JP5118615B2 - Manufacturing method of spark plug - Google Patents

Description

  The present invention relates to a method for manufacturing a spark plug used for ignition of an internal combustion engine, and more particularly to a method for manufacturing an insulator constituting the spark plug.

  In general, in a spark plug used for an internal combustion engine such as an automobile engine, a long insulator is held in a state of being inserted into a cylindrical metal shell, and is formed on the insulator. A center electrode that forms a spark discharge gap facing the ground electrode welded to the front end side of the metal shell and a terminal electrode that applies a high voltage to the center electrode are inserted into the shaft hole.

  Such an insulator is formed by press-molding the prepared raw material powder, forming a molded body having a hole to be a shaft hole, and grinding the outer surface of the obtained molded body to have a predetermined insulator shape. Then, it is manufactured by firing.

In the conventional grinding process for grinding the molded body, as shown in FIG. 5, the molded body 50 is supported with the insertion pin P5 inserted from the rear end side of the hole formed along the axial direction. It is rotated in the direction indicated by arrow F5 in FIG. On the other hand, the grinding rotary roller (rotary grindstone) 55 for grinding the molded body 50 has a peripheral surface 55a formed in a shape corresponding to the outer shape of the insulator, and is in the same direction as the arrow F5 by a rotation mechanism (not shown). Is rotated in the direction indicated by the arrow F6 in FIG. Then, by bringing the molded body 50 into contact with the peripheral surface 55a of the rotating grinding roller 55 for grinding, the outer shape of the molded body 50 is ground into a shape corresponding to the insulator (see, for example, Patent Document 1).
JP 2001-176737 A

  In recent years, spark plugs have tended to be downsized and reduced in diameter due to the increase in the area occupied by intake and exhaust valves in the combustion chamber accompanying the increase in the output of internal combustion engines. It is requested.

  However, with regard to the insulator, since it is necessary to ensure a predetermined withstand voltage performance, etc., even if the material is highly insulating, there is a limit to reducing the thickness from the outer peripheral surface to the shaft hole. There is. As a result, the influence of the diameter reduction of the insulator appears as the diameter reduction of the shaft hole.

  For this reason, when the molded body is ground in the insulator manufacturing process, a relatively small diameter insertion pin to be inserted into the hole of the molded body must be employed. As a result, the insertion pin bends due to the frictional force that the molded body receives from the rotating grinding roller, causing eccentricity (decrease in coaxiality) and hole misalignment on the tip side of the molded body to be ground. There is a risk that.

  Such a problem is more likely to appear more remarkably in recent years because the longer the spark plug that is being lengthened, the longer the insulator.

  The present invention has been made in view of the above circumstances, and the purpose thereof is to form a molded body having a hole portion to be a shaft hole of the insulator with a raw material powder in manufacturing the insulator. An object of the present invention is to provide a spark plug manufacturing method capable of suppressing the eccentricity of the molded body and the axial displacement of the hole that occur when the molded body is ground into an insulator shape.

  Hereinafter, each configuration suitable for solving the above-described problems will be described in terms of items. In addition, the effect etc. peculiar to the structure which respond | corresponds as needed are added.

Configuration 1. The manufacturing method of the spark plug of this configuration is as follows:
A molding step of molding the raw material powder into a molded body having a hole to be a shaft hole;
A predetermined insertion pin is inserted into the hole from one end in the axial direction of the molded body, and the molded body is brought into contact with a rotating grinding rotation roller while rotating, and the molded body is rotated. A grinding step in which a rotating roller for pressing is brought into contact with the molded body, a rotational force is applied to the molded body to rotate against a frictional force received from the grinding rotary roller, and the outer peripheral surface of the molded body is ground. ,
Through a firing step of firing the ground compact,
A method of manufacturing a spark plug including an insulator formed by inserting and fixing a center electrode and a terminal electrode, wherein the hole portion is a shaft hole,
In the grinding process,
A support means for supporting the molded body against a load received from the grinding rotary roller, contacting the molded body at the other end in the axial direction from the pressing rotary roller;
Pressing means for pressing the support means against the molded body;
A deflection amount detecting means for detecting a deflection amount of the insertion pin;
By using the control means for controlling the pressing means based on the detection result of the deflection amount detecting means,
The pressing force for pressing the supporting means against the molded body can be adjusted according to the amount of bending of the insertion pin.

