Traveling device

Abstract

To shorten an axial length dimension of a traveling device.SOLUTION: Between an outer periphery of a fixed housing 12 and an inner periphery of a rotating housing 16, bearings 25, 26 for rotatably supporting the rotating housing 16 are provided, and a nut member 27 is provided on a male threaded portion 12D provided on the outer periphery of the fixed housing 12, which abuts against the bearing 25 in a state of being screwed onto the male threaded portion 12D and pressurizes the bearings 25, 26. The nut member 27 includes: a bearing abutment portion 27B that abuts against an axial end face 25D of the bearing 25 in a state of being screwed onto the male threaded portion 12D of the fixed housing 12; and a cylindrical portion 27C that protrudes in the axial direction from the bearing abutment portion 27B and is inserted into an inner periphery of the bearing 25. Therefore, an axial dimension of a traveling device 11 is shortened by a depth to which the cylindrical portion 27C is inserted into an inner periphery of an inner ring 25A.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a traveling device mounted on a construction machine such as a hydraulic excavator. [Background technology]

[0002] The undercarriage of a tracked vehicle such as a hydraulic excavator has a center frame and side frames arranged on both the left and right sides of the center frame. An idler wheel is provided on one end of the side frame, and a traveling device having a drive wheel is provided on the other end of the side frame. A track (crawler) is wound around the drive wheel and the idler wheel, and the drive wheel is driven to rotate by the traveling device, causing the track to move in an orbit, thereby traveling the hydraulic excavator.

[0003] A traveling device for a hydraulic excavator generally comprises a fixed housing to which a hydraulic motor is attached, a rotating housing which is rotated relative to the fixed housing by the hydraulic motor, and a planetary gear reduction mechanism which reduces the rotation of the hydraulic motor and transmits it to the rotating housing, and a drive wheel is attached to the rotating housing. Here, a bearing which rotatably supports the rotating housing is provided between the outer periphery of the fixed housing and the inner periphery of the rotating housing, and this bearing is pressurized by a nut member which is screwed into a male thread provided on the outer periphery of the fixed housing (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 3-130917 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, it is desirable that the traveling gear of the hydraulic excavator has a structure (insole structure) that fits within the width dimension of the crawler so that falling rocks and the like during excavation work are unlikely to collide with the traveling gear. However, in Patent Document 1, the bearing is pressurized by abutting a nut member screwed onto a male thread portion formed on the outer periphery of the fixed housing against an end face of the bearing. The axial length dimension (thickness) of the nut member corresponds to the meshing length between the nut member and the male thread portion required to pressurize the bearing. As a result, the axial length dimension of the nut member increases, and the axial length dimension of the entire traveling gear increases, which creates a problem that it becomes difficult to fit the traveling gear within the width dimension of the crawler.

[0006] The present invention has been made in consideration of the above-mentioned problems in the conventional technology, and an object of the present invention is to provide a traveling device that can reduce the axial length dimension. [Means for solving the problem]

[0007] The present invention is a running device comprising a fixed housing to which a rotation source is attached, a rotatable housing that rotates relative to the fixed housing by the rotation source, a bearing that is provided between the outer periphery of the fixed housing and the inner periphery of the rotatable housing and rotatably supports the rotatable housing, and a nut member that is screwed into a male threaded portion provided on the outer periphery of the fixed housing and abuts against the bearing to pressurize the bearing, wherein the nut member has a bearing abutment portion that abuts against the axial end face of the bearing when screwed into the male threaded portion of the fixed housing, and a cylindrical portion that protrudes axially from the bearing abutment portion and is inserted into the inner periphery of the bearing. Effect of the Invention

[0008] According to the present invention, with the bearing abutment portion of the nut member abutting the end face of the bearing, the axial length dimension of the traveling device can be shortened by the amount by which the cylindrical portion of the nut member is inserted into the inner circumference of the bearing. [Brief description of the drawings]

