Bearing device

Abstract

A bearing device 1 has an inner ring 4, an outer ring 2, two (upper and lower) rows 5A, 5B of rolling elements that are between the inner ring 4 and the outer ring 2, and a porous member 8 that is between the two rows 5A, 5B of rolling elements and can be impregnated with a lubricating oil. The porous member 8 is cylindrical, has slits 32 that extend in the axial direction, and can elastically deform to expand and contract in diameter. The slits 32 include a first slit 41 that is on the upper side of the porous member 8 and a second slit 42 that is on the lower side of the porous member 8. The first slit 41 and the second slit 42 have different circumferential positions and are connected via a third slit 43 that extends in the circumferential direction.

Description

Bearing device

[0001] The present invention relates to a bearing device.

[0002] Patent Document 1 discloses a bearing device in which a porous member is provided between an inner ring and an outer ring and between two rows of rolling element rows. The porous member holds a lubricating oil such as oil. The lubricating oil is used for lubricating the bearing device.

[0003] Japanese Patent Laid-Open No. 59-208220

[0004] In addition to supporting a shaft whose center line direction is horizontal, the bearing device may also support a shaft whose center line direction is vertical. FIG. 7 is a cross-sectional view of a conventional bearing device 100 whose center line direction is vertical. In such a bearing device 100, it is desirable to achieve both low torque and long life. Therefore, grease 109 is used as a lubricant, and a cylindrical porous member 106 is provided between the upper and lower two rows of rolling element rows 104 and 105. The porous member 106 is impregnated with the base oil (lubricating oil) of the grease 109. When the base oil of the grease 109 is consumed, the base oil of the porous member 106 is supplied to the grease 109.

[0005] The porous member 106 is mounted in a state of being in contact (adhering) with the inner peripheral surface of the outer ring 102. The porous member 106 is made of, for example, urethane sponge. In this case, the porous member 106 is easily elastically deformed, and it is easy to mount the porous member 106 on the outer ring 102. However, in the case of urethane sponge, aging deterioration due to hydrolysis or the like becomes a problem. Therefore, as the material of the porous member 106, PVA (polyvinyl alcohol) sponge or polyethylene sponge is considered. However, these are difficult to elastically deform, and it becomes difficult to mount them on the outer ring 102.

[0006] Therefore, as shown in FIG. 8, the inventors of the present invention have considered a configuration in which a notch portion (slit) 107 obtained by linearly cutting a part of the circumferential direction of the cylindrical porous member 106 is provided to form a C-shaped cross section. Thereby, the elastic deformation of the porous member 106 becomes easy, and it is easy to mount it on the outer ring 102.

[0007] However, since the bearing device 100 (see Figure 7) is arranged with its centerline C in the vertical direction, the upper grease 109 and its base oil may flow downward through the notch (slit) 107, potentially leading to excessive lubrication in the lower rolling element row 105 and increasing the stirring resistance of the base oil. Therefore, the present invention aims to provide a bearing device that allows for easy installation of porous members and provides an appropriate lubrication state in the rolling element row.

[0008] The bearing device of the present invention comprises an inner ring, an outer ring, two rows of rolling elements arranged between the inner ring and the outer ring, and a porous member located between the two rows of rolling elements and capable of being impregnated with lubricating oil. The porous member has a cylindrical shape, has axially extending slits, and can be elastically deformed to reduce and expand its diameter. The slits include a first slit located on the upper side of the porous member and a second slit located on the lower side of the porous member. The first and second slits are located at different circumferential positions and are connected by a third slit that extends in the circumferential direction.

[0009] Figure 1 is a cross-sectional view of a bearing device according to an embodiment of the present invention. Figure 2 is an enlarged cross-sectional view of a part of the bearing device. Figure 3 is a perspective view of the porous member. Figure 4 is a perspective view of the porous member. Figure 5 is a cross-sectional view taken along the line V-V in Figure 1. Figure 6 is an unfolded view showing a modified example of the porous member. Figure 7 is a cross-sectional view of a conventional bearing device. Figure 8 is a perspective view of the porous member.

