JP5556590B2 - Rolling bearing - Google Patents

Description

  The present invention includes, for example, industrial machinery, robot joints and turning mechanisms, spindles of machine tools, rotary tables and spindle turning mechanisms, medical equipment, semiconductor / liquid crystal manufacturing apparatuses, optical and optoelectronic devices, and the like. The present invention relates to a rolling bearing used in the above.

  As a conventional rolling bearing, as shown in FIG. 9, a synthetic resin crown-shaped cage 15 provided with a cutting portion 14 at one place in the circumferential direction has been proposed (for example, see Patent Documents 1 and 2). . In the rolling bearing described in Patent Document 1, by providing the cutting portion 14, the tensile force generated between the ball and the pocket portion 19 due to the difference in thermal expansion coefficient between the inner and outer rings and the ball and the cage is alleviated. It is described that the wear of the cage is prevented.

  Further, in the rolling bearing described in Patent Document 2, the cutting portion 14 is provided at one place in the circumferential direction, and the circumferential width of the cutting portion 14 is defined as the extension of the cage due to the temperature change and the water absorption change, It is described that a guide clearance with the raceway is secured.

  By the way, in the rolling bearing described in Patent Document 1, the ball guide method is adopted, and the radial clearance between the ball and the pocket 19 is set to be small. (For example, when the inner ring, outer ring and ball are made of bearing steel, and the cage is made of a synthetic resin such as polyamide resin) Is difficult to expand, and the relative expansion is in the circumferential direction.

  As a result, when the circumferential clearance ΔL of the cage cutting portion 14 becomes small and the bearing temperature rise including the operating environment temperature is high, the circumferential end surfaces of the cage cutting portion 14 interfere with each other. Thus, there is a problem that heat generation, wear, and damage occur in the interference portion. In addition, when the cage is formed of a general general-purpose synthetic resin such as a polyamide resin, the cage may expand by absorbing moisture in the air, and the amount of expansion due to water absorption is also a problem.

  Moreover, in the rolling bearing described in Patent Document 2, the circumferential width of the cutting portion 14 is set to the extension of the cage due to the temperature change and the water absorption change (temperature expansion + water absorption expansion). In the condition where the direction width becomes too wide and the temperature rise is small or the dry atmosphere condition, the change in the circumferential width of the cutting portion 14 is small, and the circumferential direction between the balls at the portion sandwiching the cutting portion 14 is small. The distance becomes larger than the circumferential distance between the other balls, and uneven distribution of the balls in the circumferential direction occurs.

  If the balls are not evenly distributed in the circumferential direction, the radial rigidity of the bearing will be non-uniform in the circumferential phase (decrease in rigidity due to the phase of the unevenly distributed portion of the ball in the circumferential direction). A swing corresponding to the revolution period of the ball, a so-called NRRO value (a cycle of about once per two rotations of the inner ring) increases. In particular, when this bearing is used in a rotation support part such as a spindle of a machine tool, a rotary table, and a turning mechanism part of the spindle that require rotational accuracy, the rotation of the rotary shaft becomes large (NRRO value is large), and milling There is a problem that a striped pattern is generated on the processed surface in machining, and a stitching defect on the processed surface or a deterioration in roundness occurs in lathe processing.

JP 2003-336640 A JP 2006-226696 A

  The present invention has been made in order to eliminate such inconveniences, and the purpose of the present invention is to provide a rolling bearing that employs a cage having a structure in which a cutting portion is provided at one place in the circumferential direction, and has high rotational accuracy. Even when used for required applications, the increase in rotational asynchronous runout (NRRO) is to be kept low.

  In order to achieve the above object, a rolling bearing according to claim 1 includes an inner ring having an inner ring raceway surface on an outer peripheral surface, an outer ring having an outer ring raceway surface on an inner peripheral surface, the inner ring raceway surface, and the outer ring raceway surface. And a plurality of rolling elements provided so as to freely roll between, and a cutting portion is formed in at least one place in the circumferential direction, and the plurality of rolling elements are made of a synthetic resin that holds the rolling elements at substantially equal intervals in the circumferential direction. A rolling element inserted into two pocket portions sandwiching the cutting portion, and having a larger diameter than rolling elements inserted into other pocket portions.

