JP2017180737A - Cage for rolling bearing and rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cage for rolling bearing in which abrasion resistance on a guide surface is high while having high solid lubrication performance, and to provide a rolling bearing.SOLUTION: A cage for rolling bearing is arranged between a pair of bearing rings and holds a plurality of rolling elements at a predetermined position. The cage for rolling bearing includes: an annular body having a plurality of pocket holes for accommodating rolling elements; and a resin part formed by injection molding by resin including a solid lubricant with the body being an insert component. The resin part includes: a first portion provided on an inner peripheral surface of the pocket holes of the body and for forming a plurality of pocket surfaces which come into slide-contact with each of the rolling elements; and a second portion provided on an inner peripheral surface or an outer peripheral surface of the body and for forming a guide surface coming into slide-contact with one of the bearing rings. The second portion is constituted by resin whose comparative abrasion amount is smaller than that of the resin which constitutes the first portion.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cage for a rolling bearing (hereinafter simply referred to as “cage”) and a rolling bearing having the same.

  Rolling bearings used in rocket engine turbo pumps are used in a high-speed rotating environment in a liquid propellant. In particular, when used in liquid hydrogen or liquid oxygen, since it becomes extremely low temperature, fluid lubricants such as oil and grease used in ordinary rolling bearings cannot be applied. Therefore, for example, the one shown in Patent Document 1 has been proposed as a cage to which solid lubrication performance is added.

  Patent Document 1 discloses a cage in which a solid lubricant is injection-molded on the surface of a base material. The cage includes an annular main body having a plurality of pocket holes, and a resin portion that is injection-molded with a resin containing a solid lubricant using the main body as an insert part. The resin portion is provided on the inner peripheral surface of the pocket hole of the main body to form a pocket surface, and is provided on either the outer peripheral surface or the inner peripheral surface of the main body on the side in sliding contact with the raceway (outer ring or inner ring). To form a guide surface.

  When the rolling bearing provided with the cage rotates, the resin portion constituting the pocket surface of the cage and the rolling element come into sliding contact. Thereby, the solid lubricant in the resin portion is transferred to the surface of the rolling element, and lubrication between the rolling element and the raceway surface of the raceway is performed.

Japanese Patent Application Laid-Open No. 2014-234846

  As described above, the resin portion formed in the cage secures lubrication with the raceway surface by the transfer action (lubricant supply action) by the rolling elements on the pocket face. For this reason, it is desirable to use resin with high transferability (lubricant supply performance) for the resin part.

  On the other hand, the guide surface of the cage is in sliding contact with the guide surface of the bearing ring, but the guide surface of the cage described in Patent Document 1 is easily worn because it is formed by the resin portion. If the wear of the resin part progresses and the base material is exposed and worn, the wear powder may become a foreign substance and adversely affect the bearing function. For this reason, the guide surface of the cage needs to have high wear resistance, and is required to have a performance contrary to the pocket surface. In particular, when insert molding is performed as in the cage of Patent Document 1, since the same resin portion is formed by the pocket surface and the guide surface, the transferability of the pocket surface and the wear resistance of the guide surface are simultaneously achieved. It becomes difficult to increase.

  The problem to be solved by the present invention is to provide a rolling bearing cage having high solid lubrication performance and high wear resistance of a guide surface, and a rolling bearing provided with the cage.

  The rolling bearing cage of the present invention is a rolling bearing cage that is arranged between a pair of race rings and holds a plurality of rolling elements at a predetermined position, and has a plurality of pocket holes for accommodating the rolling elements. An annular main body, and a resin portion injection-molded with a resin containing a solid lubricant using the main body as an insert part, and the resin portion is provided on the inner peripheral surface of the pocket hole of the main body. A first portion that forms a plurality of pocket surfaces that are in sliding contact with the moving body, and a second portion that is provided on an inner peripheral surface or an outer peripheral surface of the main body and forms a guide surface that is in sliding contact with one of the race rings, The second part is made of a resin having a specific wear amount smaller than that of the resin constituting the first part.

