Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2000-04-07
2001-04-10
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
Reexamination Certificate
active
06213570
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a valve arrangement with a first and a second fluid connection, a valve member which is biased into a first position by a spring arrangement, in which the first and the second fluid connections are blocked from each other, and an actuation means adapted to move the valve element into a second position in which the first and the second fluid connections are in a primary flow connection.
Such a valve arrangement is known among others as a so-called “normally closed” valve. As is already indicated by this term, the flow connection between the fluid connections is blocked in the non-actuated condition, i.e. in the basic or normal, respectively, condition, while the flow connection between the fluid connections is made in the actuated condition. In order to block the flow connection between the fluid connections in the non-actuated condition, a valve element is biased under the action of a spring arrangement, so that it sealingly contacts a sealing seat. In order to make the flow connection between the fluid connections in the actuated condition, it is necessary that the actuation means exerts a force which is capable of at least overcoming the biasing force of the spring arrangement, so that the valve element is lifted off the sealing seat.
However, it is not sufficient for most applications if the actuation means exerts a force which is only minimally higher than the biasing force of the spring arrangement, because during operation different fluid pressures occur at the fluid connections of the valve arrangement so that, in addition, a pressure differential force acts on the valve member, which, depending on the effective direction, counteracts the force applied by the actuation means. Accordingly, the actuation means is to be designed in such a manner that the actuation force is higher than the sum of the biasing force of the spring arrangement and the maximum pressure differential force to be expected in order to ensure a reliable function of the valve arrangement. The great disadvantage is that the actuation means is virtually over-dimensioned, in particular, if a large flow cross-section in the actuated condition of the valve arrangement is required, as is the case in the majority of the applications, in order to preclude a throttle effect of the valve arrangement. A large flow cross-section, however, additionally involves a very high pressure differential force so that consequently a high actuation force is to be applied. This causes high costs and great efforts in the design of the valve arrangement. In addition, the valve arrangement requires a relatively large installation space.
In view of the above, the object of the invention is to develop a valve arrangement which avoids the above mentioned drawbacks.
SUMMARY OF THE INVENTION
For the solution of the object, the initially mentioned valve arrangement is further developed in that a further valve element is provided which is biased into a first position by a further spring arrangement, in which the first and the second fluid connections are blocked from each other, and can be brought into a second position by a further actuation means, in which the first and the second fluid connections are in a secondary flow connection, so that upon an actuation of the valve arrangement, the first and the second fluid connections initially are only in the secondary flow connection and subsequently in the primary flow connection or in the first and second flow connection, with the flow cross-section of the primary flow connection being larger than the flow cross-section of the secondary flow connection.
The decisive advantage of the inventive valve arrangement is that initially a secondary flow connection is made before the primary flow connection is made. Because of the secondary flow connection, a pressure compensation process between the fluid connections is first initiated in the case in which different fluid pressures at the fluid connections additionally exert a differential pressure force on the valve element, through which the pressure differential force is eliminated, so that the pressure differential force is no longer effective in making the primary flow connection and can no longer act detrimentally. Thus, only a relatively low actuation force is required so that the actuation means can be manufactured economically, with low efforts as well as requiring little installation space. Thereby, the flow cross-section which is primarily determined by the primary flow connection can be relatively amply dimensioned in order to preclude an undesired throttle effect in the through-flow behaviour of the valve arrangement. Due to the fact that the secondary flow connection compared to the primary flow connection has only a small flow cross-section, the pressure differential force to be overcome in making the second flow connection is negligibly low.
The actuation means and/or the further actuation means can preferably be controlled electromagnetically and/or hydraulically. In a particular manner, the actuation means which actuates the valve member for making the primary flow connection, can be controlled electromagnetically, and the further actuation means which actuates the further valve member for making the secondary flow connection can be controlled hydraulically. The further hydraulically operated actuation means can thereby be controlled via the pressure difference which exists between the fluid connections, in order to make the secondary flow connection for the purpose of initiating the pressure compensation process between the fluid connections. When the primary flow connection is made by the electromagnetically operated actuation means after the elimination of the pressure differential force, in this case, too, there is only a relatively low actuation force to be applied. This has a particularly advantageous effect on the design of the electromagnet arrangement of the actuation means, which, on the one hand, means an energy-saving and thus economical current consumption, and, on the other hand, enables an installation space-saving construction of the components of the magnetic circuit, primarily of the solenoid and the armature.
According to a preferred embodiment, the valve member as well as the further valve member can be actuated by a common actuation means. In particular, the common actuation means can be electromagnetically controlled because of the previously explained advantages. The actuation means can comprise a two-stage tappet which, in a first stage, as a function of the armature moving the actuation means, actuates the further valve member only, in order to initially make the secondary flow connection, and subsequently in a second stage to also actuate the valve member or to actuate the valve member only which makes the primary flow connection which characterises the flow behaviour of the valve arrangement. In addition, by the common actuation means, one actuation means can be saved, so that, accordingly, components and costs can be saved and a compact construction of the valve arrangement is obtained.
In a particularly preferred embodiment the valve element is dome-shaped and the further valve element is spherically formed, with the further valve element being arranged within the valve element so that the valve arrangement can be configured in a particularly installation space-saving manner.
Advantageously, the biasing force of the spring arrangement is higher than the biasing force of the further spring arrangement. This renders the actuation force for making the secondary flow connection, which depends on the biasing force of the further spring arrangement, particularly low, primarily, if different fluid pressures prevail at the fluid connections. Moreover, the further spring arrangement can be supported via the spring arrangement in order to achieve a simple and installation space-saving configuration of the valve arrangement.
Under the aspects of simplicity and saving of installation space it is advantageous if the primary flow connection is defined by a seal
Gegalski Helmut
Wald Thomas
Lucas Industries Public Limited Company
MacMillan Sobanski & Todd LLC
Schwartz Christopher P.
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