JP2014198346A - Method of manufacturing different diameter cylindrical molding by cold forging, and method of manufacturing main fitting for gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cold forging method capable of reducing a cutting step for a different diameter cylindrical molding which is a material for a main fitting.SOLUTION: After molding of a different diameter cylindrical molding 120b, a hole is opened at a rear end surface 29b of its large diameter part 22b, and at a drilling punch 240c for evagination-molding an outer peripheral surface thereof to provide a polygonal portion 23c, an extrusion sleeve 250c which allows entering of the large diameter part 22b into the inside of its own and allows a front end to enter a polygonal hole 207c of a die 200c for molding the polygonal portion 23c is externally fitted in circumferential direction with an interval being held. The sleeve 250c is linked with reciprocation of the punch 240c through a spring. When a front end of the punch 240c is driven into the rear end surface 29b of the large diameter part 22b, a portion of the sleeve that is closer to the front end is fitted in a portion of the large diameter part 22b which is closer to the rear end face 29b. When the polygonal portion 23c with a hole is evagination-molded, a thin-walled cylinder part 27c is extrusion molded between an inner peripheral surface of a portion of the sleeve which is closer to the front end, being at the rear end thereof, and the outer peripheral surface of the punch.

Description

  The present invention is a component having a different diameter cylindrical shape, such as a metal shell that is a main component of a gas sensor that measures the oxygen concentration of exhaust gas, or a metal shell that is a main component of a spark plug. The present invention relates to a manufacturing method by cold forging of a different-diameter cylindrical molded body, which is a material used for manufacturing, and a manufacturing method of a metal shell for a gas sensor manufactured from this different-diameter cylindrical molded body.

  FIG. 8 is a cross-sectional view of a gas sensor (for example, an oxygen sensor; hereinafter simply referred to as a sensor) 10 used in an automobile or a motorcycle (two-wheeled automobile). This has a metal shell 20 with a different diameter that is attached to a screw hole provided in an exhaust pipe by a screw-in method, a cylindrical sensor element 30 with a tip (lower end in the figure) closed inside, and The protective cylinder (inner protective cylinder, outer protective cylinder) 40, 41, etc., is provided to protect the inside of the element 30 and the terminal fitting 11 in the sensor. The sensor 10 generates an electromotive force between electrodes provided on the inside and outside of the element 30 based on a difference in oxygen concentration between the inside and outside of the element 30, and a lead based on this signal is drawn from the rear end (the upper end in the figure). 50 is output to the control circuit via 50 and used to detect the oxygen concentration in the exhaust gas and control the air-fuel ratio.

  As shown in FIG. 8, the metal shell 20 which is a main component of the sensor 10 has a cylindrical structure with a different diameter when viewed as a whole, and a threaded cylindrical portion having a relatively small diameter at the tip side. (Screwed small-diameter cylindrical part) 21 is formed, and a polygonal part (for example, a hexagonal part) 23 for screwing having a larger diameter is provided at the rear thereof. Further, on the rear end side following this, a cylindrical portion (hereinafter also referred to as a thin cylindrical portion) having a smaller diameter than the polygonal portion but a larger diameter than the threaded small diameter cylindrical portion 21 and having a thin cylindrical portion 27. Including a large-diameter cylindrical portion) 25. In FIG. 8, the thin cylindrical portion 27 is bent toward the center line, but this is cylindrical in the component state (see FIG. 9) as described later. In the sensor 10, a sensor element 30 is concentrically disposed and fixed inside the metal shell 20 via a seal material 13, an insulating holder 15, and the like. This fixing is performed in the assembly process before the outer protective cylinder 41 is fixed, after the sensor element 30 or the like is arranged and loaded inside the metal shell 20, the flange 43 on the outer periphery of the front end of the inner protective cylinder 40 is attached to the insulating holder 15. The thin cylindrical portion 27 at the rear end of the large-diameter cylindrical portion 25 is bent toward the inner side (center axis side) as shown in the drawing while being brought into contact with the rear end and through the O-ring 17 and directed toward the front end. It is by caulking processing that compresses.

  FIG. 9 shows the metallic shell 20 as a part before such caulking is performed. As shown in the drawing, a certain range (constant portion) from the rear end (the upper end in the drawing) to the tip (the lower end in the drawing) of the portion near the rear end of the large-diameter cylindrical portion 25 has an outer diameter suitable for caulking. The thin cylindrical portion 27 is small and thin. In the case of FIG. 9, the portion near the polygonal portion 23 in the large-diameter cylindrical portion 25 also forms the second thin-walled cylindrical portion 28 having a small outer diameter and a small thickness. This is to cause this portion to be buckled as shown in FIG. 8 during the caulking process. In addition, as shown in the figure, such a metal shell has an inner diameter that gradually increases from the threaded small-diameter cylindrical portion 21 to the rear in order to dispose the sealing material 13 and the like for holding the element 30 in a seal shape. It is formed to be large. In addition, in this application, when it is called the front-end | tip regarding a metal fitting, the lower end in FIG. 9 is said, and when it is called a rear end, it means the opposite end.

  By the way, in order to efficiently manufacture a metal shell having such a different-diameter cylindrical structure with high strength and low cost, it should be cooled to a size and shape (structure) as close to the finished product as possible. The molded body is formed by hot forging, and in this molded body, only necessary portions in terms of screws and dimensional accuracy are finished so as to have as little cutting allowance as possible. This is not limited to the metal shell constituting the oxygen sensor, and the same applies to the production of the metal shell constituting the spark plug having the same or similar different diameter cylindrical structure. For this reason, the metal shell is conventionally subjected to a plurality of (multistage) cold forging steps from a starting material (cylindrical body) obtained by cutting a low-carbon steel round bar short by cold forging. (See, for example, FIG. 1 of Patent Document 1). Then, this raw material (different diameter cylindrical molded body) 20f is a fixed range (a portion corresponding to the thin cylindrical portion 27) from the rear end to the tip of the large diameter cylindrical portion 25, or a portion closer to the polygonal portion 23. The second thin-walled cylindrical portion 28 is cut (cylindrical cutting) so as to be suitable for caulking, and finished as a metal shell (part) 20 shown in FIG.

  By the way, the different-diameter cylindrical molded body 20f shown in FIG. 10 is, for example, a first cylindrical molded body having a final diameter different from the first process molded body 20a as shown in FIGS. The six-step molded body 20f (the same molded body as the final different-diameter cylindrical molded body, which is illustrated using the same reference numerals) was sequentially molded (see FIG. 1 of Patent Document 1). Here, the outline will be explained. In the first step, the first step formed body 20a is formed by adjusting the end face of the starting material (cylindrical body) cut from the round bar, and in the second step, A different diameter cylindrical molded body (second process molded body) 20b having a small diameter portion on the front end (lower end in the figure) and a large diameter portion on the rear end (upper end in the figure) is assumed. And in the 3rd process, as shown in the left figure (A) of Drawing 12, circular hole which can constrain the outer peripheral surface of the small diameter part in this different diameter columnar molded object (2nd process molded object) 20b And a die 200c having a polygonal hole having an outer peripheral surface of a polygon part for screwing as an inner peripheral surface through an annular shelf surface and concentric with the circular hole, and the circular hole in the die Further, the small diameter portion is inserted and the front end surface thereof is supported by a support punch 220c or the like (see the left side of the center line in the left diagram in FIG. 12), and then shown on the right side of the center line in the left diagram in FIG. Thus, the punching punch 240c for forming the inner peripheral surface of the large-diameter cylindrical portion is driven into the rear end surface of the large-diameter portion (the left side of the center line in the left diagram of FIG. 12 is before the process (before molding). The right side of the center line shows the figure after the process (after molding). ). Accordingly, a hole with a bottom is formed in the rear end surface of the large-diameter portion, and the outer peripheral surface of the large-diameter portion is pressed against the inner peripheral surface of the polygonal hole to form a polygon with a hole. Part is formed, and a different-diameter molded body (third-process molded body) 20c with a polygonal section with holes is obtained.

