JP6618940B2 - Spinning method and cylindrical body having a head cone at the end - Google Patents

Description

  The present invention relates to a spinning method and a cylindrical body having a head cone at its end. More specifically, the present invention relates to a taper portion having a diameter reduction ratio larger than that of a conventional work and a conventional taper portion having a smaller ratio of tube thickness to outer diameter (t / D) without lowering productivity. The present invention relates to a spinning method capable of forming a truncated cone portion composed of a longer-diameter straight pipe portion, and a cylindrical body having such a truncated cone portion at an end.

  In this technical field, for example, the diameter of the end of a metal tubular member (work) such as a steel pipe is reduced (reduced) by spinning, and the taper and the tip of the taper are continuous. 2. Description of the Related Art A processing method for integrally forming a head cone portion composed of a small diameter straight pipe portion is known. In particular, a cylindrical member (hereinafter referred to as a “cylindrical body”) used as an outer cylinder that accommodates internal components such as a silencer and a catalytic converter disposed in an automobile exhaust system. Various spinning methods have been proposed as a technique for forming a head cone shape at the end of (). In the present specification, the term “mounting cone” refers to a shape in which a column having the same shape as that of the upper base is placed on the upper base (top surface) of a so-called “frustum cone” (for example, a truncated cone). The “head cone” refers to a portion having such a shape.

  On the other hand, from the request for weight reduction and cost reduction, it is required to reduce the plate thickness of the cylindrical body (outer cylinder) by using a workpiece having a plate thickness thinner than before. Furthermore, as the size of the built-in object accommodated in the cylindrical body increases, the difference in diameter between the unprocessed part of the cylindrical body (the part that maintains the workpiece diameter) and the small-diameter straight pipe part increases. Therefore, it is required to increase the internal volume of the cylindrical body. The ratio of the difference between the diameter of the unprocessed part and the diameter of the small-diameter straight pipe part to the diameter of the non-processed part of the cylindrical body is referred to as “reduction ratio” or “reduction ratio”. When they are the same, the larger the diameter reduction rate, the larger the diameter of the unprocessed portion of the cylindrical body and the larger the internal volume.

  By the way, the spinning process is performed by, for example, pressing a (cylindrical or plate-like) work (for example, a raw tube) against a relatively revolving mold (mandrel) with a forming tool (for example, a forming roller). It is a kind of plastic working. The spinning process is a sequential process, and the material flow occurs in the circumferential direction and the axial direction for each reciprocation (pass) of the forming tool that moves along a predetermined pattern. Therefore, in the spinning process, the thickness of the workpiece tends to fluctuate. In particular, since a stainless steel material used in an automobile exhaust system is hard, a workpiece having a small thickness to outer diameter ratio (t / D) is processed so as to have a large diameter reduction ratio at a predetermined taper angle. It is very difficult to easily cause a problem of deformation (for example, wrinkles and / or cracks) due to local reduction of the plate thickness, and it is difficult to obtain a desired shape. Hereinafter, “difficult machining” means that “a workpiece having a small ratio (t / D) between thickness (plate thickness) and outer diameter (t / D) is processed at a predetermined taper angle so as to have a large diameter reduction ratio”. Called.

  Specifically, in the spinning process according to the prior art that employs typical tool operation (movement of the forming tool along a predetermined pattern), the workpiece is shifted from the unmachined part (non-molded part) to the tapered part. The forming tool repeats unidirectional cutting (squeezing) from the starting point (taper start point) to the end (tube end) side of the workpiece (see, for example, Patent Document 1). Accordingly, the material (raw material) constituting the workpiece flows only from the starting point to the pipe end side. As a result, the plate thickness on the pipe end (small diameter straight pipe portion and taper portion) side becomes thin, and the above difficult processing is often impossible.

  Therefore, in order to solve the above-described problems, both the tapered portion and the small-diameter straight pipe portion are cut by cutting in one direction from the center (center) side to the pipe end side in the longitudinal direction of the workpiece as described above. Has been proposed (for example, see Patent Document 2), in which a tapered portion is first formed and then a small diameter straight pipe portion is formed. Specifically, in the initial to middle stages, the end of the workpiece is cut by reciprocating the forming tool in a direction inclined to the axis of the cylindrical workpiece, and the taper is formed in the final stage. The small diameter straight pipe portion is additionally formed (additional shaping) by reciprocating the forming tool in a direction parallel to and inclined, and a tapered portion and a small diameter straight pipe portion are formed. Thereby, it is supposed that the plate | board thickness of a taper part and a small diameter straight pipe part can be equalize | homogenized.

  However, according to the spinning method described above, the thickness of the taper portion formed in the initial to middle stage is large, but the thickness of the taper portion is increased along with the additional forming (further spinning processing) of the small-diameter straight pipe portion in the subsequent final stage. Becomes smaller. Therefore, the above-described problems (for example, generation of wrinkles and / or cracks) are likely to be caused, and the above-described difficult processing is also difficult.

  In particular, the longer the small-diameter straight pipe portion, the more difficult the difficult processing becomes. For example, FIG. 1 shows the diameter reduction ratios of workpieces (elementary tubes) for various cylindrical bodies having end-of-head conical parts mass-produced as outer cylinders in automobile exhaust systems. It is the graph obtained by plotting with respect to ratio (t / D) of thickness and an outer diameter. Each of these cylindrical bodies includes a small-diameter straight pipe portion having a general length (for example, about 40 mm) as an outer cylinder used for the application. As is clear from FIG. 1, from a workpiece having a t / D smaller than a predetermined value (α), a taper portion having a diameter reduction ratio larger than a predetermined value (β) and a small diameter straight longer than a predetermined length. The cylindrical body which has the mounting cone part which consists of a pipe part in an edge part is not mass-produced. Moreover, it is technically possible to realize the above difficult processing by reducing the taper angle of the taper portion. However, if the taper angle of the taper portion is reduced, the taper portion becomes longer, leading to an increase in weight and size of the cylindrical body. Therefore, such a measure is hardly a realistic solution.

  On the other hand, in the spinning process according to the conventional technique that employs the above-described typical tool operation, the above-described difficulty can be obtained by increasing the number of machining cycles instead of reducing the notch per one reciprocation (machining cycle) of the forming tool. It is technically possible to realize the processing. However, in reality, when the number of processing cycles is increased in this way, the contact time (processing time) between the forming tool and the material (which constitutes the workpiece) increases, which causes work hardening of the material and decreases formability. To do. In addition, even if a technique that can maintain the formability under such processing conditions can be found, the productivity decreases due to the increase in processing time and the manufacturing cost increases, so the number of processing cycles is increased in this way. This is also unlikely to be a realistic solution.

JP 2000-288639 A Japanese Patent No. 4182335 Japanese Patent No. 3390725

  As described above, in this technical field, without reducing productivity, a taper having a smaller diameter ratio than a conventional workpiece with a smaller ratio (t / D) between the tube thickness and the outer diameter than the conventional one. There is a need for a spinning method capable of forming a head cone part composed of a small diameter straight pipe part longer than the conventional part and a cylindrical body having such a head cone part at the end. The present invention has been made to meet such a demand.

