JP2015230077A - Solid lubrication rolling bearing and resin cage for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin cage which reduces a guide clearance for securing the high speed stability of the resin cage while securing a suitable guide clearance.SOLUTION: In a resin cage used in a solid lubrication rolling bearing, a circumferential direction area of an end face 14 of a resin cage 8 corresponding to a pillar 12 between pockets 10 is provided with a thinner portion 16, which allows an outer diameter face 18 to elastically deform into wave shape in high speed rotation.

Description

  The present invention relates to a solid lubricated rolling bearing and a resin cage for the bearing, but is not limited thereto, and can be used, for example, for a liquid fuel turbo pump main shaft bearing.

  A liquid fuel turbo pump for pumping liquid fuel of a rocket engine works to send a cryogenic fluid such as liquid hydrogen or liquid oxygen to a combustion chamber at a high pressure of 200 atm or higher. The liquid fuel turbo pump main shaft bearing is used at high speed rotation in an environment where cryogenic fluid passes at high speed. In addition, normal fluid lubricants such as oil and grease cannot be used in the above environment. Therefore, a resin composite material that employs a solid-lubricated rolling bearing, has a strength that can withstand hoop stress during high-speed rotation, and has self-lubricating properties and transferability to a sliding counterpart. Is used.

  Since the spindle speed of liquid fuel turbo pumps to be developed in the future is expected to be further increased, the development of bearings corresponding thereto is an important issue.

  Patent Document 1 describes an integrated machined cage in which a base glass woven fabric is impregnated with PTFE and a glass fiber in a surface layer is dissolved by hydrofluoric acid treatment as a resin cage for a turbo pump bearing. ing. This resin retainer, on the one hand, is made of glass woven fabric to ensure the strength against hoop stress during high-speed rotation, and on the other hand, the impregnated PTFE ensures self-lubricity and transferability to the sliding material. Thus, the bearing can be used in a cryogenic and high-speed rotation environment.

Japanese Patent Publication No. 2-20854 JP 2013-224731 A

  The resin holder described in Patent Document 1 has the following problems.

  Resin cages using glass woven fabric as a base material have a linear expansion coefficient larger than that of the material constituting the bearing race and rolling elements, so that dimensional shrinkage occurs in a cryogenic environment. On the other hand, under conditions where centrifugal force acts on the resin cage due to high-speed rotation, the influence of the low Young's modulus is promoted and the size expansion occurs. Therefore, it becomes a problem to secure an appropriate guide clearance that can cope with environmental changes in both the temperature environment and the speed environment.

  Here, the diameter of the cage guide surface (the cylindrical surface of the race ring or the washer for guiding the cage in the radial direction) and the diameter of the guide surface (inner diameter surface or outer diameter surface) of the cage This difference is called a clearance. In order to guide rotation of the cage and prevent swinging of the cage, an appropriate clearance is provided between the guide surface (inner diameter surface or outer diameter surface) of the cage in contact with the bearing ring and the contact surface of the bearing ring. It has been.

  In the case of a liquid fuel turbo pump bearing, the following two points should be taken into consideration when designing the guide clearance of the cage.

The first point is dimensional shrinkage of the resin cage in a cryogenic environment.
The difference in coefficient of linear expansion between the steel raceway and the resin cage is large, for example, about 10 × 10 ^{−6 to} 20 × 10 ⁻⁶ for steel, whereas the resin material is 50 × 10 ^−6. Since there is a difference of more than twice the degree, it is necessary to consider this point in the clearance management of the steel outer ring and the resin cage.

The second point is the expansion of the dimensions of the resin cage under high speed operation.
Since the Young's modulus of resin is smaller than that of steel, the resin cage expands and expands when a centrifugal force is applied, and the guide clearance of the resin cage is reduced. Therefore, it is necessary to consider this point.

  Under such circumstances, in order to stably guide the resin cage during high-speed operation, it is effective to make this guide clearance as small as possible. If the guide clearance is too large or too small, there are the following problems.