  Then, in the fourth step, as shown in the right view (B) of FIG. 12, this different diameter molded body (third process molded body) 20c is formed in the front end of the supporting sleeve 220d disposed on the die 200d. Is inserted into the small-diameter portion to support the tip-facing surface of the polygonal portion with a hole (see the left side of the center line in the right diagram of FIG. 12), and is retained in the hole provided in the polygonal portion with a hole With the punch 240d inserted, as shown on the right side of the center line in the right diagram of FIG. 12, a predetermined range (from the rear end (upper end in the drawing) to the front end of the outer peripheral surface of the holed polygonal portion ( The outer peripheral surface (except for the front and rear range corresponding to the polygonal portion) is reduced (squeezed) to the outer diameter before cutting of the large-diameter cylindrical portion 25 by the die 260d, and at the same time, the extrusion is performed to extend backward. The fourth process molded body 20d is obtained. Then, in the fifth step, the fifth step formed body 20e (see FIG. 11-E) is formed as a small-diameter cylindrical portion by extending the small diameter portion while forming the deep hole of the hole, and further, in the sixth step, The non-penetrating wall portion, which is the bottom wall of the hole, was punched into the final sixth step molded body (different diameter cylindrical molded body) 20f (see FIG. 11-F). Thus, the different-diameter cylindrical molded body manufactured by a plurality of multi-stage cold forgings becomes a molded body 20f as shown in FIG. In the present specification, hereinafter, the work in progress from the raw material through the cold forging process until it is formed as a different diameter cylindrical molded body is also simply referred to as a molded body. Moreover, in this application, about die | dye used for shaping | molding of a molded object, or die components, such as a punch, a front end is an end by the side of the entrance into which a raw material (molded object) is pushed among those dies. Or, the end on the side to be struck (pressed) on the material, the base end is the end opposite to the front end, and the above-mentioned metal shell and the tip and rear end of the work piece (molded product) are used properly Shall.

JP 04-371336 A

  As shown in FIG. 10, in the different-diameter cylindrical molded body 20f manufactured through the above-described multiple and multi-stage cold forging processes, the thin cylindrical portion 27 and the second thin cylindrical portion 28 that are to be caulked. The large-diameter cylindrical portion 25 that constitutes is formed into a thick-walled cylindrical portion having a substantially constant thickness at the end of the cold forging. For this reason, the large-diameter cylindrical portion 25 is not limited to the second thin-walled cylindrical portion 28 near the polygonal portion 23, but a certain range (thin-walled cylindrical portion) from the rear end on the opposite side to the polygonal portion 23 toward the front end. 27), the outer peripheral surface must be cut (turned). As a result, the conventional metal shell has many manufacturing processes, and there is a lot of cutting allowance, resulting in poor material yield and shortened cutting tool life, leading to an increase in cost. was there. For such a problem, for example, in the fourth step in the cold forging step (see the right diagram B in FIG. 12), a predetermined range (from the rear end to the front end) of the outer peripheral surface of the polygonal portion with a hole ( When the outer peripheral surface of the polygonal portion (other than the front and rear range) is reduced to a large-diameter cylindrical portion (outer diameter before cutting) and extrusion-molded, as shown in a molded body 120f shown in FIG. The outer diameter in a certain range from the rear end to the tip of the diameter cylindrical portion 25 is formed so as to be smaller than the outer diameter outside this certain range so as to form a thin cylindrical portion 27f suitable for caulking from the beginning or a size close thereto. There is also an opinion that it may be good. That is, the large-diameter cylindrical portion 25 may be formed so as to be a thick cylindrical portion 26 near the polygonal portion and a thin cylindrical portion 27f.

  Certainly, in the fourth step (see the right figure B in FIG. 12), instead of the die 260d on the fourth step (see the right figure B in FIG. 12), the inner peripheral surface (two points in the right figure B in FIG. 12) is obtained. It is theoretically possible if a die with chain line L1) is used. However, in such molding, not only backward extrusion molding while simultaneously performing two-stage diameter reduction (deformation) in the front-rear direction, the extruded gap is small, and the backward extrusion length is long. Become. As a result, the molding resistance becomes extremely large, the press load during forging increases abnormally, the burden on the die and punch (die) is large, and they are susceptible to damage, so their life is shortened. In addition, defects tend to occur in the wrapping (flow) of the plastically deformed material (meat), and defects such as cracks are likely to occur in the molded body, resulting in poor yield. For these reasons, in the fourth step as described above, the backward extrusion molding with two-stage diameter reduction (deformation) has many drawbacks and cannot be adopted.

  In view of such problems, the present invention has a method for efficiently manufacturing a tubular molded body having a different diameter, which is a work in progress of a metal shell, as shown in FIG. It is an object of the present invention to provide a method that can be manufactured automatically.

The present invention according to claim 1 has a small-diameter cylindrical portion on the front end side and a large-diameter cylindrical portion on the rear end side, and the outer diameter of the large-diameter cylindrical portion is between the front and rear of both cylindrical portions. The large-diameter cylindrical portion has a larger polygonal portion, and the constant diameter range from the rear end to the front end on the opposite side of the polygonal portion is smaller in outer diameter than the other ranges. Is a method for manufacturing by cold forging of a different-diameter cylindrical molded body formed into a thin-walled cylindrical portion with a thin wall thickness, and the other range is formed into a thick-walled thick-walled cylindrical portion,
During the cold forging process,
A cold forging step of forming a different-diameter cylindrical molded body having a small diameter portion on the front end side and a large diameter portion on the rear end side;
By punching a punch for punching the inner peripheral surface of the large-diameter cylindrical portion into the rear end surface of the large-diameter portion in the different-diameter columnar molded body, The outer peripheral surface of the diameter portion is pressed against the inner peripheral surface of the polygonal hole provided in the die so that the polygonal portion with the hole is bulged to form a different diameter molded body with the polygonal portion with the hole. A forging process,
In the manufacturing method by cold forging of the different-diameter cylindrical molded body,
When molding the different-diameter columnar molded body, the outer diameter of the large diameter portion is molded to be the outer diameter of the thin cylindrical portion,
In the cold forging process of forming the different diameter molded body with a polygonal portion with a hole,
The pushing sleeve, in which the large-diameter portion can be fitted inside itself and the front end can be fitted in a polygonal hole in the die, is kept at a constant interval in the circumferential direction with respect to the punch for punching. It is attached so that it can be moved forward and backward in an externally fitted state,
When the front end of the punch for punching is driven into the rear end surface of the large-diameter portion, the portion near the front end of the pushing sleeve is fitted into the portion near the rear end surface of the large-diameter portion to restrain the outer peripheral surface. So that
When forming the polygonal portion with holes by driving the punch for punching into the rear end surface of the large-diameter portion, the rear end portion of the polygonal portion with holes and a portion closer to the front end of the extrusion sleeve The thin cylindrical portion is extruded between the inner peripheral surface of the hole and the outer peripheral surface of the punch for punching.

