JP3201815B2 - Manufacturing method of resin gear - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a resin gear, and more particularly, to a method of manufacturing a resin gear in which teeth are formed in a crowning shape, that is, teeth are formed into a crowning shape in which bulges are appropriately bulged in the direction of tooth traces. To apply to effective technology.

[0002]

2. Description of the Related Art For example, in a spur gear of machine cutting teeth, a structure in which teeth are formed into a crowning shape by cutting is known.

On the other hand, in a resin gear manufactured by injection molding, as shown in FIG. 3, pinpoint gates are usually set at one point of a center 20 and three to four points of a web 21 and molded. ing.

[0004]

In spur gears with mechanical cutting teeth, the teeth can be formed into a crowning shape by cutting, but in resin gears manufactured by injection molding, the teeth can be formed. It is considered difficult to form a crowning shape.

For this reason, in a resin gear, the advantage of a gear having a crowned shape cannot be obtained.

On the other hand, according to the resin gear injection molding method described above, due to the warpage or shrinkage difference of the portion of the web 21, as shown in FIG. An inclination α may occur. Further, in a gear having a large thickness of the web 21, sinkage may occur at a tooth portion at the center of the web 21.

For this reason, there is a possibility that the ratio of the tooth contact or the part of the tooth contact may not be stable at a delicate place.

[0008] An object of the present invention is to provide a method of manufacturing a resin gear in which a resin gear having a crowned shape can be manufactured by a molding technique such as injection molding.

Another object of the present invention is to provide a method of manufacturing a resin gear, which can improve the flatness of a web portion and prevent adverse effects on teeth due to warpage or deformation of the web portion. It is in.

The above and other objects and novel features of the present invention will become apparent from the description of the specification and the accompanying drawings.

[0011]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, according to the method for manufacturing a resin gear of the present invention, molten resin is injected into a closed mold, and the molten resin injected into the closed mold is compressed in a direction for forming the length direction of the teeth of the resin gear. Then, the teeth are formed into a crowning shape.

In this case, the resin gear is a resin gear on which a web is formed, and the resin in the closed mold is compressed in a direction forming the thickness direction of the web with the compression. be able to.

[0014]

[0015]

[0016]

According to the method for manufacturing a resin gear of the present invention described above, the surface layer of the molten resin injected into the closed mold is cooled and solidifies and contracts in the closed mold, so that the gap between the molten resin surface and the closed mold surface is reduced. A gap is formed in the gap, and the intermediate portion of the molten resin in the direction of forming the length direction of the teeth is protruded into the gap on the opposite side by the subsequent compression to form a crowning-shaped tooth.

Therefore, according to the resin gear manufacturing method of the present invention, a resin gear having a crowned shape can be manufactured by a molding technique such as injection molding.

In this case, the resin gear is a resin gear on which a web is formed, and the resin in the closed mold is compressed in a direction forming the thickness direction of the web with the compression. Then, the flatness of the web portion of the resin gear can be improved by compression in the direction of forming the thickness direction of the web, and adverse effects on the teeth due to warpage or deformation of the web portion can be prevented.

[0019]

[0020]

[0021]

FIG. 1 is a sectional view showing a molding apparatus used in a method of manufacturing a resin gear according to an embodiment of the present invention. FIG. 2 is a perspective view showing teeth of the resin gear formed by the method. FIG. 3 is a sectional view showing a resin gear formed by a conventional method of manufacturing a resin gear.

The resin gear formed by the manufacturing method and the molding apparatus of this embodiment is a spur gear manufactured by an injection molding method. The spur gear is a web similar to the conventional resin gear shown in FIG. Are formed, and a structure having the rotation shaft 1 is provided.

As shown in FIG. 1, the molding apparatus includes a fixed lower mold 2 and a movable upper mold 3 which form a closed mold and have a perfect circular cross section in the radial direction.

The fixed lower mold 2 is accommodated and fixed in a substantially cylindrical space 4A of the fixed base 4.

