JP3415945B2 - Resin pulley and method and apparatus for manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin pulley, a method of manufacturing the same, and a manufacturing apparatus therefor, and in particular, an insert such as a bearing is arranged in the central portion and a rib for reinforcement is provided between an inner diameter portion and an outer diameter portion. The present invention relates to a resin-made pulley such as a resin-made pulley for an auto tensioner, a manufacturing method and a manufacturing apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, a direct gate of an injection molding machine is arranged at a position corresponding to the center of a resin pulley, as a means for manufacturing a resin pulley which has a circular plane shape and needs to secure circularity on the outer periphery. There is one that uses a so-called center direct gate, in which a predetermined resin material is injected from a direct gate into a cavity of a mold to form a predetermined shape. However, in this case, molding is difficult when an insert such as a bearing is arranged at the center of the resin pulley. Further, in the case of a resin pulley having a deformed portion such as a reinforcing rib in addition to the general shaped portion of the disc-shaped portion, even if the resin material is filled from the center, the resin material flows evenly through the deformed portion. Therefore, it may be difficult to secure a desired roundness on the outer peripheral surface of the resin pulley.

Therefore, conventionally, it has been proposed to increase the number of gate points so that the resin material flows in the cavity of the mold as uniformly as possible.

As a conventional resin pulley of this type, there is a technique disclosed in Japanese Patent Laid-Open No. 34260/1992.

This technique manufactures a resin pulley including a rolling bearing and a resin portion main body arranged around the rolling bearing. The resin portion main body is divided into an inner diameter cylindrical portion and an outer diameter cylindrical portion. It is composed of a disc portion connecting the both cylindrical portions and a large number of radial ribs provided on the disc portion. Then, in order to manufacture such a resin pulley, gates for resin filling are arranged at symmetrical positions in the circumferential direction sandwiching each rib on the disk portion. That is, by arranging such a gate between the inner diameter cylindrical portion and the outer diameter cylindrical portion, as a result, the temperature of the molten resin flowing into the outer diameter cylindrical portion cavity is brought close to the gate position. Is maintained as high as possible to minimize the occurrence of protrusions on the outer peripheral surface of the outer diameter cylindrical portion and improve the roundness.

[0006]

Since the conventional method and apparatus for manufacturing a resin pulley adopts a structure in which a large number of gates are provided as described above, a perfect circle on the outer peripheral surface of the outer diameter cylindrical portion is adopted. Although it is possible to improve the degree of roundness to a certain degree, there is still a limit to the improvement, and for resin pulleys such as pulleys for auto tensioners that require extremely high roundness, further roundness improvement is required. ing. In the above conventional technique, since the gate is provided between all the adjacent ribs, the amount of spool runner in the gate portion to be removed after the injection molding becomes large, and the yield of the resin material in the manufacturing is relatively high. It can be very low.

Further, in this type of resin pulley, it is important not only to have a high roundness, but also to have a small roundness difference between both sides of the pulley. If this difference is large, even if the circularity itself is good, it may cause vibration or abnormal noise, and the life of the belt may be shortened.

Therefore, an object of the present invention is to provide a resin pulley having a high roundness on the outer peripheral surface and a small difference in roundness between the two sides thereof, and a method and apparatus for manufacturing the same.

[0009]

A resin pulley according to a first aspect of the present invention comprises a bearing and a resin portion main body integrally formed on the outer periphery of the bearing by injection molding.
A disk-shaped base portion, a cylindrical inner diameter portion and an outer diameter portion that are formed so as to project on both sides in the thickness direction of the base portion along the inner peripheral portion and the outer peripheral portion of the base portion, and from the inner peripheral portion to the outer peripheral portion of the base portion. projecting in the thickness direction on both sides of the base extends radially cross-sectional shape in the radial direction
A plurality of resin-made pulleys having a plurality of substantially trapezoidal planar ribs whose shape is changed but whose cross-sectional area is substantially constant, wherein a plurality of pin gates for resin injection are provided on one side of the inner diameter portion. The pin gates are arranged at substantially equal intervals along the circumferential direction on the end face and between the adjacent ribs, and the thickness of the inner diameter portion on the side opposite to the side where the pin gates are arranged is opposite to the gate side. The thickness is smaller than the thickness of the inner diameter portion on the gate side.

A method of manufacturing a resin pulley according to a second aspect of the present invention comprises a bearing and a resin portion main body integrally formed on the outer periphery of the bearing, the resin portion main body having a disc-shaped base portion,
A cylindrical inner diameter portion and outer diameter portion that are formed so as to extend along the inner and outer peripheral portions of the base portion on both sides in the thickness direction of the base portion, and radially extend from the inner peripheral portion of the base portion to the outer peripheral portion and the thickness of the base portion. It is protruding both sides, but the cross-sectional shape a radially varying cross-section
A method for manufacturing a resin pulley having a number of substantially trapezoidal plane-shaped ribs having a substantially constant product , wherein a bearing is inserted to correspond to a base portion, an inner diameter portion, an outer diameter portion and ribs of a resin portion main body. An injection molding step of integrally molding the bearing and the resin portion main body by injecting the molten resin material into the mold cavity is provided, wherein a plurality of resin injection pin gates are provided in the inner diameter portion molding cavity. For forming the inner diameter portion on the side opposite to the side on which the pin gate is arranged, while arranging the one end surface at substantially equal intervals along the circumferential direction between adjacent rib forming cavities. The thickness of the cavity is made smaller than the thickness of the cavity for molding the gate side inner diameter portion in which the pin gate is arranged.

A resin pulley manufacturing apparatus according to a third aspect of the present invention comprises a bearing and a resin portion main body integrally formed on the outer periphery of the bearing, wherein the resin portion main body has a disc-shaped base portion,
A cylindrical inner diameter portion and outer diameter portion that are formed so as to extend along the inner and outer peripheral portions of the base portion on both sides in the thickness direction of the base portion, and radially extend from the inner peripheral portion of the base portion to the outer peripheral portion and the thickness of the base portion. It is protruding both sides, but the cross-sectional shape a radially varying cross-section
The product is a manufacturing apparatus of a resin pulley comprising a large number of substantially trapezoidal ribs having a substantially constant plane, and an insert portion for arranging and fixing a bearing as an insert, and the base portion provided around the insert portion, A cavity for forming the inner diameter portion, the outer diameter portion and the rib, and a pin gate for injecting a molten resin into the cavity are provided. Here, the pin gate is arranged along the circumferential direction on one end surface of the inner diameter portion molding cavity. A plurality of ribs at substantially equal intervals between adjacent rib forming cavities, and the thickness of the anti-gate side inner diameter forming cavity on the side opposite to the side where the pin gate is arranged is The thickness is smaller than the thickness of the arranged cavity on the gate side inner diameter portion.

[0012]

In the invention of claim 1, the base portion, the inner diameter portion, the outer diameter portion and the rib are formed by injecting a molten resin from the pin gate. Among them, the outer diameter portion is the inner diameter. The cross-sectional shape changes from the part to the radial direction, but the cross-sectional area is almost constant
Since the molten resin that has flowed to the outer diameter portion through a large number of substantially trapezoidal flat ribs and the molten resin that has flowed in the base portion themselves are simultaneously joined and molded, these molten resins are Immediately after joining at the outer diameter portion, a planar polygonal shaped body corresponding to the number of ribs provided is formed, and then a flat circular outer diameter portion is molded. Therefore, the outer shape of the outer diameter portion changes from a planar polygon corresponding to the number of many ribs to a circular shape, so that the roundness increases according to the number of ribs.
Also, since the thickness of the inner diameter on the non-gate side is smaller than the thickness on the inner diameter on the gate side, the pressure of the holding pressure that is transmitted to the non-gate side of the outer diameter via this inner diameter on the anti-gate side when holding pressure. The loss can be reduced and the holding pressure can be transmitted. Therefore, since the pressure can be favorably applied to the non-gate side of the outer diameter portion where the pressure is less likely to be exerted due to the distance from the pin gate, and the pressure can be well balanced with the gate side, the roundness can be improved. Therefore, it is possible to increase the roundness of the outer diameter portion and reduce the difference in roundness between the gate side and the non-gate side.