  In view of the above, the spinning method according to the present invention (hereinafter sometimes referred to as “the method of the present invention”) includes a tapered portion that decreases in diameter toward a tube end that is an end portion of a cylindrical member. This is a spinning processing method of forming a cylindrical body having a head cone part composed of a small diameter straight pipe part continuous with an end part on the pipe end side of the taper part. The method of the present invention includes a first step and a second step described below.

First step: executing a first cycle that is a predetermined machining cycle at least once, so that a small-diameter straight pipe portion having a first length shorter than a predetermined target length and a first smaller than a predetermined target taper angle A first head cone portion including a taper portion having a taper angle is formed.
Second step: A small-diameter straight pipe having a second length longer than the first length by performing additional machining on the first head cone by executing the second cycle, which is a predetermined machining cycle, at least once. Forming a second head cone having a portion and a tapered portion having a second taper angle greater than the first taper angle.
In the present specification, the “taper angle” refers to an angle formed by the axis of the taper portion and the generatrix of the taper portion in the cross section of the taper portion by a plane including the axis of the taper portion.

  In the first cycle, the radial direction of the tapered portion or the small-diameter straight pipe portion and Alternatively, the forming tool is moved in the axial direction.

  In the second cycle, the drawing process is performed after the stretching process. The stretching process refers to the axial direction of the workpiece from the pipe end side in the axial direction of the small diameter straight pipe part while relatively revolving the forming tool around the axis of the small diameter straight pipe part while pressing the small diameter straight pipe part with the forming tool. Is a process of increasing the length of the small diameter straight pipe portion by moving the forming tool toward the center of the tube at the center. The drawing process is a taper angle of the taper portion by moving the forming tool in the radial direction and the axial direction of the taper portion while relatively revolving around the axis of the taper portion while pressing the taper portion with the forming tool. It is a process to increase.

  As will be described in detail later, the specific movement pattern (tool operation) of the forming tool in the first cycle and the second cycle is, for example, the workpiece material, the target machining shape, machining conditions and constraints ( For example, it can be set as appropriate according to the performance and specifications of the processing machine.

  Furthermore, the cylindrical body according to the present invention (hereinafter sometimes referred to as “the present invention cylindrical body”) includes a tapered portion that decreases in diameter toward the tube end that is an end portion of the cylindrical member; It is a cylindrical body which has a mounting cone part which consists of a small diameter straight pipe part which continues to the edge part by the side of the pipe end of a taper part. In the cylindrical body of the present invention, the ratio (t / D) of the thickness of the tube wall to the outer diameter of the unprocessed portion that is a portion other than the head cone portion is smaller than 0.008, and the outer diameter of the unprocessed portion is The reduction ratio, which is the ratio of the difference from the outer diameter of the small-diameter straight pipe portion to the outer diameter of the unprocessed portion, is greater than 60%, and the taper portion axis and taper in the cross section of the taper portion by the plane including the axis of the taper portion The taper angle, which is the angle formed by the generatrix, is 20 ° or more and 45 ° or less, and the length of the small diameter straight pipe portion in the axial direction is 40 mm or more.

  According to the present invention, without reducing productivity, a tapered portion having a smaller diameter ratio than a conventional work from a work having a smaller ratio (t / D) of the tube thickness to the outer diameter than the prior art, and the conventional art. It is possible to provide a spinning method capable of forming a head cone part composed of a long small diameter straight pipe part, and a cylindrical body having such a head cone part at an end.

  Other objects, other features and attendant advantages of the present invention will be readily understood from the following description of each embodiment of the present invention.

Regarding various cylindrical bodies having end-of-head conical parts that are mass-produced as outer cylinders in automobile exhaust systems, the diameter reduction ratio of these cylindrical bodies is determined by the thickness of the workpiece (element tube) and the outer diameter. It is the graph obtained by plotting with respect to ratio (t / D). It is a schematic diagram which shows the change of the shape of the workpiece | work accompanying the flowchart explaining the flow of the process in the spinning processing method (1st method) which concerns on 1st Embodiment of this invention, and execution of a 1st method. It is a schematic diagram which shows an example of the tool operation (movement pattern of a forming roller) in the 1st cycle performed in the 1st process of the spinning processing method (2nd method) which concerns on 2nd Embodiment of this invention. It is a schematic diagram which shows an example of the tool operation | movement (movement pattern of a forming roller) in the 1st cycle performed in the 1st process of the spinning processing method (3rd method) which concerns on 3rd Embodiment of this invention. It is a schematic diagram which shows an example of the tool operation (movement pattern of a forming roller) in the 2nd cycle performed in the 2nd process of the spinning processing method (5th method) which concerns on 5th Embodiment of this invention. It is a schematic diagram which shows an example of the tool operation (movement pattern of a forming roller) in the 2nd cycle performed in the 2nd process of the spinning processing method (8th method) which concerns on 8th Embodiment of this invention. It is a typical perspective view which shows the structure of the cylindrical body (9th cylindrical body) which concerns on 9th Embodiment of this invention. Schematic showing the configuration of an intermediate cylindrical body having at its end a first step cone portion formed by the first step of the spinning method (example method) according to an embodiment of the present invention and the first step. FIG. It is a schematic diagram which shows the structure of the intermediate | middle cylindrical body which has the 2nd head cone part shape | molded by the 2nd process of the Example method and the said 2nd process in an edge part. It is a schematic diagram which shows the structure of the final cylindrical body which has the 3rd process of the Example method and the mounting cone part shape | molded by the said 3rd process in an edge part. About some cylindrical bodies which have the head cone part shape | molded by the Example method in the edge part, ratio (t / of the diameter reduction rate of these cylindrical bodies, and the thickness of a workpiece | work (element tube) and an outer diameter It is the graph obtained by plotting D) on the graph shown in FIG.

<< First Embodiment >>
The spinning method according to the first embodiment of the present invention (hereinafter may be referred to as “first method”) will be described below.

  The first method is a cylinder having a conical cone portion comprising a tapered portion that is reduced in diameter toward the tube end that is an end portion of the cylindrical member and a small-diameter straight tube portion that is continuous with the end portion on the tube end side of the tapered portion. This is a spinning method for forming a shaped body. Here, a straight tubular work (element tube) indicated by a solid line in FIG. 2A is formed by spinning, and a cylindrical body having a head cone portion indicated by a dotted line in FIG. 2A is manufactured. The case where it tries is explained. 2A to 2C are schematic views showing changes in the shape of the work accompanying the execution of the first method, and are schematic cross-sectional views of a plane including the axis of the work indicated by a one-dot chain line. is there.

  FIG. 2 illustrates the case of “coaxial spinning processing” in which all the axes of the small-diameter straight pipe portion, the tapered portion, and the unmachined portion (portion maintaining the diameter of the workpiece) of the cylindrical body coincide. However, the shape of the cylindrical body molded by the first method is not limited to the above. For example, the axis of the small-diameter straight pipe part and the axis of the unprocessed part may be parallel (but eccentric), and the axis of the small-diameter straight pipe part and the axis of the non-processed part may be in the same plane. They may intersect (tilt) at a predetermined angle, or may be in a so-called “twisted position” where the axis of the small diameter straight pipe portion and the axis of the unprocessed portion are not parallel and do not intersect.