  If the guide clearance is excessive, the resin retainer cannot be positioned in the radial direction, and the resin retainer swings in the radial direction because of the slight imbalance of the resin retainer. Wear on the inner diameter surface (cage guide surface) of the radial surface and the outer ring, which leads to damage to the bearing.

  If the guide clearance is too small, there will be no clearance between the outer diameter surface of the resin cage and the inner diameter surface of the outer ring (the cage guide surface), resulting in significant frictional motion, leading to bearing damage.

  Therefore, an object of the present invention is to provide a resin cage capable of ensuring an appropriate guide clearance while reducing the guide clearance in order to ensure high-speed stability of the resin cage.

  According to the present invention, this problem is solved by providing a meat theft in the circumferential region corresponding to the pillar in the end face of the resin cage. That is, the resin cage for a solid lubricated rolling bearing according to the present invention is provided with a meat stealer in the circumferential region corresponding to the pillar between the pockets on the end surface of the resin cage. The radial surface is elastically deformed into a wave shape.

  More specifically, in the region corresponding to the column where the outer diameter surface of the resin cage is provided with the meat steal due to the action of the centrifugal force accompanying the high speed rotation, the region where the meat steal is not provided, ie, the pocket. The outer diameter surface expands compared to the region corresponding to. Therefore, the entire outer diameter surface of the resin cage is deformed into a wave shape in the circumferential direction. As a result, a dynamic pressure effect is generated between the outer diameter surface of the resin cage and the guide surface of the outer ring. The gap between the outer diameter surface of the cage and the guide surface of the outer ring can be appropriately maintained.

  Utilizing the characteristic of low Young's modulus of the resin material, due to the centrifugal force accompanying high-speed rotation, the rigidity difference in the circumferential direction of the outer diameter surface of the resin cage, that is, the area where the meat stealing is provided and the meat stealing are not provided Based on the difference in rigidity with the region, the outer diameter surface of the resin cage is deformed into a wave shape. A positive pressure is generated by the liquid fuel passing between the outer diameter surface of the resin cage and the inner diameter surface (cage guide surface) of the outer ring, thereby enabling appropriate clearance management. In other words, despite the small clearance, the guide surfaces are separated by the dynamic pressure effect to avoid frictional contact.

  Patent Document 2 describes forming a meat stealing portion having a circumferentially repeated shape. However, the purpose of this is to improve the strength and accuracy of the resin cage by preventing the molten resin flow from being disturbed at the confluence in the annular portion and forming a weld line that is linear in the radial direction. It is what. Therefore, it is essential that the meat stealing part is present in a form that disturbs the flow of the molten resin and is constantly present throughout the entire circumference, and intermittent meat stealing in the circumferential direction, in other words, the meat stealing part is Those interrupted in the circumferential direction are excluded. This is because it is inevitable that a straight weld line is formed at the interrupted portion. Therefore, in the resin cage provided with the circumferentially repeated shape stealing portion described in Patent Document 2, it is not possible to expect a wave shape change enough to avoid frictional contact due to the dynamic pressure effect.

  According to the present invention, a resin retainer for a solid lubricated rolling bearing capable of ensuring an appropriate guide clearance while reducing a guide clearance to ensure high-speed stability of the resin retainer, and a solid lubrication using the retainer A rolling bearing can be provided.

