JP5989425B2 - Spark plug - Google Patents

Description

  The present invention relates to a spark plug.

  An internal combustion engine having a spark plug may cause preignition. Patent Document 1 discloses a spark plug shell in which serrations are formed on the inner surface of a cylindrical shaft portion. This serration is formed to increase the heat dissipation area and improve the heat dissipation effect.

JP 2007-59365 A

  It has been found that pre-ignition has a mode in which an air-fuel mixture staying in a plug pocket formed between a housing portion and an insulator receives heat and becomes high temperature. In order to suppress the pre-ignition that occurs in such a manner, for example, it is conceivable to increase the area of the portion adjacent to the plug pocket in the housing portion to promote heat dissipation from the plug pocket.

  However, when the area of the portion adjacent to the plug pocket in the housing portion is expanded as a whole along the axial direction, the cross-sectional area along the radial direction of the portion at each position along the axial direction becomes small. . For this reason, in this case, for example, there is a possibility that the movement of heat from the central portion in the axial direction to the side opposite to the side where the ground electrode is provided in the axial direction is limited. As a result, there is a possibility that the heat radiation from the plug pocket is limited by the amount that the heat radiation from the portion is limited.

  In view of the above problems, an object of the present invention is to provide a spark plug that can suitably suppress the occurrence of pre-ignition caused by the air-fuel mixture remaining in the plug pocket.

The present invention includes a housing part, an insulator held by the housing part, a center electrode exposed from the insulator, and a ground electrode that forms a discharge gap part between the center electrode and the housing part. A first non-processed region having a plug pocket between the insulator and a portion of the housing portion adjacent to the plug pocket that has not been subjected to area expansion processing, and processing that has undergone area expansion processing A spiral region having a larger inner diameter than the inner diameter of the non-working region, wherein the working region is located closer to the tip side in the axial direction than the first non-working region . A spark plug having a plurality of groove portions .

The present invention includes a housing part, an insulator held by the housing part, a center electrode exposed from the insulator, and a ground electrode that forms a discharge gap part between the center electrode and the housing part. A first non-processed region having a plug pocket between the insulator and a portion of the housing portion adjacent to the plug pocket that has not been subjected to area expansion processing, and processing that has undergone area expansion processing And the processing region is located on the tip side in the axial direction with respect to the first non-processing region, and an area enlargement process is performed on a portion of the housing portion adjacent to the plug pocket. A second non-working region that is not formed may be further provided, and the second non-working region may be positioned closer to the tip side in the axial direction than the processing region.

The present invention is the provided on the outer peripheral portion of the housing part, can be configured to the is provided a groove so as to extend along the crest of the screw part used in the fastening of the internal combustion engine.

The present invention includes a housing part, an insulator held by the housing part, a center electrode exposed from the insulator, and a ground electrode that forms a discharge gap part between the center electrode and the housing part. A first non-processed region having a plug pocket between the insulator and a portion of the housing portion adjacent to the plug pocket that has not been subjected to area expansion processing, and processing that has undergone area expansion processing And the processing region is located on the tip side in the axial direction with respect to the first non-processing region, and an area enlargement process is performed on a portion of the housing portion adjacent to the plug pocket. A non-processed second non-processed region, and a spiral groove is provided in the process region. The second non-processed region is more axial than the process region. Located distally Te, the provided on the outer circumferential portion of the housing part, it can be configured to the is provided a groove so as to extend along the crest of the screw part used in the fastening of the internal combustion engine.

  The present invention may be configured such that a tapered portion is provided inside a portion of the distal end portion of the housing portion where the end portion on the distal end side of the groove portion is located in the circumferential direction.

  According to the present invention, it is possible to suitably suppress the occurrence of pre-ignition due to the air-fuel mixture remaining in the plug pocket.