[0009] [Figure 1] 1 is a left side view showing a hydraulic excavator equipped with a traveling device according to an embodiment of the present invention. FIG. [Diagram 2] 2 is a cross-sectional view of the traveling device as viewed from the direction of arrows II-II in FIG. [Diagram 3] 3 is an enlarged cross-sectional view of a planetary gear reduction mechanism, a bearing, a nut member, etc. in FIG. 2. [Figure 4] 4 is an enlarged cross-sectional view of a main portion of a bearing, a nut member, and the like in FIG. 3. [Diagram 5] 5 is an enlarged cross-sectional view of essential parts, such as a bearing and a nut member, according to a second embodiment, taken in the same position as in FIG. 4. [Figure 6] 13 is an enlarged cross-sectional view showing a bearing, a nut member, etc. according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a traveling device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings, taking as an example a case where the traveling device is mounted on a hydraulic excavator. Note that in the embodiment, the traveling direction of the hydraulic excavator is defined as the front-rear direction, and the direction perpendicular to the traveling direction is defined as the left-right direction.

[0011] Figures 1 to 4 show a first embodiment of the present invention. In Figure 1, a hydraulic excavator 1 includes a self-propelled lower traveling body 2, an upper rotating body 4 rotatably mounted on the lower traveling body 2 via a slewing wheel 3, and a working device 5 rotatably provided on the front side of the upper rotating body 4. The hydraulic excavator 1 self-propels to a work site by the lower traveling body 2, and performs work such as excavating earth and sand using the working device 5 while rotating the upper rotating body 4.

[0012] The lower traveling body 2 is a crawler-type lower traveling body suitable for traveling on rough ground and the like. The lower traveling body 2 has a center frame 6 and left and right side frames 7 (only the left side is shown) that are arranged on the left and right sides of the center frame 6 and extend in the front-rear direction. An idler wheel 8 is rotatably provided on one end in the front-rear direction of each of the left and right side frames 7. A traveling device bracket 9 is fixed to the other end in the front-rear direction of each of the left and right side frames 7, and a traveling device 11 described below is attached to the traveling device bracket 9. A track (crawler) 10 is wound around the drive wheel 20 and the idler wheel 8 of the traveling device 11, and the lower traveling body 2 travels by driving the crawler 10 in a circular motion by the traveling device 11.

[0013] The traveling device 11 according to the first embodiment is attached to a traveling device bracket 9 fixed to the other end side in the front-rear direction of the side frame 7. As shown in Fig. 2, the traveling device 11 includes a fixed housing 12, a hydraulic motor 14, a rotating housing 16, a driving wheel 20, planetary gear reduction mechanisms 21, 22, 23, bearings 25, 26, and a nut member 27. The traveling device 11 reduces the rotation of the hydraulic motor 14 in three stages by the planetary gear reduction mechanisms 21, 22, 23, thereby rotating the driving wheel 20 with a large torque and driving the crawler belt 10 wound around the driving wheel 20 and the idler wheel 8 in a circular motion.

[0014] The fixed housing 12 is attached to a traveling device bracket 9 fixed to the side frame 7 of the lower traveling body 2. The fixed housing 12 is formed as a stepped cylinder as a whole, and the base end side (traveling device bracket 9 side) of the fixed housing 12 forms a large-diameter flange portion 12A. The tip side of the fixed housing 12 forms a cylindrical bearing attachment portion 12B, and inner rings 25A, 26A of bearings 25, 26 are attached to the bearing attachment portion 12B. The flange portion 12A is fixed to the traveling device bracket 9 using a plurality of bolts 13, and a hydraulic motor 14 is accommodated on the inner peripheral side of the fixed housing 12.

