JP2001187922A - Cage of synthetic resin for ball bearing, and method of manufacturing for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To injection-mold such a miniature or microminiature cage of a crown type as is incapable of ensuring an enough space in a flat portion between adjacent elastic claws 4, 4 to receive an ejector pin that butts thereagainst. SOLUTION: The high-precision, miniature crown type cage is manufactured via an injection molding step where a dummy molding portion 10 with an ejector pin butt portion 11 at the center is molded integrally inside of an annular body 1 for the cage and an intermediate molding 10 is released from the die with the use of the ejector pin butt portion 11. The dummy molding portion of the intermediate molding 10 thus obtained is punched out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball bearing such as a deep groove ball bearing, and more particularly to a cage made of a synthetic resin for holding a plurality of balls so as to be able to roll at equal intervals in the circumferential direction. And a method for manufacturing the same.

[0002]

2. Description of the Related Art Crown-shaped cages made of synthetic resin have been widely used as cages for ball bearings.

This crown-shaped cage is made of a molded article of a thermoplastic synthetic resin such as polyamide (66 nylon) or polyacetal, and as shown in FIG. A plurality of ball holding pockets (2) defined by corresponding spherical concave portions (3) and a pair of elastic claws (4) rising from the peripheral edge of the opening surface are provided at a plurality of positions at equal circumferential positions. The ball is forcibly fitted into each of the pockets (2) and held so as to roll freely.

Such a synthetic resin crown retainer is generally manufactured by an injection molding method using an axial draw type mold. That is, using a mold provided with a cavity corresponding to the shape of the cage between the contact surfaces of the first mold on the fixed side and the second mold on the movable side, the sprue, the runner, and the gate are used to fill the cavity with the material. After injecting and solidifying the resin, the mold is opened by moving the second mold in the axial direction, and the ejector pin provided in the mold is operated with the molded article remaining and held in the first mold. And kick it out and take it out as a product.

[0005] By the way, the above-mentioned removal of the molded product is generally performed by using a flat portion (5) between a pair of adjacent elastic claws (4) of the retainer as an ejector pin contact portion.
This is performed by pushing a tip end surface of an ejector pin against the portion to cause the elastic claw (4) to elastically deform and kick the molded product from the first mold and release the molded product.

[0006]

However, in the case of a small bearing retainer called a miniature bearing, the area of the flat portion (5) between the adjacent elastic claws (4) (4) is extremely small. Accordingly, an ejector pin to be brought into contact with the flat portion must have a small diameter. For example, when the outer diameter of the retainer is small, such as about 10 to 12 mm, an ejector pin having a small diameter of about 0.3 to 0.4 mm must be used.

[0007] When the ejector pin having such a small diameter is used, in addition to increasing the difficulty in manufacturing a mold equipped with the pin, damage to the pin at the time of ejecting operation due to insufficient strength of the ejector pin, Further, various problems such as a breakage of the molded product due to a small-diameter pin hitting the molded product immediately after molding, a deterioration of the quality of the molded product due to the occurrence of pin burrs, and the like are caused.

[0008] In recent years, in recent years, in a hard disk drive (HDD) of a portable magnetic storage device, a ball bearing used for the hard disk drive (HDD) has a particularly small size and high performance. Is required, and the provision of an ultra-small cage having a diameter of about 3 mm has been demanded. However, in the case of such an ultra-small cage, when the conventional manufacturing method is used, the flat portion between the elastic claws (4) of the cage is further narrowed, so that the ejector pin has a diameter of 0.15-0. It is necessary to use an ultra-fine diameter of about 20 mm. However, the use of such an extra-fine-diameter ejector pin exceeds the practical limit due to the above-mentioned problems, and it is difficult to stably produce such an ultra-small cage by a conventional method.

The present invention has been made to solve the above problems and to provide a novel manufacturing method capable of stably manufacturing a small or ultra-small synthetic resin cage while maintaining high productivity. With the goal.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a process of forming an intermediate molded product by an injection molding method using an axial draw type mold, and a finishing process of punching out the obtained intermediate molded product. The above object is achieved by the combination.