It is a figure which shows the principal part of the ignition plug of Example 1. It is a comparison figure of the maximum advance amount of ignition timing. It is a figure which shows the change tendency of the maximum amount of advance of ignition timing. It is a figure which shows the principal part of the ignition plug of Example 2. FIG. 6 is a diagram illustrating a main part of a spark plug according to a third embodiment. It is a figure which shows the principal part of the ignition plug of Example 4. It is a figure which shows the principal part of the ignition plug of Example 5. It is a figure which shows the principal part of the ignition plug of Example 6. It is a figure which shows the principal part of the ignition plug of Example 7. FIG. 10 is a view showing a main part of a spark plug according to an eighth embodiment.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a view showing a main part of the spark plug 1A. Fig.1 (a) shows sectional drawing of the spark plug 1A. FIG. 1B shows a bottom view of the spark plug 1A (viewed along the axial direction from the ground electrode 5 side). 1 (a) and 1 (b) show the main part of the spark plug 1A in a state of being provided in the cylinder head 10 of the internal combustion engine.

  The spark plug 1A includes a housing portion 2A, an insulator 3, a center electrode 4, and a ground electrode 5. The housing part 2A has a cylindrical shape and holds the insulator 3. The insulator 3 is provided around the center electrode 4. The center electrode 4 extends along the axial direction. And it is exposed from the insulator 3 at the tip side (when the spark plug 1A is viewed along the direction orthogonal to the central axis thereof, the side where the ground electrode 5 is provided in the axial direction). The ground electrode 5 is provided on the housing part 2A. The ground electrode 5 forms a discharge gap G with the center electrode 4.

  The spark plug 1 </ b> A is provided in the cylinder head 10. Specifically, the spark plug 1 </ b> A is fastened to the cylinder head 10 via the gasket 6. In this regard, a screw portion S used for fastening with the internal combustion engine (specifically, the cylinder head 10) is provided on the outer peripheral portion of the housing portion 2A. The cylinder head 10 forms a combustion chamber C together with a cylinder block and a piston (not shown). A discharge gap G is disposed in the combustion chamber C.

  In the combustion chamber C, an air flow F passing through the discharge gap G is generated. The airflow F is specifically a tumble flow. The air flow F can be an air flow passing through the discharge gap portion G in at least one of the intake stroke and the compression stroke of the internal combustion engine provided with the ignition plug 1A. The airflow F is not necessarily limited to the tumble flow, and may be a swirling airflow such as a swirl flow. In the internal combustion engine provided with the spark plug 1A, the spark plug 1A is provided so that the housing portion 2A does not protrude into the combustion chamber C.

  A plug pocket P is formed between the housing part 2A and the insulator 3. The plug pocket P is formed around the insulator 3 and opens to the combustion chamber C. On the other hand, in relation to the plug pocket P, the screw portion S is provided on the outer peripheral portion of the housing portion 2A including a portion located around the plug pocket P. Specifically, the screw portion S is provided on the outer peripheral portion of the cylindrical portion located on the distal end side from the portion where the gasket 6 is provided in the housing portion 2A. The cylindrical portion includes a portion located around the plug pocket P.

  The spark plug 1A includes a region R1 that is a first non-processed region where the area adjacent to the plug pocket P in the housing portion 2A is not subjected to area expansion processing, and a region that is a processed region where area expansion processing is performed. And R2. The region R2 is located closer to the tip side in the axial direction than the region R1. The regions R1 and R2 are adjacent to each other along the axial direction. The length along the axial direction is set larger in the region R2 than in the region R1. The region R2 is the rear end side from the front end position of the housing portion 2A in the axial direction (when the spark plug 1A is viewed along the direction orthogonal to the central axis, the side where the ground electrode 5 is provided in the axial direction is It is set as an area that extends to the other side. The region R1 is provided with a cylindrical inner surface.

  A groove portion D1 is provided in the region R2. The groove part D1 extends along the axial direction. Moreover, it is provided so as to form a rectangular space in the vertical cross section. The groove portion D1 is provided in a portion other than the portion where the ground electrode 5 is provided in the housing portion 2A in the circumferential direction. A plurality of (here, 11) grooves D1 are provided along the circumferential direction in the portion. The plurality of groove portions D1 are provided so that the groove portions D1 adjacent to each other along the circumferential direction in the portion are arranged at a predetermined interval.

  Next, main effects of the spark plug 1A will be described. The spark plug 1A has regions R1 and R2 in a portion adjacent to the plug pocket P in the housing portion 2A, and the region R2 is positioned on the tip side in the axial direction with respect to the region R1. For this reason, the spark plug 1A can promote heat dissipation from the plug pocket P by enlarging the area in the region R2.

