Powder lubrication method of strain wave gear device

Abstract

A powder lubrication mechanism (20) including a nozzle (24A) for injecting a solid lubricant powder in an aerosol state to a lubrication portion is incorporated into an inner space (10) of an external gear (3) of a strain wave gear device (1A). When a wave generator (4) is rotating, that is, when the strain wave gear device (1A) is operating, the solid lubricant powder in an aerosol state is injected from the nozzle (24A) toward a contact part (11), that is, the lubrication portion, so as to form a state in which an appropriate amount of the solid lubricant powder is supplied to the contact part (11), and this state is maintained. The lifespan of the strain wave gear device (1A), which is powder-lubricated, can be increased while maintaining the high efficiency state of the strain wave gear device (1A).

Description

Powder lubrication method for strain wave gear device

[0001] The present invention relates to a wave gear device, and more particularly to a powder lubrication method for a wave gear device in which solid lubricant powder is supplied in an aerosol state to lubricate contact surfaces and the like.

[0002] In Patent Documents 1 and 2, the inventors proposed a powder lubrication method in which the contact surfaces of components in a wave gearing device are lubricated with solid lubricant powder sealed or filled inside the device. In the wave gearing device described in Patent Document 1, the internal space of the external gear is filled with fine powder of an ionic compound with a layered structure as the solid lubricant. During operation of the wave gearing device, the filled fine powder is crushed between the contact surfaces of the lubricating objects, transferring to both contact surfaces and forming a thin surface film (transfer film). It is also rolled into a thin film and further fragmented, changing its shape to one that easily penetrates the contact surfaces. Lubrication is maintained by the deformed fine powder and the thin surface film (transfer film) formed on the contact surfaces. Because the rolled and fragmented fine powder and transfer film are non-viscous, viscous resistance loss is eliminated, enabling high-efficiency operation at low loads and high speeds. The wave gearing device described in Patent Document 2 is equipped with a mechanism for efficiently directing the fine powder of solid lubricant sealed or filled inside the external gear to the areas to be lubricated.

[0003] Tests conducted by the inventors have shown that the durability life of a wave gearing lubricated by a solid lubricant coating or a transferred film of solid lubricant powder is finite and is greatly influenced by the amount of micropowder used, and that if an appropriate amount is not filled, the life will be short.In other words, it is necessary to supply solid lubricant powder while the wave gearing is in operation to repair the worn coating (solid lubricant coating or transferred film) and restore an appropriate lubrication state.

[0004] When using fine solid lubricant powder with a layered structure, the fine powder is introduced into the gaps between the contact surfaces by cleavage forces, where it is rolled into a thin layer and further broken down, resulting in a temporary loss of torque, which causes a drop in efficiency. The extent and frequency of this efficiency drop are affected by various factors, including the atmosphere during operation of the strain wave gearing device, the properties of the fine powder used (load-bearing capacity, friction coefficient, cohesion, etc.), the amount of fill, and particle size. In particular, when a large amount of fine powder is supplied to the gaps between the contact surfaces of a wave generator rotating at high speed, the loss of torque causes a significant drop in efficiency, hindering stable operation of the strain wave gearing device.

[0005] In Patent Document 3, the present inventors have proposed a powder lubrication method for a wave gearing device that can continuously supply an appropriate amount of solid lubricant powder to lubrication points such as the contact surfaces of a wave generator in order to suppress a decrease in efficiency caused by torque loss that occurs when a large amount of solid lubricant powder is supplied to points to be lubricated. In this method, a pressed product of solid lubricant powder is placed inside the wave gearing device, and when the wave gearing device is in operation, a friction plate is brought into frictional contact with the pressed product to generate solid lubricant wear powder, which then lubricates the lubricated points of the wave gearing device.

[0006] International Publication No. WO 2016 / 084235 International Publication No. WO 2016 / 113847 International Publication No. WO 2023 / 026376

[0007] According to the method proposed in Patent Document 3, a large amount of solid lubricant powder does not get into the lubrication areas, such as between contact surfaces, at one time, so the wave gear device can be maintained in a stable operating state.

[0008] An object of the present invention is to propose a powder lubrication method for a wave gearing device that controls the supply of solid lubricant powder to the lubrication parts of the wave gearing device more accurately than before, thereby making it possible to maintain an appropriate lubrication state of the lubricated parts by a solid lubricant film, and to provide a wave gearing device using this method.