In other words, the invention according to claim 1 is characterized in that, on one side surface of the ring-shaped body (1), a pair of claw pieces (3) each of which rises in the axial direction from a spherical concave portion (3) and a peripheral edge of an opening of the concave portion (3). 4)
In the method for manufacturing a cage made of a synthetic resin for a ball bearing, a plurality of ball holding pockets (2) defined by A dummy molding part (10), which is continuous with the inner peripheral surface of the base of the annular body (1) and has an ejector pin contact part (11) for releasing at the center part, is integrally injection-molded to form a mold. An injection molding step of contacting the ejector pin (30) with the ejector pin contact portion (11) at the time of opening the mold to take out the intermediate molded product (A); and the dummy molding portion of the intermediate molded product (A) obtained as described above. A method of manufacturing a synthetic resin cage for a ball bearing, characterized by comprising a punching step of shearing and removing (10) at the inner peripheral surface position of the annular body (1).

According to this manufacturing method, a small or ultra-small holding member that cannot secure a sufficient space for an ejector pin contact portion between a pair of adjacent elastic claws (4) of the holder. The injection molding process can be performed without any trouble even if the ejector pin contact portion (11) is found in the dummy molding portion (10). Moreover, the ejector pin (3
It is sufficient to use one having a large thickness for each of the moldings of the annular body (1), and thus to use a thinner or ultra-fine diameter ejector pin, as compared with a case where an ejector pin having a small diameter or a very small diameter is provided. The production of the mold is easy, and the production cost can be reduced, and the production cost of the cage can be reduced. Further, an ejector pin contact portion (1) is provided at a central portion inside the annular body (1).
1) is set, and at the time of release, the part is ejected with an ejector pin (3).
0), the annular body (1)
A molding with a high accuracy of molding can be applied to the entire circumference in the circumferential direction of the mold without exerting a risk of causing harmful deformation of the annular body at the time of mold release. Goods can be obtained.

The invention according to claim 2 is characterized in that the dummy molding portion (10) is molded by a molding material injection passage corresponding to a sprue or a runner in a mold.

This makes it possible to smoothly and reliably inject the resin into the cavity for forming the annular body (1), and does not require a separate gate for molding the dummy molding part (10). Efficient injection molding can be performed without lowering the cycle,
There is no danger of insufficient filling of the molding material into the cavity (short shot), and it is possible to mold the annular portion with high molding accuracy.

The invention according to claim 3 corresponds to the first embodiment shown in FIGS. 2 to 5, and the intermediate molded product (A)
The disk-shaped disc portion (12) having at least a portion of the outer peripheral edge thereof continuous with the inner peripheral surface of the base portion of the annular body (1), and the short columnar projecting portion ( 13), and the intermediate molded product (A) is taken out using the flat top surface of the projecting portion (13) as the ejector pin contact portion (11).

According to this specific method, it is possible not only to take out the intermediate molded product (A) in the injection molding process more smoothly, but also to make the disk-shaped disk portion () into the molding cavity of the annular body (1). Since the molding material can be injected through the annular gate portion formed by the connection portion with (12), the annular body (1) to be molded can have no weld in the circumferential direction as a weak point in strength. Also, the occurrence of short shots can be reliably prevented.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the lower portion of the disk-shaped disk (12) is formed so as to protrude from the lower surface of the annular body (1). In the punching step, the dummy molded portion (10) is punched by the punch (21) in a state where the guide portion (12a) is closely fitted and positioned in the die hole (20a) of the die (20). It is characterized by the following.

Thus, in the punching process, the guide body (12a) can accurately position the annular body (1) in the radial direction, so that the inner peripheral surface of the cage can be finished with high precision. .

The invention according to claim 5 corresponds to the second embodiment shown in FIGS. 6 to 9, wherein the dummy molded portion (10) in the intermediate molded product (A) is an annular body (1).
A projecting portion (14) for a punching guide, which is located at the center of the inner side and protrudes upward, and an outer end extending radially outward from the outer peripheral surface of the lower end portion of the projecting portion (14); ) Having a plurality of runner portions (15) continuous on the inner peripheral surface of the base portion, and using the flat top surface of the projection portion (14) for punching guide as an ejector pin contact portion (11) to form an intermediate molded product. While taking out (A), in the punching process,
With the guide protrusion (14) tightly fitted and positioned in the positioning guide hole (22) provided at the tip of the punch (21), the punch (21) is turned toward the die (20). The punching of the dummy molded portion (10) is performed by making it advance.

Thus, injection molding with high accuracy of the annular body (1) portion and punching with high finishing accuracy of the inner peripheral surface can be performed.

