JP2018145987A - Manufacturing method of wave gear device - Google Patents

Abstract

In a manufacturing method of a wave gear device, an allowable torque is improved while using a desired tooth profile as an external tooth profile of a flexible external gear. In an external tooth profile determination step in step S1, a tooth profile of an external tooth of a flexible external gear is determined as desired. Next, in the simulation process of step S2, a simulation is performed in which the flexible external gear is rotated relative to the wave generator at the relative rotational speed at which the desired reduction ratio is achieved, and the movement locus of the external tooth profile is determined. Ask. Next, in the internal tooth profile determination step of step S3, the tooth profile of the internal tooth of the rigid internal gear is determined so as not to interfere with the envelope of the movement locus of the obtained external tooth profile. [Selection] Figure 3

Description

  The present invention relates to a method for manufacturing a wave gear device.

  In the tooth profile setting method of the flat wave gear device of Patent Document 1, the movement locus of the flexible external gear accompanying rotation of the wave generator is obtained by rack approximation with respect to the rigid internal gear, and the minimum extreme value of the radius of curvature of the movement locus is obtained. Ask for. Next, an arc tooth profile having an arc radius equal to or less than the minimum extreme value is adopted in the main portion of the flexible external gear, and the tooth profile of the created tooth profile of the rigid internal gear using the arc tooth profile of the flexible external gear. Ask for.

JP 2009-156461 A

In patent document 1, the tooth profile of the main part of a flexible external gear is limited to an arc tooth profile. For this reason, for example, when a desired tooth profile other than the arc tooth profile is used as the tooth profile of the main part of the flexible external gear, meshing interference is generated. Contact) and the allowable torque of the wave gear device may be reduced.
An object of the present invention is to provide a wave gear device that can improve an allowable torque while using a desired tooth profile as a tooth profile of an external tooth of a flexible external gear.

  The invention of claim 1 includes a cylindrical rigid internal gear (10) having a plurality of internal teeth (11) on the inner periphery and a cylindrical flexible external gear (10) having a plurality of external teeth (21) on the outer periphery. 20), and a wave generator (30) which is arranged inside the flexible external gear in the radial direction and flexes the flexible external gear into a non-circular shape so as to partially mesh the external teeth with the internal teeth. ), And an external tooth profile determining step (step S1) for determining the tooth profile of the external teeth as desired, and relative rotation when a desired reduction ratio is obtained. A simulation process (step S2) for obtaining a movement locus (M) of the tooth profile of the external tooth determined in the external tooth profile determination process by a simulation of relatively rotating the wave generator and the flexible external gear at a speed. ) And the trajectory obtained in the simulation step Of so as not to interfere envelope and (H), including a internal gear teeth determination process (step S3) of determining the tooth profile (K) of said internal teeth, to provide a method of manufacturing a wave gear device.

In addition, although the alphanumeric character in a parenthesis represents the corresponding component etc. in embodiment mentioned later, this does not mean that this invention should be limited to those embodiment as a matter of course. The same applies hereinafter.
According to a second aspect of the present invention, in the internal tooth shape determination step, a relief portion (14, 15) for escaping from the envelope is provided in at least one of the tooth tip (11T) and the tooth bottom (11R) of the internal tooth. Then, the tooth profile of the inner teeth may be determined.

  According to the first aspect of the present invention, after the external tooth shape of the flexible external gear is determined as desired, the flexible external gear is moved relative to the wave generator at the relative rotational speed at which the desired reduction ratio is achieved. A rotating simulation is performed to determine the movement trajectory of the external tooth profile. Next, the tooth profile of the internal tooth of the rigid internal gear is determined so as not to interfere with the envelope of the movement locus of the obtained tooth profile of the external tooth. Thereby, the tooth profile of the internal tooth in which the meshing interference is suppressed with respect to the external tooth having the desired tooth profile is obtained. For this reason, the meshing interference between the external teeth and the internal teeth can be suppressed, and the stress applied to the external teeth can be reduced. Thereby, the allowable torque can be improved.

