1. A C-tooth type harmonic reducer comprises a steel wheel (1), a flexible wheel (2) and a cam (4);

a flexible bearing (3) is arranged outside the cam (4) to form a wave generator, and the inner tooth profile of the steel wheel (1) is matched with the outer tooth profile of the flexible wheel (2); the method is characterized in that: the steel wheel (1), the flexible wheel (2) and the cam (4) are all made of engineering materials through injection molding.

2. The harmonic reducer of the C-tooth type according to claim 1, characterized in that: the flexible gear (2) is a cylindrical surrounding structure consisting of a bottom cover (21) and a vertical wall (22) vertically extending from the circumferential direction of the bottom cover; a circle of flexible bearing limiting step (26) is arranged on the inner wall of the vertical wall (22) and is lower than the top edge of the vertical wall.

3. The harmonic reducer of the C-tooth type according to claim 1, characterized in that: deformation ribs (23) distributed in the circumferential direction are arranged in the area, close to the vertical wall (22), of the bottom cover (21); in the enclosing range of the deformation ribs (23), a central positioning hole (24) and a fixing hole (25) at the periphery of the positioning hole are arranged on the bottom cover (21).

4. The harmonic reducer of the C-tooth type according to claim 1, characterized in that: the steel wheel (1) is a cylindrical circumferential surrounding flexible wheel (2), and a tooth profile (27) meshed with the tooth profile of the inner wall of the steel wheel (1) is circumferentially arranged on the outer wall of the vertical wall (22).

5. The harmonic reducer of the C-tooth type according to claim 1, characterized in that: the cam (4) is in a step circular truncated cone shape, the large end of the step circular truncated cone shape is positioned in the flexible gear (2), and the small end of the step circular truncated cone shape extends out of the flexible gear (2); the outer edge of the large end of the cam (4) is an elliptical cam, and the elliptical cam is tightly matched with the flexible bearing (3); the flexible bearing (3) is positioned between the elliptical cam and the inner wall of the flexible gear (2).

6. The harmonic reducer of the C-tooth type according to claim 1, characterized in that: the outer end of the flexible gear bottom cover (21) is connected with an output shaft (6), and the wall body of the output shaft (6) rigidly connects the output shaft and the flexible gear together through a connecting piece; the root of the output shaft (6) is positioned in the cylinder body of the steel wheel (1), and a support bearing (5) is arranged between the inner wall of the steel wheel (1) and the output shaft (6).

7. The harmonic reducer of the C-tooth type according to claim 1, characterized in that: the tooth profile and the tooth profile of the flexible gear and the steel gear are C-shaped; the tooth shape of the steel wheel is formed by the motion envelope of the tooth shape of the flexible wheel; the tooth height of the C tooth form is 30% higher than that of an involute tooth form or an arc tooth form ruler; the meshing proportion of the harmonic tooth profile of the C-shaped tooth profile is 50 percent higher than that of an involute tooth profile or an arc tooth profile.

8. The harmonic reducer of the C-tooth type according to claim 1, characterized in that: the steel wheel (1) and the cam (4) are formed by injection molding by taking PPS as a base material and adding more than 10% of carbon fiber.

9. The harmonic reducer of the C-tooth type according to claim 1, characterized in that: the flexible gear (2) is formed by injection molding by adding carbon fiber or glass fiber or graphite or PTFE or molybdenum disulfide into a base material by using one of POM (polyoxymethylene), PA (polyamide), PPS (polyphenylene sulfide) or PEEK (polyether-ether-ketone) materials.

10. The harmonic reducer of the C-tooth type according to claim 1, characterized in that: the weight proportion of the carbon fiber or the glass fiber is 5 to 35 percent; 2 to 10 percent of graphite or PTFE by weight; the weight ratio of the molybdenum disulfide is 5 to 15 percent.

Background

The harmonic reducer has the advantages of compact structure, small volume, light weight, large bearing capacity, small back clearance, high transmission precision and the like, and is widely applied to the fields of industrial robots, aerospace and precision machine tools. The harmonic speed reducer comprises a steel wheel, a flexible wheel and a wave generator, wherein the wave generator with elliptic deformation is arranged in the flexible wheel with elasticity, and the wave generator rotates to force the flexible wheel tooth form and the steel wheel tooth form to be periodically meshed and separated, so that the effect of staggered tooth difference speed reduction is realized.

