Synthetic resin cage and roller cage

Abstract

To provide a cage for a roller bearing capable of elongating a service life by suppressing generation of peeling.SOLUTION: A synthetic resin cage (1) includes: a pair of annular portions; a plurality of pillar portions extending in an axial direction and connecting the pair of annular portions; and pockets respectively formed between the adjacent pillar portions to house the rollers. The pillar portion (5) includes a plurality of first pillar portions (51) and one second pillar portion (52). The second pillar portion (52) is disposed between the first pillar portions adjacent to each other and has a first part (53) and a second part (54) axially divided by a split groove (7). A circumferential dimension of the first part (53) of the second pillar portion (52) is 0.5 times or more and 0.8 times of less of a circumferential dimension of the first pillar portion (51).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a synthetic resin cage and a roller and cage assembly. [Background technology]

[0002] It is generally known that in a synthetic resin cage, a split groove extending in the axial direction is formed in one of the multiple pillars, and the cage is opened at the split groove, making it easier to incorporate into another member such as a shaft. For example, the synthetic resin cage described in Patent Document 1 (JP Patent Publication No. 7-317773) is annular, with one location of the ring divided by a split groove.

[0003] Figure 6 is a schematic diagram of the roller and cage assembly of Patent Document 1, and Figure 7 is an enlarged view of a portion of Figure 6. As shown in Figures 6 and 7, the roller and cage assembly 100 is formed of a plurality of first pillar portions 105 and second pillar portions 106 that are arranged adjacent to the first pillar portions 105 and have split grooves 107 that extend in the axial direction. Pockets 108 that accommodate rollers 102 are formed between adjacent first pillar portions 105 and between the first pillar portions 105 and second pillar portions 106. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-317773 Summary of the Invention [Problem to be solved by the invention]

[0005] A roller and cage assembly 100 with a slot 107 as shown in FIG. 6 has reduced rigidity compared to a synthetic resin cage without the slot 107. As a result, during use, the portion where the slot 107 is formed deforms outward due to centrifugal force. This deformation is restrained by the rollers 102 housed in the pockets 108. However, when used at high rotational speeds, as shown in FIG. 7, the rollers 102 come into strong contact with the roller stoppers 109 formed on the post portions 105. This makes it easier for the oil film to break, and there is a risk of peeling occurring in the rollers 102, first post portion 105, and second post portion 106.

[0006] Furthermore, in response to recent demands for improved fuel economy, the amount of lubricating oil supplied to the roller and cage assembly is being reduced, and lubricating oil with a low dynamic viscosity is sometimes used. In this case, the amount of lubricating oil retained in the roller and cage assembly is reduced, making it difficult for an oil film to form. In addition, lubricating oil with a low dynamic viscosity reduces the oil film thickness. As a result, the rollers and raceway surface come into direct contact without an oil film in between, which can cause wear on each other.

[0007] The present invention has been made to solve the above-mentioned problems, and its object is to provide a synthetic resin cage and a roller with cage that can achieve a longer life by suppressing the occurrence of peeling. [Means for solving the problem]

[0008] A synthetic resin retainer according to one embodiment of the present invention comprises a pair of annular portions, a plurality of pillar portions extending axially to connect the pair of annular portions, and pockets formed between adjacent pillar portions for accommodating rollers, the pillar portions including a plurality of first pillar portions and one second pillar portion, the second pillar portion being arranged between adjacent first pillar portions and having a first portion and a second portion divided axially by a split groove, and the circumferential dimension of at least one of the first portion and the second portion of the second pillar portion being 0.5 to 0.8 times the circumferential dimension of the first pillar portion.

[0009] Preferably, the radial dimension of the second pillar portion is larger than the circumferential dimension of at least one of the first portion and the second portion of the second pillar portion.

[0010] A roller and cage assembly according to one aspect of the present invention comprises rollers and the above-mentioned synthetic resin cage which houses the rollers in pockets, the rollers having been subjected to carbonitriding treatment to form a carbonitrided layer on their surfaces, the carbonitrided layer having a Vickers hardness of HV720 or more, a nitrogen concentration of 0.05 mass% or more and 0.4 mass% or less, and the difference between the maximum and minimum Vickers hardness values ​​up to a depth of 0.1 mm from the surface of the roller being HV30 or less.

