JPH0434260A - Resin-made pulley - Google Patents

Abstract

PURPOSE:To decrease a protrusive part as small as possible in an external diametric cylinder part and to eliminate a flagile part in a internal diametric cylinder part so as to increase whole strength in the internal diametric cylinder part by arranging a gate in symmetrical positions in a circumferential direction interposing a rib on a disk part. CONSTITUTION:Inflow melting resin from a gate hole 10 flows in a disk part cavity 5c to spread to inner and outer diametric sides, but the melting resin, before its inflow to inner/outer diameter cylinder part cavities 3c, 4c, flows into a rib cavity 6c, because a rib 6 is more approximate than inner/outer diameter cylinder parts 3, 4 to the gate hole 10, to join inflow melting resin from the adjacent other gate hole 10 and to flow in a side of the inner/outer diameter cylinder part cavities 3c, 4c in a confluent condition, and the cavities 3c, 4c are filled with the melting resin. Since the inflow melting resin from the separate gate holes 10 flows in the inner/outer diameter cylinder part cavities 3c, 4c after joining in the rib cavity 6c, the inner/outer diameter cylinder parts 3, 4 are formed of the sufficiently mixed resin, and molding strength is uniformly obtained in each part without generating weld in the inner/outer diameter cylinder parts 3, 4.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a resin pulley integrally provided with a rolling bearing on the shaft center side.

<Prior Art> Resin pulleys with rolling bearings are widely used for belt guidance.

FIGS. 8 and 9 show the structure of a conventional resin pulley of this type.

As shown in both figures, the resin pulley is composed of a rolling bearing 10 on the shaft center side and a resin main body 2° surrounding the rolling bearing 10. The resin main body 2° is a rolling bearing l. an inner diameter cylindrical portion 3° fixed to the outer ring of the cylindrical portion, an outer diameter cylindrical portion 4° having a belt guide surface, and a disk portion 5 between the inner and outer cylindrical portions 3° and 4°.
It consists of a large number of ribs 6° radially provided between the inner and outer rotating cylinder parts 3° and 4o.

During its manufacture, a rolling bearing l is placed in the center of the cavity between the molding dies. is set, this rolling bearing 1° is used as an insert part, and the cavity around it is press-filled with molten resin, thereby forming the rolling bearing 1°. A resin main body 2° is integrally molded around the .

By the way, in this type of resin pulley, internal stress in the tensile direction remains in the main body 2°, and this internal stress is applied to the rolling bearing l. It is concentrated on the outer circumferential portion of the cylindrical portion, that is, on the inner diameter cylindrical portion of 3°. Therefore, if there is a weak part in the 3° inner diameter cylindrical part, it is easy to break from that weak part. Therefore, it is necessary to provide uniform strength to the entire 3° inner diameter cylindrical portion and eliminate any weak parts.

In this regard, the problem is the location A where the molten resins flowing from different gate holes join together. When the inflowing molten resins merge in a low temperature state, a weld occurs at the merge point A, and the strength of that point becomes weak.

Therefore, conventionally, as shown in the figure, the gate hole is formed in the inner diameter cylindrical part 3. The cavity for the inner diameter cylindrical part has a
The molten resin at a high temperature flows in and merges with the molten resin from other gate holes while remaining at a high temperature to be integrated.

By the way, on the inner diameter cylindrical portion of the resin pulley at 3 degrees, a gate of 7 degrees remains as a molding mark corresponding to the gate hole of the mold (Problem to be solved by the invention) However, in the conventional resin pulley, When the molten resins flowing from separate gate holes merge in the cavity for the inner diameter cylindrical portion, they remain at the merged point and solidify, so the degree of mutual mixing is low and the strength of the merge point A is a sufficiently large value. Must not be.

Particularly, as shown in the figure, if the distance from the gate hole to the merging point A is long, the inflowing molten resin will join after being considerably cooled, and welds are likely to occur at the merging point A.

If such a weld exists at the 3° inner diameter cylindrical portion, there is originally residual internal stress in the 3° inner cylindrical portion, so
Even if a relatively small external force acts on the weld location, cracks will occur at the weld location in combination with the action of internal stress.

Further, in the conventional resin pulley, since the outer diameter cylindrical portion 4° is separated from the gate 7°, a problem also arises with the outer diameter cylindrical portion 4°.

In other words, in the cavity for the outer diameter cylindrical part, the molten resin at a lower temperature than other parts flows into part B of the outer diameter cylindrical part cavity, which is farther away from the gate hole, so the amount of sink marks is smaller than in other parts, and after molding, the surface A convex portion is formed in the cylindrical portion, and this convex portion reduces the roundness of the outer diameter cylindrical portion 4°.

To solve this problem of the convex portion of the outer diameter cylindrical portion of 4°, the gate 7
It is conceivable to move the angle to the outer diameter side, but if the gate hole of the mold is moved to the outer diameter side, the temperature of the molten resin flowing into the cavity for the inner diameter cylindrical part will decrease, and at 3° the inner diameter cylindrical part -Layer welds are more likely to occur.

