JP3766559B2 - Synthetic resin molded gear - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a molded gear made of a synthetic resin that transmits a rotational force between two different shafts.
[0002]
[Prior art]
When spur gears are attached as gears for transmitting rotational force on two axes that are arranged so as to intersect with each other at a certain point that are not parallel to each other, as shown in FIG. Since the area of the meshing portion is reduced and the load is applied concentrated on a part of the tooth portions 11 and 11 ′, the rotational force cannot be efficiently transmitted.
Therefore, when gears are attached to mesh with two shafts arranged so as to intersect with each other, a bevel gear as shown in FIG. 5 is conventionally used.
[0003]
In this type of gear, the tooth portions 11 and 11 'are integrally formed along a conical surface having an arbitrary point on the extension line of the shaft as an apex, and the teeth are inclined with respect to the shaft. Therefore, an umbrella designed so that the inclination angles of the teeth 11 and 11 'with respect to the respective axes substantially match the inclination angle of the conical surface with the point O at which the extension lines of the two axes arranged so as to intersect each other intersect. If the gear is attached at a predetermined position, the tooth portions 11 and 11 'can be engaged with each other over almost the entire tooth width at the meshing position of the gear, and the two shafts arranged so as to intersect with each other can be efficiently operated. Rotational force can be transmitted.
[0004]
In this type of gear, a molten material such as synthetic resin is injected from a gate (not shown) into a mold (not shown) having a cavity that matches the shape of the gear as shown in FIG. After being filled in the cavity, it is molded by cooling, solidifying and releasing.
[0005]
[Problems to be solved by the invention]
By the way, due to the difference in contraction of the synthetic resin between the gate side where the synthetic resin is injected and the side opposite to the gate side (for example, the side where the molded product is projected) in the injection molding, Errors with the theoretical values such as inclination angle deviation and diameter difference are likely to occur. For this reason, even if the bevel gear is mounted at a predetermined position in the design, the meshing state changes greatly due to the above-described error, and the tooth portion of the bevel gear contacts only partly, or conversely Are too close to each other, and it is easy to disturb the rotation of the bevel gear.
Therefore, in order to optimize the meshing state of the bevel gear, it is necessary to adjust the position where the bevel gear is attached by shifting it in the axial direction.
[0006]
However, if the mounting position of the gear is shifted in the axial direction on the two shafts arranged so as to intersect with each other, the distance between the gear teeth varies greatly, so the gear teeth are too far apart from each other. However, it is easy to cause troubles in the rotation of the bevel gear by contact with each other or conversely, the tooth portions are too close to each other.
For this reason, conventionally, adjustment of the attachment position of a bevel gear was difficult, and adjustment work was complicated.
[0007]
In general, the method of manufacturing the tooth part of a mold used for injection molding is to cut the steel sheet into a desired shape by wire electric discharge machining. Known as a method that can be. However, the manufacturing method by wire electric discharge machining is basically two-dimensional processing by performing wire discharge perpendicularly to a flat steel plate, so that a spur gear mold is manufactured. However, it has been difficult to apply to the manufacture of gear molds such as bevel gears in which the teeth are not perpendicular to the rotation surface. That is, in order to process the tooth portion of the bevel gear mold, the wire discharge must be performed while the wire is inclined so that the angle with respect to the steel plate is always constant, and the control is complicated three-dimensional. Since processing is required, there exists a problem that the simplicity of wire electric discharge machining will be impaired.
[0008]
On the other hand, as a relatively simple method for manufacturing the mold of the bevel gear, for example, after forming the prototype of the bevel gear with a steel material, the periphery of the prototype is covered with metal powder containing beryllium and pressurized at a high temperature. A method is known in which a metal powder containing beryllium is solidified, and then the solidified product is cut at a predetermined location to produce a tooth portion of a mold. However, when this method is used, there is a problem that the tooth part of the mold cannot be manufactured with high accuracy.
