Lubricant seal structure, wave gear device, and actuator

Abstract

A wave gear device (1) includes a lubricant sealing structure for preventing lubricant from leaking to the outside through a gap portion (21) between a hollow input shaft (4) and an end plate (2). The lubricant sealing structure includes: an oil-repellent surface formed on a surface portion facing the gap portion (21); an oil seal (20) that seals the gap portion (21); and an oil film forming surface formed on a lip front end surface (20c) of the oil seal (20). The oil-repellent surface has a surface texture in which first fine grooves are formed in a predetermined pattern so as to obtain an oil-repellent effect on the lubricant. The oil film forming surface has a surface texture in which second fine grooves are formed in a predetermined pattern so as to obtain an oil film forming effect of the grease for the sealing lip.

Description

Technical Field

[0001] The present invention relates to a lubricant sealing structure for a wave gear device, an actuator having a wave gear device and a motor, or other mechanical devices. More specifically, the present invention relates to a lubricant sealing structure for preventing lubricant from leaking from the inside of the device to the outside through between a first component and a second component that rotate relative to each other around a central axis. Background Art

[0002] In a gear device such as a wave gear device, rotating parts such as an input shaft and an output shaft are arranged in a device housing on the fixed side with a gap. In order to prevent lubricants such as lubricating oil and grease filled in the device from leaking through the gap to other parts in the device or outside the device, an oil seal is usually used. The oil seal has an annular seal made of elastic material, which is fixed to the device housing. The sealing lip of the seal is pressed against the outer peripheral surface of the rotating part in a slidable state, thereby sealing the gap to prevent the lubricant from leaking.

[0003] Patent Document 1 (Japanese Patent Publication No. 2006-258234) proposes a lubricant sealing device for improving the sealing performance of an oil seal. In the lubricant sealing device, a fluorine-based grease having oleophobicity to the lubricant is applied to the sealing portion of a rotating component constituted by the oil seal, thereby improving the sealing performance.

[0004] Here, as a surface modification technology for sliding surfaces, etc., surface texturing such as machining fine grooves on the surface of the object is known. Patent document 2 (Japanese Patent Publication No. 2017-214996) proposes the following technology: a periodic structure of fine grating-like concave and convex is formed on the sliding surface by surface processing using a femtosecond laser, thereby preventing increased friction and burning caused by insufficient lubrication. In addition, Patent document 3 (Japanese Patent Publication No. 5465109) proposes the following technology: a lubricating fluid is sandwiched between two parts by laser processing, and a micro groove is formed on the sliding surface, thereby giving a higher friction reduction effect.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2006-258234

[0008] Patent Document 2: Japanese Patent Application Publication No. 2017-214996

[0009] Patent Document 3: Japanese Patent No. 5465109 Summary of the invention

[0010] In order to maintain the sealing performance of the oil seal, it is necessary to keep the sealing lip grease in the sealing part formed by the sealing lip at an appropriate film thickness to prevent the wear of the sealing part. In addition, if the lubricant such as the gear lubricating oil sealed inside the device intrudes into the sealing part and contacts it, the wear resistance and sealing performance of the sealing part may be reduced.

[0011] An object of the present invention is to provide a lubricant seal structure capable of maintaining the sealing performance of an oil seal by fine groove processing (surface texturing).

[0012] According to the present invention, there is provided a lubricant sealing structure for preventing lubricant from leaking from inside the device through a gap portion between a first member and a second member in a device including the first member and the second member that rotate relative to each other about a central axis.

[0013] The lubricant sealing structure of the present invention comprises:

[0014] a first surface portion of the first member and a second surface portion of the second member, which form the gap portion;

[0015] an oil seal fixed to the first surface portion and sealing the gap portion while being in slidable contact with the second surface portion;

[0016] an oil-repellent surface formed on at least one of the first surface portion and the second surface portion and located closer to the inside of the device than the oil seal; and

[0017] an oil film forming surface formed on at least one of a front end surface portion of the oil seal that contacts the second surface portion and a portion of the second surface portion that contacts the front end surface portion,

[0018] The oil-repellent surface has a surface texture in which first fine grooves are formed in a predetermined pattern so as to obtain an oil-repellent effect on the lubricant.

[0019] The first fine grooves have a groove width and a groove depth of several micrometers to several tens of nanometers, and are formed on the oleophobic surface at intervals of several micrometers to several tens of nanometers.

[0020] The oil film forming surface has a surface texture in which second fine grooves are formed in a predetermined pattern so as to obtain an oil film forming effect.

[0021] The second fine grooves have a groove width and a groove depth of several micrometers to several tens of nanometers, and are formed on the oil film forming surface at intervals of several micrometers to several tens of nanometers.

[0022] In the lubricant seal structure of the present invention, an oleophobic surface is formed on the surface of the first and second components that define the gap from the inside of the device to the sealing portion of the oil seal (a surface texture treatment is performed to improve the oleophobicity). The lubricant is repelled by the oleophobic surface and deformed into a spherical shape, thereby preventing the lubricant from flowing into the oil seal along the gap. The following disadvantages can be prevented: lubricants such as gear lubricating oils that have different properties from the grease for the seal lip from invading the sealing portion of the oil seal in large quantities, resulting in a decrease in the wear resistance and sealing performance of the sealing portion.

[0023] In addition, an oil film forming surface is formed on one or both of the lip front end surface of the sealing lip of the oil seal and the sliding surface portion of the second component. The oil film forming surface is subjected to a surface texture treatment consisting of a second fine groove for improving the oil film forming effect (fluid dynamic pressure effect or oil film retention effect). An appropriate oil film (an oil film with high rigidity and an oil film of a required thickness) can be formed / maintained between the lip front end surface and the sliding surface portion of the second component, thereby suppressing the wear of the sealing portion. Therefore, the required interference between the lip front end surface and the sliding surface of the second component can be maintained, and the sealing performance of the oil seal can be maintained.

