Shell-type rolling bearings

Abstract

The objective is to provide a shell-type rolling bearing that does not require a large interference fit to deform a housing made of soft light alloy or thin-walled metal, and that is less prone to creep when tightly fitted, while also providing sufficient protection against detachment. [Solution] A shell-type rolling bearing is provided, which has a shell-type outer ring with the raceway surface of the rolling elements on the inner diameter side of the cylindrical portion. The shell-type outer ring has at least two gently convex curved large diameter portions 5 for interference fit at intervals in the axial direction of the cylindrical portion on its outer diameter surface, and a gently continuous concave curved small diameter portion 6 between these large diameter portions 5 for interference fit.

Description

Technical Field

[0001] This invention relates to a shell-shaped rolling bearing having a shell-shaped outer ring.

Background Art

[0002] Generally, a shell-shaped rolling bearing is a rolling bearing manufactured by precisely drawing a thin steel plate to form a shell-shaped outer ring, subjecting it to a hardening treatment, and then assembling rolling elements.

[0003] In many cases, the shell-shaped rolling bearing uses the outer peripheral surface of the shaft as the raceway surface on the inner ring side without using an inner ring. The rolling elements arranged in a single row or multiple rows are held by a cage or incorporated into the inner diameter side of the shell-shaped outer ring as a "full complement" without using a cage. In addition, the shell-shaped outer ring has a flange portion, a seal, a retaining ring, or a closed end face at one or both ends of the cylindrical portion in order to hold the rolling elements and the cage.

[0004] Such a shell-shaped rolling bearing can be attached by press-fitting the outer peripheral surface of the outer ring into a shaft hole formed in a required part of the device (housing) by so-called "interference fit".

[0005] However, if the interference amount for the shaft hole of the needle roller bearing is set to be excessively large and an interference fit is performed, a large compressive stress acts around the mounting hole, so the housing around the shaft hole is likely to be deformed.

[0006] In particular, when a needle roller bearing is attached to a housing made of a light alloy by interference fit and used under conditions where the housing and the bearing become hot, since the thermal expansion coefficient of the housing is larger than that of the steel outer ring, the interference amount decreases and the outer ring is likely to cause circumferential slip (creep), and the bearing is likely to come out of the mounting hole.

[0007] For example, the conventional needle roller bearing 10 shown in Figure 4 has a cage 12 that holds rolling elements 13 consisting of a single row of needle rollers inside the shell-side outer ring 11, and is mounted by "interference fit" into the shaft hole (mounting hole) of the housing (not shown) of a swash plate type compressor such as a car air conditioner. The shell-type outer ring 11, which is made of a thin steel plate or the like, has a slit (split portion) S that diagonally crosses in the axial direction (Patent Document 1).

[0008] When this shell-type rolling bearing 10 is installed in the housing, the width of the slit S is elastically reduced beforehand, allowing it to be easily inserted into the shaft hole in a reduced diameter state. Furthermore, the shell-type outer ring 11 is then expanded by elastic force, preventing it from coming loose during use. Therefore, the shell-type rolling bearing 10 is elastically retained even when the housing and shell-type outer ring 11 become hot, and is able to address the problem of reduced clamping force. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2003-294040 [Overview of the project] [Problems that the invention aims to solve]

[0010] However, in the needle roller bearing shown in Patent Document 1 mentioned above, the raceway surface of the rolling elements of the outer ring is discontinuous at the slit portion, and the edge of the slit (split portion) comes into contact with the surface of the rotating rolling elements, making the rolling elements susceptible to damage due to the surface pressure of the edge. Therefore, such bearings have problems with durability under operating conditions, and their so-called bearing life tends to be shortened.

[0011] Furthermore, the needle roller bearing described in Patent Document 1 requires the elastic reduction of the outer ring diameter immediately before installation into the housing's shaft hole, which complicates the assembly process.

[0012] Furthermore, the needle roller bearing described in Patent Document 1 has difficulty in providing flanges or end faces that are radially inwardly formed at the ends of the cylindrical portion. Normally, flanges or end faces are necessary to hold the rollers or cages within the outer ring, but in the needle roller bearing described in the same document, it is difficult to provide such flanges or end faces because it is necessary to reduce the diameter of the outer ring during assembly.

[0013] Therefore, the objective of this invention is to solve the above-mentioned problems, to enable assembly to the housing by "interference fit" without forming slits in the shell-shaped outer ring, and moreover, to provide a shell-shaped rolling bearing or shell-shaped rolling bearing device that does not require mounting to a housing made of soft light alloy or thin-walled metal with a large interference fit that would deform the housing, and that is less prone to creep when "interference fit" and is sufficiently prevented from coming loose. [Means for solving the problem]

[0014] To solve the above problems, this invention provides a shell-type rolling bearing comprising a plurality of rolling elements that rotatably roll, a cylindrical portion, and a shell-shaped outer ring having a raceway surface on the inner diameter side of the cylindrical portion, wherein the shell-shaped outer ring has at least two gently convex curved large-diameter portions for interference fitting at intervals in the axial direction of the cylindrical portion on its outer diameter surface, and a gently continuous concave curved small-diameter portion between these large-diameter portions for interference fitting, thus forming a shell-type rolling bearing.