The flexible gear of the traditional harmonic speed reducer is made of metal materials, is formed by precise machining and is subjected to multiple heat treatments and surface process treatments, so that the high elasticity and strength of the flexible gear are realized, and the flexible gear has fatigue resistance and wear resistance of a tooth surface. This causes high cost of the harmonic flexspline, difficulty in manufacturing, and difficulty in achieving light weight and applicability.

The invention content is as follows:

the invention aims to provide a C-tooth type harmonic reducer which is suitable for a plastic harmonic reducer, has the advantages of easiness in production, low cost, light weight, high consistency, compact structure and the like, and can improve the transmission torque and the fatigue life of plastic harmonic.

In order to solve the technical problems, the invention adopts the following technical scheme:

a C-tooth type harmonic reducer comprises a steel wheel (1), a flexible wheel (2) and a cam (4); a flexible bearing (3) is arranged outside the cam (4) to form a wave generator, and the inner tooth profile of the steel wheel (1) is matched with the outer tooth profile of the flexible wheel (2); the method is characterized in that: the steel wheel (1), the flexible wheel (2) and the cam (4) are all made of engineering materials through injection molding.

Furthermore, in the technical scheme, the flexible gear (2) is a cylindrical surrounding structure formed by a bottom cover (21) and a vertical wall (22) vertically extending from the circumferential direction of the bottom cover; a circle of flexible bearing limiting step (26) is arranged on the inner wall of the vertical wall (22) and is lower than the top edge of the vertical wall.

Furthermore, in the technical scheme, deformation ribs (23) distributed in the circumferential direction are arranged in the area, close to the vertical wall (22), of the bottom cover (21); in the enclosing range of the deformation ribs (23), a central positioning hole (24) and a fixing hole (25) at the periphery of the positioning hole are arranged on the bottom cover (21).

Furthermore, in the technical scheme, the steel wheel (1) is a cylindrical circumferential surrounding flexible wheel (2), and a tooth profile (27) meshed with the tooth profile of the inner wall of the steel wheel (1) is circumferentially arranged on the outer wall of the vertical wall (22).

Furthermore, in the technical scheme, the cam (4) is in a step circular truncated cone shape, the large end of the step circular truncated cone shape is positioned in the flexible gear (2), and the small end of the step circular truncated cone shape extends out of the flexible gear (2); the outer edge of the large end of the cam (4) is an elliptical cam, and the elliptical cam is tightly matched with the flexible bearing (3); the flexible bearing (3) is positioned between the elliptical cam and the inner wall of the flexible gear (2).

Furthermore, in the technical scheme, the outer end of the flexible gear bottom cover (21) is connected with the output shaft (6), and the wall body of the output shaft (6) rigidly connects the output shaft and the flexible gear together through a connecting piece; the root of the output shaft (6) is positioned in the cylinder body of the steel wheel (1), and a support bearing (5) is arranged between the inner wall of the steel wheel (1) and the output shaft (6).

Furthermore, in the above technical scheme, the tooth profile and the tooth profile of the flexible gear and the steel gear are both C-shaped; the tooth shape of the steel wheel is formed by the motion envelope of the tooth shape of the flexible wheel; the tooth height of the C tooth form is 30% higher than that of an involute tooth form or an arc tooth form ruler; the meshing proportion of the harmonic tooth profile of the C-shaped tooth profile is 50 percent higher than that of an involute tooth profile or an arc tooth profile.

Further, in the above technical solution, the tooth tip arc radius of the C-tooth profile is smaller than the tooth tip arc radius of the involute tooth profile or the circular arc tooth profile, and the tooth root arc radius is larger than the tooth root arc radius of the involute tooth profile or the circular arc tooth profile.

Furthermore, in the technical scheme, the steel wheel (1) and the cam (4) are formed by injection molding by taking PPS as a base material and adding more than 10% of carbon fibers.

Further, in the technical scheme, the flexible gear (2) is formed by adding carbon fiber or glass fiber or graphite or PTFE or molybdenum disulfide into a base material through injection molding by adopting one of POM (polyoxymethylene), PA (polyamide), PPS (polyphenylene sulfite) or PEEK (polyether-ether-ketone) materials.

Furthermore, in the technical scheme, the weight proportion of the carbon fiber or the glass fiber is 5-35 percent; 2 to 10 percent of graphite or PTFE by weight; the weight ratio of the molybdenum disulfide is 5 to 15 percent.

