Power plants – Pressure fluid source and motor – Pulsator
Reexamination Certificate
2000-06-23
2001-12-04
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Pulsator
C060S397000, C091S001000
Reexamination Certificate
active
06324845
ABSTRACT:
TECHNICAL FIELD
The technical field of this invention is vacuum brake booster apparatus for motor vehicles.
BACKGROUND OF THE INVENTION
Power brake assist using differential pressure actuated brake boosters is standard in the motor vehicle industry. These brake boosters typically have a diaphragm separating a vacuum chamber always open to a source of vacuum, such as created in an engine intake passage, and a working chamber normally provided with vacuum but controlled by valve apparatus responsive to input brake pedal actuation to allow atmospheric air therein and thus provide brake force assist through a differential pressure across the diaphragm. In some systems, it is also known to provide a vacuum pump, either in place of the engine vacuum source or as a backup therefor, to provide a normal supplied vacuum.
The braking assist force provided by such known vacuum brake boosters is only an assist force, which is added to the force provided by the vehicle operator through the brake pedal. The vehicle operator applied force is itself transmitted directly through the booster apparatus and applied to the master cylinder, whether or not the assist braking force is generated by the vacuum brake booster. Thus, vehicles provided with such vacuum brake boosters may be stopped even in the unlikely occurrence of loss of vacuum, producing reduced or non-existent braking assist force, although reduced braking force can result in longer stopping distance. Braking systems are designed for safe stopping within specified distances at predetermined vehicle speeds, even with no braking assist; but this task is difficult for heavier vehicles, and a source of back-up vacuum is desired in some cases to ensure that such vacuum based braking assist force is not lost. The object of this invention is to provide a self-contained, compact, light-weight, backup vacuum assist apparatus, and particularly such apparatus that is capable of mounting directly to a vacuum brake booster without necessity of additional vacuum hoses and with minimal additional external electrical wiring requirements. Such apparatus is capable of helping large, heavy vehicles to meet the standards of FMVSS 135.
SUMMARY OF THE INVENTION
A self contained, supplemental vacuum assist unit is provided for use with a vacuum brake booster and a source of vacuum in a motor vehicle, wherein the vacuum brake booster has a vacuum chamber and a working pressure chamber. The unit has a housing defining an assist vacuum chamber having an opening with a fitting adapted for connection to the vacuum chamber of the vacuum brake booster and further defining an air exhaust chamber having an opening with a fitting adapted for connection to the source of vacuum. The assist vacuum chamber and the air exhaust chamber are separated by a wall having a first opening with a first unidirectional flow valve permitting air flow only from the assist vacuum chamber to the air exhaust chamber. An electric motor driven air pump is further provided in the housing with an inlet from the assist vacuum chamber and an outlet to the air exhaust chamber. The air pump is associated with a second unidirectional flow valve permitting air flow through the air pump only from the assist vacuum chamber to the air exhaust chamber. An electric circuit board is provided within the assist vacuum chamber and has a Hall effect sensor thereon to sense a magnetic field of a magnet adjacent the sensor and further has a control circuit thereon responsive to the Hall effect sensor to control operation of the electric motor driven air pump. The housing also has an opening from the assist vacuum chamber to a source of air at atmospheric pressure, the opening being closed by a flexible diaphragm. A plunger is activated by the diaphragm for axial movement therewith in response to changes in pressure thereacross; and a permanent magnet is affixed to the plunger adjacent the Hall effect sensor. The permanent magnet generates a magnetic field sensed by the Hall effect sensor, and the Hall effect sensor is responsive thereto to generate a signal changing with the position of the permanent magnet and thus of the pressure across the diaphragm.
The unit is self-contained, with the motor, pump, fluid flow passages, check valves, pressure sensor and electronics all within the housing for compact packaging within a crowded vehicle engine compartment, light weight for minimal fuel penalty, and protection of the parts from environmental dirt and humidity. In the unit, the pressure sensor incorporates a Hall effect sensor for significant cost savings and mounts the Hall effect sensor on a circuit board within the assist vacuum chamber, together with the diaphragm activated plunger and magnet, for maximum protection and convenience of design. In a preferred embodiment, the magnet is axially adjustable with respect to the plunger and adjusted in calibration for minimal temperature variation of motor pump motor switching point. In a preferred embodiment, the plunger is guided by the circuit board to maintain a specified normal distance from the Hall effect sensor in axial motion. In a preferred embodiment, separate adjustment may be made for preferred spring bias on the plunger. In a preferred embodiment, the unit is provided with a fitting for direct connection to the vacuum chamber of the booster to eliminate a connecting hose therebetween. In a preferred embodiment, the unidirectional valve associated with the air pump acts on the air outlet of the pump to create a pressure drop that increases pump efficiency. In a preferred embodiment, in which the unit is attached directly to the booster, the unit is provided with two levels of sound isolation from the booster, with isolated mounting of the motor within the housing and isolation pads on the booster attachment brackets.
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Fulks Gary Chris
Haerr Timothy Allen
Mohile Vivek V.
Poole Douglas E.
Schlangen Timothy M.
Delphi Technologies Inc.
Kershteyn Igor
Look Edward K.
Sigler Robert M.
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