[0010] <Outline of Embodiments of the Present Invention> The outline of embodiments of the present invention will be described below. (1) A bearing device according to an embodiment of the present invention comprises an inner ring, an outer ring, two rows of rolling elements arranged between the inner ring and the outer ring, and a porous member located between the two rows of rolling elements and capable of being impregnated with lubricating oil. The porous member has a cylindrical shape, has slits extending in the axial direction, and can be reduced in diameter and expanded in diameter by elastic deformation. The slits include a first slit located on the upper side of the porous member and a second slit located on the lower side of the porous member. The first slit and the second slit are located at different circumferential positions and are connected by a third slit extending in the circumferential direction.

[0011] The porous member has axially extending slits and can be elastically deformed to reduce and expand its diameter. Therefore, it is easy to install the porous member between the inner and outer rings and between two rows of rolling elements. Due to the configuration of the slits, even if the grease and its base oil located on the porous member move through the first slit, passage through the second slit is inhibited. This prevents excessive lubrication in the rolling element row located below, and an appropriate lubrication state is obtained in the rolling element row.

[0012] (2) In the bearing device of (1) above, the space between each of the two rows of rolling elements and the porous member is a grease area, and the porous member has an uneven shape at its upper end and lower end. The uneven shape increases the contact area between the upper end and lower end of the porous member and the grease. This promotes the transfer of lubricating oil between the grease and the porous member.

[0013] (3) In the bearing device of (1) or (2) above, the width dimension of the third slit is smaller than the width dimensions of the first slit and the second slit. Note that the width dimension of the slit is the dimension in the direction perpendicular to the longitudinal direction of the slit. Even if grease moves through the first slit, it is difficult for the grease to pass through the third slit, which has a smaller width dimension, and it does not reach the second slit.

[0014] (4) In any one of the bearing devices described in (1) to (3) above, the outer ring has upper and lower outer ring raceways in which the two rows of rolling elements contact each other, and the outer ring has an oil supply hole that penetrates from the outer circumferential surface to the inner circumferential surface of the outer ring and opens between the upper and lower outer ring raceways, and the circumferential regions of the first slit, the second slit, and the third slit are different from the circumferential position of the opening of the oil supply hole. Lubricating oil is supplied to the porous member through the oil supply hole. If the circumferential regions of the slits and the circumferential position of the opening of the oil supply hole coincide, the lubricating oil supplied through the oil supply hole may flow along the slits and be difficult to retain in the porous member. In contrast, as described above, because the circumferential regions of the slits and the circumferential position of the opening of the oil supply hole are different, the lubricating oil supplied through the oil supply hole is easily retained in the porous member.

[0015] (5) In any one of the bearing devices described in (1) to (4) above, the inner circumferential surface of the outer ring has an inner circumferential surface portion that contacts the outer circumferential surface of the porous member, and an annular wall portion located below the inner circumferential surface portion and having an inner diameter smaller than the inner diameter of the inner circumferential surface portion. Even if the porous member is displaced downward, the porous member will come into contact with the annular wall portion, limiting the displacement.

[0016] <Details of Embodiments of the Present Invention> [Overall Configuration of the Bearing Device] Figure 1 is a cross-sectional view of a bearing device according to an embodiment of the present invention. The bearing device 1 shown in Figure 1 rotatably supports a shaft 92 with respect to a housing 91. The direction of the center line of the shaft 92 is vertical. Therefore, the direction of the center line C of the bearing device 1 is also vertical. Figure 1 shows a cross-section (longitudinal section) of the bearing device 1 including the center line C.

[0017] The bearing device 1 includes an outer ring 2, an inner ring 4, two rows of rolling elements 5A and 5B positioned between the outer ring 2 and the inner ring 4, and a porous member 8. In this embodiment, the rolling elements are balls 6. Between the outer ring 2 and the inner ring 4, the upper rolling element row 5A is formed by a plurality of balls 6 located above, and the lower rolling element row 5B is formed by a plurality of balls 6 located below.

