JP2008036751A - Method for turning cylindrical metallic member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylindrical metallic member having coaxial different diameter portions of a large diameter cylindrical portion formed on its one end side and a small diameter cylindrical portion formed on the other end side, the large diameter cylindrical portion having a thin thickness cylindrical portion thinner than the thickness of the small diameter cylindrical portion, which cylindrical metallic member does not cause recesses on the large diameter cylindrical portion and can achieve high machining accuracy in the case of forming the thin cylindrical portion by turning the outer peripheral surface of the large diameter cylindrical portion. <P>SOLUTION: When the outer peripheral surface of the thin thickness cylindrical portion of the large diameter cylindrical portion 103 is turned, the turning operation is carried out by fixing the outer periphery 105a of the small diameter cylindrical portion 105 to the chuck 120 of a machine tool instead of the inner peripheral surface of the large diameter cylindrical portion 103. As a result, the machining accuracy is improved because the large diameter cylindrical portion 103 does not deform in chucking, and no defect is produced on the inner peripheral surface of the thin cylindrical portion. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a metal cylinder of different diameters, which is concentric and has a large-diameter cylindrical part on one end side and a small-diameter cylindrical part on the other end side, like a metal shell (metal body) for a spark plug of an automobile engine. The thin-walled cylinder is formed by turning an outer peripheral surface of the large-diameter cylinder part in which the large-diameter cylinder part is formed with a thin-walled cylinder part that is thinner than the thickness of the small-diameter cylinder part. The present invention relates to a method for forming a part.

  FIG. 4 is a cross-sectional view of the metallic cylindrical member 101 that is a material before turning of the metal shell 101b that constitutes the spark plug (ignition plug) 200 shown in FIG. 6, and the double hatched portion in FIG. The cutting allowance (machining allowance) in the turning process is shown. In manufacturing the metal shell 101b of such a spark plug 200, in order to reduce the cutting process and increase productivity or manufacturing efficiency, the material before the processing is subjected to a plurality of moldings such as upsetting and extrusion (cold forging). ) The metallic cylindrical member 101 as shown in FIG. 4 manufactured through the process is used. A metal cylindrical member 101 shown in the figure has a large-diameter cylindrical portion 103 whose inner diameter is larger than an inner diameter of a small-diameter cylindrical portion 105 (to be described later) on the right side of the figure, and the large-diameter cylindrical portion. On the left side of 103, a small-diameter cylindrical portion 105 having an inner diameter smaller than the inner diameter of the large-diameter cylindrical portion 103 and an outer diameter approximately the same as the inner diameter of the large-diameter cylindrical portion 103 is concentrically provided. Yes. However, the outer peripheral surface of the intermediate portion in the axis G direction of the large-diameter cylindrical portion 103 forms a polygonal portion (for example, a hexagon) 108.

  Such a metallic cylindrical member 101 is applied to a processing machine such as an automatic lathe, and a predetermined portion (double hatched portion in FIG. 4) such as the large-diameter cylindrical portion 103 is turned to the spark plug 200. It is manufactured as the metallic shell 101b before being assembled. The large-diameter cylindrical portion 103 of the metallic cylindrical member 101 has a shape in which a polygonal portion 108 is left in a predetermined range at an intermediate portion in the axis G direction on the right side of the circular flange portion 107 at the left end of the large-diameter cylindrical portion 103. Thus, the cutting allowance shown in FIG. 4 is cut. That is, the large-diameter cylindrical portion 103 is thicker at both the distal end portion (right end portion in FIG. 4) 109 and the proximal end portion 110 than the small-diameter cylindrical portion 105. The outer peripheral surface is processed so that the thickness becomes considerably thin (for example, about 0.7 mm to 0.8 mm). In addition, the polygonal part 108 in the large diameter cylinder part 103 is a place which makes the tool latching part for screwing after a process. This is because the processed metal shell 101b is assembled together with other parts to form a spark plug 200, and is attached to the engine by a screwing method. The polygonal part 108 is a fitting part of a screwing tool (spanner) at that time. This is where the (locking part) is made. Moreover, the screw for this screwing is formed in the outer peripheral surface of the small diameter cylinder part 105. FIG.

