Harmonic gear transmission mechanism and electric actuator

Abstract

The invention discloses a harmonic gear transmission mechanism which comprises a motor output shaft made of a rigid metal material, and an outer gear ring is arranged on the outer wall of the motor output shaft; a first bearing and a second bearing are mounted at the two ends of the inner side of the motor fixing assembly respectively; the motor stator is mounted on the motor fixing assembly; the motor rotor is arranged on the inner ring of the motor stator; the wave generator is installed on the inner ring of the motor rotor, the wave generator and the motor rotor are fixed into a whole, and the wave generator is provided with an oval inner cavity; the flexible bearing is mounted in the elliptical inner cavity of the wave generator; and the flexible gear is installed in the inner ring of the flexible bearing and installed on the output shaft of the motor through a third bearing, an inner gear ring is arranged on the inner wall of the flexible gear, and the inner gear ring is meshed with the outer gear ring. The motor output shaft serves as a rigid wheel and a terminal output shaft at the same time, the structure is compact, the size is small, and the electric actuator can be used for directly driving a valve to be opened or closed.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical transmission, and in particular to a harmonic gear transmission mechanism and an electric actuator. Background Art

[0002] Harmonic gear transmission has the characteristics of high precision and high transmission ratio, and is widely used in the fields of robotics, aerospace, and automation equipment. However, the existing harmonic gear flexspline usually adopts an external gear, and the rigid wheel adopts an internal gear ring structure. Its design leads to a large overall volume and complex installation, which is limited in applications with high volume and weight requirements. Especially in electric actuators, the existing structure is difficult to meet the design requirements of miniaturization and high efficiency. Therefore, it is particularly necessary to develop a more compact harmonic gear structure. Summary of the invention

[0003] The purpose of the present invention is to provide a harmonic gear transmission mechanism and an electric actuator to solve the problem that the existing harmonic gear structure is large in size, complex in installation, and not suitable for installation in a small space. To achieve the above purpose, the present invention adopts the following technical solutions: The present invention discloses a harmonic gear transmission mechanism, comprising: a motor output shaft, which is made of a rigid metal material, and the outer wall of the motor output shaft is provided with an outer gear ring; a motor fixing assembly, and the first bearing and the second bearing are respectively installed at the two inner ends; a motor stator, which is installed on the motor fixing assembly; a motor rotor, which is arranged on the inner ring of the motor stator; a wave generator, which is installed on the inner ring of the motor rotor and fixed with the motor rotor to form an integral body, and the two ends are rotatably installed on the motor output shaft through the first bearing and the second bearing respectively; the wave generator is provided with an elliptical inner cavity; a flexible bearing, which is installed in the elliptical inner cavity of the wave generator; a flexible wheel, which is installed in the inner ring of the flexible bearing and is installed on the motor output shaft through a third bearing, and the inner wall of the flexible wheel is provided with an inner gear ring, and the inner gear ring is meshed with the outer gear ring.

[0004] Furthermore, the flexible bearing includes a flexible retaining frame and a plurality of cylindrical bearing rollers. The flexible retaining frame is an annular thin-walled structure. A mounting groove along the axial direction is provided on the wall surface of the flexible retaining frame. The bearing roller is embedded in the mounting groove and can rotate axially in the mounting groove. The axial direction of the bearing roller is parallel to the axial direction of the flexible retaining frame.

[0005] Preferably, the flexible retaining frame is made of PEEK material or PA66 material; a plurality of bearing rollers are arranged in each of the mounting grooves, and the plurality of bearing rollers are stacked along the axial direction.

[0006] Preferably, the cross section of the mounting groove is two symmetrically arranged arcs, and the central angle corresponding to each arc is 90°≤a≤120°.

[0007] Preferably, the end of the motor output shaft is provided with a first shaft shoulder, and a plane thrust needle roller bearing is installed on the inner side end of the first shaft shoulder; the motor fixing assembly includes a fixing seat, a first fixing plate, a second fixing plate, a first fastener and a second fastener; The fixing seat is installed on the inner side of the planar thrust needle roller bearing, and the first fixing plate is fixed on the fixing seat via a first fastener; the first fixing plate and the second fixing plate are connected and fixed via a second fastener.

[0008] Furthermore, it also includes a fixed sleeve, the end of the flexible wheel is provided with a second shoulder, the fixed sleeve is coaxially installed in the wave generator with the flexible bearing, and the first axial end of the fixed sleeve abuts against the flexible bearing; the flexible wheel is installed into the inner ring of the flexible bearing and the inner ring of the fixed sleeve, and the second shoulder of the flexible wheel is tightly abutted against the second axial end of the fixed sleeve, and the end of the flexible wheel is positioned and installed on the output shaft of the motor through a third bearing.