[0018] The centerlines of the inner ring 4 and the outer ring 2 coincide, and these centerlines form the centerline C of the bearing device 1. The direction parallel to centerline C is defined as the axial direction. The direction perpendicular to centerline C is defined as the radial direction. The direction along the circle centered on centerline C is defined as the circumferential direction. In the axial direction, the upward direction is defined as the first axial direction, and the downward direction is defined as the second axial direction.

[0019] The outer ring 2 is an annular member made of steel such as bearing steel or machine structural steel. The outer ring 2 has upper and lower outer ring raceways 2b, 2b on its inner circumferential surface 2a, which contact the balls 6 of the upper and lower rows of rolling elements 5A and 5B, respectively. The outer ring 2 is fixed to the housing 91. The inner ring 4 is an annular member made of steel such as bearing steel or machine structural steel. The inner ring 4 has upper and lower inner ring raceways 4b on its outer circumferential surface 4a, which contact the balls 6 of the upper and lower rows of rolling elements 5A and 5B, respectively. The inner ring 4 is fixed to the shaft 92. The upper opening between the outer ring 2 and the inner ring 4 is sealed by an annular upper sealing member 10. The lower opening between the outer ring 2 and the inner ring 4 is sealed by an annular lower sealing member 12.

[0020] The balls 6 are components made of steel such as bearing steel. Multiple balls 6 included in the upper rolling element row 5A are interposed between the upper outer ring raceway 2b and the upper inner ring raceway 4b. Multiple balls 6 included in the lower rolling element row 5B are interposed between the lower outer ring raceway 2b and the lower inner ring raceway 4b. The bearing device 1 has a pair of upper and lower cages 7. The pair of cages 7 hold the balls 6 included in the two rows of rolling element rows 5A and 5B at equal intervals in the circumferential direction.

[0021] The porous member 8 has an outer circumferential surface 8a and an inner circumferential surface 8d, each shaped to conform to the cylinder. The porous member 8 has a slit 32 (see Figure 4), which will be described later, but its shape conforms to the cylinder centered on the center line C. The porous member 8 is located between the outer ring 2 and the inner ring 4, and between the upper and lower two rows of rolling elements 5A and 5B.

[0022] The outer circumferential surface 8a of the porous member 8 contacts a portion of the inner circumferential surface 2a of the outer ring 2. In order to attach the porous member 8 to the inner side of the outer ring 2, the worker elastically deforms the porous member 8 to reduce its diameter. Subsequently, the porous member 8 expands in diameter due to its elastic restoring force, and the porous member 8 is attached in a state of close contact with the outer ring 2. The porous member 8 has a slit 32, which will be described later, so it can easily elastically deform and reduce in diameter. The porous member 8 expands in diameter from its reduced state and is attached to the outer ring 2. For this reason, the diameter of the outer circumferential surface 8a of the porous member 8 in its free state (see Figure 3) is larger than the inner diameter of a portion of the inner circumferential surface 2a of the outer ring 2 (second inner circumferential surface portion 18).

[0023] The porous member 8 is formed from a porous material that can be impregnated with lubricating oil. This lubricating oil is used to lubricate the bearing device 1. Examples of porous materials include PVA (polyvinyl alcohol) sponge and polyethylene sponge. In addition to being able to be impregnated with lubricating oil, PVA sponge and polyethylene sponge deteriorate less over time than urethane sponge and can be used for a long period of time.

[0024] The inner circumferential surface 2a of the outer ring 2 has a first inner circumferential surface portion 16, a second inner circumferential surface portion 18, a third inner circumferential surface portion 20, a first annular groove 22, and a second annular groove 24. The first inner circumferential surface portion 16 is the upper end portion of the inner circumferential surface 2a of the outer ring 2. The first inner circumferential surface portion 16 includes the upper outer ring raceway 2b. The third inner circumferential surface portion 20 is the lower end portion of the inner circumferential surface 2a of the outer ring 2. The third inner circumferential surface portion 20 includes the lower outer ring raceway 2b. The second inner circumferential surface portion 18 is located between the first inner circumferential surface portion 16 and the third inner circumferential surface portion 20. The outer circumferential surface 8a of the porous member 8 is in contact with the second inner circumferential surface portion 18.

