JP6966370B2 - Spark plug - Google Patents

Description

The present invention relates to a spark plug, and more particularly to a spark plug containing a magnetic material.

A spark plug in which a magnetic material is arranged around a conductor insulated and held inside a main metal fitting is known in order to suppress radio wave noise generated during discharge (Patent Document 1). In the technique disclosed in Patent Document 2, the magnetic material contains a plurality of different types of magnetic materials.

Japanese Unexamined Patent Publication No. 62-150681 Japanese Unexamined Patent Publication No. 2016-9567

However, in the above-mentioned conventional technique, sufficient measures for suppressing radio wave noise have not been made.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a spark plug capable of suppressing noise more effectively.

In order to achieve this object, the spark plug of the present invention is arranged around a cylindrical main metal fitting, a conductor that is insulated and held inside the main metal fitting and extends from the front end side to the rear end side, and a conductor. It is equipped with a magnetic material. The magnetic material is composed of a plurality of magnetic members each formed of a magnetic material having a different frequency characteristic of magnetic permeability, and the plurality of magnetic members are composed of a first member and at least a part of itself from at least a part of the first member. Also includes a second member located on the outside in the radial direction.

According to the spark plug according to claim 1, the magnetic material arranged around the conductor is composed of a plurality of magnetic members each made of a magnetic material having different frequency characteristics of magnetic permeability. Noise in a wide frequency band can be suppressed by the first member and the second member having different frequency characteristics of magnetic permeability. Since at least a part of the first member is closer to the conductor than at least a part of the second member, the first member is easily affected by the magnetic field generated by the current flowing through the conductor, and the noise suppression effect of the first member. Can be easily expressed. Therefore, by appropriately setting the frequency characteristics of the first member and the second member, it is possible to obtain the noise suppression effect in a wide frequency band while controlling the noise suppression effect in each frequency band.

Of multiple magnetic member, at least a portion of the highest member the frequency showing the maximum peak of magnetic permeability of the magnetic material is disposed on the rear end side than the rear end of the metal shell. Here, on the tip side of the rear end of the main metal fitting, a part of the high frequency component of the current flowing through the conductor flows through the main metal fitting. However, on the rear end side of the main metal fitting, almost all of the high frequency components of the current flow through the conductor. Therefore, by arranging at least a part of the member having the highest frequency showing the maximum peak of the magnetic permeability of the magnetic material on the rear end side of the main metal fitting, the high frequency component of the current flowing through the conductor is suppressed. It can be made easy. Depending can be easy to suppress the high-frequency component of the noise is.

According to the spark plug according to claim 2, the tip portion of the plurality of magnetic members arranged on the tip side of the rear end of the main metal fitting is the member having the highest frequency indicating the maximum peak of the magnetic permeability of the magnetic material. The volume ratio is the smallest. Here, on the tip side of the rear end of the main metal fitting, a part of the high frequency component of the current flowing through the conductor flows through the main metal fitting. In addition, almost all of the low frequency components of the current flow through the conductor regardless of the presence of the main metal fittings. Therefore, by minimizing the volume ratio of the member having the highest frequency showing the maximum peak of magnetic permeability in the tip portion arranged on the tip side of the rear end of the main metal fitting, the ratio of other magnetic members can be increased. Since it becomes large, it is possible to easily suppress the low frequency component of the current flowing through the conductor. Depending can be easy to suppress the low-frequency component of the noise is.

According to the spark plug according to claim 3 , among the plurality of magnetic members, the rear end portion arranged on the rear end side of the main metal fitting has the highest frequency indicating the maximum peak of the magnetic permeability of the magnetic material. The ratio of the volume of the member is the largest. Here, on the tip side of the rear end of the main metal fitting, a part of the high frequency component of the current flowing through the conductor flows through the main metal fitting. However, on the rear end side of the main metal fitting, almost all of the high frequency components of the current flow through the conductor. Therefore, in the rear end portion arranged on the rear end side of the main metal fitting, the volume ratio of the member having the highest frequency showing the maximum peak of magnetic permeability is maximized, so that the current flowing through the conductor is increased. It is possible to easily suppress high frequency components. Depending can be easy to suppress the high-frequency component of the noise is.

According to the spark plug according to claim 4 , the plurality of magnetic members are the volumes of the member having the highest frequency indicating the maximum peak of the magnetic permeability of the magnetic material among the plurality of magnetic members with respect to the total volume of the plurality of magnetic members. The ratio of is the largest. Here, it is known that a magnetic material having a higher frequency showing the maximum peak of magnetic permeability (that is, a magnetic material having a function of suppressing a high frequency component of noise) has a lower maximum peak. Therefore, by the greatest volume of inhibitory effect is relatively low member of the high-frequency component of the noise, noise suppression while controlling so as not biased to low-frequency components, widened by using a plurality of magnetic members A sufficient noise suppression effect can be obtained in the entire frequency band in which noise can be suppressed.

