Eccentric swing type reduction gear

Abstract

The present invention is made in view of the problems of the conventional eccentric oscillating type reduction gear, and provides an eccentric oscillating type reduction gear that can improve the rigidity. The eccentric oscillating type reduction gear (100) comprises: an internal gear (16) arranged on a housing (22); an external gear (14); an eccentric body (12a) that causes the external gear (14) to oscillate; first and second wheel frames (18, 20) arranged on one side and the other side of the axial direction of the external gear (14); connecting pins (32, 36) that connect the first and second wheel frames (18, 20); a first main bearing (26) arranged between the housing (22) and the first wheel frame (18); and a second main bearing (28) arranged between the housing and the second wheel frame, wherein the first main bearing is composed of a bearing that can bear radial load, axial load and moment, and the second main bearing is composed of a bearing that can bear radial load and has a lower moment bearing capacity than the first main bearing.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2019-192109 filed on October 21, 2019. The entire contents of the Japanese patent application are incorporated herein by reference. Technical Field

[0002] The invention relates to an eccentric swing type speed reducer. Background Art

[0003] An eccentric oscillating type speed reducer having an internal gear and an external gear meshing with each other is known. Patent Document 1 describes a differential speed reducer having an input shaft, an external gear, an output shaft, a wheel carrier, and an internal gear arranged in a housing. The speed reducer has: a ball bearing supporting the input shaft; a connecting pin connecting the output shaft and the wheel carrier; a needle bearing arranged on the outer periphery of the input shaft and supporting the external gear; and a cross roller bearing arranged on the housing and supporting the output shaft.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2018-155265

[0005] The speed reducer described in Patent Document 1 is configured to support the output shaft by using a cross roller bearing provided between the housing and the output shaft to obtain the rigidity of the speed reducer. Therefore, if the rigidity is to be improved by this structure, the cross roller bearing needs to be enlarged, and the speed reducer becomes larger as the bearing is enlarged. Therefore, it can be said that the conventional eccentric swing type speed reducer needs to be improved in terms of improving the rigidity of the speed reducer. Summary of the invention

[0006] The present invention has been made in view of such a problem, and an object of the present invention is to provide an eccentric oscillating type reduction gear transmission capable of improving rigidity.

[0007] In order to solve the above-mentioned problems, an eccentric swing type reduction device of one embodiment of the present invention comprises: an internal gear, which is arranged on a housing; an external gear; an eccentric body, which makes the external gear swing; a first wheel frame, which is arranged on one side of the axial direction of the external gear; a second wheel frame, which is arranged on the other side of the axial direction of the external gear; a connecting pin, which connects the first wheel frame and the second wheel frame; a first main bearing, which is arranged between the housing and the first wheel frame; and a second main bearing, which is arranged between the housing and the second wheel frame, wherein the first main bearing is composed of a bearing that can withstand radial loads, axial loads and torques, and the second main bearing is composed of a bearing that can withstand radial loads and has a lower torque bearing capacity than the first main bearing.

[0008] In addition, any combination of the above-mentioned constituent elements or any form of substitution of constituent elements or expressions of the present invention in methods, systems, etc. may also be practiced as additional embodiments of the present invention.

[0009] According to the present invention, an eccentric oscillating speed reduction gear transmission capable of improving rigidity is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a side cross-sectional view schematically showing an eccentric oscillating type reduction gear transmission according to the embodiment.

[0011] Figure 2 It roughly indicates Figure 1 The front sectional view of the eccentric swing type reduction gear unit.

[0012] In the figure: 12-crankshaft, 12a-eccentric body, 14-external gear, 16-internal gear, 18-1st wheel frame, 18f-external thread, 20-2nd wheel frame, 20f-external thread, 20j-fitting part, 22-housing, 26-1st main bearing, 26j-locking part, 26m-internal thread, 26n-inner ring, 28-2nd main bearing, 28j-locking part, 28m-internal thread, 28n-inner ring, 32, 36-connecting pin, 100-eccentric swing type reduction gear device. DETAILED DESCRIPTION

[0013] Hereinafter, the preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the embodiments and the modified examples, the same or equivalent components and parts are marked with the same symbols, and repeated descriptions are appropriately omitted. In addition, in each of the drawings, the size of the components is appropriately enlarged or reduced for easy understanding. In addition, in each of the drawings, some components that are not important in the description of the embodiments are omitted.