According to the second aspect of the present invention, in the injection molding step, when the molten resin is injected from each pin gate into the cavity, the inner surface of the cavity for molding the inner diameter section is radially cross-sectioned.
The molten resin that has flowed into the outer diameter molding cavity through a large number of rib molding cavities that have a substantially trapezoidal plane shape that changes in shape but has a substantially constant cross-sectional area , and the base molding cavity itself. Both of the flowing molten resins are simultaneously joined and molded in the outer diameter portion molding cavity. Therefore, immediately after these molten resins merge in the outer diameter forming cavity, a flat polygonal shaped body corresponding to the number of ribs provided is formed, and then a flat circular outer diameter portion is formed. It Therefore, the outer shape of the outer diameter portion changes from a planar polygon corresponding to the number of many ribs to a circular shape, so that the roundness increases according to the number of ribs. As a result, it is possible to obtain a resin pulley in which the outer diameter portion has a high roundness, and particularly the central portion has a high roundness. At the same time, the wall thickness of the cavity forming the anti-gate side inner diameter portion is made smaller than the wall thickness of the gate side inner diameter portion molding cavity, so that the outer diameter portion passes through this non-gate side inner diameter portion molding cavity during pressure retention. It is possible to further reduce the pressure loss of the holding pressure transmitted to the side opposite to the gate of the molding cavity, and improve the holding pressure transmissibility. Therefore, since it is far from the pin gate, it is difficult to apply pressure to the outer diameter molding cavity, and the pressure can be applied well on the side opposite to the gate, and the pressure is balanced in a good balance with the gate, improving the roundness. Therefore, the difference in roundness from the gate side can be reduced.

In the third aspect of the invention, when the molten resin is injected into the cavity from each pin gate , the cross-sectional shape changes in the radial direction from the cavity for molding the inner diameter portion, but the cross-sectional area is
Both the molten resin that has flowed into the outer diameter molding cavity through the multiple rib molding cavities that are almost constant in a plane and trapezoidal shape , and the molten resin that has flowed through the base molding cavity itself have an outer diameter The cavities for forming parts are joined together and formed. Therefore, immediately after these molten resins merge in the outer diameter forming cavity, a flat polygonal shaped body corresponding to the number of ribs provided is formed, and then a flat circular outer diameter portion is formed. It Therefore, the outer shape of the outer diameter portion changes from a planar polygon corresponding to the number of many ribs to a circular shape, so that the roundness increases according to the number of ribs. As a result, it is possible to obtain a resin pulley in which the outer diameter portion has a high roundness, and particularly the central portion has a high roundness. At the same time, the wall thickness of the cavity forming the anti-gate side inner diameter portion is made smaller than the wall thickness of the gate side inner diameter portion molding cavity, so that the outer diameter portion passes through this non-gate side inner diameter portion molding cavity during pressure retention. It is possible to further reduce the pressure loss of the holding pressure transmitted to the side opposite to the gate of the molding cavity, and improve the holding pressure transmissibility. For this reason, since it is far from the pin gate, it is possible to satisfactorily maintain pressure even on the side opposite to the gate of the cavity for molding the outer diameter where it is hard to apply pressure, and in a well-balanced manner with the gate side. It is improved, and the difference in roundness from the gate side can be further reduced.

[0015]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 is a plan view showing a resin pulley according to an embodiment of the present invention together with a gate position. 2 shows a resin pulley according to an embodiment of the present invention together with a gate position.
FIG. FIG. 3 is a perspective view showing independently the ribs of the resin pulley of the embodiment of the present invention.

As shown in FIGS. 1 and 2, this embodiment is embodied in a resin pulley used for a pulley for an auto tensioner or the like, and a resin material such as fiber reinforced resin mixed with reinforcing fibers such as glass fiber. And has a disk-shaped (donut plate-shaped) base portion 11 having a hole at the center. Then, along the entire length of the inner peripheral portion of the base portion 11, the inner ring 13 serving as a small-diameter cylindrical flange-shaped inner diameter portion is formed.
Are formed so as to project on both sides of the base portion 11 in the substantially thickness direction with the same protruding width. However, as will be described later, the thickness (outer diameter) thereof is changed on both sides of the base 11. Also,
Along the entire length of the outer peripheral portion of the base portion 11, an outer ring 15 as a cylindrical flange-shaped outer diameter portion having a diameter larger than that of the inner ring 13 is formed so as to project on both sides in the substantially thickness direction of the base portion 11 with an equal protruding width. The protruding width of the outer ring 15 from the base 11 is larger than the protruding width of the inner ring 13 from the base 11, and the outer peripheral surface thereof is formed as a belt guide surface. Furthermore, the base 1
A large number of ribs 17 projecting from the inner peripheral portion to the outer peripheral portion of the base portion 11 on both sides in the substantially thickness direction of the base portion 11 radially extend to integrally connect the inner ring 13 and the outer ring 15. In this embodiment, the number of the ribs 17 is 18 in total, and the ribs 17 are arranged at an equal angle (angle of 20 degrees) in the circumferential direction of the base 11.
Is divided into 18 equal parts. Further, each rib 17 has a substantially trapezoidal shape in plan as shown in FIG. 3, and is formed so as to gradually widen from the inner side to the outer side in the radial direction. However, on the contrary, the thickness is formed so as to gradually decrease. Therefore, although the cross-sectional shape of each rib 17 changes in the radial direction, the cross-sectional area is almost constant.

The resin portion main body of the resin pulley according to this embodiment has a base portion 11, an inner ring 13, an outer ring 15 and a large number of ribs 1.
7 and the resin part body is molded by injection molding. Therefore, in the present embodiment, a total of six pin gates 41 are applied as gates for injecting the molten resin, and the arrangement positions of these pin gates 41 are set to the inner ring 13.
It is set on one end face. Then, as shown in FIG. 1, these pin gates 41 are arranged on the end surface of the inner ring 13 at equal intervals in the circumferential direction, and are also arranged between two adjacent ribs 17. Therefore, each pin gate 41 is arranged for every three ribs 17 in this embodiment. Along with this, the inner rings 13a and 13b on each side of the base 11 are formed to have different wall thicknesses (outer diameters) in correspondence with the arrangement of the pin gate 41. That is, as shown in FIG. 2, the thickness of the inner ring 13b on the side opposite to the side on which the pin gate 41 is arranged (gate side) (anti-gate side) is the same as the inner ring 13a on the side on which the pin gate 41 is arranged (gate side). It is relatively smaller than the wall thickness. Therefore, the resin portion main body is substantially symmetrical about the base portion 11, but the inner ring 13
Only the part of is asymmetric.

A bearing 19 such as a rolling bearing as an insert is provided on the inner peripheral surface of the inner ring 13 with respect to the resin main body so as to be integrally fixed during injection molding. There is. A coupling hole 20 for supporting and coupling to a shaft (not shown) or the like is provided at the center of the bearing 19. Further, the inner ring 13 projects inward at both ends in the width direction over the entire length in the circumferential direction, and supports the outer peripheral edge portion of the bearing 19.

