A discrete tooth harmonic reducer with a double-arc tooth profile

Abstract

The present invention discloses a discrete tooth harmonic reducer with a double circular arc tooth profile, which includes an eccentric shaft, a composite movable tooth carrier, an internal gear, a left main bearing outer ring part, and a right main bearing outer ring part. The eccentric shaft is located at the middle position of the internal gear. The eccentric bearing inner ring provided on the outer circle of the eccentric shaft is sleeved on the eccentric shaft. The composite movable tooth carrier located on one side of the internal gear includes a main bearing inner ring and a movable tooth carrier. The movable tooth carrier is located on one side wall surface of the main bearing. A number of radially or obliquely arranged movable tooth grooves are provided on the outer side of the movable tooth carrier. Movable teeth are provided in the movable tooth grooves, and extension guides are reserved on both sides of the movable tooth grooves. The movable teeth with double-sided extension guides slide reciprocally on the movable tooth grooves. The main bearing inner ring and the main bearing outer ring are connected by rolling elements provided therebetween. The left and right parts of the main bearing outer ring and the internal gear are connected to each other by connection screws provided therebetween, which can significantly reduce the contact stress and reduce the influence of the error of the movable tooth grooves on the transmission accuracy, and can effectively improve the transmission stiffness and transmission accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical transmission or speed reducers, and particularly to a discrete tooth harmonic speed reducer with a double circular arc tooth profile. Background Art

[0002] The harmonic speed reducer has the advantage of a compact structure and is applied in precision machinery. It is also an important core component of various robots. The moving tooth speed reducer can be regarded as a kind of discrete tooth harmonic speed reducer, that is, the flexible gear of the harmonic speed reducer is decomposed into a group of moving teeth moving in a radial direction or an inclined direction at a certain angle to the radial direction and a moving tooth carrier with a group of radial or inclined channels at a certain angle to the radial direction. The eccentric wheel replaces the flexible bearing of the harmonic speed reducer, and both have an internal gear ring. From the perspective of the number of separated parts, the moving tooth speed reducer has a large number of parts, many machining surfaces, generally a small transmission ratio, and complex related machining processes, so it has not been widely applied.

[0003] However, the existing harmonic speed reducer needs a flexible gear to achieve the radial movement of the teeth, but its output part does not allow deformation. Therefore, the teeth on the flexible gear will undergo complex spatial deformation during operation, and it is difficult for the tooth profile machining to meet the needs of the actual spatial meshing movement. Therefore, its tooth profile is an approximate tooth profile, and it is difficult to achieve full-width line contact in the contact situation, so the rigidity is poor. At the same time, in order to achieve large deformation, the teeth of the flexible gear need to be designed very small, so the contact area of the teeth is small and the stiffness is low. Flexibility is an important reason for the reduction of teeth, small contact surface, and low transmission stiffness. The existence of the flexible gear is also an important reason for adopting a two-tooth difference. However, both the flexible gear and the flexible bearing have high requirements for materials, which is not conducive to the control of the cost of the speed reducer. The internal gear has a small tooth profile and a complex tooth profile structure, making it difficult to adopt the grinding machining method and difficult to obtain high machining accuracy, which is not conducive to further improving the transmission accuracy of systems such as robots. Summary of the Invention

[0004] Aiming at the deficiencies in the prior art, the present invention provides a discrete tooth harmonic speed reducer with a double circular arc wedge tooth profile having higher stiffness and transmission accuracy.