[0011] Preferably, the surface of the roller is provided with a plurality of minute concave depressions, the area ratio of the depressions on the surface where the depressions are provided is 5% or more and 20% or less, the surface roughness parameter Rymax of the surface where the depressions are provided is 0.4 or more and 1.0 or less, and when the surface roughness of the surface where the depressions are provided is expressed as the parameter Rqni, the ratio Rqni(L) / Rqni(C) of the axial surface roughness Rqni(L) to the circumferential surface roughness Rqni(C) is 1.0 or less, and the circumferential surface roughness Rqni(C) is 0.11 or less.

[0012] According to the present invention, it is possible to extend the life by suppressing the occurrence of peeling. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view showing a roller and cage assembly according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view of the roller and cage assembly with the rollers removed according to the embodiment of the present invention. [Figure 3] FIG. 3 is an enlarged cross-sectional view of a part of FIG. 2. [Figure 4] 1 is a graph showing the relationship between the depth from the roller surface and the carbon concentration, nitrogen concentration, and Vickers hardness when the nitrogen concentration on the roller surface is around 0.4 mass %. [Figure 5]1 is a graph showing the relationship between the depth from the roller surface and the carbon concentration, nitrogen concentration, and Vickers hardness when the nitrogen concentration on the roller surface is around 0.7 mass %. [Figure 6] FIG. 10 is a cross-sectional view showing a conventional roller and cage assembly. [Figure 7] FIG. 7 is an enlarged view of a portion of FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and description thereof will not be repeated.

[0015] (Regarding the cage) A cage 3 according to this embodiment will be described with reference to Figures 1 to 3. With particular reference to Figure 1, the cage 3 holds a plurality of rollers 2. The cage 3 is made of synthetic resin, and specifically, polyamide or polyphenylene sulfide containing reinforcing fibers is used. The roller cage 3 that houses a plurality of rollers 2 is provided as a roller and cage assembly 1.

[0016] The cage 3 has a pair of annular portions 4 and a plurality of pillar portions 5 that connect the pair of annular portions 4 to each other. The pillar portions 5 include a plurality of first pillar portions 51 and one second pillar portion 52. As shown in FIG. 3 , the first pillar portion 51 has a circumferential dimension X. The pillar portion 51 includes one side wall surface that faces one pocket 8 and the other side wall surface that faces the other pocket 8. These opposing side wall surfaces form a pocket 8 for accommodating the rollers 2. A plurality of pockets 8 are provided at intervals in the circumferential direction. In the following explanation, the direction along the central axis of the roller and cage assembly 1 will be referred to as the "axial direction," the direction perpendicular to the central axis as the "radial direction," and the circumferential direction around the central axis as the "circumferential direction."

[0017] The split groove 7 is provided at one location on the upper side of the paper of FIGS. 1 and 2. The split groove 7 extends along the axial direction of the second pillar portion 52. The second pillar portion 52 is disposed between adjacent first pillar portions 51, and is divided axially into two portions, a first portion 53 and a second portion 54, by the split groove 7. The first portion 53 and the second portion 54 of the second pillar portion 52 preferably have substantially the same shape, and are substantially identical in circumferential dimension, axial dimension, and radial dimension. In the following explanation, the first portion 53 will be explained when explaining the second pillar portion 52. As shown in FIG. 3, the second pillar portion 52 has a circumferential dimension Y and a radial dimension Z.

[0018] The circumferential dimension Y of the first portion 53 of the second pillar portion 52 is 0.5 to 0.8 times the circumferential dimension X of the first pillar portion 51 (0.5X to 0.8Y). Here, the circumferential dimension of the first pillar portion 51 and the second pillar portion 52 refers to the linear distance between the inner diameter side edges of the pillar portions, but it need only be the circumferential dimension of the same location on the first pillar portion 51 and the first portion 53 of the second pillar portion 52. If the circumferential dimension Y of the first portion 53 of the second pillar portion 52 is less than 0.5X, it will be less than half the circumferential dimension of the first pillar portion 51, which would undesirably reduce the rigidity of the second pillar portion 52 portion of the entire pillar portion 5. Furthermore, if the circumferential dimension Y of the first portion 53 of the second pillar portion 52 exceeds 0.8X, centrifugal force acts on the rollers 2 housed in the pocket 8 formed by the side wall of the first portion 53 of the second pillar portion 52 and the side wall of the first pillar portion 51, and on the rollers 2 housed in the pocket 8 formed by the side wall of the second portion 54 of the second pillar portion 52 and the side wall of the first pillar portion 51, causing oil film breakdown. This is undesirable as it causes damage to the rollers 2, the first pillar portion 51, and the second pillar portion 52.

