Vehicle having brake system and method of operating
First Claim
1. A vehicle comprising:
- a master cylinder having an input side configured to receive an input from a brake pedal and an output side configured to provide a master cylinder output, at least one braking circuit having at least one wheel cylinder and a brake pressure generator, including a strokable piston, separate from the brake pedal;
a simulator circuit including a pedal feel simulator coupled to the master cylinder output side through a switchable simulator valve, the pedal feel simulator providing a reaction force to the brake pedal when the switchable simulator valve is in an open position;
at least one normally-open isolation valve operable to close and isolate the at least one braking circuit from the master cylinder and the simulator circuit;
a pressure sensor operable in at least one vehicle configuration to be in fluid communication with both the simulator circuit and the brake pressure generator; and
a controller programmed to, at a designated diagnostic time when no input is received from the brake pedal, establish a diagnostic circuit connecting the simulator circuit with an outlet of the brake pressure generator, and to stroke the piston in an advancing, pressure-generating direction and then retract the piston while observing a resulting brake fluid pressure decrease with the pressure sensor during piston retraction,wherein the controller is further programmed to check whether the relationship between the observed brake fluid pressure decrease and the piston retraction is within a predetermined acceptable range for continued operation of a brake-by-wire vehicle braking mode in which the master cylinder is coupled to the simulator circuit and decoupled from the at least one braking circuit, while brake fluid pressure is generated solely by the brake pressure generator.
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Accused Products
Abstract
A vehicle includes a brake pedal, a master cylinder, a braking circuit with a wheel cylinder, and a brake pressure generator with strokable piston. A pedal feel simulator is coupled to the master cylinder through a switchable valve, the simulator providing a reaction force. An isolation valve closes to isolate the braking circuit from the master cylinder and the simulator circuit. A controller is programmed to connect the simulator circuit with an outlet of the brake pressure generator, and to stroke and retract the piston at a designated diagnostic time. The controller observes a pressure decrease as the piston retracts and checks whether the pressure-decrease to piston-retraction relationship is within a predetermined acceptable range for continued operation of a brake-by-wire mode in which the master cylinder is coupled to the simulator circuit and decoupled from the braking circuit.
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Citations
20 Claims
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1. A vehicle comprising:
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a master cylinder having an input side configured to receive an input from a brake pedal and an output side configured to provide a master cylinder output, at least one braking circuit having at least one wheel cylinder and a brake pressure generator, including a strokable piston, separate from the brake pedal; a simulator circuit including a pedal feel simulator coupled to the master cylinder output side through a switchable simulator valve, the pedal feel simulator providing a reaction force to the brake pedal when the switchable simulator valve is in an open position; at least one normally-open isolation valve operable to close and isolate the at least one braking circuit from the master cylinder and the simulator circuit; a pressure sensor operable in at least one vehicle configuration to be in fluid communication with both the simulator circuit and the brake pressure generator; and a controller programmed to, at a designated diagnostic time when no input is received from the brake pedal, establish a diagnostic circuit connecting the simulator circuit with an outlet of the brake pressure generator, and to stroke the piston in an advancing, pressure-generating direction and then retract the piston while observing a resulting brake fluid pressure decrease with the pressure sensor during piston retraction, wherein the controller is further programmed to check whether the relationship between the observed brake fluid pressure decrease and the piston retraction is within a predetermined acceptable range for continued operation of a brake-by-wire vehicle braking mode in which the master cylinder is coupled to the simulator circuit and decoupled from the at least one braking circuit, while brake fluid pressure is generated solely by the brake pressure generator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of operating a vehicle utilizing a controller, the method comprising:
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operating in a primary brake-by-wire braking mode including; receiving an input from a brake pedal at an input side of a master cylinder and providing a master cylinder output corresponding to the brake pedal input at an output side of the master cylinder output, closing, by a controller signal, at least one normally-open isolation valve to isolate the output side of the master cylinder from at least one braking circuit having at least one wheel cylinder, sending a controller signal to a switchable simulator valve to open a fluid connection between the master cylinder output side and a simulator circuit including a pedal feel simulator to provide a reaction force to the brake pedal, sending a braking request signal to the controller, the braking request signal corresponding to the input from the brake pedal, and driving a brake pressure generator of the at least one braking circuit with the controller responsive to the braking request signal to achieve braking at the at least one wheel cylinder, the brake pressure generator having a strokable piston separate from the brake pedal; sending a controller signal, at a designated diagnostic time when no input is received from the brake pedal, to establish a diagnostic circuit connecting the simulator circuit with an outlet of the brake pressure generator; at the designated diagnostic time when no input is received from the brake pedal, stroking the piston of the brake pressure generator in an advancing, pressure-generating direction and then retracting the piston while observing a resulting decrease in brake fluid pressure during piston retraction; and determining with the controller, whether the relationship between the observed brake fluid pressure decrease and the piston retraction is within a predetermined acceptable range for continued operation of the primary brake-by-wire braking mode. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification