JPH07205320A - Manufacture of screw shaft made of resin - Google Patents

Abstract

PURPOSE:To contrive simplification of structure of a mold for molding a screw shaft of resin, by a method wherein a jig which has stopped its rotation is set up to the screw shaft projected through the first mold and the first mold is turned. CONSTITUTION:In a jig 58, a direction of its through hole 61 corresponds to a form of a molding space of a mold and a position of a detent pin 64 is set up beforehand so as to corresponds to a position of a recessed part 63. When setting of the jig 58 is completed, a motor 53 is turned and a mold 49 is turned clockwise through gears 54, 55. Since the mold 49 is controlled its rotation by the jig 58, a rotor shaft 40 is slid and raised within a molding space K1 and through hole 61 along a screw part 49a formed within the mold 49 according to the rotation of the mold 49.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a resin screw shaft used for a rotor shaft of a stepping motor with a lead screw, for example.

[0002]

2. Description of the Related Art First, a two-phase permanent magnet type stepping motor with a lead screw (hereinafter simply referred to as a motor) which can use a resin screw shaft manufactured according to the present invention.
Will be described with reference to FIG. The motor 1 is used, for example, for head feeding of a floppy disk drive device. The motor 1 has a stator 2 and a rotor 3, and the stator 2 is composed of a pair of stator yokes 4 and 5 surrounding the rotor 3, the main part of which is formed. Each of the stator yokes 4 and 5 is a combination of two sheet metal parts. A donut-shaped space for accommodating the exciting coils 6 and 7 is formed, and a portion facing the outer peripheral surface of the rotor 3 is illustrated. A claw pole structure of pole teeth is formed. The rotor 3 is formed of a cylindrical permanent magnet whose magnetic poles are magnetized at a constant pitch in the circumferential direction, and a rotor shaft 8 is fixed to the center thereof.

The rotor shaft 8 has a cylindrical portion 8a at the center thereof.
Is supported by the bearing 10 at the rear end 8b and the ball 11
While contacting the leaf spring 13 via the
It is supported by ball bearings 15 via balls 14.
As a result, the rotor shaft 8 is rotatably supported by the bearing 10 and the ball bearing 15 while receiving a compressive force in the axial direction (left direction (FIG. 6)) by the leaf spring 13. In addition,
The bearing 10 is fixed to the front flange 9 fixed to the stator yoke 4, and the leaf spring 13 and the ball bearing 15 are fixed to the motor frame 12 fixed to the stator yoke 5 and the front flange 9. In addition, the tip portion 8c of the rotor shaft 8
A lead screw 16 is engraved on the outer periphery of the lead screw 16, and a moving body 17 connected to a head (not shown) of the floppy disk drive device is screwed into the lead screw 16.

A rotor shaft 8 which is one component of the motor 1 configured as described above is conventionally a mold 22 incorporated in a three-plate type die set 19-21 shown in FIG. 7, for example.
It is molded by 23. The mold 22 is arranged in the die set 19 on the receiving plate 24, and the upper end of the ejector pin 26 is located below the molding space of the mold 22. The ejector pin 26 moves up and down by the feed mechanism 25 arranged below the receiving plate 24. A gear 27 is fixed to the die 22, and the gear 27 meshes with a gear 28 fixed to a rotating shaft on one side of the motor 29.

The feed mechanism 25 has a gear 30 fixed to the rotating shaft on the other side of the motor 29, a gear 31 meshing with the gear 30, a ball screw 32 screwed into a screw hole at the center of the gear 31, and the like. There is. Ball screw 32 is plate 35
The plate 35 is provided with a rotation stop pin 37. The rotation stop pin 37 restricts the rotation of the ejector pin 26. A cross-shaped convex portion 33 is formed on the upper end of the ejector pin 26 as a rotation stopping mechanism for the rotor shaft 8 formed in the mold 22. Corresponding to the convex portion 33, the rotor shaft 8 of the rotor shaft 8 is formed. A cross-shaped concave portion is formed on the tip end surface, and the convex portion 33 and the concave portion are fitted together to prevent the rotor shaft 8 from rotating.
It should be noted that this recess has a function of preventing rotation during manufacturing, and also has a function of supporting the ball 14 in the recess at the time of manufacture.

The rotor shaft 8 formed by the molds 22 and 23
Is manufactured as follows. That is, with the die sets 20 and 21 set on the upper surface of the die set 19, resin is injected from the gate 34 (resin injection port) of the die set 21 into the molding space formed in the molds 23 and 22. To do. After the injected resin has hardened, the rotor shaft 8 that is a molded product is released from the molds 22 and 23. That is, the die sets 21 and 20 are removed from the die set 19, and then the motor 29 is rotated. Motor 29
Rotation of the die 22 rotates through the gears 28 and 27, and the gear 30 of the feed mechanism 25 also rotates, and the plate 35 is guided by the guide rod 36 through the gear 31 and the ball screw 32. To rise.

Due to the rotation of the die 22 and the elevation of the plate 35, the rotor shaft 8 ascends while its rotation is restricted in the die 22. That is, since the rotation of the die 22 and the rise of the ejector pin 26 are synchronized with each other, the fitting state between the tip end surface of the lead screw 16 and the convex portion 33 of the ejector pin 26 is maintained and the rotation of the rotor shaft 8 is maintained. Is regulated. Then, in this state, the rotor shaft 8 receives the rotational force of the die 22 by the lead screw 16 and is released from the die 22 while sliding up in the cavity of the die 22 together with the ejector pin 26. Become.

The rotor shaft 8 rises in the cavity of the die 22, and the lead screw 16 moves to the screw portion 22 of the die 22.
The rotation of the motor 29 stops at the position indicated by the alternate long and two short dashes line A in FIG. At this position, the portion of the rotor shaft 8 protruding from the upper surface of the die 22, that is, the rear end portion 8b.
For example, the rotor shaft 8 is lifted by a chuck or the like with a robot (not shown) and taken out from the mold 22. This completes the manufacture of the rotor shaft 8.

[0009]

However, in the method of manufacturing the rotor shaft 8 as described above, there is a problem that the mold structure for molding the rotor shaft 8 becomes complicated. That is, when the molded rotor shaft 8 is taken out from the mold, the ejector pin 26 must be raised in synchronization with the rise of the rotor shaft 8 in order to regulate the rotation of the rotor shaft 8. Therefore, a complicated feeding mechanism 25 including gears 30 and 31 and a ball screw 32 which are rotated by the rotation of the motor 29 is required, which complicates the die structure.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a resin screw shaft, which can simplify a mold structure for molding a screw shaft with resin. To do.

[0011]

In order to achieve the above object, in the method of manufacturing a resin screw shaft according to a first aspect of the present invention, a first mold for molding a screw portion and a mold that can be contacted with and separated from the mold. A mold having a second mold is provided, and a screw shaft is molded by injecting resin into the mold to mold the screw shaft. After molding, the molded screw shaft is rotated by rotating the first mold. In a method of manufacturing a resin screw shaft that is taken out of a mold, after molding the screw shaft, the second mold is separated from the first mold, and a screw shaft rotation preventing portion protruding from the first mold is provided. It is characterized in that a jig which is not rotated is set on the first mold, and then the first mold is rotated.

In the method of manufacturing a resin screw shaft according to a second aspect of the present invention, the molded screw shaft has a structure in which the molded screw shaft is rotated after the first mold is rotated.
It is characterized in that it is taken out from the first mold by an ejector pin that moves in the mold. Further, in the method for manufacturing a resin screw shaft according to claim 3, the jig is fixed to the first mold by a magnet arranged on a contact surface with the first mold. To do.

[0013]

According to the resin screw shaft manufacturing method of the present invention, the rotation of the screw shaft is restricted by setting the jig on the portion protruding from the first mold, so that it is sufficient. The rotation preventing effect is obtained, the deformation of the screw portion is prevented, and the mechanism for synchronizing the rotation of the first mold with the removal of the rotor shaft is not required, and the mold structure is simplified. .

