WO2023102830A1

WO2023102830A1 - Harmonic reducer

Info

Publication number: WO2023102830A1
Application number: PCT/CN2021/136817
Authority: WO
Inventors: Xiaodong Cao; Xinguo FU; Zhu Zhu
Original assignee: ABB Schweiz AG
Current assignee: ABB Schweiz AG
Priority date: 2021-12-09
Filing date: 2021-12-09
Publication date: 2023-06-15
Anticipated expiration: 2024-06-09

Abstract

Embodiments of present disclosure relate to a harmonic reducer. The harmonic reducer comprises: a wave generator (10) adapted to be coupled to a motor shaft; a circular spline (30) adapted to be fixed on a base; a flex spline (20) arranged around the wave generator (10) and configured to be driven by the wave generator (10) to rotate along an inner surface of the circular spline (30); and a bearing (40) comprising a rotating member (41) and a fixing member (42), the rotating member (41) being coupled to the flex spline (20) and configured to rotate together with the flex spline (20), the fixing member (42) being coupled to the circular spline (30) and configured to support the rotating member (41), wherein a lubricant channel (50) is formed at least partly between an outer surface of the flex spline (20) and the bearing (40), and wherein the flex spline (20) is provided with at least one through hole (23) connecting the lubricant channel (50) with an inner space (60) inside the flex spline (20). The harmonic reducer according to embodiments of present disclosure is free of lubricant leakage without affecting the service life of the bearing.

Description

HARMONIC REDUCER

FIELD

Embodiments of the present disclosure generally relate to the field of reducer, and more particularly, to a harmonic reducer.

BACKGROUND

A harmonic reducer is widely used in robots. The harmonic reducer has many advantages, such as simple structure, light weight, high speed ratio and high efficiency. Usually, the harmonic reducer comprises a wave generator, a flex spline, a circular spline and a bearing. In order to supply lubricant oil to the bearing, the flex spline, the circular spline and inner and outer rings of the bearing may form a lubricant supply space in the reducer, i.e. a lubricant channel.

The lubricant channel is configured to allow the lubricant to flow to rollers of the bearing. Further, at an end of the lubricant channel, there is provided a lubricant seal to seal the lubricant channel. However, when the wave generator rotates at a high speed, the flex spline deforms periodically along with the rotation of the wave generator and as a result, the lubricant with air will be sucked into the lubricant channel. Due to the viscosity of the lubricant and the high-speed deformation of the flex spline, the lubricant channel may be closed for a period of time. In addition, there are various kinds of frictions in the lubricant channel which may cause the temperature of the lubricant channel to rise higher than the rest of the closed space. Consequently, the pressure within the lubricant channel will exceed a tolerance of the lubricant seal which leads to lubricant leakage. The lubricant leakage will increase the testing time of the prototype and greatly reduce the customer satisfaction. Therefore, how to avoid the lubricant leakage has always been an important topic in the art.

SUMMARY

In view of the foregoing problems, example embodiments of the present disclosure propose a harmonic reducer that has an efficient lubricant leakage prevention mechanism.

In a first aspect of the present disclosure, a harmonic reducer is provided. The harmonic reducer comprises a wave generator adapted to be coupled to a motor shaft; a circular spline adapted to be fixed on a base; a flex spline arranged around the wave generator and configured to be driven by the wave generator to rotate along an inner surface of the circular spline; and a bearing comprising a rotating member and a fixing member, the rotating member being coupled to the flex spline and configured to rotate together with the flex spline, the fixing member being coupled to the circular spline and configured to support the rotating member, wherein a lubricant channel is formed at least partly between an outer surface of the flex spline and the rotating member of the bearing, and wherein the flex spline is provided with at least one through hole connecting the lubricant channel with an inner space inside the flex spline.

