formed with a higher rigidity than a rigidity of the seal lip portion.

By this arrangement, as the handling portion is formed with a higher rigidity than a rigidity of the seal lip portion, a worker is prevented from making a mistake trying to carry out removing work by pressing the seal lip portion with a low rigidity, and it is thus possible to carry out a removing work by surely pressing the handling portion formed continuously from the base portion. Accordingly, as the handling portion is easy to elastically deform inward in the radial direction if the worker presses the handling portion toward the other end side of the spark plug fitting hole, removing work and attaching work of the seal member can be easily carried out, and the seal member is prevented from being damaged during a work.

Further, as the support force for supporting the seal lip portion is increased by forming the handling portion with a higher rigidity than the rigidity of the seal lip portion, a sufficient pressure is applied by the seal lip portion to the cylindrical member, and sealing with airtightness and liquid tightness is ensured between the seal member and the cylindrical member.

Still further, arrangement is preferably made such that the seal member further includes a second engaging portion provided being recessed at a part of the outer circumferential surface of the base portion, the part being close to the handling portion, the second engaging portion having an outer circumferential diameter smaller than outer circumferential diameters of the first engaging portion and the handling portion, wherein the second engaging portion engages with a second engaged portion formed protruding inward in the radial direction from the inner circumferential surface of the fitting hole.

By this arrangement, in addition to the engagement between the first engaging portion of the seal member and the first engaged portion of the base member, the second engaging portion of the seal member and the second engaged portion of the base member engage with each other. Accordingly, the holding force (fixing force) holding the seal member at the base member can be further improved. Further, as the seal member is ensured to be held at the base member by further improvement in the holding force, it is further prevented that foreign matters, oil, and moisture enter between the seal member and the base member, and sealing failure caused by entrance of foreign matters and the like can be prevented.

The outer circumferential diameter of the second engaging portion is smaller than the outer circumferential diameters of the first engaging portion and the handling portion, and the second engaging portion is formed by recessing a part of the base portion, the part being close to the handling portion, and a part with a thin thickness is thus provided in the vicinity of the handling portion. Thus, even if a force pressing the handling portion is comparatively weak, the handling portion can be elastically deformed, and the work efficiency in removing the seal member is further improved.

Further, in order to solve the above-described problems, according to the invention, provided is a plug tube seal structure for an engine, including: a cylinder head cover that is attached to an upper portion of a cylinder head and provided with a spark plug fitting hole; a plug tube that is inserted in the spark plug fitting hole and houses a spark plug therein; and an elastically deformable seal member that is fitted to the spark plug fitting hole and disposed between the cylinder head cover and the plug tube, wherein the cylinder head cover includes: a first engaged portion provided being recessed on an inner circumferential surface of the spark plug fitting hole; and a second engaged portion that is formed protruding inward in a radial direction from the inner circumferential surface of the spark plug fitting hole, and has an inner circumferential diameter smaller than an inner circumferential diameter of the first engaged portion, wherein the seal member includes: a base portion inserted in the spark plug fitting hole; a first engaging portion that is formed protruding outward in a radial direction from an outer circumferential surface of the base portion, and engages with the first engaged portion; a seal lip portion that elastically contacts with an outer circumferential surface of the plug tube; a handling portion that is formed between the base portion and the seal lip portion, protruding downward from the spark plug fitting hole, and formed with a higher rigidity than a rigidity of the seal lip portion; and a second engaging portion that is provided being recessed at a part of the outer circumferential surface of the base portion, the part being close to the handling portion, has an outer circumferential diameter smaller than outer circumferential diameters of the first engaging portion and the handling portion, and engages with the second engaged portion.

According to the present invention, the elastically deformable seal member has a handling portion protruding downward from the spark plug fitting hole, and thereby, when the handling portion is pressed toward the upper side of the spark plug fitting hole, the handling portion elastically deforms such as to shrink inward in the radial direction, the engagement state between the first engaging portion and the first engaged portion of the cylinder head cover is released, and it is thereby possible to easily remove off the seal member from the cylinder head cover without using a tool. Accordingly, the work efficiency during removing the seal member is improved.

Still further, arrangement is preferably made such that the plug tube seal structure for an engine further includes: a cap member that contacts with an upper surface of the seal member, wherein the cylinder head cover further includes a third engaged portion formed at an upper marginal portion of the spark plug fitting hole and engaged by the cap member, and wherein the seal member is held being sandwiched and pressed between the cap member and the second engaged portion.

By providing the cap member in contact with the upper surface of the seal member, it is possible to inhibit foreign matters, oil, and moisture from entering the seal member from the upper side of the spark plug fitting hole, and sealing failure caused by entrance of foreign matters and the like can be reduced.

Further, as the seal member engages with the third engaged portion of the cylinder head cover and is pressure-sandwiched and held between the cap member and the second engaged portion of the cylinder head cover, the seal member is ensured to be held at the cylinder head cover, and sealing failure of the seal member during assembling can be reduced.

