JP2014109299A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing capable of accomplishing a low torque formation while assuring an easiness in acquisition of material and accomplishing both an anti-pressure impression and a rolling fatigue life under a high level.SOLUTION: A deep groove ball bearing 1 comprises an outer ring 11, inner ring 12, a plurality of balls 13 and ball cage 15. The outer ring 11, inner ring 12 and balls 13 are made of hardened and cured steel such as JIS-SUJ2. Nitrogen concentration at an outer ring raceway surface 11A, inner ring raceway surface 12A and ball rolling surface 13A is 0.25 mass% or more, residual austenite quantity is 6 vol.% or more and 12 vol.% or less. The ball cage 15 is formed by abutting opposite surfaces of two annular bodies 20. Axial ends of the annular bodies 20 are provided with flanges 28 extending in a diametral direction. Locations of the inner ring 12 and the outer ring 11 corresponding to the flanges 28 are formed with grooves 30, 31 and then labyrinth 40 are formed by flanges 28 and grooves 30, 31.

Description

  The present invention relates to a rolling bearing, and more particularly to a rolling bearing capable of achieving a reduction in torque while achieving both high pressure scar resistance and rolling fatigue life at a high level.

  In recent years, machine life has been extended and maintenance free. As a result, the rolling fatigue life of the rolling bearing used in the machine is required to be extended. In order to achieve a longer rolling fatigue life, a measure to change the material of bearing parts (track members and rolling elements) which are parts constituting a rolling bearing can be considered. Specifically, the rolling fatigue life can be extended by adding an alloy component effective for extending the life to steel, which is a typical material for bearing parts.

  However, when a special material is used for the material of the bearing component, it may be difficult to procure the material depending on the manufacturing location, considering the current situation that the manufacturing bases are spreading all over the world. Therefore, considering such a situation, it is not necessarily preferable to increase the rolling fatigue life using a special material.

  As another measure for extending the rolling fatigue life, it has been proposed to extend the life of bearing parts and rolling bearings by heat treatment (see, for example, Patent Documents 1 to 3).

Japanese Patent Laid-Open No. 7-190072 JP 2003-226918 A JP 2000-161363 A

  On the other hand, there is a demand for energy saving of machines including fuel saving of automobiles. Along with this, a reduction in torque is required for rolling bearings used in machines such as automobiles. In order to reduce energy loss due to a rolling bearing in a machine, it is effective to adopt a ball bearing such as a deep groove ball bearing at a place where a roller bearing such as a tapered roller bearing is employed to reduce torque. In order to further save energy, it is preferable to achieve not only a change from a roller bearing to a ball bearing but also a reduction in torque of the ball bearing.

  However, the ball bearing has a problem in that it has a lower pressure dent (hardness to form an dent when the rolling element is pressed against the raceway member) than a roller bearing. Therefore, when a ball bearing is employed instead of the roller bearing, it is necessary to improve the pressure resistance of the ball bearing. Furthermore, for bearings used in many machines, including bearings that support rotating shafts in vehicles such as electric vehicles and hybrid vehicles, the downsizing is required as the machines become more compact. Improving the pressure scar resistance is important. Even when the rolling fatigue life is extended by conventional heat treatment including the above-mentioned Patent Documents 1 to 3, there is a problem that the pressure scar resistance becomes insufficient.

  In a bearing used under oil bath lubrication, the lubricating oil is excessively drawn into the bearing as the bearing rotates, and the rotational torque of the bearing increases due to the stirring resistance. In particular, in an electric vehicle or a hybrid vehicle, since high-speed motor rotation is input to the rotating shaft, a bearing that supports the motor tends to rotate at high speed, and an increase in rotational torque due to the stirring resistance is a problem. Become.

  The present invention has been made in order to solve the above-mentioned problems, and its purpose is to achieve both high pressure scar resistance and rolling fatigue life at a high level while ensuring the availability of materials. And it is providing the rolling bearing which can achieve torque reduction.

  A rolling bearing according to the present invention includes a race member, a plurality of balls disposed in contact with the race member, and a cage that holds the plurality of balls on an annular raceway at a predetermined pitch. . At least one of the race member and the plurality of balls includes 0.90% by mass or more and 1.05% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, and 0.01% by mass. % And 0.50% by mass of manganese and 1.30% by mass to 1.65% by mass of chromium, comprising a hardened and hardened steel consisting of the balance iron and impurities, and other parts This is a high-strength bearing component in which the nitrogen concentration at the contact surface, which is the contact surface, is 0.25% by mass or more and the amount of retained austenite at the contact surface is 6% by volume or more and 12% by volume or less. The cage is formed by forming hemispherical pockets that accommodate the balls in a plurality of locations in the circumferential direction on opposing surfaces of two annular members facing in the axial direction, and joining the two annular members by abutting the opposing surfaces. Has been. And, at least one of the inner diameter side and the outer diameter side of the axial end portion of the annular body is provided with a flange portion extending in the radial direction, and a groove portion is formed at a portion corresponding to the flange portion of the track member, A labyrinth is formed by the flange and the groove.

  The present inventor assumes that JIS standard SUJ2 equivalent material (JIS standard SUJ2, ASTM standard 52100, DIN standard 100Cr6, GB standard GCr5 or GCr15, and ΓOCT standard ЩX15), which is easily available in various countries around the world, is adopted as a material. We investigated the measures to achieve both high pressure scar resistance and rolling fatigue life at a high level. As a result, while adopting the above component composition, ensuring sufficient nitrogen concentration at the contact surface of bearing parts and controlling the amount of retained austenite to an appropriate amount, the pressure resistance and rolling fatigue life are at a high level. It was found that both are possible.

