JP5333749B2 - Spark plug - Google Patents

Description

  The present invention relates to a spark plug used for an internal combustion engine.

  Conventionally, a spark plug has a structure in which a center electrode, an insulator holding the center electrode, and a metal shell provided with a ground electrode at the tip are supported and fixed in the metal shell. Are known. (For example, refer to Patent Document 1).

  A spark plug used in an internal combustion engine has a ground electrode welded to the front end of the metal shell that holds the insulator in which the center electrode is inserted, and the free end of the ground electrode is connected to the front end of the center electrode. A spark discharge gap is formed facing the part. Then, spark discharge is performed between the center electrode and the ground electrode, and the fuel air exposed between the two electrodes is ignited to form a flame kernel.

  Assembling of the metal shell and insulator in the spark plug is performed by inserting the tip of the insulator from the rear opening of the metal shell toward the front and forming the insulator at the rear opening of the rear opening. This is done by press-fitting the large diameter portion. And in order to radiate the heat | fever of the heated insulator, the heat radiating member is press-fitted between the metal shell and the insulator.

  The heat dissipating member is formed in an annular shape, and an outer press-fitting contact portion that is press-fitted into the inner peripheral surface of the metal shell is formed on a part of the outer surface of the heat radiating member. An inner press-fit contact portion to be press-fitted is formed.

  When the insulator is assembled to the metal shell, the heat radiating member is press-fitted into the metal shell in advance, and then the insulator is press-fitted into the metal shell. Along with the press-fitting, a small-diameter portion (also referred to as a long leg portion) on the front side of the insulator is press-fitted into the heat dissipation member. As a result, the heat of the heated insulator is radiated to the metal shell through the heat radiating member.

JP 2007-305374 A

  However, in the above configuration, when the insulator is pressed into the heat radiating member, if the insulator has eccentricity or shaft runout, the heat radiating member does not uniformly contact over the entire outer periphery of the insulator, and the leg length In some cases, a large bending stress was applied to the rear base of the part, and the insulator was damaged.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a spark plug in which an insulator is not damaged when the insulator is assembled.

The above-described object of the present invention is achieved by the following configuration.
(1) a central electrode extending in the axial direction;
A cylindrical insulator holding the center electrode on its front side;
A cylindrical metal shell for housing a part of the insulator;
One end is joined to the front side end of the metal shell, and the other end forms a spark discharge gap with the center electrode,
An annular heat radiating member that is press-fitted into a front-side small-diameter portion that is smaller than the outer diameter of the rear portion of the insulator, and that forms a heat-dissipating path by connecting the insulator and the metal shell. A spark plug comprising:
The metal shell is a shelf that has a flat surface substantially parallel to the radial direction, and is a surface that protrudes inward in the radial direction and is included in a range of ± 30 degrees with respect to the radial direction. Have
The spark plug is characterized in that the heat radiating member is in contact with the metal shell by being supported by the flat surface of the shelf in a state of being separated from the inner peripheral surface of the metal shell.

  (2) The metal shell has a screw part for screwing into the engine on an outer peripheral surface, and the shelf part is provided on the inner side of the screw part. Spark plug.

(3) The metal shell is airtightly coupled to the rear portion of the insulator,
The relationship between the frictional force F1 at the hermetic coupling portion between the metal shell and the insulator and the frictional force F2 at the press-fitting portion between the insulator and the heat radiating member is F1> F2. The spark plug according to 1) or (2).

  (4) The spark plug according to any one of (1) to (3), wherein the heat radiating member and the shelf are fixed by material bonding.

  (5) The spark plug according to (4), wherein the material bonding is welding, brazing, or soldering.

  (6) The relationship between the adhesive force F3 at the material coupling portion between the heat dissipation member and the shelf and the frictional force F2 at the press-fitting portion between the insulator and the heat dissipation member is F2 <F3. The spark plug according to (4) or (5).

(7) While being press-fitted to the rear side of the shelf portion of the inner peripheral surface of the metal shell, and being sandwiched in the axial direction together with the heat dissipation member between the insulator and the shelf portion, A pressing member that presses the heat dissipation member toward the flat surface of the shelf;
The spark plug according to any one of (1) to (3), wherein the pressing member is separated from the heat dissipation member in the radial direction.

  (8) The relationship between the frictional force F2 at the press-fitted portion between the insulator and the heat radiating member and the frictional force F4 at the press-fitted portion between the pressing member and the metal shell is F2 <F4. The spark plug according to (7).

  (9) The metal shell has a pocket portion having an inner diameter larger than the outer diameter of the pressing member on the rear side of the portion into which the pressing member is press-fitted, and the pocket of the inner peripheral surface of the metal shell is the pocket. The spark plug according to (7) or (8), wherein a tapered surface is formed between an inner peripheral surface of the portion and a press-fitting surface into which the pressing member is press-fitted.

  (10) The pressing member has a protrusion deformed by a load at a rear end portion of the pressing member, and the pressing member is interposed between the insulator and the shelf together with the heat dissipation member in a state where the protrusion is deformed. The spark plug according to any one of (7) to (9), wherein the spark plug is sandwiched.