[0005] To achieve the above object, the present invention provides the following technical solution: A discrete tooth harmonic reducer with a double arc tooth profile, comprising an eccentric shaft, a composite movable tooth carrier, an internal gear, a left main bearing outer ring member, and a right main bearing outer ring member. The eccentric shaft is located at the middle position of the internal gear. An eccentric bearing is provided on the outer circle of the eccentric shaft, and the inner ring of the eccentric bearing is sleeved on the eccentric shaft. The composite movable tooth carrier is located on one side of the internal gear. The composite movable tooth carrier includes a main bearing inner ring and a movable tooth carrier. The movable tooth carrier is located on one side wall surface of the main bearing. A number of radially or obliquely arranged movable tooth grooves are provided on the outer side of the movable tooth carrier. Movable teeth are provided in the movable tooth grooves. The structure of the movable tooth carrier serves as an extended structure of the main bearing inner ring, and extension guides for the movable teeth are reserved on both sides of the movable tooth grooves to ensure that the movable teeth and the movable tooth grooves always maintain single-sided contact. The movable teeth with bilateral extension guides slide reciprocally on the movable tooth grooves. The left main bearing outer ring member and the right main bearing outer ring member are juxtaposed on the outer side of the main bearing inner ring and are connected by rolling elements provided between the main bearing inner ring and the main bearing outer ring. A positioning pin base body is respectively preset between the right main bearing outer ring member and the internal gear, and the right main bearing outer ring member and the internal gear are connected by a taper pin provided. The left main bearing outer ring member, the right main bearing outer ring member, and the internal gear are mutually connected by connecting screws provided.

[0006] Preferably, the tooth profile structures at the tops of the internal gear and the movable teeth include double arcs or straight lines, and the top ends of the double arcs are connected to straight lines or arcs.

[0007] Preferably, the structure of the internal gear includes a combination of four sector gears.

[0008] Preferably, the rolling element structure adopts a cross-shaped rolling element or a spherical rolling element.

[0009] Preferably, a counterweight block is provided at one end of the eccentric shaft to balance the centrifugal force of the eccentric bearing. A counterweight screw is provided on the surface of the counterweight block, and the counterweight block is connected to the eccentric shaft through the counterweight screw.

[0010] Preferably, a return spring is provided on the outer ring of the eccentric bearing. The movable teeth are pressed against the outer ring of the eccentric bearing through the return spring, and the movable teeth are retracted to a smaller radius when the pressure angle is small to maintain the continuity of movement.

[0011] Preferably, a movable tooth carrier end cover is provided on the outer side of the movable tooth carrier, and the movable tooth carrier end cover and the movable tooth carrier are connected by end cover screws provided.

[0012] Preferably, the structure of the movable teeth includes single-side extended movable teeth, double-side extended movable teeth, and non-extended movable teeth, and the lower surface of the movable teeth is set as a concave or convex arc curve or a straight line, and the top curve of the movable teeth is calculated as a corresponding tooth profile curve according to the tooth profile of the internal gear and the tooth profile at the bottom of the movable teeth.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] 1. In the present invention, the movable teeth have an extended guide rail surface, which can make the movable teeth contact with one side of the movable tooth groove of the movable tooth carrier instead of the traditional two sides when the output direction is fixed, which can significantly reduce the contact stress and reduce the influence of the movable tooth groove error on the transmission accuracy, and can effectively improve the bearing capacity and transmission accuracy.

[0015] 2. In the present invention, the tooth profile of the internal gear is composed of double arcs or straight lines, and the dressing of the grinding wheel used for grinding can adopt an inexpensive diamond pen arc dresser or a straight-line dresser, which can reduce the difficulty of dressing the grinding wheel, reduce the dressing cost, and improve the dressing accuracy.

[0016] 3. In the present invention, the double-arc tooth profile can be used to control the pressure angle of the internal gear, and by reducing the pressure angle, the transmission capacity or torque of the internal gear can be significantly improved.

[0017] 4. In the present invention, the eccentric bearing structure can replace the flexible bearing of the traditional harmonic reducer, and the manufacturing cost is lower.

[0018] 5. In the present invention, compared with the harmonic drive, the present invention has no flexible gear structure, has lower requirements for materials, and can reduce the manufacturing cost.

[0019] 6. In the present invention, compared with the harmonic drive, the reducer can achieve theoretically correct transmission, without theoretical transmission error, and is expected to obtain higher transmission accuracy.