  The first method includes a first step and a second step described below. More specifically, in the first method, as shown in the flowchart of FIG. 2, the second step (step S02) is executed after the first step (step S01).

  In the first step (step S01), the first cycle, which is a predetermined machining cycle, is executed at least once, so that the small-diameter straight pipe portion having a first length shorter than the predetermined target length and the predetermined target taper. A first head cone portion including a tapered portion having a first taper angle smaller than the corner is formed. As a result, the workpiece shown in FIG. 2A is formed into an intermediate shape as shown in FIG. In order to form a final head cone having a small-diameter straight pipe portion having a target length and a taper portion having a target taper angle, the portion indicated by hatching in FIG. It is necessary to cut (narrow down).

  As described above, in the first step, the first pipe is composed of the small-diameter straight pipe portion having the first length shorter than the predetermined target length and the tapered portion having the first taper angle smaller than the predetermined target taper angle. A head cone is formed. That is, the spinning process executed in the first step is more than the spinning process for forming the final headed cone part composed of the small diameter straight pipe part having the target length and the taper part having the target taper angle. It can be said that it is a “smooth process” that is a gradual process and can be performed easily. Accordingly, in the first step, problems such as deformation (for example, wrinkles and / or cracks) due to local reduction in the plate thickness that tend to occur in the above-described difficult processing are hardly caused. However, the shape of the cylindrical body formed in the first step is an intermediate shape that has not reached the target final shape.

  Therefore, in the second step (step S02) executed after the first step, additional processing is performed on the first head cone by executing the second cycle, which is a predetermined processing cycle, at least once. Then, a second head cone portion including a small-diameter straight pipe portion having a second length longer than the first length and a tapered portion having a second taper angle larger than the first taper angle is formed. Thus, the workpiece having the intermediate shape shown in FIG. 2B is formed into a shape closer to the final shape as shown in FIG. In the example shown in (c) of FIG. 2, the shape of the head cone is not yet the final shape, but the shape of the head cone is changed to the final shape by executing the second step. You may shape | mold.

  As described above, in the second step, an additional process is performed on the first head cone portion so that the intermediate shape of the cylindrical body approaches the final shape or matches the final shape. In this way, by forming a cylindrical body having a final shape or a shape closer to the final shape than the first mounting cone via the intermediate shape, the above-described difficult processing occurs. Problems such as deformation (for example, wrinkles and / or cracks) due to local reduction in the plate thickness that tend to occur can be effectively reduced.

  As a result, according to the first method, a taper having a larger diameter reduction ratio than the conventional one from a work having a smaller ratio (t / D) of the tube thickness to the outer diameter than the conventional one without reducing the productivity. The cylindrical body which has a head cone part which consists of a part and a small diameter straight pipe part longer than before can be shape | molded at an edge part.

  In the first cycle, the radial direction of the taper portion or the small-diameter straight pipe portion and / or the rotation of the forming tool relatively around the axis of the taper portion or the small-diameter straight pipe portion while pressing the cylindrical workpiece with the forming tool. Move the forming tool in the axial direction. The forming tool is, for example, a material of a workpiece, a target processing shape, processing conditions and restrictions (for example, processing) among various forming tools generally used in spinning processing such as a forming roller and a spatula. It can be selected appropriately according to the machine performance and specifications.

  In addition, “relatively revolving the forming tool around the axis of the tapered part or the small diameter straight pipe part” means that the axis of the tapered part is used when pressing the tapered part (or the part of the workpiece formed as the tapered part). When pressing a small diameter straight pipe part (or a part of a workpiece formed as a small diameter straight pipe part) as a reference, the forming tool is rotated around the axis when the axis of the small diameter straight pipe part is used as a reference. Point to. At this time, the work may be fixed and the forming tool may revolve around the work, the forming tool may be fixed and the work may rotate (spin), or both the work and the forming tool may be It may be rotating (that is, the workpiece may rotate and the forming tool may revolve around the workpiece).

  Furthermore, “moving the forming tool in the radial direction and / or axial direction of the tapered portion or the small diameter straight pipe portion” means that the workpiece can be cut (squeezed) in a desired direction and depth. Controls the direction of tool movement. For example, when cutting the tapered portion, the forming tool is moved in the radial direction and the axial direction (that is, obliquely), and when cutting the small diameter straight pipe portion, the forming tool is moved only in the axial direction. Also good.

  In addition, the specific movement pattern (tool operation) of the forming tool in the first cycle is not particularly limited, and among various tool operations generally employed in spinning processing for reducing diameter forming, for example, It can be appropriately selected according to the material of the workpiece, the intended processing shape, processing conditions and restrictions.

  In the second cycle, the drawing process is executed after the drawing process. The stretching process refers to the axial direction of the workpiece from the pipe end side in the axial direction of the small diameter straight pipe part while relatively revolving the forming tool around the axis of the small diameter straight pipe part while pressing the small diameter straight pipe part with the forming tool. Is a process of increasing the length of the small diameter straight pipe portion by moving the forming tool toward the center of the tube at the center. The drawing process is a taper angle of the taper portion by moving the forming tool in the radial direction and the axial direction of the taper portion while relatively revolving around the axis of the taper portion while pressing the taper portion with the forming tool. It is a process to increase.

  As described above, in the stretching process, the pipe end side in the axial direction of the small-diameter straight pipe portion is revolved around the axis of the small-diameter straight pipe portion while pressing the small-diameter straight pipe portion with the forming tool. The forming tool is moved from the center toward the tube center. Therefore, the material that has flowed from the central side to the pipe end side of the workpiece in the first step can be returned from the pipe end side to the central side by the stretching process. As a result, local plate thickness unevenness due to localization due to the flow of the material is reduced, so that problems such as deformation due to local decrease in plate thickness can be effectively reduced.

<< Second Embodiment >>
Hereinafter, a spinning method according to the second embodiment of the present invention (hereinafter may be referred to as “second method”) will be described.

  As described above, the spinning process executed in the first step is compared with the spinning process for forming the final head cone part including the small-diameter straight pipe part having the target length and the taper part having the target taper angle. Therefore, it is “easy processing” that can be executed more easily. Therefore, the tool operation in the first cycle is not particularly limited, and can be appropriately selected from various tool operations generally employed in spinning processing for reducing diameter forming.

  Specifically, for example, as in the typical tool operation according to the above-described prior art, the end portion of the workpiece from the starting point (taper start point) at which the workpiece shifts from the unmachined portion (non-molded portion) to the tapered portion. The forming tool may repeat the unidirectional cutting (squeezing) to the (tube end) side.

  That is, in the first cycle executed in the first step of the second method, the workpiece is pressed by the forming tool, and from the taper start point located at the end opposite to the tube end of the taper portion to the tube end. Move the forming tool towards.

