WO2015040739A1

WO2015040739A1 - Oil seal structure and strain wave gear device

Info

Publication number: WO2015040739A1
Application number: PCT/JP2013/075486
Authority: WO
Inventors: 善智溝口; 芳秀清澤
Original assignee: 株式会社ハーモニック・ドライブ・システムズ
Priority date: 2013-09-20
Filing date: 2013-09-20
Publication date: 2015-03-26

Abstract

A housing (4) is affixed to a first rigid internal gear (11) on the stationary side of a strain wave gear device (2), and a hollow output shaft (13) is integrally formed with a second rigid internal gear (12) that is on the drive side and rotates integrally with a flexible external gear (14). An oil seal (24) is mounted between the circular inner circumferential surface of the housing (4) and the circular outer circumferential surface of the hollow output gear (13). A seal lip part (26) of the oil seal (24) is set such that the contact width (W) with respect to the circular outer circumferential surface (13d) is 500 μm or greater. Even if the hollow output shaft (13) is manufactured from a spheroidal cast iron material, the interval between the seal lip part (26) and the circular outer circumferential surface (13d) is adequately sealed, thereby reliably preventing a lubricant from leaking to the outside.

Description

Oil seal structure and wave gear device

The present invention relates to an oil seal structure for preventing oil leakage from a bearing portion or the like of a rotating member, and a wave gear device provided with the oil seal structure. More specifically, an oil seal structure that can reliably prevent oil leakage even when a base of spheroidal graphite cast iron is exposed on the surface of the rotating member against which the lip seal portion of the oil seal is pressed, and the oil seal The present invention relates to a wave gear device having a structure.

In a device such as a wave gear device, an oil seal (lip seal) is provided between relatively rotating parts so that a lubricant such as grease does not leak to the outside. The oil seal obtains a sufficient sealing effect by giving a certain shape accuracy and surface roughness to the mounting surface of the component to which the oil seal is mounted, particularly the lip contact surface with which the lip seal portion of the oil seal contacts. be able to.

¡Parts to which the oil seal is attached may be formed from spheroidal graphite cast iron. Due to the structure of the spheroidal graphite cast iron metal structure, there are minute holes on the surface of the part. For this reason, the surface roughness of components is low, and a sufficient sealing effect may not be obtained.

In Patent Document 1, a nickel plating layer for reducing the surface roughness is provided at a portion where the lip seal is in sliding contact with the peripheral surface of the rotating shaft made of spheroidal graphite cast iron. A lip seal is brought into contact with the peripheral surface smoothed by the surface treatment to prevent the sealing function from being deteriorated by the lip seal and to extend its life.

JP 2002-115683 A

In the method described in Patent Document 1, it is necessary to form a surface treatment layer such as a nickel plating layer at an oil seal attachment site in a component such as a rotating shaft. Processing man-hours for parts such as rotating shafts increase and manufacturing costs also increase.

An object of the present invention is to propose an oil seal structure capable of obtaining a sufficient sealing effect without performing surface treatment such as plating on the surface of a cast iron part with which the lip seal portion of the oil seal contacts. is there. Another object of the present invention is to propose a wave gear device using the oil seal.

In order to solve the above problems, the present invention provides:
In an oil seal structure that seals an annular gap formed between a first member and a second member that rotate relative to each other with an oil seal,
At least the second member is a member made of spheroidal graphite cast iron, and the base of the spheroidal graphite cast iron is exposed on the circular outer peripheral surface of the second member,
The oil seal includes a seal lip portion pressed against a circular outer peripheral surface of the second member;
In the direction of the central axis of the second member on the circular outer peripheral surface, a contact width between the seal lip portion and the circular outer peripheral surface is at least 500 μm.

In the oil seal structure of the present invention, the seal lip portion of the oil seal has a wide contact area with the circular outer peripheral surface of the second member. Even if the circular outer peripheral surface of the second member with which the lip tip portion of the seal lip portion contacts is the cast iron material surface, a sufficient oil seal effect can be obtained. That is, the average particle diameter of graphite particles contained in spheroidal graphite cast iron is generally about 50 μm, and the area ratio is about 10%. Therefore, if the contact width between the lip tip of the oil seal and the circular outer peripheral surface of the second member is at least 500 μm, a sufficient sealing effect can be obtained without subjecting the second member to surface treatment.

