Patent Publication Number: US-11649814-B2

Title: Fluid device

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a fluid device comprising a fluid chamber which is designed for receiving a fluid and which is commonly delimited by a device housing and a bending-elastic membrane element which has a planar extension in a main extension plane, wherein the membrane element at its peripheral edge section is fixed to the device housing in a fluid-tight manner and wherein a membrane working section of the membrane element which is framed by the peripheral edge section, for the change of the volume of the fluid chamber can be elastically deflected in a working direction which is orientated transversely to the main extension plane by a piezoactuator of the fluid device which acts upon the membrane element whilst carrying out a stroke movement. 
     A fluid device of the aforementioned type is known from JP-H03-12917 A, said device being applied on manufacturing semiconductors and providing the possibility of sucking back a fluid which is located in a fluid channel, in order to avoid an undesired dripping at a delivery output opening. The back-sucking effect can be created by way of an underpressure which can be generated in a fluid chamber of the fluid device, with which the fluid channel is in connection. The fluid chamber is commonly delimited by a device housing and by a membrane element which is fixed to the device housing at the edge side. The underpressure can be generated by way of a membrane working section of the membrane element which delimits the fluid chamber being deflected by way of a piezoactuator, so that the volume of the fluid chamber increases. The piezoactuator is designed as a stack translator and is fastened to one of the two membrane surfaces of the bending-elastic membrane element which are opposite one another. The piezoactuator has several electrodes, to which an operating voltage can be applied, by way of which a deformation of the piezoactuator is caused, such entailing a corresponding deformation of the membrane working section of the membrane element. 
     Concerning a back-suction valve which is known from DE 19810657 A1, an underpressure which effects the sucking-back of a fluid can be generated by way of a deformable membrane, on which a piston engages, said piston being biased by a spring and whose movement is controllable by the controlled fluid impingement of a further membrane. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to provide measures which permit a simple and precise change of the volume of the fluid chamber of a fluid device. 
     For achieving the aforementioned object, in a fluid device comprising the aforementioned features the membrane element consists of a rubber-elastic material, wherein the piezoactuator comprises a drive section which extends along the membrane working section, is embedded into the membrane element and is enveloped by the rubber-elastic material of the membrane element. 
     With regard to the fluid device according to the invention, the volume of a fluid chamber can be changed by way of a piezoactuator, by way of whose actuation a rubber-elastic membrane element which forms a movable delimitation wall of the fluid chamber is deformable. The piezoactuator has a drive section which by way of actuation of the piezoactuator is deformable and which transmits its deformation onto the adjacent membrane working section, so that this executes a stroke movement transversely to the main extension plane. On account of the rubber-elasticity of the membrane element, the drive forces which are to be mustered by the drive section are relatively low, so that the piezoactuator can be operated in an energy-efficient manner Since the drive section of the piezoactuator extends in the inside of the membrane working section by way of it being embedded into the membrane element and being enveloped by the rubber-elastic material of the membrane element, the drive force can be reliably transmitted from the piezoactuator onto the membrane working section, combined with extremely compact dimensions. 
     An operating voltage of a variable magnitude can be applied to the piezoactuator, from which voltage a reversible shape change of the drive section results according to the inverse piezoelectric effect, said shape change being directly transmitted onto the membrane working section of the membrane element which envelops the drive section. By way of this, a clear assignment between the deflection of the drive section and the linear travel of the membrane working section is always ensured, which provides good preconditions for a volume change of the fluid chamber which can be closed-loop controlled in a precise manner. Depending on the degree of the deflection of the membrane working section which is created by the piezoactuator, the volume of the fluid chamber changes to a greater or lesser degree, wherein a volume enlargement can be used for example to generate an underpressure in the fluid chamber. The piezoactuator is preferably very simply controllable in a proportional manner, in order to be able to set different stroke positions of the membrane working section for specifying different volumes of the fluid chamber. The operation is possible with a low energy level, so that despite a direct control, no relevant intrinsic heating occurs. The piezoelectric concept further if necessary permits a closed-loop control of the position given the deflection of the membrane working section, so that accurately repeatable settings are possible. A reliable shielding of the piezoactuator from the fluid which is located in the fluid chamber can be achieved by the enveloping of the piezoactuator on the part of the membrane element, so that the functional capability of the piezoactuator cannot be compromised even with aggressive fluids. 
     Advantageous further developments of the invention are to be derived from the dependent claims. 
     In particular, an elastomer material is selected as a rubber-elastic material for the membrane element. Preferably, with regard to the elastomer material this is an NBR, (F)FKM, EPDM, silicone or thermoplastic elastomer. 
