JP2007170614A - Rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive rolling bearing usable continuously with fixed performance for a long time by improving wear resistance of the bearing. <P>SOLUTION: This rolling bearing A is provided with bearing rings 2, 4 arranged opposingly so as to rotate relatively, a plurality of rolling bodies 6 assembled in between raceway surfaces 2a and 4a formed in each bearing ring, respectively, so as to roll freely, and a cage 8 holding the plurality of rolling bodies rotatably. When degree of pointedness and degree of distortion in statistical distribution of surface roughness of surfaces of the bearing rings and a surface of the cage are Rk and Rsk, respectively, the working for satisfying Rk<20 and Rsk<0 is applied on at least a slide-contact face 2s of the bearing rings for the cage as first surface treatment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement in wear resistance of a bearing that supports a main shaft of a device that operates at a high speed, such as a jet engine or a gas turbine engine.

The rolling bearing that supports the main shaft of the device operated at such a high speed rotation has a sliding contact surface with respect to the cage of the bearing ring (inner ring and outer ring) and a sliding contact surface with respect to the bearing ring of the cage. May be rubbed, worn, or damaged by vibrations. Such wear and damage becomes even more severe when, for example, hard dust is mixed in the lubricating oil or when the lubricating oil is insufficient.
Conventionally, as a measure for preventing such wear and damage, for example, there has been a measure in which a surface treatment is performed on a raceway ring or a cage to form a film on the sliding contact surfaces. In this case, an example of such a coating is a TiN (titanium nitride) coating, and the TiN (titanium nitride) coating is characterized by being hard and resistant to sliding wear (see Patent Document 1). However, when the TiN film formation treatment is applied to the bearing ring and the cage, for example, a rolling bearing using normal bearing steel (high carbon chrome bearing steel, stainless steel, etc.) as its material (not coated) Compared with the bearing), the manufacturing process is longer and the manufacturing cost is increased by the TiN film forming process. When forming a TiN film, the roughness (mean square roughness (Ra value)) of the surfaces of the bearing ring and the cage (the mutual contact surfaces) of the TiN film is processed to Ra ≦ 3 μm or less, for example. It has only been done.

Further, for example, when the sliding contact surface on which the TiN film is formed is worn by vibration of the apparatus, the wear powder itself is hard, and therefore when the wear powder enters between the sliding contact surfaces of the race and the cage. The sliding contact surface may be further worn and damaged. As a result, it becomes difficult to continuously use the bearing with a constant performance over a long period of time, for example, to reduce the bearing life.
JP 2001-65569 A

  The present invention has been made in order to solve such a problem, and an object thereof is to improve the wear resistance of the bearing so that the bearing can be used continuously with a constant performance over a long period of time. It is to provide a possible low cost rolling bearing.

  In order to achieve such an object, the rolling bearing of the present invention is incorporated in a freely rotatable manner between a raceway arranged so as to be relatively rotatable and a raceway surface formed on each raceway. A plurality of rolling elements and a cage that rotatably holds the plurality of rolling elements are provided, the kurtosis in the statistical distribution of the surface roughness of the surface of the bearing ring and the surface of the cage is Rk, and the skewness is Rsk. In this case, at least the slidable contact surface of the bearing ring with respect to the cage is processed so that Rk <20 and Rsk <0 as the first surface treatment.

  In such a configuration, in addition to the first surface treatment, at least the sliding contact surface of the raceway ring and the cage surface with respect to the raceway cage is subjected to nitriding as a second surface treatment. Processing has been applied. Further, in addition to the first surface treatment, a second surface treatment is applied to at least a sliding surface of the raceway ring surface and the cage surface with respect to the raceway ring cage so that the carbon coating is formed. Is formed.

  According to the present invention, by improving the wear resistance of the bearing, it is possible to provide a low-cost rolling bearing capable of continuously using the bearing with a constant performance over a long period of time.