According to the spark plug according to claim 5, the frequency showing the maximum peak of the magnetic permeability of the magnetic material constituting the first member is higher than the frequency showing the maximum peak of the magnetic permeability of the magnetic material constituting the second member. .. Here, it is known that a magnetic material having a higher frequency showing the maximum peak of magnetic permeability (that is, a magnetic material having a function of suppressing a high frequency component of noise) has a lower maximum peak. Therefore, by arranging the first member having a higher frequency showing the maximum peak of magnetic permeability than the second member closer to the conductor than the second member, the noise suppression is controlled so as not to be biased to the low frequency component. However, it is possible to obtain a sufficient noise suppression effect in the entire frequency band in which noise can be suppressed, which has been widened by using a plurality of magnetic members.
According to the spark plug of claim 6, wherein a plurality of magnetic members so via the fixing member are fixed to each other, damage to the magnetic member by vibration or the like can be suppressed.

According to the spark plug according to claim 7 , the magnetic material contains Mn-Zn ferrite and Ni-Zn ferrite. Mn—Zn ferrite tends to suppress the low frequency component of noise, and Ni—Zn ferrite tends to suppress the high frequency component of noise. Therefore, by combining these, it is possible to obtain the noise suppression effect in a wide frequency band while controlling the noise suppression effect in each frequency band.

It is one side sectional view of the spark plug in 1st Embodiment. It is a schematic diagram of the frequency characteristic of a magnetic material. It is one side sectional view of the spark plug in 2nd Embodiment. It is one side sectional view of the spark plug in 3rd Embodiment. It is one side sectional view of the spark plug in 4th Embodiment. It is one side sectional view of the spark plug in 5th Embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a one-sided cross-sectional view of the spark plug 10 with the axis O as a boundary in the first embodiment. In FIG. 1, the lower side of the paper surface is referred to as the front end side of the spark plug 10, and the upper side of the paper surface is referred to as the rear end side of the spark plug 10 (the same applies to FIGS. 3 to 6). The spark plug 10 includes a main metal fitting 20, a conductor 30 insulated and held by the main metal fitting 20, and a magnetic body 40 arranged around the conductor 30.

The insulator 11 is a member for electrically insulating the main metal fitting 20 and the conductor 30, and is formed of alumina or the like having excellent mechanical properties and insulating properties at high temperatures. In the insulator 11, the first inner peripheral surface 12, the second inner peripheral surface 13, and the third inner peripheral surface 14 are formed in order from the rear end side to the tip side by penetrating the shaft hole along the axis O. ing. The inner diameter decreases in the order of the first inner peripheral surface 12, the second inner peripheral surface 13, and the third inner peripheral surface 14.

The insulator 11 has a large diameter portion 15 having the largest outer diameter formed in the center in the axial direction. The boundary between the first inner peripheral surface 12 and the second inner peripheral surface 13 is located inside the large diameter portion 15. On the outer peripheral surface of the insulator 11, a tip-facing surface 16 is formed on the outer peripheral surface of the third inner peripheral surface 14 on the distal end side of the large-diameter portion 15 over the entire circumference.

The main metal fitting 20 is a cylindrical member arranged on the outer periphery of the insulator 11. The main metal fitting 20 is formed of a conductive metal material (for example, low carbon steel or the like). The main metal fitting 20 includes a body portion 21 that surrounds the front end facing surface 16 of the insulator 11, a seat portion 24 that is connected to the rear end side of the body portion 21, and a bent portion 25 that is connected to the rear end side of the seat portion 24. A tool engaging portion 26 whose tip end side is connected to the bent portion 25, and a rear end portion 27 which is connected to the rear end side of the tool engaging portion 26 are provided. The body portion 21 has a male screw 22 screwed into a screw hole of an engine (not shown) formed on the outer periphery thereof, and a shelf portion 23 for locking the tip facing surface 16 of the insulator 11 from the tip side is an inner circumference. Is formed in. The seat portion 24 is a portion for closing the gap between the screw hole of the engine and the male screw 22, and the outer diameter is formed to be larger than the outer diameter of the body portion 21.

The bent portion 25 is a portion for plastically deforming (bending) and crimping and fixing when the main metal fitting 20 is assembled to the insulator 11. The tool engaging portion 26 is a portion for engaging a tool such as a wrench when tightening the screw 22 into the screw hole of the engine. The tool engaging portion 26 and the bent portion 25 surround the large diameter portion 15 of the insulator 11. The rear end portion 27 bends inward in the radial direction and is located closer to the rear end portion than the large diameter portion 15. The position of the rear end 28 of the main metal fitting 20 is determined by the position where the rear end portion 27 is bent. The main metal fitting 20 holds the tip facing surface 16 and the large diameter portion 15 of the insulator 11 by the shelf portion 23 and the rear end portion 27. The ground electrode 29 is a metal member (for example, made of a nickel-based alloy) connected to the main metal fitting 20.

The conductor 30 is composed of a plurality of members, extends from the front end side to the rear end side along the axis O, and is insulated and held inside the main metal fitting 20 via the insulator 11. In this embodiment, the conductor 30 includes a center electrode 31, a terminal fitting 32, and a resistor 33.