On the other hand, the movable upper die 3 is housed in the substantially cylindrical space 5A of the movable base 5 so as to be able to move up and down along the axial direction thereof. It is possible to move up and down.

In this case, the movable upper mold 3 can be moved up and down by at least the compression amount T with respect to the movable mold base 5.

A gate groove is formed on the surface of the movable base 5 facing the fixed base 4, and when the surfaces of the movable base 5 and the fixed base 4 are brought into contact with each other, a gate thickness t is formed at the joint. Gate 6 is formed. The gate thickness t is set smaller than the compression amount T.

In this embodiment, the molten resin injected (injected) into the closed mold cavity 7 from the gate 6 is polyacetal resin, and the temperature at the time of melting is about 200 ° C.

On the other hand, the temperature of the closed mold at that time is about 90 ° C.
Has been maintained.

Next, a method of manufacturing a resin gear using a molding apparatus having such a structure will be described.

First, the movable base 5 that has been raised is lowered and comes into contact with the fixed base 4 in the vicinity. At this time, the movable upper mold 3 descends with the descending of the movable mold base 5, but descends in a state where the movable upper mold 3 is elevated by the compression amount T with respect to the movable mold base 5.

Therefore, when the movable base 5 and the fixed base 4 are in contact with each other, the movable upper mold 3 is elevated above the fixed base 4 by the amount of compression T as shown by the dashed line in FIG.

Next, in this state, molten resin is injected from the gate 6 into the closed cavity 7 and filled therein.

When the molten resin is injected into the closed mold cavity 7 in this manner, the temperature difference between the molten resin temperature of about 200 ° C. and the closed mold temperature of about 90 ° C. causes the molten resin to come into contact with the closed mold surface. Instantly cools and begins to solidify. And
At the end of the injection, shrinkage peculiar to the molten resin starts while a solidified layer is formed on the entire surface side of the molten resin, and a minute gap is generated between the surface of the molten resin and the closed mold surface.

Next, the movable upper die 3, which has been raised by the amount of compression T from the fixed die base 4, is lowered by the amount of compression T as shown by the solid line in FIG.

When the movable upper mold 3 is lowered, the gate 6 communicating with the closed mold cavity 7 is gradually closed by the outer peripheral surface of the movable upper mold 3, and the molten resin in the closed mold cavity 7 is melted by the resin. The gears are compressed in the direction of forming the length direction of the gear teeth and in the direction of forming the thickness direction of the web, that is, compressed by the compression amount T.

The backflow of the molten resin from the gate 6 during the compression is prevented by closing the gate 6 with the outer peripheral surface of the movable upper die 3.

At the time of this compression, the molten resin in the closed cavity 7 is compared at the highest temperature near the boundary between the part forming the teeth of the resin gear and the part forming the web due to the compression of the compression amount T. The molten resin in the part with a large amount of target is trying to escape, and the molten resin in the direction of forming the length direction of the teeth (the molten resin that has started shrinking) is placed in the minute gap part generated on the opposite surface side Overhang.

As shown in FIG. 2, the overhang of the molten resin into the gap causes the center of the tooth in the longitudinal direction to expand to the maximum, thereby preventing the generation of stress per piece of the artificial tooth. Is formed.

Next, after the molten resin is further cooled and solidified, the movable upper mold 3 and the movable mold base 5 rise and separate from the fixed lower mold 2, and a resin gear as a molded product remaining in the fixed lower mold 2. Is taken out.

As described above, according to the method of manufacturing a resin gear using the molding apparatus of the present embodiment, a resin gear having a crowned shape of teeth 8 can be manufactured by a molding technique such as injection molding. As a result, for example, it is possible to obtain a resin gear peculiar to the crowning shape in which the tooth contact is stabilized, an appropriate oil film is held between the crowning tooth surfaces, and vibration and noise are reduced.