The present invention has been made in view of the above-mentioned problems, and includes reducing the convex portion of the outer diameter cylindrical part as much as possible, and also molding the inner diameter cylindrical part with sufficiently mixed resin. , the purpose is to eliminate weak points in the inner diameter cylindrical part and increase the overall strength of the inner diameter cylindrical part.

<Means for Solving the Problems> In order to achieve the above object, the present invention has the following configuration.

The resin pulley of the present invention consists of a rolling bearing and a resin part main body fixed around the bearing, and the resin part main body includes an inner diameter cylindrical part, an outer diameter cylindrical part, and a disk part between the inner and outer cylindrical parts. and a large number of radial ribs, and is characterized in that gates are arranged at symmetrical positions in the circumferential direction across the ribs on the disc part. The gate here means a molding mark left corresponding to the gate hole of the mold.

Effect> In the above configuration, when molding the resin part main body,
Molten resin is press-filled into the cavity around the rolling bearing, which is an insert part, and the molten resin flows from circumferentially adjacent gate holes and joins in the rib cavity between each gate. In this state, it flows into the cavity for the inner diameter cylindrical part. In this way, the molten resin flowing into the cavity for the inner diameter cylindrical part merges in advance, so
Mix well with each other. Therefore, no weld occurs in the inner cylindrical portion.

In addition, since each gate hole is set close to the outer diameter cylindrical part, the molten resin will flow into the outer diameter cylindrical cavity before the temperature becomes low, which will prevent the formation of convex parts. can be suppressed.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

First Embodiment Figures 1 to 3 relate to the first embodiment of the present invention, in which Figure 1 is a front view of a resin pulley, Figure 2 is an enlarged front view of a part thereof, and Figure 3. 1 is a sectional view of a mold used for manufacturing the mold.

The resin pulley of this embodiment is composed of a rolling bearing 1 on the shaft center side and a resin part main body 2 surrounding it.
The inner diameter cylindrical part 3 is fixed to the outer ring of the rolling bearing 1, the outer diameter cylindrical part 4 has a belt guide surface, and the inner and outer cylindrical parts 3.
It is the same as the conventional example described above in that it is composed of a disk portion 5 between the inner and outer cylinder portions 3 and 4, and a large number of ribs 6 provided radially between the inner and outer cylindrical portions 3 and 4. The main body of the resin part is made of fiber-reinforced nylon 610 or 612 filled with 40% reinforcing fibers such as glass fibers.

This resin pulley differs from the conventional example in that gates 7 are provided on each disk portion 5 within each interval between ribs 6, 6, and the number of gates 7 is the same as the number of ribs 6. Each gate 7 is located between two adjacent cylindrical portions 3.4 at an intermediate diameter position between the inner and outer cylindrical portions 3.4.
It is located at an intermediate position between the two ribs 6.6. Thus, looking at each rib 6, two gates 7.7 are arranged symmetrically with respect to the rib 6 on either side of the rib 6.

Moreover, there is a predetermined positional relationship between the gate 7, the rib 6, and the inner diameter cylindrical portion 3, and as shown in FIG. Virtual line a(
The intersection angle θ between the rib 7 (indicated by a dashed line) and the rib 7 is θ≦45″ (1)
The inner diameter cylindrical portion 3 is disposed on the inner diameter side of a locus b (indicated by a two-dot chain line) with respect to the center of the pulley at the intersection of the virtual line a and the rib 7, which is expressed by the inequality below.

During manufacturing, a lower mold 8 and an upper mold 9 as shown in Fig. 3 are used.
A mold consisting of is used. Then, the lower mold 8 and the upper mold 9
A rolling bearing 1 is set in the center of the cavity between the two, and the molten resin is press-fitted into the cavity around the rolling bearing 1 as an insert part.

In Fig. 3, 3c is a cavity for the inner diameter cylindrical part 3, 4c is a cavity for the outer diameter cylindrical part 4, 5c is a cavity for the disc part 5, 6c is a cavity for the rib 6, A gate hole IO is opened in the cavity 5c. 11
is a runner.

The molten resin flowing from the gate hole 10 flows inside the disc cavity 5c and spreads both on the inner diameter side 4 and on the outer diameter side, but since the rib 6 is closer to the gate hole 10 than the inner diameter cylindrical part 3, As shown by the arrow in FIG. 2, the molten resin flows into the rib cavity 6c before flowing into the inner diameter cylindrical cavity 3c, where it merges with the molten resin that has flowed from another adjacent gate hole 10. Then, in a merged state, it flows toward the cavity 3C for the inner diameter cylindrical portion, and fills the cavity 3c.

In this way, the molten resin flowing from the separate gate holes 10 joins at the rib cavity 6c located between each gate hole 10, and then flows into the inner diameter cylindrical cavity 3C, so that the resin is sufficiently mixed. Since the inner cylindrical portion 3 is molded, no weld occurs in the inner cylindrical portion 3, and the molding strength is made uniform at each portion.

Furthermore, by arranging the inner diameter cylindrical portion 3 in the positional relationship shown in equation (1) above, the intersection angles of the reinforcing fibers filled with the molten resin flowing from the adjacent gate holes 1O11O become acute angles. This is caused by the non-directionality of the reinforcing fibers, as they merge and flow into the inner diameter cylindrical cavity 3C with the reinforcing fibers oriented in the direction of travel of the molten resin.