Yet further, arrangement is preferably made such that the cap member is an annular member formed with a higher rigidity than a rigidity of the seal member, and includes: a flange portion that is formed protruding outward in a radial direction from an outer circumferential surface of the cap member and is formed with an outer circumferential diameter larger than an inner circumferential diameter of the spark plug fitting hole; and a third engaging portion that engages with the third engaged portion, wherein the third engaging portion is formed by at least two extending portions that are extending outward in a radial direction from an outer circumferential surface of the flange portion and are provided at an interval therebetween along a circumferential direction of the flange portion, wherein the third engaged portion includes: an annular support surface that is extending along the upper marginal portion of the spark plug fitting hole and supports the extending portion from an under side; a circumferential wall portion formed extending upward from an outer circumferential end of the support surface; and at least two protruding portions provided protruding inward in a radial direction from an upper end of the circumferential wall portion, with an interval therebetween along a circumferential direction of the circumferential wall portion, and wherein the extending portions can be inserted between the support surface and the protruding portions.

By this arrangement, in attaching the cap member to the cylinder head cover, the extending portions are set to positions where the protruding portions are not present and made in contact with the support surface, and thereafter the cap member is rotated. Then, as the cap member can be attached to the cylinder head cover by inserting the extending portions between the support surface and the protruding portions, the work efficiency in attaching the cap member is improved.

On the other hand, in detaching the cap member from the cylinder head cover, the cap member can be detached from the cylinder head cover by lifting the cap member after rotating the cap member such as to move the extending portions to positions where the protruding portions are not present (positions between neighboring protruding portions), and the work efficiency in removing the cap member can thereby be improved. That is, as detaching and attaching work of the cap member can be carried out without using a tool, the maintainability is improved.

Further, arrangement is preferably made such that the cap member is an annular member formed with a higher rigidity than a rigidity of the seal member, and includes: a flange portion that is formed protruding outward in a radial direction from an outer circumferential surface of the cap member and is formed with an outer circumferential diameter larger than an inner circumferential diameter of the spark plug fitting hole; and a third engaging portion that engages with the third engaged portion, wherein the third engaging portion includes: at least two extending portions that are extending outward in a radial direction from an outer circumferential surface of the flange portion and are provided with an interval therebetween along a circumferential direction of the flange portion; and opening portions formed at the respective extending portions, wherein the third engaged portion is formed by at least two protruding portions provided protruding upward from an upper marginal portion of the spark plug fitting hole, with an interval therebetween along a circumferential direction of the spark plug fitting hole, and wherein the opening portions are arranged such as to enable insertion of the protruding portions.

By this arrangement, in attaching the cap member to the cylinder head cover, as the cap member can be attached to the cylinder head cover by inserting the protruding portions into the opening portions of the cap member, the work efficiency in attaching the cap member is improved.

On the other hand, in detaching the cap member from the cylinder head cover, the protruding portions are detached from the opening portions by lifting the cap member, and the cap member can be thus detached from the cylinder head cover. Accordingly, the work efficiency in removing the cap member is improved.

That is, as detaching and attaching work of the cap member can be carried out without using a tool, the maintainability is improved.

Still further, arrangement is preferably made such that the seal member further includes a cap seal portion formed protruding upward from an upper end of the base portion, wherein a lower surface of the flange portion is provided with a groove portion in a recessed shape opening downward in which the cap seal portion is inserted, and wherein the cap member is fixed to the cylinder head cover in a state that the cap seal portion is elastically deformed such as to be vertically shrunk.

By this arrangement, the cap seal portion of the seal member is inserted in the groove portion of the cap member in a state of elastic deformation such as to shrink in the vertical direction, and thereby sealing with airtightness and liquid tightness is made between the seal member and the cap member. Consequently, it is possible to prevent foreign matters, oil, and moisture from entering between the seal member and the cap member, and sealing failure caused by entrance of foreign matters and the like can be prevented.

Advantage of the Invention

According to the present invention, it is possible to provide a seal member and a plug tube seal structure for an engine, which improve the work efficiency in removing the seal member.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below in detail, referring to the drawings. In the description, the same symbols will be assigned to the respective same element, and overlapping description will be omitted.

FIG. 1is a vertical cross-sectional view of a plug tube seal structure for an engine of a vehicle, in an embodiment of the present invention.FIG. 2Ais a vertical cross-sectional view of a cap member4,FIG. 2Bis a vertical cross-sectional view of a seal member3, andFIG. 3Cis a vertical cross-sectional view of a cylinder head cover1.

As shown inFIG. 1, the cylinder head cover1, which is a part of an engine, is provided with a spark plug fitting hole1athat is in a circular shape penetrating in the vertical direction (plate thickness direction), wherein a plug tube2is inserted inside the spark plug fitting hole1a. The seal member3is disposed between the cylinder head cover1and the plug tube2, along the entire circumference of the spark plug fitting hole1a, and the cap member4is disposed on the upper side of the seal member3.