It is a partially broken perspective view of the solid lubrication rolling bearing using the resin cage of the Example of this invention. (A) is a front view of the resin cage in FIG. 1, (B) is a BB cross-sectional view of FIG. 2 (A), (C) is a CC cross-sectional view of FIG. 2 (A), and (D) is It is the D section enlarged view of Drawing 2 (A). (A) is a front view of a resin cage showing another embodiment, (B) is a BB cross-sectional view of FIG. 3 (A), (C) is a CC cross-sectional view of FIG. 3 (A). . (A) is a front view of a resin cage showing still another embodiment, (B) is a BB cross-sectional view of FIG. 4 (A), (C) is a CC cross-sectional view of FIG. 4 (A), (D) is the D section enlarged view of Drawing 4 (A). (A) is a front view of a resin cage showing still another embodiment, (B) is a BB cross-sectional view of FIG. 5 (A), and (C) is a CC cross-sectional view of FIG. 5 (A). is there. (A) is a front view of a resin cage showing still another embodiment, (B) is a BB cross-sectional view of FIG. 6 (A), and (C) is a CC cross-sectional view of FIG. 6 (A). is there. (A) is a perspective view of a resin cage, (B) is an enlarged view of a divided piece corresponding to the shaded portion of FIG. 7 (A), and (C) is an FEM analysis result regarding deformation of the outer diameter surface of the resin cage. FIG. (A) is a front view of a rolling bearing, (B) is a typical enlarged view of the B section of FIG. 8 (A). It is a perspective view of the resin holder which shows the prior art.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a ball bearing as an example of a solid lubricated rolling bearing. This ball bearing has a bearing inner ring 2, a bearing outer ring 4, a plurality of balls 6, and a resin cage 8 as main components. In FIG. 1, the bearing inner ring 2 and the bearing outer ring 4 are partially cut out, and balls are not shown in the cut part.

  The resin retainer 8 is a bearing component for holding the balls 6 at a predetermined interval in the circumferential direction, and has a cylindrical shape as a whole, and is provided with pockets 10 at a predetermined interval in the circumferential direction. Each pocket 10 is for accommodating the ball 6 and penetrates the resin holder 8 in the radial direction. A portion that is located between the pockets 10 and separates adjacent pockets 10 is called a column 12.

  A meat stealer 16 is formed in a circumferential region corresponding to the pillar 12 in the end face 14 of the resin retainer 8. The specific aspect of the meat stealing 16 is as follows.

  One or more meat thefts 16 are provided in the circumferential region corresponding to the pillars 12 of the resin cage 8. In the embodiment shown in FIGS. 1 to 4, three meat thefts 16 are provided in the circumferential region corresponding to the pillar 12. In the embodiment shown in FIGS. 5 and 6, the circle corresponding to the pillar 12 is provided. One meat steal 16 is provided in the circumferential region. As shown in FIGS. 1 to 4, when a plurality of meat thefts 16 are provided in the circumferential region corresponding to the pillars 12, the meat thefts 16 are independent from each other as shown.

  The shape of each meat theft 16 that appears on the end face 14 of the resin holder 8 is arbitrary. As a specific example, FIGS. 1 and 2 are examples in which the shape of each meat theft 16 is an isosceles triangle and the directions of the vertices are alternately reversed. It has a truss shape. 3 and 6 show an example of a circular meat theft 16, and FIGS. 4 and 5 show an example of a rectangular meat theft 16, respectively. 4 and 5 are both rectangles having long sides in the circumferential direction, but the latter is different in that the long sides are longer than the former.

  In the case of the embodiment shown in FIGS. 2 to 5, the meat theft 16 is in the form of a bottomed recess. In the case of the embodiment shown in FIG. 6, the meat stealer 16 is in the form of a through hole. As shown in FIG. 6, in the case of the meat stealer 16 in the form of a through hole, the meat stealer 16 opens at both end surfaces 14 of the resin retainer 8, which corresponds to the case where the meat stealer 16 is provided on both end surfaces.

  In the case of the meat theft 16 in the form of a bottomed recess, it is not always necessary to provide it on the end faces 14 on both sides. If a desired deformation of the outer diameter surface can be obtained when the centrifugal force is applied only by providing the meat stealer 16 on the one end surface 14, the meat stealer 16 may be provided on the one end surface 14. On the other hand, if the meat stealing 16 is merely provided on one end surface 14 and the desired deformation of the outer diameter surface cannot be obtained even if centrifugal force is applied, the meat stealing 16 is provided on both end surfaces 14.