[0020] 7. In the present invention, compared with the harmonic drive, the movable tooth carrier has good rigidity and can obtain higher transmission stiffness. Description of the Drawings

[0021] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and are used to explain the present invention together with the embodiments of the present invention, and do not constitute a limitation to the present invention.

[0022] In the drawings:

[0023] Figure 1 is a cross-sectional view of the movable tooth reducer with an extended guide rail on one side of the movable tooth groove of the present invention;

[0024] Figure 2 is a cross-sectional view of the movable tooth reducer with extended guide rails on both sides of the movable tooth groove of the present invention;

[0025] Figure 3 is a cross-sectional view of the harmonic reducer with an internal gear having a double-arc tooth profile according to the present invention;

[0026] Figure 4 is a cross-sectional view of the harmonic reducer with an internal gear having a double-straight tooth profile according to the present invention;

[0027] Figure 5 is a structural diagram of the double-arc internal gear tooth profile according to the present invention;

[0028] Figure 6 is a structural diagram of the double-straight internal gear tooth profile according to the present invention;

[0029] Figure 7 are three structural diagrams of the movable teeth according to the present invention;

[0030] Reference numerals in the figure: 01, left part of the outer ring of the main bearing; 02, right part of the outer ring of the main bearing; 03, internal gear; 04, rolling element; 05, composite movable tooth carrier; 06, movable tooth; 07, eccentric bearing; 08, eccentric shaft; 09, taper pin; 10, connecting screw; 11, base body of the positioning pin; 12, return spring; 13, end cover screw; 14, end cover of the movable tooth carrier; 15, counterweight block; 16, counterweight screw; 17, extension guide rail; 18, first support part; 19, second support part. Detailed implementation manners

[0031] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0032] Embodiment: A discrete tooth harmonic reducer with a double circular arc tooth profile, comprising an eccentric shaft 08, a composite movable tooth carrier 05, an internal gear 03, a left main bearing outer ring 01 and a right main bearing outer ring 02. The tooth profile structure at the top of the internal gear 03 and the movable teeth 06 includes a double circular arc or a straight line, and the top of the double circular arc is connected to the straight line or the circular arc. The structure of the internal gear 03 includes a combination of four sector gears. The eccentric shaft 08 is located in the middle of the internal gear 03. An eccentric bearing 07 is provided on the outer circle of the eccentric shaft 08. The inner ring of the eccentric bearing 07 is sleeved on the eccentric shaft 08, and its structure can be all rolling bearings that can eliminate radial clearance, such as deep groove ball bearings and cylindrical roller bearings. A sliding bearing structure can also be used at low speeds. One end of the eccentric shaft 08 is provided with a counterweight 15 for balancing the centrifugal force of the eccentric bearing 07. A counterweight screw 16 is provided on the surface of the counterweight 15, and the counterweight 15 is connected to the eccentric shaft 08 through the counterweight screw 16. The composite movable tooth carrier 05 is located on one side of the internal gear 03. A return spring 12 is provided on the outer circle of the eccentric bearing 07. Through the return spring 12, the movable teeth 06 are pressed against the outer circle of the eccentric bearing 07, and the movable teeth 06 are retracted to a smaller radius when the pressure angle is small to maintain the continuity of movement. The composite movable tooth carrier 05 includes a main bearing inner ring and a movable tooth carrier. The movable tooth carrier is located on one side wall of the main bearing. A number of radially or obliquely arranged movable tooth grooves are provided on the outer side of the movable tooth carrier. Movable teeth 06 are provided in the movable tooth grooves. The structure of the movable tooth carrier serves as an extended structure of the main bearing inner ring, and extension guides 17 of the movable teeth 06 are reserved on both sides of the movable tooth grooves. The movable teeth 06 with bilateral extension guides 17 slide reciprocally on the movable tooth grooves. The left main bearing outer ring 01 and the right main bearing outer ring 02 are juxtaposed on the outer side of the main bearing inner ring and are connected by rolling elements 04 provided between the left main bearing inner ring 01 and the right main bearing outer ring 02. The structure of the rolling elements 04 includes a cross-shaped rolling element 04 or a spherical rolling element 04, such as a spherical rolling element 04. The movable tooth grooves matched with the spherical rolling elements 04 need to adopt a double circular arc structure to ensure that they can replace two separate angular contact bearings, and the left and right main bearing outer rings can adopt an integral structure with radially mounted rollers. A positioning pin base 11 is respectively preset between the right main bearing outer ring 02 and the internal gear 03, generally a cylinder, and can also have other cross-sectional shapes, such as a square. Its material can be 45 steel or other materials that are easy to ream holes and do not require quenching, so as to machine pin holes for positioning in both of them. The right main bearing outer ring 02 and the internal gear 03 are connected by a taper pin 09 provided. The left main bearing outer ring 01, the right main bearing outer ring 02 and the internal gear 03 are connected to each other by connection screws 10 provided. A movable tooth carrier end cover 14 is provided on the outer side of the movable tooth 06 frame.The movable tooth frame end cover 14 is connected to the movable tooth frame by the end cover screw 13, which ensures that the movable tooth 06 can move stably in the movable tooth groove. If necessary, the movable tooth frame end cover 14 can also form an integral structure with the composite movable tooth frame 05, which can reduce the number of parts and improve the rigidity of the parts. However, the processing of the square hole can only be carried out by using a reciprocating grinding tool. The structure of the movable tooth 06 includes a single-side extended movable tooth 06, a double-side extended movable tooth 06 and a non-extended movable tooth 06, and the lower surface of the movable tooth 06 is set to a concave or convex arc curve or a straight line. The top curve of the movable tooth 06 is calculated according to the tooth shape of the internal gear 03 and the bottom tooth shape of the movable tooth 06.