Further, the molten resin that has merged in the rib cavity 6C also heads toward the outer diameter side and fills the outer diameter cylindrical portion cavity 4C. In this case, since the gate hole IO is closer to the outer diameter cylindrical part 4 than the conventional one, the molten resin flows into the outer diameter cylindrical part cavity 4C before the temperature decreases. For this reason, the occurrence of convex portions is suppressed.

Second Embodiment FIGS. 4 and 5 relate to the second embodiment of the present invention.
The figure is a partial front view of the resin pulley, and FIG. 5 is a sectional view thereof.

In the resin pulley of this embodiment, an annular raised portion 12 is formed between the inner diameter cylindrical portion 3 and the gate 7. The rest of the configuration is the same as in the first embodiment, so corresponding parts are given the same reference numerals and explanations will be omitted.

At the time of molding, the molten resin that has flowed from the gate hole IO first flows into the cavity for the protrusion, passes through this cavity, flows into the cavity 6C for the rib, and in this cavity 6C for the rib, it flows into the other adjacent gate hole. It merges with the molten resin flowing in from 10. Therefore, the molten resins flowing from the separate gate holes 1O are merged and mixed. This is carried out earlier than in the example, and the mixing of the molding materials in the inner cylindrical portion 3 progresses further, and the reinforcing fibers filled also flow into the inner cylindrical portion 3 while being aligned in the direction of travel of the molten resin. Therefore, the strength of the cylindrical portion 3 is further made uniform.

Third Embodiment FIGS. 6 and 7 relate to the third embodiment, in which FIG. 6 is a partial front view of a resin pulley, and FIG. 7 is a sectional view of its inner diameter portion.

In the resin pulley of this embodiment, a reinforcing protrusion 13 is formed on the axial end surface of the inner diameter cylindrical portion 3.

The protrusion 13 is provided on the end surface of the inner diameter cylindrical portion 3 on an extension line of the rib 6.

The position where this protrusion 13 is formed is the confluence point of the molten resin flowing from the gate holes 10 adjacent to each other, and by providing the protrusion 13 at the confluence point of the molten resin in this way, the confluence point The thickness of the part increases and the strength increases. Therefore, even if a weld or a weld-like condition occurs at this junction, cracks are unlikely to occur.

In each of the above embodiments, the gates 7 are provided in the disk portions between all the ribs 6, but for example, the gates 7 may be provided in every second disk portion between the ribs 6. Good too.

<Effects of the Invention> As described above, according to the present invention, during molding, molten resin flowing from adjacent gate holes merges in the rib cavity and then flows into the inner diameter cylindrical cavity. , the resin is sufficiently mixed before flowing into the inner diameter side, and the inner diameter cylindrical portion is molded with the sufficiently mixed resin, and the degree of orientation of the reinforcing fibers filled therein is also improved. Therefore, no weld occurs in the inner diameter cylindrical portion, the molding strength becomes uniform, and a large molding strength is obtained as a whole.

In addition, as the gate hole approaches the outside diameter side, molten resin flows into the cavity for the outside diameter cylindrical part in a high temperature state, and a protrusion on the outer circumferential surface of the outside diameter cylindrical part, which was easy to occur in the past, It is minimized and roundness is improved.

[Brief explanation of drawings]

Figures 1 to 3 relate to the first embodiment of the present invention.
The figure is a front view of a resin pulley, FIG. 2 is an enlarged front view of a part thereof, and FIG. 3 is a sectional view of a molding die. 4 and 5 relate to a second embodiment of the present invention, with FIG. 4 being a partial front view and FIG. 5 being a sectional view thereof. 6 and 7 relate to the third embodiment of the present invention, FIG. 6 is a partial front view, and FIG. 7 is a partial front view.
The figure is a sectional view of the inner diameter portion. 8 and 9 relate to the conventional example, and FIG. 8 is a front view;
FIG. 9 is a sectional view thereof. l...Rolling bearing 2...Resin part body 3...
・Inner diameter cylindrical part 4...Outer diameter cylindrical part 5...Disc part 6...Rib 7...Gate

Claims (4)

[Claims] (1) Consisting of a rolling bearing and a resin part main body fixed around the bearing, the resin part main body includes an inner diameter cylindrical part, an outer diameter cylindrical part, a disc part between both the inner and outer cylindrical parts, and a disc part What is claimed is: 1. A resin pulley having a large number of radial ribs provided on the disk portion, wherein gates are arranged at symmetrical positions in the circumferential direction across the ribs on the disk portion. (2) The resin pulley according to claim 1, wherein the resin portion main body is filled with reinforcing fibers. (3) The resin pulley according to claim 2, wherein the imaginary line drawn from the gate to the adjacent rib and the rib have an intersection angle θ of θ≦45°. The resin pulley is characterized in that the inner diameter cylindrical portion is disposed on the inner diameter side of the locus with respect to the center of the pulley at the intersection position. (4) The resin pulley according to claim 1, wherein the gate is provided in each of the disk portions between adjacent ribs in the circumferential direction.