Furthermore, in the above technical solution, the cam adopts an elliptical profile, and the polar coordinate equation of the elliptical profile isWhere a and b are the major and minor axis lengths of the elliptical profile, p_bIs a polar shaft, and is characterized in that,is a polar angle; the polar coordinate equation of the flexible gear tooth profile isIn the formula (R)₀，θ₀) Is the polar coordinate of the center point of the circle, and R is the radius of the circle; formed by camDetermining a cam evolutePolar equation of tooth profile of flexible gearAnd cam evoluteAnd (5) approximating the fitting, and finally determining the C-shaped tooth form shape of the flexible gear tooth form by considering the addendum circle diameter, the dedendum circle diameter and the reference circle diameter of the flexible gear.

Compared with the prior art, the invention has the following beneficial effects:

the number of teeth of the traditional harmonic tooth form meshing is at most 30%, and the traditional harmonic tooth form meshing is applied to a plastic harmonic speed reducer and has the defects of small transmission torque and small rigidity. The tooth profiles of the flexible gear and the steel gear are C-shaped; the tooth shape of the steel wheel is formed by the motion envelope of the tooth shape of the flexible wheel; the C-shaped tooth profile improves the tooth height, and greatly improves the meshing number of the harmonic tooth profile to be more than 50%. The harmonic speed reducer with the C-tooth shape can obviously improve harmonic output torque and rigidity.

The flexible gear of the harmonic speed reducer is formed by injection molding of special engineering plastics and has a unique structural design, so that the functions of the traditional flexible gear are realized, and the flexible gear has the advantages of easiness in production, low cost, light weight, high consistency, compact structure and the like. In addition, due to the creative use of the C-shaped tooth, the transmission torque and the fatigue life of the harmonic waves of the plastic material can be improved.

Description of the drawings:

FIG. 1 is a schematic structural diagram of a C-tooth harmonic reducer according to the present invention.

Fig. 2 is a three-dimensional structure diagram of a flexible gear of the C-tooth harmonic reducer of the present invention.

Fig. 3 is a schematic view of the tooth engagement of the C-tooth type harmonic reducer of the present invention.

Fig. 4 is a comparison schematic diagram of the flexspline tooth profile of the C-tooth harmonic reducer of the present invention.

Fig. 5 is a schematic diagram of meshing envelope of the flexible gear tooth profile of the C-tooth harmonic reducer of the invention.

The reference numerals in fig. 1-5 are as follows: 1. a steel wheel; 2. a flexible gear; 3. a compliant bearing; 4. a cam; 5. a support bearing; 6. an output shaft; 7. traditional tooth shapes; c tooth form; 9. the tooth shape of the steel wheel; 10. the flexible gear is enveloped by the tooth form.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention is described in further detail with reference to fig. 1-5.

A harmonic reducer of a C-tooth type implemented according to the invention is shown in figures 1-2 and comprises a steel wheel 1, a flexible wheel 2 and a cam 4.

The flexible gear 2 is a cylindrical surrounding structure consisting of a bottom cover 21 and a vertical wall 22 vertically extending from the circumferential direction of the bottom cover; the bottom cover 21 is provided with deformation ribs 23 distributed circumferentially in the area close to the vertical wall 22; in the enclosing range of the deformation ribs 23, a central positioning hole 24 and a fixing hole 25 at the periphery of the positioning hole are arranged on the bottom cover 21; be less than vertical wall top edge on the 22 inner walls of vertical wall and set up the spacing step 26 of round flexible bearing, the spacing step 26 of flexible bearing can prevent flexible bearing's axial cluster, warp muscle 23 and become spiral shape evenly distributed in the flexbile gear bottom, can realize the radial elastic deformation of flexbile gear, and the axiality of flexbile gear and steel wheel is guaranteed to locating hole 24, and the moment of torsion of harmonic can be transmitted to fixed orifices 25.

The steel wheel 1 is cylindrical and circumferentially surrounds the flexible wheel 2, and a tooth profile 27 meshed with the tooth profile of the inner wall of the steel wheel 1 is circumferentially arranged on the outer wall of the vertical wall 22.

The cam 4 is in a step circular truncated cone shape, the large end of the step circular truncated cone shape is positioned in the flexible gear 2, the small end of the step circular truncated cone shape extends out of the flexible gear 2, the outer edge of the large end of the cam 4 is an elliptical cam, and the elliptical cam is tightly matched with the flexible bearing 3 to form a wave generator. The flexible bearing 3 is positioned between the elliptical cam and the inner wall of the flexible gear 2; the tooth form of the tooth form 27 of the outer wall of the flexible gear 2 is matched with the tooth form of the inner wall of the outer steel gear 1.