[0014] Furthermore, terms including numbers such as 1 and 2 are used to describe various constituent elements, but the terms are only used to distinguish one constituent element from other constituent elements, and the terms are not used to limit the constituent elements.

[0015] [Implementation Method]

[0016] Hereinafter, the structure of the eccentric oscillating type reduction gear transmission 100 according to the embodiment will be described with reference to the drawings. Figure 1 It is a side cross-sectional view schematically showing the eccentric oscillating type reduction gear transmission 100 according to the present embodiment. Figure 2 1 is a front cross-sectional view of the eccentric oscillating type reduction gear 100. In these figures, components that are not important in the description are omitted. The eccentric oscillating type reduction gear 100 of this embodiment is configured to cause one of the internal gear and the external gear to rotate by causing the external gear meshing with the internal gear to oscillate, and the resulting motion component is output from the output component to the driven device.

[0017] The eccentric oscillating type reduction gear 100 mainly includes a crankshaft 12, an external gear 14, an internal gear 16, a wheel carrier 18, 20, a housing 22, main bearings 26, 28, an eccentric body bearing 30, connecting pins 32, 36 and a crankshaft bearing 34. In the present embodiment, as connecting pins 32, 36, an inner pin 32 and a wheel carrier pin 36 are provided. Hereinafter, the direction along the central axis La of the internal gear 16 is referred to as "axial direction", and the circumferential direction and radial direction of a circle centered on the central axis La are referred to as "circumferential direction" and "radial direction", respectively. And, hereinafter, for the sake of convenience, one side in the axial direction (right side in the figure) is referred to as "input side", and the other side in the axial direction (left side in the figure) is referred to as "opposite input side" or "output side".

[0018] The eccentric oscillating speed reducer 100 of the present embodiment is a center crank type eccentric oscillating speed reducer in which the rotation center line of the crankshaft 12 and the center axis La of the internal gear 16 are arranged on the same axis. The crankshaft 12 rotates around the rotation center line by the rotational power input from the driving device (not shown). The driving device is, for example, a motor, a gear motor, an engine, etc. A hollow cylindrical coupling 38 for connecting to the output shaft of the driving device is combined on the crankshaft 12. The coupling 38 is provided with a recess 38c for embedding the output shaft of the driving device. In addition, a fitting recess 22j for fitting with the outer shell of the driving device is provided on the fifth housing 22f described later.

[0019] The crankshaft 12 of the present embodiment is an eccentric body shaft having a plurality of eccentric bodies 12a for causing the external gear 14 to swing. The eccentric body 12a can be formed integrally with the shaft body, but in this example, it is formed separately from the shaft body and is integrated by key press-fitting. The crankshaft 12 can be a hollow shaft, but in the present embodiment, it is a solid shaft. The axis of the eccentric body 12a is eccentric with respect to the rotation center line of the crankshaft 12. In the present embodiment, two eccentric bodies 12a are provided, and the eccentric phases of adjacent eccentric bodies 12a are offset from each other by 180°.

[0020] An external gear 14 is assembled on the outer periphery of each eccentric body 12a via an eccentric body bearing 30. The eccentric body bearing 30 of the present embodiment has a spherical rolling element. As the rolling element of the eccentric body bearing 30, in addition to spherical rolling elements, well-known rolling elements such as rollers (cylinders) or cones can also be used. Each external gear 14 is internally meshed with the internal gear 16. The purpose of assembling the external gears 14 into two rows is to increase the load capacity and to achieve low vibration and low noise by staggering the eccentric phase. The structure of each row of external gears 14 is the same except for the different eccentric phases.

[0021] The external gear 14 is provided corresponding to each eccentric body 12a. The external gear 14 is rotatably supported on the corresponding eccentric body 12a via the eccentric body bearing 30. The external gear 14 is provided with an inner pin hole 13 for the inner pin 32 to pass through, a center hole 15 abutting against the eccentric body bearing 30, and a wheel carrier pin hole 17 for the wheel carrier pin 36 to pass through.

