JPH0460237A - Flexible meshing type gear engagement structure - Google Patents

Abstract

PURPOSE:To reduce the extent of resistance in deflection as securing a large transmissible torque and make improvements in operating efficiency by forming an external spline, engaging an inner spline with some play and making a deflection component of an external gear absorbable, in a second shaft attached so as to correspond to a rotational component of the external gear. CONSTITUTION:First of all, a wave generator 104 is rotated by rotation of an input shaft 102, and an external gear 106 intends to rotate as being deflected and deformed on an outer circumference of the wave generator. Since the external gear 106 is inscribed with an internal gear 108 clamped to a casing 109, however, free rotation is restricted, eventually only an engaged position between these internal and external gears come to be rotated at the same speed with the input shaft 102 in consequence. Accordingly, when the input shaft 102 rotates a turn, the external gear comes to do relative rotation as far as a portion resting on a difference of tooth numbers with the internal gear as a result, so that this relative rotation is transmitted to an output shaft 110 after a deflection component is absorbed via a loose engagement between an inner spline 106C formed on an inner circumference of the external gear and an external spline 112A formed in the output shaft (2nd shaft).

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a gear mesh structure of a flexible mesh type, that is, a gear mesh structure called a so-called harmonic drive type, which is suitable for application to a small speed reducer or a speed increaser.

[Conventional technology]

BACKGROUND ART Conventionally, a flexible mesh type gear meshing structure based on a rotational principle as shown in FIG. 3 has been widely known. In the figure, reference numeral 2 denotes an input shaft (first axis), 4 a wave generator that rotates by the rotation of the input shaft 2, and 6 a wave generator that is slidably attached to the outer periphery of the wave generator 4. An external gear 8 is an internal gear with which the external gear 6 internally meshes. The wave generator 4 includes an elliptical cam body 4A provided integrally with the input shaft 2, and a visible ball bearing 4B fitted on the outer periphery of the cam body 4A and bent into an elliptical shape. Consisting of The outer ring of this ball bearing 4B is an external gear 6
is fitted. The number of teeth of the external gear 6 is smaller than the number of teeth of the internal gear 2 by 2N (N is a positive integer). In the example shown in FIG. 3, the "internal teeth" of the internal gear 8 are formed directly on the main body of the internal gear 8, or in the actual machine, the "internal teeth" of the internal gear are fitted into recesses. It is often formed by a generally cylindrical outer pin. As shown in FIGS. 3(A) to (C), now the input shaft 2
When # is rotated, the cam body 4A of the wave generator 4 is rotated, and due to the rotation of the cam #4A, the external gear 6 is flexibly deformed via the visible ball bearing 4B and is internally rotated inside the internal gear 8. Rotates tangentially. Therefore, if the internal gear 8 is now fixed to the casing, the external gear 6 will rotate relative to the internal gear 8 by the amount dependent on the difference in the number of teeth between the two gears 6.8 for each revolution of the input shaft 2. There will be relative rotation. As a result, if the deflection component of the external gear 6 is absorbed and only the rotational component is extracted as output, the output member will rotate extremely slowly relative to the input shaft 2.
A reduction gear with a large reduction ratio can be realized. Furthermore, if the rotational component of the external gear 6 is fixed, a reduction gear using the internal gear 8 as an output member can be realized. Furthermore, if the input member and the output member are reversed here, a speed increaser with a large speed increase ratio can be realized. Such a flexible mesh type gear meshing structure can obtain a large speed reduction ratio or speed increase ratio with a small number of elements, and is therefore often used in speed increase/reduction gears for small precision machines. FIG. 4 shows a conventional example of an actual flexible mesh type gear reduction gear employing this meshing supplement. The symbols in the figure correspond to the symbols in FIG. As mentioned above, the "internal teeth" of the internal gear 8 are formed by the external pin 8A. Since the external gear 6 needs to absorb the deflection component and transmit only the rotational component to the output shaft 10, it is composed of a flange portion 6A and an annular portion 6B having a larger diameter than the flange portion 6A. A housing for the ball bearing 4B is formed on the inner circumferential side of the end of the zero annular portion 6B, and external teeth that can mesh with the outer pin 8A of the internal gear 8 are formed on the outer circumferential side of the end. has been done. As described above, the external gear 6 slowly rotates while being flexibly deformed by the rotation of the input shaft 2, but this flexural deformation component is absorbed by the annular portion 6B and then the rotation component is transmitted to the output shaft 10. It has become.