[0024] According to the lubricant sealing structure of the present invention, the sealing effect of the oil seal can be improved and its sealing performance can be maintained by implementing the synergistic effect of the oil-repellent surface formed by the surface texture treatment formed by the micro-groove processing and the oil film forming surface. Therefore, the lubricant can be reliably prevented from leaking from the lubricant sealing part inside the device to the outside of the device.

[0025] Here, a micro-gap portion is formed in the gap portion and in a portion closer to the inside of the device than the oil seal. The oleophobic surface is formed in at least one of the first surface portion and the second surface portion, from a position closer to the inside of the device than the micro-gap portion to the surface portion of the micro-gap portion, and a surface portion forming the micro-gap portion. The gap size of the micro-gap portion is set to a value smaller than the diameter of the spherical lubricant formed on the oleophobic surface. The spherical lubricant formed by the oleophobic surface can be prevented from intruding into the sealing portion side through the micro-gap portion smaller than its diameter. Therefore, the lubricant can be reliably prevented from intruding into the sealing portion.

[0026] As the oil-repellent surface, an oil-repellent surface having the first microgroove formed as a whole can be used. As the oil film forming surface, an oil film forming surface having the second microgroove formed as a whole can be used. In addition, as the oil film forming surface, an oil film forming surface having a groove machined surface having the second microgroove formed and a groove unmachined surface having no second microgroove formed alternately formed can also be used.

[0027] The first microgroove and the second microgroove can be at least any one of the following grooves respectively: a groove extending in a straight line, a curve or a wave in the direction along the central axis of the device; a groove extending in a straight line, a curve or a wave in the circumferential direction centered on the central axis; a groove extending in a straight line, a curve or a wave in a direction inclined relative to the direction along the central axis; a groove extending in a spiral shape; and a groove with a mesh pattern. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic longitudinal sectional view showing a wave gear device including a lubricant seal structure according to the present invention.

[0029] Figure 2 (a) is an enlarged representation Figure 1 A partial enlarged view of the part of the wave gear device where the lubricant seal structure is assembled. Figure 2 (b) means Figure 2 (a) is an illustration of the part, Figure 2 (c) is a schematic diagram showing an oleophobic surface, Figure 2 (d) is a schematic diagram showing the oil film forming surface, Figure 2 (e) is an explanatory diagram showing another example of a micro gap.

[0030] Figure 3 It is a schematic diagram showing the effect of the lubricant seal structure.

[0031] Figure 4 (a) is a partial enlarged view showing another part of the wave gear device in which the lubricant seal structure is assembled. Figure 4 (b) means Figure 4 (a) is an illustration of the part, Figure 4 (c) is a schematic diagram showing an oleophobic surface, Figure 4 (d) is a schematic diagram showing the oil film forming surface, Figure 4 (e) is an explanatory diagram showing still another example of a micro gap.

[0032] Figure 5 (a) is a schematic longitudinal sectional view showing an actuator having a lubricant seal structure according to the present invention, Figure 5 (b) is a partial enlarged view showing a portion where a lubricant seal structure is assembled. Figure 5 (c) is a partial enlarged view showing another portion where the lubricant seal structure is assembled. DETAILED DESCRIPTION

[0033] Hereinafter, an embodiment of the lubricant seal structure to which the present invention is applied will be described with reference to the accompanying drawings. The following embodiment is a case where the lubricant seal structure of the present invention is applied to a wave gear device and an actuator having a wave gear device and a motor. The present invention can also be applied to a rotation transmission device such as a gear-type speed reducer other than a wave gear device.

[0034] [Implementation Method 1]

[0035] Figure 1 1 is a schematic longitudinal cross-sectional view showing a wave gear device according to Embodiment 1 of the present invention. The wave gear device 1 includes: a disk-shaped end plate 2 and an end plate 3, which are opposed to each other at a predetermined interval in the direction of the central axis 1a; a hollow input shaft 4, which coaxially extends through the center portions of the end plates 2 and 3; and a wave gear mechanism 5, which is assembled between the end plates 2 and 3 in a state of coaxially surrounding the hollow input shaft 4. The hollow input shaft 4 is rotatably supported by the end plates 2 and 3 via ball bearings 6 and 7. The wave gear mechanism 5 includes: a rigid internal gear 8 formed in an annular shape; an elastic external gear 9 formed in a top hat shape; a wave generator 10 with an elliptical profile; and a cross roller bearing 11, which supports the internal gear 8 and the external gear 9 in a state of relative rotation. The end plates 2 and 3 and the cross roller bearing 11 constitute a device housing.

[0036] The external gear 9 includes a flexible cylindrical body 9b having external teeth 9a formed thereon, a disc-shaped diaphragm 9c extending radially outward from the end of the cylindrical body 9b, and an annular rigid boss 9d integrally formed on the outer peripheral edge of the diaphragm 9c. The portion on the opening end side of the cylindrical body 9b having the external teeth 9a formed thereon is coaxially arranged inside the internal gear 8. A wave generator 10 is coaxially embedded inside the portion on the opening end side of the cylindrical body 9b. The wave generator 10 includes a plug portion 10a integrally formed on the outer peripheral surface of the hollow input shaft 4, and a wave bearing 10b mounted on the elliptical outer peripheral surface of the plug portion 10a. The cylindrical body 9b of the external gear 9 is bent into an elliptical shape by the wave generator 10, so that the portions of the external teeth 9a located at both ends of its major axis mesh with the internal teeth 8a of the internal gear 8.

