JP6732702B2 - Spark plug - Google Patents

Description

The present invention relates to a spark plug.

Patent Document 1 discloses an example of a spark plug. The spark plug disclosed in Patent Document 1 has a configuration in which the entire terminal fitting is housed in a through hole formed in an insulator, and the rear end edge of the terminal fitting is located at the rear end of the insulator in the through hole. It is a position retracted inward from the edge.

If the entire terminal fitting is housed in the through hole like the spark plug of Patent Document 1, the entire length of the spark plug is suppressed, and the surface of the insulator extending from the rear end edge of the metallic shell to the rear end edge of the terminal fitting. Since the length of the discharge path can be increased, the flashover phenomenon can be made less likely to occur.

JP, 11-273827, A

By the way, like the spark plug of patent document 1, when the whole terminal metal fitting is accommodated in an insulator and it does not project from the rear end side of an insulator, it becomes difficult to attach a plug cap to a terminal metal fitting. Therefore, in the spark plug of Patent Document 1, a plug cap (rubber cap) is attached so as to cover the vicinity of the rear end portion of the insulator from the outside. However, if the insulating material is simply covered with the plug cap and held only by the frictional force, the plug cap easily comes off from the insulating material.

The present invention has been made to solve the above-described problems, and a spark plug can be configured in a form that does not easily cause flashover and a form that can suppress the overall size, and the plug cap is unintentionally attached. It is an object of the present invention to provide a configuration that makes it easy to prevent the situation of coming off the spark plug.

The spark plug of the first aspect of the present invention is
An insulator having a through hole extending in the direction of the axis,
A tubular metal shell that holds the insulator inside,
A center electrode arranged in the through hole with its tip exposed from the tip of the insulator;
A terminal fitting inserted into the through hole and electrically connected to the center electrode,
A spark plug comprising:
The rear end portion of the terminal fitting is disposed on the front side of the rear end portion of the through hole,
A recess is formed in at least one of the outer peripheral surface of the insulator on the rear side of the metal shell, or on the inner peripheral surface of the through hole of the insulator on the rear side of the terminal fitting,
The recessed portion has a configuration in which it is recessed from an opening end formed in the outer peripheral surface or the inner peripheral surface along a plane direction orthogonal to the axis,
The inner wall portion on the rear end side of the recess is a locking portion configured as a vertical surface having a wall surface in a direction orthogonal to the axis or an inclined surface having a rearward position as the wall surface moves away from the opening end portion. Have.

In the spark plug of the first aspect, while suppressing the size of the entire spark plug in the front-rear direction, it is possible to secure a larger creepage distance from the terminal metal fitting to the metal shell and to prevent flashover from occurring more easily. Further, this spark plug can be fitted with a plug cap (a plug cap having a protrusion formed at a position corresponding to the recess) of a predetermined shape from the rear side with respect to the insulator. At this time, the projection formed on the plug cap and the locking portion in the recess are in a locked state, so that the plug cap is difficult to separate. Moreover, since the wall surface of the locking portion is configured as a vertical surface that is a direction orthogonal to the axis or an inclined surface that becomes a rear position as it moves away from the opening end, it faces rearward with respect to the plug cap when the plug cap is attached. Even when a force (a force in the direction of detaching from the insulator) is applied, the state in which the protrusion is caught by the locking portion is likely to be stably maintained, and the protrusion is less likely to come out of the recess. Therefore, it is possible to more effectively prevent a situation in which the plug cap is unintentionally disengaged from the spark plug.

The plug unit of the second aspect is
A spark plug of the first aspect;
A plug cap attached to the insulator from the rear side,
Including
The plug cap is
An insertion portion that is inserted into the through hole at the time of mounting,
A covering portion that covers the outer peripheral surface when mounted,
Equipped with
At least one of the insertion portion and the covering portion is formed with a protrusion that is inserted into the recess during mounting.

In the plug unit of the second aspect, in the spark plug, it is possible to suppress the overall size in the front-rear direction, secure a larger creepage distance from the terminal fitting to the metallic shell, and prevent flashover from occurring more easily. Then, the plug cap can be firmly attached to such a spark plug by inserting the insertion portion into the through hole of the insulator and covering the outer peripheral surface of the insulator with the covering portion. Furthermore, when the plug cap is mounted, the protrusion formed on the plug cap and the locking portion in the recess are in a locked state, so that the plug cap is unlikely to come off. Moreover, since the wall surface of the locking portion is configured as a vertical surface that is a direction orthogonal to the axis or an inclined surface that becomes a rear position as it moves away from the opening end, it faces rearward with respect to the plug cap when the plug cap is attached. Even when a force (a force in the direction of detaching from the insulator) is applied, the state in which the protrusion is caught by the locking portion is likely to be stably maintained, and the protrusion is less likely to come out of the recess. Therefore, it is possible to more effectively prevent a situation in which the plug cap is unintentionally disengaged from the spark plug.

In both the spark plug of the first aspect and the plug unit of the second aspect, the inner wall portion on the front end side of the recess has a guide portion configured as an inclined surface that becomes a rearward position as the wall surface moves away from the opening end portion. You may have.

In this way, if the above-described guide portion (the portion where the wall surface is configured as the inclined surface (the surface that becomes the rearward position as the distance from the opening end portion) is provided on the inner wall portion on the front end side in the recessed portion, When the cap is attached to the insulator from the rear side, the protrusion fed from the rear side hits the guide portion, and the inclination of the guide portion facilitates smooth guiding into the recess. Then, if the protrusions are more easily inserted into the recesses, the adhesion between the protrusions and the recesses can be more easily enhanced.

In both the spark plug of the first aspect and the plug unit of the second aspect, the inner wall portion of the recess on the opening end side has an enlarged width portion in which the opening width in the front-rear direction gradually increases toward the opening end. May be.