[Problem that the invention attempts to solve]

However, in such a conventional flexible mesh type gear meshing structure, if the length in the axial direction of the annular portion 6B of the external gear 6 is short, the deflection at the end of the annular portion can be well absorbed. There was a problem in that this length had to be set quite long because the rotational load would increase. In order to avoid this problem at all, that is, to shorten the length of the annular portion 6B of the external gear 6 in the axial direction, the external gear itself must be made of a material that is sufficiently flexible. In this case, not only the transmittable torque becomes smaller, but also the rise and fall characteristics become worse and backlash occurs due to the torsion of the external gear 6 itself, especially when starting, stopping, reversing, etc. Or, problems such as ratcheting (when an excessive load is applied, the external gear bends and the external teeth and internal teeth become misaligned by one tooth) tend to occur. Furthermore, if this type of flexible mesh gear device is used in the wrist of an industrial robot, etc., it is necessary to pass the input shaft for another speed-up/deceleration device, but this is not possible with the conventional structure. However, since the flange portion 6A of the external gear 6 takes up a considerable amount of space, there is a problem in that the diameter of the hollow portion (hollow diameter) for passing the input shaft therethrough cannot be made large. The present invention has been made in view of the above-mentioned problems of the prior art, and makes it possible to form an external gear from a material with relatively high rigidity, thereby ensuring a large transmittable torque. while reducing deflection resistance (rotational load), increasing efficiency, and improving backlash and ratcheting properties.
Furthermore, it is an object of the present invention to provide a flexible mesh type gear meshing structure that can reduce the length in the axial direction to realize a reduction in the size and weight of the entire device, and can also have a large hollow diameter passing through the entire device.

[Means to solve the problem]

The present invention includes a first shaft, a wave generator mounted to correspond to rotation of the first shaft, and a wave generator slidably mounted on the outer periphery of the wave generator and arranged along the outer periphery of the wave generator. Flexural meshing comprising: an external gear capable of flexural deformation, an internal gear with which both non-nuclear gears are internally meshed, and a second shaft attached so as to correspond to the rotational component of the external gear. In the type gear meshing structure, the external gear has a substantially cylindrical shape, external teeth that mesh with the internal gear are formed on the outer periphery of the cylindrical shape, and the wave motion is formed on a part of the inner periphery of the cylindrical shape. The housing for attachment to the generator has an internal spline formed in the other part thereof, and an external part on the second shaft that can loosely engage with the internal spline and absorb the deflection component of the external gear. By forming the spline, the above object is achieved.

[Effect]

For convenience of explanation, the operation will now be explained by taking as an example a reduction gear in which the internal gear is fixed, the first shaft is the input shaft, and the second shaft is the output shaft. First, the wave generator is rotated by rotation of the input shaft. As the wave generator rotates, the external gear tries to rotate while being bent and deformed on the outer periphery of the wave generator. However, since the external gear is inscribed in the internal gear fixed to the gaging, free rotation is restricted, and in the end, only the meshing position of the internal gear and external gear changes at the same speed as the input shaft ( Therefore, when the input shaft rotates once, the external gear rotates relative to the internal gear by an amount that depends on the difference in the number of teeth between the input shaft and the internal gear. The rotation is transmitted to the output shaft after the deflection component is absorbed through the loose engagement between the internal spline formed on the inner periphery of the external gear and the external spline formed on the output shaft. Since the external gear does not need to absorb all of the deflection by itself as in the past, it is possible to form it from a material with relatively high machinability, and the axial length can be made extremely short. You will be able to do this. Furthermore, since there is no flange portion as in the past, the entire device can be made smaller and lighter than in the past, and a large hollow diameter can be realized. As described above, a speed increaser can be achieved by reversing the input and output members with the same meshing structure and using the second shaft as the input shaft and the first shaft as the output shaft. Furthermore, it is also possible to realize a reduction gear using an internal gear as an output member with the same meshing structure. In this case, the explanation is the same as that up to the part where the external gear is deflected and rotated via the wave generator due to the rotation of the first shaft (input shaft). However, in this case, the internal gear is not fixed, but instead, the external gear is restrained via the internal and external splines so that it cannot rotate at all. Therefore, the meshing position with the internal gear changes (rotates) due to the deflection of the external gear, so in the end, for one revolution of the input shaft, the internal gear (output member) changes by the amount that depends on the difference in the number of teeth with the external gear. As a result of the displacement, a reduction gear can be realized. In this case as well, a speed increaser can be realized by reversing the input/output members.