[0009] In order to solve the above problems, the powder lubrication method for a wave gear device of the present invention supplies solid lubricant powder in the form of an aerosol toward lubrication locations of a wave gear device, and lubricates the lubrication locations using the solid lubricant powder that has reached the lubrication locations. The aerosol contains the solid lubricant powder with a particle size of 20 μm or less as a solid phase, and a liquefied gas or compressed gas as a gas phase, and the solid lubricant powder is molybdenum disulfide (MoS ２ ), tungsten disulfide (WS ２ ), and polytetrafluoroethylene (PTFE), or a mixture of at least two of these powders.

[0010] Furthermore, a wave gearing device of the present invention comprises: a rigid internal gear; a flexible external gear arranged coaxially inside the internal gear; a wave generator arranged coaxially inside the external gear; a lubrication portion where the inner peripheral surface of the external gear and the outer peripheral surface of the wave generator come into contact; and a powder lubrication mechanism that supplies solid lubricant powder in an aerosol state toward the lubrication portion to form a solid lubricant film on the lubrication portion, wherein the aerosol contains, as a solid phase, the solid lubricant powder having a particle size of 20 μm or less, and as a gas phase, a liquefied gas or a compressed gas.

[0011] Here, the solid lubricant powder is molybdenum disulfide (MoS ２ ), tungsten disulfide (WS ２ ), and polytetrafluoroethylene (PTFE), or a mixture of at least two of these powders can be used.

[0012] In the wave gear device of the present invention, in order to be able to supply an appropriate amount of aerosol (solid lubricant powder) to the lubrication portion at the appropriate timing, the powder lubrication mechanism comprises a nozzle that sprays the aerosol toward the lubrication portion, a supply path that guides the aerosol to the nozzle, and a valve mechanism that opens and closes the nozzle or adjusts the opening degree.

[0013] In the wave gear device of the present invention, the powder lubrication mechanism further includes an aerosol generator that generates the aerosol that is introduced to the nozzle via the supply path. The aerosol generator can be incorporated inside the external gear. Alternatively, the aerosol generator can be an external component, and the aerosol can be introduced from outside into the nozzle located inside the wave gear device.

[0014] The wave generator of the wave gear device comprises, for example, a rigid wave plug and a wave bearing mounted on the elliptical outer peripheral surface of the wave plug, the wave bearing being a rolling bearing with a plurality of rolling elements mounted in a rollable state between the outer ring and the inner ring. In order to prevent the solid lubricant powder contained in the aerosol sprayed from the nozzle from directly adhering to the outer ring raceway surface and the inner ring raceway surface, it is desirable that the wave generator be provided with a shielding plate that blocks the flow of the aerosol from the nozzle toward the respective rolling element raceway surfaces of the outer ring and the inner ring.

[0015] In the present invention, instead of pre-filling or disposing fine powder of solid lubricant inside the wave gearing, the solid lubricant powder is supplied in an aerosol state to the lubrication points inside the wave gearing. The solid lubricant powder remains in an aerosol state near the lubrication points for a long period of time. The solid lubricant powder penetrates and transfers between the contact surfaces of the lubricated points, repairing the solid lubricant film formed on the lubricated points. Unlike when the solid lubricant powder is supplied to the lubricated points by scattering or diffusing it inside the wave gearing, the supply of the solid lubricant to the lubricated points can be precisely controlled by controlling the supply flow rate of the aerosol, and the lubrication state of the lubricated points can be maintained in an appropriate state. Furthermore, because the solid lubricant is supplied in an aerosol state, the appropriate amount of solid lubricant powder can be supplied to the lubricated points at the required time, thereby maintaining an appropriate lubrication state provided by the solid lubricant film and extending the life of the wave gearing.

[0016] 1A is a schematic vertical cross-sectional view showing a wave gear device according to a first embodiment to which the present invention is applied; FIG. 1B is a schematic vertical cross-sectional view showing a modified example of the wave gear device of FIG. 1A; and FIG. 1C is a schematic vertical cross-sectional view showing a wave gear device according to a second embodiment to which the present invention is applied.

[0017] Hereinafter, embodiments of a wave gear device to which the present invention is applied will be described with reference to the drawings. Note that the following embodiments are merely examples of the present invention and are not intended to limit the present invention to the embodiments.

