JP2011226615A - Method for producing power transmission member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shape a high-accuracy small diameter part at low cost when shaping the small diameter part by applying drawing to an end part of a steel pipe.SOLUTION: By applying the drawing to the end part of the steel pipe 30, the small diameter part 4 formed with a power-transmitting connection element on an outside diameter face is shaped. By applying the drawing to the end part 30b in a state of restraining both end faces 30a1, 30b1 of the steel pipe 30, the small diameter part 4 is shaped. Thus, a situation that the thickness of the end part 30b applied with the drawing freely move in an axial direction according to the drawing is prevented.

Description

  The present invention relates to a method of manufacturing a power transmission member incorporated in a power transmission device of an automobile or various industrial machines.

  As a power transmission device for automobiles, for example, there are a drive shaft and a propeller shaft configured by connecting two constant velocity universal joints with an intermediate shaft. A connecting element such as a spline is connected to the outer diameter of both ends of the intermediate shaft as a power transmission member constituting these power transmission devices so that the intermediate shaft and the inner joint member of the constant velocity universal joint can be transmitted with torque. Are provided. As the intermediate shaft, a solid type machined from a solid bar or a hollow type machined from a steel pipe (pipe material) can be used. The hollow type tends to be frequently used because of the necessity in terms of functions such as improvement in rigidity and NVH characteristics (see, for example, Patent Document 1).

  Moreover, there exists an outer joint member of a constant velocity universal joint as a power transmission member which has connection elements, such as a spline, in an end part outer diameter. The outer joint member includes a cup portion that accommodates the inner joint member, the torque transmission member, and the like on the inner periphery, and a shaft portion that extends in the axial direction from the bottom portion of the cup portion. It is provided on the outer diameter of the end of the portion on the side opposite to the cup. The shaft portion having the connecting element may be formed of a hollow shaft for the same reason as described above (see, for example, Patent Document 2).

  Since the torsional torque is continuously applied to the connecting element of the power transmission member during operation of the power transmission device, the connecting element needs to have high strength. Therefore, the connecting element is often provided integrally on the outer diameter surface of the small-diameter portion formed into a thick wall by subjecting the end portion of the steel pipe to drawing (plastic working). In addition, examples of the drawing process include a pressing process in which a steel pipe is pushed in an axial direction with respect to a die, and a swaging process in which a striking force is applied at a high speed in a radial direction while rotating the steel pipe around its axis. it can.

  FIG. 8 shows an example of a drawing method conventionally employed. First, as shown in FIG. 8A, one end surface of the steel pipe 83 is held and restrained by a holding die 81 arranged on one end side of the die 80. In this state, as shown in FIG. 8B, the other end 84 of the steel pipe 83 is pushed into the pressurizing part 80a of the die 80, and the small diameter part 85 is formed. When the forming of the small diameter portion 85 is completed, the other end face 86 of the steel pipe 83 (the shaft end on the side where the small diameter portion 85 is formed) comes into contact with the discharge die 82 disposed on the other end side of the die 80. Then, the discharge die 82 is moved closer to the die 80, and the steel pipe 83 pushed into the die 80 is discharged from the die 80. Thereby, the drawing process for the other end 84 of the steel pipe 83 is completed.

  As shown in FIG. 8B, the small diameter portion 85 is thicker than the other end portion 84 before drawing. However, in the above method, the thickness (inner diameter surface shape) of the small diameter portion 85 tends to be non-uniform in the axial direction. Specifically, as shown in the enlarged view in FIG. 8B, the region X on the shaft end side of the small-diameter portion 85 has a tapered shape in which the thickness is gradually reduced toward the shaft end side. A connecting element such as a spline is formed on the outer diameter surface of the small-diameter portion 85 in a later processing step, but if the connecting element is provided on the outer diameter surface of the small-diameter portion 85 whose thickness is not uniform in the axial direction, twisting occurs. There is a risk that the load capacity with respect to torque will be insufficient. Therefore, conventionally, there is a case where the small-diameter portion 85 is formed to be longer than necessary, and a measure such as truncating the region X on the shaft end side where accuracy is not ensured may be taken, but this reduces the yield, Processing cost increases.

JP 2002-349538 A JP 2006-64060 A JP 2007-247847 A

  For example, as described in Patent Document 3, the above-described problem can be solved by performing drawing in a state where an inner diameter restraining type (also referred to as a mandrel) is inserted into the inner periphery of the end of the steel pipe. If an inner diameter constraining type is inserted in the inner periphery of the end of the steel pipe, the inner diameter of the end of the steel pipe is plastically deformed to follow the outer diameter surface of the inner diameter constraining type. This is because the accuracy is improved as compared with the case of not using it.

  However, in the embodiment shown in FIG. 8, when drawing is performed in a state where an inner diameter constraining mold is inserted into the inner periphery of the end of the steel pipe, the load applied to the die is increased, and the life of the die may be shortened. Further, when molding the small diameter portion, the flow of the meat toward the inner diameter side is restricted by the inner diameter restraining mold, so that there is a demerit that the increase in the wall thickness is limited as compared with the case where the inner diameter restraining mold is not used. Even if the inner diameter restraint type is used, if a thicker steel pipe is used, a small-diameter portion with a predetermined accuracy can be formed, but this reduces the merit in terms of cost and weight by using a hollow shaft. .

  In view of the above, the main object of the present invention is to provide a manufacturing method capable of solving the above-mentioned various problems that occur when forming a small-diameter portion by drawing a steel pipe, thereby providing highly accurate and durable power. It is to be able to manufacture the transmission member at a low cost.

  In order to achieve the above object, in the present application, as a first invention, a power transmission member in which a connecting element for power transmission is provided on an outer diameter surface of a small diameter portion formed by drawing an end portion of a steel pipe In this manufacturing method, there is provided a method for manufacturing a power transmission member, characterized in that a small diameter portion is formed by drawing the end portion in a state where both end faces of the steel pipe are constrained. Here, the drawing process referred to in the present invention includes a pressing process in which the steel pipe is pushed in the axial direction with respect to the die, and a swaging that imparts a radially inward striking force at a high speed while rotating the steel pipe around its axis. Processing is included. Examples of the power transmission connecting element include splines and serrations in which crests (teeth) and troughs (tooth bottoms) extending in the axial direction are alternately formed in the circumferential direction. The same applies to the second invention described below.

  As described above, if drawing is performed on the end of the steel pipe (hereinafter also referred to as a work part) with both end surfaces constrained, the free movement of the meat of the work part accompanying the drawing is performed in the axial direction. Can be regulated. Therefore, it is possible to increase the thickness of the entire region in the axial direction of the processed portion almost evenly, and it is possible to obtain a small-diameter portion with higher accuracy than when the conventional method shown in FIG. 8 is adopted. As a result, it is not necessary to form the small-diameter portion to be longer than necessary, and it is not necessary to cut the accuracy inaccuracy region of the small-diameter portion, so that it is possible to simultaneously improve the yield and reduce the manufacturing cost. In addition, if the manufacturing method according to the present invention is used, it is possible to obtain a small-diameter portion with higher accuracy than in the case where the conventional method is adopted, and therefore, the necessity for inserting an inner-diameter constraining die on the inner periphery of the workpiece is low. Become. Therefore, it is possible to avoid the shortening of the die life and the weight and cost of the power transmission member.

  However, problems such as shortening the life of the die can be effectively solved by constricting both ends of the steel pipe and drawing the part to be processed with the inner diameter constraining die inserted into the inner periphery of the part to be processed. In addition, a small-diameter portion with higher accuracy can be formed. As described above, according to the manufacturing method of the present invention, it is possible to mold a small-diameter portion with higher accuracy than before. This is because it is sufficient to use a smaller diameter.

  The manufacturing method according to the first aspect of the present invention is a preferable method for forming a small-diameter portion having an outer diameter dimension larger than the inner diameter dimension of the workpiece, and when a larger drawing amount needs to be secured, Specifically, it is difficult to apply when molding a small diameter portion having an outer diameter smaller than the inner diameter of the workpiece. However, there are naturally cases where it is necessary to form a small-diameter portion having an outer diameter smaller than the inner diameter of the processed portion in order to further increase the strength (thickness). Therefore, it is necessary to improve even in such a case.