[0015] A hole spline portion 12C is formed on the inner peripheral surface of the tip of the bearing mounting portion 12B, and a third stage carrier 23C, which will be described later, is splined to the hole spline portion 12C. A male thread portion 12D is formed on the outer peripheral surface of the tip of the bearing mounting portion 12B, and a nut member 27, which will be described later, is screwed to the male thread portion 12D. Here, as shown in FIG. 4, the outer diameter dimension D1 (φD1) of the male thread portion 12D is set to be smaller than the outer diameter dimension D (φD) of the bearing mounting portion 12B (D1 <D)。

[0016] The hydraulic motor 14 serving as a rotation source is attached to the end face on the base end side of the fixed housing 12 using a plurality of bolts 14A. The base end side of a rotating shaft 15 is spline-connected to the output shaft 14B of the hydraulic motor 14. A sun gear 21A, which will be described later, is integrally formed with the tip of the rotating shaft 15, and the rotation output of the hydraulic motor 14 is transmitted via the rotating shaft 15 to a first-stage planetary gear reduction mechanism 21, which will be described later.

[0017] The rotating housing 16 is rotatably attached to the fixed housing 12 via bearings 25 and 26. The rotating housing 16 includes an attachment base portion 17, a housing cylinder portion 18, and a cover portion 19, and is disposed coaxially with the fixed housing 12. The rotating housing 16 rotates relative to the fixed housing 12 as the rotation of the hydraulic motor 14 is transmitted to it via planetary gear reduction mechanisms 21, 22, and 23. As a result, the drive wheel 20 attached to the rotating housing 16 is rotationally driven.

[0018] The inner peripheral surface of the base end side (traveling device bracket 9 side) of the mounting base portion 17 forms a bearing mounting portion 17A to which outer rings 25B, 26B of the bearings 25, 26 are attached. A large-diameter, disk-shaped flange portion 17B is provided on the outer peripheral side of the bearing mounting portion 17A, and the drive wheel 20 is attached to the flange portion 17B using a plurality of bolts 17C. The tip side of the mounting base portion 17 forms a large-diameter cylindrical portion 17D, and a housing tube portion 18 is attached to the axial end face of the large-diameter cylindrical portion 17D.

[0019] An annular flange 18A is provided on the outer peripheral surface of the base end side (traveling device bracket 9 side) of the housing cylinder 18. The flange 18A is attached to the end face of the large diameter cylindrical portion 17D constituting the mounting base portion 17 by using a plurality of bolts 18B. An annular internal gear 18C and an internal gear 18D are formed on the inner peripheral surface of the housing cylinder 18 with a gap therebetween in the axial direction. Three-stage planetary gear reduction mechanisms 21, 22, and 23 are housed on the inner peripheral side of the housing cylinder 18, and a first-stage planetary gear 21B and a second-stage planetary gear 22B mesh with the internal gear 18C, and a third-stage planetary gear 23B meshes with the internal gear 18D.

[0020] The lid portion 19 is attached by using a plurality of bolts 19A to the end face on the tip side of the open end of the tubular housing portion 18. The lid portion 19 is formed in a disk shape and covers the open end of the tubular housing portion 18.

[0021] The three-stage planetary gear reduction mechanisms 21, 22, and 23 are housed in the rotating housing 16. These three-stage planetary gear reduction mechanisms 21, 22, and 23 reduce the rotation of the hydraulic motor 14 by three stages, and rotate the drive wheels 20 attached to the mounting base portion 17 of the rotating housing 16 with a large torque.

[0022] The first-stage planetary gear reduction mechanism 21 includes a sun gear 21A integrally formed at the tip of the rotating shaft 15, a plurality of planetary gears 21B (only one shown) that mesh with the sun gear 21A and the internal gear 18C of the housing cylinder portion 18 and revolve around the sun gear 21A while rotating on its own axis, and a carrier 21C that rotatably supports the plurality of planetary gears 21B. The first-stage planetary gear reduction mechanism 21 reduces the speed of rotation of the sun gear 21A and transmits the revolutions of the plurality of planetary gears 21B to the second-stage sun gear 22A via the carrier 21C.

