JP2006224159A - Flat die for worm shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat die for rolling with which there is no need of providing a work with a flat part in a fixed width, thus the limitation of workpiece shape is reduced, and its bending by rolling is reduced, thus the straightening of bending is made needless. <P>SOLUTION: The edge parts of a screw part 71 forming a die tooth flank 71 at the upper face of a die 7 on the side opposite to the moving directions mc, op by rolling in a worm shaft 10 are made into boundary lines 23, 24 continuously changed corresponding to moving loci formed in the edge parts of a rolled part 2 on the circumferential face of a columnar stock according to rolling, and relief faces 20, 21 are formed on the upper face of the die other than the boundary lines 23, 24. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a flat die for rolling a worm shaft, which is a shaft with a worm gear.

  2. Description of the Related Art Conventionally, a worm shaft, which is a shaft with a worm gear used for a small motor or the like, has a worm gear formed on a peripheral rolling portion of a cylindrical material by rolling. That is, the cylindrical material is moved in opposite directions while being pressed by a pair of rolling flat dies, thereby rotating the cylindrical material to form a worm gear at the peripheral surface rolling portion.

When the worm shaft is formed by the conventional rolling process, as shown in FIG. 1, due to the load imbalance at the end of the rolling die, the worm shaft is cut off, that is, the circumferential rolling of the cylindrical material. Bending 5 occurs at the end of part 2. Since the bend 5 generated in the worm shaft 10 causes abnormal vibration and noise when incorporated in a small motor, a process such as bending correction is required to keep the bend 5 of the worm shaft 10 within a certain level. There was a problem that there was. As means for solving such a problem, Patent Document 1 proposes a method of correcting the bending with a correction die attached to a flat die during rolling by using the walking generated by rolling the worm shaft. However, in this method, it is necessary to provide a flat part with a certain width as a pressing part of the correction die adjacent to the worm shaft machining part, that is, the peripheral surface rolling part of the cylindrical material, and it is limited to the applicable workpiece. Was necessary. Also, in the worm rolling process, as the machining progresses, the rolling radius corresponding to the lead angle of the flat die and the actual rolling radius shift, causing the workpiece to move in the axial direction, and the effective gear width of the war gear There was a problem of shortening.
JP 2003-145242 A

The object of the present invention is to solve such a conventional problem, there is no need to provide a flat portion having a constant width on the workpiece, there are few restrictions on the work shape, the bending by the rolling process is small, and the bending correction is unnecessary. It is to provide a flat die.
Another object of the present invention is to provide a rolling flat die in which the effective tooth width is not shortened by walking by rolling.

  For this reason, the present invention relates to a rolling die for a worm shaft that is arranged between a pair of dies and forms a worm gear on a peripheral rolling portion of a cylindrical material. The end of the screw part that forms the die tooth surface of the upper surface of the die is a boundary line that is continuously changed to match the walking locus formed by the rolling process of the peripheral surface rolling part of the cylindrical material. The above problem has been solved by providing a flat die for a worm shaft, wherein a relief surface is formed on the upper surface of the die outside the boundary line.

  In the present invention, the end of the threaded portion forming the die tooth surface of the die upper surface opposite to the walking direction by the rolling process of the worm shaft is formed by the rolling process of the peripheral surface rolling part end of the cylindrical material. As the boundary line is continuously changed to match the walking trajectory, and the relief surface is formed on the upper surface of the die outside the boundary line, the cut-off portion on the opposite side to the walking direction, that is, the peripheral surface of the cylindrical material The amount of rolling at the end of the rolled portion is no longer increased, the bending of the worm shaft is reduced, and bending correction becomes unnecessary. Further, even if the worm shaft moves in the axial direction, depending on the position of the worm gear from the beginning to the end of rolling, only the range where the worm gear should be formed, that is, the peripheral surface rolling portion of the cylindrical material, is the die tooth. Therefore, the force that generates the bend of the cut-off part on the opposite side to the walking direction is not applied greatly, the tooth width does not change with walking, and the effective tooth width necessary for the worm is increased. It became possible to secure.

  That is, in rolling the worm shaft, the rolling radius of the actual work piece changes as the machining progresses with respect to the designed rolling radius corresponding to the lead angle of the flat die, and the worm shaft moves in the axial direction. Although the walking phenomenon is known, the major factor of the bending that occurs during rolling of the worm shaft is the unbalance load that occurs at the worm end cut-off, and the unbalance load depends on the walking direction of the worm shaft. Pay attention to the fact that the worm gear becomes larger at the end of the worm gear on the opposite side, and in order to reduce the amount of rolling at the end of the worm gear, even if the worm shaft moves in the axial direction during rolling, Depending on the position of the shaft, the other teeth so that the teeth of the die, that is, the thread portion forming the die tooth surface of the upper surface of the die, act only in the range where the worm gear should be formed. Scan relief surface is formed on the upper surface portion was allowed to escape by chamfering.