[0009]
In addition, as another method for producing the tooth portion of the bevel gear mold, there is a method in which a mold is formed by plating a steel bevel gear around the original mold. If it is manufactured using this method, the tooth mold part can be manufactured with high accuracy, but it takes a lot of work to complete the manufacturing because the plating film must be stacked in layers. There was a problem.
[0010]
For this reason, conventionally, when a gear is attached to two shafts arranged so as to intersect with each other and meshed with the gear, a great amount of labor is required until the gear is manufactured, and after the manufactured gear is attached to the shaft. It took time and effort to adjust the meshing position.
[0011]
Therefore, the present invention is a synthetic resin-made gear that transmits rotational force between two shafts arranged so as to intersect with each other, and can be easily manufactured, and the meshing accuracy can be achieved without adjusting the mounting position of the gear after manufacturing. It is an object to provide a gear that can improve the speed.
[0012]
[Means for Solving the Problems]
In order to achieve this object, a synthetic resin molded gear according to the present invention includes a rim integrated with a plurality of teeth on an outer peripheral surface, a boss disposed concentrically inside the rim, and the rim. And a disc-shaped web integrally formed with a disc-shaped web connecting the boss, by providing a concentric thin portion in the vicinity of the connection portion of the web with the rim, only the thin portion is provided. The rim can be elastically deformed with respect to the web .
[0013]
Moreover, in this invention, it is preferable to form the said thin part in the connection part vicinity with the said rim | limb of the said web .
[0014]
In addition, a plurality of the thin portions can be formed on the web.
[0015]
Moreover, although the said thin part should just be provided by forming a groove | channel on the at least one surface side of the said web, you may be provided by forming a groove | channel in the position which the both surfaces of the said web oppose, respectively.
[0016]
In the present invention, the groove is preferably formed in a U-shaped section, a V-shaped section or a U-shaped section.
[0017]
The gear of the present invention is preferably injection-molded with a thermoplastic elastomer.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1A and 1B show an embodiment of a gear according to the present invention, in which FIG. 1A is a plan view and FIG. 1B is an AA cross-sectional view of the gear shown in FIG.
FIG. 2 is a state explanatory view showing a meshing state of the tooth portions when the gear of this embodiment is attached to two different shafts.
3 (a) to 3 ( c) are cross-sectional views of main parts showing other embodiments of the gear according to the present invention.
[0019]
As shown in FIG. 1A, the gear according to the present embodiment includes a cylindrical rim 12 integrated with a plurality of tooth portions 11 on an outer peripheral surface, a boss 13 concentrically positioned with the rim 12, and a boss 13 and a disc-shaped web 14 connected to the rim 12, and these are integrally formed as a gear 10.
The gear of the present invention is significantly different from the conventional gear because the thin wall portion is provided with a thin portion concentrically on the web to enable elastic deformation in the thin wall portion, thereby meshing with another gear having a different shaft direction. In some cases, the thin-walled portion is elastically deformed, and the teeth are meshed with the other gears in a state of being aligned with each other so as to face each other (see FIG. 2).
[0020]
That is, in this embodiment, as shown in FIG. 1B, the outer peripheral surface of the rim 12 and the tooth traces of the tooth portion 11 are formed in parallel to the axis. Further, as shown in FIGS. 1A and 1B, a thin portion 15 is formed concentrically on the web 14 in the vicinity of the connection portion with the rim 12. The thin-walled portion 15 is composed of grooves 16 and 17 formed concentrically on both sides of the web 14, and the wall thickness t1 is thinner than the wall thickness t2 of other portions, and a force greater than a predetermined amount is applied to the tooth portion 11. Is applied, the tooth portion 11 is elastically deformed and the direction of the tooth portion 11 at the meshing position can be changed to mesh with the tooth portions of other gears having different shaft orientations so as to face each other. It has become way.