     The piezoactuator is fixed to the membrane element, in particular in a manner such that together with the membrane element it forms a subassembly which can be handled in a unitary manner. The piezoactuator and the membrane element are preferably immovable relative to one another. On assembly of the fluid device, the previously put-together subassembly can be unitarily inserted into the device housing, by which means a rational and inexpensive manufacture is possible. 
     The aforementioned subassembly can be manufactured in a particularly inexpensive manner by way of the drive section of the piezoactuator being peripherally overmoulded by injection moulding with the rubber-elastic material of the membrane element on manufacturing the membrane element. In this manner, a very intimate connection between the piezoactuator and the membrane element can be achieved. The two components can adhere to one another. 
     Alternatively, for example there is also the possibility of manufacturing the membrane element independently of the piezoactuator and of forming an elongate receiving recess in the inside of the membrane element independently of the piezoactuator, said receiving recess lying in the main extension plane and into which the piezoactuator is inserted with its drive section. 
     If according to the previously mentioned design the drive section of the piezoactuator is peripherally overmoulded with the rubber-elastic material of the membrane element, the receiving recess automatically results by way of the material of the membrane element clinging onto the outer periphery of the drive section of the piezoactuator. 
     The elongate receiving recess in particular is designed in the manner of a blind-hole and is open at one side in the region of the peripheral edge section of the membrane element. At the open side of the receiving recess, the piezoactuator can project out with a further length section which connects onto the drive section and which can be used in particular for the electrical contacting. 
     The membrane element is expediently designed in a plate-like manner. 
     It is seen as being favourable if the membrane element in the region of its peripheral edge section has a rectangular, elongate outer contour, so that it has an elongate shape which extends along an imaginary membrane longitudinal axis. The outer contour is expediently rounded at the corners. The drive section of the piezoactuator is expediently aligned parallel to the membrane longitudinal axis. 
     The membrane element as a separating wall is preferably arranged in the device housing in a manner such that it subdivides a housing interior of the device housing into the fluid chamber and a further housing chamber. In order for the stroke movement of the membrane working section not to be compromised by overpressure or underpressure which prevails in the further housing chamber, the further housing chamber is expediently constantly in connection with the surroundings via at least one breathing opening, so that the further housing chamber can be denoted as a breathing chamber. The at least one breathing opening in particular also prevents the adhering of the rubber-elastic membrane to the housing wall if the device housing is designed such that the membrane element bears on the housing wall in the non-deflected state of the membrane working section. This design is advantageous, in order to be able to realise dimensions of the device housing which are narrow in the working direction of the stroke movement. 
     A rear-side housing wall of the device housing which lies opposite the membrane element at the side which is opposite to the fluid chamber in the working direction, on its inner surface which faces the membrane element comprises a surface structure which consists of a field of numerous deepenings and prominences. A possible adhering of the membrane element to the device housing is also effectively prevented by way of this. The membrane element can be rear-vented over a large surface. Additionally or alternatively, a corresponding surface structure can be formed on the rear-side membrane surface of the membrane element which faces the housing rear wall, in order to interact with the housing rear wall. 
     The membrane element has a rear-side membrane surface which is away from the fluid chamber. Expediently, a groove arrangement is formed in this rear-side membrane surface on the longitudinal side next to the drive section of the piezoactuator. For example, a longitudinal groove extends along the drive section of the piezoactuator in the membrane element at both sides of the drive section. The groove arrangement ensures a high flexibility of the membrane element event given an otherwise relative large thickness of the membrane element which is selected in order for example to ensure a high stability of the membrane element even in the case of a relatively high fluid pressure. 
     The drive section of the piezoactuator expediently comprises an electrode arrangement, to which an operating voltage which causes the stroke movement of the membrane working section can be applied in a variable magnitude. A stroke position of the membrane working section and accordingly a desired volume of the fluid chamber can be set depending on the magnitude of the operating voltage. 
     The piezoactuator expediently comprises a piezoelectrically inactive carrier element which in the region of the drive section on at least one of its two longitudinal sides which face in the working direction is equipped with a piezoelement which has piezoelectric characteristics and which at its sides which are away from one another in the working directly is flanked by an electrode of the electrode arrangement. The piezoactuator can be designed for example as a bimorph or as a trimorph. On using an electrically conductive carrier layer, the carrier layer itself be directly used as an electrode. For example, a conductive carrier layer can consist of a carbon-fibre material. 
     In particular, trimorph piezoactuators provide the advantage of an active bending in both directions. If here too, it is mainly the bending in only one direction which is used in order to vary the volume of the fluid chamber, then it can occur that given a deactivated piezoactuator, this and thus also the membrane element does not exactly assume its completely non-deformed plane idle position due to typical hysteresis effects of the piezo laminate construction. In order to counteract the hysteresis and to guarantee the bringing of the membrane element into its plane surface alignment, the second piezoelement can be briefly activated with a suitable voltage level. 
