Patent Description:
There is known a dump truck as a large-sized transporter vehicle for transporting crushed stones, earth and sand, and the like excavated in a mine or the like. The dump truck is provided with a vehicle body in which vehicle wheels are arranged, and a vessel (loading platform) disposed to be capable of lifting/tilting on a frame of the vehicle body. The vehicle body of the dump truck is provided with a vehicle drive unit for driving left and right front wheels and left and right rear wheels. The dump truck travels and moves to a desired transport site by the vehicle drive unit in a state where cargoes of crushed stones or the like are loaded on the vessel.

Here, a vehicle drive unit in the dump truck includes a spindle having one axial side attached to the vehicle body, a wheel that is positioned in the other axial side of the spindle to be disposed on an outer peripheral side of the spindle and on which a tire is attached, wheel bearings that rotatably support the wheel in relation to the spindle, an electric motor located on the axial one side of the spindle, a shaft connected to an output shaft of the electric motor, a planetary gear reduction mechanism that decelerates rotation of the shaft, which is transmitted to the wheel, and a shaft bearing that rotatably supports the shaft in relation to the spindle.

Here, the shaft connected to the output shaft of the electric motor is rotatably supported by the shaft bearing. This shaft bearing is attached through a bearing retainer to an inner peripheral surface side of the spindle. That is, an attaching flange in a disc shape is disposed on an inner peripheral surface of the spindle to project to a radially inner side. The bearing retainer is attached to this attaching flange using bolts or the like. The shaft bearing is supported by the bearing retainer (Patent Document <NUM>).

Incidentally, in the large-sized dump truck used in the mine or the like, not only the weight of the vehicle body is large but also the weight of the cargoes loaded on the vessel is also large. As a result, large loads act on the spindle supporting the wheel, to which the tire is attached, in relation to the vehicle body by the weight of the vehicle body and the weight of the cargoes. A dump truck tire on the market has an upper limit to an outer radial dimension. Therefore, the dump truck large in vehicle body weight generally responds to an increase on the vehicle body weight by increasing a width dimension of the tire. Thereby, since an axial dimension of the spindle increases and a bending load acting on the spindle also increases, it is necessary to enhance strength of the spindle.

In general, in the dump truck according to the conventional technology the spindle of the vehicle drive unit is formed by casting. Therefore, in the dump truck large in vehicle body weight it is preferable to form the spindle by forging for enhancing the strength of the spindle. In this case, the forged spindle has the strength higher than the cast spindle and further, can be formed in a compact manner. Therefore, it is possible to trim the weight of the spindle. Accordingly, the dump truck provided with the forged spindle can increase capacities of the cargoes by an amount corresponding to a reduction in weight of the vehicle body to enhance workability at the time of transporting the cargoes. Patent Document <NUM> discloses a travel assembly suited for arrangement on a vehicle such as a mining dump truck, which is provided with a travel motor, a planetary speed reduction mechanism for transmitting rotation of the travel motor at a lower rotational speed, a spindle forming an axle, and a wheel supported on the spindle via a tapered roller bearing and rotatable by the planetary speed reduction mechanism.

Incidentally, it is not realistic to manufacture the spindle by stamping forging using a huge forging die. Therefore, in a case of forming a spindle large in shape by forging, the spindle is manufactured by free forging using a core bar. In a case of forming a cylindrical spindle by free forging, in a state where a core bar is caused to be fitted in an inner peripheral surface side of a material (forging material) of the hollow spindle, it is necessary to apply the forging to an outer peripheral side of the material.

However, in a case of forming the spindle by the free forging using the core bar, it is necessary to remove the core bar from the inner peripheral surface side of the forged spindle. Therefore, a complicated concavity and convexity shape cannot be formed on the inner peripheral surface of the spindle. In this way, even in a case of trying to form the spindle by forging for enhancing the strength of the spindle, there is posed a problem that it is difficult to dispose an attaching flange for attaching a bearing retainer on the inner peripheral surface of the spindle. It should be noted that there is a method in which a spindle having a thick cylindrical portion is in advance formed by forging, and after that, the attaching flange is formed by cutting the inner peripheral surface of the thick cylindrical portion. However, in this method, a yield ratio of the material is low and cutting work of the material becomes necessary in addition to the forging work, and as a result, there is a problem that a manufacturing cost thereof increases.

An aspect of the present invention has an object of providing a dump truck in which a retainer composed of a material different from a spindle is disposed on an inner peripheral surface side of the spindle to which a shaft bearing can be attached using this retainer.

The object is solved as set out in the appended set of claims. In particular, a dump truck is provided with a vehicle drive unit comprising a cylindrical spindle an axial one side of which is attached to a vehicle body and on an inner peripheral surface at an axial other side of which a female spline portion is formed, a wheel that is positioned in the axial other side of the spindle to be disposed on an outer peripheral side of the spindle and on which a tire is attached, wheel bearings that are arranged between the spindle and the wheel to rotatably support the wheel in relation to the spindle, a rotation source located on the axial one side of the spindle, a shaft that is connected to an output shaft of the rotation source, is axially inserted in an inner peripheral surface side of the spindle and projects from the other end side of the spindle, a planetary gear reduction device that is positioned on the axial other side of the spindle to be disposed between the shaft and the wheel and is provided with a plurality of planetary gears rotatably supported by a carrier spline-coupled to the female spline portion of the spindle, and a shaft bearing that is positioned closer to the axial one side than the carrier of the planetary gear reduction device to be disposed on the inner peripheral surface side of the spindle and rotatably supports the shaft in relation to the spindle.

The aspect of the present invention is characterized in that on the inner peripheral surface side of the spindle, a retainer is disposed to be positioned, the retainer being formed of a material different from the spindle and retaining the shaft bearing, and the retainer is provided thereon with a male spline portion spline-coupled to the female spline portion of the spindle.