[0023] The second-stage planetary gear reduction mechanism 22 includes a sun gear 22A splined to the first-stage carrier 21C, a plurality of planetary gears 22B meshing with the sun gear 22A and the internal gear 18C of the housing cylinder 18 and revolving around the sun gear 22A while rotating on their own axes, and a carrier 22C rotatably supporting the plurality of planetary gears 22B. The second-stage planetary gear reduction mechanism 22 reduces the speed of rotation of the sun gear 22A and transmits the revolutions of the plurality of planetary gears 22B to the third-stage sun gear 23A via the carrier 22C.

[0024] The third-stage planetary gear reduction mechanism 23, which is the final stage, is composed of a sun gear 23A splined to the second-stage carrier 22C, a plurality of planetary gears 23B that mesh with the sun gear 23A and the internal gear 18D of the accommodating cylindrical portion 18 and revolve around the sun gear 23A while rotating on their own axes, and a carrier 23C that rotatably supports the plurality of planetary gears 23B.

[0025] Here, the third stage carrier 23C is splined to the hole spline portion 12C of the fixed housing 12. Therefore, the revolution of the multiple planetary gears 23B supported by the carrier 23C is transmitted to the rotating housing 16 via the internal gear 18D of the accommodating cylinder portion 18. As a result, the rotating housing 16 rotates relative to the fixed housing 12 while being reduced in three stages by the planetary gear reduction mechanisms 21, 22, and 23.

[0026] An annular floating seal 24 is provided between the mounting base portion 17 of the rotating housing 16 and the fixed housing 12. The rotating housing 16 is filled with lubricating oil (not shown) for lubricating the planetary gear reduction mechanisms 21, 22, 23, bearings 25, 26, etc., and the floating seal 24 seals this lubricating oil inside the rotating housing 16.

[0027] The bearings 25 and 26 are provided between the fixed housing 12 and the rotating housing 16, and support the rotating housing 16 rotatably relative to the fixed housing 12. These two bearings 25, 26 are, for example, tapered roller bearings, and are arranged between the fixed housing 12 and the rotating housing 16 with a gap in the axial direction. As shown in FIG. 3, the bearings 25, 26 have inner rings 25A, 26A, outer rings 25B, 26B, and a plurality of rolling elements 25C, 26C. The inner ring 25A of the bearing 25 and the inner ring 26A of the bearing 26 are fitted to the outer peripheral surface of the bearing mounting portion 12B of the fixed housing 12, respectively. The outer ring 25B of the bearing 25 and the outer ring 26B of the bearing 26 are fitted to the inner peripheral surface of the bearing mounting portion 17A of the mounting base portion 17 constituting the rotating housing 16, respectively.

[0028] The nut member 27 is screwed onto the male thread portion 12D formed on the bearing attachment portion 12B of the fixed housing 12. By screwing the nut member 27 onto the male thread portion 12D, the nut member 27 comes into contact with an axial end face 25D of the inner ring 25A of the bearing 25 and presses it against the bearing 26. As a result, the nut member 27 presses the two bearings 25, 26 provided between the fixed housing 12 and the rotating housing 16 in the axial direction.

[0029] As shown in FIG. 3 and FIG. 4, the nut member 27 is formed in a stepped cylindrical shape as a whole, and includes a female threaded portion 27A, a bearing abutment portion 27B, and a cylindrical portion 27C. The female threaded portion 27A is formed on the inner peripheral surface of the nut member 27, and is screwed into the male threaded portion 12D formed on the bearing attachment portion 12B of the fixed housing 12. The bearing abutment portion 27B faces the bearing 25 in the axial direction, and abuts against an axial end face 25D of the inner ring 25A constituting the bearing 25 in a state in which the female threaded portion 27A is screwed into the male threaded portion 12D of the fixed housing 12. The cylindrical portion 27C protrudes in the axial direction from the end face of the bearing abutment portion 27B on the bearing 25 side, and is inserted into the inner peripheral side of the inner ring 25A constituting the bearing 25. The outer peripheral surface 27D of the cylindrical portion 27C fits into the inner peripheral surface 25E of the inner ring 25A.