     Above all, the realisation of a lamella-like longitudinal design is recommended for the piezoactuator. In particular, this is the case if the piezoactuator is designed as a piezo bending transducer, which is preferred. 
     The piezoactuator which is designed as a piezo bending transducer preferably has a drive section which for creating the stroke movement of the membrane working section can execute a deflection movement. The deflection movement, starting from an idle position which is present given a deactivated piezoactuator, can expediently be carried out in opposite directions, in order to be able to actively deflect the membrane working section in two directions which are opposite to one another. 
     In particular, the piezoactuator is designed and arranged such that in the region of the peripheral edge section of the membrane element it is supported in the working direction at two locations which are distanced to one another in the main extension plane of the membrane element, each by way of a rigid support structure of the device housing. The membrane working section which given an electrical activation of the piezoactuator bulges out in an arcuate manner extends between the two support structures. On account of this deformation behaviour, a volume change of the fluid chamber can be set in a particularly exact manner. The application of an operating voltage to the piezoactuator causes an extension of the piezo-material in the direction of the electric field, here therefore in the working direction, which leads to the piezoelement on the one hand becoming thicker and on the other hand simultaneously undergoing a reduction of its length. In combination with a piezoelectrically inactive carrier element which carries the piezoelement and does not participate in the deformation, this leads to the mentioned arcuate deformation of the drive section of the piezoactuator, which results in a corresponding deformation of the complete system consisting of the piezoelement and the membrane element. 
     Expediently, the membrane element in the region of the support structure comprises recesses, into which the support structures engage, by which means the membrane element is positively fixed relative to the device housing in the main extension plane. In particular, this is advantageous if the membrane element at its peripheral end section is only fixed to the drive housing in a non-positive and/or material manner, for example by way of clamping and/or a bonding connection. 
     In particular, the piezoactuator is designed such that it comprises a base section which connects axially onto the drive section and which in a freely ending manner projects out of the membrane element. This base section can be used for the electrical contacting of the piezoactuator. Concerning the stroke movement of the membrane working section, the base section expediently executes a pivoting movement, whose movement direction is opposite to the momentary stroke movement of the membrane working section. 
     Concerning a particularly advantageous embodiment, the fluid device is provided with a position detection device which is designed for the detection of a relative position which changes given the stroke movement of the membrane working section between the piezoactuator and the device housing. The position detection device permits a particularly precise and always reproducible setting of the volume which is desired of the fluid chamber. Since the stroke position of the membrane working section has an effect upon the volume of the fluid chamber, wherein in particular a proportional dependency is present, a reliable volume setting can be carried out on account of the determined position values. Different measuring principles, for whose implementation the position detection device is designed, are considered for the position detection. For example capacitive or inductive position detection is possible. 
     It is seen as being particularly expedient if the position detection device comprises two detection components which cooperate with one another, in the design of a permanent magnet, and a sensor which can be actuated by the permanent magnet, wherein the one of these two detection components is arranged on the base section of the piezoactuator which carries out a pivoting movement given the stroke movement of the membrane working section and the other detection component is arranged in a stationary manner with respect to the device housing. The sensor which is designed for example as a Hall sensor is seated on the device housing, whereas the permanent magnet is attached to the base section of the piezoactuator. The sensor can be attached directly to the device housing or to an additional component, for example a circuit board, which is fixed to the device housing. 
     The fluid device preferably comprises an electronic control device which is electrically connected onto the piezoactuator on operation of the fluid device and by way of which an operating voltage can be specified in a certain magnitude, in order to be able to set at least one stroke position of the membrane working section which is assumed with respect to the device housing. The electronic control device in particular is designed in order to effect a charge feed or charge discharge with respect to an electrode arrangement of the piezoactuator in accordance with requirements. For example, the electronic control device comprises a high voltage stage. Depending on the magnitude of the applied operating voltage, a stroke movement of the membrane working section and a positioning of the membrane working section in a defined stroke position can be effected with the help of the control device, wherein the set stroke position each corresponds to a certain volume of the fluid chamber. 
     It is particularly favourable if the electronic control device is designed for a closed-loop controlled setting of the stroke position of the membrane working section, wherein the closed-loop control is effected on the basis of the position measurement values which are determined by the position detection device. A closed-loop control of the volume of the fluid chamber is effected in an indirect manner by the closed-loop control of the position, since the piezoactuator has a reproducible deformation behaviour, and thus an unambiguous assignment between the individual stroke positions of the membrane working section and the momentary volume of the fluid chamber exists. 