[0037] The boss 9d of the external gear 9 is sandwiched between the end plate 2 and the outer ring 12 of the cross roller bearing 11 from both sides in the direction of the central axis 1a, and in this state, the three components are fastened and fixed. The internal gear 8 is sandwiched between the end plate 3 and the inner ring 13 of the cross roller bearing 11 from both sides in the direction of the central axis 1a, and in this state, the three components are fastened and fixed.

[0038] The hollow input shaft 4 is a rotation input member connected to a motor or the like. When the hollow input shaft 4 rotates, the wave generator 10 rotates integrally with the hollow input shaft 4, so that the meshing position of the external gear 9 relative to the internal gear 8 moves in the circumferential direction. A relative rotation corresponding to the difference in the number of teeth between the two gears 8 and 9 occurs. For example, the end plate 2 to which the external gear 9 is fastened serves as a fixed side member, and the end plate 3 to which the internal gear 8 is fastened serves as a rotation output member, and relative rotation (reduced rotation) is output from the end plate 3.

[0039] The lubricated parts inside the wave gear device 1 include the meshing part between the external gear 9 and the internal gear 8, the contact part between the external gear 9 and the wave generator 10, the wave bearing 10b of the wave generator 10, the sliding part of the cross roller bearing 11, the sliding part of the ball bearings 6 and 7, etc. The wave gear device 1 is equipped with a lubricant seal structure for preventing the lubricant sealed or applied to the above parts from leaking out from the inside of the device to the outside. The wave gear device 1 of this example is equipped with a lubricant seal structure including an oil seal 20, a lubricant seal structure including an oil seal 30, and a lubricant seal structure including an oil seal 40.

[0040] The lubricant sealing structure including the oil seal 20 seals between the inner peripheral surface portion 2a of the end plate 2 and the outer peripheral surface portion 4a on the shaft end side of one of the hollow input shafts 4, thereby preventing the lubricant from leaking out of the device from the lubricant sealing portion 26 between the external gear 9 between the end plates 2 and 3 and the hollow input shaft 4. Similarly, the lubricant sealing structure including the oil seal 30 seals between the inner peripheral surface 3a of the end plate 3 and the outer peripheral surface portion 4b on the shaft end side of the other side of the hollow input shaft 4, thereby preventing the lubricant from leaking out of the device from the lubricant sealing portion 26. The lubricant sealing structure including the oil seal 40 seals between the outer ring 12 and the inner ring 13 of the cross roller bearing 11, thereby preventing the lubricant from leaking out of the device from the lubricant sealing portion 46 formed between the external gear 9, the cross roller bearing 11, and the internal gear.

[0041] (Lubricant sealing structure between end plate 2 and hollow input shaft 4)

[0042] Figure 2 (a) is an explanatory diagram showing a lubricant sealing structure including an oil seal 20 for sealing between the end plate 2 and the shaft end of the hollow input shaft 4. Figure 2 (b) is a half cross-sectional view showing a portion of the wave gear device 1 where a lubricant seal structure including an oil seal 20 is incorporated. Figure 2 (c) is a schematic diagram showing an example of an oleophobic surface, Figure 2 (d) is a schematic diagram showing an example of an oil film forming surface.

[0043] One end of the hollow input shaft 4 is rotatably supported by the end plate 2 via a ball bearing 6. One end of the hollow input shaft 4 passes through the center of the end plate 2 and protrudes to the outside of the device. A gap portion 21 is formed between the inner peripheral surface portion 2a of the inner peripheral edge portion of the end plate 2 and the outer peripheral surface portion 4 of the shaft end of the hollow input shaft 4 opposite to the inner peripheral surface portion 2a, which communicates with the outside of the device from the ball bearing 6 side (lubricant sealing portion 26 side). The gap portion 21 is sealed by an oil seal 20. The oil seal 20 includes an annular seal 20a made of an elastic material, the seal 20a is embedded and fixed to the inner peripheral surface portion 2a of the end plate 2, and the lip front end surfaces 20c and 20d of the seal lip 20b (main lip, auxiliary lip) of the seal 20a are pressed against the outer peripheral surface portion 4a of the hollow input shaft 4 in a slidable manner.

[0044] The outer peripheral surface portion 4a of the hollow input shaft 4 includes: an outer peripheral surface portion 4b for sealing sliding, on which the lip front end surfaces 20c and 20d of the oil seal 20 slide, and an outer peripheral surface portion 4c from the outer peripheral surface portion 4b to the portion where the inner ring 61 of the ball bearing 6 is mounted. A partition plate portion 2c is formed on the inner peripheral surface portion 2a of the end plate 2, and the partition plate portion 2c protrudes radially inward between the oil seal 20 and the ball bearing 6. The inner peripheral end surface portion 2d of the partition plate portion 2c faces the outer peripheral surface portion 4c of the hollow input shaft 4 at a narrower interval than other parts of the gap portion 21, and this portion is a circular ring-shaped micro gap 22.

[0045] The outer peripheral surface portion 4c of the hollow input shaft 4 is an oil-repellent surface. Figure 2 In (a), the range of the oil-repellent surface is indicated by a fine dot pattern. The oil-repellent surface has a surface texture in which the first fine grooves 23 are formed in a predetermined pattern so as to obtain an oil-repellent effect for the lubricant leaking from the ball bearing 6 toward the micro-gap 22. For example, Figure 2 As shown in (c), the first fine groove 23 is a groove extending in the direction of the central axis 1a, and is formed at a constant interval over the entire circumference of the outer peripheral surface portion 4c. The first fine groove 23 has a groove width and a groove depth of several micrometers to tens of nanometers, and is formed on the oil-repellent surface at intervals of several micrometers to tens of nanometers. In addition, the size of the small gap 22 formed in a part of the gap portion 21 between the hollow input shaft 4 and the end plate 2 is set to a value smaller than the particle size of the lubricant spheroidized on the oil-repellent surface. In addition, the oil-repellent surface can be formed on the inner peripheral end surface portion 2d of the end plate 2. In this case, it is sufficient to divide the inner peripheral end surface portion 2d of the partition plate portion 2c of the end plate 2 that defines the small gap 22 and the end surface portions on both sides connected thereto into oil-repellent surfaces.

