Bearing lubrication structure

Abstract

A bearing greasing structure of the present disclosure comprises: a hollow housing; an outer bearing with an outer ring held on an inner circumferential surface of the housing; a first rotating body that is hollow, and fixed to an inner ring of the outer bearing; an inner bearing with an outer ring held on an inner circumferential surface of the first rotating body; and a second rotating body fixed to an inner ring of the inner bearing. The housing has a first greasing path into which lubricant to be supplied to the inner bearing is introduced. A downstream side of the first greasing path communicates with a first sealed space sealed between the housing and the first rotating body. The first rotating body has a second greasing path with an upstream side communicating with the first sealed space. A downstream side of the second greasing path communicates with a second sealed space sealed between the first rotating body and the second rotating body. The inner bearing is disposed in the second sealed space.

Description

Technical Field

[0001] The present invention relates to a grease supply structure for supplying a lubricant to a bearing.

Background Art

[0002] Patent Document 1 below discloses an injection molding machine capable of moving an injection screw by converting the rotational movement of a ball screw into a linear movement by a combination of the ball screw and a ball nut and pressing a pusher plate. This injection molding machine has the following configuration.

[0003] A screw sleeve provided with an injection screw is provided in a through hole of a pusher plate via a bearing. Therefore, the screw sleeve is rotatable with respect to the pusher plate. The ball screw is provided on the inner peripheral portion of the screw sleeve via a bearing. Therefore, the ball screw is rotatable with respect to the screw sleeve. In the injection molding machine having such a configuration, the injection screw rotates during metering and kneading, and the ball screw rotates during injection. Therefore, during molding, the inner ring and the outer ring of the bearing between the ball screw and the screw sleeve rotate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, the bearing between the ball screw and the screw sleeve is often used under severe conditions. Therefore, the bearing between the ball screw and the screw sleeve needs to be regularly greased (lubricant supplied) in order to enhance durability.

[0006] In the case of a configuration in which the inner and outer rings rotate as described above, if an attempt is made to lubricate the bearing between the ball screw and the screw sleeve from an automatic lubrication device via a tube, the tube will rotate, making automatic lubrication using a tube impossible. Therefore, it is conceivable to manually lubricate the bearing using a grease gun while the injection molding machine is stopped.

[0007] However, in this case, the injection molding machine must be stopped, leading to a decrease in its operating rate. Furthermore, since lubrication is performed manually, problems such as forgetting to lubricate and the difficulty of the lubrication process arise. Therefore, a lubrication structure that allows for easy lubrication of bearings with rotating inner and outer rings is desired, with a simple configuration. [Means for solving the problem]

[0008] One aspect of the present disclosure is a bearing lubrication structure comprising: a hollow housing; an outer bearing whose outer ring is held on the inner circumferential surface of the housing; a hollow first rotating body fixed to the inner ring of the outer bearing; an inner bearing whose outer ring is held on the inner circumferential surface of the first rotating body; and a second rotating body fixed to the inner ring of the inner bearing, wherein the housing has a first lubrication passage through which a lubricant supplied to the inner bearing passes, the downstream side of the first lubrication passage communicates with a sealed first sealing space between the housing and the first rotating body; the first rotating body has a second lubrication passage whose upstream side communicates with the first sealing space, the downstream side of the second lubrication passage communicates with a sealed second sealing space between the first rotating body and the second rotating body, and the inner bearing is disposed within the second sealing space. [Effects of the Invention]

[0009] According to one embodiment, a lubrication structure can be provided that allows for easy lubrication of a bearing in which the inner and outer rings rotate, with a simple configuration. [Brief explanation of the drawing]