  The rolling bearing according to claim 2 is rollable between an inner ring having an inner ring raceway surface on an outer peripheral surface, an outer ring having an outer ring raceway surface on an inner peripheral surface, and the inner ring raceway surface and the outer ring raceway surface. A plurality of rolling elements provided on the synthetic resin, and a synthetic resin cage that has a cutting portion formed in at least one place in the circumferential direction and holds the plurality of rolling elements at substantially equal intervals in the circumferential direction. The longitudinal elastic modulus of the rolling element inserted into the two pocket portions sandwiching the cutting portion is larger than the longitudinal elastic modulus of the rolling element inserted into the other pocket portion.

  Furthermore, the rolling bearing according to a third aspect is characterized in that, in the invention according to the first or second aspect, at least one of the cut surfaces is provided with a concave groove for storing a lubricant.

  Furthermore, the rolling bearing according to claim 4 is characterized in that, in the invention according to claims 1 to 3, the rolling element is a ball.

Furthermore, the rolling bearing according to claim 5 is characterized in that, in the invention according to claims 1 to 3, the rolling element is a cylindrical roller.

  Since the rolling bearing of the present technology is configured as described above, an increase in rotational asynchronous runout (NRRO) can be suppressed even when high rotational accuracy is required for the bearing. Thus, it is possible to realize a rolling bearing that does not cause problems such as ball striking damage and that has excellent rotational accuracy.

It is principal part sectional drawing for demonstrating the rolling bearing which concerns on 1st Embodiment of this invention. FIG. 2 is a cross-sectional view of a crown-shaped cage incorporated in the rolling bearing shown in FIG. 1. FIG. 2 is a partial perspective view of a crown-shaped cage incorporated in the rolling bearing shown in FIG. 1. It is the figure which fractured | ruptured the part seen from the arrow B direction of FIG. It is principal part sectional drawing for demonstrating the structure of the crown-shaped holder | retainer integrated in the rolling bearing shown in FIG. 1, and a rolling element. It is principal part sectional drawing for demonstrating the structure of the crown-shaped holder | retainer integrated in the rolling bearing which concerns on 2nd Embodiment of this invention, and a rolling element. It is principal part sectional drawing for demonstrating the structure of the crown-shaped holder | retainer integrated in the rolling bearing which concerns on 3rd Embodiment of this invention, and a rolling element. It is principal part sectional drawing for demonstrating the structure of the crown-shaped holder | retainer integrated in the rolling bearing which concerns on 4th Embodiment of this invention, and a rolling element. It is principal part sectional drawing which looked at the conventional cage | basket from the axial direction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an essential part showing a state in which two rows of single-row ball bearings according to the first embodiment of the present invention are combined, FIG. 2 is a cross-sectional view showing a ball guide cage, and FIG. 4 is a partial perspective view as seen from the inner side in the direction, FIG. 4 is an arrow view as seen from the direction of arrow B in FIG. 2, and FIG. 5 illustrates the configuration of the crown-shaped cage and rolling elements incorporated in the rolling bearing shown in FIG. FIG. 6 is a cross-sectional view of a main part for explaining the configuration of a crown-shaped cage and rolling elements incorporated in a rolling bearing according to a second embodiment of the present invention, and FIG. Sectional drawing for demonstrating the structure of the crown-shaped cage and rolling element incorporated in the rolling bearing according to the third embodiment, FIG. 8 is a crown incorporated in the rolling bearing according to the fourth embodiment of the present invention. It is principal part sectional drawing for demonstrating the structure of a shape holder and a rolling element.

  As shown in FIG. 1, a rolling bearing 10 (hereinafter also referred to as a narrow ball bearing 10) of this embodiment is an angular ball bearing, and two rows of angular ball bearings are combined in the back (contact angle is C). Array). Each rolling bearing 10 is freely rollable between an inner ring 11 having an inner ring raceway surface 11a on an outer peripheral surface, an outer ring 12 having an outer ring raceway surface 12a on an inner peripheral surface, and an inner ring raceway surface 11a and an outer ring raceway surface 12a. A plurality of balls (rolling elements) 13 provided, and a cutting portion 14 (see FIG. 5) is formed at one place in the circumferential direction, and the plurality of balls 13 is made of a synthetic resin that holds the balls 13 in the circumferential direction at substantially equal intervals. The crown-shaped cage 15 is provided. Further, non-contact type seal members 16 are mounted on the inner peripheral surfaces of the outer ends of the outer rings 12 of the two rows of narrow ball bearings 10 in the axial direction. The seal member 16 may be a contact type, and the material and shape are not particularly limited.

