Patent Grant
10790638
This patent application is based on and claims priority to Japanese Patent Application No. 2019-008329, filed on Jan. 22, 2019 in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
The present disclosure relates to a spark plug used in an internal combustion engine and a method of manufacturing the spark plug.
In an internal combustion engine such as an automobile engine, etc., a spark plug is used as an ignition system. The spark plug is attached to a cylinder head by screwing a mounting screw provided in an outer periphery of the spark plug into a female screw formed in a plug hole of the cylinder head. When the spark plug is attached to the cylinder head, a discharge gap formed at a tip of the spark plug is located in a combustion chamber.
In such a situation, when a gas in the combustion chamber leaks out of the combustion chamber between the female screw and the spark plug, malfunction of the engine occurs. Hence, airtightness is required between the spark plug and the cylinder head.
In view of this, an outer periphery of a housing of a conventional spark plug has a circular pressure contact surface pressed against a seat surface formed in a cylinder head. The seat surface of the cylinder head is formed in a tapered state extended toward an outer periphery thereof toward a base thereof. The pressure contact surface of the spark plug is also formed in a tapered state so as to face the seat surface. The pressure contact surface is pressed against the seat surface by screwing a mounting screw into a female screw provided in the plug hole of the cylinder head thereby generating longitudinal force. Hence, both adhesion between the pressure contact surface and the seat surface and airtightness between the spark plug and the cylinder head are ensured.
However, the international standard ISO 28741:2013 regulates that a taper angle between seat surfaces of a cylinder head is 60 degrees +0/−1 degrees, and a taper angle between pressure contact surfaces of a spark plug is 63 degrees ±0.1 degrees. That is, the standard regulates that the taper angle of the pressure contact surface of the spark plug is larger than the taper angle of the seat surface of the cylinder head. Thus, when the spark plug is attached to the cylinder head, an outer periphery of the pressure contact surface of the spark plug is necessarily pressed against the seat surface of the cylinder head.
Here, a circular pressure contact surface formed on the outer periphery of the housing of the conventional spark plug is extended from a tip of a cylindrical parallel surface (herein below simply referred to as a parallel surface) parallel to an axis. Hence, since an angular portion formed on the outer periphery of the pressure contact surface (i.e. a corner between the pressure contact surface and the parallel surface) is radially positioned at the parallel surface, the angular portion is relatively closer to the outer periphery of the housing. When the corner is positioned relatively closer to the outer periphery of the housing, other objects are likely to interfere with the corner, for example, during a manufacturing process of manufacturing the spark plug. As a result, the corner including an outer peripheral edge of the pressure contact surface can have dents.
Specifically, when barrel metal plating is applied to the housing, the corner can be hit thereby having the dent thereon. That is, in the barrel metal plating, multiple pre-metal plating housings are installed in a basket called a barrel containing metal plating solution, and the barrel is rotated to apply metal plating to surfaces of respective housings. This barrel metal plating is highly productive at low cost when preparing the housings, because many housings can be plated at once. On the other hand, however, due to collision between the housings in the barrel, dents can be made on the housing surfaces. In particular, because it has a square shape on the relatively outer periphery of the housing between the pressure contact surface and the parallel surface of the housing, the corner easily interferes with other housings or the like during the barrel metal plating, thereby probably suffering a dent thereon.
When an unevenness (e.g., a dent) is formed on the corner including the outer peripheral edge of the pressure contact surface, adhesion between the outer peripheral edge of the pressure contact surface and the seat surface of the cylinder head is likely to be reduced. As a result, airtightness between the spark plug and the cylinder head can be decreased.
The present invention has been made to address such problems and an object thereof is to provide a spark plug used in an internal combustion engine enabled to ensure airtightness between the spark plug and the cylinder head.