The center electrode 31 is a rod-shaped member, and a core material made of copper or a copper alloy is covered with nickel or a nickel-based alloy. The center electrode 31 is locked to the boundary between the second inner peripheral surface 13 and the third inner peripheral surface 14, and the tip is exposed from the tip of the insulator 11. The center electrode 31 faces the ground electrode 29 via a spark gap. The terminal fitting 32 is a rod-shaped member to which a high-voltage cable (not shown) is connected, and is made of a conductive metal material (for example, low carbon steel or the like). The terminal fitting 32 is fixed to the rear end of the insulator 11 with the tip end side inserted inside the second inner peripheral surface 13 of the insulator 11 and the outer peripheral surface separated from the first inner peripheral surface 12.

The resistor 33 is a member for suppressing radio wave noise generated at the time of sparking, and is arranged inside the second inner peripheral surface 13. The resistor 33 is formed of a composition containing glass particles as a main component, ceramic particles other than glass, and a conductive material. The first connecting portion 34 is a conductive member that connects the center electrode 31 and the resistor 33. The second connecting portion 35 is a conductive member that connects the resistor 33 and the terminal fitting 32. The center electrode 31, the terminal fitting 32 and the resistor 33 are connected by the first connecting portion 34 and the second connecting portion 35 to form the conductor 30. A current flows through the conductor 30 during sparking.

The magnetic body 40 is a member arranged inside the first inner peripheral surface 12 around the terminal fitting 32. The magnetic material 40 is composed of a plurality of magnetic members, each of which is made of a magnetic material having a different frequency characteristic of initial magnetic permeability (hereinafter referred to as “magnetic permeability”). The plurality of magnetic members constituting the magnetic body 40 include the first member 41 and the second member 42. The first member 41 and the second member 42 are cylindrical members having different diameters.

The plurality of magnetic members (first member 41 and second member 42) have a front end portion 43 arranged on the front end side of the rear end 28 with the rear end 28 of the main metal fitting 20 as a boundary, and a front end portion 43 more than the rear end 28. It is divided into a rear end portion 44 arranged on the rear end side and the rear end portion 44. The first member 41 and the second member 42 are arranged at both the front end portion 43 and the rear end portion 44. Since the thicknesses of the first member 41 and the second member 42 in the radial direction are the same, the volume ratio of the first member 41 in the tip portion 43 is smaller than the volume ratio of the second member 42 in the tip portion 43. (That is, the ratio of the first member 41 is the smallest).

In the present embodiment, the second member 42 is arranged on the outer side in the radial direction of the first member 41 over the entire length in the axial direction. The first member 41 is made of Ni—Zn ferrite, and the second member 42 is made of Mn—Zn ferrite. The first member 41 and the second member 42 are fixed to each other by the fixing member 45.

Examples of the fixing member 45 include an adhesive that adheres the first member 41 and the second member 42 to each other, and a filler that fills the gap between the first member 41 and the second member 42. The fixing member 45 may be arranged in the entire portion where the first member 41 and the second member 42 face each other, or may be partially arranged. The fixing member 45 may be an organic substance or an inorganic substance. Examples of the fixing member 45 for the inorganic substance include glass and cement. When the fixing member 45 fixes the first member 41 and the second member 42 to each other, damage to the first member 41 and the second member 42 due to vibration or the like can be suppressed.

The spark plug 10 is manufactured, for example, by the following method. First, molded bodies of the first member 41 and the second member 42 are obtained by extrusion molding or the like, and then these are fired to obtain the first member 41 and the second member 42. The first member 41 and the second member 42 are fixed to each other by the fixing member 45.

Next, the center electrode 31 is inserted from the rear end side of the insulator 11, and the center electrode 31 is locked at the boundary between the second inner peripheral surface 13 and the third inner peripheral surface 14. Next, after filling the raw material powder of the first connecting portion 34 around the center electrode 31, the first connecting portion 34 filled inside the second inner peripheral surface 13 using a compression rod (not shown). Pre-compress the raw material powder.

Next, the raw material powder of the resistor 33 is supplied to the inside of the second inner peripheral surface 13, and the raw material powder of the resistor 33 is filled on the raw material powder of the first connection portion 34. After pre-compressing the raw material powder of the resistor 33 filled inside the second inner peripheral surface 13 using a compression rod (not shown), the second connecting portion 35 is inside the second inner peripheral surface 13. Fill with raw material powder. Using a compression rod (not shown), the raw material powder of the second connection portion 35 filled in the second inner peripheral surface 13 is precompressed.

After inserting the first member 41 and the second member 42 inside the first inner peripheral surface 12 of the insulator 11, the insulator 11 is transferred into the furnace, for example, the resistor 33, the first connection portion 34, and the second member. The temperature is higher than the softening point of the glass component contained in each raw material powder of the connection portion 35. After heating, the terminal fitting 32 is inserted inside the first member 41, and the raw material powder of the second connecting portion 35 is axially compressed by the tip of the terminal fitting 32. As a result, the resistor 33, the first connection portion 34, and the second connection portion 35 are formed inside the insulator 11.

Next, the insulator 11 is transferred to the outside of the furnace, and the main metal fitting 20 to which the ground electrode 29 is previously bonded is assembled to the outer periphery of the insulator 11. Next, the ground electrode 29 is bent so that the tip of the ground electrode 29 faces the center electrode 31, and the spark plug 10 is obtained.