[0021]
Since the gear of the present embodiment is configured as described above, when it is attached to two different shafts, as shown in FIG. 2, the thin portions 15, 15 of the gears 10, 10 'attached to the two shafts are provided. 'Is elastically deformed, and the tooth portions 11, 11' are meshed with each other in a state where the directions of the teeth are aligned substantially over the entire tooth width. For this reason, even if it is a spur gear, it can transmit a rotational force efficiently with the whole tooth width also between two axes | shafts which cross | intersect. In the illustrated embodiment, the gears 10 and 10 'are attached to two shafts arranged so that their extension lines intersect each other, but the teeth due to elastic deformation of the thin portions 15 and 15' are provided. If the portions 11 and 11 ′ are satisfactorily engaged with each other, the two shafts to which the gears 10 and 10 ′ are attached may be in a twisted relationship with each other without intersecting the respective extension lines.
[0022]
Further, the gear of the present embodiment has a diameter difference in the tooth portion of the actually formed gear due to a difference in shrinkage ratio of the resin melted on the gate side and the opposite side of the gate side when the gear is injection molded. Even if it occurs, the meshed state can be improved by elastically deforming the thin portions 15 and 15 'of the gear as described above.
Further, the tooth trace of the tooth portion 11 of the present embodiment is perpendicular to the rotation surface of the gear 10. Therefore, the tooth mold portion of the injection mold can be manufactured by using a wire electric discharge machining, for example, by horizontally cutting a flat steel material placed horizontally while discharging with a wire. And wire electrical discharge machining has the advantage that it can process simply and with high precision compared with the manufacturing method using the metal powder containing beryllium as mentioned above, and the manufacturing method which gave plating.
[0023]
Therefore, according to the synthetic resin gear of the present embodiment, it is possible to easily manufacture the mold, and without adjusting the mounting position, errors in injection molding, on the opposite side of the gate side and the gate side. The meshing accuracy can be improved without being affected by the difference in diameter caused by the difference in shrinkage rate of the molten resin.
[0024]
In addition, in the gear of this invention, the form of a thin part is not limited to embodiment of FIG. 1, For example, the shape of the grooves 16 and 17 which comprise the thin part 15 is shown in FIG. As shown in 3 (c), it may be formed in a U shape, a U shape, or a V shape. Also, the shape of the thin walled portion, the thickness of the thin portion, number number of the thin portion, c E Bed width, also including a web connection position viewed from the tooth width direction of the gear, the magnitude of the torque accompanying the rotation of the gear If designed in consideration of the above, the same effects as those in the above embodiments can be obtained.
[0025]
In addition, as a synthetic resin material used for injection molding a molded gear made of synthetic resin, polyacetal is generally used, but when a thermoplastic elastomer is used as a synthetic resin material when injection molding the gear of the present invention, It can be made more easily elastically deformed at the thin portion of the web.
[0026]
【The invention's effect】
As described above, according to the present invention, it is easy to manufacture a formed gear, and the bite when mounted between two shafts arranged so as to intersect with each other without readjusting the mounting position after manufacturing. The alignment accuracy can be improved.
[Brief description of the drawings]
1A and 1B show an embodiment of a gear according to the present invention, in which FIG. 1A is a plan view and FIG. 1B is a cross-sectional view of the gear shown in FIG.
FIG. 2 is a state explanatory view showing a meshing state of tooth portions when the gear of the present embodiment is attached to two different shafts.
FIG. 3 is a cross-sectional view of a main part showing another embodiment of a gear according to the present invention.
FIG. 4 is a state explanatory view showing a meshing state of tooth portions when a spur gear is attached to two different shafts.
FIG. 5 is a state explanatory view showing a meshing state of teeth when a bevel gear is attached to two different shafts.
[Explanation of symbols]
10, 10 'gear 11, 11' tooth part 12, 12 'rim 13, 13' boss 14, 14 'web 15, 15' thin part 16, 17 groove

Claims (1)

A synthetic resin in which a rim integrated with a plurality of teeth on the outer peripheral surface, a boss concentrically arranged inside the rim, and a disk-shaped web connecting the rim and the boss are integrally formed. In the molded gear made of
A synthetic resin made by providing a thin portion concentrically in the vicinity of a connection portion of the web with the rim so that the rim can be elastically inclined with respect to the web only in the thin portion. Molding gears.

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