The oil seal structure of the present invention can be applied to a wave gear device. The wave gear device includes a rigid internal gear, a flexible external gear that can be bent in a radial direction, and a partial engagement with the internal gear by bending the external gear in a radial direction. And a wave generator. The oil seal structure prevents lubricant leakage between the internal gear or the internal tooth side member that rotates integrally with the internal gear and the external gear or the external tooth side member that rotates integrally with the external gear. Can be used.

The oil seal structure according to the present invention includes a wave gear device that includes an internal gear or an internal tooth side member that rotates integrally with the internal gear and a wave generator or a member that rotates integrally with the wave generator. It can be used to prevent lubricant leakage.

Furthermore, in the oil seal structure of the present invention, when the wave gear device includes a bearing disposed between the internal gear and the external gear, or the wave gear device is between the internal gear and the wave generator. Can be used to prevent leakage of the lubricant from between the inner and outer rings of these bearings.

It is explanatory drawing which shows the flat type wave gear apparatus of Embodiment 1 to which this invention is applied, and sectional drawing which shows an oil seal. It is a longitudinal cross-sectional view which shows the cup type wave gear apparatus of Embodiment 2 to which this invention is applied. It is a longitudinal cross-sectional view which shows the hollow type wave gear apparatus of Embodiment 3 to which this invention is applied.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1A is an explanatory view showing a rotary actuator provided with a flat wave gear device according to Embodiment 1, and FIG. 1B is a cross-sectional view showing an oil seal thereof. The rotary actuator 1 includes a wave gear device 2 and a motor 3 attached coaxially to the wave gear device 2. In FIG. 1, a portion of the wave gear device 2 is shown in cross section. In the following description, the side of the motor 3 in the direction of the unit center axis 1a in the wave gear device 2 is referred to as an input side, and the side opposite to the motor 3 is referred to as an output side.

The wave gear device 2 includes a cylindrical unit housing 4. The unit housing 4 includes a substantially disk-shaped input side housing 5 located on the motor 3 side and a cylindrical output side housing 6 located on the opposite side. The input side housing 5 includes an input side end plate portion 7 having a constant thickness extending in a direction orthogonal to the unit center axis 1a. The outer end face of the input side end plate portion 7 is a flat end face extending in a direction perpendicular to the unit center axis 1a, and the motor 3 is attached to the end face. A circular center hole 8 is formed in the input side end plate portion 7. The output-side housing 6 includes an output-side end plate portion 9 that extends in the direction orthogonal to the unit center axis 1a at the outer end facing the output side. The output side end plate portion 9 is formed with a circular center hole 10 extending through the output side end plate portion 9.

In the unit housing 4, an annular first rigid internal gear 11 and an annular second rigid internal gear 12 are arranged in parallel in a coaxial state. The first rigid internal gear 11 is a stationary-side rigid internal gear disposed on the input side, and is fixed to the input-side housing 5. The second rigid internal gear 12 is a drive-side rigid internal gear disposed on the output side with respect to the first rigid internal gear 11. A hollow output shaft 13 is integrally formed at the output side end portion of the second rigid internal gear 12. The hollow output shaft 13 has a large-diameter flange 13a at the rear end of the input side, and the outer peripheral end portion of the flange 13a is connected to the output-side end portion of the second rigid internal gear 12. Yes. The shaft portion 13 b on the output side of the hollow output shaft 13 projects to the output side through a circular center hole 10 formed in the output side housing 6.

A cylindrical flexible external gear 14 is disposed coaxially inside the first and second rigid

internal gears

11 and 12 arranged in parallel. The flexible external gear 14 can mesh with both the first and second rigid

internal gears

11 and 12. The number of teeth of the flexible external gear 14 is the same as the number of teeth of the second rigid internal gear 12 on the driving side, but 2n (n) than the number of teeth of the first rigid internal gear 11 on the stationary side. Is a positive integer), usually two.