  In the rolling bearing cage of the present invention, the pocket surface slidably in contact with the rolling element is formed of a resin (first portion) containing a solid lubricant, and the guide surface slidably in contact with the race is made of resin (second portion). Since it is formed, lubrication can be performed by transferring the solid lubricant contained in the resin to the rolling elements. In this case, since the second part forming the guide surface is made of a resin having a specific wear amount smaller than that of the resin constituting the first part, the second part has higher wear resistance than the first part. . That is, while ensuring solid lubricating performance (lubricity) with the solid lubricant, the guide surface has higher wear resistance than the pocket surface, and wear of the cage body can be suppressed.

  The said 1st part may mix | blend the said 1st part in the ratio of 45-80 vol% whose main component resin is a thermoplastic resin, 20-40 vol% of solid lubricants, and 0-15 vol% of reinforcing materials. As a result, the pocket surface has high transferability and excellent solid lubricating performance. Further, the second part may contain more than 15 vol% reinforcing material. As a result, the guide surface is excellent in wear resistance.

  The rolling bearing of the present invention includes the rolling bearing cage of the present invention, a pair of race rings, and a plurality of rolling elements. This rolling bearing is particularly effective when used in a rocket engine turbo pump that requires high solid lubrication performance in a cryogenic environment, high strength performance by high speed operation, and high reliability.

  As described above, the rolling bearing retainer of the present invention and the rolling bearing including the cage can improve the wear resistance of the guide surface while having high solid lubricating performance.

It is sectional drawing of the rolling bearing which shows embodiment of this invention. It is a perspective view of the holder | retainer which comprises the rolling bearing of the said FIG. It is a cage which comprises the rolling bearing of the said FIG. 1, (a) is a front view, (b) is BB sectional drawing of (a), (c) is the C section enlarged view of (b). The time of injection molding of the cage of the present invention is shown, (a) is a perspective view, (b) is a sectional view. It is sectional drawing of the turbo pump for rocket engines in which the rolling bearing of this invention was integrated.

  FIG. 1 shows an angular ball bearing as a rolling bearing according to an embodiment of the present invention. The angular ball bearing includes a pair of race rings (inner ring 1 and outer ring 2), a plurality of rolling elements (ball 3), and a cage 4. Angular contact ball bearings are used in a non-lubricated environment, that is, in an environment where a fluid lubricant such as oil or grease is not used. The angular ball bearing has a contact angle as illustrated. The contact angle is defined as an angle formed by a plane (radial plane) perpendicular to the bearing center axis and an action line (shown by a one-dot chain line in FIG. 1) of the resultant force transmitted to the rolling element by the raceway. . The angular ball bearing of the present embodiment is a so-called outer ring guide bearing that guides the cage 4 in the radial direction by bringing the outer circumferential surface of the cage 4 and the inner circumferential surface of the outer ring 2 into sliding contact.

  A raceway surface 5 is provided on the outer peripheral surface of the inner ring 1. A raceway surface 6 is provided on the inner peripheral surface of the outer ring 2. The inner ring 1 and the outer ring 2 are made of metal, for example, martensitic stainless steel (SUS440C or the like). The plurality of balls 3 are arranged between the raceway surface 5 of the inner ring 1 and the raceway surface 6 of the outer ring 2. The ball 3 is formed of a metal such as martensitic stainless steel (SUS440C or the like) or a ceramic material. Note that a PTFE sputtering coating for the purpose of reducing initial friction may be applied to the raceway surface 5 of the inner ring 1, the raceway surface 6 of the outer ring 2, and the surface of the ball 3.