[0022] The inner pin hole 13 and the wheel carrier pin hole 17 are arranged at positions of the outer gear 14 that are offset from the center thereof. A plurality of inner pin holes 13 are arranged corresponding to the inner pin 32 described later. In this example, six inner pin holes 13 are arranged at intervals of 60° in the circumferential direction. A plurality of wheel carrier pin holes 17 are arranged corresponding to the wheel carrier pin 36 described later. In this example, three wheel carrier pin holes 17 are arranged at intervals of 120° in the circumferential direction. The center hole 15 is a hole that is arranged at the center of the outer gear 14 and through which the eccentric body 12a is inserted.

[0023] like Figure 1 As shown, the housing 22 is cylindrical as a whole, and an internal gear 16 is provided on its inner circumference. The housing 22 of this embodiment includes a first housing 22b, a second housing 22c, a third housing 22d, a fourth housing 22e and a fifth housing 22f, which are connected in sequence from the opposite side of the input to the input side in the axial direction. The internal gear 16 is provided on the inner circumference of the third housing 22d. The first to fifth housings 22b to 22f are generally hollow cylindrical and are integrated, for example, by bolts. In this example, the third housing 22d is connected to the second housing 22c by bolts B1. Moreover, the first to fifth housings 22b to 22f are connected together by bolts B2. Specifically, the second housing 22c and the third housing 22d are connected together by bolts B1 inserted from the input side of the third housing 22d and screwed with the second housing 22c. Furthermore, the first to fifth housings 22b to 22f are fastened together by bolts B2 which are inserted from the output side of the first housing 22b and screwed into the fifth housing 22f.

[0024] The internal gear 16 meshes with the external gear 14. The internal gear 16 of the present embodiment includes an internal gear body that is integrated with the housing 22, and an outer pin 16a (pin member) that is rotatably supported by the internal gear body and constitutes the internal teeth of the internal gear 16. The number of internal teeth of the internal gear 16 (the number of outer pins 16a) is slightly greater than the number of external teeth of the external gear 14 (in this example, only one more).

[0025] The carriers 18 and 20 are arranged on the axial side of the external gear 14. The carriers 18 and 20 include a first carrier 18 arranged on the side opposite to the input side of the external gear 14 and a second carrier 20 arranged on the side on the input side of the external gear 14. The carriers 18 and 20 are disc-shaped and support the crankshaft 12 rotatably via the crankshaft bearing 34.

[0026] The first wheel frame 18 and the second wheel frame 20 are connected together via the inner pins 32 and the wheel frame pins 36. The inner pins 32 and the wheel frame pins 36 penetrate the plurality of external gears 14 axially at a position radially offset from the axis of the external gear 14. A plurality of inner pins 32 are arranged at prescribed intervals around the central axis La of the internal gear 16. In the present embodiment, six inner pins 32 are arranged at intervals of 60° in the circumferential direction. The inner pins 32 of the present embodiment are provided separately from the wheel frames 18 and 20. The inner pins 32 may also be provided integrally with any one of the wheel frames 18 and 20.

[0027] The inner pin 32 and the wheel frame pin 36 are connecting pins connecting the first wheel frame 18 and the second wheel frame 20. The terminal end of the input side of the inner pin 32 is embedded in the bottomed recessed portion 20c formed on the second wheel frame 20, and the terminal end on the opposite side of the input is embedded in the bottomed recessed portion 18c formed on the first wheel frame 18. The inner pin 32 connects the first wheel frame 18 and the second wheel frame 20 by embedding its two terminal ends in the recessed portions of each wheel frame.

[0028] The inner pin 32 passes through the inner pin hole 13 formed in the outer gear 14. The circumferential movement of the inner pin 32 is restricted by the input opposite side of the second wheel frame 20 and the input side of the first wheel frame 18. A clearance (i.e., gap) is provided between the inner pin 32 and the inner pin hole 13 for absorbing the swing component of the outer gear 14. The inner pin 32 partially contacts the inner wall surface of the inner pin hole 13.