According to the aspect of the present invention, the male spline portion of the retainer is spline-coupled to the female spline portion of the spindle, whereby it is possible to retain the retainer at the inner peripheral surface side of the spindle with an appropriate degree of freedom (gap) in the axial direction and in the rotational direction in a locking state. Accordingly, without disposing the attaching flange or the like, the shaft bearing can be attached to the inner peripheral surface side of the spindle.

Hereinafter, a dump truck according to an embodiment of the present invention will be in detail explained with reference to the accompanying drawings.

In the figure, a dump truck <NUM> is provided with a vehicle body <NUM> having a strong frame structure. Left and right front wheels <NUM> are rotatably arranged on the front side of the vehicle body <NUM>, and left and right rear wheels <NUM> are rotatably arranged on the rear side of the vehicle body <NUM> (in any case, the left wheel only is shown in the figure). The left and right front wheels <NUM> form part of steered wheels that are steered (for a steering operation) by an operator of the dump truck <NUM>. A front-wheel side suspension 3A formed of a hydraulic shock absorber and the like is disposed between the vehicle body <NUM> and the left and right front wheels <NUM>.

The left and right rear wheels <NUM> form part of drive wheels of the dump truck <NUM> and are driven and rotated by an after-mentioned vehicle drive unit <NUM>. As shown in <FIG> and <FIG>, the rear wheel <NUM> includes dual tires of an inner tire 4A and an outer tire 4A in the axial direction, and an after-mentioned wheel <NUM> on which each of the tires 4A is attached. A rear-wheel side suspension 4B formed of a hydraulic shock absorber and the like are arranged between the vehicle body <NUM> and the left and right rear wheels <NUM>.

A vessel (loading platform) <NUM> is mounted on the vehicle body <NUM> to be capable of lifting and tilting. The vessel <NUM> is formed, for example, as a large-sized container having an entire length of <NUM> to <NUM> meters for loading a large volume of heavy baggage such as crushed stones. A rear-side bottom portion of the vessel <NUM> is coupled to a rear end side of the vehicle body <NUM> through a coupling pin <NUM> and the like to be capable of lifting and tilting (inclination-rotating). In addition, a protector 5A is integrally disposed on a front-side top portion of the vessel <NUM> in such a manner as to cover an after-mentioned cab <NUM> from the upper side.

The cab <NUM> is disposed in the front portion of the vehicle body <NUM> to be positioned under the protector 5A disposed on the vessel <NUM>. The cab <NUM> forms part of an operator's room which an operator of the dump truck <NUM> gets in and off. An operator's seat, an activation switch, an accelerator pedal, a brake pedal, a handle for steering, a plurality of operating levers (none of them is shown in the figure), and the like are arranged inside the cab <NUM>. The protector 5A of the vessel <NUM> protects the cab <NUM>, for example, from flying stones such as rocks by covering the cab <NUM> as a whole from the upper side. In addition, the protector 5A of the vessel <NUM> has a function of protecting the operator within the cab <NUM> at the falling-down or the like of the dump truck <NUM>.

An engine <NUM> is positioned under the cab <NUM> to be disposed on the front side of the vehicle body. The engine <NUM> is configured by, for example, a large-sized diesel engine, and drives an on-board power generator, a hydraulic pump as a hydraulic source (none of them is shown in the figure) and the like for rotation. Pressurized oil delivered from the hydraulic pump is supplied to after-mentioned hoist cylinders <NUM>, a steering cylinder for power steering (not shown in the figure) and the like.

The hoist cylinder <NUM> is disposed to be capable of expanding and contracting in the upper-lower direction between the vehicle body <NUM> and the vessel <NUM>. The hoist cylinder <NUM> is positioned between the front wheel <NUM> and the rear wheel <NUM> to be located on both of left and right sides of the vehicle body <NUM> (the left wheel only is shown in the figure). Each of the hoist cylinders <NUM> expands and contracts in the upper-lower direction by delivery/suction of the pressurized oil from/to the hydraulic pump to lift and tilt (inclination-rotate) the vessel <NUM> around the coupling pin <NUM>.

An axle housing <NUM> for the rear wheel <NUM> is disposed on a rear lower side of the vehicle body <NUM> and forms part of the vehicle body <NUM>. The axle housing <NUM> is formed as a cylindrical body which extends in the left-right direction between the left and right rear wheels <NUM>. The axle housing <NUM> is attached through the rear-wheel side suspension 4B to the rear side of the vehicle body <NUM>. The after-mentioned spindle <NUM> is fixed to each of both end sides of the axle housing <NUM> in the left-right direction.

The vehicle drive unit <NUM> is disposed on each of the left and right rear wheels <NUM> of the dump truck <NUM>. As shown in <FIG>, the vehicle drive unit <NUM> includes the spindle <NUM>, a wheel <NUM>, wheel bearings <NUM>, <NUM>, an electric motor <NUM>, a shaft <NUM>, a planetary gear reduction device <NUM>, a retainer <NUM>, and a shaft bearing <NUM>, which will be described later. The vehicle drive unit <NUM> decelerates rotation of the electric motor <NUM> by the planetary gear reduction device <NUM> and drives the rear wheels <NUM> as drive wheels of the dump truck <NUM> by large rotational torque. It should be noted that the vehicle drive units <NUM> arranged respectively in the left and right rear wheels <NUM> are configured with the same structure. Therefore, hereinafter an explanation will be made of the vehicle drive unit <NUM> disposed in the left rear wheel <NUM>.

The spindle <NUM> is disposed on the axial other side of the axle housing <NUM>. The spindle <NUM> is formed in a stepped cylindrical shape axially extending within the after-mentioned wheel <NUM>. The spindle <NUM> is configured by a large-diameter cylindrical portion 12A positioned at the axial one side, an intermediate cylindrical portion 12B positioned at the axial intermediate part and a small-diameter cylindrical portion 12C positioned at the axial other side. The large-diameter cylindrical portion 12A is formed in a cup shape to gradually reduce in diameter toward the intermediate cylindrical portion 12B. An axial one end of the large-diameter cylindrical portion 12A is fixed on an end edge portion of the axle housing <NUM> using a plurality of bolts <NUM>. The small-diameter cylindrical portion 12C is formed in a cylindrical shape to be smaller in diameter than the intermediate cylindrical portion 12B and is located on an inner peripheral surface side of an after-mentioned wheel attaching cylinder <NUM>. The small-diameter cylindrical portion 12C of the spindle <NUM> rotatably supports the wheel attaching cylinder <NUM> through the wheel bearings <NUM>,<NUM>.