  At the same time, the spark plug 1A can ensure the cross-sectional area of the housing portion 2A along the radial direction in the portion where the region R1 is set. For this reason, the spark plug 1A can ensure the movement of heat of the housing portion 2A from the region R2 side to the region R1 side in the axial direction. As a result, it is possible to prevent the heat dissipation from the plug pocket P from being restricted due to the restriction of such heat transfer. For this reason, the spark plug 1A can suitably suppress the occurrence of preignition caused by the air-fuel mixture remaining in the plug pocket P.

  FIG. 2 is a comparison diagram of the maximum advance amount of the ignition timing. FIG. 3 is a diagram showing a change tendency of the maximum advance amount of the ignition timing. 2 and 3 show the maximum amount of advance angle at which preignition does not occur when ignition is stopped in an internal combustion engine that is operating under predetermined conditions. FIG. 2 shows the maximum amount of advance for the spark plug 1A and the spark plug 1A ′. In FIG. 3, the maximum advance amount when the area of the portion adjacent to the plug pocket P in the housing portion 2A is changed by the length along the axial direction of the groove portion D1 while the volume of the plug pocket P is made equal. Indicates a change trend. In FIG. 3, the vertical axis represents the maximum advance amount based on the spark plug 1A ′, and the horizontal axis represents the area enlargement magnification based on the spark plug 1A ′. The spark plug 1A ′ is not provided with the groove portion D1, and by expanding the inner diameter of the portion of the housing portion 2A adjacent to the plug pocket P, the volume of the plug pocket P is made equal to that of the spark plug 1A. It has become.

  As can be seen from FIG. 2, the spark plug 1A can increase the maximum advance amount of the ignition timing more than the spark plug 1A '. As shown in FIG. 3, it can be seen that the maximum advance amount of the ignition timing gradually increases as the area increases, so that the degree of increase gradually decreases. In this regard, when evaluating the difficulty of occurrence of pre-ignition with the maximum advance amount of ignition timing, if the maximum advance amount is 1 ° CA larger than that of the spark plug 1A ′, the effect of suppressing pre-ignition is sufficiently obtained. Can be judged. For this reason, the spark plug 1A can be configured to satisfy the following conditions.

That is, here, in order to obtain a maximum advance angle of 1 ° CA larger than that of the spark plug 1A ′, the spark plug 1A has 1. It is necessary to secure three times the area. On the other hand, the spark plug 1A ′ is a spark plug in which the thread size of the thread portion S is specifically 14 mm and the area of the portion adjacent to the plug pocket P is 320 mm ² . For this reason, an area of 320 × 1.3, that is, 416 mm ² is required to obtain a maximum advance angle of 1 ° CA. Further, considering application to spark plugs having different screw sizes, the required area is 416 × A / 14, that is, approximately 29.7 × A, where the screw size is A.

  Therefore, the spark plug 1A can be specifically configured to have an area of 29.7 × A or more in a portion adjacent to the plug pocket P in the housing portion 2A from the viewpoint of evaluation by the maximum advance amount. This also applies to spark plugs 1B to 1H described later.

  The spark plug 1A may be configured to satisfy the following conditions. Here, as shown in FIGS. 1A and 1B, when the depth along the radial direction of the groove D1 is L1, and the length along the axial direction is K, the area is one groove D1. Increase by about 2 × L1 × K. On the other hand, the area of the portion adjacent to the plug pocket P in the housing portion 2A is 2 × 3.14 × r × U, that is, 6 × 3 × 14 × r × U, where r is the radius and U is the length along the axial direction of the plug pocket P. .28 × r × U. And 1.3 times this area is 8.16 × r × U.