FIG. 2 is a schematic diagram of the frequency characteristics of the magnetic materials constituting the first member 41 and the second member 42. In FIG. 2, the horizontal axis represents frequency and the vertical axis represents magnetic permeability. μ'is the real component (inductance component) of complex permeability, μ ″ is the imaginary component (resistance component) of complex permeability. Μ'takes an almost constant value up to a certain frequency, but the frequency is high. Then, the magnetic flux density cannot follow the change in the magnetic field, and a phase delay occurs. Therefore, μ'decreases and μ'increases as the frequency increases. Both the first member 41 and the second member 42 show a maximum peak of μ ″ near the frequency at which μ ′ begins to decrease.

The frequency indicating the maximum peak of the magnetic permeability of the magnetic material (Ni—Zn ferrite) constituting the first member 41 is the frequency indicating the maximum peak of the magnetic permeability of the magnetic material (Mn—Zn ferrite) constituting the second member 42. Higher than. When μ "is used at a high frequency, the first member 41 and the second member 42 convert noise into heat and absorb it by a resistance component, respectively.

In the spark plug 10, since the first member 41 and the second member 42 having different magnetic permeability frequency characteristics are arranged around the conductor 30, the radio wave noise generated by the current flowing through the conductor 30 during sparking is widened. It can be suppressed in the frequency band. Since the first member 41 is closer to the conductor 30 than the second member 42, the first member 41 is easily affected by the magnetic field generated by the current flowing through the conductor 30, and the noise suppression effect of the first member 41 is exhibited. It can be done easily. Therefore, by appropriately setting the frequency characteristics of the first member 41 and the second member 42, it is possible to obtain the noise suppression effect in a wide frequency band while controlling the noise suppression effect in each frequency band.

Since the frequency showing the maximum peak of the magnetic permeability of the magnetic material constituting the first member 41 is higher than the frequency showing the maximum peak of the magnetic permeability of the magnetic material constituting the second member 42, the magnetic permeability of the second member 42 The maximum peak of is higher than the maximum peak of the magnetic permeability of the first member 41. On the other hand, the maximum peak of the magnetic permeability of the first member 41, which has a high frequency indicating the maximum peak of the magnetic permeability, is lower than the maximum peak of the magnetic permeability of the second member 42. Therefore, by arranging the first member 41 closer to the conductor 30 than the second member 42, it became wider by using a plurality of magnetic members while controlling the noise suppression so as not to be biased to the low frequency component. A sufficient noise suppression effect can be obtained in the entire frequency band in which noise can be suppressed.

Here, on the tip side of the rear end 28 of the main metal fitting 20, a part of the high frequency component of the current flowing through the conductor 30 flows through the main metal fitting 20. However, on the rear end side of the main metal fitting 20 with respect to the rear end 28, almost all of the high frequency components of the current flow through the conductor 30. Therefore, by arranging a part of the first member 41 having a high frequency indicating the maximum peak of the magnetic permeability of the magnetic material on the rear end side of the rear end 28 of the main metal fitting 20, the high frequency of the current flowing through the conductor 30 is obtained. It is possible to easily suppress the components. Therefore, it is possible to easily suppress the high frequency component of noise.

In particular, since the first member 41 is arranged over the entire length of the rear end portion 44, the resistance of the first member 41 is compared with the case where the first member 41 is arranged over a part of the entire length of the rear end portion 44. The effect of suppressing high frequency components by the components can be improved.

Almost all of the low-frequency components of the current flow through the conductor 30 regardless of the presence of the main metal fitting 20. Therefore, by making the ratio of the volume of the first member 41 the smallest in the tip portion 43, the volume of the second member 42 having a high effect of suppressing the low frequency component can be relatively increased. As a result, it is possible to easily suppress the low frequency component of the current flowing through the conductor 30. Therefore, it is possible to easily suppress the low frequency component of noise.

In particular, since the second member 42 is arranged over the entire length of the front end portion 43 and the rear end portion 44, compared with the case where the second member 42 is arranged in a part of the front end portion 43 and the rear end portion 44. The effect of suppressing the low frequency component by the resistance component of the second member 42 can be improved.

The second member 42 formed of Mn—Zn ferrite has a low maximum peak frequency and a high magnetic permeability, and the first member 41 formed of Ni—Zn ferrite has a low magnetic permeability. The frequency of the maximum peak can be increased. Therefore, by combining these ferrites, a noise suppression effect can be obtained in a wide frequency band.

Further, since the resistor 33 is arranged in a part of the conductor 30, the resistor 33 converts the low frequency component of the current flowing through the conductor 30 into heat and absorbs it. Therefore, in addition to the noise attenuation effect of the magnetic body 40, the noise attenuation effect of the resistor 33 can be obtained.