Here, an auxiliary machine for an automobile (hereinafter referred to as an auxiliary machine) such as an alternator, a compressor, a pump, a fan and the like as an example to which the resin pulley of this embodiment can be applied uses an engine as a drive source. Since it is driven through the coupling device, it has a fluctuation range of the rotation speed from low rotation speed to high rotation speed according to the engine rotation speed. In particular, when the auxiliary machine is driven to rotate at high rotation speed, the temperature of the auxiliary machine becomes high due to the heat from the engine, and the usage conditions of the resin pulley used for the auxiliary machine become very severe. Therefore, as the bearing 19 of the resin pulley, it is preferable to use a rolling bearing that can be applied to a wider range of use conditions than a sliding bearing. That is, when a rolling bearing is used, more stable performance can be exhibited.

Next, an apparatus for manufacturing the resin pulley constructed as described above will be described.

FIG. 4 is a sectional view showing a mold of a resin pulley manufacturing apparatus according to an embodiment of the present invention.

As shown in FIG. 4, the mold has an upper mold 21 and a lower mold 23. In each of the upper mold 21 and the lower mold 23, a portion other than the bearing 19 of the resin pulley, that is, the inner ring 13 is formed. , A cavity having a shape corresponding to a half portion in the thickness direction (axial direction) of the resin portion main body composed of the base portion 11, the outer ring 15 and the rib 17 is formed by engraving, and the mating surface (parting line) 25 is a resin pulley. It is arranged so as to come to the center of the outer ring 15 in the axial direction. Then, when the upper mold 21 and the lower mold 23 are clamped, as shown in FIG. 4, these cavities are integrated to form a molding space corresponding to the shape of the resin pulley excluding the bearing 19. ing. That is, the molding space is the cavity 3 for molding the inner ring 13 as the inner diameter portion.
1, a cavity 33 for molding the base portion 11, a cavity 35 for molding the outer ring 15 as an outer diameter portion, and a cavity 37 for molding the rib 17.

An insert portion 39 which is a space having a shape corresponding to the bearing 19 is provided on the inner peripheral side of the cavity 31 for molding the inner ring 13, and the bearing 19 is inserted into the insert portion 39 by a fixing member (not shown). It is designed to be fixed as. As a fixing member for fixing the bearing 19 to the insert portion 39 of the mold, there is a core pin or a collet. When the core pin is used, the mold structure can be made relatively simpler than that of the collet. on the other hand,
When the collet is used, the mold structure may be slightly complicated, but the productivity is higher and the production efficiency is very good. In particular, when the collet is used, the work of setting the rolling bearing in the mold is easy, and the positional accuracy of the fixed portion of the rolling bearing after fixing is high.

Further, in this embodiment, the cavities 31, 3 are
The pin gates 41 are used as gates for injecting the molten resin into the parts 3, 35, 37, and the tips of the plurality of pin gates 41 are circumferentially aligned with one end of the cavity 31 for molding the inner ring 13 and the like. The pin gates 41 are arranged at intervals, and are arranged in the cavities 31 for molding the inner ring 13 between the adjacent ribs 17. That is, in the present embodiment, as shown in FIGS. 1 and 2, a total of six pin gates 41 corresponding to the eighteen ribs 17 are included in the inner ring 13.
Three ribs 17 are arranged at equal intervals (each at an angle of 60 degrees) so as to face one end surface (upper surface in FIG. 4) in the width direction of the cavity 31 for molding, and each pin gate 41. Is arranged on the end surface of the cavity 31 for molding the inner ring 13 at an intermediate position between the adjacent ribs 17. Each pin gate 41 is connected to a runner 43, and melted resin injected from an injection device into a spool (neither is shown)
Cavity 3 from pin gate 41 via runner 43
When the molten resin is injected into the inner ring 13, the cavity 31 for molding the inner ring 13, the cavity 33 for molding the base portion 11 and the cavity 37 for molding the rib 17 are injected.
Flow into the cavity 35 for molding the outer ring 15 and flow into all the cavities 31, 33, 35, 37.
Is to be filled.

Here, the pin gate 41 is accompanied by opening of the mold in consideration of the shape of the circular resin molded product, particularly the shape and thickness of the inner peripheral portion of the base portion 11 which becomes the gate position of the inner ring 13 and the like. The diameter is selected to be as large as possible within the range that allows automatic removal of the gate solidified material. That is, in the pin gate 41, the gate sealing time is made as long as possible, the pressure holding time of the molten resin in the cavity 35 for molding the outer ring 15 is made long, and the orientation of the reinforcing fibers such as glass fibers is made as small as possible. The diameter is made as large as possible so as to provide a non-uniform state, and in this embodiment, a gate diameter of 2 mm is used in order to obtain the best result from this viewpoint.

Further, in the present embodiment, the cavity 31 for molding the inner ring 13 has a pin gate centered on the cavity 33 for molding the base 11 corresponding to the thickness of the gate inner ring 13a and the anti-gate inner ring 13b. The side on which 41 is arranged and the side opposite thereto have the same width, but the cavity thickness is changed. That is, the anti-gate side inner ring molding cavity 31 on the side opposite to the side on which the pin gate 41 is disposed.
The cavity thickness of b is smaller than the cavity thickness of the gate side inner ring molding cavity 31a in which the pin gate 41 is arranged. In other words, the thickness of the gate side inner ring molding cavity 31a is made larger than the thickness of the non-gate side inner ring molding cavity 31b.
It is preferable that the difference in the thickness of the inner ring molding cavity between the gate side and the counter gate side, that is, the difference in the wall thickness between the gate side inner ring 13a and the counter gate side inner ring 13b, is large to some extent. However, if this difference is too large, the difference in rigidity between the gate side and the non-gate side of the formed inner ring 13 becomes excessive, which is not preferable. Therefore, it is generally preferable that the thickness difference is about 10 to 40% of the thickness of the gate-side inner ring molding cavity 31a that is appropriately set in terms of the flowability of the molten resin and the like. Then, the cavity 3 for molding the inner ring on the side opposite to the gate is formed by this difference in thickness
It is preferable to reduce the thickness (outer diameter) of 1b.

Next, a method of manufacturing a resin pulley using the resin pulley manufacturing apparatus of this embodiment having the above-described structure will be described.

First, the bearing 19 is placed as an insert in the insert portion 39 at a predetermined position and fixed by a fixing member, and the upper mold 21 and the lower mold 23 are clamped to form the bearing 19.
Cavities (molding spaces) 31, 3 having shapes corresponding to the shapes of the inner ring 13, the base 11, the ribs 17, and the outer ring 15 around the
3, 35, 37 are formed, and the molten resin from the injection device is
It is injected from the pin gate 41 into the cavities 31, 33, 35, 37 via the spool and the runner 43. Then, the molten resin first flows in from one end portion in the width direction of the cavity 31 for molding the inner ring 13 and flows in the width direction to fill the inside of the cavity 31 and to the cavity 31 for molding the inner ring 13. It flows into the continuous cavity 11 for molding the base portion 11 and expands in the circumferential direction, and at the same time the outer ring 15
It flows radially towards the molding cavity 35. At the same time, the molten resin injected from the pin gate 41 flows in the circumferential direction along the outer peripheral surface of the cavity 31 for molding the inner ring 13, as shown by the arrow in FIG. The cavity 37
Flows in. At this time, the molten resin from each pin gate 41 independently flows into the cavity 37 for molding the rib 17 in the immediate vicinity (on both sides) of the pin gate 41, and the molten resin from the adjacent pin gates 41 is placed between the pin gates 41. Of the three ribs 17, they join the central cavity 17 for molding the rib 17 and flow into the cavity 37. The inflow amount of the molten resin at this time is about half of the inflow amount of the molten resin flowing from each pin gate 41 into the cavity 37 for molding the rib 17 in the immediate vicinity thereof, and as a result, from the two adjacent pin gates 41 to the center. The amount of molten resin that flows into the cavity 37 for molding the rib 17 of the
It is substantially the same as the inflow amount of the molten resin flowing from 1 to the rib 37 molding cavity 37 in the vicinity thereof.