[0046] Next, an oil film forming surface is formed on the outer peripheral surface portion 4a of the hollow input shaft 4 and on the outer peripheral surface portion 4b on which the lip front end surfaces 20c and 20d slide. The oil film forming surface may also be formed on the lip front end surfaces 20c and 20d of the oil seal 20. The oil film forming surface has a surface texture in which the second fine grooves 24 are formed in a predetermined pattern so as to obtain the oil film forming effect of the grease for the seal lip. For example, Figure 2 As shown in (d), the second fine groove 24 is a groove extending in the circumferential direction and is formed at a constant interval in the direction of the central axis 1a. The second fine groove 24 has a groove width and a groove depth of several micrometers to several tens of nanometers, and is formed on the oil film forming surface at intervals of several micrometers to several tens of nanometers. The oil film forming surface can be formed over the entire circumference of the outer peripheral surface portion 4b of the hollow input shaft 4. It can also be formed in a partial area of ​​the outer peripheral surface portion 4b. In addition, sometimes the groove machined surface on which the second fine groove 24 is formed and the groove unmachined surface on which the groove is not formed are alternately formed in the circumferential direction on the outer peripheral surface portion 4b.

[0047] In addition, various groove patterns can be used as groove patterns of the first microgrooves 23 and the second microgrooves 24 that form the oleophobic surface. For example, the following groove pattern can be used: the first microgrooves 23 extending in a straight line, a curve, or a wave in the direction along the central axis 1a are formed at a constant interval in the circumferential direction. The first microgrooves 23 can be the following groove pattern: the first microgrooves 23 extending in a straight line, a curve, or a wave in the circumferential direction centered on the central axis 1a are formed at a constant interval in the direction of the central axis 1a. It can also be formed as a groove pattern consisting of the first microgrooves extending in a straight line, a curve, or a wave in a direction inclined relative to the direction along the central axis 1a. In addition, it can also be formed as a groove pattern consisting of the first microgrooves 23 extending in a spiral shape at a constant pitch in the direction of the central axis 1a. In addition, it can also be formed as a mesh-like pattern in which the first microgrooves extending in the direction of the central axis 1a intersect with the first microgrooves extending in the circumferential direction.

[0048] In this example, a small gap 22 having the same gap size is formed in the gap portion 21 that communicates with the outside of the device from the ball bearing 6 side (lubricant sealing portion 26 side). Figure 2 As shown in (e), instead of the minute gap 22, a minute gap 22A whose gap size gradually decreases from the lubricant sealing portion 26 side toward the outside of the device may be provided. For example, the inner peripheral end surface portion 2d of the partition plate portion 2c may be a tapered inner peripheral end surface portion. In this case, at least the minimum gap size of the minute gap 22A may be set to a value smaller than the particle size of the lubricant spheroidized on the oleophobic surface.

[0049] Figure 3Schematic diagram showing the effect of the lubricant sealing structure of this example. The lubricant flows out from the ball bearing 6 side inside the device through the gap portion 21 between the hollow input shaft 4 and the end plate 2 and toward the sealing portion formed by the oil seal 20. The outer peripheral surface portion 4c of the hollow input shaft 4 is an oil-repellent surface throughout the entire circumference. The lubricant flowing out from the ball bearing 6 side is repelled by the oil-repellent surface and is transformed into spherical particles before invading the tiny gap 22. The tiny gap 22 is smaller than the diameter of the spherical lubricant particles 25 formed, so the lubricant can be prevented from flowing into the tiny gap 22. The lubricant can be prevented from passing through the tiny gap 22 and reaching the sealing portion of the oil seal 20 (the lip front end surface 20c of the sealing lip and the outer peripheral surface portion 4b of the hollow input shaft 4). As a result, the sealing effect of the oil seal 20 can be maintained.

[0050] An oil film forming surface is formed over the entire circumference of the outer peripheral surface portion 4b of the hollow input shaft 4 on which the lip front end surface 20c of the oil supply seal 20 slides. The oil film forming surface has a dynamic pressure generating effect of forming a highly rigid oil film of the lubricant (grease for sealing lip) between the lip front end surface 20c and the outer peripheral surface portion 4b of the hollow input shaft 4. Alternatively, the oil film forming surface has an oil film retaining effect of retaining the lubricant (grease for sealing lip) so that an oil film of a desired thickness can be formed. Therefore, it is possible to prevent the oil film from being short at the sealing portion, and to prevent the sealing performance from being reduced due to wear of the sliding portion. In addition, since it is possible to prevent wear of the sliding portion, it is possible to maintain the interference between the lip front end surface 20c and the outer peripheral surface portion 4b of the hollow input shaft 4.

[0051] The lubricant sealing structure including the oil seal 30 formed at the other axial end portion of the hollow input shaft 4 is formed in the same structure as the lubricant sealing structure including the oil seal 20 described above and is formed in a substantially symmetrical structure with the lubricant sealing structure.

[0052] (Lubricant sealing structure between outer ring 12 and inner ring 13 of cross roller bearing 11)

[0053] Next, a lubricant sealing structure including the oil seal 40 that seals the gap between the outer ring 12 and the inner ring 13 of the cross roller bearing 11 will be described. Figure 4 (a) is an explanatory diagram showing a lubricant sealing structure including an oil seal 40 for sealing between the outer ring 12 and the inner ring 13, Figure 4 (b) is a half cross-sectional view showing a portion of the wave gear device where a lubricant seal structure including an oil seal 40 is incorporated. Figure 4 (c) is a schematic diagram showing an oleophobic surface, Figure 4 (d) is a schematic diagram showing the oil film forming surface.