Here, the spindle <NUM> is formed by free forging using a core bar, for example and has a strength larger than the spindle formed by casting. The spindle <NUM> has an outer peripheral side on which a brake attaching portion 12D positioned in a boundary part between the large-diameter cylindrical portion 12A and the intermediate cylindrical portion 12B and an annular stepped portion 12E positioned in a boundary part between the intermediate cylindrical portion 12B and the small-diameter cylindrical portion 12C are integrally formed. An annular flange plate <NUM> made of a material different from the spindle <NUM> is fixed on the brake attaching portion 12D by means of welding or the like. An after-mentioned brake housing 41A is fixed on the flange plate <NUM>. A motor attaching seat 12F is formed on an axial one end of the large-diameter cylindrical portion 12A, and the after-mentioned electric motor <NUM> is attached to the motor attaching seat 12F.

On the other hand, an axial other end (front end) of the small-diameter cylindrical portion 12C is formed as an open end, and a female spline portion <NUM> is formed on an inner peripheral surface of the small-diameter cylindrical portion 12C at the axial other side. A male spline portion 39B of an after-mentioned carrier <NUM> is spline-coupled to the female spline portion <NUM>, and a male spline portion 42E of the after-mentioned retainer <NUM> is spline-coupled to the female spline portion <NUM>. A retainer fitting portion <NUM> is disposed on an inner peripheral surface of the small-diameter cylindrical portion 12C adjacent to the female spline portion <NUM>. A cylindrical outer peripheral surface 42D of the retainer <NUM> is loosely fitted in the retainer fitting portion <NUM>. A one-side annular groove 12J is formed over an entire circumference on an inner peripheral surface, which is closer to an axial one side (the intermediate cylindrical portion 12B-side) than the female spline portion <NUM>, of the small-diameter cylindrical portion 12C (refer to <FIG>). An after-mentioned stop ring <NUM> is attached to the one-side annular groove 12J. In addition, another-side annular groove <NUM> is formed over an entire circumference on a section, which is separated closer to the axial other side than the one-side annular groove 12J, of the female spline portion <NUM> formed on the small-diameter cylindrical portion 12C (refer to <FIG>). An after-mentioned stop ring <NUM> is attached to the other-side annular groove <NUM>.

The wheel <NUM> is positioned in the axial other side of the spindle <NUM> to be disposed on the outer peripheral side of the spindle <NUM>. The tires 4A of the rear wheel <NUM> are attached to the wheel <NUM>. The wheel <NUM> is schematically configured by a cylindrical rim 15A extending in the left-right direction, and the wheel attaching cylinder <NUM> fixed and disposed on the inner peripheral surface side of the rim 15A. The two tires 4A are arranged in parallel on the outer periphery side of the rim 15A.

The wheel attaching cylinder <NUM> is rotatably disposed on the outer peripheral side of the spindle <NUM>. The rim 15A of the wheel <NUM> is removably attached to the outer peripheral side of the wheel attaching cylinder <NUM> by means of press fitting or the like. The wheel attaching cylinder <NUM> is formed as a cylindrical body having a hollow cylindrical portion 16A and an extending cylindrical portion 16B. The hollow cylindrical portion 16A is rotatably supported through the wheel bearings <NUM>, <NUM> on the spindle <NUM> (small-diameter cylindrical portion 12C). The extending cylindrical portion 16B axially extends toward an after-mentioned internal gear <NUM> from an outer peripheral side end portion of the hollow cylindrical portion 16A.

The wheel bearings <NUM>, <NUM> are arranged between the small-diameter cylindrical portion 12C of the spindle <NUM> and the wheel attaching cylinder <NUM> (hollow cylindrical portion 16A) of the wheel <NUM>. The wheel bearings <NUM>, <NUM> each are configured using, for example, an identical conical bearing or the like, and rotatably support the wheel <NUM> on the outer peripheral side of the spindle <NUM>. Here, an outer race of the one wheel bearing <NUM> is axially positioned by the hollow cylindrical portion 16A of the wheel attaching cylinder <NUM>. An inner race of the wheel bearing <NUM> is axially positioned by an annular bearing retainer <NUM> abutting on a stepped portion 12E of the spindle <NUM>. An outer race of the other wheel bearing <NUM> is axially positioned by the hollow cylindrical portion 16A of the wheel attaching cylinder <NUM>. An inner race of the other wheel bearing <NUM> is axially positioned by an annular bearing retainer <NUM> fixed on an open end of the small-diameter cylindrical portion 12C of the spindle <NUM>.

The electric motor <NUM> as the rotation source is positioned within the axle housing <NUM> to be disposed on the axial one side of the spindle <NUM>. A plurality of attaching flanges 21A are arranged to a casing of the electric motor <NUM>, and the attaching flanges 21A are removably arranged to the motor attaching seat 12F of the spindle <NUM> using bolts or the like. In the electric motor <NUM>, a rotor (not shown in the figure) rotates in the forward or backward direction by supply of electric power from the power generator (not shown in the figure) mounted on the vehicle body <NUM>, and rotation of the rotor is outputted by an output shaft 21B. A base end of the output shaft 21B is connected to be integral with the rotor of the electric motor <NUM>, and a tip end of the output shaft 21B projects to an exterior from the casing of the electric motor <NUM>. The shaft <NUM> is connected coaxially to a tip end of the output shaft 21B.