[0030] As shown in FIG. 4, the female screw portion 27A of the nut member 27 is formed over the entire axial region of the bearing contact portion 27B and the cylindrical portion 27C. Further, the outer diameter dimension D2 (φD2) of the cylindrical portion 27C of the nut member 27 is set smaller than the outer diameter dimension D (φD) of the bearing mounting portion 12B (D2 < D). In the present embodiment, the outer diameter dimension D2 of the cylindrical portion 27C is formed slightly smaller than the outer diameter dimension D of the bearing mounting portion 12B, and the outer peripheral surface 27D of the cylindrical portion 27C is fitted to the inner peripheral surface 25E of the inner ring 25A of the bearing 25 in an interference fit or press fit state. Further, the axial dimension L of the cylindrical portion 27C (the protruding length of the cylindrical portion 27C protruding from the bearing contact portion 27B of the nut member 27) is set to be equal to or greater than the pitch P of the female screw portion 27A (L ≧ P).

[0031] In this way, with the bearing contact portion 27B of the nut member 27 in contact with the inner ring 25A (end face 25D) of the bearing 25 and the bearings 25, 26 being axially pressed, the cylindrical portion 27C of the nut member 27 is inserted (overlapped) by the axial dimension L on the inner peripheral side of the inner ring 25A. As a result, the axial dimension of the entire traveling device 11 can be shortened by the axial dimension L of the cylindrical portion 27C. In this case, a uniform female screw portion 27A having a sufficient length is formed on the inner peripheral surfaces of the bearing contact portion 27B and the cylindrical portion 27C of the nut member 27. Thereby, the fastening force of the nut member 27 screwed to the male screw portion 12D of the fixed housing 12 is ensured, and the bearings 25, 26 can be appropriately pressed by the nut member 27.

[0032] The anti-rotation member 28 is attached to the bearing abutment portion 27B of the nut member 27 and prevents the nut member 27 from rotating relative to the male thread portion 12D of the fixed housing 12. The anti-rotation member 28 is attached to the end face of the bearing abutment portion 27B of the nut member 27 opposite the bearing 25 by using a bolt 28A. A plurality of engagement grooves 12E (only one shown) are formed at the tip of the bearing attachment portion 12B of the fixed housing 12 on which the male thread portion 12D is formed. The nut member 27 is prevented from rotating by the tip of the anti-rotation member 28 engaging with any one of the plurality of engagement grooves 12E. As a result, the bearings 25, 26 are maintained in a state in which they are pressurized by the nut member 27.

[0033] The traveling device 11 according to the first embodiment has the above-mentioned configuration, and when the hydraulic excavator 1 travels, pressure oil is discharged from a hydraulic pump (neither of which is shown) driven by the engine, and this pressure oil is supplied to the hydraulic motor 14, thereby rotating and driving the hydraulic motor 14. The rotation of the hydraulic motor 14 is transmitted to a first-stage planetary gear reduction mechanism 21 via a rotating shaft 15, and then transmitted to the rotating housing 16 in a state where it is reduced in three stages by a second-stage planetary gear reduction mechanism 22 and a third-stage planetary gear reduction mechanism 23. As a result, the driving wheel 20 fixed to the rotating housing 16 rotates with a large torque, and the crawler belt 10 wound around the driving wheel 20 and the idler wheel 8 is driven to rotate, and the hydraulic excavator 1 travels.

[0034] The bearings 25, 26, which support the rotatable housing 16 relative to the fixed housing 12 while the hydraulic excavator 1 is traveling, are attached between the bearing attachment portion 12B of the fixed housing 12 and the bearing attachment portion 17A of the rotatable housing 16 (mounting base portion 17). A male thread portion 12D is formed on the outer circumferential surface of the bearing attachment portion 12B, and an inner ring 25A of the bearing 25 is pressed in the axial direction by a nut member 27 screwed onto the male thread portion 12D. This allows the bearings 25, 26 to support the rotatable housing 16 with an appropriate amount of pressure applied, allowing the drive wheels 20 to rotate smoothly.

