JP2008039037A - Bearing for wave gear device - Google Patents

Abstract

A bearing for a wave gear device that has high rigidity, low torque, and high durability, and is compact and lightweight.
A wave gear device 20 is disposed inside a rigid internal gear 21, a flexible external gear 22 disposed inside the rigid internal gear 21, and a flexible external gear 22. A wave generator 23 for bending the flexible external gear 22 in the radial direction and partially meshing with the rigid internal gear 21 and moving the meshing positions of both gears 21 and 22 in the circumferential direction; Prepare. A wave gear device bearing 30 that supports the rigid internal gear 21 and the flexible external gear 22 so as to be relatively rotatable is a rear combination angular ball bearing, and includes a pair of outer ring raceway surfaces 31a and 31a, and a pair of outer ring raceway surfaces 31a and 31a. At least one of the inner ring raceway surfaces 32a and 32a and the rolling surfaces of the balls 33 and 33 is lubricated with a lubricating oil and a fluorine resin having a vapor pressure at 20 ° C. of 1 × 10 ⁻⁵ Pa or less by oil plating. A lubricant film made of a lubricant containing
[Selection] Figure 2

Description

  INDUSTRIAL APPLICABILITY The present invention is used in a clean environment such as a vacuum environment or a clean room (hereinafter sometimes referred to as “vacuum environment etc.”), and includes a rigid internal gear and a flexible external gear of a wave gear device. The present invention relates to a bearing for a wave gear device that is rotatably supported.

  2. Description of the Related Art Conventionally, a wave gear device with a small backlash and a low reduction ratio has been used as a speed reducer in a drive mechanism such as a robot. As the wave gear device, a cup type, a top hat type, a flat type, and the like have been devised depending on the shape of the flexible external gear to be incorporated, and all operations are the same (for example, see Patent Documents 1 and 2). .

  As shown in FIG. 7, the top hat type wave gear device 1 includes an annular rigid internal gear 2, a silk hat type flexible external gear 3 having a smaller number of teeth than the rigid internal gear 2, and an elliptical shape. It is mainly composed of a wave generator 4 having a shape outline. The flexible external gear 3 is arranged inside the rigid internal gear 2, and the flexible external gear 3 is deflected in the radial direction by the wave generator 4 to be partially with respect to the rigid internal gear 2. Engage. When the wave generator 4 is rotated by the rotation of the motor or the like, the meshing position of the two gears 2 and 3 is moved in the circumferential direction, and the two gears 2 and 3 are relatively rotated at a rotation speed corresponding to the difference in the number of teeth.

  The wave gear device 1 is connected to a motor and is provided around a hollow input shaft 5 having a cam plate portion 5a having an elliptical outline of the wave generator 4 on the outer peripheral surface. Around the hollow input shaft 5, first and second end plates 8, 9 supported via ball bearings 6, 7 are arranged so as to sandwich the wave gear device 1 between the axial directions, One end plate 8 is fastened and fixed to the flexible external gear 3, and the second end plate 9 is fastened and fixed to the rigid internal gear 2. Since one of the first end plate 8 and the second end plate 9 is connected to the load side and the other is fixed so as not to rotate, the decelerated rotation is output from the end plate side connected to the load side. Transmitted to the load side.

Further, in such a wave gear device 1, a cross roller bearing 10 (see FIG. 7) that can receive a moment load as a bearing that supports the rigid internal gear 2 and the flexible external gear 3 so as to be relatively rotatable. And 4-point contact ball bearings are used.
JP-A-9-217798 JP 2005-308131 A

  By the way, the above-mentioned cross roller bearing is a cylindrical roller that is alternately inclined by 45 degrees with respect to the center of the bearing, and can be loaded with radial load, axial load, and moment load. The capacity is determined, and the moment load that can be applied is limited by the bearing dimensions.

  Further, since the cylindrical rollers are rotated at an angle of 90 degrees with each other, the rotational friction is large, resulting in a large rotational torque. Furthermore, due to its structure, there is a short space (bearing space volume) in which the lubricant can be enclosed, and there is a problem in durability.

  In addition, since the cylindrical roller is inclined at 45 degrees with respect to the center of the bearing, the outer diameter of the inner ring and the outer ring is increased due to the restriction of the bearing cross-section height and the outer diameter becomes larger than the inner diameter. Therefore, there is a problem that the weight of the bearing is increased.

  Also, when a four-point contact ball bearing is applied, the moment load that can be applied cannot be increased as in the case of the cross roller bearing.

  Furthermore, the wave gear device used in a vacuum environment or the like is hardly allowed to be contaminated by dust generation or the like. In general, in bearings used in such an environment, the amount of lubricant that scatters or evaporates to the outside is reduced by using a fluorine-based lubricant, but there is a lack of lubrication and a decrease in durability. Forced. In addition, it has been devised to coat the rolling site with a fluoropolymer solid lubricant, but in situations where a relatively large axial load is applied, the solid lubricant may be peeled off or missing, or dust may be generated due to wear. Therefore, it may be insufficient in terms of durability and low dust generation.

