Aerospace rolling bearing and aerospace strain wave gearing

Abstract

The wave bearing (43) of the aerospace harmonic gear unit (1) comprises: an inner ring (45) formed of bearing steel, an outer ring (44) formed of Asada Sante stainless steel, and balls (46) formed of ceramic. A ceramic coating (48) formed by the AD method is formed on the inner ring (45) formed of bearing steel as a rust-proof coating. In the aerospace harmonic gear unit (1) that uses solid lubrication (powder lubrication), rust prevention of the inner ring (45) of the wave bearing (43) formed of bearing steel can be reliably performed. By appropriately setting the coefficients of linear expansion of the inner ring (45), outer ring (44), and balls (46), even in the space environment where large temperature changes occur, the change in the radial clearance of the wave bearing (43) can be suppressed to a range that will not cause any hindrance in actual use.

Description

Technical Field

[0001] This invention relates to: aerospace rolling bearings and aerospace harmonic gear devices used in outer space where the ambient temperature is extremely low (approximately -70°C to approximately -270°C) and the vacuum level is below approximately 10⁻⁴ Pa. Prior Technology

[0002] Mechanisms aboard artificial satellites and spacecraft navigating in the extremely low temperatures and vacuum of outer space, such as the joints of robotic arms, sometimes use harmonic gear systems as speed reducers. As is widely known, a harmonic gear system consists of three parts: a rigid internal gear, a flexible external gear, and a harmonic generator. The harmonic generator includes a rigid cam plate and a wave bearing mounted on the outer circumference of the rigid cam plate.

[0003] Wave bearings and other rolling bearings used in extremely low temperature and vacuum environments can use lubricants such as lubricating oil and grease. Lubrication is achieved by forming a film of solid lubricant on the lubricated area or by supplying solid lubricant powder to the lubricated area. As rolling bearings used in extremely low temperature environments, Patent Documents 1 and 2 disclose rolling bearings with outer and inner rings made of martensitic stainless steel, bearing steel, etc., and rolling elements made of ceramic. [Previous Technical Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2000-220641 [Patent Document 2] Japanese Patent Application Publication No. 2000-74069 Summary of the Invention

[0005] [The problem the invention aims to solve] In rolling bearings consisting of inner and outer rings made of steel and rolling elements made of ceramic, the difference in the linear expansion coefficients of steel and ceramic leads to a decrease in the internal clearance of the bearing at lower temperatures. In particular, at extremely low temperatures below -70°C, the difference in the linear expansion coefficients of steel and ceramic results in a reduction in the radial clearance between the inner and outer rings, causing adverse effects such as hindering the proper rotational movement of the rolling elements.

[0006] In view of this, for aerospace rolling bearings, it is desirable to use a combination of ceramic rolling elements, an outer ring of Asada Sante stainless steel, and an inner ring of bearing steel. In this case, by utilizing the difference in the coefficients of linear expansion of these components, the change in radial clearance of the rolling bearing caused by "large temperature changes" can be suppressed.

[0007] However, bearing steel is prone to rust, especially in applications such as aerospace rolling bearings that perform solid lubrication (powder lubrication) in a vacuum, where rust prevention is difficult. Furthermore, if a general rust-preventive coating is applied to the inner ring formed by the bearing steel, the heat applied to the inner ring during coating will cause the bearing steel to anneal, resulting in problems such as a decrease in strength.

[0008] The purpose of this invention is to provide an aerospace rolling bearing and an aerospace harmonic gear device. The aerospace rolling bearing can suppress changes in radial clearance caused by temperature variations and performs appropriate anti-rust treatment on the bearing rings that are lubricated by solids or powders. The aerospace harmonic gear device includes a harmonic generator that uses the aerospace rolling bearing as a wave bearing. [Solutions]

[0009] The aerospace rolling bearing of the present invention, It comprises an inner ring, an outer ring, and a plurality of rolling elements arranged in a rotatable manner between the inner ring and the outer ring; it can be lubricated by a solid lubricant coating or solid lubricant powder, and can be used in low-temperature and vacuum environments, characterized in that: The aforementioned inner ring is made of bearing steel. The aforementioned outer ring is made of Matian Santie stainless steel. The aforementioned rolling element is made of ceramic. At least a portion of the aforementioned inner ring surface is covered with a rust-preventive coating. The aforementioned rust-preventive coating is a ceramic coating formed by the AD method (Aerosol Deposition method).