  According to the configuration 1, the pressing force pressing the support means against the molded body can be adjusted according to the amount of bending of the insertion pin, so that the load from the grinding rotary roller applied to the molded body and the support means from the support means can be adjusted. The grinding process can be performed in a more optimal state in which the insertion force is balanced with the pressing force and the insertion pin is less bent.

  As a result, when the molded body is ground, even when a relatively small diameter insertion pin is inserted into the hole of the molded body, the frictional force received by the molded body from the rotating rotating roller for grinding, etc. Therefore, it is possible to suppress the occurrence of a problem that the insertion pin is bent. As a result, it is possible to suppress the occurrence of eccentricity or axial misalignment of the hole on the other end side opposite to the one end side where the insertion pin of the molded body to be ground is inserted.

  In addition, the load that the compact receives from the grinding rotary roller changes as appropriate according to the grinding situation (for example, the resistance increases as the grinding progresses), so that the insertion pin is not bent from the grinding rotary roller. If the support means is always pressed against the load with a constant strong force, the molded body will break due to the pressing force from the support means when the load applied to the compact from the rotating roller for grinding is relatively small. It can happen.

  On the other hand, according to the present configuration 1, when the load applied to the compact from the grinding rotary roller is relatively small, the force for pressing the support means can be weakened. Can be suppressed.

  Here, the “amount of bending of the insertion pin” refers to the amount of positional deviation between the proximal end portion and the distal end portion of the insertion pin in the radial direction of the insertion pin.

Configuration 2. The manufacturing method of the spark plug of this configuration is as follows:
A molding step of molding the raw material powder into a molded body having a hole to be a shaft hole;
A predetermined insertion pin is inserted into the hole from one end in the axial direction of the molded body, and the molded body is brought into contact with a rotating grinding rotation roller while rotating, and the molded body is rotated. A grinding step in which a rotating roller for pressing is brought into contact with the molded body, a rotational force is applied to the molded body to rotate against a frictional force received from the grinding rotary roller, and the outer peripheral surface of the molded body is ground. ,
Through a firing step of firing the ground compact,
A method of manufacturing a spark plug including an insulator formed by inserting and fixing a center electrode and a terminal electrode, wherein the hole portion is a shaft hole,
In the grinding process,
A support means for supporting the molded body against a load received from the grinding rotary roller, contacting the molded body at the other end in the axial direction from the pressing rotary roller;
Pressing means for pressing the support means against the molded body;
Load detecting means for detecting a load that the molded body receives from the grinding rotary roller;
By using the control means for controlling the pressing means based on the detection result of the load detecting means,
The pressing force for pressing the supporting means against the molded body can be adjusted according to the load that the molded body receives from the grinding roller.

  According to Configuration 2, the pressing force pressing the support means against the molded body can be adjusted according to the load that the molded body receives from the grinding rotary roller, whereby the load from the grinding rotary roller on the molded body is adjusted. And the pressing force from the support means, and the grinding process can be performed in a more optimal state with less bending of the insertion pin. As a result, the same effects as those of the above configuration 1 are achieved.

Configuration 3. The manufacturing method of the spark plug of this configuration is the above configuration 1 or 2,
The position at which the support means contacts the molded body from the position at which the rotating roller for grinding contacts the molded body is 270 ° greater than 180 ° in the rotational direction of the molded body around the insertion pin. The position is shifted by a smaller predetermined angle.

