JP2513173C - - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark plug for an internal combustion engine having improved wear resistance (hereinafter referred to as a spark plug). 2. Description of the Related Art Conventionally known spark plugs having a noble metal tip are subjected to resistance welding after caulking a noble metal tip 5 as shown in FIGS. 1 and 2, or as shown in FIG. The noble metal tip is fixed to the center electrode 3 or the ground electrode 4. However, the conventional configuration has the following problem. (1) As shown in FIGS. 1 and 2, the method of performing resistance welding after crimping requires a crimping, which complicates the structure such as forming the concave portion 3 b, and particularly crimps with the ground electrode 4. It is very difficult to form the shape, and there is a problem in mass production. (2) As shown in FIG. 3, in the method of performing only resistance welding, the manufacturing method is certainly easy, but the reliability after welding poses a problem. (3) Further, as disclosed in French Patent No. 1435473, a conical rod is formed on an end face of the center electrode by inserting a cylindrical platinum rod into a center electrode melted by a high-frequency furnace, The conical rod firmly fixes the platinum rod in the center electrode. However, the use of such a high-frequency furnace has a problem in that the apparatus becomes very large and mass-produced. [0005] As described above, conventionally, noble metal chips could not be firmly fixed to the electrodes by an easy manufacturing method which does not pose a problem in mass production. The present invention has been made in view of the above-described problems, and manufactures a spark plug that can easily obtain a spark plug in which a noble metal member can be firmly fixed even if the environment is suddenly changed. It is intended to provide a method. Therefore, the present invention provides an insulator, a center electrode held by the insulator, a housing fixed to the insulator, and provided on the housing. A ground electrode facing the center electrode; and a flat electrode provided on at least one of the center electrode and the ground electrode, the flat electrode facing the ground electrode and the center electrode.
A method for manufacturing a spark plug for an internal combustion engine comprising a noble metal member having a size that can be joined without protruding a contact surface with a pole or the ground electrode, wherein the noble metal member having a flat shape is sandwiched. A spark plug for an internal combustion engine in which the noble metal member is provided on at least one of the center electrode and the ground electrode by performing resistance welding such that a raised portion formed of the one electrode holding the noble metal member is formed. Is provided. Therefore, in the present invention, with the above configuration, when the noble metal member is fixed to the electrode, the noble metal member is formed integrally with at least one of the center electrode and the ground electrode on the outer periphery of the noble metal member. As the raised portion holding the noble metal member is formed, by performing resistance welding on at least one of the noble metal member and the center electrode or the ground electrode, since the noble metal member is provided on the center electrode or the ground electrode,
A raised portion can be formed very easily around the noble metal member. Since the raised portion integrated with the electrode holds the noble metal member, even if the environment is suddenly changed, the bonding between the noble metal member and the electrode is performed only at the end face of the noble metal tip. In addition, since the center electrode or the ground electrode also holds the outer periphery of the noble metal member, the noble metal member can be firmly fixed to the center electrode or the ground electrode. Hereinafter, the present invention will be described in detail with reference to specific examples. FIG. 4 is a sectional view of the tip of the spark plug of the present invention. Reference numeral 3 denotes a center electrode of the spark plug according to the present invention, which is a conventionally known N which is excellent in heat resistance and corrosion resistance in which Cr, Fe, or the like is added to Ni applied to a normal spark plug.
It is made of an i-base alloy and is sealed in a shaft hole 2 a of the insulator 2. A small-diameter portion 3b having a smaller diameter than the body portion 3a of the center electrode 3 is formed at the tip of the center electrode 3, and the tip surface of the small-diameter portion 3b is made of platinum as a noble metal. ,
A noble metal plate 5 which is a noble metal member having a flat fixing portion 5a having a diameter of 0.7 mm to 1.0 mm and a thickness of about 0.1 mm to 0.4 mm, and a facing portion 5b facing a ground electrode 4 described later. However, the central electrode 3 is fixed by resistance welding without protruding from the contact surface with the small diameter portion 3b. Similarly to the center electrode 3, the housing 1 has a ground electrode made of a conventionally well-known Ni-based alloy excellent in heat and corrosion resistance in which Cr, Fe, or the like is added to Ni applied to a normal spark plug. Noble metal 4 is welded, and a portion of the ground electrode 4 opposite to the noble metal plate 5 of the center electrode 3 includes a fixed portion 6a having a flat shape and an opposing portion 6b opposed to the noble metal plate 5. As long as the noble metal plate 6 as a member does not protrude from the contact surface with the ground electrode 4, it is fixed by resistance welding. That is, in the present embodiment, the facing portions 5b and 6b of the noble metal plates 5 and 6 of the electrodes 3 and 4 are fixed so as to face each other. Next, FIG. 5 is an enlarged view of the opposite portion of the noble metal plates 5 and 6, and FIG.
FIG. 6 shows an A sectional view. As is clear from FIGS. 5 and 6, in the spark plug of the present invention, the raised portions 3c and 4a of the material of the electrodes 3 and 4 by resistance welding are formed.
The raised portions 3c, 4a are formed over the entire circumference of the flat fixing portions 5a, 6a of the noble metal plates 5, 6, and the raised portions 3c, 4a
The noble metal plates 5 and 6 are securely fixed to the small-diameter portion 3b of the center electrode 3 and the ground electrode 4 at the raised portions 3c and 4a. Next, a method of joining the noble metal plates 5 and 6 to the respective electrodes 3 and 4 of the spark plug of the present invention will be described in detail. First, when joining the noble metal plate 5 to the distal end of the small-diameter portion 3b of the center electrode 3, the noble metal plate 5 is placed on the distal end surface of the small-diameter portion 3b, and an electrode (not shown) used for resistance welding is attached to the center electrode 3 And the noble metal plate 5. By passing a current between the electrodes, resistance heat is generated between the center electrode 3 and the noble metal plate 5 by contact resistance, and by utilizing this heat, the mother portion of the small-diameter portion 3b of the center electrode 3 is generated. While softening part of the material,
By pressing the noble metal plate 5 against the small diameter portion 3b, the noble metal plate 5
By embedding the flat fixed portion 5a in the small diameter portion 3b, the raised portion 3c is formed. At this time, in this embodiment, the pressing force is 14 kg, the current is 800 A, and the energizing time is 5 cycles. In the ground electrode 4, the noble metal plate 6 is placed at a position opposite to the noble metal plate 5 joined to the small-diameter portion 3b of the center electrode 3, and under the same conditions as when the noble metal plate 5 is joined to the center electrode 3. The fixing portion 6a of the noble metal plate 6 was also fixed to the ground electrode 4. As described above, resistance heat generated by resistance welding is generated between each of the electrodes 3 and 4 and each of the electrode plates 5 and 6, and the respective electrodes 3 and 4 and each of the noble metal plates 5 are generated by the resistance heat. , 6 are softened and solid-dissolved, and the precious metal plates 5, 6 are pressed against the softened portion, so that the noble metal plates 5, 6 protrude over the entire circumference of the fixed portions 5a, 6a. 3c and 4a are formed. According to the above embodiment, the noble metal plate 5, which can be joined without protruding the joining surface even in a small area of the tip end face, such as the small diameter portion 3b formed at the tip of the center electrode 3, 6, the noble metal plates 5, 6 from the side due to the external force are formed by crimping over the entire circumference of the fixed portions 5a, 6a of the noble metal plates 5, 6 by the weld raised portions 3c, 4a. Of the noble metal plates 5 and 6 due to the repetition of the cooling / heating cycle due to the difference in linear expansion coefficient between the base metal of the center electrode 3 and the ground electrode 4 and the noble metal plates 5 and 6 can be prevented. Further, when iridium is added to platinum, the hardness increases, and therefore, it is suitable for the above welding. The present invention is not limited to the above embodiments, and various modifications are possible as follows. (1) The materials of the noble metal plates 5 and 6 are palladium, iridium,
Of course, rhodium, gold, and alloys thereof may be used. (2) The shapes of the noble metal plates 5 and 6 can be various shapes such as a circle, a rectangle, and a star. In summary, according to the present invention, the noble metal member is formed such that a raised portion integrally formed with at least one of the center electrode and the ground electrode is formed on the outer periphery of the flat noble metal member. By performing resistance welding on at least one of the center electrode and the ground electrode, a noble metal member is formed on at least one of the center electrode and the ground electrode.
Provide. Therefore , a raised portion can be formed very easily on the outer periphery of the noble metal member. And even with such an easy method, the noble metal member is formed integrally with the electrode holding the noble metal member, and the raised portion holding the noble metal member is formed, so that the noble metal member is firmly attached to the center electrode or the ground electrode. Can be retained.