[0025] The first annular groove 22 is located between the first inner circumferential surface portion 16 and the second inner circumferential surface portion 18. The first annular groove 22 is provided along the entire circumference in the circumferential direction. The first annular groove 22 is recessed radially outward relative to the first inner circumferential surface portion 16 and the second inner circumferential surface portion 18. The second annular groove 24 is located between the second inner circumferential surface portion 18 and the third inner circumferential surface portion 20. The second annular groove 24 is provided along the entire circumference in the circumferential direction. The second annular groove 24 is recessed radially outward relative to the second inner circumferential surface portion 18 and the third inner circumferential surface portion 20.

[0026] Figure 2 is an enlarged cross-sectional view of a part of the bearing device 1 shown in Figure 1. The inner diameter D18 of the second inner circumferential surface portion 18 of the outer ring 2 is larger than the inner diameter D16 of the first inner circumferential surface portion 16 and the inner diameter D20 of the third inner circumferential surface portion 20. The second inner circumferential surface portion 18 is recessed radially outward relative to the first inner circumferential surface portion 16 and the third inner circumferential surface portion 20.

[0027] The first annular groove 22 has an upper annular wall 22a, a lower annular wall 22b, and a bottom surface 22c. The upper annular wall 22a is a wall portion that extends radially inward from the upper edge of the bottom surface 22c. The inner periphery of the upper annular wall 22a connects to the lower end edge of the first inner circumferential surface 16. The upper annular wall 22a has an annular wall portion 22a1 that protrudes radially inward from the second inner circumferential surface 18. The lower annular wall 22b is a wall portion that extends radially inward from the lower edge of the bottom surface 22c. The inner periphery of the lower annular wall 22b connects to the first end edge 18a of the second inner circumferential surface 18. The first end edge 18a is the upper end edge of the second inner circumferential surface 18.

[0028] The second annular groove 24 has an upper annular wall 24a, a lower annular wall 24b, and a bottom surface 24c. The upper annular wall 24a is a wall portion that extends radially inward from the upper edge of the bottom surface 24c. The inner periphery of the upper annular wall 24a connects to the second end edge 18b of the second inner circumferential surface portion 18. The second end edge 18b is the axially lower end edge of the second inner circumferential surface portion 18. The lower annular wall 24b is a wall portion that extends radially inward from the lower edge of the bottom surface 22c. The inner periphery of the lower annular wall 22b connects to the upper end edge of the third inner circumferential surface portion 20. The lower annular wall 24b has an annular wall portion 24b1 that protrudes radially inward from the second inner circumferential surface portion 18. In this embodiment, the inner diameter of the annular wall portion 24b1 is the same as the inner diameter D20 of the third inner circumferential surface portion 20.

[0029] A portion of the upper end face 8b of the porous member 8 faces the upper annular wall portion 22a1. A portion of the lower end face 8c of the porous member 8 faces the lower annular wall portion 24b1. The porous member 8 is provided in the range between the upper annular wall portion 22a1 and the lower annular wall portion 24b1 in the axial direction. Note that the end faces 8b and 8c of the porous member 8 may be in contact with the annular wall portions 22a1 and 24b1. The axial movement of the porous member 8 is restricted by the annular wall portions 22a1 and 24b1.

[0030] As described above, the inner circumferential surface 2a of the outer ring 2 has a second inner circumferential surface portion 18 that contacts the outer circumferential surface 8a of the porous member 8, and an annular wall portion 24b1 located below the second inner circumferential surface portion 18. The inner diameter (D20) of the annular wall portion 24b1 is smaller than the inner diameter D18 of the second inner circumferential surface portion 18. With this configuration, even if the porous member 8 is displaced downwards, it will come into contact with the annular wall portion 24b1, limiting the displacement.

[0031] The porous member 8 is positioned to block the first annular groove 22 and the second annular groove 24. An annular space K1 is provided between the first annular groove 22 and the outer circumferential surface 8a of the porous member 8. An annular space K2 is provided between the second annular groove 24 and the outer circumferential surface 8a of the porous member 8.

