Fluid handling – Non-valving motion of the valve or valve seat – Rotary motion of a reciprocating valve
Reexamination Certificate
1999-10-13
2002-10-08
Walton, George L. (Department: 3753)
Fluid handling
Non-valving motion of the valve or valve seat
Rotary motion of a reciprocating valve
C137S625660, C251S126000
Reexamination Certificate
active
06460561
ABSTRACT:
The present invention relates to a valve with a valve piston more particularly for a control or regulating valve according to the preamble of claim
1
. The invention also relates to a valve equipped with this valve piston according to claim
13
and to a pressurised medium apparatus for a motor vehicle having a pressurised medium source and a hydraulic consumer according to the preamble of claim
16
.
Valve pistons of valves of the kind mentioned above are used as valve bodies in the case of piston valves or also slide valves, wherein they are also occasionally referred to as valve actuators.
In general terms a valve of this kind has a valve bore in which the valve piston is axially guided and axially displaceable. A valve of this kind can thereby be formed as a control valve and has the task of controlling the start, stop as well as direction and pressure of through-flow volumes of the fluid flow in a hydraulic system. With a control valve of this kind it is thus possible to influence the flow capacity in the hydraulic system or hydraulic apparatus.
Valve pistons of this kind can however also be used in a similar way in regulating valves where the behaviour of the regulated characteristic value has an influence on the input characteristic value of the regulating valve.
Common to the said valves is the fact that the valve piston in the valve bore is subjected to a reciprocating movement which takes place in the longitudinal direction of the valve bore. When the direction of movement of the valve piston is reversed the valve piston is initially braked and then accelerated again in the opposite direction. A valve piston which is formed as a pressure balance is at some time still also biased on one side by a spring which has a hysteresis in its characteristic.
When the valve piston moves in the valve bore which is filled at least in part with a pressurised fluid, for example a pressurised oil, as the valve piston changes its direction so changes in the friction state occur, namely transitions from the sliding friction state to the sticking friction state and then again into the sliding friction state as the valve piston takes up its movement again. This makes it clear that hysteresis phenomena also occur here which together with the spring hysteresis already mentioned, lead to a corresponding displacement of the characteristic. If for example the through flow characteristic through the valve is considered then the actual through flow characteristic differs from the theoretical through flow characteristic as a result of the hysteresis phenomena mentioned.
It has already been attempted to use when controlling a valve a control signal superimposed with a vibration. A valve with a pressurised medium apparatus is also known from DE196 26 520 A1 wherein the control value is generated from at least two control value parts wherein one control value part is modulated with a first frequency and the second control value is modulated with a second frequency.
This known valve can be used for example in a hydraulic pressurized medium apparatus in order to control the operating pressure supplied to a hydraulic consumer according to a desired characteristic.
FIG. 1
of the drawing shows by way of example a characteristic curve of the operating pressure over the time which arises when using the known valve previously described. As can be readily seen from the graphs however the use of this known valve leads to vibration problems as a result of vibrations superimposed in the control. Thus if this known valve is used for controlling a hydraulic consumer in a hydraulic system the pressure vibrations apparent in both the rising and falling branch of the characteristic are transferred through the pipeline system of the hydraulic apparatus also to the hydraulic consumer so that the pressure vibrations which are present have a negative influence on the operating behaviour. Also further control members are regularly provided in the pipelines of the hydraulic system in the form of valves on which the pressure vibrations of the known valve likewise have a negative effect.
If the pressure vibrations spreading out in the pipe line system meet for example seated valves (poppet valves), then the valve cone is excited so that this excitation leads to the valve cone striking its seat. It is readily apparent that this seat impact can also cause mechanical damage to the valve seats and valve cone.
In addition to the hysteresis leading to displacements of the characteristic with the hydraulic system equipped with the known valve, problems also arise relating to pressure vibrations which lead in general to problems regarding the stability of the component parts present in the hydraulic system and also have a negative effect on the work characteristic of the hydraulic consumers present in the system, for example can result in noises occurring as a result of the pressure vibrations. AS a result of the vibration which is superimposed on the control value, with the known valve it can furthermore lead to considerable wear on the valve bore since the valve piston of the known valve is set in relatively rapid reciprocating movement in the valve bore.
The object of the present invention is therefore, in order to remove the drawbacks outlined above, to provide a valve piston and a valve equipped therewith so that on the one hand the influence of the hysteresis on the characteristic curve is reduced and on the other hand any excitation to vibration in the hydraulic system is avoided. The risk of wear on the valve bore is also to be reduced.
To achieve this the invention has the features indicated in claim
1
relating to the valve piston. Advantageous developments of the valve piston are provided in the other claims. Furthermore the invention proposes a valve according to claim
13
to solve the problem outlined above relating to the valve. A use of the valve piston is given in claim
14
and a pressurised medium apparatus with a valve according to the invention has the features of claim
16
.
The invention is based on the knowledge that the undesired hysteresis phenomena in the valve characteristic are caused to a considerable extent by the friction states described above when the valve piston reverses its direction of movement. The pressure vibrations existing in the hydraulic system are produced as a result of the superimposed vibrations in the control of the known valve piston controlled with a reciprocating control value. Both problems can be solved in that a valve piston is used which can dispense with control through an oscillating control value, and which eliminates the problems when reversing the direction of movement with the changes in the friction state.
The invention therefore provides a valve piston for a control or regulating valve to be mounted displaceable and axially guided in a valve bore wherein the valve piston has a fluid throughflow region which is designed so that the valve piston can be brought into rotation by the fluid passing through the fluid throughflow region.
By the term fluid throughflow region is thereby meant an area on the valve piston which, when the valve piston is located in the valve bore of a valve and the pressurised fluid is flowing through the valve, comes into contact with the flowing pressurised fluid. In other words therefore the fluid throughflow region of the valve piston according to the invention is designed so that the valve piston is driven to rotate through the fluid throughflow region of the valve piston, namely when the pressurised fluid of the hydraulic apparatus in which the valve is located enters into the valve bore, flows past the fluid throughflow region and flows out again from the valve bore.
Thus if the pressurised fluid of the hydraulic apparatus flows through the control valve or regulating valve equipped with the valve piston according to the invention, then the valve piston is set in rotation through the fluid flow by means of the fluid throughflow region so that the processes of reversing the direction of movement with the standstills which take place inb
Darby & Darby
LuK Getriebe-Systeme GmbH
Walton George L.
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