[0010] [Figure 1]This is a right side view showing an example of an injection molding machine to which the bearing lubrication structure according to the first embodiment of the present invention is applied, with a portion shown in cross-section. [Figure 2] This is a right side view showing a modified example of the bearing lubrication structure according to the first embodiment, with a portion shown in cross-section. [Figure 3] This is a right side view showing the lubrication structure of a bearing according to a second embodiment of the present invention, with a portion shown in cross-section. [Figure 4] This is a right side view showing a modified example of the bearing lubrication structure according to the second embodiment, with a portion shown in cross-section. [Figure 5] This is a right side view showing the lubrication structure of a bearing according to the third embodiment of the present invention, with a portion shown in cross-section. [Figure 6] This is a right side view showing a modified example of the bearing lubrication structure according to the third embodiment, with a portion shown in cross-section. [Modes for carrying out the invention]

[0011] Hereinafter, a bearing lubrication structure according to one aspect of the present disclosure will be described with reference to the drawings. Referring to Figure 1, the bearing lubrication structure according to the first embodiment will be described. The bearing lubrication structure comprises a housing 1, an outer bearing 2, a first rotating body 3, an inner bearing 4, and a second rotating body 5. Here, the case in which the present invention is applied to an injection molding machine 6 will be described. Note that the apparatus to which the present invention is applied is not limited to an injection molding machine 6.

[0012] The injection molding machine 6 comprises a front plate 7 and a rear plate 8 arranged facing each other, a guide rod 9 connecting the front plate 7 and the rear plate 8, a housing 1 slidably mounted on the guide rod 9, a first rotating body 3 rotatably mounted in the housing 1 and immovable in the axial direction, an injection screw 10 mounted on the first rotating body 3, a second rotating body 5 rotatably mounted in the first rotating body 3 and immovable in the axial direction, and a ball nut 11 mounted on the rear plate 8. The injection molding machine 6 can move the injection screw 10 by converting the rotational motion of the second rotating body 5, which is screwed into the ball nut 11, into linear motion and pressing the housing 1.

[0013] The front plate 7 is plate-shaped. An injection cylinder 12 is provided on the front plate 7. The rear plate 8 is plate-shaped. The rear plate 8 has a through hole 13 that penetrates in the thickness direction. The front plate 7 and the rear plate 8 are connected by a plurality of rod-shaped guide rods 9. Specifically, the rear plate 8 is fixed to one axial end of the guide rod 9 (the right end in Figure 1), and the front plate 7 is fixed to the other axial end of the guide rod 9 (the left end in Figure 1), so that the front plate 7 and the rear plate 8 are connected facing each other.

[0014] The housing 1 is in the shape of a thick plate. The housing 1 has multiple through holes 14 that penetrate in the thickness direction (which is also the axial direction of the guide rod 9). The housing 1 is installed on the guide rod 9 by passing the guide rod 9 through the through holes 14. When the guide rod 9 is passed through the through holes 14, a cylindrical bush 15 is provided between the inner circumferential surface of the through holes 14 and the outer circumferential surface of the guide rod 9. In this way, the housing 1 is installed on the guide rod 9 so as to be slidable along the axial direction of the guide rod 9.

[0015] The housing 1 has a through hole 16 that penetrates in the thickness direction. The through hole 16 is located approximately in the center of the housing 1. In the illustrated example, the through hole 16 is a stepped hole. That is, the through hole 16 has a small diameter hole 17 located on one axial end and a large diameter hole 18 located on the other axial end. Since the housing 1 is provided with a through hole 16, in other words, the housing 1 is hollow with an inner circumferential surface.

[0016] The first rotating body 3 has a columnar main body 19 and a retaining portion 20 for holding the inner bearing 4, which will be described later. The main body 19 is a stepped cylindrical shape and has a large diameter portion 21 located at one axial end of the main body 19 (the right end in Figure 1) and a small diameter portion 22 adjacent to the large diameter portion 21. The main body 19 has a circular recess 23 on one axial end face when viewed from the rear. The recess 23 opens at one axial end of the main body 19. In the illustrated example, the recess 23 is stepped and has a large diameter hole 24 located at one axial end and a small diameter hole 25 located at the other axial end. Since the first rotating body 3 is provided with a recess 23, in other words, the first rotating body 3 is hollow with an inner circumferential surface. An injection screw 10 is fixed to the other axial end of the main body 19 by bolts or the like. The retaining portion 20 is plate-shaped and has a through hole 26 that penetrates in the thickness direction. The first rotating body 3 is rotatably held in the housing 1 via an outer bearing 2. In the first embodiment, the outer bearing 2 is, for example, a ball bearing.