[0015] As described above, the shell-type rolling bearing of this invention has large-diameter portions for interference fit formed by gently convex curved surfaces at at least two locations on the outer diameter surface of the shell-type outer ring. Therefore, in the interference-fitted state, the radially inward pressure received by the gently convex large-diameter portions for interference fit is received by the entire shell-type outer ring having a gently concave curved surface continuous with the convex curved surface, and the stress can be distributed almost evenly across the entire shell-type outer ring of such a specific shape. Therefore, the magnitude of stress in the shell-shaped outer ring becomes smaller due to reduced local variation and overall averaging.

[0016] Therefore, even with a shell-type outer ring made of thin-walled material, the rigidity against inward pressure in the radial direction is increased, eliminating the need to press-fit it into the shaft hole with a large interference fit that would deform the housing. Moreover, the high rigidity of the shell-type outer ring ensures a stable "tight fit" that prevents detachment and also prevents creep, resulting in a shell-type rolling bearing.

[0017] Furthermore, the large-diameter portion for interference fitting, due to its convex curved shape and high rigidity, acts as a "return" or "anchor" to help prevent it from coming loose.

[0018] The creep prevention and anti-loosening effects of the specific shape described above are more effectively achieved by increasing the rigidity near both ends of the cylindrical portion, which is achieved by providing flanges or end faces at both ends of the cylindrical portion.

[0019] Furthermore, if the sum of the axial widths of the large-diameter interlocking portion and the small-diameter portion continuous therewith is 65% or more of the bearing width in the shell-type rolling bearing, the large-diameter interlocking portion of the shell-type rolling bearing is positioned at or near the end of a cylindrical portion having a particularly rigid flange or end face. This further enhances the rigidity of the shell-type outer ring against radially inward pressure, thereby ensuring sufficient creep prevention and retention of the shaft hole.

[0020] Furthermore, a shell-type rolling bearing device consisting of the shell-type rolling bearing and a housing having a shaft hole into which the shell-type outer ring of the shell-type rolling bearing can be fitted, provides the same creep prevention and anti-loosening effects from the shaft hole as described above, because the shell-type rolling bearing, whose rigidity is enhanced by the specific shape described above, is press-fitted into the shaft hole.

[0021] The above-described shell-type rolling bearing device eliminates the need to pre-process the outer diameter when pressing the shell-type rolling bearing into the shaft hole, and also eliminates the need to set a large interference fit that would deform a housing made of a soft light alloy or a thin-walled metal housing.

[0022] In such a shell-type rolling bearing device, it is preferable that the difference in radius between the large-diameter portion for interference fit and the radius of the shaft hole is 5 to 40% with respect to the interference amount, so that a large interference amount that would deform a housing made of a soft light alloy or a thin-walled metal housing is not required, and the shell-type rolling bearing can be assembled in a "press fit" state with stable anti-loosening.

Advantages of the Invention

[0023] According to the present invention, by forming gently convex curved surface-shaped large-diameter portions for interference fit at at least two locations on the outer diameter surface of the cylindrical portion of the shell-type outer ring, and forming gently continuous concave curved surface-shaped small-diameter portions therebetween, stress can be dispersed almost evenly throughout the entire shell-type outer ring, enhancing the rigidity against the radial inward pressure of the shell-type outer ring, and not requiring a large interference amount that would deform a housing made of a soft light alloy or a thin-walled metal housing. Also, in the "press fit" state, creep is less likely to occur, and it is possible to achieve a shell-type rolling bearing and a shell-type rolling bearing device in which the shell-type rolling bearing is attached to a housing and is sufficiently anti-loosening.