According to a sixth aspect of the present invention, an undercut portion (13) is provided on the lower peripheral surface of the short columnar projection (13) in the third aspect or on the lower peripheral surface of the punching guide projection (14) in the fifth aspect. 13a) and (14a), and the intermediate molded product (A) is ejected by the ejector pins (3) during the mold opening process.
(0) is surely retained and held in one of the molds on the side having (0).

Thus, in the injection molding process, the removal of the intermediate molded product (10) by the ejector pins (30) can be performed more smoothly and reliably.

Further, the invention according to claim 7 is characterized in that the center of the lower surface of the disk-shaped disk portion (12) in claim 3 or the center of the lower surface of the punching guide protrusion (14) in claim 5 is provided in the axial direction. The elongated columnar handling part (1
6) is integrally formed.

Thus, the intermediate molded product (1
The alignment / alignment operation of 0) can be easily performed by using the handling section (16), and the punching process can be automated.

The invention according to claim 8 is the invention according to claims 1 to 7 above.
The invention provides a cage for a ball bearing manufactured according to the invention of the present invention, and enables a relatively inexpensive cage with high precision to be provided.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION A ball bearing retainer to which the present invention is applied is made of a thermoplastic resin such as polyamide resin (66 nylon or the like) or polyacetal resin. As shown in FIG. One side surface of the annular body (1) is defined by a spherical concave portion (3) corresponding to the shape of the outer peripheral surface of the ball and a pair of elastic claws (4) (4) rising in the axial direction from the peripheral edge of the opening. A plurality of ball holding pockets (2) are provided at equal positions in the circumferential direction.

This cage is manufactured by a combination of an injection molding step and a press punching step of shearing off a dummy molded portion of the intermediate molded body obtained by the injection molding step.
Hereinafter, this manufacturing method will be described based on specific illustrated embodiments. In this specification, the terms "up and down" are used with reference to the direction of the paper surface of FIG.

<Embodiment 1> A first embodiment is shown in FIGS.

(Injection Molding Step) First, an intermediate molded product (A) as shown in FIG. 2 is molded by an injection molding method using an axitol draw-type mold.

The intermediate molded product (A) has a dummy molded part (10) integrally molded inside the annular body (1).

The dummy molded part (10) has a disc-shaped disk part (12) whose upper part of the outer peripheral edge is continuous with the inner peripheral surface of the base of the pocket bottom of the annular body (1), and a short columnar part protruding from the center part of the upper surface. It has a protruding portion (13) and a slightly tapered cylindrical handling portion (16) protruding long in the axial direction from the center of the lower surface of the disc portion (12). The flat top surface of the short columnar projecting portion (13) is used as an ejector pin contact portion (11) for taking out a molded product at the time of release from the mold, and an outer peripheral surface of a base end portion of the projecting portion (13). Is provided with an undercut portion (13a) composed of a plurality of small-diameter concave portions so that the intermediate molded product (A) can be reliably left and held in the first mold on the fixed side when the mold is opened. .

The lower portion of the disc portion (13) projects below the lower surface of the annular body (1), and the projecting portion constitutes a punching guide portion (12a) for a later-described punching process. It is assumed.

At the time of injection molding of the intermediate molded product (A), at least a part of the dummy molded portion (10) is molded by an injection passage of a molding material in a cavity for molding an annular body. For example, in this embodiment, it is assumed that the disk portion (12) and the short columnar protrusion (13) are formed by a molding material injection passage corresponding to a sprue or a runner in a mold. Thereby, it is not necessary to separately provide a sprue, a runner, and further a gate in the mold for molding the dummy molded portion, and the mold structure can be simplified.
The molding material can be reliably and smoothly injected into the cavity.

After the molding material resin has been injected into the cavity and solidified, the movable mold is subsequently moved in the axial direction to open the mold. At this time, the intermediate molded product (A)
Due to the presence of the undercut portion (13a), the undercut portion (13a) is reliably retained and held in the fixed mold. Then, subsequently, the ejector pin (30) is advanced, and the tip thereof is connected to the protruding portion (13).
By pressing against the ejector pin contact portion (11) formed by the flat top surface, the elastic claws (4) and (4) are elastically deformed to take out the intermediate molded product (A) as shown in FIG. I do.

(Punching Step) As shown in FIG. 4, a press punching machine using a die (20) and a punch (21) as shown in FIG. As a result, shearing and removal are performed at the inner peripheral surface position of the annular body (1).