In this way, each of the six pin gates 41 has three cavities 37 for molding 18 ribs 17 and three cavities 37 for molding these three ribs 17.
The molten resin flows into the cavities 37 for molding the ribs 17 and the cavities 33 for molding the base 11 in a form of taking charge of the portions of the cavities 33 for molding the base 11 which are continuous to the cavities 35 for molding the outer ring 15. And flows in the longitudinal direction (radial direction of the cavity 33 for molding the base portion 11).

The flow state (flow pattern) of the molten resin at this time will be described below.

FIG. 5 is an explanatory view showing a resin flow pattern in the method of manufacturing the resin pulley according to the embodiment of the present invention.

In the figure, first, the cavities 31, 3 are shown.
The molten resin flowing in the inner rings 3, 35, 37 from the inner ring 13 side to the outer ring 15 side is, as indicated by the chain double-dashed line in FIG. 5, for a while from the position immediately after being injected and injected from the six pin gates 41. Corresponding to the number of the pin gates 41, they are developed in a substantially hexagonal shape in a plane and in a substantially radial direction, and are filled up to the middle of the inner ring 13 part and the rib 17. Then, the molten resin flows into the cavity 3
While flowing inside 1, 33, 35, 37 to the outer ring 15 side,
Inside the cavity 37 for molding the eighteen ribs 17, the base portion 11
It advances faster than the inside of the cavity 33 for molding, the shape is transferred to a plane substantially octagonal corresponding to the number of the 18 ribs 17 and developed, and when the end of the cavity 37 for molding the rib 17 is reached, The outer shape is shown by the solid line in FIG. And
Finally, when the outer periphery of the molten resin flowing in the cavity 33 for molding the base portion 11 flows into the cavity 35 for molding the outer ring 15 and joins with the molten resin from the cavity 37 for molding the ribs 17, the molten resin melts. The resin has cavities 33 and 35 between the ends of the cavity 37 for molding the rib 17.
The remaining resin fills the remaining space, and the shape of the molten resin shifts from an approximately 18-sided plane to a circle. As a result, the cylindrical outer ring 15
The part is molded and the entire shape of the resin pulley is completed.

The resin flow pattern was obtained as a result of flow analysis by computer aided engineering (CAE). According to this simulation, a very uniform temperature distribution and filling state were obtained throughout the flow process. Was given.

In the case of a normal resin pulley, it is preferable to inject the molten resin from each pin gate 41 at the same time from the viewpoint of uniform resin flow. However, depending on the type or shape of the resin pulley, The injection timing may be controlled to obtain the most uniform flow condition.

Next, after the molten resin has been filled in the cavities 31, 33, 35, 37 of the mold in this way, a pressure is applied to the filled molten resin in the pressure holding stage. In this case, since the cavity 35 for molding the outer ring 15 on the side opposite to the gate is separated from the pin gate 41 particularly at the end portion, the holding pressure is less likely to be applied than on the gate side. Therefore, in this embodiment, as described above, the thickness of the anti-gate side inner ring molding cavity 31b is made smaller than that of the gate side inner ring molding cavity 31a. The pressure loss of the holding pressure reaching the outer ring 15 molding cavity 35 on the side opposite to the gate via 31b is further reduced. Therefore, in this pressure-holding stage, the holding pressure is satisfactorily applied to the cavity 35 for molding the outer ring 15 on the side opposite to the gate, similarly to the gate side. As a result, the outer ring 15
The pressure balance in the molding cavity 35 is also improved.

Here, the roundness of the resin pulley manufactured as described above will be specifically described based on the measurement result.

FIG. 6 is a table comparing the roundness of the resin pulley manufactured by the manufacturing method of the embodiment of the present invention with the roundness of the resin pulley manufactured by the conventional manufacturing method. .

Here, the resin pulley has an outer diameter of 80 mm,
A resin pulley for an auto tensioner having a bearing outer diameter of 47 mm and a width of 26 mm. As a molding material, 6 nylon containing 43% of glass fiber as a reinforcing fiber, 6.6 nylon,
Polyamide resin such as 11 nylon and 12 nylon (PA
6/12 GF43, for example, 77G43 manufactured by DuPont
L black) is used. Further, the conventional method of manufacturing a resin pulley uses a multi-point gate in which a pin gate is arranged between the ribs of the base, as in the technique disclosed in JP-A-4-34260. The "roundness" is a measurement of the roundness (difference of unevenness) on the outer peripheral surface of the outer ring 15 which is the belt guide surface of the resin pulley, and the "gate side" means that the pin gate 41 is arranged. The circularity of the end surface (the left end surface in FIG. 2) of the outer peripheral surface 15 of the outer ring
“Center” means the circularity of the outer ring 15 outer peripheral surface at the center position in the width direction, and “anti-gate side” means the end surface of the outer ring 15 outer surface on the side opposite to the side where the pin gate 41 is arranged (see FIG. 2). Roundness of the center right edge).

As shown in the roundness measurement result of FIG. 6, the resin pulley manufactured by the method of this embodiment has a roundness of any portion more than that manufactured by the conventional method. It has a high roundness. In particular, the portion requiring the highest roundness for guiding the belt is the central portion in the width direction of the outer peripheral surface of the outer ring 15, and the roundness of this portion is 32 μm, which is smaller than that of the conventional method. You can see that it has improved dramatically.

Further, in the resin pulley of this example, the thickness of the inner ring molding cavity 31b on the side opposite to the gate of the mold is smaller than that of the gate side inner ring molding cavity 31a, and the thickness of the gate side inner ring 13a is 2 The thickness of the inner ring 13b on the side opposite to the gate is set to 2.0 mm, while the thickness of the inner ring 13b on the side opposite to the gate is set to 2.0 mm. The difference with is also very small. That is, the circularity on the gate side is 57 μm, while the circularity on the anti-gate side is 58 μm, both of which are high roundness, while the difference is only 1 μm.

FIG. 7 shows a measurement chart of the roundness of the resin pulley of this embodiment, which is made of a resin for comparison without changing the wall thickness of the inner ring 15 between the gate side and the non-gate side. It is a table shown in comparison with that of a pulley. The roundness (μm) is shown in the center of each roundness measurement chart.

In FIG. 7, the circularity measurement chart of the resin pulley of this embodiment is shown in the center row, and the resin pulleys for comparison are the gate inner ring 13a and the non-gate side inner ring 13.
Both of the thicknesses of b are 2.5 mm or 2.0 mm, and these roundness measurement charts are shown in the left column and the right column, respectively. As shown in this table, the resin pulley of the comparative example manufactured in the same manner without changing the wall thickness of the inner ring 15 between the gate side and the non-gate side has good roundness, The difference in roundness between the gate side and the anti-gate side tends to be large. Therefore, from the comparison with these comparative examples, the thickness of the anti-gate side inner ring 13b is set to the gate side inner ring 1
It can be seen that the difference in circularity between the gate side and the non-gate side of the outer peripheral surface of the outer ring 15 can be reduced by making the thickness smaller than 3a.