  FIG. 3 is a schematic diagram illustrating an example of tool operation (movement pattern of the forming roller) in the first cycle executed in the first step of the second method. As schematically shown in (a), in the first step of the second method, the workpiece W is pressed by the molding roller R while moving the molding roller R as a molding tool from the taper start point Pt toward the pipe end Pe. To do.

  More specifically, as shown in (b), in the first cycle executed first, while pressing the workpiece W by the forming roller R, it is shown in (a) of the unprocessed workpiece W (element tube). Further, the forming roller R is moved from the point 1 corresponding to the taper start point Pt to the point 2 located on the inner side (side closer to the axis) of the pipe end Pe of the raw pipe (solid arrow). As a result, a gentle taper portion and a short (and still large in diameter) small diameter straight pipe portion are formed. Then, the molding roller R is moved away from the workpiece W to the point 3, and the molding roller R is returned to the starting point 1 (open arrow). Thus, in FIG. 3, the black arrow indicates “the movement of the forming roller R in a state where the workpiece W is pressed”, and the white arrow indicates “the molding in a state where it is not in contact with the workpiece W”. The “movement of the roller R” is shown respectively.

  In the first cycle to be executed next, the forming roller R is moved from point 1 toward point 4 located inside (close to the axis) from point 2 (black arrow). Thereby, the taper part which has a taper angle larger than the 1st cycle performed initially, and a long (and smaller diameter) small diameter straight pipe part are shape | molded. Then, the forming roller R is moved away from the workpiece W to the point 3 and returned to the point 1 (open arrow). Thereafter, the first cycle is repeatedly executed in the same manner as described above to form the first head cone portion described above.

  That is, in the tool operation shown in this example, the forming roller R is moved as follows: point 1 → point 2 → point 3 → point 1 → point 4 → point 3 → point 1 → point 5 → point 3 → point 1. Move. Note that points 2, 4 and 5 shown in (b) correspond to the pipe end Pe at that time. In this example, the positions of the points 2, 4 and 5 in the axial direction (left-right direction as viewed in the drawing) are not changed, but the actual position of the pipe end Pe is determined by the execution of the machining cycle in each molding process. It changes every moment.

  As described above, in the first step of the second method, the forming tool (forming roller R) is moved from the taper start point Pt located closer to the tube center Pc than the tube end Pe toward the tube end Pe. The workpiece W is pressed with a forming tool. Therefore, the material (raw material) constituting the workpiece W flows only from the taper start point Pt, which is the starting point of tool operation, to the pipe end side Pe. As a result, the material may be biased (localized) toward the pipe end Pe side, resulting in uneven thickness.

  However, also in the second step of the second method, as in the second step of the first method described above, a forming tool (from the tube end Pe side toward the tube center Pc side in the axial direction of the small diameter straight pipe portion ( A stretching process is performed in which the small diameter straight pipe portion is pressed by a molding tool while moving the molding roller R). Therefore, even if the material flows from the center Pc side of the workpiece W to the tube end Pe side in the first step, the material can be returned from the tube end Pe side to the center Pc side by the stretching process in the second step. it can. As a result, local unevenness of the plate thickness due to localization due to the flow of the material is reduced. Therefore, even if the tool operation as described above is employed in the first step, the local decrease in the plate thickness It is possible to effectively reduce problems such as deformation caused by.

  In the first step of the second method, the tool operation does not necessarily have to be adopted in all the first cycles, and may be combined with other tool operations as necessary.

<< Third Embodiment >>
The spinning method according to the third embodiment of the present invention (hereinafter sometimes referred to as “third method”) will be described below.

  As described above, in the first step of the second method, the forming tool repeats cutting in one direction from the taper start point to the pipe end side. However, for example, as described in Patent Document 2 described above, the taper portion and the small-diameter straight pipe portion can be formed by reciprocating the forming tool in a direction parallel to the workpiece axis and a direction inclined. Good.

  That is, in the first cycle executed in the first step of the third method, while pressing the workpiece with the forming tool, the taper start point and the pipe end located at the end opposite to the pipe end of the taper part. The forming tool is reciprocated in the region between.

  FIG. 4 is a schematic diagram showing an example of tool operation (movement pattern of the forming roller) in the first cycle executed in the first step of the third method. As schematically shown in (a), in the first step of the third method, the forming roller R as a forming tool is reciprocated in the region between the taper start point Pt and the pipe end Pe by the forming roller R. Press the workpiece W.

  More specifically, as shown in (b), in the first cycle executed first, while pressing the workpiece W by the forming roller R, it is shown in (a) of the unprocessed workpiece W (element tube). Further, the forming roller R is moved from the point 1 corresponding to the taper start point Pt to the point 2 located on the inner side (side closer to the axis) of the pipe end Pe of the raw pipe (solid arrow). Thereby, a gentle taper part is temporarily shape | molded. Then, while pressing the workpiece W by the molding roller R, the molding roller R is moved parallel to the axis of the workpiece W, and molding is performed up to a point 3 at a position corresponding to a point on the tapered surface of the taper portion to be molded. The roller R is moved (black arrow). Thereby, the small diameter straight pipe part slightly smaller in diameter than the unprocessed part of the workpiece W is temporarily formed.

  Further, the forming roller R is moved from the point 3 to the point 1 while pressing the work W by the forming roller R (black arrow). Thereby, a part of taper surface of the taper part to be molded is molded. Finally, the forming roller R is returned from the point 1 to the point 3 (the hatched arrow). At this time, although the forming roller R presses the workpiece W, the moving path is the same as the immediately preceding moving path except that the moving direction is reversed. That is, the surface of the tapered surface formed by the movement of the forming roller R from the point 3 to the point 1 is leveled by the movement of the forming roller R from the point 1 to the point 3.

  As described above, the black arrow in FIG. 4 indicates “movement of the forming roller R in a state where the workpiece W is pressed” as in FIG. 3. On the other hand, the hatched arrow indicates “movement of the forming roller R in a state where it is in contact with the work W but is not actively cut”.

  In the first cycle to be executed next, the forming roller R is moved from the point 3 toward the point 4 located on the inner side (closer to the shaft) than the point 2. As a result, the gentle tapered portion is temporarily formed again (black arrow). Then, the forming roller R is moved in parallel to the axis of the workpiece W, and the forming roller R is moved to a point 5 at a position corresponding to a point on the tapered surface of the taper portion to be formed (black arrow). . Thereby, the small diameter straight pipe part slightly smaller in diameter than the unprocessed part of the workpiece W is temporarily formed again.

  Further, the molding roller R is moved from the point 5 to the point 3 while pressing the workpiece W by the molding roller R (black arrow). Thereby, a part of taper surface of the taper part to be molded is molded. Finally, the forming roller R is returned from the point 3 to the point 5 (arrows with diagonal lines). Thereby, the surface of the taper surface formed by the movement of the forming roller R from the point 5 to the point 3 is leveled. Thereafter, the first cycle is repeatedly executed in the same manner as described above to form the first head cone portion described above.