[0010] In the AD process, an aerosol containing ceramic microparticles, which are the raw material for a rust-preventive coating, dispersed in a gas, is subjected to high-speed impacts on the surface of an inner ring substrate made of bearing steel, thereby forming a coating of ceramic microparticles on the surface of the inner ring substrate. The ceramic raw material can be oxide ceramics such as alumina and zirconium oxide, or carbide ceramics such as silicon nitride and silicon carbide. The formation of the rust-preventive coating using the AD process can be performed at room temperature.

[0011] Here, the thickness of the rust-preventive coating is preferably 1μm to 5μm. Furthermore, in cases where a rust-preventive coating has already been formed on the rolling surface of the rolling element on the outer circumferential surface of the inner ring, there is a possibility that the rust-preventive coating may peel off due to contact resistance caused by the passage of the rolling element. Therefore, it is preferable to pre-form a rust-preventive coating on the surface of the inner ring, excluding the rolling surface.

[0012] In addition, SUJ2 can be used as the bearing steel for the inner ring, SUS440C can be used as the stainless steel for the outer ring, and Si3N4 can be used as the ceramic for the rolling element.

[0013] By employing the aerospace rolling bearing of this invention, the situation where "the radial clearance between the inner and outer rings decreases due to temperature changes in extremely low-temperature environments below -70°C" can be suppressed to a range that will not cause any hindrance in practical use, thus maintaining the proper rolling state of the ceramic rolling elements. Furthermore, in the case of "the inner ring formed by lubricating bearing steel under extremely low temperatures and vacuum conditions through solid lubrication (powder lubrication)," a ceramic coating produced using the AD method is formed as a rust-preventive coating. According to the AD method, since the bearing steel is not exposed to high temperatures during coating formation, the adverse effect of "the heat during the formation of the rust-preventive coating causing a decrease in the strength of the inner ring formed by the bearing steel" is avoided, and rust formation can be reliably prevented.

[0014] Furthermore, by using the aerospace rolling bearing of the present invention as a wave bearing in a harmonic generator, an aerospace harmonic gear device suitable for use in extremely low temperature and vacuum environments can be obtained. That is, the aerospace harmonic gear device of the present invention is characterized by having: Rigid internal gears; A flexible external gear that can mesh with the aforementioned internal gear; The harmonic generator partially meshes the aforementioned external gear with the aforementioned internal gear by bending it radially, and moves the meshing position of the two gears toward the circumference of the aforementioned internal gear. The aforementioned harmonic generator includes: a rigid cam plate; and a wave bearing mounted between the outer peripheral surface of the cam plate and the inner peripheral surface of the aforementioned external gear. The aforementioned wave bearing is an aerospace rolling bearing with the above-described structure.

[0015] In aerospace harmonic gear systems, solid lubricant powder can be used to lubricate various lubrication points. In this case, the aerospace harmonic gear system includes a lubrication mechanism for supplying solid lubricant powder, which lubricates the sliding portion between the external gear and the wave bearing, as well as other lubrication points of the wave bearing.

[0016] As a lubrication mechanism, a mechanism configured as follows can be adopted. That is, the lubrication mechanism has a powder storage bag formed of a "mesh-structured and flexible sheet material", in which the aforementioned solid lubricant powder is stored. The aforementioned powder storage bag is installed in a part of the aforementioned external gear that can be repeatedly flexed by the aforementioned harmonic generator. In order to release the aforementioned solid lubricant powder through the mesh of the aforementioned powder storage bag, the particle size of the aforementioned solid lubricant powder and the size of the aforementioned mesh are set.

[0017] As solid lubricants, three types are known: soft metals such as silver (Ag) and lead (Pb); layered crystalline materials such as molybdenum disulfide (MoS2), tungsten disulfide (WS2), and graphite; and polymers such as polytetrafluoroethylene (PTFE) and polyimide (PI). For example, layered crystalline materials can be used as solid lubricant powders. Simple Explanation of the Diagram

[0018] [Figure 1A] is a longitudinal cross-sectional view showing a chimney-type aerospace harmonic gear device according to Embodiment 1 of the present invention. [Figure 1B] is an explanatory diagram showing the meshing state of the flexible external gear and the rigid internal gear in the harmonic gear device of Figure 1A. [Figure 2A] is a longitudinal cross-sectional view showing a cup-shaped aerospace harmonic gear device according to Embodiment 2 of the present invention. [Figure 2B] is an end view of the harmonic gear device in Figure 2A. [Figure 3A] is a longitudinal cross-sectional view showing a flat-plate type aerospace harmonic gear device according to Embodiment 3 of the present invention. [Figure 3B] is an end view of the harmonic gear device in Figure 3A. Implementation