  In other words, the position where the support means contacts the molded body is opposite to the rotational direction of the molded body with the insertion pin as an axis from the position where the rotating roller for grinding contacts the molded body. The position is shifted by a predetermined angle in the direction larger than 90 ° and smaller than 180 °.

  At the time of grinding, a dynamic frictional force is applied in the tangential direction at the contact point with the grinding rotary roller, and a reaction force of the force pressing the compact against the grinding rotary roller is applied in the normal direction. On the other hand, the grinding rotary roller and the supporting means are brought into contact with the molded body in the above positional relationship as in the configuration 3, so that the supporting means resists the dynamic friction force in the contact direction and the reaction force in the normal direction. Grinding can be performed in a state where the molded body is supported, and the operational effects of the above-described configurations 1 and 2 can be further ensured.

  Further, the longer the overall length of the molded body, or the thinner the diameter, the easier the insertion pin bends when subjected to a load from the grinding rotary roller. Examples of the shape of the molded body to which the configuration is more effectively applied include those described in the following configurations 4 and 5.

Configuration 4. The manufacturing method of the spark plug of this configuration is any one of the above configurations 1 to 3,
The molded body has a length in the axial direction of 80 mm or more.

Configuration 5. The manufacturing method of the spark plug of this configuration is any one of the above configurations 1 to 4,
The molded body is characterized in that an inner diameter of the hole is 5 mm or less.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, the spark plug 1 obtained by the spark plug manufacturing method of the present invention will be described. FIG. 1 is a partially cutaway front view showing a spark plug 1. In FIG. 1, the axis C1 direction of the spark plug 1 is defined as the vertical direction in the drawing, the lower side is described as the front end side of the spark plug 1, and the upper side is described as the rear end side.

  The spark plug 1 is composed of a long insulator 2, a cylindrical metal shell 3 that holds the insulator 2, and the like.

  A shaft hole 4 is formed through the insulator 2 along the axis C1. A center electrode 5 is inserted and fixed on the front end side of the shaft hole 4, and a terminal electrode 6 is inserted and fixed on the rear end side. A resistor 7 is disposed between the center electrode 5 and the terminal electrode 6 in the shaft hole 4, and both ends of the resistor 7 are connected to the center electrode via conductive glass seal layers 8 and 9. 5 and the terminal electrode 6 are electrically connected to each other.

  More specifically, the shaft hole 4 of the insulator 2 includes a small-diameter hole portion 4a formed on the front end side, and a large-diameter hole portion 4b formed on the rear end side of the small-diameter hole portion 4a. It is composed of And the taper surface or the R-shaped convex part receiving surface 4c is formed in the connection part of the small diameter hole part 4a and the large diameter hole part 4b.

  The terminal electrode 6 and the resistor 7 are accommodated in the shaft hole 4 of the insulator 2 in a state of being inserted into the large diameter hole portion 4b, and the center electrode 5 is accommodated in the state of being inserted into the small diameter hole portion 4a. ing. The center electrode 5 protrudes from the tip of the insulator 2, and the terminal electrode 6 protrudes from the rear end of the insulator 2. A fixing convex portion 5a is formed at the rear end portion of the center electrode 5 so as to protrude outward from the outer peripheral surface thereof, and the fixing convex portion 5a is locked to the convex portion receiving surface 4c. Thus, the center electrode 5 is fixed.

  On the other hand, the insulator 2 has a corrugation portion 10 formed on the rear end side in the outer shape portion, a flange-shaped large diameter portion 11 formed to protrude radially outward at a substantially central portion in the axis C1 direction, A middle body portion 12 having a smaller diameter on the front end side than the large diameter portion 11, and a smaller diameter portion on the front end side than the middle body portion 12, and a combustion chamber of an internal combustion engine (engine). And a leg length portion 13 exposed to. Of the insulator 2, the distal end side including the large-diameter portion 11, the middle trunk portion 12, and the leg long portion 13 is accommodated in a metal shell 3 formed in a cylindrical shape. A step portion 14 is formed at the connecting portion between the leg long portion 13 and the middle trunk portion 12, and the insulator 2 is locked to the metal shell 3 at the step portion 14.

