JPH07317773A - Manufacture of holder made of synthetic resin - Google Patents

Abstract

PURPOSE:To prevent generation of bleaching and crack or the like when opening at a portion of an expanding groove for building in the other member by instilling synthetic resin into a cavity through one gate faced to the position opposite for to the vicinity of the expanding groove of the cavity. CONSTITUTION:Synthetic resin-made holder C is formed by providing an annular body 1 with a plurality of pockets 2 having a rectangular section and dividing the annular body by the expanding groove 3 formed at one place along the radial direction of the annular body. A mold for forming the synthetic resin- made holder C by injection molding is provided with a cavity corresponding to the shape of the holder C, one place of gate G faced to the position facing to a pillar part 5a adjacent to the expanding groove 3 of this cavity, and is manufactured by instilling synthetic resin into the cavity through one place of gate G. Therefore generation of the longitudinal weld line at the vertical bridge portion 4 of the pockets 2 and the pillars 5 between the pockets 2.

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 cage made of synthetic resin used for rolling bearings by injection molding.

[0002]

2. Description of the Related Art A retainer made of synthetic resin is usually annular, but in some cases, the retainer cannot be incorporated in a member such as a shaft. In that case, as shown in FIG.
In addition, a plurality of pockets 92 are provided, and a synthetic resin cage C having a shape in which a ring is divided by forming a split groove 93 at one location of the main body 91 is used. The cage C is
Since it can be opened at the split groove 93, it can be easily incorporated into other members.

The cage C made of synthetic resin is usually provided at a plurality of locations (see FIGS. 1A and 1B) of a mold (not shown) having a cavity corresponding to the shape of the cage C in order to maintain dimensional accuracy. It is manufactured by injecting a synthetic resin into the cavity through gates G (shown by broken lines) provided at three places (so-called multi-point gate system). In the above-mentioned multi-point gate molding, a weld line (hereinafter, referred to as “vertical weld line”) W, which is generated at a position where the synthetic resins injected from the respective gates G meet, is formed along the axial direction of the ring. As shown by the alternate long and short dash line in the figure, the number and positions of the gates G, the conditions for injecting the synthetic resin from each gate G, etc. are appropriately adjusted so as to be positioned at the pillar portion 95 between the pockets 92. This is because if the vertical weld line W is located in the upper and lower bridge portions 94 of the pocket 92, the strength of the bridge portion 94 is weakened.

[0004]

However, in particular, various engineering plastics such as nylon 6 are used.
When a relatively hard synthetic resin material such as a polyamide resin such as No. 6 or polyphenylene sulfide (PPS) is used, even if the vertical weld line W is positioned at the pillar portion 95, it is possible to When the cage C is opened at the split groove 93 for assembling, whitening occurs near the vertical weld line W, and the strength of the whitened portion is greatly reduced, or along the vertical weld line W. There is a problem that the cage C is damaged due to cracking or the like.

This is because the orientation of the reinforcing fibers is not uniform in the portion of the vertical weld line W, and the orientation is disturbed, so that when the above-mentioned various synthetic resins which are particularly hard and have little flexibility are used. It is considered that the cause is that the strength reduction when the cage C is opened at the split groove 93 is significantly larger than that at other portions. An object of the present invention is to open a part in a split groove for incorporation into another member,
An object of the present invention is to provide a manufacturing method for manufacturing a synthetic resin cage in which whitening or cracking does not occur.

[0006]

In order to solve the above-mentioned problems, a method of manufacturing a synthetic resin cage according to the present invention is made of a synthetic resin having an annular shape and one of the rings is divided by a split groove. When manufacturing the cage by injection molding using a mold having a cavity corresponding to the shape of the cage, the cavity is passed through one gate facing a position corresponding to the vicinity of the split groove. It is characterized in that a synthetic resin is injected into the cavity.

[0007]

According to the method of manufacturing the synthetic resin cage of the present invention having the above-described structure, the synthetic resin is introduced into the cavity of the mold from one gate facing the position corresponding to the vicinity of the split groove. Since the cage made of synthetic resin is molded by the so-called one-point gate method of injecting, the cage is split into the upper and lower bridge portions of the pocket or the pillar portion between the pockets as in the conventional multi-point gate method. There is no vertical weld line that would cause a decrease in strength when opened in the area.
Therefore, according to the present invention, it is possible to manufacture a synthetic resin cage in which whitening or cracking does not occur when it is opened at the split groove portion for incorporation into another member.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The manufacturing method of the present invention will be described below by taking as an example the case of manufacturing a synthetic resin cage having the shape shown in FIG. 1 and used for, for example, needle roller bearings and cylindrical roller bearings. The synthetic resin cage C shown in FIG. 1 has a plurality of pockets 2 (eight in the figure) having a rectangular cross section in an annular body 1.
In addition to the above, the split groove 3 is formed at one location of the main body 1 along the axial direction of the ring to divide the ring.

