Fluid handling – Self-proportioning or correlating systems – Supply and exhaust type
Patent
1995-12-29
1998-07-07
Hepperle, Stephen M.
Fluid handling
Self-proportioning or correlating systems
Supply and exhaust type
13762569, B60I 1314, G05D 1610
Patent
active
057753598
DESCRIPTION:
BRIEF SUMMARY
FIELD AND BACKGROUND OF THE INVENTION
The present invention proceeds from a hydraulic pressure control valve, especially a hydraulic power brake valve.
Such a pressure control valve developed as a power brake valve is known from Federal Republic of Germany DE 35 45 975 A1. That valve has, within a valve housing, a valve bore into which a supply channel, a brake pressure channel as load pressure, and a tank channel debouch spaced axially from each other, the supply channel being arranged between the brake pressure channel and the tank channel. Furthermore, in the known power brake valve in accordance with the preamble to claim 1, the valve bore contains a control piston which is displaceable in a first direction into a first end position defined by a stop in which the supply channel and the brake pressure channel are connected to each other and in a second direction into a second end position in which the brake pressure channel and the tank channel are connected to each other. Between these positions, the control piston can assume a control position in which it separates the brake pressure channel with zero overlap or a slight positive overlap from the supply channel and the tank channel. In the known power brake valve, the control piston has a central longitudinal bore into which there debouches a transverse bore the diameter of which corresponds to the clear distance between the supply channel and the tank channel and which is located in the region between these two channels in the control position of the control piston. The longitudinal bore of the control piston is conducted in the region of the brake pressure channel by further bore again outward into a region of the control piston which is provided with a recess. Furthermore, the longitudinal bore is also open at the end of the recessed section of the control piston. Via the transverse bores and the longitudinal bores, the brake pressure channel is connected upon movement of the control piston out of the control position in the one direction to the supply channel and upon movement in the other direction to the tank channel.
In power brake systems pressures of up into the region of 100 bar are built up, depending on the external force exercised on the power brake valve. It is characteristic in this connection that a graph in which the time required for the pressure build-up is plotted against the final pressure show a region having a strong curvature. For brake pressures which are above this region, the time for the building-up of the pressure is at least approximately always the same. Below that region, the time for the building-up of the pressure increases greatly for smaller brake pressures. This is due to the fact that, on the one hand, the amount of pressure fluid flowing through the valve depends only slightly on the brake pressure which is building up and that, on the other hand, the control valve no longer enters into its first end position with the maximum cross section of flow in the case of lower final pressures. Approximately the same amount of pressure fluid must then flow through a cross section which is smaller than for higher final pressures. A rapid reaction of a hydraulic system to a control signal is generally of advantage. In particular, a rapid build-up of pressure in a brake system is favorable since in that way the safety of the persons travelling in vehicles equipped with such a brake system is increased and the feel of braking is improved.
SUMMARY OF THE INVENTION
Accordingly, the object of the invention is to develop a hydraulic pressure control valve, particularly a hydraulic power brake valve with which short times for the building up of pressure to very low final pressures can be obtained.
This object is achieved in accordance with the invention with a hydraulic pressure control valve wherein the load channel is arranged between the supply channel and the tank channel, that the control piston has a radial recess for direct connection of the load channel with the supply channel, and that in the first end position of the
REFERENCES:
patent: 3570523 (1971-03-01), Pauliukonis
patent: 3958495 (1976-05-01), Bernhoft
patent: 5123450 (1992-06-01), Wood et al.
Literature: Systematik der hydraulischen Widerstandsschaltungen in Ventilen und Regelkreisen, Backe, W. In: Book series "Oilhydraulic and Pneumatic", Krausskopf-Publisher, 1974, pp. 35-39, 54, pp. 57-59.
Farber Martin A.
Hepperle Stephen M.
Mannesmann AG
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