Valves and valve actuation – Electrically actuated valve – Remote or follow-up control system for electrical actuator
Reexamination Certificate
1999-10-26
2001-02-06
Shaver, Kevin (Department: 3754)
Valves and valve actuation
Electrically actuated valve
Remote or follow-up control system for electrical actuator
C251S129010, C137S554000
Reexamination Certificate
active
06182941
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a micro-valve arrangement comprising a micro-valve which has a housing produced in by a micro-structuring method, such housing having two mutually opposite housing layers, between which a valve chamber is defined, in which a diaphragm- or plate-like valve member is located, at least one of the two housing layers having at least one fluid duct extending therein, such duct opening opposite to the valve member at a port, in controlling cooperation with the valve member, into the valve chamber, and an electrical actuator for presetting the relative position of the valve member in relation to the duct port.
A micro-valve arrangement of this type is for example disclosed in the European patent publication 0 485 739 A1.
It comprises a micro-valve with a multi-layer housing, which is produced by a micro-structuring method. A valve member, whose structure is produced from a middle layer housing layer, is located in a valve chamber defined between two further housing layers and may be operated with the aid of an electrostatic actuator. In at least one of the outer housing layers a fluid duct extends, which so opens into the valve chamber that its duct port is opposite to the valve member. By means of the actuator the valve member can be shifted between a closed position covering the duct port and an open position clear of the duct port in which it is at a greater distance from the duct port.
For many applications of micro-valves it would be convenient to obtain information as regards the current position of switching and consequently the current position of the valve member. Although it would in principle be possible to find the position of switching of the micro-valve on the basis of the state of operation of the actuator, in the event of possible improper functioning of the micro-valve there is no guarantee that the state of the operation of the actuator and the state of switching of the valve member do in fact comply with one another. Although it would be feasible to provide for direct detection of the position of the valve member with the aid of a sensor arranged externally on the housing, this would generally be likely to prevent designs with a extremely small overall size of the micro-valve.
SUMMARY OF THE INVENTION
One object of the invention is to provide a micro-valve arrangement of the type initially mentioned, with which reliable information may be obtained about the position of the valve member.
In order to achieve these and/or other objects appearing from the present specification, claims and drawings, in the present invention the micro-valve comprises a position finding means for finding the position of the valve member on the basis of the measured capacitance of a capacitor, such capacitor comprising two capacitor faces which are opposite to each other in the direction of motion of the valve member and are respectively provided on the valve member and on one of the housing layers.
It is in this manner that the micro-valve is provided with a position finding means, whose principal components are able to be integrated in the micro-valve in the form of the capacitor faces. Since the measured capacitance is a function of the distance between the two capacitor faces, it is possible to derive from this the actual distance between the valve member and the duct port in controlling cooperation therewith in a simple fashion and thus to find the position of the valve member. Thus there is an extremely simple and reliable way of monitoring the switching state of the micro-valve. Moreover it is possible for the measured capacitance to be employed when required as a regulation signal or quantity in order in connection with a suitable control means to perform the necessary positioning of the valve member in a manner dependent on the desired pressure and/or flow rate, such positioning being more particularly in connection with continuous action of the micro-valve.
Further advantageous developments of the invention are defined in the claims.
In the case of a particularly simple design the capacitor faces are directly formed by the electrode faces of an electrostatic actuator. This renders the separate provision of capacitor faces unnecessary, since the electrode faces present in any case for the operation of the valve member may be employed with a double function as capacitor faces as well. However in certain conditions it may also be advantageous as well to design the capacitor and the electrostatic actuator separately and independent of each other, the capacitor faces on the one hand and the electrode faces on the other hand being more especially provided on opposite sides of the valve member.
In order to measure the capacitance of the capacitor, the micro-valve arrangement is preferably provided with a suitable capacitance measuring means. Its principle of operation may for example be based on the application of AC to the capacitor faces and finding the current which flows.
In order to be able to design for variable output pressures and/or rates of flow with the micro-valve arrangement the micro-valve is preferably in the form of a continuous action valve and in this respect more particularly as a proportional valve. In this case the actuator may be provided with a voltage source with a variably adjustable output value so that the instantaneous relative position between the valve member and the associated duct port is dependent on the currently set output voltage.
A micro-valve designed in the form of a continuous action micro-valve is suitable more especially for use in regulated operation. For this purpose a regulating means may be provided, which provides a control signal on the basis of the measured capacitance as the true or actual value and a predeterminable target value, such control signal being utilized for the operation of the actuator and permitting a variable position of the valve member in a manner dependent on the current control signal. The target value may for instance correspond to a pressure or rate of flow value desired on the output side of the micro-valve. In this respect it is advantageous that as a rule it is possible to dispense with the use of additional pressure and/or flow rate sensors so that a low price regulation system is possible.
Further advantageous developments and convenient forms of the invention will be understood from the following detailed descriptive disclosure of one embodiment thereof in conjunction with the single figure of the accompanying drawing. The drawing shows a preferred design of the micro-valve arranged in accordance with the invention, the micro-valve itself being shown in cross section and in conjunction with an associated regulator means.
REFERENCES:
patent: 4826131 (1989-05-01), Mikkor
patent: 5065978 (1991-11-01), Albarda et al.
patent: 5216273 (1993-06-01), Doering et al.
patent: 5323999 (1994-06-01), Bonne et al.
patent: 5566703 (1996-10-01), Watanabe et al.
patent: 5855850 (1999-01-01), Sittler
patent: 5870007 (1999-02-01), Carr et al.
patent: 38 09 597 A1 (1989-10-01), None
patent: 39 13 678 C1 (1990-07-01), None
patent: 197 44 292 A1 (1998-04-01), None
patent: 196 50 116 C1 (1998-04-01), None
patent: 0 485 739 A1 (1992-05-01), None
Post Peter
Scheurenbrand Hans
Vollmer Herbert
Weinmann Michael
Festo AG & Co.
Hoffmann & Baron , LLP
Keasel Eric
Shaver Kevin
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