The mold for molding the synthetic resin cage C by injection molding is a cavity (not shown) corresponding to the shape of the cage C and a column of the cavity adjacent to the split groove 3. One gate G (shown by a broken line in the drawing) facing a position corresponding to the portion 5a is provided. Then, the molten synthetic resin is injected into the cavity through the gate G at the one position, whereby the manufacturing method of the present invention is performed, and the synthetic resin cage C is manufactured.

According to the above manufacturing method, as described above,
It is possible to prevent vertical weld lines from being generated in the upper and lower bridge portions 4 of the pocket 2 or the pillar portion 5 between the pockets 2. Therefore, the manufactured synthetic resin cage C
Has excellent characteristics in that whitening or cracking does not occur when it is opened in the split groove 3 for incorporation into another member.

In the above manufacturing method, a weld line (hereinafter referred to as a "horizontal weld line") ω may be formed in the pillar portion 5 between the pockets 2 substantially along the circumferential direction of the ring, as indicated by the chain line in the figure. There is a nature. However, unlike the vertical weld line, the horizontal weld line ω does not cause whitening or cracks when the cage C is opened at the split groove 3 and affects the characteristics of the cage C. Since it does not exist, some occurrence is acceptable.

In the case of the cage C of FIG. 1 having the pocket 2 having a rectangular cross section, the position of the gate G is as shown in FIG.
It is limited within the range corresponding to the pillar portion 5a adjacent to the split groove 3. This is because when the gate G is placed at a position outside the range of the pillar portion 5a and corresponding to the bridge portion 4 slightly apart from the split groove 3 as shown in FIG.
The synthetic resin injected from the above flows in the cavity as shown by the double-dashed line arrow in the figure, and joins at the portion of the bridge portion 4 on the opposite side with the pocket 2 interposed therebetween. Weld line W is generated. For this reason, when the cage C is opened at the portion of the split groove 3 for incorporation into another member, there is a risk of whitening or cracking at the portion of the vertical weld line W.

On the other hand, as shown in FIGS. 2 (a) and 2 (b), when the gate G is arranged within the range corresponding to the pillar portion 5a adjacent to the split groove 3, the position is slightly moved up and down. Also, the synthetic resin injected from the gate G flows in the cavity as indicated by the double-dashed line arrow in the figure, and the pillar portion 5 between the pockets 2 is formed.
Since they join together from above and below, only a horizontal weld line ω is generated in the pillar portion 5 as shown by the alternate long and short dash line in both figures, which causes whitening and cracks in the bridge portion 4 and the pillar portion 5. No vertical weld line occurs. Therefore, the characteristics of the cage C are not affected.

Therefore, in the case of the synthetic resin cage C having the pocket 2 having a rectangular cross section, the gate G must be arranged so as to face the column portion 5a adjacent to the split groove 3. is there. In the case of a cage having pockets having a cross-sectional shape other than a rectangular cross-section, the resin flow is different, so the position of the gate is not limited to the position described above. In short, the gate may be arranged at least in the vicinity of the split groove, depending on the shape of the pocket, and at a position where vertical weld lines that cause whitening, cracks, or the like are not generated.

The horizontal weld line ω is, as described above,
It has almost no effect on the characteristics of the cage C, but it should not be generated if possible. For that purpose, it is desirable to set the molding conditions such as the resin temperature and the mold temperature at the time of injecting the synthetic resin from the gate G, or the injection pressure to be higher than in the case of the conventional multi-point gate system. As the synthetic resin that is the raw material of the synthetic resin cage C, any of various conventionally known synthetic resins used for cages can be used, but in particular, they have excellent mechanical properties and heat resistance. In the usual manufacturing method, a hard synthetic resin, which may cause whitening or cracks when the cage is opened at the split groove portion, is preferably used.

Examples of the above-mentioned hard synthetic resin include, but are not limited to, polyamide resins such as nylon 66 and nylon 46, polyphenylene sulfide (PPS), polyether ether ketone (PE).
Engineering plastics such as EK), polyether sulfone (PES), polyether nitrile (PEN), and aromatic polyamide are listed.

Examples of the reinforcing fiber to be mixed with the synthetic resin include glass fiber, carbon fiber, fibrous silica lime (wollastonite), silicon carbide fiber, boron fiber, alumina fiber, Si-Ti-C. -O fibers, metal fibers (copper, steel, stainless steel, etc.), aromatic polyamide (aramid) fibers, potassium titanate whiskers, graphite whiskers, silicon carbide whiskers, silicon nitride whiskers, alumina whiskers and the like can be mentioned.

The mixing ratio of the reinforcing fiber is not particularly limited, but it is preferably 10 to 40% by weight based on all the components.
If the blending ratio of the reinforcing fibers is less than the above range, the mechanical properties and heat resistance of the cage may be insufficient. Conversely, if the blending ratio of the reinforcing fibers exceeds the above range, to other members It becomes difficult to open at the part of the split groove due to the assembling of, and if it is forcibly opened, there is a possibility that whitening or cracking is likely to occur in the bridge portion and the like.