[0017] The outer bearing 2 has an annular outer-ring spacer 31 that connects the adjacent first bearing 27 and second bearing 28, and the outer ring 29 of the first bearing 27 and the outer ring 30 of the second bearing 28, and an annular inner-ring spacer 34 that connects the inner ring 32 of the first bearing 27 and the inner ring 33 of the second bearing 28. A cylindrical gap is formed between the outer-ring spacer 31 and the inner-ring spacer 34. The outer bearing 2 with such a configuration is provided in the housing 1 by holding the outer ring 29 of the first bearing 27 and the outer ring 30 of the second bearing 28 on the inner peripheral surface of the large-diameter hole 18. In a state where the outer bearing 2 is provided in the housing 1, the outer ring 29 of the first bearing 27 located on one axial end side (the right end side in FIG. 1) of the outer bearing 2 contacts the stepped portion between the large-diameter hole 18 and the small-diameter hole 17, and the outer ring 30 of the second bearing 28 located on the other axial end side of the outer bearing 2 contacts the pressing portion 36 provided in the housing 1. The pressing portion 36 is plate-shaped and is fixed to the axial other end surface of the housing 1 with bolts or the like. The pressing portion 36 has a through-hole 37 penetrating in the thickness direction. In this way, the outer rings (29, 30) of the outer bearing 2 are held on the inner peripheral surface of the hollow housing 1.

[0018] The main body portion 19 of the first rotating body 3 is held by the inner ring 32 of the first bearing 27 and the inner ring 33 of the second bearing 28. At this time, the outer peripheral surface of the small-diameter portion 22 of the main body portion 19 is fixed to the inner rings 32 of the first bearing 27 and the inner rings 33 of the second bearing 28. In a state where the first rotating body 3 is held by the outer bearing 2, the inner ring 32 of the first bearing 27 contacts the stepped portion between the large-diameter portion 21 and the small-diameter portion 22, and the inner ring 33 of the second bearing 28 contacts the annular pressing portion 72 provided on the first rotating body The pressing portion 72 is fixed to the first rotating body 3 in a state where the first rotating body 3 penetrates therethrough. In this way, the first rotating body 3 is fixed to the inner rings (32, 33) of the outer bearing 2. In a state where the first rotating body 3 is fixed to the outer bearing 2, the other axial end portion (the left end portion in FIG. 1) of the first rotating body 3 penetrates the opening on the other axial end side of the through-hole 16 of the housing 1 and the through-hole 37 of the pressing portion 36.

[0019] The second rotating body 5 is columnar. In the illustrated example, the other end side in the axial direction of the second rotating body 5 (the left end side in FIG. 1) is stepped columnar and has a large-diameter portion 39 and a small-diameter portion 40. The second rotating body 5 is rotatably supported by the first rotating body 3 via an inner bearing 4. The inner bearing 4 is, for example, a ball bearing. In the first embodiment, a plurality of inner bearings 4 are used, but one may also be used.

