Braking system with power brake, braking force proportioning, anti-skid, and traction control functions

A braking system for providing a braking force proportioning function for a vehicle having at least two wheels, which comprises:

• at least two brakes, including wheel cylinders, responsive to a fluid pressure to retard the rotation of the wheels;
• a master cylinder actuated by a vehicle operator for generating a controlled fluid pressure;
• a source of a predetermined fluid pressure substantially higher than said controlled fluid pressure;
• a reservoir for a brake fluid;
• at least two pressure modulators in fluid communication with said wheel cylinders, said master cylinder, said source and said reservoir for respectively controlling fluid pressures communicated to respective wheel cylinders;
• each of said pressure modulator comprising;
• valve means responsive to said controlled fluid pressure for controlling fluid communication between said source and associated wheel cylinder and between said reservoir and associated wheel cylinder so that a modulated fluid pressure which is a multiple of said controlled fluid pressure is communicated to associated wheel cylinder during normal braking operation;
• electronically controllable first biasing means for biasing said valve means so that said modulated fluid pressure communicated to associated wheel cylinder is reduced upon energization of said first biasing means;
• and,
• electronically controllable second biasing means for controlling fluid communication between said source and associated wheel cylinder and between said reservoir and associated wheel cylinder so that said modulated fluid pressure communicated to associated wheel cylinder is increased upon energization of said second biasing means;
• sensing means associated with the wheels for sensing load conditions imposed upon respective wheels and delivering signals in accordance with the load conditions;
• and,
• control means responsive to said signals and cooperating with said first and second biasing means for controlling said first and second biasing means so that fluid pressures communicated from said pressure modulators to respective wheel cylinders are proportioned in accordance with the load conditions at said wheels during braking force proportioning operation of the braking system.

A braking system for providing a braking force proportioning function for a vehicle having at least two wheels, which comprises:

• at least two brakes, including wheel cylinders, responsive to a fluid pressure to retard the rotation of the wheels;
• a master cylinder actuated by a vehicle operator for generating a controlled fluid pressure;
• a source of a predetermined fluid pressure substantially higher than said controlled fluid pressure;
• a reservoir for a brake fluid;
• at least two pressure modulators in fluid communication with said wheel cylinders, said master cylinder, said source and said reservoir for respectively controlling fluid pressures communicated to respective wheel cylinders;
• each of said pressure modulators comprising;
• valve means responsive to said controlled fluid pressure for controlling fluid communication between said source and associated wheel cylinder and between said reservoir and associated wheel cylinder so that a modulated fluid pressure which is a multiple of said controlled fluid pressure is communicated to associated wheel cylinder during normal braking operation;
• electronically controllable first biasing means for biasing said valve means so that said modulated fluid pressure communicated to associated wheel cylinder is reduced upon energization of said first biasing means;
• and,
• electronically controllable second biasing means for controlling fluid communication between said source and associated wheel cylinder and between said reservoir and associated wheel cylinder so that said modulated fluid pressure communicated to associated wheel cylinder is increased upon energization of said second biasing means;
• sensing means associated with the wheels for sensing the rotational speeds of the wheels and delivering signals in accordance with the speeds;
• and,
• control means responsive to said signals and cooperating with said first and second biasing means for sensing a potential wheel skid condition and controlling said first and second biasing means so that fluid pressures communicated from said pressure modulators to respective wheel cylinders are proportioned in accordance with the potential wheel skid conditions at said wheels during braking force proportioning operation of the braking system to avoid the potential wheel skid condition.

A braking system for providing a braking force proportioning function for a vehicle having at least two wheels, which comprises:

• at least two brakes, including wheel cylinders, responsive to a fluid pressure to retard the rotation of the wheels;
• a master cylinder actuated by a vehicle operator for generating a controlled fluid pressure;
• a source of a predetermined fluid pressure substantially higher than said controlled fluid pressure;
• a reservoir for a brake fluid;
• at least two pressure modulators in fluid communication with said wheel cylinders, said master cylinder, said source and said reservoir for respectively controlling fluid pressures communicated to respective wheel cylinders;
• each of said pressure modulators comprising;
• valve means responsive to said controlled fluid pressure for controlling fluid communication between said source and associated wheel cylinder and between said reservoir and associated wheel cylinder so that a modulated fluid pressure which is a multiple of said controlled fluid pressure is communicated to associated wheel cylinder during normal braking operation;
• electronically controllable first biasing means for biasing said valve means so that said modulated fluid pressure communicated to associated wheel cylinder is reduced upon energization of said first biasing means;
• and,
• electronically controllable second biasing means for controlling fluid communication between said source and associated wheel cylinder and between said reservoir and associated wheel cylinder so that said modulated fluid pressure communicated to associated wheel cylinder is increased upon energization of said second biasing means;
• sensing means associated with the wheels for sensing the rotational speeds of the wheels and delivering signals in accordance with the speeds;
• and,
• control means responsive to said signals and cooperating with said first and second biasing means for sensing a potential wheel spin condition and controlling said first and second biasing means so that fluid pressures communicated from said pressure modulators to respective wheel cylinders are proportioned in accordance with the potential wheel skid conditions at said wheels during braking force proportioning operation of the braking system to avoid the potential wheel spin condition.