  Therefore, in the present application, as a second invention, in a method of manufacturing a power transmission member in which a connecting element for power transmission is provided on an outer diameter of a small diameter portion formed by drawing an end portion of a steel pipe, Provided is a method for manufacturing a power transmission member, characterized in that both ends of a steel pipe are constrained immediately after drawing is started, and the small diameter portion is formed by further drawing in that state. Here, “immediately after the drawing process is started” means that, for example, the tip of the steel pipe is drawn to form a small-diameter portion at the tip, and the constraining die is brought into contact with the end surface of the processed part of the steel pipe. It is intended to be when it becomes possible (see FIG. 5).

  In this case, although the accuracy is slightly inferior to the manufacturing method according to the first invention, a small-diameter portion with higher accuracy can be obtained as compared with the conventional method. Also in the manufacturing method according to the second aspect of the present invention, the processed portion may be drawn with the inner diameter restraining mold inserted in the inner periphery of the processed portion.

  In any of the production methods according to the present invention described above, the restraining force (holding force) on both end faces of the steel pipe during drawing is set to 1 MPa or more. Thereby, at the time of a drawing process, the precision fall of the small diameter part resulting from the flesh of the to-be-processed part escaping to an axial direction can be suppressed or prevented.

  The above-described method for manufacturing a power transmission member according to the present invention can be preferably applied when manufacturing an intermediate shaft in which a small diameter portion is formed at both end portions and two constant velocity universal joints are connected. The power transmission member manufacturing method according to the present invention includes an outer joint member for a constant velocity universal joint in which a small-diameter portion is formed at one end portion and a cup portion that accommodates a torque transmission member on the inner periphery is joined to the other end portion. The present invention can also be preferably applied when manufacturing the shaft portion.

  As described above, according to the present invention, it is possible to solve various problems that have occurred when forming a small-diameter portion by drawing a steel pipe. Therefore, it is possible to manufacture a power transmission member with high accuracy and durability at low cost.

It is a front view which shows the whole structure of a drive shaft. It is a front view of the intermediate shaft shown in FIG. It is sectional drawing which shows notionally the drawing process which concerns on 1st Embodiment of this invention, (a) A figure is a figure which shows the step before drawing, (b) The figure is a figure which shows the step in drawing is there. It is sectional drawing which shows notionally the drawing process which concerns on 2nd Embodiment of this invention, (a) A figure shows the stage before drawing, (b) The figure shows the stage in drawing is there. It is sectional drawing which shows notionally the drawing process which concerns on 3rd Embodiment of this invention, (a) A figure is a figure which shows the step before drawing, (b) A figure is a figure which shows the step in drawing. is there. It is sectional drawing which shows notionally the drawing process which concerns on 4th Embodiment of this invention, (a) A figure is a figure which shows the step before drawing, (b) The figure is a figure which shows the step in drawing is there. It is a front view of the outside joint member manufactured including the manufacturing method of the present invention. It is sectional drawing which shows the drawing process which concerns on the conventional method typically, (a) A figure shows the step before drawing, and (b) The figure shows the step in drawing.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  FIG. 1 shows the overall structure of a drive shaft as a power transmission device that transmits power (rotational torque) from an engine to drive wheels. This drive shaft is capable of transmitting torque to the sliding type constant velocity universal joint 10 arranged on the engine side, the fixed type constant velocity universal joint 20 arranged on the drive wheel side, and the two constant velocity universal joints 10, 20. An intermediate shaft 1 as a power transmission member to be connected is provided as a main configuration.

  The sliding type constant velocity universal joint 10 is a so-called tripod type (TJ), an outer joint member 11 having a cup portion 12 and a shaft portion 13, and a tripod member as an inner joint member accommodated in the inner periphery of the cup portion 12. 14 and a roller 16 as a torque transmission member as main components. The tripod member 14 is provided with three leg shafts 15 extending in the radial direction at equal intervals in the circumferential direction, and one roller 16 is rotatably fitted to the outer periphery of each leg shaft 15. Note that a double offset type (DOJ) may be used as the sliding constant velocity universal joint 10.