  Specifically, by adopting the above component composition, it is possible to use the above-mentioned national standard steel that is easily available in various countries as a material. And on the premise of using the steel of the said component composition, the nitrogen concentration in a contact surface is raised to 0.25 mass% or more, and a rolling fatigue life is prolonged by hardening by hardening. it can. Here, when the amount of retained austenite is not particularly adjusted, the amount of retained austenite at the contact surface is about 20 to 40% by volume in relation to the amount of nitrogen. However, in such a state where the amount of retained austenite is large, there arises a problem that the pressure resistance is lowered. On the other hand, pressure scar resistance can be improved by reducing the amount of retained austenite to 12% by volume or less. On the other hand, when the amount of retained austenite is reduced to less than 6% by volume, the rolling fatigue life, particularly the rolling fatigue life in an environment in which hard foreign matter enters the bearing (foreign matter mixed environment) is lowered. Therefore, the amount of retained austenite at the contact surface is preferably 6% by volume or more.

  In the rolling bearing of the present invention, the bearing part (at least one of the race member and the plurality of balls) employs a JIS standard SUJ2 equivalent material that is easily available in various countries as a material, and the nitrogen concentration at the contact surface is 0. The amount of residual austenite is 25% by mass or more and 6% by volume or more and 12% by volume or less. As a result, the bearing component constituting the rolling bearing of the present invention is a high-strength bearing component capable of achieving both a high level of scratch resistance and rolling fatigue life while ensuring the availability of materials. It has become. From the viewpoint of further improving the pressure scar resistance, the amount of retained austenite on the contact surface may be 10% or less. Moreover, when the nitrogen concentration in a contact surface exceeds 0.5 mass%, while the cost for making nitrogen infiltrate into steel becomes high, it will become difficult to adjust the amount of retained austenite to a desired range. Therefore, the nitrogen concentration on the contact surface is preferably 0.5% by mass or less, and may be 0.4% by mass or less.

  Furthermore, in the cage constituting the rolling bearing of the present invention, a radially extending flange is provided on at least one of the inner diameter side and the outer diameter side of the axial end of the annular body, and A groove portion is formed at a portion corresponding to the portion, and a labyrinth is formed by the flange portion and the groove portion. This labyrinth can prevent the lubricating oil from flowing into the bearing. Moreover, since the labyrinth is formed by the collar part provided in the annular body and the groove part formed in the track member, the formation of the labyrinth can be achieved only by changing the shape of the cage and the track member, for example. Therefore, it is possible to suppress the increase in the number of parts and the number of assembly steps, and to suppress the manufacturing cost.

  As described above, according to the rolling bearing of the present invention, by providing the raceway member, the rolling element, and the cage as described above, it is possible to ensure the availability of the material while maintaining the pressure resistance and rolling. It is possible to provide a rolling bearing capable of achieving both high fatigue life and a low torque.

  In the rolling bearing, the two annular bodies may have the same shape. By doing in this way, the manufacturing cost of components (annular body) can be reduced.

  In the rolling bearing, the cage may have a target shape in the axial direction. By doing in this way, when the centrifugal force is loaded on the cage by the operation of the bearing, the two annular bodies constituting the cage mutually suppress deformation thereof. As a result, it is possible to suppress the drop of the ball due to the deformation of the cage and the interference between the cage and the track member.

  In the rolling bearing, the race member may be the high-strength bearing component. Since the raceway member that is particularly required to improve the pressure dent resistance is the high-strength bearing component, it is easy to apply the bearing to an application in which a large load is applied.

  In the rolling bearing, the contact surface may have a hardness of 60.0 HRC or more. As a result, the rolling fatigue life and the pressure scar resistance can be further improved.

  In the rolling bearing, the hardness of the contact surface may be 64.0 HRC or less. When the hardness of the contact surface where the nitrogen concentration is increased to 0.25% by mass or more is maintained in a state exceeding 64.0 HRC, it is difficult to adjust the residual austenite to 12% by volume or less. By setting the hardness of the contact surface to 64.0 HRC or less, it becomes easy to adjust the amount of retained austenite to a range of 12% by volume or less.

  In the rolling bearing, a pocket groove extending in a radial direction of the annular body may be formed in the pocket of the annular body. Thereby, the contact area between the cage and the ball can be reduced, and a reduction in torque can be achieved.

  Further, the pocket groove portion may be formed so as to penetrate the inner diameter side and the outer diameter side of the annular body. Thereby, the lubricating oil between the cage and the ball is discharged by centrifugal force, and a further reduction in torque can be achieved.

  In the rolling bearing, a groove portion between pockets extends in the radial direction of the annular body on the facing surface between adjacent pockets of the annular body and penetrates so as to connect the inner diameter side and the outer diameter side of the annular body. May be formed. Thereby, the lubricating oil between the cage and the ball is discharged by centrifugal force, and a further reduction in torque can be achieved.

  In the rolling bearing, the axial thickness of the flange is preferably 0.15 mm or more and 20% or less of the ball diameter.

  When the axial thickness of the heel portion is smaller than 0.15 mm, insufficient strength of the heel portion and poor molding are likely to occur. On the other hand, if the axial thickness of the collar is larger than 20% of the diameter of the ball, the axial dimension of the inner and outer rings increases with the increase of the axial dimension of the cage, and the bearing becomes compact. Be inhibited. The occurrence of such a problem can be suppressed by setting the thickness of the collar portion in the axial direction within the appropriate range.

  In the rolling bearing, the end surface of the cage may have a planar shape. As a result, it is possible to reduce the agitation resistance of the lubricating oil that enters the thinning portion, and to achieve further reduction in torque.

  In the rolling bearing, the cage is made of polyamide resin, polyether ether ketone resin, or polyphenylene sulfide resin. These materials are suitable as materials constituting the cage of the rolling bearing of the present invention.

  In the above rolling bearing, when the ball is pressed against the raceway member so that the maximum contact surface pressure is 4.4 GPa, the depth of the impression formed on the raceway member is preferably 0.5 μm or less. As a result, a sufficient level of pressure resistance can be ensured. The depth of the indentation is more preferably 0.2 μm or less.

  The rolling bearing can be used, for example, in a motor or a speed reducer of a vehicle that uses a motor or a motor as a power source. Moreover, it is preferable that the collar part of the said cage is located so that the linear inflow of the lubricating oil to the inside of a bearing may be inhibited, and the said collar part comprises a labyrinth structure.

