Vehicle differential housing and method of NVH testing

A drive module and a system for performing NVH testing on the drive module are provided. The system includes two pins extending from a platform and at least one qualified surface. A differential housing includes two surfaces, each having an opening formed therein. The differential housing further includes a clamping surface. The drive module is mounted to the platform by inserting the pins into the openings to align the drive module in a plane. A clamping pressure clamps the differential housing to the qualified surface to align the drive module in a second direction that is perpendicular to the plane such that the drive module pinion and axles are aligned with the energy sources of the system.

FIELD OF THE INVENTION

The subject invention relates to a vehicle having a differential housing and axle assembly, and more particularly, to an assembly configured for mounting to a noise, vibration and harshness (NVH) test assembly.

BACKGROUND

Vehicles, such as automobiles and trucks for example, include a differential housing and axle assembly, sometime colloquially referred to as a drive module. The drive module is connected to the vehicle engine by a prop-shaft. The prop-shaft transmits rotational energy (torque) developed by the vehicle engine to the assembly, which in turn transmits the rotational energy to the wheels. In a rear-wheel drive vehicle, the prop-shaft directly couples the assembly to the vehicle's transmission. In an all-wheel or four-wheel drive vehicle, additional components may also be included, such as a power take-off unit for example.

It should be appreciated that the rotation of the gears within the drive module may generate or transmit vibrations. These vibrations may in some instances become a noise source that may be transmitted to the vehicle compartment. Testing equipment and methods have been developed to allow the measurement of NVH prior to installation in the vehicle. The NVH testing methods typically involve connecting an energy source (e.g. a motor) to the pinion shaft entering the differential housing and at each wheel. Alignment of the rotating shafts needs to be accomplished within desired specifications otherwise inconsistent test results may occur. It has been found that alignment of the shafts and clamping of the drive module to the test fixture are large contributors to NVH tester repeatability and throughput issues.

Accordingly, it is desirable to provide a drive module that facilitates NVH testing with a desired level of reliability.

SUMMARY OF THE INVENTION

In one exemplary embodiment of the invention, a system for performing a noise, vibration and harshness (NVH) testing on a vehicle differential housing and axle assembly is provided. The assembly includes a differential housing having a first surface with a first hole, a second surface with a second hole and a third surface. The assembly further having a pinion, a first axle and a second axle. The system comprises a platform and a first pin extending from a first qualified surface. The first pin sized and arranged on the platform to be received in the first hole. A second pin extends from a second qualified surface, the second pin sized and arranged on the platform to be received in the second hole. A third qualified surface is arranged on the platform to engage the third surface. A first energy source is operably coupled to the platform and aligned along a first axis, the first energy source being configured to align with the pinion along the first axis. A second energy source is coupled to the platform and aligned along a second axis, the second axis being perpendicular to the first axis, the second energy source being configured to align with the first axle along the second axis. A third energy source is coupled to the platform and aligned with the second axis, the third energy source being configured to align with the second axle along the second axis.

In another exemplary embodiment of the invention, a differential housing and axle assembly configured to mount on an NVH testing apparatus is provided. The NVH testing apparatus having a first pin, a second pin and at least one qualified surface. The assembly comprising a differential housing having a pinion bore and a pair of opposing axle bores. The differential housing having a first side and an opposing second side, the first side having a first surface with a first hole formed therein, a second surface with a second hole formed therein and a third surface. The second side includes a first clamping surface opposite the first surface. A second clamping surface is arranged opposite the second surface and a third clamping surface is arranged opposite the third surface, wherein the first hole is sized and positioned to receive the first pin and the second hole is sized and positioned to receive the second pin. A pinion is arranged in the pinion bore and configured to couple with the NVH testing apparatus. A first axle extends from one of the opposing axle bores. A second axle extends from the other of the opposing axle bores.

In yet another exemplary embodiment of the invention, a method of NVH testing of a differential housing and axle assembly is provided. The method comprising the steps of: providing a test apparatus having a platform, a first pin, second pin and at least one qualified surface, the test apparatus further having a first energy source, a second energy source and a third energy source, first energy source being aligned along a first axis, the second energy source and third energy source being aligned along a second axis; providing a differential housing and axle assembly, the assembly including a housing having a first surface with a first hole formed therein, a second surface with a second hole formed therein and a third surface, the assembly further including a pinion arranged in the housing, a first axle and a second axle; inserting the first pin into the first hole and the second pin into the second hole; aligning the first axle and second axle with the second axis; aligning the pinion with the first axis; clamping the third surface to the at least one qualified surface; and coupling the pinion to the first energy source, the first axle to the second energy source and the second axle to the third energy source.

