JP7783752B2 - Synthetic resin cage and roller cage - Google Patents

Description

The present invention relates to a synthetic resin cage and a roller and cage assembly.

It is generally known that in synthetic resin cages, a split groove extending axially is formed in one of the multiple pillars, and the cage is opened at the split groove, making it easier to incorporate into other components 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 on the ring being divided by a split groove.

Figure 6 is a schematic diagram of the roller and cage assembly disclosed in 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 the second pillar portions 106.

Japanese Patent Application Publication No. 7-317773

A roller and cage assembly 100 with a slot 107, as shown in Figure 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 speeds, as shown in Figure 7, the roller stop 109 formed on the post portion 105 comes into strong contact with the rollers 102. 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.

Furthermore, due 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 held 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.

This invention was made to solve the above-mentioned problems, and its purpose is to provide a synthetic resin cage and roller with cage assembly that can extend the life by suppressing the occurrence of peeling.

A synthetic resin cage according to one embodiment of the present invention comprises a pair of annular portions, a plurality of column sections extending axially to connect the pair of annular portions, and pockets formed between adjacent column sections to accommodate rollers. The column sections include a plurality of first column sections and one second column section. The second column section is disposed between adjacent first column sections and has a first section and a second section divided axially by a split groove. The circumferential dimension of at least one of the first and second sections of the second column section is between 0.5 and 0.8 times the circumferential dimension of the first column section.

Preferably, the radial dimension of the second columnar portion is greater than the circumferential dimension of at least one of the first and second portions of the second columnar portion.

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 have been subjected to carbonitriding treatment to form a carbonitrided layer on their surfaces; the carbonitrided layer has 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 is HV30 or less.

Preferably, the roller surface 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.

The present invention makes it possible to extend the service life by suppressing the occurrence of peeling.

1 is a cross-sectional view showing a roller and cage assembly according to an embodiment of the present invention; FIG. 2 is a perspective view of the roller and cage assembly with the rollers removed according to the embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view of a portion of FIG. 2 . 10 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 %. 10 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 %. FIG. 10 is a cross-sectional view showing a conventional roller and cage assembly. FIG. 7 is an enlarged view of a portion of FIG. 6.

Embodiments of the present invention will be described in detail with reference to the drawings. Note that identical or corresponding parts in the drawings will be designated by the same reference numerals, and their description will not be repeated.

(Regarding the cage)
A cage 3 according to this embodiment will be described with reference to Figures 1 to 3. Referring particularly 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.

The cage 3 has a pair of annular portions 4 and multiple pillar portions 5 that connect the pair of annular portions 4 to each other. The pillar portions 5 include multiple 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 facing one pocket 8 and the other side wall surface facing the other pocket 8. These opposing side wall surfaces form a pocket 8 for accommodating the rollers 2. Multiple pockets 8 are provided at intervals in the circumferential direction. In the following description, the direction along the central axis of the roller and cage assembly 1 is 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."

The split groove 7 is provided at one location on the upper side of the paper in Figures 1 and 2. The split groove 7 extends along the axial direction of the second columnar portion 52. The second columnar portion 52 is disposed between adjacent first columnar 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 columnar portion 52 preferably have substantially the same shape, and are substantially identical in circumferential, axial, and radial dimensions. In the following explanation, the first portion 53 will be explained when explaining the second columnar portion 52. As shown in Figure 3, the second columnar portion 52 has a circumferential dimension of Y and a radial dimension of Z.

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

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 with the circumferential dimension Y of the second pillar portion 52 set to 0.8X did not suffer damage to the rollers 2 due to oil film breakdown. On the other hand, it was found that the roller and cage assembly 1 with the circumferential dimension Y of the second pillar portion 52 set to 1.0X suffered oil film breakdown and peeling occurred on the rollers 2 and the cage 3.

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

In this embodiment, the column portion 5 has, for example, a straight shape extending in the axial direction, but is not limited to this. Furthermore, although not shown in the figures, it is preferable that the side wall surface of the column portion 5 (the surface facing the pocket 8) is provided with an inner claw (roller stopper) to prevent the rollers 2 from falling out toward the inner diameter side, and the side wall surface of the column portion 5 is provided with an outer claw (roller stopper) to prevent the rollers 2 from falling out toward the outer diameter side.

(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. The chemical composition of the rollers 2 is, for example, as follows:

The roller 2 has a plurality of minute concave recesses on its surface. Specifically, the plurality of minute concave recesses are randomly formed on either the rolling surface or the raceway surface of the inner and outer rings, creating a micro-roughened surface. This micro-roughened surface has a recess area ratio of 5% to 20%, and the surface roughness parameter Rymax of the surface on which the recesses are formed is 0.4 to 1.0. By setting the recess area ratio to 5% to 20% and the surface roughness parameter Rymax of the surface on which the recesses are formed 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 harsh lubrication conditions with an oil film parameter Λ = 0.13.

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 ratio of 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. Here, 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 curve over the measurement length, and is also known as the root-mean-square roughness (ISO 4287:1997). Rqni is calculated numerically from the enlarged, recorded cross-sectional curve and roughness curve, and is measured by moving the roughness meter's stylus in the width and circumferential directions.

