Power plants – Pressure fluid source and motor – Pulsator
Patent
1998-05-26
1999-09-21
Lopez, F. Daniel
Power plants
Pressure fluid source and motor
Pulsator
F15B 708
Patent
active
059539160
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a master cylinder, in particular for a hydraulic automotive vehicle brake system.
A master cylinder of this type is disclosed in U.S. Pat. No. 5,187,934. To ensure pressure compensation between the pressure chamber and the supply chamber and the function of replenishment from the supply chamber into the pressure chamber, pressure compensation ports configured as bores are provided in the pistons of the prior art master cylinder which are designed as plungers. The bores are adequate for pressure compensation and for the protection of the replenishment action during bleeding of the brake system. However, when the master cylinder is intended for use in brake systems with traction slip control, driving dynamics control or other independently operable brake systems, a small number of bores are not sufficient to furnish the fluid flow which is required by the pump of the brake system. The small cross-section of the bores produces an excessive throttling resistance, with the result that the fluid volume required in the independently controlled braking mode (for example, traction slip control or driving dynamics control) cannot be made available in a sufficiently short time. The provision of a larger number of bores increases the manufacturing costs and, thus, is uneconomical.
An object of the present invention is to overcome the problem mentioned with respect to the state of the art without unreasonably increasing the manufacturing costs.
SUMMARY OF THE INVENTION
Therefore, according to the present invention, several slits extending in the circumferential direction are provided instead of the compensating bores in the piston. Compared to the bores, the advantage of the slits is that they have a larger cross-section and, also, smaller axial dimensions. This avoids excessive wear of the sealing element, especially, of the inside sealing lip of a sealing sleeve. Further, the slits permit a sufficient fluid flow to the pump of the controlled brake system. Besides, the small width of the slits satisfies the requirement of achieving smallest possible lost travels in a special way.
In a preferred aspect of the present invention, the slits are positioned in the groove bottom of a circumferential groove. It is thereby ensured, even without an accurate deburring action, that sharp edges which might damage the sealing elements are not produced at the slits when the slits are recessed. More particularly, the circumferential groove is given flat flanks which also prevents the sealing elements from being damaged when overridden.
The slits can be made in various manufacturing processes, such as milling, for example, by a disc-milling cutter, sawing, or by eccentric internal side turning or turning outside diameter processes. Basically, the slits may also be punched when the pistons are made of heatproof material, such as steel, where a thinner wall thickness is possible. A round boundary line between the web and the slit occurs when single of multiple radial milling is effected, or also with slits made by eccentric turning. Correspondingly straight boundary lines can be produced by single, double or multiple continuous milling.
Favorably, the piston of the present invention can be made of metal or plastic.
Further advantages of the present invention can be seen in the following description by way of the Figures.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings,
FIG. 1 is a longitudinal cross-sectional view of a master cylinder of the present invention.
FIG. 2 is a cross-sectional view of a piston of a master cylinder of the present invention on the level of the supply slits.
FIGS. 3 to 5 show further pistons corresponding to the FIG. 2 embodiment.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a master cylinder with a housing 1 in which a stepped bore 2 is incorporated that is closed by a cover 3. Cover 3 is undetachably connected to the housing 1 by a wire 4.
Bearing against a step 5 of bore 2 is a guide element 6 which comprises two partial elements 7,
REFERENCES:
patent: 2127290 (1938-08-01), Farina
patent: 2195244 (1940-03-01), Ericson
patent: 5121686 (1992-06-01), Schonlau et al.
patent: 5187934 (1993-02-01), Mori
patent: 5251446 (1993-10-01), Mori et al.
Jungmann Udo
Konig Harald
Kreh Heinrich
Wurl Gerhard
ITT Manufacturing Enterprises Inc.
Lopez F. Daniel
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