Fluid handling – Flow affected by fluid contact – energy field or coanda effect – Means to regulate or vary operation of device
Patent
1992-08-07
1993-12-21
Chambers, A. Michael
Fluid handling
Flow affected by fluid contact, energy field or coanda effect
Means to regulate or vary operation of device
137819, 137833, 25112906, F15C 104
Patent
active
052714314
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a microvalve.
BACKGROUND
A valve is already known from U.S. Pat. No. 3,457,933, Craft, where a fluid stream is directed into two chambers by a piezo-electrically actuated flexible tongue. However, this valve is not contructed of wafers.
A microvalve is already known from not previously published German Patent Application P 39 19 876, corresponding to U.S. Pat. No. 5,161,774, which is produced as a multi-layer structure. The particular importance of this micro-mechanical valve lies in a type of construction, where the static pressure is compensated, which is essentially realized in three layers. With the microvalve not actuated, the fluid flows into an annular chamber the bottom surface of which is formed by an annular diaphragm and which is closed off at the top by the closing member seated on the valve seat. Because of the pressure-compensated construction of the valve, the pre-stressing force of the diaphragm results in a tight seat of the closing member on the valve seat, so that the connection to the outlet connector is blocked. A closed-off cavity, in which a defined pressure is present and to the bottom surface of which an electrode has been applied, is located underneath the annular diaphragm. This electrode is used for electrostatic opening of the valve. To close the valve, the electrostatic drive is shut off, whereupon the closing member again rests on the valve seat because of the effect of the restoring force of the annular membrane The mode of operation of this microvalve requires a complicated structure, where the dimensions of the individual structural elements must be adapted to each other.
THE INVENTION
In contrast to this, the microvalve has the advantage that its mode of operation does not require static pressure compensation, for which reason its structure, and in this connection its manufacture, too, are considerably simplified. Standard processes of micro-mechanics and -electronics can be employed to a large extent in its manufacture. The microvalve of the invention can be employed particularly advantageously as a not tightly sealing control valve. Control of the flow direction of the fluid flow or fluid stream by means of a flexible tongue made of the structure of the wafer, which in the position of rest is oriented parallel to the direction of flow, is advantageous.
It is also advantageous that microvalves, when used as injection valves or in servo valves, for example, are impervious to shock and dirt. The microvalve of the invention can also be advantageously actuated by means of an electro-thermal drive, since a high degree of switching dynamics can be achieved because of its small size and direct cooling by the fluid flowing through. It is also advantageous that almost no switching noises appear in the course of using the microvalve and there is very little wear. It must also be considered to be a particular advantage that a plurality of microvalves can be combined in many ways, so that a large range of flow-through variations can be simply realized.
It is particularly advantageous if opening and closing of the valve takes place hydraulically, in that the flexible tongue placed upstream of the actual closing device controls the flow direction of the fluid flow or fluid stream. The pressure difference between the two sides of the diaphragm, required for the excursion of the closing member, is built up by the fluid flow or fluid stream itself. Accordingly, no reference pressure which must be preset is required. When orienting the flexible tongue opposite the flow direction of the fluid flow or fluid stream, the flexible tongue can be used advantageously as a stream deflector. It is particularly advantageous that the flexible tongue can be deflected under electrical control. This can take place piezo-electrically or thermo-electrically. For this purpose the flexible tongue is advantageously constructed in several layers. A structure with two layers in the form of a piezo-electrical bimorph or with two layers with different therma
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Grauer Thomas
Mettner Michael
Chambers A. Michael
Robert & Bosch GmbH
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