DESCRIPTION OF THE EMBODIMENTS

In accordance with an embodiment of the invention,FIG. 1illustrates a vehicle20having a differential assembly and axle assembly, which are collectively referred to as drive module22. It should be appreciated that the vehicle20may be an automobile, truck, van or sport utility vehicle for example. As used herein, the term vehicle is not limited to just an automobile, truck, van or sport utility vehicle, but may also include any self-propelled or towed conveyance suitable for transporting a burden. The vehicle20may include an engine24, such as a gasoline or diesel fueled internal combustion engine. The engine24may further be a hybrid type engine that combines an internal combustion engine with an electric motor for example. The engine24and drive module22are coupled to a frame or other chassis structure26. The engine24is coupled to the drive module22by a transmission28and a driveshaft30. The transmission28may be configured to reduce the rotational velocity and increase the torque of the engine output. This modified output is then transmitted to the drive module22via the driveshaft30. The drive module22transmits the output torque from the driveshaft30through a differential gear set32to a pair of driven-wheels34via axles36.

The differential gear set32is arranged within a differential housing42. The differential gear set32receives the output from the driveshaft30via a pinion gear40that transmits the torque to a ring gear44. The pinion40includes a shaft that is coupled to the driveshaft30by a flange46. The differential gear set32is supported for rotation within the housing42by a pair of differential bearings. The differential gear set32includes side gears38arranged within a housing42that are coupled to and support one end of the axles36. The coupling of rotational components, such as the flange46to the pinion40or the side gears38to the axles36for example, may be accomplished using a spline connection.

In one embodiment, each axle36extends into an axle tube54. The axle tube54includes a hollow interior that extends the length thereof. At one end of the axle tube54a bearing56is mounted to support the end of the axle36adjacent the driven-wheel34. A shaft seal57is located between the bearing56and the wheel34. A wheel mounting flange58is coupled to the end of the axle36adjacent the bearing56. The flange58provides an interface for mounting of the driven-wheel34.

The vehicle24further includes a second set of wheels60arranged adjacent the engine24. In one embodiment, the second set of wheels60is also configured to receive output from the engine24. This is sometimes referred to as a four-wheel or an all-wheel drive configuration. In this embodiment, the vehicle20may include a transfer case62that divides the output from the transmission28between the front and rear driven wheels34,60. The transfer case62transmits a portion of the output to a front drive module64, which may include additional components such as a differential gear set66and axles68that transmit the output to the wheels60.

It should be appreciated that within the drive modules22,64, the transmission28, the driveshaft30and the differential gear sets32,66there are a number of rotational components that transfer rotational energy or torque to the wheels. It should further be appreciated that it is desirable to reduce or minimize any noise or vibration from these rotating members from transferring into the vehicle compartment.

Referring now toFIG. 2andFIG. 3, an exemplary NVH test apparatus70is shown for testing the drive module22. It should be appreciated that while embodiments herein describe the NVH test apparatus70with respect to the rear drive module22, this is for exemplary purposes and the claimed invention should not be so limited. In other embodiments, the test apparatus70may also be adapted to test the front differential housing and axle assembly64. The NVH test apparatus70includes a first energy source, such as motor72, that is adapted to couple with the flange46. The NVH test apparatus70further includes a pair of opposing energy sources, such as motors74,76that each couple with one of the wheel flanges58. It should be appreciated that the motors72,74,76may be selectively energized to transmit torque to the pinion40or the axles36respectively. The NVH test apparatus70may further have sensors (not shown), such as accelerometers for example, as is known in the art, for measuring vibration at different points on the drive module22.

The drive module22is mounted to the NVH test apparatus70via a platform78. It should be appreciated that the platform78is fixed relative to the motors72,74,76. The platform78is a substantially rigid structure that is configured to hold the drive module22during operation. In the exemplary embodiment, the platform includes at least three qualified surfaces83,84,85each with an opposing clamp member. As used herein the term “qualified surface” means a surface that has been fabricated, positioned and oriented within a desired specification to allow accurate and consistent measurement or testing of a tested article. In one embodiment, the qualified surfaces83,84,85include two pins80,82that extend therefrom. As will be discussed in more detail below, the pins80,82and the surfaces83,84,85cooperate to hold the drive module22in a desired location and orientation relative to the motors72,74,76such that the pinion40and axles36are aligned within a desired specification. Adjacent the pins80,82and surface84are clamping members, such as a rotary clamp86that includes an arm88that is movable between a released position and an engaged position. When in the engaged position, the arm88includes a clamping surface that contacts qualified surfaces, such as machined pads for example, on the housing42with sufficient force to hold the drive module22on the pins80,82and against the surfaces83,84,85in the desired position and orientation for testing.