Further, since the molten resin in the closed mold cavity 7 is compressed in the direction of forming the thickness direction of the web,
By the compression in the direction of forming the thickness direction of the web, the flatness of the web portion of the resin gear can be improved, and the adverse effect on the teeth due to the warpage or deformation of the web portion can be prevented. For example, stabilization of tooth contact can be achieved.

Further, the gate 6 is closed by the outer peripheral surface of the movable upper die 3 when approaching, and the outer peripheral surface of the movable upper die 3 is moved by the separation of the movable upper die 3 from the fixed lower die 2.
The gate 6 is opened from the gate 6, so that the molten resin is injected from the gate 6 into the closed cavity 7, the gate 6 is opened and closed, the fixed lower mold 2 and the movable upper mold 3 are opened. The contacting / separating step between them can be smoothly performed by a simple structure.

As described above, the invention made by the inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say.

For example, in the above-described embodiment, the upper mold side is movable and comes into contact with and separates from the lower mold side. However, in the present invention, for example, both the upper mold side and the lower mold side are used. May be configured to move and contact with each other.

In the above embodiment, the gate 6 is formed at the joint between the upper mold side and the lower mold side. In the present invention, for example, the upper mold side or the lower mold side is formed. It is also possible to adopt a configuration formed on either one of the lower mold side.

Further, in the above embodiment, the gate 6 communicating with the closed mold cavity 7 is gradually closed by the outer peripheral surface of the movable mold 3 as the movable upper mold 3 is lowered, and the closed mold cavity is closed. The molten resin in 7 is the compression amount T
However, in the present invention, when the movable upper mold 3 is lowered, the gate 6 communicating with the closed mold cavity 7 is completely closed by the outer peripheral surface of the movable upper mold 3. Thereafter, the movable upper mold 3 may be further lowered to compress the molten resin in the closed mold cavity 7 by the compression amount T.

[0048]

Advantageous effects obtained by typical ones of the inventions disclosed by the present application will be briefly described as follows.
It is as follows.

(1) According to the method for manufacturing a resin gear of the present invention, the surface layer of the molten resin injected into the closed mold is cooled and solidifies and contracts in the closed mold, so that the surface of the molten resin and the closed mold surface are separated. A gap is formed between the gaps, and the resulting molten resin in the direction of forming the length direction of the teeth is protruded into the gap on the opposite side, thereby forming a crowning-shaped tooth.

Therefore, according to the resin gear manufacturing method of the present invention, a resin gear having a crowned shape can be manufactured by a molding technique such as injection molding.

(2) In the above case, the resin gear is a resin gear on which a web is formed, and the resin in the closed mold is compressed in the direction of forming the thickness direction of the web with the compression. With this manufacturing method, the flatness of the web portion of the resin gear can be improved by compression in the direction of forming the thickness direction of the web, and the adverse effect on the teeth due to the warpage or deformation of the web portion can be prevented. Can be.

[0052]

[0053]

[Brief description of the drawings]

FIG. 1 is a sectional view showing a molding apparatus used in a method for manufacturing a resin gear according to an embodiment of the present invention.

FIG. 2 is a perspective view showing tooth portions of a resin gear formed by the manufacturing method.

FIG. 3 is a cross-sectional view showing a resin gear formed by a conventional method for manufacturing a resin gear.

[Description of Signs] 1 Rotary shaft 2 Fixed lower mold 3 Movable upper mold 4 Fixed mold base 4A Space 5 Movable base 5A Space 6 Gate 7 Cavity 8 Teeth 20 Center 21 Web T Compression amount t Gate thickness α Slope

Claims (2)

(57) [Claims] 1. Injecting molten resin into a closed mold, compressing the molten resin injected into the closed mold in a direction forming the length direction of the teeth of the resin gear, and forming the teeth into a crowning shape. A method for manufacturing a resin gear. 2. The method according to claim 1, wherein the resin gear is a resin gear on which a web is formed, and the resin in the closed mold is compressed in a direction forming a thickness direction of the web with the compression. A method for manufacturing a resin gear according to claim 1.