  The present invention has been made in view of the above-described circumstances, and the object thereof can be suitably used in a vacuum environment or the like, has high rigidity, low torque, high durability, and is compact and lightweight. An object of the present invention is to provide a bearing for a wave gear device.

The above object of the present invention is achieved by the following configurations. That is, a rigid internal gear, a flexible external gear arranged inside the rigid internal gear, and a flexible external gear arranged inside the flexible external gear, the flexible external gear being arranged in the radial direction And a wave generator that partially meshes with the rigid internal gear and moves the meshing position of both gears in the circumferential direction. A bearing for a wave gear device that supports a flexible external gear so as to be relatively rotatable, wherein the bearing is one of the rigid internal gear and the flexible external gear, or a housing to which the one is fixed. An outer ring that can be fitted in the inner ring, the other of the rigid internal gear and the flexible external gear, or an inner ring that can be fitted on a shaft portion to which the other is fixed, and a pair of outer ring raceways of the outer ring And a plurality of balls arranged with a contact angle between a pair of inner ring raceway surfaces of the inner ring, An angular ball bearing of a type, wherein at least one of the pair of outer ring raceway surfaces, the pair of inner ring raceway surfaces, and the rolling surface of the balls is subjected to a vapor pressure at 20 ° C. by oil plating treatment. Is characterized in that a lubricating film made of a lubricant containing a lubricating oil of 1 × 10 ⁻⁵ Pa or less and a fluororesin is formed.

  Here, the oil plating process refers to a process for attaching a thin film to the outer ring raceway surface, the inner ring raceway surface, or the ball rolling surface. For example, as described later, the lubricant film according to the present invention can be formed by attaching a diluted lubricant to a rolling surface or the like and removing the diluted solvent by heat treatment.

  Therefore, since the wave gear device bearing of the present invention is a double-sided angular contact ball bearing of the rear combination type, it has high rigidity, low torque and high durability, and can be compact and lightweight.

Further, if a lubricating film is formed with a lubricant containing a lubricating oil having a vapor pressure of 1 × 10 ⁻⁵ Pa or less at 20 ° C. and a fluororesin, the lubricant is always supplied to the raceway surface, so Since the excess lubricating oil is trapped by the fluororesin without being in direct contact with the moving surface, the lubricating action is stably maintained with low dust generation and low outgas. Further, since the fluidity is maintained unlike the solid lubricant film, dust generation due to peeling, missing, and abrasion generated in the solid lubricant film is suppressed. Further, since the lubricating film is formed by the oil plating process, the rotational resistance is extremely small as compared with normal grease lubrication, and therefore, highly accurate rotational performance can be obtained.

As described above, the lubricating oil in the present invention has a vapor pressure at 20 ° C. of 1 × 10 ⁻⁵ Pa or less, and the lower the vapor pressure, the less outgas is preferable. On the other hand, when the vapor pressure at 20 ° C. exceeds 1 × 10 ⁻⁵ Pa, the effect of suppressing outgassing cannot be sufficiently obtained even if a fluororesin is added.
Furthermore, in the past, it was necessary to suppress dust generation and outgas by forming a thin lubricating film, but in the present invention, the effect of suppressing dust generation and outgas can be obtained by adding fluororesin, The lubricating film can be formed to be slightly thicker, so that the durability can be improved. That is, it is desirable to form the lubricating film to such an extent that it can cover the roughness peaks on the surface on which the lubricating film is to be formed. If the lubricating film becomes thinner than this, some of the above peaks will be easily exposed, and it will be easy to scrape off the oil film on the other side of contact, resulting in local seizure easily and durability. This is because the property becomes insufficient. On the other hand, if the lubricating film becomes too thick, excess lubricant is likely to be scattered, so that the effect of suppressing dust generation and outgassing decreases. Such adjustment of the thickness of the lubricating film can be performed, for example, by adjusting the dilution concentration of the diluted solution of the lubricant that adheres to the surface on which the lubricating film is to be formed in the oil plating process described later. .
Accordingly, the wave gear device bearing of the present invention is suitable for use in a vacuum or a clean room such as a precision machine manufacturing factory because the amount of dust generation and outgas is very low.

  As the fluororesin, in addition to polytetrafluoroethylene (hereinafter abbreviated as PTFE), tetrafluoroethylene perfluorovinyl ether copolymer (PFA), fluorinated ethylene propylene copolymer (FEP), etc. are preferably used. Can be used.

In addition, if a fluorine-based lubricating oil is used as the lubricating oil, the volatility is extremely low, so there is little outgas.
In this case, the content of the fluororesin in the lubricant is preferably 5% by mass or more and 40% by mass or less. When the content of the fluororesin is lower than 5% by mass, the dust generation suppressing effect is deteriorated, and when the content is higher than 40% by mass, the content of the lubricating oil is decreased, so that the lubricity is deteriorated. More desirably, it is 10 mass% or more and 30 mass% or less.