Next, a second embodiment will be described with reference to FIG. In the first embodiment, the case where the magnetic member is arranged on the tip side of the rear end 28 of the main metal fitting 20 has been described. On the other hand, in the second embodiment, the case where the magnetic member is arranged only on the rear end side of the rear end 28 of the main metal fitting 20 will be described. The same parts as those described in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 3 is a one-sided cross-sectional view of the spark plug 50 in the second embodiment. In addition, in FIG. 3, the illustration on the tip side of the spark plug 50 with respect to the seat portion 24 is omitted (the same applies to FIGS. 4 to 6).

The insulator 51 of the spark plug 50 is formed with a first inner peripheral surface 52 and a second inner peripheral surface 53 in this order from the rear end side to the front end side. The second inner peripheral surface 53 is connected to the third inner peripheral surface 14 (see FIG. 1). The first inner peripheral surface 52 has a larger inner diameter than the second inner peripheral surface 53. The boundary between the first inner peripheral surface 52 and the second inner peripheral surface 53 is located on the rear end side of the rear end 28 of the main metal fitting 20.

The magnetic body 54 is arranged inside the first inner peripheral surface 52 around the terminal fitting 32. The plurality of magnetic members constituting the magnetic body 54 include the first member 55 and the second member 56. The first member 55 and the second member 56 are cylindrical members having different diameters, and the first member 55 and the second member 56 are entirely arranged on the rear end side of the rear end 28 of the main metal fitting 20. In the present embodiment, the second member 56 is arranged radially outside the first member 55 over the entire length in the axial direction. The first member 55 is made of Ni—Zn ferrite, and the second member 56 is made of Mn—Zn ferrite. The first member 55 and the second member 56 are fixed to each other by a fixing member 45 (see FIG. 1).

According to the spark plug 50, by arranging the first member 55 and the second member 56 on the rear end side of the rear end 28 of the main metal fitting 20, they are arranged on the tip side of the rear end 28 of the main metal fitting 20. It is possible to suppress low-frequency components and high-frequency components of the current flowing through the conductor 30 while omitting the magnetic material.

The third embodiment will be described with reference to FIG. In the first embodiment and the second embodiment, the case where the second members 42 and 56 are arranged outside the radial direction of the entire first members 41 and 55 has been described. On the other hand, in the third embodiment, a case where the second member 65 is arranged outside a part of the first member 62 in the radial direction will be described. The same parts as those described in the first embodiment and the second embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 4 is a one-sided sectional view of the spark plug 60 according to the third embodiment.

The magnetic body 61 built in the spark plug 60 is arranged inside the first inner peripheral surface 52 around the terminal fitting 32. The plurality of magnetic members constituting the magnetic body 61 include the first member 62 and the second member 65. The first member 62 projects toward the rear end side from the cylindrical first portion 63 that contacts the terminal fitting 32 and the first inner peripheral surface 52, and the radially inner portion of the rear end of the first portion 63. It is provided with a cylindrical second portion 64 and the like. The second member 65 is a cylindrical member arranged on the rear end side of the first part 63 of the first member 62 and radially outside the second part 64.

The first member 62 and the second member 65 are entirely arranged on the rear end side of the rear end 28 of the main metal fitting 20. The first member 62 and the second member 65 are fixed to each other by a fixing member 45 (see FIG. 1).

The first member 62 is made of Ni—Zn ferrite, and the second member 65 is made of Mn—Zn ferrite. The frequency showing the maximum peak of the magnetic permeability of the first member 62 is higher than the frequency showing the maximum peak of the magnetic permeability of the second member 65. Since the second part 64 of the first member 62 is closer to the conductor 30 than the second member 65, it is easily affected by the magnetic field generated by the current flowing through the conductor 30. Therefore, the noise suppression effect of the second part 64 of the first member 62 can be easily exhibited.

In the spark plug 60, the ratio of the volume of the first member 62 having a high frequency showing the maximum peak of magnetic permeability to the volume of the magnetic member arranged on the rear end side of the rear end 28 of the main metal fitting 20 is the largest. Since almost all of the high frequency components of the current flow through the conductor 30 on the rear end side of the main metal fitting 20 with respect to the rear end 28, the first member 62 can easily suppress the high frequency components of the current flowing through the conductor 30. Therefore, it is possible to easily suppress the high frequency component of noise.

In the spark plug 60, the ratio of the volume of the first member 62 having a high frequency showing the maximum peak of magnetic permeability to the total volume of the magnetic member is the largest. The maximum peak of the magnetic permeability of the first member 62 is lower than the maximum peak of the magnetic permeability of the second member 65, but by making the ratio of the volume of the first member 62 the largest, the noise of the low frequency component due to the second member 65. By using the first member 62 and the second member 65 while controlling so as not to be overly focused on suppression, a sufficient noise suppression effect can be obtained in the entire range of the widened noise-suppressable frequency band.

The fourth embodiment will be described with reference to FIG. In the third embodiment, the case where the magnetic material is arranged only on the rear end side of the rear end 28 of the main metal fitting 20 has been described. On the other hand, in the fourth embodiment, the case where the magnetic material is arranged on the tip side of the rear end 28 of the main metal fitting 20 will be described. The same parts as those described in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 5 is a one-sided sectional view of the spark plug 70 according to the fourth embodiment.

