EP2204888B1

EP2204888B1 - Spark plug cap and plug cap mount structure

Info

Publication number: EP2204888B1
Application number: EP10150069A
Authority: EP
Inventors: Tomohiro Fuma; Junpei Ohta
Original assignee: NGK Spark Plug Co Ltd
Current assignee: Niterra Co Ltd
Priority date: 2009-01-06
Filing date: 2010-01-05
Publication date: 2011-10-12
Anticipated expiration: 2030-01-05
Also published as: ATE528832T1; JP5237835B2; EP2204888A1; BRPI0905198A2; JP2010160900A

Abstract

There is provided a plug cap for electrically connecting a high-tension cord to a spark plug fixed to an internal combustion engine. The plug cap includes an electrical connection member capable of making an electrical connection between the spark plug and the high-tension cord, a resin molded member covering at least part of an outer circumferential surface of the electrical connection member and a cover member covering at least an outer circumferential surface of the resin molded member and formed of an elastic rubber material softer than a resin material of the resin molded member. The resin molded member has a protruding portion radially outwardly extending in at least one direction. The cover member covers the protruding portion of the resin molded member in such a manner that at least part of the protruding portion is engaged with a cap mounting portion of the engine via the cover member.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a spark plug cap and a plug cap mount structure for an internal combustion engine.
A plug cap, also called "plug socket" or "plug connector", is used for electrically connecting a high-tension cord to a spark plug in an internal combustion engine so that the spark plug generates a spark discharge with the application of a high tension from an ignition coil or a distributor to the spark plug through the high-tension cord. In general, the plug cap includes a cylindrical cap body made of a rubber or resin material and equipped with an electrical connection member, a plug connection hole formed in one end of the cap body and a cord connection hole formed in the other end of the cap body to establish an electrical connection between the spark plug and the high-tension cord through the electrical connection member by fitting connection terminals of the spark plug and the high-tension cord into the plug connection hole and the cord connection hole, respectively.
The plug cap receives vibrations caused by operation of the internal combustion engine through the spark plug and the high-tension cord. Particularly, the plug connection hole and the cord connection hole are susceptible to engine vibrations. When a load is exerted on the connection between the connection terminal of the spark plug and the plug connection hole of the plug cap due to the engine vibrations, the connection terminal of the spark plug and the plug connection hole of the plug cap may be worn away to produce metal dust or chips. The adhesion of such metal dust or chips to the connection terminal of the spark plug become a cause of a current leakage (flashover) from the connection terminal to metal shell of the spark plug and then to the internal combustion engine, whereby the spark plug cannot secure a proper and stable spark discharge.
In order to reduce the influence of the engine vibrations on the plug cap, it is conceivable to form a flanged portion on an outer circumferential surface of the cap body of the plug cap and insert the plug cap in a plug hole of the internal combustion engine. This makes it possible to stabilize the mounted state of the plug cap by holding the plug cap with the connection terminal of the spark plug and with the inner circumferential surface of the plug hole. There is however often a case that the plug hole cannot be formed in the internal combustion engine in view of the engine design restrictions etc.
As another technique to reduce the influence of the engine vibrations on the plug cap, Japanese Laid-Open Patent Publication No. 2001-155837 proposes the formation of a rubber protrusion with an engagement hole on the outer circumferential surface of the plug cap so that the plug cap can be attached to the connection terminal of the spark plug with a cap supporting protrusion of the internal combustion engine engaged in the engagement hole of the rubber protrusion of the plug cap. This makes it possible to stabilize the mounted state of the plug cap by holding the plug cap with the connection terminal of the spark plug and with the cap supporting protrusion of the engine and further makes it possible to stabilize the mounted state of the plug cap and limit the influence of the engine vibrations on the plug cap more effectively by minimizing the clearance between the engagement hole of the plug cap and the cap supporting protrusion of the engine.

