Electrically-operated disc brake assemblies for vehicles

Details Electrically-operated disc brake assemblies for vehicles Electrically-operated disc brake assemblies for vehicles

1998-10-15

2001-05-15

Oberleitner, Robert J. (Department: 3613)

Brakes

Operators

Electric

C074S424790

Reexamination Certificate

active

06230855

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is the National Stage under 35 U.S.C § 371 of PCT application PCT/GB96/02639, filed Oct. 30, 1996, which designated the United States, and which claimed priority to the Great Britain application 95226321.2, filed Nov. 4, 1995.
This invention relates to improvements in electrically-operated disc brake assemblies for vehicles of the kind in which a friction member is adapted to be applied to a rotatable brake disc by a brake-applying means including an electric motor, and transmission means in the form of a linear actuator comprising a screw device is adapted to apply an axially-directed brake-applying force to the friction member in response to operation of the motor.
A brake of the kind set forth is known from EP-A-0 339 024. In the brake of EP-A-0 339 024 the electric motor is used to drive an input to a reduction gearbox, and the gearbox is adapted to translate the high speed movement of the motor into a controlled high torque output to the screw device.
According to a first aspect, the invention provides an electrically-operated disc brake assembly for vehicles in which a friction member is adapted to be applied to a rotatable brake disc by a brake-applying means including an electric motor and a transmission means in the form of a linear actuator comprising a screw device adapted to apply an axially-directed brake-applying force to the friction member in response to operation of the motor, characterised in that the screw-device comprises inner and outer co-operating screw-threaded members with the outer member comprising the armature of the electric motor.
According to a second aspect, the invention provides an electrically-operated disc brake assembly for vehicles in which a friction member is adapted to be applied to a rotatable brake disc by a brake applying means including an electric motor and a transmission means in the form of a linear actuator comprising a screw fence adapted to apply an axially-directed brake-applying force to the friction member in response to operation of the motor, characterised in that the screw-device comprises inner and outer co-operating screw-threaded members with the inner member co-operating with the armature of the motor, and the armature having an axially sliding coupling with an extension of the inner member.
Since the motor substantially surrounds the linear actuator such a construction has a number of advantages.
The brake is more compact since its overall length is reduced in comparison with other, similar brakes. This improves package size and eliminates installation problems.
The consequential increase in the diameter of the motor changes the characteristics of the motor in such a way that output torque is increased with corresponding decrease in output speed. The increase in motor diameter thereby changes the motor to a low speed high torque motor enabling us to omit a conventional, reduction, gearbox.
Conveniently the linear actuator is of the fine pitch roller screw type and is relied upon to achieve the necessary reduction between the outer screw-threaded member and the inner screw-threaded member.
In one construction the outer screw-threaded member is journalled at opposite ends for rotation on a pair of axially spaced thrust bearings which take the actual thrust on the member when the brake is applied.
In another construction the thrust on the outer screw-threaded member is taken out on a caliper or housing of the brake through a thrust bearing, the member otherwise being journalled for rotation at axially spaced positions.
In another embodiment the linear actuator acts on the friction member through a load spreader or tappet which acts as a heat shield.
When the inner member is rotated by the armature, the outer member which acts on the friction member is keyed against rotation.


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