  The retainer 4 is disposed between the outer ring 2 and the inner ring 1 and includes a main body 7 and a resin portion 8 as shown in FIGS. 2 and 3. The main body 7 has an annular shape as shown in FIG. 2, and has a cylindrical shape in the illustrated example. A plurality of pocket holes 9 are provided in the body 7 at equal intervals in the circumferential direction, and one ball 3 is accommodated in each pocket hole 9. The main body 7 is formed of a material having a higher strength than the resin portion 8, and is formed of, for example, a resin composite material or a metal. As the resin composite material, a fiber reinforced plastic material such as CFRP or GFRP can be used. Further, as the metal, for example, a molten material such as an aluminum alloy, a magnesium alloy, carbon steel, stainless steel, or a copper alloy, or a sintered metal can be used. In particular, in the case of a bearing used in a high-speed rotation environment, it is preferable to use a material having a high specific strength. Examples of such a material include CFRP, GFRP, aluminum alloy, titanium alloy, and magnesium alloy. In the case of a bearing used for a liquid hydrogen turbo pump, it is preferable to use a material having low hydrogen reactivity. Examples of such a material include CFRP, GFRP, and an aluminum alloy. Furthermore, in the case of a bearing used for a liquid oxygen turbo pump, it is preferable to use a material having low oxidation reactivity. An example of such a material is GFRP.

  The resin portion 8 is formed by injection molding using the main body 7 as an insert part, and has a first portion 8a and a second portion 8b as shown in FIGS. The first portion 8 a is provided on the inner peripheral surface of each pocket hole 9 of the main body 7, and the first portion 8 a covers the entire inner surface of the cylindrical surface of the pocket hole 9 in the illustrated example. The surface (inner peripheral surface) of the first portion 8 a provided in each pocket hole 9 functions as a pocket surface 10 that is in sliding contact with each rolling element 3. As shown in FIG. 3A, the second portion 8 b is provided on the outer peripheral surface of the main body 7, and in the illustrated example, the second portion 8 b covers almost the entire cylindrical outer peripheral surface of the main body 7. The surface (outer peripheral surface) of the second portion 8 b functions as a guide surface 11 that is in sliding contact with the inner peripheral surface of the outer ring 2. The thickness of the first portion 8a and the thickness of the second portion 8b are uniform, preferably 0.1 mm or more in consideration of fluidity at the time of injection molding, and 0.2 mm in consideration of reliability against wear. The above is more preferable. The first portion 8a and the second portion 8b are cut at the boundary portion (that is, the edge portion of the outer peripheral surface of the main body 7 with the pocket hole 9), and the main body 7 is slightly exposed.

  The first portion 8a and the second portion 8b are formed of a resin containing a solid lubricant. As the main component resin, for example, thermoplastic resins such as polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyamide (PA), and the like can be used. In particular, when used in a cryogenic environment, it is desirable to use PEEK having a small linear expansion coefficient from the viewpoint of impact resistance, chemical resistance, and adhesion to the main body 7. As the solid lubricant, fluorine resin (for example, PTFE, ETFE, PFA), molybdenum disulfide, graphite, or the like can be used.

  In the above resin, it is preferable that the first portion 8a has a main component resin (thermoplastic resin) of 45 to 80 vol% or more that can be injection-molded. In addition, the solid lubricant needs to be blended in an amount of 5 vol% or more in consideration of lubricity. In particular, when used in a cryogenic environment such as liquid nitrogen or liquid oxygen, the solid lubricant should be 20 vol% or more. Is preferred. On the other hand, when the solid lubricant exceeds 40 vol%, it becomes difficult to mix when kneading with the main component resin, and the dispersibility at the time of injection molding is lowered. As mentioned above, it is preferable that the mixture ratio of a solid lubricant shall be 20-40 vol%. By setting it as such a structure, the 1st part 8a becomes what was excellent in lubricity and transferability.

  You may mix | blend a reinforcing material with resin which forms the 1st part 8a. As the reinforcing material, it is desirable to use a material having an effect of increasing the wear resistance of the cage and suppressing the linear expansion coefficient. For example, glass fiber (GF), carbon fiber (CF), magnesium oxide and the like can be used. Among these, GF is a reinforcing material that can be used in dry lubrication, and nonflammable GF is suitable in an environment where a dry state occurs temporarily (particularly in the initial stage of operation). In the first portion 8a, the reinforcing material can be omitted.