[0035] Here, the nut member 27 has a bearing abutment portion 27B that abuts against an end face 25D of the inner ring 25A of the bearing 25, and a cylindrical portion 27C that protrudes in the axial direction from the end face of the bearing abutment portion 27B on the bearing 25 side. Then, the female threaded portion 27A is screwed into the male threaded portion 12D of the fixed housing 12, and the bearing abutment portion 27B is in abutment against the inner ring 25A of the bearing 25 (end face 25D), and the cylindrical portion 27C fits into the inner peripheral side of the inner ring 25A of the bearing 25.

[0036] In this manner, with the bearing abutment portion 27B of the nut member 27 abutting against the end face 25D of the inner ring 25A of the bearing 25 and the bearings 25, 26 being axially pressurized, the cylindrical portion 27C of the nut member 27 is inserted (overlapped) into the inner peripheral side of the inner ring 25A by the axial dimension L. As a result, the axial dimension of the traveling device 11 can be shortened by the axial dimension L of the cylindrical portion 27C overlapping with the inner ring 25A. As a result, as shown in FIG. 2, the traveling device 11 can be accommodated within the width dimension A of the crawler belt 10, and the traveling device 11 can be protected from falling rocks and the like during excavation work.

[0037] Here, for example, when the output of the traveling device 11 is increased, there is a concern that the axial dimension of the entire traveling device 11 will increase as the tooth width of the sun gears 21A, 22A, 23A constituting the planetary gear reduction mechanism 21, 22, 23 or the tooth width of the planetary gears 21B, 22B, 23B increases. In contrast, according to this embodiment, the cylindrical portion 27C of the nut member 27 overlaps with the inner ring 25A of the bearing 25, thereby offsetting the increase in the tooth width of the gears constituting the planetary gear reduction mechanism 21, 22, 23. As a result, even if the output of the traveling device 11 is increased, the traveling device 11 can be accommodated within the width dimension A of the crawler belt 10, and the traveling device 11 can be protected.

[0038] Thus, the traveling device 11 according to the embodiment comprises a fixed housing 12 to which a hydraulic motor 14 is attached, a rotatable housing 16 which rotates relative to the fixed housing 12 by the hydraulic motor 14, bearings 25, 26 which are provided between the outer periphery of the fixed housing 12 and the inner periphery of the rotatable housing 16 and which rotatably support the rotatable housing 16, and a nut member 27 which is screwed into a male threaded portion 12D provided on the outer periphery of the fixed housing 12 and abuts against the bearing 25 to pressurize the bearings 25, 26, and the nut member 27 comprises a bearing abutment portion 27B which abuts against the axial end face 25D of the bearing 25 when screwed into the male threaded portion 12D of the fixed housing 12, and a cylindrical portion 27C which protrudes axially from the bearing abutment portion 27B and is inserted into the inner periphery of the bearing 25.

[0039] According to this configuration, the nut member 27 is screwed onto the male threaded portion 12D of the fixed housing 12 (bearing mounting portion 12B), and the cylindrical portion 27C of the nut member 27 is fitted onto the inner periphery of the inner ring 25A in a state where the bearing abutment portion 27B of the nut member 27 is abutted against the axial end face 25D of the inner ring 25A constituting the bearing 25. As a result, the axial dimension of the traveling device 11 can be shortened by the amount of overlap of the cylindrical portion 27C with the inner ring 25A (axial dimension L of the cylindrical portion 27C). Moreover, a uniform female threaded portion 27A having a sufficient length is formed on the inner periphery of the bearing abutment portion 27B and the cylindrical portion 27C of the nut member 27. As a result, the fastening force of the nut member 27 screwed onto the male threaded portion 12D of the fixed housing 12 is ensured, so that the bearings 25, 26 can be appropriately pressurized by the nut member 27.