  (11) The above-described (7) to (10), wherein a metal buffer member softer than the heat radiating member and the pressing member is disposed between the heat radiating member and the pressing member in the axial direction. ) Spark plug according to any one of the above.

According to the configuration of (1), the heat radiating member protrudes inward in the radial direction of the shelf in a state of being separated from the inner peripheral surface of the metal shell, and is included in a range of ± 30 degrees with respect to the radial direction. it is a surface, since it is supported by radial and substantially parallel flat surfaces, when press fitting the insulator to the heat radiating member, eccentric to the insulator, even axial runout, the heat radiating member and the ledges of Since the positional relationship in the axial direction is maintained, bending stress applied to the insulator can be reduced and damage to the insulator can be prevented.

  According to the configuration of (2), since the shelf is provided inside the threaded portion that is screwed with the engine, the heat radiated from the heat radiating member to the metal shell is quickly radiated to the engine. Therefore, the heat dissipation efficiency is further increased.

  According to the configuration of (3), the metal shell and the insulator are thermally expanded, and in particular, when the insulator extends in the axial direction relative to the metal shell, the insulator is insulated from the metal shell. A tensile stress is generated between the hermetic coupling portion with the body and the press-fitting portion between the insulator and the heat dissipation member. At this time, since F1> F2, even if the generated tensile stress exceeds the frictional force F2, the insulator slides in the axial direction with respect to the heat radiating member, and the tensile stress is less than the frictional force F2. As a result, the airtightness of the metal shell and the insulator is not affected, and the airtightness can be ensured. Further, even if the insulator slides in the axial direction with respect to the heat radiating member, the press-fitting structure between the heat radiating member and the insulator is maintained, so that heat dissipation from the insulator to the heat radiating member can be ensured. Here, as an airtight structure between the metal shell and the insulator, a fitting structure such as press fitting, shrink fitting, cold fitting, interference fitting due to a diameter difference, or a caulking structure can be employed.

  According to the configuration of (4), since the heat radiating member is material-bonded to the shelf of the metal shell, the heat radiating member and the metal shell are kept in close contact with each other, the contact thermal resistance is reduced, and the heat is radiated. The heat dissipation effect from the member to the metal shell is improved.

  According to the configuration of (5), since the heat radiating member is coupled to the shelf by welding, brazing, or soldering, the heat radiating member and the metal shell are kept in close contact with each other, and the heat radiating effect on the metal shell is improved. To do.

  According to the configuration of (6), the metal shell and the insulator thermally expand, and particularly when the insulator extends in the axial direction relative to the metal shell, the heat radiating member includes the heat radiating member and the shelf. Tensile stress is generated between the material coupling part with the part and the press-fitting part between the insulator and the heat dissipation member. At this time, since F2 <F3, even if the generated tensile stress exceeds the frictional force F2, the insulator slides in the axial direction with respect to the heat radiating member, and the tensile stress is less than the frictional force F2. Therefore, the material coupling portion between the heat radiating member and the shelf is not broken. Further, even if the insulator slides in the axial direction with respect to the heat radiating member, the press-fitting structure between the heat radiating member and the insulator is maintained, so that heat dissipation from the insulator to the heat radiating member can be ensured.

  According to the structure of said (7), since a heat radiating member is pressed by the shelf by the pressing member, the contact with a heat radiating member and a shelf becomes favorable and the heat dissipation effect improves.

  According to the configuration of (8), the metal shell and the insulator are thermally expanded. In particular, even when the insulator extends in the axial direction relative to the metal shell, F2 <F4. The insulator slides in the axial direction with respect to the heat radiating member, and the press-fitted portion between the pressing member and the metal shell is not destroyed. Further, even if the insulator slides in the axial direction with respect to the heat radiating member, the press-fitting structure between the heat radiating member and the insulator is maintained, so that heat dissipation from the insulator to the heat radiating member can be ensured.

  According to the configuration of (9), since there is a pocket portion, it is possible to prevent the pressing member from being inserted in an inclined state when the pressing member is inserted into the press-fit portion, and the pocket portion to the press-fit portion are tapered. Since it is a surface, it is easy to insert.

  According to the configuration of (10) above, the pressing member is sandwiched between the insulator and the shelf in a state where the projection is plastically deformed or elastically deformed, so that the contact between the heat dissipation member and the shelf is stabilized. can do. Moreover, the dimension variation in the axial direction of each component which comprises spark plugs, such as an insulator, a metal fitting, and a heat radiating member, can be absorbed.

  According to the configuration of (11), since the buffer member is deformed when the heat radiating member is pressed by the pressing member, the close contact state between the heat radiating member and the shelf is more stable, and the heat dissipation is improved.

  According to the present invention, the heat radiating member press-fitted into the insulator is configured to be movable in the radial direction on the flat surface of the shelf formed on the metal shell. Therefore, when the insulator is inserted into the metal shell, even if the insulator is eccentric or oscillating, the heat dissipating member moves in the radial direction and the axial relationship between the heat dissipating member and the shelf is maintained. The bending stress does not act on the insulator, and the insulator can be prevented from being damaged. Further, the heat received by the insulator can be efficiently radiated to the shelf of the metal shell through the heat radiating member.