  By the way, in the machining of such a small (small diameter) metallic cylindrical member 101, conventionally, as shown in FIG. 5, the inner peripheral surface 103b (see FIG. 4) of the large diameter cylindrical portion 103 is chucked. It was fixed (held) at 1 and turned under that condition. In the fixing, for example, by pushing a plurality of claws 40 that are arranged at intervals in the circumferential direction with a rod 30 having a tapered tip, the claw 40 is moved by the wedge action, A chuck having a structure in which the inner peripheral surface 103b of the large-diameter cylindrical portion 103 is pressed and fixed by pushing to the outer peripheral surface side has been used (Patent Document 1).

On the other hand, the reason why the large-diameter cylindrical portion 103 is processed into a thin wall as described above is that when the spark plug 200 is assembled using the processed metal shell 101b completed as a part, the thin-walled portion (109, 110) This is to perform caulking easily. That is, the spark plug 200 shown in FIG. 6 is a state in which the thin wall portion of the distal end portion 109 of the large-diameter cylindrical portion 103 is folded inward while the insulator 301 is inserted inside the metal shell 101b after completion. By compressing in the axial direction, the talc (seal material) 303 is compressed, and the thin wall portion of the base end portion 110 is assembled together with the tip end portion 109 thereof. As described above, the large-diameter cylindrical portion 103 of the metal shell 101b that forms the spark plug 200 includes the distal end portion 109 and the proximal end portion 110 that are formed of a thin portion that is extremely thin. On the other hand, the spark plug 200 in recent years has been reduced in diameter due to downsizing of the internal combustion engine and the like, and the metal shell 101b has also been reduced in size and diameter. Therefore, the thinning of the distal end portion 109 and the proximal end portion 110 is increasingly required in recent years.
JP 2002-11543 A

  When such a metal cylindrical member 101 is fixed on the inner peripheral surface 103b of the large-diameter cylindrical portion 103 with the chuck 1 as described above and the outer peripheral surface is turned, When the tubular member 101 is removed from the chuck 1, there is a problem that the thin-walled portion of the large-diameter cylindrical portion 103 is deformed and the required dimensional accuracy may not be obtained. This is caused by chucking (fixing) the inner peripheral surface 103b of the large-diameter cylindrical portion 103 so as to expand. In other words, the large-diameter cylindrical portion 103 has a shape in which a portion where the claw (or top) 40 of the chuck hits is locally expanded outwardly by a radially outward pressing force (pushing force) accompanying the chuck. Therefore, the inner peripheral surface 103b is elastically deformed like a polygon when viewed from the direction of the axis G. Specifically, it is as follows.

  In the above-described fixing by the chuck 1, the inner peripheral surface 103 b of the large-diameter cylindrical portion 103 is slightly outwardly corresponding to the claw 40 with respect to the original circle (cylinder) due to the fixing force. Elastically deforms to bulge out. Therefore, when the outer peripheral surface of the large-diameter cylindrical portion 103 is processed in this deformed state, the processed outer peripheral surface is a perfect circle until the metal cylindrical member 101 is removed from the chuck after the processing (front). When this is removed from the chuck after turning, the deformation (elastic deformation) that has occurred with the chuck is restored, so that the portion corresponding to the claw 40 on the outer peripheral surface becomes a concave shape, and the roundness is reduced. It is damaged and partially thin. Further, in this fixing, a portion of the inner peripheral surface 103b of the large-diameter cylindrical portion 103 that is hit by the chuck claw (or top) 40 tends to be scratched. If there is such a dent or scratch, then when assembling the large-diameter cylindrical portion 103 as described above when assembling as a spark plug, uniform deformation in the circumferential direction is obtained due to the dent or scratch. As a result, there has been a problem in that appearance defects and accuracy defects are caused. And such a problem exists also in the process of the metal cylindrical member which makes the main metal fitting in the gas sensor for engines which has the same structure fundamentally.