The magnetic body 71 built in the spark plug 70 is arranged inside the first inner peripheral surface 12 around the terminal fitting 32. The plurality of magnetic members constituting the magnetic body 71 include a first member 72 and a second member 75 formed in a cylindrical shape. The first member 72 is made of Ni—Zn ferrite, and the second member 75 is made of Mn—Zn ferrite. The frequency indicating the maximum peak of the magnetic permeability of the first member 72 is higher than the frequency indicating the maximum peak of the magnetic permeability of the second member 75.

The first member 72 is a cylindrical first portion 73 that contacts the terminal fitting 32 and the first inner peripheral surface 12, and a cylinder that projects toward the tip side from the radially inner portion of the tip of the first portion 73. The second part 74 of the shape and the like are provided. The second member 75 projects from the cylindrical first portion 76 in contact with the terminal fitting 32 and the first inner peripheral surface 12 and the radially outer portion of the rear end of the first portion 76 toward the rear end side. It is provided with a cylindrical second portion 77 and the like. The second part 77 of the second member 75 is arranged outside the second part 74 of the first member 72 in the radial direction. The volume of the first member 72 is larger than the volume of the second member 75 (that is, the volume of the first member 72 is the largest).

Since the second part 74 of the first member 72 is closer to the conductor 30 than the second part 77 of the second member 75, it is easily affected by the magnetic field generated by the current flowing through the conductor 30. Therefore, the noise suppression effect of the second part 74 of the first member 72 can be easily exhibited.

The plurality of magnetic members (first member 72 and second member 75) have a tip portion 78 arranged on the tip side of the rear end 28 with the rear end 28 of the main metal fitting 20 as a boundary, and a tip portion 78 of the rear end 28. It is divided into a rear end portion 79 arranged on the rear end side and the rear end portion 79. The first part 76 of the second member 75 constitutes the tip portion 78, and the second part 77 and the first member 72 of the second member 75 form the rear end portion 79. Since the first member 72 does not exist in the tip portion 78, the volume ratio of the first member 72 in the tip portion 78 is smaller than the volume ratio of the second member 75 in the tip portion 78 (that is, the ratio of the first member 72). Is the smallest). On the other hand, in the rear end portion 79, the volume ratio of the first member 72 is larger than the volume ratio of the second member 75 (that is, the ratio of the first member 72 is the largest).

Since the spark plug 70 has the smallest volume ratio of the first member 72 in the tip portion 78, in other words, the volume ratio of the second member 75 can be increased in the tip portion 78. Since almost all of the low-frequency component of the current flows through the conductor 30 regardless of the presence of the main metal fitting 20, the second member 75 arranged at the tip portion 78 on the tip side of the rear end 28 of the main metal fitting 20 causes the current to flow. It is possible to easily suppress the low frequency component of the current flowing through the conductor 30. Therefore, it is possible to easily suppress the low frequency component of noise.

Further, since the spark plug 70 has the largest volume ratio of the first member 72 in the rear end portion 79, the rear end portion 79 can easily suppress the high frequency component of the current flowing through the conductor 30. Therefore, it is possible to easily suppress the high frequency component of noise.

The spark plug 70 has the largest ratio of the volume of the first member 72 to the total volume of the magnetic member. The maximum peak of the magnetic permeability of the first member 72 is lower than the maximum peak of the magnetic permeability of the second member 75, but by making the ratio of the volume of the first member 72 the largest, the noise of the low frequency component due to the second member 75 By using the first member 72 and the second member 75 while controlling so as not to be overly focused on suppression, a sufficient noise suppression effect can be obtained in the entire range of the widened noise-suppressable frequency band.

The fifth embodiment will be described with reference to FIG. In the first to fourth embodiments, the case where the magnetic material is composed of two magnetic members (first member and second member) has been described. On the other hand, in the fifth embodiment, the case where the magnetic material 81 is composed of three magnetic members will be described. The same parts as those described in the first embodiment are designated by the same reference numerals, and the following description will be omitted. FIG. 6 is a one-sided sectional view of the spark plug 80 according to the fifth embodiment.

The magnetic body 81 built in the spark plug 80 is arranged inside the first inner peripheral surface 12 around the terminal fitting 32. The plurality of magnetic members constituting the magnetic body 81 include a first member 82, a second member 85, and a third member 89 formed in a cylindrical shape. The first member 82 and the second member 85 are made of Ni—Zn ferrite, and the third member 89 is made of Mn—Zn ferrite. The frequency showing the maximum peak of magnetic permeability is higher in the order of the first member 82, the second member 85, and the third member 89. The first member 82, the second member 85, and the third member 89 are fixed to each other by the fixing member 45 (see FIG. 1).

The frequency indicating the maximum peak of magnetic permeability is set in the first member 82 and the second member 85 by making the ratios of Ni and Zn different from each other. In the present embodiment, the initial magnetic permeability of the first member 82 is 120, the initial magnetic permeability of the second member 85 is 1500, and the initial magnetic permeability of the third member 89 is 5000. However, this is an example and is not limited to this.

The first member 82 is a cylindrical first portion 83 that contacts the terminal fitting 32 and the first inner peripheral surface 12, and a cylinder that projects toward the tip side from the radially inner portion of the tip of the first portion 83. The second part 84 of the shape and the like are provided.