  The fixed type constant velocity universal joint 20 is a so-called Barfield type (BJ), and includes an outer joint member 21 having a cup portion 22 and a shaft portion 23, an inner joint member 24 accommodated in the inner periphery of the cup portion 22, and a cup. A ball 25 serving as a torque transmitting member disposed between the portion 22 and the inner joint member 24, and an inner diameter surface of the cup portion 22 and an outer diameter surface of the inner joint member 24. And a cage 26 that holds the same direction. An undercut free type (UJ) may be used as the fixed type constant velocity universal joint 20.

  Splines 2 are integrally provided on the outer diameters at both ends of the intermediate shaft 1 as connecting elements for power transmission. The spline 2 on one end side is fitted into the hole of the tripod member 14 of the sliding type constant velocity universal joint 10, so that the intermediate shaft 1 and the tripod member 14 of the sliding type constant velocity universal joint 10 can transmit torque. Connected to The spline 2 on the other end side is fitted into the hole of the inner joint member 24 of the fixed type constant velocity universal joint 20, whereby the intermediate shaft 1 and the inner joint member 24 of the fixed type constant velocity universal joint 20 are torqued. It is connected so that it can be transmitted.

  Both constant velocity universal joints 10 and 20 are filled with a lubricant such as grease. In order to prevent external leakage of the lubricant and entry of foreign matter from the outside of the joint, the outer joint member between the outer joint member 11 of the sliding type constant velocity universal joint 10 and the intermediate shaft 1 and the outer joint member of the fixed type constant velocity universal joint 20. Cylindrical boots 8 and 9 are respectively mounted between the intermediate shaft 21 and the intermediate shaft 1.

  FIG. 2 shows the intermediate shaft 1 shown in FIG. The intermediate shaft 1 is a shaft-shaped member formed from a steel pipe (pipe material) and has a hollow in the entire axial direction. The intermediate shaft 1 is disposed at the axially intermediate portion and at both axial ends, And a small diameter portion 4 having a spline 2 formed on the radial surface. The large diameter portion 3 and each small diameter portion 4 are connected via a taper portion 5, a boot fixing portion 6 and a minimum diameter portion 7. As the steel pipe for forming the intermediate shaft 1, for example, one made of carbon steel for mechanical structure such as SKTM or STMA or one made of alloy steel for mechanical structure such as SCr or SCM can be used.

  A hardened layer is formed on the intermediate shaft 1. In the present embodiment, the hardened layer is a portion indicated by hatching in FIG. 2, specifically, the entire axial direction of the intermediate shaft 1 and the entire thickness from the inner diameter surface to the outer diameter surface. Is formed. The hardened layer is only required to be formed at a site where strength is particularly required, and does not necessarily have to be formed over the entire axial direction of the intermediate shaft 1. Although illustration is omitted, for example, it is not necessary to form a hardened layer in a portion of the small diameter portion 4 on the shaft end side with respect to the region where the spline 2 is formed on the outer diameter surface. Further, the hardened layer does not necessarily have to be formed over the entire thickness of the intermediate shaft 1, and the hardened layer may not be formed on a partial thickness on the inner diameter side of the intermediate shaft 1. This is effective in preventing the occurrence of burning cracks during the thermosetting process.

  The intermediate shaft 1 having the above-described configuration can be manufactured, for example, as follows. First, an intermediate formed body having a large diameter portion 3 and a small diameter portion 4 integrally formed by drawing (plastic working) a predetermined portion in the axial direction of the steel pipe, and then the outer diameter surface of the small diameter portion 4 of the intermediate formed body The spline 2 is formed by performing a rolling process or the like. And after giving thermosetting processes, such as induction hardening, carburizing hardening, or carbonitriding hardening, to a predetermined part, the intermediate shaft 1 as a finished product is obtained by performing an appropriate finishing process as needed.

  Of the manufacturing steps of the intermediate shaft 1 manufactured as described above, the step of drawing the steel pipe, which is the gist of the present invention, to form an intermediate formed body, in particular, drawing the end of the steel pipe. The step of forming the small diameter portion 4 will be described in detail below.