According to a second aspect of the present invention, the extruding sleeve is attached to the punch for punching so as to be interlocked with a forward and backward movement of the punch for punching via a spring. When the front end of the punch is driven into the rear end surface of the large diameter portion, the portion near the front end of the pushing sleeve is fitted into the portion near the rear end surface of the large diameter portion by the action of the spring, and the outer peripheral surface thereof is It is made to restrain, It is a manufacturing method by cold forging of the different diameter cylindrical molded object of Claim 1 characterized by the above-mentioned.
According to the third aspect of the present invention, the extrusion sleeve has a polygon in which at least a certain outer peripheral surface from the front end to the base end can enter the inner peripheral surface of the polygon of the die. It is the manufacturing method by cold forging of the different diameter cylindrical molded object of any one of Claim 1 or 2 characterized by the above-mentioned.

The present invention according to claim 4 is a method of manufacturing a metal shell for a gas sensor constituting a gas sensor,
The metal shell for gas sensor has a small-diameter cylindrical portion on the front end side and a large-diameter cylindrical portion on the rear end side, and an outer diameter larger than the outer diameter of the large-diameter cylindrical portion between the front and rear of both cylindrical portions. The large-diameter cylindrical portion has a square portion, and the large-diameter cylindrical portion has a certain range from the rear end to the tip side opposite to the polygonal portion, the outer diameter being smaller than the other ranges, and the certain range is thick. Formed into a thin thin cylindrical part, and the other range is formed from a different diameter cylindrical molded body formed into a thick thick cylindrical part,
Moreover, the different diameter cylindrical formed body is formed by cold forging, and during the cold forging step of forming the different diameter tubular formed body,
A first cold forging step of forming a different-diameter cylindrical molded body having a small diameter portion on the front end side and a large diameter portion on the rear end side;
By punching a punch for punching the inner peripheral surface of the large-diameter cylindrical portion into the rear end surface of the large-diameter portion in the different-diameter columnar molded body, The outer diameter surface of the diameter portion is pressed against the inner periphery surface of the polygonal hole provided in the die, and the polygonal portion with the hole is bulged to form a different diameter molded body with the polygonal portion with the hole. 2 cold forging process,
A method for manufacturing a metal shell for a gas sensor, comprising:
In the first cold forging step of forming the different-diameter columnar molded body, the outer diameter of the large-diameter portion is molded so as to be the outer diameter of the thin-walled cylindrical portion,
In the second cold forging step of forming the different diameter molded body with a polygonal portion with a hole,
The pushing sleeve, in which the large-diameter portion can be fitted inside itself and the front end can be fitted in a polygonal hole in the die, is kept at a constant interval in the circumferential direction with respect to the punch for punching. It is attached so that it can be moved forward and backward in an externally fitted state,
When the front end of the punch for punching is driven into the rear end surface of the large-diameter portion, the portion near the front end of the pushing sleeve is fitted into the portion near the rear end surface of the large-diameter portion to restrain the outer peripheral surface. So that
When forming the polygonal portion with holes by driving the punch for punching into the rear end surface of the large-diameter portion, the rear end portion of the polygonal portion with holes and a portion closer to the front end of the extrusion sleeve And extruding the thin cylindrical portion between the inner peripheral surface and the outer peripheral surface of the punch for punching,
Thereafter, out of the outer peripheral surface of the polygonal portion with holes formed in the second cold forging step, the outer peripheral surface of a predetermined range from the rear end to the tip of the polygonal portion with holes is changed to the large diameter portion. A third cold forging step is included in which extrusion molding is performed to reduce the outer diameter of the thick-walled cylindrical portion and extend backward.

According to a fifth aspect of the present invention, the extruding sleeve is attached to the punch for punching so as to be interlocked with a forward and backward movement of the punch for punching via a spring. When the front end is driven into the rear end surface of the large-diameter portion, the portion near the front end of the pushing sleeve is fitted into the portion near the rear end surface of the large-diameter portion by the action of the spring to restrain the outer peripheral surface. The method of manufacturing a metal shell for a gas sensor according to claim 4, wherein:
In the present invention according to claim 6, in the extrusion sleeve, at least an outer peripheral surface in a certain range from the front end to the base end is a polygon that can enter the inner peripheral surface of the polygon of the die. The method for manufacturing a metal shell for a gas sensor according to any one of claims 4 and 5, wherein

  In the present invention, the above-described configuration is characterized in that the thin cylindrical portion is extruded in a step corresponding to the third step of the conventional cold forging step. In the extrusion process of the thin-walled cylindrical portion, when the front end of the punch for punching is driven into the rear end surface of the large-diameter portion, the portion near the front end is located near the rear end surface of the large-diameter portion. The outer peripheral surface is constrained by fitting into the part. When forming the polygonal portion with a hole by driving the punch for punching into the rear end surface of the large-diameter portion, the rear end of the polygonal portion with the hole, and the front end of the extrusion sleeve Since the thin cylindrical portion is extruded between the inner peripheral surface of the offset portion and the outer peripheral surface of the punch for punching, in this molding step (stage), an extreme increase in molding resistance occurs. There is nothing. Therefore, after that, the desired different diameter cylindrical molded body can be finally obtained without any problems by sequentially turning to the fourth and subsequent steps similar to the conventional one. Here, in the present invention, the reason why the molding resistance is not extremely increased in the molding process of the thin cylindrical portion is that the length pushed backward at the front end of the extrusion sleeve is only the length of the thin cylindrical portion. The length is not too big. In addition, the diameter is only reduced by one stage. The other deformation is only the deformation due to the bulge forming that is pressed against the inner peripheral surface of the polygonal hole, which is the same as in the conventional third step, which is the same as the conventional third step. This is because it is only performed in the front.

  2. The extrusion sleeve according to claim 1, wherein when the front end of the punch for punching is driven into the rear end surface of the large-diameter portion, the portion near the front end of the extrusion sleeve is defined as a portion near the rear end surface of the large-diameter portion. The holed polygon is formed when the holed polygonal part is formed by driving the holed punch into the rear end surface of the large diameter part. It may be driven and controlled so that the thin cylindrical portion is extruded between the inner peripheral surface of the portion near the front end of the extrusion sleeve and the outer peripheral surface of the punch for punching. . However, as described in claim 2, the extruding sleeve is attached to the punch for punching so that the forward and backward movement of the punch for punching is interlocked with a spring, and the punch for punching is performed. When the front end of the sleeve is driven into the rear end surface of the large-diameter portion, the portion near the front end of the pushing sleeve is fitted into the portion near the rear end surface of the large-diameter portion by the action of the spring to restrain the outer peripheral surface. It is good to do so. By doing so, it is not necessary to separately drive and control the extruding sleeve, so that the configuration of the pressing device can be simplified.

