JP7188388B2 - Decelerator - Google Patents

Description

The present invention relates to a speed reducer.

2. Description of the Related Art Conventionally, a speed reducer is known that reduces power obtained from an electric motor or the like and outputs the power. For example, Japanese Unexamined Patent Application Publication No. 2010-4582 teaches a strain wave gear reducer that reduces the rotational force transmitted from a wave generator to a flexspline through thin-walled bearings and outputs the reduced torque from a circular spline. The external gear of the flexspline bent into an elliptical shape by the wave generator meshes with the internal gear of the circular spline at its major axis and is separated from the internal gear at its minor axis. Therefore, when the wave generator makes one clockwise rotation, the flexspline moves more counterclockwise than the circular spline due to the difference in the number of teeth between the external gear and the internal gear. Therefore, the circular spline outputs such rotation of the flexspline, so that the strain wave gear reducer can obtain a reduction ratio corresponding to the difference in the number of teeth. Conventionally, ball bearings are used for thin-walled bearings.

Japanese publication: JP 2010-4582

However, miniaturization of ball bearings has limitations in terms of its structure. Along with this limit, miniaturization of the speed reducer has also become difficult. Also, the smaller the ball bearing, the more expensive it becomes. Therefore, the manufacturing cost of the speed reducer has increased as the size of the speed reducer has been reduced.

An object of the present invention is to provide a reduction gear that is more compact and inexpensive.

An exemplary speed reducer of the present invention includes a rotating member that is rotatable about a rotating shaft and has a major diameter and a minor diameter when viewed from the rotating shaft, and an external gear that has a plurality of external teeth arranged in the circumferential direction. an annular internal gear having a plurality of circumferentially arranged internal teeth and surrounding the rotating shaft, wherein the external gear has a cylindrical shape surrounding the rotating shaft and is radially deformable. wherein the radially outer side surface of the rotary member is slidably and directly in contact with the radially inner side surface of the cylindrical portion, and the plurality of external teeth are in contact with the cylindrical portion The plurality of internal teeth are provided on the radially inner side surface of the internal gear, and the external teeth of the external gear are provided on the radially inner side surface of the rotating member in the major axis direction of the rotating member. It is configured to mesh with the internal teeth of the internal gear.

According to the exemplary speed reducer of the present invention, a more compact and inexpensive speed reducer can be provided.

FIG. 1 is a cross-sectional view showing an example of a speed reducer. FIG. 2 is a front view of the speed reducer as seen from the front side in the axial direction. FIG. 3 is an enlarged view of a part of the cross-sectional structure of the speed reducer. FIG. 4 is a diagram for explaining another configuration example of the rotating member.

Exemplary embodiments of the invention are described below with reference to the drawings.

In this specification, in the speed reducer 100, a direction parallel to a rotation axis RA, which will be described later, is called an "axial direction." The direction along the axial direction from the rotating member 1 to be described later toward the lid portion 23 to be described later is referred to as one side in the axial direction and is referred to as the “axial rear side”, and the direction from the lid portion 23 to the rotating member 1 along the axial direction is referred to as the “rear side”. The other side in the axial direction is referred to as the “front side in the axial direction”. In each component, the end on the rear side in the axial direction is called the "rear end", and the end on the front side in the axial direction is called the "front end". In addition, in each component, the surface facing the rear in the axial direction is called the “back surface”, and the surface facing the front in the axial direction is called the “front surface”.

A direction perpendicular to the rotation axis RA is called a "radial direction", and a rotation direction about the rotation axis RA is called a "circumferential direction". A direction radially toward the rotation axis RA is referred to as "radial inner", and a direction radially away from the rotation axis RA is referred to as "radial outer". In each component, the radially inner end is called an "inner end" and the radially outer end is called an "outer end". In addition, among the side surfaces of each component, the side surface facing radially inward is referred to as the "inner surface", and the side surface facing radially outward is referred to as the "outer surface".

Among the radial directions, the direction LD in which the width of the rotating member 1 is the longest when viewed from the axial direction is called the "longitudinal direction LD", and the direction SD in which the width of the rotating member 1 is the shortest when viewed from the axial direction is called " called "minor axis direction SD". Furthermore, the direction MD in which the ratio of the major axis direction component and the minor axis direction component is the same among the radial directions is referred to as the "intermediate direction MD". The "major direction LD", the "minor direction SD", and the "middle direction MD" extend in the circumferential direction about the rotation axis RA as the rotating member 1 rotates. Rotate.