Brief Description of the Drawings

[0024] [Figure 1] Cross-sectional view showing a shell-type rolling bearing of an embodiment and a housing having a shaft hole, cut along a plane including the shaft [Figure 2] Explanatory drawing schematically showing the outer diameter surface shape of the shell-type outer ring of the main part A in FIG. 1 [Figure 3] Explanatory drawing showing the state and interference amount when the shell-type outer ring of the shell-type rolling bearing of the embodiment is incorporated into the shaft hole of the housing [Figure 4] Cross-sectional view of a conventional needle roller bearing described in Patent Document 1

Embodiments for Carrying Out the Invention

[0025] Embodiments of this invention will be described below with reference to the attached drawings. The shell-type rolling bearing 1 of this embodiment of the invention shown in Figure 1 is a shell-type rolling bearing comprising a plurality of rolling elements (rollers) 2 that roll rotatably and a cage 3 that rotatably holds them, and a shell-type outer ring 4 having radially inward-facing annular flanges 4b at both ends of a cylindrical portion 4a having the raceway surface of the rolling elements 2 on the inner diameter side. The main part A of the shell-type rolling bearing has, as schematically shown in an enlarged view in Figure 2, two gently convex curved large-diameter portions 5 for interference fit at both ends of the outer diameter surface spaced apart in the axial direction, and a gently continuous concave curved small-diameter portion 6 between these large-diameter portions 5 for interference fit.

[0026] The rolling elements 2 used in the shell-type rolling bearing 1 of the embodiment are shown as a single row of needle rollers, but well-known forms of rolling elements can be adopted depending on the intended use of the bearing. Such rolling elements are not limited to a single row; they may also be in a double row, and for example, the rolling elements may be balls.

[0027] Furthermore, the cage 3 that rotatably holds the rolling elements 2 can be of a known form other than those shown. For example, a molded cage made of resin such as polyamide resin, a stamped metal cage, a welded cage, etc., can be used, and a cage-equipped roller bearing can be used in which the rolling elements such as needle rollers are held in place without being separated from the cage. Alternatively, a full-roller shell-type rolling bearing may be used without a cage.

[0028] The illustrated shell-shaped outer ring 4 is formed by deep drawing using a blank made by die-cutting a strip of steel (e.g., SCM415) into a disc shape as the forming material, and an annular flange portion 4b facing radially inward is formed at one or both ends of the cylindrical portion 4a during the forming process.

[0029] In other words, the flange portion 4b can be formed at one end of the cylindrical portion by drawing the blank of the shell-shaped outer ring 4 from a cup shape to a cylindrical shape with one end closed, and bending the edge on the opening side radially inward during this process.

[0030] Instead of such a flange portion 4b, a closed end face (side plate) may be provided, and these can be sealed with a seal as needed. The other closed end (bottom face) may be left as an end face without punching (bottom punching) while leaving the flange portion, or it may be closed by attaching a side plate formed in a separate process.

[0031] On the outer diameter surface of the cylindrical portion 4a of such a shell-shaped outer ring 4, at least two gently convex curved large-diameter interlocking portions 5 are formed at intervals in the axial direction by drawing, pressing, grinding, polishing, etc. The two large-diameter interlocking portions 5 are positioned at both ends of the cylindrical portion 4a to increase the rigidity of the shell-shaped outer ring due to its predetermined shape.

[0032] To form a concave, curved, small-diameter portion 6 that smoothly continues between at least two large-diameter portions 5 for interference fit, it can be formed by drawing, pressing, grinding, polishing, etc., similar to the method for forming the large-diameter portions 5 for interference fit described above.

[0033] The combined axial width a (Figure 2) of the large-diameter section 5 for interference fit and the small-diameter section 6 continuous therewith accounts for 65% or more of the bearing width B (Figures 1 and 2) of the shell-type rolling bearing. As a result, the large-diameter section 5 for interference fit is positioned near the flange section 4b or end face, which have relatively high rigidity.

[0034] The large diameter portion 5 for interference fit is the part with the largest outer diameter of the convex curved surface, and the small diameter portion 6 is the part with the smallest outer diameter located between the large diameter portions 5 at both ends. The total width a corresponds to the distance between the points corresponding to the outer diameter of the small diameter portion on the axially outer side of the two convex curved surfaces. If there are multiple convex curved surfaces, the total width a corresponds to the distance between the points furthest axially outer.

[0035] By forming a cylindrical portion 4a with a specific shape that has microscopic irregularities in this way, the rigidity of the cylindrical portion 4a against radially inward pressure is sufficiently increased, and the creep prevention effect of the shell-type rolling bearing 1 and the anti-loosening effect of the housing 7 from the shaft hole 8 are more effectively achieved.

[0036] As shown in Figures 1 and 2, the diameter difference h1 and h2 between the radius r1 and r2 of the large diameter portion 5 for interference fit with respect to the radius r of the shaft hole 8 is 5 to 40% of the interference fit H.

[0037] In other words, the radii r1 and r2 of the large diameter portion 5 for interference fit are smaller than the radius obtained by adding the interference fit H, which is normally set according to the material and shaft diameter of the shell-shaped outer ring 4 and housing 7, and are larger than the shaft bore inner diameter (shown by the lower dashed line in Figure 2) r by h1 and h2 respectively, and it is preferable that these radii are within the range of 5 to 40% of the interference fit H.