  3A and 3B are cross-sectional views conceptually showing the drawing process according to the first embodiment of the present invention. The forming apparatus shown in the figure is a so-called pressing apparatus or a die 40 provided with a pressing part 40a for pressing the end part of the steel pipe 30 radially inward to form the reduced diameter part 4, and the die 40. The holding die 41 and the end face constraining die 42 that are coaxially arranged on one end side and the other end side of the main body are provided as main components. The holding die 41 and the end face constraining die 42 are respectively attached to an appropriate driving mechanism (not shown) and can move in the axial direction.

  The forming apparatus (die 40) of this embodiment is for forming a small diameter portion 4 having an outer diameter larger than the inner diameter d of the steel pipe 30 at the end of the steel pipe 30. Therefore, the inner diameter D1 of the pressurizing portion 40a of the die 40 is set to be smaller than the outer diameter d1 of the end of the steel pipe 30 and larger than the inner diameter d of the end of the steel pipe 30. (D <D1 <d1). The outer diameter dimension D2 of the end face constraining die 42 is set to be smaller than the inner diameter dimension D1 of the pressurizing portion 40a and larger than the inner diameter dimension d of the end portion of the steel pipe 30 (d <D2 <D1). ).

  In the above configuration, first, as shown in FIG. 3A, the holding die 41 holds the one end 30 a of the steel pipe 30 so as to constrain the one end face 30 a 1, and then the holding die 41 and the steel pipe 30 are put into a die 40. Move close to it. Before the other end 30b of the steel pipe 30 reaches the pressurizing part 40a of the die 40, the end face constraining mold 42 is moved to the holding mold 41 side, and the both end faces 30a1 and 30b1 of the steel pipe 30 are moved to the holding mold 41 and the end face constraining type. 42 is restrained (clamped). In this state, as shown in FIG. 3B, the holding die 41 and the end face constraining die 42 are moved synchronously to the right side in the drawing, and the other end 30 b of the steel pipe 30 is pushed into the pressurizing portion 40 a of the die 40. Thereby, the other end part 30b of the steel pipe 30 is drawn, and the small diameter part 4 having an outer diameter corresponding to the inner diameter D1 of the pressurizing part 40a is formed.

  Although illustration is omitted, after the small diameter portion 4 is formed on the other end portion 30b of the steel pipe 30, the steel pipe 30 can be discharged from the die 40 by moving the end face constraining die 42 to the holding die 41 side.

  In this way, if the end portion of the steel pipe 30 is subjected to drawing processing in a state in which both end faces 30a1, 30b1 of the steel pipe 30 are constrained, the meat of the steel pipe end portion (processed portion) to which drawing processing is performed, It is possible to restrict the axial movement freely along with the drawing process. Therefore, it is possible to increase the thickness of the entire area in the axial direction of the processed part substantially evenly, and the thickness difference in the axial direction is small (or no thickness difference) compared to the case where the conventional method shown in FIG. 8 is adopted. ) A highly accurate small diameter portion 4 can be obtained. As a result, it is not necessary to form the small-diameter portion to be longer than necessary, and to cut the poorly-accurate portion on the shaft end side of the small-diameter portion after the drawing process as in the prior art. Accordingly, it is possible to simultaneously improve the yield and reduce the manufacturing cost.

  The restraining force of both end faces 30a1 and 30b1 of the steel pipe 30 at the time of drawing is set to 1 MPa or more. By doing so, it is possible to effectively prevent free axial movement of the meat of the processed part due to drawing, which is effective in increasing the accuracy of the small diameter part 4.

  Further, with the method described above, it is possible to form the small-diameter portion 4 with higher precision than the conventional method shown in FIG. 8, and therefore drawing is performed with the inner diameter constraining mold inserted in the inner periphery of the workpiece. The necessity to apply, that is, the necessity to regulate the plastic flow to the inner diameter side of the meat accompanying drawing is reduced. Therefore, the life of the die 40 can be extended.

