Lubrication arrangement for a drive axle of a haul vehicle

A drive axle assembly is provided that improves lubrication to the components of the drive axle assembly. As the wheel differential rotates, lubricant is splashed and lubricates bearings and other associated components of the differential assembly. In addition, lubricant is pumped by rotation of the first and second spur gears and is fed to the radial face of a forward bearing through a lubrication passage through a plurality of passages.

TECHNICAL FIELD

The present invention relates to a center axle assembly for an articulated haul vehicle and more particularly to a lubricating arrangement for a support bearing of a drive shaft for the center axle assembly.

BACKGROUND

Haul trucks, both on and off highway, include three axles a forward axle, a center axle and a rear axle. Output from a power source is supplied to all three axles via drive shafts. A transmission is directionally engaged to power the axle assemblies. While the forward axle assembly may be operatively engaged/disengaged through the use of a drop box to allow the truck to be operated in an all-wheel drive mode. Each axle assembly includes a differential gear set that includes a pinion gear in mesh with a ring gear. The pinion gears of the forward and rear axle assemblies are generally directly driven via drive shafts through splined connections via a yoke. While the center axle includes a through shaft that drives a series of gears to drive the pinion gear and lastly the differential wheel.

The through shaft is supported at each end by a pair of bearings. One pair of bearings support a forward end of the through shaft and an additional pair of bearings support a rear end of the through shaft.

There is a need to provide lubrication to components of the center axle assembly and particularly the support bearings for the through shaft. Conventional methods of lubricating the bearings include the use of splash lubrication from the pinion gear and bevel gear during operation of the haul truck. However, due to location of each bearing splash lubrication from the pinion gear and the bevel gear rotation cannot reach all of the bearings at the front end of the center axle assembly. A known method for lubricating components of the center axle assembly is shown in U.S. Pat. No. 7,258,641 issued to Green et al on Aug. 21, 2007 and assigned to Dana Corporation. In the “641” patent, lubricant splashed from the ring gear is collected and is then distributed by a bearing supporting the output side gear for rotation within the housing for the assembly. The bearing directs lubricant to the differential gears where seals and/or close tolerances retain the lubricant and allow it to flow to the surfaces of the input shaft and the helical side gear disposed about the input shaft. The output side gear disposed about the output shaft may also include a passage allowing lubricant to flow through the gear to the bearing surfaces of the output shaft and output side gear. Not all center axle assemblies have the differential gears and close tolerances are costly to manufacture.

The present disclosure is directed to overcoming one or more of the deficiencies as set forth above.

SUMMARY OF THE INVENTION

In one aspect of the present disclosure a drive axle assembly includes a housing and an input shaft extending into the housing and disposed about an axis of rotation. A first spur gear is disposed about the input shaft and the axis of rotation, the first spur gear is configured to provide power to a first wheel differential and includes a ring gear. A second spur gear is disposed about a pinion shaft. The pinion shaft is configured to provide power to the first wheel differential via a pinion gear. The second spur gear is drivingly coupled to the first spur gear. A forward bearing is positioned forward and adjacent the first spur gear, the bearing is disposed about the input shaft and supports the input shaft for rotation within the housing. A rearward bearing is positioned rearward and adjacent the first spur gear, the bearing is disposed about the input shaft and supports the input shaft for rotation within the housing. The first and second spur gears pump a lubricant from the housing to a lubrication passage and supply the lubricant to a radial face of at least one of the forward and rearward bearings.

In another aspect of the present disclosure a drive axle assembly includes a housing and an input shaft extending into the housing and disposed about an axis of rotation. A through shaft is connected to the input shaft at a first end and being supported by a pair of bearings at a second end. A first spur gear is disposed about the input shaft and the axis of rotation, the first spur gear is configured to provide power to a first wheel differential, the first wheel differential includes a ring gear. A second spur gear is disposed about a pinion shaft, the pinion shaft is configured to provide power to the first wheel differential via a pinion gear, and the second spur gear is drivingly coupled to the first spur gear. A bearing is positioned adjacent the first spur gear and disposed about the input shaft and supports the input shaft for rotation within the housing. The first and second spur gears pump lubricant from the housing to the lubricant passage and to at least one of the forward and rearward bearings supporting the input shaft.