The shaft <NUM> is connected to the output shaft 21B of the electric motor <NUM>. The shaft <NUM> is formed by a single bar element inserted axially in the inner peripheral surface side of the spindle <NUM> (small-diameter cylindrical portion 12C). The shaft <NUM> inputs the rotation of the output shaft 21B of the electric motor <NUM> to the planetary gear reduction device <NUM>. An axial one side (a base end side) of the shaft <NUM> is connected (spline-coupled) to the output shaft 21B of the electric motor <NUM>. An axial other side (a tip end side) of the shaft <NUM> projects from the axial other end of the spindle <NUM> (the open end of the small-diameter cylindrical portion 12C) toward the planetary gear reduction device <NUM>. An after-mentioned sun gear <NUM> is attached to the tip end of the shaft <NUM>. In addition, a bearing attaching portion 22A in which a step is axially formed is disposed on an axial intermediate section of the shaft <NUM>. The shaft bearing <NUM> is attached on the bearing attaching portion 22A. The axial intermediate section of the shaft <NUM> is rotatably supported on the spindle <NUM> (small-diameter cylindrical portion 12C) by the shaft bearing <NUM>.

An outer drum <NUM> forms part of the wheel attaching cylinder <NUM> together with the internal gear <NUM>. The outer drum <NUM> is formed in a stepped cylindrical shape having an annular flange portion 23A. The outer drum <NUM> sandwiches the internal gear <NUM> with an end edge part of the extending cylindrical portion 16B constituting the wheel attaching cylinder <NUM>. A plurality of long bolts <NUM> inserted in the flange portion 23A of the outer drum <NUM> and the internal gear <NUM> are threaded in the end edge part of the extending cylindrical portion 16B. Thereby, the internal gear <NUM> is fixed between the extending cylindrical portion 16B of the wheel attaching cylinder <NUM> and the outer drum <NUM>.

The planetary gear reduction device <NUM> is positioned in the axial other side of the spindle <NUM> to be disposed between the wheel attaching cylinder <NUM> of the wheel <NUM> and the shaft <NUM>. The planetary gear reduction device <NUM> is configured by a first-stage planetary gear reduction mechanism <NUM> and a second-stage planetary gear reduction mechanism <NUM>. The planetary gear reduction device <NUM>, by transmission of the rotation of the electric motor <NUM> (output shaft 21B) through the shaft <NUM>, decelerates the rotation of the electric motor <NUM> by two stages, which is transmitted to the wheel attaching cylinder <NUM>. Therefore, the wheel <NUM> is driven and rotated together with the tires 4A of the rear wheel <NUM> by a large rotational force (torque).

The first-stage planetary gear reduction mechanism <NUM> is configured by the sun gear <NUM> spline-coupled to the tip end of the shaft <NUM>, a plurality (one piece only is shown in the figure) of planetary gears <NUM> and the carrier <NUM>. The plurality of planetary gears <NUM> are engaged to the sun gear <NUM> and a ring-shaped internal gear <NUM>. The carrier <NUM> rotatably supports the plurality of planetary gears <NUM> through support pins <NUM>.

The carrier <NUM> is removably fixed at its outer peripheral side on an end surface at the axial other side of the outer drum <NUM> united with the wheel attaching cylinder <NUM> by a plurality of bolts 31A. A disk-shaped lid plate <NUM> is removably attached to the carrier <NUM> at the inner peripheral surface side using bolts or the like. The lid plate <NUM> is removed from the carrier <NUM>, for example, at the time of maintenance or inspection of engaging portions between the sun gear <NUM> and the planetary gears <NUM>.

The ring-shaped internal gear <NUM> is formed by using a ring gear to surround the sun gear <NUM> and the plurality of planetary gears <NUM> from a radial outside, and is relatively rotatably located through a radial gap to an inner peripheral surface of the outer drum <NUM>. Internal teeth are formed on an inner peripheral surface of the internal gear <NUM> over an entire circumference thereof, and the plurality of planetary gears <NUM> are all the time engaged to the internal teeth. The rotation of the internal gear <NUM> is transmitted through a coupling <NUM> to the second-stage planetary gear reduction mechanism <NUM>.

As the sun gear <NUM> is rotated integrally with the shaft <NUM> by the electric motor <NUM>, the first-stage planetary gear reduction mechanism <NUM> converts the rotation of the sun gear <NUM> into a rotating movement of each of the planetary gears <NUM> on its axis and a revolving movement thereof. Further, the rotating movement on its axis (rotation) of each of the planetary gears <NUM> is transmitted to the internal gear <NUM> and the rotation of the internal gear <NUM> is transmitted through the coupling <NUM> to the second-stage planetary gear reduction mechanism <NUM>. On the other hand, the revolving movement of each of the planetary gears <NUM> is transmitted to the outer drum <NUM> as rotation of the carrier <NUM>. In this case, the outer drum <NUM> is united with the wheel attaching cylinder <NUM> and the internal gear <NUM>. Therefore, the revolving movement of each of the planetary gears <NUM> is controlled to the rotation synchronized with the internal gear <NUM>.

The coupling <NUM> is disposed in a position between the first-stage planetary gear reduction mechanism <NUM> and the second-stage planetary gear reduction mechanism <NUM> and rotates integrally with the first-stage internal gear <NUM>. An outer peripheral side of the coupling <NUM> is spline-coupled to the first-stage internal gear <NUM>. An inner peripheral side of the coupling <NUM> is spline-coupled to an after-mentioned second-stage sun gear <NUM>. The coupling <NUM> transmits rotation of the first-stage internal gear <NUM> to the second-stage sun gear <NUM> to rotate the sun gear <NUM> integrally with the first-stage internal gear <NUM>.

The second-stage planetary gear reduction mechanism <NUM> is configured by the cylindrical sun gear <NUM> that is located on the outer peripheral side of the shaft <NUM>, a plurality of planetary gears <NUM> (only one piece of them is shown in the figure), and the cylindrical carrier <NUM>. The plurality of planetary gears <NUM> are engaged to the sun gear <NUM> and the ring-shaped internal gear <NUM>. The carrier <NUM> rotatably supports the plurality of planetary gears <NUM> through support pins <NUM>.