  Furthermore, after the assembly of the insulator to the metal shell, the heat dissipation member is bonded to the shelf of the metal shell, so that the contact between the heat dissipation member and the shelf can be improved and the heat dissipation effect can be improved.

  Furthermore, by pressing the heat radiating member against the shelf of the metal shell by the pressing member, the contact between the heat radiating member and the shelf can be improved and the heat radiation effect can be improved.

It is sectional drawing of the spark plug which concerns on 1st Embodiment of this invention. It is an expanded sectional view of the important section of a spark plug. It is a partially cutaway perspective view of the main part showing the structure of the spark plug. It is an expanded sectional view of the important section showing a 2nd embodiment of a spark plug. It is a partially cutaway perspective view of the main part showing the structure of the spark plug. It is an expanded sectional view of the important section showing comparative example 1 of a spark plug. It is an expanded sectional view of the important section showing comparative example 2 of a spark plug. It is an expanded sectional view of the important section showing a 3rd embodiment of a spark plug. It is an expanded sectional view of the important section showing a 4th embodiment of a spark plug. It is an expanded sectional view of the important section showing comparative example 3 of a spark plug. It is a characteristic view which shows an experimental result. It is an expanded sectional view of the important section showing a 5th embodiment of a spark plug. It is an expanded sectional view of the important section showing a 6th embodiment of a spark plug. It is an expanded sectional view of the important section showing a 7th embodiment of a spark plug. It is an expanded sectional view of the important section showing comparative example 4 of a spark plug. It is an expanded sectional view of the important section showing comparative example 5 of a spark plug. It is an expanded sectional view of the important section showing comparative example 6 of a spark plug. It is a characteristic view which shows an experimental result.

  Hereinafter, preferred embodiments of the spark plug according to the present invention will be described with reference to the drawings.

First Embodiment FIG. 1 is a cross-sectional view showing the overall configuration of a spark plug according to a first embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view showing the main configuration of the spark plug, and FIG. 3 is the main configuration of the spark plug. FIG.
In the description of the present embodiment, the overall configuration of the spark plug will be described, and then the configuration of the main part will be described.

  The spark plug 10 according to the present embodiment includes a cylindrical metal shell 11 and a cylindrical insulator 12 that is fitted into the metal shell 11 and has its tip 12a exposed from the tip 11a of the metal shell 11. A center electrode 13 disposed in the insulator 12 such that the tip end portion 13a of the insulator 12 is exposed from the tip end portion 12a of the insulator 12, and a ground electrode 14 fixed to the tip end portion 11a of the metal shell 11. Etc. are mainly provided.

  In the following description, the lower side of the mounting surface B of the engine head A shown in FIG. 1, that is, the combustion chamber side in the axial direction of the center electrode 13 is “front side”, and the opposite side is “rear side”. ".

  The metal shell 11 is made of carbon steel or the like, and the surface is galvanized as necessary. On the outer peripheral surface of the metal shell 11, for example, a mounting screw portion 15 for mounting to the engine head A of an internal combustion engine is formed in the circumferential direction. In the insulator 12 made of a ceramic sintered body such as alumina, the terminal fitting 17 is exposed at the end on the rear side (upper side in the drawing) of the through hole 16 formed in the axial direction. The center electrode 13 is inserted and fixed at the front end (downward in the figure) with the tip 13a exposed. Inside the center electrode 13, a copper core 13b is provided.

  In addition, a resistor 18 is disposed in an intermediate portion between the terminal fitting 17 and the center electrode 13 in the through-hole 16, and conductive glass seal layers 19, 20 is arranged. That is, the center electrode 13 and the terminal fitting 17 are electrically connected through the resistor 18 and the conductive glass seal layers 19 and 20. The conductive glass seal layers 19 and 20 and the resistor 18 form a conductive coupling layer.

  A shelf 21 having an inner diameter gradually decreasing toward the front side is formed on the inner wall of the metal shell 11. Further, a step portion 22 having an outer diameter gradually decreasing toward the front side is formed on the outer wall of the insulator 12 so as to face the shelf portion 21 of the metal shell 11.

  When the insulator 12 is press-fitted into the rear opening of the metal shell 11, the gap between the metal shell 11 and the insulator 12 is hermetically closed.

  A gas seal portion 23 protruding outward in the radial direction is formed on the rear side of the metal shell 11, and a gasket 24 is disposed on the front side of the gas seal portion 23. The contact surface of the engine head A that contacts the gasket 24 is the mounting surface portion B.

  Further, the gas seal portion 23 has a circular shaft cross-sectional shape, the tool engagement portion 25 on the rear side of the gas seal portion 23 has a hexagonal cross-sectional shape, and is used to fix the spark plug 10 to the engine head A. The spark plug 10 is screwed into the engine head A by engaging a tool with the tool engaging portion 25.