The wave generator 15 having an elliptical contour is attached to the inside of the flexible external gear 14. The wave generator 15 includes a rigid plug 15a having an elliptical contour and a constant thickness, and a wave bearing 15b attached to the elliptical outer peripheral surface. The wave bearing 15b is a ball bearing provided with a flexible bearing ring that can bend in the radial direction. The flexible external gear 14 is bent in an elliptical shape by the wave generator 15, and the flexible external gear 14 has first and second rigid internal teeth at both ends in the major axis direction of the elliptical shape. The

gears

11 and 12 are partially engaged with each other. When the wave generator 15 is rotated, these meshing positions move in the circumferential direction. The flexible external gear 14 having a small number of teeth rotates integrally with the second rigid internal gear 12 on the driving side with respect to the stationary first rigid internal gear 11 having a large number of teeth. The rotation of the second rigid internal gear 12 is extracted from the hollow output shaft 13 and transmitted to a load-side member (not shown).

Next, the motor 3 includes a cylindrical motor housing 17, and a large-diameter flange 18 is formed at the front end of the motor housing 17. The front end surface of the flange 18 is a flat mounting end surface 19 orthogonal to the unit center axis 1a. At the center of the attachment end surface 19, a circular protrusion 20 is formed that protrudes by a predetermined width toward the wave gear device 2 side. From the center of the circular protrusion 20, the tip end side shaft portion 21 a of the motor shaft 21 protrudes. The distal end side shaft portion 21 a extends through a shaft hole 15 c formed in the rigid plug 15 a of the wave generator 15, and is fixed to the wave generator 15.

A regulating ring 22 is fitted into an annular gap formed between the circular inner peripheral surface of the circular center hole 8 and the circular outer peripheral surface of the circular protrusion 20. During operation of the rotary actuator 1, the flexible external gear 14 moves in the direction of the unit center axis 1a. When the flexible external gear 14 moves to the input side, the end of the flexible external gear 14 comes into contact with the regulating ring 22 and its movement is regulated. Similarly, when moving in the reverse direction, the other end of the flexible external gear 14 hits the end face 13c of the hollow output shaft 13, and the movement is restricted.

Here, the circular outer peripheral surface of the shaft portion 13b (second member) of the hollow output shaft 13 formed integrally with the second rigid internal gear 12 and the circular center hole 10 of the output side housing 6 (first member) are formed. Between the circular inner peripheral surfaces, an annular gap 23 opened to the output side is formed. An annular oil seal 24 is attached to the gap 23, and the space between the shaft portion 13b and the output side housing 6 is sealed. That is, the circular outer peripheral surface of the hollow output shaft 13 that is an external tooth side member that rotates integrally with the flexible external gear 14 and the output side housing 6 that is an internal tooth side member that rotates integrally with the first rigid internal gear 11. An oil seal 24 seals the space between the circular center hole 10 and the circular inner peripheral surface.

As shown in an enlarged view in FIG. 1B, the oil seal 24 includes an annular attachment portion 25 made of an elastic body such as an elastomer, an annular seal lip portion 26 made of an elastic body, and these attachment portions 25. And an annular metal plate 27 having an L-shaped cross section spanned between the seal lip portion 26 and an annular coil spring 28 attached to the inner peripheral surface of the seal lip portion 26.

The mounting portion 25 includes a circular outer peripheral surface 25 a having the same outer diameter, and is fitted in a state of being in close contact with the circular inner peripheral surface 6 a formed on the output-side housing 6. The seal lip portion 26 extends from the inner peripheral edge portion of the metal plate 27 toward the input side, and the front end portion thereof includes a lip front end portion 26a having a chevron-shaped inner peripheral surface protruding radially inward. It has become. The lip tip portion 26a is a slope having a larger inclination angle on the input side slope 26c than on the output side slope 26b. In addition, a dust lip portion 29 that protrudes obliquely toward the radially inner side and the output side is formed at a portion of the seal lip portion 26 on the inner peripheral edge side of the metal plate 27. The tip ends of the lip tip portion 26 a and the dust strip portion 29 are in contact with the circular outer peripheral surface 13 d of the shaft portion 13 b of the hollow output shaft 13.

