Anti-lock brake system with piezoelectric brake actuator
First Claim
1. An electrical braking system, comprising:
- first friction braking means comprising;
a first piezoelectric ceramic layer having opposing first and second major faces; and
a first prestress layer bonded to said first major face of said piezoelectric ceramic layer;
wherein said first prestress layer normally applies a compressive force to said first piezoelectric ceramic layer;
a first moveable member to be braked;
an electric controller for generating a first electrical output signal for operating said first friction braking means in accordance with brake force demand inputs, said electric controller having an input side and an output side;
a first electrical conductor connected on a first end to said output side of said electric controller and on a second end across said first and second faces of said first piezoelectric ceramic layer of said first friction braking means;
actuating means for generating a first brake force demand input signal for said controlling means, said actuating means comprising;
a mechanical input device for generating a variable mechanical signal;
an electrical signal generator for generating a first brake force demand input signal proportional to said variable mechanical signal;
said electrical signal generator being in mechanical communication with said mechanical input device and in electrical communication with said input side of said electric controller;
a first wheel slip sensing means for determining a first wheel-road slippage condition, said first wheel slip sensing means comprising;
a first wheel speed sensor for sensing a peripheral wheel speed;
said first wheel speed sensor having an output signal proportional to said peripheral wheel speed;
first slip computing means for computing an acceleration and a vehicle body speed;
said first slip computing means comparing said sensed peripheral wheel speed to said computed acceleration and said computed vehicle body speed to determine if said first wheel-road slippage condition exists; and
first signal generation means for generating a second brake force demand input signal indicative of said first wheel-road slippage condition;
said first signal generation means being in electrical communication with said input side of said electric controller;
whereby electrically energizing said first friction braking means moves said friction braking means into contact with said first moveable member;
and whereby a first braking force is generated by moving said first friction braking means into contact with said first moveable member.
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Abstract
An anti-lock braking system includes a moveable member to be braked and a friction brake for applying a braking force. A controller actuates the friction brake in accordance with braking force demands. Braking force demands are determined by the controller by electrical input signals received from a signal generator that is mechanically linked to the brake pedal, as well as by signals from a slip sensor. The slip sensor records values from wheel speed sensor and computes values that may indicate a slippage condition. Based on the recorded and computed values, the slip sensor and sends electric signals to the controller. The friction brake includes a prestressed piezoelectric element that is lightweight, less cumbersome, and highly controllable as compared with prior anti-lock braking devices, and is actuated via electrical signals rather than a mechanical system. A modification is disclosed in which an anti-lock system is placed on each wheel with independent slip sensors providing signals to controllers that control application of braking forces over each wheel as necessary.
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Citations
7 Claims
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1. An electrical braking system, comprising:
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first friction braking means comprising;
a first piezoelectric ceramic layer having opposing first and second major faces; and
a first prestress layer bonded to said first major face of said piezoelectric ceramic layer;
wherein said first prestress layer normally applies a compressive force to said first piezoelectric ceramic layer;
a first moveable member to be braked;
an electric controller for generating a first electrical output signal for operating said first friction braking means in accordance with brake force demand inputs, said electric controller having an input side and an output side;
a first electrical conductor connected on a first end to said output side of said electric controller and on a second end across said first and second faces of said first piezoelectric ceramic layer of said first friction braking means;
actuating means for generating a first brake force demand input signal for said controlling means, said actuating means comprising;
a mechanical input device for generating a variable mechanical signal;
an electrical signal generator for generating a first brake force demand input signal proportional to said variable mechanical signal;
said electrical signal generator being in mechanical communication with said mechanical input device and in electrical communication with said input side of said electric controller;
a first wheel slip sensing means for determining a first wheel-road slippage condition, said first wheel slip sensing means comprising;
a first wheel speed sensor for sensing a peripheral wheel speed;
said first wheel speed sensor having an output signal proportional to said peripheral wheel speed;
first slip computing means for computing an acceleration and a vehicle body speed;
said first slip computing means comparing said sensed peripheral wheel speed to said computed acceleration and said computed vehicle body speed to determine if said first wheel-road slippage condition exists; and
first signal generation means for generating a second brake force demand input signal indicative of said first wheel-road slippage condition;
said first signal generation means being in electrical communication with said input side of said electric controller;
whereby electrically energizing said first friction braking means moves said friction braking means into contact with said first moveable member;
and whereby a first braking force is generated by moving said first friction braking means into contact with said first moveable member. - View Dependent Claims (2, 3, 4, 5, 6, 7)
de-energizing means for electrically de-energizing said first friction braking means in response to said second brake force input signal indicative of said first wheel road slippage condition;
whereby electrically de-energizing said first friction braking means moves said first friction braking means out of contact with said first moveable member.
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3. The apparatus according to claim 2,
wherein said first moveable member to be braked comprises a rotating disk having a first braking surface. -
4. The apparatus according to claim 3,
wherein said first friction braking means is adjacent said first braking surface of said rotating disk. -
5. The apparatus according to claim 4,
wherein said rotating disk further comprises a second braking surface in opposing relation to said first braking surface. -
6. The apparatus according to claim 5, further comprising:
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second friction braking means comprising;
a second piezoelectric ceramic layer having opposing first and second major faces; and
a second prestress layer bonded to said first major face of said second piezoelectric ceramic layer;
wherein said second prestress layer normally applies a compressive force to said first piezoelectric ceramic layer;
said second friction braking means being adjacent said second braking surface of said rotating disk;
and a second electrical conductor connected on a first end to said output side of said electric controller and on a second end across said first and second faces of said second piezoelectric ceramic layer of said second friction breaking means, said electric controller being adapted to generate a second electrical output signal for operating said third friction braking means in accordance with brake force demand inputs;
whereby electrically energizing said second friction braking means moves said second friction braking means into contact with said second braking surface of said first moveable member.
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7. The apparatus according to claim 6, further comprising:
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third friction braking means comprising;
a third piezoelectric ceramic layer having opposing first and second major faces; and
a third prestress layer bonded to said first major face of said piezoelectric ceramic layer;
wherein said third prestress layer normally applies a compressive force to said third piezoelectric ceramic layer;
a second moveable member to be braked;
a third electrical conductor connected on a first end to said output side of said electric controller and on a second end across said first and second faces of said third piezoelectric ceramic layer of said third friction braking means said electric controller being adapted to generate a third electrical output signal for operating said third friction braking means in accordance with brake force demand inputs;
a second wheel slip sensing means for determining a second wheel-road slippage condition, said second wheel slip sensing means comprising;
second wheel speed sensor for sensing a peripheral wheel speed;
said second wheel speed sensor having an output signal proportional to said peripheral wheel speed;
second slip computing means for computing an acceleration and a vehicle body speed;
said second slip computing means comparing said sensed peripheral wheel speed to said computed acceleration and said computed vehicle body speed to determine if said second wheel-road slippage condition exists; and
second signal generation means for generating a third brake force demand input signal indicative of said second wheel-road slippage condition;
said second signal generation means being in electrical communication with said input side of said electric controller;
whereby electrically energizing said third friction braking means moves said third friction braking means into contact with said second moveable member;
and whereby a third braking force is generated by moving said third friction braking means into contact with said second moveable member.
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Specification