It should be noted that the names of directions, ends, surfaces, etc. described above do not indicate the positional relationship, direction, etc. when incorporated into an actual device.

<1. embodiment>
FIG. 1 is a cross-sectional view showing an example of the speed reducer 100. As shown in FIG. Note that FIG. 1 is a cross-sectional structure showing an example of the speed reducer 100 . FIG. 2 is a front view of the speed reducer 100 seen from the front side in the axial direction. FIG. 3 is an enlarged view of a part of the cross-sectional structure of the speed reducer 100. As shown in FIG. Note that FIG. 1 shows a cross-sectional structure of the speed reducer 100 cut along a plane including the rotation axis RA. Also, FIG. 3 corresponds to a portion surrounded by a dashed line in FIG.

<1-1. Configuration of Reducer>
The reducer 100 is a strain wave gear reducer including a rotating member 1 , an external gear 2 , an internal gear 3 and a bearing 4 . The speed reducer 100 reduces the speed of rotation of the rotating member 1 and transmits the rotational force of the rotating member 1 to the internal gear 3 via the external gear 2 . The rotating member 1 has a rotating base 11 , a rotating portion coating film 12 , and a hole portion 111 . The external gear 2 has a plurality of external teeth 21 , a flexible cylindrical portion 22 , a lid portion 23 and a shaft 24 . The tubular portion 22 has a tubular base portion 221 and a tubular portion coating film 222 . The internal gear 3 has an annular shape surrounding the rotation axis RA. The internal gear 3 has a plurality of internal teeth 31 . A plurality of internal teeth 31 are provided on the inner surface of the internal gear 3 and are arranged in the circumferential direction. A bearing 4 is provided between the shaft 24 of the external gear 2 and the internal gear 3 . Via bearings 4 , internal gear 3 rotatably holds shaft 24 of external gear 2 . Although the bearings 4 are ball bearings in this embodiment, they are not limited to this example and may be other types of bearings such as sleeve bearings. The distance between the shaft 24 and the internal gear 3 is sufficiently wide even when compared with the radial sizes of the respective components 1 to 3, and the bearing 4 can be a generally available inexpensive product. Therefore, the bearing 4 does not adversely affect reduction in size and cost reduction of the speed reducer 100 in the present invention. In addition, although the speed reducer 100 is provided with a coating film C, the structure of the coating film C will be described later.

<1-1-1. Configuration of Rotating Member>
The rotating member 1 has a shape having a major axis and a minor axis when viewed from the rotation axis RA, and is rotatable about the rotation axis RA. The rotating member 1 is positioned inside the external gear 2 , more specifically, radially inward of the cylindrical portion 22 .

The rotating member 1 is a so-called cam, and has a periphery whose distance from the rotation axis RA is not constant when viewed from the axial direction, and gives various motions to other members around the periphery while rotating. In this embodiment, the rotating member 1 gives the external gear 2 rotational motion in the circumferential direction and deforming motion in the radial direction on its outer surface while rotating.

The outer surface of the rotating member 1 is in direct contact with the inner side surface 22a of the cylindrical portion 22 so as to be slidable. In this way, the rotating member 1 is in direct contact with the cylindrical inner side surface 22a of the external gear 2, so that, for example, the rotating rotating member 1 is indirectly connected to the cylindrical inner side surface 22a of the external gear 2 via the ball bearing. Compared to the contact configuration, the speed reducer 100 can be made more compact. In addition, compared to the configuration in which the ball bearings are in direct contact with each other, the speed reducer 100 of the present embodiment can transmit the torque of the rotating member 1 to the internal gear 3 with a smaller number of parts. The manufacturing cost of machine 100 can be reduced. Therefore, it is possible to provide the reduction gear 100 which is more compact and inexpensive.