[0032] The spaces between the two rows of rolling elements 5A and 5B and the porous member 8 are grease regions G1 and G2. Grease, a semi-solid lubricant, is loaded into each of the upper and lower grease regions G1 and G2. The grease contains a base oil, a thickener, and additives. The upper grease region G1 is adjacent to the upper outer ring raceway 2b and the row of rolling elements 5A. The lower grease region G2 is adjacent to the lower outer ring raceway 2b and the row of rolling elements 5B.

[0033] The base oil of the grease in the upper grease region G1 is supplied to the rolling element row 5A through the upper outer ring raceway 2b. The base oil of the grease in the lower grease region G1 is supplied to the rolling element row 5B through the lower outer ring raceway 2b. The upper and lower grease regions G1 and G2 are adjacent to the porous member 8, and the grease in each of the grease regions G1 and G2 may be in contact with the porous member 8.

[0034] The outer ring 2 has an oil supply hole 28. The oil supply hole 28 is a hole that penetrates from the outer circumferential surface 2c to the inner circumferential surface 2a of the outer ring 2. The oil supply hole 28 opens on the inner circumferential surface 2a between the upper and lower outer ring raceways 2b, 2b. In this embodiment, the oil supply hole 28 opens at the bottom surface 22c of the first annular groove 22. The oil supply hole 28 is a hole for supplying lubricating oil from the outside of the bearing device 1 to the inside of the bearing device 1. The lubricating oil is supplied to the inside of the bearing device 1 (porous member 8) through the oil supply hole 28. The lubricating oil is the base oil of the grease.

[0035] [Regarding the porous member 8] Figure 3 is a perspective view of the porous member 8 in a free state, showing the state before it is attached to the inner circumference of the outer ring 2. Figure 4 is a perspective view of the porous member 8, an image showing the state in which it is attached to the inner circumference of the outer ring 2 (hereinafter referred to as the "attached state"). As described above, the porous member 8 has a cylindrical shape. The porous member 8 has slits 32 that extend in the axial direction. The slits 32 include a first slit 41 located on the upper side of the porous member 8 and a second slit 42 located on the lower side of the porous member 8. In the attached state shown in Figure 4, the first slit 41 and the second slit 42 are long and narrow gaps in the axial direction. The porous member 8 can be reduced in diameter and expanded in diameter by elastic deformation through the slits 32.

[0036] The porous member 8 has a third slit 43 extending in the circumferential direction. In the installed state shown in Figure 4, the third slit 43 is a long, narrow gap in the circumferential direction. The first slit 41 and the second slit 42 are located at different circumferential positions and are connected through the third slit 43 in the installed state shown in Figure 4. In the installed state, the width dimension W3 of the third slit 43 is smaller than the width dimension W1 of the first slit 41 and the width dimension W2 of the second slit 42 (W3 < W1, W3 < W2). Note that the width dimension of the slit is the dimension in the direction perpendicular to the longitudinal direction of the slit. In the installed state, the width dimension W1 of the first slit 41 and the width dimension W2 of the second slit 42 are both greater than zero. In the installed state, the width dimension W3 of the third slit 43 may be zero or greater than zero.

[0037] When attaching the porous member 8 to the outer ring 2, the porous member 8 is first reduced in diameter and then expanded. In order not to impair the change in shape, it is preferable that the width dimension W3 of the third slit 43 is greater than zero. However, the width dimension W3 is smaller than the width dimension W1 and also smaller than W2.

[0038] In this embodiment, the first slit 41 and the second slit 42 are long gaps (axial gaps) in a direction parallel to the center line C. The direction perpendicular to the longitudinal direction of the gap that becomes the first slit 41 (i.e., the circumferential direction) is the width direction of the first slit 41. The dimension in that width direction is the width dimension W1. The direction perpendicular to the longitudinal direction of the gap that becomes the second slit 42 (i.e., the circumferential direction) is the width direction of the second slit 42. The dimension in that width direction is the width dimension W2.