     The fluid device can be applied in arbitrary situations, in which it is a case of setting the volume of a fluid chamber in accordance with requirements. For example, a volume setting can be effected in order to specify a fluid volume which is relevant to a subsequent metering procedure, this for example being in the fields of semiconductor industry or laboratory automation. 
     A particularly advantageous use for the fluid device lies in its application as a fluid suction device, wherein an underpressure can be created by a volume increase of the fluid chamber which is caused by way of the piezoactuator, by way of which underpressure fluid which is located in the fluid channel which is connected to the fluid chamber can be sucked into the fluid chamber. By way of this, for example a post-dripping of liquid in the case of metering procedures can be prevented. Metering procedures are commonplace in many fields, such as for example in medical technology or also with industrial applications and for example in circuit board manufacture on metering a photo resist onto circuit boards or wafers for semiconductor manufacture. 
     A particularly expedient fluid device has two fluid channels which communicate with the fluid chamber, wherein a first fluid channel is an exit channel, through which fluid which is located in the fluid chamber can flow out of the fluid chamber, whilst a second fluid channel is an entry channel, through which fluid can flow into the fluid chamber. A shut-off unit which is assigned to the second fluid channel can selectively release or block the second fluid channel, in order to permit or prevent a passage of fluid. Such a shut-off unit represents for example a metering valve if the fluid device is used as a metering device or as a constituent of a metering device. In order, after completion of a metering procedure, to prevent a post-dripping of liquid fluid, the piezoactuator is held in an operational state during the metering, with which operational state the fluid volume of the fluid chamber is reduced. After stopping the metering procedure, the fluid volume is enlarged by way of a suitable control of the piezoactuator, so that a desired quantity of fluid is sucked back out of the exit channel into the fluid chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is hereinafter explained in more detail by way of the accompanying drawings. There are shown in: 
         FIG.  1    a perspective representation of a preferred design of the fluid device according to the invention, in the context of a metering device, 
         FIG.  2    the arrangement of  FIG.  1    from a different viewing angle and in a partially cut-open state of a device housing of the fluid device, 
         FIG.  3    an isometric exploded representation of the arrangement according to  FIGS.  1  and  2   , 
         FIG.  4    a longitudinal section according to section line IV-IV of  FIGS.  1 ,  6  and  7   , in which the membrane working section assumes an non-deflected home position, so that the fluid chamber has a maximal volume, wherein a channel plate which is evident in  FIGS.  1  to  3    is not represented, 
         FIG.  5    a further longitudinal section in the same section plane as  FIG.  4   , wherein the membrane working section is shown on assuming a deflected operational position, so that the fluid chamber has a reduced volume, 
         FIG.  6    a cross section according to section line VI-VI of  FIG.  4   , 
         FIG.  7    a cross section according to section line VII-VII of  FIG.  4   , 
         FIG.  8    an individual representation of a subassembly which can be unitarily handled, comprising the membrane element and the assigned piezoactuator of the fluid device of  FIGS.  1  to  7    in a viewing direction from the side of the fluid chamber, and 
         FIG.  9    a further illustration of the subassembly according to  FIG.  8    in a rear view with a view upon the rear side which is away from the fluid chamber. 
     
    
    
     DETAILED DESCRIPTION 
     A fluid device which in its entirety is provided with the reference numeral  1  is evident from the drawing, said fluid device being shown in a preferred design and application as a fluid suction device  1   a  and herein in the scope of an advantageous integration into a metering device  2  for fluid media. 
     Essential constituents of the fluid device  1  are expediently grouped together in a device unit  12  which can be realised in compact dimensions. The device unit  12  is preferably fastened to the channel plate  9  in a releasable manner. The channel plate  9  has a carrier surface  10 , on which the device unit  12  is assembled. By way of example, the device unit  12  is clamped to the carrier surface  10  by way of fastening screws  11  which pass through it and which are screwed into the channel plate  9 . The channel plate  9  is not shown in  FIGS.  4  to  9   . 
     The fluid device  1  has a device housing  3 . With regard to the illustrated embodiment example, the device housing is a housing of the device unit  12  which is designed in a separate manner with respect to the channel plate  9 . However, constructional shapes of the fluid device  1  concerning which a physical subdivision into a device unit  12  and a channel plate  9  is not present are also possible, so that the channel plate  9  is an integral constituent of the device housing  3 . 
     The fluid device  1  comprises a bending-elastic membrane element  4  which by way of example is a constituent of the device unit  12  and is thus combined with the device housing  3  such that together with the device housing it delimits a chamber  5  which on operation of the fluid device  1  receives fluid and is therefore denoted as a fluid chamber  5  for a better differentiation. 