  The material of the resin cage 8 is selected from super engineering plastic, high engineering plastic, and general-purpose engineering plastic that are excellent in self-lubricating property and transferability to the sliding material and that can be compression molded or heat compression molded. . Specific examples include polytetrafluoroethylene (PTFE), polyimide (PI), polyethylene (PE) and the like. In particular, it is desirable to use PTFE which is excellent in transferability to the sliding material and self-lubricating property.

The manufacturing process of the resin cage 8 includes a compression molding process and a machining process described below.
In the compression molding step, the selected resin material is filled in a heated mold, and is pressed and molded by a compression molding machine. The molding pressure is 10 MPa or more. Furthermore, if there is a concern about dimensional changes during use of the bearing due to residual compressive stress in compression molding, an annealing process may be performed.

  The resin retainer 8 is a resin composite that compresses and integrally forms a resin material as described above, and uses an aluminum alloy as a base material to provide self-lubricating properties and transferability to a sliding counterpart. The material may be insert molded.

  Meat stealing 16 is formed on the end surface 14 of the resin cage 8 by cutting the molded product obtained in the compression molding process. Note that the pocket 10 is processed before or after the meat stealing 16 is processed, and finish processing is performed in order to obtain dimensional accuracy of necessary inner diameter, outer diameter, and width.

  With respect to the deformation amount of the outer diameter surface 18 of the resin cage 8, an analysis result as shown in FIG. 7C was obtained by FEM analysis. The analysis conditions are as follows.

Resin cage outer diameter: φ60
Cage rotational speed: 34,000 min ^-1
Material: Super engineering plastic
(Bearly FL3000, manufactured by NTN Corporation)
Young's modulus: 5 GPa
Poisson's ratio: 0.3
Linear expansion coefficient: 50 × 10 ⁻⁶
Specific gravity: 2.3

  As for the analysis model, the example is a resin holder provided with a triangular shape steal as shown in FIG. 2, and the comparative example is a conventional resin holder without a meat steal as shown in FIG. . Considering the axial direction and periodic symmetry, the analysis was performed using the model (divided piece) shown in FIG. Here, FIG. 7 (A) corresponds to the resin cage shown in FIGS. 2 and 9, except that the resin cage of FIG. FIG. 7B is an enlarged view of the portion. Naturally, there is no meat theft in the resin holder of FIG. 9, but FIG. 7B is a partially enlarged view of the resin holder of FIG.

  In FIG. 7C showing the analysis results, the horizontal axis indicates the circumferential phase (deg), and the vertical axis indicates the radial displacement (μm). This is a measurement and plot of the position of, and shows the deformation of the outer diameter surface 18 of the cyclically symmetric model including pockets and columns when the rotational speed is given.

  In the case of the comparative example, the deformation of the outer diameter surface 18 is slight. That is, the phase near the center of the pocket (0 deg) is about 80 μm, and gradually and linearly increases from there, and the phase near the center of the column (15 deg) is about 100 μm. This is considered to correspond to the slight difference in mass between the pocket portion and the column portion due to the shape of the resin cage 8.

  In the case of the example, a noticeable wave shape deformation can be seen. That is, there is a maximum diameter portion of about 170 μm in the phase of 0 deg and a phase of about 12 deg, a minimum diameter portion of about 120 μm in the phase of about 7 deg, and the maximum diameter portion and the minimum diameter portion of the outer diameter surface. There is a difference (groove depth d) of about 60 μm. As can be seen from the fact that the maximum diameter portion corresponds to the phase with the meat stealing, it is considered that the mass of the portion is reduced by providing the meat stealing, and the influence of the centrifugal force is reduced accordingly.

  The value of the groove depth d satisfies d / D = 1000 which is effective for generating the dynamic pressure effect. Reference sign D represents the outer diameter of the resin retainer 8 as shown in FIG. Here, FIG. 8A corresponds to the front view of the rolling bearing of FIG. 1, and FIG. 8B expands the portion B of FIG. 8A and incorporates the contents of FIG. 7C. It is shown schematically. In FIG. 8A, illustration of meat theft is omitted.