According to the method of manufacturing a resin screw shaft according to the second aspect, after the first mold is rotated and the screwed state of the mold and the screw portion of the screw shaft is released, The molded screw shaft is pushed up in the first mold by, for example, an ejector pin that moves upward. As a result, the screw shaft slides up on the straight portion of the first mold on which the screw is not formed, and is reliably taken out from the mold.
Furthermore, according to the method of manufacturing a resin screw shaft according to claim 3, the jig is fixed to the first mold by a magnet, and the jig is allowed to move in the surface direction. Even if there is a deviation in the center position of the shaft stopper, this deviation is automatically corrected by the movement of the jig in the surface direction.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. 1 and 2 show a rotor shaft manufactured by a manufacturing method according to the present invention, FIG. 1 is a side view thereof, and FIG. 2 is a sectional view taken along line II-II of FIG. The rotor shaft 40 is integrated with, for example, the rotor 3 and applied to the two-phase permanent magnet type stepping motor 1 shown in FIG.

The rotor shaft 40 has a columnar portion 40a, and a lead screw 41 is formed at the tip portion (one end side) of the columnar portion 40a, and the ball 14 ( A concave portion 42 is formed to accommodate (see FIG. 6). As shown in FIG. 2, a rotation preventing portion 43 having a large diameter portion 43a and a cutout portion 43b and having a substantially elliptical cross section is formed at the rear end portion (the other end side) of the columnar portion 40a.
On the rear end surface of the rotation stopping portion 43, a recess 44 for accommodating the ball 11 (see FIG. 6) is formed. In addition, the lead screw 41 has a cylindrical portion 4 having a mountain diameter that is the outermost diameter.
It is set to be equal to or smaller than the outer diameter of 0a.

The equipment for manufacturing the rotor shaft 40 is, as shown in FIG. 3, a three-plate type die set 46.
The die set 46 has a die 49 rotatably disposed therein, and the die set 47 has a die 50 disposed therein. The upper end of an ejector pin 51 that can move up and down faces the lower part of the cavity K1 of the mold 49. The ejector pin 51 has a flat upper end surface and a lower end fixed to a vertically movable plate 52. A gear 55 is fixed to the mold 49, and the gear 55 is connected to the rotating shaft of the motor 53 via the gear 54. On top of this mold 49, mold 5
0 is installed, and the die set 48 having the gate 56 is installed on the upper surface of the mold 50.

Next, a method of manufacturing the rotor shaft 40 using the molds 49 and 50 will be described with reference to FIGS. First, with the die sets 46 to 48 set as shown in FIG. 3, from the gate 56 of the die set 48, for example, resin such as polyester resin or ABS resin is used to mold 49, 50.
It is injected into the molding spaces K1 and K2 at a predetermined pressure. Then, after the resin injected into the molding spaces K1 and K2 is cured, the die set 48, the die set 47, and the mold 50 are removed from the die set 46. As a result, the rotor shaft 40
The portion formed by the mold 50, that is, the rotation stopping portion 43 is exposed while protruding from the upper surface of the die set 46.

Next, as shown in FIG. 4, a jig 58 is fitted in the rotation preventing portion 43 and set. The jig 58 is configured as shown in FIGS. 4 and 5. That is, the jig 58 is the cylindrical portion 5 made of metal such as aluminum.
9 and a fixed portion 60, and the rotor shaft 4 is provided in the cylindrical portion 59.
A through hole 61 having a sectional shape substantially the same as the sectional shape of the anti-rotation portion 43 of 0 is formed. The fixed portion 60 has a bottom surface 60a, which is a contact surface with the die set 46, for example, 18
Two permanent magnets 62, which are out of phase with each other by 0 degrees, are embedded, and a rotation stop pin 64 is fixed so as to project.
A ring-shaped protrusion 65 is integrally formed at the center of the bottom surface 60a. In addition, on the upper surface of the die set 46, the recess 63 into which the rotation stopping pin 64 and the protrusion 65 are fitted.
And 66 are formed, a gap 67 is formed between the protrusion 65 and the recess 66, and a gap 68 is formed between the detent pin 64 and the recess 63.

In this jig 58, the detent portion 43 is inserted into the through hole 61, the protrusion 65 is positioned in the recess 66, and the detent pin 64 is fitted into the recess 63, so that the magnetic force of the magnet 62 is applied. It is set by fixing it on the upper surface of the die set 46. The jig 58 has a through hole 61.
Is set in advance so that the direction corresponds to the shape of the molding space K2 of the mold 50 (see FIG. 3) and the position of the rotation stop pin 64 corresponds to the position of the recess 63.