  The metal shell 3 is formed in a cylindrical shape from a metal such as low carbon steel, and a screw portion (male screw portion) 15 for attaching the spark plug 1 to the engine head is formed on the outer peripheral surface thereof. A seat portion 16 is formed on the outer peripheral surface on the rear end side of the screw portion 15, and a ring-shaped gasket 18 is fitted on the screw neck 17 on the rear end of the screw portion 15. Further, on the rear end side of the metal shell 3, a tool engaging portion 19 having a hexagonal cross section for engaging a tool such as a wrench when the metal shell 3 is attached to the engine head is formed. 1 is provided with a caulking portion 20 for holding the insulator 2.

  Further, a step portion 21 for locking the insulator 2 is provided on the inner peripheral surface of the metal shell 3. The insulator 2 is inserted from the rear end side to the front end side of the metal shell 3, and the rear end of the metal shell 3 is engaged with the step portion 14 of the metal shell 3. It is fixed by caulking the opening on the side radially inward, that is, by forming the caulking portion 20. An annular plate packing 22 is interposed between the step portions 14 and 21 of both the insulator 2 and the metal shell 3. Thereby, the airtightness in the combustion chamber is maintained, and the fuel air entering the gap between the leg long portion 13 of the insulator 2 exposed to the combustion chamber and the inner peripheral surface of the metal shell 3 is prevented from leaking outside.

  Further, in order to make the sealing by caulking more complete, annular ring members 23 and 24 are interposed between the metal shell 3 and the insulator 2 on the rear end side of the metal shell 3, and the ring member 23 , 24 is filled with powder of talc (talc) 25. That is, the metal shell 3 holds the insulator 2 via the plate packing 22, the ring members 23 and 24, and the talc 25.

  A ground electrode 27 having a substantially L shape is joined to the front end surface 26 of the metal shell 3. That is, the ground electrode 27 is disposed so that the base end portion thereof is welded to the front end surface 26 of the metal shell 3, the front end side is bent back, and the inner side surface thereof faces the front end portion of the center electrode 5. ing. A spark discharge gap 28 is formed between the inner side surface of the tip of the ground electrode 27 and the tip surface of the center electrode 5.

  Next, a method for manufacturing the spark plug 1, particularly a method for manufacturing the insulator 2 which is a characteristic part of the present invention, will be described in detail.

  In the manufacturing process of the insulator 2, first, an additive element material that functions as a sintering aid is blended with the alumina powder as a main component to prepare a raw material powder. Then, a green binder slurry is obtained by adding and mixing a hydrophilic binder and water as a solvent to the obtained raw material powder. Then, the forming substrate slurry is spray-dried by a spray drying method or the like, and adjusted to a granular forming substrate granulated product.

  In the subsequent molding step, the obtained green granulated material for molding is filled in a rubber press mold and is subjected to rubber press molding with a press pin inserted, thereby forming the original shape of the insulator 2 as shown in FIG. A cylindrical molded body 30 is obtained. A hole 31 to be the shaft hole 4 is formed in the molded body 30 by the press pin.

  Next, a grinding step of grinding the outer shape of the obtained molded body 30 into a shape corresponding to the insulator 2 is performed. Here, the grinding process will be described in detail with reference to FIGS. FIG. 2 is a schematic cross-sectional view for explaining the shape of the molded body 30 and its supporting form in the grinding process, and FIG. 3 shows a grinding rotary roller, a presser rotary roller, and supporting means used in the grinding process. It is a schematic diagram for demonstrating the contact positional relationship of the support roller as a, and the molded object 30. FIG.