  That is, in the tool operation shown in this example, point 1 → point 2 → point 3 → point 1 → point 3 → point 4 → point 5 → point 3 → point 5 → point 6 → point 7 → point 5 → point 7 In this way, the forming roller R is moved. Note that points 2, 4 and 6 shown in (b) correspond to the pipe end Pe at that time. As described above, the position of the pipe end Pe changes with the execution of the machining cycle in each molding step.

  As described above, in the first step of the third method, the work W is pressed by the forming tool while reciprocating the forming tool (forming roller R) in the region between the taper start point Pt and the pipe end Pe. Therefore, compared to the second method in which the work tool is pressed by the forming tool while moving the forming tool from the taper start point Pt toward the pipe end Pe in the first step, the thickness of the tapered portion and the small diameter straight pipe portion is uniform. Can be

  In the first step of the third method, the tool operation does not necessarily have to be adopted in all the first cycles, and may be combined with other tool operations as necessary.

<< 4th Embodiment >>
Hereinafter, a spinning method according to the fourth embodiment of the present invention (hereinafter, sometimes referred to as “fourth method”) will be described.

  In the second step of the spinning method according to various embodiments of the present invention including the first method to the third method described above, the second cycle in which the drawing process is executed after the drawing process is executed as described above. Run at least once. As a result, the first mount cone portion formed in the first step is subjected to additional processing, and the second mount cone portion having a shape closer to the final shape or the same shape as the final shape is formed. Is done.

  The specific tool operation in the stretching process is as follows: the pipe end side in the axial direction of the small diameter straight pipe portion while revolving the forming tool relatively around the axis of the small diameter straight pipe portion while pressing the small diameter straight pipe portion with the forming tool There is no particular limitation as long as the length of the small-diameter straight pipe portion is increased by moving the forming tool from the center toward the tube center.

  In the second step of the fourth method, the second cycle is executed twice or more. And in the extending | stretching process performed in each 2nd cycle, a shaping | molding tool is moved so that the area | region of the small diameter straight pipe part pressed with a shaping | molding tool may not mutually overlap.

  Specifically, for example, the starting point of the movement of the forming roller R in the second cycle of the stretching process is not positioned closer to the pipe end than the end point of the movement of the forming roller R in the previously executed second cycle of the stretching process. Define tool operation. Thereby, it is possible to prevent the moving ranges of the forming rollers from overlapping each other in the stretching process of the second cycle executed a plurality of times.

  As described above, in the second step of the fourth method, the regions of the small diameter straight pipe portions pressed by the forming roller R in the respective stretching processes do not overlap each other. Therefore, since the movement of the forming roller R in the stretching process can be reduced, the productivity of the method of the present invention can be improved.

  In the second step of the fourth method, the tool operation does not necessarily have to be adopted in all second cycles, and may be combined with other tool operations as necessary.

<< 5th Embodiment >>
Hereinafter, a spinning method according to the fifth embodiment of the present invention (hereinafter may be referred to as “fifth method”) will be described.

  In the second step of the fourth method described above, the forming tool is moved so that the regions of the small-diameter straight pipe portions pressed by the forming tool do not overlap each other in the second cycle stretching process executed a plurality of times. As a specific example of such a tool operation, for example, there is one in which the forming tool is moved so as to gradually expand the small-diameter straight pipe portion toward the central side in each stretching process.

  Therefore, in the second step of the fifth method, in the stretching process, while pressing the small diameter straight pipe portion with a forming tool, from the end opposite to the pipe end of the small diameter straight pipe portion toward the center of the tube. Move the forming tool.

  FIG. 5 is a schematic diagram showing an example of tool operation (movement pattern of the forming roller) in the second cycle executed in the second step of the fifth method. As schematically shown in (a), in the second cycle stretching process of the fifth method, a forming tool (from the end opposite to the pipe end Pe of the small diameter straight pipe part toward the center Pc side) The length of the small diameter straight pipe portion is increased by pressing the workpiece W by the forming roller R while moving the forming roller R). In the drawing process performed after the stretching process, the taper angle of the taper portion is increased by pressing the workpiece W by the molding roller R while reciprocating the molding roller R between the end point of the stretching process and the taper start point Pt. Increase.

  More specifically, as shown in (b), in the first cycle to be executed first, the head cone shown in (a) while pressing the workpiece W (small diameter straight pipe portion) by the forming roller R. The forming roller R is moved in parallel with the axis of the workpiece W from a point A corresponding to the pipe end Pe of the part to a point B located on the tube center Pc side (black arrow). Thereby, the length of a small diameter straight pipe part is increased. That is, the stretching process is executed. Next, while pressing the workpiece W by the forming roller R, the forming roller R is moved from the point B to the point C corresponding to the taper start point Pt of the head cone shown in FIG. The forming roller R is moved from point B to point D located closer to the center Pc than point B (black arrow). Thereby, the taper angle of the taper portion is increased. That is, the aperture process is executed. At this time, the length of the small diameter straight pipe portion is also slightly increased (from point B to point D).

  In the second cycle to be executed next, the forming roller R is moved in parallel with the axis of the workpiece W from the point D to the point E located on the tube center Pc side (solid arrow). Thereby, the length of the small diameter straight pipe portion is further increased. That is, the stretching process is executed. Next, while pressing the workpiece W by the forming roller R, the forming roller R is moved from the point E to the point C, and then from the point C to the point F located closer to the center Pc than the point E. The forming roller R is moved (black arrow). Thereby, the taper angle of the taper portion is further increased. That is, the aperture process is executed. At this time, the length of the small diameter straight pipe portion is also slightly increased (from point E to point F). Thereafter, the second cycle is repeatedly executed in the same manner as described above to form the second head cone portion described above.

  In this example, at the end of the second step, the forming roller R is returned to the point X corresponding to the pipe end Pe at that time (the hatched arrow). At this time, the surface of the small diameter straight pipe portion formed by the stretching process of the second cycle is leveled by moving the forming roller R parallel to the axis of the workpiece W while pressing the small diameter straight pipe portion by the forming roller R. You may make it. That is, in the tool operation shown in this example, the forming roller R is moved in the order of point A → point B → point C → point D → point E → point C → point F →.

  As described above, also in FIG. 5, the black arrow indicates “the movement of the forming roller R while the workpiece W is being pressed”. On the other hand, the hatched arrow indicates “movement of the forming roller R in a state where it is in contact with the work W but is not actively cut”.

  In general, the small-diameter straight pipe portion in the second cycle executed after the diameter of the small-diameter straight pipe portion in the second cycle executed first among the second cycles executed a plurality of times in the second step. Tool operation is set so that the diameter of the tool becomes smaller. In this example, the size of the diameter of the small-diameter straight pipe portion when the small-diameter straight pipe portion is pressed by the forming roller R is expressed by the position of the forming roller. “Target diameter = X ≦... F ≦ E ≦ D ≦ B ≦ A ”.