[0020] The plurality of inner bearings 4 are provided on the inner peripheral surface of the recess 23 of the first rotating body 3 in a state of being in contact with each other. At this time, the outer ring 41 of the inner bearing 4 is held on the inner peripheral surface of the large-diameter hole portion 24 of the recess 23, so that the inner bearing 4 is provided on the first rotating body 3. In a state where the plurality of inner bearings 4 are provided on the first rotating body 3, the outer ring 41 of the inner bearing 4 located on the inner side of the recess 23 is in contact with the step portion between the large-diameter hole portion 24 and the small-diameter hole portion 25, and the outer ring 41 of the inner bearing 4 located on the opening side of the recess 23 is in contact with the pressing portion 20 provided on the main body portion 19. The pressing portion 20 is fixed to one end surface in the axial direction of the main body portion 19 with a bolt or the like. In this way, the outer ring 41 of the inner bearing 4 is held on the inner peripheral surface of the hollow first rotating body 3.

[0021] The small-diameter portion 40 of the second rotating body 5 is held by the inner ring 43 of the inner bearing 4 in a state where the second rotating body 5 penetrates the through-hole 26 of the pressing portion 20 of the first rotating body 3. At this time, the outer peripheral surface of the small-diameter portion 40 of the second rotating body 5 is fixed to the inner ring 43 of the inner bearing 4. In a state where the second rotating body 5 is held by the plurality of inner bearings 4, the inner ring 43 of the inner bearing 4 located on the opening side of the recess 23 is in contact with the step portion between the small-diameter portion 40 and the large-diameter portion 39, and the inner ring 43 of the inner bearing 4 located on the inner side of the recess 23 is in contact with an annular pressing portion 45 provided on the small-diameter portion 40 of the second rotating body 5. The pressing portion 45 is fixed to the other end in the axial direction of the small-diameter portion 40 in a state where the small-diameter portion 40 is inserted. In this way, the second rotating body 5 is fixed to the inner ring of the inner bearing 4. In the first embodiment, the inner bearing 4 and the outer bearing 2 are arranged in an inner and outer double layer.

[0022] The second rotating body 5 has male threads on its outer surface, except for the other end in the axial direction. The second rotating body 5 is screwed into a ball nut 11 provided on the rear plate 8. The ball nut 11 is fixed non-rotatably to a through hole 13 in the rear plate 8. The second rotating body 5, screwed into the ball nut 11 on the rear plate 8, passes through the through hole 13 in the rear plate 8. That is, one end in the axial direction of the second rotating body 5 protrudes from the through hole 13 in the rear plate 8. The one end in the axial direction of the second rotating body 5 passes through an annular load cell 46 provided on the rear plate 8. The load cell 46 is fixed to the rear plate 8 by bolts or the like.

[0023] Next, the operation of the injection molding machine 6 will be described. In the injection molding machine 6, only the injection screw 10 rotates during metering and mixing, and only the second rotating body 5 rotates during injection. Therefore, the injection molding machine 6 has a motor 47 that rotates the first rotating body 3 to which the injection screw 10 is fixed, and a motor 48 that rotates the second rotating body 5. The motor 47 is provided in the housing 1. A drive pulley 49 is fixed to the drive shaft of the motor 47. A belt 51 is wrapped around the drive pulley 49 provided on the motor 47 and a driven pulley 50 provided on the other axial end of the first rotating body 3. The motor 48 is provided in the housing 1 such that the first rotating body 3 is positioned between the motor 47 and the motor 48. A drive pulley 52 is fixed to the drive shaft of the motor 48. A belt 54 is wrapped around the drive pulley 52 provided on the motor 48 and a driven pulley 53 provided on the second rotating body 5.

[0024] With this configuration, during metering and mixing, the injection screw 10 can be rotated by driving motor 47 with motor 48 stopped. By rotating the injection screw 10, the metering and mixing operation is performed, and molten resin is fed to the tip of the injection cylinder 12. During injection, the second rotating body 5 can be rotated by driving motor 48 with motor 47 stopped. By rotating the second rotating body 5, the housing 1 is moved towards the injection cylinder 12, and the injection screw 10 is moved inside the injection cylinder 12 and injected.