  In this embodiment, in order to save space in the axial direction, the axial sectional width B and the radial sectional height H of the rolling bearing 10 (= (outer ring outer diameter D−inner ring inner diameter d) / 2) and The cross-sectional dimension ratio (B / H) is set to B / H <0.63.

  B / H is theoretically B / H> 0, but in reality, considering the design, selection, etc. of the ball diameter, cage, and seal member to be used, B / H> 0. 10, preferably B / H> 0.20, more preferably B / H> 0.30.

  Further, in the case of standard size ball bearings defined by the International Organization for Standardization (ISO), those with a B / H of around 1.0 account for the majority. Therefore, if B / H <0.5 is set, the narrow ball bearings 10 for two rows can be disposed in the width direction space for about one row of standard ball bearings, and space saving can be achieved.

  In the case of angular contact ball bearings, only one axial load can be received in one row and moment load cannot be received. However, by combining two or more rows, the axial load and moment load in both directions can be reduced. Load becomes possible. In addition, since preload can be applied, it is possible to save space and increase radial rigidity, axial rigidity, moment rigidity, and the like.

  Moreover, if B / H <0.25, it is possible to arrange four rows of narrow ball bearings in a space in the width direction of about one row of standard ball bearings with further space saving, and further increase rigidity. Improvement is possible.

  Also, by setting (B / H) to less than 0.63, when the bearing is incorporated in the shaft or housing (especially when it is assembled by clearance fitting with the shaft or housing), the outer ring is pressed against the end face, and the inner ring is the bearing. It is possible to suppress deformation of the inner and outer rings (especially worsening of roundness) when they are fixed with nuts, etc., as well as torque failure and rotation accuracy caused by deformation, or problems such as increased heat generation, wear and seizure. Can be prevented.

  Furthermore, by setting (B / H) to less than 0.63, the width of the bearing is about half that of a conventional standard single-row ball bearing, so the ball diameter is also about half that of a conventional ball bearing. Conversely, the number of balls per row increases at least twice, and the bearing stiffness increases compared to conventional ball bearings.

  The dimension series defined by the International Organization for Standardization (ISO) is 18 (for example, 6820), 19 (for example, 6938), 10 (for example, 7016A), 02 (for example, 7224C), 03 (for example, 7350A). In the case of standard size ball bearings such as the above, when the inner diameter of the bearing is φ5 mm to φ500 mm, the cross-sectional dimension ratio (B / H) is B / H = 0.63 to 1.17. Since the ball bearing 10 is narrow in the axial direction, it does not correspond to the above-described cross-sectional dimension ratio.

  In the narrow ball bearing 10 of this embodiment, in order to increase the load capacity and rigidity of the bearing, the pitch between the balls 13 adjacent in the circumferential direction is made as small as possible, and the number of balls is increased as much as possible. In a normal ball bearing, the number of balls is at most about 30 to 40 or less per row, but in this embodiment, 50 or more, preferably 60 or more, more preferably 70 or more per row. .

  In the case of an angular contact ball bearing, the contact angle is approximately 60 ° or less, preferably 50 ° or less in order to suppress the ball and the inner / outer ring groove contact portion from riding on the shoulder portion of the inner / outer ring groove when a large moment load is applied. More preferably, it is 40 ° or less, but if it is less than 20 °, the allowable axial load and moment rigidity are lowered, which is not preferable. The appropriate ball diameter in the present embodiment varies depending on whether or not a seal member or the like is mounted. However, in order to increase rigidity, if the ball diameter is extremely reduced, the surface pressure between the contact portions between the balls and the track grooves of the inner and outer rings is reduced. In general, the pressure resistance is likely to be reduced, so that generally 30 to 90% of the bearing width (B) is desirable.

Furthermore, in this embodiment, the axial pitch of the balls 13 is shifted as much as possible to the side opposite to the combination side end face (FIG. 1: X ₁ > X ₂ ), and the ring portion 17 (see FIGS. 2 to 5) of the cage 15 is provided. It is arranged so as to be on the bearing combination end face side, so that the axial thickness of the ring portion 17 is increased, and the distance between operating points for increasing moment rigidity can be increased.

  In addition, the bearing material is not particularly limited, such as standard bearing steel (SUJ2 or SUJ3), but if necessary, these materials improve mechanical properties such as dimensional stability and wear resistance of the bearing. In order to achieve this, sub-zero processing may be performed on at least one of the inner ring 11 and the outer ring 12.