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments pertain to an aerospace harmonic gear device that uses the aerospace ball bearing of the present invention as a wave bearing in a harmonic generator. The aerospace rolling bearing of the present invention is not limited to ball bearings; other rolling bearings such as roller bearings and crossed roller bearings can also be used. Furthermore, the aerospace rolling bearing of the present invention can also be applied to bearings in aerospace drive mechanisms other than harmonic gear devices.

[0020] (Implementation Form 1) Figure 1A is a longitudinal sectional view showing the aerospace harmonic gear device according to Embodiment 1 of the present invention, and also shows a partially enlarged view of the wave bearing portion. Figure 1B is an explanatory diagram showing the meshing state of the rigid internal gear and the flexible external gear of the aerospace harmonic gear device. The aerospace harmonic gear device 1 (hereinafter referred to as "harmonic gear device 1") is used in outer space at extremely low temperatures of -70°C to -270°C and a vacuum of less than 10⁻⁴ Pa.

[0021] The harmonic gear device 1 includes: a rigid, annular internal gear 2; a flexible, chimney-shaped external gear 3; and a harmonic generator 4 with an elliptical profile. The external gear 3 includes: a cylindrical body 31 that can flex in the radial direction; a diaphragm 32 that expands radially outward from the rear end of the cylindrical body 31; a rigid, annular hub 33 integrally formed on the outer periphery of the diaphragm 32; and external teeth 34 formed on the outer peripheral surface of the front end of the cylindrical body 31. The external teeth 34 can mesh with the internal teeth 24 of the internal gear 2.

[0022] The harmonic generator 4 includes: a rigid cam plate 41; and a wave bearing 43 mounted on the outer peripheral surface 42 of the elliptical profile of the cam plate 41. The wave bearing 43 includes: an outer ring 44 and an inner ring 45 that can flex in the radial direction; a plurality of balls 46 mounted in a rolling state between the two rings; and a ball retainer 47 that holds each ball 46 in the circumferential direction at certain intervals. The wave bearing 43 is an aerospace ball bearing constructed using the present invention. Although the outer ring 44 and inner ring 45 of the wave bearing 43 are perfectly circular, they are flexed into an elliptical shape by being mounted on the outer peripheral surface 42 of the elliptical profile of the cam plate 41.

[0023] As shown in Figure 1B, the external gear 3, bent into an elliptical shape by the harmonic generator 4, meshes with the internal gear 2 on both sides of the major axis L of the ellipse. Once the harmonic generator 4 rotates by a motor (not shown), the meshing position of the two gears 2 and 3 moves in the circumferential direction, and relative rotation corresponding to the difference in the number of teeth between the two gears is generated between them. One gear is fixed, and the other gear outputs a decelerated rotation.

[0024] In the wave bearing 43, the inner ring 45 is made of bearing steel, such as SUJ2. The outer ring 44 is made of Asahi stainless steel, such as SUS440C. The ball 46 is made of ceramic, such as Si3N4.

[0025] Referring to the enlarged view in Figure 1A, a rust-proofing treatment is applied to the surface of the inner ring 45. A rust-proofing coating is formed on the surface of the inner ring 45 as a rust-proofing treatment. The rust-proofing coating is a ceramic coating 48 formed by the AD method (aerosol deposition). The thickness of the ceramic coating 48 is approximately 1 μm to approximately 5 μm. The portion of the curved surface extending in the circumferential direction on the outer circular circumferential surface of the inner ring 45 forms the rolling surface 45a. In this example, the ceramic coating 48 is formed to cover the surface portion 45c of the inner ring 45 other than the rolling surface 45a and the inner circumferential surface 45b connected to the outer circumferential surface 42 of the cam plate. The ceramic coating 48 can also be formed on the inner circumferential surface 45b of the inner ring 45, as is also the case in embodiments 2 and 3 below.

