Hollow reducer for high precision control

Abstract

A hollow reducer for high precision control includes a pin wheel housing and two-stage reduction components disposed in the pin wheel housing. A first-stage reduction component includes a driving wheel on a servo motor, a dual gear, and a planet wheel; and a second-stage reduction component includes 2-3 eccentric shafts distributed uniformly, cycloidal gears, a pin, rigid disks, and bearings, wherein two eccentric sections of the eccentric shaft support the cycloidal gears by means of the bearings, shaft extensions on two sides of the eccentric section of the eccentric shaft are supported on the left and right rigid disks by the bearings, and the rigid disks are supported on two sides of the pin wheel housing by the bearings.

Claims

1. A hollow reducer for high precision control, comprising a pin wheel housing (1) and two-stage reduction components disposed in the pin wheel housing: a first-stage reduction component comprising a driving wheel (13) on a servo motor, a dual gear (8), and a planet wheel (12), wherein the dual gear (8) comprises a driven wheel (6) and a sun wheel (7), the driven wheel (6) is meshed with the driving wheel (13), the sun wheel (7) is meshed with the planet wheel (12), the planet wheel (12) is connected to a shaft extension end of an eccentric shaft (11) of a second-stage reduction component, the dual gear (8) is formed with a line-passing pipe (8a) which defines an inner hole of the dual gear (8), and two sides of the dual gear (8) are respectively supported on a right rigid disk (5) and a corresponding position on a robot body by a first bearing (10) and a second bearing (9); and the second-stage reduction component comprising 2-3 eccentric shafts (11) distributed uniformly, cycloidal gears, a pin (17), a left rigid disk (16), and the right rigid disk (5), wherein the cycloidal gears comprise a left cycloidal gear (3) and a right cycloidal gear (4), two eccentric sections of the eccentric shaft (11) are provided with a third bearing (15) used for supporting the cycloidal gears, shaft extensions on two sides of the eccentric section are respectively supported in peripheral holes of the left rigid disk (16) and the right rigid disk (5) by a fourth bearing (14), the left rigid disk (16) and the right rigid disk (5) are respectively supported in inner holes on two sides of the pin wheel housing (1) by a fifth bearing (2), flanges uniformly distributed on the left rigid disk (16) pass through corresponding holes on the cycloidal gears and are connected to the right rigid disk (5) by means of screws and positioning pins to form a rigid body, the cycloidal gears are subjected to equidistant-radial moving composite modification, and a radial gap and two backlashes Δc are formed between the pin (17) and a tooth socket of each cycloidal gear by the modification, wherein: the backlash between the pin (17) and the tooth socket of the each cycloidal gear is Δc=(0.7-5)λ(mm), in the formula, λ is a thermal expansion amount of the cycloidal gears in the case when the reducer works at a rated torque: λ=(d.sub.0Δ.sub.t)α.sub.t=0.00062d.sub.0 (mm), a thermal expansion coefficient of bearing steel is α.sub.t=1.379.Math.10.sup.−5 (1/° C.), do is an average diameter of the cycloidal gears, and a temperature rise is Δ.sub.t=45° C.; and the cycloidal gears are subjected to positive equidistant-positive radial moving composite modification, and a return difference formed by the positive equidistant-positive radial moving composite modification is reduced to satisfy a design requirement by means of an anti-backlash principle.

2. The hollow reducer for high precision control according to claim 1, wherein the backlash between the pin (17) and the tooth socket of each cycloidal gear is Δc=0.7λ (mm).

3. The hollow reducer for high precision control according to claim 1, wherein the third bearing (2) is a single-row radial thrust ball bearing with a seal or a thin-wall sealed four-point contact ball bearing or a thin-wall sealed crossed roller bearing.

Description

DESCRIPTION OF DRAWINGS

(1) In order to clearly illustrate the technical solution in the embodiments of the present application, the drawing to be used in description of the embodiments will be briefly introduced below. It is apparent that the drawing described below only involves one embodiment of the present application. Those of ordinary skill in the art, without making creative effort, can obtain other accompanying drawings according to these accompanying drawings.

(2) The sole FIGURE is a schematic diagram of a structural section of a preferable embodiment of a hollow reducer for high precision control in the present application.