  As a sub-zero treatment method, for example, immediately after quenching, an atmosphere of about −150 ° C. is formed using liquid nitrogen, and tempering is performed after the sub-zero treatment. Then, the sub-zero process and the tempering process are repeated several times. In the sub-zero treatment using liquid nitrogen as the cooling solvent, the number of repetitions may be at most about 3. Residual austenite (γR) in the structure is transformed into martensite by the sub-zero treatment. In addition, since the stabilization of the crystal grains is promoted, this improves the mechanical properties such as prevention of dimensional change with time and wear resistance.

  In the case of the present embodiment, since the axial widths of the inner ring 11 and the outer ring 12 are narrow, there is a tendency that dimensional changes such as warpage and roundness failure tend to occur. Accordingly, the sub-zero treatment can suppress the dimensional change with time, and in particular, in rotation support parts such as a rotary table of a machine tool, a spindle turning mechanism part, and a rotary mechanism part such as a drum of a printing machine that require bearing accuracy. When the narrow ball bearing 10 of the present embodiment is used, it is possible to prevent malfunctions of the equipment due to deterioration of the bearing accuracy, and it is possible to maintain a good function in the long term.

For example, in vacuum applications and corrosive environments, in addition to bearing steel, stainless steel materials that are corrosion resistant materials (for example, martensitic stainless steel materials such as SUS440C, austenitic stainless steel materials such as SUS304, precipitation of SUS630, etc.) Hardened stainless steel materials), titanium alloys and ceramic materials (eg, Si ₃ N ₄ , SiC, Al ₂₎
O ₃ , ZrO _2, etc.) may be employed.

The lubrication method is not particularly limited, and mineral oil grease or synthetic oil grease (for example, lithium or urea) or oil can be used in a general usage environment. Oil, or a solid lubricant such as fluororesin or MOS ₂ can be used.

  As shown in FIGS. 2 to 4, the ball guide retainer 15 includes a ring portion 17, and column portions 18 projecting in a plurality of axial directions at substantially equal intervals in the circumferential direction on one end portion of the ring portion 17. A large number of pockets 19 formed between the pillars 18 to hold the balls 13 so as to roll in the circumferential direction, and the balls 13 formed at the tip of the pockets 19 on the side opposite to the ring parts 17. And a pair of ball locking portions that prevent the slipping out of the flexible crown-shaped cage. The material of the cage 15 is, for example, a synthetic resin material such as polyamide, polyacetal, or polyphenylene sulfide, and a material in which a reinforcing material such as glass fiber or carbon fiber is mixed into the synthetic resin material is used as necessary.

  Further, as shown in FIG. 5, the retainer 15 cuts between the pocket portions 19 adjacent to each other at least at one place in the circumferential direction of the ring portion 17 to form a cut portion 14, and sandwiches the cut portion 14. The diameters of the rolling elements 13a inserted into the two pocket portions 19 are larger than the diameter dimensions of the rolling elements 13b inserted into the other pocket portions 19. Here, ΔL is the optimum clearance of the cut portion 14 in consideration of the temperature rise of the bearing and water absorption of the cage.

  In the narrow ball bearing 10 as in the present embodiment, the cutting portion 14 is formed in the circumferential direction of the crown-shaped cage 15, and the rolling elements 13 a inserted into the two pocket portions 19 sandwiching the cutting portion 14. By making the diameter dimension larger than the diameter dimension of the rolling element 13b inserted into the other pocket part 19, the following effects are produced.

  That is, when the rolling elements 13 having the same diameter are inserted into the conventional cage 15 shown in FIG. 9, the circumferential pitch between the rolling elements 13 is larger in the cut portion 14 than in the other portions. For this reason, a difference occurs in the rigidity balance in the radial direction due to the uneven distribution of the rolling elements 13, and as a result, a rotational runout (rotational asynchronous runout: NRRO) for each revolution cycle (= rotation cycle of the cage) of the rolling body 13 occurs. There is concern about the increase.

  On the other hand, in this embodiment, it is set as the structure which makes the radial dimension of the rolling element 13a inserted in the two pocket parts 19 which pinch | interpose the cutting part 14 larger than the radial dimension of the rolling element 13b inserted in the other pocket part 19. As a result, the difference in the rigidity balance in the radial direction due to the uneven distribution of the rolling elements 13 is canceled out, so that an increase in NRRO can be suppressed. Further, the circumferential clearance between the rolling element 13 and the cage 15 is expected to reduce the circumferential clearance due to the relative expansion of the cage due to the temperature rise of the bearing and the water absorption expansion under a predetermined condition. The clearance does not become zero.