[0026] In the wave bearing 43 of this example, if the change in the radial clearance of the track portion between the inner ring 45 and the outer ring 44 in a true circular state due to the change in ambient temperature is denoted as ΔR, the change ΔR can be defined by the following conditional expression (1). in, d: Diameter of ball bearing 46 (mm) D: Pitch circle diameter (PCD) of ball bearing 46 (mm) α: Coefficient of linear expansion of outer ring 44 (1 / ℃) β: Coefficient of linear expansion of inner ring 45 (1 / ℃) γ: Coefficient of linear expansion of ball bearing 46 (1 / ℃) ΔT: Change in ambient temperature (°C)

[0027] Ideally, the gap should not change even if the ambient temperature changes. The condition that makes the change ΔR in the ideal state zero is to satisfy the following condition (2), and the linear expansion coefficients α, β, and γ of the outer ring 44, inner ring 45, and ball 46 are specified respectively.

[0028] The inventors of this case have confirmed the following situation: In the wave bearing 43 used in an extremely low temperature environment of -70℃ to -270℃, when the pitch circle diameter D and the diameter d of the ball 46 of the wave bearing 43 have been assigned, in order to meet the following condition (3), as long as the linear expansion coefficients α, β and γ of the outer ring 44, inner ring 45 and ball 46 are set, the change in radial clearance ΔR can be suppressed to a range that will not cause any hindrance in actual use.

[0029] In the wave bearing 43, for example, the pitch circle diameter (PCD) of the ball 46 is 80 mm, and the diameter d of the ball 46 is 8 mm. Furthermore, the bearing steel used for the inner ring 45 is SUJ2, with a coefficient of linear expansion β of 12.5 × 10⁻⁶. The stainless steel used for the outer ring 44 is SUS440C, with a coefficient of linear expansion α of 10.2 × 10⁻⁶. The ceramic used for the ball 46 is Si₃N₄, with a coefficient of linear expansion γ of 2.6 × 10⁻⁶.

[0030] When the change in ambient temperature ΔT is set to 260℃, due to Therefore, it becomes: And it meets the above condition (3).

[0031] Furthermore, the change in radial clearance ΔR obtained from condition (1) is: However, it should be included in the scope that will not cause any hindrance in actual use.

[0032] The harmonic gear assembly 1 includes a lubrication mechanism (not shown in the figures). The lubrication points of the harmonic gear assembly 1 include: a sliding portion of the wave bearing 43 and a sliding portion between the outer ring 44 of the wave bearing 43 and the inner circumferential surface of the external gear 3. These lubrication points are lubricated by solid lubricant powder supplied from the lubrication mechanism. Alternatively, a solid lubricant film formed on the surface of the lubrication points can be used as the lubrication mechanism. Furthermore, the ball retainer 47 can be a self-lubricating type retainer made of phenol resin or the like.

[0033] As explained above, in the wave bearing 43 of the harmonic gear device 1 in this example, the inner ring 45 is made of bearing steel, the outer ring 44 is made of Asada steel stainless steel, and the balls 46 are made of ceramic. In this way, even in the extremely low temperatures of -70°C to -270°C, where temperature variations of approximately 260°C occur in space environments, the change in radial clearance ΔR of the wave bearing 43 can be suppressed to a range that will not hinder practical use. Furthermore, a ceramic coating 48, produced using the AD method, is formed for rust prevention of the inner ring 45 made of bearing steel. Thus, rust prevention of the inner ring 45 of the wave bearing 43, which is lubricated by a solid lubricant coating or solid lubricant powder, will not lead to adverse effects such as a decrease in the strength of the inner ring 45, ensuring reliable operation.

[0034] The above example illustrates the application of the aerospace rolling bearing of the present invention to a wave bearing of a "chimney-type harmonic gear device". The present invention is also applicable to wave bearings of cup-type and flat-plate type harmonic gear devices.

[0035] (Implementation Form 2) Figures 2A and 2B are cross-sectional and end-view views showing one example of a cup-shaped aerospace harmonic gear device employing Embodiment 2 of the present invention. The cup-shaped aerospace harmonic gear device 100 (hereinafter simply referred to as "harmonic gear device 100") includes: a rigid internal gear 120; a flexible external gear 130 disposed inside the internal gear 120 and forming a cup shape; and an elliptical harmonic generator 140 embedded inside the external gear 130. Within the external gear 130, a cylindrical body 131 with external teeth 134 is flexed into an elliptical shape by the harmonic generator 140. The two ends of the major axis L of the ellipse in the external teeth 134 mesh with the internal teeth 124 of the annular internal gear 120.