  As is clear from the above description, according to the rolling bearing of the present invention, both the pressure resistance and the rolling fatigue life are compatible at a high level and the torque is reduced while ensuring the availability of materials. A rolling bearing that can be achieved can be provided.

It is a schematic sectional drawing which shows the structure of a deep groove ball bearing. It is a schematic perspective view which shows the state before the assembly of an annular body. It is a schematic perspective view which shows the state after the assembly of an annular body. It is a general | schematic expanded view which shows the state before the assembly of an annular body. It is a schematic sectional drawing in alignment with the AA of FIG. It is a schematic sectional drawing in alignment with the BB line of FIG. It is a general | schematic expanded view which shows the state after the assembly of an annular body. It is a schematic sectional drawing which follows the CC line of FIG. It is a schematic sectional drawing which follows the DD line | wire of FIG. It is a schematic sectional drawing which shows the structure of the modification of a deep groove ball bearing. It is a schematic sectional drawing which shows the structure of the other modification of a deep groove ball bearing. It is a schematic perspective view which shows the structure of the modification of a holder | retainer. It is a flowchart which shows the outline of the manufacturing method of a bearing. It is a figure which shows the relationship between tempering temperature and indentation depth. It is a figure which shows the relationship between tempering temperature and hardness. It is a figure which shows the relationship between a true strain and a true stress. It is a figure which expands and shows the area | region (alpha) of FIG. It is a figure which shows the measurement result of a bearing torque.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  Referring to FIG. 1, a deep groove ball bearing 1 that is a rolling bearing in an embodiment of the present invention includes an outer ring 11 as a first race member that is a bearing component, and an inner ring as a second race member that is a bearing component. 12, a ball 13 as a plurality of rolling elements that are bearing parts, and a cage 15.

  The outer ring 11 is formed with an outer ring rolling surface 11A as an annular first rolling surface. The inner ring 12 is formed with an inner ring rolling surface 12A as an annular second rolling surface facing the outer ring rolling surface 11A. Further, a ball rolling surface 13 </ b> A (the surface of the ball 13) as a rolling element rolling surface is formed on the plurality of balls 13. The outer ring rolling surface 11A, the inner ring rolling surface 12A, and the ball rolling surface 13A are contact surfaces of these bearing components. The balls 13 are in contact with each of the outer ring rolling surface 11A and the inner ring rolling surface 12A on the ball rolling surface 13A, and are arranged at a predetermined pitch in the circumferential direction by an annular retainer 15. It is rotatably held on an annular track. With the above configuration, the outer ring 11 and the inner ring 12 of the deep groove ball bearing 1 are rotatable relative to each other.

  The outer ring 11, the inner ring 12, and the ball 13 that are bearing parts are 0.90 mass% to 1.05 mass% carbon, 0.15 mass% to 0.35 mass% silicon, and 0.01 mass. It is made of a hardened and hardened steel containing not less than 0.5% and not more than 0.50% by mass of manganese and not less than 1.30% and not more than 1.65% by mass of chromium, and the balance iron and impurities. In the region including the outer ring rolling surface 11A, the inner ring rolling surface 12A, and the ball rolling surface 13A as contact surfaces, nitrogen enriched layers 11B, 12B, having a higher nitrogen concentration than the inner 11C, 12C, 13C, 13B is formed. The nitrogen concentration in the outer ring rolling surface 11A, the inner ring rolling surface 12A and the ball rolling surface 13A as contact surfaces which are the surfaces of the nitrogen-enriched layers 11B, 12B, and 13B is 0.25% by mass or more. Furthermore, the amount of retained austenite on the outer ring rolling surface 11A, the inner ring rolling surface 12A, and the ball rolling surface 13A is 6% by volume or more and 12% by volume or less.

  The cage 15 may be made of metal or resin, but in the present embodiment, polyamide resin (PA46, PA66, PA9T, etc.), polyetheretherketone resin (PEEK), or polyphenylene is used. It consists of sulfide resin (PPS).

  The outer ring 11, the inner ring 12 and the ball 13 which are bearing parts in the present embodiment are made of steel having a component composition of the JIS standard SUJ2 equivalent steel, so that the material is easily available in various countries around the world. And on the premise of using the steel of the said component composition, the nitrogen concentration in outer ring rolling surface 11A, inner ring rolling surface 12A and ball rolling surface 13A is increased to 0.25% by mass or more and is hardened and hardened. As a result, the rolling fatigue life is extended. And, the amount of retained austenite is reduced to 12% by volume or less, so that the pressure scar resistance is improved, and the amount of retained austenite is made to be 6% by volume or more. The rolling fatigue life of is maintained at an appropriate level. As a result, the outer ring 11, the inner ring 12 and the ball 13 are bearing parts capable of achieving both a high level of scratch resistance and a rolling fatigue life while ensuring the availability of materials.

  On the other hand, referring to FIG. 1 to FIG. 3, the retainer 15 is formed with hemispherical pockets 22 for accommodating the balls 13 in a plurality of locations in the circumferential direction on opposing surfaces 21 of two annular bodies 20 facing in the axial direction. The two annular bodies 20 are joined by abutting the opposed surfaces 21. In the annular body 20, a concave wall removal portion 27 is formed between adjacent pockets 22. Thereby, the retainer 15 is reduced in weight. The cage 15 has a symmetrical shape in the axial direction. Moreover, the end surface of the retainer 15 has a planar shape (see FIG. 1).

  And with reference to FIG. 1, the collar part 28 extended in radial direction is provided in the internal-diameter side and outer-diameter side of the axial direction edge part of the annular body 20. As shown in FIG. On the other hand, a groove portion 30 is formed in a portion of the inner ring 12 corresponding to the flange portion 28. Further, a groove portion 31 is formed in a portion of the outer ring 11 corresponding to the flange portion 28. A labyrinth 40 is formed by the flange portion 28 and the groove portions 30 and 31.