Hereinafter, a rolling bearing according to an embodiment of the present invention will be described with reference to the accompanying drawings. The present invention can be applied to a rolling bearing having an arbitrary configuration, and the configuration of the bearing to which the present invention is applied (for example, the form and size of inner and outer rings, rolling elements, and cages) is particularly great. Although not limited, the rolling bearing A having the bearing configuration shown in FIG. 1 will be described below as an example.
As shown in FIG. 1, the rolling bearing A of this embodiment includes a raceway 2a formed on a raceway (an inner ring 2 and an outer race 4) facing each other so as to be relatively rotatable, and a facing surface 2s of the inner race 2. A plurality of rolling elements (balls) 6 and a plurality of rolling elements (balls) 6 are rotatably held one by one between the raceway surface 4a formed on the opposite surface 4s of the outer ring 4 and the outer ring 4. And a cage 8.

  In addition, in the structure shown in FIG. 1, the inner ring | wheel 2 becomes a structure which can be divided | segmented into an axial direction at a predetermined position. In this case, as an example, the inner ring 2 can be divided into a first inner ring 10 and a second inner ring 12 at a substantially central position of the width of the inner ring 2, and the first inner ring 10 and the second inner ring 12 can be divided. The inner ring 12 is joined to the inner ring 2 by, for example, adhesion or welding. In addition, the first inner ring 10 and the second inner ring 12 are formed with a concave curved raceway surface 10a and a raceway surface 12a each having a predetermined radius of curvature as an example, and these raceway surfaces 10a and 12a are connected to each other. A raceway surface 2a of the inner ring 2 is configured. The raceway surface 4 a of the outer ring 4 is formed so as to face the raceway surface 10 a of the first inner ring 10 and the raceway surface 12 a of the second inner ring 12.

  In such a configuration, each of the rolling elements (balls) 6 of the bearing A includes the raceway surface 2 a of the inner ring 2 (the raceway surface 10 a of the first inner ring 10 and the raceway surface 12 a of the second inner ring 12) and the outer ring 4. This is a so-called three-point contact bearing that contacts the raceway surface 4a at one point. The inner ring 2 may be an integrated inner ring 2 that is formed integrally with the first inner ring 10 and the second inner ring 12 instead of being divided into the first inner ring 10 and the second inner ring 12. Further, the outer ring 4 may be divided and configured in place of the inner ring 2 or together with the inner ring 2.

  Further, the outer ring 4 is chamfered continuously along the circumferential direction at both ends of the outer diameter portion thereof in a flat shape. Furthermore, an outer peripheral surface 4g on one end side (for example, the right side in FIG. 1A) of the outer diameter portion of the outer ring 4 is provided with a flange portion 4f in an annular and continuous manner along the circumferential direction. In this case, the flange portion 4f is formed with a plurality of through-holes 4k penetrating the flange portion 4f in the axial direction at predetermined positions on the circumference. The bearing A can be fixed to the housing by inserting a bolt (not shown), a screw, a rivet, etc.) and fastening the fixing member to the housing (not shown).

Further, the cage 8 has a hollow cylindrical shape inside, and both end portions (inner peripheral end surfaces) 8a, 8a of the inner peripheral surface thereof are in sliding contact with the opposing surfaces 2s, 2s of the inner ring 2 facing each other. , Guided by the inner ring 2, rotates together with the inner ring 2, and revolves between the inner and outer rings.
The cage 8 is alternately provided with pockets 8p for holding the respective rolling elements 6 and column portions 8h for connecting adjacent pockets 8p along the circumferential direction. Further, on the inner peripheral surface of the column portion 8h, two inner peripheral concave curved surfaces 8b and 8b are formed continuously from the inner peripheral end surfaces 8a and 8a, respectively, and one continuous continuous curved surface 8b and 8b is provided. An inner peripheral convex portion 8c is formed at a substantially central position of the inner peripheral surface. Further, on the outer peripheral surface of the column portion 8h, one outer peripheral convex portion 8t is formed at a substantially central position of the outer peripheral surface continuously from the outer peripheral facing surfaces 8s and 8s facing the opposing surfaces 4s and 4s of the outer ring 4. Has been.
In this case, the inner peripheral convex portion 8 c is formed to protrude from the inner peripheral end surface 8 a by a predetermined length in the direction of the inner ring 2, the cage 8 is assembled between the inner and outer rings, and the inner peripheral end surface 8 a is opposed to the inner ring 2. A predetermined interval can be provided between the tip 8d of the inner circumferential convex portion 8c and the raceway surface 2a (10a, 12a) of the inner ring 2 in a state of sliding contact with the surface 2s. Further, the outer peripheral convex portion 8t is formed to protrude from the outer peripheral facing surface 8s by a predetermined length in the direction of the outer ring 4, and similarly, the inner peripheral end surface 8a is in sliding contact with the opposing surface 2s of the inner ring 2. In FIG. 5, a predetermined interval can be provided between the tip 8u of the outer peripheral convex portion 8t and the raceway surface 4a of the outer ring 4.