When the setting of the jig 58 is completed, the motor 5
3 is rotated, and the mold 49 is rotated clockwise (FIG. 5) via the gears 54 and 55. Since the rotation of the die 40 is restricted by the jig 58, the rotor shaft 40 moves along with the screw portion 49a formed in the die 49 along with the rotation of the die 49. The inside of the through hole 61 is slid up. At this time, the ejector pin 51
Remains at the initial position and does not synchronize with the rise of the rotor shaft 40. Needless to say, the rotation direction of the motor 53 is set so that the rotor shaft 40 is pulled out of the mold 49 by the rotation of the mold 49.

Then, the rotation of the motor 53 is stopped at a position where the lead screw 41 of the rotor shaft 40 and the screw portion 49a of the die 49 are released from the screwed state. At this position, the lead screw 41 moves into the molding space K1 of the mold 49.
The upper part is ready to slide up. In this state, the ejector pin 51 is lifted together with the plate 52 by a feed mechanism such as a cylinder to move the rotor shaft 40.
Is projected onto the jig 58 by a predetermined length. This protruding part
For example, the rotor shaft 40 is removed by chucking with a robot or the like. Then, the jig 58 is chucked and taken out. At this time, the jig 58 and the rotor shaft 40 may be removed at the same time. The outer diameter of the lead screw 41 is equal to that of the cylindrical portion 40.
The rotor shaft 40 can be easily taken out from the mold 49 because it is set to be the same as or smaller in diameter than a.

By the way, when the center of the cylindrical portion 40a of the rotor shaft 40 and the detent portion 43 is deviated, the jig 58 is used.
The gap is automatically corrected by. That is, the jig 5
8 is fixed on the die set 46 by the magnet 62, and the protrusion 65, the rotation stop pin 64, and the die set 4 are attached.
Since the gaps 67 and 68 are formed between the gap 6 and 6, the movement in the vertical direction is restricted, but the movement in the surface direction is allowed to some extent. Therefore, when the jig 58 is set, if there is a deviation between the centers of the columnar portion 40a and the rotation preventing portion 43, the jig 58 in which the rotation preventing portion 43 is inserted as the rotor shaft 40 rises , The surface is moved on the die set 46, and the deviation is corrected.

As described above, in the above embodiment, when the molded rotor shaft 40 is taken out from the mold 49, the ejector pin 51 does not need to be synchronized with the rise of the rotor shaft 40 due to the rotation of the motor 53, and Since the rotor shaft 40 slides upward while being prevented from rotating in the through hole 61, it is not necessary to provide the jig 58 exhibiting the rotation preventing function with the interlocking mechanism with the mold 49. As a result, the mechanism for taking out the rotor shaft 40 from the mold 49 is simplified and the mold structure can be simplified. Further, the internal stress applied to the screw portion 49a of the mold 49 can be reduced, the wear of the mold 49 can be prevented, and the maintenance cost of the mold 49 can be reduced.

Further, the rotor shaft 40 is pushed up by the ejector pin 51 rising from below the molding space K1 after the screwing state of the lead screw 41 and the screw portion 49a of the mold 49 is released, so that the mold is It is surely taken out from 49. Further, since the jig 58 is fixed on the die set 46 by the magnet 62, the jig 58 is allowed to move in the surface direction, and the columnar portion 40a and the rotation stop portion 43 are allowed.
The positional deviation between the rotor shaft 40 and the rotor shaft 40 is automatically corrected to prevent the rotor shaft 40 from being bent, and the rotor shaft 40 can be taken out from the mold 49 more smoothly.

Further, a cutout portion 43b is formed in the rotation preventing portion 43 of the rotor shaft 40, and the rotor shaft 40 is formed in this portion.
Since the rotation is restricted, the rotation force of the mold 49 when it is taken out from the mold 49 can be reliably received by the rotation preventing portion 43, and a sufficient rotation preventing effect can be obtained. In particular, since the whirl-stop portion 43 is molded by the die 50 on the die 49, its shape has no effect on the removal of the rotor shaft 40 from the die 49, and the whirl-stop portion 43 is fixed to the cylindrical portion 40a. It can be easily formed into a larger diameter, and the anti-rotation effect is further enhanced. In addition, by the rotation stopping portion 43,
There is also an additional effect that the rotation of the rotor 3 and the rotor shaft 40 after molding is prevented.