(3) Reference signs in the accompanying drawing: 1. pin wheel housing; 3. left cycloidal gear; 4. right cycloidal gear; 6. driven wheel; 7. sun wheel; 8. dual gear; 10. first bearing; 9. second bearing; 15. third bearing; 14. fourth bearing; 2. fifth bearing; 11. eccentric shaft; 12. planet wheel; 13. driving wheel; 5. right rigid disk; 16. left rigid disk; and 17. pin.

DETAILED DESCRIPTION

(4) The technical solutions in the embodiments of the present application will be described clearly and completely below. It is apparent that, those embodiments described are only a part of the embodiments of the present application, rather than all of them. All the other embodiments obtained by those of ordinary skill in the art without making creative effort based on the embodiments in the present application shall fall into the protection scope of the present application.

(5) As shown in the sole FIGURE, the embodiment of the present application includes the following:

(6) A hollow reducer for high precision control includes a pin wheel housing 1 and two-stage reduction components disposed in the pin wheel housing. A first-stage reduction component includes a driving wheel 13 on a servo motor, a dual gear 8, and a planet wheel 12, wherein the dual gear 8 includes a driven wheel 6 and a sun wheel 7, the driven wheel 6 is meshed with the driving wheel 13, the sun wheel 7 is meshed with the planet wheel 12, the planet wheel 12 is connected to a shaft extension end of an eccentric shaft 11 of a second-stage reduction component, the dual gear 8 is formed with a line-passing pipe 8a which defines an inner hole of the dual gear 8, and two sides of the dual gear 8 are respectively supported on a right rigid disk 5 and a corresponding position on a robot body by a first bearing 10 and a second bearing 9. The second-stage reduction component includes 2-3 eccentric shafts 11 distributed uniformly, cycloidal gears, a pin 17, a left rigid disk 16, and the right rigid disk 5, wherein the cycloidal gears include a left cycloidal gear 3 and a right cycloidal gear 4, two eccentric sections of the eccentric shaft 11 are provided with a third bearing 15 used for supporting the cycloidal gear, shaft extensions on two sides of the eccentric section are respectively supported in peripheral holes of the left rigid disk 16 and the right rigid disk 5 by a fourth bearing 14, the left rigid disk 16 and the right rigid disk 5 are respectively supported in inner holes on two sides of the pin wheel housing 1 by a fifth bearing 2, flanges uniformly distributed on the left rigid disk 16 pass through corresponding holes on the cycloidal gear and are connected to the right rigid disk 5 by means of screws and positioning pins to form a rigid body, the cycloidal gear is subjected to equidistant-radial moving composite modification, and a radial gap and two backlashes Δc are formed between the pin 17 and a tooth socket of the cycloidal gear by the modification. The backlash is Δc=(0.7-5)λ (mm), wherein in the formula, a thermal expansion amount of the cycloidal gear in the case when the reducer works at a rated torque is λ=(d0Δt)αt=0.00062d0 (mm).

(7) A thermal expansion coefficient of bearing steel is α.sub.t=1.379.Math.10.sup.−5 (1/° C.), wherein d.sub.0 is an average diameter of the cycloidal gear, and a temperature rise is Δ.sub.t=45° C.

(8) The backlash Δc is correlated with factors such as machining accuracy of a spacing between pins, machining accuracy of a pin diameter, a fitting spacing between the pin and a half-embedded hole, a pitch deviation of the cycloidal gear, and a deviation generated by assembly, and is also correlated with the model of the reducer. When the backlash Δc is excessively small, a temperature rise is easy to occur; and when the backlash Δc is excessively large and a rotation speed is relatively high, vibration is easy to occur.

(9) Thermal-structural Coupling Analysis of RV Reducers, North China University of Technology (June 2016): “there is less domestic study on thermal-structural coupling of RV reducers, and thermal dissipation conditions of the grease lubrication used in the reducers are not good. During operation, various situations are closely correlated with thermal conditions. Hence, it is necessary to consider effects of the temperature on the component volume, so as to avoid an expansion jam due to the excessively high temperature. Cycloidal gears serve as a main heat source.”

(10) The backlash between the pin 17 and the tooth socket of the cycloidal gear is Δc=(0.8-3)λ (mm).

(11) The backlash between the pin 17 and the tooth socket of the cycloidal gear is Δc=(0.9-2)λ (mm).