  In the grinding process, as shown in FIG. 2, the insertion pin P1 is fitted into the hole 31 from the rear end side in the axial direction of the molded body 30 (the side on which the corrugation 10 of the insulator 2 is formed). The outer peripheral surface of the molded body 30 is processed by the grinding rotation roller 35 in a state where 30 is rotatably supported from the rear end side.

  The rotating roller 35 for grinding used here has a peripheral surface 35a corresponding to the outer shape of the insulator (the molded body 30 shrinks when fired, so the dimensions thereof are different). An abrasive layer is formed on 35a. And the rotation roller 35 for grinding rotates to the direction shown by the arrow F2 in FIG.2, 3 centering on the rotating shaft center G2 parallel to the axial direction of the shaft center G1 of the penetration pin P1 by the drive of the motor which is not shown in figure. It is like that.

  The presser rotating roller 37 is made of silicon resin or the like having a large frictional resistance with the molded body 30, and rotates a rotation axis G3 parallel to the axial direction of the axis G1 of the insertion pin P1 by driving a motor (not shown). It rotates in the direction indicated by the arrow F3 in FIGS. As a result, a rotational force rotating in the direction indicated by the arrow F1 in FIGS. 2 and 3 is applied to the compact 30 against the frictional force received from the rotating roller 35 for grinding. In the present embodiment, the pressing rotary roller 37 is disposed corresponding to a portion that becomes the large-diameter portion 11 of the insulator 2.

  The support roller 38 is for supporting the molded body 30 against the load received from the grinding rotary roller 35, and the axial end side of the molded body 30 relative to the press rotary roller 37 (the leg length of the insulator 2). On the side where the portion 13 is formed). The support roller 38 rotates about the rotation axis G4 in the same direction as the pressing rotation roller 37 (direction indicated by an arrow F4 in FIGS. 2 and 3) due to a frictional force received from the molded body 30.

  The insertion pin P1 is made of a material having high rigidity, such as a cemented carbide, so that deformation is less likely to occur during grinding. The insertion pin P1 includes a small-diameter shaft portion corresponding to the small-diameter hole portion 4a of the insulator 2 and a large-diameter shaft portion corresponding to the large-diameter hole portion 4b. It has a corresponding shape. However, the distal end of the small-diameter shaft portion of the insertion pin P1 protrudes from the distal end side of the through-hole 31. An annular pressing rubber 33 is attached to the insertion pin P1 to facilitate positioning of the molded body 30 during grinding, or the grinding rotary roller 35 comes into contact with the insertion pin P1 and both are damaged. Or prevent it.

  Under the above configuration, as shown in FIG. 3, the entire axial direction of the outer peripheral surface of the molded body 30 at an arbitrary circumferential position is brought into contact with the rotating grinding rotary roller 35 and the rotating rotary roller for presser foot. 37 is brought into contact with the molded body 30 to support the molded body 30 while applying a rotational force rotating in the direction indicated by the arrow F1 in FIGS. 2 and 3 against the frictional force received from the grinding rotary roller 35. The molded body 30 is supported by the roller 38 and grinding is performed.

  Here, with reference to FIG. 3, the arrangement configuration of the molded body 30, the grinding rotary roller 35, the pressing rotary roller 37, and the support roller 38 on an orthogonal plane orthogonal to the axial direction of the axis G1 of the insertion pin P1. Will be described.

  In this embodiment, the axis G1 of the insertion pin P1, the rotation axis G2 of the grinding rotary roller 35, and the rotation axis G3 of the presser rotary roller 37 are positioned on substantially the same horizontal plane. As a result, the position S1 where the pressing rotary roller 37 contacts the molded body 30 is shifted by 180 ° in the rotational direction F1 of the molded body 30 from the position S2 where the grinding rotary roller 35 contacts the molded body 30. It has become.