  In this embodiment, the bearing A has Rk and skewness (skewness) in the statistical distribution of the surface roughness of the surface of the raceway (inner ring 2 and outer ring 4) and the surface of the cage 8. ) Is Rsk, at least the slidable contact surface of the bearing ring with respect to the cage 8 is processed so that Rk <20 and Rsk <0 as surface treatment (first surface treatment). In the configuration shown in FIG. 1, as an example, the bearing A has a surface treatment (first surface treatment) Rk <20 on the opposing surface 2 s of the inner ring 2 (specifically, the sliding surface with respect to the cage 8). In addition, processing is performed so that Rsk <0.

  The processing method for performing the surface treatment (first surface treatment) is such that the kurtosis (Rk) and the skewness (Rsk) of the facing surface 2s of the inner ring 2 are Rk <20 and Rsk <0. Any method can be used as long as it can be processed, and there is no particular limitation here. For example, by performing a predetermined grinding process as a surface treatment on the facing surface 2s of the inner ring 2, the values of kurtosis (Rk) and skewness (Rsk) are Rk <20 and Rsk <0. The facing surface 2s of the inner ring 2 may be processed. Furthermore, you may perform a predetermined | prescribed grinding | polishing process as needed. In this case, for example, various grinders and polishers may be used for the predetermined grinding process and polishing process. Further, the lower limit values of the kurtosis (Rk) and the skewness (Rsk) are set to predetermined values depending on, for example, the operating conditions of the bearing A, the manufacturing cost, etc., and are not particularly limited here.

Here, as the surface treatment (first surface treatment) according to the present embodiment, processing is performed in which the kurtosis (Rk) and skewness (Rsk) values of the surface are Rk <20 and Rsk <0. In addition, a test was conducted to verify the wear resistance performance of a predetermined sample. The test contents and test results will be described below.
In the test, two rotating rings were prepared as samples, and the outer diameter surface (outer peripheral surface) of one rotating ring was subjected to a grinding process so that Rk <20 and Rsk <0 (hereinafter, referred to as “surface treatment”). The rotating ring subjected to the processing is referred to as the present ring), and the outer diameter surface (outer peripheral surface) of the other rotating ring was subjected to grinding so as to satisfy Rk> 20 and Rsk> 0 (hereinafter, the corresponding ring) A processed rotating ring is called a comparative ring). Then, the wear resistance performance of the case ring and the comparison ring was verified by comparing the dynamic friction coefficients when the case ring and the comparison ring were respectively rotated at a predetermined speed under a predetermined condition.

  Specifically, using a slip tester as shown in FIG. 1 (b), a load weight W is set at a predetermined position of the tester, and a pin is placed on the rotating ring R (the present ring and the comparison ring) In a state where a load of 20 to 100 (N) was applied from P, the shaft S on which the rotating ring R was fitted was rotated at a maximum speed of 20000 rotation per minute (maximum speed 20000 (rpm)). And the dynamic friction coefficient of the rotating ring R at this time was measured about the case where this ring and a comparison ring are applied as the rotating ring R, respectively. During the test, the temperature of the internal space where the rotating ring R rotates was adjusted by the heater H in the range of room temperature (room temperature) to 250 ° C. In addition, during the test, a lubricant (for example, MIL-L-23699 equivalent oil (MIL: Military Specifications and Standards)) is jetted (jet lubricated) to the rotating ring R, and the rotation is performed by the jet lubrication. The ring R continued to rotate smoothly. In this case, the lubricating oil supply temperature was set to 150 ° C. at the maximum.