With these embodiments, by providing at least one through hole on the flex spline, the lubricant channel is in communication with the inner space inside the flex spline. Consequently, during the rotation of the flex spline, once the pressure within the lubricant channel increases, the lubricant probably along with air may flow from the lubricant channel into the inner space inside the flex spline via the through hole so that the pressure within the lubricant channel can be reduced. Thus, the pressure within the lubricant channel will not exceed the tolerance of the radial seal, thereby preventing the lubricant from leaking through the radial seal. At the same time, the holding force of the radial seal will not need to be increased. Therefore, the service life of the bearing will not be affected.

In some embodiments, the flex spline comprises: an axial part extending from the wave generator in a direction parallel to a central axis A of the flex spline; and a radial part extending from a distal end of the axial part away from the wave generator in a direction perpendicular to the rotation axis A, wherein the at least one through hole is arranged on the radial part. With these embodiments, by providing the through hole on the radial portion of the flex spline, the fatigue strength of the flex spline will be reduced so that the service life of the flex spline will not be affected.

In some embodiments, the radial part comprises: a first section coupled to the rotating member; and a second section extending from the first section to the distal end of the axial part, wherein a thickness of the first section is greater than a thickness of the second section, and the at least one through hole is arranged on the second section and/or the first section. With these embodiments, by arranging the through hole on the first section and/or the second section selectively, an increased flexibility of the design is provided.

In some embodiments, the radial part extends inwards from the distal end of the axial part, and the second section is located outside the first section radially, and wherein at least a portion of the lubricant channel is formed between the rotating member and the radial part. With these embodiments, the flex spline may be formed into a cup shape, and a lubricant leakage prevention mechanism can be applied to the cup-shaped harmonic reducer.

In some embodiments, the at least one through hole is arranged on the second section close to the distal end of the axial part. With these embodiments, by arranging the through hole near the distal end of the axial portion, the influence of the through hole on the fatigue strength of the flex spline will be reduced.

Alternatively, in some embodiments, the radial part extends outwards from the distal end of the axial part, and the first section is located outside the second section radially, and wherein the fixing member is arranged around the axial part and at least a portion of the lubricant channel is formed between the fixing member and the radial part. With these embodiments, the flex spline may be formed into a hat shape, and a lubricant leakage prevention mechanism can be applied to the hat-shaped harmonic reducer.

In some embodiments, the at least one through hole is arranged on the second section close to the first section. With these embodiments, by arranging the through hole near the mounting section of the flex spline, the influence of the through hole on the fatigue strength of the flex spline will be reduced.

In some embodiments, the lubricant channel extends along at least a portion of an outer surface of the first section, and the at least one through hole is arranged on the first section. With these embodiments, by arranging the through hole at a position where the first section forms a part of the lubricant channel, the inner space inside the flex spline and the lubricant channel can be directly connected via the through hole.

In some embodiments, the harmonic reducer comprises: a flange coupled to the flex spline; a flange coupled to the flex spline; a first radial seal arranged between the first section and the bearing; and a second radial seal arranged between the first section and the flange, wherein the at least one through hole is closer to the second section than the first radial seal and the second radial seal. With these embodiments, by arranging the at least one through hole radially inwards relative to the radial seals, the lubricant flowing via the through hole will not leak through a slit between the rotating member of the bearing and the flex spline as well as a slit between the flex spline and the flange.

In some embodiments, the harmonic reducer further comprises a pressure relief mechanism configured to block the at least one through hole when a pressure inside the lubricant channel is below a predefined threshold and open the at least one through hole when the pressure inside the lubricant channel is above the predefined threshold. With these embodiments, the pressure within the lubricant channel can be adjusted by the pressure relief mechanism.

In some embodiments, the bearing comprises a recess at an surface of the bearing facing the at least one through hole, and wherein the pressure relief mechanism comprises: a spring provided in the recess; a cover provided in the inner space and comprising a conical surface configured to abut against and cover the at least one through hole; wherein the cover is connected to the spring so that the cover is pulled towards the at least one through hole. With these embodiments, when the pressure within the lubricant channel increases and overcomes the stress applied to the cover by the spring, the cover will be pushed inwards by the lubricant such that the at least one through hole opens, thereby allowing the lubricant in the lubricant channel to flow into the inner space. As the lubricant flows into the inner space, the pressure within the lubricant channel is reduced, thereby preventing the lubricant leakage.

