Fluid-pressure and analogous brake systems – With pump
Reexamination Certificate
1999-01-21
2001-01-09
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
With pump
C188S072100, C303S113100, C303SDIG001, C303S003000, C303S155000
Reexamination Certificate
active
06170921
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relate generally to braking systems for use in motor vehicles, and more particularly to the use of a magnetostrictive pump assembly for such a braking system.
Generally, conventional braking systems include an accumulator for accumulating hydraulic pressure to be used for the braking operation of the vehicle and further have an apparatus of controlling the hydraulic pressure of the accumulator. The hydraulic pressure in the accumulator is typically controlled by an electric motor-driven pump associated with a pressure sensor which senses the accumulator pressure. The outlet of the pump is connected to the accumulator. The motor-driven pump draws brake fluid from a reservoir and pumps the brake fluid to the accumulator to increase the fluid pressure in the accumulator.
The accumulator pressure control apparatus is operated such that the motor-driven pump is operated in response to the accumulator pressure falling below a predetermined lower limit and deenergized when the accumulator pressure reaches a predetermined upper limit. One problem with such an accumulator pressure control apparatus is that it is difficult to accurately keep the accumulator pressure in a predetermined range due to the delay between actuation and deactivation of the motor and the resulting output from the pump.
Further, such a delay in the pump operation method causes difficulty to quickly stop the pump at the time of termination of the braking operation. This disadvantage is particularly magnified when a slip control or anti-lock brake system is applied to each wheel and integrated with the brake system, as the non-simultaneous actuation of a brake at each wheel increases the delay in stopping the motor and results in generation of noises and vibration due to continued pump operation.
SUMMARY OF THE INVENTION
The present invention overcomes the disadvantages described above by providing an actuation system powered by a magnetostrictive pump assembly. The pumping action of the magnetostrictive pump assembly is provided by the linear expansion and contraction of a magnetostrictive material in response to an external magnetic field. The magnetostrictive material reacts in a dimensionally predictable, repeatable manner to the magnetic changes. Additionally, as the magnetostrictive material reacts essentially instantaneously, any delay between actuation or deactivation is practically eliminated. Further, although the displacement of the pump is relatively small, it can be cycled at extremely high frequencies to provide substantial pumping capacity. Also, because of the relatively small displacement, the magnetostrictive pump effectively has no moving parts.
The present invention generally employs the magnetostrictive pump assembly to operate a fluid ram such as a brake cylinder connected to an actuator such as a brake. A first accumulator is connected to an input of the fluid ram to store a fluid which actuates the fluid ram. A second accumulator is similarly connected to an output of the fluid ram to receive the used fluid after actuation of the fluid ram. The magnetostrictive pump assembly is connected between the first accumulator and second accumulator, to transfer the fluid from the second accumulator to the first accumulator such that the fluid is maintained at a high pressure for activation of the fluid ram.
In use with a braking system, the magnetostrictive pump assembly and fluid ram can be integrated within a brake caliper. The magnetostrictive pump assembly can be selectively operated by an electric signal to pressurize the fluid and actuate the fluid ram. The fluid ram applies a force to a brake rotor connected to a wheel of a vehicle for applying a braking force to the wheel. Rapid operation of the magnetostrictive pump assures that fluid ram is immediately available for activation of the brake.
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Butler Douglas C.
Carlson & Gaskey & Olds
Meritor Heavy Vehicle Systems LLC
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