[0054] A gap portion 41 is formed between the inner circumferential surface portion 12a of the outer ring 12 and the outer circumferential surface portion 13a of the inner ring 13 opposite to the inner circumferential surface portion 12a. The gap portion 41 is connected to the outside of the device from the track groove 14. The gap portion 41 is sealed by the oil seal 40. The oil seal 40 includes an annular seal 40a made of elastic material, the seal 40a is embedded in and fixed to the inner circumferential surface portion 12a of the outer ring 12, and the lip front end surfaces 40c and 40d of the sealing lip 40b (main lip, auxiliary lip) of the seal 40a are pressed against the outer circumferential surface portion 13a of the inner ring 13 in a slidable manner.

[0055] The outer peripheral surface portion 13a of the inner ring 13 and the outer peripheral surface portion 13b on the track groove 14 side are oil-repellent surfaces and have a surface texture in which the first fine grooves 43 are formed in a predetermined pattern. Figure 4 In (a), the formation range of the oil-repellent surface is indicated by a fine dot pattern. The outer peripheral surface portion 13c where the lip front end surfaces 40c and 40d of the oil seal 40 slide is an oil film retaining surface, and the second fine grooves 44 have a surface texture formed in a predetermined pattern. Figure 4 In (a), the formation range of the oil film forming surface is indicated by a relatively thick dot pattern. The inner peripheral surface portion 12b is formed on the inner peripheral surface portion 12a of the outer ring 12 and is opposite to the outer peripheral surface portion 13b as an oil-repellent surface at a slight interval. A slight gap 42 is formed between them. The inner peripheral surface portion 12b can also be an oil-repellent surface with the first fine grooves formed in a predetermined pattern over the entire circumference.

[0056] For example, Figure 4 As shown in (c), the first fine grooves 43 are grooves extending in the direction of the central axis 1a and are formed at constant intervals over the entire circumference of the outer peripheral surface portion 13b. The first fine grooves 43 have a groove width and a groove depth of several micrometers to several tens of nanometers and are formed on the oleophobic surface at intervals of several micrometers to several tens of nanometers.

[0057] In addition, if Figure 4 As shown in (d), the second fine groove 44 is a groove extending in the circumferential direction and is formed at a constant interval in the direction of the central axis 1a. The second fine groove 44 has a groove width and a groove depth of several micrometers to tens of nanometers, and is formed on the oil film forming surface at intervals of several micrometers to tens of nanometers. The oil film forming surface can be formed over the entire circumference of the outer peripheral surface portion 13c of the inner ring 13. It can also be formed in a partial area of ​​the outer peripheral surface portion 13c. Alternatively, sometimes the groove machined surface on which the second fine groove 44 is formed and the groove unmachined surface on which the groove is not formed are alternately formed in the circumferential direction on the outer peripheral surface portion 13c.

[0058] In addition, a small gap 42 having the same gap size is formed in the gap portion 41 that communicates from the track groove 14 to the outside of the device. Figure 4As shown in (e), instead of the minute gap 42, a minute gap 42a whose gap size gradually decreases from the track groove 14 side (lubricant sealing part side) toward the oil seal 40 side (device outside side) may be configured. For example, the inner peripheral surface portion 12b of the outer ring 12 can be a tapered inner peripheral end surface portion. At least the minimum gap size of the minute gap 42a can be set to a value smaller than the particle size of the lubricant spheroidized on the oil-repellent surface.

[0059] The lubricant flows out from the track groove 14 side of the cross roller bearing 11 inside the device through the gap portion 41 between the outer ring 12 and the inner ring 13 and toward the sealing portion formed by the oil seal 40. The lubricant flowing out from the cross roller bearing 11 side is repelled by the oil-repellent surface and is transformed into spherical particles before invading the tiny gap 42. The tiny gap 42 is smaller than the diameter of the spherical lubricant particles formed, so the lubricant can be prevented from flowing into the tiny gap 42. The lubricant can be prevented from passing through the tiny gap 42 and reaching the sealing portion of the oil seal 40 (the sliding portion between the lip front end faces 40c, 40d of the sealing lip and the outer peripheral surface portion 13c of the inner ring 13). As a result, the sealing effect of the oil seal 40 can be maintained.

[0060] In addition, an oil film forming surface is formed over the entire circumference of the outer peripheral surface portion 13c of the inner ring 13 on which the lip front end surfaces 40c and 40d of the oil seal 40 slide. The oil film forming surface has a dynamic pressure generating effect of forming a highly rigid oil film of the lubricant (grease for the sealing lip) between the lip front end surfaces 40c and 40d and the outer peripheral surface portion 13c of the inner ring 13. Alternatively, the oil film forming surface has an oil film retaining effect of retaining the lubricant (grease for the sealing lip) so that an oil film of a desired thickness can be formed. Therefore, it is possible to prevent the oil film from being short at the sealing portion, and to prevent the sealing performance from being reduced due to wear of the sliding portion.

[0061] [Implementation Method 2]

[0062] Figure 5 (a) is a schematic longitudinal sectional view showing an actuator having a lubricant seal structure according to the present invention, Figure 5 (b) is a partial enlarged view showing a portion where a lubricant seal structure is assembled. Figure 5 (c) is a partial enlarged view showing another portion where the lubricant seal structure is assembled.