The fluorine-based lubricating oil is 10% by mass to 98% by mass of the fluorine-based lubricating oil having no functional group in the molecular structure and 90% by mass or less of 2% by mass of the fluorine-based lubricating oil having the functional group in the molecular structure. The above is preferable. As described above, the fluorine-based lubricating oil having a high affinity with the material constituting the raceway surface and the like, and using the fluorine-based lubricating oil having a functional group in the molecular structure, is firmly attached to the raceway surface and the like. By forming the film, durability and dust generation suppression effect can be improved.
On the other hand, fluorinated lubricants having functional groups in the molecular structure generally have high vapor pressure and are likely to generate outgas. Therefore, while maintaining the effects brought about by strong adhesion to the material, the conditions of the environment used It is desirable to adjust the content so that the amount of outgas in accordance with the above will be obtained.

  That is, by adding a fluororesin to the lubricant, outgas can be suppressed as compared with the conventional case, but in an environment where the demand for outgas suppression is more severe, a functional group is included in the composition as described above, that is, the molecular structure. It is desirable that the fluorine-based lubricating oil is composed of 10% by mass or more and 98% by mass or less of the fluorine-based lubricating oil not having, and 90% by mass or less and 2% by mass or more of the fluorine-based lubricating oil having a functional group in the molecular structure. Further, in an environment where the requirement for outgas suppression is more severe, 50 mass% or more and 98 mass% or less of fluorine-based lubricating oil having no functional group in the molecular structure and 50 mass% of fluorine-based lubricating oil having a functional group in the molecular structure. It is desirable that the fluorine-based lubricating oil is composed of 2% by mass or less. Furthermore, in an environment where the demand for outgas suppression is the most severe, it is possible to suppress outgassing by using only a fluorine-based lubricating oil having no functional group in the molecular structure as a fluorine-based lubricating oil and adding a fluororesin. desirable.

The lubricating oil may contain alkylated cyclopentane or polyphenyl ether as a main component, and such lubricating oil has a vapor pressure at 20 ° C. of 1 × 10 ⁻⁵ Pa or less. There is an effect of suppressing outgas even in vacuum. In addition, these hydrocarbon-based lubricating oils are superior in lubricity compared to fluorine-based lubricating oils, and the service life of the wave gear device bearing is extended.

  In this case, the content of the fluororesin in the lubricant is preferably 5% by mass or more and 60% by mass or less. When the fluororesin content is lower than 5% by mass, the dust generation suppressing effect deteriorates. When the fluororesin content is higher than 60% by mass, the lubricating oil content decreases, resulting in deterioration in lubricity and torque. Will increase. More desirably, it is 5 mass% or more and 40 mass% or less.

Further, in the bearing for a wave gear device of the present invention, the lubricant film is a lubricant diluted solution composed of 0.5% by mass or more and 10% by mass or less of the lubricant and 99.5% by mass or less of the diluent solvent, The oil film may be formed by attaching the lubricating film to the surface to be formed and heating at 50 ° C. to 250 ° C. for 15 minutes to 300 minutes to remove the dilution solvent. By the treatment, it is possible to form a lubricating film that exhibits the above-described functions and effects.
In this case, when the content of the lubricant is lower than 0.5% by mass, the lubricating film adhering to the raceway surface and the rolling surface becomes too thin, so that the durability becomes insufficient as described above. On the other hand, if the content is higher than 10% by mass, the diluted lubricant solution is sticky, adversely affects uniform adhesion and workability, and the lubricating film becomes too thick. Will be invited.

  As for the heating temperature and the heating time, when the upper limit temperature and the upper limit heating time are exceeded, the lubricity of the lubricant constituting the lubricating film deteriorates, and the raceway surfaces of the inner member and the outer member It causes a decrease in hardness and a dimensional change of the rolling surface of the rolling element. Conversely, if the temperature is set too low or the heating time is short, the diluting solvent cannot be completely removed. For this reason, during the actual oil plating treatment, the heating temperature and the heating are within the above range and are sufficient to remove the dilution solvent according to the type and content of the dilution solvent used. Set the time. In consideration of the material constituting the raceway and the like, for example, when using a steel that has been quenched and tempered, the heating temperature and the heating time are set so as not to cause the above-mentioned hardness reduction and dimensional change.

Here, examples of the adhesion method of the diluted lubricant solution include application and spraying. Alternatively, a method of pulling up after being immersed in the lubricant diluted solution can also be used. In this case, the assembled rolling device may be immersed, or the components of the rolling device may be immersed to form a lubricating film and then assembled.
The dilution solvent can be used as a solvent for both lubricating oil and fluororesin, and specific examples thereof include Novonec for alternative fluorocarbon-based dilution solvents, perfluorocarbon (PFC), and fluorine-based inert solutions. (Sumitomo 3M Co., Ltd.), Bertrell (DuPont Co., Ltd.), Galden (Audimont Co., Ltd.) and the like. When using a hydrocarbon-based lubricating oil, hexane or the like can be used as a diluent solvent.