SUMMARY OF THE INVENTION

The plug cap mount technique of Japanese Laid-Open Patent Publication 2001-155837 has the problem that the influence of the engine vibrations on the plug cap may not be reduced sufficiently due to insufficient rigidity of the rubber protrusion.
It is therefore an object of the present invention to provide a plug cap capable of securing a stable mounted state and improved vibration resistance without a deterioration in ease of mounting.
According to one aspect of the present invention, there is provided a plug cap for electrically connecting a high-tension cord to a spark plug fixed to an internal combustion engine, comprising: an electrical connection member connected at one end thereof to the spark plug and at the other end to the high-tension cord to establish an electrical connection between the spark plug and the high-tension cord; a resin molded member covering at least part of an outer circumferential surface of the electrical connection member; and a cover member formed of an elastic rubber material softer than a resin material of the resin molded member and covering at least an outer circumferential surface of the resin molded member, characterized in that: the resin molded member has a protruding portion radially outwardly extending in at least one direction so as to be engageable with a cap mounting portion of the engine; and the cover member covers the protruding portion of the resin molded member in such a manner that at least part of the protruding portion of the resin molded member comes into contact with the cap mounting portion of the engine via the cover member.
According to another aspect of the present invention, there is provided a plug cap for electrically connecting a high-tension cord to a spark plug fixed to an internal combustion engine, comprising: a cap body having one end formed with a plug connection hole to receive a connection terminal of the spark plug and the other end formed with a cord connection hole to receive a connection terminal of the high-tension cord; and a protrusion formed on the cap body so as to be engageable with a cap mounting portion of the engine, characterized in that: the protrusion has a resin portion and a rubber portion made of an elastic rubber material softer than a resin material of the resin portion and covering the resin portion in such a manner that at least part of the resin portion comes into contact with the cap mounting portion of the engine via the rubber portion.
According to still another aspect of the present invention, there is provided a plug cap mount structure for an internal combustion engine, comprising: a cap mounting portion formed on the engine; and a plug cap attached to a spark plug fixed to the engine to electrically connect a high-tension cord to the spark plug, the plug cap comprising: an electrical connection member connected at one end thereof to the spark plug and at the other end to the high-tension cord to establish an electrical connection between the spark plug and the high-tension cord; a resin molded member covering at least part of an outer circumferential surface of the electrical connection member, characterised by the resin molded member having a protruding portion radially outwardly extending in at least one direction and engaged with the cap mounting portion of the engine; and a cover member formed of an elastic rubber material softer than a resin material of the resin molded member and covering at least an outer circumferential surface of the resin molded member including a surface of the protruding portion of the resin molded member in such a manner that at least part of the protruding portion of the resin molded member comes into contact with the cap mounting portion of the engine via the cover member.
The other objects and features of the present invention will also become understood from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of plug cap according to a first embodiment of the present invention.
FIG. 2 is a partially cutaway perspective view of the plug cap according to the first embodiment of the present invention.
FIG. 3 is a section view of the plug cap according to the first embodiment of the present invention.
FIG. 4 is a section view of an engagement protrusion of the plug cap according to the first embodiment of the present invention.
FIG. 5 is a perspective view of a plug cap according to a second embodiment of the present invention.
FIG. 6 is a section view of an engagement protrusion of the plug cap according to the second embodiment of the present invention.
FIG. 7 is a schematic view showing a modification of the engagement protrusion of the plug cap.
FIGS. 8A and 8B are schematic views showing modifications of the engagement protrusion of the plug cap.
FIGS. 9A and 9B are schematic views showing modifications of the modifications of the engagement protrusion of the plug cap.
FIGS. 10A and 10B are schematic views showing modifications of the engagement protrusion of the plug cap.

DESCRIPTION OF THE EMBODIMENTS

The present invention will be described in detail below by way of the following embodiments, in which like parts and portions are designated by like reference numerals to avoid repeated explanations thereof.