[0025] The bearing lubrication structure according to the first embodiment is applied to the injection molding machine 6 described above. The bearing lubrication structure comprises a hollow housing 1, an outer bearing 2 whose outer ring is held on the inner circumferential surface of the housing 1, a hollow first rotating body 3 fixed to the inner ring of the outer bearing 2, an inner bearing 4 whose outer ring is held on the inner circumferential surface of the first rotating body 3, and a second rotating body 5 fixed to the inner ring of the inner bearing 4. The housing 1, outer bearing 2, first rotating body 3, inner bearing 4, and second rotating body 5 have the configuration described above.

[0026] As shown in Figure 1, the housing 1 has a first lubrication passage 55 through which lubricant supplied to the inner bearing 4 passes. The upstream opening of the first lubrication passage 55 opens to the outside of the housing 1. A lubrication port 56, consisting of a grease nipple or the like, is provided at the upstream opening of the first lubrication passage 55. A lubrication device that automatically supplies lubricant is connected to the lubrication port 56. The downstream side of the first lubrication passage 55 communicates with a sealed first sealing space 57 between the housing 1 and the first rotating body 3. The first sealing space 57 is formed when the opening of a cylindrical gap located between the inner circumferential surface of the housing 1 and the outer circumferential surface of the first rotating body 3 is sealed with a sealing member.

[0027] The sealing member comprises a first sealing material 58 provided on the outside of the first bearing 27 and a second sealing material 59 provided on the outside of the second bearing 28. The first sealing material 58 seals one axial end (the right end in Figure 1) of the cylindrical gap between the outer ring spacer 31 and the inner ring spacer 34. The second sealing material 59 seals the other axial end of the cylindrical gap between the outer ring spacer 31 and the inner ring spacer 34. By sealing the cylindrical gap between the outer ring spacer 31 and the inner ring spacer 34, a first sealing space 57 is formed. When the cylindrical gap sealed by the first sealing material 58 and the second sealing material 59 is the first sealing space 57, the downstream side of the first lubrication passage 55 communicates with the first sealing space 57 through an outer through-hole 60 provided in the outer ring spacer 31.

[0028] As shown in Figure 1, the first rotating body 3 has a second lubrication passage 61 through which lubricant that has flowed from the first lubrication passage 55 through the first sealing space 57 passes. The upstream side of the second lubrication passage 61 is in communication with the first sealing space 57. In the first embodiment, the cylindrical gap between the outer ring spacer 31 and the inner ring spacer 34 is the first sealing space 57. Therefore, the upstream side of the second lubrication passage 61 is in communication with the first sealing space 57 through an inner through-hole 62 provided in the inner ring spacer 34.

[0029] The downstream side of the second lubrication passage 61 communicates with a sealed second sealing space 63 between the first rotating body 3 and the second rotating body 5. The second sealing space 63 is formed by sealing the opening of a cylindrical gap located between the inner circumferential surface of the first rotating body 3 and the outer circumferential surface of the second rotating body 5 with a sealing member 64. The sealing member 64 seals the gap between the inner circumferential surface of the first rotating body 3 and the outer circumferential surface of the second rotating body 5 on the opening side of the recess 23. The sealing member 64 is annular and is provided between the inner circumferential surface of the retaining portion 20 of the first rotating body 3 and the outer circumferential surface of the large diameter portion 39 of the second rotating body 5. The sealing member 64 is a conventionally known oil seal, but is not limited thereto. An inner bearing 4 is arranged in the second sealing space 63 formed in this way.

[0030] As shown in Figure 1, the first rotating body 3 penetrates the housing 1 and therefore has an exposed surface 65 that is exposed from the housing 1. Typically, the exposed surface 65 is the outer circumferential surface of the retaining portion 20 of the first rotating body 3. The first rotating body 3 has a discharge passage 66 that discharges the lubricant in the second sealing space 63 to the outside of the housing 1. The discharge passage 66 is provided, for example, in the retaining portion 20 of the first rotating body 3. The discharge passage 66 is a flow path for discharging the lubricant that has passed through the inner bearing 4. Therefore, the upstream side of the discharge passage 66 communicates with the portion between the inner bearing 4 and the sealing member 64. The outlet of the discharge passage 66 opens to the exposed surface 65.