[0040] In the embodiment, the inner ring 25A of the bearing 25 fits into the outer peripheral surface of the fixed housing 12 provided with the male thread portion 12D, and the outer peripheral surface 27D of the cylindrical portion 27C of the nut member 27 fits into the inner peripheral surface 25E of the inner ring 25A of the bearing 25. According to this configuration, the inner ring 25A of the bearing 25 fits into the outer peripheral surface of the fixed housing 12 and the outer peripheral surface 27D of the cylindrical portion 27C of the nut member 27, so that the bearing 25 can be stably held between the fixed housing 12 and the rotating housing 16.

[0041] Next, Fig. 5 shows a second embodiment of the present invention. The feature of this embodiment is that, when the nut member is screwed onto the male thread of the fixed housing, the outer peripheral surface of the cylindrical portion of the nut member fits over the entire inner peripheral surface of the inner ring of the bearing. In this embodiment, the same components as those in the first embodiment are given the same reference numerals, and their description will be omitted.

[0042] In the drawing, the nut member 31, similar to the nut member 27 according to the first embodiment, is screwed into the male thread portion 12D formed on the bearing attachment portion 12B of the fixed housing 12. The nut member 31 abuts against an axial end face 25D of an inner ring 25A constituting the bearing 25, and presses the inner ring 25A toward the bearing 26, thereby pressurizing the two bearings 25, 26 in the axial direction.

[0043] The nut member 31 is formed in a stepped cylindrical shape by a female threaded portion 31A, a bearing abutment portion 31B, and a cylindrical portion 31C. The female threaded portion 31A is formed on the inner peripheral surface of the nut member 31, and is screwed into the male threaded portion 12D of the fixed housing 12 (bearing attachment portion 12B). The bearing abutment portion 31B faces the bearing 25 in the axial direction, and abuts against an end surface 25D of the inner ring 25A of the bearing 25 in a state in which the female threaded portion 31A is screwed into the male threaded portion 12D of the fixed housing 12. The cylindrical portion 31C protrudes in the axial direction from the end surface of the bearing abutment portion 31B on the bearing 25 side, and the outer peripheral surface 31D of the cylindrical portion 31C fits into an inner peripheral surface 25E of the inner ring 25A of the bearing 25.

[0044] Here, the axial dimension (projection length) L2 of the cylindrical portion 31C projecting from the bearing abutment portion 31B is set to be larger than the axial dimension B of the inner ring 25A of the bearing 25. The axial dimension of the male thread portion 12D of the fixed housing 12 is also set to a length corresponding to the axial dimension of the female thread portion 31A. As a result, when the female thread portion 31A of the nut member 31 is screwed into the male thread portion 12D of the fixed housing 12, the outer peripheral surface 31D of the cylindrical portion 31C is configured to fit into the entire inner peripheral surface 25E of the inner ring 25A of the bearing 25. Moreover, since a large length (engagement length) of the screwing of the female thread portion 31A and the male thread portion 12D can be secured, the axial dimension C of the bearing abutment portion 31B is set to be smaller than the bearing abutment portion 27B of the nut member 27 according to the first embodiment.

[0045] The traveling device 11 according to this embodiment includes the nut member 31 as described above, and when assembling the mounting base portion 17 of the rotatable housing 16 to the fixed housing 12 via the bearings 25, 26, first, the inner ring 26A of the bearing 26 is fitted into the bearing mounting portion 12B of the fixed housing 12. Next, the bearing mounting portion 17A of the mounting base portion 17 is fitted into the outer ring 26B of the bearing 26.

[0046] Meanwhile, with the cylindrical portion 31C of the nut member 31 fitted into the inner ring 25A of the bearing 25, the female threaded portion 31A of the nut member 31 is screwed into the male threaded portion 12D of the fixed housing 12, and the nut member 31 is tightened together with the bearing 25. This allows the bearings 25, 26 to rotatably support the mounting base portion 17 with the bearings 25, 26 being appropriately pressurized in the axial direction. Then, by engaging the tip of the anti-rotation member 28 attached to the bearing abutment portion 31B of the nut member 31 with the engagement groove 12E formed in the fixed housing 12 (bearing mounting portion 12B), the nut member 31 is prevented from rotating, and the bearings 25, 26 can be maintained in a pressurized state.