First Embodiment

Referring to FIGS. 1 to 3, a plug cap 100 according to a first embodiment of the present invention is provided for electrically connecting a high tension cord 60 to a spark plug 50 fixed to an internal combustion engine so as to apply a high tension from an ignition coil to the spark plug 50 through the high tension cord 60. Herein, the term "top" refers to a high-tension cord side; and the term "bottom" refers to a spark plug side as viewed in the drawings. These terms are used for purposes of illustration and are not intended to limit the invention to any particular orientation.
As shown in FIG. 1, the plug cap 100 has a cap body 1, a plug connection hole 4 and a cord connection hole 5.
The cap body 1 is circular in cross section and is bent at a point to define an axial body part 2 extending along a first axis C1 on a bottom side of the bending point and a bent body part 3 extending on a top side of the bending point along a second axis C2 that intersects with the first axis C at a given angle. The cap body 1 is not however limited to the bent shape and can alternatively be formed into a linear shape or a curved shape. The plug connection hole 4 is formed in a bottom end of the axial body part 2 of the cap body 1 along the direction of the first axis C 1 so that a connection terminal of the spark plug 50 is fitted in and connected to the plug connection hole 4. The cord connection hole 5 is formed in a top end of the bent body part 3 of the cap body 1 along the direction of the second axis C2 so that a connection terminal of the high-tension cord 60 is fitted in and connected to the cord connection hole 5.
More specifically, the cap body 1 includes an electrical connection member equipped with a cord fixing screw 15, a contact plate 16, a contact spring 17, a setting cap 7, a resistive element 18 and a connector fitting 19 to make an electrical connection between the spark plug 50 and the high-tension cord 60, a resin molded member 6 covering at least part of an outer circumferential surface of the electrical connection member and a cover member 9 covering at least an outer circumferential surface of the resin molded member 6 as shown in FIGS. 2 and 3.
The resin molded member 6 is formed of a resin material having relatively high heat resistance. Suitable examples of the resin material of the resin molded member 6 are a thermosetting resin such as phenol resin or unsaturated polyester resin and a thermoplastic resin material such as PPS (polyphenylene sulfide) resin. The resin molded member 6 has a bent shape extending along the axial body part 2 and bent body part 3 of the cap body 1. A hole 8 is formed in a top end of the resin molded member 6 in the direction of the second axis C2.
The cover member 9 is formed of an insulating rubber material having sufficient heat resistance to withstand heat from the engine and being elastic and softer than the resin material of the resin molded member 6. Suitable examples of the rubber material are a silicon rubber, an acrylic rubber and an EPDM (ethylene propylene dien monomer) rubber.
As shown in FIGS. 1 to 3, the cover member 9 includes a main cover portion 10 located around the outer circumferential surface of the resin molded member 6 and cylindrical end portions 11 and 12 located on bottom and top sides of the main cover portion 10. The bottom end portion 11 is made smaller in outer diameter than the main cover portion 10. A through hole 13 is formed in the bottom end portion 11 in the direction of the first axis C1 to define a part of the plug connection hole 4. When the connection terminal of the spark plug 50 is fitted in the plug connection hole 14, the end portion 11 of the cover member 9 covers the connection terminal of the spark plug 50 so as to prevent the occurrence of a current leakage (flashover) from the connection terminal of the spark plug 50. The top end portion 12 is narrowed at an axially middle position thereof to be smaller in outer diameter than the main cover portion 10. A through hole 14 is formed in the top end portion 12 in the direction of the second axis C2 to define the cord connection hole 5 together with the hole 8 of the resin molded member 6. When the connection terminal of the high-tension cord 60 is fitted in the cord connection hole 5, the end portion 12 of the cover member 9 closes the opening of the cord connection hole 5 so as to prevent the entry of water into the cord connection hole 5.
