Planetary gear transmission systems or components – Differential planetary gearing – Bevel gear differential
Utility Patent
1999-05-26
2001-01-02
Ta, Khoi Q. (Department: 3681)
Planetary gear transmission systems or components
Differential planetary gearing
Bevel gear differential
C475S235000
Utility Patent
active
06168545
ABSTRACT:
TECHNICAL FIELD
This invention relates to geared automotive differential mechanisms for transferring torque from a vehicle engine to each of two vehicle traction wheels.
BACKGROUND ART
Differential mechanisms commonly used in automotive vehicle drivelines are capable of transferring driving torque from an engine-driven drive shaft to each of two axle half shafts for the vehicle traction wheels. The differential mechanism typically comprises a differential carrier housing that is driven by a pinion connected drivably to the torque output element of a multiple-ratio, geared transmission. Differential pinions in the differential carrier housing drivably engage side gears, one side gear being connected drivably to the inboard end of one axle half shaft, and the other side gear being drivably connected to the inboard side of the other axle half shaft.
In the case of a limited slip differential, it is known design practice to use a friction clutch for establishing a mechanical torque bias. Friction elements of the clutch are carried by the differential carrier housing and by a differential side gear. It is preferable to provide a separate friction clutch for each of the two side gears. A spring is used for loading the friction elements of the differential clutches. This establishes friction torque bias which inhibits differential motion of the side gears for any torque value that is lower than a threshold breakaway torque.
In other known limited slip differential designs, the clutches are loaded by pressure rings situated within the differential carrier housing. The pressure rings rotate in unison with the housing, but they are adapted for axial adjustment within the housing as torque is delivered to the differential carrier. A differential pinion shaft engages a cam surface on the pressure rings so that an axial force is developed on the pressure rings, the magnitude of the force being proportional to the torque delivered to the carrier housing. The friction elements of the clutches are located symmetrically within the differential carrier housing. As torque is delivered to the carrier housing, a torque bias is established that is proportional to the transmitted torque. The torque bias in such differentials is determined by the number of clutch discs and by the geometry of the cam formed on the pressure rings.
U.S. patent application Ser. No. 09/114,505, filed Jul. 13, 1998, entitled “DIFFERENTIAL SPEED-SENSITIVE AND TORQUE-SENSITIVE LIMITED SLIP COUPLING”, which is assigned to the assignee of the present invention, discloses a limited slip differential that includes a mechanical torque bias established by pressure rings and that also includes a hydrostatic, speed-sensitive torque bias. The speed-sensitive torque bias is established by a positive-displacement pump having driving and driven elements that are connected, respectively, to one of the side gears and to the differential carrier housing. Thus, when the differential side gear rotates relative to the carrier housing, hydrostatic torque resistance is established. That torque resistance creates a torque bias that complements the mechanical torque bias established by the pressure rings. The hydrostatic torque bias is speed-sensitive because the volume of hydrostatic pressure fluid displaced by the positive-displacement pump is proportional to the relative speeds of the differential carrier housing and the side gear.
DISCLOSURE OF INVENTION
The differential mechanism of the invention has features that are common to limited slip differential mechanisms of the type described in the preceding discussion. It includes a geared differential assembly including differential pinions and two side gears, one side gear being connected to each of two axle half shafts. A pair of cammed thrust rings or pressure rings is situated adjacent each of two friction clutch assemblies enclosed within the differential carrier housing. As in the case of the mechanical torque-sensitive bias feature described in application Ser. No. 09/114,505, the friction clutch discs of the present invention are frictionally engaged as torque is transmitted from the differential carrier through each of the side gears to the axle half shafts. The force acting on the friction discs through the cammed pressure rings is proportional to the torque being transmitted. The force of the pressure rings is opposed by a spring that establishes a preload on the friction disks. During operation of the vehicle driveline with relatively low engine throttle settings, the engaging force on the clutch friction elements increases at a relatively low rate as the force of the clutch spring is overcome. When the clutch spring is fully deflected as the engine throttle setting is advanced, the force applied to the clutch friction elements by the pressure rings increases at an increased rate. The presence of the spring, therefore, provides a delayed action in the buildup of a torque bias as the engine throttle is increased from a low setting to a wide-open setting.
When the limited slip differential of the present invention is used in a vehicle such as a racing vehicle, variable throttle settings are effected by the driver during turning maneuvers. It is common practice for the driver to relax the throttle setting as the vehicle enters a curve and to increase the throttle setting as the turning maneuver proceeds. In such a maneuver, the vehicle normally tends to understeer, especially when the driver advances the throttle setting from an intermediate value toward the wide-open throttle setting. By providing a modified rate of increase of the torque bias with increasing throttle setting throughout a range of throttle settings less than the intermediate value, and by providing an increased rate of increase of the torque bias at advanced throttle settings greater than the intermediate throttle setting, the driver has greater control of the vehicle during a powered turn because the understeering tendency is substantially reduced.
It is an objective of the invention to provide a limited slip differential that incorporates a changing rate of increase of the torque bias with increasing throttle settings. The invention accordingly comprises a geared differential mechanism with two side gears that distribute torque to the driver axle shafts, which are coaxially aligned. At least one planetary pinion engages each side gear. A carrier housing rotatably supports the pinion, and the carrier is driven by a torque input member.
At least one friction disc of a pair of friction clutches is secured to the carrier, and a companion disc is secured to a side gear. A cammed pressure ring is located in the carrier housing between the pinion and the side gear. Axial thrust forces developed by the pressure ring create a friction torque bias.
A spring in the carrier housing acts on the pressure ring for each clutch to oppose the thrust forces, thereby delaying the development of the friction torque bias. Provision is made for the spring to be bottomed out against the differential carrier housing when the torque sensitive force applied to the clutch disk assembly by the pressure ring exceeds an intermediate value that is less than the torque bias created when the engine operates near a wide-open throttle setting.
REFERENCES:
patent: 2949792 (1960-08-01), Smith
patent: 3724289 (1973-04-01), Kennicutt
patent: 5059160 (1991-10-01), Raniero
patent: 5215506 (1993-06-01), Hara
patent: 5299986 (1994-04-01), Fabris et al.
patent: 5310388 (1994-05-01), Okcuoglu et al.
patent: 5536215 (1996-07-01), Shaffer et al.
patent: 5595214 (1997-01-01), Shaffer et al.
patent: 5611746 (1997-03-01), Shaffer
patent: 5938556 (1999-08-01), Lowell
patent: 58-221046 (1983-12-01), None
patent: 61-67629 (1986-04-01), None
patent: 2-176236 (1990-07-01), None
patent: 9-60710 (1997-03-01), None
patent: 7-293665 (1997-11-01), None
patent: 11-182650 (1997-11-01), None
Bliss McGlynn P.C.
McLaren Automotive Group, Inc.
Ta Khoi Q.
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