  The present invention has been made in view of these problems, and is concentric and has a large-diameter cylindrical portion on one end side and a small-diameter cylindrical portion on the other end side like the above-described metal cylindrical member. A metal cylindrical member having a different diameter, wherein the large-diameter cylindrical portion is formed with a thin cylindrical portion that is thinner than a thickness of the small-diameter cylindrical portion, and an outer periphery of the large-diameter cylindrical portion An object of the present invention is to provide a turning method capable of improving machining accuracy without causing the above-described dents or the like in the large-diameter cylindrical portion when the surface is turned to form the thin-walled cylindrical portion.

To achieve the above object, the present invention according to claim 1 is a metal cylindrical member of different diameters having a large-diameter cylindrical portion on one end side and a small-diameter cylindrical portion on the other end side. In forming the thin cylindrical portion by turning the outer peripheral surface of the large diameter cylindrical portion in the one where the thin cylindrical portion forming the thin wall is formed in the diameter cylindrical portion compared to the thickness of the small diameter cylindrical portion.
A turning method for a metallic cylindrical member, wherein the outer peripheral surface of the small-diameter cylindrical portion is fixed by a chuck of a processing machine and turned. The metal cylindrical member is exemplified by a spark plug metal shell or a gas sensor metal shell.

  In the present invention, as described above, when turning a large-diameter cylindrical portion of a metal cylindrical member to a thin-walled cylindrical portion with a processing machine, the inner peripheral surface is fixed (held) with a chuck and turned. Since the outer peripheral surface of the small-diameter cylindrical portion is fixed by the chuck, the outer peripheral surface of the large-diameter cylindrical portion is not dented or scratched on the inner peripheral surface after the processing. Thereby, for example, a metal cylindrical member is a part used as a metal shell for a spark plug, and when assembling the spark plug, the large diameter cylindrical portion is compressed and deformed as described above and caulked. Even if it exists, it can prevent causing problems, such as an external appearance defect, in the spark plug after the assembly. In the present invention, among the above-described metal cylindrical members, which are small parts and are required to have a high processing accuracy, a more remarkable effect is expected.

  An embodiment of the present invention will be described in detail with reference to FIGS. However, in this embodiment, the metal cylindrical member 101 which is a workpiece is the same as that shown in FIG. 4, but the shape and structure thereof will be described in more detail based on FIG. 1. That is, this metallic cylindrical member 101 is a material for manufacturing the metal shell 101b that constitutes the spark plug 200 of FIG. 6, and has a large inner diameter on the right side of FIG. 1 (for example, 12 mm). On the left side of the diameter cylindrical portion 103 and the large diameter cylindrical portion 103, the inner diameter is smaller than the inner diameter of the large diameter cylindrical portion 103, and the outer diameter is the same size as the inner diameter of the large diameter cylindrical portion 103. The small diameter cylinder part 105 is concentric. And the outer peripheral surface 108a of the intermediate | middle site | part of the axis line G direction of this large diameter cylinder part 103 has comprised the polygon. In such a metallic cylindrical member 101, the double hatched portion in FIG. 1 is a part to be turned. The large-diameter cylindrical portion 103 of the metallic cylindrical member 101 has a shape in which a polygonal portion 108 is left in a predetermined range at an intermediate portion in the axis G direction on the right side of the circular flange portion 107 at the left end of the large-diameter cylindrical portion 103. As shown in the cutting allowance shown in FIG. 1, both the distal end portion 109 and the proximal end portion 110 sandwiching the polygonal portion 108 are turned into thin portions as compared with the thickness of the small-diameter cylindrical portion 105 by turning. Is set to In addition, the polygon part 108 in the large diameter cylinder part 103 is a place which makes the tool latching part for screwing after processing (finished product) and assembling as the spark plug 200 as above-mentioned.