  Although the overall configuration of the spark plug 10 has been described above, the configuration and operation of the main part will be described below with reference to FIGS. 2 and 3. 2 is an enlarged view of a portion surrounded by a dotted line in FIG. 1, and the same members are denoted by the same reference numerals, and redundant description is omitted or simplified.

  In the present embodiment, on the front side of the metal shell 11, a shelf portion 31 is formed on the inner peripheral surface and has a flat surface extending in the radial direction and substantially parallel to the radial direction. The shelf 31 is formed in an annular shape on the inner peripheral surface of the metal shell 11. The flat surface substantially parallel to the radial direction means a surface included in a range of ± 30 degrees with respect to the radial direction, and a flat surface parallel to the radial direction is more preferable.

  On the other hand, an annular heat radiating member 32 is fixed to the front side small diameter portion (leg long portion) 12b of the insulator 12 by press fitting. The heat dissipating member 32 is formed of a metal having excellent heat conduction in a ring shape and a substantially square cross section, and is manufactured as a member separate from the metal shell 11 and the insulator 12.

  When assembling the spark plug 10, the insulator 12 is inserted from the rear opening of the metal shell 11. Prior to this, the heat radiating member 32 is loaded in advance on the rear side of the shelf 31 of the metal shell 11. When the insulator 12 is inserted in this state, the front-side small diameter portion 12 b of the insulator 12 is press-fitted into the opening of the heat dissipation member 32. What should be noted in this configuration is that when the insulator 12 is press-fitted, the heat radiation member 32 moves in the radial direction even if the insulator 12 has eccentricity or shaft runout, so that bending stress applied to the insulator 12 is reduced. This can prevent the insulator 12 from being damaged.

  That is, when the insulator 12 and the heat radiating member 32 abut, the heat radiating member 32 can move on the shelf 31 in the radial direction. Therefore, even if the insulator 12 has eccentricity or shaft runout, the heat dissipating member 32 moves in the radial direction, and the positional relationship in the axial direction between the heat dissipating member 32 and the shelf 31 is maintained. It is possible to suppress the bending of the insulator 12 by preventing the bending stress from being exerted on the insulator by being properly press-fitted into the member 32.

  On the other hand, when the spark plug 10 is used, the temperature in the combustion chamber of the engine head A rises and the insulator 12 also becomes high temperature. The heat received by the insulator 12 is conducted from the outer peripheral surface of the insulator 12 to the heat radiating member 32. Since the heat dissipating member 32 forms a heat dissipating path between the insulator 12 and the metal shell 11, the heat conducted to the heat dissipating member 32 is conducted from the front end surface 32 a of the heat dissipating member 32 to the shelf 31, and the shelf Heat is radiated through the metal shell 11 integrated with the portion 31.

  In addition, since the insulator 12 has a press-fit structure in which the insulator 12 is assembled by press-fitting, the load applied to the shelf 31 is smaller than that of a spark plug having a crimped structure (see FIG. 17). The directional thickness can be reduced. For this reason, the axial distance from the front-end | tip of the insulator 12 to the thermal radiation member 32 can be shortened by the part which the shelf part 31 became thin, and the thermal radiation effect can be improved. Further, if the axial distance from the tip of the insulator 12 to the heat radiating member 32 is the same as the axial distance from the tip of the insulator to the plate packing in the spark plug (see FIG. 17) of the caulking structure. The axial distance from the tip of the insulator 12 to the shelf 31 can be increased by the amount that the axial thickness of the shelf 31 is reduced. Thereby, the backfire resulting from carbon pollution can be suppressed and the frequency of misfire malfunction can be lowered | hung. Thus, in the spark plug of the present embodiment, it is possible to improve the stain resistance while ensuring heat dissipation.

Second Embodiment Next, a second embodiment of the present invention will be described.
FIG. 4 is an enlarged cross-sectional view showing the main configuration of the spark plug 10, and FIG. 5 is a partially cutaway perspective view showing the main configuration. In addition, about the code | symbol, the same code | symbol is attached | subjected to the same member similarly to the above.

  In the second embodiment, the shelf 31 is configured in the same manner as described above, but the shape of the heat dissipation member 33 is different. That is, although the heat radiating member 33 is formed in an annular shape, the cross section is formed in an L shape, and the front end surface 33 a serves as a contact surface with the shelf portion 31. Further, a small diameter portion 33b is formed on the inner peripheral surface of the heat radiating member 33, and the insulator 12 is press-fitted into the small diameter portion 33b.

  Also in the second embodiment, the assembly of the metal shell 11 to the insulator 12 is performed in the same manner as in the first embodiment. And when the insulator 12 and the heat radiating member 33 contact | abut, the heat radiating member 33 can move on the shelf part 31 to a radial direction. Therefore, even if the insulator 12 has eccentricity or shaft runout, the heat radiating member 33 moves in the radial direction, so that the bending stress applied to the insulator 12 can be reduced and the insulator 12 can be prevented from being damaged.