  On the other hand, the rotational axis G4 of the support roller 38 is located slightly below the rotational axis G3 of the pressing rotary roller 37. More specifically, the position S3 at which the support roller 38 contacts the molded body 30 is 270 ° greater than 180 ° in the rotational direction F1 of the molded body 30 from the position S2 at which the grinding rotary roller 35 contacts the molded body 30. The position is shifted by a smaller predetermined angle A. In the present embodiment, the predetermined angle A is set to 225 °. That is, a straight line connecting the axis G1 of the insertion pin P1 and the rotation axis G4 of the support roller 38 to the horizontal line connecting the axis G1 of the insertion pin P1 and the rotation axis G3 of the pressing roller 37 is formed. The body 30 is inclined 45 ° in the rotation direction F1.

  Further, in the present embodiment, the pressing force pressing the support roller 38 against the molded body 30 is adjustable. This configuration will be described in detail below. The pressing rotary roller 37 that applies a rotational force to the molded body 30 is always pressed against the molded body 30 with a constant force.

  As shown in FIG. 2, the support roller 38 is pressed against the molded body 30 by an air cylinder 40 as a pressing means.

  Further, a laser displacement meter 41 as a deflection amount detecting means is disposed at a position facing the tip of the insertion pin P1 on the extension line of the axis G1 of the insertion pin P1. The laser displacement meter 41 includes a light emitting element such as a semiconductor laser and a detection element that receives light emitted from the semiconductor laser and reflected by an object, and detects the amount of displacement of the tip of the insertion pin P1. It is configured to be possible. Thereby, the amount of positional deviation between the base end portion (reference position) of the insertion pin P1 and the distal end portion with respect to the radial direction of the insertion pin P1 is detected as the deflection amount of the insertion pin P1.

  Furthermore, in the present embodiment, a control device 42 is provided as control means for controlling the air cylinder 40 based on the detection result of the laser displacement meter 41. For example, the control device 42 considers that the load from the grinding rotary roller 35 applied to the molded body 30 is greater than the pressing force from the support roller 38 when the amount of deflection of the insertion pin P1 increases toward the support roller 38. The support roller 38 is pressed against the molded body 30 with a stronger force. On the contrary, if the bending amount of the insertion pin P1 becomes larger toward the grinding rotary roller 35, it is considered that the pressing force from the support roller 38 applied to the molded body 30 is larger than the load from the grinding rotary roller 35. The force for pressing the roller 38 against the molded body 30 is weakened.

  As described above, in the present embodiment, the load from the grinding rotary roller 35 and the pressing force from the support roller 38 applied to the molded body 30 are controlled by appropriately controlling the air cylinder 40 according to the bending amount of the insertion pin P1. Thus, the grinding process can be performed in a more optimal state in which the insertion pin P1 is less bent.

  The molded body 30 that has undergone the grinding process as described above is removed from the insertion pin P1, and then sent to the next firing process.

  In the firing step, the molded body 30 that has been ground is fired within a firing temperature range of 1450 ° C to 1700 ° C. Then, further glaze is applied and finish baking is performed, and the insulator 2 is completed.

  The spark plug 1 is completed by inserting and fixing the center electrode 5 and the terminal electrode 6 to the insulator 2 manufactured in this way and attaching the insulator 2 to the metal shell 3.

  As described above in detail, in the present embodiment, when the molded body 30 is ground, the insertion pin P1 that is inserted into the hole 31 of the molded body 30 is inserted even when a relatively small diameter is employed. Generation | occurrence | production of the malfunction that the pin P1 will bend can be suppressed. As a result, it is possible to suppress the occurrence of eccentricity and axial misalignment of the hole on the tip side of the molded body 30 to be ground.

  In addition, it is not limited to the description content of embodiment mentioned above, For example, you may implement as follows.

  (A) In the above embodiment, the insulator shown in FIG. 1 is given as an example of an insulator to which the present invention is applied. Of course, the present invention is also applied to grinding of insulators having other outer shapes. can do.