Here, the second-stage internal gear <NUM> is formed using a ring gear surrounding the sun gear <NUM> and the plurality of planetary gears <NUM> from a radial outside. The internal gear <NUM> is integrally fixed between the wheel attaching cylinder <NUM> (the extending cylindrical portion 16B) and the outer drum <NUM> using long bolts <NUM>. Internal teeth are formed on the inner peripheral surface of the internal gear <NUM> over an entire circumference thereof, and the plurality of planetary gears <NUM> are engaged to the internal teeth.

A cylindrical projecting portion 39A is formed in the center part of the second-stage carrier <NUM> integrally therewith to project toward the spindle <NUM>. The male spline portion 39B is formed on an outer peripheral surface of the cylindrical projecting portion 39A at an axial one side (at the spindle <NUM>-side) thereof. The male spline portion 39B of the carrier <NUM> is spline-coupled to the female spline portion <NUM> of the spindle <NUM> (small-diameter cylindrical portion 12C). Accordingly, the carrier <NUM> is configured to be incapable of rotating relative to the spindle <NUM>.

Therefore, the revolving movement of the respective planetary gear <NUM> (rotation of the carrier <NUM>) is restrained by the spindle <NUM>. As the sun gear <NUM> is put in rotation integrally with the coupling <NUM>, the second-stage planetary gear reduction mechanism <NUM> converts the rotation of the sun gear <NUM> into rotation of the planetary gear <NUM> on its axis. The rotation of the planetary gear <NUM> on its axis is transmitted to the internal gear <NUM>, which causes the internal gear <NUM> to be decelerated for rotation. Therefore, the rotational torque of large output obtained by speed reduction of two stages through the first-stage planetary gear reduction mechanisms <NUM> and the second-stage planetary gear reduction mechanisms <NUM> is transmitted to the wheel attaching cylinder <NUM> to which the internal gear <NUM> is fixed, whereby the rear wheel <NUM> is driven for rotation.

A brake hub <NUM> is attached to the wheel attaching cylinder <NUM>. The brake hub <NUM> is formed as a cylindrical body axially extending between the wheel attaching cylinder <NUM> and an after-mentioned wet brake device <NUM>. An axial other side of the brake hub <NUM> (the wheel attaching cylinder <NUM>-side) is fixed to a hollow cylindrical portion 16A of the wheel attaching cylinder <NUM> by bolts 40A. An axial one side of the brake hub <NUM> radially faces an outer peripheral surface of the intermediate cylindrical portion 12B of the spindle <NUM>.

The wet brake device <NUM> is disposed through the brake hub <NUM> between the spindle <NUM> and the wheel attaching cylinder <NUM>. The wet brake device <NUM> is configured by a wet multi-plate type of hydraulic brake and applies braking forces to the wheel attaching cylinder <NUM>. The wet brake device <NUM> has a brake housing 41A. The brake housing 41A is attached to the flange plate <NUM> fixed to the brake attaching portion 12D of the spindle <NUM>. A plurality of non-rotation-side brake plates 41B and a plurality of rotation-side brake plates 41C are arranged within the brake housing 41A. The plurality of non-rotation-side brake plates 41B and the plurality of rotation-side brake plates 41C are arranged to axially alternately overlap with each other. An outer peripheral side of the non-rotation-side brake plate 41B is engaged to the brake housing 41A. An inner peripheral side of the rotation-side brake plate 41C is engaged to the brake hub <NUM>. A brake movable element 41D is disposed within the brake housing 41A. The brake movable element 41D axially moves by a brake liquid pressure to cause frictional contact between the plurality of non-rotation-side brake plates 41B and the plurality of rotation-side brake plates 41C.

The brake liquid pressure is supplied to an oil chamber of the brake housing 41A in response to a depressing operation of a brake pedal (not shown in the figure). Thereby, the wet brake device <NUM> axially moves the brake movable element 41D. The brake movable element 41D causes the frictional contact between the plurality of non-rotation-side brake plates 41B and the plurality of rotation-side brake plates 41C. Thereby, braking forces are applied to the wheel attaching cylinder <NUM> on which the brake hub <NUM> is fixed.

Next, an explanation will be made of a retainer used in the present embodiment with reference to <FIG>.

The retainer <NUM> is disposed on the inner peripheral surface side of the small-diameter cylindrical portion 12C configuring the spindle <NUM>. The retainer <NUM> retains the shaft bearing <NUM> within the small-diameter cylindrical portion 12C. The retainer <NUM> is made of a material different (different element) from the spindle <NUM> and is formed in a stepped cylindrical shape as a whole. A shaft insertion hole 42A formed of a stepped hole and a bearing fitting hole 42B are formed coaxially on an inner peripheral surface side of the retainer <NUM>. The shaft <NUM> is inserted in the shaft insertion hole 42A. The bearing fitting hole 42B is formed of a bottomed hole, in which the shaft bearing <NUM> is attached. An annular groove 42C is formed on an inner peripheral surface of the bearing fitting hole 42B over an entire circumference thereof. An after-mentioned stop ring <NUM> is attached on the annular groove 42C.

An axial one side (electric motor <NUM>-side) of the retainer <NUM> is formed as the cylindrical outer peripheral surface 42D. The cylindrical outer peripheral surface 42D is, for example, loosely fitted in the retainer fitting portion <NUM> of the spindle <NUM>. The male spline portion 42E is formed on an axial other side (planetary gear reduction device <NUM>-side) of the retainer <NUM>. The male spline portion 42E is spline-coupled to the female spline portion <NUM> formed on the small-diameter cylindrical portion 12C of the spindle <NUM>. It should be noted that it is not necessary that the groove number of the male spline portion 42E is equal to that of the female spline portion <NUM>. A concavity groove 42F is disposed on an axial intermediate part of the retainer <NUM> over an entire circumference thereof, and the concavity groove 42F partitions the cylindrical outer peripheral surface 42D and the male spline portion 42E therebetween. The concavity groove 42F has an outer diameter dimension shorter than the cylindrical outer peripheral surface 42D and is configured to function as a back clearance to a cutting blade at the time of forming the male spline portion 42E.