The cylinder head cover1as a base member is made from a synthetic resin and is attached to the top of a cylinder head, not shown. As shown inFIG. 1andFIG. 2C, the upper wall11of the cylinder head cover1is provided with an opening portion11ain a circular shape that is vertically (along axial direction) penetrating, and the lower marginal portion of the opening portion11ais provided with a cylindrical fitting wall12extending downward by a certain length. The fitting wall12has a circular hole portion12aformed continuously from the opening portion11a. In the present embodiment, the spark plug fitting hole1ais formed by the opening portion11aof the upper wall11and the hole portion12aof the fitting wall12. Incidentally, a cylinder head cover1made from metal may be used.

A groove portion12bis formed on the upper part of the inner circumferential surface of the fitting wall12, being annularly recessed. A protruding portion12cprotruding inward in the radial direction by a certain length is formed on the lower part of the inner circumferential surface (in more detail, the inner circumferential surface on the lower side of the fitting wall12) of the fitting wall12.

The upper wall11of the cylinder head cover1is provided with a fastening portion13extending upward by a certain length, and the fastening portion13is formed continuously from a part of the outer circumferential surface of the fitting wall12. The fastening portion13is provided with a bolt insertion hole13afor insertion of a bolt B, and a nut N screw engaging with the bolt B is fixed to the inside of the bolt insertion hole13a.

FIG. 3is an exploded perspective view of the cylinder head cover1, the seal member3, and the cap member4.FIGS. 4A and 4Billustrate the cylinder head cover1, the seal member3, and the cap member4, whereinFIG. 4Ais a partial enlarged perspective view showing a state that the cap member4is detached, and diagram4B is a partial enlarged perspective view showing a state that the cap member4is attached.

As shown inFIG. 3andFIGS. 4A and 4B, the upper marginal portion of the of the spark plug fitting hole1ais provided with a support surface14, a circumferential wall portion15, and plural (two) protruding portions16,16.

The support surface14is an annular horizontal surface that supports the extending portion43of the later-described cap member4from the lower side in contact. The support surface14is extending along the upper marginal portion of the spark plug fitting hole1a.

The circumferential wall portion15is a cylindrical wall portion formed extending upward from the outer circumferential end of the support surface14by a certain length. The circumferential wall portion15is provided standing from the support surface14such as to surround the upper marginal portion of the spark plug fitting hole1a.

The protruding portions16,16are protruding inward in the radial direction by a certain length from the upper part of the inner circumferential surface of the circumferential wall portion15, and are provided with an equal interval along the circumferential direction of the circumferential wall portion15. The protruding portions16are formed in a curved surface shape (arc shape) with a substantially same curvature as that of the circumferential wall portion15.

In the present embodiment, the groove portion12bcorresponds to ‘a first engaged portion’ described in a claim; the protruding portion12ccorresponds to ‘a second engaged portion’ described in a claim; and the support surface14, the circumferential wall portion15, and the protruding portions16correspond to ‘a third engaged portion’ described in a claim.

Returning toFIG. 1, the plug tube2is a metal member in a cylindrical shape and is used, being appropriately selected from known plug tubes to be used. The upper portion (one end) of the plug tube2as a cylindrical member is inserted in the spark plug fitting hole1a, and the lower portion (the other end) is fixed to a cylinder head, not shown. The upper portion of the plug tube2is fixed to the cylinder head cover1through the seal member3. A part of a plug top coil21is attachably/detachably housed inside the upper side of the plug tube2, and a spark plug, not shown, is attachably/detachably housed inside the lower side.

The plug top coil21has an axial portion21ainserted inside the plug tube2, a main body portion21bformed with a larger diameter on the top of the axial portion21a, and a flange portion21cprotruding outward in the radial direction by a certain length from the outer circumferential surface of the main body portion21b. The lower surface of the main body portion21bis provided with an annular groove portion21d. The flange portion21cis provided with a bolt insertion hole21eto insert the bolt B. The plug top coil21is fixed to the upper surface of the cylinder head cover1by the bolt B inserted in the bolt insertion hole21eand the bolt insertion hole13a.

As shown inFIG. 1andFIG. 2B, the seal member3is formed substantially in a cylindrical shape with openings at the upper and lower surfaces, and is formed from a material (for example, rubber) that is elastically deformable. As shown inFIG. 1, the seal member3is sandwiched between the inner circumferential surface of the spark plug fitting hole1aand the outer circumferential surface of the plug tube2, and is used to make sealing with airtightness and liquid tightness between the cylinder head cover1and the plug tube2. The seal member3has a base portion31, a protruding portion32, a seal lip portion33, a handling portion34, a groove portion35, and a cap seal portion36(seeFIG. 2B.

The base portion31is an annular part inserted in the spark plug fitting hole1a. The base portion31is extending along the vertical direction.

The protruding portion32is a part that engages with (fits to) the groove portion12b. The protruding portion32is formed, protruding outward by a certain length in the radial direction from the outer circumferential surface of the upper portion of the base portion31.