As described above, the resin pulley of the above-described embodiment comprises the bearing 19 and the resin portion main body integrally formed on the outer periphery of the bearing 19 by injection molding.
A disk-shaped base 11 having a hole in the center, an inner ring 13 as a small-diameter cylindrical inner diameter portion formed on both sides in the thickness direction of the base 11 along the inner periphery of the base 11, and an outer periphery of the base 11. An outer ring 15 as a large-diameter cylindrical outer diameter portion that is formed so as to project on both sides in the thickness direction of the base portion 11 along the portion, and the base portion 1.
18 ribs 17 that extend radially from the inner ring 13 of the inner peripheral portion of 1 to the outer ring 15 of the outer peripheral portion and project to both sides in the thickness direction of the base 11 and are arranged at equal angles in the circumferential direction of the base 11.
In which a total of six pin gates 41 for resin injection are provided on one end surface of the inner ring 13 of the inner peripheral portion of the base portion 11 at equal intervals (equal angles). ), And each of the pin gates 41 is arranged on the end face of the inner ring 13 at the central position between the adjacent ribs 17,
Further, the wall thickness (outer diameter) of the anti-gate side inner ring 13b on the side opposite to the side where the pin gate 41 is arranged is equal to the wall thickness (outer diameter) of the gate side inner ring 13a on the side where the pin gate 41 is arranged.
It is smaller than.

Therefore, according to the resin pulley of the above-described embodiment, when molding this by injection molding, the molten resin injected from the pin gate 41 causes the base portion 11, the inner ring 13 as the inner diameter portion, and the outer ring as the outer diameter portion. Among them, the outer ring 15 as an outer diameter portion flows from the inner ring 13 of the inner peripheral portion of the base portion 11 to the outer peripheral portion of the base portion 11 through the eighteen ribs 17. Since both the molten resin and the molten resin that has flowed through the base portion 11 themselves merge at the same time, immediately after these molten resins merge at the outer ring 15, depending on the number of ribs 17 provided, A flat 18-sided polygonal shaped body is formed, and then the flat circular outer ring 15 is formed. Therefore, the outer shape of the outer ring 15 shifts from a flat surface octagonal shape corresponding to the number of the eighteen ribs 17 to a circular shape, so that the roundness thereof increases according to the number of the ribs 17. As a result, the roundness of the outer ring 15 is improved, and in particular, a high roundness is obtained in the central portion of the outer ring 15. Along with this, since the thickness of the anti-gate side inner ring 13b is made smaller than that of the gate side inner ring 13a, the anti-gate side inner ring 17b transmits the anti-gate side inner ring 17b to the anti-gate side of the outer ring 15 through the anti-gate side inner ring 17b. The pressure loss of the pressure can be reduced and its transmissibility can be further enhanced. Therefore, since the pressure is applied favorably to the non-gate side of the outer ring 15 which is difficult to apply the pressure because it is separated from the gate, and the pressure is applied in a well-balanced manner with the gate side, the roundness can be improved. As a result, the difference in roundness between the gate side and the non-gate side of the outer ring 15 can be further reduced.

Therefore, the resin pulley of the above embodiment is
Since the circularity of the outer ring 15 as the outer diameter portion is high and the difference in circularity between the gate side and the non-gate side is small, the fluttering of the belt during rotation is reduced and the noise during operation can be reduced. , It is possible to reduce uneven rotation.
Further, the contact frictional resistance between the belt guide surface of the outer ring 15 and the belt can be reduced, and the product life of the resin pulley and the belt can be extended.

Further, in the resin pulley of this embodiment, the rolling bearing is adopted as the bearing 19 which takes charge of the rotating portion as described above to ensure further durability, and the roundness of the outer ring 15 which is the belt contacting portion is ensured. Since it has high accuracy, it is ideal as a pulley. In particular, it is suitable as a resin pulley for an auto tensioner for automobile accessories, such as vibration prevention, heat resistance, and rotation resistance.

Further, the method of manufacturing the resin pulley of the above-mentioned embodiment comprises the bearing 19 and the resin portion main body integrally formed on the outer periphery of the bearing 19, and the resin portion main body is a disk having a hole in the center thereof. -Shaped base portion 11, an inner ring 13 as a small-diameter cylindrical inner diameter portion that is formed to project on both sides in the thickness direction of the base portion 11 along the inner peripheral portion of the base portion 11, and the base portion 11 along the outer peripheral portion of the base portion 11. An outer ring 15 as a large-diameter cylindrical outer diameter portion that is formed on both sides in the thickness direction, and radially extends from the inner ring 13 at the inner peripheral portion of the base portion 11 to the outer ring 15 at the outer peripheral portion and in the thickness direction of the base portion 11. A method for manufacturing a resin pulley, comprising a total of 18 ribs 17 protruding on both sides and arranged at an equal angle in the circumferential direction of the base 11, wherein the bearing 19 is inserted, and the inner ring 13 of the resin body is inserted. , Base 11, outer ring 15 and ribs 17 Corresponding mold cavity 3
1, 33, 35, 37 by injecting a molten resin material to integrally mold the bearing 19 and the resin portion main body, and an injection molding process including mold clamping, injection, and pressure holding steps, Here, a total of 6 pin gates 41 for resin injection are arranged at equal intervals (equal angles) along the circumferential direction on one end surface of the cavity 31 for molding the inner ring 13 in the inner peripheral portion of the base portion 11. At the same time, each of the pin gates 41 is arranged on the end face of the inner ring 13 molding cavity 31 at the central position between the adjacent ribs 17 molding cavities 37, and the anti-gate on the side opposite to the side where the pin gates 41 are arranged. The thickness of the cavity 31b for molding the inner side ring 13b is
Gate side inner ring 13a on the side where the pin gate 41 is arranged
The thickness is smaller than the thickness of the molding cavity 31a.

Therefore, according to the method of manufacturing the resin pulley of the above embodiment, in the injection molding process, the molten resin is injected from the pin gates 41 into the cavities 31, 33 and 3.
When injected into 5, 37, the inner ring 13 of the inner peripheral portion of the base 11
A total of 18 ribs 17 from the molding cavity 31 through the molding cavity 37 and the outer ring 15 on the outer peripheral portion of the base portion 11.
Both the molten resin that has flowed into the molding cavity 35 and the molten resin that has flowed through the molding cavity 33 itself of the base portion 11 merge together in the molding cavity 35 of the outer ring 15 as the outer diameter portion for molding. To be done. For this reason, these molten resins are used in the cavity 3 for molding the outer ring 15.
Immediately after merging in 5, the flat 18-sided polygonal shaped body corresponding to the number of the ribs 17 provided in total 18 is formed, and then the flat circular outer ring 15 is formed. Therefore, the outer shape of the outer ring 15 shifts from a flat surface octagonal shape corresponding to the number of the eighteen ribs 17 to a circular shape, so that the roundness thereof increases according to the number of the ribs 17. As a result, the roundness of the outer ring 15 is improved,
In particular, it is possible to obtain a resin pulley having a high roundness at the central portion of the outer ring 15. Along with this, since the thickness of the cavity 31b for molding the anti-gate side inner ring 13b is made smaller than the thickness of the cavity 31a for molding the gate side inner ring 13a, the pressure loss in this cavity 31b becomes smaller, whereby the pin gate is formed. The outer ring 15 which is hard to be applied with the holding pressure in the holding pressure stage because it is separated from 41.
The pressure transmissibility is enhanced on the side opposite to the gate of the molding cavity 35, and the pressure is favorably and well-balanced with the gate side. Therefore, since the anti-gate side of the outer ring 15 is formed with sufficient pressure to improve the roundness, not only the roundness is high, but also the difference in roundness between the gate side and the anti-gate side is small. A resin pulley can be obtained.