  The collar portion 28 is formed so as to extend in a direction orthogonal to the axial direction. On the other hand, the groove portion 30 on the inner ring 12 side is provided to be recessed so as to form a step at the outer diameter axial end portion of the inner ring 12. The groove 31 on the outer ring 11 side is provided to be recessed so as to form a step at the inner diameter axial end of the outer ring 11. In addition, the collar part 28 and the groove parts 30 and 31 of the holder | retainer 15 are not the positional relationship which always contacts. That is, the flange portion 28 and the groove portions 30 and 31 are in contact with each other only under specific conditions or completely non-contact.

  As described above, the labyrinth 40 configured by the flange portion 28 of the retainer 15 and the groove portions 30 and 31 of the outer ring 11 and the inner ring 12 prevents the lubricating oil from flowing excessively into the bearing. The cage 15 has an axially symmetrical shape in which a flange portion 28 is provided at the axial end of the annular body 20. Therefore, when the centrifugal force is loaded under high speed rotation, the two annular bodies 20 constituting the cage 15 suppress the deformation of each other, so that the deformation of the cage 15 can be suppressed. As a result, it is possible to avoid the balls 13 from dropping from the pockets 22 and the cage 15 from interfering with other parts such as the outer ring 11 and the inner ring 12. Furthermore, since the labyrinth 40 is formed by the flange portion 28 provided integrally with the annular body 20 and the groove portions 30, 31 formed integrally with the outer ring 11 and the inner ring 12, the formation of the labyrinth 40 is This is achieved only by changing the shape of the cage 15, the outer ring 11 and the inner ring 12. Therefore, an effective labyrinth 40 can be formed while avoiding an increase in the number of parts and the number of assembly steps.

  As described above, the deep groove ball bearing 1 according to the present embodiment includes the outer ring 11, the inner ring 12, the ball 13, and the cage 15, thereby ensuring the availability of materials and the pressure resistance and rolling resistance. The dynamic fatigue life can be achieved at a high level, and a low torque can be achieved.

  Here, in the present embodiment, as shown in FIG. 1, the axial thickness t of the flange portion 28 is 0.15 mm or more and 20% or less of the diameter D of the ball 13. Thus, by setting the axial thickness t of the flange portion 28, the strength of the flange portion 28 can be secured and the forming of the flange portion 28 is facilitated, and the axial dimension of the bearing becomes larger than the limit. Nor. If the thickness t in the axial direction of the flange portion 28 is smaller than 0.15 mm, the strength of the flange portion 28 and insufficient molding are likely to occur. Further, when the axial thickness t of the flange portion 28 is larger than 20% of the diameter D of the ball 13, the outer ring 11 and the inner ring 12 are prevented from protruding from the bearing end surface of the cage 15. The axial dimension (groove width) of the groove portions 30 and 31 must be increased. As a result, the axial dimensions of the outer ring 11 and the inner ring 12 are increased, and the entire bearing is increased in size. That is, the result is that the downsizing of the deep groove ball bearing 1 is hindered.

  In addition, the cage 15 in the present embodiment is configured by combining two annular bodies 20 as follows. 2 to 6, in each of the two annular bodies 20, the outer diameter side convex portion 23 is formed by extending the outer diameter side of one circumferential end of the pocket 22 in the axial direction. At the same time, the inner diameter side recess 24 is formed by recessing the inner diameter side. Furthermore, the inner diameter side of the other circumferential end of the pocket 22 is extended in the axial direction to form an inner diameter side convex portion 25, and the outer diameter side is recessed to form an outer diameter side concave portion 26. Thus, in each of the two annular bodies 20, the outer diameter side convex portion 23 and the inner diameter side concave portion 24 are formed at one circumferential end portion of the pocket 22, and the inner diameter side convex portion is formed at the other circumferential end portion. By adopting the structure in which the outer diameter side recess 26 and the outer diameter side recess 26 are formed, the two annular bodies 20 can have the same shape. As a result, for example, the cage 15 can be configured by using a pair of annular bodies 20 manufactured by one mold, and the cost can be reduced.

  Then, two annular bodies 20 having the above structure are prepared, and the outer diameter side convex portion 23 of one annular body 20 is inserted into the outer diameter side concave portion 26 of the other annular body 20, and By inserting the inner diameter side convex portion 25 into the inner diameter side concave portion 24 of the other annular body 20, the outer diameter side convex portion 23 and the inner diameter side convex portion 25 are engaged in the axial direction. Further, the engagement surfaces 23a, 25a of the outer diameter side convex portion 23 and the inner diameter side convex portion 25 are thicker on the distal end side than the proximal end sides of the outer diameter side convex portion 23 and the inner diameter side convex portion 25. It is formed to be inclined with respect to the axial direction (see FIGS. 5 and 6).

  As shown in FIGS. 7 to 9, the opposing surfaces 21 of the two annular bodies 20 are brought into contact with each other, and the outer diameter side convex portion 23 and the inner diameter side convex portion 25 are engaged in the axial direction with a predetermined interference. As a result, a frictional force is generated along the engagement surfaces 23a, 25a of the outer diameter side convex portion 23 and the inner diameter side convex portion 25. Further, the engagement surfaces 23a, 25a between the outer diameter side convex portion 23 and the inner diameter side convex portion 25 are thicker at the distal end side than the proximal end sides of the outer diameter side convex portion 23 and the inner diameter side convex portion 25. By tilting with respect to the axial direction, an axial component of the reaction force generated in the normal direction of the engagement surfaces 23a, 25a of the outer diameter side convex portion 23 and the inner diameter side convex portion 25 appears.

  Axial component of the frictional force generated along the engagement surfaces 23a, 25a of the outer diameter side convex portion 23 and the inner diameter side convex portion 25 and the reaction force generated in the normal direction of the engagement surfaces 23a, 25a. As a result, the two annular bodies 20 can be reliably prevented from separating in the axial direction even when a large centrifugal force is applied due to high rotation.