[0038] Although the diagram shows the case where the diameter difference h1 and h2 in the two large-diameter interlocking sections 5 are the same, they may be different, and the same applies when there are three or more large-diameter interlocking sections 5.

[0039] The small-diameter portion 6 may be larger in diameter than the shaft hole 8 to contribute to the interference fit, or it may be smaller in diameter than the shaft hole 8 to not contribute, and is formed in a concave curved shape so as to be smoothly continuous between the large-diameter portions 5 for interference fit.

[0040] When the outer diameter of the outer ring of a shell-type rolling bearing is 40 mm or more, it is sufficient to form a groove-like concave curved surface with a depth of, for example, 5 to 10 μm, in which case the diameter difference h1 and h2 will be approximately 5 to 15 μm.

[0041] Furthermore, as shown in Figure 3, the shell-type outer ring 4 and housing 7 of the shell-type needle roller bearing 1 The fitting is achieved by press-fitting the shell-type outer ring 4 of the shell-type needle roller bearing 1 along the direction of the arrow in the figure, and then pressing it into place with a tolerance of, for example, 5 to 100 μm in microns, to achieve the desired effect. The numerical range of the tolerance is appropriately determined depending on the outer diameter of the outer ring and the housing material.

[0042] The interference fit H, which serves as the basis for setting the diameter differences h1 and h2 in the shell-type rolling bearing of this invention, is a general interference fit dimension (μm) set based on the "interference fit" tolerance class of the shaft or hole specified in JIS B(0401).

[0043] For example, if the outer ring diameter of a shell-type rolling bearing is 40 mm, the interference fit at room temperature is 10-120 μm for iron-based bearings and 10-150 μm for light alloy bearings. Furthermore, since the diameter of the roller's inscribed circle after press-fitting will vary depending on the housing material and rigidity, it is desirable to determine the fit (interference) in advance by measuring it through testing.

[0044] If the difference in radius between the radius of the shaft hole 8 and the radius of the large-diameter interlocking portion 5 is less than 10% of the interlocking allowance H, the effect of preventing the housing from coming loose from the shaft hole will decrease, and the effect of sufficiently preventing creep will also decrease. Therefore, although it may be usable under certain operating conditions, the aforementioned return effect will be reduced. For this reason, if the desired effect is to be obtained more sufficiently, it is preferable to set the value to 10% or more.

[0045] Furthermore, if the aforementioned numerical limit exceeds 40%, the raceway surface shape of the shell-shaped outer ring 4 may bend after being press-fitted into the shaft hole 8 of the housing 7, which may lead to a decrease in bearing function and is therefore undesirable.

[0046] By mounting the shell-type rolling bearing 1 described above to the housing 7 in an interference fit under the intended conditions, the high rigidity due to the specific gently curved surface shape of the shell-type outer ring 4 prevents it from coming loose in the shaft hole 8 of the housing 7 with a relatively small interference fit, and also prevents creep, resulting in a shell-type rolling bearing device that is mounted with a stable "interference fit" even with a small interference fit. [Explanation of symbols]

[0047] 1.10 Shell-type rolling bearings 2, 13 Rolling elements 3, 12 Cage 4, 11 Shell-shaped outer ring 4a Cylindrical section 4b Tsuba 5. Large diameter section for tightening fit 6 Small diameter section 7 Housing 8 shaft holes H closing fee S-slit

Claims

1. Multiple rolling elements that can rotate freely, and a cylindrical portion and a raceway surface provided on the inner diameter side of the cylindrical portion It comprises a shell-shaped outer ring, The shell-type outer ring has at least two gently convex curved large-diameter portions for interference fit at intervals in the axial direction of the cylindrical portion on its outer diameter surface, and a gently continuous concave curved small-diameter portion between these large-diameter portions for interference fit, forming a shell-type rolling bearing.

2. The shell-type rolling bearing according to claim 1, having flanges protruding radially inward from one or both axial ends of the cylindrical portion.

3. The shell-type rolling bearing according to claim 1 or 2, wherein the total axial width of the at least two large-diameter portions for interference fit and the small-diameter portions continuous therewith is 65% or more of the bearing width of the shell-type rolling bearing.

4. A shell-type rolling bearing according to claim 1 or 2, This shell-type rolling bearing consists of a housing having a shaft hole into which the shell-type outer ring can be compressed and fitted, A shell-type rolling bearing device in which the difference in diameter between the radius of the shaft hole and the radius of the large-diameter portion for interference fit is 5 to 40% of the interference fit.

5. The shell-type rolling bearing described in claim 3, This shell-type rolling bearing consists of a housing having a shaft hole into which the shell-type outer ring can be compressed and fitted, A shell-type rolling bearing device in which the difference in diameter between the radius of the shaft hole and the radius of the large-diameter portion for interference fit is 5 to 40% of the interference fit.

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