The width (radial thickness) from the circular outer peripheral surface 25a of the oil seal 24 to the tip of the lip tip 26a is larger than the radial width of the gap 23 to which the oil seal 24 is attached. Accordingly, the lip tip portion 26a of the seal lip portion 26 of the oil seal 24 is mounted in the gap 23 in a crushed state. The lip tip portion 26a of the oil seal 24 mounted in the gap is pressed against the circular outer peripheral surface 13d of the shaft portion 13b and is in close contact with the circular outer peripheral surface 13d with a predetermined contact width W in the direction of the unit center axis 1a. Is formed. By appropriately setting the elastic characteristics, dimensions, and the like of the oil seal 24, the contact width W of the lip tip portion 26a can be set to a target dimension or more.

In this example, the contact width W is set to be 500 μm or more. The hollow output shaft 13 formed integrally with the second rigid internal gear 12 is a shaft formed of spheroidal graphite cast iron, like the second rigid internal gear 12. The base of the spheroidal graphite cast iron is exposed on the circular outer peripheral surface 13 d of the hollow output shaft 13. When a generally used oil seal is used, there is a possibility that the space between the circular outer peripheral surface 13d and the lip tip of the oil seal cannot be reliably sealed. In this example, since the contact width W is sufficiently large, the space between them can be reliably sealed, and the lubricant can be reliably prevented from leaking from the inside of the wave gear device 2 to the outside.

(Embodiment 2)
FIG. 2 is a longitudinal sectional view showing a cup-type wave gear device according to the second embodiment. The wave gear device 30 includes a cylindrical unit housing 31. An annular flange 32 having a constant width is coaxially connected and fixed to an end of the input side IN on one side of the unit center axis 31a in the unit housing 31. A rigid internal gear 33 is integrally attached to the inner peripheral surface of the annular flange 32, and an inner tooth 33a is formed on the circular inner peripheral surface.

A cup-shaped flexible external gear 34 is coaxially arranged inside the rigid internal gear 33. The flexible external gear 34 is arranged in a state where the open end faces the input side IN. The flexible external gear 34 includes a cylindrical body 34a that can be bent in the radial direction, a diaphragm 34b that extends inward in the radial direction continuously to the end of the output side OUT of the cylindrical body 34a, and a diaphragm 34b. An annular boss 34c formed continuously on the inner peripheral edge of the cylindrical body 34a and an outer tooth 34d formed on the outer peripheral surface portion on the opening end side of the cylindrical body 34a. A cup-shaped bottom surface portion is defined by the diaphragm 34b and the boss 34c.

A wave generator 35 having an elliptical contour is fitted inside a portion of the cylindrical body portion 34a where the external teeth 34d are formed. The wave generator 35 includes a rigid plug 35b having a hollow portion 35a and a wave bearing 35c attached to the elliptical outer peripheral surface. The wave bearing 35c is a ball bearing having an inner ring and an outer ring that can be bent in the radial direction. The flexible external gear 34 is bent in an elliptical shape by the wave generator 35, and external teeth 34 d located at both ends of the long axis mesh with the internal teeth 33 a of the rigid internal gear 33.

An annular pressing plate 36 is coaxially attached to the input side IN end surface 34e of the boss 34c of the flexible external gear. A disc-shaped output flange 37 is coaxially attached to the end face 34f of the output side OUT of the boss 34c. A circular protrusion 37 a protruding to the input side IN is formed at the center of the output flange 37. The circular protrusion 37a is fitted into the central through hole of the boss 34c and the central through hole of the holding plate 36. Thereby, the three

members

37, 34c, and 36 are positioned so as to be coaxial.

The pressing plate 36 is temporarily fixed to the boss 34c by a plurality of temporary fixing screws 38. In addition, a plurality of tap holes 44 are formed in the holding plate 36 at predetermined angular intervals. Boss side bolt insertion holes 45 are formed in the bosses 34c at positions corresponding to the tap holes 44, respectively. Similarly, flange-side bolt insertion holes 46 are also formed in the output flange 37 at positions corresponding to the boss-side bolt insertion holes 45.

Next, the output flange 37 is rotatably supported by the unit housing 31 via the cross roller bearing 47. The output flange 37 has a cylindrical portion 37c that protrudes toward the input side IN at the outer peripheral edge. A portion of the cylindrical body portion 34a of the flexible external gear 34 on the diaphragm 34b side is located inside the cylindrical portion 37c.