  Thus, in the cage 15 in the present embodiment, the outer diameter side convex portion 23 and the inner diameter side concave portion 24, the inner diameter side convex portion 25 and the outer diameter side concave portion are provided at both ends in the circumferential direction of the pocket 22 of the annular body 20. 26 is provided. Thus, when a large centrifugal force is applied due to high rotation, even if one annular body 20 and the other annular body 20 are separated from each other in the axial direction to open the pocket 22, It becomes easy to maintain the state where 13 is accommodated in the pocket 22 (see FIG. 7).

  Furthermore, in the coupling structure in the present embodiment, the inclination angle θ (see FIGS. 5 and 6) of the engaging surfaces 23a, 25a between the outer diameter side convex portion 23 and the inner diameter side convex portion 25 is set to 5 ° or more. Is preferred. By setting the inclination angle θ in this way, it becomes easy to suppress deformation of the engagement surfaces 23a and 25a when a large centrifugal force is applied due to high rotation. In addition, the axial component of the reaction force can be reliably applied to the engagement surfaces 23a and 25a, and it becomes easy to ensure the coupling force between the two annular bodies 20. If the inclination angle θ of the engagement surfaces 23a and 25a is smaller than 5 °, it becomes difficult to suppress the deformation of the engagement surfaces 23a and 25a when a large centrifugal force is applied due to high rotation. There is a possibility that it is difficult to reliably apply the axial component of the reaction force to the surfaces 23a and 25a.

Further, in the present embodiment, as shown in FIGS. 8 and 9, the inner diameter side convex portion 25 is thicker than the outer diameter side convex portion 23 (t _IN > t _OUT ). By making the inner diameter side convex portion 25 thicker than the outer diameter side convex portion 23 in this manner, the inner diameter side made thicker than the outer diameter side convex portion 23 when a large centrifugal force is applied due to high rotation. Since the mass of the convex portion 25 is larger than that of the outer diameter side convex portion 23, the inner diameter side convex portion 25 is deformed more largely than the outer diameter side convex portion 23. Here, the engagement surfaces 23a and 25a of the outer diameter side convex portion 23 and the inner diameter side convex portion 25 are thicker on the distal end side than the proximal end sides of the outer diameter side convex portion 23 and the inner diameter side convex portion 25. Therefore, the deformation of the inner diameter side convex portion 25 increases the coupling force between the outer diameter side convex portion 23 and the inner diameter side convex portion 25 at the engagement surfaces 23a, 25a. Works.

  The two (a pair of) annular bodies 20 described above are preferably made of a synthetic resin from the viewpoint of reducing the weight of the cage 15. Here, from the viewpoint of cost and oil resistance, any one synthetic resin selected from the group consisting of PPS (polyphenylene sulfide), PA66 (polyamide 66) or PA46 (polyamide 46) is selected as the material of the annular body 20. It is effective to do. For example, if the lubricating oil used contains many resin-aggressive components (for example, phosphorus and sulfur), the oil resistance is excellent in the order of PPS, PA46, and PA66, so use PPS. Is preferred. On the other hand, from the viewpoint of the cost of the resin material, it is advantageous in the order of PA66, PA46, and PPS. Therefore, it is desirable to select the material constituting the annular body 20 in consideration of the resin aggression and cost of the lubricating oil used. In addition, as other resin materials, PA9T (polyamide 9T), PEEK (polyether ether ketone), a phenol resin, etc. are employable. Such a resin cage can be molded by, for example, injection molding. Note that even a resin cage may be molded by shaving.

  In the above-described embodiment, the case where the flange portion 28 is formed to extend in a direction orthogonal to the axial direction has been described. However, the present invention is not limited to this, and the flange portion 28 is attached to the shaft. You may form so that it may extend in the direction inclined with respect to the direction orthogonal to a direction. Specifically, as shown in FIG. 10, the flange portion 28A may be formed so as to be bent inward in the axial direction, and as shown in FIG. 11, the flange portion 28B is bent so as to be bent outward in the axial direction. It may be formed. Such a collar part 28A, 28B can also form the labyrinth 40 by the combination with the outer ring 11 and the inner ring 12.

  Moreover, in the said embodiment, although the case where the collar part 28 was provided in both the inner diameter side and outer diameter side of the axial direction edge part of the holder | retainer 15 was demonstrated, this invention is not limited to this, You may employ | adopt the structure which provides the collar part 28 only in either one of the internal diameter side and the outer diameter side of the axial direction edge part of the holder | retainer 15. FIG. It is preferable that the flange portion 28 of the retainer 15 is formed so as to be positioned so as to inhibit the linear flow of the lubricating oil into the bearing.

  Furthermore, in the above embodiment, the case has been described in which the cage 15 has an axially symmetrical shape in which the flange portion 28 is provided at the axial end of the annular body 20, but the rolling bearing of the present invention is not limited to this. Absent. Specifically, for example, when the bearing is used under the condition that the inflow direction of the lubricating oil is constant and the influence of centrifugal force is small, the axially asymmetric shape in which the flange portion 28 is formed only on one side in the axial direction is used. It may be adopted.

  Furthermore, referring to FIG. 12, pocket grooves 22 </ b> A extending in the radial direction of the annular body 20 may be formed in the pockets 22 of the annular body 20. Thereby, the contact area of the retainer 15 and the ball 13 can be reduced, and a reduction in torque can be achieved.

  Further, as shown in FIG. 12, the pocket groove portion 22 </ b> A may be formed penetrating so as to connect the inner diameter side and the outer diameter side of the annular body 20. Thereby, the lubricating oil between the cage 15 and the ball 13 is discharged by centrifugal force, and a further reduction in torque can be achieved. In the example shown in FIG. 12, a pair of pocket groove portions 22 </ b> A are formed across the region so as not to include the region that is the outermost in the axial direction in the pocket 22. Thereby, the lubricating oil between the cage 15 and the ball 13 is discharged by centrifugal force, and a further reduction in torque can be achieved.