Accordingly, one aspect of the present disclosure provides a novel spark plug used in an internal combustion engine. The spark plug has a tubular housing. An outer periphery of the tubular housing includes: a parallel surface formed parallel to an axis of the spark plug and a circular pressure contact surface located closer to a tip of the spark plug and radially inward more than the parallel surface. The pressure contact surface has a tapered shape in that a diameter decreases towards the tip. The pressure contact surface is pressed against a cylinder head. The outer periphery of the tubular housing further includes a connection surface to connect an outer peripheral edge of the pressure contact surface with an end of the parallel surface. The connection surface is located closer to a base of the spark plug than an extension line extended along and away from the pressure contact surface.
Another aspect of the present disclosure provides a novel method of producing a spark plug for internal combustion engine. The method comprises the step of forming an inclined surface inclined to a radially outward from the body of the spark plug toward a base thereof as a preparation step. A part of the inclined surface becomes a pressure contact surface to be pressed against a cylinder head. The method further comprises the step of forming a cylindrical surface parallel to a longitudinal direction from an outer peripheral edge of the inclined surface toward the base in the preparation step. A part of the cylindrical surface becomes a parallel surface. The method further comprises the step of applying barrel plating to the housing substrate as a barrel plating step. After completing the barrel plating step, the method further comprises the step of applying machining to a substrate corner caused during the preparation step on a border between the inclined surface and the cylindrical surface until the substrate corner is deformed into the connection surface while the inclined surface and the cylindrical surface are changed to the pressure contact surface and the parallel surface, respectively.
Yet another aspect of the present disclosure provides a novel method of producing a spark plug for an internal combustion engine, which includes a housing that accommodates a cylindrical porcelain insulator and is caulked at its base. To prepare a housing substrate, the method comprises the step of forming an inclined surface inclined radially outward from the body of the spark plug toward a base of the spark plug as a preparing step. A part of the inclined surface becomes a pressure contact surface. The method further comprises the step of forming a cylindrical surface parallel to a longitudinal direction of the spark plug from an outer peripheral edge of the inclined surface toward the base also as a preparing step. A part of the cylindrical surface becomes a parallel surface. The method further comprises the step of applying barrel plating to the housing substrate as a barrel plating step. After completing the barrel plating step, the method further comprises the step of forming an assembly at least by inserting a porcelain insulator into the housing substrate as an insertion step. The method further comprises the step of bringing a substrate corner caused during the preparing step on a border between the inclined surface and the cylindrical surface into contact with a supporting surface formed parallel to the connection surface in an inner periphery of a tubular supporting jig from above the supporting surface in a first contacting step. The method further comprises the step of bringing a caulking jig into contact with the base of the housing substrate from above the base of the housing substrate in a second contacting step. After completing the first contacting step and the second contacting step, the method further comprises the step of applying a compressive force to the housing substrate in the longitudinal direction by bringing the supporting jig and the caulking jig close to each other in the longitudinal direction as a simultaneous processing step until the base of the housing substrate is plastically deformed and a caulked portion is formed by the compressive force. The method further comprises the step of simultaneously pressing a substrate corner against the supporting surface by the compressive force until the substrate corner is plastically deformed into a connection surface facing the supporting surface while the inclined surface and the cylindrical surface are changed to a pressure contact surface and a parallel surface, respectively.
A more complete appreciation of the present disclosure and many of the attendant advantages of the present disclosure will be more readily obtained as substantially the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views thereof, and to
First, as shown in
The pressure contact surface 2c is disposed closer to a tip of the spark plug 1 than the parallel surface 2a is and radially inside an extension line extended along and away from and away from an outer periphery of the parallel surface 2a. The pressure contact surface 2c is formed in a tapered state in which a diameter reduces toward the tip of the spark plug 1. As shown in
Further, as shown in
More specifically, the spark plug 1 can be used as an ignition system in an internal combustion engine mounted on an automobile or a cogeneration system and the like. One end of the spark plug 1 in the longitudinal direction Z is connected to an ignition coil (not shown), the other end of the spark plug 1 in the longitudinal direction Z is disposed in a combustion chamber 12 of the internal combustion engine (see
Herein below, when it is simply referred to, a longitudinal direction Z means a longitudinal direction of the spark plug 1 unless otherwise particularly mentioned. Further, one side of the spark plug 1 inserted first into the combustion chamber 12 in the longitudinal direction Z is referred to as a tip side. By contrast, the other side opposite thereto is referred to as a base side. Further, when it is simply referred to, a radial direction means that of the spark plug 1.