  Further, the heat received by the insulator 12 is conducted from the outer peripheral surface of the insulator 12 to the heat radiating member 33, and the heat conducted to the heat radiating member 33 is conducted from the front end face 33 a of the heat radiating member 33 to the shelf 31. Then, heat is radiated through the metal shell 11 integrated with the shelf 31.

Next, a comparative example for comparing the heat dissipation characteristics of the first embodiment will be described.
Comparative Example 1
FIG. 6 is an enlarged cross-sectional view of a main part showing the configuration of the spark plug.
In this comparative example 1, the heat dissipation member is not provided as a separate member. That is, a shelf 27 having an inner diameter gradually decreasing toward the front side is provided on the inner wall surface of the metal shell 11, and a heat radiating portion 27a whose end is pressed against the insulator 12 is formed by thinning its tip. is there. The heat radiation part 27a is formed in an annular shape.

  Therefore, when the insulator 12 is press-fitted from the rear side opening of the metal shell 11, the insulator 12 is inserted through the metal shell 11 while being pressed against the heat radiating portion 27a, and when the insulator 12 is press-fitted to a predetermined position, the insulator 12 is inserted. The tip of the heat radiating portion 27a comes into pressure contact with the entire outer periphery of the.

  According to this configuration, the heat of the insulator 12 is conducted to the heat radiating portion 27 and radiated to the metal shell 11.

Comparative Example 2
FIG. 7 is an enlarged cross-sectional view of a main part showing the configuration of the spark plug.
The heat dissipating member 28 in the second comparative example is manufactured as a separate member from the metal shell 11 and the insulator 12. Although the heat radiating member 28 is formed in an annular shape, an outer press-fit contact portion 28a that is press-fitted into the inner wall surface of the metal shell 11 is formed in a part of the outer surface, and the insulator 12 is press-fitted into a part of the inner peripheral surface. For this purpose, an inner press-fit contact portion 28b is formed.

  When the insulator 12 is press-fitted into the metal shell 11, the insulator 12 is press-fitted with the heat radiating member 28 fitted therein. And if it press-fits to a predetermined position, the thermal radiation member 28 will be fixed in the press-fit state between the metal shell 11 and the insulator 12.

  The heat received by the insulator 12 is conducted to the inner press-fit contact portion 28b and is radiated from the outer press-fit contact portion 28a to the metal shell 11.

Next, the results of a comparative experiment between Example 1 that is the configuration of the first embodiment and Comparative Examples 1 and 2 will be described.
Experimental result 1
In the experiment, the heat sink and insulator were assembled to the metal shell, and then disassembled to confirm the condition of damage to the insulator. The number used for the experiment is 100 for the first example and comparative examples 1 and 2.
In the structure of Example 1, the damage of the insulator was 0 among 100 test examples.
In the structure of Comparative Example 1, among the 100 test examples, 4 insulators were damaged.
In the structure of the comparative example 2, the damage of the insulator was 3 out of 100 test examples.
From these results, it can be seen that the structure of Example 1 can prevent the insulator from being damaged.

Third Embodiment Next, a third embodiment of the present invention will be described.
FIG. 8 is an enlarged cross-sectional view of a main part showing the configuration of the spark plug.
In the third embodiment, the heat dissipation member 33 shown in the second embodiment (see FIGS. 4 and 5) is applied. Also in the third embodiment, the insulator 12 is press-fitted into the heat radiating member 33 on the shelf portion 31 except that the heat radiating member 33 and the shelf portion 31 are joined by laser welding as a material bond after the press-fitting. ing. In FIG. 8, the shaded portion indicates a laser welded portion. Note that the relationship of F2 <F3 is set, where F3 is the adhesive force at the coupling position between the shelf 31 and the heat radiating member 33 and F2 is the friction force between the insulator 12 and the heat radiating member 33.

  According to this configuration, when the insulator 12 is press-fitted into the heat radiating member 33, the heat radiating member 33 can move on the shelf 31 as described above, so that the insulator 12 can be prevented from being damaged.

  On the other hand, the heat dissipating member 33 constitutes a heat dissipating path from the insulator 12 to the metal shell 11, but since the metal shell 11 and the heat dissipating member 33 are integrated by laser welding after press-fitting, the close state of both is maintained, Heat dissipation efficiency is improved.

Fourth Embodiment Next, a fourth embodiment of the present invention will be described.
FIG. 9 is an enlarged cross-sectional view of a main part showing the configuration of the spark plug.
In the fourth embodiment, the heat dissipation member 33 shown in the second embodiment is applied. The fourth embodiment also has a configuration in which the insulator 12 is press-fitted into the heat dissipation member 33 on the shelf portion 31. However, the third embodiment is that the heat dissipation member 33 and the shelf portion 31 are solder-joined with the solder 40 after the press-fit. It is different from the embodiment.

  According to this configuration, when the insulator 12 is press-fitted into the heat radiating member 33, the heat radiating member 33 can move in the radial direction on the shelf 31 as described above, so that the insulator 12 can be prevented from being damaged.