Therefore, in order to obtain a maximum advance angle of 1 ° CA, an area increase of 8.16 × r × U−6.28 × r × U, that is, 1.88 × r × U is required. For this reason, when the number of necessary groove portions D1 is N, the following equation (1) is established. Moreover, the following formula (2) is obtained by rearranging the formula (1). For this reason, the spark plug 1A can be specifically configured to satisfy the formula (2) from the viewpoint of evaluation based on the maximum advance amount. At the same time, the spark plug 1A can be configured such that the interval between the adjacent grooves D1 along the circumferential direction is 0.5 mm or more.
N ≧ 1.88 × r × U / (2 × L1 × K) (1)
N ≧ 0.94 × r × U / (L1 × K) (2)

  Specifically, the spark plug 1A has a configuration in which the groove portion D1 is provided in the region R2, so that the air current F flowing from the combustion chamber C into the plug pocket P can be disturbed by the plug pocket P. As a result, heat dissipation from the plug pocket P can be promoted by promoting heat exchange performed between the air-fuel mixture remaining in the plug pocket P and the groove D1.

  FIG. 4 is a view showing a main part of the spark plug 1B. 4 (a) and 4 (b) show the spark plug 1B in the same manner as FIGS. 1 (a) and 1 (b). The spark plug 1B is substantially the same as the spark plug 1A, except that the housing part 2B is provided instead of the housing part 2A. The housing part 2B is substantially the same as the housing part 2A, except that the groove part D2 is provided instead of the groove part D1. The groove portion D2 is provided with a plurality of groove portions D2 such that the groove portion D2 is provided so as to form a triangular space in the vertical cross section, and the groove portions D2 adjacent to each other along the circumferential direction are arranged adjacent to each other. Except for the point, it is substantially the same as the groove D1.

  Next, main effects of the spark plug 1B will be described. The spark plug 1B has regions R1 and R2 similar to the spark plug 1A, and the region R2 is positioned on the tip side in the axial direction with respect to the region R1. For this reason, the spark plug 1B can suitably suppress the occurrence of pre-ignition, like the spark plug 1A. On the other hand, the spark plug 1B specifically has a configuration in which a groove D2 is provided in the region R2. In this respect, the spark plug 1B configured in this way can also promote heat dissipation from the plug pocket P by increasing the area and promoting disturbance.

  The spark plug 1B can suitably increase the area by providing a plurality of groove portions D2 so that the groove portions D2 adjacent to each other along the circumferential direction are arranged adjacent to each other.

  FIG. 5 is a view showing a main part of the spark plug 1C. 5 (a) and 5 (b) show a spark plug 1C as in FIGS. 1 (a) and 1 (b). The spark plug 1C is substantially the same as the spark plug 1A, except that the housing part 2C is provided instead of the housing part 2A. The housing part 2C is substantially the same as the housing part 2A except that a groove part D3 is provided instead of the groove part D1.

  The groove part D3 is provided in the region R2 similarly to the groove part D1. On the other hand, the groove portion D3 extends in the circumferential direction and is provided in a ring shape over the entire circumference. The groove part D3 is provided so as to form a triangular space in the vertical cross section. A plurality of groove portions D3 are provided along the axial direction. The plurality of groove portions D3 are provided such that adjacent groove portions D3 are disposed adjacent to each other along the axial direction. The plurality of groove portions D3 may be provided such that adjacent groove portions D3 are arranged at predetermined intervals along the axial direction.

  Next, main effects of the spark plug 1C will be described. The spark plug 1C has regions R1 and R2 similarly to the spark plug 1A, and the region R2 is positioned on the tip side in the axial direction with respect to the region R1. For this reason, the spark plug 1C can suitably suppress the occurrence of pre-ignition, like the spark plug 1A. On the other hand, the spark plug 1C specifically has a configuration in which a groove D3 is provided in the region R2. In this regard, even the spark plug 1C configured in this way can promote heat dissipation from the plug pocket P by increasing the area and promoting disturbance.