In this way, if the inner wall portion of the recess on the opening end side has a width expansion portion (a portion in which the opening width in the front-rear direction increases toward the opening end portion), the protrusion is formed when the plug cap is mounted. The portion is more easily inserted from the opening end side.

In both the spark plug of the first aspect and the plug unit of the second aspect, the recess may be formed on the outer peripheral surface of the insulator at a position rearward of the metal shell.

With this configuration, the spark plug can be attached with the plug cap in which the protrusion (the portion to be inserted into the recess) is provided in the portion that covers the outer peripheral surface of the insulator. In particular, since the mounting structure is such that the outer peripheral surface of the insulator is covered from the outside, it becomes easier to mount the plug cap, and on the other hand, it becomes difficult to remove the plug cap after mounting. Further, if it is the outer peripheral surface, the concave portion is easily formed, so that the manufacturing advantage can be enjoyed.

In both the spark plug of the first aspect and the plug unit of the second aspect, the recess may be formed on the inner peripheral surface of the insulator at a position rearward of the terminal fitting.

According to this structure, the spark plug can be equipped with the plug cap having the protrusion provided in the portion inserted into the through hole. In particular, since the mounting structure is such that a part of the plug cap is press-fitted into the through hole, the plug cap has a structure that is more unlikely to come off, and moreover, the characteristic configuration of the present application (where the protrusion is inside the recess If a plug is inserted and a mounting structure for locking with the locking portion is added, these features act synergistically and the plug cap becomes more difficult to come off. Therefore, the attached state of the plug cap can be maintained more stably.

In both the spark plug of the first aspect and the plug unit of the second aspect, the through hole has an inner diameter reducing portion at a position on the front side with respect to the concave portion, the inner diameter of the inner peripheral surface becoming smaller as the inner diameter becomes closer to the front side. May be.

With this configuration, the tip end side of the insertion portion (portion to be inserted into the through hole) of the plug cap is more easily inserted into the inner side of the through hole, and after insertion, the stopper is more firmly retained near the recess. Will be done. This makes it possible to stably maintain the tip end side of the insertion portion of the plug cap (the portion that is press-fitted to the front side of the recess) in a press-fitted state with high adhesion.

In both the spark plug of the first aspect and the plug unit of the second aspect, a plurality of recesses may be formed in the insulator. The plurality of recesses may include outer recesses formed on the outer peripheral surface of the insulator and inner recesses formed on the inner peripheral surface of the insulator. The outer concave portion and the inner concave portion may be arranged at positions displaced in the front-rear direction.

If the inner peripheral portion and the outer peripheral portion of the insulator are respectively formed in this manner, the plug cap can be mounted more firmly, and if the outer concave portion and the inner concave portion are displaced in the front-rear direction. The reduction in the thickness of the insulator due to the formation of the recess inside and outside is suppressed, and the thickness can be more easily secured.

In both the spark plug of the first aspect and the plug unit of the second aspect, the inner concave portion may be arranged rearward of the outer concave portion.

When forming the inner concave portion in the through hole, it is easier to form the inner concave portion closer to the rear end (opening) of the through hole, which is a great merit in manufacturing. If the outer recess is on the rear side of the metal shell, even if it exists on the front side to some extent, there is little manufacturing demerit. Therefore, the above positional relationship is advantageous in terms of manufacturing while ensuring the thickness of the insulator.

In both the spark plug of the first aspect and the plug unit of the second aspect, a second recess different from the recess may be formed on the rear end surface of the insulator.

By doing so, it is possible to secure a longer creepage distance from the terminal fitting to the metallic shell, and it is possible to make the flashover phenomenon less likely to occur.

According to the present invention, it is possible to configure the spark plug in a form that is unlikely to cause flashover and in which the overall size can be suppressed, and a configuration that easily prevents a situation where the plug cap is unintentionally disengaged from the spark plug. Can be provided.

It is a cross-sectional schematic diagram which shows an example of the plug unit provided with the spark plug of 1st Embodiment. It is a cross-sectional schematic diagram which illustrates only the spark plug of the plug unit of FIG. It is a cross-sectional schematic diagram which illustrates only the plug cap of the plug unit of FIG. It is an expanded sectional view which expands and shows a part of plug unit of FIG. It is explanatory drawing which expands a part of spark plug of FIG. 2 and demonstrates a dimensional relationship.

A. First Embodiment A1. Basic Configuration of Plug Unit FIG. 1 is a schematic sectional view showing the overall configuration of a plug unit 100 as a first embodiment of the present invention. FIG. 2 is a schematic sectional view showing only the spark plug 1 of the plug unit 100 shown in FIG. The line CL shown in FIGS. 1 and 2 indicates the central axis of the spark plug 1. The cross sections shown in FIG. 1 and FIG. 2 are cut surfaces cut along the central axis CL at the position of the central axis CL.

In the following description, the central axis CL is also referred to as “axis line CL”, and the direction parallel to the central axis CL is also referred to as “axial direction”. The axial direction is the front-rear direction, the spark discharge gap g side is the front side of the spark plug 1 in the axial direction, and the plug cap 110 side is the rear side in the axial direction. The spark discharge gap g side in the axial direction is also referred to as the front end side of the spark plug 1, and the plug cap 110 side in the axial direction is also referred to as the rear end side.

The plug unit 100 shown in FIG. 1 includes a spark plug 1 and a plug cap 110, and the plug cap 110 is attached near the rear end of the spark plug 1.

First, an outline of the spark plug 1 will be described with reference to FIGS. The spark plug 1 includes an insulator 3, a center electrode 4, a terminal fitting 5, a metal shell 7, an electrical connecting portion 60, and a ground electrode 8.

