DE20019705U1 - Piezo bending transducer unit and piezo valve equipped with it - Google Patents

Description

G 19394 - 18.10.2000

FESTO AG & Co. 73734 Esslingen Piezo bending transducer unit and equipped with it

Piezo valve

The invention relates to a piezo bending transducer unit containing at least two piezoelectric bending transducers and to a piezo valve suitable for controlling fluid flows, which is equipped with such a bending transducer unit.

WO 98/25061 discloses a piezo valve that is equipped with two piezoelectric bending transducers arranged side by side and fixed separately to the valve housing. Each bending transducer contains a piezo body that has several layers of piezo material and an electrode arrangement. The electrode arrangement is part of a flexible contacting strand made of plastic material and containing electrical conductors, which leads out of the valve and enables the contacting required to feed in the control voltage.

Although the continuous contacting strand simplifies the contacting of the electrodes contained in the individual bending transducers, the assembly of the piezo valve, including the necessary adjustment of the bending transducers, is still relatively complicated.

It is the object of the present invention to take measures that enable a simplification of the manufacture and/or assembly of bending transducers.

To solve this problem, a piezo bending transducer unit is provided which contains at least two bending transducers, each of which has at least one piezo body containing one or more piezo material layers with an associated electrode arrangement and which are arranged side by side with mutually parallel deflection planes, wherein they are firmly connected to one another in one piece at one end region of the bending transducer unit with the piezo material layers of their piezo bodies.

The task is further solved by a piezo valve, which is equipped with a piezo bending transducer unit of the previously mentioned design.

The at least two bending transducers are thus combined to form a fixed structural unit, with the fixed connection taking place at one end of the bending transducer unit, where the piezo material layers of the piezo bodies on both sides are connected to one another in one piece. This integral design makes it possible to easily manufacture several bending transducers at the same time, with the relative position between the bending transducers already being fixed after the bending transducer unit has been manufactured. Since only one component in the form of the

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Bending transducer unit must be mounted and adjusted, which simplifies the assembly of devices equipped with the bending transducers, in particular of piezo valves equipped with several bending transducers.

Advantageous further developments of the invention emerge from the subclaims.

Especially in conjunction with a piezo valve, the end region of the bending transducer unit having the one-piece connection of the bending transducers can form a bearing section by means of which the bending transducer unit is fixed in use with respect to the valve housing of the piezo valve.

The piezo bodies of the individual bending transducers can be designed in such a way that individual control is possible, allowing the user to control activation as desired.

Especially if several valve openings of a piezo valve are to be controlled alternately, it is advantageous to electrically connect the bending transducers of the bending transducer unit in such a way that they automatically execute a deflection movement in the opposite direction when a corresponding control voltage is applied.

In conjunction with a piezo valve, the end area of the bending transducer unit with the one-piece connection between the bending transducers is expediently used as a bearing

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cut is used, via which the bending transducer unit is firmly clamped in the associated valve housing, so that all bending transducers are clamped simultaneously.

The invention is explained in more detail below with reference to the accompanying drawings, in which:

Fig. 1 shows a longitudinal section through a piezo valve according to the invention, which is equipped with a piezo bending transducer unit of the design according to the invention,

Fig. 2 is a perspective view of the piezo valve of Fig. 1, with the valve housing largely not shown in order to make the piezo bending transducer unit more visible, and

Fig. 3 is a detailed view of the piezo bending transducer unit used in the piezo valve according to Fig. 1 and 2 in a plan view of one of its two larger longitudinal sides.

The piezo valve 1 shown in the drawing has an elongated valve housing 2 which defines a valve chamber 3 inside.

In the valve chamber 3, two piezoelectric bending transducers 4, 5 are arranged parallel to each other and are an integral part of an elongated

chen piezo bending transducer unit 6. The latter is shown separately in Fig.

To obtain the bending transducer unit 6, the two bending transducers 4, 5 are firmly connected to one another at one end via a bearing section 7, which defines one of the two axial end regions of the bending transducer unit.

The bending transducer unit 6 is connected to the valve housing 2 via its bearing section in a housing-fixed manner. This is done in particular by clamping the bearing section 7 in a housing-fixed manner, which in the exemplary embodiment is implemented by embedding it in a casting compound 8 introduced into the valve housing 2. The casting compound 8 is applied in the end section of the valve chamber 3 associated with the bearing section 7 and, after hardening, creates a rigid connection between the bearing section 7 and the surrounding wall of the valve housing 2.

