Patent Application
20100022345
The present invention relates to an axle assembly and more particularly to an axle assembly with a braking feature.
Various devices for braking a vehicle are known. The devices may be located at the wheels for frictionally braking the wheels, or within the driveline of the vehicle for braking some structure within the driveline and thus the wheels as well.
The prior art devices, however, suffer from several disadvantages. For example, one significant disadvantage of the prior art devices is that they cannot brake the axle half shafts of a vehicle both equally and unequally relatively simply and inexpensively. Thus, it would be advantageous for a device to be able to selectively brake both axle half shafts in an equal and unequal manner with a device that is relatively simple and inexpensive.
The present invention comprises a shaft having rotors of a first clutch pack attached thereto. A ball ramp is located in contact with the first clutch pack to selectively compress the rotors in first clutch pack and brake the shaft. A gear, attached to the shaft, transmits a braking force to a differential. The differential has a second clutch pack located therein. The second clutch pack permits equal and unequal distribution of brake torque to the axle half shafts connected to the differential.
The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which:
It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless the claims expressly state otherwise.
Turning now to
The drive system 10 also comprises a drive assembly 26 mounted adjacent the inboard end portions 28 of each axle 16, 18. The drive assembly 26 comprises a transaxle housing 30. The transaxle housing 30 has rotatably mounted therein a drive shaft 32. The drive shaft 32 may be rotatably driven by any input, such as a propeller shaft (not shown) from a prime mover, such as an internal combustion engine or electric motor (not shown). The drive shaft 32 is mounted for rotation within the housing 30 by bearings 34 located between the shaft 32 and the housing 30.
The drive shaft 32 has a gear 36 that is directly meshed with a gear 38 on a driven shaft 40, also within the transaxle housing 30. The driven gear 38 is mounted for rotation within the transaxle housing 30 by at least two bearings 42. The driven gear 38 has a first end portion 44, a second end portion 46 and an intermediate portion 48 between the end portions 44, 46.
The second end portion 46 has the meshed gear 38. Immediately adjacent the meshed gear 38 is an intermediate gear 50. Adjacent, but outboard of, the intermediate gear 50 is a first clutch pack 52.
The first clutch pack 52 is located outside of the transaxle housing 30 in a clutch pack housing 54 that is attached to the transaxle housing 30, such as by mechanical fasteners 56. The first clutch pack 52 comprises a plurality of stators 58 and rotors 60. The rotors 60 are splined to the driven shaft 40 for rotation therewith and for axial movement there along. The stators 58 are fixedly attached to the transaxle housing 30.
A ball ramp 62 is located immediately outboard of said driven shaft 40 and the first clutch pack 52. As schematically depicted in
Looking now at
Turning now to
The ring gear 84 may be attached to the differential case 86 in any manner including welding and/or mechanical fasteners. As best seen in
The differential case 86 houses at least one pinion gear, a spider shaft and at least one side gear. In the preferred depicted embodiment, the differential case 86 has two pinion gears 96, 98 meshed with two side gears 100, 102 where the pinion gears 96, 98 are connected by a spider shaft 104 to form a differential 105.
The differential case 86 is mounted for rotation within the transaxle housing 30 by at least two bearings 106. Preferably, the bearings 106 sit in bearing seats 108 integrally formed with the outermost axial portions 110 of the differential case 86.
An interior surface 112 of the differential case 86 defines a second clutch pack groove 114. Preferably, a plurality of friction disks 116, a plurality of reaction plates 117 and a biasing member 118 are located within the second clutch pack groove 114. At least a portion 120 of one of the side gears 100 may also be located within the second clutch pack groove 114. The plurality of friction disks 116 are splined for axial movement along one of the side gears 100.
A biasing member 118, such as a conical spring washer, biases the plurality of friction disks 116 and the reaction plates 117 against one another and the interior surface 112 of the differential case 86.
The side gears 100, 102 are splined to the axle half shafts 16, 18 to impart rotational motion from the side gears 100, 102 to the shafts 16, 18.