At this time, the punching guide portion (12a) formed of the downwardly projecting portion of the disk portion (12) in the dummy molding portion (10) is tightly fitted into the die hole (20a) of the die (20). The center position of the annular body (1) is aligned with the center position of the die (20) and positioned.
In this state, the disc (1) is pressed by the punch (21).
2) is sheared at the position of the inner peripheral surface of the annular body (1), and the dummy molded portion (10) is separated and removed from the annular body (1). The punch (21) used has a receiving hole (21a) formed on the lower surface side of the punch (21a) with a sufficient margin for receiving the short columnar projection (13).

By the above-described punching process, an annular body (1) as a retainer product is obtained by separating and removing the dummy molded portion (10) from the intermediate molded product (A) as shown in FIG. .

<Embodiment 2> This second embodiment is shown in FIGS.
In this embodiment, the shape of the dummy molding portion (10) is changed from that of the first embodiment.

That is, the dummy molded portion (10) of the intermediate molded product (A) is located at the center of the inner side of the annular body (1), and the punching projecting upward from the annular body (1) is formed by the guide projection ( 14) a plurality of runner portions (15) extending radially outward from the outer peripheral surface at the lower end of the protruding portion (14) and having outer ends continuous with the lower inner peripheral surface of the annular body (1); It is made to have.

The flat top surface of the guide protrusion (14) is used as an ejector pin contact portion (11),
The lower outer peripheral surface of the protruding portion (14) is formed in a downward tapered shape, the surface forms an undercut portion (14a), and the upper outer peripheral surface is formed in an upwardly tapered shape, and punching is performed. The guide portion (14b) for positioning at the time is configured.

Therefore, in the case of this embodiment, in the injection molding process, the molding material is injected and filled into the molding cavity of the annular body (1) by the guide projection (14) and the runner in the dummy molding part (10). It is performed through a molding material injection passage in a mold for molding the part (15). As shown in FIG. 7, when removing the intermediate molded product (10) after opening the mold, the tip of the ejector pin (30) is pressed against the contact portion (11) on the top surface of the guide protrusion (14). This is done by kicking out of the mold.

Further, in the punching step, as shown in FIG. 8, during the advancement of the punch (21), the dummy molding portion (10) is inserted into the positioning guide hole (22) provided on the tip end surface thereof. After the protrusion (14) for punching guide is tightly fitted to perform relative positioning, the punch (2)
1) is further advanced toward the die (20) side, and the outer end of the runner portion (15) is sheared at the inner peripheral surface position of the annular body (1) to separate the dummy molded portion (10). The removal is performed.

FIG. 9 shows the ring-shaped body (1) having a pocket as a cage product thus separated and the dummy molded portion (10) in a separated state.

In the second embodiment, as shown in FIG. 6, the radial runner portion (15) can be provided on the inner peripheral surface of the base between the pockets (2) of the annular body (1).
The present invention can be applied to a cage having a small thickness at the bottom of the pocket.

[0045]

According to the manufacturing method of the present invention according to the first to sixth aspects, as described above, a necessary and sufficient area for the ejector pin contact portion between the pair of elastic claws of the crown-shaped cage is provided. Even in the case of a small or ultra-small cage in which space cannot be secured, it can be manufactured efficiently, with high accuracy, and relatively inexpensively.

Further, in the invention according to claim 7, handling operations such as mechanical alignment operation and transfer of the intermediate molded product after injection molding can be easily performed using the handling portion, and furthermore, punching can be performed. This has the effect of enabling complete automation of the machining process.

The invention according to claim 8 makes it possible to provide a high-precision cage at a low cost even if the cage is small or ultra-small.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a general shape of a synthetic resin crown retainer to which the present invention is applied.

FIG. 2 is a perspective view of an intermediate molded product obtained in the injection molding step of the first embodiment.

FIG. 3 is a front view showing the intermediate molded product of FIG.

FIG. 4 is a vertical sectional view showing a punching step of the intermediate molded product of FIG. 3;

FIG. 5 is a front view showing the annular body and the dummy molded portion after punching in the first embodiment in a separated state.

FIG. 6 is a perspective view of an intermediate molded product obtained in the injection molding step of the second embodiment.

FIG. 7 is a front view showing the intermediate molded product of FIG.

8 is a longitudinal sectional view showing a punching process of the intermediate molded product of FIG. 7;

FIG. 9 is a perspective view showing an annular body and a dummy molded portion after punching in a second embodiment in a separated state.