In addition to the reinforcing fibers, various additives such as fillers and stabilizers may be added to the synthetic resin. The molten and kneaded synthetic resin to which the above-mentioned respective components are added is formed into a shape usable as a molding material, such as a pellet or a powder, as in the conventional case, and then used for molding.

Specific Example Nylon 6 with 32% by Weight of All Components Added Glass Fiber
6 is the shape shown in FIG. 1 (however, the number of pockets is not 8 but 1
6) for molding a synthetic resin cage C having
Injected by injection molding into a cavity corresponding to the retainer C from a single gate G facing a position corresponding to the pillar portion 5a adjacent to the split groove 3 of the cavity, and injection is performed using the synthetic resin. Cage C was manufactured. The dimensions of each part of the cage C are as follows.・ Outer diameter: 24 mm Inner diameter: 20 mm Height: 17 mm ・ Number of pockets: 8 Height: 13 mm Width: 2 mm ・ Split groove width: 1 mm When the appearance of the obtained cage C was observed, it was found to be horizontal to the column part 5. Was observed, but no vertical weld line was observed in the bridge portion 4 and the pillar portion 5.

Comparative Example Nylon 6 with 32% by weight of all components added with glass fiber
6 in the shape shown in FIG. 5 (however, the number of pockets is 1 instead of 8)
6) for molding a synthetic resin cage C having
It is injected into the cavity corresponding to the cage C from three gates G of this cavity by injection molding,
The cage C made of synthetic resin was manufactured. The dimensions of each part of the cage C were the same as in the specific example.

As a result of observing the appearance of the obtained cage C, vertical weld lines W were observed at two places of the column portion 95, which are indicated by the alternate long and short dash line in FIG. Strength test The split groove of the synthetic resin cage C manufactured in the above specific examples and comparative examples was opened at a constant speed in the direction indicated by the black arrow in FIG. 3, and the relationship between the opening amount (S in the figure) and the load Was measured, it was found that the cage of the comparative example had an opening amount of the split groove of 6.5 mm.
At the stage of (load 0.5 kgf), cracks occurred along the vertical weld line W, so the measurement was stopped.

On the other hand, in the cage of the specific example, as shown in FIG. 4, the opening amount and the load showed a substantially proportional relationship until the test was completed at the stage where the opening amount of the split groove was 26 mm. When the cage of the specific example was observed during the strength test, no whitening or cracking was observed by the end of the test.
When the cage of the specific example was removed from the test apparatus after the test was completed, it was observed that the cage returned to its original shape due to its own elasticity.

In the cage of the specific example, when the split groove is opened with the rollers mounted in the respective pockets, the roller falls when the opening amount is 17 mm. Does not break until it reaches 26 mm, which means that the practical range of split groove opening (17 mm or less)
Then, it turned out that it has sufficient resistance.

[0025]

As described above in detail, according to the method for manufacturing a cage made of synthetic resin of the present invention, the cage is formed into an annular shape without generating vertical weld lines that cause whitening or cracking. Moreover, it is possible to manufacture a synthetic resin cage having a shape in which one portion of the ring is divided by the split groove. Therefore, according to the present invention, it has the above-mentioned special shape and is made of a particularly hard and less flexible synthetic resin, and
It has a unique effect that a cage made of synthetic resin, in which whitening or cracking does not occur when opened at the split groove portion for incorporation into another member, can be manufactured by ordinary injection molding.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a synthetic resin cage manufactured by a manufacturing method of the present invention and a position of a gate for resin injection for manufacturing the cage.

2A to 2C are developed side views for explaining the relationship between the gate position and the weld line generation position.

FIG. 3 is a plan view illustrating a method of measuring strength when a synthetic resin cage is opened at a split groove portion.

FIG. 4 is a graph showing the relationship between the opening amount of the split groove portion and the load at that time of the cage according to the specific example, measured by the above-described measuring method.

FIG. 5 is a perspective view showing an example of a synthetic resin cage manufactured by a conventional manufacturing method and a position of a gate for resin injection for manufacturing the cage.

[Explanation of symbols]

 C Synthetic resin cage G Gate 3 Split groove

Continuation of the front page (72) Inventor Shigetaka Ashida 3-5-8 Minamisenba, Chuo-ku, Osaka City Koyo Seiko Co., Ltd.

Claims (1)

[Claims] 1. A cage made of synthetic resin, which is annular and has a shape in which one portion of the ring is divided by a split groove, is manufactured by injection molding using a mold having a cavity corresponding to the shape of the cage. In the method, a synthetic resin holder is manufactured by injecting a synthetic resin into the cavity through one gate facing a position corresponding to the vicinity of the split groove of the cavity.