The housing 2 is formed in a cylindrical (i.e., tubular) state and made of heat-resistant conductive material, such as iron, nickel, iron-nickel alloy, stainless steel, etc. Although not shown in the drawings, a surface of the housing 2 is plated with nickel or zinc and the like. By applying such metal plating to the surface of the housing 2, a corrosion resistance of the housing 2 can be increased. As described later, the metal plating is applied to the surface of the housing 2 by a barrel metal plating process.
Further, as shown in
Further, as shown in
The thinned surface 2d has a cylindrical shape parallel to the longitudinal direction Z. The thinned surface 2d has a smaller outer diameter than each of respective portions of the housing 2 adjacent to both sides of the thinned surface 2d in the longitudinal direction Z. The thinned surface 2d serves as an escape groove to accept partial entrance of a die for rolling use when the mounting screw 24 is rolled. Specifically, by providing the thinned surface 2d, the die for rolling use is prevented from interfering with a portion other than the mounting screw 24. Further, as shown in
The inclined connection surface 2e is formed in a tapered shape in which a diameter decreases toward the tip side. Further, the inclined connection surface 2e has a taper angle greater than the pressure contact surface 2c has. In the longitudinal cross-section, each of the extension lines extended along and away from the inclined connection surfaces 2e is linear and parallel to the inclined connection surface 2e. As shown in
As described earlier, the pressure contact surface 2c has the tapered shape that shrinks toward the tip side. That is, in the longitudinal cross-section, the pressure contact surface 2c is inclined linearly to a radially inner portion toward the tip side.
As shown in
Further, as shown in
Further, a seat taper angle θf, i.e., a taper angle of the seat surface 11f of the cylinder head 11, is 60 degrees +0/−1 degrees also in compliance with the international standard ISO 28741:2013. The seat taper angle θf is formed by a pair of extension lines extended along and away from the respective seat surfaces 11f in the longitudinal cross-section when the spark plug 1 is attached to the cylinder head 11. That is, in the longitudinal cross-section, each of the extension lines Lf of the seat surfaces 11f is linear and is parallel to the seat surfaces 11f.
Accordingly, since the pressure contact taper angle θc is greater than the seat taper angle θf, an outer peripheral edge of the pressure contact surface 2c is pressed against the seat surface 11f of the cylinder head 11 when the spark plug 1 is attached to the cylinder head 11. Further, as shown in
Further, the connection surface 2b has a tapered shape in which a diameter decreases toward the tip side. That is, as shown in
In this embodiment, the connection taper angle θb is less than 59 degrees. That is, the connection taper angle θb is smaller than 59 degrees, which is less than the minimum angle of 60 degrees +0/−1 degrees provided by the international standard ISO 28741:2013 as a seat surface taper angle θf of the cylinder head 11. Hence, as shown in
As described earlier, the parallel surface 2a is cylindrical parallel to the longitudinal direction Z. An outer diameter of the parallel surface 2a is greater than an outer diameter of the mounting screw 24. Further, in the longitudinal cross section, an angle between the pressure contact surface 2c and the connection surface 2b is greater than an angle between an extension line Lc of the pressure contact surface 2c and an extension line La of the parallel surface 2a. Here, when multiple parallel surfaces parallel to the longitudinal direction Z are provided on the outer periphery of the housing 2 at positions closer to the base than the pressure contact surface 2c, the most tip side parallel surface serves as the parallel surface 2a providing the extension line La. Further, a length of the parallel surface 2a in the longitudinal direction Z is greater than a distance between the parallel surface 2a and the mounting screw 24 in the longitudinal direction Z.