As shown in FIG. 2, the metal shell 7 has a substantially cylindrical shape, and is formed so as to hold a part of the insulator 3 while accommodating it inside. The metal shell 7 has a body portion 7A formed on the front end side, and a threaded portion 9 formed on the outer peripheral surface of the body portion 7A. A seat portion 7B is formed on the rear end side of the body portion 7A in the metal shell 7, and an annular gasket 17 is fitted between the seat portion 7B and the screw portion 9. On the rear end side of the seat portion 7B, a deformation portion 7C, a tool engagement portion 7D, and a caulking portion 7E are formed in this order toward the rear end side. The spark plug 1 is attached to a cylinder head of an internal combustion engine (not shown) using the screw portion 9.

As shown in FIG. 2, the insulator 3 is held on the inner peripheral portion of the metal shell 7 through the talc 10 and the packings 11 and 12, and the vicinity of the front end portion is projected from the front end surface of the metal shell 7, It is fixed to the metal shell 7. The through hole 2 is a shaft hole that is formed so as to penetrate between the front end portion and the rear end portion of the insulator 3, and extends in the direction of the axis line CL. The through hole 2 has a small diameter portion 15 that holds the center electrode 4 on the front end side of the insulator 3, and a middle diameter portion 14 that houses the electrical connection portion 60 on the rear side of the small diameter portion 15. The inner peripheral surface of each of the small-diameter portion 15 and the medium-diameter portion 14 is a cylindrical surface having the axis CL as the center, and the inner periphery of the medium-diameter portion 14 is smaller than the diameter (inner diameter) of the inner peripheral surface of the small-diameter portion 15. The diameter of the surface (inner diameter) is larger. Further, between the small-diameter portion 15 and the medium-diameter portion 14, a tapered stepped portion 13 that expands toward the rear side so that the diameter of the inner peripheral surface increases toward the rear side is formed in the through hole 2. It is provided as a part. The insulator 3 is preferably a material having mechanical strength, thermal strength, electrical strength, and the like, and examples of such a material include a ceramic sintered body containing alumina as a main component.

The center electrode 4 is an electrode arranged in the through hole 2 and is held at the front end side of the through hole 2 as shown in FIG. 2 and has a front end portion (tip portion) protruding from the front end surface of the insulator 3. It is exposed. The center electrode 4 is held in a state of being insulated from the metal shell 7. The center electrode 4 has a large diameter shaft portion 4A (flange portion) having a relatively large outer diameter formed on the rear end side, and a small diameter shaft portion 4B having an outer diameter smaller than the large diameter shaft portion 4A has a large diameter shaft portion 4A. It is housed in the small-diameter portion 15 in a structure connected to the front side of the. The large diameter shaft portion 4A is locked to the step portion 13 of the through hole 2. The center electrode 4 is preferably formed of a material having thermal conductivity, mechanical strength, etc. In the example of FIG. 2, for example, inside the electrode base material 4C made of a nickel alloy containing nickel as a main component, It is formed by embedding a core material 4D made of copper or an alloy containing copper as a main component.

The ground electrode 8 is a rod-shaped member made of, for example, the same material as that of the center electrode 4, and has its base end joined to the front end face (front end face) of the metal shell 7 by welding or the like. The tip side of the ground electrode 8 is bent in a direction intersecting the axis CL, and the side surface 8A on the tip side faces the ignition part 29 at the front end (tip) of the center electrode 4 with a gap g. The gap g between the side surface 8A and the ignition part 29 is a spark discharge gap (spark gap). A noble metal tip may be provided on one or both of the center electrode 4 and the ground electrode 8.

The terminal metal fitting 5 is a metal fitting that is inserted into the through hole 2 and electrically connected to the center electrode 4, and a voltage for performing spark discharge between the center electrode 4 and the ground electrode 8 is externally centered. It is used to apply to the electrode 4. The terminal fitting 5 is arranged on the rear side of a second seal layer 62 described later and is in contact with the second seal layer 62. When the plug cap 110 is attached to the spark plug 1 as shown in FIG. 1, a conductive elastic body 153 (described later) provided on the plug cap 110 and the terminal fitting 5 are held in contact with each other. The entire terminal fitting 5 is housed in the through hole 2, and the rear end portion of the terminal fitting 5 is located in front of the rear end portion of the through hole 2 (opening on the rear end side of the insulator 3). positioned. The terminal fitting 5 is made of, for example, low carbon steel or the like, and a Ni metal layer is formed on its surface by plating or the like.

The electrical connection portion 60 is arranged inside the through hole 2 between the center electrode 4 and the terminal fitting 5. The electrical connection portion 60 functions as a conduction path that electrically connects the center electrode 4 and the terminal fitting 5 and conducts them. The electrical connection portion 60 includes a resistor 63, a first seal layer 61, and a second seal layer 62.

The resistor 63 has conductivity and functions as an electric resistance between the terminal fitting 5 and the center electrode 4. The resistor 63 functions as an electric resistance to suppress the generation of radio noise (noise) during spark discharge. The resistor 63 is formed of a resistor material formed by sintering a resistor composition containing glass powder and conductive powder containing carbon.

The first seal layer 61 and the second seal layer 62 are layers that seal the inside of the through hole 2. The first seal layer 61 and the second seal layer 62 can be formed by sintering seal powder containing glass powder such as sodium borosilicate glass and metal powder such as Cu and Fe. The first seal layer 61 is a layer that seals and fixes the insulator 3 and the center electrode 4 in the through hole 2, and functions as a conduction path that electrically connects these. The second seal layer 62 is a layer that seals and fixes the insulator 3 and the terminal fitting 5 in the through hole 2, and functions as a conduction path that electrically connects these.