The seal lip portion33is a part that is in elastic contact (press-contact) with the outer circumferential surface of the plug tube2to make sealing with airtightness and liquid tightness between the seal member3and the plug tube2. The seal lip portion33is extended inward in the radial direction from the lower end of the handling portion34, and has a bent portion33abent such as to be convex downward, and a seal portion33bextending upward from the end portion of the radially inner side of the bent portion33a.

The seal portion33bis a part that is distant inward in the radial direction by a certain length from the handling portion34, and is an annular part through which the plug tube2is inserted. The seal portion33bis, as shown inFIG. 2B, formed such that the thickness gradually becomes larger from the lower side to the upper side. The inner circumferential surface of the seal portion33bis provided with a tapered surface33cwhose diameter gradually becomes smaller from the lower side to the upper side. The upper end of the seal portion33bis a free end, as shown inFIG. 1, and the inner circumferential surface on the upper end side is in elastic contact with the outer circumferential surface of the plug tube2. In the present embodiment, as the seal portion33bpresses the plug tube2by the urging force (elasticity) of the bent portion33a, a sufficient pressure is applied to the plug tube2, and sealing with airtightness and liquid tightness is ensured between the seal member3and the plug tube2.

The handling portion34is a part that a worker presses in detaching/attaching the seal member3from/to the cylinder head cover1. The handling portion34is formed between the base portion31and the seal lip portion33, and is in a state of being protruding (exposed) downward from the spark plug fitting hole1a. The handling portion34is formed such as to be thicker than the seal lip portion33, and has a higher rigidity than the seal lip portion33. The outer circumferential surface of the handling portion34is, as shown inFIG. 2B, provided with a tapered surface34awhose diameter gradually becomes smaller from the upper side to the lower side. Thus, oil or moisture deposited on the handling portion34comes to easily fall by the own weight along the tapered surface34a, and deterioration of the seal member3caused by deposition of oil or the like can be reduced.

Returning toFIG. 1, the groove portion35is an annular part that engages with (fits to) the protruding portion12cof the cylinder head cover1. The groove portion35is recessed, adjacent to the handling portion34, on the outer circumferential surface of the base portion31. The minimum outer circumferential diameter of the groove portion35is smaller than the maximum outer circumferential diameters of the protruding portion32and the handling portion34.

The cap seal portion36is an annular part that is in elastic contact (press contact) with the lower surface of the cap member4. The cap seal portion36is formed, protruding upward by a certain length from the upper end of the base portion31, as shown inFIG. 2B. The cap seal portion36is elastically deformed such as to vertically shrink in a state that the cap member4is fixed to the cylinder head cover1, as shown inFIG. 1. Thus, sealing with airtightness and liquid tightness is done between the seal member3and the cap member4.

In the present embodiment, the protruding portion32corresponds to ‘a first engaging portion’ described in a claim, and the groove portion35corresponds to ‘a second engaging portion’ described in a claim.

The cap member4is a part that restricts vertical relative movement of the seal member3to prevent the seal member3from getting off from the upper side of the spark plug fitting hole1a. The cap member4is in contact with the upper surface of the seal member3, and is formed by a material (for example, a metal or a synthetic resin) with a higher rigidity than that of the material of the seal member3. The cap member4is arranged to be attachable and detachable to/from the cylinder head cover1.

The cap member4has, as shown inFIG. 4A, a circumferential wall portion41, a flange portion42, and plural (two) extending portions43,43.

The circumferential wall portion41is an annular wall portion extending along the vertical direction. The circumferential wall portion41is, as shown inFIG. 1, inserted in (fitting-engaged with) the groove portion21dof the plug top coil21, and is thus connected to the plug top coil21.

As shown inFIG. 4A, the flange portion42is an annular portion formed protruding outward in the radial direction by a certain length from the outer circumferential surface of the lower portion of the circumferential wall portion41. The outer circumferential diameter of the flange portion42is, as shown inFIG. 1, formed slightly larger than the inner circumferential diameter of the spark plug fitting hole1a. The lower surface of the flange portion42is provided with an annular groove portion42arecessed such as to be open downward, and the cap seal portion36of the seal member3is inserted in the groove portion42a.

The extending portions43are parts that are inserted between the support surface14and the protruding portions16of the cylinder head cover1. The extending portions43are formed protruding outward in the radial direction by a certain length from the outer circumferential surface of the flange portion42, as shown inFIG. 4A, and are provided with an equal interval therebetween along the circumferential direction of the flange portion42. The extending portion43is formed in a curved surface shape (arc shape) with a curvature substantially the same as those of the circumferential wall portion15and the protruding portions16. The length of the extending portions43along the circumferential direction is formed to be smaller than the intervals between the neighboring protruding portions16,16, and to be substantially the same as the length of the protruding portions16along the circumferential direction.

