JP2008055649A - Worm wheel molding mold and molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold which can accurately resin-mold a worm wheel with an undercut part formed at an addendum and a method for molding the worm wheel. <P>SOLUTION: The worm wheel molding mold 100 has a mold 10 in which a base part 11 and a plurality of extension parts 12 extending from the base part 11 and forming a tooth groove 5 between tooth parts 2 and 2 are formed and which can be separated in the axial direction from the molded worm wheel 1 and a mold 20 in which a cylinder part 21 having an inner circumference surface 23 for forming the addendum 3 and a plurality of projections 22 projecting inward in the radial direction from the inner circumference surface 23 of the cylinder part 21 and forming the undercut part 4 at the addendum 3 are formed and which is combined with the mold 10 to make the cylinder part 21 surround the extension parts 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a molding die and a molding method for resin molding a worm wheel.

A known worm wheel mold is described in Patent Document 1 described later. This molding die includes a slide core for forming a plurality of teeth (tooth gaps, tooth tips) of the worm wheel. A plurality of slide cores are provided corresponding to each tooth portion, and are arranged radially. Each slide core moves independently in the radial direction.
JP 2002-254478 A

  However, in the above-described molding die, the plurality of slide cores for forming the tooth portions move independently of each other. Therefore, when the worm wheel is molded with resin, the accuracy between the tooth portions tends to vary, and the teeth It was difficult to ensure the accuracy of the entire department.

  In particular, when an undercut portion is provided at the tooth tip in order to further increase the meshing area with the worm, the structure of each slide core becomes more complicated, making it difficult to ensure the accuracy of the entire tooth portion. It was.

  Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a molding die and a molding method that can more accurately resin-mold a worm wheel provided with an undercut portion on a tooth tip. .

  In order to solve the above-mentioned problem, the first technical means taken in the present invention is to resin-mold a worm wheel in which an undercut portion is provided at a tooth tip of a tooth portion as described in claim 1. The worm wheel molding die is provided with a base portion and a plurality of extending portions that extend from the base portion to form tooth spaces between the tooth portions, and are formed axially from the worm wheel after molding. A first mold that can be detached, a cylindrical portion having an inner peripheral surface for forming the tooth tip, and an undercut portion that protrudes radially inward from the inner peripheral surface of the cylindrical portion to form the undercut portion. And a second mold combined with the first mold so that the cylindrical portion surrounds the extending portion.

  In the worm wheel molding die, the second die is arranged such that the convex portions are positioned between the adjacent extension portions in the first die with respect to the circumferential direction of the second die. It may be combined with the first mold. The extension portion extends from the base portion along a direction in which the tooth groove of the worm wheel extends, and an end portion of the plurality of extension portions opposite to the base portion is the first portion. It is good to isolate | separate regarding the circumferential direction of the type | mold of each.

  In order to solve the above-mentioned problem, the second technical means taken in the present invention is to resin-mold a worm wheel in which an undercut portion is provided at a tooth tip of a tooth portion as described in claim 4. The worm wheel forming method is provided with a base portion and a plurality of extending portions extending from the base portion to form tooth spaces between the tooth portions, and separated from the worm wheel after forming in an axial direction. A first mold that can be formed, a cylindrical portion having an inner peripheral surface for forming the tooth tip, and an undercut portion that protrudes radially inward from the inner peripheral surface of the cylindrical portion to form the undercut portion. And a second die that is combined with the first die so that the cylindrical portion surrounds the extension portion, and the worm after molding the first die A first step of disengaging from the wheel and a line following the first step. Following the second step, the second step of rotating the second die relative to the worm wheel so that the convex portion of the second die faces the tooth space of the worm wheel. And a third step of detaching the second die from the worm wheel in an axial direction so that the convex portion of the second die moves along the tooth groove of the worm wheel. It is that.