Next, the outline of the plug cap 110 will be described with reference to FIGS. 1 and 3.
As shown in FIG. 1, the plug cap 110 is configured as a cap that is attached to the insulator 3 from the rear side, and has a form as shown in FIG. The plug cap 110 mainly includes a cover member 112 and a conductive portion 150.

The cover member 112 is made of rubber, other resin material, or the like, and has a property of insulating and elastically deformable. The cover member 112 partially covers the insertion portion 120 that is inserted into the through hole 2 of the insulator 3 when being attached to the spark plug 1 (see FIG. 1) and the outer peripheral surface 3A of the insulator 3 when being attached. And a covering portion 130 for covering. As shown in FIG. 3, the covering portion 130 and the insertion portion 120 are respectively formed with protrusions 141 and 142 which are inserted into the recesses (outer recess 71, inner recess 72) of the insulator 3 when mounted. The details of the connection structure for connecting the plug cap 110 and the spark plug 1 will be described later.

The conductive part 150 is embedded in the plug cap 110 and is configured as an electrical connection path. The conductive part 150 includes a wiring part 151 made of a conductive material, a terminal part 152 connected to an end of the wiring part 151, and a conductive elastic body 153 contacting the terminal part 152.

The wiring portion 151 is an electric wire portion to which a high voltage is applied. The terminal portion 152 is a terminal connected to the end portion of the wiring portion 151 and is made of a metal material. The conductive elastic body 153 is a terminal that is connected to the terminal portion 152, is configured by a conductive member that elastically deforms in the axial direction, and is configured as a spring member such as a coil spring, for example. In the mounted state as shown in FIGS. 1 and 4, the conductive elastic body 153 is arranged to be interposed between the terminal portion 152 and the terminal fitting 5 in a compressed state. At this time, the conductive elastic body 153 serves as the terminal. The contact force is applied to the terminal fitting 5 while being in contact with the fitting 5.

A2. Connection Structure Between Plug Cap and Spark Plug Next, a connection structure for connecting the plug cap 110 to the spark plug 1 will be described in detail with reference to FIGS.

As shown in FIG. 4, the insulator 3 of the spark plug 1 is provided with an outer recess 71, an inner recess 72, and a rear end recess 73, respectively. The outer concave portion 71, the inner concave portion 72, and the rear end side concave portion 73 are portions into which the protrusions 141, 142, 143 formed on the plug cap 110 are inserted, and the protrusions 141, 142 are attached when the plug cap 110 is mounted. , 143 respectively.

The outer recess 71 corresponds to an example of a “recess”, and is formed at a position on the outer peripheral surface 3</b>A of the insulator 3 on the rear side of the metal shell 7. In the example of FIG. 4, the caulking portion 7E forms the rear end portion of the metal shell 7, and the outer recess 71 is formed on the rear side of the rear end of the caulking portion 7E. The outer recess 71 has a configuration in which it is recessed from the opening end 71B formed on the outer peripheral surface 3A along a plane direction orthogonal to the axis CL. The outer recess 71 is annularly configured as a groove extending in the circumferential direction around the axis CL, and has an outer diameter at a position inside the groove of the outer recess 71 that is larger than an outer diameter of the outer peripheral surface 3A at a position outside the outer recess 71. It has a groove-like shape such that it becomes smaller.

The inner wall portion on the rear end side of the outer concave portion 71 is configured as a locking portion 71C with which a part of the plug cap 110 is locked. The locking portion 71C is formed in an annular shape around the axis CL, and at any position in the circumferential direction, the wall surface of the locking portion 71C is configured as a front-facing surface and is a plane orthogonal to the axis CL. It is a vertical surface configured to follow the direction. The direction of the wall surface of the locking portion 71C may be completely coincident with the plane direction orthogonal to the axis CL, or may be slightly inclined with respect to the plane direction orthogonal to the axis CL. Since such a locking portion 71C is formed in an annular shape around the axis line CL, the force in the direction for separating the plug cap 110 from the spark plug 1 in the mounted state as shown in FIG. 4 (FIG. 4). When a force in the direction of the arrow F shown by is applied, the locking portion 71C locks on the rear end side wall portion (locked portion) of the protrusion 141, and the rearward movement of the protrusion 141 is prevented. Acts to regulate.

The inner wall portion of the outer recess 71 on the front end side is configured as a guide portion 71D that guides the protrusion 141 of the plug cap 110 into the outer recess 71. The guide portion 71D has a wall surface that is configured to face diagonally rearward, and is configured as an inclined surface that becomes a rearward position as the wall surface moves away from the opening end portion 71B. The wall surface of the guide portion 71D inclines toward the front position as it goes to the outside in the radial direction orthogonal to the axis line CL (the side away from the axis line CL) at any position in the circumferential direction, and at any position in the circumferential direction. Is also configured as a taper surface that is inclined so as to be positioned rearward as it approaches the axis CL, and such a guide portion 71D is configured in an annular shape around the axis CL.

FIG. 5 is a partially enlarged view of a cut surface of the spark plug 1 which is cut in the direction of the axis CL through the axis CL. As shown in FIG. 5, the inner wall portion of the outer concave portion 71 on the side of the opening end portion 71B is configured as a width widening portion 81 whose opening width in the front-rear direction gradually increases as the opening end portion 71B is approached. The widened portion 81 is formed continuously from the innermost portion (bottom portion) 71E of the outer recessed portion 71 to the opening end portion 71B at any position in the circumferential direction, and the axial line CL is provided at any position in the circumferential direction. In the radial direction orthogonal to, the opening width in the front-rear direction becomes smaller as it gets closer to the axis CL, and the opening width in the front-rear direction becomes larger as it gets farther from the axis CL.