  In addition, the different diameter molded body with a polygon part with a hole provided with the said thin cylindrical part is sent to the 4th process corresponded in the above-mentioned conventional cold forging process. In this case, as in the prior art, a supporting sleeve is externally fitted to the small-diameter portion of the different-diameter molded body, and a tip-facing surface that forms a boundary between the small-diameter portion and the polygonal portion with the hole is formed on the outer peripheral surface of itself. In a state where the shape retaining punch is inserted into the hole provided in the polygonal portion with the hole, the outer peripheral surface of the predetermined range from the rear end to the tip is provided among the outer peripheral surfaces of the polygonal portion with the hole. The extrusion molding may be performed in which the outer diameter of the thick cylindrical portion of the large diameter cylindrical portion is reduced and stretched backward. And by this extrusion molding, a large diameter cylindrical part is shape | molded by the thick cylindrical part and the said thin cylindrical part of the back. Thus, after that, the fifth step similar to the conventional cold forging step described above is carried out to deep drill the hole and extend as a small diameter cylindrical portion, and the same as the conventional cold forging step. Turn to 6 steps and punch the bottom wall of the hole. In this way, a small diameter cylindrical portion is provided on the front end side and a large diameter cylindrical portion is provided on the rear end side, and a polygonal portion whose outer diameter is larger than the outer diameter of the large diameter cylindrical portion between the front and rear of both cylindrical portions. The large-diameter cylindrical portion has a certain range from the rear end to the tip opposite to the polygonal portion, the outer diameter is smaller than the other ranges, and the certain range is thin. It is possible to obtain a desired different-diameter cylindrical molded body which is formed into a thin cylindrical portion and is formed into a thick cylindrical portion where the other range is thick. That is, the different-diameter cylindrical molded body obtained in this way is the one shown in FIG. 13, so that it is suitable for the caulking process performed on the large-diameter cylindrical portion 25 in the subsequent machining. In the cutting process for achieving the above, at least the processing step of the thin cylindrical portion 27f can be greatly reduced, so that not only the processing cost but also the material can be saved.

  Invention of Claim 4 is a case where the different diameter cylindrical molded object in Claim 1 becomes this metal fitting for gas sensors, During the cold forging process which forms this different diameter cylindrical molded object, The third cold forging step is included. That is, in the invention according to claim 4, after the second cold forging step, of the outer peripheral surface of the polygonal portion with holes formed in the second cold forging step, A third cold forging step is included in which an outer peripheral surface in a predetermined range from the rear end to the front end is reduced to the outer diameter of the thick cylindrical portion in the large-diameter portion and is extended backward. It is a manufacturing method of the metal fittings for gas sensors. Therefore, it is obvious that the above-described effect similar to that of the invention described in claim 1 can be obtained from the configuration. In addition, each invention of Claims 5 and 6 corresponds to each invention of Claims 2 and 3, and therefore, when the different-diameter cylindrical molded body is the metal shell for the gas sensor, The same effects as those of the inventions of claims 2 and 3 can be obtained.

It is a figure explaining embodiment which actualized the manufacturing method of this invention, Comprising: The half sectional view explaining the molded object shape | molded by each process. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view including a mold for explaining a first step and a second step until a different-diameter cylindrical molded body is formed in an embodiment, and the left figure A shows a first step, and a center line The left half section of the figure is before molding, the right half section of the center line is the figure after molding, the right figure B shows the second step, the left half section of the center line is before molding, the right half section of the center line is molded Each figure after. It is typical sectional drawing including the metal mold | die explaining the principal part process (3rd process) of this invention which shape | molds the different diameter molded object with a polygon part with a hole in embodiment, The principal part enlarged view, Comprising: The left half section of the line is before molding, and the right half section of the center line is each figure after molding. The figure explaining the deformation | transformation state of the raw material until a polygon part with a hole is shape | molded in the 3rd process of FIG. It is typical sectional drawing containing the metal mold | die explaining a 4th process in embodiment, Comprising: The left half cross section of a center line is each figure after shaping | molding, and the right half cross section of a center line is after shaping | molding. It is typical sectional drawing containing the metal mold | die explaining a 5th process in embodiment, Comprising: The left half section of a centerline is each figure after shaping | molding, and the right half section of a centerline is after shaping | molding. It is typical sectional drawing containing the metal mold | die explaining a 6th process in embodiment, Comprising: The left half cross section of a center line is each figure after shaping | molding, and the right half cross section of a center line is after shaping | molding. The schematic structure sectional view explaining an example of the conventional gas sensor. FIG. 9 is a half cross-sectional view of a component state before assembly of a metal shell used in the gas sensor of FIG. 8. FIG. 10 is a half cross-sectional view of a work in progress of a metal shell (formed body before machining) at a stage where the metal shell of FIG. 9 is formed by cold forging. Sectional drawing explaining the molded object shape | molded by each process, when shape | molding the metal fitting in-process of FIG. 10 by cold forging. The typical sectional view containing the metallic mold explaining the 3rd process and the 4th process among the processes in which the fabrication object of Drawing 11 is fabricated. The half sectional view explaining the metal shell work-in-progress shape desired as a molded object before machining.

  The embodiment which actualized the manufacturing method by cold forging of the different diameter cylindrical molded object concerning this invention is described in detail, referring FIGS. However, the different-diameter cylindrical molded body manufactured in this embodiment is a material for manufacturing a metal shell for a gas sensor, and is the same as the different-diameter cylindrical molded body 120f shown in FIG. For this reason, although description of itself is abbreviate | omitted, a gas sensor is demonstrated again based on FIG. 8, FIG. FIG. 8 is a cross-sectional view of a gas sensor (for example, oxygen sensor) 10 used in an automobile or a motorcycle. This has a metal shell 20 with a different diameter that is attached to a screw hole provided in an exhaust pipe by a screw-in method, a cylindrical sensor element 30 with a tip (lower end in the figure) closed inside, and The protective cylinder (inner protective cylinder, outer protective cylinder) 40, 41, etc., is provided to protect the inside of the element 30 and the terminal fitting 11 in the sensor. The sensor 10 generates an electromotive force between electrodes provided on the inside and outside of the element 30 based on a difference in oxygen concentration between the inside and outside of the element 30, and a lead based on this signal is drawn from the rear end (the upper end in the figure). 50 is output to the control circuit via 50 and used to detect the oxygen concentration in the exhaust gas and control the air-fuel ratio.

  Further, as shown in FIG. 8, the metal shell 20 that is a main component of the sensor 10 has a cylindrical structure with a different diameter when viewed as a whole, and a threaded cylindrical portion having a relatively small diameter at the tip side. (Screwed small-diameter cylindrical part) 21 is formed, and a polygonal part (for example, a hexagonal part) 23 for screwing having a larger diameter is provided at the rear thereof. Further, on the rear end side following this, a cylindrical portion (hereinafter also referred to as a thin cylindrical portion) having a smaller diameter than the polygonal portion but a larger diameter than the threaded small diameter cylindrical portion 21 and having a thin cylindrical portion 27. Including a large-diameter cylindrical portion) 25. In FIG. 8, the thin cylindrical portion 27 is bent toward the center line, but this is cylindrical in the component state (see FIG. 9) as described later. In the sensor 10, a sensor element 30 is concentrically arranged and fixed inside the metal shell 20 via a sealing material 13, an insulating holder 15, and the like. This fixing is performed in the assembly process before the outer protective cylinder 41 is fixed, after the sensor element 30 or the like is arranged and loaded inside the metal shell 20, the flange 43 on the outer periphery of the front end of the inner protective cylinder 40 is attached to the insulating holder 15. The thin cylindrical portion 27 at the rear end of the large-diameter cylindrical portion 25 is bent toward the inner side (center axis side) as shown in the drawing while being brought into contact with the rear end and through the O-ring 17 and directed toward the front end. It is by caulking processing that compresses.

