JP3962379B2 - A method of manufacturing a lead screw for a linear actuator. - Google Patents

Description

  The present invention relates to a method for manufacturing a lead screw used in a linear actuator.

  A linear actuator to which a lead screw is attached is provided, for example, in a floppy (registered trademark) disk drive (FDD), and is used for linear movement when a carriage mounted with a magnetic head accesses a desired track.

  FIG. 3 is a perspective view of a floppy (registered trademark) disk drive device 50 provided with a linear actuator 40 to which a conventional lead screw 30 is attached.

  As shown in FIG. 3, in the floppy (registered trademark) disk drive device 50, the presser spring 42 of the lead screw 30 extending from the carriage 51 presses the needle 43 against the groove of the lead screw 30. When the lead screw 30 is rotated by the stepping motor 41, the carriage 51 slides on the guide bar 53 and moves linearly. The magnetic head 52 mounted on the carriage 51 can access a track on a desired magnetic disk (not shown) by forward and reverse rotation of the stepping motor 41.

  FIG. 4 is a side view of the linear actuator 40 in which the lead screw 30 is attached to the stepping motor 41.

  As shown in FIG. 4, a stepping motor 41 is attached to a side plate 55 of a floppy disk drive 50 (see FIG. 1), and one end of the lead screw 30 is a pivot bearing (not shown) in the stepping motor 41. The other end is supported by a pivot bearing 45 attached to a base 44 to which the stepping motor 41 is fixed.

  As the lead screw 30 used for the floppy (registered trademark) disk drive device 50, a metal rod such as brass or stainless steel provided with a desired thread is appropriately engraved.

  However, the lead screw 30 has high dimensional accuracy, but the processing method is complicated, the manufacturing cost is high, the productivity is not excellent, and it cannot be provided at a low cost.

  In order to solve this problem, a lead screw having a resin-molded thread portion has been put into practical use by Patent Document 1 “Lead Screw Molding Method” proposed by the present applicant.

  FIG. 5 is a partial cross-sectional view of the lead screw 60 having the resin-molded thread portion 63.

  As shown in FIG. 5, the lead screw 60 is manufactured in such a manner that a wall portion 61 a of a metal pipe 61 made of stainless steel or the like is placed at a position along a spiral corresponding to a screw thread portion 63 formed in the metal pipe 61. A plurality of holes 62 are penetrated at intervals of each other, and a molding die 69 in which a screw groove 68 is engraved in order to resin-mold a threaded portion 63 that fits the row of the holes 62 is formed. The metal pipe 61 is positioned by fitting the row of holes 62 and the screw grooves 68 in the cavity 67, and a resin material is filled from the outside of the row of holes 62 penetrating the wall body portion 61a of the metal pipe 61. The peak portion 63 is resin-molded, and a highly accurate and inexpensive lead screw can be manufactured by this technique.

  FIG. 6 is a side view of a lead screw 60 having a resin-molded screw thread 63.

  As shown in FIG. 6, the lead screw 60 is supported via a ball 66 on a pivot bearing 45 fixed to the base 44.

  The inside of the metal pipe 61 is filled with a resin 64 at the time of resin molding of the threaded portion 63, and the ball 66 is in contact with the resin 64.

  The lead screw 60 has no problem in pitch characteristics, but the temperature difference of the resin 64, that is, the expansion coefficient causes a slight difference in the origin position between the ambient temperature and the high temperature (for example, 80 ° C.), and the rotation of the stepping motor. There may be a slight difference in the linear movement distance due to.

JP-A-8-118371

  The present invention has been made in view of the above, and even if the ambient temperature becomes high, the slight displacement of the origin position due to the resin filled in the metal pipe is surely prevented, and the stepping motor is rotated. It is an object of the present invention to provide a method of manufacturing a lead screw for a linear actuator that precisely performs linear movement.

In the method of manufacturing a lead screw for a linear actuator according to the present invention, a procedure for penetrating a plurality of holes at predetermined intervals in a wall portion of a metal pipe and a position where resin to be filled is not in direct contact with the ball. A step of inserting a plug of a predetermined size into the end of the metal pipe, a step of positioning the metal pipe at a predetermined position in the cavity of the molding die, and a wall portion of the metal pipe Filling the resin material from the outside of the row of holes provided and molding the screw thread part, filling the resin inside the metal pipe, and filling the resin inside the metal pipe, A procedure for removing the stopper and a procedure for disposing a ball in direct contact with the end of the metal pipe are provided.

In the method of manufacturing a lead screw for a linear actuator according to the present invention, a procedure for penetrating a plurality of holes at predetermined intervals in a wall portion of a metal pipe and a position where resin to be filled is not in direct contact with the ball. A step of inserting a plug of a predetermined size into the end of the metal pipe, a step of positioning the metal pipe at a predetermined position in the cavity of the molding die, and a wall portion of the metal pipe Filling the resin material from the outside of the row of holes provided and molding the screw thread part, filling the resin inside the metal pipe, and filling the resin inside the metal pipe, Since it has a procedure for removing the plug and a procedure for disposing a ball that directly contacts the end of the metal pipe, the resin filled in the metal pipe and the ball are avoided from direct contact, and the ambient temperature is high temperature The lead screw to securely prevent a slight displacement of the origin position by the resin filled in the metal pipe even since it can be easily manufactured.

  Embodiments of the present invention will be described below.

FIG. 1 is a side view of a lead screw 10 of a reference example .

  As shown in FIG. 1, the lead screw 10 is welded to a metal pipe 11 such as stainless steel, a spiral protruding thread 13 formed by resin molding on the outer periphery of the metal pipe 11, and an end of the metal pipe 11. And supported by a pivot bearing 45 fixed to the base 44 via the ball 16.