[0029] A plurality of carrier pins 36 are provided at predetermined intervals around the center axis La of the internal gear 16. In the present embodiment, three carrier pins 36 are provided at intervals of 120° in the circumferential direction. The terminal end portion of the input side of the carrier pin 36 is embedded in a bottomed recess 20d formed on the second wheel frame 20, and the terminal end portion on the opposite side of the input is embedded in a bottomed recess 18d formed on the first wheel frame 18. The carrier pin 36 connects the first wheel frame 18 and the second wheel frame 20 by embedding its two terminal ends in the recesses of each wheel frame. In addition, the carrier pin 36 may be provided integrally with either of the wheel frames 18 and 20.

[0030] The carrier pin 36 passes through the carrier pin hole 17 formed in the external gear 14. The carrier pin 36 does not contact the inner wall surface of the carrier pin hole 17. A sleeve-shaped cylindrical component 36s is sleeved on the outer periphery of the carrier pin 36. Each end surface of the cylindrical component 36s abuts against the end surface of the second carrier 20 and the end surface of the first carrier 18, thereby playing the role of a spacer.

[0031] Here, a component that outputs rotational power to a driven device (not shown) is referred to as an output component, and a component fixed to an external component for supporting the eccentric oscillating type reduction gear 100 is referred to as a fixed component. The output component of this embodiment is the first wheel carrier 18, and the fixed component is the housing 22. The output component is rotatably supported on the fixed component via main bearings 26 and 28.

[0032] The crankshaft bearing 34 includes an input side crankshaft bearing 34 disposed between the second carrier 20 and the crankshaft 12 and an input opposite side crankshaft bearing 34 disposed between the first carrier 18 and the crankshaft 12. Various known bearings can be used as the crankshaft bearing 34. In the present embodiment, a ball bearing is used as the crankshaft bearing 34.

[0033] Next, a characteristic structure of the eccentric oscillating speed reduction gear transmission 100 according to the present embodiment will be described.

[0034] The reducer described in Patent Document 1 is a cantilever structure in which a pin for outputting the output torque is supported only on the output side relative to the housing, and therefore cannot be said to have high rigidity. In a structure in which the pin is supported by only one cross roller bearing, the load capacity of the bearing will be insufficient. Therefore, in order to improve the rigidity of the reducer, it is necessary to use a large cross roller bearing, which will increase the size of the reducer. Therefore, the eccentric swing type reduction device 100 of the present embodiment adopts a double support structure in which the connecting pin (inner pin 32 and wheel carrier pin 36) is supported on the output side and the input side relative to the housing 22. According to this structure, the rigidity can be improved while suppressing the enlargement. In the present embodiment, in order to realize the double support structure of the connecting pin, a second wheel carrier 20 and a second main bearing 28 are provided on the input side.

[0035] The main bearings 26 and 28 include a first main bearing 26 disposed between the first wheel carrier 18 and the housing 22, and a second main bearing 28 disposed between the second wheel carrier 20 and the housing 22. In this embodiment, the first main bearing 26 is supported by the first and second housings 22b and 22c, and the second main bearing 28 is supported by the fourth and fifth housings 22e and 22f.

[0036] The output side of the eccentric oscillating type reduction gear 100 is applied with a larger load and torque than the input side. Therefore, a larger radial load, axial load and torque are applied to the first main bearing 26 disposed between the first wheel carrier 18 and the housing 22 than the second main bearing 28 disposed between the second wheel carrier 20 and the housing 22. Therefore, in the present embodiment, the first main bearing 26 is composed of a bearing that can bear radial loads, (bidirectional) axial loads and torques, and the second main bearing 28 is composed of a bearing that can bear radial loads and has a lower torque bearing capacity than the first main bearing 26.

[0037] According to this structure, the rigidity of the eccentric oscillating type reduction gear 100 can be improved and the load capacity can be increased compared to the case where a bearing with a low load and moment bearing capacity is arranged between the first wheel frame 18 and the housing 22. In addition, compared to the case where bearings with a high bearing capacity are arranged on both the input side and the output side, it is more advantageous in terms of cost.