  FIG. 9 shows the metallic shell 20 as a part before such caulking is performed. As shown in the drawing, a certain range (constant portion) from the rear end (the upper end in the drawing) to the tip (the lower end in the drawing) of the portion near the rear end of the large-diameter cylindrical portion 25 has an outer diameter suitable for caulking. The thin cylindrical portion 27 is small and thin. In the case of FIG. 9, the portion near the polygonal portion 23 in the large-diameter cylindrical portion 25 also forms the second thin-walled cylindrical portion 28 having a small outer diameter and a small thickness. This is to cause this portion to be buckled as shown in FIG. 8 during the caulking process. In addition, as shown in the figure, such a metal shell has an inner diameter that gradually increases from the threaded small-diameter cylindrical portion 21 to the rear in order to dispose the sealing material 13 and the like for holding the element 30 in a seal shape. It is formed to be large. Thus, such a metal shell, that is, a gas sensor metal shell, is obtained by performing necessary processing on the large-diameter cylindrical portion 25 and the like in the different-diameter cylindrical molded body 120f shown in FIG.

  Hereinafter, by cold forging, from the first step using a columnar material S made of low carbon steel as a starting material, to forming (manufacturing) the different diameter cylindrical molded body 120f in the sixth step (final forging step). Each of the steps will be described in order according to the steps, with reference to the molded bodies 120a to 120f shown in FIG. 2, 3, and 5 to 7, the left side of the center line (axis) is the half of the shape of the material (molded body) before being molded in the process. The cross section is shown, and the right side shows the half cross section of the molded body after molding in the process. In the cross-sectional views shown in FIGS. 2 to 7, hatching is omitted except for the molded body.

(First step)
As shown in the left figure A of FIG. 2, material is taken and cut in a circular hole (hole) 203a of the same diameter up and down provided in the first process die 200a corresponding to the finished product. A cylindrical material (cylindrical body) S is loaded (see the left side of the center line of the left figure A in FIG. 2). However, the lower end of the inner peripheral surface of the circular hole 203a is provided with a fillet radius along the circumferential direction. After this loading, the material S is placed between both end faces by a supporting cylindrical punch (pin) 220a inserted and arranged with the lower end of the circular hole 203a as the front end (the upper end in the figure) and a circular punch 240a driven from above. Compress with. By doing so, the end face and the like are corrected or arranged as shown on the right side of the center line in the figure, a round is given to the angle formed by the tip surface (lower end in the figure) and the outer peripheral surface, and a recess is formed in the center of the tip surface. And a first process molded body 120a having a shallow tapered recess at the center of the rear end face is formed (see FIG. 1-A). Note that the outer diameter of the first step molded body 120a is slightly smaller than the outer diameter of the thin cylindrical portion 27f in the large diameter cylindrical portion 25 of the molded body 120f shown in FIG. In addition, after this shaping | molding, the punch 240a is extracted, the cylindrical punch (pin) 220a for a support is knocked out, and the 1st process molded object 102a is taken out. Hereinafter, in each step, driving of the support punch and the knockout pin (or knockout sleeve) for supporting the material, taking out of the molded body, and the like are conventionally known matters, and thus the description thereof will be omitted as appropriate.

(Second step)
As shown in the right diagram B of FIG. 2, the second step die 200b having a small-diameter circular hole having a small diameter on the lower side and a large diameter on the upper side is inserted into the large-diameter circular hole 203b on the upper side in the figure. The one-step molded body 120a is loaded from the front end side (see the left side of the center line in the right view B of FIG. 2). Here, the inner diameter of the small-diameter circular hole 205b is substantially the same as the outer diameter of the small-diameter cylindrical portion 21f of the compact shown in FIG. 13, and the inner diameter of the large-diameter circular hole 203b is the compact shown in FIG. The outer diameter of the thin cylindrical portion 27f of 120f is substantially the same. After this loading, the first process molded body 120a is compressed by the supporting cylindrical pin 220b and the sleeve 240b inserted and arranged with the lower end of the small-diameter circular hole 205b as the front end, and the circular punch 260b driven from above. By doing so, as shown on the right side of the center line in FIG. 5B, the rear end side has a large diameter portion 22b, and a small diameter portion 21b is extruded through a taper taper portion at the rear end side. A second process molded body 120b forming a cylindrical molded body is molded (see FIG. 1-B). In addition, the process (this example 2nd process) which shape | molds this 2nd process molded object 120b is corresponded to the "1st cold forging process" in the invention of Claim 4.

(Third step)
A 3rd process is demonstrated based on FIG. 3, FIG. In the third step, the die shown in FIG. 3, a punch for punching, or the like is used as the mold. That is, the die 200c in the lower part of the figure includes a circular hole 203c capable of restraining the outer peripheral surface of the small diameter portion 21b in the second process molded body (different diameter cylindrical molded body) 120b, and an annular shelf surface concentric with the circular hole. A polygonal hole 207c is formed via 205c with the polygon of the outer peripheral surface of the polygonal portion 23 of the molded body 120f shown in FIG. 13 as the inner peripheral surface. In the circular hole 203c in the die 200c, a supporting cylindrical pin 220c and a sleeve 270c are inserted and arranged with the lower end as a front end.

  On the other hand, in the illustration of the die 200c, a punching punch 240c for making a circular hole with a bottom in the rear end surface 29b of the large diameter portion 22b of the second process molded body (different diameter cylindrical molded body) 120b. Are arranged concentrically (coaxially) with the circular hole 203c and the polygonal hole 207c. The punching punch 240c is for forming the inner peripheral surface of the large-diameter cylindrical portion 25 that forms the thick-walled cylindrical portion 26 and the thin-walled cylindrical portion 27f in the molded body 120f. The inner diameter of the large-diameter cylindrical portion is substantially the same, and the cross section is circular. However, the front end portion of the punching punch 240c is relatively thin and has a stepped diameter so that the inner peripheral surface of the intermediate portion of the molded body 120f is molded. Thus, by punching the punching punch 240c into the rear end surface 29b of the large-diameter portion 22b, the hole is made in the rear end surface 29b, and the outer peripheral surface of the large-diameter portion is used as the inner periphery of the polygonal hole 207c. It is formed so that the polygonal part with a hole can be shape | molded by pressing to a surface and carrying out bulging shaping | molding.