  However, as shown in FIGS. 4 (a) and 4 (b), drawing is performed in a state where the inner diameter restraining mold is inserted into the inner periphery of the portion to be processed (end portion 30a or 30b) while restricting both end faces 30a1 and 30b1. You may do it. In the molding apparatus shown in the figure, in addition to the end face restraint mold 42 shown in FIG. 3, an inner diameter restraint mold 43 is arranged. The inner diameter restricting die 43 is inserted into the inner periphery of the end face restricting die 42 so as to be relatively movable, and is held in a state of protruding from the end face restricting die 42 toward the holding die 41 in the illustrated example. The protruding amount of the inner diameter restraint die 43 is in a state in which the end face restraint die 42 is in contact with the end face of the steel pipe 30 (a state where both end faces 30a1 and 30b1 of the steel pipe 30 are restrained by the holding die 41 and the end face restraint die 42). It is set to such a value that the tip portion is inserted into the steel pipe 30 up to a position exceeding the inner end of the small diameter portion 4 to be molded. Further, the outer diameter dimension D3 of the inner diameter restraining die 43 is set to a value that is smaller than the inner diameter dimension d of the end portion of the steel pipe 30 and corresponds to the inner diameter dimension of the small diameter portion 4 to be molded.

  In the above configuration, first, as shown in FIG. 4A, the holding die 41 holds the one end 30 a of the steel pipe 30 so as to constrain the one end face 30 a 1, and then the holding die 41 and the steel pipe 30 are put into a die 40. Move close to it. Before the other end portion 30b of the steel pipe 30 reaches the pressurizing portion 40a of the die 40, the end surface constraining die 42 is moved to the holding die 41 side, and the end surface constraining die 42 is brought into contact with the other end surface 30b1 of the steel pipe 30. As a result, the inner diameter restraint die 43 is inserted into the inner periphery of the other end 30 b of the steel pipe 30, and both end faces 30 a 1, 30 b 1 of the steel pipe 30 are restrained and clamped by the holding die 41 and the end face restraint die 42. In this state, when the holding die 41 and the end face constraining die 42 are moved synchronously to the right side in the drawing and the other end 30b of the steel pipe 30 is pushed into the pressurizing part 40a of the die 40, the other end 30b of the steel pipe 30 is drawn. The small diameter portion 4 is formed (see FIG. 4B).

  If the drawing is performed in this manner, the thickness of the other end 30b of the steel pipe 30 is plastically deformed (plastic flow) so as to follow the outer diameter surface of the inner diameter constraining die 43. Compared to the case where no mold is used, the small-diameter portion 4 with higher accuracy can be formed. At this time, it is possible to obtain a high-precision small-diameter portion 4 having a small thickness difference in the axial direction or no thickness difference by the amount of drawing performed in a state where both end faces 30a1 and 30b1 of the steel pipe 30 are constrained. Therefore, as the inner diameter restraining die 43, it is sufficient to use a small-diameter one that has a small contact allowance with the inner diameter surface of the processed portion of the steel pipe 30 at the time of drawing. Therefore, it is possible to prevent as much as possible problems such as shortening of the die life, which is a concern when drawing with the inner diameter constraining die inserted into the inner circumference of the other end of the steel pipe holding and restraining only one end. Can do.

  In this case as well, as in the case shown in FIG. 3, the restraining force of the both end faces 30a1 and 30b1 of the steel pipe 30 at the time of drawing is set to 1 MPa or more.

  In the embodiment described above, the end face constraining die 42 arranged on the other end side of the die 40 is moved before the other end portion 30b of the steel pipe 30b reaches the pressurizing portion 40a of the die 40. The both end surfaces 30a1 and 30b1 of the steel pipe 30 are constrained and clamped, but the end surface constraining mold 42 is a position where the other end surface 30b1 of the steel pipe 30 is constrained in advance, specifically, a solid line in FIG. You may make it wait in the position shown (or the position shown to Fig.4 (a)).

  FIG. 5 is a modification of the embodiment shown in FIG. 3 and is for securing a larger drawing amount than the embodiment described above. Specifically, the end portions 30a and 30b of the steel pipe 30 are connected to the ends thereof. It is a schematic sectional drawing of the shaping | molding apparatus for shape | molding the small diameter part 4 of an outer diameter dimension smaller than the part internal diameter dimension d. In this case, the inner diameter dimension D1 of the pressing portion 40a of the die 40 is set to be smaller than the inner diameter dimension d of the end portion of the steel pipe 30 (D1 <d).