In some embodiments, the harmonic reducer further comprises a flange coupled to a radial part of the flex spline, wherein the flange comprises a recess at a surface of the flange facing the at least one through hole, and wherein the pressure relief mechanism comprises: a spring arranged in the recess; a cover arranged in the recess and comprising a conical surface configured to abut against and cover the at least one through hole; wherein the cover is coupled to the spring so that the cover is pushed towards the at least one through hole. With these embodiments, when the pressure within the lubricant channel increases and overcomes the stress applied to the cover by the spring, the cover will be pushed away from at least one through hole, thereby allowing the lubricant in the lubricant channel to flow into the inner space. As the lubricant flows into the inner space, the pressure within the lubricant channel is reduced. Further, by arranging the spring in the flange, the spring may not interference with the lubricant channel.

In some embodiments, the at least one through hole comprises a plurality of through holes distributed centrosymmetrically on the radial part. With these embodiments, by providing a plurality of through holes, the prevention of the lubricant leakage can be achieved more efficiently.

DESCRIPTION OF DRAWINGS

Through the following detailed descriptions with reference to the accompanying drawings, the above and other objectives, features and advantages of the example embodiments disclosed herein will become more comprehensible. In the drawings, several example embodiments disclosed herein will be illustrated in an exemplary and in a non-limiting manner, wherein:

Fig. 1A schematically illustrates a cross-sectional view of a harmonic reducer according to some embodiments of the present disclosure;

Fig. 1B schematically illustrates an enlarged view of a part of the harmonic reducer of Fig. 1A;

Fig. 1C schematically illustrates a perspective view of a part of the harmonic reducer of Fig. 1A;

Fig. 2A schematically illustrates a cross-sectional view of a harmonic reducer according to some further embodiments of the present disclosure;

Fig. 2B schematically illustrates an enlarged view of a part of the harmonic reducer of Fig. 2A;

Fig. 2C schematically illustrates a perspective view of a part of the harmonic reducer of Fig. 2A;

Fig. 3 schematically illustrates a cross-sectional view of a part of a harmonic reducer according to yet further embodiments of the present disclosure;

Fig. 4A schematically illustrates a cross-sectional view of a part of a harmonic reducer with a pressure relief mechanism according to some embodiments of the present disclosure; and

Fig. 4B schematically illustrates a cross-sectional view of a part of a harmonic reducer with a pressure relief mechanism according to some further embodiments of the present disclosure.

Throughout the drawings, the same or similar reference symbols are used to indicate the same or similar elements.

DETAILED DESCRIPTION OF EMBODIEMTNS

Principles of the present disclosure will now be described with reference to several example embodiments shown in the drawings. Though example embodiments of the present disclosure are illustrated in the drawings, it is to be understood that the embodiments are described only to facilitate those skilled in the art in better understanding and thereby achieving the present disclosure, rather than to limit the scope of the disclosure in any manner.

As described above, conventionally, in order to prevent lubricant leakage at the lubricant seal, a holding force applied to the lubricant seal needs to be increased, for example by increasing the friction between the radial seal and the bearing. However, the increase of the holding force may lead to more wear of the bearing. To address the fallbacks discussed above, example embodiments of the present disclosure relate to a lubricant leakage prevention mechanism.

In the following, example constructions and operating principles of the harmonic reducer will be described with reference to Figs. 1A-4B. Figs. 1A-1C schematically illustrate a cup-shaped harmonic reducer according to some embodiments of the present disclosure in different perspectives. Figs. 2A-2C schematically illustrate a hat-shaped harmonic reducer according to some further embodiments of the present disclosure in different perspectives. Fig. 3 schematically illustrates a cross-sectional view of a part of a harmonic reducer according to yet further embodiments of the present disclosure. Figs. 4A-4B schematically illustrate cross-sectional views of a part of the harmonic reducer with a pressure relief mechanism according to different embodiments of the present disclosure.