The inner ring 47a of the cross roller bearing 47 is mounted on the outer peripheral surface of the cylindrical portion 37c. Further, the position in the axial direction is defined by an annular inner ring receiver 47c fixed to the end surface of the input side IN in the cylindrical portion 37c. The outer ring 47 b of the cross roller bearing 47 is mounted on the inner peripheral surface of the unit housing 31, and the position in the axial direction is defined by the outer peripheral end surface of the output side OUT of the annular flange 32.

Here, an oil seal 49 is mounted in an annular gap 48 between the circular inner peripheral surface 31 d formed at the output side end of the unit housing 31 and the circular outer peripheral surface 37 d of the output flange 37. The oil seal 49 seals between the inner and

outer rings

47a and 47b of the cross roller bearing 47 so that the lubricant does not leak outside. As the oil seal 49, one having the same structure as the oil seal 24 shown in FIG. Even in this case, the contact width between the lip tip of the oil seal 49 and the circular outer peripheral surface 37d of the output flange 37 may be 500 μm or more.

The output panel 50, which is a driven member, is fastened to the output flange 37 of the wave gear device 30 having this configuration, as indicated by the phantom line in FIG. Bolt insertion holes 51 are formed in the output panel 50 at positions corresponding to the bolt insertion holes 46 of the output flange 37.

The circular end surface of the output panel 50 and the end surface 37b of the output flange 37 of the wave gear device 30 are positioned and overlapped. In this state, the fastening bolts 52 are inserted into the respective bolt insertion holes 51 from the output panel 50 side. The fastening bolt 52 is screwed into the tap hole 44 formed in the holding plate 36 through the bolt insertion hole 51, the flange side bolt insertion hole 46, and the boss side bolt insertion hole 45. By screwing and fixing the plurality of fastening bolts 52, the output panel 50, which is a driven member, is fastened to the output flange 37. On the other hand, for example, a motor shaft of a drive motor is connected and fixed to the wave generator 35 (not shown). The annular flange 32 fixed to the unit housing 31 is fixed to a member (not shown) on the fixed side.

When the wave generator 35 rotates at a high speed, the meshing position of the flexible external gear 34 with respect to the rigid internal gear 33 moves in the circumferential direction. Accordingly, relative rotation occurs between the

gears

33 and 34 in accordance with the difference in the number of teeth of the

gears

33 and 34. In this example, the flexible external gear 34 rotates, and the reduced rotation output is taken out via the output flange 37 fixed to the boss 34c. The output board 50 turns around the unit center axis 31a by the deceleration rotation output.

(Embodiment 3)
FIG. 3 is a longitudinal sectional view showing a hollow wave gear device according to the third embodiment. The wave gear device 60 includes an annular rigid internal gear 62 having a rectangular cross section. A cup-shaped flexible external gear 63 is coaxially arranged inside the rigid internal gear 62. Inside the flexible external gear 63, a wave generator 64 is disposed that bends the flexible external gear 63 into an elliptical shape and partially meshes with the rigid internal gear 62. Further, the wave gear device 60 is formed with a unit hollow portion 65 extending through the central portion in the direction of the central axis 61a.

A disc-shaped first unit end plate 66 is integrally formed on one end surface 62 a of the rigid internal gear 62. The first unit end plate 66 extends in a direction orthogonal to the central axis 61a. A bearing 67 is mounted on the inner peripheral surface of the central through hole of the first unit end plate 66, and one first shaft end portion 64 a of the wave generator 64 is supported by the bearing 67 in a rotatable state. An oil seal 81 is attached at a position adjacent to the bearing 67. The oil seal 81 prevents the lubricant from leaking out from between the inner and outer rings of the bearing 67.

The oil seal 81 includes an annular outer peripheral metal plate 81a having an L-shaped cross section, and an annular seal lip portion 81b made of an elastic body attached to the inside. The contact width between the tip end portion of the seal lip portion 81b and the circular outer peripheral surface 64c of the first shaft end portion 64a is set to be 500 μm or more. Thereby, even if the first shaft end portion 64a of the wave generator 64 is made of spheroidal graphite cast iron, the oil seal 81 can surely prevent leakage of the lubricant.