It is understood that other possibilities for fixing the bearing section 7 in the housing of the piezo valve are also possible.

In the deactivated state, the bending transducer unit 6 has a plate-like flat shape extending in a main extension plane and has a slot-like intermediate space 12 separating the two bending transducers 4, 5 from each other, which extends from the free front end of the bending

converter 4, 5 extends towards the rear to the beginning of the storage section 7.

Electrical contact means 13, 14 connected to the two bending transducers 4, 5 are led out of the valve housing 2 and enable the application of a control voltage required for the operation of the bending transducers 4, 5. The application of the control voltage results in the bending or deflection of the affected bending transducer 4, 5 transversely to its longitudinal direction, with the deflection movement being indicated in Fig. 1 by the double arrow 15. The deflection movements of the two bending transducers 4, 5 take place in mutually parallel deflection planes 16, 17, which run at right angles to the main extension plane of the deactivated bending transducer unit 6.

The piezo valve of the embodiment is designed as a 3/2-way valve. In the deflection path of the first bending transducer 4, a first valve opening 18 to be controlled is placed, which is surrounded by a valve seat 22 and is connected to a feed channel 23 leading to the outside. In the deflection path of the other, second bending transducer 5, there is a controllable second valve opening 19 with a valve seat 22 that is also associated with it and is connected to a vent channel 24 that leads to the atmosphere, for example. Both valve openings 18, 19 open into the valve chamber 3 on the inner surface of the valve housing 2, which also constantly communicates with a working channel 25 that is provided for connecting a consumer to be controlled by fluid, for example a fluid-operated drive.

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In the deactivated state and without additional measures, the bending transducers 4, 5 would each be arranged at a small distance from the associated valve seat 22 according to Figure 1. In the exemplary embodiment, however, effective spring means 26 are provided between the valve housing 2 and the first bending transducer 4, which preload the first bending transducer 4 into its closed position in which it rests on the associated valve seat and closes the relevant first valve opening 18 (Figure 2). In this way, when the bending transducers 4, 5 are deactivated, an initial state exists in which the working channel 25 is connected to the vent channel 24 via the valve chamber 3 and is thus vented, while at the same time the feed channel 23 is blocked. By appropriately controlling the bending transducers 4, 5, a switch can be made from this, for example, such that the second bending transducer 5 blocks the second valve opening 19 and thus the vent channel 24, while at the same time the first bending transducer 4 is lifted off the associated first valve opening 18 against the actuating force of the spring means 26 and thus the working channel 25 is fed with pressure medium from the feed channel 23 through the valve chamber 3. The pressure medium is, for example, a gaseous medium such as compressed air or a hydraulic medium.

The design and type of control of the bending transducers 4, 5 described here are examples. It goes without saying that other valve designs and valve functions are also possible.

functionalities can be realized on the basis of the bending transducer unit 6.

Within the framework of the bending transducer unit 6, the two bending transducers 4, 5 are firmly and in particular rigidly connected to one another. The rigidity of the connection depends largely on the stiffness of the piezo material of the bending transducers 4, 5 on both sides.

The reason for this is that each bending transducer 4, 5 in the exemplary embodiment has, for example, two piezo material layers 27a, 27b arranged one above the other in parallel layer planes, which are integrally connected to one another in the region of the bearing section 7 to form the latter. In other words, the bending transducer unit 6 is a multi-layer body which has several piezo material layers arranged one above the other in layers, which have an approximately U-shaped outline to form the two bending transducers 4, 5, so that the slotted outer contour according to Fig. 3 is produced.

The two piezo material layers 27a, 27b of a respective bending transducer 4, 5 could be part of a single piezo body, which, when controlled accordingly, enables deflection essentially in only one direction, so that one could speak of a unimorph structure. In the exemplary embodiment, however, there is a bimorph structure, with each piezo material layer 27a, 27b being part of a piezo body equipped with an electrode arrangement 32a, 32b.

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28a, 28b and wherein the piezo bodies 28a, 28b are firmly connected to one another lengthwise, for example by gluing, such that a deflection of the respective bending transducer 4, 5 is possible in either direction as desired by electrical control.