  Furthermore, as shown in FIG. 12, the opposing surface 21 between adjacent pockets 22 of the annular body 20 extends in the radial direction of the annular body 20 and connects the inner diameter side and the outer diameter side of the annular body 20. Thus, an inter-pocket groove 21A may be formed. Thereby, the lubricating oil between the cage 15 and the ball 13 is discharged by centrifugal force, and a further reduction in torque can be achieved.

  In the outer ring 11, the inner ring 12, and the ball 13, the hardness of the outer ring rolling surface 11A, the inner ring rolling surface 12A, and the ball rolling surface 13A, which are contact surfaces, is preferably 60.0 HRC or more. As a result, the rolling fatigue life and the pressure scar resistance can be further improved.

  In the outer ring 11, the inner ring 12 and the ball 13, the hardness of the outer ring rolling surface 11A, the inner ring rolling surface 12A and the ball rolling surface 13A is preferably 64.0 HRC or less. This makes it easy to adjust the amount of retained austenite on the outer ring rolling surface 11A, the inner ring rolling surface 12A, and the ball rolling surface 13A to a range of 12% by volume or less.

  The deep groove ball bearing 1 in the present embodiment can be used, for example, in a motor or a speed reducer of a vehicle that uses a motor or a motor as a power source.

  Next, a bearing component (high-strength bearing component; raceway member and ball) and a rolling bearing manufacturing method according to the present embodiment will be described. With reference to FIG. 13, a steel material preparation process is first implemented as process (S10). In this step (S10), a steel material made of JIS standard SUJ2 equivalent steel such as JIS standard SUJ2, ASTM standard 52100, DIN standard 100Cr6, GB standard GCr5 or GCr15, and ΓOCT standard X15 is prepared. Specifically, for example, a steel bar or a steel wire having the above composition is prepared.

  Next, a forming step is performed as a step (S20). In this step (S20), for example, forging, turning and the like are performed on the steel bars and steel wires prepared in step (S10), so that the outer ring 11, the inner ring 12, and the ball 13 shown in FIG. A molded member formed into a shape such as is produced.

  Next, a carbonitriding step is performed as a step (S30). In this step (S30), the formed member produced in step (S20) is carbonitrided. This carbonitriding process can be performed as follows, for example. First, the molded member is preheated in a temperature range of about 780 ° C. to 820 ° C. for a period of 30 minutes to 90 minutes. Next, the preheated molded member is heated in an atmosphere in which ammonia gas is further introduced into an endothermic gas such as RX gas whose carbon potential is adjusted by adding propane gas or butane gas as an enriched gas. And carbonitrided. The temperature of the carbonitriding process can be set to 820 ° C. or higher and 880 ° C. or lower, for example. The carbonitriding time can be set according to the nitrogen concentration of the nitrogen-enriched layer to be formed on the molded member, and can be set to 3 hours or more and 9 hours or less, for example. Thereby, a nitrogen rich layer can be formed, suppressing decarburization of a forming member.

  Next, a quenching process is implemented as process (S40). In this step (S40), the molded member on which the nitrogen-enriched layer is formed by the carbonitriding process in step (S30) is quenched by being rapidly cooled from a predetermined quenching temperature. By setting the quenching temperature to 860 ° C. or less, it becomes easy to adjust the balance between the solid solution amount and the precipitation amount of carbon and the amount of retained austenite in the subsequent tempering step. Further, by setting the quenching temperature to 820 ° C. or higher, it becomes easy to adjust the balance between the solid solution amount and the precipitation amount of carbon and the amount of retained austenite in the subsequent tempering step. The quenching treatment can be carried out, for example, by immersing the molded member in a quenching oil as a coolant maintained at a predetermined temperature.

  Next, a tempering step is performed as a step (S50). In this step (S50), the molded member quenched in the step (S40) is tempered. Specifically, for example, the tempering treatment is performed by holding the molded member in an atmosphere heated to a temperature range of 210 ° C. or higher and 300 ° C. or lower for a time period of 0.5 hours or longer and 3 hours or shorter.

  Next, a finishing process is performed as a process (S60). In this step (S60), the contact surface that is a surface that comes into contact with other components by processing the molded member that has been tempered in step (S50), that is, the outer ring rolling surface 11A of the deep groove ball bearing 1, A ring rolling surface 12A and a ball rolling surface 13A are formed. As the finishing process, for example, a grinding process can be performed. Through the above steps, the outer ring 11, the inner ring 12, the ball 13, and the like, which are bearing parts in the present embodiment, are completed.

  Furthermore, an assembly process is performed as a process (S70). In this step (S70), the outer ring 11, the inner ring 12, and the ball 13 produced in steps (S10) to (S60) are combined with the separately prepared cage 15 and the like, and the deep groove in the first embodiment is combined. A rolling bearing (ball bearing) such as the ball bearing 1 is assembled. The cage 15 can be manufactured by various methods such as resin injection molding and metal pressing as described in the first embodiment. Thereby, the manufacturing method of the rolling bearing in the said embodiment is completed.

  Here, in the step (S30), the nitrogen concentration of the outer ring rolling surface 11A, the inner ring rolling surface 12A and the ball rolling surface 13A of the deep groove ball bearing 1 which is a contact surface is the contact surface by finishing in the subsequent step (S60). The formed member is carbonitrided so as to be 0.25% by mass or more. That is, in consideration of the allowance in the step (S60), etc., the nitrogen enriched layer 11B in which the nitrogen amount is adjusted so that the nitrogen concentration on the surface after completion of the contact surface can be 0.25% by mass or more. , 12B, 13B are formed.

  Further, in the step (S50), the amount of retained austenite on the outer ring rolling surface 11A, the inner ring rolling surface 12A, and the ball rolling surface 13A of the deep groove ball bearing 1 which is the contact surface by the finishing process in the subsequent step (S60). The molded member is tempered so as to be 6 volume% or more and 12 volume% or less. That is, considering the machining allowance in the step (S60) and the like, the retained austenite is obtained by tempering so that the amount of retained austenite on the surface after completion of the contact surface can be 6% by volume or more and 12% by volume or less. The amount is adjusted. Thereby, the high intensity | strength bearing component in the said embodiment can be manufactured.

