JPH08312731A - Silk hat-type wave gear device - Google Patents

Abstract

PURPOSE: To decrease starting torque and improve the life of a device in a silk hat-type wave gear device. CONSTITUTION: A silk hat-shaped flexible external gear of a silk hat-type wave gear device is provided with a tooth part 24 on the tip of a body part. The thickness of the tooth part 24 is gradually decreased through a transition part 29, and the tooth part is continued to the part having the thin part of the body part. The outer periphery of the transition part 29 is specified by a bent curved line 26, and a radius of curvature of the curved line is set to a size in the range of 60 to 70% of the length of the tooth part 24. As a result, force required in widening the tooth part 24 into an oval shape can be decreased, accordingly, starting torque can be decreased, and load of a bearing of a wave generator is decreased, and the life of it is therefore improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a top hat type wave gear device having a top hat type flexible external gear,
The present invention relates to an improvement of the top hat type flexible external gear.

[0002]

2. Description of the Related Art A wave gear device is known in which its flexible external gear has a top hat shape, and is generally called a top hat type wave gear device. In this type of device, a top hat-shaped flexible external gear is arranged inside a rigid internal gear,
The external gear is flexed in the radial direction by a wave generator fitted inside the external gear, and the external teeth are partially meshed with the internal teeth on the side of the rigid internal gear. The wave generator is connected to a high-speed rotation source such as a drive motor to receive high-speed rotation. The number of external and internal teeth is 2n (n is a positive integer)
And when the wave generator rotates, in response,
The meshing position of both gears also moves in the circumferential direction, and relative rotation according to the difference in the number of teeth occurs between these gears. This rotation can be taken out from one side of both gears as decelerated rotation.

[0003]

Here, in general, the wave gear device, including the top hat type having the above-described structure, is required if the starting torque can be reduced accordingly. The output of the motor can also be reduced. Therefore, it is possible to reduce the size and weight of the actuator incorporating the wave gear device and the motor and to reduce the cost.

An object of the present invention is to realize the reduction of the starting torque in a top hat type wave gear device by paying attention to this point.

[0005]

In order to solve the above-mentioned problems, in the top hat type wave gear device of the present invention, the cross-sectional shape of the ends of the outer teeth of the top hat-shaped flexible external gear is provided. Is defined as follows. That is, the top hat-shaped flexible external gear has a cylindrical body,
The external teeth formed on the outer circumference of the one opening end, an annular diaphragm that continuously extends outward in the radial direction from the other opening end of the body portion, and an outer peripheral edge of the annular diaphragm. And a ring-shaped boss.

The shape of the end portion of the external tooth in the external gear on the side of the annular diaphragm in the tooth trace direction is such that the end of the external tooth in the tooth trace direction when viewed in the axial direction of the apparatus. It is defined by a curved curve that smoothly connects to the straight line parallel to the apparatus axis line that defines the outer peripheral surface of the body portion that is continuous with this. The present invention is characterized in that the radius of curvature of the curve is set to be a length between 60 and 70% of the length of the tooth portion of the external tooth. It is preferable that the radius of curvature is set to about 66% of the length of the tooth portion of the external tooth.

[0007]

In the top hat-shaped flexible externally toothed gear of the present invention, the curvature of the curve defining the end portion of the external tooth portion in the tooth trace direction is generally used in the past. It is larger than in the case of a flexible externally toothed gear, and therefore, the portion from the end of the tooth portion to the body portion becomes thin, and the rigidity of the cylindrical body portion including the tooth portion decreases. As a result, the force required to bend the outer teeth in the radial direction, that is, the load that the wave generator must bear is reduced, and the starting torque can be reduced.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 show the overall construction of the top hat type wave gear device of this embodiment. In this figure, the device 11 comprises an annular rigid internal gear 12 and a top hat-shaped flexible external gear 13 arranged inside thereof.
And an elliptical wave generator 14 fitted inside.

The flexible external gear 13 has a cylindrical body portion 22.
And an annular diaphragm 23 having an inner peripheral end continuous with the base end opening, and a thick annular boss 25 continuously formed integrally with the outer peripheral end of the diaphragm 23. The outer peripheral portion of the front end side open end of the body portion 22 includes a tooth portion 24 integrally formed with an outer tooth 24a in the circumferential direction. The annular boss 25 is for attachment to another member (not shown), and by this boss 25, the body 2
2 and the diaphragm 23 are supported in a cantilevered state.

On the other hand, the wave generator 14 includes a hollow hub 14a.
And an elliptical rigid cam plate 14b fitted on the outer periphery thereof and a ball bearing 14c fitted on the outer periphery thereof. By the wave generator 14, the tooth portion 24 of the flexible external gear is bent into an elliptical shape, and the external tooth portions located at both ends of the elliptical major axis become the internal teeth 12a of the rigid internal gear 12. Be meshed. In this state, when the wave generator 14 rotates about the device axis 11a, these meshing positions rotate in the circumferential direction. Due to this rotation, a relative rotational motion is generated between the flexible external gear 13 and the rigid internal gear 12 according to the difference in the number of teeth between the external teeth and the internal teeth. Therefore, for example, the rigid internal gear 12 is fixed and the wave generator 1
When 4 is a high-speed rotation input element, the external gear 13 serves as a deceleration rotation output element, from which a greatly decelerated rotation output can be extracted.