     A piezoelectric actuator of the fluid device  1  which is denoted as a piezoactuator  7  is assigned to the membrane element  4 . For the actuation of the piezoactuator  7 , the fluid device  1  expediently comprises an electronic control device  8  which is only indicated schematically and which by way of example is arranged away from the device unit  12 . 
     The device housing  3  has a longitudinal axis  19 , a height axis  20  which is at right angles thereto and a transverse axis  21  which is at right angles to the two aforementioned axes  19 ,  20 . The device housing  3  has a longitudinal design, wherein it has larger dimensions in the axis direction of the longitudinal axis  19  than in the axis directions of the height axis  20  and the transverse axis  21 . The dimensions in the axis direction of the transverse axis  21  are preferably lower than the dimensions in the axis direction of the height axis  20 , so that the device housing  3  has a narrow ledge-like shape. However, the device housing  3  can also be realised in other proportions. 
     The axis directions of the longitudinal axis  19 , the height axis  20  and the transverse axis  21  are hereinafter also defined as the length direction  10 , the height direction  20  and the transverse direction  21  for a simple denotation whilst using identical reference numerals. 
     The device housing  3  encompasses a housing interior  14 . The membrane element  4  as well as the piezoactuator  7  is located in the housing interior  14 . 
     The membrane element  4  preferably has a plate-like design. At its narrow side, it preferably has a rectangular, elongate outer contour  18 . The four corner regions in particular are rounded. The membrane element  4  is thus arranged in the housing interior such that a membrane longitudinal axis  6  which runs in the longitudinal direction of the membrane element  4  runs parallel to the longitudinal axis  19  of the device housing  3 . 
     The membrane element  4  extends planarly in a main extension plane  15 . The membrane element  4  is preferably arranged in the housing interior  14  such that the direction of the normal to the main extension plate  15  coincides with the transverse direction  21 . 
     The outer contour  18  is defined by the peripheral course of a peripheral edge section  17  of the membrane element  4 . 
     At its peripheral edge section  17 , the membrane element  4  is fixed to the device housing  3  in a fluid-tight manner. For this, by way of example it is clamped at its peripheral edge section  17  between two first and second housing parts  29 ,  30  of the device housing  2  which are opposed to one another in the transverse direction  21 . The sealing results from the fact that the membrane element  4  consists of a rubber-elastic material which is elastically pressed together by way of the clamping in the region of the peripheral edge section  17 . 
     The rubber-elastic material of the membrane element  4  is preferably an elastomer material. 
     Since the membrane element  4  as a whole is designed in a fluid-tight manner, it subdivides the housing interior  14  into two part-spaces amid sealing, of which part-spaces the one forms the fluid chamber  5  and the other by way of example has no further function but for ensuring an unhindered movability of the membrane element  4  constantly communicates with the atmosphere and is therefore denoted as a breathing chamber  25  for an improved differentiation. On the part of the device housing  3 , the breathing chamber  25  is delimited by a housing rear wall  26  which is designed as a constituent of the first housing part  29  and which lies opposite a rear-side membrane surface  39  of the membrane element  4  and through which one or more breathing openings  16  pass, said breathing openings permitting a continuous air exchange with the atmosphere which surrounds the device housing  3 . 
     The two housing parts  29 ,  30  by way of example are screwed to one another by way of fastening screws  13 , but can also be fastened to one another in a different manner. 
     By way of example, the first housing part  29  has a recess  41  which at the rear side is delimited by the housing wall  26  and at its open front side is closed by the second housing part  30 . The second housing part  30  forms a housing front wall  22  which delimits the fluid chamber  5  at a front side which lies opposite the membrane element  4  in the transverse direction  21 . The second housing part  30  is expediently conceived as a cover which immerses into the recess  41  and bears on a support surface  41   a  of the first housing part  29  which is formed by a shouldering of the inner contour the recess  41 . 
     An account of the rubber-elasticity of the membrane element  4 , a membrane section which is framed by the peripheral edge section  17  and which for an improved differentiation is denoted as a membrane working section  27  is reversibly bendable or deflectable in a direction which is at right angles to the main extension plane  5 , thus by way of example in the transverse direction  21 . The deflection movement or bending movement which takes place with such a procedure is hereinafter denoted as the stroke movement  28  and is illustrated by a double arrow. 
     The membrane working section  27  is shown in an operational position in  FIG.  4   , with regard to which it is a non-deflected home position. Here, the membrane element  4  completely extends in the main extension plane  15 . The membrane element  4  is preferably subjected to no mechanical biasing in the non-deflected home position of the membrane working section  27 . 
     An operational position of the membrane working section  27  which is deflected in the transverse direction  21  with respect to the home position is evident from  FIG.  5   . The membrane working section  27  is hereby distanced at least regionally to the imaginary main extension plane  15  which passes through the peripheral edge section  17 , wherein the distance is greatest in a surface-central region  23  and starting from there gradually decreases towards the peripheral end section  17  in the longitudinal direction  19 . 