As a result of the measurement, the value of the dynamic friction coefficient of the rotating ring R (the present ring and the comparative ring) at a predetermined rotating speed (sliding speed) is shown in FIG. As is clear from the figure, when the sliding speed is 0, 20, 40, 60, 80, and 100 meters (m / sec) per second, the dynamic friction coefficient values of this ring are all comparative rings. It is smaller than the value of the dynamic friction coefficient. In addition, when the sliding speed is 20 meters per second (m / sec) or more, the value of the dynamic friction coefficient of the present ring is stable at about 0.12 (during this time, the value of the dynamic friction coefficient of the comparison ring is 0). About 30).
Thus, according to the present ring subjected to the surface treatment (first surface treatment) according to the present embodiment, the value of the dynamic friction coefficient is conspicuous as compared with the comparison ring not subjected to the first surface treatment. It was verified by the above-mentioned test that it was verified that it was reduced and that excellent wear resistance performance could be exhibited.

Further, as the surface treatment (first surface treatment) according to the present embodiment, processing was performed in which the values of the kurtosis (Rk) and the skewness (Rsk) of the surface were Rk <20 and Rsk <0. The wear resistance performance of a given rolling bearing was also tested and verified. The test contents and test results will be described below.
In this test, two rolling bearings were prepared as samples, and one of the rolling bearings was subjected to surface treatment on the inner ring outer diameter surface (cage guide surface (sliding contact surface with respect to the cage)), Rk = 16. 6 and Rsk = −0.5 was applied (hereinafter, the rolling bearing subjected to the processing was referred to as the present bearing). On the other hand, in the other rolling bearing, Rk = 74.2 and Rsk = 7.0 as the surface treatment on the inner ring outer diameter surface (the cage guide surface (sliding contact surface with respect to the cage)). Grinding was performed (hereinafter, the rolling bearing subjected to the processing is referred to as a comparative bearing). Then, after rotating the present bearing and the comparative bearing for a predetermined time at a predetermined speed under a predetermined condition, by comparing the state of the inner ring outer diameter surface (sliding contact surface with respect to the cage) of both bearings, The wear resistance performance of the bearing and the comparative bearing was verified.

  Specifically, a ball bearing A (inner diameter d (φ): 100 (mm), outer diameter D (φ): 150 (mm), width B: 25 used at a high speed as shown in FIG. (mm)), and the inner ring 2 is mounted for one minute in a state where the inner ring 2 is assembled (for example, externally fitted) so that the inner ring 2 is inclined at a predetermined angle with respect to a shaft (not shown). And 15000 rotation speed (15000 (rpm)). In this case, a load of 5000 (N) was applied to the bearing A as an axial load during the test. Further, during the test, a predetermined lubricating oil was sprayed onto the bearing A at 6 liters per minute (6 (l / min)) to lubricate the bearing A so that the bearing A continued to rotate smoothly. And the state of the inner ring | wheel outer diameter surface (sliding contact surface with respect to a holder | retainer) of the bearing A (this bearing and comparative bearing) after progress for a predetermined time was confirmed.

As a result, in the comparative bearing after the test, the occurrence of damage (wear) due to friction was observed on the inner ring outer diameter surface (sliding contact surface with respect to the cage) and the inner diameter surface of the cage (sliding contact surface with respect to the inner ring). On the other hand, in the bearing after the test, no damage (abrasion) due to friction was observed on the inner ring outer diameter surface (sliding contact surface with respect to the cage) and the inner diameter surface of the cage (sliding contact surface with respect to the inner ring). There wasn't. In this case, the bearing after the test showed no damage (wear) on the portion (surface) other than the inner ring outer diameter surface and the cage inner diameter surface.
As described above, according to the present bearing subjected to the surface treatment (first surface treatment) according to the present embodiment, the wear resistance is remarkably improved as compared with the comparative bearing not subjected to the first surface treatment. It was verified by the above-mentioned test that it was verified that the wear resistance performance was excellent.