  In the step (S50), the molded member is preferably tempered in a temperature range of 240 ° C. or higher and 300 ° C. or lower. As a result, carbon solid-dissolved in the substrate by the quenching process is precipitated as a carbide at an appropriate ratio. As a result, an appropriate balance between solid solution strengthening and precipitation strengthening is achieved, and the pressure resistance of the outer ring 11, inner ring 12, and ball 13 that are bearing parts is improved.

  Experiments were conducted to investigate the effects of heat treatment conditions on the characteristics of bearing parts. First, a flat plate made of JIS standard SUJ2 was prepared, preheated at 800 ° C. for 1 hour, then heated to 850 ° C. in an atmosphere in which ammonia gas was added to RX gas and kept for 4 hours for carbonitriding. Thereafter, the flat plate was quenched and hardened by being immersed in the quenching oil as it was from 850 ° C. which is the heating temperature in the carbonitriding treatment. Further, the flat plate was tempered at various temperatures. A SUJ2 standard rolling bearing steel ball having a diameter of 19.05 mm was pressed against the obtained flat plate with a load of 3.18 kN (maximum contact surface pressure 4.4 GPa), held for 10 seconds, and then unloaded. And the pressure dent resistance was investigated by measuring the depth of the dent formed on the flat plate by pressing the steel ball. Further, the surface hardness of the same test piece was measured with a Rockwell hardness meter. FIG. 14 shows the result of the investigation of the pressure scar resistance and FIG. 15 shows the result of the hardness measurement.

  Referring to FIGS. 14 and 15, the surface hardness decreases as the tempering temperature increases, while the indentation depth has a minimum value. Specifically, by setting the tempering temperature to 240 ° C. or more and 300 ° C. or less, the indentation depth is 0.2 μm or less. From this point of view, it can be said that the tempering temperature is preferably 240 ° C. or more and 300 ° C. or less from the viewpoint of improving the pressure dent resistance.

Here, it is considered that the optimum value of the tempering temperature is determined as follows. When quenching is performed, carbon is in a solid solution state in the steel substrate. On the other hand, when tempering is performed, a part of the carbon solid-dissolved in the substrate is precipitated as a carbide (for example, Fe ₃ C). At this time, the higher the temperature of the tempering treatment, the lower the contribution of solid solution strengthening to the yield strength of the steel and the greater the contribution of precipitation strengthening. Then, by performing the tempering process in a temperature range of 240 ° C. or more and 300 ° C. or less, the balance of these strengthening mechanisms becomes optimal, and the yield strength takes a maximum value, so that the pressure-proof scar resistance is particularly high.

  In addition, the reason why the indentation has the maximum value despite the monotonously decreasing surface hardness measured based on the deformation of the steel by pressing the indentation as in the case of the indentation depth measurement is as follows. It is considered to be street.

FIG. 16 is a diagram showing the relationship between the true stress and the true strain at each tempering temperature of a tensile test piece (JIS Z2201 No. 4 test piece) subjected to a treatment in which only the carbonitriding process is omitted in the heat treatment for the flat plate. . FIG. 16 is a true stress-true strain diagram modeled with an n-th power hardening elastoplastic material. The characteristics are different according to the following equation at the boundary of σ _Y yield stress.

Here, σ is the true stress, E is the Young's modulus, ε is the true strain, K is the plastic coefficient, n is the work hardening index, and σ _Y is the yield stress. However, the Young's modulus E was measured by a resonance method, and the processing effect index n and the composition coefficient K were measured by a tensile test. These were substituted into the above two formulas, and the intersection point was set as σ _Y.

  Here, the true strain level in the measurement of the indentation depth corresponds to the region α in FIG. 16, whereas the true strain level in the hardness measurement corresponds to the region β in FIG. And when the yield point in the area | region (alpha) corresponding to the measurement area | region of an indentation depth is confirmed with reference to FIG. 17, the yield point becomes high in the range whose tempering temperature is 240 degreeC-300 degreeC. In the case of low temperature, the yield point is lowered. On the other hand, referring to FIG. 16, it can be seen that, in the region β corresponding to the surface hardness measurement region, if the same strain amount is applied, a larger stress is required as the tempering temperature is lowered. Due to such a phenomenon, although the hardness is lowered as compared with the case where the tempering temperature is 180 ° C. to 220 ° C., the tempering temperature is set to 240 ° C. to 300 ° C. It is thought to improve.

  In addition to the tempering temperature, the amount of retained austenite on the surface, depth of indentation, life, ring crushing strength, and aging rate were investigated for the test pieces heat-treated under conditions in which the surface nitrogen concentration and the quenching temperature were changed.

Here, the indentation depth was measured in the same manner as described above. The case where the indentation depth was less than 0.2 μm was evaluated as B, the case where the indentation depth was 0.2 to 0.4 μm was evaluated as C, and the case where the indentation depth was 0.4 μm or more was evaluated as D. The service life of the bearing is used for the transmission under the condition that the oil film parameter becomes 0.5 under clean oil lubrication after forming the indentation on the raceway surface under the same conditions as the measurement of the indentation depth. This was carried out by simulating the loading conditions. The life of a test piece having a quenching temperature of 850 ° C., a tempering temperature of 240 ° C., and a surface nitrogen content of 0.4% by mass is defined as a reference (B). The case was rated as D. The ring crushing strength was evaluated by preparing a ring having an outer diameter of 60 mm, an inner diameter of 54 mm, and a width of 15, and compressing the ring with a flat plate in the radial direction, and investigating the load at which cracks occurred. The case where the load at the time of a crack generation was 5000 kgf or more was evaluated as A, the case where it was 3500-5000 kgf was evaluated as B, and the case where it was less than 3500 kgf was evaluated as D. Moreover, the secular change rate was evaluated by holding the test piece at 230 ° C. for 2 hours and measuring the dimensional change amount of the outer diameter before the heat treatment. Where the amount of change is of 10.0 × 10 ⁵ or less A, B the case of ^{10.0 × 10 5 ~30.0 × 10 5} , the case of ^{30.0 × 10 5 ~90.0 × 10 5} C The case of 90.0 × 10 ⁵ or more was evaluated as D. The test results are shown in Table 1.