  On the other hand, an extrusion sleeve 250c having an inner diameter larger than the outer diameter is externally fitted coaxially (concentrically) to the punching punch 240c via a spacer (circular tube) 260c. By this spacer (circular tube) 260c, a portion near the front end of the pushing sleeve 250c is held at a constant interval (cylindrical gap) in the circumferential direction with respect to the punching punch 240c. This interval (cylindrical gap) is where the thin cylindrical portion 27f is pushed out as will be described later, and this interval (cylindrical gap) is always present at the front end of the spacer (circular tube) 260c in this example. Is set to be retained. On the other hand, the pushing sleeve 250c has a circular inner peripheral surface, and its inner diameter is slightly larger than the outer diameter of the large diameter portion 22b, and is substantially the same as the outer diameter of the thin cylindrical portion 27f in the molded body 120f shown in FIG. It is said that. The outer surface of the extrusion sleeve 250c is a polygon that can be inserted into the polygonal hole 207c of the die 200c with a clearance fit.

  The base end (the upper end in the figure) of the punching punch 240c is fixed to a block 280c fixed to the movable platen above the press device. The extrusion sleeve 250c is connected to the lower surface of the block 280c via a spring (for example, a compression coil spring) 290c, and is interlocked and synchronized with the punching punch 240c by the lowering or raising of the movable platen. It is provided so as to move forward (down) or reverse (up) substantially the same amount. However, the punch for punching 240c is advanced by a predetermined stroke, punched into the rear end surface 29b of the large diameter portion 22b to make a hole, and the outer peripheral surface of the large diameter portion is pressed against the inner peripheral surface of the polygonal hole 207c to swell. When performing the extrusion molding, the thin cylindrical portion 27f is rearwardly extruded at a distance (cylindrical space) between the outer peripheral surface 243c of the punching punch 240c and the inner peripheral surface near the front end 253c of the extrusion sleeve 250c. The strength of the spring 290c is set so that the pushing sleeve 250c is finally pushed back relatively to the base end side with respect to the punching punch 240c. It should be noted that the amount to be pushed back may be regulated by a stopper means, for example, as described later, so that the thin cylindrical portion 27f is extruded within a predetermined range (length). In addition, the spacer (circular tube) 260c is suspended by a spring on the block 280c (not shown), for example, and is pushed down in the interval (cylindrical space) according to the downward movement of the punching punch 240c. It is provided so as to move upward by a springback in the upward movement.

  For this reason, the spring 290c is at least when the punching punch 240c advances and its front end 245c contacts the rear end surface 29b of the large diameter portion 22b of the different diameter cylindrical molded body 120b loaded in the die 200c (or Immediately before the collision, the portion (inner peripheral surface) near the front end 253c of the pushing sleeve 250c is set to fit into the portion near the rear end surface 29b of the large diameter portion 22b (see FIG. 4-A). In other words, the pushing sleeve 250c is connected to the lower surface of the block 280c via the spring 290c, but before the collision, the portion closer to the rear end face 29b of the outer circumferential surface of the large diameter portion 22b is for pushing. The spring 290c so that the front end 253c of the pushing sleeve 250c is positioned with respect to the front end 245c of the punching punch 240c so as to be surrounded and restrained (restricted) by the inner peripheral surface of the sleeve 250c near the front end 253c. Is attached through.

  The driving of the punching punch 240c is instantaneously terminated, but the initial stage where the front end 245c of the punching punch 240c is driven into the rear end surface 29b of the large diameter portion 22b by the driving is large as shown in FIG. The diameter portion 22b is compressed and deformed (upward deformation) toward the tip side. At this time, the pushing sleeve 250c is also moved forward through the spring 290c so that the inner peripheral surface surrounds and restrains (regulates) the portion of the outer peripheral surface of the large-diameter portion 22b closer to the rear end surface 29b. Is set. That is, the strength of the spring is such that the inner peripheral surface near the front end of the pushing sleeve 250c surrounds the portion near the rear end surface 29b of the outer peripheral surface of the large diameter portion 22b, even with respect to the initial upset deformation. What is necessary is just to set by performing a test press so that it may restrain (regulation). And as shown to FIG. 4-C, the bulge deformation of the large diameter part 22b advances by drilling a hole by advance of the punch for punching 240c. When the driving is completed, as shown in FIG. 4-D, the outer peripheral surface is pressed against the inner peripheral surface of the polygonal hole 207c, and the space on the inner peripheral surface side of the polygonal hole is filled with the material material. Will be. That is, according to this, the extrusion sleeve 250c is pushed back to the base end side relative to the punching punch 240c because the spring 290c is compressed by the material. However, the pushing back (retreating) is less than the position where the thin cylindrical portion 27f is to be extruded between the inner peripheral surface near the front end of the pushing sleeve 250c and the outer peripheral surface 243c of the punching punch 240c. It is set to be stopped by stopper means (not shown) so as not to move backward. That is, the front end 253c of the extrusion sleeve 250c is set so that the thin cylindrical portion 27f does not recede from the position where the extrusion molding should be performed.

  Thus, in the third step, the small-diameter portion 21b of the different-diameter cylindrical molded body 120b is inserted into the circular hole 203c of the die 200c and loaded. After the loading, the second step molding is performed by the supporting cylindrical pin 220c and the sleeve 270c inserted and arranged with the lower end of the circular hole 203c as the front end, the punching punch 240c driven from above, and the extrusion sleeve 250c interlocked therewith. The body 120b is compressed. That is, by punching the punching punch 240c with a predetermined stroke into the rear end surface 29b of the large-diameter portion 22b in the loaded second process molded body, a hole with a bottom on the rear end surface is formed with a predetermined depth, and a hole is provided. A polygonal portion 23c is formed, but at the end of the driving, a portion between the inner peripheral surface near the front end 253c of the pushing sleeve 250c and the outer peripheral surface 243c of the punching punch 240c is provided with many holes. A thin cylindrical portion 27f is extruded at the rear end of the square portion 23c (see FIG. 4-D).

  Thus, after this molding, the extrusion sleeve 250c is lifted together with the punching punch 240c, so that the polygonal portion with a hole, which is a molded body having the thin cylindrical portion 27f at the rear end of the polygonal portion 23c with the hole, is obtained. A diameter molded body (third process molded body) 120c is obtained (see FIG. 1-C). In addition, the process (this example 3rd process) which shape | molds this 3rd process molded object 120c is corresponded to the "2nd cold forging process" in the invention of Claim 4. By such a third step, the large-diameter portion 22b in the second-step molded body 120b is drilled with a bottom hole at the rear end surface 29b, and the outer peripheral surface is pressed against the inner peripheral surface of the polygonal hole 207c. Although it is formed as a polygonal portion 23c with a hole by bulging, the inner peripheral surface near the front end 253c of the pushing sleeve 250c that has been pushed in when the punching punch 240c has been driven, and the punching punch 240c. A thin cylindrical portion 27f (a portion corresponding to 27f of the molded body in FIG. 13) is extrusion-molded at the rear end of the polygonal portion 23c with a hole between the outer peripheral surface 243c and the outer peripheral surface 243c. Therefore, in the third step (stage), the thin cylindrical portion 27f can be formed without any problem. After that, the third step molded body 120c in which the thin cylindrical portion 27f is extrusion-molded at the rear end of the polygonal portion 23c with a hole in this way is subjected to the fourth and subsequent steps similar to the conventional cold forging step described above. By sequentially turning to this step, it is possible to finally obtain a desired different-diameter cylindrical molded body 120f.