[0036] The harmonic generator 140 includes: a rigid cam plate 141 fixed to the outer peripheral surface of the rotary input shaft 170; and a wave bearing 143 mounted on the elliptical outer peripheral surface 142 of the rigid cam plate 141. The wave bearing 143 is an aerospace (ultra-low temperature environment) ball bearing constructed using the present invention. The wave bearing 143, bent into an elliptical shape by the rigid cam plate 141, is embedded inside the external gear 130, holding the external gear 130 and the rigid cam plate 141 in a position where they can rotate relative to each other.

[0037] The wave bearing 143 is, for example, formed of a full-roller type deep groove ball bearing. The wave bearing 143 includes: a circular inner ring 145 that can flex in the radial direction and a circular outer ring 144 that can flex in the radial direction; a plurality of balls 146 are inserted into an annular ball track formed between the two rings in a rollable state. Each ball 146 is inserted into the ball track in a state where adjacent balls 146 are in contact with each other or in a state with a slight gap.

[0038] Even in the wave bearing 143 of this example, its inner ring 145 is made of bearing steel, its outer ring 144 is made of Asada steel stainless steel, and its balls 146 are made of ceramic. Furthermore, if the diameter of the balls 146 is set to d and its pitch circle diameter is set to D, the linear expansion coefficient of the outer ring 144 is set to α, the linear expansion coefficient of the inner ring 145 is set to β, and the linear expansion coefficient of the balls 146 is set to γ, the values ​​of these linear expansion coefficients are set to satisfy the above conditional expression (3).

[0039] In the wave bearing 143, the inner ring 145 is made of bearing steel, such as SUJ2. The outer ring 144 is made of stainless steel, such as SUS440C. The ball bearing 146 is made of ceramic, such as Si3N4.

[0040] Rust prevention treatment is applied to the surface of the inner ring 145. A rust-preventive coating is formed on the surface of the inner ring 145 as a rust prevention treatment. The rust-preventive coating is a ceramic coating 148 formed by the AD method (aerosol deposition). The thickness of the ceramic coating 148 is about 1 μm to about 5 μm. As shown in the partial enlarged view of FIG2A, a rolling surface 145a extending in the circumferential direction is formed on the circular outer peripheral surface of the inner ring 145. In this example, a ceramic coating 148 is formed to cover the surface portion 145c of the inner ring 145 other than the "rolling surface 145a and the inner peripheral surface 145b of the outer peripheral surface 142 mounted on the rigid cam plate".

[0041] In addition, the harmonic gear device 100 includes a lubrication mechanism 150. The lubrication points of the harmonic gear device 100 include: a sliding portion of the wave bearing 143, and a sliding portion between the outer ring 144 of the wave bearing 143 and the inner circumferential surface of the cylindrical body 131 of the external gear 130. These lubrication points are lubricated by solid lubricant powder 160 supplied from the lubrication mechanism 150.

[0042] The lubrication mechanism 150 in this example includes a powder storage bag 151 formed from a thin sheet material with a mesh structure and flexibility. Solid lubricant powder 160 is stored in the powder storage bag 151. The powder storage bag 151 is installed in the portion of the external gear 130 that is repeatedly flexed by the harmonic generator 140. In this example, the powder storage bag 151 is an annular bag with dimensions corresponding to the inner end face of the diaphragm 132 of the external gear 130, and is installed on the inner end face of the diaphragm 132 by means of an adhesive or the like. Furthermore, a porous metal annular fixing plate 152 is fixed to the hub 133 of the external gear 130, and the powder storage bag 151 is held between the annular fixing plate 152 and the diaphragm 132, along the inner end face of the diaphragm 132.

[0043] To release solid lubricant powder 160 through the mesh of the powder collection bag 151, the mesh size is larger than the particle size of the solid lubricant powder. When the harmonic gear device 100 is driven, the harmonic generator 140 repeatedly flexes various parts of the external gear 130. The portion of the diaphragm 132, as indicated by the arrow in the figure, is also repeatedly flexed. Vibration and deformation are also applied to the powder collection bag 151 arranged along the diaphragm 132, causing the collected solid lubricant powder to be released from the mesh towards the inner space 135 of the external gear 130. The solid lubricant powder 160 released into the inner space 135 is supplied to the lubrication target area, thereby lubricating the target area. The powder collection bag 151 can also be arranged in a location in the external gear 130 other than the diaphragm 132, for example, along the inner circumferential surface of the cylindrical body 131.