The outer end of the bottom cover 21 of the flexible gear 2 is connected with an output shaft 6, the root of the output shaft 6 is positioned in the cylinder body of the steel gear 1, and a support bearing 5 is arranged between the inner wall of the steel gear 1 and the output shaft 6. The output shaft 6 is a hollow shaft, connecting holes corresponding to the fixing holes 25 are arranged on the wall body of the output shaft 6 up and down, and the output shaft 6 and the bottom cover 21 of the flexible gear 2 are rigidly connected together through connecting pieces similar to bolts. The support bearing 5 takes all the forces of the output shaft 6 except the rotational torque.

As shown in figure 3, the rotation of the wave generator forces the tooth form of the flexible gear 2 to be periodically meshed with and separated from the tooth form of the steel gear 1, so as to achieve the effect of speed reduction. The tooth profile and the tooth profile of the flexible gear and the steel gear are C-shaped; the tooth shape of the steel wheel is formed by the motion envelope of the tooth shape of the flexible wheel.

The cam 4 profile of the wave generator related by the invention adopts an elliptical profile (namely, an elliptical cam at the outer edge of the large end of the cam 4), and the long axis and the short axis of the ellipse are according to the speed of the harmonic reducerThe ratio and the gear module are determined, and the polar coordinate equation of the elliptic curve isWherein a and b are the lengths of the major and minor axes of the elliptic curve, rho_bIs a polar shaft, and is characterized in that,is a polar angle.

The flexible gear tooth profile determining process comprises the following steps of firstly setting the flexible gear tooth profile to adopt an arc tooth profile, and then setting the polar coordinate equation of the tooth profile to beIn the formula (R)₀，θ₀) Is the polar coordinate of the center point of the circle, and R is the radius of the circle. By cam elliptic profile lineThe evolute S can be determined from the differential geometry, whereinThe evolute being a cam profileEnvelope of the normal family, through coordinate transformation, the polar coordinate equation of the tooth profile of the flexible gear tooth profileAnd evoluteAnd (5) approximating the fitting, and finally determining the C-shaped tooth form of the flexible gear by considering the diameter of the addendum circle, the diameter of the dedendum circle and the diameter of the reference circle of the flexible gear. And obtaining a flexible gear tooth form envelope 10 by a finite element analysis method according to the rotation rule of the wave generator and the deformation condition of the flexible gear C tooth form 8, and drawing the steel gear tooth form 9.

The specific structure of the C-shaped flexible gear is described by combining with the attached figure 4, the tooth height of the C-shaped flexible gear tooth profile 8 of the flexible gear tooth profile 27 is H1, the reference tooth height of the traditional involute tooth profile or circular arc tooth profile 7 used as a reference is H2, the tooth height H1 of the C-shaped flexible gear tooth profile 8 is 30% higher than the height H2 of a reference ruler of the involute tooth profile or circular arc tooth profile, the circular arc radius of the tooth top is reduced, the circular arc radius of the tooth root is increased, and the stress condition of the tooth profile is improved. Namely, the tooth top arc radius of the C-shaped tooth profile is smaller than the tooth top arc radius of the involute tooth profile or the circular arc tooth profile, and the tooth root arc radius is larger than the tooth root arc radius of the involute tooth profile or the circular arc tooth profile. The meshing proportion of the harmonic tooth form is 50% higher than that of the involute tooth form or the circular arc tooth form, and the rigidity and the transmission torque of an output shaft are improved. According to the rotation rule of the wave generator and the deformation condition of the C-shaped gear 8 of the flexible gear, the flexible gear tooth-shaped envelope 10 shown in figure 5 is obtained through a finite element analysis method, and the steel gear tooth shape 9 is drawn.

The steel wheel 1, the flexible wheel 2 and the cam 4 are injection molded by engineering materials.

The steel wheel 1 and the cam 4 are preferably formed by injection molding of PPS (polyphenylene sulfide) as a base material and more than 10% of carbon fibers; the flexible gear 2 is formed by injection molding by adding carbon fiber or glass fiber or graphite or PTFE or molybdenum disulfide into a base material by using one of materials such as POM, PA, PPS or PEEK and the like.

In the engineering material, the weight ratio of carbon fiber or glass fiber is 5-35% to increase the rigidity and wear resistance of parts, the weight ratio of graphite or PTFE is 2-10% to improve the self-lubricating property and wear resistance of the flexible gear, and the weight ratio of molybdenum disulfide is 5-15% to improve the wear resistance.

It should be noted that, according to the implementation requirement, each step/component described in the present application can be divided into more steps/components, and two or more steps/components or partial operations of the steps/components can be combined into new steps/components to achieve the purpose of the present invention.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.