Specifically, the spark plug 1C can be configured to satisfy the following conditions from the viewpoint of evaluation based on the maximum advance amount. That is, when the depth along the radial direction of the groove D3 is L2, the area increases by about 2 × 2 × π × r × L2, that is, 4 × π × r × L2, per groove D3. On the other hand, to obtain a maximum advance angle of 1 ° CA, it is necessary to increase the area by 416 × A / 14−320 × A / 14, that is, approximately 6.71 × A. Therefore, when the number of necessary grooves D3 is M, the following expression (3) is established. Moreover, the following formula (4) is obtained by rearranging the formula (3). For this reason, the spark plug 1C can be configured to satisfy the formula (4).
M ≧ 6.71 × A / (4 × π × r × L2) (3)
M ≧ 1.68 × A / (π × r × L2) (4)

  FIG. 6 is a view showing a main part of the spark plug 1D. 6 (a) and 6 (b) show a spark plug 1D as in FIGS. 1 (a) and 1 (b). The spark plug 1D is substantially the same as the spark plug 1A, except that the housing part 2D is provided instead of the housing part 2A. The housing part 2D is substantially the same as the housing part 2A, except that the groove part D4 is provided instead of the groove part D1.

  The groove part D4 is provided in the region R2 similarly to the groove part D1. On the other hand, the groove D4 is a spiral groove. The groove portion D4 is provided so as to extend along the crest portion of the screw portion S. The groove part D4 is provided so as to form a triangular space in a vertical section thereof or a section including a plane including the central axis of the spark plug 1D.

  Next, main effects of the spark plug 1D will be described. The spark plug 1D has regions R1 and R2 similar to the spark plug 1A, and the region R2 is positioned on the tip side in the axial direction with respect to the region R1. For this reason, the spark plug 1D can suitably suppress the occurrence of pre-ignition, like the spark plug 1A. On the other hand, the spark plug 1D specifically has a configuration in which a groove D4 is provided in the region R2. In this respect, the spark plug 1D configured in this way can also promote heat dissipation from the plug pocket P by increasing the area and promoting disturbance. The spark plug 1D can be configured to satisfy the expression (4), where L2 is the depth along the radial direction of the groove D4 from the viewpoint of evaluation based on the maximum advance amount.

  By providing the spark plug 1D so as to extend the groove portion D4 along the crest portion of the screw portion S, it is possible to prevent the strength and heat conductivity of the housing portion 2D from being lowered as described below. That is, for example, in the spark plug 1A, the distance along the radial direction from the groove D1 to the threaded portion S increases or decreases depending on the position along the axial direction. As a result, there is a possibility that the strength of the housing part 2A may be reduced at a position where the separation distance becomes small. Moreover, there is a possibility that the movement (heat transfer) of the housing part 2A from the region R2 side to the region R1 side in the axial direction at the position where the separation distance becomes small is suppressed.

  On the other hand, the spark plug 1D is provided so that the groove D4 extends spirally along the crest of the screw part S, so that the distance along the radial direction from the groove D4 to the screw part S is along the axial direction. It is also possible to suppress changes depending on the position. As a result, it is possible to suppress a decrease in strength and heat conductivity of the housing part 2D.

  FIG. 7 is a view showing a main part of the spark plug 1E. 7 (a) and 7 (b) show the spark plug 1E as in FIGS. 1 (a) and 1 (b). The spark plug 1E is substantially the same as the spark plug 1A, except that the housing part 2E is provided instead of the housing part 2A. The housing part 2E is substantially the same as the housing part 2A, except that a protrusion B is provided instead of the groove D1.

  In the housing part 2E, a projection B is provided in the region R2 instead of the groove D1. The protrusion B is a rod-shaped protrusion, and extends along the radial direction. A plurality of protrusions B are equally provided along the circumferential direction and the axial direction. In providing the protrusion B, the inner diameter of the housing part 2E in the region R2 can be set to be larger than the inner diameter of the housing part 2E in the region R1.

  Next, main effects of the spark plug 1E will be described. The spark plug 1E has regions R1 and R2 similarly to the spark plug 1A, and the region R2 is positioned on the tip side in the axial direction with respect to the region R1. For this reason, the spark plug 1E can suitably suppress the occurrence of pre-ignition, like the spark plug 1A. On the other hand, the spark plug 1E specifically has a configuration in which a protrusion B is provided in the region R2. In this respect, the spark plug 1E thus configured can also promote heat dissipation from the plug pocket P by increasing the area and promoting disturbance.