[0044] (Implementation Form 3) Next, Figures 3A and 3B are longitudinal sectional views and end views showing a flat-plate type aerospace harmonic gear device according to Embodiment 3 of the present invention. The flat-plate type aerospace harmonic gear device 200 (hereinafter referred to as "harmonic gear device 200") includes a stationary internal gear 221 and a driving internal gear 222, which are rigid internal gears. The internal gears 221 and 222 are arranged side-by-side coaxially, and a cylindrical flexible external gear 230 is disposed inside them. An elliptical harmonic generator 240 is embedded inside the external gear 230. By means of the harmonic generator 240, the external gear 230 is flexed into an elliptical shape, and at both ends of the major axis L of the ellipse, the external teeth 234 mesh with both the internal teeth 221a of the internal gear 221 and the internal teeth 222a of the internal gear 222. For example, the number of teeth of the stationary internal gear 221 is 2n more than that of the driving internal gear 222 (n is a positive integer), and the number of teeth of the external gear 230 is the same as that of the driving internal gear 222.

[0045] The harmonic generator 240 includes: a rigid cam plate 241; and a wave bearing 243 mounted on the outer peripheral surface 242 of the elliptical profile of the cam plate 241. The wave bearing 243 includes: an outer ring 244 and an inner ring 245 that can flex in the radial direction; a plurality of balls 246 mounted in a rollable state between the two rings; and a ball retainer 247 that holds each ball 246 in the circumferential direction at certain intervals. The wave bearing 243 is an aerospace ball bearing constructed using the present invention. Although the outer ring 244 and inner ring 245 of the wave bearing 243 are perfectly circular, they are flexed into an elliptical shape by being mounted on the outer peripheral surface 242 of the elliptical profile of the cam plate 241.

[0046] The external gear 230, bent into an elliptical shape by the harmonic generator 240, meshes with internal gears 221 and 222 on both sides of the major axis L of the ellipse. Once the harmonic generator 240 is driven to rotate by a motor (not shown) or the like, the meshing position of the internal gear 221 and the external gear 230 on the stationary side will move in the circumferential direction, and the external gear 230 will rotate at a reduced speed. The reduced speed is output from the internal gear 222 on the drive side, which rotates integrally with the external gear 230.

[0047] Even in the wave bearing 243 of this example, its inner ring 245 is made of bearing steel, its outer ring 244 is made of Asada steel stainless steel, and its balls 246 are made of ceramic. Furthermore, if the diameter of the balls 246 is set to d and its pitch circle diameter is set to D, the linear expansion coefficient of the outer ring 244 is set to α, the linear expansion coefficient of the inner ring 245 is set to β, and the linear expansion coefficient of the balls 246 is set to γ, the values ​​of these linear expansion coefficients are set to satisfy the above conditional expression (3).

[0048] Furthermore, a rust-proofing treatment is applied to the surface of the inner ring 245. A rust-proofing coating is formed on the surface of the inner ring 245 as a rust-proofing treatment. As shown in the enlarged view of Figure 3A, the rust-proofing coating is a ceramic coating 248 formed by the AD method (aerosol deposition). The thickness of the ceramic coating 248 is approximately 1 μm to approximately 5 μm. A rolling surface 245a extending in the circumferential direction is formed on the outer circular circumferential surface of the inner ring 245. In this example, the ceramic coating 248 is formed to cover the surface portion 245c of the inner ring 245, excluding the rolling surface 245a and the inner circumferential surface 245b.

[0049] The harmonic gear assembly 200 includes a lubrication mechanism (not shown in the figures). The lubrication points of the harmonic gear assembly 200 include: a sliding portion of the wave bearing 243 and a sliding portion between the outer ring 244 of the wave bearing 243 and the inner circumferential surface of the external gear 230. These lubrication points are lubricated by solid lubricant powder supplied from the lubrication mechanism. Alternatively, a solid lubricant film formed on the surface of the lubrication points can be used as the lubrication mechanism. Furthermore, the ball retainer 247 can be a self-lubricating type retainer made of phenolic resin or the like.