[Brief description of the drawings]   FIG.   It is sectional drawing which shows the conventional spark plug.   FIG. 2   FIG. 2 is a front view for explaining manufacturing of the electrode unit of FIG. 1.   FIG. 3   It is a front view of the electrode part in the other example of the prior art.   FIG. 4   FIG. 2 is a cross-sectional view showing one embodiment of the present invention.   FIG. 5   FIG. 5 is an enlarged sectional view showing a main part of FIG. 4.   FIG. 6   It is AA sectional drawing of FIG.   [Explanation of symbols]   3 Center electrode   3a Body of center electrode   3b Small diameter part of center electrode   3c, 4a swell   4 Ground electrode   5, 6 precious metal members

Claims (1)

Claims: (1) An insulator, a center electrode held by the insulator, a housing fixed to the insulator, a ground electrode provided on the housing and facing the center electrode, the center electrode or the or the ground electrode provided on at least one of the ground electrode is the center electrode or the forms a flat shape facing the center electrode
A method of manufacturing a spark plug for an internal combustion engine comprising a noble metal member having a size that can be joined without protruding a joining surface with a ground electrode, wherein the noble metal member having a flat shape is held by holding the noble metal member. A method for manufacturing a spark plug for an internal combustion engine, wherein the noble metal member is provided on at least one of the center electrode and the ground electrode by performing resistance welding so that a raised portion formed of the one electrode is formed. . (2) The noble metal member is provided on at least one of the center electrode and the ground electrode by resistance welding so that the raised portion is formed on the entire outer periphery of the noble metal member. 13. A method for producing a spark plug for an internal combustion engine according to claim 12. (3) The pressure, the amount of current, and the duration of current of the resistance welding are formed integrally with at least one of the center electrode and the ground electrode on the outer periphery of the noble metal member, and a raised portion for holding the noble metal member is formed. 2. The method for manufacturing a spark plug for an internal combustion engine according to claim 1, wherein the spark plug is set so as to be set.