[0031] In the lubrication structure of the first embodiment, the lubricant supplied from the lubrication device flows into the first sealing space 57 through the first lubrication passage 55. The lubricant flows from the first sealing space 57 into the second sealing space 63 through the second lubrication passage 61. As a result, the lubricant is supplied to the inner bearing 4. Subsequently, the lubricant is discharged to the outside of the housing 1 through the discharge passage 66. Therefore, according to the lubrication structure of the first embodiment, the inner bearing 4, in which the inner ring 43 and outer ring 41 rotate, can be easily lubricated while the injection molding machine 6 is in operation with a simple configuration, and is particularly suitable for automating lubrication.

[0032] In the lubrication structure of the first embodiment, the outlet of the discharge passage 66 opens to the exposed surface 65. Therefore, the lubrication structure of the first embodiment can be made simpler compared to a configuration in which the lubricant is discharged through the housing 1.

[0033] Next, a modified example of the bearing lubrication structure according to the first embodiment will be described using Figure 2. Note that components having the same reference numerals as those used in the first embodiment have the same function, and therefore their descriptions may be omitted below. The lubrication structure of this modified example has a plurality of first lubrication passages 55 and a plurality of second lubrication passages 61.

[0034] As shown in Figure 2, the lubrication structure of this modified example has two first lubrication passages 55, 55 and two second lubrication passages 61, 61 corresponding to each of the two first lubrication passages 55, 55. The two first lubrication passages 55, 55 are provided at positions opposite each other with the first rotating body 3 in between. The two second lubrication passages 61, 61 are provided at positions opposite each other with the first rotating body 3 in between. Accordingly, two external through holes 60, 60 are provided in the outer ring spacer 31, and two internal through holes 62, 62 are provided in the inner ring spacer 34.

[0035] In this modified lubrication structure, the lubricant is supplied to the second sealing space 63 from two supply passages. Therefore, according to this modified lubrication structure, the lubricant can be efficiently supplied into the second sealing space 63.

[0036] Next, the bearing lubrication structure according to the second embodiment of the present invention will be described with reference to Figure 3. Note that components having the same reference numerals as those used in the first embodiment may be omitted from further description as they perform the same function. The lubrication structure of the second embodiment differs from that of the first embodiment in the configuration of the first sealing space 57.

[0037] As shown in Figure 3, the through hole 16 of the housing 1 is a stepped hole. The through hole 16 has a small diameter hole 67 located on one axial end of the through hole 16 and a large diameter hole 69 located on the other axial end of the through hole 16.

[0038] Multiple outer bearings 2 are installed in the large-diameter hole 69 of the through hole 16, in contact with each other. At this time, the outer rings 79 of the outer bearings 2 are held by the inner circumferential surface of the large-diameter hole 69, thereby installing the outer bearings 2 in the housing 1. When the multiple outer bearings 2 are installed in the housing 1, the outer rings 79 of the outer bearings 2 located at one axial end of the through hole 16 are in contact with the stepped portion between the large-diameter hole 69 and the small-diameter hole 67, and the outer rings 79 of the outer bearings 2 located at the other axial end of the through hole 16 are in contact with a retaining portion 36 provided in the housing 1. The retaining portion 36 is in the shape of a thick plate and is fixed to the other axial end surface of the housing 1 with bolts or the like. The retaining portion 36 has a through hole 37 that penetrates in the thickness direction. The through hole 37 is a stepped hole.