  As described above, in the second step of the fifth method, the stretching process of the second cycle that is executed this time is started from the position of the forming roller R at the time when the drawing process of the second cycle that was performed previously is completed. The Thereby, the area | regions of the small diameter straight pipe part pressed by the shaping | molding roller R in each extending | stretching process can be prevented more reliably from each other. Therefore, since the movement of the forming roller R in the stretching process can be reduced more reliably, the productivity of the method of the present invention can be improved more reliably.

  In the second step of the fifth method, it is not always necessary to employ the above tool operation in all the second cycles, and may be combined with other tool operations as necessary.

<< 6th Embodiment >>
Hereinafter, the spinning method according to the sixth embodiment of the present invention (hereinafter may be referred to as “sixth method”) will be described.

  In the second step of the fourth method and the fifth method described above, the second cycle is executed twice or more, and molding is performed so that the areas of the small-diameter straight pipe portions pressed by the molding tool in each stretching process do not overlap each other. Move the tool. Thereby, since the movement of the shaping | molding tool in an extending | stretching process can be decreased, the productivity of this invention method can be improved.

  However, when the tool operation as described above is adopted, for example, depending on the workpiece material, the target machining shape, machining conditions and restrictions (for example, the performance and specifications of the machining machine), etc. In some cases, the tube end side of the tube portion expands to form a flare shape. If the spread on the tube end side in such a flare-like shape becomes excessively large, for example, there is a possibility that it may lead to problems such as generation of wrinkles at the time of subsequent molding of the small-diameter straight pipe portion. In order to reduce such a problem, it is desirable to increase the frequency of pressing the small diameter straight pipe portion with the forming tool in the second step.

  Therefore, in the second step of the sixth method, the second cycle is executed twice or more. And at least a part of the area of the small diameter straight pipe part pressed by the forming tool in the previous drawing process overlaps at least a part of the area of the small diameter straight pipe part pressed by the forming tool in the current drawing process. The molding tool is moved as follows.

  As described above, in the second step of the sixth method, at least a part of the region of the small diameter straight pipe portion pressed by the forming tool in each stretching process of the second cycle executed a plurality of times overlaps each other. Therefore, the area | region of the small diameter straight pipe part pressed several times with a shaping | molding tool in an extending | stretching process can be increased. As a result, for example, even if a flare-like shape as described above appears in the small diameter straight pipe portion in the middle of the second step, it is pressed by the forming tool, so that the spread thereof is suppressed from becoming excessively large. Thereby, problems, such as a wrinkle generate | occur | producing at the time of the shaping | molding process of a small diameter straight pipe part after that, can be reduced.

  In the second step of the sixth method, the tool operation does not necessarily have to be adopted in all the second cycles, and may be combined with other tool operations as necessary.

<< 7th Embodiment >>
Hereinafter, the spinning method according to the seventh embodiment of the present invention (hereinafter may be referred to as “seventh method”) will be described.

  According to the second step of the sixth method described above, at least a part of the region of the small diameter straight pipe portion pressed by the forming tool is overlapped with each other in each stretching process of the second cycle executed a plurality of times. Thereby, the area | region of the small diameter straight pipe part pressed several times with a shaping | molding tool in an extending | stretching process can be increased, and problems, such as the generation | occurrence | production of the wrinkles resulting from the appearance of the flare-like shape in a small diameter straight pipe part, can be reduced. . As a specific example of such a tool operation, for example, there is one in which the forming tool is moved so as to gradually expand the small-diameter straight pipe portion toward the central side in each stretching process.

  Therefore, in the stretching process of the second step of the seventh method, the forming tool is moved from the tube end toward the center of the tube while pressing the small diameter straight pipe portion with the forming tool. That is, the starting point of the stretching process executed in the second cycle is the pipe end.

  According to the above, the frequency of being pressed by the forming tool in the stretching process of the second step can be increased toward the tube end side of the small diameter straight pipe portion, and thus the appearance of the flare-shaped shape described above can be more effectively reduced. be able to.

  In the second step of the seventh method, the tool operation does not necessarily have to be adopted in all the second cycles, and may be combined with other tool operations as necessary.

<< Eighth Embodiment >>
Hereinafter, the spinning method according to the eighth embodiment of the present invention (hereinafter may be referred to as “eighth method”) will be described.

  According to the second step of the seventh method described above, by setting the starting point of the stretching process executed in the second cycle as the pipe end, the frequency of being pressed by the forming tool in the stretching process of the second step is reduced. It is possible to reduce the appearance of a flare-shaped shape more effectively by increasing the height toward the tube end side of the portion. However, the above-mentioned tool operation causes the material (material) constituting the small-diameter straight pipe part to flow from the pipe end side to the pipe center side, reducing the plate thickness near the pipe end, There is a risk of increase.

On the other hand, in order to use the starting point of the stretching process performed in the second cycle as the pipe end as described above, it is necessary to return the forming tool to the pipe end after the drawing process performed after the stretching process is completed. . The position where the squeezing process is performed is closer to the center than the tube end, and approaches the center every time the second cycle is repeated. Therefore, when the forming tool is returned to the pipe end after the drawing process is completed, the forming tool is moved from the tube center side to the pipe end. At this time, the small diameter straight pipe portion is pressed by the forming tool. Accordingly, it is possible to return the material to flow from the tube end to the tube central side by the previous stretching from the tube central side to the tube end. As a result, it is possible to reduce problems such as local reduction in thickness and / or spots due to localization due to the flow of the material.

  Therefore, in the stretching process of the second step of the eighth method, after moving the forming tool to the pipe end while pressing the small diameter straight pipe portion with the forming tool, the pipe end while pressing the small diameter straight pipe portion with the forming tool. The forming tool is moved from the center toward the tube center.

  FIG. 6 is a schematic diagram showing an example of tool operation (movement pattern of the forming roller) in the second cycle executed in the second step of the eighth method. As schematically shown in (a), in the stretching process of the second cycle of the eighth method, the workpiece W (by the forming roller R) is moved by the forming roller R while moving the forming tool (forming roller R) to the pipe end Pe at the start of the stretching process. The length of the small-diameter straight pipe portion is increased by pressing the work W by the forming roller R while moving the forming roller R from the pipe end Pe toward the tube center Pc. . In the drawing process performed after the stretching process, the taper angle of the taper portion is increased by pressing the workpiece W by the molding roller R while reciprocating the molding roller R between the end point of the stretching process and the taper start point Pt. Increase.

  More specifically, as shown in (b), in the first cycle to be executed first, the head cone shown in (a) while pressing the workpiece W (small diameter straight pipe portion) by the forming roller R. The forming roller R is moved in parallel with the axis of the workpiece W from a point A corresponding to the pipe end Pe of the part to a point B located on the tube center Pc side (black arrow). Thereby, the length of a small diameter straight pipe part is increased. That is, the stretching process is executed. Next, while pressing the workpiece W by the forming roller R, the forming roller R is moved from the point B to the point C corresponding to the taper start point Pt of the head cone shown in FIG. The forming roller R is moved from point B to point D located closer to the center Pc than point B (black arrow). Thereby, the taper angle of the taper portion is increased. That is, the aperture process is executed. At this time, the length of the small diameter straight pipe portion is also slightly increased (from point B to point D).