The second member 85 projects from the cylindrical first portion 86 in contact with the terminal fitting 32 and the first inner peripheral surface 12 and the radially outer portion of the rear end of the first portion 86 toward the rear end side. It is provided with a cylindrical second portion 87 and a cylindrical third portion 88 projecting from a radially inner portion of the tip of the first portion 86 toward the tip side. The second part 87 of the second member 85 is arranged outside the second part 84 of the first member 82 in the radial direction.

The third member 89 projects from the cylindrical first portion 90 in contact with the terminal fitting 32 and the first inner peripheral surface 12 and the radially outer portion of the rear end of the first portion 90 toward the rear end side. It is provided with a cylindrical second portion 91 and the like. The second part 91 of the third member 89 is arranged outside the third part 88 of the second member 85 in the radial direction. The volume of the first member 82 is the largest among the first member 82, the second member 85, and the third member 89.

Since the second part 84 of the first member 82 is closer to the conductor 30 than the second part 87 of the second member 85, it is easily affected by the magnetic field generated by the current flowing through the conductor 30. Therefore, the noise suppression effect of the second part 84 of the first member 82 can be easily exhibited. Further, since the third part 88 of the second member 85 is closer to the conductor 30 than the second part 91 of the third member 89, it is easily affected by the magnetic field generated by the current flowing through the conductor 30. Therefore, the noise suppression effect of the third part 88 of the second member 85 can be easily exhibited.

The plurality of magnetic members (first member 82, second member 85, and third member 89) have a tip portion 92 arranged on the tip side of the rear end 28 with the rear end 28 of the main metal fitting 20 as a boundary. It is divided into a rear end portion 93 arranged on the rear end side of the rear end 28. The first part 90 of the third member 89 constitutes the tip portion 92, and the second part 91, the second member 85 and the first member 82 of the third member 89 form the rear end portion 93. Since the first member 82 does not exist in the tip portion 92, the volume ratio of the first member 82 in the tip portion 92 is the smallest. On the other hand, the volume ratio of the first member 82 in the rear end portion 93 is the largest.

Since the spark plug 80 has the smallest volume ratio of the first member 82 in the tip portion 92, in other words, in the tip portion 92, the frequency of the maximum peak of magnetic permeability is lower than that of the first member 82 (this). In the embodiment, the volume ratio of the second member 85 and the third member 89) can be increased. Almost all of the low-frequency components of the current flow through the conductor 30 regardless of the presence of the main metal fitting 20, so that the tip portion 92 can easily suppress the low-frequency components of the current flowing through the conductor 30. Therefore, it is possible to easily suppress the low frequency component of noise.

The spark plug 80 has the largest volume ratio of the first member 82 at the rear end portion 93. Here, a part of the high frequency component of the current flowing through the conductor 30 flows through the main metal fitting 20 on the tip side of the rear end 28 of the main metal fitting 20, but almost on the rear end side of the rear end 28 of the main metal fitting 20. Everything flows through the conductor 30. Therefore, the rear end portion 93 can easily suppress the high frequency component of the current flowing through the conductor 30. Therefore, it is possible to easily suppress the high frequency component of noise.

Further, since the second member 85, which has the lowest frequency of the maximum peak of magnetic permeability next to the first member 82, is arranged at the rear end portion 93, the high frequency component of the current flowing through the conductor 30 is transmitted by the second member 85. It can be more easily suppressed.

The spark plug 80 has the largest ratio of the volume of the first member 82 to the total volume of the magnetic member. The maximum peak of the magnetic permeability of the first member 82 is lower than the maximum peak of the magnetic permeability of the second member 85 and the maximum peak of the magnetic permeability of the third member 89, but by increasing the volume ratio of the first member 82. , The noise suppression effect of the high frequency component by the first member 82 can be ensured. Therefore, it is possible to obtain a sufficient noise suppression effect in the entire range of the widened noise-suppressable frequency band while controlling the noise suppression by the second member 85 and the third member 89 so as not to be biased.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It is easy to guess.

In the first to fourth embodiments, the magnetic body 40, 54, 61, 71 is composed of two magnetic members, and in the fifth embodiment, the magnetic body 81 is composed of three magnetic members. It is not always limited to this. The number of magnetic members constituting the magnetic material can be appropriately set to 2 or more (for example, 4 or 5).

In the embodiment, the case where the resistor 33 built in the conductor 30 is a monolithic type in which the raw material powder is molded and fired inside the insulators 11 and 51 has been described, but the present invention is not limited to this. Of course, it is possible to insert a prefabricated resistor into the insulators 11 and 51 to form a resistor. Also, as a matter of course, the resistor can be omitted.

In the embodiment, the case where the second connecting portion 35 is formed by firing the raw material powder has been described, but the present invention is not limited to this. Of course, it is possible to form the second connecting portion 35 with an elastic body such as a conductive spring.