  In the worm wheel molding method, with respect to the circumferential direction of the second mold, the first mold and the second mold are arranged such that the convex portions are positioned between the extending portions adjacent to each other in the first mold. It is better to combine these types. The extension portion extends from the base portion along a direction in which the tooth groove of the worm wheel extends, and an end portion of the plurality of extension portions opposite to the base portion is the first portion. In the first step, the first mold is formed along the direction from the end of the extension portion opposite to the base to the base. It is better to disengage from the rear worm wheel.

  According to the first technical means, a plurality of tooth spaces in the worm wheel are resin-molded at a time by the first die, and a plurality of tooth tips provided with undercut portions are resin-formed by the second die at a time. Molded. Therefore, in resin molding of the worm wheel, variation in accuracy between the respective tooth portions is suppressed, and the accuracy of the entire tooth portion is more easily ensured. Thereby, the worm wheel in which an undercut part is provided in a tooth tip can be resin-molded more accurately.

  According to the second technical means, by performing the first to third steps, the plurality of tooth grooves in the worm wheel are resin-molded at a time by the first mold, and the undercut portion is provided. The plurality of tooth tips to be formed are resin-molded at once by the second mold. Therefore, in resin molding of the worm wheel, variation in accuracy between the respective tooth portions is suppressed, and the accuracy of the entire tooth portion is more easily ensured. Thereby, the worm wheel in which an undercut part is provided in a tooth tip can be resin-molded more accurately.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a perspective view of a worm wheel molding die 100 according to the present invention, and FIG. 2 is a perspective view of a worm wheel 1 that is resin-molded using the worm wheel molding die 100.

  The worm wheel molding die 100 is for resin molding of a worm wheel 1 as shown in FIG. 2 in which an undercut portion 4 is provided on a tooth tip 3 of a tooth portion 2 (numbering is only partly). is there. The worm wheel mold 100 includes a mold 10 and a mold 20.

  The mold 10 is provided with an annular base portion 11 and a plurality of extending portions 12 (numbers are only partly). The extending part 12 is a part for forming a tooth gap 5 (tooth surface, tooth bottom) between the tooth parts 2 and 2 in the worm wheel 1 and extends from the base part 11 in the axial direction. The plurality of extending portions 12 are arranged at intervals in the circumferential direction of the base portion 11, and are integrated by the base portion 11. More specifically, the extension portion 12 extends from the base portion 11 along the direction in which the tooth groove 5 of the worm wheel 1 extends, and the end portion of the extension portion 12 on the side opposite to the base portion 11 is a mold. Each of the ten circumferential directions is separated. More specifically, each extending portion 12 individually molds the entire axial direction (from one axial end side to the other axial end side) of the tooth groove 5 of the worm wheel 1 by the extending portion 12 alone. As described above, the tooth groove 5 extends from one end side in the axial direction to the other end side. Furthermore, since the plurality of extending portions 12 are connected to and integrated with the base portion 11 at one end portion in the axial direction, the entire axial direction of the plurality of tooth spaces 5 can be formed by the mold 10 alone.

  The mold 20 is provided with a cylindrical tube portion 21 and a plurality of convex portions 22 (numbers are only partly). The inner peripheral surface 23 of the cylindrical part 21 is a part for forming the tooth tip 3 of the tooth part 2 in the worm wheel 1. The convex portion 22 protrudes radially inward from the inner peripheral surface 23 at the axially central portion of the cylindrical portion 21. The convex part 22 is a part for forming the undercut part 4 formed in the axial center part in the tooth tip 3 of the worm wheel 1. The plurality of convex portions 22 are arranged at intervals in the circumferential direction of the cylindrical portion 21, and are integrated by the cylindrical portion 21. Thus, the mold 20 is formed on the axial end portion side (both sides) of the inner peripheral surface 23 of the inner peripheral surface 23 by molding the axial end portion side (both sides) of the tooth tip 3 of the worm wheel 1. In the convex part 22 formed in the axial direction center part, the undercut part 4 located in the axial direction center part of the tooth tip 3 of the worm wheel 1 is formed. That is, the mold 20 can form the entire axial direction of the tooth tip 3 including the undercut portion 4 of the worm wheel 1 alone. Furthermore, since the convex part 22 is arrange | positioned at intervals in the circumferential direction in the internal peripheral surface of the cylinder part 21, the several tooth tip 3 can be formed by this type | mold 20 independently.