A pressure modulator for modulating a fluid pressure communicated to a hydraulic device, which comprises:

• a housing having therein a controlled pressure chamber communicated with a source of a controlled fluid pressure, an inlet chamber communicated with a source of a predetermined fluid pressure substantially higher than said controlled fluid pressure, an outlet chamber communicated with said hydraulic device, a low pressure chamber communicated with a reservoir for a hydraulic fluid, and an output pressure chamber communicated with said outlet chamber, said low pressure chamber being in fluid communication with said output pressure chamber, said inlet chamber being in fluid communication with said outlet chamber;
• first flow control means for controlling fluid communication between said inlet and outlet chambers;
• second flow control means for controlling fluid communication between said output pressure and low pressure chambers;
• a valve member responsive to fluid pressure in said outlet and controlled pressure chambers and cooperating with said first and second flow control means for regulating fluid communication between said inlet and outlet chambers and between said output pressure and low pressure chambers, said valve member having for said controlled pressure chamber a pressure receptive area which is a multiple of a pressure receptive area for said outlet chamber member so that fluid pressure communicated to the hydraulic device is a multiple of the controlled fluid pressure;
• and,
• solenoid means, including a solenoid coil mounted to the housing and an armature integral with said valve member, for biasing the valve member against fluid pressure in said controlled pressure chamber.

A pressure modulator for modulating a fluid pressure communicated to a hydraulic device, which comprises:

• a housing having therein a controlled pressure chamber communicated with a source of a controlled fluid pressure, an inlet chamber communicated with a source of a predetermined fluid pressure substantially higher than said controlled fluid pressure, an outlet chamber communicated with said hydraulic device, a low pressure chamber communicated with a reservoir for a hydraulic fluid, and an output pressure chamber communicated with said outlet chamber, said inlet chamber being in fluid communication with said outlet chamber, said low pressure chamber being in fluid communication with said outlet chamber;
• a valve member responsive to fluid pressure in said output pressure and controlled pressure chambers for regulating fluid communication between said inlet and outlet chambers and between said outlet and low pressure chambers, said valve member having for said controlled pressure chamber a pressure receptive area which is a multiple of a pressure receptive area for said output pressure chamber member so that fluid pressure communicated to the hydraulic device is a multiple of the controlled fluid pressure;
• first solenoid means, including a first solenoid coil mounted to the housing and an armature integral with said valve member, for biasing the valve member against fluid pressure in said controlled pressure chamber to reduce fluid pressure communicated to the hydraulic device when energized;
• and,
• second solenoid means, including a second solenoid coil mounted to the housing and the armature, for biasing the valve member against fluid pressure in said output pressure chamber to increase fluid pressure communicated to the hydraulic device when energized.

A pressure modulator for modulating a fluid pressure communicated to a hydraulic device, which comprises:

• a housing having therein a stepped bore, a controlled pressure chamber communicated with a source of a controlled fluid pressure, an inlet chamber communicated with a source of a predetermined fluid pressure substantially higher than said controlled fluid pressure, an outlet chamber communicated with the hydraulic device, and a low pressure chamber communicated with a reservoir for a hydraulic fluid, said inlet chamber being in fluid communication with said outlet chamber, said low pressure chamber being in fluid communication with said outlet chamber, said housing also having a valve seat formed between a large diameter section and a small diameter section of said stepped bore;
• a valve member movably received in the large diameter section of the bore and spring-biased into sealing engagement with the valve seat to control fluid communication between the inlet and outlet chambers;
• a first sensing piston movably received in the small diameter section of the bore and responsive to fluid pressure in the outlet chamber to cooperate with the valve member to control fluid communication between the outlet and low pressure chambers and to control the position of the valve member;
• a second sensing piston responsive to fluid pressure in the controlled pressure chamber to urge the first sensing piston into engagement with the valve member, causing the valve member to move away from the valve seat to permit fluid communication between the inlet and outlet chambers;
• said second sensing piston having a pressure receptive area which is a multiple of a pressure receptive area of the first sensing piston so that fluid pressure communicated to the hydraulic device is a multiple of the controlled fluid pressure;
• first solenoid means, including a first solenoid coil mounted to the housing and an armature integral with said valve member, for biasing the first sensing piston to move against the force of the second sensing piston to reduce fluid pressure communicated to the hydraulic device when energized;
• and,
• second solenoid means, including a second solenoid coil mounted to the housing and the armature, for biasing the first sensing piston against fluid pressure in the outlet chamber to increase fluid pressure communicated to the hydraulic device when energized.