  In the above embodiment, the size of the molded body 30 is not particularly mentioned. However, the longer the overall length of the molded body 30 is, or the smaller the diameter is, the smaller the load from the grinding rotary roller 35 is. Since the insertion pin P1 is easily bent when it is received, the molded body 30 (corresponding to the insulator 2 having an axial length of 64 mm or more) or a large hole 31 is obtained. If the present invention is applied in manufacturing a molded body 30 (corresponding to the insulator 2 in which the inner diameter of the large-diameter hole portion 4b is 4 mm or less) in which the inner diameter of the radial shaft portion is 5 mm or less, the effect is more exhibited. The

  (B) In the above embodiment, the grinding process is performed by only one grinding roller 35. However, the present invention is not limited to this. For example, after the roughing process is performed by the first grinding roller, The finishing grinding process may be performed by the second grinding rotary roller. Further, unlike the insertion pin P1, the grinding process may be performed using an insertion pin whose tip does not protrude from the tip of the molded body 30. In this way, after the outer peripheral surface of the molded body 30 is ground, the grinding of the tip 30 of the molded body 30 into a rounded surface is continuously performed by a grinding rotary roller for cutting the tip. be able to.

  (C) In the above embodiment, the support roller 38 is employed as a support means for supporting the molded body 30. For example, other members such as a spherical member, a U-shaped member, and a belt-shaped member may be used as the support means instead of the roller. For example, as shown in FIG. 4, instead of the support roller 38 of the above-described embodiment, a belt B1 hung between two tension rollers 45a and 45b may be employed as a support means to support the molded body 30. .

  (D) In the above embodiment, the position S3 where the support roller 38 comes into contact with the molded body 30 is 225 ° in the rotational direction F1 of the molded body 30 from the position S2 where the grinding rotary roller 35 comes into contact with the molded body 30. It is set to a shifted position. Not only this but position S3 which support roller 38 contacts is good also as a different position from the above-mentioned embodiment. However, during grinding, a dynamic frictional force is applied in a tangential direction at the position S2 where the grinding rotary roller 35 comes into contact with the molded body 30, and a reaction force of the force pressing the molded body 30 against the grinding rotary roller 35. Therefore, the position S3 where the support roller 38 contacts is shifted from the position S2 where the grinding rotary roller 35 contacts within the range of more than 180 ° and less than 270 ° in the rotation direction F1 of the molded body 30. Preferably it is in position.

  Furthermore, it is good also as a structure which can change position S3 which the support roller 38 contacts with respect to the molded object 30 in the rotation direction F1 of the molded object 30. FIG. If it does in this way, it can respond more efficiently according to the load from the rotation roller for grinding which changes suitably according to the grinding situation.

  Further, with respect to the position S1 where the pressing rotary roller 37 contacts the molded body 30, a position shifted by 180 ° in the rotational direction F1 of the molded body 30 from the position S2 where the grinding rotary roller 35 contacts the molded body 30. The position is not limited to the above, and different positions may be used.

  (E) In the above-described embodiment, a configuration in which one press rotating roller 37 and one support roller 38 are provided is shown. However, the configuration is not limited thereto, and a configuration in which a plurality of each roller is provided may be employed. When a plurality of support rollers 38 are provided, at least one of them may be disposed as in the above embodiment.

  (F) In the above embodiment, the deflection amount of the insertion pin P1 is detected by the laser displacement meter 41, and the air cylinder 40 is controlled based on this. For example, a load cell may be attached to the insertion pin P1 as load detecting means, a load received from the grinding rotary roller 35 may be detected, and the air cylinder 40 may be controlled in accordance with the change in the load. If it does in this way, the same operation effect as the above-mentioned embodiment is produced.

  (G) In the above embodiment, the air cylinder 40 is employed as the pressing means. However, the present invention is not limited to this, and any other means can be used as long as the position of the support roller 38 can be displaced, such as a hydraulic cylinder or a servo motor. A configuration may be adopted.