[0063] The actuator 100 is a hollow type actuator having a hollow portion extending through the center thereof, and includes a motor 110 and a wave gear device 120. The motor 110 includes a hollow motor shaft 111, a rotor 112 mounted on the outer peripheral surface of the hollow motor shaft 111, and a stator 113 coaxially surrounding the rotor 112. Both ends of the hollow motor shaft 111 are rotatably supported by a motor housing 116 via ball bearings (only one ball bearing 114 is shown in the figure).

[0064] A large-diameter mounting flange 117 is provided at the front end of the motor housing 116. A wave gear device 120 is coaxially mounted on the front surface of the mounting flange 117. The wave gear device 120 includes: a rigid internal gear 121; a top-hat-shaped flexible external gear 122; a wave generator 123; a cross roller bearing 124 that supports the internal gear 121 and the external gear 122 in a state of relative free rotation; and a disc-shaped output shaft 125.

[0065] The wave generator 123 includes a hollow input shaft 126 coaxially connected to the hollow motor shaft 111, and a plug 127 having an elliptical profile is integrally formed on the outer peripheral surface of the hollow input shaft 126. A wave bearing 128 is mounted on the elliptical outer peripheral surface of the plug 127. The cylindrical body portion of the external gear 122 having the external teeth 122a formed thereon is bent into an elliptical shape by the wave generator 123, so as to partially mesh with the internal teeth 121a of the internal gear 121.

[0066] The annular boss 122c of the external gear 122 is sandwiched between the mounting flange 117 and the outer ring 124b of the cross roller bearing 124, and in this state, the three components are fastened and fixed. The internal gear 121 is sandwiched between the inner ring 124a of the cross roller bearing 124 and the output shaft 125, and in this state, the three components are fastened and fixed. The output rotation of the motor 110 is input to the wave generator 123 from the hollow motor shaft 111. When the wave generator 123 rotates, the internal gear 121 is decelerated, and the decelerated rotation is output from the output shaft 125 connected to the internal gear 121 to the load side (not shown).

[0067] The lubricated parts inside the wave gear device 120 are the meshing part between the external gear 122 and the internal gear 121, the contact part between the external gear 122 and the wave generator 123, the wave bearing 128 of the wave generator 123, the cross roller bearing 124, etc. In order to prevent the lubricant from leaking from the lubricant sealing parts 131 and 132 inside the wave gear device 120 to the outside of the device or the motor 110 side, the lubricant sealing structure including the oil seal 140, the lubricant sealing structure including the oil seal 150, and the lubricant sealing structure including the oil seal 160 are assembled in the wave gear device 120.

[0068] (Lubricant sealing structure between the hollow input shaft 126 and the output shaft 125)

[0069] like Figure 5As shown in (b), in the wave gear device 120, the hollow input shaft 126 rotating at high speed and the output shaft 125 rotating at reduced speed are sealed by a lubricant sealing structure having an oil seal 140. The internal space of the external gear 122 provided with the wave bearing 128 is a lubricant sealing portion 131 in which the lubricant supplied to the wave bearing 128 and the sliding portion between the wave bearing 128 and the external gear 122 is sealed. Between the hollow input shaft 126 and the output shaft 125, a gap portion 141 is formed that communicates from the wave bearing 128 located on the inside of the device to the outside of the device. The end of the gap portion 141 on the outside of the device is sealed by the oil seal 140.

[0070] An end surface portion 126a and an outer peripheral surface portion 126b are formed at the end portion of the hollow input shaft 126. A protruding portion 125a protruding toward the end surface portion 126a is formed at the inner peripheral edge portion of the output shaft 125. An oil seal 140 is mounted between the protruding portion 125a and the outer peripheral surface portion 126b of the hollow input shaft 126. A seal 140a of the oil seal 140 is embedded and fixed to the inner peripheral surface portion of the protruding portion 125a of the output shaft 125. A lip front end surface 140c of a seal lip 140b of the seal 140a is pressed against the outer peripheral surface portion 126b of the hollow input shaft 126 in a slidable manner.

[0071] In addition, the front end face 125b of the protruding portion 125a of the output shaft 125 is opposed to the end face portion 126a of the hollow input shaft 126 with a small gap in the direction of the central axis 100a. A small gap portion 142 is formed between the front end face 125b and the end face portion 126a. The gap size of the small gap portion 142 is constant, but the gap size may be gradually reduced from the wave bearing 128 side toward the oil seal 140 side.

[0072] The entire end surface portion 126a of the hollow input shaft 126 and the portion up to the middle of the outer peripheral surface portion 126b are oil-repellent surfaces formed with the first fine grooves. The portion of the outer peripheral surface portion 126b where the lip tip surface 140c of the seal lip 140b of the oil supply seal 140 slides is an oil film forming surface formed with the second fine grooves. In addition, in the protruding portion 125a of the output shaft 125, its tip surface 125b and the outer peripheral surface portion 125c of a constant width connected to the tip surface 125b are oil-repellent surfaces formed with the first fine grooves.

[0073] Each oleophobic surface has a surface texture in which first fine grooves are formed in a predetermined pattern so as to obtain oleophobicity for the lubricant sealed in the lubricant sealing portion 131. The first fine grooves have a groove width and a groove depth of several micrometers to several tens of nanometers, and are formed on the oleophobic surface at intervals of several micrometers to several tens of nanometers. In addition, the gap size of the micro-gap portion is set to a value smaller than the diameter of the spherical lubricant formed on the oleophobic surface.

[0074] On the other hand, the oil film forming surface has a surface texture in which second fine grooves are formed in a predetermined pattern so as to obtain an oil film forming effect. The second fine grooves have a groove width and a groove depth of several micrometers to several tens of nanometers and are formed on the oil film forming surface at intervals of several micrometers to several tens of nanometers. Figure 5 In (b), the formation ranges of the oil-repellent surface and the oil film-forming surface are shown in a dot pattern.