[0009] Preferably, the wave generator is tightly fitted with the motor rotor by interference fit to form a whole; the two ends of the motor rotor are respectively positioned and installed by a first bearing and a second bearing, and a wave spring is used to axially position the motor rotor.

[0010] Wherein, the flexible wheel is made of elastic metal material, carbon fiber reinforced epoxy resin-based composite material or glass fiber reinforced epoxy resin-based composite material.

[0011] Preferably, the ratio of the major axis to the minor axis of the elliptical inner cavity of the wave generator is 1.05-1.08:1; the difference in the number of teeth meshing between the inner gear ring and the outer gear ring is 2, and the structural speed ratio is 1:30.

[0012] The invention also discloses an electric actuator, comprising the above-mentioned harmonic gear transmission mechanism.

[0013] Due to the adoption of the above scheme, the present invention has the following beneficial effects: 1. The flexible wheel of the present invention adopts an inner gear ring, and an outer gear ring is arranged on the output shaft, which is different from the gear position of the existing flexible wheel and the rigid wheel. The output shaft is used as the rigid wheel part of the harmonic gear transmission mechanism and as the terminal output shaft at the same time. It has a compact structure, a small size, and has the advantages of high transmission efficiency and convenient installation. It can be used as an electric actuator to directly drive the valve to open or close.

[0014] 2. The present invention fixes the wave generator directly on the motor rotor without connecting it in other ways, which simplifies the structure and makes it more compact as a whole. The wave generator is integrated with the motor rotor as a power input element. The elliptical inner cavity of the wave generator forces the flexible wheel to produce periodic elastic deformation, thereby meshing with the outer gear ring of the output shaft to output power. This meshing method not only maintains the high-precision characteristics of the harmonic gear transmission, but also improves the transmission efficiency.

[0015] 3. The flexible bearing of the present invention omits the inner and outer ring structures of conventional bearings by inlaying cylindrical bearing rollers in the flexible cage, and has a more compact structure, which facilitates the miniaturization design of the harmonic gear mechanism.

[0016] 4. A plurality of bearing rollers are arranged in each mounting groove on the flexible bearing of the present invention, and the plurality of bearing rollers are stacked axially. Through this structure, gaps are formed between the plurality of bearing rollers, which is more conducive to storing lubricating oil and effectively improves the lubrication conditions of the bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the harmonic gear transmission mechanism of the present invention.

[0018] Figure 2 yes Figure 1 Schematic cross-section diagram of .

[0019] Figure 3 yes Figure 1 Schematic diagram of the decomposition.

[0020] Figure 4 yes Figure 3 View from another angle.

[0021] Figure 5 It is a structural schematic diagram of the flexible bearing of the present invention.

[0022] Figure 6 yes Figure 5 Schematic diagram of the decomposition.

[0023] Figure 7 yes Figure 5 Partial section of the schematic diagram in the E direction.

[0024] Figure 8 It is a schematic diagram of the cross-sectional arc of the mounting groove.

[0025] Fig. 9 is a cross-sectional view of the wave generator of the present invention.

[0026] Fig.10 Schematic diagram of the installation of wave generator and motor rotor.

[0027] Fig.11is a schematic diagram of the flexible bearing and fixed sleeve mounted to the wave generator.

[0028] Fig.12 It is a schematic diagram of the installation of the flexible wheel-2 into the inner ring of the flexible bearing.

[0029] Fig.13 yes Figure 1 AA cross-section diagram of .

[0030] Fig.14 It is a schematic diagram of the meshing of the inner ring gear and the outer ring gear.

[0031] Main component symbols: 1: Motor output shaft, 11: Outer gear ring, 12: First shaft shoulder, 2: Motor stator, 3: Motor rotor, 4: Wave generator, 5: Flexible bearing, 51: Flexible retaining frame, 511: Mounting groove, 52: Bearing roller, 6: Flexible wheel, 61: Inner gear ring, 62: Second shaft shoulder, 71: Plane thrust needle roller bearing; 72: First bearing, 73: Second bearing, 74: Third bearing, 81: Fixed seat, 82: First fixing plate, 83: Second fixing plate, 84: Hexagon socket countersunk screw, 851: Screw, 852: Nut, 9: Wave spring, 10: Fixed sleeve. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Embodiment 1 like Figures 1 to 4 As shown, this embodiment discloses a harmonic gear transmission mechanism, including: a motor output shaft 1, a motor fixing assembly, a motor stator 2, a motor rotor 3, a wave generator 4, a flexible bearing 5 and a flexible wheel 6.