It is a partially broken front view which shows the whole spark plug of this embodiment. It is a cross-sectional schematic diagram for demonstrating the shape of the molded object, its support form, etc. in a grinding process. It is a schematic diagram for demonstrating arrangement | positioning structure of a molded object, the rotation roller for grinding, the rotation roller for pressing, and a support roller. It is a schematic diagram for demonstrating the support form of the molded object in another embodiment. It is a perspective view of the molded object and the rotating roller for grinding for demonstrating the conventional grinding process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Spark plug, 2 ... Insulator, 3 ... Main metal fitting, 4 ... Shaft hole, 5 ... Center electrode, 6 ... Terminal electrode, 30 ... Molded object, 31 ... Hole, 35 ... Rotary roller for grinding, 37 ... Presser Rotating roller 38, support roller, 40 ... air cylinder, 41 ... laser displacement meter, 42 ... control device, P1 ... insertion pin.

Claims (5)

A molding step of molding the raw material powder into a molded body having a hole to be a shaft hole;
A predetermined insertion pin is inserted into the hole from one end in the axial direction of the molded body, and the molded body is brought into contact with a rotating grinding rotation roller while rotating, and the molded body is rotated. A grinding step in which a rotating roller for pressing is brought into contact with the molded body, a rotational force is applied to the molded body to rotate against a frictional force received from the grinding rotary roller, and the outer peripheral surface of the molded body is ground. ,
Through a firing step of firing the ground compact,
A method of manufacturing a spark plug including an insulator formed by inserting and fixing a center electrode and a terminal electrode, wherein the hole portion is a shaft hole,
In the grinding process,
A support means for supporting the molded body against a load received from the grinding rotary roller, contacting the molded body at the other end in the axial direction from the pressing rotary roller;
Pressing means for pressing the support means against the molded body;
A deflection amount detecting means for detecting a deflection amount of the insertion pin;
By using the control means for controlling the pressing means based on the detection result of the deflection amount detecting means,
A method for manufacturing a spark plug, characterized in that a pressing force for pressing the supporting means against the molded body can be adjusted in accordance with a bending amount of the insertion pin. A molding step of molding the raw material powder into a molded body having a hole to be a shaft hole;
A predetermined insertion pin is inserted into the hole from one end in the axial direction of the molded body, and the molded body is brought into contact with a rotating grinding rotation roller while rotating, and the molded body is rotated. A grinding step in which a rotating roller for pressing is brought into contact with the molded body, a rotational force is applied to the molded body to rotate against a frictional force received from the grinding rotary roller, and the outer peripheral surface of the molded body is ground. ,
Through a firing step of firing the ground compact,
A method of manufacturing a spark plug including an insulator formed by inserting and fixing a center electrode and a terminal electrode, wherein the hole portion is a shaft hole,
In the grinding process,
A support means for supporting the molded body against a load received from the grinding rotary roller, contacting the molded body at the other end in the axial direction from the pressing rotary roller;
Pressing means for pressing the support means against the molded body;
Load detecting means for detecting a load that the molded body receives from the grinding rotary roller;
By using the control means for controlling the pressing means based on the detection result of the load detecting means,
A method for manufacturing a spark plug, characterized in that a pressing force for pressing the supporting means against the molded body can be adjusted according to a load that the molded body receives from the rotating roller for grinding.   The position at which the support means contacts the molded body from the position at which the rotating roller for grinding contacts the molded body is 270 ° greater than 180 ° in the rotational direction of the molded body around the insertion pin. The method for manufacturing a spark plug according to claim 1 or 2, wherein the position is shifted by a smaller predetermined angle.   The method of manufacturing a spark plug according to any one of claims 1 to 3, wherein the molded body has an axial length of 80 mm or more.   The spark plug manufacturing method according to any one of claims 1 to 4, wherein the molded body has an inner diameter of the hole portion of 5 mm or less.

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