[0018] 1A is a schematic longitudinal cross-sectional view showing an example of a strain wave gearing to which the present invention is applied. The strain wave gearing 1A includes an annular, rigid internal gear 2, a cup-shaped, flexible external gear 3, and a wave generator 4 with an elliptical contour. The external gear 3 is arranged coaxially inside the internal gear 2. The strain wave gearing 1A is installed in a vertical position, for example, with its axis 1a extending vertically and the open end of the cup-shaped external gear 3 facing upward.

[0019] The external gear 3 has a cylindrical body 3a that is flexible in the radial direction, and external teeth 3b are formed on the outer peripheral surface portion of the open end of this cylindrical body 3a. A diaphragm 3c is formed on the opposite end of the cylindrical body 3a, extending radially inward. An annular, rigid boss 3d is formed on the inner peripheral edge of the diaphragm 3c. The boss 3d is sandwiched between an annular pressing member 5 and the device housing 6, and in this state, the boss 3d is fastened to the device housing 6 by a plurality of fastening bolts 7.

[0020] The wave generator 4 comprises a rigid wave plug 4a and a wave bearing 4b (wave generator bearing) mounted on the outer peripheral surface of the elliptical contour of the wave plug. The wave bearing 4b comprises a flexible inner ring 4c, a flexible outer ring 4d, a plurality of balls 4e mounted between the inner and outer rings, and a cage 4f that holds the balls 4e at predetermined angular intervals in the circumferential direction. The wave generator 4 is mounted inside the portion of the cylindrical body portion 3a of the external gear 3 where the external teeth 3b are formed.

[0021] The strain wave gear device 1A is used as a reducer. For example, the internal gear 2 is coaxially connected and fixed to an output shaft 8 located above, the wave generator 4 is connected and fixed to an input shaft 9 such as a motor rotating shaft located above, and the external gear 3 is fixed to a device housing 6, which is a fixed member located below. High-speed rotation input to the wave generator 4 is significantly reduced via the external gear 3 and the internal gear 2, and the reduced rotation is output from the internal gear 2 to the output shaft 8.

[0022] (Powder Lubrication Mechanism) Here, lubrication inside the wave gear device 1A is achieved by a solid lubricant coating or a transferred film of solid lubricant powder. The main lubricated parts inside the wave gear device 1A include the meshing contact portion (tooth portion) 11 between the internal gear 2 and the external gear 3, and the contact portion 12 between the inner circumferential surface 3f of the cylindrical body portion 3a of the external gear 3 and the outer ring outer circumferential surface 4g of the wave generator 4. The contact surfaces of the contact portion 12 (inner circumferential surface 3f, outer ring outer circumferential surface 4g) communicate with an inner space 10 of the external gear 3. The inner space 10 is the space between the diaphragm 3c and the wave generator 4 inside the cylindrical body portion 3a of the external gear 3.

[0023] The wave gear drive 1A is equipped with a powder lubrication mechanism 20A that supplies solid lubricant powder in the form of an aerosol to the internal lubrication parts. The powder lubrication mechanism 20A sprays the solid lubricant powder in the form of an aerosol toward the contact part 12, which is the lubrication part. The solid lubricant powder 22 contained in the sprayed aerosol 21 is supplied to the contact part 12, lubricating each contact surface (3f, 4g) of the contact part 12. The meshing contact part 11 is also lubricated by the solid lubricant powder 22 that passes between the contact part 12 and the inner and outer rings of the wave bearing 4b and wraps around to the meshing contact part (tooth part) 11.

[0024] The aerosol 21 sprayed from the powder lubrication mechanism 20A contains, as a solid phase, solid lubricant powder 22 having a particle size of 20 μm or less, and, as a gas phase, liquefied gas or compressed gas 23. The solid lubricant powder 22 is molybdenum disulfide (MoS ２ ), tungsten disulfide (WS ２ ), and polytetrafluoroethylene (PTFE), or a mixture of at least two of these powders.

[0025] In this way, as the solid lubricant powder 22, fine powder of an ionic compound having a layered structure is supplied in the form of an aerosol toward the contact portion B, which is the lubrication portion, within the internal space 10 of the external gear 3. During operation of the wave gearing 1A, the solid lubricant powder 22 is crushed between the contact surfaces of the lubrication portion, transferred to both contact surfaces (3f, 4g), forming a thin surface film (transfer film). It is also rolled thinly and further subdivided, changing its shape to one that can easily penetrate into the contact surfaces. Lubrication is maintained by the changed shape of the solid lubricant powder 22 and the transfer film, which is a thin surface film formed on the contact surfaces (3f, 4g). Because the rolled and subdivided solid lubricant powder 22 and the transfer film are non-viscous, no viscous resistance loss occurs, enabling highly efficient operation at low loads and high speeds.