[0019] The inventors actually created two samples of the roller and cage assembly 1 and conducted evaluation tests. The two samples had the circumferential dimension Y of the first portion 53 and second portion 54 of the second pillar portion 52 set to 0.8X and 1.0X. It was found that the roller and cage assembly 1 in which the circumferential dimension Y of the second pillar portion 52 was set to 0.8X did not experience damage to the rollers 2 due to oil film breakdown. On the other hand, it was found that the roller and cage assembly 1 in which the circumferential dimension Y of the second pillar portion 52 was set to 1.0X experienced oil film breakdown and peeling occurred on the rollers 2 and the cage 3.

[0020] The radial dimension Z of the first portion 53 of the second pillar portion 52 is larger than the circumferential dimension Y of the first portion 53 of the second pillar portion 52 (Z>Y). By making the radial dimension Z of the first portion 53 of the second pillar portion 52 larger than the circumferential dimension Y, the strength of the cage 3 can be improved. Note that it is preferable that the radial dimension of the first pillar portion 51 is approximately the same as the radial dimension of the second pillar portion 52.

[0021] The pillar portion 5 in this embodiment has, for example, a straight shape extending in the axial direction, but is not limited to this. Furthermore, although not shown, it is preferable that the side wall surface of the pillar portion 5 (the surface on the pocket 8 side) is provided with inner claws (roller stops) to prevent the rollers 2 from falling off to the inner diameter side, and the side wall surface of the pillar portion 5 is provided with outer claws (roller stops) to prevent the rollers 2 from falling off to the outer diameter side.

[0022] (About the rollers) Next, the rollers 2 will be described. In this embodiment, the rollers 2 are needle rollers, but they may have other shapes, such as cylindrical rollers or rod-shaped rollers. In addition, the chemical composition of the rollers 2 is, for example, as follows:

[0023] [Table 1]

[0024] Each roller 2 has a plurality of minute concave recesses formed on its surface. Specifically, the plurality of minute concave recesses are randomly formed on either the rolling surface or the raceway surfaces of the inner and outer rings to form a micro-roughened surface. This micro-roughened surface has a recess area ratio of 5% to 20% and a surface roughness parameter Rymax of 0.4 to 1.0. By setting the recess area ratio to 5% to 20% and the surface roughness parameter Rymax of the recessed surface to 0.4 to 1.0, a high oil film formation effect can be achieved even under conditions where the oil film thickness is extremely thin, and a sufficient life extension effect can be achieved even under extremely severe lubrication conditions with an oil film parameter Λ = 0.13.

[0025] Furthermore, when the surface roughness is measured in both the axial and circumferential directions of each surface and expressed as the parameter Rqni, the ratio Rqni(L) / Rqni(C), the axial surface roughness Rqni(L) to the circumferential surface roughness Rqni(C), is 1.0 or less. Surface processing techniques to achieve this micro-roughness include special barrel polishing, but shot blasting can also be used. The parameter Rqni is the square root of the average value obtained by integrating the square of the deviation in height from the roughness center line to the roughness profile over the measurement length, also known as root-mean-square roughness (ISO 4287:1997). Rqni is calculated numerically from enlarged, recorded cross-sectional and roughness profiles, and is measured by moving the roughness tester's stylus in the width and circumferential directions.

[0026] The circumferential surface roughness Rqni(C) is preferably 0.11 or less. This is because the Rqni value affects the oil film parameter. This value is the roller roughness Ra specified in JIS B 1506 multiplied by 1.1, and it is said that there is a relationship of Rq ≒ 1.1Ra. By forming multiple minute recesses on the surface of roller 2 and specifying the surface roughness of roller 2, it is possible to cope with lean lubrication conditions.

[0027] The method and conditions for measuring the parameter Rymax are as follows: It is preferable to measure at two locations, for example, that are opposite to each other in the diametric direction.

[0028] Parameter calculation standard: JIS B 0601:1994 (Surfcom JIS 1994) Cutoff type: Gaussian Measurement length: 5λ Cutoff wavelength: 0.25 mm Measurement magnification: ×10000 Measurement speed: 0.30mm / s Measurement location: Center of roller Number of measurements: 2 Measuring device: Surface roughness measuring instrument Surfcom 1400A (Tokyo Seimitsu Co., Ltd.)