Further, since the gap (guide gap s in FIG. 8B) effective for generating the dynamic pressure effect is desirably 1: 1 with the groove depth d, the above analysis result is obtained. If it considers, about 60 micrometers is desirable.
Thus, by obtaining the dynamic pressure effect, even when the outer diameter surface 18 of the resin retainer 8 and the inner diameter surface (the retainer guide surface) of the outer ring 4 approach each other, alignment is performed to prevent contact and appropriately It becomes possible to secure a clearance.

  The effects of the above-described embodiments can be summarized and listed as follows.

  In the resin cage for a solid lubricated rolling bearing of the embodiment, the meat stealer 16 is provided in the circumferential region corresponding to the column 12 between the pocket 10 and the pocket 10 in the end surface 14 of the resin cage 8. The outer diameter surface 18 is elastically deformed into a wave shape during high-speed rotation. The outer diameter surface 18 of the resin retainer 8 is deformed into a wave shape to obtain a dynamic pressure effect, and the outer diameter surface 18 of the resin retainer 8 and the inner diameter surface (the retainer guide surface) of the outer ring 4 approach each other. Even when it is aligned, it can prevent contact and ensure proper clearance.

  One or more meat steals 16 can be provided per circumferential region. When providing a plurality of meat thefts 16 in one circumferential region, it is desirable that the meat thefts 16 are independent of each other.

  The meat stealer 16 may be in the form of a bottomed recess or in the form of a through hole. In the case of meat stealing in the form of a through-hole, it opens to both end faces of the resin cage, but in the case of meat stealing in the form of a bottomed recess, it can be provided only on one end face.

  In manufacturing the resin cage, a resin composite material that has been provided with self-lubricating properties and transferability to a sliding counterpart material is integrally formed by compression molding. Alternatively, an aluminum alloy may be used as a base material, and a resin composite material imparted with self-lubricating properties and transferability to a sliding counterpart material may be insert-molded.

  The resin cage can use a solid lubricated rolling bearing as a component.

  The above-mentioned solid lubricated rolling bearing can be used for a liquid fuel turbo pump that cannot use a normal lubricant.

  Although the embodiments of the present invention have been described with reference to the drawings, the present invention is not limited to the embodiments described and illustrated herein, and various modifications can be made without departing from the scope of the claims. Can do.

2 Bearing inner ring 4 Bearing outer ring 6 Ball (rolling element)
8 Resin cage 10 Pocket 12 Pillar 14 End face 16 Meat stealing 18 Outer diameter surface

Claims (9)

  Solid lubricated rolling that allows the outer diameter surface to be elastically deformed into a wave shape during high-speed rotation by providing meat stealing in the circumferential region corresponding to the pillar between the pockets of the end surface of the resin cage Resin cage for bearings.   The resin retainer for a solid-lubricated rolling bearing according to claim 1, wherein one or a plurality of thefts are provided per circumferential region.   The resin retainer for a solid lubricated rolling bearing according to claim 1 or 2, wherein the meat theft is in the form of a bottomed recess.   The resin retainer for a solid lubricated rolling bearing according to claim 1 or 2, wherein the meat theft is in the form of a through hole. The resin retainer for a solid lubricated rolling bearing according to claim 2, wherein a plurality of thefts provided for each circumferential region are independent of each other.   The resin retainer for a solid lubricated rolling bearing according to any one of claims 1 to 5, wherein a resin composite material imparted with self-lubricating properties and transferability to a sliding counterpart material is integrally formed by compression molding.   The resin cage for a solid lubricated rolling bearing according to any one of claims 1 to 5, wherein an aluminum alloy is used as a base material, and a resin composite material having self-lubricating properties and transferability to a sliding counterpart material is insert-molded. .   A solid lubricated rolling bearing using the resin retainer according to claim 1.   The solid lubricated rolling bearing according to claim 8, which is used for a liquid fuel turbo pump.

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