  When the small diameter portion 4 having an outer diameter smaller than the inner diameter d is formed by drawing at the end of the steel pipe 30 as in the present embodiment, the embodiment shown in FIG. As described above, it is physically difficult to constrain both end faces 30a1 and 30b1 of the steel pipe 30 from the stage before drawing. Therefore, at the start / initial stage of drawing shown in FIG. 5A, the end face constraining die 42 is disposed (standby) in the vicinity of the outlet of the pressurizing unit 40a.

  In this embodiment, the small diameter portion 4 can be formed as follows. First, as shown in FIG. 5A, after holding one end 30a of the steel pipe 30 so as to restrain the one end face 30a1 by the holding mold 41, the holding mold 41 and the steel pipe 30 are moved closer to the die 40. The other end 30 b of the steel pipe 30 is pushed into the pressurizing part 40 a of the die 40. Then, when the tip of the other end portion 30b of the steel pipe 30 is drawn, the end face constraining die 42 that has been waiting in the vicinity of the outlet of the pressurizing portion 40a is brought into contact with the other end face 30b1 of the steel pipe 30 to The both end faces 30a1 and 30b1 of the 30 are restrained and clamped by the holding mold 41 and the end face restraining mold 42. The restraining force at this time is set to 1 MPa or more as in the embodiment described above. In this state, the holding die 41 and the end face constraining die 42 are moved synchronously to push the remaining part of the other end 30b of the steel pipe 30 into the pressurizing part 40a of the die 40, thereby forming the small diameter part 4 having a predetermined length.

  In this case, at the initial stage of drawing, the other end face 30b1 of the steel pipe 30 has to be constrained, so that the accuracy of the small diameter portion 4 is slightly inferior to the case where the manufacturing method shown in FIG. 3 is adopted. As a result, it is sufficiently higher than the conventional method shown in FIG. Therefore, it is not necessary to form the small-diameter portion 4 as long as the conventional method shown in FIG. Moreover, even if it becomes necessary to cut the small diameter part 4, the cutting length becomes much shorter than when the small diameter part is formed by the conventional method. Accordingly, it is possible to simultaneously improve the yield and reduce the manufacturing cost.

  Even when the small-diameter portion 4 having an outer diameter smaller than the inner-diameter dimension d is formed at the end of the steel pipe 30, as shown in FIG. Drawing can be performed in the state. The molding apparatus of the present embodiment is substantially a combination of the configurations shown in FIGS. 4 and 5, and as shown in FIG. 6A, the die 40 is added at the start / initial stage of drawing. An end face constraining mold 42 and an inner diameter constraining mold 43 are arranged in the vicinity of the outlet of the pressure part 40a. The inner diameter constraining die 43 protrudes closer to the holding die 41 than the pressurizing portion 40a, and can be inserted into the inner periphery of the work portion of the steel pipe 30 before the start of drawing.

  In the molding apparatus having the above configuration, first, as shown in FIG. 6A, after holding the one end 30a of the steel pipe 30 so as to restrain the one end face 30a1 by the holding mold 41, the holding mold 41 is driven. Then, the other end 30 b of the steel pipe 30 is pushed into the pressurizing part 40 a of the die 40. When the steel pipe 30 moves closer to the die 40 to some extent, the inner diameter restraining die 43 is inserted into the inner periphery of the other end 30b of the steel pipe 30. When the drawing is performed on the tip of the other end 30b of the steel pipe 30, the end face restraint die 42 comes into contact with the other end face 30b1 of the steel pipe 30, and the both end faces 30a1 and 30b1 of the steel pipe 30 are the holding die 41 and the end face restraint type. 42 is restrained and clamped. The restraining force at this time is also set to 1 MPa or more as in the embodiment described above. In this state, the holding die 41 and the constraining die 43 are moved synchronously to push the remaining part of the other end 30b of the steel pipe 30 into the pressing part 40a of the die 40, thereby forming the small diameter part 4 having a predetermined length.