Here, as shown in
Further, when a diameter of the parallel surface 2a is Φa and as a solution of a fractional expression (Φa−Φb)/2 is represented by r1 (i.e., a distance between the parallel surface 2a and the outer peripheral edge of the pressure contact surface 2c in the radial direction 9), the r1 preferably satisfies the below described inequation:
0.2 mm≤r1≤0.75 mm.
That is, since a depth of a dent possibly formed on the substrate corner 43 of the housing substrate 4 during barrel metal plating is less than 0.2 mm as described later, formation of the dent on the pressure contact surface 2c can be easily prevented by setting the length of r1 to be 0.2 mm or more.
Further, as shown in the below described first table, the ISO 28741: 2013 also provides values of Φa and Φc (a standard taper diameter) corresponding to diameters of the mounting screws 24 are M12 and M14, respectively. In the first table, the standard taper diameter described earlier is represented by Φc. Also, an equality (Φa −Φc)/2=r2 is calculated based on the values Φa and Φc provided by the ISO 28741:2013 is shown in the first table. Hence, the value r2 can be the allowable maximum value of the value r1 capable of securing sealability between the pressure contact surface 2c and the seat surface 11f in conformity to the ISO 28741: 2013.
As can be seen from the first table, the value (Φa −Φc)/2 always exceeds a range of r2 allowed by the ISO 28741: 2013 when the value r1 exceeds 0.75 mm. Thus, the value r1 is desirably 0.75 mm or less. Further, because the value r2 does not exceed the allowable range determined by the ISO 28741:2013, the value r1 is more preferably 0.3 mm or less.
Further, as shown in
The tool engaging portion 22 has a hexagonal outer shape when viewed in the longitudinal direction Z. Further, as shown in
Specifically, the caulked portion 25 is pressure joined by pressure applied toward the tip side. Specifically, the caulked portion 25 is pressure joined to a porcelain insulator 3 described later in detail. Although not shown in the drawings, the caulked portion 25 can be pressure joined to the porcelain insulator 3 through a separate member disposed between the porcelain insulator 3 and the housing 2.
Specifically, the porcelain insulator 3 is held inside of the housing 2. The porcelain insulator 3 is cylindrical and made of insulation material such as alumina, etc. Further, the housing 2 has a housing protrusion 23 radially projecting inward. Hence, the porcelain insulator 3 is supported by the housing protrusion 23 from below the porcelain insulator 3 at its portion closer to the tip end. However, the porcelain insulator 3 can be supported by the housing protrusion 23 via a separate annular member.
A tip of the porcelain insulator 3 protrudes from a tip of the housing 2. A porcelain step 31 is formed radially inside of the porcelain insulator 3. A diameter of an inner periphery of the porcelain insulator 3 closer to the tip side than the porcelain step 31 is smaller than that of the porcelain insulator 3 closer to the base than the porcelain step 31. Hence, the porcelain step 31 of the porcelain insulator 3 supports the central electrode 17, thereby holding the central electrode 17 inside of the porcelain insulator 3.
Specifically, the central electrode 17 is composed of a cylindrical body made of conductive material such as Ni-based alloy, etc., and accommodates metal such as Cu, etc., with excellent thermal conductivity. A tip of the central electrode 17 protrudes from a tip of the porcelain insulator 3. On one side of the central electrode 17 closer to the base in an interior of the porcelain insulator 3, a resistor 14 is disposed via a conductive glass seal 13.
Specifically, the resistor 14 is prepared by heating a resistor composition composed of resistor material, such as carbon, ceramic powder, etc., and glass powder. The resistor composition is simultaneously enclosed adhering to the central electrode 17. Otherwise, the resistor 14 can be prepared by inserting a cartridge type resistor. The glass seal 13 is composed of copper glass prepared by mixing copper powder with glass. Further, a terminal metal 15 is disposed closer to the base than the resistor 14 is while connecting to the glass seal 13. The terminal metal 15 may be composed of iron alloy.