Fig. 1A schematically illustrates a cross-sectional view of a cup-shaped harmonic reducer according to some embodiments of the present disclosure. As shown in Fig. 1A, the harmonic reducer comprises a wave generator 10, a flex spline 20, a circular spline 30 and a bearing 40. The wave generator 10 is adapted to be coupled to a motor shaft (not shown) , for example a motor shaft of a motor for a robot joint. The circular spline 30 is adapted to be fixed on a base, for example the robot joint. The flex spline 20 is arranged around the wave generator 10 and configured to be driven by the wave generator 10 to rotate along an inner surface of the circular spline 30. During the rotation of the flex spline 20, an outer thread arranged on the outer surface of the flex spline 20 engages with an inner thread arranged on the inner surface of the circular spline 30.

The bearing 40 comprises a rotating member 41 and a fixing member 42. In the example embodiment as illustrated in Fig. 1A, the rotating member 41 is an inner ring of a cross roller bearing and the fixing member 42 is an outer ring of the cross roller bearing. The rotating member 41 is coupled to the flex spline 20 and configured to rotate together with the flex spline 20. The rotating member 41 may be further coupled to other members to output torque generated by the rotation of the flex spline 20. The fixing member 42 is coupled to the circular spline 30 and configured to support the rotating member 41. For example, the fixing member 42 may be coupled to a flange part of the circular spline 30 by means of bolts. A lubricant channel 50 is formed at least partly between an outer surface of the flex spline 20 and the rotating member 41 of the bearing 40.

In the example embodiment illustrated in Fig. 1A, the flex spline 20 may comprise a cup-shaped body and the harmonic reducer may be referred to as a cup-shaped harmonic gear. The flex spline 20 comprises an axial part 22 and a radial part 21. The axial part 22 extends from the wave generator 10 to a distal end 221 in a direction parallel to a central axis A of the flex spline 20, i.e. in an axial direction. The radial part 21 extends from the distal end 221 of the axial part 22 away from the wave generator 10 in a direction perpendicular to the rotation axis A, i.e. in a radial direction. In this example embodiment, the radial part 21 extends inwards from the distal end 221 of the axial part 22. The detailed structure of the radial part 21 will be described later with reference to Fig. 2B.

In this example embodiment, the lubricant channel 50 may comprise four sections. A first section of lubricant channel 50 extends along the outer surface of the flex spline 20 between the flex spline 20 and the circular spline 30 as well as an axial portion 411 of the rotating member 41 enclosing a part of the axial part 22. A second section of the lubricant channel 50 extends radially along at least a part of the outer surface of the radial part 21 between the radial part 21 and the rotating member 41. A third section of the lubricant channel 50 extends from the first portion of the lubricant channel 50 radially to the fixing member 42. A fourth section of the lubricant channel 50 extends axially between the fixing member 42 and rotating member 41. Rollers of the bearing 40 are arranged at the fourth portion of the lubricant channel 50.

It should be appreciated that the lubricant channel 50 is formed between different components of the harmonic reducer. The size and shape of the lubricant channel 50 depends on the structures of the components. For example, the bearing 40 may have various forms which could lead to different structures of the lubricant channel 50. With regard to the structure of the lubricant channel 50, the present disclosure does not suggest any limitations.

Further, at an end of the fourth portion of the lubricant channel 50, a lubrication seal 70 is provided to prevent the lubricant from flowing out of the lubricant channel 50. As discussed above, for the purpose of preventing the pressure within the lubricant channel 50 from exceeding the tolerance of the lubrication seal 70, the flex spline 20 is provided with at least one through hole 23. The at least one through hole 23 connects the lubricant channel 50 with an inner space 60 inside the flex spline 20 so that the lubricant can flow from the lubricant channel 50 into the inner space 60 to avoid increase of the pressure within the lubricant channel 50.