In the cut surface shown in FIG. 5 (the cut surface that passes through the axis CL and is cut in the direction of the axis CL), the linear portion of the locking portion 71C (the portion of the locking portion 71C that is linearly configured by the cutting surface). The angle θ2 formed by the axis CL and the axis CL is 90°. In addition, in the cut surface shown in FIG. 5, the linear portion of the guide portion 71D (a portion of the guide portion 71D that is linearly configured by the cut surface) and the straight portion of the outer peripheral surface 3A (the cut surface is linear. The angle θ4 formed by the formed portion and the portion formed substantially parallel to the axis CL) is larger than 90°. Note that the angle θ2 formed by the straight line portion of the locking portion 71C and the axis line CL is 90° and the straight line portion of the guide portion 71D is not limited to the cut surface of FIG. The angle θ4 formed by the linear portion of the outer peripheral surface 3A is larger than 90°.

The inner recess 72 corresponds to an example of a “recess” and is formed on the inner peripheral surface 3</b>B of the insulator 3 at a position rearward of the terminal fitting 5. Specifically, the rear end portion of the terminal fitting 5 is arranged in the front-rear direction in front of the rear end portion of the metal shell 7, and the inner recess 72 is located rearward of the rear end portion of the metal shell 7. It is arranged. The inner recess 72 is configured to be recessed from an opening end 72B formed on the inner peripheral surface 3B along a plane direction orthogonal to the axis CL. The inner concave portion 72 is configured in an annular shape as a groove portion that extends in the circumferential direction around the axis CL, and has a smaller inner diameter than that of the inner peripheral surface 3</b>B at the outer position of the inner concave portion 72. It is getting bigger.

The inner wall portion of the inner recess 72 on the rear end side is configured as a locking portion 72C with which a part of the plug cap 110 is locked. The locking portion 72C is configured in an annular shape around the axis CL, and at any position in the circumferential direction, the wall surface of the locking portion 72C is configured as a front-facing surface and is a plane orthogonal to the axis CL. It is a vertical surface configured to follow the direction. The direction of the wall surface of the locking portion 72C may be completely aligned with the plane direction orthogonal to the axis CL, or may be slightly inclined with respect to the plane direction orthogonal to the axis CL. Since such a locking portion 72C is formed in an annular shape around the axis line CL, when a force is applied to the plug cap 110 in the direction to separate it from the spark plug 1 in the mounted state as shown in FIG. The locking portion 72C locks on the rear end side wall portion (locked portion) of the protrusion 142, and acts so as to restrict the rearward movement of the protrusion 142.

The inner wall portion on the front end side of the inner recess 72 is configured as a guide portion 72D that guides the protrusion 142 of the plug cap 110 into the inner recess 72. The guide portion 72D has a wall surface that is configured as a surface that is oriented obliquely rearward, and is configured as an inclined surface that becomes a rear position as the wall surface moves away from the opening end portion 72B. The wall surface of the guide portion 72D inclines so as to be at the front position as it goes to the inner side (the side closer to the axis CL) in the radial direction orthogonal to the axis CL at any position in the circumferential direction, and at any position in the circumferential direction. Is also formed as a taper surface that is inclined so as to be located at the rear position as it goes away from the axis CL, and such a guide portion 72D is formed in an annular shape around the axis CL.

As shown in FIG. 5, the inner wall portion of the inner recess 72 on the side of the opening end 72B is configured as a widened portion 82 in which the opening width in the front-rear direction gradually increases as the opening end 72B is approached. The width widening portion 82 is configured to extend from the innermost portion (bottom portion) 72E of the inner concave portion 72 to the opening end portion 72B at any position in the circumferential direction, and at any position in the circumferential direction, the axial line CL is formed. In the radial direction orthogonal to, the opening width in the front-rear direction increases as it approaches the axis CL, and the opening width in the front-rear direction decreases as the distance from the axis CL increases.

In the cut surface shown in FIG. 5, an angle θ1 formed by the straight line portion of the locking portion 72C (a portion of the lock portion 72C that is linearly configured by the cut surface) and the axis CL is 90°. There is. Further, in the cut surface shown in FIG. 5, the straight portion of the guide portion 72D (a portion of the guide portion 72D that is linearly configured by the cut surface) and the straight portion of the inner peripheral surface 3B (specifically, An angle θ3 formed by the cut surface and the inner diameter reducing portion 2A) is larger than 90°. The angle θ1 formed by the straight line portion of the locking portion 72C and the axis line CL is 90° and the straight line portion of the guide portion 72D is not limited to the cut surface of FIG. The angle θ3 formed by the linear portion of the inner peripheral surface 3B (portion of the inner diameter reducing portion 2A) is larger than 90°.

The reduced inner diameter portion 2A is configured as a part of the through hole 2 formed in the insulator 3, and is formed at a position on the front side of the inner recess 72 with the front end portion of the opening end portion 72B as the rear end portion. ing. The inner diameter reducing portion 2A is a portion in which the inner diameter of the inner peripheral surface 3B becomes gradually smaller toward the front side. In the cut surface shown in FIG. 5, the angle θ5 formed by both inner wall portions of the reduced inner diameter portion 2A is larger than 0° and smaller than 90°, and the inner diameter of the cut surface in any direction passing through the axis CL is The angle formed by both inner wall portions of the reduced portion 2A is constant. On the front side and the rear side of the reduced inner diameter portion 2A, constant inner diameter portions 2C and 2B having a constant inner diameter are formed, respectively. The inner peripheral surfaces of the constant inner diameter portions 2C and 2B are cylindrical surfaces centering on the axis CL, and the inner diameters of the constant inner diameter portions 2C and 2B are the same. Further, the inner peripheral surface 3B has a larger inner diameter at the front end portion than at the rear end portion at the opening end portion 72B.