Further, a ground electrode 16 is connected to a tip surface of the housing 2. Specifically, a discharge gap G is formed between the ground electrode 16 and the central electrode 17. A part of the ground electrode 16 faces the tip surface of the central electrode 17 in the longitudinal direction Z. Hence, the discharge gap G formed between the tip surface of the central electrode 17 and the ground electrode 16 extends along the direction Z.
Now, with reference to
First, in the preparation step, a housing substrate 4 is prepared. As shown in
The housing substrate 4 is produced by applying cold forging and cutting processes to material such as iron, etc., constituting the housing 2. At least a rolling process is also applied to a mounting screw 24. It is noted here that a surface of the housing substrate 4 is not plated, in contrast to the housing 2. Further, before it is caulked, a portion of a base 45 of the housing substrate 4 to provide a caulked portion (see a reference numeral 25 in
Further, a ground electrode substrate 44 is connected to a tip of the housing substrate 4. Specifically, the ground electrode substrate 44 has a liner columnar shape and is extended in the longitudinal direction Z. Hence, by bending a tip side of the ground electrode substrate 44 toward a radially inside, an L-shaped ground electrode (see reference numeral 16 in
Further, as shown in
Specifically, in the barrel metal plating step, in a barrel 51 serving as a bucket-shape container, a cathode 52, multiple housing substrates 4 and multiple barrel plating media 53 are installed. The barrel 51 is then soaked in plated solution 55 filled in a metal plating tank 54. Although not shown, the barrel 51 has holes in a wall thereof to allow the metal plating solution 55 to penetrate into the barrel 51 through the holes. The barrel plating media 53 is spherical and made of metal. Hence, each of the multiple housing substrates 4 is electrically connected to the cathode 52 through the barrel plating media 53.
Further, an anode 56 is also placed in the metal plating tank 54. Then, the barrel 51 is rotated around a central axis of the barrel 51 while applying a voltage between the anode 56 and the cathode 52. Thus, the large number of housing substrates 4 and the barrel plating media 53 are stirred in the barrel 51, so that surfaces of the housing substrates 4 can be substantially equally plated.
Here, because it is formed radially at the same position as the cylindrical surface 42, the substrate corner 43 is located radially outside the housing 2. In addition, the substrate corner 43 is angular. As a result, the substrate corner 43 is likely to collide with other housing substrates 4 or the like and is prone to generate a dent d.
After completing the barrel plating step, an assembly step of attaching components, such as the porcelain insulator 3, the central electrode 17, etc., to the housing substrate 4 is performed to be held inside of the housing 2. Specifically, in the assembly step, the porcelain insulator 3 accommodating the central electrode 17, the glass seal 13, the resistor 14 and the terminal metal 15 are inserted into the housing substrate 4 from the base of the housing substrate 4. Then, the base 45 of the housing substrate 4 is caulked to the porcelain insulator 3 by pressing the base 45 toward the tip side while deforming the base 45 radially inward. At the same time, the L-shaped ground electrode 16 is prepared by bending a central portion of the ground electrode substrate 44. Here, a result of the assembly step assembling the housing substrate 4 and the porcelain insulator 3 or the like is shown in an upper side in
After completing the barrel plating step and the assembly step, a processing step is performed as shown in
More specifically, as shown in
Further, an inner diameter of the supporting surface 58 is smaller than a diameter of the substrate corner 43, and an outer diameter of the supporting surface 58 is greater than the diameter of the substrate corner 43. Thus, when the housing substrate 4 holding the porcelain insulator 3 or the like is inserted into the supporting jig 57 from the base of the supporting jig 57, the substrate corner 43 of the housing substrate 4 contacts the supporting surface 58 of the supporting jig 57.
Hence, as shown in
Further, a portion not deformed by the surface pressing in the inclined surface 41 corresponds to the pressure contact surface 2c. A portion not deformed by the surface pressing in the cylindrical surface 42 corresponds to the parallel surface 2a as well.