[0029] In the case of minute concave dimples provided on the rolling surface of a roller, the area ratio of the dimples to the entire rolling surface shall be 5% to 20% and the average area of ​​the dimples shall be 30μm when excluding areas with an equivalent circular diameter of 3μmφ or less. 2 More than 100μm 2 Rymax is between 0.4 μm and 1.0 μm, the area ratio of pits is over 20%, and the average area is 100 μm 2 If the value exceeds this, the effective contact length decreases, and the effect of long life tends to decrease.

[0030] Quantitative measurement of pitting can be performed by enlarging the roller surface and quantifying the image using a commercially available image analysis system. White areas in the image are analyzed as flat surface areas, and minute pits are analyzed as black areas. For example, when analyzing using Pierce Corporation's LA-525 image analysis system, the original image's shading is first clarified using an enhancement filter, and then very small black areas with an equivalent circular diameter of 3 μm or less are removed using a noise eraser. The size, distribution, and area ratio of the remaining minute pits after noise erasure are determined and the roller surface is evaluated. Measurement conditions for this are, for example, as follows: When measuring the area ratio and average area of ​​pits on components such as the rolling elements and raceways of a rolling bearing, it is preferable to measure at two diametrically opposed locations, as with the above parameters Rymax and Rqni.

[0031] Observation field: 826 μm x 620 μm Measurement location: Center of roller Number of measurements: 2

[0032] Roller 2 in this embodiment is subjected to, for example, nitriding or carbonitriding, and a carbonitrided layer is formed on the surface. The carbonitrided layer preferably has a Vickers hardness of HV720 or more and a nitrogen concentration of 0.05 mass% or more and 0.4 mass% or less. A Vickers hardness of HV720 or more can strengthen the surface of roller 2, thereby improving the resistance of roller 2 itself to peeling. A nitrogen concentration of 0.05 mass% or more can bond with carbon to prevent a decrease in hardness, while a nitrogen concentration of 0.4 mass% or less can promote bonding with carbon to maintain hardness. A nitrogen concentration of more than 0.4 mass% is not preferable because it reduces hardness.

[0033] The carbonitrided layer preferably has a difference in Vickers hardness between the surface and a depth of 0.1 mm from the surface of HV 40 or less. This makes it possible to reduce the difference in Vickers hardness between the surface and a depth of 0.1 mm from the surface, thereby improving the resistance of roller 2 itself to peeling.

[0034] Figures 4 and 5 are graphs showing the relationship between the carbon concentration, nitrogen concentration, and Vickers hardness and the depth from the surface of roller 2. Figure 4 shows the case where the nitrogen concentration on the surface of roller 2 is 0.4 mass%, and Figure 5 shows the case where the nitrogen concentration on the surface of roller 2 is 0.7 mass%.

[0035] As shown in Figure 5, when the nitrogen concentration on the surface of roller 2 is 0.7 mass%, the carbon concentration and Vickers hardness vary more greatly as the depth from the surface of roller 2 increases. In contrast, as shown in Figure 4, when the nitrogen concentration on the surface of roller 2 is 0.4 mass%, the carbon concentration remains relatively constant, and the Vickers hardness remains almost constant, even as the depth from the surface of roller 2 increases. This shows that in order to maintain the hardness of the surface of roller 2, it is preferable to keep the nitrogen concentration at 0.4 mass% or less.

[0036] Furthermore, as shown in Figure 5, the Vickers hardness is plotted at five locations, with the maximum value being HV780 and the minimum value being HV720. In other words, the difference between the maximum and minimum Vickers hardness values ​​is HV60, and it was found that there is a large variation depending on the depth from the surface of roller 2. In contrast, as shown in Figure 4, the Vickers hardness is plotted at five locations, with the maximum value being HV800 and the minimum value being HV770. In other words, the difference between the maximum and minimum Vickers hardness values ​​is HV30, and it was found that the difference in Vickers hardness is small even as the depth from the surface of roller 2 increases. This shows that it is preferable that the difference between the maximum and minimum Vickers hardness values ​​be HV30 or less within a range of 0.1 mm deep from the surface of roller 2.

[0037] A roller and cage assembly 1 with these characteristics can be used in a structure that rotates with a dmn value, which is the product of the pitch circle diameter dm (mm) and the rotation speed N (rpm), of 150,000 or more. In addition, the roller and cage assembly 1 has a kinematic viscosity of 27mm at 40°C. 2 / s or less, kinematic viscosity at 100°C is 8.0mm 2 A low viscosity lubricant, such as / s or less, is used.