The cord fixing screw 15 is formed of a conductive metal material such as brass and tapered down toward the top. The cord fixing screw 15 has a bottom end embedded in the resin molded member 6 and a top threaded end protruding in the cord connection hole 5 so that the connection terminal of the high-tension cord 60 is screwed onto the threaded end of the cord fixing screw 15 and fixed in position in the cord connection hole 5 with a lead of the high-tension cord 60 brought into contact with the cord fixing screw 15.
The contact plate 16 is formed of a conductive metal material such as stainless steel and held between a bottom end surface of the cord fixing screw 15 and a top end surface of the setting cap 7 to make an electrical connection to the contact spring 17.
The setting cap 7 is formed of a conductive metal material such as brass. The setting cap 7 has an inverted U shape cross section to be fitted on the contact spring 17 with the top end surface of the setting cap 7 held in contact with the contact, plate 16.
The contact spring 17 is formed of a conductive metal material such as hard stainless steel and is electrically connected at a top end thereof to the contact plate 16 via the setting cap 7 and at a bottom end thereof to the resistive element 18.
The resistive element 18 is formed into a substantially cylindrical column shape of a conductive ceramic material and is electrically connected at a top end thereof to the contact spring 17 and at a bottom end thereof to the connector fitting 19. Herein, the resistive element 18 has a given electrical resistance (e.g. 5 kΩ) so as to suppress radio noise caused due to the generation of a spark discharge by the spark plug 50.
The connector fitting 19 is formed of a conductive metal material such as brass. The connector fitting 19 has a cylindrical shape with a top end closed and held in contact with the bottom end of the resistive element 19 and an axial hole 20 formed in the direction of the first axis C1 to define the plug connection hole 4 together with the through hole 13 of the cover member 9. Further, a connector spring 21 is disposed around a bottom end of the connector fitting 19 so as to fasten the connector fitting 19 radially inwardly and, when the connection terminal of the spark plug 50 is fitted in the plug connection hole 4, fix the terminal end of the spark plug 50 stably in position.
The electrical connection member thus electrically connects the high-tension cord 60 to the spark plug 50 through the cord fixing screw 15, the contact plate 16, the setting cap 7, the contact spring 17, the resistive element 18 and then the connector fitting 19 by pushing the connection terminal of the spark plug 50 into the axial hole 20 of the plug fitting 19 within the plug connection hole 4 and by screwing the connection terminal of the high-tension cord 60 onto the cord fixing screw 15 within the cord connection hole 5.
As shown in FIGS. 2 to 4, the resin molded member 6 has a protruding portion 25 extending radially outwardly and engaged with a cap mounting portion of the engine. On the other hand, the cover member 9 has a cover portion 27 protruding from the main cover portion 10 to cover the protruding portion 25 of the resin molded member 6 so that at least part of the protruding portion 25 of the resin molded member 6 comes into contact with the cap mounting protrusion of the engine via the cover portion 27 as shown in FIGS. 1 to 4.
In the first embodiment, the cap mounting portion has a fixing protrusion 24 formed on the engine in the direction of the first axis C1, i.e., the axis of the spark plug 50 as shown in FIGS. 1 to 3.
Further, the protruding portion 25 of the resin molded member 6 extends, when viewed in the direction of the first axis C1, in a direction perpendicular to the direction of the first axis C1 and opposite to the direction of the second axis C2 into which the bent body part 3 of the cap body 1 is bent relative to the axial body part 2 of the cap body 1. A through hole 23 of larger size than the fixing protrusion 24 of the engine is formed in a tip end of the protruding portion 25.
The cover portion 27 of the cover member 9 covers the whole surface of the protruding portion 25 of the resin molded member 6 including an inner circumferential surface of the through hole 23 of the protruding portion 25 to define an engagement hole 28 of substantially the same size as the fixing protrusion 24 of the engine.