Next, a cross roller bearing 68 that is a unit bearing is disposed adjacent to the other end face 62 b of the first rigid internal gear 62. The outer ring 68 a of the cross roller bearing 68 is fastened and fixed to the end surface 62 b of the rigid internal gear 62. A disc-shaped second unit end plate 69 is integrally formed on the end surface of the inner ring 68 b of the cross roller bearing 68 opposite to the rigid internal gear 62. The second unit end plate 69 extends in a direction perpendicular to the central axis 61a and is fixed to the outer peripheral surface of an annular boss 63c that defines the center portion of the cup bottom surface of the cup-shaped flexible external gear 63. ing.

Here, an oil seal 82 is mounted between the end surface of the outer ring 68 a and the circular outer peripheral surface 69 a of the second unit end plate 69. The oil seal 82 prevents the lubricant from leaking from between the inner and outer rings of the cross roller bearing 68. The oil seal 82 includes an annular metal plate 83 bent in two stages, an outer peripheral side seal portion 84 made of an elastic body having an L-shaped cross section fixed to the inner peripheral surface of the metal plate 83, and a metal plate 83. An annular seal lip portion 85 made of an elastic body attached to the lower end edge of the ring and an annular coil spring 86 attached to the inner peripheral surface of the seal lip portion 85 are provided.

The contact width between the lip tip of the seal lip 85 and the circular outer peripheral surface 69a of the second unit end plate 69 is set to be 500 μm or more. Thereby, even if the 2nd unit end plate 69 is a member made from a spheroidal graphite cast iron, between the seal lip part 85 and the circular outer peripheral surface 69a can be sealed reliably. A dust lip 87 is also formed on the seal lip 85.

Next, inside the flexible external gear 63, a bearing holder 70 fixed to the boss 63c is disposed. A second bearing 71 is attached to the bearing holder 70. By the second bearing 71, the second shaft end portion 64b on the boss 63c side of the wave generator 64 is supported in a freely rotatable state.

For example, the rigid internal gear 62 is fastened and fixed to a fixed side member (not shown), the first shaft end portion 64a of the wave generator 64 is connected to a high-speed rotation shaft such as a motor shaft (not shown), and a flexible external tooth A second unit end plate 69 fixed to the gear 63 is fastened to a driven member (not shown). In this case, the stationary side unit housing of the wave gear device 60 is constituted by the rigid internal gear 62, the first unit end plate 66, and the outer ring 68 a of the cross roller bearing 68. The rotation-side unit housing is constituted by the inner ring 68 b of the cross roller bearing 68 and the second unit end plate 69.

When the wave generator 64 is rotated, the meshing position of the external teeth 63a of the flexible external gear 63 with respect to the internal teeth 62c of the rigid internal gear 62 moves in the circumferential direction. The number of teeth of the flexible external gear 63 is 2n (n: a positive integer), usually 2 (n = 1) less than the number of teeth of the rigid internal gear 62. Therefore, when the meshing position moves in the circumferential direction, relative rotation corresponding to the number of teeth difference occurs in both

gears

62 and 63. Reduced rotation decelerated according to the difference in the number of teeth is output from the flexible external gear 63 to the driven member (not shown) via the second unit end plate 69.

Claims

In an oil seal structure that seals an annular gap formed between a first member and a second member that rotate relative to each other with an oil seal,
The second member is a member made of spheroidal graphite cast iron, and the base of the spheroidal graphite cast iron is exposed on the circular outer peripheral surface of the second member,
The oil seal includes a seal lip portion pressed against a circular outer peripheral surface of the second member;
In the direction of the central axis of the second member on the circular outer peripheral surface, the contact width between the seal lip portion and the circular outer peripheral surface is at least 500 μm.
A rigid internal gear,
A flexible external gear capable of bending in the radial direction;
A wave generator that flexes the external gear in a radial direction and partially meshes with the internal gear;
An oil seal structure according to claim 1;
Have
The first member is an internal gear side member that rotates integrally with the internal gear or the internal gear,
The wave gear device, wherein the second member is the external gear, an external tooth side member that rotates integrally with the external gear, or a member that rotates integrally with the wave generator.
A bearing disposed between the internal gear and the external gear;
The wave gear device according to claim 2, wherein the oil seal structure seals between an outer ring and an inner ring of the bearing.
A bearing disposed between the internal gear and the wave generator;
The wave gear device according to claim 2, wherein the oil seal structure seals between an outer ring and an inner ring of the bearing.