  Which of the manufacturing methods described above is adopted may be selected according to the small diameter portion 4 (the outer diameter size) to be formed. When forming the small diameter part 4 in the one end part 30a and the other end part 30b of the steel pipe 30, the manufacturing method to be selected may be the same or different from each other.

  In the above, the configuration of the present invention is applied when the small diameter portion 4 is formed by pressing the steel pipe 30 against the die 40 in the axial direction. However, the configuration of the present invention rotates the steel pipe 30 around its axis. However, it can be preferably applied also when the small-diameter portion 4 is formed by swaging processing that imparts a striking force inward in the radial direction at a high speed. In the swaging machine, the die 40 is divided into a plurality of parts such as four or six in the circumferential direction.

  The manufacturing method according to the present invention described above is not limited to be applied only when the hollow intermediate shaft 1 is manufactured. Other power transmission members, for example, outer joint members as shown in FIG. 7 are manufactured. This can also be preferably applied. The outer joint member 50 shown in the figure can be incorporated into the slide-type constant velocity universal joint 10 of the drive shaft shown in FIG. 1 and can accommodate the inner joint member and the torque transmission member on the inner periphery. 51 and a hollow shaft portion 52 extending in the axial direction from the bottom portion of the cup portion 51. The cup part 51 and the shaft part 52 are joined and integrated by friction welding or welding (here, friction welding). A small-diameter portion 4 is formed on the end portion of the shaft portion 52 on the side opposite to the cup portion 51 by the method described above with reference to FIGS. 3 to 6, and power transmission is performed on the outer diameter surface of the small-diameter portion 4. Connecting elements (here, spline 2) are integrally provided.

  In the above, the manufacturing method according to the present invention is applied when manufacturing various power transmission members constituting the drive shaft. However, the present invention is applicable to various power transmissions constituting other power transmission devices such as a propeller shaft. It can be preferably applied also when manufacturing a member.

1 Intermediate shaft (power transmission member)
2 Splines (connecting elements)
3 Large-diameter portion 4 Small-diameter portion 10 Sliding constant velocity universal joint 11 Fixed constant velocity universal joint 30 Steel pipe 30a One end portion 30a1 One end surface 30b Other end portion 30b1 Other end surface 40 Die 40a Pressurizing portion 41 Holding mold 42 End surface constraining type 43 ID restriction type

Claims (8)

In the manufacturing method of the power transmission member in which the connecting element for power transmission is provided on the outer diameter surface of the small diameter part formed by drawing the end of the steel pipe,
A method for manufacturing a power transmission member, comprising forming a small-diameter portion by drawing the end portion in a state where both end faces of the steel pipe are constrained.   The method for manufacturing a power transmission member according to claim 1, which is applied when forming a small-diameter portion having an outer diameter dimension larger than an inner diameter dimension of the end portion. In the manufacturing method of the power transmission member in which the connecting element for power transmission is provided on the outer diameter surface of the small diameter part formed by drawing the end of the steel pipe,
A method for manufacturing a power transmission member, comprising: constraining both end faces of a steel pipe immediately after drawing of the end portion is started, and further forming the small diameter portion by further drawing in that state.   The method for manufacturing a power transmission member according to claim 3, which is applied when forming a small diameter portion having an outer diameter smaller than an inner diameter of the end.   The manufacturing method of the power transmission member as described in any one of Claims 1-4 which set the binding force of the both end surfaces of a steel pipe to 1 Mpa or more.   The method for manufacturing a power transmission member according to any one of claims 1 to 5, wherein a drawing process is performed on the end portion in a state where an inner diameter restraining mold is inserted in an inner periphery of the end portion.   The power transmission member according to any one of claims 1 to 6, wherein the steel pipe has a small-diameter portion formed at both ends thereof and constitutes an intermediate shaft that couples the two constant velocity universal joints so as to transmit torque. Manufacturing method.   The steel pipe constitutes a shaft portion of an outer joint member for a constant velocity universal joint in which a small diameter portion is formed at one end portion and a cup portion that accommodates a torque transmission member on the inner periphery is joined to the other end portion. The manufacturing method of the power transmission member as described in any one of Claims 1-6.

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