[0034] The motor output shaft 1 is made of a rigid metal material, such as 40Cr rigid metal material, which is equivalent to a rigid wheel of a harmonic gear. Different from the harmonic gear structure on the market, the motor output shaft 1 of the present invention is provided with an outer gear ring 21 on the outer wall, which is directly designed as a part of the motor output shaft as a power output element of the entire atypical harmonic gear structure, and can directly drive the valve to open and close. A first shaft shoulder 12 is provided at the end of the motor output shaft 1, and a plane thrust needle roller bearing 71 is installed on the inner end of the first shaft shoulder to facilitate smoother rotation of the motor output shaft.

[0035] The motor fixing assembly includes a fixing seat 81, a first fixing plate 82, a second fixing plate 83, a first fastener and a second fastener. The fixing seat 81 is installed on the inner side of the plane thrust needle roller bearing 7. The first fixing plate 82 and the second fixing plate 83 are respectively located on both sides of the motor output shaft 1. The first fixing plate 82 is fixed to the fixing seat 81 by a first fastener. In the present embodiment, the first fastener can be a plurality of hexagon socket countersunk screws 84, and the first fixing plate 82 is provided with corresponding screw holes, and the hexagon socket countersunk screws 84 are locked into the screw holes, thereby locking the first fixing plate 82 and the fixing seat 81. Of course, in other embodiments, other first fasteners can also be used for fixing. The first fixing plate 82 and the second fixing plate 83 are connected and fixed by a second fastener. The second fastener can be a plurality of screws 851 and nuts 852, and the screws 851 pass through the second fixing plate 83 and are locked on the first fixing plate 82, and the nuts 852 are locked on the end side of the second fixing plate 83. Of course, in other embodiments, the first fixing plate 82 and the second fixing plate 83 may also be connected by other second fasteners.

[0036] A first bearing 72 and a second bearing 73 are mounted on inner sides of the first fixing plate and the second fixing plate, respectively.

[0037] The motor stator 2 is installed between the first fixing plate 82 and the second fixing plate 83. The motor rotor 3 is arranged on the inner ring of the motor stator 2.

[0038] The wave generator 4 is installed on the inner ring of the motor rotor 3 and fixedly formed into one body with the motor rotor 3. There are many ways to fix the wave generator 4 and the motor rotor 3 into one body. For example, in this embodiment, the wave generator 4 is tightly matched with the motor rotor 3 by interference fit. In other embodiments, the wave generator 4 can also be fixedly formed into one body with the motor rotor 3 by key connection or bonding. After the motor rotor 3 and the wave generator 4 are formed into one body, they are positioned and installed by the first bearing 72 and the second bearing 73 respectively, and the wave spring 9 is used to position the motor rotor axially.

[0039] like Fig. 9 As shown, the wave generator 4 is provided with an elliptical inner cavity. The ratio of the major axis e to the minor axis f of the elliptical inner cavity is set to be 1.05-1.08:1. As in this embodiment, the major axis e of the ellipse is 68 mm, the minor axis f is 64.4 mm, and the cavity is used to install the flexible bearing 5.

[0040] like Figure 5-7As shown, the flexible bearing 5 includes a flexible cage 51 and a plurality of cylindrical bearing rollers 52. The flexible cage 51 is an annular thin-walled structure, and a mounting groove 511 along the axial direction is provided on the wall surface of the flexible cage 51. The bearing rollers 52 are embedded in the mounting groove 511 and can rotate axially in the mounting groove 511. The axial direction 52 of the bearing rollers is parallel to the axial direction of the flexible cage 51. The flexible cage 51 is made of PEEK material or PA66 material. PEEK is a polymer elastic material with physical and chemical properties such as high temperature resistance and chemical corrosion resistance.

[0041] Combination Figure 7 , 8 As shown, the cross section of the mounting groove 511 is two symmetrically arranged arcs L, and the central angle of each arc L is 80°≤a≤120°. Figure 8 , two arc shapes of the mounting groove are illustrated, where L3 and L4 are one embodiment, in which case L3 and L4 are symmetrically arranged relative to the central axis C, and the angle of the central angle corresponding to each is a1=80°. L1 and L2 are another embodiment, in which case L1 and L2 are symmetrically arranged relative to the central axis C, and the angle of the central angle corresponding to each is a2=120°. The mounting groove 511 is arranged in two arc shapes, such as Figure 7 As shown, the bearing roller 52 is then embedded so that the outer cylindrical surface of the bearing roller 52 protrudes from the flexible retaining frame 51 at the inner circumference and the outer circumference, thereby achieving the requirement of double-layer rolling connection of the inner circumference and the outer circumference.