FIG. 3 is a view showing a vertical cross section of the above-described top hat-shaped flexible external gear 13 taken along a plane including the device axis 11a, and FIG. 4 is an enlarged view of the external teeth. FIG. As shown in these figures, in the flexible external gear 13, the tooth portion 24 on the tip side has a sufficient thickness, and external teeth 24a are formed on the outer periphery thereof. The length of the external tooth 24a in the tooth trace direction is indicated as L.
A curved curve 26 is continuously connected to an end 24b of the external tooth 24a in the tooth trace direction, and the curve 26 smoothly continues to a straight line 27 defining the outer peripheral surface of the cylindrical body portion 22. ing. The inner peripheral surface of the cylindrical body portion 22 is defined by a straight line 28 from the tip end side to the opening end side to the diaphragm 23 side. Therefore, the body 2
The thickness of 2 is substantially constant in the tooth portion 24 on the tip side, and the transition portion 29 of continuous thickness is continuous with this, that is, the outside is defined by the curve 26 and the inside is defined by the straight line 28. The thickness gradually decreases in the portion where it is formed, and the outside and the inside which continue to this portion have a constant thin thickness in the portion defined by the straight lines 27 and 28.

In this example, the radius of curvature of the curve 26 is 66% of the tooth length L (R = 0.66L). In the top hat-shaped flexible external gear that is generally used in the past, the portion corresponding to the curve 26 is defined by a curve having a radius of curvature of 83% of the length of the tooth portion. . In FIG. 4, a conventional curve is shown by an imaginary line. Thus, in this example, the curve 26
The radius of curvature is increased so that the transition portion of this wall thickness is thinned as a whole.

By increasing the curvature of this portion,
It was confirmed that the force required to spread the tooth portion 24 in an elliptical shape was small. Also, by doing so, it is naturally confirmed that the rigidity of the entire trunk portion is lowered, but it was also confirmed that this does not cause any particular adverse effect. Therefore, according to this example, the starting torque of the device can be reduced. Further, since the load acting on the bearing 14c of the wave generator is reduced, the life of the device can be extended.

According to experiments conducted by the present inventors, the radius of curvature R of the outer curved curve defining the thick transition portion 29 is R.
It has been confirmed that, by setting the dimension to be between 60% and 70% of the tooth length L, the starting torque can be reduced and the device life can be improved without any practical problems.

[0016]

As described above, in the top hat type wave gear device of the present invention, the shape of the end portion in the tooth trace direction on the diaphragm side of the outer teeth of the top hat external gear is determined by the device. When viewed by cutting in the axial direction,
Specified by a curved curve that smoothly connects from the end of the external tooth in the tooth trace direction to the straight line parallel to the device axis that defines the outer peripheral surface of the body part that is continuous to this, The radius of curvature is set to be between 60 and 70% of the length of the tooth portion of the external tooth. By adopting this configuration, the rigidity of the cylindrical body including the teeth is reduced, and the force required to flex the outer teeth in the radial direction, that is, the load that the wave generator must bear is reduced. As a result, the starting torque can be reduced and the life of the device can be improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a top hat type wave gear device that is an embodiment of the present invention.

FIG. 2 is a side view of the device of FIG. 1 viewed from the direction of the arrow.

3 is a sectional view showing a top hat-shaped flexible external gear of the apparatus of FIG.

4 is an enlarged partial cross-sectional view showing an enlarged transition portion of the wall thickness in the flexible external gear of FIG.

[Explanation of symbols]

 11 Wave Gear Device 11a Device Axis 12 Rigid Internal Tooth Gear 13 Flexible Top Tooth Gear of Top Hat Shape 14 Wave Generator 22 Cylindrical Body 23 Diaphragm 24 Teeth 24a External Teeth 24b External Teeth of Diaphragm End of direction 25 Boss 26 Curve 27, 28 that defines the transition portion of the wall thickness Straight line 29 Transition portion of the thickness L Length of external teeth R Curvature radius of the curve

Claims (2)

[Claims] 1. A ring-shaped rigid internal gear, a flexible external gear arranged inside the ring-shaped internal gear, and a wave generator mounted inside the ring-shaped internal gear. The flexible external gear is bent in the radial direction so that its external teeth are partially meshed with the internal teeth of the rigid internal gear, and the meshing positions thereof are moved in the circumferential direction. Thus, in the wave gear device configured to generate relative rotation between the rigid internal gear and the flexible external gear according to the number of teeth difference, and extract the relative rotational motion as a decelerated rotational output, The flexible externally toothed gear is configured such that a cylindrical body portion, the outer teeth formed on the outer periphery of the one open end, and the outer toothed end of the body portion are continuously connected to the outer side in the radial direction. And expanding annular diaphragm and the outer peripheral edge of this annular diaphragm Has a top hat shape with a continuous annular boss, and the shape of the end portion in the tooth trace direction on the side of the annular diaphragm in the external teeth is as seen when cut in the axial direction of the device. , Defined by a curved curve that smoothly connects from the end of the external tooth in the tooth trace direction toward a straight line parallel to the apparatus axis line that defines the outer peripheral surface of the body portion that is continuous with the end And the radius of curvature of the curve is set to be a length between 60 and 70% of the length of the tooth portion of the external tooth, the top hat type wave gear device. 2. The top hat type wave gear device according to claim 1, wherein the radius of curvature of the curve is set to about 66% of the length of the tooth portion of the external tooth.