Furthermore, in the bearing for a wave gear device of the present invention, the center line average roughness Ra of the outer ring raceway surface and the inner ring raceway surface is 0.02 μm or more and 0.2 μm or less, respectively, and the centerline average roughness of the rolling surface of the rolling element is set. Ra may be 0.002 μm or more and 0.01 μm or less.
By setting the surface roughness as described above, it is possible to suppress the contact surface pressure and improve the durability. At the same time, by setting the surface roughness as described above, the amount of the lubricating film can be suppressed to a small amount, so that excessive lubricating oil can be prevented from scattering and the effect of suppressing dust generation and outgas can be enhanced.

According to the bearing for the wave gear device of the present invention, one of the rigid internal gear and the flexible external gear, or the outer ring that can be fitted in the housing to which the one is fixed, the rigid internal gear and the flexible gear. A plurality of external gears, or an inner ring that can be fitted onto a shaft portion to which the other is fixed, a pair of outer ring raceway surfaces of the outer ring and a pair of inner ring raceways of the inner ring with a contact angle. Since it is a double-row angular contact ball bearing having a back combination type provided with a row of balls, it has high rigidity, low torque and high durability, and can be compact and lightweight. Further, at least one of the pair of outer ring raceway surfaces, the pair of inner ring raceway surfaces, and the rolling surface of the ball has a vapor pressure at 20 ° C. of 1 × 10 ⁻⁵ Pa or less by oil plating treatment. Since a lubricating film made of a lubricant containing lubricating oil and fluororesin is formed, it can be suitably used in a vacuum environment or the like.

  Hereinafter, the bearing for wave gear devices concerning each embodiment of the present invention is explained in detail with reference to drawings.

(First embodiment)
FIG. 1 is a cross-sectional view showing a top hat type wave gear device to which the wave gear device bearing of the first embodiment is applied. The wave gear device 20 is used in a vacuum, a clean room, or the like, and has a ring-shaped rigid internal gear 21 in which inner teeth 21a are formed on the inner peripheral surface, and a top-hat-type movable gear disposed on the inner side. A flexible external gear 22 and a wave generator 23 fitted inside the gear 22 are provided.

  The flexible external gear 22 includes a cylindrical body 22a, an annular diaphragm 22b extending continuously from one end of the body 22a at right angles to the outside in the radial direction, and an annular formed integrally with the diaphragm 22b. Boss 22c and cylindrical outer teeth 22d formed on the outer peripheral surface of the body 22a. The number of teeth of the outer teeth 22d is set to be smaller than the number of teeth of the inner teeth 21a (in this embodiment, two fewer than the inner teeth 21a).

  The wave generator 23 includes, for example, an annular rigid cam plate 24 having an elliptical contour, and an outer peripheral surface of the rigid cam plate 24 and a portion where the external teeth 22d of the flexible external gear are formed. A ball bearing 25 fitted between them. A hollow input shaft 26 to which a motor output shaft (not shown) and the like are connected is formed at the center of the rigid cam plate 24.

  In the wave gear device 20, when the rigid cam plate 24 connected to the motor output shaft rotates, the flexible external gear 22 is bent into an elliptical shape by the elliptical rigid cam plate 24 via the ball bearing 25. The meshing position of the inner teeth 21a and the outer teeth 22d meshed at two locations in the circumferential direction moves in the circumferential direction. Since the number of teeth of the internal teeth 21a and the external teeth 22d is different, a relative rotation corresponding to the difference in the number of teeth occurs between the internal teeth 21a and the external teeth 22d, and is greatly decelerated compared to the input rotational speed. The Then, by fixing one of the rigid internal gear 21 and the flexible external gear 22, a reduced rotation output can be obtained from the other gear.

  Here, between the outer peripheral surface of the rigid internal gear 21 and the inner peripheral surface of the housing 27 to which the flexible external gear 22 and the bolt are fixed, the rigid internal gear 21 and the flexible external gear 22 are provided. The wave gear device bearing 30 is disposed so as to rotatably support the shaft.

  As shown in FIG. 2, the bearing 30 includes a pair of outer rings 31 and 31 that can be fitted in the housing 27, a pair of inner rings 32 and 32 that can be fitted on the rigid internal gear 21, and the outer rings 31 and 31. A plurality of balls 33, 33 arranged in a double row with a contact angle α between the pair of inner ring raceway surfaces 32a, 32a of the pair of outer ring raceway surfaces 31a, 31a and the inner rings 32, 32; And a retainer 34, 34 having pockets for holding 33 respectively. The contact angle α of the balls 33, 33 in each row is opposite to each other.

  The pair of outer rings 31, 31 are fixed in the axial direction by an inwardly stepped portion 27 a formed in the housing 27 and a cover member 41 fixed to the axial end surface of the housing 27 with a bolt 40. On the other hand, the pair of inner rings 32, 32 is axially formed by an outward stepped portion 21 b formed on the rigid internal gear 21 and a pressing member 43 fixed to the axial end surface of the rigid internal gear 21 with a bolt 42. In addition to being fixed, the dimensions of the rigid internal gear 21 and the pressing member 43 are managed, and the end surface of the inner ring 32 is pressed by fastening the bolt of the pressing member 43, so that an appropriate preload is applied to the bearing.