[0075] The lubricant flows from the wave bearing 128 side inside the device through the gap portion 141 between the hollow input shaft 126 and the output shaft 125 toward the sealing portion formed by the oil seal 140. The lubricant is repelled by the outer peripheral surface portion 125c which is an oil-repellent surface and is deformed into spherical particles before invading the micro-gap portion 142. The micro-gap portion 142 is smaller than the particle size of the formed spherical lubricant and is defined by the oil-repellent surface. Therefore, the lubricant can be prevented from flowing into the micro-gap portion, and the lubricant can be prevented from reaching the sealing portion of the oil seal 140 (the sliding portion between the lip front end surface 140c of the sealing lip and the outer peripheral surface portion 126c of the hollow input shaft 126). As a result, the sealing effect of the oil seal 140 can be maintained.

[0076] In addition, an oil film forming surface is formed over the entire circumference of the outer peripheral surface portion 126c of the hollow input shaft 126 where the lip front end surface 140c of the oil supply seal 140 slides. The oil film forming surface has a dynamic pressure generating effect of forming a highly rigid oil film of the lubricant (grease for the sealing lip) between the lip front end surface 140c and the outer peripheral surface portion 126c. Alternatively, the oil film forming surface has an oil film retaining effect of retaining the lubricant (grease for the sealing lip) so that an oil film of a desired thickness can be formed. Therefore, it is possible to prevent the oil film from being short at the sealing portion, and it is possible to prevent the sealing performance from being reduced due to wear of the sealing lip 140b of the seal 140a as a sliding component.

[0077] (Lubricant Sealing Structure Between Wave Gear Device 120 and Motor 110)

[0078] Figure 5 The lubricant sealing structure with the oil seal 150 shown in (c) can prevent the lubricant from leaking from the wave gear device 120 side to the motor 110 side. The ball bearing 114 is mounted between the inner peripheral edge portion 117a of the mounting flange 117 as a fixing member and the shaft end portion of the hollow motor shaft 111 facing the inner peripheral edge portion 117a. The front end of the shaft end portion of the hollow motor shaft 111 passes through the mounting flange 117 from the mounting portion of the ball bearing 114 and protrudes toward the wave gear device 120 side.

[0079] A gap portion 151a communicating with the wave gear device 120 side is formed between the outer peripheral surface portion 111a of the shaft end portion of the hollow motor shaft 111 and the inner peripheral surface portion 117b of the inner peripheral edge portion of the mounting flange 117. A minute gap portion 151b communicating with the gap portion 151a is formed between the end surface portion 117c on the wave gear device 120 side of the inner peripheral edge portion of the mounting flange 117 and the end surface portion 126d of the hollow input shaft 126 of the wave gear device 120. The lubricant sealing portion 131 inside the wave gear device 120 communicates with the inside of the motor 110 via the minute gap portion 151b and the gap portion 151a. The gap size of the minute gap portion 151b is constant, but the gap size may be gradually reduced from the motor 110 side toward the wave gear device 120 side.

[0080] The gap 151a is sealed by the oil seal 150. The seal 150a of the oil seal 150 is fitted and fixed to the inner peripheral surface 117b of the mounting flange 117. The lip front end surfaces 150b and 150c of the seal lip of the seal 150a are slidably pressed against the outer peripheral surface 111a of the hollow motor shaft 111.

[0081] The end surface portion 117c of the mounting flange 117 is an oil-repellent surface formed with the first fine groove. The end surface portion 126d of the hollow input shaft 126 opposite thereto is also an oil-repellent surface formed with the first fine groove. In addition, the outer peripheral surface portion 126e of the hollow input shaft 126 with a constant width connected to the end surface portion 126d is also an oil-repellent surface formed with the first fine groove. On the other hand, the outer peripheral surface portion 111a of the hollow motor shaft 111 on which the lip front end surfaces 150b and 150c of the oil supply seal 150 slide is an oil film forming surface formed with the second fine groove.

[0082] Each oleophobic surface has a surface texture in which first fine grooves are formed in a predetermined pattern so as to obtain oleophobicity for the lubricant sealed in the lubricant sealing portion 131. The first fine grooves have a groove width and a groove depth of several micrometers to several tens of nanometers, and are formed on the oleophobic surface at intervals of several micrometers to several tens of nanometers. In addition, the gap size of the micro-gap portion is set to a value smaller than the diameter of the spherical lubricant formed on the oleophobic surface.

[0083] The oil film forming surface has a surface texture with second fine grooves formed in a predetermined pattern so as to obtain an oil film forming effect. The second fine grooves have a groove width and a groove depth of several micrometers to several tens of nanometers and are formed on the oil film forming surface at intervals of several micrometers to several tens of nanometers. Figure 5 In (c) , the formation ranges of the oil-repellent surface and the oil film-forming surface are also shown in a dot pattern.

[0084] The lubricant flows out from the inside of the wave gear device 120 through the minute gap portion 151b and the gap portion 151a and toward the motor 110 side. The gap portion 151a is sealed by the oil seal 150. In addition, the lubricant is repelled by the outer peripheral surface portion 126e, the end surface portion 126d, and the end surface portion 117c, which are oil-repellent surfaces, and is transformed into spherical particles before invading the minute gap portion 151b. The minute gap portion 151b is smaller than the particle size of the formed spherical lubricant, so the lubricant can be prevented from flowing into the minute gap portion 151b. The lubricant can be prevented from reaching the sealing portion of the oil seal 150 (the sliding portion between the lip front end surfaces 150b and 150c of the oil seal 150 and the outer peripheral surface portion 111a of the hollow motor shaft 111). As a result, the sealing effect of the oil seal 150 can be maintained.