  FIG. 3 to FIG. 6 are schematic views showing a resin molding aspect of the worm wheel 1 using the worm wheel molding die 100. Moreover, FIG. 7 is a figure which shows the procedure of the shaping | molding method concerning this embodiment.

  First, as shown in FIG. 3, the cavity 50 is formed by the molds 10 and 20 described above and the other molds 30 and 40. The cavity 50 is filled with molten resin. The mold 20 is combined with the mold 10 so that the inner peripheral surface 23 of the cylindrical portion 21 surrounds the extending portion 12 of the mold 10. In a state where the mold 10 and the mold 20 are combined, the convex portion 22 of the mold 20 is located between the adjacent extending portions 12 and 12 in the mold 10 in the circumferential direction of the mold 20 (mold 10).

  When the molten resin filled in the cavity 50 is hardened, the worm wheel 1 is formed in the cavity 50 as shown in FIG.

  Next, as shown in FIG. 5, the mold 40 (see FIG. 3) and the mold 10 are moved axially from the molded worm wheel 1, in particular, from the end opposite to the base 11 of the extension 12 to the base. 11 (first step). During this time, the mold 10 is moved in the axial direction with respect to the worm wheel 1 while rotating relative to the worm wheel 1 by the twist angle of the worm wheel 1 about the axis Ax shown in the drawing.

  Subsequently, the protrusion 20 on the inner peripheral surface 23 of the mold 20 faces the tooth groove 5 of the worm wheel 1 after molding (that is, the position where the extended portion 12 of the mold 10 occupied / was located). As described above, relative rotation with respect to the worm wheel 1 around the axis Ax is performed (second step).

  After the second step is performed, the convex portion 22 of the mold 20 is located in the tooth groove 5 (see FIG. 2) of the worm wheel 1. Therefore, as shown in FIG. 6, the mold 20 is detached from the worm wheel 1 in the axial direction (right direction in FIG. 6) so that the convex portion 22 of the mold 20 moves along the tooth groove 5 of the worm wheel 1. (Third step).

  As described above, according to the worm wheel molding die 100 and the molding method using the worm wheel molding die 100 according to the present embodiment, the plurality of tooth spaces 5 in the worm wheel 1 are resin-molded by the die 10 at the same time, and The plurality of tooth tips 3 provided with the cut portions 4 are resin-molded at once by the mold 20. Therefore, when the worm wheel 1 is resin-molded, variations in accuracy between the respective tooth portions 2 and 2 are suppressed, and the accuracy of the entire tooth portion 2 is more easily ensured. Thereby, the worm wheel 1 in which the undercut part 4 is provided in the tooth tip 3 can be resin-molded more accurately.

  Further, since the mold 10 and the mold 20 are combined so that the convex portion 22 is positioned between the adjacent extending portions 12 in the mold 10 with respect to the circumferential direction of the mold 20, the tooth gap 5 and the tooth tip 3 The mold 10 can be easily detached from the mold 20 and the molded worm wheel, while the mold 10 and the mold 20 can be individually molded.

  The extending portion 12 extends from the base portion 11 along the direction in which the tooth groove 5 of the worm wheel 1 extends, and ends of the plurality of extending portions 12 opposite to the base portion 11 are formed on the mold 10. Since they are separated from each other in the circumferential direction, it is possible to easily realize a form in which the mold 10 can be detached from the molded worm wheel 1 in the axial direction.

  Furthermore, since the plurality of extending portions 12 are connected to and integrated with the base portion 11 at one end portion in the axial direction, the entire axial direction of the plurality of tooth spaces 5 can be formed by the mold 10 alone. As a result, the entire tooth groove 5 of the worm wheel 1 can be formed by the single mold 10, so that no parting line is formed in the tooth groove 5 of the formed worm wheel 1. Therefore, the worm wheel 1 having good meshing accuracy can be formed.