  Preferably, the lead angle of the flat die or the material of the columnar material is set so that the walking direction of the worm shaft during rolling is one direction. That is, by setting the lead angle of the rolling flat die or appropriately setting the material of the columnar material, walking during rolling can be made in one direction. In this case, it is sufficient to provide the chamfering relief of the flat die only on the side opposite to the walking direction side, so that the die can be easily manufactured.

  The present invention will be described with reference to FIGS. FIG. 2 is a cross-sectional view of an essential part of a worm shaft rolling flat die showing an embodiment of the present invention. A worm shaft 10 which is a shaft with a worm gear used for a small motor or the like is formed by rolling a cylindrical material. A worm gear 4 is formed on the surface rolling part 2. The workpiece 8 which is a cylindrical material has workpiece patterns 1 and 3 at both ends. The workpiece patterns 1 and 3 are rotatably held by a center holding device (not shown), and the rolled portion 2 of the workpiece 8 is Rolling flat dies 6 and 7 are sandwiched and rolled to move them in the opposite directions while pressing, thereby rotating the cylindrical material to plastically process the worm gear 4 on the peripheral surface rolling part 2 of the worm shaft 10 To form. In general, in the rolling processing of screws and worm shafts, a so-called walking phenomenon is known in which the workpiece 8 moves in the axial direction along the workpiece axis during processing. Normally, the lead angle α of the die teeth of the flat die, that is, the thread portion forming the die tooth surface on the upper surface of the die, is manufactured constant, so that the rolling radius of the workpiece 8 changes as the rolling process proceeds, The workpiece moves in the axial direction, and a walking phenomenon occurs. According to the observations by the inventors, when the rolling process is performed such that the workpiece walking direction is 11 as shown in FIG. 1, the worm gear 4 and the handle 3 are located in the vicinity of the workpiece walking direction. It turns out that the bending of the work 5 occurs.

  FIG. 3A is a side view of the main part of the first embodiment of the present invention as viewed in the direction of arrow A in FIG. 2, that is, the lower die 7 as an elevation view, and FIG. 7 shows a cross section of the lower die 7 at the radial movement positions a, b, and c by rolling the workpiece during machining. 4A is a graph showing the amount of walking, which is the amount of movement that the workpiece in FIG. 3A moves in the axial direction by rolling, and FIG. 4B is the axis by which the workpiece in FIG. 5A is rolled. It is a graph which shows the walk amount which is the movement amount which moves to a direction.

  In the first embodiment, as shown in FIG. 3, the relative positional relationship between the flat die 7 and the work 13 changes as the machining progresses as 13 → 14 → 15. Focusing on the relative positional relationship between the flat die and the workpiece in the axial direction of the workpiece, the workpiece walks in the direction mc in the figure from the machining start position 13 to the position 14, and the position 15 near the machining end position from the machining position 14. In the meantime, the work walks in the op direction of the figure. That is, assuming that the part where the worm gear 4 is to be machined is 72, the machined part 72 moves in the axial direction in the middle of the workpiece 13 → 14 → 15 as the machining progresses. At this time, the movement of the workpiece in the axial direction draws a curve as shown in FIG. As a feature of the present embodiment, the end of the screw portion 71 that forms the die tooth surface 71 of the upper surface of the die 7 on the side opposite to the walking direction mc, op by the rolling process of the worm shaft 10 is rolled on the circumferential surface of the cylindrical material. Part 2 Boundary lines 23 and 24 that are continuously changed to match the walking trajectory formed by the rolling process, and the screw part that forms the die tooth surface 71 on the upper surface of the die 7 on the same side as the walking direction mc The boundary line of 71 end was set to 22, and relief surfaces 19, 20, and 21 were formed on the die upper surface outside the boundary lines 22, 23, and 24. By this chamfering, only the portion 72 where the worm 4 is to be processed is brought into contact with the flat die 7 so as to be involved in the processing. As shown in the cross section of FIG. 3 (b), the chamfer relief surfaces 19, 20, and 21 are formed so that the size of the chamfer relief surfaces 19, 20, and 21 changes continuously with the traveling direction of the dice. For this reason, even if walking occurs in the workpiece, only the necessary and sufficient range is always rolled, so the bending of the workpiece is very small and the bending of the rounded portion on the opposite side to the walking direction is made. Therefore, the tooth width does not change with walking, and the effective tooth width necessary for the worm can be secured. In this embodiment, the boundary lines 22, 23, and 24 of the chamfer relief surfaces 19, 20, and 21 are formed to be curved, but they are formed by straight lines or combinations of straight lines that are easy to manufacture. However, almost the same effect can be obtained.