[0038] The structures of the first main bearing 26 and the second main bearing 28 are not limited, but in the present embodiment, the first main bearing 26 is a cross roller bearing and the second main bearing 28 is a ball bearing. By using the cross roller bearing for the first main bearing 26, it is possible to support loads and moments in multiple directions applied between the first wheel carrier 18 and the housing 22. By using the ball bearing for the second main bearing 28, it is possible to achieve a double support structure at a low cost, and it is possible to reduce the loss torque of the second main bearing 28, thereby improving the transmission efficiency of the reduction gear. The first main bearing 26 includes an inner ring 26n, an outer ring 26e, and a rolling element 26b. The second main bearing 28 includes an inner ring 28n, an outer ring 28e, and a rolling element 28b.

[0039] If the first main bearing 26 is composed of a bearing (cross roller bearing) that can bear radial load, (bidirectional) axial load and moment, and the second main bearing 28 is arranged, the first wheel frame 18 and the second wheel frame 20 will be in a three-point supported state, so there is a possibility that a large radial load will be generated on the bearings due to the eccentricity between the two main bearings, causing the bearing load to become excessive. Therefore, at least one of the outer ring 28e and the inner ring 28n of the second main bearing 28 of this embodiment is clearance-fitted. At this time, the allowable range of eccentricity between the two main bearings can be expanded according to the size of the clearance.

[0040] The second main bearing 28 of the present embodiment is configured so that the internal clearance is larger than the internal clearance of the first main bearing 26. In this case, the permissible range of eccentricity can be further expanded according to the size of the internal clearance.

[0041] In the present embodiment, the inner ring 26n of the first main bearing 26 is provided with an internal thread 26m, and the internal thread 26m is screwed with the external thread 18f of the first wheel frame 18. At this time, the bonding strength between the first main bearing 26 and the first wheel frame 18 is improved. In addition, the next process can be performed immediately after the bonding. In addition, in the present embodiment, the inner ring 28n of the second main bearing 28 is also provided with an internal thread 28m, and the internal thread 28m is screwed with the external thread 20f of the second wheel frame 20.

[0042] In the present embodiment, a cylindrical fitting portion 18j is provided on the outer periphery of the first wheel frame 18 adjacent to the input side of the external thread 18f, and a locking portion 26j that is lock-fitted with the fitting portion 18j of the first wheel frame 18 is provided on the inner periphery of the inner ring 26n of the first main bearing 26 adjacent to the input side of the internal thread 26m. The inner diameter of the locking portion 26j is larger than the outer diameter of the external thread 18f. By performing the lock-fitting, the misalignment of the axial center between the first wheel frame 18 and the first main bearing 26 can be reduced. In addition, similarly to the first main bearing 26, a locking portion 28j that is lock-fitted with the fitting portion 20j provided on the second wheel frame 20 is provided on the inner periphery of the inner ring 28n of the second main bearing 28.

[0043] Next, the operation of the eccentric oscillating speed reducer 100 of the above structure will be described. If the rotational power is transmitted from the driving device to the crankshaft 12, the eccentric body 12a of the crankshaft 12 rotates around the rotation center line passing through the crankshaft 12. The eccentric body 12a that performs eccentric motion partially contacts the center hole 15 via the eccentric body bearing 30, thereby causing the external gear 14 to oscillate. At this time, the external gear 14 oscillates in a manner that rotates around the rotation center line of the crankshaft 12 with its own axis. If the external gear 14 oscillates, the meshing positions of the external gear 14 and the internal gear 16 are sequentially offset. As a result, for each rotation of the crankshaft 12, one of the external gear 14 and the internal gear 16 rotates by an amount equivalent to the difference in the number of teeth between the external gear 14 and the internal gear 16. In the present embodiment, the external gear 14 rotates by itself, and the decelerated rotation is output from the first wheel frame 18 via the inner pin 32.

[0044] The examples of the embodiments of the present invention are described in detail above. The above embodiments are only specific examples for implementing the present invention. The contents of the embodiments do not limit the technical scope of the present invention. Various design changes such as changes, additions, and deletions of constituent elements can be made without departing from the scope of the inventive concept specified in the technical solution. In the above embodiments, the contents that can make such design changes are explained with the phrases such as "embodiment" and "in the embodiment", but this does not mean that design changes are not allowed without the contents of such phrases. In addition, the hatched lines marked on the cross-section of the accompanying drawings do not limit the material of the objects marked with the hatched lines.