[0039] The main body portion 19 of the first rotating body 3 is held by the inner ring 80 of the outer bearing 2. At this time, the outer circumferential surface of the small diameter portion 22 of the main body portion 19 is fixed to the inner ring 80 of the outer bearing 2. When the first rotating body 3 is held by the outer bearing 2, the inner ring 80 of the outer bearing 2 located on one axial end side of the through hole 16 is in contact with the stepped portion between the large diameter portion 21 and the small diameter portion 22, and the inner ring 80 of the outer bearing 2 located on the other axial end side of the through hole 16 is in contact with the annular retaining portion 72 provided on the first rotating body 3.

[0040] The first sealing space 57 is formed by sealing the axial opening of the cylindrical gap located between the housing 1 and the first rotating body 3 with an annular third sealing material 74, and sealing the axial opening of the cylindrical gap located between the housing 1 and the first rotating body 3 with an annular fourth sealing material 75. In the second embodiment, the fourth sealing material 75 seals the gap between the inner circumferential surface of the small diameter hole of the through hole 37 of the retaining portion 36 and the outer circumferential surface of the first rotating body 3. With this configuration, the outer bearing 2 is placed in the first sealing space 57. At this time, gaps are formed between the outer bearing 2 located on the axial end side of the through hole 16 and the third sealing material 74, and between the outer bearing 2 located on the axial end side of the through hole 16 and the fourth sealing material 75.

[0041] In this way, the outer bearing 2 is positioned within the first sealing space 57 such that a first portion 76 remains at one axial end of the first sealing space 57 and a second portion 77 remains at the other axial end of the first sealing space 57. In this case, the downstream side of the first lubrication passage 55 is in communication with the first portion 76. The upstream side of the second lubrication passage 61 is in communication with the second portion 77.

[0042] In the lubrication structure of the second embodiment, the lubricant supplied from the lubrication device flows into the first portion 76 of the first sealing space 57 through the first lubrication passage 55. The lubricant flows from the first portion 76 of the first sealing space 57 through the outer bearing 2 to the second portion 77. The lubricant flows from the second portion 77 of the first sealing space 57 through the second lubrication passage 61 into the second sealing space 63. As a result, the lubricant is supplied to the inner bearing 4. The lubricant is then discharged to the outside of the housing 1 through the discharge passage 66.

[0043] Next, a modified example of the bearing lubrication structure according to the second embodiment will be described using Figure 4. Note that components having the same reference numerals as those used in the first embodiment have the same function, and therefore their descriptions may be omitted below. The lubrication structure of this modified example has a plurality of first lubrication passages 55 and a plurality of second lubrication passages 61.

[0044] As shown in Figure 4, the lubrication structure of this modified example has two first lubrication passages 55, 55 and two second lubrication passages 61, 61 corresponding to each of the two first lubrication passages 55, 55. The two first lubrication passages 55, 55 are located opposite each other with the first rotating body 3 in between. The two second lubrication passages 61, 61 are located opposite each other with the first rotating body 3 in between.

[0045] Next, the bearing lubrication structure according to the third embodiment of the present invention will be described with reference to Figure 5. Note that components having the same reference numerals as those used in the first embodiment have the same function, and therefore their descriptions may be omitted below. The lubrication structure of the third embodiment differs from that of the first embodiment in the configuration of the first sealing space 57.

[0046] As shown in Figure 5, the annular fifth sealant 78 is provided between the housing 1 and the first rotating body 3 such that a gap is formed between it and the outer bearing 2. Typically, the fifth sealant 78 is provided such that a gap is formed between it and the first bearing 27. This creates a first sealing space 57 between the first sealant 58 of the first bearing 27 and the fifth sealant 78. That is, in the third embodiment, the fifth sealant 78 is provided between the housing 1 and the first rotating body 3 such that a gap is formed between it and the sealing member provided on the outer bearing 2. In this way, the outer bearing 2 is positioned adjacent to the first sealing space 57.

[0047] The outer bearing 2 is a bearing having an outer ring spacer 31 and an inner ring spacer 34, but it may also be a standard ball bearing. In this case, a sealing member is provided for the outer bearing.