[0050] 1: Aerospace Harmonic Gear Unit (Harmonic Gear Device) 2: Internal gears 3: External gears 4: Harmonic Generator 24: Internal teeth 31: Cylindrical body 32: Membrane 33: Wheel hub 34: External teeth 41: Cam plate 42: Outer perimeter 43: Wave bearing 44: Outer Ring Road 45: Inner Ring 45a: Rolling surface 45b: Inner circumferential surface 45c: Surface portion 46: Ball bearing 47: Ball retainer 48: Ceramic Coating 100: Aerospace Harmonic Gear Unit (Harmonic Gear Unit) 120: Internal gear 124: Internal teeth 130: External gear 131: Cylindrical body 132: Membrane 133: Wheel hub 134: External teeth 135: Inner Space 140: Harmonic Generator 141: Rigid Cam Plate 142: Outer Peripheral Surface 143: Wave bearing 144: Outer Ring Road 145: Inner Ring 145a: Rolling surface 145b: Inner circumferential surface 145c: Surface portion 146: Ball bearing 148: Ceramic Coating 150: Lubrication mechanism 151: Powder Storage Bag 152: Circular fixing plate 160: Solid lubricant powder 170: Rotate input shaft 200: Harmonic Gear Unit for Aerospace Applications (Harmonic Gear Unit) 221: Internal gear 221a: Internal teeth 222: Internal gear 222a: Internal teeth 230: External gear 234: External teeth 240: Harmonic Generator 241: Cam plate 242: Outer Peripheral Surface 243: Wave bearing 244: Outer Ring 245: Inner Ring 245a: Rolling surface 245b: Inner circumferential surface 245c: Surface portion 246: Ball bearing 247: Ball retainer 248: Ceramic Coating L: Long axis

Claims

1. An aerospace rolling bearing comprising an inner ring, an outer ring, and a plurality of rolling elements arranged in a rotatable manner between the inner ring and the outer ring, and lubricated by a solid lubricant coating or solid lubricant powder, for use in low-temperature and vacuum environments, wherein the inner ring is formed of bearing steel, the outer ring is formed of Asahi steel stainless steel, the rolling elements are formed of ceramic, and at least a portion of the surface of the inner ring is formed with a rust-preventive coating, the rust-preventive coating being a ceramic coating formed by aerosol deposition, the rust-preventive coating being formed on the surface of the inner ring in a manner other than the rolling surface on which the rolling elements roll.

2. The aerospace rolling bearing as requested in item 1, wherein the maximum thickness of the aforementioned rust-preventive coating is 5 μm.

3. The aerospace rolling bearing of claim 1, wherein the bearing steel used as the inner ring material is SUJ2, the stainless steel used as the outer ring material is SUS440C, and the ceramic used as the rolling element material is Si3N4.

4. The aerospace rolling bearing of claim 1, wherein the aforementioned rust-proof coating is formed on the aforementioned surface of the aforementioned inner ring, in a portion other than the rolling surface on which the aforementioned rolling element rolls, the maximum thickness of the aforementioned rust-proof coating is 5 μm, the bearing steel used as the material of the aforementioned inner ring is SUJ2, the stainless steel used as the material of the aforementioned outer ring is SUS440C, and the ceramic used as the material of the aforementioned rolling element is Si3N4.

5. An aerospace harmonic gear device comprising: a rigid internal gear; a flexible external gear meshing with the internal gear; and a harmonic generator that flexes the external gear radially to partially mesh with the internal gear, thereby causing the meshing position of the two gears to move circumferentially toward the internal gear, wherein the harmonic generator comprises: a rigid cam plate; and a wave bearing mounted between the outer peripheral surface of the cam plate and the inner peripheral surface of the external gear, wherein the wave bearing is an aerospace rolling bearing as described in any one of claims 1 to 4.

6. The aerospace harmonic gear device of claim 5, wherein a lubrication mechanism is provided for supplying solid lubricant powder, the solid lubricant powder lubricating the sliding portion between the aforementioned external gear and the aforementioned wave bearing, and the aforementioned wave bearing.

7. The aerospace harmonic gear device of claim 6, wherein the aforementioned lubrication mechanism includes a powder storage bag formed of a sheet material having a mesh structure and flexibility, wherein the aforementioned solid lubricant powder is stored in the aforementioned powder storage bag, wherein the aforementioned powder storage bag is installed in the portion of the aforementioned external gear that is repeatedly flexed by the aforementioned harmonic generator, and wherein the mesh of the aforementioned powder storage bag is of a size through which the aforementioned solid lubricant powder can pass.

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