[0033] Figure 1 The extended guide rail 17 of the movable tooth groove of the middle movable tooth rack is mainly used to ensure that the movable tooth 06 is still in a good supporting state when it extends outward to the maximum radial position, ensuring that the movable tooth 06 always maintains single-sided contact with the movable tooth groove, instead of the traditional movable tooth reducer, where the movable tooth 06 always contacts the corner points on both sides of the movable tooth groove, which can significantly reduce the contact stress and meshing accuracy, and avoid the transmission accuracy of the movable tooth 06 being affected by the manufacturing errors on both sides of the movable tooth groove. Because the left side of the movable tooth 06 cooperates with the extended plane, the top tooth shape can be partially not manufactured, so it can maintain full contact with one side of the movable tooth groove;

[0034] Figure 2 The extended planes are retained on both sides of the movable tooth groove of the movable tooth frame, so that the left and right sides of the movable tooth 06 have the extended first support portion 18 and the second support portion 19. However, the inner gear 03 needs to be made into a 3-4 petal structure so that the inner gear 03 with a smaller inner diameter can be installed in the groove of the composite movable tooth frame 05 with a larger diameter. Figure 3 is a cross-sectional view of a discrete tooth harmonic reducer having a double arc internal gear tooth profile; Figure 4 The invention is an embodiment in which the arc radius of the double arc tooth shape reaches infinity.

[0035] Figure 5 and Figure 6 They are Figure 3 and Figure 4 The tooth profiles of the internal gear 03 of two structures. Figure 5The tooth profile of the internal gear 03 consists mainly of curves AB and CD. In principle, these curves can be of any shape, but in this invention, arc curves that are symmetric at both ends are adopted, and these two arcs are not concentric. Therefore, the pressure angle during transmission can be significantly reduced, and the load-bearing capacity of the reducer can be improved. At the same time, the arc structure is also adopted to enable the grinding wheel to be dressed by a diamond pen dresser when grinding the internal gear. The diamond pen rotates around a certain axis to form an arc dressing. In this way, using the dresser at a single point to dress the grinding wheel can not only improve the dressing accuracy of the grinding wheel but also eliminate the diamond roller to reduce the manufacturing cost. In traditional oscillating tooth reducers, such as the conjugate circular-arc oscillating tooth drive, a whole arc, i.e., a part of a cylinder, is mostly used as the tooth profile of the internal gear 03 or the tooth profile at the top of the oscillating tooth 06. Generally, this is not conducive to reducing the transmission pressure angle and improving the transmission capacity. Figure 6 A straight tooth profile is adopted. It can be considered that the straight lines EF and GH are the extreme cases when the radii of the arcs AB and CD tend to infinity. This kind of tooth profile is easy to obtain higher manufacturing accuracy;