As already discussed before, the earlier technology provides a plug cap with a protrusion of rubber so that the plug cap can be attached to a spark plug with a cap supporting protrusion of an internal combustion engine engaged in an engagement hole of the rubber protrusion but has the problem that the influence of engine vibrations on the plug cap may not be reduced sufficiently due to insufficient rigidity of the rubber protrusion. It is conceivable to form the protrusion of the plug cap from a relatively high rigid resin material in place of the rubber material. In this case, however, the cap supporting protrusion of the engine cannot be readily engaged in the engagement hole of the high rigid resin protrusion in the occurrence of even a slight dimensional error in the cap supporting protrusion and the engagement hole when the engagement hole is formed to minimize the clearance between the cap supporting protrusion and the engagement hole for more stable mounting of the plug cap.
In the first embodiment, by contrast, the protruding portion 25 of the resin molded member 6 and the cover portion 27 of the cover member 9 constitutes an engagement protrusion 22 held with the cap mounting portion of the engine by insertion of the fixing protrusion 24 in the engagement hole 28 when the plug cap 100 is attached to the connection terminal of the spark plug 50. This allows the plug cap 100, in a mounted state, to be held with the connection terminal of the spark plug 50 and with the cap mounting portion (fixing protrusion 24) of the engine.
As the resin molded member 6, including the protruding portion 25, is integrally formed of the resin material higher in rigidity than the rubber material, the protruding portion 25 can provide sufficient rigidity to the engagement protrusion 22 of the plug cap 100 so as to stabilize the mounted state of the plug cap 100 and reduce or prevent the influence of engine vibrations on the plug cap 100 by engagement of the engagement protrusion 22 with the cap mounting portion of the engine. Further, the cover portion 27 of the cover member 9 covers the whole surface of the protruding portion 25 so that the cap mounting portion of the engine does not comes into direct contact with the resin protruding portion 25 but comes with the cover portion 27. Even if a dimensional error occurs in the protruding portion 25, the cover portion 27 and/or the fixing protrusion 24, the cover member 9 (cover portion 27) can absorb such a dimensional error as the cover member 9 is integrally formed of the elastic rubber material softer than the resin material of the resin molded member 6. With the engagement hole 28 of the engagement protrusion 22 defined by covering the inner circumferential surface of the through hole 23 of the resin protruding portion 25 with the cover member 9 (cover portion 27), the fixing protrusion 24 of the cap mounting portion of the engine can be readily engaged in the engagement hole 28 of the engagement protrusion 22 due to elasticity of the rubber material. It is therefore possible to secure the stable mounted state and improved vibration resistance of the plug cap 100 and obtain easy mounting of the plug cap 100 without a deterioration in ease of mounting by engagement of the high-rigidity resin protruding portion 25 with the cap mounting portion of the engine via the rubber cover portion 27. It is further possible to protect the resin molded member 6 and, by extension, the electrical connection member from the engine heat by covering the resin molded member 6 with the rubber cover member 9 as the rubber material generally shows higher heat resistance and voltage resistance than those of a resin material.
In addition, a flanged region 26 is formed on a tip end of the fixing protrusion 24 whereas a large thickness region 71 is formed on a base end of the fixing protrusion 24 to protrude toward the flanged region 26 as shown in FIGS. 1 to 3. Once the fixing protrusion 24 is engaged in the engagement hole 28 of the engagement protrusion 22, the flanged region 26 functions as a movement restriction member (or means) of the plug cap 100 that holds the cover portion 27 between the flanged region 6 and the large thickness region 71 and thereby prevents the protruding portion 25 from moving in its engagement/disengagement direction relative to the cap mounting portion. This leads to the more stable mounted state and further improved vibration resistance of the plug cap 100.