  On the other hand, the heat radiating member 33 constitutes a heat radiating path from the insulator 32 to the metal shell 11. However, since the metal shell 11 and the heat radiating member 33 are integrated by soldering, the close contact state between them is maintained, and the heat radiating efficiency is increased. Will improve.

Comparative Example 3
FIG. 10 is an enlarged cross-sectional view of the main part showing the configuration of the spark plug.
In this comparative example 3, a stepped portion 35 having a diameter gradually reduced toward the front side is formed on the outer wall of the insulator 12, and a shelf portion 36 having an inner diameter gradually decreased toward the front side is formed on the inner wall of the metal shell 11. Has been. The step portion 35 and the shelf portion 36 are formed at substantially the same inclination angle, and are formed with a predetermined gap G therebetween, so that an upper surface and a lower surface are formed between the metal shell 11 and the insulator 12. An annular gap G inclined in the same direction is formed.

  An annular heat dissipation member 37 having a U-shaped cross section is disposed in the gap G. The rear surface of the heat radiating member 37 is formed as an inclined surface along the step portion 35, and the front surface is formed as an inclined surface along the shelf portion 36. The heat radiating member 37 is not press-fitted into either the metal shell 11 or the insulator 12 and is sandwiched between the step portion 35 and the shelf portion 36.

Next, with reference to FIG. 11, the result of the thermal value measurement test of Example 3, Example 4, and Comparative Example 3 which are the structure of 3rd Embodiment and 4th Embodiment is demonstrated.
Test Method The heat value measurement test is based on the SAE standard, and the outline of this test is as follows.

  In other words, the SC17.6 (SAE J2203) engine with a compression ratio of 5.6 and an ignition timing set to 30 ° BTDC was assembled with a sample (spark plug of each example and comparative example) and benzol was mainly used. Using this fuel, a certain amount of supercharging was performed while operating the engine at a rotational speed of 2700 rpm, and the fuel injection amount at which the temperature of the combustion chamber reached the maximum was adjusted by the supercharging amount.

  Then, the increase of the supercharging amount and the adjustment of the fuel injection amount were repeated, and the supercharging pressure immediately before the occurrence of preignition (early ignition) was specified. Thereafter, by performing fine adjustment of the specified supercharging pressure and adjustment of the fuel injection amount, the engine output when the engine operates stably for 3 minutes is measured, and the average high pressure (PSI) is calculated. The average existence high pressure was specified as the heat value of each sample.

Experimental Results As shown by white circles in FIG. 11, in Examples 3 and 4, the average effective pressure (PSI) is increased as compared with Comparative Example 3, and the high heat value, that is, the heat drawability is improved. As a result.

Fifth Embodiment Next, a fifth embodiment of the present invention will be described.
FIG. 12 is an enlarged cross-sectional view showing a configuration of a main part of the spark plug.
In the fifth embodiment, the heat dissipation member 32 described in the first embodiment (see FIGS. 2 and 3) is applied as the heat dissipation member. And the buffer member 41 is arrange | positioned at the back side of the thermal radiation member 32, and the press member 42 is arrange | positioned at the back side further. The buffer member 41 is formed by annularly forming a flat metal plate that is softer than the heat radiating member 32 and the pressing member 42. The pressing member 42 has an annular shape and an L-shaped cross section, and the axial projection 42a is formed thin, and is plastically or elastically deformed by pressing (load) from the axial direction.

  Further, any of the heat radiating member 32, the buffer member 41, and the pressing member 42 is manufactured as a separate member from the metal shell 11 and the insulator 12.

  When press-fitting the insulator 12 into the metal shell 11, the heat radiating member 32, the buffer member 41, and the pressing member 42 are fitted into the metal shell 11 in this order, and then the insulator 12 is press-fitted.

As a result, the heat radiation member 32, the buffer member 41, and the pressing member 42 are disposed in a stacked state between the shelf portion 31 and the step portion 35. The frictional force F2 between the insulator 12 and the heat radiating member 32 and the frictional force F4 between the metal shell 11 and the pressing member 42 are set in a relationship of F2 <F4.
Here, in order to satisfy the relationship of F2 <F4, the axial length of the interference fit between the insulator 12 and the heat radiating member 32 is L2, and the interference fit between the pressing member 42 and the metal shell 11 is When the length in the axial direction is L4, L4 is made larger than L2, and the contact area between the pressing member 42 and the metal shell 11 is made larger than the contact area between the insulator 12 and the heat dissipation member 32. A method is mentioned.

  Note that the opening on the side of the metal shell 11 where the pressing member 42 is inserted has a pocket portion 26 (see FIG. 1) having an inner diameter larger than the outer diameter of the pressing member 42, and the inner peripheral surface of the pocket portion 26. A tapered surface is formed between the press fitting surface of the metal shell 11. Thereby, insertion of the pressing member 42 becomes easy.