It should be appreciated that the at least one through hole 23 may comprise various shapes according to actual needs, such as regular shapes like round, rectangular, triangular as well as irregular shapes suitable for specific situations. In this regard, the present disclosure does not suggest any limitations.

Fig. 1B schematically illustrates an enlarged view of a part of the harmonic reducer of Fig. 1A. As shown in Fig. 1B, the radial part 21 comprises a first section 211 and a second section 212. The second section 212 extends radially inwards from the distal end 221 of the axial part 22 to the first section 211. That is, the second section 212 is located outside the first section 211 radially. The first section 211 may comprise mounting holes for bolts used to connect the first section 211 with the rotating member 41. In order to provide the mounting holes, a thickness of the first section 211 is usually greater than a thickness of the second section 212. In this example embodiment, the at least one through hole 23 is arranged on the second section 212. Alternatively or additionally, the at least one through hole 23 may be arranged on the first section 211.

Fig. 1C schematically illustrates a perspective view of a part of the harmonic reducer of Fig. 1A. As shown in Fig. 1C, a proximal end surface of the circular spline 30 adapted to be fixed on the base is illustrated. The cup-shaped flex spline 20 is arranged inside the circular spline 30. The radial part 21 comprises the first section 211 and the second section 212. A plurality of bolts are arranged in a plurality of mounting holes of the first section 211. There are four through holes 23 centrosymetrically distributed on the second section 213. Further, in order to minimize the influence of the through holes 23 on the fatigue strength of the flex spline 20, the through holes 23 are located close to the axial part 22 of the flex spline 20.

It should be appreciated that other numbers of through holes 23 can be provided. In this regard, the present disclosure suggests no limitations.

Fig. 2A schematically illustrates a cross-sectional view of a hat-shaped harmonic reducer according to some embodiments of the present disclosure. For the sake of brevity, the descriptions with regard to the structures and elements similar to those illustrated in Fig. 1A will be omitted. As shown in Fig. 2A, the difference between the harmonic reducers in Fig. 2A and Fig. 1A is that the flex spline 20 comprises a hat-shaped body and the radial part 21extends outwards from the distal end 221 of the axial part 22.

Further, in the example as illustrated in Fig. 2A, a rotating member 41 of the bearing 40 is an outer ring of a cross roller bearing and a fixing member 42 of the bearing 40 is an inner ring of the cross roller bearing. The rotating member 41 is coupled to the flex spline 20 and configured to rotate together with the flex spline 20. The fixing member 42 is coupled to the circular spline 30 and configured to support the rotating member 41. For example, the fixing member 42 may be coupled to a flange part of the circular spline 30 by bolts. A lubricant channel 50 is formed at least partly between an outer surface of the flex spline 20 and the fixing member 42 of the bearing 40.

In this example embodiment, the lubricant channel 50 may comprise three sections. A first section of lubricant channel 50 extends along the outer surface of the flex spline 20 between the flex spline 20 and the circular spline 30 as well as the fixing member 42. A second section of the lubricant channel 50 extends radially between the outer surface of the radial part 21 facing the circular spline 30 and a distal end of the fixing member 42 away from the circular spline 30. A third section of the lubricant channel 50 extends axially between the fixing member 42 and the rotating member 41. The rollers of the bearing 40 are arranged at the third section of the lubricant channel 50.

Further, at an end of the third section of the lubricant channel 50, a lubrication seal 70 is provided to prevent the lubricant from flowing out of the lubricant channel 50. As discussed above, for the purpose of preventing the pressure within the lubricant channel 50 from exceeding the tolerance of the lubrication seal 70, the flex spline 20 is provided with at least one through hole 23. The at least one through hole 23 connects the lubricant channel 50 with an inner space 60 inside the flex spline 20 so that the lubricant can flow from the lubricant channel 50 into the inner space 60 to avoid increase of the pressure within the lubricant channel 50.