Furthermore, the detent portion 43 is attached to the rotor shaft 40.
Since the rotation preventing portion 43 does not increase the contact pressure with the through hole 61 so much, the rotation preventing torque of the rotor shaft 40 can be obtained. Further, since a twisting force is applied from the outer circumference of the rotor shaft 40, the outer diameter of the rotor shaft 40 is slightly reduced in diameter, so that separation from the mold 49 is promoted, and as a result, friction of the mold 49 is reduced. , Mold release becomes easy. Further, at that time, the stress applied to the rotor shaft 40 is also reduced, so that the lead screw 4 of the rotor shaft 40 is
The deformation of No. 1 and the breakage of the rotation preventing portion 43 are reduced.

Further, since the rotation stopping mechanism is not required on the tip end surface of the rotor shaft 40, the concave portion 4 for accommodating the balls 14 is formed.
2 can be set to a sufficient size, a large contact surface with the ball 14 (rolling surface of the ball 14) can be secured, and the recess 42 is prevented from being scratched or deformed, so that the ball 14 can rotate well. You can get the status. From these things, the rotor shaft 40 having the highly accurate lead screw 41 is obtained, and the rotational motion of the rotor 3 is accurately transmitted to the moving body 17, so that the high quality motor 1 is obtained.

Although the detent portion is formed in a substantially elliptical cross section in the above embodiment, it may be formed in an appropriate shape such as a polygonal shape such as a hexagonal shape or an octagonal shape, or a star shape. Is also good. Further, in the above embodiment, the screw shaft is applied to the rotor shaft with the lead screw of the two-phase permanent magnet type stepping motor, but the rotor shaft with the screw of other motors, or any other screw shaft formed of resin. Can be applied to. Further, the material of the rotor shaft, the shape of the rotation preventing portion, the shape of the jig, the configuration of the mold and its rotating mechanism and the like in the above embodiment are examples, and various modifications can be made without departing from the gist of the present invention. Needless to say.

[0030]

As described in detail above, in the resin screw shaft manufacturing method of the present invention, the mechanism for taking out the molded screw shaft from the mold is simplified, and the mold structure is simplified. There is an effect that it can be made into a material.

[Brief description of drawings]

FIG. 1 is a side view of a resin screw shaft manufactured by a manufacturing method according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a cross-sectional view of a molding die that can carry out the manufacturing method according to the present invention.

FIG. 4 is a cross-sectional view for explaining a manufacturing method using the molding die.

[Fig. 5] Bottom view of the jig

FIG. 6 is a cross-sectional view of a lead screw type two-phase permanent magnet type stepping motor common to the embodiment of the present invention and the conventional example.

FIG. 7 is a sectional view of a conventional molding die.

[Explanation of symbols]

 1 --- Motor 2 --- stator 3 --- rotor 40 --- rotor shaft 40a-cylindrical part 41 --- -Lead screw 43 --- Rotating portion 43a-Large-diameter portion 43b-Small-diameter portion 46-48 ... Die set 49, 50 ... Mold 51 ...・ ・ ・ Ejector pin 58 ・ ・ ・ ・ ・ Jig 60 ・ ・ ・ ・ ・ Fixed part 60a ・ ・ ・ ・ ・ Bottom surface 61 ・ ・ ・ ・ ・ ・ Through hole 62 ・ ・ ・ ・ ・ Magnet 64 ・ ・ ・.... Rotating pins

Claims (3)

[Claims] 1. A mold having a first mold for molding a screw part and a second mold capable of coming into contact with and separating from the mold, and injecting resin into the mold to form a screw shaft. After molding, after molding, the first
In a method of manufacturing a resin screw shaft in which a molded screw shaft is taken out of the mold by rotating the mold, the second mold is separated from the first mold after the screw shaft is molded,
A screw shaft protruding from the first mold is set with a jig that is prevented from rotating with respect to the first mold, and then the first mold is rotated. Production method. 2. The molded screw shaft is taken out of the first mold by an ejector pin that moves in the mold after the rotation of the first mold.
The method for manufacturing a resin screw shaft according to claim 1. 3. The resin mold according to claim 1, wherein the jig is fixed to the first mold by a magnet arranged on a contact surface with the first mold. Manufacturing method of screw shaft.