[0039] The third slit 43 is a long gap along the circumferential direction of the cylindrical porous member 8. The direction perpendicular to the longitudinal direction of the gap that becomes the third slit 43 (i.e., the axial direction) is the width direction of the third slit 43. The dimension in that width direction is the width dimension W3. As described above, the porous member 8 of this embodiment has zigzag-shaped slits (41, 42, 43) along the axial direction which is the vertical direction.

[0040] As shown in Figures 3 and 4, the porous member 8 has a cylindrical main body 30 and slits 32. The slits 32 are provided such that a portion of the circumferential direction of the upper 301 and lower 302 of the main body 30 is missing. The upper 301 of the main body 30, located above the third slit 43, has a C-shape in cross-section (see Figure 5). Similarly, the lower 302 of the main body 30, located below the third slit 43, also has a C-shape in cross-section. Figure 5 is a cross-sectional view taken along the line V-V in Figure 1, showing a cross-section (cross-section) of the bearing device 1 along a plane perpendicular to the center line C.

[0041] The upper part 301 of the main body 30 has a first end face 301a and a second end face 301b. The first end face 301a is the end face on one side in the circumferential direction of the upper part 301 of the main body 30. The second end face 301b is the end face on the opposite side of the upper part 301 of the main body 30 in the circumferential direction from the first end face 301a. The first end face 301a and the second end face 301b face each other with a predetermined distance between them. When installed, the space between the first end face 301a and the second end face 301b becomes the first slit 41.

[0042] The lower part 302 of the main body 30 has a third end face 302a and a fourth end face 302b. The third end face 302a is an end face on one side in the circumferential direction of the lower part 302 of the main body 30. The fourth end face 302b is an end face on the opposite side of the third end face 302a in the circumferential direction of the lower part 302 of the main body 30. The third end face 302a and the fourth end face 302b face each other with a predetermined interval. In the mounted state, the space between the third end face 302a and the fourth end face 302b is the second slit 42.

[0043] The porous member 8 (see FIG. 3) has a fifth end face 303a facing downward in the second axial direction and a sixth end face 303b facing upward in the first axial direction. The fifth end face 303a is a surface connecting the first end face 301a and the third end face 302a. The sixth end face 303b is a surface connecting the second end face 301b and the fourth end face 302b. The space between the fifth end face 303a and the sixth end face 303b is the third slit 43.

[0044] In the case of this embodiment, each of the first end face 301a, the second end face 301b, the third end face 302a, and the fourth end face 302b is a surface that is linear along the axial direction. The fifth end face 303a is perpendicular to each of the first end face 301a and the third end face 302a. The sixth end face 303b is perpendicular to each of the second end face 301b and the fourth end face 302b. The fifth end face 303a and the sixth end face 303b are surfaces that are long and flat in an arc shape along the circumferential direction.

[0045] Regarding the circumferential direction of the porous member 8 (main body 30), as shown in FIG. 4, the region from the second end face 301b to the third end face 302a is the region where the first slit 41, the second slit 42, and the third slit 43 exist in the circumferential direction. The existence region Q is a region including the third slit 43. As shown in FIG. 5, the existence region Q and the circumferential position of the opening 281 of the oil supply hole 28 are different. More specifically, the existence region Q and the oil supply hole 28 are arranged at positions on opposite sides of the center line C. The opening 281 is the position on the inner circumferential surface 2a (bottom surface 22c of the first annular groove 22) of the outer ring 2.

[0046] As described above, the lubricating oil is supplied to the porous member 8 through the oil supply hole 28. If the region Q where the slit 32 is present and the circumferential position of the opening 281 of the oil supply hole 28 coincide, the lubricating oil supplied through the oil supply hole 28 may flow along the slit 32 and be difficult to be retained on the upper portion 301 of the porous member 8. On the other hand, as in the present embodiment, since the region Q where the slit 32 is present and the circumferential position of the oil supply hole 28 are different, the lubricating oil supplied through the oil supply hole 28 is easily retained on the upper portion 301 of the porous member 8.