[0038] In the cage 3 of the roller and cage assembly 1 according to this embodiment, the circumferential dimension Y of the portions 53, 54 of the second post section 52, which are divided into two by the split groove 7, is between 0.5 and 0.8 times the circumferential dimension X of the first post section 51. This makes it possible to suppress the centrifugal force acting on the rollers 2 arranged adjacent to the split groove 7, thereby preventing oil film breakdown. This makes it possible to suppress peeling of the cage 3 and rollers 2, thereby extending their service life.

[0039] Furthermore, the radial dimension Z of the first portion 53 of the second pillar portion 52 is set to be larger than the circumferential dimension Y of the first portion 53 of the second pillar portion 52. By making the radial dimension Z of the first portion 53 of the second pillar portion 52 larger than the circumferential dimension Y, the strength of the cage 3 can be improved.

[0040] From the above, by adjusting the values ​​of the circumferential dimension Y and radial dimension Z of the second pillar portion 52, it is possible to reduce the centrifugal force acting on the rollers 2 arranged adjacent to the second pillar portion 52 and also maintain the strength of the second pillar portion 52, thereby achieving a longer lifespan for the retainer 3.

[0041] In rollers 2 of roller and cage assembly 1 according to this embodiment, the hardness of the carbonitrided layer is HV720 or more, the nitrogen concentration in the surface of roller 2 is 0.05 mass% or more and 0.4 mass% or less, and the difference between the maximum and minimum Vickers hardness values ​​up to a depth of 0.1 mm from the surface of roller 2 is HV40 or less, so that the hardness of roller 2 can be increased and wear of roller 2 itself can be suppressed. Furthermore, by providing minute concave-shaped indentations in the surface of roller 2 and setting the area ratio of the indentations, surface roughness, etc., it is possible to further increase the hardness of roller 2 and suppress wear.

[0042] In this way, the roller and cage assembly 1 according to this embodiment can suppress the occurrence of peeling even when the cage 3 has split grooves 7, and furthermore, since the strength of the rollers 2 is increased, the life of the roller and cage assembly 1 as a whole can be extended.

[0043] The embodiments disclosed herein should be considered as illustrative and not restrictive. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0044] 1,100 Roller with cage, 2,102 Roller, 3 Cage, 4 Annular portion, 5,105 Column portion, 7,107 Slot, 8,108 Pocket, 51,105 First column portion, 52,106 Second column portion, 53 First portion, 54 Second portion, X, Y Circumferential dimension, Z Radial dimension.

Claims

1. a pair of annular portions, a plurality of pillar portions extending in the axial direction and connecting the pair of annular portions, and pockets formed between adjacent pillar portions for accommodating rollers; The pillar portion includes a plurality of first pillar portions and one second pillar portion, The second pillar portion is disposed between adjacent first pillar portions and has a first portion and a second portion that are axially divided by a split groove, A synthetic resin cage, wherein the circumferential dimension of at least one of the first portion and the second portion of the second pillar portion is 0.5 to 0.8 times the circumferential dimension of the first pillar portion.

2. The synthetic resin cage according to claim 1 , wherein a radial dimension of the second pillar portion is larger than a circumferential dimension of at least one of the first portion and the second portion of the second pillar portion.

3. The above and the rollers are accommodated in the pockets; and the synthetic resin cage according to claim 1 or 2 is provided. The rollers are subjected to carbonitriding treatment to form a carbonitrided layer on their surfaces, The carbonitrided layer has a Vickers hardness of HV720 or more, The nitrogen concentration of the carbonitrided layer is 0.05 mass% or more and 0.4 mass% or less, The difference between the maximum and minimum Vickers hardness values ​​from the surface of the roller to a depth of 0.1 mm is HV30 or less.

4. A plurality of minute concave depressions are provided on the surface of the roller, an area ratio of the recesses on the surface having the recesses is 5% or more and 20% or less; a surface roughness parameter Rymax of the surface provided with the recesses is 0.4 or more and 1.0 or less; When the surface roughness of the surface provided with the recesses is expressed by a parameter Rqni, the ratio Rqni(L) / Rqni(C) of the axial surface roughness Rqni(L) to the circumferential surface roughness Rqni(C) is 1.0 or less, 4. The roller and cage assembly according to claim 3, wherein said circumferential surface roughness Rqni(C) is 0.11 or less.

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