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 believed 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 accommodate lean lubrication conditions.

Examples of the method and conditions for measuring the parameter Rymax are as follows. It is preferable to measure at two diametrically opposed locations.

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.)

In the case of minute concave depressions provided on the rolling surface of the roller, the area ratio of the depressions to the entire rolling surface is set to 5% to 20%, and the average area of the depressions is set to 30 μm2 to 100 ^μm2 when excluding areas with an equivalent circular diameter of ³ μm or less. If Rymax is 0.4 μm to 1.0 μm, the area ratio of the depressions exceeds 20%, and the average area exceeds 100 ^μm2 , the effective contact length decreases, and the effect of long life tends to decrease.

To quantitatively measure dents, the roller surface is enlarged and the image can be quantified using a commercially available image analysis system. White areas in the image are analyzed as flat surface areas, and tiny dents 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 tiny dents remaining after removal with the noise eraser are determined, and the roller surface is evaluated. Measurement conditions in this case are, for example, as follows. Furthermore, when measuring the area ratio and average area of dents 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 parameters Rymax and Rqni above.

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

In this embodiment, roller 2 is subjected to a process such as nitriding or carbonitriding to form a carbonitrided layer on its surface. The carbonitrided layer preferably has a Vickers hardness of HV720 or higher and a nitrogen concentration of 0.05% to 0.4% by mass. A Vickers hardness of HV720 or higher strengthens the surface of roller 2, thereby improving the resistance of roller 2 itself to peeling. A nitrogen concentration of 0.05% by mass or higher bonds with carbon to prevent a decrease in hardness, while a nitrogen concentration of 0.4% by mass or lower promotes bonding with carbon to maintain hardness. A nitrogen concentration of more than 0.4% by mass is undesirable because it reduces hardness.

It is preferable that the difference in Vickers hardness between the surface and a depth of 0.1 mm from the surface of the carbonitrided layer be HV40 or less. This reduces the difference in Vickers hardness between the surface and a depth of 0.1 mm from the surface, improving the resistance of the roller 2 itself to peeling.

Figures 4 and 5 are graphs showing the relationship between the depth from the surface of roller 2 and the carbon concentration, nitrogen concentration, and Vickers hardness. 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%.

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 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.

As shown in Figure 5, Vickers hardness is plotted at five points, with the maximum value being HV780 and the minimum value being HV720. This means that the difference between the maximum and minimum Vickers hardness values is HV60, indicating a large variation depending on the depth from the surface of roller 2. In contrast, as shown in Figure 4, Vickers hardness is plotted at five points, with the maximum value being HV800 and the minimum value being HV770. This means that the difference between the maximum and minimum Vickers hardness values is HV30, indicating that the difference in Vickers hardness is small even as the depth from the surface of roller 2 increases. This shows that within a depth range of 0.1 mm from the surface of roller 2, it is preferable for the difference between the maximum and minimum Vickers hardness values to be HV30 or less.

A roller and cage assembly 1 having these characteristics can be used in a structure in which it rotates with a dmn value, which is the product of the pitch circle diameter dm (mm) and the rotational speed N (rpm), of 150,000 or more. Furthermore, a lubricating oil with a low viscosity, such as a kinematic viscosity of 27 mm ² /s or less at 40°C and a kinematic viscosity of 8.0 mm ² /s or less at 100°C, is used for the roller and cage assembly 1.

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 reduces the centrifugal force acting on the rollers 2 arranged adjacent to the split groove 7, thereby preventing oil film breakdown. This prevents peeling of the cage 3 and rollers 2 and extends their service life.

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

As a result, by optimizing the values of the circumferential dimension Y and radial dimension Z of the second columnar section 52, it is possible to reduce the centrifugal force acting on the rollers 2 arranged adjacent to the second columnar section 52 and maintain the strength of the second columnar section 52, thereby further extending the life of the cage 3.

The rollers 2 of the roller and cage assembly 1 according to this embodiment have a carbonitrided layer with a hardness of HV720 or more, a nitrogen concentration on the surface of roller 2 of 0.05 mass% to 0.4 mass%, 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 of HV40 or less, thereby increasing the hardness of roller 2 and suppressing wear of roller 2 itself. Furthermore, by providing minute concave depressions on the surface of roller 2 and setting the area ratio and surface roughness of the depressions, the hardness of roller 2 can be further increased and wear can be suppressed.

In this way, the roller and cage assembly 1 according to this embodiment is able to suppress peeling even when using a cage 3 with split grooves 7, and because the strength of the rollers 2 is increased, the life of the roller and cage assembly 1 as a whole can be extended.

The implementations disclosed herein should be considered illustrative and not restrictive. The scope of the present invention is indicated by the claims, not the above description, and all modifications within the meaning and scope of the claims are intended to be embraced.

1,100: Roller and cage assembly; 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 (4)

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. The synthetic resin cage according to claim 1, wherein the radial dimension of the second columnar portion is greater than the circumferential dimension of at least one of the first and second portions of the second columnar portion. 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. 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.