In one embodiment, at least one of the qualified surfaces83,84,85defines a first plane the drive module is aligned to in the engaged position. The axis of rotation for the axles36is generally parallel with this first plane. Further, when in the engaged position, the qualified surfaces83,84,85may align the drive module22with a second plane that is perpendicular to the first plane. The pinion gear40axis of rotation is generally parallel to or co-planar with the second plane.

Referring now toFIGS. 4 and 5, an exemplary differential housing42is shown for use in the drive module22and with the NVH test apparatus70. In this embodiment, the housing42includes a plurality of mounting features arranged on opposing surfaces that are configured to engage the pins80,82and surfaces83,84,85when the drive module22is mounted on the platform78. These mounting features include a pair of openings88,90formed in a machined surface92. The surface92further includes a portion94that is positioned to engage the surface84when the assembly is mounted on the platform78. The openings88,90and the portion94are positioned within controlled tolerances relative to the three orthogonal centerlines96,98,100of the bore102for the bearings that support the pinion40and the three orthogonal centerlines104,106,108of the axle bores110. In one embodiment, the openings88,90have a diameter of 14.3 mm+/−0.035 mm and are located with a true position 0.25 mm to the centerlines96,98,104. In this embodiment, the locating surfaces83,84,85have a profile of 0.25 mm to the centerlines96,98,104and a tolerance of 0.1 mm profile of surface83to surfaces84,83and 0.1 mm profile of surface85to surfaces84,85. Each of the surface finishes of the surface finishes is 3.2 RA.

The housing42further includes a plurality of surfaces or machined pads112arranged opposite surface92. The surface112provides a surface for the arms88to contact when in the engaged position. It should be appreciated that while the embodiment illustrated inFIGS. 4-5show the mounting features as being arranged on the rear surface, meaning the surface opposite the pinion40, the claimed invention should not be so limited. In another embodiment, the mounting features may be located on a different portion of the housing42, such as on the rib114for example. Further, while the illustrated embodiment shows the openings88,90formed in a common surface with the portion94, the claimed invention should not be so limited. In other embodiments, the openings88,90may be formed in surfaces that are offset from both each other and the portion94for example.

In operation, the drive module22is placed on the platform78by placing the pins80,82into the openings88,90with the arms88in the released position. The rotary clamps86are actuated, moving the arms88into the engaged position with the arms contacting the surfaces112pushing the surface92into contact with the surfaces83,85and the portion94into contact with the surface84. It should be appreciated that the pins80,82and openings88,90align the drive module22in the X-Z plane relative to the motors72,74,76while the surfaces83,84,85align the drive module22in the Y direction. This provides advantages in the clamping of the drive module22onto the platform78in a manner that reliably and repeatedly positions and aligns the pinion40and axles36with the motors72,74,76respectively within the desired tolerances to allow reliable and repeatable NVH testing.

In the embodiment illustrated inFIGS. 4-5, the platform78is oriented generally vertically with the clamping pressure being generally oriented in the horizontal direction (e,g, generally parallel to the axis of the pinion40). Referring now toFIGS. 6-8an embodiment is illustrated of an drive module22that is configured to be installed on an NVH testing apparatus70that has clamping pressure oriented in the vertical direction (e.g. generally perpendicular to the axis of the pinion40). In this embodiment, the platform78is oriented with the pins80,82directed upward. The housing42includes two surfaces116,118(FIG. 8) arranged on the bottom side (e.g. closer to the ground when oriented in the operating position). Each surface116,118includes an opening hole120,122sized to receive the pins80,82. The bottom side further includes a pair of pads or machined surfaces124,126arranged on the housing42adjacent the bore110where the axle tubes54exit the housing42. The pads124,126are positioned to contact and be supported by the surfaces84on the platform78. It should be appreciated that while the illustrated embodiment shows a pair of pads124,126adjacent each axle tube54, in other embodiments, a single pad may be used on each side.

On the top side of housing42(FIG. 7), a pair of machined surfaces128,130are arranged opposite the surfaces116,118respectively. The top side of housing42further includes a pair of pads or machined surfaces132,134that are arranged opposite the pads124,126. The surfaces128,130are arranged to cooperate with one or more arms136that apply clamping pressure thereto and hold the drive module22in place. The pads132,134are similarly arranged to cooperate with one or more arms138. It should be appreciated that the arms136,138may be any suitable clamping device, such as a rotary clamp or a swing arm type clamp for example, that may be configured to engage the surfaces128,130and pads132,134to hold the assembly on the platform78during testing. Further it should be appreciated that the pins80,82and the openings120,122are arranged to align the drive module22relative to the motors72,74,76in the X-Y plane while the surfaces84,116,118,124,126align the drive module22in the Z direction.