Incidentally, the numbers of the extending portions43and the protruding portions16are not limited as long as being two at least. In the present embodiment, the extending portions43correspond to ‘a third engaging portion’ described in a claim.

The central portion of the cap member4is provided with an insertion hole4athat is in a circular shape and is vertically penetrating. A part of the plug top coil21is inserted in the insertion hole4a, as shown inFIG. 1, such as to fill in the insertion hole4a. Thus, it is prevented that foreign matters or the like enter the seal member3from the insertion hole4aof the cap member4. The inner circumferential diameter of the insertion hole4ais formed smaller than the inner circumferential diameter of the spark plug fitting hole1a.

Incidentally, in the present embodiment, the groove portion35engages with the protruding portion12c; the cap member4is in contact with the upper surface of the seal member3; and the plug top coil21connected with the cap member4is fastened to the cylinder head cover1by the bolt B. Thereby, a sandwich-pressure holding structure for the seal member3can be obtained wherein the seal member3is held between the cap member4and the protruding portion12cby a sandwiching pressure.

A plug tube seal structure for an engine in an embodiment according to the present invention is arranged basically as described above. In the following, detaching work and attaching work of the seal member3will be described, referring toFIGS. 5A to 5C, as appropriate.

Incidentally,FIGS. 5A to 5Care vertical cross-sectional views for illustrating a process of removing the seal member3.

Before detaching the seal member3from the cylinder head cover1, as shown inFIGS. 5A and 5B, the bolt B is detached, the plug top coil21is thus detached from the cylinder head cover1in advance, and the cap member4is detached in advance. Further, the cylinder head cover1is detached from the cylinder head in advance.

Then, as shown inFIG. 5B, the handling portion34of the seal member3is pressed upward in the axial direction.

Herein, the handling portion34is elastically deformed such as to shrink inward in the radial direction so that the protruding portion32is detached from the groove portion12bof the cylinder head cover1, and the protruding portion12cof the cylinder head cover1is detached from the groove portion35. That is, the engagement state between the seal member3and the cylinder head cover1is released.

Subsequently, as shown inFIGS. 5B and 5C, the handling portion34is further pressed upward in the axial direction so that the seal member3is thereby moved to the upper side and thus the seal member3is detached from the cylinder head cover1.

Incidentally, if a structure is arranged such that the seal member3is detached from the upper side of the spark plug fitting hole1ain a state that the cylinder head cover1is attached to the cylinder head, in case that moisture or mud is deposited on the upper surface of the cylinder head cover1, moisture or the like may enter the inside of the engine during the work of detaching the seal member3. In this situation, in the present embodiment, a structure has been arranged as follows. That is, by making the handling portion34of the seal member3protrude from the lower side of the spark plug fitting hole1a, it is made impossible to press the handling portion34and detach the seal member3unless the cylinder head cover1is detached from the cylinder head. Thus, in detaching the seal member3, as the cylinder head cover1has been detached from the cylinder head without fail, it is possible to prevent that moisture or the like deposited on the upper surface of the cylinder head cover1enters the inside of an engine.

In the following, attaching work and detaching work of the cap member4will be described, referring toFIGS. 4A and 4B, as appropriate.

For attaching the cap member4to the cylinder head cover1, the seal member3is to have been attached in advance to the cylinder head cover1, as shown inFIG. 4A.

Then, the extending portions43are set to respective positions where the protruding portions16are not present, and made contact with the support surface14(seeFIGS. 4A and 4B).

Subsequently, when the cap member4is rotated and the extending portions43are thus inserted between the support surface14and the protruding portions16, the cap member4is attached to the cylinder head cover1.

Incidentally, after attaching the seal member3and the cap member4to the cylinder head cover1, the cylinder head cover1is attached to the cylinder head. At this moment, the upper side of the plug tube2attached to the cylinder head is inserted into the seal member3(seal lip portion33) (seeFIG. 1). Further, the axial portion21aof the plug top coil21is inserted into the insertion hole4aand the plug tube2from the upper side of the cap member4, and then the flange portion21cof the plug top coil21is fixed to the cylinder head cover1by the bolt B.

On the other hand, in detaching the cap member4from the cylinder head cover1, the cap member4is rotated such that the extending portions43moves to respective positions where the protruding portions16are not present (seeFIGS. 4A and 4B).

Then, when the cap member4is lifted up, the cap member4is detached from the cylinder head cover1.

By the plug tube seal structure for an engine in the present embodiment described above, as the elastically deformable seal member3has the handling portion34protruding downward from the spark plug fitting hole1a, when the handling portion34is pressed upward in the axial direction (toward the upper side of the spark plug fitting hole1a), the handling portion34is elastically deformed such as to shrink inward in the radial direction; the engagement state between the protruding portion32and the groove portion12bof the cylinder head cover1can be released; and the engagement state between the groove portion35and the protruding portion12cof the cylinder head cover1can be released. Accordingly, the seal member3can be easily removed off from the cylinder head cover1without using a tool.

Consequently, the work efficiency in removing the seal member3is improved.