The outer surface of the rotating member 1 includes an inclined surface 1a that inclines radially outward in the longitudinal direction LD of the rotating member 1 toward the front side in the axial direction. In this way, when the cylindrical portion 22 is deformed in the radial direction according to the rotation of the rotating member 1, the cylindrical portion inner side surface 22a is inclined with respect to the axial direction parallel to the rotation axis RA. At this time, the tubular portion 22 is deformed radially outward in the longitudinal direction LD of the rotary member 1 . Therefore, the inner side surface 22a of the cylindrical portion is inclined radially outward toward the front side in the axial direction, and is likely to come into surface contact with the similarly inclined inclined surface 1a of the rotating member 1 . Therefore, in the longitudinal direction LD of the rotary member 1, a larger contact area can be secured between the two than in a configuration in which the rotary member 1 is not provided with the inclined surface 1a. You can use less pressure. Therefore, since the rotating member 1 and the cylindrical portion 22 are less likely to be worn, the life of the rotating member 1 and the cylindrical portion 22 can be extended.

The inclination angle θ (see FIG. 3) of the inclined surface 1a with respect to the axial direction is preferably 0.1° or more and 1.0° or less. With this configuration, the inclination angle θ of the inclined surface 1a of the rotary member 1 with respect to the axial direction is likely to be the same as the inclination angle of the cylinder inner side surface 22a with respect to the axial direction.
Therefore, the inclined surface 1a of the rotating member 1 is more likely to come into surface contact with the cylindrical inner side surface 22a.

The inclination angle θ of the inclined surface 1a with respect to the axial direction is from the major axis direction LD of the rotating member 1 to the minor axis direction S.
It becomes smaller toward D, and becomes 0° in the intermediate direction MD of the rotating member 1 .

Note that the inclined surface 1a may be parallel to the axial direction from the middle direction MD to the minor axis direction SD of the rotary member 1, that is, the inclination angle θ of the inclined surface 1a may be 0°. In this way, the inclination angle θ of the inclined surface 1a with respect to the axial direction is more likely to be the same as the inclination angle of the cylinder inner side surface 22a with respect to the axial direction, and the contact area is further widened. be able to. Therefore, the wear of the rotating member 1 and the cylindrical portion 22 can be more effectively suppressed, and the life of the rotating member 1 and the cylindrical portion 22 can be further extended.

Alternatively, the inclined surface 1a may be inclined radially inward toward the front side in the axial direction in the minor axis direction SD of the rotating member 1 .

In addition, in the minor axis direction SD of the rotating member 1, the outer surface of the rotating member 1 may be spaced radially inward from the cylindrical portion inner surface 22a (see FIG. 4). In FIG. 4, a portion of the outer surface of the rotating member 1 is slidably and directly in contact with the inner side surface 22a of the cylindrical portion, and the other portion of the outer surface of the rotating member 1 extends radially inward from the inner surface 22a of the cylindrical portion. is seperated. More specifically, from the longitudinal direction LD of the rotating member 1 to the intermediate direction MD, the outer surface of the rotating member 1 is slidably in contact with the cylinder inner surface 22a. On the other hand, in the middle direction MD to the minor axis direction SD of the rotating member 1, the outer surface of the rotating member 1 is separated from the cylindrical inner surface 22a. At this time, for example, an arc portion viewed from the axial direction from the middle direction MD to the minor diameter direction SD of the rotary member 1 may be cut across the axial direction. In other words, the outer shape of the rotating member 1 as seen from the axial direction is arc-shaped from the major axis direction LD to the intermediate direction MD, and linear or cylindrical as shown in FIG. 4 from the intermediate direction MD to the minor axis direction SD. It may have a curved shape radially away from 22a. In particular, as shown in FIG. 4, the rotating member 1 can be easily molded by making the outer end portion of the rotating member 1 straight from the middle direction MD to the minor axis direction SD of the rotating member 1 when viewed from the axial direction. Become.

The main material of the rotating member 1 is one of oil-impregnated sintered metal, ceramic, and plastic. More specifically, the material of the rotary base 11 is one of oil-impregnated sintered metal, ceramic, and plastic. The oil-impregnated sintered metal is a porous metal material containing an oil component. It can be produced by holding it. Ceramics are, for example, alumina-titanium carbide (Al ₂ O ₃ --TiC) based materials. The plastic is, for example, PTFE (polytetrafluoroethylene). By using these materials with good sliding properties, it is possible to further reduce torque transmission loss and further suppress the reduction in efficiency of the speed reducer 100 .

The rotating part coating film 12 is provided on the outer surface of the rotating base part 11, and is provided on a region of the outer surface of the rotating member 1 that is in contact with at least the cylinder inner surface 22a. In this way, torque transmission loss from the rotating member 1 to the external gear 2 can be reduced. Furthermore, the wear of the rotating member 1 can be suppressed by the rotating portion coating film 12 . The rotating part coating film 12 is a part of the coating film C provided in the speed reducer 100 .