In yet another aspect of the present disclosure a haul vehicle includes a frame assembly having at least a front portion and a rear portion, an articulation joint connects the front and rear portions and is adapted to allow pivotal movement about the joint by the front and rear portions. A front, center and rear axles supports the frame assembly and includes a plurality of ground engaging devices attached to the axles. An operator compartment is also supported by the frame assembly. A bed adapted to carry a load is also connected to the frame assembly. An engine that generates torque is supported by the frame assembly. A transmission is coupled to the engine for receiving the torque, the transmission having an output coupling for providing the torque to the front, center and rear axles. The center axle includes a drive axle assembly.

DETAILED DESCRIPTION

Referring now toFIGS. 1 and 2, a haul vehicle10is shown as being, for example, an articulated truck for carrying loads through a plurality of work cycles. The haul vehicle10includes an operator station or cab12, a bed14and a main frame16. Main frame16includes a front portion20, a rear portion22and an articulation joint24for steering the haul vehicle10. The articulation joint24connects the front and rear portions20,22and allows for pivotal movement about the articulation joint24of the front and rear portions20,22through an axis26so that the haul vehicle10can be steered via hydraulic cylinders (not shown). Front portion20of main frame16is supported by a front axle30(FIG. 2), and rear portion22of main frame16is supported by a center axle32and a rear axle34. A plurality of ground engaging devices38are supported on the front axle30, center axle32and rear axle34.

Power is provided to the front axle30, center axle32and rear axle34by an engine40(FIG. 2), a transmission42(FIG. 2), and a transfer box44for receiving the torque and transferring the torque to a plurality of drive shafts50,52,54,56(FIG. 2). The plurality of ground engaging devices38(one each) are attached to each end of the front axle, center axle and rear axle30,32,34and are preferably used for traversing a grade60.

Power from the engine40is transferred to the transmission42by direct connection. The transmission42includes a plurality of gears (not shown) that may be engaged in various combinations to achieve desired gear ratios for powering the haul vehicle10at various speeds and output torques. In addition, the gears control the direction of rotation of the output of the transmission42to establish forward and reverse movement of the haul vehicle10. Output from the transmission42is sent to transfer box44by drive shaft50. Transfer box44divides the rotational input into two directions and provides output to drive shafts52and54. The output to drive shaft52may be selectively activated to enable the haul vehicle10to operate in an all-wheel drive mode. Drive shaft54connects to the input of center axle32and drive shaft56is connected to rear axle34.

FIG. 3illustrates a cross sectional view of a drive axle assembly70of the center axle22taken vertically along axis of rotation68. As stated prior center axle32receives input from drive shaft54and is connected to the rear axle34through drive shaft56. Center axle22is provided to drive two of the plurality of ground engaging devices38supported on either side of center axle32on axle half shafts (not shown) extending from center axle32. Center axle32is particularly adapted for use in haul vehicle10. It should be understood, however, that the present invention is not limited to use in haul vehicle10and may be used in a wide variety of tandem axle vehicles. Drive axle assembly70may include a housing72, an input yoke74, an output yoke76, a pinion shaft assembly80and a wheel differential82.

Housing72provides structural support for the other components of drive axle assembly70. Housing72also protects the other components of drive axle assembly70from foreign objects, the elements and contains a level of lubricant78. Housing72may be made from conventional metals and/or metal alloys such as steel and may include multiple cover members90,92,94, and96that are sized relative to components of drive axle assembly70and coupled together using conventional fasteners98.

An input shaft100transmits power from the drive shaft54to drive axle assembly70. Shaft100may be made from conventional metals and/or metal alloys. Shaft100is driven by the drive shaft54through input yoke74. The input yoke74may be splined to the forward end of input shaft100and may be retained thereon by a fastener104and a washer which are disposed into a threaded aperture106that extends into the forward end of shaft100. A cover107is disposed about input yoke100. Input yoke100is received within an opening in cover member107. Input yoke100is sealed for rotation about the axis of rotation68within an opening in cover107by a seal108disposed within the opening.

Input shaft100includes a first spur gear110that transfers torque to a second spur gear112to pinion shaft assembly80. First and second spur gears110,112may be for example helical spur gears or any other conventional gear in the art and may be made from conventional metals and/or metal alloys. Spur gear110is disposed about input shaft100and is rotatable therewith.

Input shaft100is rotatable through the support of a forward and a rearward bearing116,117positioned on each side of first spur gear110. One side of the rearward bearing117may contact a shoulder118positioned in cover92and the other side is shouldered against the rearward portion of the first spur gear110. The forward bearing116shoulders against the forward side of the first spur gear110. A cover120, held in place by fasteners, contacts the forward bearing116providing preload and retaining forward and rearward bearings116,117the first spur gear110and the input shaft100and preventing axial movement thereof. The cover120also forms a radial cavity121in front of the forward bearing116.