  In the second cycle to be executed next, after the small diameter straight pipe portion is pressed by the forming roller R, the forming roller R is moved from the point D to the pipe end Pe in parallel to the axis of the workpiece W, and then the pipe end. The forming roller R is moved from Pe to the point D in parallel with the axis of the workpiece W (arrows with diagonal lines). As a result, the surface of the small-diameter straight pipe portion formed by the stretching process in the second cycle is leveled. For example, local reduction in thickness and / or spots and flare due to localization due to the flow of the material Problems such as the appearance of the shape can be reduced. Further, the forming roller R is moved in parallel with the axis of the workpiece W to a point E located on the tube center Pc side with respect to the point D (solid arrow). Thereby, the length of a small diameter straight pipe part is increased. That is, the stretching process is executed. Next, while pressing the workpiece W by the forming roller R, the forming roller R is moved from the point E to the point C, and then from the point C to the point F located closer to the center Pc than the point E. The forming roller R is moved (black arrow). Thereby, the taper angle of the taper portion is further increased. That is, the aperture process is executed. At this time, the length of the small diameter straight pipe portion is also slightly increased (from point E to point F). Thereafter, the second cycle is repeatedly executed in the same manner as described above to form the second head cone portion described above.

  In this example, at the end of the second step, the forming roller R is returned to the point X corresponding to the pipe end Pe at that time (the hatched arrow). At this time, the surface of the small-diameter straight pipe portion formed by the stretching process of the second cycle is moved by moving the molding roller R parallel to the axis of the workpiece W while pressing the small-diameter straight pipe portion by the molding roller R. You may make it equal. That is, in the tool operation shown in this example, the forming roller R is moved in the order of point A → point B → point C → point D → point A → point E → point C → point F →. .

  As described above, also in FIG. 6, the black arrow indicates “movement of the forming roller R while pressing the workpiece W”. On the other hand, the hatched arrow indicates “movement of the forming roller R in a state where it is in contact with the work W but is not actively cut”.

  In general, the small-diameter straight pipe portion in the second cycle executed after the diameter of the small-diameter straight pipe portion in the second cycle executed first among the second cycles executed a plurality of times in the second step. Tool operation is set so that the diameter of the tool becomes smaller. Also in this example, when the size of the diameter of the small diameter straight pipe portion when the small diameter straight pipe portion is pressed by the forming roller R is expressed by the position of the forming roller, “target diameter = X ≦... F ≦ E ≦ D ≦ B ≦ A ”.

  As described above, in the second step of the eighth method, in addition to the tool operation in the second step of the fifth method described above, the forming tool (forming roller R) is moved to the pipe end Pe at the start of the stretching process. The work W (small diameter straight pipe portion) is pressed by the forming roller R. As a result, the surface of the small-diameter straight pipe portion formed by the stretching treatment in the second cycle is leveled, for example, a local reduction in thickness and / or spots and flare due to localization due to the flow of the material. Problems such as the appearance of the shape can be reduced.

  In the second step of the eighth method, it is not always necessary to employ the above tool operation in every second cycle, and it may be combined with other tool operations as necessary.

  As described above, the spinning method according to some embodiments of the present invention has been described in detail. The method of the present invention including various embodiments of the present invention including these embodiments includes the first step and the first step described above. In addition to the two steps, one or more processing steps may further be included before the first step, between the first step and the second step, and / or after the second step.

  For example, if the shape of the cylindrical body formed by the second step has not yet coincided with the final shape, a third step of additionally machining the second head cone is further provided after the second step. A cylindrical body having a final shape may be manufactured. In addition, when the smoothness of the surface of the cylindrical body formed by the second step is insufficient, the number of processing cycles is increased instead of reducing the cut per processing cycle compared to the second step. A third step may be further provided after the second step to improve the smoothness of the surface of the cylindrical body.

  In the above description, the positions such as the start position (start point) and the end position (end point) of the movement of the forming tool are expressed as “points”. However, as described above, when the present invention is executed, since the forming tool is relatively revolved around the workpiece axis, these points actually mean a circumferential line.

<< Ninth Embodiment >>
Hereinafter, a cylindrical body according to the ninth embodiment of the present invention (hereinafter, may be referred to as a “ninth cylindrical body”) will be described.

  As described at the beginning of the present specification, the present invention is formed not only from the spinning method as described above, but also from a workpiece having a smaller ratio (t / D) between the tube thickness and the outer diameter than in the prior art. The present invention also relates to a cylindrical body having an end portion having a tapered conical portion composed of a tapered portion having a larger diameter reduction ratio than the conventional one and a small diameter straight pipe portion longer than the conventional one.

  The ninth cylindrical body is a truncated cone portion comprising a tapered portion that is reduced in diameter toward the tube end that is an end portion of the cylindrical member, and a small-diameter straight tube portion that is continuous with the end portion on the tube end side of the tapered portion. It is a cylindrical body which has. Furthermore, the ninth cylindrical body has features (1) to (4) listed below. In the following description, description will be given with reference to the reference numerals shown in FIG. 7, which is a schematic perspective view showing the configuration of the ninth cylindrical body.

(1) The ratio (t / D) of the thickness of the tube wall (t) to the outer diameter (D) of the unprocessed portion (11) that is a portion other than the head cone portion is smaller than 0.008.
(2) Ratio of difference (D−d) between outer diameter (D) of raw part (11) and outer diameter (d) of small diameter straight pipe part to outer diameter (D) of raw part ((D− The diameter reduction ratio d) / D) is greater than 60%.
(3) The taper angle that is an angle formed by the axis of the taper portion and the generatrix of the taper portion in the cross section of the taper portion by a plane including the axis of the taper portion is 20 ° or more and 45 ° or less,
(4) The length (L) in the axial direction of the small diameter straight pipe portion (13) is 40 mm or more.

  As described at the beginning of this specification, a workpiece having a small ratio (t / D) of the plate thickness (t) to the outer diameter (D) is processed so as to have a large diameter reduction ratio at a predetermined taper angle. In particular, as the length (L) of the small-diameter straight pipe portion (13) increases, such difficult processing becomes more difficult. Therefore, as described with reference to the graph of FIG. 1, a small-diameter straight pipe portion having a general length (eg, about 40 mm) as an outer cylinder used in an application such as an automobile exhaust system, A cylindrical body having a tapered cone at the end composed of a taper angle and a tapered portion having a diameter reduction ratio larger than a predetermined value (β) has a t / D smaller than a predetermined value (α). Is not in mass production.

  The above features (1) to (4) of the ninth cylindrical body cannot be achieved by a cylindrical body mass-produced in the technical field. According to the ninth cylindrical body, for example, it is possible to meet the demand for weight reduction and cost reduction in the technical field without reducing productivity.

  The cylindrical body of the present invention including the ninth cylindrical body can be easily manufactured by the spinning method according to the present invention including the spinning method according to the various embodiments described above.