  On the other hand, the small diameter cylindrical portion 105 of the metal cylindrical member 101 is formed in a straight tube shape, and is set to be relatively thicker than the thickness of the thin portion (109, 110) of the large diameter cylindrical portion 103. . The outer diameter of the small diameter cylindrical portion 105 is formed to be smaller than the outer diameter of the thin portion of the large diameter cylindrical portion 103. It should be noted that a screw is formed on the outer peripheral surface 105a of the small-diameter cylindrical portion 105, for example, by rolling in a post-process of processing the outer peripheral surface of the large-diameter cylindrical portion 103. Further, in the metal cylindrical member 101 of FIG. 1, a convex portion 106 protruding in a circumferential flange shape inwardly is formed on the inner peripheral surface of the small diameter cylindrical portion 105 in the material. Such a metallic cylindrical member (material) 101 is made of steel or stainless steel, and after being subjected to a number of forming processes by cold forging, as shown in FIG. As shown by double hatching, a slight machining allowance is added to the outer peripheral surface of the large-diameter cylindrical portion 103.

  In this embodiment, the outer peripheral surface of the large-diameter cylindrical portion 103 of such a metallic cylindrical member 101 is processed as follows by a processing machine (for example, an automatic lathe). That is, as shown in FIG. 2, the outer peripheral surface 105 a of the small-diameter cylindrical portion 105 is fixed (held) by the claws (for example, four claws) 133 of the chuck 120 on the rotation spindle (spindle) 121 of the lathe. The spindle 121 is rotated under the state, and, for example, a cutting tool (bite) 150 having a cutting edge formed corresponding to the cutting allowance of double hatching is pressed to the outer peripheral surface of the large-diameter cylindrical portion 103 by a predetermined amount. It is to cut with. 2 illustrates a collet chuck type chuck that is tightened by pulling the four claws 133 disposed in the spindle 121 by the taper of the outer peripheral surface thereof.

  Thus, when machining the outer peripheral surface of the large-diameter cylindrical portion 103 in this way, the inner peripheral surface 103b of the large-diameter cylindrical portion 103 is fixed with a claw of the chuck as before. Instead, the outer peripheral surface 105a of the small diameter cylindrical portion 105 is fixed by the chuck 120 and processed. Therefore, in the fixing by the chuck 120, the outer peripheral surface 105a of the thick small-diameter cylindrical portion 105 is pressed in a reduced diameter shape by the claw 133, so that the large-diameter cylindrical portion 103 is deformed by the fixing. There is almost no damage and no scratches occur. Therefore, even after the metal cylindrical member 101 is removed from the chuck 120 after processing, the large-diameter cylindrical portion 103 can maintain the required roundness (cylindrical) with accuracy, and scratches on the inner peripheral surface 103b are generated. Nor. In addition, although the deformation | transformation based on fixation with the nail | claw 133 of the chuck | zipper 120 arises in the small diameter cylindrical part 105, the deformation | transformation can be made small because it is small diameter, and the deformation | transformation is restored | removed by removing from the chuck | zipper 120. To do. In addition, a part of the outer peripheral surface 105a of the small-diameter cylindrical portion 105 is scratched by the fixing. However, since a screw is formed on such an outer peripheral surface 105a in a later process, there is no problem. FIG. 3 is a half sectional view of the metallic cylindrical member 101 after processing the outer peripheral surface of the large diameter cylindrical portion 103.

  Thus, after such a turning process is finished, the outer peripheral surface 105a of the small-diameter cylindrical portion 105 is threaded, and an ignition terminal is welded to the tip of the small-diameter cylindrical portion 105. It is completed as a part before assembling as a plug), and is then used for assembling a spark plug. In the assembly, as shown in FIG. 6, an insulator 301 having electrodes inserted therein is inserted inside the metal cylindrical member 101, so that the tip 109 of the large-diameter cylindrical portion 103 is inserted. At the same time that the thin portion is bent inward, crimping is performed so that the thin portion is compressed in the axial direction. In this case, the thin portion of the distal end portion 109 and the base end portion 110 should be free from dents and scratches as in the prior art. Therefore, uniform deformation in the circumferential direction can be obtained, so that it is possible to prevent appearance failure and accuracy failure in the spark plug.