[0026] More specifically, the powder lubrication mechanism 20A includes a nozzle 24A that sprays the aerosol 21 toward the contact portion B, which is the lubrication site; a supply pipe 25A that guides the aerosol 21 to the nozzle 24A; and an aerosol generator 26A that supplies the aerosol to the nozzle 24A via the supply pipe 25A. The nozzle 24A and supply pipe 25A are incorporated into the inner space 10 of the external gear 3 of the harm gear device 1A, and the supply pipe 25A is attached to a frame 27A that is attached to the boss 3d of the external gear 3. The supply pipe 25A passes through the central opening of the boss 3d and is led out of the harm gear device 1 and connected to the external aerosol generator 26A via external piping 28A. In this example, two nozzles 24A are positioned at 180° angular intervals around the axis 1a. Each nozzle 24A sprays the aerosol 21 from a position below the contact portion B toward the contact portion 12, which is located diagonally upward and radially outward. The number of nozzles 24A may be three or more.

[0027] The external aerosol generator 26A is, for example, a spray type, and includes a pressure-resistant container 29A containing solid lubricant powder and liquefied gas or pressurized gas; a valve mechanism 30A consisting of an electromagnetic valve or the like that closes an aerosol outlet formed in the pressure-resistant container 29A; and a drive control unit 31A that controls the valve mechanism 30A to open, close, and adjust the aperture of the aerosol outlet. The drive control unit 31A opens and closes the aerosol outlet based on commands from, for example, a higher-level controller that controls the drive of the harm gear device 1A. For example, when the wave generator 4 is rotating, aerosol is supplied at a predetermined flow rate and sprayed from the nozzle 24A. Furthermore, an appropriate amount of aerosol (solid lubricant powder) can be supplied to the lubricated portion at the required timing depending on the lubrication state of the lubricated portion.

[0028] The aerosol generating mechanism may be a type that generates the aerosol by supplying a carrier gas (liquefied gas or pressurized gas) from the outside to a container in which the solid lubricant powder is sealed, instead of a spray type. The material of the container that must be pressure-resistant is preferably stainless steel, aluminum alloy, chemically stable resin, etc., taking into consideration light weight, the amount of gas released, etc.

[0029] Here, it is desirable to prevent the aerosol 21 (solid lubricant powder 22) sprayed from the nozzle 24A from being directly sprayed onto the outer ring raceway surface and inner ring raceway surface of the wave bearing 4b of the wave generator 4. In this example, the cage retainer 41 of the wave bearing 4b is used as a shielding plate to prevent the aerosol 21 from being directly sprayed onto the outer ring raceway surface and inner ring raceway surface.

[0030] The retainer retainer 41 is attached to the lower end surface of the wave plug 4a that faces the nozzle 24. The retainer retainer 41 has an elliptical contour so that it can cover and conceal the gap between the inner and outer rings of the wave bearing 4b, which is attached to the outer peripheral surface of the elliptical contour of the wave plug 4a and is elliptically bent. In other words, the elliptical contour shape of the retainer retainer 41 is set so that the gap between the inner and outer rings is covered and concealed by the retainer retainer 41 when viewed from the nozzle 24 side along the direction of the axis 1a.

[0031] The contact surfaces (3f, 4g) of the contact portion 12, which is the lubrication site, may be subjected to a surface treatment to promote the supply of lubricant powder to these contact surfaces and to promote the retention of solid lubricant powder on these contact surfaces. For example, surface texturing such as fine grooves extending parallel to the axis 1a at a fine pitch may be applied to one or both of these contact surfaces, i.e., the inner peripheral surface 3f of the cylindrical body portion 3a of the external gear 3 and the outer ring outer peripheral surface 4g of the wave generator 4.

[0032] (Modification) In the above-described strain wave gearing 1A, the aerosol generator 26A of the powder lubrication mechanism 20A is disposed outside the strain wave gearing. Alternatively, the aerosol generator 26A can also be built into the strain wave gearing 1A.