Here, since the substrate corner 43 is made into the tapered connection surface 2b by the surface pressing, the pressure contact surface 2c is necessarily formed further radially inside of the housing substrate 4 than a position at which the substrate corner 43 is previously located. Thus, the pressure contact surface 2c can be formed further radially inside of the housing substrate 4 than a position of the dent d conventionally formed on the substrate corner 43. Thus, the pressure contact surface 2c formed after completing the processing step can prevent it from having the dent d.
Further, after completing the processing step, a new corner E is formed over the entire circumference of the spark plug 1 between the pressure contact surface 2c and the connection surface 2b. The corner E includes the outer peripheral edge of the pressure contact surface 2c pressed against the seat surface 11f of the cylinder head 11 when the spark plug 1 is attached to the internal combustion engine. However, as described above, since the pressure contact surface 2c is disposed further radially inside the substrate corner 43 previously present in the housing substrate 4 and the corner E is also located further radially inside the substrate corner 43. Thus, the new corner E can also be prevented from having dent d as well.
Further, in the processing step, the above-described step 21 is formed by the surface pressing at the boundary between the parallel surface 2a and the connection surface 2b. Due to presence of the step 21, it is recognized that the connection surface 2b is formed by the surface pressing in the processing step. Accordingly, the spark plug 1 according to this embodiment can be effectively produced.
Now, various advantages obtainable in this embodiment are herein below described. First, in the spark plug 1 for the internal combustion engine use, the pressure contact surface 2c pressed against the cylinder head 11 is connected to the parallel surface 2a via the connection surface 2b and located further radially inside the parallel surface 2a. Thus, the outer peripheral edge of the pressure contact surface 2c in close contact with the cylinder head 11 can be positioned further radially inside the parallel surface 2a of housing 2. Thus, during a manufacturing process of manufacturing the spark plug 1 and transportation of the spark plug 1 after manufacturing thereof, other objects rarely interfere with the outer peripheral edge of the pressure contact surface 2c, so that dents are rarely generated on the outer peripheral edge of the pressure contact surface 2c. Accordingly, adhesion between the outer peripheral edge of the pressure contact surface 2c and the cylinder head 11 can be satisfactorily maintained, and accordingly airtightness between the spark plug 1 and the cylinder head 11 can be easily ensured.
Further, the connection surface 2b connecting the outer peripheral end of the pressure contact surface 2c to the tip of the parallel surface 2a is located within the region closer to the base than the extension lines Lc extended along and away from the pressure contact surface 2c in the longitudinal cross-section. Thus, since the connection surface 2b does not hit the cylinder head 11, the pressure contact surface 2c can be highly likely to contact the cylinder head 11, so that adhesion between the pressure contact surface 2c and the cylinder head 11 can be easily ensured.
Further, in the longitudinal cross-section, the connection surface 2b is linearly radially inwardly inclined toward the tip side of the spark plug 1. Thus, the new corner E appears between the outer peripheral edge of the pressure contact surface 2c and the connection surface 2b. Accordingly, when the outer peripheral edge of the pressure contact surface 2c is pressed against the seat surface 11f of the cylinder head 11, due to presence of the corner E between the pressure contact surface 2c and the connection surface 2b, a portion in the pressure contact surface 2c (actually) pressed against the seat surface 11f can be immediately recognized. Thus, after the spark plug 1 is fabricated, it is easy to confirm whether the dent is formed at a portion of the pressure contact surface 2c pressed against the seat surface 11f.
Further, the connection taper angle θb is less than 59-degrees. That is, as described earlier, the connection taper angle θb is smaller than the minimum value of the seat surface taper angle θf of the cylinder head 11 defined by the international standard ISO 28741:2013 (i.e., 60 degrees +0/−1 degrees). Thus, when the spark plug 1 is attached to the internal combustion engine, the connection surface 2b can prevent interference with the seat surface 11f. That is, since the pressure contact surface 2c can be highly likely to pressure contact the seat surface 11f, sealing property between the pressure contact surface 2c and the seat surface 11f can be further effectively ensured.