Fig. 2B schematically illustrates an enlarged view of a part of the harmonic reducer of Fig. 2A. As shown in Fig. 2B, the radial part 21 comprises a first section 211 and a second section 212. The second section 212 extends radially outwards from the distal end 221 of the axial part 22 to the first section 211. That is, the first section 211 is located outside the second section 211 radially. The first section 211 may comprise mounting holes for bolts used to connect the first section 211 with the rotating member 41. In order to provide the mounting holes, a thickness of the first section 211 is greater than a thickness of the second section 212. In this example embodiment, the at least one through hole 23 is arranged on the second section 212. Alternatively or additionally, the at least one through hole 23 may be arranged on the first section 211 which will be described later with reference to Fig. 3.

Fig. 2C schematically illustrates a perspective view of some parts of the harmonic reducer of Fig. 2A. As shown in Fig. 2C, a distal end surface of the flex spline 20 adapted to be coupled to the rotating member 41 is illustrated. The hat-shaped flex spline 20 is arranged around the wave generator 10. The radial part 21 comprises the first section 211 and the second section 212. A plurality of mounting holes for bolts of the first section 211 is provided on the first section 211. There are four through holes 23 centrosymetrically distributed on the second section 213. Further, in order to minimize the influence of the through holes 23 on the fatigue strength of the flex spline 20, the through holes 23 are located close to the first section 211.

Fig. 3 schematically illustrates a cross-sectional view of a part of a harmonic reducer according to some yet further embodiments of the present disclosure. For the sake of brevity, the descriptions with regard to the structures and elements similar to those illustrated in Fig. 2A will be omitted. As shown in Fig. 3, the difference between the harmonic reducers in Fig. 3 and Fig. 2A is that the harmonic reducer further comprises a flange 73, a first radial seal 71 and a second radial seal 72. The flange 73 is coupled to a distal end of the first section 211 away from the circular spline 30 and configured to output a torque generated by the rotation of the flex spline 20. The first radial seal 71 is arranged between the first section 211 and the rotating member 41 to seal the lubricant channel 50. The second radial seal 72 is arranged between the first section 211 and the flange 73 to prevent the lubricant from flowing out of a lubricant path between the radial part 21 and the flange 73. The lubricant channel 50 extends along a portion of an outer surface of the first section 211, and the at least one through hole 211 is arranged on the first section 211 adjacent to at least a portion of the lubricant channel 50 so that once the through hole 23 is provided, the lubricant channel 50 is in communication with the lubricant path between the first section 211 and the flange 73. The lubricant may further flow from the lubricant path to the inner space 60. The at least one through hole 23 is provided on the first section 211 and closer to the second section 212 than the first radial seal 71 and the second radial seal 72.

It should be appreciated that the at least one through hole 23 may be arranged either on the first section 211 or on the second section 212, or arranged on both of the first second 211 and the second section 212.

Fig. 4A schematically illustrates a cross-sectional view of a part of a harmonic reducer with a pressure relief mechanism according to some embodiments of the present disclosure. As shown in Fig. 4A, the harmonic reducer further comprises a pressure relief mechanism 80. The pressure relief mechanism 80 is configured to block the at least one through hole 23 when a pressure inside the lubricant channel 50 is below a predefined threshold and open the at least one through hole 23 when the pressure inside the lubricant channel 50 is above the predefined threshold.

In the example embodiment illustrated in Fig. 4A, the fixing member 41 of the bearing 40 comprises a recess 41 at a surface of the fixing member 41 facing the at least one through hole 23 across the lubricant channel 50. The pressure relief mechanism 80 comprises a spring 81 provided in the recess 41. The pressure relief mechanism 80 further comprises a cover 82 provided in the inner space 60. The cover 82 comprises a conical surface configured to abut against the at least one through hole 23 which may has a round shape. The cover 82 is connected to the spring 81 so that the cover 82 is pulled towards the at least one through hole 23. That is, the cover 82 and the spring 81 are provided on different side of the at least one through hole 23. The conical surface of the cover 82 is kept abutting against the edge of the at least one through hole 23 by the pulling stress of the spring 81.