  Also in the fifth embodiment, the assembly of the insulator 12 to the metal shell 11 is performed in the same manner as in the first embodiment. When the insulator 12 and the heat radiating member 32 come into contact with each other, the heat radiating member 32 can move on the shelf 31 in the radial direction. Therefore, even if the insulator 12 has eccentricity or shaft runout, the heat radiating member 32 moves in the radial direction, so that the bending stress applied to the insulator 12 can be reduced and damage to the insulator 12 can be prevented.

  Further, the heat received by the insulator 12 is conducted from the outer peripheral surface of the insulator 12 to the heat radiating member 32, and the heat conducted to the heat radiating member 32 is conducted from the front end surface 32 a of the heat radiating member 32 to the shelf 31. Then, heat is radiated through the metal shell 11 integrated with the shelf 31.

  On the other hand, at the stage where the assembling is completed as shown in the figure, the protrusion 42 a is pressed by the step portion 35 and is plastically deformed or elastically deformed, and the heat radiating member 32 is pressed against the shelf portion 31 via the buffer member 41. As a result, the heat radiating member 32 and the shelf 31 are in close contact with each other, heat conduction between the heat radiating member 32 and the shelf 31 is efficiently performed, and the heat radiating effect is improved.

Sixth Embodiment Next, a sixth embodiment of the present invention will be described.
FIG. 13 is an enlarged cross-sectional view of the main part showing the configuration of the spark plug.
The sixth embodiment is different from the fifth embodiment in that the buffer member 41 shown in the fifth embodiment is omitted.

  In this configuration, when the insulator 12 is press-fitted into the metal shell 11, the heat dissipation member 32 and the pressing member 42 are fitted into the metal shell 11 and then the insulator 12 is press-fitted. When the insulator 12 and the heat radiating member 32 come into contact with each other during the press-fitting, the heat radiating member 32 can move on the shelf 31 in the radial direction. Therefore, even if the insulator 12 has eccentricity or shaft runout, the heat radiating member 32 moves in the radial direction, so that the bending stress applied to the insulator 12 can be reduced and damage to the insulator 12 can be prevented.

  Further, the heat received by the insulator 12 is conducted from the outer peripheral surface of the insulator 12 to the heat radiating member 32, and the heat conducted to the heat radiating member 32 is conducted from the front end surface 32 a of the heat radiating member 32 to the shelf 31. Then, heat is radiated through the metal shell 11 integrated with the shelf 31.

  Further, at the stage where the assembly of the metal shell 11 and the insulator 12 is completed, the heat dissipation member 32 is pressed against the shelf 31 by the pressing member 42, so that the heat dissipation effect is improved as described above.

7th Embodiment FIG. 14: is an expanded sectional view of the principal part which shows the structure of a spark plug.
In the seventh embodiment, a shelf 38 whose inner diameter gradually decreases toward the tip side is formed on the inner wall surface of the metal shell 11. The inclination angle of the shelf 38 with respect to the radial direction is set to about 30 °. The heat radiating member 43 applied to this embodiment is annular, the front inclined surface 43a corresponds to the inclination angle of the shelf 38, and the rear surface is a flat surface along the radial direction.

  Moreover, although the pressing member 42 is arrange | positioned so that it may laminate | stack on the back side of the heat radiating member 43, this pressing member 42 can use what was applied in 5th, 6th embodiment.

  In this configuration, when the insulator 12 is press-fitted into the metal shell 11, the heat dissipation member 43 and the pressing member 42 are fitted into the metal shell 11 and then press-fitted. When the insulator 12 and the heat dissipating member 43 come into contact with each other during the press-fitting, the heat dissipating member 43 can move on the shelf 31 in the radial direction. Therefore, even if the insulator 12 has eccentricity or shaft runout, the heat radiating member 43 moves in the radial direction, so that the bending stress applied to the insulator 12 can be reduced and damage to the insulator 12 can be prevented.

  Further, the heat received by the insulator 12 is conducted from the outer peripheral surface of the insulator 12 to the heat radiating member 43, and the heat conducted to the heat radiating member 43 is transferred from the inclined surface 43 a on the front side of the heat radiating member 43 to the shelf 31. Conducted and dissipated through the metal shell 11 integral with the shelf 31.

  Further, at the stage where the assembly of the metal shell 11 and the insulator 12 is completed, the heat dissipation member 32 is pressed against the shelf 38 by the pressing member 42, so that the heat dissipation effect is improved as described above.

Comparative Example 4
FIG. 15 is an enlarged cross-sectional view of a main part showing the configuration of the spark plug.
In this comparative example 4, the shelf 36 formed on the metal shell 11 and the step 35 formed on the insulator 12 may be the same as those in the comparative example 3 (see FIG. 10). A packing 44 having an annular shape and a U-shaped cross section is disposed between the two. However, the packing 44 is not press-fitted and supported by either the metal shell 11 or the insulator 12.