[0047] The traveling device 11 according to the second embodiment has the nut member 31 as described above, and in this embodiment as well, the female threaded portion 31A of the nut member 31 is screwed into the male threaded portion 12D of the fixed housing 12 (bearing attachment portion 12B), and the cylindrical portion 31C of the nut member 31 is fitted to the inner peripheral side of the inner ring 25A with the bearing abutment portion 31B of the nut member 31 abutting against the end face 25D of the inner ring 25A of the bearing 25. In this way, by overlapping the cylindrical portion 31C with the inner ring 25A, the axial dimension of the traveling device 11 can be shortened.

[0048] Moreover, in this embodiment, when the female threaded portion 31A of the nut member 31 is screwed into the male threaded portion 12D of the fixed housing 12, the outer peripheral surface 31D of the cylindrical portion 31C fits over the entire inner peripheral surface 25E of the inner ring 25A of the bearing 25. This ensures a large length (engagement length) over which the female threaded portion 31A and the male threaded portion 12D are screwed together, so that the axial dimension C of the bearing abutment portion 31B can be set smaller than that of the bearing abutment portion 27B of the nut member 27 according to the first embodiment. As a result, the axial dimension of the traveling device 11 can be further shortened by the amount that the axial dimension C of the bearing abutment portion 31B is reduced.

[0049] In the first embodiment, the outer peripheral surface 27D of the cylindrical portion 27C of the nut member 27 is fitted into the inner peripheral surface 25E of the inner ring 25A constituting the bearing 25 in a transition fit or tight fit state. However, the present invention is not limited to this, and may be configured as a nut member 27' according to a modified example shown in Fig. 6. That is, the nut member 27' may be configured to include the female thread portion 27A, the bearing abutment portion 27B, and the cylindrical portion 27C', and the cylindrical portion 27C' may be inserted with a radial gap 32 without being fitted into the inner peripheral surface 25E of the inner ring 25A of the bearing 25.

[0050] In addition, in the embodiment, a configuration is illustrated in which a three-stage planetary gear reduction mechanism 21, 22, 23 is provided within the rotating housing 16, but the present invention is not limited to this, and the configuration may also be one in which, for example, a two-stage or less, or four-stage or more, planetary gear reduction mechanism is provided. [Explanation of symbols]

[0051] 11 Running gear 12 Fixed housing 12D Male thread 14 Hydraulic motor (rotation source) 16 Rotating housing 25,26 Bearings 25A Inner ring 27, 27', 31 Nut member 27B,31B Bearing contact part 27C,27C′,31C Cylindrical part

Claims

1. a stationary housing to which a rotation source is attached; a rotating housing that is rotated relative to the fixed housing by the rotation source; a bearing provided between an outer periphery of the fixed housing and an inner periphery of the rotating housing to rotatably support the rotating housing; a nut member that is screwed into a male thread portion provided on an outer periphery of the fixed housing and abuts against the bearing to pressurize the bearing, A traveling device characterized in that the nut member comprises a bearing abutment portion that abuts against the axial end face of the bearing when screwed into the male threaded portion of the fixed housing, and a cylindrical portion that protrudes axially from the bearing abutment portion and is inserted into the inner side of the bearing.

2. an inner ring of the bearing is fitted to an outer peripheral surface of the fixed housing on which the male thread portion is provided, 2. The traveling device according to claim 1, wherein an outer circumferential surface of the cylindrical portion of the nut member is fitted into an inner circumferential surface of an inner ring of the bearing.

3. The cylindrical portion of the nut member has an axial dimension larger than an inner ring of the bearing, 3. The traveling device according to claim 2, wherein an outer circumferential surface of the cylindrical portion fits over an entire inner circumferential surface of an inner ring of the bearing when the nut member is screwed onto the male threaded portion of the fixed housing.

Images