  Further, the contact angle α of the back combination type angular ball bearing 30 is appropriately set in the range of 25 to 40 degrees, and the extension line L of the contact angle α is axially inward from the axial end surfaces of the inner rings 32 and 32. Thus, it is set so as to intersect with the inner peripheral surfaces of the inner rings 32, 32.

  Thus, by using the back combination type angular ball bearing 30 for the wave gear device 20, the operating point distance is increased by the back combination, the moment load is improved, and the rigid internal gear 21 ensures the moment. It is comprised so that a load can be loaded.

  Further, the rear combination angular ball bearing 30 has a small rotational torque because both the raceway surfaces 31a and 32a and the ball 33 are in point contact. On the other hand, the balls 33 are appropriately arranged by the cage 34, the bearing space volume can be sufficiently secured, and the grease life can be extended. For this reason, conventionally, maintenance for replenishing grease has been performed in a wave gear device to which a cross roller bearing is applied. However, in a wave gear device using a back combination type angular ball bearing 30, grease replenishment is not performed. It can be used until the endurance time of the wave gear device is reached.

  Furthermore, the back combination type angular contact ball bearing 30 can reduce the bearing cross-sectional height, reduce the wall thickness, and reduce the weight as compared with the cross roller bearing.

  Further, the outer rings 31, 31, inner rings 32, 32, balls 33, 33, and cages 34, 34 are formed of a metal material generally used for bearings, for example, a metal material having corrosion resistance. It is formed by. This type of metal material includes bearing steel such as JIS standard SUJ2, martensitic stainless steel such as JIS standard SUS440C, precipitation hardening stainless steel such as JIS standard SUS630, and carburizing and nitriding treatments for these metal materials. And those subjected to an appropriate curing heat treatment such as diamond-like carbon film treatment. For light load applications, for example, austenitic stainless steel such as JIS standard SUS304 or SUS316, or a titanium alloy subjected to surface hardening treatment can be used. For the balls 33, 33, ceramics such as silicon nitride, alumina, zirconia can be used in addition to the above metal materials.

  Among the metal materials and ceramics listed above, it is preferable to use a material having corrosion resistance. In particular, the outer rings 31 and 31 and the inner rings 32 and 32 are made of martensitic stainless steel, and the balls 33 and 33 are martensite. It is desirable to use stainless steel and ceramic. The reason is as follows. Usually, in order to give the bearing corrosion resistance, a method of adding a rust inhibitor to the lubricant is taken. However, since this rust preventive agent tends to evaporate compared with the component of the fluorine-type lubricant which comprises the lubricating film of this invention, addition of a rust preventive agent will become a factor which increases dust generation and outgas. Therefore, if corrosion-resistant materials are used for the outer rings 31, 31, the inner rings 32, 32, etc., the corrosion resistance can be realized and the amount of lubricant used can be reduced, so that the dust generation and outgas suppression targeted by the present invention are also achieved. be able to.

  The retainers 34 and 34 are preferably made of brass, titanium, or the like in addition to the above metal materials, but may be made of a synthetic resin material. As this synthetic resin material, for example, fluorine resin such as PTFE, ethylene tetrafluoroethylene (ETFE), engineering such as polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyether sulfone (PES), nylon 46, etc. Plastics can also be used. These synthetic resin materials may contain reinforcing fibers such as glass fibers.

  The rear combination angular contact ball bearing 30 has oil on the outer ring raceway surfaces 31 a and 31 a of the outer rings 31 and 31, the inner ring raceway surfaces 32 a and 32 a of the inner rings 32 and 32, and the rolling surfaces of the balls 33 and 33. A lubricating film F made of a fluorine-based lubricant is formed by the plating process. FIG. 3 is an enlarged schematic view showing the formation state of the lubricating film on the outer ring raceway surface 31 a, the inner ring raceway surface 32 a, or the rolling surfaces of the balls 33 and 33. The lubricating film F exceeds the roughness peak line (indicated by the alternate long and short dash line B in the figure) on the surface D on which the lubricating film F is to be formed (the position indicated by the solid line E in the figure). Until) is formed. Thus, the durability can be improved by covering the surface D with the lubricating film to such an extent that the roughness peaks are not exposed. The lubricating film F is desirably covered with the lubricating film so as to exceed the roughness peak line, but may be formed to a position equivalent to the peak line. In this case, since the amount of the lubricating film is small, dust generation and outgas are less. Further, as shown in FIG. 3, the lubricating film F is desirably formed continuously on the raceway surface or the like, but may be formed discontinuously, for example, in an island shape.

