JPH0577656U - Gears for reduction gears - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the number of parts of the reduction gear and improve the mass productivity of reduction gears. [Structure] A large gear 1 made of synthetic resin is injection-molded in a state in which a part of a small gear 2 made of iron is wrapped. The large gear 1 is integrally formed with a boss portion 1g that covers the inner peripheral surface of the hole at the center of the small gear 2.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a gear used in a gear type speed reducer.

[0002]

[Prior Art]

 In gear type speed reducers used for small motors with reduction gears, etc., a large gear that meshes with the driving shaft gear and a small gear that meshes with the driven shaft gear are generally integrated with their central axes aligned. As a result, a reduction gear is configured, and a fixed shaft is fitted into a hole formed by penetrating the center portion of the reduction gear in the axial direction to rotatably support the reduction gear. In this type of small reduction gear, the large gear with a relatively small transmission load is made of synthetic resin, and the small gear with a relatively large transmission load is made of iron.

FIG. 3 shows an example of a conventional gear for a speed reducer of this type (showing a cross section including an axis). In FIG. 3, 1 is a large gear, 2 is a small gear, and 3 is a small gear 2. It is a bearing fitted in the center. The large gear 1 is made of synthetic resin, and as shown in FIGS. 4 (A) and 4 (B), a tooth portion 1b is formed on the outer circumference of a disc-shaped gear body 1a, and a gear portion 1a is formed at the center of the gear body 1a. On the inner circumference of the provided hole 1e, convex portions 1c and concave portions 1d are alternately formed. The small gear 2 is made of iron, and as shown in FIGS. 5 (A) and 5 (B), a large-diameter cylindrical portion 2a having teeth 2b formed on the outer periphery, and a large gear convex portion 1c and a concave portion 1d. Each of them has a small diameter cylindrical portion 2e having a concave portion 2c and a convex portion 2d formed in the outer periphery thereof, and a hole 2g is provided at the center of the cylindrical portion 2a. The bearing 3 is made of a sintered oil-impregnated alloy, and is formed into a cylindrical shape as shown in FIG. 6. The outer diameter of the bearing 3 is set so as to be press-fitted into the hole 2g at the center of the pinion gear 2. ing. A through hole 3a into which a fixed shaft of the speed reducer is fitted is formed in the center of the bearing 3.

In the gear for the reduction gear described above, the convex portion 1c formed in the hole 1e in the central portion of the large gear 1 and the concave portion 2c and the convex portion formed on the outer periphery of the cylindrical portion 2e of the small gear 2 in the concave portion 1d. With the two gears 2d fitted together, the small-diameter cylindrical portion 2e of the small gear is press-fitted into the large gear hole 1e, and the bearing 3 is pressed into the small gear 2 hole 2g. The bearing 3 was integrally connected.

[0005]

[Problems to be solved by the device]

 In the above conventional gears for reduction gears, the separately manufactured large gear, small gear, and bearing are joined together by press-fitting and integrated, so there are many parts and press-fitting of each part. Since the dimensional accuracy of the joint is required to be high, there is a problem that the manufacturing cost becomes high.

An object of the present invention is to improve the above-mentioned conventional problems, and to provide a gear for a speed reducer, which has a small number of parts, is low in cost, and is excellent in mass productivity.

[0007]

[Means for Solving the Problems]

 The present invention relates to a gear for a reduction gear in which a large gear made of synthetic resin and a small iron gear having a hole through which a shaft passes through are integrated with their respective central axes aligned. is there. In the present invention, the large gear is injection molded with a part of the small gear wrapped therein. The large gear integrally has a boss portion that covers the inner peripheral surface of the hole at the center of the small gear.

[0008]

[Action]

 As described above, when a part of the large gear encloses a part of the iron small gear, the large gear and the small gear can be integrally connected without press-fitting. If the large gear is provided with a boss that covers the inner peripheral surface of the hole in the center of the small gear, the boss of the large gear can be lubricated due to the self-lubricating property of the synthetic resin. Therefore, it is not necessary to provide a separate bearing made of a sintered oil-impregnated alloy or the like.

With the above configuration, the wall thickness of the cylindrical portion 2 of the pinion gear can be reduced, and the outer diameter of the pinion gear can be reduced accordingly, so that the gear ratio per one step can be increased. Wear.