[0048] Next, a modified example of the bearing lubrication structure according to the third embodiment will be described using Figure 6. Note that components having the same reference numerals as those used in the first embodiment have the same function, and therefore their descriptions may be omitted below. The lubrication structure of this modified example has a plurality of first lubrication passages 55 and a plurality of second lubrication passages 61.

[0049] As shown in Figure 6, the lubrication structure of this modified example has two first lubrication passages 55, 55 and two second lubrication passages 61, 61 corresponding to each of the two first lubrication passages 55, 55. The two first lubrication passages 55, 55 are provided at positions opposite each other with the first rotating body 3 in between. The two second lubrication passages 61, 61 are provided at positions opposite each other with the first rotating body 3 in between.

[0050] It should be noted that the present invention is not limited to the embodiments and modifications described above, and any modifications and improvements that can achieve the objectives of the present invention are included in the present invention.

[0051] For example, in each of the embodiments and modifications described above, the number of second lubrication passages 61 may be greater than the number of first lubrication passages 55. [Explanation of Symbols]

[0052] 1 Housing 2 Outer bearing 3. First Rotating Body 4. Inner bearing 5. Second Rotational Body 27 First bearing 28 Second bearing 29. Outer ring of the first bearing 30. Outer ring of the second bearing 31 Outer wheel spacer 32 Inner ring of the first bearing 33 Inner ring of the second bearing 34 Inner Wheel Spacer 55 1st greasing path 57 First sealed space 58. First sealing material 59 Second sealing material 60 Outer through hole 61 2nd greasing path 62 Inner through hole 63 Second sealed space 65 Exposed surface 66 Exhaust channel 76 Part 1 77 Part 2

Claims

1. A hollow housing, An outer bearing whose outer ring is held on the inner circumferential surface of the housing, A first rotating body, which is hollow and fixed to the inner ring of the outer bearing, An inner bearing in which the outer ring is held on the inner circumferential surface of the first rotating body, The system comprises a second rotating body fixed to the inner ring of the inner bearing, The housing has a first lubrication passage through which lubricant supplied to the inner bearing passes, The downstream side of the first lubrication passage is in communication with the sealed first sealing space between the housing and the first rotating body. The first rotating body has a second lubrication passage whose upstream side is in communication with the first sealing space, The downstream side of the second lubrication passage is in communication with the sealed second sealing space between the first rotating body and the second rotating body. The inner bearing is positioned within the second sealing space. The first rotating body has an exposed surface that is exposed from the housing, A bearing lubrication structure wherein the exposed surface has an outlet for a discharge passage that discharges the lubricant in the second sealing space to the outside of the housing.

2. The outer bearing comprises a first bearing and a second bearing, the outer rings of which are connected and the inner rings of which are connected; an outer ring spacer connecting the outer ring of the first bearing and the outer ring of the second bearing; and an inner ring spacer connecting the inner ring of the first bearing and the inner ring of the second bearing. One axial end of the cylindrical gap between the outer ring spacer and the inner ring spacer is sealed by the first sealing material, and the other axial end of the cylindrical gap is sealed by the second sealing material. The cylindrical gap sealed by the first sealing material and the second sealing material is defined as the first sealing space. The downstream side of the first lubrication passage is in communication with the first sealing space through an external through-hole provided in the outer ring spacer. The bearing lubrication structure according to claim 1, wherein the upstream side of the second lubrication passage is connected to the first sealing space through an inner through-hole provided in the inner ring spacer.

3. The outer bearing is positioned within the first sealing space such that a first portion remains at one axial end of the first sealing space and a second portion remains at the other axial end of the first sealing space. The downstream side of the first lubrication passage is in communication with the first portion, The bearing lubrication structure according to claim 1, wherein the upstream side of the second lubrication passage is in communication with the second portion.

4. The bearing lubrication structure according to claim 1, wherein the outer bearing is arranged adjacent to the first sealing space.

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