[0036] Figure 7 a, b, and c are respectively three structural forms of the oscillating tooth 06, namely, the single-sided extended oscillating tooth 06, the double-sided extended oscillating tooth 06, and the non-extended oscillating tooth 06. Their sectional views are respectively Figure 7 d and e. The lower surface of the oscillating tooth 06 is a concave or convex arc curve, including a straight line, which reduces the processing cost. The tooth top curve of the oscillating tooth 06 is a tooth profile curve calculated based on the tooth profile of the internal gear 03, the tooth profile at the bottom of the oscillating tooth 06, and the tooth profile of the eccentric bearing 07 or the excitator. It can be processed by a grinding machine, and its manufacturing cost can be controlled to a very low level; Figure 7 In, the small hole located at the lower end of the oscillating tooth 06 is used to pass through the return spring 12.

[0037] The working principle is as follows:

[0038] 1) Change the flexible bearing of the harmonic reducer to a common bearing installed on the eccentric shaft 08, which can reduce the manufacturing cost of the flexible bearing, improve the load-bearing capacity of the bearing, and at the same time enable the reducer to obtain a higher reduction ratio. In order to achieve dynamic balance, a counterweight 15 is installed on the eccentric shaft 08;

[0039] 2) Design the tooth profile of the internal gear 03 as a structure composed of two spliced arcs. The tops of the two arcs can be connected by a straight line or an arc, so that the reducer can obtain a smaller pressure angle;

[0040] 3) Design the internal gear 03 as a structure composed of four sector gears. It is connected to the outer ring of the main bearing through the connecting screw 10 and the taper pin 09, so that the internal gear 03 is easy to grind and process;

[0041] 4) The oscillating gear carrier structure is used as an extension structure of the inner ring of the main bearing, and the extended guide rails 17 of the oscillating gears are reserved on both sides of the oscillating gear slots, so that the oscillating gears 06 with bilateral extended guide rails 17 can slide on the slots; since the pressure of the internal gear 03 on the oscillating gears 06 is transmitted to one surface of the oscillating gear slot instead of the usual two surfaces, when an external force acts on the outer side of the oscillating gear 06, the oscillating gear 06 will contact the two side corner points of the oscillating gear slot, so the contact stress is large and the wear is fast. In this way, the maximum compressive stress of the oscillating gear 06 on the oscillating gear slot can be reduced, thereby reducing wear;

[0042] 5) In order to enable the oscillating gear 06 to reliably return to a smaller radius, a return spring is inserted into the oscillating gear 06 to ensure that the oscillating gear 06 does not interfere with the normal operation of the rising oscillating gear 06 during the return stroke.

[0043] Among them, the oscillating gear 06 can have bilateral extended guide rails, unilateral extended guide rails, or the extended guide rails can be removed when the load is small, so that the manufacturing cost is lower.

[0044] Among them, when there is only a unilateral extended guide rail 17 on the oscillating gear slot of the oscillating gear carrier or the oscillating gear slot has double extended guide rails 17, when the oscillating gear carrier is made into a left-right split structure, the internal gear 03 can be made into a complete structure instead of a four-piece sector gear.

[0045] Among them, the return spring 12 for returning the oscillating gear 06 can be installed on both sides of the oscillating gear 06.