In the embodiment, the inner diameters of the first inner peripheral surfaces 12, 52 of the insulators 11, 51 are made larger than the inner diameters of the second inner peripheral surfaces 13, 53, and the first inner peripheral surfaces 12, 52 and the terminal fitting 32 are formed. Although the case where the magnetic materials 40, 54, 61, 71, 81 are provided in the gaps of the above is described, the present invention is not necessarily limited to this. For example, while making the inner diameters of the first inner peripheral surfaces 12, 52 the same as the inner diameters of the second inner peripheral surfaces 13, 53, the terminal fittings 32 are made thinner to make the first inner peripheral surfaces 12, 52 and the terminal fittings. Of course, it is possible to create a gap between the 32 and 32 and provide a magnetic material in the gap.

In the embodiment, the case where the magnetic members are fixed to each other by the fixing member 45 has been described, but the present invention is not limited to this. Of course, it is possible to omit the fixing member 45.

In the embodiment, the case where the magnetic bodies 40, 54, 61, 71, 81 are arranged around the terminal fitting 30 has been described, but the present invention is not limited to this. Of course, it is possible to arrange a magnetic material around the center electrode 31, the resistor 33, and the like. This is because, similarly to the terminal fitting 30, a current flows through the center electrode 31, the resistor 33, and the like during sparking, so that the noise suppression effect of the magnetic material can be obtained.

10,50,60,70,80 spark plugs
11 Insulator 20 Main metal fittings 28 Rear end of main metal fittings 30 Conductors 40, 54, 61, 71, 81 Magnetic material 41, 55, 62, 72, 82 First member (magnetic member)
42,56,65,75,85 Second member (magnetic member)
43,78,92 Tip part 44,79,93 Rear end part 45 Fixing member

Claims (7)

With a tubular insulator,
Cylindrical main metal fittings arranged on the outer circumference of the insulator,
A conductor held inside the main metal fitting via the insulator and extending from the front end side to the rear end side,
A spark plug comprising a magnetic material arranged around the conductor and inside the insulator.
The magnetic material is composed of a plurality of magnetic members each formed of a magnetic material having a different frequency characteristic of magnetic permeability.
Wherein the plurality of magnetic member includes a first member, seen including a second member at least a part of itself which is located outward in the radial direction from at least a portion of said first member,
Among the plurality of magnetic members, at least a part of the member having the highest frequency indicating the maximum peak of the magnetic permeability of the magnetic material is a spark plug arranged on the rear end side of the main metal fitting. With a tubular insulator,
Cylindrical main metal fittings arranged on the outer circumference of the insulator,
A conductor held inside the main metal fitting via the insulator and extending from the front end side to the rear end side,
A spark plug comprising a magnetic material arranged around the conductor and inside the insulator.
The magnetic material is composed of a plurality of magnetic members each formed of a magnetic material having a different frequency characteristic of magnetic permeability.
Wherein the plurality of magnetic member includes a first member, seen including a second member at least a part of itself which is located outward in the radial direction from at least a portion of said first member,
Of the plurality of magnetic members, the tip portion arranged on the tip side of the main metal fitting is the volume of the member having the highest frequency indicating the maximum peak of the magnetic permeability of the magnetic material among the plurality of magnetic members. Spark plug with the smallest percentage. With a tubular insulator,
Cylindrical main metal fittings arranged on the outer circumference of the insulator,
A conductor held inside the main metal fitting via the insulator and extending from the front end side to the rear end side,
A spark plug comprising a magnetic material arranged around the conductor and inside the insulator.
The magnetic material is composed of a plurality of magnetic members each formed of a magnetic material having a different frequency characteristic of magnetic permeability.
Wherein the plurality of magnetic member includes a first member, seen including a second member at least a part of itself which is located outward in the radial direction from at least a portion of said first member,
Among the plurality of magnetic members, the rear end portion arranged on the rear end side of the main metal fitting is the member having the highest frequency indicating the maximum peak of the magnetic permeability of the magnetic material among the plurality of magnetic members. Spark plug with the largest volume ratio. With a tubular insulator,
Cylindrical main metal fittings arranged on the outer circumference of the insulator,
A conductor held inside the main metal fitting via the insulator and extending from the front end side to the rear end side,
A spark plug comprising a magnetic material arranged around the conductor and inside the insulator.
The magnetic material is composed of a plurality of magnetic members each formed of a magnetic material having a different frequency characteristic of magnetic permeability.
Wherein the plurality of magnetic member includes a first member, seen including a second member at least a part of itself which is located outward in the radial direction from at least a portion of said first member,
The plurality of magnetic members are spark plugs in which the ratio of the volume of the member having the highest frequency indicating the maximum peak of the magnetic permeability of the magnetic material among the plurality of magnetic members to the total volume of the plurality of magnetic members is the largest. .. The frequency indicating the maximum peak of the magnetic permeability of the magnetic material constituting the first member is higher than the frequency indicating the maximum peak of the magnetic permeability of the magnetic material constituting the second member according to any one of claims 1 to 4. The listed spark plug. The spark plug according to any one of claims 1 to 5 , wherein the plurality of magnetic members are fixed to each other via a fixing member. The spark plug according to any one of claims 1 to 6 , wherein the magnetic material contains Mn-Zn ferrite and Ni-Zn ferrite.

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