Further, as the handling portion34is formed with a higher rigidity than the rigidity of the seal lip portion33, a worker is prevented from making a mistake trying to carry out removing work by pressing the seal lip portion33with a low rigidity, and it is thus possible to carry out a removing work by surely pressing the handling portion34formed continuously from the base portion31. Accordingly, as the handling portion34is easy to elastically deform inward in the radial direction if the worker presses the handling portion34upward in the axial direction, removing work and attaching work of the seal member3can be easily carried out, and the seal member3is prevented from being damaged during a work.

Further, as the support force for supporting the seal lip portion33is increased by forming the handling portion34with a higher rigidity than the seal lip portion33, a sufficient pressure is applied by the seal lip portion33to the plug tube2, and sealing with airtightness and liquid tightness is ensured between the seal member3and the plug tube2.

The outer circumferential diameter of the groove portion35is smaller than the outer circumferential diameters of the protruding portion32and the handling portion34, the groove portion35is formed by recessing a part of the base portion31, the part being close to the handling portion34, and a part with a thin thickness is thus provided in the vicinity of the handling portion34. Thus, even if a force pressing the handling portion34is comparatively weak, the handling portion34can be elastically deformed, and the work efficiency in removing the seal member3is further improved.

Still further, in addition to the engagement between the protruding portion32of the seal member3and the groove portion12bof the cylinder head cover1, the groove portion35of the seal member3and the protruding portion12cof the cylinder head cover1engage with each other. Accordingly, the holding force (fixing force) holding the seal member3at the cylinder head cover1can be further improved. Further, as the seal member3can be surely held at the cylinder head cover1by further improvement in the holding force, it is further prevented that foreign matters, oil, and moisture enter between the seal member3and the cylinder head cover1, and sealing failure caused by entrance of foreign matters and the like can be prevented.

Still further, by providing the cap member4in contact with the upper surface of the seal member3and providing the plug top coil21such as to fill in the insertion hole4aof the cap member4, it is possible to prevent foreign matters, oil, and moisture from entering the seal member3from the upper side of the spark plug fitting hole1a, and sealing failure caused by entrance of foreign matters and the like can be prevented.

Yet further, the cap seal portion36of the seal member3is inserted in the groove portion42aof the cap member4in a state of shrinking in the vertical direction, and thereby sealing with airtightness and liquid tightness is made between the seal member3and the cap member4. Consequently, it is possible to prevent foreign matters, oil, and moisture from entering between the seal member3and the cap member4, and sealing failure caused by entrance of foreign matters and the like can be prevented.

Further, as the seal member3is sandwiched and held between the cap member4and the protruding portion12cof the cylinder head cover1, the seal member3can be surely held at the cylinder head cover1, and sealing failure of the seal member3during assembling can be reduced.

Still further, in attaching the cap member4to the cylinder head cover1, the extending portions43are set to positions where the protruding portions16are not present and made in contact with the support surface14, and thereafter the cap member4is rotated. Then, as the cap member4can be attached to the cylinder head cover1by inserting the extending portions43between the support surface14and the protruding portions16, the work efficiency in attaching the cap member4is improved.

On the other hand, in detaching the cap member4from the cylinder head cover1, the cap member4can be detached from the cylinder head cover1by lifting the cap member4after rotating the cap member4such as to move the extending portions43to positions where the protruding portions16are not present, and the work efficiency in removing the cap member4can thereby be improved.

That is, as detaching and attaching work of the cap member4can be carried out without using a tool, the maintainability is improved.

An embodiment according to the present invention has been described above in details with reference to the drawings, however, the invention is not limited thereto, and modifications and changes can be made, as appropriate, without departing from the spirit of the invention.

The present embodiment has been descried taking an example of an engine for a vehicle, however, it is needless to say that an internal combustion engine related to the present invention can be applied to an engine for a vessel, a general purpose machine, and the like other than vehicles.

Further, in the present embodiment, the outer circumferential surface of the handling portion34is made as the tapered surface34awhose diameter becomes gradually smaller from the upper side to the lower side, however, without being limited thereto, for example, the outer circumferential surface of the handling portion34may be made a vertical surface34bformed with a constant outer diameter along the axial direction (along the vertical direction) as shown inFIGS. 6A and 6B.

In this case, as shown inFIG. 6A, arrangement may be made such that, omitting the groove portion35, the outer circumferential surface of the handling portion34is extended to the lower part of the outer circumferential surface of the protruding portion32so that the outer circumferential surface of the handling portion34is an vertical surface34b, or arrangement may be made such that, as shown inFIG. 6B, the outer circumferential surface of the handling portion34is a vertical surface34bwhile the groove portion35is provided. Also with such an arrangement, as oil or moisture deposed on the handling portion34becomes easier to fall along the vertical surface34bby the own gravity, deterioration of the seal member3caused by deposition of oil or the like can be reduced.