When the pressure within the lubricant channel 50 increases and overcomes the stress applied to the cover 82 by the spring 81, the cover 82 will be pushed inwards by the lubricant and the at least one through hole 23 opens, thereby allowing the lubricant in the lubricant channel 50 to flow into the inner space 60. As the pressure within the lubricant channel 50 decreases, the cover 82 will return to the previous position. The movement of the cover 82 will be limited by the interaction between the conical surface of the cover 82 and the round edge of the at least one through hole 23.

It should be appreciated that the at least one through hole 23 may comprise various shapes and the shape and dimension of the cover 82 depends on the shapes of the through hole 23. In this regard, the present disclosure does not suggest any limitations.

Further, although it is described with reference to a cup-shaped harmonic reducer, it should be appreciated that this configuration can also be applied to a hat-shaped harmonic reducer.

Fig. 4B schematically illustrates a cross-sectional view of a part of a harmonic reducer with a pressure relief mechanism according to some further embodiments of the present disclosure. As shown in Fig. 4B, the harmonic reducer further comprises a pressure relief mechanism 80 different from that illustrated in Fig. 4A. The harmonic reducer further comprises a flange 73 coupled to a radial part 21 of the flex spline 20, similar to the structure as illustrated in Fig. 3. The flange 73 comprises a recess 731 at a surface of the flange 73 facing the at least one through hole 23. A spring 81 of the pressure relief mechanism 80 is arranged in the recess 731. The pressure relief mechanism 80 further comprises a cover 82 arranged in the recess 731 and the cover 82 comprises a conical surface configured to abut against and cover the at least one through hole 23. The cover 82 is coupled to the spring 81 so that the cover 82 is pushed towards the at least one through hole 23.

When the pressure within the lubricant channel 50 increases and overcomes the stress applied to the cover 82 by the spring 81, the cover 82 will be pushed towards the flange 73 by the lubricant and the at least one through hole 23 opens, thereby allowing the lubricant in the lubricant channel 50 to flow into the inner space 60. As the pressure within the lubricant channel 50 decreases, the cover 82 will return to the previous position. In this embodiment, the pressure relief mechanism 80 and the lubricant channel 50 are located on different sides of the flex spline 20. Therefore, the pressure relief mechanism 80 will not affect the lubricant flow in the lubricant channel 50.

In some embodiments, the at least one through hole 23 may comprise a plurality of through holes 211 distributed centrosymmetrically on the radial part 21.

It should be appreciated that the above detailed embodiments of the present disclosure are only to exemplify or explain principles of the present disclosure and not to limit the present disclosure. Therefore, any modifications, equivalent alternatives and improvement, etc. without departing from the spirit and scope of the present disclosure shall be included in the scope of protection of the present disclosure. Meanwhile, appended claims of the present disclosure aim to cover all the variations and modifications falling under the scope and boundary of the claims or equivalents of the scope and boundary.

Claims

A harmonic reducer, comprising:

a wave generator (10) adapted to be coupled to a motor shaft;

a circular spline (30) adapted to be fixed on a base;

a flex spline (20) arranged around the wave generator (10) and configured to be driven by the wave generator (10) to rotate along an inner surface of the circular spline (30) ; and

a bearing (40) comprising a rotating member (41) and a fixing member (42) , the rotating member (41) being coupled to the flex spline (20) and configured to rotate together with the flex spline (20) , the fixing member (42) being coupled to the circular spline (30) and configured to support the rotating member (41) ,

wherein a lubricant channel (50) is formed at least partly between an outer surface of the flex spline (20) and the bearing (40) , and