[0085] In addition, an oil film forming surface is formed over the entire circumference of the portion of the outer peripheral surface portion 111a of the hollow motor shaft 111 where the lip front end surfaces 150b and 150c of the oil supply seal 150 slide. The oil film forming surface has a dynamic pressure generating effect of forming a highly rigid oil film of the lubricant (grease for sealing lips) between the lip front end surfaces 150b and 150c and the outer peripheral surface portion 111a. Alternatively, the oil film forming surface has an oil film retaining effect of being able to retain the lubricant (grease for sealing lips) so that an oil film of a desired thickness can be formed. Therefore, it is possible to prevent the oil film from being short at the sealing portion, and to prevent the sealing performance from being reduced due to wear of the sealing lip of the seal 150a as a sliding component. In addition, the interference between the lip front end surfaces 150b and 150c and the outer peripheral surface portion 111a of the hollow motor shaft 111 can be maintained.

[0086] In addition, the lubricant sealing structure composed of the oil seal 160 in the wave gear device 120 is arranged in the portion of the cross roller bearing 124 that supports the external gear 122 and the internal gear 121 so that they can rotate freely relative to each other. In other words, it is arranged to seal the gap between the inner ring 124a and the outer ring 124b of the cross roller bearing 124. This lubricant sealing structure is different from the one used in the first embodiment. Figure 4 The lubricant sealing structure of the oil seal 40 shown is substantially the same, so the detailed description is omitted.

Claims

1. A lubricant sealing structure for preventing lubricant from leaking out from inside the device through a gap between a first component and a second component in a device having a first component and a second component that rotate relative to each other about a central axis, The lubricant sealing structure comprises: a first surface portion of the first member and a second surface portion of the second member, which form the gap portion; an oil seal fixed to the first surface portion and sealing the gap portion while being in slidable contact with the second surface portion; an oil-repellent surface formed on at least one of the first surface portion and the second surface portion and located closer to the inside of the device than the oil seal; as well as an oil film forming surface formed on at least one of a front end surface portion of the oil seal that contacts the second surface portion and a portion of the second surface portion that contacts the front end surface portion, The oil-repellent surface has a surface texture in which first fine grooves are formed in a predetermined pattern so as to obtain an oil-repellent effect on the lubricant. The first fine grooves have a groove width and a groove depth of several micrometers to several tens of nanometers, and are formed on the oleophobic surface at intervals of several micrometers to several tens of nanometers. The oil film forming surface has a surface texture in which second fine grooves are formed in a predetermined pattern so as to obtain an oil film forming effect. The second fine grooves have a groove width and a groove depth of several micrometers to several tens of nanometers, and are formed on the oil film forming surface at intervals of several micrometers to several tens of nanometers. A minute gap portion is formed in the gap portion and at a location closer to the inside of the device than the oil seal. The oleophobic surface is formed on at least one of the first surface portion and the second surface portion, on a surface portion from a position closer to the inside of the device than the minute gap portion to the minute gap portion, and on a surface portion forming the minute gap portion, The second fine groove of the oil film forming surface is a groove extending in the circumferential direction around the central axis. The first fine grooves of the oil-repellent surface are grooves extending in the direction of the central axis.

2. The lubricant sealing structure according to claim 1, characterized in that: The first fine groove is formed on the entire oleophobic surface, The second fine groove is formed on the entire or a part of the oil film forming surface, or a groove processed surface on which the second fine groove is formed and a groove unprocessed surface on which the second fine groove is not formed are alternately formed.

3. A wave gear device, comprising: Input shaft; A wave gear mechanism that reduces the speed of rotation of the input shaft and outputs the speed; a device housing that supports the input shaft in a rotatable state via a bearing; as well as The lubricant seal structure according to claim 1, which prevents the lubricant from leaking from the inside of the device to the outside through the gap portion formed between the inner peripheral surface portion of the device housing and the outer peripheral surface portion of the input shaft; The device housing is the first component, and the inner peripheral surface of the device housing is divided into the first surface portion. The input shaft is the second member, and the outer peripheral surface portion of the input shaft is divided into the second surface portion.

4. A wave gear device, comprising: A roller bearing that supports a rigid internal gear and a flexible external gear so that they can rotate freely relative to each other; and The lubricant seal structure according to claim 1, which prevents the lubricant from leaking to the outside through a gap portion formed between the inner peripheral surface portion of the outer ring of the roller bearing and the outer peripheral surface portion of the inner ring; The outer ring is the first component, and the inner peripheral surface of the outer ring is divided into the first surface portion. The inner ring is the second member, and the outer peripheral surface of the inner ring is divided into the second surface portion.

5. A wave gear device comprising an input shaft, a wave gear reduction mechanism for reducing the rotation of the input shaft, and an output shaft for outputting the reduced rotation; The wave gear device further comprises a lubricant seal structure according to claim 1, which prevents lubricant from leaking from the inside of the wave gear device to the outside through a gap portion formed between a first surface portion of the output shaft and a second surface portion of the input shaft opposed to the first surface portion. The output shaft is the first member, and the input shaft is the second member.

6. An actuator, comprising: motor; a wave gear device coaxially mounted on a mounting flange provided at a front end of the motor; a motor shaft that passes through the mounting flange and extends inside the wave gear device; an input shaft coaxially connected to the front end portion of the motor shaft inside the wave gear device; as well as The lubricant seal structure according to claim 1, which prevents the lubricant from leaking from the wave gear device into the interior of the motor through a gap portion formed between a first surface portion of the inner peripheral edge portion of the mounting flange and second surface portions of the motor shaft and the input shaft that are opposed to the first surface portion; The mounting flange is the first member, and the motor shaft and the input shaft are the second member.

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