  Further, the mold 20 is formed on the axial end portion side (both sides) of the inner peripheral surface 23 of the inner peripheral surface 23, and the axial end portion side (both sides) of the tooth tip 3 of the worm wheel 1 is formed. Since the undercut portion 4 located at the central portion in the axial direction of the tooth tip 3 of the worm wheel 1 is formed in the convex portion 22 formed in the central portion, the mold 20 is a tooth including the undercut portion 4 of the worm wheel 1. The entire axial direction of the tip 3 can be formed by the mold 20 alone. Furthermore, since the plurality of convex portions 22 are arranged at intervals in the circumferential direction on the inner peripheral surface of the cylindrical portion 21, the plurality of tooth tips 3 can be formed by the mold 20 alone. As a result, the entire tooth tip 3 of the worm wheel 1 can be molded by the single mold 20, so that no parting line is formed on the tooth tip 3 of the molded worm wheel 1. Therefore, the worm wheel 1 having good meshing accuracy can be formed.

1 is a perspective view of a worm wheel molding die 100 according to the present invention. The perspective view of the worm wheel 1 resin-molded using the mold 100 for worm wheel shaping | molding. The schematic diagram which shows the aspect of resin molding of the worm wheel 1 using the mold 100 for worm wheel shaping | molding. The schematic diagram which shows the aspect of resin molding of the worm wheel 1 using the mold 100 for worm wheel shaping | molding. The schematic diagram which shows the aspect of resin molding of the worm wheel 1 using the mold 100 for worm wheel shaping | molding. The schematic diagram which shows the aspect of resin molding of the worm wheel 1 using the mold 100 for worm wheel shaping | molding. The figure which shows the shaping | molding method of the worm wheel concerning this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Worm wheel 2 Tooth part 3 Tooth tip 4 Undercut part 5 Tooth groove 10 type | mold (1st type | mold)
11 Base 12 Extension 20 Type (second type)
21 cylindrical part 22 convex part 23 inner peripheral surface 100 worm wheel mold

Claims (4)

A worm wheel molding die for resin molding a worm wheel in which an undercut portion is provided at a tooth tip of a tooth portion,
A first die that is provided with a base and a plurality of extending portions that respectively extend from the base to form tooth spaces between the tooth portions; and is removable from the worm wheel after molding in an axial direction;
A cylindrical portion having an inner peripheral surface for forming the tooth tip, and a plurality of convex portions for projecting radially inward from the inner peripheral surface of the cylindrical portion to form an undercut portion on the tooth tip are provided. A second mold that is combined with the first mold so that the cylindrical portion surrounds the extending portion;
A mold for forming a worm wheel, comprising:   The second mold is combined with the first mold so that the convex portions are located between the extending portions adjacent to each other in the first mold in the circumferential direction of the second mold. The worm wheel molding die according to claim 1.   The extension portion extends from the base portion along a direction in which the tooth groove of the worm wheel extends, and ends of the plurality of extension portions on the side opposite to the base portion are the first mold. 3. The worm wheel molding die according to claim 1, wherein the worm wheel molding die is separated from each other in the circumferential direction. A worm wheel molding method for resin molding a worm wheel in which an undercut portion is provided at a tooth tip of a tooth portion,
A first die that is provided with a base and a plurality of extending portions that respectively extend from the base to form tooth spaces between the tooth portions; and is removable from the worm wheel after molding in an axial direction;
A cylindrical portion having an inner peripheral surface for forming the tooth tip, and a plurality of convex portions for projecting radially inward from the inner peripheral surface of the cylindrical portion to form an undercut portion on the tooth tip are provided. A second mold that is combined with the first mold so that the cylindrical portion surrounds the extending portion;
Use
A first step of separating the first mold from the molded worm wheel;
The second step is carried out following the first step, and the second die is rotated relative to the worm wheel so that the convex portion of the second die faces the tooth groove of the worm wheel. When,
A third step is performed subsequent to the second step, and the second die is axially separated from the worm wheel so that the convex portion of the second die moves along the tooth groove of the worm wheel. And the process of
A worm wheel molding method comprising:

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