Further, according to this embodiment, the manufacturing method of manufacturing the spark plug 1 used in the internal combustion engine has the barrel plating step of applying barrel plating to the housing substrate 4 having the inclined surface 41 and the cylindrical surface 42. Thus, productivity of the housing 2 can be enhanced while reducing the cost for plating the housing 2. Further, since the surface of the housing substrate 4, in particular the surface of the substrate corner 43 located between the inclined surface 41 and the cylindrical surface 42 has a corner closer to the outer periphery of the housing substrate 4, a dent can be undesirably generated.
Thus, according to this embodiment, the manufacturing method of manufacturing the spark plug 1 has a processing step of applying deburring processing to the substrate corner 43 located between the inclined surface 41 and the cylindrical surface 42 in the housing substrate 4 to change the substrate corner 43 to the connection surface 2b, the inclined surface 41 to the pressure contact surface 2c, and the cylindrical surface 42 to the parallel surface 2a, respectively, after completing the barrel plating step. Thus, even if the dent is accidentally generated in the substrate corner 43 in the barrel plating process, since the pressure contact surface 2c formed after the processing step is located radially inner side than the substrate corner 43, the pressure contact surface 2c can be prevent from having a dent. Thus, in the manufacturing method of manufacturing the spark plug 1 in this embodiment, adhesion between the outer peripheral edge of the pressure contact surface 2c and the cylinder head 11 can be easily ensured, and accordingly airtightness between the spark plug 1 and the cylinder head 11 can be easily ensured as well.
As described heretofore, according to this embodiment, a spark plug for internal combustion engine use is capable of ensuring airtightness between the spark plug and the cylinder head.
Now, a second embodiment of the present disclosure is described with reference to
The method of manufacturing the spark plug 1 according to the second embodiment includes a preparation step, a barrel plating step, and an insertion step. The method further includes a first contacting step, a second contacting step and a simultaneous processing step as well. The preparation step and the barrel plating step in this embodiment are substantially the same as employed in the first embodiment.
However, in this embodiment, the insertion step is carried out after the barrel plating step. Specifically, as shown in
Specifically, as shown in
Further, in the second contacting step, a caulking jig 61 having a cylindrical shape contacts a base 45 of the housing substrate 4 from above the base. The caulking jig 61 has a jig contacting surface 62 at a tip of in its inner periphery. A diameter of the inner periphery increases toward the tip side. The jig contacting surface 62 is formed over the entire circumference of the inner periphery of the caulking jig 61. In a cross-section including a plug central axis parallel to the longitudinal direction Z, the jig contacting surface 62 has an arc shape tightly fitting an outer periphery of the caulked portion 25 of the housing 2 obtained after the caulking process. Further, after completing the first contacting step and the second contacting step, a simultaneous process is performed as described below.
Specifically, in the simultaneous processing step, a compressive force in the longitudinal direction Z is applied to the housing substrate 4 by bringing the supporting jig 57 and the caulking jig 61 close to each other in the longitudinal direction Z. Hence, the base 45 of the housing substrate 4 is plastically deformed by the compressive force thereby forming the caulked portion 25 as shown in
That is, in the simultaneous processing step, the caulked portion 25 and the connection surface 2b are formed at the same time by bringing the supporting jig 57 and the caulking jig 61 close to each other in the longitudinal direction Z and thereby generating compressive force applied from the supporting jig 57 and the caulking jig 61 to act on the housing substrate 4 in the longitudinal direction Z. As a result, a portion in the inclined surface 41 not deformed by the surface pressing corresponds to (i.e., serves as) the pressure contact surface 2c. A portion in the cylindrical surface 42 not deformed by the surface pressing corresponds to (i.e., serves as) the parallel surface 2a. Hence, as described heretofore, the spark plug 1 of this embodiment can be effectively preferably produced.