  FIG. 8 is a view showing a main part of the spark plug 1F. FIGS. 8A and 8B show the spark plug 1F in the same manner as FIGS. 1A and 1B. The spark plug 1F is substantially the same as the spark plug 1A, except that the housing part 2F is provided instead of the housing part 2A. The housing part 2F is substantially the same as the housing part 2A except that the hole part H is provided instead of the groove part D1. In the housing part 2F, a hole H is provided in the region R2 instead of the groove D1. The hole H extends along the radial direction. Further, a plurality of them are equally provided along the circumferential direction and the axial direction.

  Next, main effects of the spark plug 1F will be described. The spark plug 1F has regions R1 and R2 similarly to the spark plug 1A, and the region R2 is positioned on the tip side in the axial direction with respect to the region R1. For this reason, the spark plug 1F can suitably suppress the occurrence of pre-ignition, like the spark plug 1A. On the other hand, the spark plug 1F is specifically configured to have a hole H in the region R2. In this respect, the spark plug 1F configured in this way can also promote heat dissipation from the plug pocket P by increasing the area and promoting disturbance.

  FIG. 9 is a view showing a main part of the spark plug 1G. 9 (a) and 9 (b) show a spark plug 1G as in FIGS. 1 (a) and 1 (b). The spark plug 1G is substantially the same as the spark plug 1A, except that the housing part 2G is provided instead of the housing part 2A. The housing portion 2G is substantially the same as the housing portion 2A, except that the portion adjacent to the plug pocket P further includes a region R3 that is a second non-processed region that is not subjected to area expansion processing. Similar changes can be applied to the spark plugs 1B to 1F, for example.

  The region R3 is located closer to the tip side in the axial direction than the region R2. In this regard, the spark plug 1G has a region adjacent to the plug pocket P in the housing portion 2G in the order of the region R3, the region R2, and the region R1 from the front end side. Of the regions R1, R2, and R3, adjacent regions along the axial direction are adjacent to each other. The length along the axial direction of the region R3 is set to be larger than the clearance Δd along the radial direction between the housing portion 2G and the insulator 3 at the distal end position of the housing portion 2G. The region R3 is set as a region extending from the front end position of the housing portion 2G to the rear end side.

  Next, main effects of the spark plug 1G will be described. Here, in the case of the spark plug 1A, the region R2 is set as a region extending from the front end position of the housing portion 2A to the rear end side. However, if the area is enlarged in the region R2 set in this way, the energy of the flame kernel is easily absorbed by the housing portion 2A, and the ignitability may be deteriorated. On the other hand, the ignition plug 1G has the region R3, so that deterioration in ignitability can be further suppressed as compared with the ignition plug 1A. Specifically, by setting the length of the spark plug 1G along the axial direction of the region R3 to be larger than the clearance Δd serving as the initial flame entry clearance, deterioration of ignitability can be suitably suppressed.

  FIG. 10 is a view showing a main part of the spark plug 1H. 10 (a) and 10 (b) show a spark plug 1H in the same manner as FIGS. 1 (a) and 1 (b). The spark plug 1H is substantially the same as the spark plug 1D except that the housing part 2H is provided instead of the housing part 2D. The housing portion 2H is substantially the same as the housing portion 2D except that the housing portion 2H further includes a tapered portion T. The tapered portion T is provided inside the portion of the distal end portion of the housing portion 2H where the end portion on the distal end side of the groove portion D4 is located in the circumferential direction. The end portion on the distal end side of the groove portion D4 is provided at a portion facing the ground electrode 5 in the distal end portion of the housing portion 2H when viewed along the axial direction from the distal end side.

  Next, main effects of the spark plug 1H will be described. The spark plug 1H can suitably suppress the occurrence of pre-ignition, like the spark plug 1D. Moreover, it can suppress that the intensity | strength and heat conductivity of the housing part 2H fall similarly to the spark plug 1D. On the other hand, by providing the spark plug 1H with the taper portion T, it is possible to further reduce the inflow resistance of the airflow F flowing into the plug pocket P from the combustion chamber C and to strengthen the airflow along the groove portion D4. As a result, it is possible to favorably promote heat dissipation from the plug pocket P by suitably causing disturbance in the plug pocket P.