  As mentioned above, although the spinning method and the cylindrical body which concern on various embodiment of this invention were demonstrated, it demonstrates in detail below, referring drawings for the typical Example of this invention.

<Tubular body>
The configuration of the cylindrical body according to this example was the same as that shown in FIG. Specific dimensions and the like of each part will be described in the description of the manufacturing procedure described later. In this embodiment, a straight pipe having a thickness (t) of 1 mm formed of a stainless steel material was used as a workpiece.

《Production procedure》
In this example, the third step as the finishing step was performed after the first step and the second step described above. Details of each processing step will be described below.

<First step>
In the first step, as shown in FIG. 8A, a procedure corresponding to the third method described above was adopted. Specifically, in the first cycle that is repeatedly executed in the first step, the workpiece is pressed by the forming roller, and the taper start point Pt and the pipe end Pe located at the end opposite to the pipe end of the taper part. The forming roller was reciprocated in the area between. Accordingly, as shown in FIG. 8B, a small-diameter straight pipe portion having a first length (19 mm) shorter than a predetermined target length (46 mm) and a predetermined target taper angle (θ = 32 °). A first head cone having a smaller first taper angle (θ = 22 °) was formed. That is, the cylindrical body at this stage has an intermediate shape.

<Second step>
In the second step, as shown in FIG. 9A, a procedure corresponding to the above-described eighth method was adopted. Specifically, in the stretching process of the second cycle that is repeatedly executed in the second step, the molding roller is moved to the pipe end Pe while pressing the small-diameter straight pipe portion with the molding roller, and then the small-diameter straight pipe with the molding roller. The forming roller was moved from the tube end Pe toward the tube center Pc while pressing the portion. Accordingly, as shown in FIG. 9B, a small diameter straight pipe portion having a second length (32 mm) shorter than a predetermined target length (46 mm) and a predetermined target taper angle (θ = 32 °). A second head cone having a taper portion having a smaller second taper angle (θ = 26 °) was formed. That is, the cylindrical body at this stage still has an intermediate shape, not a final shape.

<Third step>
In the third step, as shown in FIG. 10A, basically the same procedure as in the second step was adopted. However, in the third step, the number of machining cycles was increased instead of reducing the cut per machining cycle as compared to the second step. As a result, the smoothness of the surface of the cylindrical body is improved and, as shown in FIG. 10B, a small diameter straight pipe portion having a predetermined target length (46 mm) and a predetermined target taper angle (θ = A conical portion having a taper portion having 32 °) was formed. That is, the cylindrical body at this stage has a final shape. Moreover, the diameter reduction rate in the taper part of the cylindrical body at this stage is larger than 60%.

<Evaluation>
According to the above-described embodiment method, it is accompanied while reducing problems such as the occurrence of deformation (for example, wrinkles and / or cracks) due to local reduction of the plate thickness without reducing productivity. Easily to form a cylindrical body having an end portion with a conical cone portion composed of a small-diameter straight pipe portion having a length that cannot be achieved by a conventionally produced mass-produced cylindrical body and a tapered portion having a taper angle. Can be molded.

  FIG. 11 shows a cylindrical body (black square plot) having an end cone portion formed by the above-described embodiment method and some other cylindrical bodies (white) 1 was obtained by plotting the diameter reduction ratio of these cylindrical bodies and the ratio (t / D) between the thickness of the workpiece (element tube) and the outer diameter (t / D) in the graph shown in FIG. As is apparent from the graph, each of the cylindrical bodies according to the present embodiment has a small-diameter straight pipe portion having a predetermined target length (46 mm) and a tapered portion having a predetermined target taper angle (32 °). In spite of having the mounting cone part which consists of this at the edge part, the diameter reduction rate and t / D which cannot be achieved with the cylindrical body mass-produced conventionally are achieved simultaneously.

  Therefore, according to the embodiment cylindrical body, for example, it is possible to meet the demand for weight reduction and cost reduction in the technical field without reducing the productivity.

  In the foregoing, for the purpose of illustrating the present invention, several embodiments and examples having specific configurations have been described with reference to the accompanying drawings. However, the scope of the present invention is illustrative only. It should be understood that the present invention should not be construed as being limited to the embodiments and examples, and that modifications can be made as appropriate within the scope of the matters described in the claims and the specification.

  DESCRIPTION OF SYMBOLS 10 ... Cylindrical body, 11 ... Unprocessed part, 12 ... Tapered part, 13 ... Small diameter straight pipe part, Pc ... Pipe center, Pt ... Taper starting point, Pe ... Pipe end, D ... Outer part outer diameter, d ... the outer diameter of the small diameter straight pipe part, t ... the plate thickness of the unprocessed part, and L ... the length of the small diameter straight pipe part.

Claims (3)

A cylindrical shape having a conical conical portion comprising a tapered portion that is reduced in diameter toward the tube end that is an end portion of the tubular member, and a small-diameter straight tube portion that is continuous with the end portion on the tube end side of the tapered portion. A spinning method for forming a body,
By executing the first cycle, which is a predetermined machining cycle, at least once, it has a small diameter straight pipe portion having a first length shorter than a predetermined target length and a first taper angle smaller than a predetermined target taper angle. A first step of forming a first head cone comprising a tapered portion;
A small-diameter straight pipe portion having a second length longer than the first length by performing additional processing on the first head cone portion by executing a second cycle which is a predetermined machining cycle at least once; A second step of forming a second head cone portion comprising a taper portion having a second taper angle larger than the first taper angle;
Including
In the first cycle, the taper part or the small diameter straight pipe part while relatively revolving the molding tool around the axis of the taper part or the small diameter straight pipe part while pressing a cylindrical workpiece with the forming tool. Moving the forming tool in the radial direction and / or axial direction of
In the second cycle, the pipe is formed in the axial direction of the small diameter straight pipe portion while relatively revolving the forming tool around the axis of the small diameter straight pipe portion while pressing the small diameter straight pipe portion by the forming tool. executing a drawing process that increases toward the tube central side length of the small-diameter straight tube portion by moving the forming tool only toward the side of KanHisashi a center in the axial direction of the end or al the work Then, while pressing the tapered portion with the forming tool, the forming tool is moved in the radial direction and the axial direction of the tapered portion while relatively revolving around the axis of the tapered portion. Squeezing process to increase the taper angle of the taper part ,
At the end of the second step, in the axial direction of the small-diameter straight pipe portion, the molding tool is relatively revolved around the axis of the small-diameter straight pipe portion while pressing the small-diameter straight pipe portion with the forming tool. Performing a leveling process to move the forming tool toward the tube end ;
Spinning method. The spinning method according to claim 1,
In the first cycle, while pressing the workpiece with the forming tool, the forming tool is moved from the taper start point located at the end of the tapered portion opposite to the tube end toward the tube end. ,
Spinning method. The spinning method according to claim 1,
In the first cycle, the forming tool is pressed in the region between the taper starting point located at the end opposite to the tube end of the tapered portion and the tube end while pressing the workpiece with the forming tool. Reciprocate,
Spinning method.

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