[0010]

【Example】

 FIG. 1 is a cross-sectional view of the upper half of an embodiment of the present invention, in which 1 is a large gear made of synthetic resin and 2 is a small iron gear. As shown in FIGS. 2 (A) and 2 (B), the small gear 2 has a cylindrical portion 2a having a toothed portion 2b having a tooth profile which meshes with a driven shaft gear of a reduction gear formed on the outer periphery, and one end of the cylindrical portion 2a. It has a cylindrical portion 2a and a flange portion 2f formed integrally therewith, and a plurality of recesses 2d are formed on the outer periphery of the flange portion 2f. An axial through hole 2g having an inner diameter larger than the outer diameter of the fixed shaft of the reduction gear is formed in the shaft center portion of the small gear 2. The small gear 2 can be formed by cutting a steel material, but is generally manufactured by a powder metallurgy method using an iron-based sintered alloy.

The large gear 1 is made of a thermoplastic synthetic resin, has a substantially disk-shaped gear body 1 a having a toothed portion 1 b having a toothed shape that meshes with a driving shaft gear of a reduction gear on the outer periphery, and a center portion of the small gear 2. It integrally has a boss portion 1f that covers the inner peripheral surface of the hole 2g that penetrates through, and the large gear 1 and the small gear 2 are arranged in a state of sharing their respective central axes. A through hole 1g into which the fixed shaft of the speed reducer is fitted is formed inside the boss portion 1f.

The large gear 1 is injection-molded in a state of enclosing the flange portion 2f of the small gear 2. As the thermoplastic synthetic resin forming the large gear 1, it is suitable to use, for example, a polyacetal resin (POM) having self-lubricating property. The plastic synthetic resin is not limited to the polyacetal resin.

The resin forming the large gear 1 covers the inner peripheral surface of the through hole 2g of the small gear 2 and wraps the flange portion 2f, and the resin also enters the concave portion 2d on the outer periphery of the flange portion 2f. Therefore, the large gear 1 and the small gear 2 are firmly coupled and integrated. The boss portion 1f of the large gear serves as a bearing that is fitted to a fixed shaft provided in the reduction gear to support the reduction gear, and due to the self-lubricating property of the resin forming the boss portion, seizure with the fixed shaft occurs. Is prevented. Therefore, it is not necessary to provide a separate bearing made of oil-impregnated alloy.

When the inner peripheral surface of the hole 2g penetrating the central portion of the small gear 2 is covered with the boss portion 15 of the large gear 1 as described above, the wall thickness of the cylindrical portion 2a of the small gear 2 can be reduced. The outer diameter of the small gear can be reduced, and the gear ratio per step can be increased.

[0015]

[Effect of the device]

 As described above, according to the present invention, since the large gear is injection-molded in a state of enclosing a part of the small gear, the large gear and the small gear do not have to be press-fitted, which requires high processing accuracy. It has the advantage that it can be connected to gears and the productivity of gears for reduction gears can be increased. Further, since the boss portion that covers the inner peripheral surface of the hole at the center of the small gear is provided integrally with the large gear, the bearing made of sintered oil-impregnated alloy or the like can be omitted, and the structure of the speed reducer can be simplified. There are advantages.

Further, according to the present invention, since the outer diameter of the pinion gear can be reduced, there is an advantage that the gear ratio per one step can be increased.

[Brief description of drawings]

FIG. 1 is a side view of an embodiment of the present invention showing the upper half in section.

2A is a front view of a pinion gear used in the embodiment of FIG. 1, and FIG. 2B is a vertical sectional view of FIG.

FIG. 3 is a cross-sectional view showing a conventional example.

4A is a front view of a large gear used in the conventional example of FIG. 3, and FIG. 4B is a vertical sectional view of FIG.

5A is a front view of a small gear used in the conventional example of FIG. 3, and FIG. 5B is a vertical sectional view of FIG.

6A is a sectional view of a bearing used in the conventional example of FIG. 3, and FIG. 6B is a vertical sectional view of FIG.

[Explanation of symbols]

 1 large gear 1b large gear tooth 1f boss 2 small gear 2b small gear tooth 2g small gear center hole

Claims (1)

[Scope of utility model registration request] 1. A gear for a speed reducer in which a large gear made of synthetic resin and a small gear made of iron having a hole through which a shaft penetrates are integrated with their central axes aligned with each other. Is injection-molded in a state of enclosing a part of the small gear, and the large gear is integrally formed with a boss portion covering the inner peripheral surface of the hole at the center of the small gear. Gears for machines.