  As described above, according to the present invention, at least a sliding contact surface (inner ring outer diameter surface (cage guide surface)) of the bearing ring with respect to the cage of the surface of the bearing ring and the surface of the cage with respect to the rolling bearing. As the processing (first surface treatment), processing in which the kurtosis (Rk) and skewness (Rsk) values of the sliding contact surface satisfy Rk <20 and Rsk <0 (for example, low-cost cutting) It is possible to improve the wear resistance of the bearing and prevent damage to the bearing. Thereby, the said bearing can be continuously used with fixed performance over a long period of time.

  Further, in addition to the above-described first surface treatment, at least the sliding contact surface (for example, the bearing ring with respect to the cage) of the surface of the bearing ring (for example, the inner ring) and the surface of the cage with respect to the rolling bearing (for example, The inner ring outer diameter surface (cage guide surface)) may be subjected to nitriding as a surface treatment (second surface treatment). Thereby, the wear resistance of the bearing can be further improved, and damage to the bearing can be prevented more effectively. As a result, the bearing can be used continuously with a constant performance over a longer period.

  For example, a high-speed rotating bearing (for example, a ball bearing A shown in FIG. 1A) used in a high-temperature environment such as an aircraft jet engine or a gear box is an AISI (American Iron and Steel Institute: USA). It can be made of heat-resistant bearing steel using heat-resisting high-speed steel material (M50 material) of the Steel Association. In this case, first, surface treatment (first surface treatment) is performed on the sliding surface (for example, inner ring outer diameter surface (cage guide surface)) of the bearing ring (for example, inner ring) with respect to the cage of the bearing A. As described above, a process (for example, a low-cost cutting process) in which the kurtosis (Rk) and the skewness (Rsk) of the sliding contact surface are Rk <20 and Rsk <0 is performed. Further, nitriding treatment may be performed on the sliding contact surface as surface treatment (second surface treatment). As such nitriding treatment, for example, low-temperature nitriding treatment at a treatment temperature of 300 to 400 ° C. may be performed.

  In this case, since the nitriding treatment can be performed by any method, the treatment method is not particularly limited here. For example, nitriding can be performed by various nitriding methods such as a gas nitriding method, a salt bath nitriding method, and a gas nitriding method. As an example of a suitable method, “NV-300” manufactured by Air Water Co., Ltd. The following NV nitriding process can be used. The NV nitriding treatment method is a method of performing nitriding treatment by combining gas activation treatment (fluorination treatment) and gas nitriding treatment.

  Here, in addition to the first surface treatment described above on the outer surface of the inner ring (sliding contact surface with respect to the cage), the wear resistance is similarly applied to the bearing subjected to nitriding as a second surface treatment. A performance test was performed and verified. As a result, it was confirmed that, for example, the wear resistance of a bearing used in a high temperature environment and rotating at high speed can be improved, and damage to the bearing can be effectively prevented.

  Further, in addition to the above-described first surface treatment, at least the sliding contact surface (for example, the bearing ring with respect to the cage) of the surface of the bearing ring (for example, the inner ring) and the surface of the cage with respect to the rolling bearing (for example, A surface treatment (second surface treatment) may be applied to the inner ring outer diameter surface (cage guide surface) to form a carbon coating (for example, a DLC (Diamond Like Carbon) coating). Thereby, the wear resistance of the bearing can be further improved, and damage to the bearing can be prevented more effectively. As a result, the bearing can be used continuously with a constant performance over a longer period.

  For example, a bearing that is used in a high-temperature environment such as an aircraft jet engine or a gear box and rotates at high speed (for example, the ball bearing A shown in FIG. 1A) is, for example, a heat-resistant bearing using the M50 material described above. Can be composed of steel. In this case, first, surface treatment (first surface treatment) is performed on the sliding surface (for example, inner ring outer diameter surface (cage guide surface)) of the bearing ring (for example, inner ring) with respect to the cage of the bearing A. As described above, a process (for example, a low-cost cutting process) in which the kurtosis (Rk) and the skewness (Rsk) of the sliding contact surface are Rk <20 and Rsk <0 is performed. In addition, a surface treatment (second surface treatment) may be applied to the sliding contact surface to form a DLC film.