  FIG. 5A is a side view of the main part of the second embodiment of the present invention as viewed in the direction of the arrow A in FIG. 2, that is, the lower die 7a as an elevation view, and FIG. The cross section of the lower die 7a at the radial movement positions a ′, b ′, and c ′ is shown by rolling the workpiece during the machining. Lower die 7a lead angle β is set slightly larger than lead angle α of the first embodiment (or a workpiece material may be selected instead) so that the walking direction is only on the op side during rolling. It is a thing. FIG. 4B is a graph showing a walking amount that is a movement amount in which the workpiece in FIG. 5A moves in the axial direction by rolling. In the second embodiment, as shown in FIG. 5A, the relative positional relationship between the flat die 7a and the workpiece 16 changes as machining progresses in the order of 16 → 17 → 18. At this time, the work walks in the op direction in the figure. That is, if the worm 4 is a part 2 to be machined, the machined part 2 moves from 16 to 17 to 18 as the machining proceeds to the op side. At this time, the movement of the workpiece in the axial direction draws a curve as shown in FIG. In the present embodiment, the flat die 7a has an end portion of the screw portion 73 that forms the die tooth surface 73 on the upper surface of the die 7a opposite to the walking direction op by the rolling process of the worm shaft 10, and the peripheral surface of the cylindrical material. Rolling part 2 Thread part that forms the die tooth surface 73 on the upper surface of the die 7a on the same side as the walking direction op, with the boundary line 27 continuously changed in accordance with the walking locus formed by the rolling process The boundary line at the end of 73 is 28, and relief surfaces 25 and 26 are formed on the upper surface of the die outside the boundary lines 27 and 28. By this chamfering, only the portion 74 where the worm 4 is to be processed comes into contact with the flat die 7a and is involved in the processing. As shown in the cross section of FIG. 5 (b), the chamfer relief surfaces 25 and 26 are formed so that the size of the chamfer relief surfaces 25 and 26 changes continuously with the direction of travel of the die. For this reason, even if a work occurs, only a necessary and sufficient range is always rolled, so that the bending of the work becomes very small and the necessary tooth width can be secured. In this embodiment, the boundary lines 27 and 28 are formed so as to be curved. However, even if the boundary lines 27 and 28 are formed along a straight line along the curved line, substantially the same effect can be obtained. In the second embodiment of the present invention, the threaded end portion 75 forming the die tooth surface of the upper surface of the die on the same side as the walking direction by the rolling process of the worm shaft is used as the peripheral surface rolled portion on the same side of the workpiece. The boundary line 27 was continuously changed in accordance with the walking locus formed by the rolling process at the end 2a, and the relief surface 25 was formed on the upper surface of the die outside the boundary line 27. Thereby, a required tooth width can be secured in a wider range. Even if the chamfered portion is only 26 on the side opposite to the step and the chamfered portion 25 is omitted, the same effect can be obtained with respect to prevention of bending of the workpiece.

The top view of the worm shaft which formed the worm shaft by the conventional rolling process. The principal part sectional view of the flat die for worm shaft rolling which shows the embodiment of the present invention. FIG. 3A is a side view of the main part of the first embodiment of the present invention as viewed in the direction of the arrow A in FIG. 2, that is, the lower die 7 as an elevation view, and FIG. The work shows a cross section of the lower die 7 at the radial movement positions a, b, c by rolling. FIG. 3A is a graph showing a walking amount, which is a movement amount in which the workpiece in FIG. 3A moves in the axial direction by rolling, and FIG. 5B is an axial direction in which the workpiece in FIG. 5A is rolled. It is a graph which shows the amount of walking which is the amount of movement to move. (A) is the principal part side view which looked at the A direction of FIG. 2 of the 2nd Embodiment of this invention, ie, the lower die 7 as an elevation view, (b) is the process in (a) The cross section of the lower die 7a at the radial movement positions a ′, b ′, and c ′ by rolling the workpiece is shown.

Explanation of symbols

1, 3: Cylindrical handle 2: Rolled surface of cylindrical material
4: Worm gears 6, 7, 7a: Flat dies for rolling
8, 13, 14, 15, 16, 17, 18: Work 10: Worm shaft
23, 24, 27, 28: Border 19, 20, 21, 25, 26: Relief surface
71, 73: Die tooth surface (thread part)
mc, op: walking direction
α, β: Die tooth surface lead angle

Claims (3)

  In a worm shaft rolling flat die that is placed between a pair of dies to form a worm gear on the peripheral rolling surface of a cylindrical material, the die teeth on the upper surface of the die opposite to the walking direction by the worm shaft rolling process The thread end that forms the surface is a boundary line that is continuously changed to match the walking trajectory formed by the rolling process of the peripheral surface rolling portion of the cylindrical material, and outside the boundary line A flat die for a worm shaft, wherein a relief surface is formed on the upper surface of the die.   The flat die for a worm shaft according to claim 1, wherein the lead angle of the flat die or the material of the columnar material is set so that the walking direction of the worm shaft during rolling is one direction.   The end of the threaded portion that forms the die tooth surface of the upper surface of the die on the same side as the walking direction by the rolling process of the worm shaft is formed by the rolling process on the end of the circumferential surface of the cylindrical material. The flat die for a worm shaft according to claim 1 or 2, wherein a boundary line that is continuously changed in accordance with a walking locus is formed, and a relief surface is formed on the upper surface of the die outside the boundary line.

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