The outer concave portion 71 and the inner concave portion 72 are arranged in the insulator 3 so as to be displaced in the front-rear direction. Specifically, the inner concave portion 72 is arranged rearward of the outer concave portion 71. In the example of FIG. 5, the rear end of the inner recess 72 is arranged rearward of the rear end of the outer recess 71, and from the rear end of the insulator 3 to the rear end of the inner recess 72 (the locking portion 72C). The distance L21 from the rear end portion of the insulator 3 to the rear end portion (locking portion 71C) of the outer concave portion 71 is larger than the distance L11 up to (4). Further, the front end portion of the inner recess 72 is also located rearward of the rear end portion (locking portion 71C) of the outer recess portion 71, from the rear end portion of the insulator 3 to the front end portion (open end) of the inner recess portion 72. The distance L21 from the rear end portion of the insulator 3 to the rear end portion (locking portion 71C) of the insulator 3 is larger than the distance L12 to the front end of the portion 72B. The distance L22 from the rear end of the insulator 3 to the front end of the outer recess 71 (the front end of the opening end 71B) is smaller than the distance from the rear end of the insulator 3 to the rear end of the metal shell 7, In the example of FIG. 5, the distance is larger than the distance from the rear end of the insulator 3 to the front end of the reduced inner diameter portion 2A (the rear end of the constant inner diameter portion 2C).

The rear end side concave portion 73 corresponds to an example of a “second concave portion”, and functions as a portion into which a part (projection portion 143) of the plug cap 110 is inserted in the mounted state as shown in FIG. 4. The rear end side recess 73 is configured as a recess different from the above-described recesses (outer recess 71 and inner recess 72) formed on the outer peripheral surface 3A and the inner peripheral surface 3B. The rear end side recessed portion 73 is formed in a ring shape as a groove portion that extends in the circumferential direction around the axis CL, and the rear end side recessed portion 73 is dug toward the front side on the rear end surface 3C of the insulator 3. The front end portion of the inner wall portion of the rear end side recess 73 is the innermost portion.

As shown in FIGS. 1 and 4, the plug cap 110 is attached to the insulator 3 of the spark plug 1 configured as described above. As shown in FIG. 3, the plug cap 110 is formed in a shaft shape extending in the direction of the center line CL2, and a hole 114 is formed on one end side of the cover member 112 in the axial direction. The hole 114 is a part that accommodates and covers the vicinity of the rear end of the insulator 3 in the mounted state as shown in FIG. The portion of the cover member 112 in which the hole 114 is formed has a cylindrical shape, and the protrusion 141 is formed on the inner peripheral surface of the hole 114. The protrusion 141 is arranged on the inner peripheral surface of the hole 114 so as to extend in the circumferential direction around the center line CL2, and has a form protruding toward the center line CL2. The inner diameter of the portion of the inner peripheral surface of the hole 114 other than the protrusion 141 is approximately the same as the outer diameter of a part of the outer peripheral surface 3A (a portion of the region covered by the covering portion 130 other than the outer recess 71). Has become. In the hole 114, the inner diameter of the portion of the protrusion 141 is about the same as the outer diameter of the portion of the outer recess 71 of the insulator 3.

The insertion portion 120 is a portion that is inserted into the through hole 2 in the mounted state as shown in FIG. 4, and protrudes from the bottom portion of the hole portion 114 along the direction of the center line CL2 (specifically, It is formed in a cylindrical shape so as to project to the outside of the hole 114). A protrusion 142 is formed on the inner side of the insertion portion 120 with respect to the protrusion 141 (on the bottom side of the hole 114 ). The protrusion 142 extends in the circumferential direction around the center line CL2 on the outer peripheral surface of the insertion portion 120, and has a form (flange form) protruding toward the side away from the center line CL2. The outer diameter of the portion of the outer peripheral surface of the insertion portion 120 other than the protrusion 142 is approximately the same as the inner diameter of a part of the inner peripheral surface 3B of the insulator 3 (a region other than the inner recess 72 on the rear side of the terminal fitting 5). Has become. The outer diameter of the protruding portion 142 is approximately the same as the inner diameter of the inner concave portion 72 of the insulator 3.

As shown in FIG. 3, a protrusion 143 is formed at the bottom of the hole 114 in such a size that it fits into the above-mentioned rear end side recess 73. The protruding portion 143 is a portion to be inserted into the rear end side concave portion 73 in the mounted state as shown in FIG. The protrusion 143 is annularly arranged at the bottom of the hole 114 so as to extend in the circumferential direction around the center line CL2, and has a form protruding in the direction along the center line CL2.

A3. Effect According to the plug unit 100 described above, in the spark plug 1, while suppressing the overall size in the front-rear direction, a larger creepage distance from the terminal metal fitting 5 to the metal shell 7 is ensured to further prevent flashover. be able to. Then, the plug cap 110 is firmly attached to the spark plug 1 such that the insertion portion 120 is inserted into the through hole 2 of the insulator 3 and the outer peripheral surface 3A of the insulator 3 is covered with the covering portion 130. You can Further, when the plug cap 110 is mounted, the protrusions 141 and 142 formed on the plug cap 110 are engaged with the engaging portions 71C and 72C formed on the outer recess 71 and the inner recess 72, respectively. Therefore, it becomes difficult for the plug cap 110 to come off. Moreover, since the wall surfaces of the locking portions 71C and 72C are configured as vertical surfaces that are orthogonal to the axis Cl, the wall surfaces of the locking portions 71C and 72C are not attached to the plug cap 110 when the plug cap 110 is attached, as in the direction of arrow F shown in FIG. On the other hand, even if a backward force (a force in the direction of separating from the insulator 3) is applied, the state in which the protrusions 141 and 142 are caught by the locking portions 71C and 72C is likely to be stably maintained, and the protrusions 141 and It becomes difficult for 142 to come out of each recess (the outer recess 71 and the inner recess 72). Therefore, it is possible to more effectively prevent a situation in which the plug cap 110 is unintentionally disengaged from the spark plug 1.