Further, the apparatus for manufacturing a resin pulley of the above-mentioned embodiment comprises a bearing 19 and a resin portion main body integrally formed on the outer periphery of the bearing 19, and the resin portion main body has a circular plate having a hole in the center thereof. -Shaped base portion 11, an inner ring 13 as a small-diameter cylindrical inner diameter portion that is formed to project on both sides in the thickness direction of the base portion 11 along the inner peripheral portion of the base portion 11, and the base portion 11 along the outer peripheral portion of the base portion 11. An outer ring 15 as a large-diameter cylindrical outer diameter portion that is formed on both sides in the thickness direction, and radially extends from the inner ring 13 at the inner peripheral portion of the base portion 11 to the outer ring 15 at the outer peripheral portion and in the thickness direction of the base portion 11. A resin pulley manufacturing apparatus comprising a total of 18 ribs 17 projecting on both sides and arranged at equal angles in the circumferential direction of the base 11, and an insert portion 39 for arranging and fixing the bearing 19 as an insert, Of the insert portion 39 The inner ring 13 provided on the circumference, a base 11, outer ring 15 and each of the cavities 31, 33, 35, 37 of the ribs 17 for forming the cavity 31,3
3, 35, 37, and a pin gate 41 for injecting a molten resin, wherein the pin gate 41 is a cavity 31 forming the inner ring 13 of the inner peripheral portion of the base 11.
A total of 6 pieces are arranged at equal intervals (equal angles) along the circumferential direction on one end face, and each of the pin gates 41 is formed with a cavity 37 for molding the inner ring 13 at a central position between the adjacent cavities 37 for molding ribs 17. 31, the thickness of the cavity 31b for forming the anti-gate side inner ring 13b on the side opposite to the side on which the pin gate 41 is arranged is set to the thickness for forming the gate side inner ring 13a on the side on which the pin gate 41 is arranged. The thickness is smaller than the thickness of the cavity 31a.

Therefore, according to the resin pulley manufacturing apparatus of the above embodiment, when molding the resin pulley using the resin pulley, the molten resin is injected from the pin gates 41 into the cavities 31, 33, 35 and 37. When injected, the melt flows from the cavity 31 for molding the inner ring 13 on the inner peripheral portion of the base 11 into the cavity 35 for molding the outer ring 15 on the outer peripheral portion of the base 11 through a total of 18 ribs 17 for molding the ribs 17. Both the resin and the molten resin that has flowed in the cavity 33 itself for molding the base portion 11 are merged and molded at the same time in the cavity 35 for molding the outer ring 15 as the outer diameter portion. For this reason, immediately after these molten resins merge in the cavity 35 for molding the outer ring 15, a flat 18-sided polygonal shaped body corresponding to the number of ribs 17 provided in total 18 is formed, and then the flat circular outer ring 15 is formed. Is molded. Therefore, the outer shape of the outer ring 15 is a flat surface 18 corresponding to the number of the ribs 18.
The roundness of the rib 17 changes because it changes from square to circular.
It increases according to the number of. As a result, the roundness of the outer ring 15 is improved, and in particular, the roundness at the central portion of the outer ring 15 can be increased. Also, along with this, the inner ring 13b on the side opposite to the gate
The thickness of the cavity 31b for molding is the inner ring 13a on the gate side.
Since the thickness is smaller than the thickness of the molding cavity 31a, it is necessary to further reduce the pressure loss of the holding pressure transmitted to the outer ring 15 on the side opposite to the gate 15 through the cavity 31b during the pressure holding stage. You can As a result, the cavity 3 for molding the outer ring 15 is hard to be kept in the pressure-holding stage because it is separated from the pin gate 41.
Even on the side opposite to the gate of No. 5, the holding pressure can be applied satisfactorily and in good balance with the gate side. Therefore, the anti-gate side of the outer ring 15 is formed with sufficient pressure and the roundness is improved, so that the difference in roundness from the gate side can be reduced. Therefore, according to the resin pulley manufacturing apparatus of the above embodiment, it is possible to obtain a resin pulley having a high roundness and a small roundness difference between the gate side and the non-gate side.

Further, in the above embodiment, the gate diameter of the pin gate 41 is set to about 2 mm, which is the maximum diameter within the range where the automatic cutting of the solidified material of the gate accompanying the mold opening is not impaired. Therefore, the gate sealing time is extended and the outer ring 1
A sufficient holding pressure is applied to the molten resin of No. 5, and the outer ring 1
The roundness of 5 can be further improved. In addition, when the gate diameter is increased, the orientation of the glass fibers as the reinforcing fibers contained in the molten resin is reduced and they are in a non-uniform state, so that the shrinkage rate of the resin during cooling becomes uniform. The roundness of can be further improved. Further, the rib 17 that is usually used for reinforcement is used as a path for resin flow during molding, and the rib 17 is used.
Since there are 18 radial lines, 6 pin gates 4
The outer shape of the molten resin injected from No. 1 can be smoothly changed from a substantially hexagonal plane to an approximately 18-sided plane so that the outer ring 15 has a circular shape, and the flow conditions are also uniform. You can In the resin pulley molded as described above, in particular, the resin that has flowed to the outer peripheral portion of the cavity 33 for molding the base portion 11 and the resin that has flowed to the end of the cavity 37 for molding the ribs 17 are outer rings. 15
Join at the widthwise central part of the molding cavity 35,
Since the pressure distribution is further increased, it is possible to further increase the circularity of the central portion in the width direction of the outer race 15, which is a portion that guides the belt and is the most important portion as a resin pulley such as an auto tensioner pulley. Therefore, the product quality can be further improved.

By the way, in the above embodiment, the pin gate 4
1 is provided corresponding to 18 ribs 17 in total, which is a divisor thereof, and a total of 6 ribs are provided by one pin gate 41, and these ribs are surrounded by one end surface of the inner ring 13. Although the pin gates 41 are arranged at equal intervals in the direction, the number and arrangement of the pin gates 41 are not limited to this in the case of implementing the present invention, and the resin is radially spread in the cavity to uniformly fill the cavity. Anything can be used as long as it works. For example, a total of nine pin gates 41 are provided for a total of 18 ribs 17, and the pin gates 41 are arranged at the central positions between the adjacent ribs 17, and one pin gate 41 takes charge of the two ribs 17 to allow the resin flow. May be changed from a substantially 9-sided shape to a 18-sided shape. Alternatively, as long as the resin can be radially expanded and uniformly filled in the cavity, the number of pin gates 41 is not set to be a divisor of the number of ribs 17, but is set to, for example, 3 to 5 or 7 or more. 41 for inner ring 1
3 may be arranged at equal intervals in the circumferential direction so that the flow of resin is changed from a substantially regular polygonal shape in a plane to an 18-sided shape.