  According to the second aspect of the present invention, even if the tooth profile varies due to a processing error or the like, the meshing interference can be suppressed by the escape portion.

It is a typical front view of the wave gear device manufactured by the manufacturing method of one embodiment of the present invention. It is a schematic sectional drawing of a wave gear apparatus. It is a flowchart which shows the manufacturing process of a wave gear apparatus. It is the schematic which shows the envelope of a movement locus | trajectory, and the tooth profile of an internal tooth.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic front view of a wave gear device 1 manufactured by a manufacturing method according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of the wave gear device 1. As shown in FIG. 1, the wave gear device 1 includes a rigid internal gear 10, a flexible external gear 20, and a wave generator 30.
The rigid internal gear 10 is a cylindrical gear and has a plurality of internal teeth 11 on its inner periphery. The rigid internal gear 10 is formed of a highly rigid member such as a metal member.

The flexible external gear 20 is disposed inside the rigid internal gear 10 in the radial direction. The flexible external gear 20 is a cylindrical gear having a plurality of external teeth 21 on the outer periphery thereof. The rigid internal gear 10 and the flexible external gear 20 that are both cylindrical gears have a common center axis C.
In the present embodiment, the flexible external gear 20 is made of a thin cup-shaped metal elastic body, and includes a cylindrical portion 22 and a flange portion 23. The external teeth 21 are formed on the outer periphery of the cylindrical portion 22. The flange portion 23 extends radially inward from one axial end of the cylindrical portion 22. An output shaft (not shown) is attached to the flange portion 23. The number of teeth Z2 of the external teeth 21 is smaller than the number of teeth Z1 of the internal teeth 11. In the present embodiment, the number of teeth Z1 of the external teeth 21 is two less than the number of teeth Z2 of the internal teeth 11, and the difference in the number of teeth ΔZ (ΔZ = Z2−Z1) is 2 (ΔZ = 2). However, the tooth number difference ΔZ is arbitrary and is not particularly limited in the present invention.

As will be described in detail later, the flexible external gear 20 can be bent into an elliptical shape by elastic deformation as shown in FIG. Then, the outer teeth 21 and the inner teeth 11 are engaged with each other at both ends P1 of the elliptical long axis, and the outer teeth 21 and the inner teeth 11 are separated at both ends P2 of the elliptical short axis. It becomes.
As shown in FIG. 1 and FIG. 2, the wave generator 30 is disposed inside the cylindrical portion 22 of the flexible external gear 20 in the radial direction. The wave generator 30 includes a flexible bearing 40 and an elliptical cam 50 as a non-circular cam. The flexible bearing 40 has flexibility and is disposed inside the cylindrical portion 22 in the radial direction. The elliptical cam 50 is disposed inside the flexible bearing 40 in the radial direction. That is, the flexible bearing 40 is externally fitted to the elliptical cam 50, and the cylindrical portion 22 of the flexible external gear 20 is externally fitted to the flexible bearing 40.

  The flexible bearing 40 includes an inner ring 41 that is externally fitted to the elliptical cam 50, an outer ring 42 that is internally fitted to the cylindrical portion 22 of the flexible external gear 20, and a plurality of flexible bearings 40 that are interposed between the inner ring 41 and the outer ring 42. Ball 43 and a retainer (not shown). A raceway groove (not shown) is formed on the outer circumference of the inner ring 41 and the inner circumference of the outer ring 42, and the ball 43 is interposed between the raceway grooves of the inner ring 41 and the outer ring 42. The balls 43 are sandwiched between the inner ring 41 and the outer ring 42 so as to be able to rotate and revolve, while being separated from each other by a retainer.