[0033] FIG. 1B is a schematic longitudinal cross-sectional view showing an example of a wave gearing device incorporating an aerosol generator for a powder lubrication mechanism. The basic configuration of the wave gearing device 1B shown in FIG. 1B is identical to that of the wave gearing device 1A described above, so corresponding components are designated by the same reference numerals and their description is omitted. In the wave gearing device 1B, a powder lubrication mechanism 20B is incorporated into the inner space 10 of the cup-shaped external gear 3. The powder lubrication mechanism 20B includes a nozzle 24B that sprays aerosol 21 toward the contact portion 12 (the lubrication portion), a valve mechanism 30B equipped with an electromagnetic valve or the like for opening and closing the nozzle 24B and adjusting its aperture, and a drive controller 31B for the valve mechanism 30B. An aerosol generator 26B supplies the aerosol 21 to the nozzle 24B via the valve mechanism 30B. In this example, two nozzles 24B are positioned at an angular interval of 180° around the axis 1a.

[0034] [Embodiment 2] Figure 2 is a schematic longitudinal cross-sectional view showing a wave gear device according to Embodiment 2 of the present invention. The wave gear device 100 of Embodiment 2 includes a rigid internal gear 102, a top-hat-shaped flexible external gear 103, and a wave generator 104 arranged inside the external gear 103. It also includes a hollow input shaft 105, end plates 106 and 107 on both sides, and a bearing 108 that supports the internal gear 102 and the external gear 103 in a relatively rotatable state. A plug 104a of the wave generator 104 is integrally formed on the outer peripheral surface of the hollow input shaft 105. The wave gear device 100 is used as a reducer. For example, the end plate 106 to which the external gear 103 is attached serves as a fixed device housing, and the end plate 107 attached to the internal gear 102 serves as an output shaft for reduced rotation.

[0035] Lubrication inside the wave gearing 100 is achieved by a solid lubricant coating or a transferred film of solid lubricant powder. The main lubricated parts inside the wave gearing 100 include the meshing contact portion (tooth portion) 111 between the internal gear 102 and the external gear 103, and a contact portion 112 between the inner circumferential surface 103f of the cylindrical body portion of the external gear 103 and the outer ring outer circumferential surface 104g of the wave generator 104. The contact surfaces (inner circumferential surface 103f, outer ring outer circumferential surface 104g) of the contact portion 112 communicate with an inner space 110 of the external gear 103. The inner space 110 is the space inside the cylindrical body portion of the external gear 103, between the hollow input shaft 105, the wave generator 104, and one of the end plates 106.

[0036] (Powder Lubrication Mechanism) The wave gear drive 100 is equipped with a powder lubrication mechanism 120 that supplies solid lubricant powder toward the internal lubrication parts. The powder lubrication mechanism 120 sprays the solid lubricant powder in an aerosol state toward the contact part 112, which is the lubrication part. The solid lubricant powder 122 contained in the sprayed aerosol 121 is supplied to the contact part 112, lubricating each contact surface (103 f, 104 g) of the contact part 112. The meshing contact part 111 is also lubricated by the solid lubricant powder 122 that passes between the contact part 112 and the inner and outer rings of the wave bearing 104 b and wraps around to the meshing contact part (tooth part) 111.

[0037] The aerosol 121 sprayed from the powder lubrication mechanism 120 contains, as a solid phase, solid lubricant powder 122 having a particle size of 20 μm or less, and, as a gas phase, liquefied gas or compressed gas 123. The solid lubricant powder 122 is molybdenum disulfide (MoS ２ ), tungsten disulfide (WS ２ ), and polytetrafluoroethylene (PTFE), or a mixture of at least two of these powders.

[0038] In this way, as the solid lubricant powder 122, fine powder of an ionic compound having a layered structure is supplied in an aerosol state toward the contact portion 112, which is the lubrication portion, within the internal space 110 of the external gear 103. During operation of the wave gearing device 100, the solid lubricant powder 122 is crushed between the contact surfaces of the lubricated portion and transferred to both contact surfaces (103f, 104g), forming a thin surface film (transfer film). It is also rolled thin and further subdivided, changing its shape to one that can easily penetrate into the contact surfaces. Lubrication is maintained by the changed shape of the solid lubricant powder 122 and the transfer film, which is a thin surface film formed on the contact surfaces (103f, 104g). Because the rolled and subdivided solid lubricant powder 122 and the transfer film are non-viscous, no viscous resistance loss occurs, enabling highly efficient operation at low loads and high speeds.