[0047] 〔Regarding the bearing device 1〕 As described above, the bearing device 1 has a porous member 8 that is located between two rows of rolling element rows 5A and 5B and can be impregnated with lubricating oil. The slit 32 of the porous member 8 has a first slit 41 located on the upper side of the porous member 8 and a second slit 42 located on the lower side of the porous member 8, as described above (see FIG. 4). The first slit 41 and the second slit 42 have different circumferential positions and are connected through a third slit 43 that extends in the circumferential direction. With this configuration, even if the grease in the grease region G1 (see FIG. 1) located above the porous member 8 and the base oil (lubricating oil) of the grease move downward through the first slit 41, the passage through the second slit 42 is inhibited.

[0048] Therefore, lubrication excess does not occur in the lower rolling element row 5B. The grease in the upper grease region G1 and the base oil (lubricating oil) of the grease are mainly used for lubricating the upper rolling element row 5A. Thus, an appropriate lubrication state is obtained in the upper and lower rolling element rows 5A and 5B.

[0049] In the case of the present embodiment, as described above (see FIG. 4), the width dimension W3 of the third slit 43 is smaller than the width dimension W1 of the first slit 41 and the width dimension W2 of the second slit 42. For this reason, even if the grease in the upper grease region G1 moves through the first slit 41 due to its own weight, it is difficult for the grease to pass through the third slit 43 with a small width dimension. Therefore, the grease in the grease region G1 does not reach the second slit 42.

[0050] As shown in Figure 2, the oil supply hole 28 opens above the bottom of the first annular groove 22. The lubricating oil supplied from the oil supply hole 28 is temporarily stored in the first annular groove 22 for retention in the porous member 8. For example, if the lubricating oil is supplied from the oil supply hole 28 before the porous member 8 is impregnated with the lubricating oil, excess lubricating oil will be generated that is not impregnated into the porous member 8. Even in this case, the excess lubricating oil is stored in the annular space K1 of the first annular groove 22 and does not flow back through the oil supply hole 28. The lubricating oil in the annular space K1 is eventually impregnated into and retained by the porous member 8.

[0051] The opening 281 of the oil supply hole 28 is located in an upper position between the upper and lower pair of outer ring raceways 2b, 2b. Therefore, the lubricating oil supplied from the oil supply hole 28 is supplied to an upper position (upper part 301) of the porous member 8. The lubricating oil is impregnated from the upper part 301 of the porous member 8, supplied from the upper part 301 to the lower part 302, and retained throughout the entire area.

[0052] The second annular groove 24 (the lower annular space K2) accumulates lubricating oil that travels downward through the porous member 8. This makes it possible to suppress the supply of lubricating oil to the lower outer ring raceway 2b and inner ring raceway 4b more than necessary.

[0053] The outer circumferential surface 4a of the inner ring 4 has a first outer circumferential surface portion 34, a second outer circumferential surface portion 36, and an annular recess 38. The first outer circumferential surface portion 34 is the portion of the outer circumferential surface 4a that faces the first inner circumferential surface portion 16 of the outer ring 2. The first outer circumferential surface portion 34 includes the upper inner ring raceway 4b. The second outer circumferential surface portion 36 is the portion of the outer circumferential surface 4a that faces the third inner circumferential surface portion 20 of the outer ring 2. The second outer circumferential surface portion 36 includes the lower inner ring raceway 4b.

[0054] The annular recess 38 has a shape that is recessed radially inward from the first outer peripheral surface portion 34 and the second outer peripheral surface portion 36. The annular recess 38 is provided in a range that is longer in the axial direction than the total length (entire axial range) of the porous member 8. The porous member 8 is provided on the inner circumference side of the outer ring 2, and when assembling the bearing device 1, the annular recess 38 allows a part of the outer ring 2 on which the porous member 8 is mounted to be brought closer to a part of the outer peripheral surface 4a of the inner ring 4. As a result, the distance between the inner ring 4 and the outer ring 2 increases on the side 180 degrees opposite to the distance that has been brought closer. From this increased distance, it becomes possible to insert the ball 6 between the inner ring 4 and the outer ring 2.