(4th process)
That is, in the fourth step, as shown in FIG. 5, for example, the inner peripheral surface provided in the lower die 200d has a different diameter molded body with a polygonal portion with a hole (third process molded body) 120c. Has a circular hole capable of restraining the small-diameter portion 21c (the portion corresponding to 21f of the molded body in FIG. 13), and the outer peripheral surface has a polygon formed slightly smaller than the polygon of the polygonal portion with the hole. The small diameter portion 21c is inserted into the upper portion of the supporting sleeve 220d. The upper end of the sleeve 220d supports a polygonal tip-facing surface that forms a boundary between the small diameter portion 21c and the polygonal portion 23c with a hole. Then, a shape-retaining punch (similar to the punch for punching used in the third step) 240d is inserted into the hole provided in the polygonal portion 23c with a hole (see the left in FIG. 5). And in this state, the outer peripheral surface of the predetermined range which goes to a front-end | tip from a rear end (illustration upper end) among the outer peripheral surfaces of the polygon part 23c with a hole of the large diameter cylindrical part 25 of the molded object 120f shown in FIG. Extrusion is performed to extend backward so as to reduce the outer diameter of the thick-walled cylindrical portion 26. The die 260d used for this molding has a polygonal inner peripheral surface polygonal hole 263d substantially coinciding with the outer peripheral surface of the polygonal portion 23c with a hole on the front end side, and is concentric to the rear thereof, as shown in FIG. A circular hole 265d that coincides with the outer peripheral surface of the thick cylindrical portion 26 in the large diameter cylindrical portion 25 of the molded body 120f shown in FIG. Therefore, the die 260d is coaxially attached to the shape-retaining punch 240d and attached to a movable platen (not shown) in the upper part of the figure, and the die 260d is supported by a support sleeve 220d or the like. The shape-retaining punch 240d is moved forward by a predetermined amount. By doing so, the outer peripheral surface of the polygonal portion 23c with a hole is composed of the thick cylindrical portion 26 and the thin cylindrical portion 27f formed in the previous step behind the polygonal portion 23 in the molded body 120f of FIG. The large diameter cylindrical portion 25 is formed. Thus, after this molding step, the fourth step molded body 120d shown in FIG. 1-D is obtained. In addition, the process (this example 4th process) which shape | molds this 4th process molded object 120d is corresponded to the "3rd cold forging process" in the invention of Claim 4. Thereafter, as in the prior art, in the fifth step, deep hole drilling (drilling of the front hole) and stretching of the small diameter part are performed in the fifth step, and the hole bottom wall is punched in the sixth step.

(5th process)
That is, in the fifth step, as shown in FIG. 6, a circular hole 203e capable of constraining the outer peripheral surface of the small diameter portion of the fourth step molded body 120d, and concentric with the circular hole, via the annular shelf surface 205e. Using this die 200e formed so as to have a polygonal hole (shaped hole) 207e whose inner peripheral surface is the polygon of the outer peripheral surface of the polygonal portion 23 of the molded body 120f shown in FIG. A small diameter portion of the molded body 120d is inserted into 203e (see the left side of the center line in FIG. 6). The small diameter portion is supported by the front ends of the support punches 220e and 230e, and has a column portion having the same outer diameter as the inner diameter of the large diameter cylindrical portion 25 in the molded body 120f of FIG. A deep hole punch 260e having the same diameter as the inner diameter of the small-diameter cylindrical portion 21f and having a columnar portion with a predetermined length is driven in at the front end of the portion. As a result, as shown on the right side of the center line in the figure, deep hole drilling is performed, and in response to the drilling, a small diameter cylindrical portion 21e (a portion corresponding to 21f of the molded body in FIG. 13) is stretched. In addition, a fifth process molded body 120e is obtained (see FIG. 1-E).

(6th process)
And in a 6th process, as shown in FIG. 7, the bottom wall of the deep hole bottom in the 5th process molded object 120e should just be punched out with a punch. That is, using the die 200f having the circular hole 203f into which the extended small-diameter cylindrical part 21e can be inserted and the ring 210f for constraining the outer peripheral surface of the polygonal part 23, the tip of the small-diameter cylindrical part 21e is placed in the circular hole 203f. A support sleeve 230f for supporting the above is inserted and disposed. Under this condition, the bottom wall is punched with a bottom wall punching punch 240f having a cylindrical shape. Thus, the different diameter cylindrical molded body (sixth process molded body) 120f shown in FIG. 13 can be obtained (see FIG. 1-F). That is, the small-diameter cylindrical portion 21f is provided on the front end side, and the large-diameter cylindrical portion 25 is provided on the rear end side, and the polygonal portion having an outer diameter larger than the outer diameter of the large-diameter cylindrical portion between the two cylindrical portions. 23, and the large-diameter cylindrical portion 25 has a constant range from the rear end to the front end opposite to the polygonal portion 23, the outer diameter being smaller than the other ranges, and the constant range is It is possible to obtain the different-diameter cylindrical molded body 120f which is formed into the thin cylindrical portion 27f having a small thickness and is formed into the thick cylindrical portion 26 in which the other range is thick without any molding problems. Then, the different-diameter cylindrical molded body 120f obtained in this way can save the material cost as apparent from the case of FIG. 10, and in the subsequent machining, the large-diameter cylindrical portion 25 When the outer peripheral surface is cut so as to be suitable for caulking, the cutting process can be reduced for the thin cylindrical portion 27c near the rear end, so that the machining cost can be reduced.

  The different-diameter cylindrical molded body produced by the present invention is not limited to the shape in the above embodiment, and the length ratio in the axial direction to the diameter is appropriately changed in design. Can be applied. Moreover, the processing part at the time of cutting a different diameter cylindrical molded object and making it the finished product of a metal shell is not limited to the thing in the said example. That is, in the above example, the main body shown in FIG. 9 of the shape and structure of the large-diameter cylindrical portion that cuts the outer peripheral surface of the thick-walled cylindrical portion near the polygon to form a thin cylindrical portion for buckling deformation. Although the present invention has been embodied on the assumption that it is a metal fitting, the present invention can be applied even to a different-diameter cylindrical molded body used for manufacturing a metal fitting that does not assume such deformation. And when not forming such a thin cylindrical part for buckling deformation, the further reduction of the cutting process is achieved relatively.

  It should be noted that the shape, arrangement, vertical position, combination, etc. of the die, punch, or sleeve mold exemplified in the above embodiment can be embodied as appropriate. In the molding process, the die, punch, sleeve, and knockout sleeve (pin or punch) may be driven forward or backward in conjunction with each other as appropriate. Further, in the above example, the extruding sleeve is attached so as to interlock with the forward and backward movement of the punch for punching via a spring, and when the front end of the punch for punching is driven into the rear end surface of the large diameter portion, The portion near the front end of the pushing sleeve was fitted into the portion near the rear end face of the large diameter portion by the action of the spring to restrain the outer peripheral surface, but the pushing sleeve is driven by a spring, Of course, it may be controlled. In other words, the extruding sleeve is attached to the punch for punching so as to be fitted to the punch for punching so as to maintain a constant interval in the circumferential direction, and can be moved forward and backward with respect to the punch for punching. Separately from the punch for driving, drive control may be performed so as to move forward and backward. Even if a spring is used, the spring is not limited to a compression coil spring, and various known springs can be used.