【Example】

Embodiments of the present invention will be described in detail below based on the drawings. FIG. 1 is a cross-sectional view of a flexible mesh gear reducer to which the present invention is applied, and FIG. 2 is a cross-sectional view taken along the line II--II in FIG. 1 showing the tooth shape and meshing state of each gear. This reducer includes an input shaft (first shaft) 102 and an input shaft 1
a wave generator 104 that rotates with the rotation of the wave generator 102; and an external gear 10 that is slidably attached to the outer periphery of the wave generator 104 and can be bent and rotated around the outer periphery of the wave generator 104.
6, an internal gear 108 fixed to gauging 109 and internally meshed with the external gear 106, and external gear 1
Output shaft (second shaft) 11 that rotates in response to the rotation component of 06
0. The wave generator 104 consists of an elliptical cam body 104A integrated with the input shaft 102 and a visible ball bearing 104B attached to the outer periphery of the cam body 104A. This configuration is the same as the conventional one. The internal gear 108 has a bolt 11 attached to the gauging 109.
4, and the outer pin 108A forms an inner tooth having a circular arc tooth shape. The structure of this internal gear 108 is also the same as the conventional one. The external gear 106 has a substantially cylindrical shape, and external teeth 106A that mesh with an external pin (internal tooth) 108A of the internal gear 108 are formed on the outer periphery of the cylindrical shape. Also, the ball bearing 104B of the wave generator 104 is attached to a part of the inner periphery of this cylindrical shape (the right half in the figure) in the housing 106.
B is formed. Furthermore, an internal spline 106C is formed in another part (the left half in the figure). External gear 10
The external teeth 106A of No. 6 have a trochoidal waveform, and the internal splines are JISD2001 automotive involute splines. However, in the present invention, each tooth profile is not limited to these. Note that the number of teeth of the external gear 106 is two fewer than the number of teeth of the internal gear 108. The output shaft 110 has a bearing 1 in the casing 109.
It is rotatably attached via 14 and 116. An external spline plate 112 is integrally attached to the output shaft 110 via bolts 118, and has an external spline 112A that can be loosely engaged with the internal spline 106C of the external gear 106. The number of teeth of the outer spline 112A of this outer spline plate 112 is the same as the number of teeth of the inner spline 106C of the external gear 106. Further, the external spline 112A has a tip circle diameter that is smaller than the root diameter of the internal spline 106C by approximately twice the amount of deflection of the external gear 106. Furthermore, this outer spline 1121. t, the arcuate tooth thickness of the pitch circle is smaller than the tooth gap on the pitch circle of the internal spline 106C by approximately twice the amount of deflection of the external gear 106. As a result, the internal spline 106C and the external spline 112A constitute a constant velocity gear mechanism that can absorb the deflection of the external gear 104 without any trouble.
Only the rotation component of No. 6 is transmitted to the output shaft 110. Next, the operation of this embodiment will be explained. The rotation of the input shaft 102 rotates the elliptical cam body 104A of the wave generator 104, and bends the ball bearing 104B provided on the outer periphery of the cam body 104A. This ball bearing 1
The external gear 106 attached to 04 is an external pin (internal gear) 108A of an internal gear 108 fixed to the casing.
Since the external gear 106 is restrained from freely rotating on its own axis, the external gear 106 changes (rotates) only its internal meshing position while being inscribed in the internal gear 108. Due to this change (rotation) of the internal meshing position, the external gear 10
Since the difference between the number of teeth of 6 and the number of teeth of the internal gear 108 is 2, the external gear 106 will eventually undergo meshing displacement (rotation) by 2 teeth for each rotation of the input shaft 102. As a result, one rotation of the input shaft 102 is twice the number of teeth of the external gear 106.
The speed is reduced to The movement of this external gear 106 is caused by the external tooth! Due to the loose fit between the inner spline 106C of 106 and the outer spline 112A of outer spline plate 112, the deflection component is completely absorbed, and only the rotational component is taken out and transmitted to the output shaft 112. FIG. 2 shows the external pin (internal tooth) 108A of the internal gear 108, the external tooth 106A of the external gear 106, and the internal spline 106C.
The meshing state of the first outer spline 112A is shown. As the external gear 106 is deformed into an elliptical shape by the wave generator 104, the external gear 106 is connected to the outer pin 108A of the internal gear 108 and the 2gIIpfrC1 part, 0 on the long axis side of the ellipse.
On the other hand, the outer spline plate 112 meshes with the outer spline 112A at the intermediate portion between the major axis and the minor axis, that is, at four locations A1 to A4 in FIG. 2 while being stretched. According to this embodiment, ■ meshing at C1 and 02 parts and A1
- A lick in which the engagement in A4 is a tension engagement;
There is no backlash. ■Since the outer spline 112A and the inner spline 106C mesh at four locations, the number of meshing teeth is large, which is advantageous for power transmission.
■CI can provide sufficient strength even if it is short in the axial direction, ■CI,
The meshing at the C2 part and the meshing at A+ to A4 (because there are many meshes) provides excellent ratcheting performance. - The internal gear 108 has internal teeth formed of the external pin 108A, so the external gear 106 It is possible to obtain advantages such as rolling contact with the material and less wear. Note that a speed increaser can be realized by reversing the input and output shafts in the same meshing structure as in the above embodiment. Further, in the above embodiment, an example was shown in which the internal gear 108 was fixed, but by fixing the output shaft 110 with the exactly same meshing structure and making the internal gear 108 rotatable,
It is possible to easily realize an increase/decrease gear that uses the internal gear 108 as an output shaft (or input shaft). Further, in the above embodiment, the output shaft 110 is solid, but it is extremely easy to change the design to a so-called hollow shaft type reducer, which can be made hollow and simply inserts the input shaft of the mating member. be. In this embodiment, the external gear 10
6 is much more compact than the conventional one, so even in such a case there is an advantage that the hollow diameter can be made large.