Further, the pin gates 41 can be arranged in a circumferential direction of the inner ring 13 at equal intervals, or can be arranged with a slight gap therebetween so long as the uniform filling of the resin is not impaired. It may be arranged at substantially equal intervals in the circumferential direction of 13. Furthermore, in addition to arranging each pin gate 41 on the inner ring 13 at the central position between the adjacent ribs 17,
As long as the uniform filling of the resin is not impaired, the ribs 17 can be arranged at any positions between the ribs 17, and the positions can be changed appropriately. The gate diameter of the pin gate 41 is about 2 mm.
In addition to the above, as long as the gate sealing time is set as long as possible and the automatic removal of the gate solidified material due to mold opening is possible, it can be changed appropriately according to various conditions such as the shape and size of the resin pulley. You may. However, with an ordinary resin pulley, if the gate diameter is set to about 2 mm, it is possible to secure a very high roundness as described above.

The number of ribs 17 is not limited to 18,
The pulley may be appropriately changed depending on the purpose of use of the resin pulley and the degree of reinforcement, but if the number of ribs 17 is large, the outer shape of the molten resin when molding the outer ring 15 is a flat polygonal shape close to a circle. It is possible to improve the roundness. In addition, when the number of ribs 17 is changed, the number of pin gates 41 is correspondingly changed to change each pin gate 41.
Are arranged between the adjacent ribs 17. That is, the number of ribs 17 and the number of pin gates 41 and the ratio of these numbers may be any combination other than the above as long as the uniform filling of the resin is not impaired.

In addition to the rolling bearing, the bearing 19 as an insert may be any other type of bearing such as a sliding bearing or its elements, and may be a bush or core for reinforcement. You can also Further, the above-mentioned resin pulley can be applied not only as a pulley for an auto tensioner but also as any kind of pulley, and also as a drive or driven pulley.

[0057]

As described above, the resin pulley according to the invention of claim 1 comprises the bearing and the resin portion main body integrally formed on the outer periphery of the bearing by injection molding.
A disk-shaped base portion, a cylindrical inner diameter portion and an outer diameter portion that are formed so as to project on both sides in the thickness direction of the base portion along the inner peripheral portion and the outer peripheral portion of the base portion, and from the inner peripheral portion to the outer peripheral portion of the base portion. projecting in the thickness direction on both sides of the base extends radially cross-sectional shape in the radial direction
A plurality of resin-made pulleys having a plurality of substantially trapezoidal planar ribs whose shape is changed but whose cross-sectional area is substantially constant, wherein a plurality of pin gates for resin injection are provided on one side of the inner diameter portion. The pin gates are arranged at substantially equal intervals along the circumferential direction on the end face and between the adjacent ribs, and the thickness of the inner diameter portion on the side opposite to the side where the pin gates are arranged is opposite to the gate side. The thickness is smaller than the thickness of the inner diameter portion on the gate side.

Therefore, according to this resin pulley,
When this is molded by injection molding, the molten resin injected from the pin gate forms the base portion, the inner diameter portion, the outer diameter portion, and the ribs. Of these, in particular, the outer diameter portion has a large number of ribs from the inner diameter portion. Since both the molten resin that has flowed to the outer diameter portion through it and the molten resin that has flowed in the base portion itself merge at the same time, a large number of them are provided immediately after they merge in the outer diameter portion. A flat polygonal shaped body corresponding to the number of ribs is formed, and then a flat circular outer diameter portion is formed. Therefore, the outer shape of the outer diameter portion changes from a planar polygon corresponding to the number of many ribs to a circular shape, so that the roundness increases according to the number of ribs. As a result, the roundness of the outer diameter portion can be improved, and in particular, the roundness at the central portion of the outer diameter portion can be increased. Along with this, since the thickness of the inner diameter portion on the non-gate side is made smaller than the thickness of the inner diameter portion on the gate side, in the pressure-holding stage, it is transmitted to the anti-gate side of the outer diameter portion via the inner diameter portion on the anti-gate side. It is possible to further reduce the pressure loss of the pressure and enhance the transmissibility of the holding pressure. Therefore, it is possible to maintain good pressure even on the outer diameter part on the side opposite the gate away from the gate, so improve the roundness and reduce the difference in roundness from the outer diameter part on the gate side. You can

As described above, since the roundness of the outer diameter portion can be increased and the difference between the roundnesses on both sides thereof can be reduced, the fluttering of the belt or the like during rotation can be reduced,
It is possible to reduce noise during operation and reduce uneven rotation. Further, the contact friction resistance between the belt guide surface of the outer diameter portion and the belt can be reduced, and the product life of the resin pulley and the belt can be extended.

A method of manufacturing a resin pulley according to a second aspect of the present invention comprises a bearing and a resin portion main body integrally formed on the outer periphery of the bearing, the resin portion main body having a disc-shaped base portion,
A cylindrical inner diameter portion and outer diameter portion that are formed so as to extend along the inner and outer peripheral portions of the base portion on both sides in the thickness direction of the base portion, and radially extend from the inner peripheral portion of the base portion to the outer peripheral portion and the thickness of the base portion. It is protruding both sides, but the cross-sectional shape a radially varying cross-section
A method for manufacturing a resin pulley having a number of substantially trapezoidal plane-shaped ribs having a substantially constant product , wherein a bearing is inserted to correspond to a base portion, an inner diameter portion, an outer diameter portion and ribs of a resin portion main body. It is equipped with an injection molding process in which the bearing and the resin body are integrally injection-molded by injecting the molten resin material into the mold cavity, where a plurality of pin gates for resin injection are provided for molding the inner diameter portion. The cavity is formed on one end surface of the cavity at substantially equal intervals in the circumferential direction between adjacent rib molding cavities, and is formed on the side opposite to the side on which the pin gate is arranged, on the side opposite to the gate. The thickness of the cavity for use is smaller than the thickness of the cavity for molding the gate side inner diameter portion in which the pin gate is arranged.

Therefore, according to this method of manufacturing the resin pulley, when the molten resin is injected into the cavity from each of the pin gates in the injection molding step, the resin is ejected from the inner diameter molding cavity through a large number of rib molding cavities. The molten resin that has flowed into the cavity for forming the diameter part, and
Both of the molten resins that have flowed in the base molding cavity itself are simultaneously joined and molded in the outer diameter molding cavity. Therefore, immediately after these molten resins merge in the outer diameter forming cavity, a flat polygonal shaped body corresponding to the number of ribs provided is formed, and then a flat circular outer diameter portion is formed. It Therefore, the outer shape of the outer diameter portion changes from a planar polygon corresponding to the number of many ribs to a circle,
The roundness increases with the number of ribs. As a result, it is possible to obtain a resin pulley having a high roundness at the outer diameter portion, and particularly a high roundness at the center of the outer diameter portion. Along with this, the thickness of the anti-gate side inner diameter molding cavity was made smaller than the thickness of the gate inner diameter molding cavity. It is possible to further reduce the pressure loss of the holding pressure transmitted to the anti-gate side of the cavity and enhance the holding pressure transmissibility. Therefore, it is possible to satisfactorily apply pressure to the cavity for molding the outer diameter portion on the side opposite to the gate away from the pin gate. It is possible to reduce the difference in circularity from the diameter portion. Therefore, according to this manufacturing method,
It is possible to obtain a resin pulley in which not only the circularity of the outer diameter portion is high but also the circularity difference on both sides thereof is small.