When an oil-impregnated sintered metal is used as the material of the rotating base 11, the rotating part coating film 12 may be provided on the outer surface of the rotating base 11, but should not be provided on the outer surface of the rotating base 11. is preferred. In other words, when an oil-impregnated sintered metal is used, it is preferable that the rotary base 11 is in direct contact with the cylindrical inner side surface 22a. By doing so, it is possible to prevent the oil component oozing from the oil-impregnated sintered metal constituting the rotary base 11 to the outer surface of the rotary base 11 from being blocked by the rotary part coating film 12 . Therefore, the lubricating action of the exuded oil component can reduce torque transmission loss from the rotating member 1 to the external gear 2 , thereby suppressing wear of the rotating member 1 .

The hole 111 is provided in the center of the rotation base 11 when viewed from the axial direction, and penetrates the rotation base 11 in the axial direction. For example, a rotor shaft of a rotary electric motor (not shown) is connected to hole portion 111 . The rotary motor rotates the rotating member 1 .

<1-1-2. Structure of External Gear>
The external gear 2 is positioned radially inward of the internal gear 3 and is rotatable around the rotation axis RA.

The plurality of external teeth 21 are provided on the outer surface of the cylindrical portion 22 of the external gear 2 and are arranged in the circumferential direction. The external teeth 21 of the external gear 2 mesh with the internal teeth 31 of the internal gear 3 in the major axis direction LD of the rotary member 1, and are separated from the internal teeth 31 of the internal gear 3 in the minor axis direction SD of the rotary member 1. ing. The number of external teeth 21 is less than the number of internal teeth 31 of the internal gear 3 . Therefore, when the rotating member 1 rotates once, the rotational position of the external gear 2 in the circumferential direction is the difference in the number of teeth obtained by subtracting the number of the external teeth 21 from the number of the internal teeth 31 relative to the rotational position of the internal gear 3. in the direction of rotation of the rotating member 1 by a distance corresponding to . Due to this action, the rotation of the external gear 2 is decelerated at a ratio corresponding to the difference in the number of teeth, and the internal gear 3 outputs the reduced rotational force transmitted from the external gear 2 .

The tubular portion 22 has a tubular shape surrounding the rotation axis RA and extends axially forward from the lid portion 23 . The tubular portion 22 is flexible and deformable in the radial direction. In this embodiment, when viewed from the axial direction, the cylindrical portion 22 is bent into the same shape as the rotating member 1 having a long diameter and a short diameter ( See Figure 3).

The cylindrical portion coating film 222 is provided on the inner side surface of the cylindrical base portion 221, and more specifically, is provided on at least a region of the cylindrical portion inner side surface 22a that contacts the rotating member 1. As shown in FIG. In this way, torque transmission loss from the rotating member 1 to the external gear 2 can be reduced. Furthermore, the wear of the tubular portion 22 can be suppressed by the tubular portion coating film 222 . The cylindrical portion coating film 222 is a part of the coating film C included in the speed reducer 100 .

The lid portion 23 is positioned axially rearward of the rotating member 1 in the axial direction parallel to the rotation axis RA. The lid portion 23 has a circular shape when viewed from the axial direction in this embodiment.

The shaft 24 extends axially rearward from the lid portion 23 .

<1-1-3. Structure of Coating Film>
Next, the configuration of the coating film C will be described. At least one of the rotating member 1 and the cylindrical portion 22 of the external gear 2 has a coating film C. As shown in FIG. In this embodiment, both the rotating member 1 and the cylindrical portion 22 have the coating film C. As shown in FIG. However, the present invention is not limited to this example, and either the rotating member 1 or the cylindrical portion 22 may have the coating film C. FIG. In other words, the rotating member 1 may have the rotating portion coating film 12 , but the cylindrical portion 22 may not have the cylindrical portion coating film 222 . Alternatively, the cylindrical portion 22 may have the cylindrical portion coating film 222 , but the rotating member 1 may not have the rotating portion coating film 12 .

In this way, for example, the coating film C for reducing friction between the rotating member 1 and the cylindrical portion 22 reduces torque transmission loss caused by the sliding of the rotating member 1 on the inner side surface 22a of the cylindrical portion. can. Therefore, the reduction in efficiency of the speed reducer 100 can be suppressed. Furthermore, the coating film C can suppress wear of the rotating member 1 and the cylindrical portion 22 .