Comparative Example 5
FIG. 16 is an enlarged cross-sectional view of the main part showing the configuration of the spark plug.
In the comparative example 5, the shelf 36 formed on the metal shell 11 and the step 35 formed on the insulator 12 may be the same as those in the comparative example 3 (see FIG. 10). Moreover, although the heat radiating member 45 is formed in an annular shape, a part of the surface facing the front side is formed on the tapered surface 45a so as to extend along the shelf 36, and the thinner and cylindrical heat receiving portion 45b is formed on the front side. Is formed. An annular packing 46 having a U-shaped cross section is disposed on the rear side of the heat dissipating member 45, but the front surface of the packing 46 is formed as a flat surface along the radial direction. The member 45 is pressed against a flat surface in the radial direction.

Comparative Example 6
FIG. 17 is an enlarged cross-sectional view of the main part showing the configuration of the spark plug.
In this comparative example 6, a plate packing 47 is interposed between the step portion 35 formed on the insulator 12 and the shelf portion 36 formed on the metal shell 11.
According to this configuration, the metal shell 11 and the insulator 12 are hermetically sealed, and the heat of the insulator 12 is radiated to the metal shell 11 via the plate packing 47.

Next, with reference to FIG. 18, the result of the thermal value measurement test of Examples 5 and 6 and Comparative Examples 4, 5 and 6, which are the structures of the fifth and sixth embodiments, will be described.
Test Method The heat value measurement test is based on the SAE standard and is the same as described above.

Experimental Results As shown by white circles in FIG. 18, in Examples 5 and 6, the average effective pressure (PSI) is increased as compared with Comparative Examples 4, 5, and 6, and the high heat value, that is, the heat drawability. The result was improved.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimension, numerical value, form, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

DESCRIPTION OF SYMBOLS 10 Spark plug 11 Main metal fitting 11a The front-end | tip part of a main metal fitting 12 Insulator 12a The front-end | tip part of an insulator 13 Central electrode 13a The front-end | tip part of a center electrode 16 Through-hole 17 Terminal metal fitting 18 Resistor 19,20 Conductive glass seal 21,22 27, 31, 36, 38 Shelf portion 25 Tool engaging portion 26 Pocket portion 28, 32, 33, 37, 43 Heat radiating member 35 Step portion 41 Buffer member 42 Pressing member 44, 46, 47 Packing A Engine head

Claims (11)

A central electrode extending in the axial direction;
A cylindrical insulator holding the center electrode on its front side;
A cylindrical metal shell for housing a part of the insulator;
One end is joined to the front side end of the metal shell, and the other end forms a spark discharge gap with the center electrode,
An annular heat radiating member that is press-fitted into a front-side small-diameter portion that is smaller than the outer diameter of the rear portion of the insulator, and that forms a heat-dissipating path by connecting the insulator and the metal shell. A spark plug comprising:
The metal shell is a shelf that has a flat surface substantially parallel to the radial direction, and is a surface that protrudes inward in the radial direction and is included in a range of ± 30 degrees with respect to the radial direction. Have
The spark plug is characterized in that the heat radiating member is in contact with the metal shell by being supported by the flat surface of the shelf in a state of being separated from the inner peripheral surface of the metal shell.   2. The spark plug according to claim 1, wherein the metal shell has a screw portion for screwing into the engine on an outer peripheral surface, and the shelf portion is provided inside the screw portion. The metal shell is airtightly coupled to the rear portion of the insulator;
The relationship between the frictional force F1 at the airtight coupling portion between the metal shell and the insulator and the frictional force F2 at the press-fitted portion between the insulator and the heat radiating member is F1> F2. The spark plug according to 1 or 2.   The spark plug according to any one of claims 1 to 3, wherein the heat radiating member and the shelf are fixed by material bonding.   The spark plug according to claim 4, wherein the material bonding is welding, brazing, or soldering.   The relationship between the adhesive force F3 at the material coupling portion between the heat radiating member and the shelf and the frictional force F2 at the press-fitted portion between the insulator and the heat radiating member is F2 <F3. The spark plug according to 4 or 5. The heat dissipation member is pressed into the rear side of the shelf portion of the inner peripheral surface of the metal shell and is sandwiched in the axial direction together with the heat dissipation member between the insulator and the shelf portion. Further comprising a pressing member that presses toward the flat surface of the shelf,
The spark plug according to claim 1, wherein the pressing member is separated from the heat dissipation member in the radial direction.   The relationship between the frictional force F2 at the press-fitting portion between the insulator and the heat radiating member and the frictional force F4 at the press-fitting portion between the pressing member and the metal shell is F2 <F4. Spark plug as described in.   The metallic shell has a pocket portion having an inner diameter larger than the outer diameter of the pressing member on the rear side of the portion into which the pressing member is press-fitted, and the inner portion of the inner circumferential surface of the metallic shell is inside the pocket portion. The spark plug according to claim 7 or 8, wherein a tapered surface is formed between a peripheral surface and a press-fitting surface into which the pressing member is press-fitted.   The pressing member has a protrusion deformed by a load at its rear end, and the pressing member is sandwiched between the insulator and the shelf together with the heat radiating member in a state where the protrusion is deformed. The spark plug according to any one of claims 7 to 9.   The metal buffer member softer than the heat radiating member and the pressing member is disposed between the heat radiating member and the pressing member in the axial direction. Spark plug.

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