【Effect of the invention】

As explained above, according to the present invention, since the axial length of the external gear can be particularly shortened, the entire device can be made smaller and lighter, and the regularity, backlash resistance, and It becomes possible to obtain an increase/decelerator with excellent ratcheting properties. Further, when the flexible mesh type gear meshing structure according to the present invention is applied to a so-called hollow shaft type speed increase/reduction gear, the hollow diameter can be made very large.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of a flexible mesh gear reducer to which the present invention is applied, Fig. 2 is a sectional view taken along line U-II in Fig. 1, and Fig. 3 (A
) to (C) are skeleton diagrams for explaining the rotation principle of the flexible mesh gear mesh structure, and FIG. 4 is a diagram showing an example of a reducer to which the conventional flexible mesh gear mesh structure is applied. 1
It is a longitudinal cross-sectional view corresponding to the figure. 2... Input shaft (first axis), 4... Wave generator, 6... External gear, 6A... External tooth, 6B... Housing, 6C... Internal spline, 8... ... Internal gear, 8A... External pin (internal teeth), 9... Gauging, 0... Output shaft (second shaft). Sub-agent Yasuhiro Makino Keisuke Matsuyama Satoshi Takaya

Claims (1)

[Claims] (1) A first shaft, a wave generator mounted to correspond to the rotation of the first shaft, and a wave generator mounted slidably on the outer periphery of the wave generator and deflected along the outer periphery of the wave generator. A flexible mesh type comprising a deformable external gear, an internal gear with which the external gear internally meshes, and a second shaft attached to correspond to the rotational component of the external gear. In the gear meshing structure, the external gear has a substantially cylindrical shape, and external teeth that mesh with the internal gear are formed on the outer periphery of the cylindrical shape, and
A housing for attachment to the wave generator is formed on a part of the inner periphery of the cylindrical shape, and an internal spline is formed on the other part, and the second shaft is loosely engaged with the internal spline. A flexible mesh type gear meshing structure, characterized in that an external spline capable of absorbing a deflection component of the external gear is formed.