The coating film C is any one of a DLC (diamond-like carbon) film, a fluororesin film, a resin film containing a lubricant, and a nickel plating containing a fluororesin. The lubricant contains at least one of graphite (black lead), molybdenum disulfide (MoS ₂ ), and fluororesin. Also, the resin film containing lubricant is a film provided using a composite resin material in which lubricant as described above is mixed with any one of polyamide-imide resin, polyimide resin, and epoxy resin, for example.

The DLC film, the fluororesin film, the resin film containing the lubricant, and the nickel plating containing the fluororesin have smaller coefficients of friction than the aforementioned materials used for the rotating base 11 and the cylindrical base 221 . Therefore, by using these materials for the coating film C, transmission loss of torque from the rotating member 1 to the cylindrical portion 22 of the external gear 2 can be further reduced.

When the coating film C is either a DLC film or nickel plating containing fluororesin, the arithmetic average roughness Ra of the coating film C is preferably 0.2 [μm] or less. Further, when the coating film C is either a fluorine resin film or a resin film containing a lubricant, the arithmetic mean roughness Ra of the coating film C is 0.4 [μm] or less. preferable. For these surface roughnesses, the arithmetic mean roughness Ra specified in JIS B0601:2001 (corresponding international standard ISO 4287:1997) is adopted. In this embodiment, a stylus-type surface roughness measuring instrument specified in JIS B0651:2001 (corresponding international standard ISO 3274:1996) is used for surface roughness measurement.

By setting the arithmetic mean roughness Ra of the coating film C within the above range, the initial wear amount of the coating film C at the time of initial use of the speed reducer 100 can be suppressed. For example, during initial use, the dimensions of the member provided with the coating film C change according to the amount of initial wear. If the surface roughness of the coating film C provided on at least one of the rotating member 1 and the cylindrical portion 22 is within the above range in terms of arithmetic mean roughness Ra, the member provided with the coating film C will not change in dimension. The initial wear amount of the coating film C can be suppressed to such an extent that the deterioration of the performance of the speed reducer 100 caused by the above is not so noticeable.

<2. Others>
The embodiments of the present invention have been described above. It should be noted that the scope of the present invention is not limited to the above-described embodiments. The present invention can be implemented with various modifications without departing from the gist of the invention. In addition, the matters described in the above-described embodiments can be appropriately and arbitrarily combined as long as there is no contradiction.

INDUSTRIAL APPLICABILITY The present invention is useful for reduction gears that reduce the rotational force of a rotating member and transmit it to an internal gear.

DESCRIPTION OF SYMBOLS 100... Reduction gear, 1... Rotation member, 1a... Inclined surface, 11... Rotation base, 111... Hole, 12... Rotation part coating film, 2... Outside Tooth gear 21 External tooth 22 Cylindrical portion 22a Cylindrical inner surface 221 Cylindrical base 222 Cylindrical coating film 23 Lid 24... shaft, 3... internal gear, 31... internal tooth, 4... bearing, ?... inclination angle, C... coating film, RA... rotating shaft, LD・・・Major axis direction, SD・・・Minor axis direction, MD・・・Middle direction

Claims (1)

a single rotating member rotatable about an axis of rotation and having a major axis and a minor axis when viewed from the axis of rotation;
an external gear having a plurality of external teeth arranged in a circumferential direction;
an annular internal gear having a plurality of circumferentially arranged internal teeth and surrounding the rotating shaft;
with
The external gear further has a cylindrical portion that surrounds the rotating shaft and is radially deformable,
an outer surface of the rotating member on the radially outer side is slidably and directly in contact with an inner surface of the cylindrical portion on the radially inner side of the cylindrical portion;
The plurality of external teeth are provided on a radially outer side surface of the cylindrical portion,
The plurality of internal teeth are provided on a radially inner side surface of the internal gear,
the external teeth of the external gear mesh with the internal teeth of the internal gear in the longitudinal direction of the rotating member;
The external gear further has a cover positioned on one side of the rotating member in the axial direction parallel to the rotating shaft,
the cylindrical portion extends from the lid portion to the other side in the axial direction,
A reduction gear including an outer surface on the radially outer side of the rotating member including an inclined surface that inclines radially outward toward the other side in the axial direction in the longitudinal direction of the rotating member.

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