     The membrane working section  27  can be assume operational positions which are deflected to a different extent and which differ from one another in their distance which is present with respect to the main extension plane  15 . 
     The direction of the stroke movement  28  which by way of example coincides with the transverse direction  21  is hereinafter also denoted as the working direction  32  and is rendered recognisable by a dot-dashed line. Positions of the membrane working section  27  which can be achieved in the course of the stroke movement  28  are hereinafter also denoted as stroke positions of the membrane working section  27 . 
     The volume of the fluid chamber  5  depends on the momentary stroke position of the membrane working section  27 . The further the membrane working section  27  is deflected in the direction towards the housing front wall  22 , the smaller is the fluid chamber volume. 
     The operating states of the fluid device  1  which are shown in  FIGS.  4  and  5   , in  FIG.  4    define a maximal volume and in  FIG.  5    a minimal volume of the fluid chamber  5 . 
     The stroke movement  28  of the membrane working section  27  can be created by the piezoactuator  7 . Different stroke positions of the membrane working section  27  can be set by the piezoactuator  7 , either in a stepwise manner or preferably stepless manner. Each set stroke position can be retained for as long as desired. 
     According to the illustrated embodiment example, the piezoelectric actuator  7  is preferably designed as a piezo bending transducer. In particular, it has a longitudinal extension with a lamella-like design, as is quite evident from  FIG.  3   . The piezoactuator  7  is arranged in the housing interior  14  in a manner such that its longitudinal axis  37  runs parallel to the longitudinal axis  19  of the device housing and further expediently in the non-deflected home position of the membrane element  4  runs parallel to the main extension plane  15 . 
     A front length section of the piezoactuator  7  forms a drive section  42  which for generating the stroke movement  28  acts upon the membrane working section  27 . A rear length section of the piezoactuator  7  which is denoted as a base section  43  and which by way of example is used for the electrical contacting of the piezoactuator  7  connects onto this drive section  42  in the longitudinal direction  37 . 
     The drive section  42  extends in the inside of the membrane element  4  along the membrane working section  27 . This is realised by way of the drive section  42  being embedded into the membrane element  4  and being enveloped by the rubber-elastic material of the membrane element  4 . 
     Expediently, the drive section  42  is encompassed completely all around by the membrane element  4  with the exception optionally of two locations in the region of the peripheral edge section  18 , said regions being distanced to one another in the longitudinal direction  37  and being where the membrane element  4  expediently each has a fixation recess  44 , into which a support structure  45  which is formed on the device housing  3  engages. The fixation recesses  44  by way of example are located in the rear-side membrane section  46  which lies between the drive section  42  and the housing rear wall  26 , whilst the support structures  45  are formed on the inner surface  47  of the housing rear wall  26  which face the membrane element  4 . Each support structure  45  is preferably designed as a projection, wherein it is particularly a rib-like projection which extends parallel to the height axis  20 . Hereby, each fixation recess  44  is then expediently designed with the shape of a longitudinal slot. 
     By way of the engagement of the support structures  45  into the fixation recesses  44 , the membrane element  4  additionally to the edge-side clamping is positively prevented from a relative movement relative to the device housing  3  in the longitudinal direction  19 . By way of this, the membrane element  4  reliably retains the desired position within the device housing  3 . 
     The support structures  45  preferably extend through the rear-side membrane section  46  up to the drive section  42 , so that this is supported in a direct manner at one side by way of the device housing  3  at two locations which are distanced to one another in the longitudinal direction  37 . On the side which lie opposite the support structures  45  in the transverse direction  21 , expediently no direct housing-side support of the drive section  42  is effected and here the fixation is limited to the clamping of the peripheral edge section  17 . 
     Differing from the embodiment example, the support structures  45  could be formed on the housing front wall  22  instead of on the housing rear wall  26 . 
     Given the electrical actuation of the piezoactuator  7 , its drive section  42  bends in the transverse direction  21  in the region which lies between the two support structures  45 . This procedure is denoted as the deflection movement  48  of the drive section  42 . Given the deflection movement  48 , the distance between the drive section  42  and the housing front wall  22  changes. Since the drive section  42  is encompassed by the membrane working section  27  of the membrane element  4 , the membrane working section  27  participates in the deflection movement  48 , from which the stroke movement  28  of the membrane drive section  27  which is orientated in the same direction results. 
     In the electrically deactivated state, when the piezoactuator  7  is discharged, the drive section  42  assumes a non-deflected idle position. The deflection movement  48  can be created by way of electrical actuation. The deflection movement  48 , starting from the idle position, can expediently be created in the transverse direction  27  in one of two opposite directions, in order to be able to actively deflect the membrane working section  27  in two directions which are opposite to one another. 