[0045] In the following, a modification example is described. In the drawings and description of the modification example, the same reference numerals are given to the same or equivalent components and parts as those in the embodiment. The description repeated with the embodiment is appropriately omitted, and the structure different from the embodiment is described in detail.

[0046] [Modifications]

[0047] In the description of the embodiment, an example is shown in which the eccentric oscillating type reduction gear is a center crank type eccentric oscillating type reduction gear, but the present invention is not limited to this. The eccentric oscillating type reduction gear of the present invention may also be a reduction gear based on various principles having a connecting pin that passes through an external gear and a wheel carrier that supports the connecting pin. For example, the eccentric oscillating type reduction gear may also be a so-called distributed eccentric oscillating type reduction gear in which a plurality of crankshafts are arranged at a position offset from the axis of the internal gear.

[0048] In the embodiment, an example in which the first main bearing 26 is a crossed roller bearing is shown; however, the first main bearing 26 may be another type of bearing, such as a four-point contact ball bearing, as long as it can withstand radial loads, (bidirectional) axial loads and moments.

[0049] In the embodiment, the second main bearing 28 is an example of a ball bearing, but the second main bearing 28 may be another type of bearing, such as a roller bearing, as long as it can withstand radial loads and has a lower moment bearing capacity than the first main bearing 26.

[0050] In the embodiment, an example is shown in which both the inner pin 32 and the wheel carrier pin 36 are supported by the first and second wheel carriers 18 and 20, but the present invention is not limited thereto. For example, the inner pin 32 may be supported by only one of the first and second wheel carriers 18 and 20 and not supported by the other wheel carrier. Furthermore, the wheel carrier pin 36 may not be provided.

[0051] In the embodiment, an example in which two external gears 14 are provided is shown; however, one or three or more external gears 14 may be provided depending on desired characteristics.

[0052] In the embodiment, the main bearings 26 and 28 are described as having inner rings, but the present invention is not limited thereto. One or both of the main bearings 26 and 28 may be configured not to have an inner ring.

[0053] In the above, the output member of the embodiment is described as the wheel carrier 18, and the housing 22 is fixed to the external member. Alternatively, the housing 22 may be used as the output member, and the wheel carrier 18 may be fixed to the external member.

[0054] The above-mentioned modifications also have the same functions and effects as those of the embodiment.

[0055] Any combination of the constituent elements and modifications of the above-described embodiments is also effective as an embodiment of the present invention. A new embodiment generated by the combination has the effects of the combined embodiments and modifications.

Claims

1. An eccentric oscillating reduction gear device, comprising: an input shaft; an internal gear disposed on a housing; an external gear; an eccentric body, the external gear being oscillated by the rotation of the input shaft; a first wheel carrier, disposed on one side of the axial direction of the external gear; a second wheel carrier, disposed on the other side of the axial direction of the external gear; a connecting pin connecting the first wheel carrier and the second wheel carrier; a first main bearing, disposed between the housing and the first wheel carrier; and a second main bearing, disposed between the housing and the second wheel carrier, wherein the eccentric oscillating reduction gear device is characterized in that: A bearing is provided between the input shaft and the second carrier. The first main bearing and the second main bearing are of different types. The first main bearing is composed of a bearing capable of bearing radial load and axial load and a bearing capable of bearing torque alone. The second main bearing is composed of a bearing capable of bearing radial load and a lower moment bearing capacity than the first main bearing. The first main bearing is a crossed roller bearing or a four-point contact ball bearing, and the second main bearing is a ball bearing of a different type from that of the first main bearing.

2. The eccentric oscillating type reduction gear device according to claim 1, characterized in that: At least one of the outer ring and the inner ring of the second main bearing is clearance-fitted.

3. The eccentric oscillating speed reduction device according to claim 1 or 2, characterized in that: An internal clearance of the second main bearing is larger than an internal clearance of the first main bearing.

4. The eccentric oscillating speed reduction device according to claim 1 or 2, characterized in that: An internal thread is provided on the inner ring of the first main bearing, and the internal thread is threadedly engaged with the external thread of the first carrier.

5. The eccentric oscillating type reduction gear device according to claim 4, characterized in that: The inner ring of the first main bearing has a locking portion that is lockably engaged with the first carrier.

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