The retainer <NUM> is configured such that in a state where the cylindrical outer peripheral surface 42D is fitted in the retainer fitting portion <NUM> of the spindle <NUM> (small-diameter cylindrical portion 12C), the male spline portion 42E is spline-coupled to the female spline portion <NUM>. As a result, the retainer <NUM> made of a material different from the spindle <NUM> is attached within the small-diameter cylindrical portion 12C of the spindle <NUM> to be in a locking state on a condition of keeping an appropriate degree of freedom (gap) in the axial direction and in the rotational direction. At this time, the cylindrical outer peripheral surface 42D of the retainer <NUM> is loosely fitted in the retainer fitting portion <NUM> of the spindle <NUM>, and the retainer <NUM> is positioned in a radial direction of the spindle <NUM>. One end surface <NUM> positioned in the axial one side of the retainer <NUM> abuts on an after-mentioned stop ring <NUM>, and the other end surface <NUM> positioned in the axial other side of the retainer <NUM> abuts on an after-mentioned stop ring <NUM>.

The pair of stop rings <NUM>, <NUM> are arranged on an inner peripheral surface of the small-diameter cylindrical portion 12C configuring the spindle <NUM>. The stop rings <NUM>, <NUM> each are configured by a stop ring for hole. The stop ring <NUM> is attached to the one-side annular groove 12J of the spindle <NUM> and abuts on the one end surface <NUM> of the retainer <NUM>. The stop ring <NUM> is attached to the other-side annular groove <NUM> of the spindle <NUM> and abuts on the other end surface <NUM> of the retainer <NUM>. In this way, the one end surface <NUM> of the retainer <NUM> abuts on the stop ring <NUM> and the other end surface <NUM> of the retainer <NUM> abuts on the stop ring <NUM>, whereby an axial movement of the retainer <NUM> in relation to the spindle <NUM> is restricted.

Here, as shown in <FIG>, a radial gap formed between the female spline portion <NUM> of the spindle <NUM> and the male spline portion 42E of the retainer <NUM> is defined as S1. In addition, a radial gap formed between the female spline portion <NUM> of the spindle <NUM> and the male spline portion 39B of the carrier <NUM> is defined as S2. The radial gap S1 is set to be smaller than the radial gap S2 (S1 < S2).

In this way, the radial gap S2 between the female spline portion <NUM> of the spindle <NUM> and the male spline portion 39B of the carrier <NUM> is set to be relatively large. Thereby, for example, in a case where core misalignment is made between a center axis of the internal gear <NUM> and a center axis of the shaft <NUM>, the carrier <NUM> can move radially in a range of the radial gap S2. As a result, when the rotation of the shaft <NUM> is decelerated by the planetary gear reduction device <NUM>, it is possible to automatically adjust (align) the center axis of the internal gear <NUM> and the center axis of the shaft <NUM>. On the other hand, the radial gap S1 between the female spline portion <NUM> of the spindle <NUM> and the male spline portion 42E of the retainer <NUM> is set to be relatively small. Thereby, it is possible to suppress the retainer <NUM> from radially rattling in the spindle <NUM>. Accordingly, the shaft bearing <NUM> retained by the retainer <NUM> can stably retain the axial intermediate part of the shaft <NUM>.

A sleeve <NUM> is disposed in the bearing attaching portion 22A of the shaft <NUM>. The sleeve <NUM> includes a cylindrical bearing fitting portion 45A, a collar portion 45B, and a male screw portion 45C. The collar portion 45B is formed in a disc shape having a diameter larger than that of the bearing fitting portion 45A. The male screw portion 45C is disposed at the opposite side to the collar portion 45B to put the bearing fitting portion 45A in between. The sleeve <NUM> has an inner peripheral side as press-fitted into the shaft <NUM>. The sleeve <NUM> is united with the shaft <NUM> in a position of abutting on the bearing attaching portion 22A.

The shaft bearing <NUM> is positioned closer to an axial one side than the carrier <NUM> in the planetary gear reduction device <NUM> to be disposed on the inner peripheral surface side of the spindle <NUM>. The shaft bearing <NUM> is retained between the retainer <NUM> attached to the inner peripheral surface side of the spindle <NUM> (small-diameter cylindrical portion 12C) and the sleeve <NUM>. The shaft bearing <NUM> rotatably supports the shaft <NUM> in relation to the spindle <NUM>. The shaft bearing <NUM> includes an inner race 46A, an outer race 46B, and many rolling elements 46C arranged between the inner race 46A and the outer race <NUM>6B. The inner race 46A is fitted in the bearing fitting portion 45A of the sleeve <NUM>. The outer race 46B is fitted in the bearing fitting hole 42B of the retainer <NUM>.

The outer race 46B of the shaft bearing <NUM> is fitted in the bearing fitting hole 42B of the retainer <NUM> and is axially positioned by the stop ring <NUM>. The inner race 46A of the shaft bearing <NUM> is axially positioned between a nut <NUM> screwed to the male screw portion 45C of the sleeve <NUM> and the collar portion 45B of the sleeve <NUM>. Thereby, the axial intermediate part of the shaft <NUM> is supported by the shaft bearing <NUM> to suppress the core swing at the axial intermediate part of the long shaft <NUM>.

The dump truck <NUM> according to the present embodiment has the configuration as described above, and next, an operation thereof will be explained.

First, when an operator which gets in the cab <NUM> of the dump truck <NUM> activates the engine <NUM>, the hydraulic pump as a hydraulic source is driven and rotated and electric power is generated by the power generator (none thereof is shown in the figure). At the time the dump truck <NUM> is driven to travel, the electric power is supplied from the power generator to the electric motor <NUM>. Thereby the electric motor <NUM> is activated to rotate the output shaft 21B, and the shaft <NUM> connected to the output shaft 21B is rotated.