  The inside of the metal pipe 11 is filled with a resin 14 from a hole 12 penetrating through the wall 11a of the metal pipe 11 when the screw thread portion 13 is molded with resin, and the screw thread portion 13 and the resin are filled through the hole 12. The threaded portion 13 is securely fixed to the metal pipe 11 by communicating with 14.

  Since the ball 16 is welded to the metal pipe 11, even if the ambient temperature becomes high, the influence of the resin 14 filled in the metal pipe 11 on the origin position can be eliminated.

  The lead screw 10 is manufactured at a desired interval at a position along the spiral corresponding to the thread 13 that is resin-molded on the metal pipe 11 on the wall 11a of the metal pipe 11 such as stainless steel. The metal pipe 11 is pre-manufactured in advance so that the hole 16 is penetrated, the ball 16 is welded to the end of the metal pipe 11, and the thread 13 is resin-molded in conformity with the row of holes 12. It is positioned in a cavity of a mold (not shown), filled with a resin material from the outside of the row of holes 12 penetrating through the wall 11a of the metal pipe 11, and molded into the screw thread 13 and resin pipe. 21 is filled with resin.

As described above, in the lead screw 10 of the reference example , since the ball 16 is welded to the metal pipe 11, even if the ambient temperature becomes high, the origin position by the resin 14 filled in the metal pipe 11 is slightly small. Deviation can be reliably prevented. Further, the lead screw 10 that reliably prevents a slight deviation of the origin position due to the resin 14 filled in the metal pipe 11 can be easily manufactured by the above manufacturing method even if the ambient temperature becomes high.

FIG. 2 is a side view of the lead screw 20 of the first embodiment according to the present invention.

  As shown in FIG. 2, the lead screw 20 is in contact with a metal pipe 21 such as stainless steel, a spiral protruding thread portion 23 formed by resin molding on the outer periphery of the metal pipe 21, and an end portion of the metal pipe 21. The ball 26 is supported by a pivot bearing 45 fixed to the base 44 via the ball 26.

  The inside of the metal pipe 21 is filled with a resin 24 through a hole 22 penetrating the wall portion 21a of the metal pipe 21 when the screw thread portion 23 is molded with the resin, and the screw thread portion 23 and the resin are filled through the hole 22. The threaded portion 23 is securely fixed to the metal pipe 21 by communicating with 24.

  The resin 24 filled in the metal pipe 21 is inserted after the plug 25 is inserted during resin molding and removed after the resin molding, so that the resin 24 does not protrude from the end of the metal pipe 21 and does not contact the ball 26. Therefore, the ball 26 is in direct contact with the metal pipe 21, and the influence on the origin position by the resin 24 filled in the metal pipe 21 can be eliminated even when the ambient temperature becomes high.

  The lead screw 20 is manufactured at a desired interval at a position along a spiral corresponding to a thread portion 23 formed by resin molding on the metal pipe 21 on the wall 21a of the metal pipe 21 such as stainless steel. The plug 25 having a predetermined size is inserted into the end portion of the metal pipe 21, and the metal pipe 21 is formed so that the screw thread portion 23 is fitted with the row of the holes 22 and is resin-molded. Is positioned in the cavity of a pre-manufactured mold (not shown), filled with a resin material from the outside of the row of holes 22 penetrating through the wall 21a of the metal pipe 21, and the thread 23 is In addition to resin molding, the plug 25 is removed after filling the metal pipe 21 with resin. The ball 26 is attached between the end of the metal pipe 21 and the pivot bearing 45.

As described above, in the lead screw 20 of the first embodiment related to the present invention, the resin 24 is not filled up to the end of the metal pipe 21 by the plug 25, so the metal pipe 21 and the ball 26 of the pivot bearing 45 are made of metal. Thus, even if the ambient temperature becomes high, a slight deviation of the origin position due to the resin 24 filled in the metal pipe 21 can be reliably prevented. Further, the lead screw 20 that reliably prevents a slight deviation of the origin position due to the resin 24 filled in the metal pipe 21 can be easily manufactured by the above manufacturing method even if the ambient temperature becomes high.

It is a side view of the lead screw of a reference example . It is a side view of the lead screw of a 1st embodiment concerning the present invention. It is a perspective view of a floppy (registered trademark) disk drive device provided with a linear actuator to which a conventional lead screw is attached. It is a side view of the linear actuator which attached the conventional lead screw to the stepping motor. It is a partial cross section figure when manufacturing the conventional lead screw which has a thread part of resin molding by resin molding. It is a side view of the conventional lead screw which has a thread part of resin molding.

Explanation of symbols

10, 20 Lead screw 11, 21 Metal pipe 11a, 21a Wall portion 12, 22 Hole 13, 23 Thread portion 14, 24 Resin 16, 26 Ball 25 Plug 44 Base 45 Pivot bearing

Claims (1)

A procedure for penetrating a plurality of holes at predetermined intervals in the wall of the metal pipe;
Inserting a plug of a predetermined size at the end of the metal pipe so that the resin to be filled is not in direct contact with the ball;
Positioning the metal pipe at a predetermined position in the cavity of the molding die;
Filling the resin material from the outside of the row of holes penetrating through the wall of the metal pipe and molding the screw thread portion, and filling the resin inside the metal pipe;
After filling the inside of the metal pipe with resin, removing the stopper;
And a step of disposing a ball in direct contact with the end of the metal pipe. A method of manufacturing a lead screw for a linear actuator.

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