Second Embodiment

A plug cap 101 according to a second embodiment of the present invention is structurally similar to the plug cap 100 of the first embodiment, except for the shapes of the engagement protrusion 22 of the plug cap 101 and the cap -protruding portion of the engine as shown in FIGS. 5 and 6.
In the second embodiment, the cap protruding portion has a recess 37 cut in the engine or a protrusion on the engine for engagement of the engagement protrusion 22 of the plug cap 101. When viewed in the direction of engagement of the engagement protrusion 22 in the recess 37, the recess 37 is the smallest in width at an opening 39 thereof to define a small width region 72 and is made larger in width toward the back to define a large width region 73. The small width region 72 may not be defined at the opening 39 of the recess 37 but alternatively be defined at a back of the opening 39 (at a position between the opening 39 and the large width region 73) of the recess 37.
The engagement protrusion 22 is constituted by a protruding portion 34 of the resin molded member 6 and a cover portion 40 of the cover member 9.
The protruding portion 34 of the resin molded member 6 includes a narrowed region 38 of relatively small width at a substantially middle position in the protruding direction of the protruding portion 34 and an enlarged region 35 of larger width than the narrowed region 38 at a tip end of the protruding portion 34 so that so , that the narrowed region 38 and the enlarged region 35 correspond to the small width region 72 and large width region 73 of the recess 37, respectively. The enlarged region 35 is made smaller in size than the large width region 73.
The cover portion 40 of the cover member 9 covers the whole surface of the protruding portion 34 so that the enlarged region 35 of the protruding portion 35 mates and engages with the inner circumferential surface of the recess 37 (large width region 73) via the cover portion 40 by insertion of the engagement protrusion 22 in the recess 37.
It is therefore possible in the second embodiment to stabilize the mounted state of the plug cap 10 1 and improve the vibration resistance of the plug cap 101 without a deterioration in ease of mounting by engagement of the high-rigidity resin protruding portion 34 with the cap mounting portion of the engine via the rubber cover portion 40 in the same manner as in the first embodiment.
Furthermore, the width A of the enlarged region 35 of the protruding portion 34 is preferably made larger than the width B of the opening 39 (small width region 72) of the recess 37 so as to, even in the event of a breakage in the cover portion 40, prevent the protruding portion 34 from being detached from the recess 37. This leads to the more stable mounted state and further improved vibration resistance of the plug cap 101.
Although the present invention has been described with reference to the above-specific embodiments of the invention, the invention is not limited to these exemplary embodiments. Various modification and variation of the embodiments described above will occur to those skilled in the art in light of the above teachings.
Although a single protruding portion 25, 34 is formed on the resin molded member 6 in each of the first and second embodiments, the number of protruding portions on the resin molded member 6 is not limited to one. The resin molded member 6 may alternatively have a plurality of protruding portions. For example, the resin molded member 6 can have two protruding portions 25a and 25b extending in different directions and covered by the cover member 9 as shown in FIG. 7. The formation of such a plurality of protruding portions 25a and 25b enables further stabilization of the mounted state of the plug cap 100, 101 and further improvement of the vibration resistance of the plug cap 100, 101.