The inner ring 41 and the outer ring 42 of the flexible bearing 40 have a perfect circle shape when not fitted to the elliptical cam 50. The major axis of the ellipse of the elliptic cam 50 is set larger than the inner diameter of the inner ring 41 when it is a perfect circle, and the minor axis of the ellipse of the elliptic cam 50 is set smaller than the inner diameter of the inner ring 41 when it is a perfect circle.
For this reason, as shown in FIG. 1, the elliptical cam 50 arranged on the inner side in the radial direction of the inner ring 41 presses the inner ring 41 outward in the radial direction at two places of the long diameter portion (upper and lower two places in FIG. 2). Then, the inner ring 41 is elastically deformed into an elliptical shape. The outer ring 42 is elastically deformed into an oval shape by the inner ring 41 via the ball 43. The inner ring 41 and the outer ring 42 elastically deformed into an elliptical shape are displaced in the circumferential direction at positions where they become elliptical long diameter portions as the elliptical cam 50 rotates.

  That is, the wave generator 30 presses two locations that are 180 degrees out of phase in the circumferential direction of the flexible external gear 20 toward the outer peripheral side (see black arrows in FIG. 1), and the flexible external gear 20 By elastically deforming 20 into an elliptical shape, the external teeth 21 of both end portions P1 of the elliptical long axis formed by the flexible external gear 20 are engaged with the internal teeth 11. As the wave generator 30 rotates, the meshing position of the flexible external gear 20 and the rigid internal gear 10 moves in the circumferential direction. Thereby, relative rotation according to the number difference ΔZ between the external teeth 21 and the internal teeth 11 occurs between the flexible external gear 20 and the rigid internal gear 10.

  Next, FIG. 3 is a flowchart showing manufacturing steps of the wave gear device 1. With reference to FIG. 3, first, in the external tooth profile determination step of step S1, the tooth profile of the external teeth 21 of the flexible external gear 20 is determined as desired. As a tooth profile of the external tooth 21, an arbitrary tooth profile such as an arc tooth profile or a trochoid tooth profile can be used in addition to the involute tooth profile. Hereinafter, the tooth profile of the external tooth 21 determined in step S1 is referred to as a determined tooth profile.

  Next, in the simulation process of step S2, a simulation is performed in which the elliptical cam 50 of the wave generator 30 and the flexible external gear 20 are rotated relative to each other at the relative rotational speed when the desired reduction ratio J is achieved. The movement locus M of the determined tooth profile of the external tooth 21 determined in the external tooth profile determining step is obtained (see the solid line in FIG. 4). The simulation is performed in consideration of elastic deformation of the flexible external gear 20 by FEM analysis.

  Since the reduction ratio J is J = −Z1 / (Z2−Z1) with respect to the number of teeth Z1 of the output-side external teeth 21 and the number of teeth Z2 of the input-side internal teeth 11, the elliptical cam 50 is rotated at an angular velocity. The simulation is performed by rotating the flexible external gear 20 at the rotational angular velocity θ2 [θ2 = −2π / Z1] while rotating at θ1 [θ1 = 2π / (Z2−Z1)]. For example, if the reduction ratio J is 50, while the elliptical cam 50 of the wave generator 30 is rotated once, the flexible external gear 20 is rotated 1/50 in the direction opposite to the rotational direction of the elliptical cam 50. Then, a simulation for obtaining the movement locus M of the determined tooth profile of the external tooth 21 is performed.

  Next, in the internal tooth profile determination process in step S3, the tooth profile K of the internal tooth 11 of the rigid internal gear 10 (one point in FIG. 4 is selected so as not to interfere with the envelope H of the movement locus M obtained in the simulation process in step S2. (See chain line). At least a portion of the determined tooth profile K may include a shape that matches the envelope H. Moreover, in the internal tooth profile determination step of step S3, the escape portion 14 that escapes from the envelope H is provided in the tooth tip 11T of the internal tooth 11, and the escape portion 15 that escapes from the envelope H is provided in the tooth bottom 11R of the internal tooth 11. Thus, the tooth profile K of the inner tooth 11 is determined.

  In this embodiment, after the tooth profile of the external tooth 21 of the flexible external gear 20 is determined to be a desired determination tooth profile, it is flexible with respect to the wave generator 30 at a relative rotational speed when the desired reduction ratio J is achieved. The movement locus M of the determined tooth profile of the external tooth 21 is obtained by performing a simulation of relatively rotating the external gear 20. Next, the tooth profile of the internal teeth 11 of the rigid internal gear 10 is determined so as not to interfere with the envelope H of the obtained movement trajectory M.