Further, a configuration and operation of the spark plug 1 of this embodiment is substantially the same as employed in the first embodiment.
Now, a manufacturing method of manufacturing the spark plug 1 of this embodiment is briefly described herein below. That is, as one of steps of the manufacturing method, the compressive force is applied to the housing substrate 4 in the longitudinal direction Z by bringing the supporting jig 57 and the caulking jig 61 close to each other in the longitudinal direction Z in the simultaneous processing step. Specifically, in the simultaneous compression step, the caulked portion 25 is formed by applying the compressive force and thereby plastically deforming the base 45 of the housing substrate 4. At the same time, with the compression force, the substrate corner 43 is pressed against the supporting surface 58 for deburring, and thereby plastically deforming the substrate corner 43 to form the connection surface 2b facing the supporting surface 58 while changing the inclined surface 41 and the cylindrical surface 42 to the pressure contact surface 2c and the flat surface 2a, respectively. In this way, in the simultaneous processing step, by bringing the supporting jig 57 and the caulking jig 61 close to each other in the longitudinal direction Z, the caulked portion 25 and the connection surface 2b of the housing 2 can be formed at the same time. Thus, productivity of the housing 2 can be effectively enhanced.
Further, also in this embodiment, the manufacturing method of manufacturing the spark plug 1 has a barrel plating step. Thus, productivity of the housing 2 can be enhanced while reducing the cost for plating the housing 2. On the other hand, however, because the surface of the housing substrate 4, in particular, the substrate corner 43 located is located between the inclined surface 41 and the cylindrical surface 42 at a corner formed on a side of the housing substrate 4 closer to its outer periphery, a dent can be generated.
Thus, as described above, also in this embodiment, the manufacturing method of manufacturing the spark plug 1 has the simultaneous processing step performed after the barrel plating step to form the connection surface 2b at the substrate corner 43 of the housing substrate 4 and change the inclined surface 41 and the cylindrical surface 42 to the pressure contact surface 2c and the parallel surface 2a, respectively. Hence, as in the manufacturing method of manufacturing the spark plug 1 in a second aspect, adhesion between the outer peripheral edge of the pressure contact surface 2c and the cylinder head 11, and accordingly airtightness between the spark plug 1 and the cylinder head 11 can be easily ensured. Further, substantially the same advantage can be obtained in this embodiment as obtained in the first embodiment.
Now, a third embodiment of the present disclosure will be described with reference to
Specifically, in this embodiment, the connection surface 2b is formed on the housing substrate 4 by applying roller rolling. To perform the roller rolling, one side of each of multiple rollers 7 is pressed against the substrate corner 43 of the housing substrate 4. Each of the rollers 7 is columnar with a cylindrical side surface. More specifically, the sides of the rollers 7 and the substrate corner (see reference numeral 43 in
Here, in this embodiment, the roller rolling is carried out after completing the barrel plating step. Further, the roller rolling can be performed either after or before components such as a porcelain insulator, etc., are accommodated in the housing substrate 4. Further, the substrate corner 43 of the housing substrate 4 can be cut in a cutting process to form a cut surface and serves as the connecting surface. Remaining configurations and operations are substantially the same as in the first embodiment.
Further, in this embodiment, the substantially same advantages can be obtained as obtained in the first embodiment.
Numerous additional modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present disclosure may be executed otherwise than as specifically described herein. For example, the present disclosure is not limited to the above-described spark plug used in an internal combustion engine and may be altered as appropriate. Further, the present disclosure is not limited to the above-described methods of producing a spark plug used in the internal combustion engine and may be altered as appropriate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-008329 | Jan 2019 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6357274 | Tanaka | Mar 2002 | B1 |
| 6548945 | Tamura | Apr 2003 | B1 |
| Number | Date | Country | |
|---|---|---|---|
| 20200235551 A1 | Jul 2020 | US |