In addition, the center line average roughness Ra of the outer ring raceway surface 31a and the inner ring raceway surface 32a in the present embodiment is 0.02 μm or more and 0.2 μm or less, respectively, and the center line average roughness of the rolling surfaces of the balls 33 and 33 is set. Ra is set to 0.002 μm or more and 0.01 μm or less. By setting such surface roughness, the amount of the lubricating film F to be formed can be suppressed, and the dust generation suppressing effect can be improved.
The fluorine-based lubricant that forms the lubricating film F contains PTFE powder and fluorine-based lubricating oil as a fluororesin, and is in a so-called gel form.

As the fluorine-based lubricating oil, for example, a fluoropolyether polymer or a polyfluoroalkyl polymer is used. The fluoropolyether polymer is a polymer having a unit represented by the general formula -C _X F _2X -O- (X is an integer of 1 to 4) as a main repeating unit, and has a number average molecular weight of 1,000 to 1,000. The thing which is 50000 is mentioned. The polyfluoroalkyl polymer is represented by the formula R ₁ — (CF ₂ ) _n —R ₂ (n is a natural number), and R ₁ and R ₂ include those represented by the following chemical formula 1. It is done. R ₁ and R ₂ may be the same or different.

  Moreover, in addition to the thing which does not have a functional group in molecular structure, you may add a fixed amount what has a functional group in molecular structure to fluorine-type lubricating oil. As this functional group, those having a high affinity for metals, for example, an epoxy group, an amino group, a carboxyl group, a hydroxyl group, a mercapto group, a sulfone group or an ester group are preferred, and fluorine having a functional group in the molecular structure. Examples of the system lubricant include those represented by the following chemical formulas 2 and 3.

  More specifically, as the above-mentioned fluorine-based lubricating oil, a mixture with perfluoropolyether (PFPE) or a derivative thereof, for example, the trade name FONBLIN Y standard of Augmont Co., Ltd., fomblin emulsion (FE20, EM04, etc.) Alternatively, fomblin Z derivatives (FONBLIN Z DEAL, FONBLIN Z DIAC, FONBLIN Z DISOC, FONBLIN Z DOL, FONBLIN Z DOLTX2000, FONBLIN Z TETRAOL, etc.) are preferably used.

As the fluororesin, PTFE, tetrafluoroethylene perfluorovinyl ether copolymer (PFA), fluorinated ethylene propylene copolymer (FEP), and the like can be used.
A mixture of the fluorinated lubricant and the PTFE powder is used as the fluorinated lubricant. However, since the concentration is high when PTFE powder is mixed with the above exemplified fluorine-based lubricating oil, a diluted fluorine-based lubricant diluted with an appropriate diluent solvent is used for the oil plating process as described later. It is preferable.

Next, an example of the oil plating process will be described.
First, the outer rings 31, 31, inner rings 32, 32, balls 33, 33 and cages 34, 34 are assembled to complete the back combination angular ball bearing 30, and after degreasing and cleaning, the outer rings 31, 31 and A necessary amount of the prepared fluorine-based lubricant diluted solution is injected into the portion where the balls 33, 33 are present between the inner rings 32, 32 using a spoid or the like. Thereafter, by rotating the bearing 30 several times, the fluorine-based lubricant diluted solution is applied to the rolling parts and sliding parts of the outer rings 31, 31, inner rings 32, 32, balls 33, 33 and cages 34, 34. Adhere. The supply of the fluorine-based lubricant diluted solution may be performed by coating or spraying using a spray. Or you may supply a fluorine-type lubricant dilution solution by pulling up the bearing 30 assembled in the storage tank of a fluorine-type lubricant dilution solution after immersion.

  The fluorine-based lubricating oil prepared here is, for example, 90% by mass of Fomblin Z 25 (fluorine-based lubricating oil having no functional group in the molecular structure) and Fomblin Z DOL (fluorine having a functional group in the molecular structure). System lubricant) 10 mass%. Further, the diluted fluorine-based lubricant diluted solution was prepared by adjusting a fluorine-based lubricant prepared by mixing 80% by mass of this fluorine-based lubricant and 20% by mass of PTFE powder having a particle diameter of 1 μm or less. It is obtained by diluting with a diluting solvent Asahiklin AK-225 (manufactured by Asahi Glass Co., Ltd.) until it reaches to%.

  Thereafter, the entire back combination angular contact ball bearing 30 to which the fluorine-based lubricant diluted solution is adhered is heated at 120 to 140 ° C. for about 30 minutes to remove the diluted solvent contained in the adhered fluorine-based lubricant diluted solution. To do. In this way, a lubricating film made of a fluorine-based lubricant can be formed.

Note that as the lubricating oil constituting the lubricating film F, a hydrocarbon-based lubricating oil may be used instead of the fluorine-based lubricating oil. In this case, the center line average roughness Ra of the outer ring raceway surface 31a and the inner ring raceway surface 32a is 0.02 μm or more and 0.2 μm or less, more preferably 0.02 μm or more and 0.08 μm or less. Further, the center line average roughness Ra of the rolling surfaces of the balls 33 and 33 is not less than 0.002 μm and not more than 0.01 μm, and more preferably not less than 0.002 μm and not more than 0.005 μm.
The lubricant forming the lubricating film F contains fluororesin powder and a lubricating oil containing alkylated cyclopentane or polyphenyl ether as a main component, and is in a so-called gel form.