21b Small diameter portion 21f on the front end side of the different diameter cylindrical molded body 21f Small diameter cylindrical portion 22b Large diameter portion on the rear end side of the different diameter cylindrical molded body
23 Polygonal portion 23c Polygonal portion with hole 25 Large diameter cylindrical portion 27f Thin cylindrical portion 26 Thick cylindrical portion 29b Rear end surface 120b of large diameter portion Different diameter cylindrical molded body 120c Different diameter molded body with hole polygonal portion 120f Different diameter cylindrical molded body 200c Die 207c used to mold a different diameter molded body with a polygonal part with a hole Polygonal hole 240c of a die used to mold a different diameter molded body with a polygonal part with a hole Drilling punch 243c for forming the inner peripheral surface of the large diameter cylindrical portion Outer peripheral surface 245c of the punch for punching the inner peripheral surface of the large diameter cylindrical portion Front end 250c of the punch for forming the inner peripheral surface of the large diameter cylindrical portion Extrusion Sleeve 253c Extrusion sleeve front end 290 Spring

Claims (6)

It has a small diameter cylindrical part on the front end side and a large diameter cylindrical part on the rear end side, and has a polygonal part whose outer diameter is larger than the outer diameter of the large diameter cylindrical part between the front and rear of both cylindrical parts, The large-diameter cylindrical portion is formed into a thin cylindrical portion with a constant range from the rear end to the tip opposite to the polygonal portion, the outer diameter being smaller than the other ranges, and the constant range being thin. The other range is a manufacturing method by cold forging of a different diameter cylindrical molded body formed into a thick thick cylindrical portion,
During the cold forging process,
A cold forging step of forming a different-diameter cylindrical molded body having a small diameter portion on the front end side and a large diameter portion on the rear end side;
By punching a punch for punching the inner peripheral surface of the large-diameter cylindrical portion into the rear end surface of the large-diameter portion in the different-diameter columnar molded body, The outer peripheral surface of the diameter portion is pressed against the inner peripheral surface of the polygonal hole provided in the die so that the polygonal portion with the hole is bulged to form a different diameter molded body with the polygonal portion with the hole. A forging process,
In the manufacturing method by cold forging of the different-diameter cylindrical molded body,
When molding the different-diameter columnar molded body, the outer diameter of the large diameter portion is molded to be the outer diameter of the thin cylindrical portion,
In the cold forging process of forming the different diameter molded body with a polygonal portion with a hole,
The pushing sleeve, in which the large-diameter portion can be fitted inside itself and the front end can be fitted in a polygonal hole in the die, is kept at a constant interval in the circumferential direction with respect to the punch for punching. It is attached so that it can be moved forward and backward in an externally fitted state,
When the front end of the punch for punching is driven into the rear end surface of the large-diameter portion, the portion near the front end of the pushing sleeve is fitted into the portion near the rear end surface of the large-diameter portion to restrain the outer peripheral surface. So that
When forming the polygonal portion with holes by driving the punch for punching into the rear end surface of the large-diameter portion, the rear end portion of the polygonal portion with holes and a portion closer to the front end of the extrusion sleeve A method for producing a tubular molded body having a different diameter by cold forging, wherein the thin cylindrical portion is extruded between an inner peripheral surface of the punch and an outer peripheral surface of the punch for punching.   The extruding sleeve is attached to the punch for punching so that the drilling punch moves forward and backward via a spring, and the front end of the punch for punching is attached to the rear end surface of the large-diameter portion. When driven, the front end portion of the pushing sleeve is fitted into the rear end surface portion of the large-diameter portion by the action of the spring, and the outer peripheral surface is restrained. The manufacturing method by cold forging of the different diameter cylindrical molded object of Claim 1.   2. The extrusion sleeve according to claim 1, wherein at least an outer peripheral surface in a certain range from the front end to the base end is a polygon that can enter the inner peripheral surface of the polygon of the die. The manufacturing method by cold forging of the different diameter cylindrical molded object of any one of 2. A method of manufacturing a metal shell for a gas sensor constituting a gas sensor,
The metal shell for gas sensor has a small-diameter cylindrical portion on the front end side and a large-diameter cylindrical portion on the rear end side, and an outer diameter larger than the outer diameter of the large-diameter cylindrical portion between the front and rear of both cylindrical portions. The large-diameter cylindrical portion has a square portion, and the large-diameter cylindrical portion has a certain range from the rear end to the tip side opposite to the polygonal portion, the outer diameter being smaller than the other ranges, and the certain range is thick. Formed into a thin thin cylindrical part, and the other range is formed from a different diameter cylindrical molded body formed into a thick thick cylindrical part,
Moreover, the different diameter cylindrical formed body is formed by cold forging, and during the cold forging step of forming the different diameter tubular formed body,
A first cold forging step of forming a different-diameter cylindrical molded body having a small diameter portion on the front end side and a large diameter portion on the rear end side;
By punching a punch for punching the inner peripheral surface of the large-diameter cylindrical portion into the rear end surface of the large-diameter portion in the different-diameter columnar molded body, The outer diameter surface of the diameter portion is pressed against the inner periphery surface of the polygonal hole provided in the die, and the polygonal portion with the hole is bulged to form a different diameter molded body with the polygonal portion with the hole. 2 cold forging process,
A method for manufacturing a metal shell for a gas sensor, comprising:
In the first cold forging step of forming the different-diameter columnar molded body, the outer diameter of the large-diameter portion is molded so as to be the outer diameter of the thin-walled cylindrical portion,
In the second cold forging step of forming the different diameter molded body with a polygonal portion with a hole,
The pushing sleeve, in which the large-diameter portion can be fitted inside itself and the front end can be fitted in a polygonal hole in the die, is kept at a constant interval in the circumferential direction with respect to the punch for punching. It is attached so that it can be moved forward and backward in an externally fitted state,
When the front end of the punch for punching is driven into the rear end surface of the large-diameter portion, the portion near the front end of the pushing sleeve is fitted into the portion near the rear end surface of the large-diameter portion to restrain the outer peripheral surface. So that
When forming the polygonal portion with holes by driving the punch for punching into the rear end surface of the large-diameter portion, the rear end portion of the polygonal portion with holes and a portion closer to the front end of the extrusion sleeve And extruding the thin cylindrical portion between the inner peripheral surface and the outer peripheral surface of the punch for punching,
Thereafter, out of the outer peripheral surface of the polygonal portion with holes formed in the second cold forging step, the outer peripheral surface of a predetermined range from the rear end to the tip of the polygonal portion with holes is changed to the large diameter portion. A method of manufacturing a metal shell for a gas sensor, comprising a third cold forging step in which extrusion molding is performed to reduce the outer diameter of the thick-walled cylindrical portion and extend backward.   The extruding sleeve is attached to the punch for punching so that the drilling punch moves forward and backward via a spring, and the front end of the punch for punching is attached to the rear end surface of the large-diameter portion. When driven, the front end portion of the pushing sleeve is fitted into the rear end surface portion of the large-diameter portion by the action of the spring, and the outer peripheral surface is restrained. The manufacturing method of the metal fitting for gas sensors of Claim 4.   The extrusion sleeve has a polygonal shape in which at least an outer peripheral surface in a certain range from the front end to the base end is a polygon that can enter the inner peripheral surface of the polygon of the die. 6. A method for producing a metal shell for a gas sensor according to any one of 5 above.

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