[0042] In particular, a plurality of bearing rollers 52 are embedded in the mounting groove 511 of the flexible bearing 5 of the present invention, and the plurality of bearing rollers 52 are stacked in the axial direction. Figure 5 , Figure 6 In each mounting groove 511 in the figure, two bearing rollers 52 are embedded in the axial stack, that is, a two-layer bearing roller 52 structure is formed. Each bearing roller 52 is set with a diameter of 5mm and a height of 12mm. Since there is a connection gap between the two layers of bearing rollers 52, it is more conducive to storing lubricating oil, which effectively improves the lubrication conditions of the bearing. The flexible bearing 5 of the present invention omits the inner ring and outer ring structure of the conventional bearing, and refines the bearing structure to make it smaller, which is conducive to the design of a small space structure.

[0043] An inner gear ring 61 is provided on the inner wall of the flexible wheel 6, and the inner gear ring 61 meshes with the outer gear ring 11. Figure 2 , 3 As shown, the outer gear ring 11 is only located at a position corresponding to the end of the motor output shaft 1, and the inner gear ring 61 is located at a position corresponding to the right end of the flexible wheel 6. The left end of the flexible wheel 6 is mounted on the motor output shaft 1 through the third bearing 74. Fig.12 As shown, the end of the flexible wheel 6 is provided with a second shoulder 62. Fig.11 As shown, in order to facilitate the installation of the flexible bearing, a fixed sleeve 10 is provided, and the fixed sleeve 10 and the flexible bearing 5 are coaxially installed in the wave generator 4, and the first axial end (D1 end) of the fixed sleeve 10 abuts against the flexible bearing 5. Fig.12 In the embodiment, the flexible wheel 6 is installed into the inner ring of the flexible bearing 5 and the inner ring of the fixed sleeve 10, and the second shaft shoulder 62 of the flexible wheel 6 is tightly pressed against the second axial end (D2 end) of the fixed sleeve 10. The end of the flexible wheel 6 is positioned and installed on the motor output shaft 1 through the third bearing 74.

[0044] The flexible spline 6 is made of elastic metal material, carbon fiber reinforced epoxy resin-based composite material or glass fiber reinforced epoxy resin-based composite material. In this embodiment, the flexible spline 6 is made of 40CrMoNiA high-toughness material.

[0045] The installation process of the present invention is as follows: (1) Install the planar thrust needle roller bearing 71 and the fixing seat 81.

[0046] (2) The first fixing plate 82 is fixed to the fixing seat 81 by means of six hexagon socket countersunk screws 84. The motor stator 2 is installed between the first fixing plate 82 and the second fixing plate 83 and fixed by means of six screws and six nuts.

[0047] (3) Combination Fig.10 The motor rotor 3 is tightly matched with the wave generator 4 by interference fit to form a whole, and then positioned and installed by the first bearing 72 and the second bearing 73 respectively, and the motor rotor 3 is axially positioned by the wave spring 9.

[0048] (4) Combination Fig.11 The flexible bearing 5 is directly installed in the elliptical inner cavity of the wave generator 4 and is axially fixed by a fixed sleeve 10.

[0049] (5) Combination Fig.12 The flexible wheel 6 is directly installed in the inner ring of the flexible bearing 5, and a third bearing 74 is arranged between the flexible wheel 6 and the motor output shaft 1 to facilitate the circular motion of the flexible wheel 6.

[0050] Combination Fig.13 , Fig.14As shown, the difference in the number of teeth of the inner gear ring 61 and the outer gear ring 11 is 2 (for example, in this embodiment, the number of teeth of the inner gear ring is 64, and the number of teeth of the outer gear ring is 62), and the structural speed ratio is 1:30. When the wave generator 4 rotates, the inner gear ring 61 of the flexible wheel 6 in the corresponding long axis direction just completely engages with the outer gear ring 11 of the motor output shaft 1; in the short axis direction, the inner gear ring 61 is completely disengaged from the outer gear ring 11. When the wave generator 4 rotates, the radial displacement of any point on the inner gear ring 61 of the flexible wheel 6 will change in a manner similar to a sine wave. Through this structure, the flexible wheel 6 interacts with the motor output shaft 1 to achieve the purpose of transmitting motion. After power is turned on, the motor starts to work, and the motor rotor 3 starts to make circular motion. Since the wave generator 4 and the motor rotor 3 form an integrated structure and follow the circular motion, the elliptical shape of the inner cavity of the wave generator 4 will regularly force the inner gear ring 61 on the flexible wheel 6 and the outer gear ring 11 on the motor output shaft 1 to perform periodic meshing motion, thereby achieving torque enhancement and speed reduction effects.