(12) The backlash between the pin 17 and the tooth socket of the cycloidal gear is Δc=(1-1.4)λ (mm).

(13) The backlash between the pin 17 and the tooth socket of the cycloidal gear is Δc≈1.1λ (mm). Reference is made to the following table:

(14) TABLE-US-00001 RV- RV- RV- RV- RV- RV- RV- 20E 40E 80E 110E 160E 320E 450E Average 104     128     164     184     204     229     310     diameter d0 of the cycloidal gear (Thermal 0.077 0.096 0.122 0.138 0.152 0.176 0.232 expansion + compensation amount) λ Backlash 0.083 0.101 0.133 0.152 0.159 0.186 0.248 theoretical value Δc Δc ≈ 1.1λ 1.08  1.05  1.09  1.1  1.05  1.06  1.07 

(15) It should be noted that when the backlash Δc is excessively small, thermal expansion between the cycloidal gear and the pin 17 during loaded operation leads to noise increase, wear, vibration, and decrease of the service life.

(16) The cycloidal gear is subjected to positive equidistant-positive radial moving composite modification. An acting force between the gear tooth and the pin in the positive equidistant-positive radial moving composite modification is 49% that in negative equidistant-negative radial moving composite modification; and a bearing force in the positive equidistant-positive radial moving composite modification is 1.71 times that in the negative equidistant-negative radial moving composite modification. A return difference of the positive equidistant-positive radial moving composite modification is reduced to satisfy a design requirement by means of an anti-backlash principle.

(17) In equidistant modification, an increase in the wheel grinding radius indicates a positive equidistance; and on the contrary, a decrease in the wheel grinding radius indicates a negative equidistance.

(18) In radial moving modification, a grinding wheel departing from the center of a working table indicates positive radial moving; and on the contrary, the grinding wheel moving towards the center of the working table indicates negative radial moving.

(19) The third bearing 2 is a single-row radial thrust ball bearing with a seal or a thin-wall sealed four-point contact ball bearing that can bear a radial load, a two-way thrust load, and a capsizing moment, in which case a main machine structure can be simplified and the backlash can be adjusted very easily. The third bearing may also be a thin-wall sealed crossed roller bearing with a load capacity 5-15 times a rated load of a ball bearing due to line contact between a roller bearing and a roller path thereof, in which case the reliability is high and the service life is long. By application of a pre-load to the crossed roller bearing, the rigidity and rotation accuracy can be increased effectively.

(20) The bearing with a seal is adopted to increase the service life of the bearing, as proved in the following:

(21) (1) “Poor lubrication is a main cause leading to early-stage damage of bearings” (Liu Zejiu, Application Manual of Rolling Bearings, page 891).

(22) (2) “Early-stage failures of bearings are usually not due to the fatigue damage caused by materials, but are due to pressing marks generated on the rolling contact surface and resulting from gradual deterioration of the lubricating grease after contaminants enter the bearings.” (Sealing Technology of Sealed Deep Groove Ball Bearings, Bearings, May 2009).

(23) (3) “In the case of a compact structure, it is better to use a radial ball bearing provided with seals on two faces. Lubricating grease sufficient for use in the whole service life is loaded into the radial ball bearing provided with seal rings on two faces.” (Eiseman, Design and Application Manual of Rolling Bearings, page 221).

(24) The hollow reducer for high precision control provided by the present application, compared with the prior art, has the following advantages:

(25) (1) The backlash Δc generated by the equidistant-radial moving composite modification in the present application is closely correlated with the thermal expansion amount λ of the cycloidal gear, thus achieving good dynamic characteristics, i.e., no overheating during operation at a rated load.

(26) (2) A domestic machine tool of the present application has conventional manufacturing accuracy, a simple process, and a low cost, so that suppression from the Japanese company by lowering down the price does not pose a threat.

(27) (3) External dimensions of the present application are the same as those of the RV reducer of Nabtesco, Japan, so the reducer of the present application can replace the RV reducer.

(28) The above descriptions are only the embodiments of the present application and do not intend to limit the patent scope of the present application. Equivalent structure or equivalent process conversions made based on the descriptions of the present application or those directly or indirectly applied in other related technical fields are similarly involved in the patent protection scope of the present application.