A resin pulley manufacturing apparatus according to a third aspect of the present invention comprises a bearing and a resin portion main body integrally formed on the outer periphery of the bearing, wherein the resin portion main body has a disc-shaped base portion,
A cylindrical inner diameter portion and outer diameter portion that are formed so as to extend along the inner and outer peripheral portions of the base portion on both sides in the thickness direction of the base portion, and radially extend from the inner peripheral portion of the base portion to the outer peripheral portion and the thickness of the base portion. It is protruding both sides, but the cross-sectional shape a radially varying cross-section
The product is a manufacturing apparatus of a resin pulley comprising a large number of substantially trapezoidal ribs having a substantially constant plane, and an insert portion for arranging and fixing a bearing as an insert, and the base portion provided around the insert portion, A cavity for forming the inner diameter portion, the outer diameter portion and the rib, and a pin gate for injecting a molten resin into the cavity are provided. Here, the pin gate is arranged along the circumferential direction on one end surface of the inner diameter portion molding cavity. A plurality of ribs at substantially equal intervals between adjacent rib forming cavities, and the thickness of the anti-gate side inner diameter forming cavity on the side opposite to the side where the pin gate is arranged is The thickness is smaller than the thickness of the arranged cavity on the gate side inner diameter portion.

Therefore, according to this resin pulley manufacturing apparatus, when the resin pulley is molded by this, if molten resin is injected from each of the pin gates into the cavity, a large number of ribs are molded from the cavity for molding the inner diameter portion. Both the molten resin that has flowed through the cavity into the outer diameter molding cavity and the molten resin that has flowed through the base molding cavity itself are simultaneously joined and molded in the outer diameter molding cavity. Therefore, immediately after these molten resins merge in the outer diameter forming cavity, a flat polygonal shaped body corresponding to the number of ribs provided is formed, and then a flat circular outer diameter portion is formed. It Therefore, the outer shape of the outer diameter portion changes from a planar polygon corresponding to the number of many ribs to a circular shape, so that the roundness increases according to the number of ribs. As a result, it is possible to obtain a resin pulley having a high roundness at the outer diameter portion, and particularly a high roundness at the center of the outer diameter portion. Along with this, the thickness of the anti-gate side inner diameter molding cavity was made smaller than the thickness of the gate inner diameter molding cavity. It is possible to further reduce the pressure loss of the holding pressure transmitted to the anti-gate side of the cavity and enhance the holding pressure transmissibility. Therefore, it is possible to satisfactorily apply pressure to the cavity for molding the outer diameter portion on the side opposite to the gate away from the pin gate. It is possible to reduce the difference in circularity from the diameter portion. Therefore, according to this manufacturing apparatus, it is possible to obtain a resin pulley in which not only the circularity of the outer diameter portion is high, but also the difference in the circularity on both sides thereof is small.

[Brief description of drawings]

FIG. 1 is a plan view showing a resin pulley according to an embodiment of the present invention together with a gate position.

FIG. 2 is a sectional view taken along the line AA of FIG. 1 showing a resin pulley according to an embodiment of the present invention together with a gate position.

FIG. 3 is a perspective view showing ribs of a resin pulley according to an embodiment of the present invention.

FIG. 4 is a sectional view showing a mold of a resin pulley manufacturing apparatus according to an embodiment of the present invention.

FIG. 5 is an explanatory view showing a resin flow pattern in the method of manufacturing the resin pulley according to the embodiment of the present invention.

FIG. 6 is a table comparing the roundness of a resin pulley manufactured by a manufacturing method according to an embodiment of the present invention with the roundness of a resin pulley manufactured by a conventional manufacturing method.

FIG. 7 is a table showing a roundness measurement chart of a resin pulley manufactured by a manufacturing method according to an embodiment of the present invention and a resin pulley manufactured for comparison.

[Explanation of symbols]

11 base 13 Inner ring (inner diameter) 13a Gate side inner ring (inner diameter part) 13b Anti-gate side inner ring (inner diameter part) 15 Outer ring (outer diameter part) 17 ribs 19 bearings 31 Inner ring molding cavity 31a Gate-side inner ring molding cavity 31b Anti-gate side inner ring molding cavity 33 Base Molding Cavity 35 Outer ring molding cavity 37 Rib molding cavity 39 Insert 41 pin gate

Front page continuation (72) Inventor Motoharu Niki 1-3-17 Kyomachibori, Nishi-ku, Osaka City, Osaka Prefecture NTT Corporation (56) Reference JP-A-2-44701 (JP, A) (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 45/00-45/84 F16H 55/48

Claims (3)

(57) [Claims] 1. A bearing and a resin portion main body integrally formed on the outer periphery of the bearing by injection molding, wherein the resin portion main body extends along a disc-shaped base portion and an inner peripheral portion and an outer peripheral portion of the base portion. a cylindrical inner diameter and an outer diameter which is formed projecting in the thickness direction on both sides of the base, protrudes in the thickness direction on both sides of the base portion extends radially to the outer peripheral portion from the inner periphery of the base portion, the cross-sectional radially
Plane approximately trapezoidal shape in which the surface shape changes but the cross-sectional area is almost constant
A plurality of ribs made of resin, wherein a plurality of pin gates for resin injection are provided on one end surface of the inner diameter portion at substantially equal intervals along the circumferential direction and between adjacent ribs. And the thickness of the inner diameter portion on the side opposite to the side where the pin gate is arranged is smaller than the thickness of the inner diameter portion on the gate side where the pin gate is arranged. . 2. A bearing and a resin portion main body integrally formed on the outer periphery of the bearing, wherein the resin portion main body has a disc-shaped base portion, and a thickness of the base portion along the inner peripheral portion and the outer peripheral portion of the base portion. A cylindrical inner diameter portion and an outer diameter portion that are formed on both sides in the depth direction,
While extending radially from the inner peripheral portion of the base to the outer peripheral portion and projecting to both sides in the thickness direction of the base , the cross-sectional shape changes in the radial direction.
A method for manufacturing a resin pulley comprising: a plurality of substantially trapezoidal ribs each having a substantially constant cross section , wherein the bearing is inserted, and a base portion, an inner diameter portion, an outer diameter portion, and ribs of the resin portion main body are inserted. An injection molding step of integrally molding the bearing and the resin portion main body by injecting a molten resin material into a mold cavity corresponding to Inner diameters on the side opposite to the side on which the pin gates are arranged, which are arranged at substantially equal intervals along the circumferential direction on the end surface on one side of the molding cavities and between the adjacent rib molding cavities. A method of manufacturing a resin pulley, wherein the thickness of the part forming cavity is smaller than the thickness of the gate side inner diameter part forming cavity in which the pin gate is arranged. 3. A bearing and a resin portion main body integrally formed on the outer periphery of the bearing, wherein the resin portion main body has a disc-shaped base portion, and a thickness of the base portion along the inner peripheral portion and the outer peripheral portion of the base portion. A cylindrical inner diameter portion and an outer diameter portion that are formed on both sides in the depth direction,
Projecting in the thickness direction on both sides of the base portion extends radially to the outer peripheral portion from the inner periphery of the base, but changes cross-sectional shape in the radial direction
A resin pulley manufacturing apparatus having a large number of substantially trapezoidal plane-shaped ribs each having a substantially constant cross-sectional area , wherein an insert portion for arranging and fixing the bearing as an insert and a peripheral portion of the insert portion are provided. The base portion, the inner diameter portion, the outer diameter portion, and a cavity for rib molding, and a pin gate for injecting a molten resin into the cavity, the pin gate in a circumferential direction on one end surface of the inner diameter portion molding cavity. Along with substantially equal intervals, and a plurality of ribs between adjacent rib molding cavities, the thickness of the anti-gate side inner diameter portion molding cavity on the side opposite to the side where the pin gate is arranged, An apparatus for manufacturing a resin pulley, wherein the thickness is smaller than the thickness of the gate side inner diameter molding cavity in which the pin gate is arranged.