The rotation of the shaft <NUM> is transmitted from the sun gear <NUM> of the first-stage planetary gear reduction mechanism <NUM> to the plurality of planetary gears <NUM>. The rotation of each of the plurality of planetary gears <NUM> is transmitted through the internal gear <NUM> and the coupling <NUM> to the sun gear <NUM> of the second-stage planetary gear reduction mechanism <NUM>. The rotation of the sun gear <NUM> is transmitted to the plurality of planetary gears <NUM>. At this time, the male spline portion 39B of the carrier <NUM> supporting the planetary gears <NUM> is spline-coupled to the female spline portion <NUM> of the spindle <NUM> (small-diameter cylindrical portion 12C). Therefore, the rotation of the carrier <NUM> (the revolving movements of the respective planetary gears <NUM>) is restricted.

As a result, each of the planetary gears <NUM> rotates only on its axis around the sun gear <NUM>, and the rotation decelerated by the rotation of each of the planetary gears <NUM> on its axis is transmitted to the internal gear <NUM> fixed to the wheel attaching cylinder <NUM>. Thereby, the wheel attaching cylinder <NUM> rotates with the large rotational torque obtained by the speed reduction of the two stages through the first-stage planetary gear reduction mechanisms <NUM> and the second-stage planetary gear reduction mechanisms <NUM>. In consequence, the left and right rear wheels <NUM> as the drive wheel can rotate together with the wheel attaching cylinder <NUM> to drive the dump truck <NUM> for travel.

The dump truck <NUM> travels between a loading work area and a discharging work area. In the loading work area, cargoes of crushed stones excavated in the mine or the like are loaded on the vessel <NUM>. In the discharging work area, the cargoes loaded on the vessel <NUM> are discharged.

Incidentally, in the large-sized dump truck <NUM> used in the mine or the like, not only the weight of the vehicle body <NUM> is large but also the weight of the cargo loaded on the vessel <NUM> is large. As a result, large loads act on the spindle <NUM> supporting the rear wheel <NUM> through the wheel <NUM> by the weight of the vehicle body <NUM> and the weight of the cargo. In this case, by forming the spindle <NUM> by forging, it is possible to enhance the strength of the spindle <NUM> more than the spindle formed by casting. However, in a case of forming the spindle <NUM> by forging, it is difficult to form an attaching flange for attaching the retainer <NUM> or the like on the inner peripheral surface side of the spindle <NUM>.

On the other hand, according to the present embodiment, the male spline portion 42E is formed on the retainer <NUM> disposed on the inner peripheral surface side of the spindle <NUM>. The male spline portion 42E is spline-coupled to the female spline portion <NUM> of the spindle <NUM>. Thereby, even in a case of forming the spindle <NUM> high in strength by forging, it is possible to attach the retainer <NUM> to the spindle <NUM> in the locking state. In addition, it is possible to rotatably support the axial intermediate part of the shaft <NUM> by the shaft bearing <NUM> retained by the retainer <NUM>. Accordingly, the core swing in the axial intermediate part of the long shaft <NUM> is restricted. The rotation of the electric motor <NUM> (output shaft 21B) is smoothly transmitted through the shaft <NUM> to the planetary gear reduction device <NUM>.

As a result, it is possible to cause the dump truck <NUM> to stably travel by the vehicle drive unit <NUM>. In addition, it is possible to enhance the strength of the spindle <NUM> by forming the spindle <NUM> by forging. Accordingly, even in a case where the dump truck <NUM> is large-sized, it is possible to improve the durability of the vehicle drive unit <NUM>. Further, the spindle <NUM> formed by forging has the strength higher than the spindle formed casting and in addition thereto, can be formed in a compact manner. Therefore, it is possible to achieve the lightweight of the spindle <NUM>. As a result, the dump truck <NUM> provided with the spindle <NUM> formed by forging can increase the capacity of the loading object by the amount corresponding to a reduction in vehicle body weight to enhance the workability at the time of transporting the loading object.

In this way, the dump truck <NUM> according to the present embodiment is provided with the vehicle drive unit <NUM> including the cylindrical spindle <NUM> the axial one side of which is attached to the vehicle body <NUM> and on the axial other side of which the female spline portion <NUM> is formed, the wheel <NUM> that is positioned in the axial other side of the spindle <NUM> to be disposed on the outer peripheral side of the spindle <NUM> and to which the tire 4A is attached, the wheel bearings <NUM>, <NUM> that are arranged between the spindle <NUM> and the wheel <NUM> to rotatably support the wheel <NUM> in relation to the spindle <NUM>, the electric motor <NUM> located on the axial one side of the spindle <NUM>, the shaft <NUM> that is connected to the output shaft 21B of the electric motor <NUM>, is inserted axially in the inner peripheral surface side of the spindle <NUM> and projects from the axial other side of the spindle <NUM>, the planetary gear reduction device <NUM> that is positioned in the axial other side of the spindle <NUM> to be disposed between the shaft <NUM> and the wheel <NUM> and includes the plurality of planetary gears <NUM> rotatably supported by the carrier <NUM> spline-coupled to the female spline portion <NUM> of the spindle <NUM>, and the shaft bearing <NUM> that is positioned closer to the axial one side than the carrier <NUM> of the planetary gear reduction device <NUM> to be disposed on the inner peripheral surface side of the spindle <NUM> and rotatably supports the shaft <NUM> in relation to the spindle <NUM>.

In addition, the retainer <NUM> is disposed and positioned on the inner peripheral surface side of the spindle <NUM>, the retainer <NUM> being formed of a material different (different element) from the spindle <NUM> and retaining the shaft bearing <NUM>, and the male spline portion 42E spline-coupled to the female spline portion <NUM> of the spindle <NUM> is disposed on the retainer <NUM>.

