Machine element or mechanism – Control lever and linkage systems – Foot operated
Reexamination Certificate
1999-04-01
2001-10-09
Luong, Vinh T. (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Foot operated
C074S560000
Reexamination Certificate
active
06298746
ABSTRACT:
TECHNICAL FIELD
This invention relates to a motor vehicle brake pedal.
BACKGROUND OF THE INVENTION
A traditional motor vehicle brake system includes a plurality of hydraulically actuated wheel brakes, a master cylinder, and a brake pedal. The brake pedal includes a pedal lever on a body of the motor vehicle linked to a piston assembly in the master cylinder. To apply the wheel brakes, an operator pushes on a foot pad on the pedal lever to pivot the pedal lever and linearly stroke the piston assembly in the master cylinder. The linear stroke of the piston assembly is opposed or resisted by a force attributable to fluid pressure in the wheel brakes and in a plurality of hydraulic channels between the wheel brakes and the master cylinder. The “pedal force” with which the operator must push on the foot pad to apply the wheel brakes mirrors the fluid pressure force opposing the stroke of the master cylinder piston assembly and initially increases slowly relative to pivotal movement of the pedal lever, i.e. relative to “pedal travel”, as compliance in the wheel brakes and in the hydraulic channels is taken up. Then, pedal force increases at an increasing rate, i.e. exponentially, relative to pedal travel as the wheel brakes become applied. Motor vehicle operators perceive this relationship between pedal travel and pedal force as the “feel” of the brake system and, because of the widespread use of such traditional brake systems for many years, expect generally the same feel from all motor vehicle brake systems. Accordingly, in a motor vehicle brake system in which fluid pressure to apply a wheel brake is created independently of a brake master cylinder by an electro-hydraulic apparatus such as a pump and an electric motor, i.e. in a “brake-by-wire” brake system, the brake pedal is adapted to artificially mimic or emulate the feel of the brake pedal in a traditional brake system. For example, brake pedals described in U.S. Pat. Nos. 5,729,979 and 5,603,217, issued Mar. 24, 1998 and Feb. 18, 1997, respectively, and assigned to the assignee of the this invention, include elastomeric compliant elements which, when squeezed, mimic the fluid pressure force which opposes pedal travel in a traditional motor vehicle brake system. A brake pedal according to this invention is a novel alternative to prior brake pedals which emulate, in a brake-by-wire brake system, the fluid pressure force which opposes pedal travel in a traditional motor vehicle brake system.
SUMMARY OF THE INVENTION
This invention is a new and improved brake pedal for a motor vehicle brake-by-wire brake system including a pedal lever pivotally supported on a body of the motor vehicle, a foot pad on the pedal lever, and a compliant member having a plurality of parallel beams thereon defining cantilever springs. A pedal force on the foot pad effects pivotal movement, i.e. “pedal travel”, of the pedal lever from a release position toward a brake full apply position. The parallel beams defining cantilever springs are arrayed in series between the pedal lever and the motor vehicle body and engage successively so that the effective stiffness of the compliant member increases during pedal travel as succeeding ones of the parallel beams flex resiliently in cantilever spring bending. The stiffness of each of the parallel beams and the magnitudes of a plurality of clearance spans therebetween are “tuned” to yield a pedal force which initially increases slowly relative to pedal travel and then increases exponentially relative to pedal travel thereby emulating the relationship between pedal force and pedal travel of a brake pedal in a traditional motor vehicle brake system. Elastic pads on the parallel beams cushion the engagement of each parallel beam against the next succeeding parallel beam.
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Delphi Technologies Inc.
Luong Vinh T.
Sigler Robert M.
LandOfFree
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