An example of such an alkylated cyclopentane is tri (2-octyldodecyl) cyclopentane. As tri (2-octyldodecyl) cyclopentane, for example, Synthetic Oil 2001A (trade name) manufactured by Nye Luvicants is commercially available. Also, tri-n-octylcyclopentane, tetra-n-octylcyclopentane, penta-n-octylcyclopentane, tri-n-nonylcyclopentane, penta-n-nonylcyclopentane, penta-n-decylcyclopentane, An alkylated cyclopentane such as penta-n-dodecylcyclopentane, tetra-2-ethylhexylcyclopentane, etc. has a vapor pressure of 1 × 10 ⁻⁵ Pa or less at 20 ° C. (for example, 1 × 10 ⁻⁷ to 1 × 10 ^-8 Pa), it can be used as a lubricating oil. If such an alkylated cyclopentane is used, the lubricant is hardly evaporated even when the back combination angular ball bearing of the present invention is used in a vacuum.

  As the polyphenyl ether, for example, a phenyl ether type synthetic oil manufactured by Matsumura Oil Research Co., Ltd. can be used. Of these, pentaphenyl ether, tetraphenyl ether, monoalkyl tetraphenyl ether, dialkyl tetraphenyl ether, monoalkyl triphenyl ether can be used. Phenyl ether and alkyl diphenyl ether can be preferably used. Since these polyphenyl ethers have a low vapor pressure and excellent heat resistance, there is little outgas even in a vacuum or in a high temperature environment.

Next, an example of an oil plating process when using a hydrocarbon-based lubricating oil will be described.
First, the outer rings 31, 31, inner rings 32, 32, balls 33, 33 and cages 34, 34 are assembled to complete the back combination angular ball bearing 30, and after degreasing and cleaning, the outer rings 31, 31 and A necessary amount of a diluted lubricant solution is injected between the inner rings 32 and 32 where the balls 33 and 33 are present by a spoid or the like. Thereafter, by rotating the bearing 30 several times, the diluted solution is adhered to the outer ring 31, the inner ring 32, 32, the balls 33, 33, and the rolling parts and sliding parts of the cages 34, 34. The diluent may be supplied by coating or spraying using a spray. Alternatively, the diluted solution may be supplied by pulling up the bearing 30 assembled in the diluted solution storage tank after immersion.

  The lubricant prepared here is composed of, for example, 60% by mass of Synthetic Oil 2001A (trade name) manufactured by Nye Luvicants, and 40% by mass of PTFE powder having a particle diameter of 1 μm or less. This diluted solution of the lubricant was obtained by diluting the lubricant with a diluent solvent such as hexane or Asahi Clin AK-225 (manufactured by Asahi Glass Co., Ltd.) to 1% by mass. As the fluororesin, a dry film RA / IPA manufactured by DuPont Co., Ltd. in which PTFE was dispersed in a solvent was used.

  Thereafter, the entire back combination type angular contact ball bearing 30 to which the diluted solution is adhered is heated at 100 to 140 ° C. for about 30 minutes to remove the diluted solvent contained in the adhered diluted solution. In this way, the lubricating film F can be formed, and a wave gear device bearing that can be suitably used in a vacuum environment or the like can be configured.

(Second Embodiment)
Next, a wave gear device bearing according to a second embodiment of the present invention will be described in detail with reference to FIGS. In addition, the same code | symbol is attached | subjected about a part equivalent to 1st Embodiment, and description is abbreviate | omitted or simplified.

  Similar to the first embodiment, the wave gear device bearing 50 of the present embodiment is a back combination angular ball bearing incorporated into the top hat type wave gear device 20, and a pair of outer rings that can be fitted in the housing 27. 51, 51, a pair of inner rings 52, 52 that can be externally fitted to the rigid internal gear 21, a pair of outer ring raceway surfaces 51a, 51a of the outer rings 51, 51 and a pair of inner ring raceway surfaces 52a, 52a of the inner rings 52, 52. There are provided a plurality of balls 53, 53 arranged in a double row with a contact angle α therebetween, and cages 54, 54 having pockets for holding the balls 53, 53 in each row, respectively. Further, as in the first embodiment, the pair of inner rings 52, 52 are pressed in the axial direction by the bolts 42 via the pressing members 43, thereby applying an appropriate preload to the bearings.

Here, in the back combination type angular contact ball bearing 50 of the present embodiment, the outer end surfaces 52b, 52b of the pair of inner rings 52, 52 are axially outward from the outer end surfaces 51b, 51b of the pair of outer rings 51, 51. It protrudes. Further, flanges 52c and 52c are formed axially outward from the inner ring raceway surfaces 52a and 52a of the pair of inner rings 52 and 52, and the flanges 52c and 52c are in the vicinity of the pitch circle PCD of the balls 53 and 53, specifically. In addition, the height extends to a position slightly lower than the pitch circle PCD. Thereby, a load point can be expanded and moment rigidity can be improved more and the restriction | limiting in the dimension of the housing 27 or the press member 43 can be eased.
Also in this embodiment, the contact angle α of the back combination type angular contact ball bearing 50 is appropriately set in the range of 25 to 40 degrees, and the extension line L of the contact angle α is the axis of the inner rings 52 and 52. It is set so as to cross the inner peripheral surfaces of the inner rings 52, 52 on the inner side in the axial direction from the direction outer end surfaces 52b, 52b.