Thereby, the tooth profile of the internal tooth 11 in which the meshing interference is suppressed with respect to the external tooth 21 having a desired tooth profile is obtained. For this reason, the meshing interference between the external teeth 21 and the internal teeth 11 can be suppressed, and the stress applied to the external teeth 21 can be reduced. Thereby, the allowable torque of the wave gear device 1 can be improved.
Since an optimal tooth profile that suppresses the meshing interference between the external teeth 21 and the internal teeth 11 is obtained, vibration and noise can be suppressed. Further, by suppressing the meshing interference, the number of meshing teeth of the outer teeth 21 and the inner teeth 11 can be increased (that is, the contact area between the contact tooth surfaces can be increased), and the allowable torque can also be improved from this point. .

In the present embodiment in which a desired tooth profile can be used as the tooth profile of the external tooth 21, an elliptic cam with a small diameter difference between the major axis and the minor axis of the ellipse is obtained by using a non-involute tooth profile as the tooth profile of the outer tooth 21. 50 can be used. In that case, it is possible to reduce the stress applied to the external teeth 21 and the flexible external gear 20 and contribute to the improvement of the allowable torque.
Further, in the internal tooth profile determination step of step S3, the tooth profile of the internal tooth 11 is determined by providing relief portions 14 and 15 that escape from the envelope H on the tooth tip 11T and the tooth bottom 11R. For this reason, even if there are variations in the tooth shapes of the external teeth 21 and the internal teeth 11 due to processing errors or the like, the meshing interference can be suppressed by the escape portions 14 and 15. In addition, what is necessary is just to provide an escape part in at least one of the tooth tip 11T and the tooth bottom 11R.

  The present invention is not limited to the above-described embodiment. For example, a polygonal cam (not shown) can be used as the non-circular cam instead of the elliptical cam. In the above embodiment, the so-called cup-shaped flexible external gear 20 has been described. However, as the flexible external gear 20, the flange portion 23 extends outward in the radial direction of the cylindrical portion 22. The present invention can also be applied to a so-called top hat type or a so-called flat type constituted only by the cylindrical portion 22.

  DESCRIPTION OF SYMBOLS 1 ... Wave gear apparatus, 10 ... Rigid internal gear, 11 ... Internal tooth, 11R ... Tooth bottom, 11T ... Tooth tip, 14 ... Escape part, 15 ... Escape part, 20 ... Flexible external gear, 21 ... External tooth, 22 ... cylindrical part, 23 ... flange part, 30 ... wave generator, 40 ... flexible bearing, 41 ... inner ring, 42 ... outer ring, 43 ... ball, 50 ... elliptical cam (non-circular cam), H ... envelope, K ... tooth profile (inner teeth), M ... movement trajectory

Claims (2)

A cylindrical rigid internal gear having a plurality of internal teeth on the inner periphery, a cylindrical flexible external gear having a plurality of external teeth on the outer periphery, and a radially inner side of the flexible external gear; A wave generator for bending the flexible external gear into a non-circular shape and partially meshing the external teeth with the internal teeth, comprising:
An external tooth profile determining step for determining a desired tooth profile of the external teeth;
Movement of the tooth profile of the external tooth determined in the external tooth profile determination step by simulation of relatively rotating the wave generator and the flexible external gear at a relative rotational speed at which a desired reduction ratio is obtained A simulation process for obtaining a trajectory;
A method for manufacturing a wave gear device, comprising: an internal tooth profile determining step for determining a tooth profile of the internal tooth so as not to interfere with an envelope of the movement locus obtained in the simulation process.   2. The wave motion according to claim 1, wherein in the internal tooth profile determination step, the tooth profile of the internal tooth is determined by providing an escape portion that escapes from the envelope at at least one of a tooth tip and a tooth bottom of the internal tooth. Manufacturing method of gear device.

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