Each piezo body 28a, 28b of a respective bending transducer 4, 5 could also have a multi-layer structure with several piezo material layers instead of the single-layer structure present in the embodiment. The bending transducers could also each have only one piezo body with only one piezo material layer.

Finally, it would also be possible to design the bending transducers 4, 5 in the manner of so-called trimorph bending transducers, in which a carrier layer is located between the two piezo bodies 28a, 28b.

Mixed forms with different bending transducer structures within the bending transducer unit 6 could also be realized.

In Fig. 3, the electrodes of the electrode arrangement 27a placed on the top of the bending transducers 4, 5 are indicated by hatching. A comparable electrode structure is located on the underside of the bending transducers. In the area of the bearing section 7, outgoing electrical conductors 33 lead to the electrical contact means 13, 14, which

enable the electrical control of the bending transducer unit 6.

The bending transducers 4, 5 can, for example, be designed in such a way that individual control is possible and independent operation can take place. However, it would also be conceivable to have an electrical connection such that when a control voltage is applied, both bending transducers 4, 5 automatically carry out a predetermined movement, for example a deflection movement in opposite directions. This connection can be provided directly on the bending transducer unit 6.

One advantage of the bending transducer unit 6 is that it simultaneously combines several individual bending transducers 4, 5 into a rigid, self-supporting structural unit, which has a common bearing section 7 that enables all bending transducers 4, 5 to be fixed in place at the same time, whereby mutual alignment of the individual bending transducers 4, 5 can be omitted. Only the bending transducer unit 6 as a whole needs to be aligned.

The bearing section 7 preferably has a rectangular or square contour.

When aligning the bending transducer unit 6 in the valve housing 2, it can be helpful if the valve housing 2 has a stabilizing projection 33 which, when the bending transducer unit 6 is mounted, can be inserted into the slot-like space 12.

and whose length is selected such that it is suitable for supporting the longitudinal alignment of the bending transducer unit 6.

To produce the bending transducer unit 6, it is advisable to use a number of layer components made of piezo material that corresponds to the desired number of piezo material layers, which correspond to the desired outline of the bending transducer unit 6 and which are layered on top of one another and firmly connected to one another, taking into account the electrode arrangements. In principle, it is also possible to produce the bending transducer unit 6 with just a single layer component. The starting point can be a rectangular, elongated piezo material plate, into which an incision is made by removing material to form the slot-like intermediate space 12.

The bending transducer unit 6 can therefore be imagined to be constructed in such a way that either a single layer component or several layer components 29a, 29b stacked on top of one another are present, which consist of piezo material and have a one-piece structure, wherein several strip bodies extending parallel to one another, each belonging to a bending transducer, extend from an end region defining the bearing section 7.

Claims (7)

1. Piezo bending transducer unit, with at least two bending transducers ( 4 , 5 ), each of which has at least one piezo body ( 28 a, 28 b) containing one or more piezo material layers ( 27 a, 27 b) with an associated electrode arrangement ( 32 a, 32 b) and which are arranged side by side with mutually parallel deflection planes ( 16 , 17 ), wherein they are firmly connected to one another in one piece at one end region ( 7 ) of the bending transducer unit ( 6 ) with the piezo material layers ( 27 a, 27 b) of their piezo bodies ( 28 a, 28 b). 2. Piezo bending transducer unit according to claim 1, characterized in that the end region having the one-piece connection of the bending transducers ( 4 , 5 ) forms a bearing section ( 7 ) for fixing the bending transducer unit ( 6 ) in the use state. 3. Piezo bending transducer unit according to claim 1 or 2, characterized in that the bending transducers ( 4 , 5 ) are designed such that individual control is possible. 4. Piezo bending transducer unit according to one of claims 1 to 3, characterized by an electrical connection such that the bending transducers ( 4 , 5 ) automatically carry out a deflection movement in the opposite direction when a corresponding control voltage is applied. 5. Piezo bending transducer unit according to one of claims 1 to 4, characterized in that a slot-like intermediate space ( 12 ) is provided between adjacent bending transducers. 6. Piezo valve, characterized by a piezo bending transducer unit according to one of claims 1 to 5 arranged in a valve housing ( 2 ). 7. Piezo valve according to claim 6, characterized in that the bending transducer unit ( 6 ) is firmly clamped with its end region having the one-piece connection with respect to the valve housing ( 2 ).