In addition, the cages 54 and 54 of the present embodiment are synthetic resin crown-type cages, and the column portions 54a and 54a are provided so as to prevent interference with the flange portions 52c and 52c of the inner rings 52 and 52. It is formed to incline radially outward from the base toward the tip.
The cages 54 and 54 may be constituted by metal press cages 54 'and 54' as shown in FIG. 6 instead of the synthetic resin crown-shaped cage. A machined cage may be used.
Other configurations and operations are the same as those in the first embodiment.

  In addition, this invention is not limited to the thing of said embodiment, A change, improvement, etc. are possible suitably.

  In the top hat type wave gear device of the present embodiment, the outer ring of the back combination type angular ball bearing is fitted in the housing to which the flexible external gear is fixed, and the inner ring is fitted in the rigid internal gear. However, the outer ring may be fitted into the flexible external gear, and the inner ring may be fitted to the shaft portion to which the rigid internal gear is fixed. The back combination type angular contact ball bearing of the present invention can also be applied to the top hat type wave gear device shown in FIG.

In the present embodiment, the wave gear device has been described only for the top hat type, but the bearing for the wave gear device of the present invention can also be applied to a cup type or a flat type.
For example, in a cup-type wave gear device bearing, the outer ring of the back combination type angular ball bearing is fitted into a rigid internal gear or a housing to which the rigid internal gear is fixed, and the inner ring is flexible. The external gear or the flexible external gear is fitted on the shaft portion to which the external gear is fixed.

  In the present embodiment, the pair of outer rings and the pair of inner rings are arranged adjacent to each other. However, when there is a space, a spacer is arranged between the pair of outer rings and between the pair of inner rings. As a result, the bearing span can be increased and the rigidity can be further improved.

  Furthermore, the configuration of the back combination type angular ball bearing can be improved as appropriate, and the pair of outer rings may be formed integrally or may include a seal member.

  In the present embodiment, the lubricating film F is formed on the rolling surfaces of the pair of outer ring raceway surfaces 31a and 31a, the pair of inner ring raceway surfaces 32a and 32a, and the balls 33 and 33. It may be formed on at least one of the surfaces 31a, 31a, the pair of inner ring raceway surfaces 32a, 32a, and the rolling surfaces of the balls 33, 33, and is formed only on the rolling surfaces of the balls 33, 33. Also good.

It is sectional drawing of the wave gear apparatus with which the bearing for wave gear apparatuses which concerns on 1st Embodiment of this invention is applied. It is an expanded sectional view of the bearing for wave gear apparatuses of FIG. It is an expanded sectional view which shows the formation state of a lubricating film. It is sectional drawing of the wave gear apparatus with which the bearing for wave gear apparatuses which concerns on 2nd Embodiment of this invention is applied. It is an expanded sectional view of the bearing for wave gear apparatuses of FIG. It is an expanded sectional view of the bearing for wave gear devices concerning the modification of a 2nd embodiment. It is sectional drawing of the wave gear apparatus using the conventional cross roller bearing.

Explanation of symbols

20 Wave gear device 21 Rigid internal gear 22 Flexible external gear 23 Wave generator 27 Housing 30 Rear combination angular contact ball bearing 31 Outer ring 31a Outer ring raceway surface 32 Inner ring 32a Inner ring raceway surface 33 Ball α Contact angle F Lubrication film

Claims (1)

A rigid internal gear, a flexible external gear disposed inside the rigid internal gear, and a flexible external gear disposed inside the flexible external gear, bending the flexible external gear in the radial direction. A wave generator that partially meshes with the rigid internal gear and moves the meshing position of both gears in the circumferential direction. A wave gear bearing that supports an external gear so as to be relatively rotatable,
The bearing includes one of the rigid internal gear and the flexible external gear, or an outer ring that can be fitted in a housing to which the one is fixed, the rigid internal gear, and the flexible external gear. A plurality of inner rings that can be fitted onto a shaft portion to which the other is fixed, a pair of outer ring raceway surfaces of the outer ring and a pair of inner ring raceway surfaces of the inner ring with a contact angle. A rear combination angular contact ball bearing with a ball,
At least one of the pair of outer ring raceway surfaces, the pair of inner ring raceway surfaces, and the rolling surface of the balls has a vapor pressure at 20 ° C. of 1 × 10 ⁻⁵ Pa or less by oil plating treatment. A bearing for a wave gear device, wherein a lubricating film made of a lubricant containing a lubricating oil and a fluororesin is formed.

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