  The second portion 8b is made of a resin having a specific wear amount smaller than that of the resin constituting the first portion 8a. For example, the specific wear amount is determined by measuring the wear volume and the friction distance according to the test method and test conditions specified in JIS K7218 “Plastic sliding wear test method”, and dividing the wear volume by the product of the test load and the friction distance. It is the value. It means that it is excellent in abrasion resistance, so that the value of specific wear amount is small. In order for the resin constituting the second portion 8b to have a smaller specific wear amount than the resin constituting the first portion 8a, the resin composition of the second portion 8b is different from the resin composition of the first portion 8a. Let Here, “the resin composition is different” includes both the case where the components constituting the resin are different and the case where the components constituting the resin are the same, but the proportions of the component amounts are different. As will be described later, when the first portion 8a and the second portion 8b are simultaneously molded, the molding conditions (temperature, etc.) are common between the first portion 8a and the second portion 2b. It is preferable to make the components to be the same and to change the proportions of the component amounts.

  For this reason, in this embodiment, the 2nd part 8b assumes that the component which comprises resin is the same as the 1st part 8a, and the ratio of the amount of components differs. Specifically, in the resin constituting the second portion 8b, the reinforcing material is blended in an amount of more than 15 vol%, whereas in the resin constituting the first portion 8a, the reinforcing material is added at a ratio of 0 to 15 vol%. Blend. Thereby, the 2nd part 8b is more excellent in abrasion resistance than the 1st part 8a.

  When the angular ball bearing rotates, the pocket surface 10 of the cage 4 and the ball 3 are in sliding contact. As a result, the solid lubricant in the resin portion 8 is transferred to the surface of the ball 3, and the solid lubricant transferred to the ball 3 causes the ball 3 to move between the raceway surface 5 of the inner ring 1 and the raceway surface 6 of the outer ring 2. Lubrication is performed.

  As described above, in the present embodiment, the resin constituting the first portion 8a and the resin constituting the second portion 8b have different compositions, and the second portion 8b is more than the resin constituting the first portion 8a. However, the guide surface 11 has excellent wear resistance while ensuring high solid lubricating performance (lubricity and transferability) on the pocket surface 10 because it is made of a resin having a small specific wear amount. Thus, wear of the cage body 7 can be suppressed.

  Next, the manufacturing method of said holder | retainer 4 is demonstrated.

  First, the main body 7 is formed. For example, the main body 7 is formed of a resin composite material made of a resin containing reinforcing fibers such as carbon fibers and glass fibers. Alternatively, the main body 7 made of metal (melting material) is formed by machining (cutting or the like) or plastic working (pressing or forging) the metal. Alternatively, the main body 7 made of sintered metal is formed by sintering a green compact obtained by compression-molding the mixed metal powder at a predetermined sintering temperature.

  Thereafter, a minute recess is formed on the surface of the main body 7 for the purpose of improving the adhesion between the main body 7 and the resin portion 8. The minute recesses are formed by a roughening process such as an etching process (sodium etching, plasma etching, etc.), shot blasting, or thermal spraying. The surface roughness of the main body 7 after the roughening treatment is preferably larger than the dimensional change amount in the radial direction of the cage due to the difference in linear expansion coefficient between the main body 7 and the resin portion 8. Note that the roughening treatment may be omitted. For example, when the main body 7 is made of sintered metal, countless fine holes are formed on the surface of the main body 7, and thus the roughening treatment is unnecessary. .

  Thereafter, as shown in FIG. 4A, the resin portion 8 is injection-molded using the main body 7 as an insert part. As shown in FIG. 4B, the cavity 26 includes a first cavity 27 that molds the first portion 8 a of the resin portion 8 and a second cavity 28 that molds the second portion 8 b of the resin portion 8. The first gate 31 that fills the first cavity 27 with the resin material is a multi-point pin gate that is provided in a plurality at predetermined intervals along the circumferential direction. The second gate 32 that fills the resin material in the second cavity 28 is a multi-point pin gate provided in a plurality at predetermined intervals along the circumferential direction. FIG. 4B shows a state in which the cavities 27 and 28 and the gates 31 and 32 are filled with resin (shown by dots).