wherein the flex spline (20) is provided with at least one through hole (23) connecting the lubricant channel (50) with an inner space (60) inside the flex spline (20) .
The harmonic reducer of Claim 1, wherein the flex spline (20) comprises:

an axial part (22) extending from the wave generator (10) in a direction parallel to a central axis (A) of the flex spline (20) ; and

a radial part (21) extending from a distal end (221) of the axial part (22) away from the wave generator (10) in a direction perpendicular to the rotation axis (A) ,

wherein the at least one through hole (23) is arranged on the radial part (21) .
The harmonic reducer of Claim 2, wherein the radial part (21) comprises:

a first section (211) coupled to the rotating member (41) ; and

a second section (212) extending from the first section (211) to the distal end (221) of the axial part (22) ,

wherein a thickness of the first section (211) is greater than a thickness of the second section (212) , and the at least one through hole (23) is arranged on the second section (212) and/or the first section (211) .
The harmonic reducer of Claim 3, wherein the radial part (21) extends inwards from the distal end (221) of the axial part (22) , and the second section (212) is located outside the first section (211) radially, and

wherein at least a portion of the lubricant channel (50) is formed between the rotating member (41) and the radial part (21) .
The harmonic reducer of Claim 4, wherein the at least one through hole (23) is arranged on the second section (212) close to the distal end (221) of the axial part (22) .
The harmonic reducer of Claim 3, wherein the radial part (21) extends outwards from the distal end (221) of the axial part (22) , and the first section (211) is located outside the second section (212) radially, and

wherein the fixing member (42) is arranged around the axial part (22) , and at least a portion of the lubricant channel (50) is formed between the fixing member (42) and the radial part (21) .
The harmonic reducer of Claim 6, wherein the at least one through hole (23) is arranged on the second section (212) close to the first section (213) .
The harmonic reducer of Claim 6, wherein the lubricant channel (50) extends along at least a portion of an outer surface of the first section (211) , and the at least one through hole (211) is arranged on the first section (211) .
The harmonic reducer of Claim 8, further comprising:

a flange (73) coupled to the flex spline (20) ;

a first radial seal (71) arranged between the first section (211) and the bearing (40) ; and

a second radial seal (72) arranged between the first section (211 and the flange (73) ,

wherein the at least one through hole (23) is closer to the second section (212) than the first radial seal (70) and the second radial seal (80) .
The harmonic reducer of Claim 1, further comprising a pressure relief mechanism (80) configured to block the at least one through hole (23) when a pressure inside the lubricant channel (50) is below a predefined threshold and open the at least one through hole (23) when the pressure inside the lubricant channel (50) is above the predefined threshold.
The harmonic reducer of Claim 10, wherein the bearing (40) further comprises a recess (41) at an surface of the bearing (40) facing the at least one through hole (23) , and

wherein the pressure relief mechanism (80) comprises:

a spring (81) arranged in the recess (41) ; and

a cover (82) arranged in the inner space (60) and comprising a conical surface configured to abut against and cover the at least one through hole (23) ;

wherein the cover (82) is coupled to the spring (82) so that the cover (81) is pulled towards the at least one through hole (23) .
The harmonic reducer of Claim 10, further comprising a flange (73) coupled to a radial part (21) of the flex spline (20) ,

wherein the flange (73) comprises a recess (731) at a surface of the flange (73) facing the at least one through hole (23) , and

wherein the pressure relief mechanism (80) comprises:

a spring (81) arranged in the recess (731) ;

a cover (82) arranged in the recess (731) and comprising a conical surface configured to abut against and cover the at least one through hole (23) ;

wherein the cover (82) is coupled to the spring (81) so that the cover (82) is pushed towards the at least one through hole (23) .
The harmonic reducer of Claim 2, wherein the at least one through hole (23) comprises a plurality of through holes (211) distributed centrosymmetrically on the radial part (21) .