Thereby, the male spline portion 42E of the retainer <NUM> is spline-coupled to the female spline portion <NUM> of the spindle <NUM>. Accordingly, it is possible to retain the retainer <NUM> at the inner peripheral surface side of the spindle <NUM> with an appropriate degree of freedom (gap) in the axial direction and in the rotational direction in the locking state. Accordingly, even in a case of using the spindle <NUM> difficult to dispose the attaching flange or the like on the inner peripheral surface side, the shaft bearing <NUM> can be attached through the retainer <NUM> formed as the different material to the inner peripheral surface side of the spindle <NUM>. As a result, it is possible to rotatably support the axial intermediate part of the long shaft <NUM> by the shaft bearing <NUM> and restrict the core swing of the shaft <NUM>. Accordingly, the rotation of the electric motor <NUM> (output shaft 21B) can be smoothly transmitted through the shaft <NUM> to the planetary gear reduction device <NUM>. Thereby, it is possible to cause the dump truck <NUM> to stably travel by vehicle drive unit <NUM>.

In the present embodiment, the radial gap S1 formed between the female spline portion <NUM> of the spindle <NUM> and the male spline portion 42E of the retainer <NUM> is set to be smaller than the radial gap S2 formed between the female spline portion <NUM> of the spindle <NUM> and the male spline portion 39B formed in the carrier <NUM>.

In this way, the radial gap S2 is set to be relatively large, and thereby, for example, even in a case where the core misalignment is made between the center axis of the internal gear <NUM> and the center axis of the shaft <NUM>, the carrier <NUM> can move radially in a range of the radial gap S2. As a result, when the rotation of the shaft <NUM> is decelerated by the planetary gear reduction device <NUM>, it is possible to automatically adjust (align) the center axis of the internal gear <NUM> and the center axis of the shaft <NUM>. On the other hand, the radial gap S1 is set to be relatively small, and thereby, it is possible to suppress the retainer <NUM> from radially rattling within the spindle <NUM>. Accordingly, the shaft bearing <NUM> retained by the retainer <NUM> can stably retain the axial intermediate part of the shaft <NUM>.

In the present embodiment, the pair of the stop rings <NUM>, <NUM> restricting the axial movement of the retainer <NUM> and the retainer fitting portion <NUM> of radially positioning the retainer <NUM> by the fitting of the cylindrical outer peripheral surface 42D therein are arranged on the inner peripheral surface of the spindle <NUM>.

As a result, the axial movement of the retainer <NUM> to the spindle <NUM> is restricted by the pair of the stop rings <NUM>, <NUM>. In addition, the radial movement of the retainer <NUM> to the spindle <NUM> is restricted by the retainer fitting portion <NUM>. As a result, it is possible to position the retainer <NUM> in the axial direction and in the radial direction in relation to the spindle <NUM>.

It should be noted that the embodiment shows a case of using the spindle <NUM> formed by forging, as an example. However, the present invention is not limited thereto, but the retainer <NUM> may be attached to an inner peripheral surface side of a spindle formed by casting, for example. In this case, since it is not necessary to dispose an attaching flange or the like on the inner peripheral surface side of the spindle, the shape of the casting die can be simplified and the casting die can be manufactured in less costs.

The embodiment shows as an example a case where the groove number of the female spline portion <NUM> formed in the spindle <NUM> is different from that of the male spline portion 42E formed in the retainer <NUM>. However, the present invention is not limited thereto, but the groove number of the male spline portion 42E in the retainer <NUM> may be formed to be equal to that of the female spline portion <NUM> in the spindle <NUM>.

Claim 1:
A dump truck provided with a vehicle drive unit (<NUM>) comprising:
a cylindrical spindle (<NUM>) an axial one side of which is attached to a vehicle body (<NUM>) and on an inner peripheral surface at an axial other side of which a female spline portion (<NUM>) is formed;
a wheel (<NUM>) that is positioned in the axial other side of the spindle (<NUM>) to be disposed on an outer peripheral side of the spindle (<NUM>) and on which a tire (4A) is attached;
wheel bearings (<NUM>, <NUM>) that are arranged between the spindle (<NUM>) and the wheel (<NUM>) to rotatably support the wheel (<NUM>) in relation to the spindle (<NUM>);
a rotation source (<NUM>) located on the axial one side of the spindle (<NUM>);
a shaft (<NUM>) that is connected to an output shaft (21B) of the rotation source (<NUM>), is inserted axially in an inner peripheral surface side of the spindle (<NUM>) and projects from the other end side of the spindle (<NUM>);
a planetary gear reduction device (<NUM>) that is positioned in the axial other side of the spindle (<NUM>) to be disposed between the shaft (<NUM>) and the wheel (<NUM>) and is provided with a plurality of planetary gears (<NUM>) rotatably supported by a carrier (<NUM>) spline-coupled to the female spline portion (<NUM>) of the spindle (<NUM>); and
a shaft bearing (<NUM>) that is positioned closer to the axial one side than the carrier (<NUM>) in the planetary gear reduction device (<NUM>) to be disposed on the inner peripheral surface side of the spindle (<NUM>) and rotatably supports the shaft (<NUM>) in relation to the spindle (<NUM>),
on the inner peripheral surface side of the spindle (<NUM>), a retainer (<NUM>) is disposed to be positioned, the retainer being formed of a material different from the spindle (<NUM>) and retaining the shaft bearing (<NUM>); characterized in that
the retainer (<NUM>) is provided thereon with a male spline portion (42E) spline-coupled to the female spline portion (<NUM>) of the spindle (<NUM>); and
a radial gap (S1) formed between the female spline portion (<NUM>) of the spindle (<NUM>) and the male spline portion (42E) of the retainer (<NUM>) is set to be smaller than a radial gap (S2) formed between the female spline portion (<NUM>) of the spindle (<NUM>) and another male spline portion (39B) formed in the carrier (<NUM>) .