  With reference to Table 1, in the test piece which satisfy | fills all the conditions of surface nitrogen concentration 0.25-0.5 mass%, quenching temperature 820-860 degreeC, and tempering temperature 240-300 degreeC, all the said Excellent evaluation was obtained for the items.

  An experiment was conducted to confirm the torque reduction effect according to the present invention. The experimental procedure is as follows.

  First, the cage is an ordinary resin cage, and the inner ring, outer ring and ball are subjected to ordinary quenching treatment (the material is JIS standard SUJ2), and the raceway groove curvature is 1.02 for the inner ring and 1.04 for the outer ring. A deep groove ball bearing was produced (Sample A). Further, a deep groove ball bearing in which the structure of the cage was changed to that described in the above embodiment based on FIGS. 1 to 9 with respect to Sample A was also produced (Sample B). Further, the heat treatment of the inner ring, outer ring and ball is changed for sample B to provide the high-strength bearing component described in the above embodiment, and the raceway groove curvature is 1.048 for the inner ring and 1.12 for the outer ring. A modified deep groove ball bearing was also produced (Sample C).

Then, the samples A to C are subjected to a radial load of 3 kN, a rotational speed of 6000 min ⁻¹ , a lubricating oil ATF (Automatic Transmission Fluid), and an oil bath lubrication having an oil surface height of the lowest rolling element PCD (Pitch Circle Diameter) position. Rotating torque was measured under the conditions described above. The experimental results are shown in FIG.

  Referring to FIG. 18, Sample B employing the cage of the present invention achieves a torque reduction of nearly 80% with respect to Sample A. And the sample C which is an Example of this invention implement | achieves about 30% of torque reduction with respect to the sample B further. From this, it is confirmed that the torque reduction can be achieved by adjusting the raceway groove curvature to an appropriate size in the rolling bearing of the present invention, more specifically, by increasing the raceway groove curvature.

  In sample C, the inner ring and the outer ring are high-strength bearing parts, so that the pressure-proof marks are improved. Using this, in Sample C, the torque reduction is achieved by increasing the raceway groove curvature. One of the factors that increase the bearing torque is the slip component between the raceway surface and the ball (differential slip, spin slip, etc.). By increasing the groove curvature, the slip component can be reduced. Because. In the present application, the “groove curvature” means a ratio of the radius of curvature of the rolling surface in the cross section perpendicular to the circumferential direction of the raceway to the radius of the ball.

  Further, in the above-described embodiments and examples, the deep groove ball bearing has been described as an example of the rolling bearing of the present invention. The present invention can be applied to various types of rolling bearings (ball bearings).

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The rolling bearing of the present invention can be particularly advantageously applied to a rolling bearing that is required to achieve both high pressure scar resistance and rolling fatigue life at a high level.

  DESCRIPTION OF SYMBOLS 1 Deep groove ball bearing, 11 Outer ring, 11A Outer ring rolling surface, 11B, 12B, 13B Nitrogen rich layer, 11C, 12C, 13C Inside, 12 Inner ring, 12A Inner ring rolling surface, 13 balls, 13A Ball rolling surface, 15 Cage, 20 annular body, 21 facing surface, 21A inter-pocket groove, 22 pocket, 22A pocket groove, 23 outer diameter side convex part, 23a engagement surface, 24 inner diameter side concave part, 25 inner diameter side convex part, 26 outer diameter side Concave part, 27 Carbide part, 28, 28A, 28B Gutter part, 30, 31 Groove part, 40 labyrinth.

Claims (10)

A track member;
A plurality of balls arranged in contact with the track member;
A cage for holding the plurality of balls on an annular track at a predetermined pitch;
At least one of the track member and the plurality of balls is
0.90% by mass or more and 1.05% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, 0.01% by mass or more and 0.50% by mass or less of manganese, Containing 30% by weight or more and 1.65% by weight or less chromium, comprising a hardened and hardened steel consisting of the balance iron and impurities,
The nitrogen concentration in the contact surface that is a surface in contact with another component is 0.25% by mass or more,
A high-strength bearing component in which the amount of retained austenite at the contact surface is 6% by volume or more and 12% by volume or less,
The cage is
A hemispherical pocket for accommodating the ball is formed in a plurality of circumferential positions on opposite surfaces of two annular members facing in the axial direction, and the two annular members are joined by abutting the opposing surfaces. ,
A flange extending in the radial direction is provided on at least one of the inner diameter side and the outer diameter side of the axial end of the annular body,
A groove portion is formed in a portion corresponding to the flange portion of the track member,
A rolling bearing in which a labyrinth is formed by the flange and the groove.   The rolling bearing according to claim 1, wherein the two annular bodies have the same shape.   The rolling bearing according to claim 1, wherein the race member is the high-strength bearing component.   The rolling bearing according to claim 1, wherein the contact surface has a hardness of 60.0 HRC or more.   The rolling bearing according to claim 1, wherein the contact surface has a hardness of 64.0 HRC or less.   The rolling bearing according to any one of claims 1 to 5, wherein a pocket groove portion extending in a radial direction of the annular body is formed in the pocket of the annular body.   An inter-pocket groove extending in the radial direction of the annular body and penetrating so as to connect the inner diameter side and the outer diameter side of the annular body is formed on the facing surface between the adjacent pockets of the annular body. The rolling bearing according to claim 1, wherein the rolling bearing is provided.   The rolling bearing according to any one of claims 1 to 7, wherein an axial thickness of the flange portion is 0.15 mm or more and 20% or less of a diameter of the ball.   The rolling bearing according to claim 1, wherein an end surface of the cage has a planar shape.   The rolling bearing according to claim 1, wherein the cage is made of a polyamide resin, a polyether ether ketone resin, or a polyphenylene sulfide resin.

Images