Further, as shown inFIG. 7, the structure of the cylinder head cover1and the cap member4may be modified. Incidentally, the following description will be made in details on differences from the foregoing embodiment, the same symbols will be assigned to the respective same elements as those in the foregoing embodiment, and overlapping description will be omitted.

Regarding referential drawings,FIGS. 7A and 7Bare illustrations of a cylinder head cover1, a seal member3, and a cap member4in a first modified example, whereinFIG. 7Ais a partial enlarged perspective view showing a state that the cap member4is detached, andFIG. 7Bis a partial enlarged perspective view showing a state that the cap member4is attached.

The first modified example is different from the foregoing embodiment in that plural (three) protruding portions17,17, . . . are provided protruding upward from the upper marginal portion of the spark plug fitting hole1aby a certain length, and plural (three) extending portions43,43, . . . are respectively provided with opening portions43a.

The protruding portions17are formed in a curved surface shape with substantially the same curvature as the curvature of the spark plug fitting hole1a, and are provided with an equal interval along the circumferential direction of the spark plug fitting hole1a.

Each protruding portion17is formed by a main body portion17aprotruding upward by a certain length from the upper surface of the upper wall11, and a claw portion17bextending outward in the radial direction from the outer circumferential surface of the upper portion of the main body portion17a.

The claw portion17bis a part that catches on (contacts) the upper surface of an extending portion43in a state that the protruding portion17is inserted through the opening portion43a. The outer circumferential surface of the claw portion17bis provided with a tapered surface17cthat is gradually inclined outward in the radial direction as going from the upper side toward the lower side.

The extending portions43are provided with an equal interval along the circumferential direction of the flange portion42. Each extending portions43are provided with an opening portion43athat is vertically penetrating. The opening portions43aare formed in a shape matching with the protruding portions17and are arranged to enable insertion of the protruding portions17. Incidentally, the numbers of the protruding portions17and the extending portions43are not limited as long as two or more.

In the present modified example, the extending portions43(opening portions43a) correspond to ‘a third engaging portion’ described in a claim, and the protruding portions17correspond to ‘a third engaged portion’ described in a claim.

Incidentally, in attaching the cap member4to the cylinder head cover1, when the opening portions43aof the extending portions43are inserted into the protruding portions17, the inner surfaces of the opening portions43aand the claw portions17bof the protruding portions17come in contact with each other, and the claw portions17bare elastically deformed inward such as to shrink in the radial direction by pushing the extending portions43.

Then, when the opening portions43ahave got down over the claw portions17b, the claw portions17breturn to the original state; the claw portions17bcatches on the upper surfaces of the extending portions43; and the lower sides of the main body portions17aare inserted into the opening portions43a. Thus, the cap member4is attached to the cylinder head cover1.

On the other hand, in detaching the cap member4from the cylinder head cover1, by lifting the cap member4while elastically deforming the claw portions17b, the protruding portions17are detached from the opening portions43a, and the cap member4is detached from the cylinder head cover1.

The work efficiency in detaching and attaching the cap member4is improved also in the present modified example. That is, as it is possible to carry out detaching and attaching work of the cap member4without using a tool, the maintainability is improved.

Further, the structure of the cylinder head cover1and the cap member4may be modified, as shown inFIGS. 8A to 8C. Incidentally, the following description will be made in details on differences from the first modified example, the same symbols will be assigned to the respective same elements as those in the first example, and overlapping description will be omitted.

Regarding referential drawings,FIGS. 8A to 8Care illustrations of a cylinder head cover1, a seal member3, and the cap member4in a second modified example, whereinFIG. 8Ais a partial enlarged perspective view showing a state that the cap member is detached,FIG. 8Bis cross-sectional view taken along I-I line inFIG. 8A, andFIG. 8Cis a partial enlarged vertical cross-sectional view showing a state that the cap member4is attached.

As shown inFIG. 8A, the second modified example is different from the first modified example in that plural (four) protruding portions17,17, . . . are provided protruding upward by a certain length from the support surface14(only three are shown inFIG. 8A), and extending portions43are formed at the outer circumferential lower end of the flange portion42.

As shown inFIG. 8C, an extending portion43is a part that is inserted between the circumferential wall portion15of the cylinder head cover1and the protruding portions17.

The extending portion43is, as shown inFIGS. 8B and 8C, formed by an annular portion43bextending downward by a certain length from the outer circumferential end of the flange portion42, and plural (four) hook portions43c,43cthat are extending inward by a certain length in the radial direction from the inner circumferential lower end of the annular portion43band are provided with an equal interval along the circumferential direction of the annular portion43b.

The hook portions43care parts that are located on the lower side of the claw portions17bin a state that the cap member4is fixed to the cylinder head cover1, as shown inFIG. 8C. That is, in the present modified example, the hook portions43cand the protruding portions17prevent the cap member4from getting off to the upper side from the cylinder head cover1. The length of the hook portions43calong the circumferential direction is, as shown inFIG. 8A, smaller than the interval between the neighboring protruding portions17,17and the length of the protruding portions17along the circumferential direction. Further, the interval between neighboring hook portions43c,43cis larger than the length of the protruding portions17along the circumferential direction.