     The membrane element  4  extends in the inside of the device housing  3  only along a part length of the housing interior. A further part-space of the housing interior  14  connects onto the membrane element  4  in the longitudinal direction  19 , said part-space hereinafter being denoted as the contacting chamber  49  for a better differentiation, since the electrical contacting of the piezoactuator  7  is effected in it. 
     A receiving recess  50  which is designed in manner of a blind hole and is merely open at one side, specifically in a region of the outer contour  18  of the membrane element  4  which faces the contacting chamber  49 , is formed in the membrane element  4 . There, the piezoactuator  7  projects with its base section  43  out of the membrane element  4  and into the contacting chamber  49 . The drive section  42  of the piezoactuator  7  extends within the receiving recess  50 . 
     The piezoactuator  7  with its drive section  42  is preferably fixed into the receiving recess  50  in a manner such that the membrane element  4  and the piezoactuator  7  are immovable relative to one another and form a componentry which is held together in a fixed manner and which on assembly of the fluid device  1  can be inserted as a unit into the device housing  3 . 
     For example, the piezoactuator  7  is inserted and in particular pressed into the premanufactured receiving recess  50 . Another realisation form envisages the membrane element being integrally formed around the drive section  42  with the injection moulding manufacture, so that the drive section  42  is peripherally overmoulded by the material of the membrane element  4 . 
     The base section  43  in the contacting chamber is not mechanically connected to the device housing  3  with the exception of the electrical contacting measures. It projects in a freely ending manner into the contacting chamber  49 , so that it can execute a relative movement with respect to the device housing  3  in the transverse direction  21 . 
     The piezoactuator  7  comprises a strip-like carrier element  53  which extends in the longitudinal direction  37  and which is piezoelectrically inactive and thus has no piezoelectric characteristics. The carrier element  53  extends over the entire length of the piezoactuator  7 . 
     In the region of the drive section  42 , the carrier element  53  at its opposite longitudinal sides which point in the working direction  28  are each occupied by a plate-like piezoelement which has piezoelectrically characteristics. The piezoelements  54  are fixedly connected and in particular bonded to the carrier element. Each piezoelement  54  consists of a piezoelectric material, in particular a piezeoceramic. 
     Each piezoelement  54  at its sides which are way from one another in the working direction  28  is flanked by an electrode  55 ,  56  which for the improved differentiation are denoted as the first electrode  55  and the second electrode  56 . All electrodes  55 ,  56  together form an electrode arrangement  57  of the piezoactuator  7 . 
     It is advantageous if according to the embodiment example the carrier element  53  comprises electrically conductive characteristics and directly assumes the function of the first electrode  55  for both piezoelements  54 . The second electrode  56  expediently consists of an electrically conductive coating of the piezoelement  54  which is deposited for example as a metallisation. 
     On account of the embedding of the drive section  42 , the piezoelement  54  does not come into contact with the fluid which is located in the fluid chamber  5 , which ensures an operation with minimal interruption. 
     Electrical leads  58  which in the operatically ready state of the fluid device  1  are connected to the electronic control device  8  are connected in the contacting chamber  49  to the electrode arrangement  57 . Specifically, the electrical leads  58  are connected to several, in particular resiliently designed connection contacts  62  which are fixed in the device housing  3  in the region of a lower side  63 , said lower side facing the carrier surface  10 , and are led out of said device housing. A circuit board  64  which is provided with strip conductors  65 , with which the connection contacts  62  are electrically contacted in the state of the device unit  12  being assembled on the carrier surface  10  is seated in a deepening of the carrier surface  10 . These strip conductors  65  are in electrical connection with the electronic control device  8  in a preferably releasable manner via arbitrarily designed electrical leads  66 . 
     The electronic control device  8  is designed in order to provide an electrical operating voltage of a variable magnitude which can be applied to the electrode arrangement  57  via the electrical leads  66 . The control device  8  has its own device, in order to permit the charge feed and charge discharge with respect to the electrodes  55 ,  56 , such being necessary for the variable control. 
       FIG.  4    illustrates the operating state, concerning which the operating voltage is equal to zero, so that the drive section  42  assumes the non-deflected home position. In contrast to this,  FIG.  5    shows an operating state with an operating voltage of larger than zero, concerning which the drive section  42  is deflected with an arcuate shape amid the reduction of the volume of the fluid chamber  5 . The movement of the drive section  42  between different operating states is effected in the course of the deflection movement  48 . The stroke movement  28  of the membrane working section  27  is always entailed by this deflection movement  48 . 
