Fluid handling – Systems – Multi-way valve unit
Patent
1997-11-17
1999-08-17
Michalsky, Gerald A.
Fluid handling
Systems
Multi-way valve unit
91375A, F15B 910
Patent
active
059379006
DESCRIPTION:
BRIEF SUMMARY
The invention pertains to a rotary slide steering valve for supplying an actuator with hydraulic pressure which consists of an input shaft, an output shaft, a centering spring element and a valve element, wherein the valve element consists of at least two elements that can be turned relative to one another and comprise control bores for supplying and returning the hydraulic medium as well as the hydraulic medium line to and the hydraulic medium return line from both sides of the actuator.
Steering valves of this type are, in particular, used in power steering systems. The design of such power steering systems is generally known. An input shaft that is coupled to a steering rod is connected to an output shaft that is provided with a pinion via a centering spring element. The pinion acts on the toothed rack of the steering system. It is known to utilize steering valves in steering systems of this type. In this case, a conventional rotary valve element is provided which connects or disconnects hydraulic lines that end in bores when the input shaft is turned relative to the output shaft. Hydraulic fluid is pumped through the system under pressure by a pump. If the input shaft is turned relative to the output shaft, hydraulic pressure is supplied to a hydraulic motor that boosts the toothed rack movement in one of two possible directions.
Steering valves of this type are actuated by turning the input shaft relative to the output shaft. In this case, a torsional moment must be overcome by the centering spring element arranged between the input shaft and the output shaft, e.g., a torsion rod.
In one known steering valve of this type, a valve sleeve is provided which is engaged with the output shaft and surrounds the input shaft. This valve sleeve comprises control grooves that are moved such that they are situated congruently with bores for conveying the hydraulic medium which extend outside a housing in order to realize the control function.
In another type of rotary slide steering valve, bores that essentially extend in the axial direction are moved such that they are situated congruently.
One example of such a rotary slide steering valve is known from DE-OS 4,209,647. In this case, a sleeve that is connected to the input shaft is surrounded by a valve sleeve that is connected to the output shaft such that both sleeves overlap one another within the region of the annular surfaces that face one another. Bores that are connected to the hydraulic lines are arranged within the region of these annular surfaces in both sleeves. The bores can be arranged congruently or separated from one another by turning the input shaft relative to the output shaft, i.e., the corresponding lines are connected or disconnected. A servo control is realized in this fashion. Corresponding rotary slide steering valves are known from DE-OS 2,833,009 and DE-PS 4,232,570.
Another steering valve which, however, is not realized in the form of a rotary slide steering valve is known from DE 1,101,187 A1, whereby the hydraulic medium is initially conveyed to corresponding grooves of the input shaft via a valve sleeve. An output line that ends within the region of the end face is either connected to a pressure line or a pressure relief line by turning the input shaft relative to the output shaft.
These known rotary slide steering valves require a number of additional components. Consequently, the structural size of the steering valve becomes excessively large and its manufacture is associated with high cost. Due to the valve sleeves, the conveyance of the pressure medium to the annular surfaces is quite difficult, i.e., it is frequently required to provide bores that are combined with one another several times or may be connected to one another by transversely extending channels. In a valve with a control sleeve, a minimum tolerance usually must be observed because the sleeve is deformed during the operation of the valve by the hydraulic pressure. This may lead to increased friction. Consequently, the previously mentioned manufacture of these rota
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Michalsky Gerald A.
TRW Fahrwerksysteme GmbH & Co. KG
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