Machine element or mechanism – Gearing – Nonplanetary gearing differential type
Reexamination Certificate
2000-01-28
2001-08-07
Wright, Dirk (Department: 3681)
Machine element or mechanism
Gearing
Nonplanetary gearing differential type
Reexamination Certificate
active
06269712
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the field of differentials for vehicle drive trains and pertains particularly to positively locking differentials for motor vehicles.
Land vehicles, such as automobiles, trucks, buses and the like, typically utilize what has become known as an open differential for the final drive system. An automotive differential is a mechanical assembly, often a system of gears, which is located in the driving axle of a vehicle. It applies power to the wheels while at the same time allowing a difference in their rotational speeds; this difference occurs when the vehicle turns because the outside wheel rotates faster than the inside wheel due to its larger turning radius. Differentials accomplish this function in various ways, depending on their particular designs.
Differentials go back to the beginnings of the automotive era, but many of them had major traction problems in difficult terrain. Differentials have evolved into two broad classes: (1) Standard, or “open” differentials, and (2) Traction-adding differentials. Open differentials are by far the most common because they are inexpensive and do a good job for the majority of vehicles on the highway. However, open differentials have one major drawback: They can provide only limited power in marginal traction situations. To overcome this drawback, mechanical traction-adding differentials have been developed. These types of differentials are divided into two classes: (1) Limited Slip differentials, and (2) Locking differentials. Limited slip differentials are furler divided into two general classes: (1) Clutch type and (2) Gear type. Locking differentials also are further divided into two general classes: (1) Automatic and (2) Manual (activated by the driver). This invention is concerned primarily with automatic locking differentials, since they are the most widely used lockers and exist in a variety of designs. Other types of traction-enhancing devices and systems also have been developed, notably viscous coupling differentials and electronic traction control (ETC); however, these and other exotic designs are not mechanical lockers. Many designs have been tried over the years to overcome these traction problems, and some were produced either as factory-installed units or as after-market devices. While many of them have been satisfactory in many respects, they also have some drawbacks. Among these drawbacks are complexity, lack of reliability, cost, and adverse vehicle handling characteristics. Thus, a need exists for a simple, inexpensive, reliable and effective locking differential.
DEFINITION OF TERMS
Differential Carrier: Sometimes used interchangeably with the term differential case, the correct description of the differential carrier is that it is the housing in which the drive pinion, ring gear, and differential case are installed, and it is a part of the axle housing assembly. Thus, it holds, or carries, the differential case assembly and is therefore called the carrier. It may be an integral design in which it also supports the axle tubes, or it may be a drop-out design in which it is removable from the vehicle as the complete differential and carrier assembly.
Differential Case: Sometimes used interchangeably with the term differential carrier, the correct description of the differential case is that it is the round housing to which the ring gear is bolted and which contains the differential gear assembly. It is assembled into the differential carrier, and is not visible from the outside.
Locker. A Locker is an automotive differential that can provide up to 100% of the incoming power to either wheel yet also allow differentiation in a turn. One comment on terminology: The terms “locker” and “locking differential” have incorrectly been frequently used interchangeably with “limited slip” differential over the years. A limited-slip differential is generally a friction- or binding-type of design that is capable of providing only a limited amount of power to each wheel when the other one has lost traction. A full-locking differential, or “locker,” however, can provide up to 100% of the available power to either wheel even if the other one is off the ground or if an axle shaft is broken. Thus, the terms “locker” and “locking” properly refer only to full-locking (100%) types of designs.
SUMMARY AND OBJECTS OF THE INVENTION
It is the primary object of the present invention to provide a locking differential that is simple, effective and smooth in its operation.
In accordance with a primary aspect of the invention, a full-locking differential drive mechanism, comprised of an input drive means which is composed of a pair of opposed spaced drive races, each having an inner diameter, a coupling block disposed between said races and including coupling means for coupling them to drive together, output driven means comprising a pair of co-axially disposed coupler members, each having an outer diameter disposed within said drive races inner diameters, and a roller assembly disposed between said inner diameters and said outer diameters and operative to couple said drive races to said coupler members, thus producing a bi-directional over-running roller clutch.
REFERENCES:
patent: 4643284 (1987-02-01), Hardt et al.
patent: 5971123 (1999-10-01), Ochab et al.
patent: 6176359 (2001-01-01), Krisher
The Maxham Firm
Wright Dirk
LandOfFree
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