A method of utilizing the invention described above begins with the operator engaging the brake pedal 82 in the operator's compartment of the vehicle. The brake pedal 82 is attached to the cable assembly 78. When the pedal 82 is depressed, a cable 122 in the assembly 78 pulls on the pivoting lever arm 72, causing it to rotate. The lever arm 72 pivots about the mounting point 74 on the first clutch pack housing 54. When the lever arm 72 pivots about point 74, the lever arm 72 pulls on the brake actuator rod 68. As tension is applied to the brake actuator rod 68, the ball ramp 62 rotates about the center of the driven shaft 40. Rotation of the ball ramp 62 forces the balls 66 within the ball ramp 62 up their respective ramps 64. This action forces the ball ramp 62 apart resulting in an axial movement of the ball ramp 62.
The axial movement of the ball ramp 62 compresses the first clutch pack 52 since the two are located in direct contact with one another. The compression of the first clutch pack 52 causes friction to develop between the stators 58 and rotors 60 in the clutch pack 52. A predetermined amount of axial movement of the ball ramp 62 results in a predetermined amount of friction in the first clutch pack 52 which reduces and then stops the rotation of the rotors 60 with respect to the stators 58. The rotors 60, being attached to the driven shaft 40, prevent the shaft 40 from turning.
It can be appreciated that when the driven shaft 40 is no longer providing a rotational force to the ring gear 84 secured to the differential case 86, no rotational force will be transmitted to the axle half shafts 16, 18, thus effectively braking the vehicle. When there is no relative motion between the axle half shafts 16, 18, an equal braking torque is applied to the axle half shafts 16, 18 as shown in
When the brake pedal 82 is not deflected beyond a predetermined point or when it is released, a spring 124 biases the actuator rod 68 back into its original position. This causes the ball ramp 62 to move axially away from the first clutch pack 52, which reduces the compressive force on the first clutch pack 52. With the compressive force reduced or eliminated, the frictional force between the stators 58 and the rotors 60 is reduced or eliminated permitting the rotors 60 to rotate with respect to the stators 58.
A second clutch pack 126 is located within the differential case 86. The second clutch pack 126 is comprised of the friction disks 116, the reaction plates 117 and the biasing member 118. The biasing member 118 compresses the friction disks 116 and the reaction plates 117 against one another and against the interior surface 112 of the differential case 86. Thus, it can be appreciated that the friction disks 116 and reaction plates 117 are typically preloaded in compression by the biasing member 118.
Each of the friction disks 116 are splined for axial movement along one side gear 100 and the disks 116 rotate with the side gear 100, differential case 86 and ring gear 84 as long as both axle half shafts 16, 18 are rotating at the same speed. If a wheel and its associated tire attached to one of the axle half shafts 16 or 18 begins to rotate faster than the other tire/wheel/axle half shaft, such as in a turn, the disks 116 and plates 117 resist this relative rotation. The resistance is provided by the biasing member 118 compressing the disks 116 and the plates 117 together to develop friction between the disks 116 and the plates 117. It can therefore be appreciated that the stiffness of the biasing member 118 and the friction between the disks 116 and the plates 117 determines how much torque is required to produce relative motion of the axle half shafts 16, 18.
Based on the foregoing, it can also therefore be appreciated that the second clutch pack 112 permits unequal braking torque to be supplied to the two axle half shafts 16, 18. Thus, when a braking force is applied to the driven shaft 40 via the first clutch pack 52, the braking force can be varied through the second clutch pack 126 so that the two different braking forces can be applied to each axle half shaft 16, 18 and thus the wheels and tires connected to them, as shown in
Varying the torque bias between the shafts 16, 18, and thus the wheels/tires, is distinctly advantageous when one drive wheel is on a slippery surface with a low coefficient of friction and the other wheel has good traction as the braking torque required to stop the vehicle can be supplied to the wheel with good traction.
In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiments. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.