Further, the direction of protrusion of the protruding portion, 25, 34 of the resin molded member 6 is not limited to that of the first or second embodiment although the protruding portion 25, 34 extends radially outwardly in the direction opposite to the direction into which the bent body part 3 of the cap body 1 is bent relative to the axial body part 2 of the cap body 1 in each of the first and second embodiments. The protrusion direction of the protruding portion 25, 34 can be modified as appropriate depending on the engine layout etc. For example, the protruding portion 25 may alternatively extend in a direction at a certain angle with respect to the direction into which the bent body part 3 of the cap body 1 is bent relative to the axial body part 2 of the cap body 1 as shown in FIG. 8A. As shown in FIG. 8B, the resin molded member 6 may have a protruding portion 41 extending in substantially the same direction as the direction into which the bent body part 3 of the cap body 1 is bent relative to the axial body part 2 of the cap body 1. In this case, the protruding portion 41 is engaged with a fixing protrusion 42 of the engine at a position relatively close to the center of gravity of the plug cap 100, 101. It is thus possible to limit an increase in load on the connection between the plug cap 100, 101 and the spark plug 50 and obtain further improvement in the vibration resistance of the plug cap 100, 101. In the case where the vibration resistance varies depending on the mounting angle, it is desirable to set the most effective, optimum mounting angle.
Although the cover portion 27, 40 of the cover member 9 covers the whole surface of the protruding portion 26, 34 of the resin molded member 6 in the first and second embodiments, the cover portion 27, 40 does not necessarily covers the whole surface of the protruding portion 26, 34. It suffices that the cover portion 27, 40 covers at least part of the protruding portion 26, 34 such that the at least part of the protruding portion 26, 34 comes into contact with the cap mounting portion of the engine via the cover portion 27, 40.
The configuration of the electrical connection member is not limited to that of the first or second embodiment although the electrical connection member is provided by connecting the cord fixing screw 15, the contact plate 16, the contact spring 17, the setting cap 7, the resistive element 18 and the connector fitting 19 in the first and second embodiments. The electrical connection member can be any means capable of making an electrical connection between the spark plug 50 and the high-tension cord 60. For example, the electrical connection member may alternatively be provided by electrically connecting the contact spring 17 and the connector fitting 19 without the resistive element 18 or be provided by connecting a lead wire or wires between the spark plug 50 and the high-tension cord 60.
Furthermore, the configuration of the movement restriction member is not limited to that of the first embodiment although the flanged region 26 is formed as the movement restriction member on the protrusion 24 of the engine. The movement restriction member can be any means capable of preventing the protruding portion 25 of the resin molded member 6 from moving in its engagement/disengagement direction relative to the cap mounting portion of the engine. For example, the movement restriction member may have a nut 43 and a screw thread formed on a fixing protrusion 51 of the cap mounting portion so as to, after engaging the protrusion 51 in the engagement hole 28, screw the nut 43 onto the screw thread of the protrusion 51 and thereby prevent movement of the protruding portion 25 in its disengagement direction relative to the protrusion 51 as shown in FIG. 9A. In place of such a screw/nut mechanism, any other fixing means such as a socket or a clip can be used. The movement restriction member may alternatively have a stage 45 formed at a base end of a fixing protrusion 61 of the cap mounting portion so as to prevent movement of the protruding portion 25 in its engagement direction relative to the protrusion 61 by contact of the cover portion 27 with the stage 45 as shown in FIG. 9B. Any of the above movement restriction members can be used in combination thereof.
Although each of the engagement hole 28 (through hole 23) and the fixing protrusion 24 is rectangular in cross section as shown in FIG. 4 in the first embodiment, the shapes of the engagement hole 28 (through hole 23) and the fixing protrusion 24 are not limited to those of the first embodiment. The engagement hole 28 (through hole 23) and the fixing protrusion 24 can alternatively be circular in cross section as shown in FIG. 10A or be hexagonal in cross section as shown in FIG 10B.
The scope of the invention is defined with reference to the following claims.