In addition, in the plug unit 100 of the first embodiment, the inner wall portion on the front end side of the outer recess portion 71 has a guide portion 71D configured as an inclined surface which becomes a rear position as the wall surface moves away from the opening end portion 71B. There is. If the guide portion 71D is provided in this manner, when the covering portion 130 of the plug cap 110 is mounted on the insulator 3 from the rear side, the protrusion 141 fed from the rear side hits the guide portion 71D, and the guide portion 71D. The inclination of facilitates smooth guiding into the outer recess 71. If the protrusion 141 is more easily inserted into the outer recess 71, the adhesion between the protrusion 141 and the outer recess 71 can be more easily enhanced. The inner wall portion of the inner recess 72 on the front end side also has a similar guide portion 72D, and the same effect can be produced.

In addition, in the plug unit 100 of the first embodiment, the inner wall portion of the outer concave portion 71 on the side of the opening end portion 71B has the widening portion 81 in which the opening width in the front-rear direction gradually increases toward the opening end portion 71B. There is. If the width-enlarged portion 81 is provided in this manner, the protrusion 141 is more easily inserted from the opening end portion 71B side when the plug cap 110 is mounted. The inner wall portion of the inner concave portion 72 on the side of the opening end 72B also has the similar widened portion 82, and the same effect can be produced.

In addition, in the plug unit 100 of the first embodiment, the outer recess 71 is formed on the outer peripheral surface 3A of the insulator 3 at a position rearward of the metal shell 7. According to this configuration, the plug cap 110 as shown in FIG. 3 (the plug cap in which the protrusion 141 is provided on the portion covering the outer peripheral surface 3A of the insulator 3) can be favorably attached to the spark plug 1. In particular, since the mounting structure is such that the outer peripheral surface 3A of the insulator 3 is covered from the outside, the plug cap 110 can be mounted more easily, while the plug cap 110 is less likely to be removed after mounting. Further, with the outer peripheral surface 3A, since the concave portion is easily formed, the manufacturing advantage can be enjoyed.

Further, in the plug unit 100 of the first embodiment, the inner recess 72 is formed on the inner peripheral surface 3B of the insulator 3 at a position rearward of the terminal fitting 5. According to this configuration, the plug cap 110 as shown in FIG. 3 (the plug cap in which the protrusion 142 is provided in the portion to be inserted into the through hole 2) can be favorably attached to the spark plug 1. In particular, since the mounting structure is such that a part of the plug cap 110 is press-fitted into the through hole 2, the plug cap 110 has a structure that is more unlikely to come off, and moreover, the characteristic configuration of the present application (projection part If 142 is inserted into the inner concave portion 72 and an attachment structure that locks with the locking portion 72C is added, these features act synergistically and the plug cap 110 becomes more difficult to come off. Therefore, the attached state of the plug cap 110 is likely to be maintained more stably.

Further, in the plug unit 100 of the first embodiment, the through hole 2 has an inner diameter reducing portion 2A at a position on the front side of the inner recess 72, the inner diameter reducing portion 2A having a smaller inner diameter on the inner peripheral surface 3B toward the front side. There is. With this configuration, the tip end side of the insertion portion 120 (portion to be inserted into the through hole 2) formed in the plug cap 110 is easily inserted into the inner side of the through hole 2, and after the insertion, the inner recess 72 is formed. In the vicinity of, it will be more firmly prevented from coming off. As a result, the tip end side of the insertion portion 120 of the plug cap 110 (the portion that is press-fitted to the front side of the recess) can be stably maintained in a press-fitted state with high adhesion.

Further, in the plug unit 100 of the first embodiment, the outer concave portion 71 and the inner concave portion 72 are formed on the outer peripheral portion and the inner peripheral portion of the insulator 3, respectively, and the outer concave portion 71 and the inner concave portion 72 are displaced in the front-rear direction. It is located in. If the outer concave portion 71 and the inner concave portion 72 are respectively formed in this way, the plug cap 110 can be mounted more firmly, and if the outer concave portion 71 and the inner concave portion 72 are displaced in the front-rear direction, The reduction in the thickness of the insulator 3 due to the formation of the recesses inside and outside is suppressed, and the thickness can be more easily ensured.

Further, the inner concave portion 72 is arranged rearward of the outer concave portion 71. When the inner recess 72 is formed in the through hole 2, it is easier to form the inner recess 72 closer to the rear end (opening) of the through hole 2, which is a great merit in manufacturing. If the outer concave portion 71 is on the rear side of the metal shell 7, even if it exists on the front side to some extent, there is little disadvantage in manufacturing. Therefore, the above-mentioned positional relationship is advantageous in terms of manufacturing while ensuring the thickness of the insulator 3.

The rear end surface 3C of the insulator 3 is formed with a rear end side recess 73 (second recess) different from the recesses (the inner recess 72 and the outer recess 71) locked by the outer peripheral surface 3A or the inner peripheral surface 3B. .. By doing so, it is possible to secure a longer creepage distance from the terminal fitting 5 to the metallic shell 7, and it is possible to make the flashover phenomenon less likely to occur.

<Other Embodiments>
The present invention is not limited to each aspect and modified example of the embodiments of the present specification, and can be realized with various configurations without departing from the gist thereof. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each mode described in the column of the outline of the invention are to solve some or all of the above-mentioned problems, or In order to achieve some or all of the above effects, the replacement and combination can be appropriately performed. If the technical features are not described as essential in this specification, they can be deleted as appropriate. For example, the following is applicable as a modified example.