[Explanation of symbols]

 A: Intermediate molded product 1 ... Annular body 2 ... Pocket 3 ... Spherical recess 4 ... Elastic claw 10 ... Dummy molded part 11 ... Eject pin contact part 12 ... Disc-shaped disc portion 12a: punching guide portion 13: short columnar projecting portion 13a: undercut portion 14: projecting portion for punching guide 14a: undercut portion 15: runner portion 16. ..Handling part 20 ・ ・ ・ Dies 21 ・ ・ ・ Punch

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiyoshi Yamamoto 3-3-5 Temmabashi, Kita-ku, Osaka City Inside Nakanishi Kinzoku Kogyo Co., Ltd. (72) Inventor Tatsuya Minamiyama 3-3-5 Temmabashi, Kita-ku, Osaka City F-term in Nakanishi Metal Industry Co., Ltd. (reference) 3J101 AA02 AA32 AA42 AA54 AA62 BA25 BA50 DA14 EA31 EA36 EA37 FA44

Claims (8)

[Claims] 1. A side surface of an annular body (1) is defined by a spherical concave portion (3) and a pair of claw pieces (4) rising axially from an opening periphery of the concave portion (3). In a method for manufacturing a cage made of a synthetic resin for ball bearings, in which a plurality of ball holding pockets (2) are provided at equal circumferential positions, the annular body (1) is provided inside the annular body (1). ), A dummy molded part (10) which is continuous with the inner peripheral surface of the base and has an ejector pin contact part (11) for releasing at the center part is integrally injection-molded, and the ejector pin is opened when the mold is opened. An injection molding step in which an ejector pin (30) is brought into contact with the contact portion (11) to take out the intermediate molded product (A); and the dummy molded portion (10) of the intermediate molded product (A) obtained above is formed into an annular body. (1) a punching step of shearing and removing at the inner peripheral surface position. Method for producing a synthetic resin cage for a ball bearing. 2. The synthetic resin holder for a ball bearing according to claim 1, wherein the dummy molding portion is molded by an injection passage of a molding material corresponding to a sprue or a runner in a mold. Method of manufacturing the vessel. 3. A disk-shaped disk part (1) in which at least a part of an outer peripheral edge of the dummy molded part (10) in the intermediate molded product (A) is continuous with an inner peripheral surface of a base part of the annular body (1).
2) and a short columnar projecting portion (1
3. The intermediate molded product (A) is taken out by using the flat top surface of the projecting portion (13) as an ejector pin contact portion (11). A method for producing a synthetic resin cage for a ball bearing as described in the above. 4. A lower portion of the disk-shaped disk (12) is formed so as to protrude from a lower surface of the annular body (1), and the protruding portion forms a punching guide portion (12a). The synthetic resin for ball bearings according to claim 3, wherein the punching (21) punches the dummy molded portion (10) with the die (12a) tightly fitted and positioned in the die hole (20a) of the die (20). Cage and manufacturing method thereof. 5. A dummy guide portion (10) of the intermediate molded product (A) is located at a central portion inside the annular body (1) and protrudes upward from the punch guide (14). A plurality of runner portions (15) extending radially outward from the outer peripheral surface at the lower end of the portion (14) and having an outer end continuous with the inner peripheral surface at the base of the annular body (1); The intermediate molded product (A) is taken out using the flat top surface of the guide protrusion (14) as the ejector pin contact portion (11), and in the punching process, the guide protrusion (1) is used.
4) The punch (21) is advanced toward the die (20) with the punch (21) advanced toward the die (20) in a state where the punch (21) is tightly fitted and positioned in the positioning guide hole (22) provided at the tip of the punch (21). The synthetic resin cage for a ball bearing according to claim 1 or 2, wherein the part (10) is stamped. 6. The short columnar projection according to claim 3,
An undercut portion (13) is formed on the lower peripheral surface of the projection or the lower peripheral surface of the protrusion (14) for punching guide according to claim 5.
a) Forming (14a) to ensure that the intermediate molded product (A) remains and remains in one of the molds having the ejector pins (30) during the mold opening process. The synthetic resin cage for a ball bearing according to claim 3 or 5, and a method for manufacturing the same. 7. The disk-shaped disk portion (1) according to claim 3,
A column-shaped handling portion (16) extending in the axial direction is integrally formed at the center of the lower surface of (2) or at the center of the lower surface of the punching guide protrusion (14) in claim 5. 3. A cage made of a synthetic resin for a ball bearing and a method for manufacturing the same. 8. A synthetic resin cage for a ball bearing manufactured by the manufacturing method according to claim 1.