[0039] The powder lubrication mechanism 120 includes a nozzle 124 that sprays aerosol 121 toward the contact portion 112, which is the lubrication site, a supply pipe 125 that guides the aerosol 121 to the nozzle 124, and an aerosol generator 126 that supplies the aerosol to the nozzle 124 via the supply pipe 125. The nozzle 124 and supply pipe 125 are incorporated into the inner space 110 of the external gear 103 of the strain wave gear device 100, and the supply pipe 125 is extended to the outside through the end plate 106, which is the fixed member, and connected to the aerosol generator 126 disposed externally via external piping 128. In this example, two nozzles 124 are arranged at angular intervals of 180° around the axis 100a. Three or more nozzles 124 may be arranged at equal angular intervals in the circumferential direction.

[0040] The external aerosol generator 126 has a structure similar to that of a typical spray-type aerosol generator, and includes a pressure-resistant container 129 containing solid lubricant powder and liquefied gas or pressurized gas, a valve mechanism 130 consisting of an electromagnetic valve or the like that closes an aerosol outlet formed in the pressure-resistant container 129, and a drive control unit 131 that controls the valve mechanism 130 to open, close, and adjust the aperture of the aerosol outlet. The drive control unit 131 opens and closes the aerosol outlet based on commands from, for example, a higher-level controller that controls the drive of the harm gear device 100. For example, when the wave generator 104 is rotating, aerosol is supplied at a predetermined flow rate and sprayed from the nozzle 124. Furthermore, an appropriate amount of aerosol (solid lubricant powder) can be supplied to the lubricated portion at the required timing depending on the lubrication state of the lubricated portion.

[0041] The aerosol generating mechanism may be a type that generates the aerosol by supplying a carrier gas (liquefied gas or pressurized gas) from the outside to a container in which the solid lubricant powder is sealed, instead of a spray type. The material of the container that must be pressure-resistant is preferably stainless steel, aluminum alloy, chemically stable resin, etc., taking into consideration light weight, the amount of gas released, etc.

[0042] 1B, the aerosol generator 126 of the powder lubrication mechanism 120 may also be incorporated into the inner space 110 of the external gear 103.

Claims

1. A powder lubrication method for a wave gearing device, comprising: supplying solid lubricant powder in the form of an aerosol toward a lubrication portion of a wave gearing device; lubricating the lubrication portion using the solid lubricant powder that has reached the lubrication portion; and wherein the aerosol contains the solid lubricant powder with a particle size of 20 μm or less as a solid phase, and a liquefied gas or compressed gas as a gas phase.

2. In the powder lubrication method for a wave gear device according to claim 1, the solid lubricant powder is molybdenum disulfide (MoS ２ ), tungsten disulfide (WS ２ ), and polytetrafluoroethylene (PTFE), or a mixture of at least two of these powders.

3. A wave gear device comprising: a rigid internal gear; a flexible external gear arranged coaxially inside the internal gear; a wave generator arranged coaxially inside the external gear; a lubrication portion where the inner peripheral surface of the external gear and the outer peripheral surface of the wave generator come into contact; and a powder lubrication mechanism that supplies solid lubricant powder in an aerosol state toward the lubrication portion to form a solid lubricant film on the lubrication portion, wherein the aerosol contains, as a solid phase, the solid lubricant powder having a particle size of 20 μm or less, and as a gas phase, a liquefied gas or a compressed gas.

4. In the strain wave gear device according to claim 3, the solid lubricant powder is molybdenum disulfide (MoS ２ ), tungsten disulfide (WS ２ ), and polytetrafluoroethylene (PTFE), or a mixture of at least two of these powders.

5. A wave gear device according to claim 4, wherein the powder lubrication mechanism comprises a nozzle that sprays the aerosol toward the lubrication portion, a supply path that guides the aerosol to the nozzle, and a valve mechanism that opens and closes the nozzle or adjusts the opening degree of the nozzle.

6. A wave gear device according to claim 5, wherein the powder lubrication mechanism further comprises an aerosol generator that generates the aerosol that is introduced to the nozzle via the supply path.

7. A wave gear device as claimed in claim 5, wherein the wave generator comprises a rigid wave plug and a wave bearing attached to the elliptical outer peripheral surface of the wave plug, the wave bearing being a rolling bearing with a plurality of rolling elements arranged between an outer ring and an inner ring, and the wave generator further comprises a shielding plate that blocks the flow of the aerosol from the nozzle towards the rolling element raceway surfaces formed on each of the outer ring and the inner ring.

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