  In the above embodiment, the metallic tubular member 101 is embodied in the spark plug metal shell 101b. However, the metallic tubular member 101 to be processed in the present invention is not limited to this. That is, in addition to this, the metal shell 401 for the gas sensor 400 for an engine as shown in FIG. 7 includes a large-diameter cylindrical portion 403 on one end side thereof, and the large-diameter cylindrical portion 403. Of course, the present invention can be applied as long as it is concentric to the other end side and includes the small-diameter cylindrical portion 405. The gas sensor 400 is for detecting an oxygen concentration in a gas to be measured such as exhaust gas discharged from an internal combustion engine or the like, and has an internal electrode (layer) and an external electrode (layer) on the inner and outer surfaces, respectively. A detection element 421 made of a hollow shaft (cylindrical) solid electrolyte with a closed end (lower end in the figure) and a metal shell 401 etc. attached to the exhaust gas pipe while holding the detection element 421 inside. ing. The gas sensor 401 is attached to an exhaust gas pipe of an internal combustion engine via a metal shell 401, and an internal electrode (reference electrode) on an inner peripheral surface (inner wall surface) of the detection element 421 is used as a reference gas (atmosphere), and an outer peripheral surface ( The external electrode (measurement electrode) on the outer wall surface is brought into contact with the exhaust gas, an electromotive force is generated between both electrodes corresponding to the oxygen concentration difference between the inner and outer surfaces of the detection element 421, and a signal based on this electromotive force is generated in the control circuit. It is used to control the air-fuel ratio by detecting the oxygen concentration in the exhaust gas. In FIG. 7, a protective cover (cap) 420 is attached to the small-diameter cylindrical portion 405, and the large-diameter cylindrical portion 403 surrounds terminal fittings 471, 491 and the like connected to each electrode of the element 421. A protective cylinder 431 is attached to the inside and covers the inside.

  That is, the metal cylindrical member to be processed of the present invention has a large-diameter cylindrical portion on one end side, like a metal cylindrical member used for a metal shell for a spark plug or a gas sensor. In a metal part having a small-diameter cylindrical part on the side and having a small-diameter cylindrical part, wherein the large-diameter cylindrical part is formed with a thin cylindrical part that is thinner than a thickness of the small-diameter cylindrical part The thin cylindrical portion can be widely applied by turning the outer peripheral surface of the large diameter cylindrical portion, and the use of the component is not limited. Further, in the above description, the present invention has been embodied in the processing machine having four chuck claws, but it goes without saying that the present invention can be embodied regardless of the number of chucks. . Further, in the above, an automatic lathe is embodied as an example in a processing machine, but any machine that can turn the outer peripheral surface of a metal cylindrical member may be used. Therefore, it is naturally fixed by a chuck in a normal lathe. It can also be applied when turning.

The half sectional view of the metal cylindrical member used for the embodiment of the present invention. Sectional drawing for description of the state which turns the metal cylindrical member of FIG. The half sectional view of the metal cylindrical member after processing the outer peripheral surface of a large diameter cylinder part. Sectional drawing of a metal cylindrical member. FIG. 5 is a cross-sectional view for explaining the conventional metal cylindrical member of FIG. A half sectional view of a spark plug. Sectional drawing of a gas sensor.

Explanation of symbols

101, 401 Metal cylindrical member 101b Spark plug metal shell 103, 403 Metal cylindrical member large-diameter cylindrical portion 103b Large-diameter cylindrical inner surface 105, 405 Metal cylindrical member small-diameter cylindrical portion 105a Small diameter Outer peripheral surfaces 109 and 110 of the cylindrical portion Thin-walled cylindrical portion 120 Chuck 200 of the processing machine Spark plug 400 Gas sensor

Claims (3)

A metal tubular member of a different diameter having a large-diameter cylindrical portion on one end side and a small-diameter cylindrical portion on the other end side, wherein the large-diameter cylindrical portion is thinner than the thickness of the small-diameter cylindrical portion. In forming the thin-walled cylindrical part, the outer peripheral surface of the large-diameter cylindrical part is turned to form the thin-walled cylindrical part.
A turning method for a metallic cylindrical member, wherein the outer peripheral surface of the small diameter cylindrical portion is fixed by a chuck of a processing machine for turning.   The method of turning a metal cylindrical member according to claim 1, wherein the metal cylindrical member is a metal shell for a spark plug.   The method for turning a metal cylindrical member according to claim 1, wherein the metal cylindrical member is a metal shell for a gas sensor.

Images