  When the spark plug 1H is provided in the cylinder head 10, the position along the circumferential direction of the ground electrode 5 is generally not determined at a predetermined position. In this regard, as shown in FIG. 10B, the ground electrode 5 faces the air flow F when the open end of the ground electrode 5 is viewed along the axial direction from the tip side with the spark plug 1H provided in the cylinder head 10. May be arranged to do. On the other hand, when the ground electrode 5 is arranged in this way, pre-ignition is likely to occur due to the air-fuel mixture staying in the plug pocket P as described below.

  That is, in this case, outflow of the airflow that is about to flow out from the plug pocket P among the airflow that the ground electrode 5 is about to flow into the plug pocket P and the airflow that is about to flow out of the plug pocket P is prevented. Moreover, since the outflow of the airflow from the plug pocket P is prevented, the inflow of the airflow into the plug pocket P is less likely to occur due to the balance between the inflow and outflow of the airflow. As a result, since the air-fuel mixture easily stays in the plug pocket P, preignition easily occurs due to the air-fuel mixture staying in the plug pocket P.

  On the other hand, the spark plug 1H has a configuration in which the end portion on the front end side of the groove portion D4 is provided in a portion facing the ground electrode 5 in the front end portion of the housing portion 2H when viewed along the axial direction from the front end side. Thereby, the taper part T can be provided in the said part. For this reason, the spark plug 1H is configured as described above, whereby the inflow of the airflow F can be promoted particularly when the air-fuel mixture tends to stay in the plug pocket P according to the position of the ground electrode 5 in the combustion chamber C. The occurrence of pre-ignition can also be suitably suppressed.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed. For example, the groove portion does not necessarily have to be formed so as to form a triangular or quadrangular space in the vertical cross section, and may be provided so as to form a space of another shape.

Spark plug 1A, 1A ', 1B, 1C, 1D, 1E, 1F, 1G, 1H
Housing part 2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H
Reiko 3
Center electrode 4
Ground electrode 5
Gasket 6
Cylinder head 10

Claims (5)

A housing portion; an insulator held by the housing portion; a center electrode exposed from the insulator; and a ground electrode that forms a discharge gap portion between the center electrode; and the housing portion and the insulator Having a plug pocket between
A first non-processed area that is not subjected to area expansion processing in a portion of the housing portion adjacent to the plug pocket, and a processing area that is subjected to area expansion processing;
The processing region is located on the tip side in the axial direction with respect to the first non-processing region ;
The spark plug having a plurality of spiral grooves each having an inner diameter larger than the inner diameter of the non-processed area . A housing portion; an insulator held by the housing portion; a center electrode exposed from the insulator; and a ground electrode that forms a discharge gap portion between the center electrode; and the housing portion and the insulator Having a plug pocket between
Of the housing part, the first non-processed area that has not been subjected to area expansion processing in a portion adjacent to the plug pocket, and a processing area that has been subjected to area expansion processing,
The processing region is located on the tip side in the axial direction with respect to the first non-processing region;
A second non-processed region that is not subjected to area expansion processing in a portion adjacent to the plug pocket in the housing part,
A spark plug in which the second non-machined region is located on the tip side in the axial direction with respect to the machined region. The spark plug according to claim 1 ,
Wherein provided on the outer peripheral portion of the housing portion, the spark plug is provided with the groove so as to extend along the crest of the screw part used in the fastening of the internal combustion engine. A housing portion; an insulator held by the housing portion; a center electrode exposed from the insulator; and a ground electrode that forms a discharge gap portion between the center electrode; and the housing portion and the insulator Having a plug pocket between
A first non-processed area that is not subjected to area expansion processing in a portion of the housing portion adjacent to the plug pocket, and a processing area that is subjected to area expansion processing;
The processing region is located on the tip side in the axial direction with respect to the first non-processing region;
Of the housing portion, the portion adjacent to the plug pocket further has a second non-processed area that is not subjected to area expansion processing, and a spiral groove is provided in the processing area,
The second non-working region is located on the tip side in the axial direction with respect to the working region;
An ignition plug provided in the outer peripheral portion of the housing portion and provided with the groove portion so as to extend along a threaded portion used for fastening with the internal combustion engine. The spark plug according to claim 3, wherein
A spark plug provided with a tapered portion inside a portion of the distal end portion of the housing portion where the end portion on the distal end side of the groove portion is located in the circumferential direction.

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