  Resin that forms the first portion 8 a is injected from the first gate 31 into the first cavity 27, and resin that forms the second portion 8 b is injected from the second gate 32 into the second cavity 28. Thus, when the 1st part 8a and the 2nd part 8b are shape | molded simultaneously, shortening of manufacturing lead time can be aimed at. In addition, the molten resin enters into the minute recesses on the surface of the main body 7 and solidifies, so that the main body 7 and the resin portion 8 are firmly fixed. When the resin is cured, the mold is opened and the cage 4 is removed from the mold.

  In each of the above-described embodiments, the outer ring guide rolling bearing that guides the cage by being brought into sliding contact with the inner peripheral surface of the outer ring has been described. However, the present invention is not limited thereto, and the cage is guided by sliding contact with the outer peripheral surface of the inner ring. The present invention may be applied to a rolling bearing for an inner ring guide. In this case, the second portion is provided on the inner peripheral surface of the main body of the cage, and the inner peripheral surface of the second portion functions as a guide surface (not shown).

  FIG. 5 shows a rocket engine turbo pump incorporating the angular ball bearing described above. This turbo pump compresses liquid oxygen gas in a liquid hydrogen / liquid oxygen two-stage combustion rocket engine. Although not shown, the two-stage combustion rocket engine also includes a similar turbo pump that compresses liquid hydrogen gas. The turbine shaft 71 of the turbo pump is initially driven by the liquid fuel combustion gas flowing from the pre-burner pump inlet to the pre-burner pump outlet, and then fully driven by the liquid fuel combustion gas flowing from the turbine gas inlet to the turbine gas outlet. Is done. The liquid oxygen gas flowing in from the main pump inlet is compressed and discharged from the main pump outlet, and supplied to the combustion chamber. The turbine shaft 71 is formed of a nickel-based superalloy having a high fatigue strength at an extremely low temperature, such as Inconel material. The turbine shaft 71 is supported by a double row angular ball bearing 72 formed by combining two angular ball bearings. The pair of angular contact ball bearings constituting the double row angular contact ball bearing 72 has a contact angle that is symmetric with respect to the axis perpendicular to the axis.

  The angular ball bearing described above can be applied not only to a turbo pump for a rocket engine but also to other uses. For example, it can be incorporated into a device used in a vacuum environment, such as a space device such as an artificial satellite. In addition, the angular ball bearing described above is not limited to a use in an extremely low temperature environment, and can be used in an environment at room temperature or higher, for example.

  Further, in each of the above embodiments, the angular ball bearing has been described as the solid lubricated rolling bearing according to the present invention. However, the present invention is not limited to this, and the present invention is not limited to this. It is also possible to apply to roller bearings such as.

DESCRIPTION OF SYMBOLS 1 Inner ring 2 Outer ring 3 Ball 4 Cage 7 Main body 8 Resin part 8a First part 8b Second part 9 Pocket hole 11 Guide surface

Claims (5)

A rolling bearing retainer that is arranged between a pair of race rings and holds a plurality of rolling elements in a predetermined position,
An annular main body having a plurality of pocket holes for accommodating the rolling elements, and a resin portion formed of a resin containing a solid lubricant,
The resin part is provided on the inner peripheral surface of the pocket hole of the main body, and is provided on the inner peripheral surface or the outer peripheral surface of the first part that forms a plurality of pocket surfaces that are in sliding contact with the rolling elements, A second portion that forms a guide surface that is in sliding contact with the raceway ring,
The cage for a rolling bearing, wherein the second portion is made of a resin having a specific wear amount smaller than that of the resin constituting the first portion.    2. The first part according to claim 1, wherein the main component resin is a thermoplastic resin and is blended at a ratio of 45 to 80 vol%, a solid lubricant is 20 to 40 vol%, and a reinforcing material is blended at a ratio of 0 to 15 vol%. The cage for rolling bearings as described.   The cage for a rolling bearing according to claim 1 or 2, wherein the second portion contains a reinforcing material in an amount of more than 15 vol%.   A rolling bearing comprising the rolling bearing retainer according to claim 1, a pair of race rings, and a plurality of rolling elements.   The rolling bearing according to claim 4, wherein the rolling bearing is used in a rocket engine turbo pump.

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