In the spark plug 1 of the first embodiment, as an example in which a plurality of "recesses" are formed, an outer recess 71 is formed on the outer peripheral surface 3A of the insulator 3 and an inner recess 72 is formed on the inner peripheral surface 3B. However, either one of the outer concave portion 71 and the inner concave portion 72 may not be provided.

In the spark plug 1 of the first embodiment, an example in which the outer peripheral surface 3A of the insulator 3 is provided with one outer concave portion 71 and the inner peripheral surface 3B is provided with one inner concave portion 72 is shown. The outer peripheral surface may be provided with two or more outer recesses, and in this case, the plug cap may be formed with two or more protrusions to be inserted into the two or more outer recesses. Alternatively, the inner peripheral surface of the insulator may be provided with two or more inner recesses, and in this case, the plug cap may be formed with two or more protrusions to be inserted into the two or more inner recesses. Good.

In the spark plug 1 of the first embodiment, an example is shown in which the wall surfaces of the locking portions 71C and 72C are configured as vertical surfaces along the plane direction orthogonal to the axis Cl, but in any locking portion, It may be configured as an inclined surface such that the wall surface becomes a rearward position as it moves away from the opening end. For example, as long as it is the locking portion of the outer concave portion, it may be configured as an inclined surface that becomes a rear position at any position in the circumferential direction as it approaches the axis. Further, as long as it is the locking portion of the inner concave portion, it may be configured as an inclined surface that becomes a rear position at any position in the circumferential direction as it goes away from the axis. That is, the angle θ1 shown in FIG. 5 can be an angle exceeding 90°, and the angle θ2 can be an angle less than 90°. With this configuration, when a backward force (a force in a direction of separating from the insulator) is applied to the plug cap when the plug cap is attached, the state in which the protrusion is caught is more easily maintained.

In the first embodiment, the outer concave portion 71 and the inner concave portion 72 are each configured as a groove portion, and each groove portion is continuously formed over the entire range in the circumferential direction, but the present invention is not limited to this example. The outer recessed portion 71 may be configured as a recessed portion formed only in a part (a predetermined one place or a predetermined plurality of places) in the circumferential direction on the outer peripheral surface 3A of the insulator 3, and for example, on the outer peripheral surface 3A. It may be configured as a groove portion intermittently formed in the direction. Similarly, the inner concave portion 72 may be formed as a concave portion formed only in a part (a predetermined one place or a plurality of predetermined places) in the circumferential direction on the inner peripheral surface 3B of the insulator 3. It may be configured as a groove portion intermittently formed in the circumferential direction on the circumferential surface 3B.

DESCRIPTION OF SYMBOLS 1... Spark plug 2... Through hole 2A... Inner diameter reduction part 3... Insulator 4... Center electrode 5... Terminal metal fitting 7... Metal shell 71... Outer recessed part (recessed part)
72... Inner recess (recess)
73... Rear end side recess (second recess)
71B, 72B... Open end 71C, 72C... Engaging part 71D, 72D... Guide part 81, 82... Width expansion part 100... Plug unit 110... Plug cap 120... Insertion part 130... Cover part 141, 142, 143... Protrusion Department

Claims (10)

An insulator having a through hole extending in the direction of the axis,
A tubular metal shell that holds the insulator inside,
A center electrode arranged in the through hole in a state where the tip portion of the insulator is exposed from the tip portion of the insulator,
A terminal fitting inserted into the through hole and electrically connected to the center electrode,
A spark plug comprising:
The rear end portion of the terminal fitting is disposed on the front side of the rear end portion of the through hole,
A recess is formed in at least one of the outer peripheral surface of the insulator on the rear side of the metal shell, or on the inner peripheral surface of the through hole of the insulator on the rear side of the terminal fitting,
The recess has a configuration in which the recess is formed along the plane direction orthogonal to the axis from the opening end formed on the outer peripheral surface or the inner peripheral surface,
The inner wall portion of the recess on the rear end side is a locking portion configured as a vertical surface having a wall surface in a direction orthogonal to the axis or an inclined surface having a rearward position as the wall surface moves away from the opening end portion. Spark plug with. The spark plug according to claim 1, wherein the inner wall portion of the recess on the front end side has a guide portion that is configured as an inclined surface that becomes a rearward position as the wall surface moves away from the opening end portion. The spark plug according to claim 1 or 2, wherein the inner wall portion of the recess on the opening end side has a width widening portion whose opening width in the front-rear direction gradually increases toward the opening end. The spark plug according to any one of claims 1 to 3, wherein the recess is formed at a position rearward of the metal shell on the outer peripheral surface. The spark plug according to any one of claims 1 to 3, wherein the recess is formed at a position rearward of the terminal fitting on the inner peripheral surface. The spark plug according to claim 5, wherein the through-hole has an inner diameter reducing portion at a position on the front side of the recess, the inner diameter reducing portion having an inner diameter on the front side that becomes smaller. A plurality of the recesses are formed in the insulator,
The plurality of recesses includes an outer recess formed on the outer peripheral surface and an inner recess formed on the inner peripheral surface,
The spark plug according to any one of claims 1 to 6, wherein the outer recess and the inner recess are arranged at positions displaced in the front-rear direction. The spark plug according to claim 7, wherein the inner concave portion is arranged rearward of the outer concave portion. The spark plug according to any one of claims 1 to 8, wherein a second recess different from the recess is formed on a rear end surface of the insulator. A spark plug according to any one of claims 1 to 9,
A plug cap attached to the insulator from the rear side,
Including
The plug cap is
An insertion portion that is inserted into the through hole at the time of mounting,
A covering portion that covers the outer peripheral surface when mounted,
Equipped with
A plug unit in which at least one of the insertion portion and the covering portion has a protrusion that is inserted into the recess during mounting.

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