[0051] Embodiment 2 This embodiment discloses an electric actuator, characterized in that it includes the harmonic gear transmission mechanism of embodiment 1. The motor output shaft 1, as the power output element of the entire electric actuator, can be directly connected to the valve stem of the valve through a connection method, and finally drive the valve to open and close, thereby achieving the ultimate purpose of the actuator.

[0052] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A harmonic gear transmission mechanism, characterized in that: include: The motor output shaft is made of a rigid metal material, and an outer gear ring is arranged on the outer wall of the motor output shaft; The motor fixing assembly has a first bearing and a second bearing mounted on both inner ends thereof; The motor stator is mounted on the motor fixing assembly; The motor rotor is arranged on the inner ring of the motor stator; A wave generator is installed on the inner ring of the motor rotor and fixedly integrated with the motor rotor, and two ends are rotatably installed on the motor output shaft through the first bearing and the second bearing respectively; the wave generator is provided with an elliptical inner cavity; A flexible bearing is installed in the elliptical inner cavity of the wave generator; The flexible wheel is installed in the inner ring of the flexible bearing and is installed on the output shaft of the motor through the third bearing. The inner wall of the flexible wheel is provided with an inner gear ring, and the inner gear ring is meshed with the outer gear ring.

2. The harmonic gear transmission mechanism according to claim 1, characterized in that: The flexible bearing includes a flexible retaining frame and a plurality of cylindrical bearing rollers. The flexible retaining frame is an annular thin-walled structure. A mounting groove along the axial direction is arranged on the wall surface of the flexible retaining frame. The bearing roller is embedded in the mounting groove and can rotate axially in the mounting groove. The axial direction of the bearing roller is parallel to the axial direction of the flexible retaining frame.

3. The harmonic gear transmission mechanism according to claim 2, characterized in that: The flexible retaining frame is made of PEEK material or PA66 material; a plurality of bearing rollers are arranged in each of the mounting grooves, and the plurality of bearing rollers are stacked along the axial direction.

4. The harmonic gear transmission mechanism according to claim 2, characterized in that: The cross section of the installation groove is two symmetrically arranged arcs, and the central angle corresponding to each arc is 90°≤a≤120°.

5. The harmonic gear transmission mechanism according to claim 1, characterized in that: The end of the motor output shaft is provided with a first shaft shoulder, and a plane thrust needle roller bearing is installed at the inner end of the first shaft shoulder; the motor fixing assembly includes a fixing seat, a first fixing plate, a second fixing plate, a first fastener and a second fastener; The fixing seat is installed on the inner side of the planar thrust needle roller bearing, and the first fixing plate is fixed on the fixing seat via a first fastener; the first fixing plate and the second fixing plate are connected and fixed via a second fastener.

6. The harmonic gear transmission mechanism according to claim 5, characterized in that: It also includes a fixed sleeve, the end of the flexible wheel is provided with a second shoulder, the fixed sleeve is coaxially installed in the wave generator with the flexible bearing, and the first axial end of the fixed sleeve abuts against the flexible bearing; the flexible wheel is installed in the inner ring of the flexible bearing and the inner ring of the fixed sleeve, and the second shoulder of the flexible wheel is tightly abutted against the second axial end of the fixed sleeve, and the end of the flexible wheel is positioned and installed on the output shaft of the motor through a third bearing.

7. The harmonic gear transmission mechanism according to claim 1, characterized in that: The wave generator is tightly matched with the motor rotor by interference fit to form a whole; the two ends of the motor rotor are respectively positioned and installed by a first bearing and a second bearing, and a wave spring is used to axially position the motor rotor.

8. The harmonic gear transmission mechanism according to claim 1, characterized in that: The flexible wheel is made of elastic metal material, carbon fiber reinforced epoxy resin-based composite material or glass fiber reinforced epoxy resin-based composite material.

9. The harmonic gear transmission mechanism according to claim 1, characterized in that: The ratio of the major axis to the minor axis of the elliptical inner cavity of the wave generator is 1.05-1.08:1; the difference in the number of teeth meshing between the inner gear ring and the outer gear ring is 2, and the structural speed ratio is 1:

30.

10. An electric actuator, characterized in that: It comprises the harmonic gear transmission mechanism as claimed in any one of claims 1 to 9.

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