In the present modified example, the extending portion43(hook portions43c) corresponds to ‘a third engaging portion’ described in a claim, and the protruding portions17(the claw portions17b) correspond to ‘a third engaged portion’ described in a claim.

Incidentally, in attaching the cap member4to the cylinder head cover1, the hook portions43care set to positions, where the protruding portions17are not present, and are made contact with the support surface14.

At this moment, parts, where the hook portions43care not formed, of the annular portion43bare located between the circumferential wall portion15and the protruding portions17.

Then, when the cap member4is rotated and the hook portions43cof the extending portion43are thus inserted between the support surface14and the claw portions17bof the protruding portions17, the cap member4is attached to the cylinder head cover1.

On the other hand, in detaching the cap member4from the cylinder head cover1, the cap member4is rotated such that the hook portions43cmove to positions, where the protruding portions17are not present.

Then, when the cap member4is lifted, the cap member4is detached from the cylinder head cover1.

Also in the present modified example, the work efficiency in detaching and attaching the cap member4is improved. That is, as detaching and attaching work of the cap member4can be carried out without using a tool, the maintainability is improved.

Further, the structure of the cylinder head cover1and the cap member4may be modified as shown inFIGS. 9A and 9B. Incidentally, the following description will be made in details on differences from the first modified example, the same symbols will be assigned to the respective same elements as those in the first example, and overlapping description will be omitted.

In the referential drawings,FIGS. 9A and 9Bare illustrations of a cylinder head cover1, a seal member3, and a cap member4in a third modified example, whereinFIG. 9Ais a partial enlarged perspective view showing a state that the cap member4is detached, andFIG. 9Bis a partial enlarged perspective view showing a state that the cap member4is attached.

The third modified example is different from the foregoing first modified example in that a single protruding portion17is formed, protruding upward by a certain length from an upper marginal portion of the spark plug fitting hole1a, a single extending portion43having an opening portion43ais formed on the outer circumferential surface of a flange portion42, and a fastening portion44is formed extending outward by a certain length in the radial direction from the outer margin of the upper surface of the flange portion42.

The protruding portion17is linearly formed and disposed on the side opposite to a fastening portion13with the spark plug fitting hole1abetween them.

The extending portion43is formed substantially in a rectangular shape and has an opening portion43ain a rectangular shape.

The fastening portion44is formed by a standup portion44ain s curved surface shape protruding upward by a certain length from the upper surface of the flange portion42and a fitting portion44bin a horizontal shape extending outward in the radial direction by a certain length from the outer surface of the upper end of the standup portion44a. The fitting portion44bis provided with a bolt insertion hole44cpenetrating through in the vertical direction. Incidentally, the flange portion21cof the plug top coil21is disposed on the upper side of the fitting portion44b(seeFIG. 1).

In the present modified example, the cylinder head cover1, the cap member4, and the plug top coil21are integrally connected by inserting a bolt B through the bolt insertion hole13aof the cylinder head cover1, the bolt insertion hole44cof the cap member4, and the bolt insertion hole21eof the plug top coil21, and by screw-engaging the bolt B with a nut N. That is, the cap member4is fixed to the cylinder head cover1, using fastening means for fastening the cylinder head cover1and the plug top coil21.

In the present modified example, the extending portion43(the opening portion43a) and the fastening portion44correspond to ‘a third engaging portion’ described in a claim, and the protrusion portion17and the fastening portion13correspond to ‘a third engaged portion’ described in a claim.

Incidentally, in attaching the cap member4to the cylinder head cover1, when the protruding portion17is inserted into the opening portion43aof the extending portion43, the inner surface of the opening portion43aand the claw portion17bof the protruding portion17come in contact with each other, wherein the claw portion17bis elastically deformed such as to shrink inward in the radial direction by pushing the extending portion43.

Then, when the opening portion43ahas got down over the claw portion17b, the claw portion17breturns to the original state, the claw portion17bcatches on the upper surface of the extending portion43, and the lower side of the main body portion17ais inserted into the opening portion43a.

Further, the bolt B is inserted through the bolt insertion hole13aof the cylinder head cover1, the bolt insertion hole44cof the cap member4, and the bolt insertion hole21eof the plug top coil21, and the bolt B is screw-engaged with the nut N.

Through the above-described process, the cap member4is attached to the cylinder head cover1.

On the other hand, in detaching the cap member4from the cylinder head cover1, the fastening state between the cylinder head cover1, the cap member4, and the plug top coil21is released by removing the bolt B.

Then, when the cap member4is lifted while elastically deforming the claw portion17b, the protruding portion17is detached from the opening portion43a, and the cap member4is detached from the cylinder head cover1.

Also in the present modified example, the work efficiency in detaching and attaching the cap member4is improved.

DESCRIPTION OF REFERENCE SYMBOLS