Input shaft100may be splined to a through shaft122. Through shaft122is provided to transmit a portion of the power provided by input shaft100and the through shaft122to the rear drive axle assembly34(shown inFIG. 2) through drive shaft56. Shaft122is conventional in the art, and is coaxially disposed relative to input shaft100along axis68and includes a pilot portion124at its forward end on which input shaft100is journaled. Shaft122extends through openings in housing members92and94respectively, and is journaled within by a pair of bearings positioned in a bearing cage128housed in an opening of housing member96.

Pinion shaft assembly80transfers power from first spur gear110to wheel differential82. Pinion shaft assembly80may include second spur gear112helical driven to transfer torque to a pinion shaft140. Gear112may be drivingly coupled to shaft140through axially extending splines (not shown) on shaft140. Shaft140may be rotationally supported by bearings142,144within bearing cages in covers90and92. Pinion shaft140includes a pinion gear146at a rearward end.

Wheel differential82is provided to allow the ground engaging members38supported on either side of center axle assembly32to rotate at different speeds. Assembly82includes a ring gear150, and a conventional bevel gear set152disposed within a differential carrier154. Ring gear150transfers torque from pinion gear146to gear set152and is conventional in the art. Ring gear150may be made from conventional metals and/or metal alloys and may comprise a hypoid gear. Gear150is affixed to carrier154or may be integral therewith. Gear set152is provided to transfer torque from ring gear84to the axle half shafts (not shown) supporting the ground engaging members in a conventional manner.

Referring now toFIG. 4, a cut away portion, taken along a portion of section line4-4inFIG. 2and isolated from some of the components inFIG. 3, of the drive axle assembly70showing the housing72will be described in greater detail. A lubrication passage160is formed in cover member90of housing72. Specifically, lubrication passage160is formed by a plurality of passages162that extend from an outside surface164of cover90. A first passage166may be formed into cover member90in an upward manner so that it exits on an interior168of housing72tangential to an outer surface170of the first spur gear110. A second passage172is formed from a mounting surface174of cover member90at an inclined manner intersecting perpendicular to first passage166. A generally vertical passage176is formed from the exterior164at a predetermined depth and intersects the second passage172. Lastly a generally horizontal passage178is formed from the outside surface164of housing72and exits on the interior168of cover90. The generally horizontal passage178forms a lubrication outlet182adjacent a radial face180of the forward bearing116. The plurality of passages are each shown as being blocked from the exterior164in a conventional manner as by threaded or force fit plugs (not shown) so that contaminants are not allowed to enter the interior168of housing72. However, it should be understood that cast holes would work as well. While the specific description of the drive axle assembly70has focused on the center axle32, it should be understood that a front or a rear axle30,34that drives the pinion assembly80via first and second spur gears110,112and does not include a through shaft122will be equally applicable.

INDUSTRIAL APPLICABILITY

Referring now toFIGS. 3 and 4, the lubrication system for the drive axle assembly70of the center axle will be described in greater detail. During operation of the haul vehicle10, rotational input power is provided to drive axle assembly70via drive shaft54. As the wheel differential82is rotated lubricant is splashed and lubricates bearings126,142,144and the rear bearing117and other associated components of the drive axle assembly70. In addition, lubricant78is pumped by second spur gear112to first spur gear110. The lubricant78pumped by first and second spur gears110,112is feed to the radial face180of forward bearing116through the lubrication passage160through the plurality of passages162following the directional arrows shown inFIG. 4. Specifically, lubricant78is expelled from the first spur gear110in a tangential manner into first passage166. From the first passage166lubricant78flows downward, via the pumping action from the first and second spur gears110,112and gravity, to the second passage172. Lubricant78finishes by flowing through the generally vertical and horizontal passages172,178to the interior168of the housing72into the radial cavity121between the forward surface180of the forward bearing116and the cover120.

It should be recognized that through the design of the drive axle assembly70, by controlling various aspects such as dimension and ratios, more or less lubrication can be provided to the forward bearing116. For example by controlling the dimensions of the plurality of passages162, the viscosity of the lubricant78and clearances between the first spur gear110and the cover member90the amount of lubricant78feed to the forward and rearward bearings116,117may be controlled. In this manner, the drive axle assembly70provides increased lubrication to components that are above the lubricant78level in the housing72and farthest away from any splash lubrication that is provided by the differential wheel82rotation.

While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it is well understood by those skilled in the art that various changes and modifications can be made in the invention without departing from the spirit and scope of the invention.