[0055] [Modified Porous Member 8] Figure 6 is an unfolded view showing a modified version of the porous member 8. The porous member 8 in this modified version is also cylindrical in shape, similar to the forms in Figures 3 and 4, and has slits 32 extending in the axial direction, which can be reduced in diameter and expanded in diameter by elastic deformation. The slits 32 have a first slit 41 and a second slit 42. The first slit 41 and the second slit 42 are at different circumferential positions and are connected by a third slit 43 extending in the circumferential direction. These points are the same as the porous member 8 shown in Figures 3 and 4.

[0056] The porous member 8 shown in Figure 6 has an uneven shape at its upper end 51 and lower end 52, respectively. The upper end 51 has a plurality of recesses 511 along its circumferential direction. The lower end 52 has a plurality of recesses 521 along its circumferential direction. In the configuration shown in Figure 6, the upper end 51 and lower end 52 each have an uneven shape along their entire circumferential direction, but they may have an uneven shape only in parts. At least one recess 511 and one recess 521 are provided at the upper end 51 and lower end 52, respectively.

[0057] The uneven shape increases the contact area between the upper end 51 and lower end 52 of the porous member 8 and the grease in the upper and lower grease regions G1 and G2, respectively. This promotes the transfer of lubricating oil between the grease and the porous member 8. Grease from grease region G1 may be provided in the upper recess 511. Grease from grease region G2 may be provided in the lower recess 521. The uneven shape of the porous member 8 increases the amount of grease. The uneven shape of the porous member 8 contributes to extending the lifespan of the lubrication performance.

[0058] [Other] In the bearing device 1 of each of the above embodiments, the third slit 43 in the porous member 8 is a long, smooth gap along the circumferential direction. As a variation of the third slit 43, the third slit 43 may have a long portion along the circumferential direction, but may also have a gap with irregularities along its length. For example, the third slit 43 may have a zigzag shape.

[0059] The embodiments described above are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than by the embodiments, and includes all modifications within the scope of equivalence to the configurations described in the claims.

[0060] 1 Bearing device 2 Outer ring 2a Inner surface 2b, 2b Outer ring raceway 2c Outer surface 4 Inner ring 5A, 5B Rolling element row 8 Porous member 8a Outer surface 18 Second inner surface portion (inner surface portion) 24b1 Annular wall portion 28 Lubrication hole 281 Opening 32 Slit 41 First slit 42 Second slit 43 Third slit 51 Upper end 52 Lower end G1 Grease area G2 Grease area Q Area where slits exist W1 Width dimension W2 Width dimension W3 Width dimension

Claims

1. A bearing device comprising an inner ring, an outer ring, two rows of rolling elements positioned between the inner ring and the outer ring, and a porous member located between the two rows of rolling elements and capable of being impregnated with lubricating oil, wherein the porous member is cylindrical in shape, has axially extending slits and can be elastically deformed to reduce and expand its diameter, the slits include a first slit located on the upper side of the porous member and a second slit located on the lower side of the porous member, the first slit and the second slit are at different circumferential positions and are connected by a third slit extending in the circumferential direction.

2. The bearing device according to claim 1, wherein the space between each of the two rows of rolling elements and the porous member is a grease region, and the porous member has an uneven shape at its upper end and lower end, respectively.

3. The bearing device according to claim 1 or claim 2, wherein the width dimension of the third slit is smaller than the width dimensions of the first slit and the second slit.

4. The bearing device according to claim 1 or claim 2, wherein the outer ring has upper and lower outer ring raceways in which the two rows of rolling elements contact each other, the outer ring has an oil supply hole that penetrates from the outer circumferential surface to the inner circumferential surface of the outer ring and opens between the upper and lower outer ring raceways, and the circumferential regions of the first slit, the second slit, and the third slit are different from the circumferential position of the opening of the oil supply hole.

5. The bearing device according to claim 1 or claim 2, wherein the inner circumferential surface of the outer ring has an inner circumferential surface portion that contacts the outer circumferential surface of the porous member, and an annular wall portion located below the inner circumferential surface portion and having an inner diameter smaller than the inner diameter of the inner circumferential surface portion.

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