  In addition, since this DLC film can be formed by performing arbitrary surface treatment (2nd surface treatment), the processing method is not specifically limited here. For example, a hydrocarbon (CH) gas is sealed in a predetermined vacuum chamber, and an applied voltage is applied to a base material (for example, an inner ring) connected to a DC power source. As a result, plasma is generated in the vacuum chamber, and a DLC film can be formed on the surface of the base material (for example, the inner ring surface). The DLC film does not have a grain boundary due to its amorphous structure, and has a smooth surface compared to a polycrystalline structure such as a TiN (titanium nitride) film, for example, tribological characteristics (wear characteristics, friction characteristics, Excellent lubrication characteristics). The DLC film is a carbon film (carbon film) having physical properties similar to diamond, and has a higher hardness than, for example, a TiN film.

  Here, in addition to the first surface treatment described above on the outer surface of the inner ring (sliding contact surface with respect to the cage), a second surface treatment is further applied to the bearing formed with the DLC film. The wear performance was tested and verified. As a result, it was confirmed that, for example, the wear resistance of a bearing used in a high temperature environment and rotating at high speed can be improved, and damage to the bearing can be effectively prevented.

  In the present embodiment described above, the surface treatment (first surface treatment and second surface treatment) is performed only on the sliding surface (inner ring outer diameter surface (cage guide surface)) with respect to the cage of the inner ring. However, the entire surface of the inner ring may be subjected to surface treatment (first surface treatment and second surface treatment). Further, surface treatment (first surface treatment and second surface treatment) may be applied only to the sliding surface (outer ring inner diameter surface (cage guide surface)) of the outer ring with respect to the cage. Treatment (first surface treatment and second surface treatment) may be performed. In this case, surface treatment (first surface treatment and second surface treatment) may be selectively performed on either the inner ring or the outer ring depending on the guide method of the cage incorporated between the race rings. That is, when the cage is an inner ring guide, the inner ring may be subjected to surface treatment (first surface treatment and second surface treatment). When the cage is an outer ring guide, the outer ring is subjected to surface treatment (first surface treatment). Treatment and second surface treatment) may be performed. Regardless of the cage guide method, both the inner ring and the outer ring may be subjected to surface treatment (first surface treatment and second surface treatment).

Further, surface treatment (first surface treatment and second surface treatment) is performed only on the sliding contact surface (for example, cage inner diameter surface (tracking ring guide surface)) with respect to the raceway (inner race or outer race) of the cage. Alternatively, surface treatment (first surface treatment and second surface treatment) may be performed on the entire surface of the cage.
Further, surface treatment (first surface treatment and second surface treatment) may be applied to both the raceway ring (inner ring and outer ring) and the cage.
In addition, in this embodiment mentioned above, although the ball was applied as a rolling element, you may apply a roller. Further, the bearing may have a double row configuration (two or more rows) in addition to a single row configuration.

(a) is a cross-sectional view showing a configuration example of a rolling bearing according to an embodiment of the present invention, (b) is a cross-sectional view showing a configuration example of a slip test machine for testing the wear resistance performance of a sample, (c) is a diagram showing the result of testing the wear resistance performance of the sample using the sliding tester shown in FIG. (b) as the value of the dynamic friction coefficient with respect to the sliding speed.

Explanation of symbols

2 Inner rings 2a, 4a Raceway surface 2s Sliding contact surface 4 Outer ring 6 Rolling element 8 Cage A Rolling bearing

Claims (3)

A bearing ring disposed so as to be capable of relative rotation, a plurality of rolling elements that are rotatably incorporated between raceways formed on each of the race rings, and a holder that rotatably holds the plurality of rolling elements. A rolling bearing with a vessel,
When the kurtosis in the statistical distribution of the surface roughness of the surface of the bearing ring and the surface of the cage is Rk and the skewness is Rsk, at least the sliding contact surface with respect to the cage of the bearing ring is Rk as the first surface treatment. A rolling bearing characterized by being processed so that <20 and Rsk <0.   In addition to the first surface treatment, nitriding treatment is performed as a second surface treatment on at least the sliding surface of the raceway surface and the cage surface with respect to the raceway cage. The rolling bearing according to claim 1. In addition to the first surface treatment, a second surface treatment is applied to at least a sliding contact surface of the raceway ring and the cage surface with respect to the raceway cage to form a carbon coating. The rolling bearing according to claim 1, wherein the rolling bearing is provided.

Images