  Next, with reference to FIG. 6, the rolling bearing 10 which concerns on 2nd Embodiment of this invention is demonstrated. In this rolling bearing 10, the longitudinal elastic modulus of the rolling element 13 a inserted into the two pocket portions 19 sandwiching the cutting portion 14 is made larger than the longitudinal elastic modulus of the rolling element 13 b inserted into the other pocket portions 19. Other configurations are the same as those of the first embodiment of the present invention. By adopting such a configuration, the difference in the rigidity balance in the radial direction due to the uneven distribution of the rolling elements 13 is offset, so that an increase in NRRO can be suppressed.

  Next, with reference to FIG. 7, the rolling bearing 10 which concerns on 3rd Embodiment of this invention is demonstrated. This rolling bearing 10 is configured such that in the rolling bearing 10 of the first or second embodiment, a concave groove 20a for collecting a lubricant is provided on the cut surface of the cutting portion 14 of the cage 15. As shown in FIG. 7, if the concave groove 20 a that holds the lubricant is provided, it is possible to improve the lubrication condition of the contact portion of the cage 15 in the cutting portion 14. In addition, if the groove 20a is opened in the axial direction as shown in FIG. 7, when the cage 15 is manufactured by injection molding, the mold is released in the axial direction (axial axial draw). When the cage 15 is taken out from the mold, it can be easily taken out without interference with the mold. The concave groove 20a that holds the lubricant may be provided in at least one of the cut portions.

  Next, with reference to FIG. 8, the rolling bearing 10 which concerns on 4th Embodiment of this invention is demonstrated. The rolling bearing 10 has a structure in which the rolling groove 10b of the first or second embodiment is provided with a concave groove 20b for storing a lubricant as in the third embodiment. However, the shape of the concave groove 20b is a groove. The width of the groove bottom is wider than the opening. If the groove 20b has a shape as shown in FIG. 8, the effect of retaining the lubricant inside the groove 20b is enhanced even when centrifugal force is applied during rotation of the cage, and the friction at the cutting portion 14 during rotation of the bearing is increased. Heat generation is further reduced, and wear and damage can be reliably prevented.

  The rolling bearing of the present invention includes, for example, industrial machines, robot joints and turning mechanisms, machine tool spindles, rotary tables and spindle turning mechanisms, medical equipment, semiconductor / liquid crystal manufacturing apparatuses, optical and optoelectronic devices, etc. It can utilize suitably for a rotation support part.

DESCRIPTION OF SYMBOLS 10 Rolling bearing 11a Inner ring raceway surface 11 Inner ring 12a Outer ring raceway surface 12 Outer ring 13 Rolling body 14 Cutting part 15 Cage 16 Seal member 17 Ring part 18 Column part 19 Pocket part

Claims (5)

  An inner ring having an inner ring raceway surface on an outer peripheral surface, an outer ring having an outer ring raceway surface on an inner peripheral surface, a plurality of rolling elements provided rotatably between the inner ring raceway surface and the outer ring raceway surface, A rolling bearing provided with a synthetic resin cage having a cutting portion formed in at least one circumferential direction and holding the plurality of rolling elements at substantially equal intervals in the circumferential direction. A rolling bearing characterized in that a diameter of a rolling element inserted into one pocket portion is larger than a diameter of a rolling element inserted into another pocket portion.   An inner ring having an inner ring raceway surface on an outer peripheral surface, an outer ring having an outer ring raceway surface on an inner peripheral surface, a plurality of rolling elements provided rotatably between the inner ring raceway surface and the outer ring raceway surface, A rolling bearing provided with a synthetic resin cage having a cutting portion formed in at least one circumferential direction and holding the plurality of rolling elements at substantially equal intervals in the circumferential direction. A rolling bearing characterized in that a longitudinal elastic modulus of a rolling element inserted into one pocket portion is larger than a longitudinal elastic modulus of a rolling element inserted into another pocket portion. The rolling bearing according to claim 1, wherein a concave groove for storing a lubricant is provided on at least one of the cut surfaces.   The rolling bearing according to claim 1, wherein the rolling element is a ball.   The rolling bearing according to claim 1, wherein the rolling element is a cylindrical roller.

Images