[0046] Finally, it should be noted that the above are only preferred examples of the present invention and are not used to limit the present invention. For example, the scheme of using 2 rows or 3 rows of eccentric wheels or the scheme of using different bearing structures, and also the scheme of designing the tooth top curve of the internal gear or the oscillating gear into a straight line or an arc. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A discrete tooth harmonic reducer with a double arc tooth profile, characterized in that: It includes an eccentric shaft, a composite movable tooth carrier, an internal gear, the left part of the outer ring of the main bearing, and the right part of the outer ring of the main bearing. The eccentric shaft is located at the middle position of the internal gear. An eccentric bearing is provided on the outer ring of the eccentric shaft, and the inner ring of the eccentric bearing is sleeved on the eccentric shaft. The composite movable tooth carrier is located on one side of the internal gear. The composite movable tooth carrier includes an inner ring of the main bearing and a movable tooth carrier. The movable tooth carrier is located on one side wall surface of the main bearing. A number of radially or obliquely arranged movable tooth grooves are provided on the outer side of the movable tooth carrier. Movable teeth are provided in the movable tooth grooves. The structure of the movable tooth carrier serves as an extended structure of the inner ring of the main bearing, and extension guides for the movable teeth are reserved on both sides of the movable tooth grooves to ensure that the movable teeth and the movable tooth grooves always maintain single-sided contact. The movable teeth with bilateral extension guides slide reciprocally on the movable tooth grooves. The left part of the outer ring of the main bearing and the right part of the outer ring of the main bearing are juxtaposed on the outer side of the inner ring of the main bearing, and are connected by rolling elements provided between the inner ring of the main bearing and the outer ring of the main bearing. Positioning pin bases are respectively preset between the right part of the outer ring of the main bearing and the internal gear, and the right part of the outer ring of the main bearing and the internal gear are connected by taper pins provided. The left part of the outer ring of the main bearing, the right part of the outer ring of the main bearing, and the internal gear are mutually connected by connecting screws provided.

2. The discrete tooth harmonic reducer with a double arc tooth profile according to claim 1, wherein: The tooth profile structures of the top of the internal gear and the movable teeth include double arcs or straight lines, and the top of the double arcs is connected to the straight line or arc.

3. A discrete tooth harmonic reducer with a double circular arc tooth profile according to claim 1, characterized in that: The structure of the internal gear includes a combination of four sector gears.

4. A discrete tooth harmonic reducer with a double arc tooth profile according to claim 1, characterized in that: The rolling element structure adopts a cross-shaped rolling element or a spherical rolling element.

5. A discrete tooth harmonic reducer with a double-arc tooth profile according to claim 1, characterized in that: One end of the eccentric shaft is provided with a counterweight block for balancing the centrifugal force of the eccentric bearing. A counterweight screw is provided on the surface of the counterweight block, and the counterweight block is connected to the eccentric shaft through the counterweight screw.

6. A discrete tooth harmonic reducer with a double arc tooth profile according to claim 1, characterized in that: A return spring is provided on the outer ring of the eccentric bearing. The movable teeth are pressed against the outer ring of the eccentric bearing through the return spring, and the movable teeth are retracted to a smaller radius when the pressure angle is small to maintain the continuity of movement.

7. A discrete tooth harmonic reducer with a double arc tooth profile according to claim 1, characterized in that: A movable tooth carrier end cover is provided on the outer side of the movable tooth carrier. The movable tooth carrier end cover and the movable tooth carrier are connected by end cover screws provided.

8. A discrete tooth harmonic reducer with a double circular arc tooth profile according to claim 1, characterized in that: The structure of the movable teeth includes single-sided extended movable teeth, double-sided extended movable teeth, and non-extended movable teeth. The lower surface of the movable teeth is set as a concave or convex arc curve or a straight line, and the top curve of the movable teeth is a corresponding tooth profile curve calculated according to the tooth profile of the internal gear and the tooth profile of the bottom of the movable teeth.

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