Claims

A plug cap (100; 101) for electrically connecting a high-tension cord (60) to a spark plug (50) fixed to an internal combustion engine, comprising:
an electrical connection member (15, 16, 7, 17, 18, 19) connected at one end thereof to the spark plug (50) and at the other end to the high-tension cord (60) to establish an electrical connection between the spark plug (50) and the high-tension cord (60);

a resin molded member (6) covering at least part of an outer circumferential surface of the electrical connection member (15, 16, 7, 17, 18, 19); and

a cover member (9) formed of an elastic rubber material softer than a resin material of the resin molded member (6) and covering at least an outer circumferential surface of the resin molded member (6), characterized in that:
the resin molded member (6) has a protruding portion (25; 34; 25a, 25b; 41) radially outwardly extending in at least one direction so as to be engageable with a cap mounting portion (24; 37; 42; 51; 61) of the engine; and

the cover member (9) covers the protruding portion (25; 34; 25a, 25b; 41) of the resin molded member (6) in such a manner that at least part of the protruding portion (25; 34; 25a, 25b; 41) of the resin molded member (6) comes into contact with the cap mounting portion (24; 37) of the engine via the cover member (9).
The plug cap (100) according to claim 1, wherein the cap mounting portion has a protrusion (24; 42; 51; 61); wherein the protruding portion (25; 25a, 25b; 41) of the resin molded member (6) has a hole (23); and wherein the cover member (9) covers an inner circumferential surface of the hole (9) of the protruding portion (25; 25a, 25b; 41) to define an engagement hole (28) in which the protrusion (24; 42; 51; 61) of the cap mounting portion is engageable.
The plug cap (101) according to claim 1, wherein the cap mounting portion has a recess (37) cut in either the engine or a protrusion on the engine; wherein the recess (37) includes a small width region (72) at an opening side thereof and a large width region (73) at a back side thereof; wherein the protruding portion (34) of the resin molded member (6) includes a narrowed region (38) corresponding to the small width region (72) and an enlarged region (35) corresponding to the large width region (73) so that the protruding portion (34) is engageable in the recess (37) via the cover member (9); and wherein the enlarged region (35) has a width (A) larger than a width (B) of the small width region (72).
The plug cap according to any one of claims 1 to 3, further comprising a movement restriction member (26; 43; 45) capable, of preventing a movement of the protruding portion (25) in an engagement/disengagement direction thereof relative to the cap mounting portion (24; 51; 61) of the engine.
The plug cap (100; 101) according to any one of claims 1 to 4, wherein the resin molded member (6) has a plurality of protruding portions (25a, 25b) engaged with the cap mounting portion of the engine.
A plug cap (100; 101) for electrically connecting a high-tension cord (60) to a spark plug (50) fixed to an internal combustion engine, comprising:
a cap body (1) having one end formed with a plug connection hole (4) to receive a connection terminal of the spark plug (50) and the other end formed with a cord connection hole (5) to receive a connection terminal of the high-tension cord (60); and

a protrusion (22) formed on the cap body (1) so as to be engageable with a cap mounting portion (24; 37; 42; 51; 61) of the engine, characterized in that:
the protrusion (20) has a resin portion (25; 34; 25a, 25b; 41) and a rubber portion (27; 40) made of an elastic rubber material softer than a resin material of the resin portion (25; 34; 25a, 25b; 41) and covering the resin portion (25; 34; 25a, 25b; 41) in such a manner that at least part of the resin portion (25; 34; 25a, 25b; 41) comes into contact with the cap mounting portion (24; 37; 42; 51; 61) via the rubber portion (27; 40).
A plug cap mount structure for an internal combustion engine, comprising:
a cap mounting portion (24; 37; 42; 51; 61) formed on the engine; and

a plug cap (100; 101) attached to a spark plug (50) fixed to the engine to electrically connect a high-tension cord (60) to the spark plug (50), the plug cap comprising:
an electrical connection member (15, 16, 7, 17, 18, 19) connected at one end thereof to the spark plug (50) and at the other end to the high-tension cord (60) to establish an electrical connection between the spark plug (50) and the high-tension cord (60);

a resin molded member (6) covering at least part of an outer circumferential surface of the electrical connection member (15, 16, 7, 17, 18, 19), characterised by the resin molded member (6) having a protruding portion (25; 34; 25a, 25b; 41) radially outwardly extending in at least one direction and engaged with the cap mounting portion (24; 37; 42; 51; 61) of the engine; and

a cover member (9) formed of an elastic rubber material softer than a resin material of the resin molded member (6) and covering at least an outer circumferential surface of the resin molded member (6) including a surface of the protruding portion (25; 34; 25a, 25b; 41) of the resin molded member (6) in such a manner that at least part of the protruding portion (25; 34; 25a, 25b; 41) of the resin molded member (6) comes into contact with the cap mounting portion (24; 37; 42; 51; 61) of the engine via the cover member (9).