     On account of the exemplarily present trimorph construction type, with regard to the exemplary piezoactuator  7  the deflection movement  48  can be actively created in both directions. Concerning an embodiment example which is not illustrated, the piezoactuator  7  is of a monomorphous or bimorphous type, so that an active deflection is only effected in one direction, whilst the restoring is created by way of the inherent spring elasticity. 
     The control of the piezoactuator on both sides is preferred, in order by way of an activated counter piezolayer to compensate remains of deformations given a discharged piezoactuator, such deformations being caused by hysteresis. 
     In all cases, the volume which is enclosed in the fluid chamber  5  can be variably set by way of a suitable control of the piezoactuator  7 . 
     The fluid device  1  can be operated with every arbitrary fluid. The preferred application is effected with a liquid, but nonetheless a gaseous fluid for example pressurised air can also be used. 
     It is advantageous if the device housing  3  is designed such that the membrane working section  27  bears on the housing rear wall  26  in the non-deflected home position. The volume of the breathing chamber  25  is therefore at least almost equal to zero in the non-deflected home position. This permits a design of the device housing  3  with very small dimensions in the transverse direction  21 . 
     In order to prevent the membrane element  4  which for example consists of silicone material from sticking to the housing rear wall  26  at the inside, the housing rear wall  26  on its inner surface  47  which faces the membrane element  4  is expediently provided with a surface structure  68  which consist of a multitude of deepenings and prominences. In combination with the at least one breathing opening  16 , thus a continuous rear-venting of the membrane working section  7  is given, such counteracting the adhering. 
     A surface structure  68  with a multitude of prominences and deepenings which lie therebetween can alternatively or additionally be formed on the rear-side membrane surface  39  which faces the inner surface  47 . 
     The membrane element  4  has an imaginary membrane transverse axis  72  which is at right angles to the membrane longitudinal axis  6  and which runs parallel to the height axis  20  of the device housing  3 . The piezoactuator  7  is preferably arranged such that its membrane working section  27  runs in the axis direction of the membrane transverse axis  72  centrally in the membrane element  4  and thus has an equally large distance to the two longitudinal sides  95   a ,  95   b  of the membrane element  4 . 
     In order to be able to encompass the drive section  42  all around, a certain thickness of the membrane element  4  at right angles to the main extension plane  15  is necessary. In order despite this to obtain a very good rubber-elastic deformation capability for the membrane working section  27 , it is advantageous if the membrane element  4  on its rear-side membrane surface  39  is provided with a groove arrangement  73  which reduces the wall thickness. The groove arrangement  73  expediently extends on both sides of the drive section  42  in the axis direction of the membrane longitudinal axis  6 . By way of example, the groove arrangement  73  comprises two longitudinal grooves  73   a ,  73   b  which flank the drive section  42  on opposite longitudinal sides. 
     Since the base section  43  receives no support within the contacting chamber  49 , given the stroke movement  28  of the membrane drive section  27  which is created by the piezoactuator, it executes a pivoting movement  74  relative to the device housing  3 , said pivoting unit being indicated by the double arrow and specifically being in a the same plane, in which the deflection movement  48  also take space. 
     The fluid device  1  is preferably provided with a position detection device  33  which is provided for detecting the current pivoting position of the base section  43 . Since the pivoting position of the base section  43  is directly dependent on the stroke position of the drive section  42 , the measured pivoting position permits precise information on the momentary volume of the fluid chamber  5 . Furthermore, by way of a targeted setting of the pivoting position, a volume of the fluid chamber  5  which is desired for a certain application case can be set. 
     The position measurement values which are determined by the position detection device  33 , in the case of the illustrated embodiment example are fed to the electronic control device  8  which is capable of carrying out a closed-loop controlled setting of the stroke position of the membrane working section  27  and thus indirectly also of the volume of the fluid chamber  5 , on the basis of the position measurement values as the actual values. The position detection device  33  is connected onto the electronic control device  8  via electrical leads. These electrical leads  75  are connected to the position detection device  33  via strip conductors  65  of the circuit board  64 . 
     The position detection device  33  is expediently integrated at least partly into the device unit  12 . 
     By way of example, the position detection device  33  comprises two first and second detection components  34 ,  35  which cooperate with one another in a contactless manner and which given the pivoting movement  74  of the base section  43  carry out a relative movement to one another. Whereas the first detection component  34  is arranged on the base section  43  and thus participates in its pivoting movement  74 , the second detection component  35  is arranged in a stationary manner with respect to the device housing  3 . By way of example, the second detection component  35  is situated outside the device housing  3 , wherein it is expediently seated on the circuit board  64 . By way of example, the second detection component  35  is situated in the region of the lower side  63  of the device housing  3  which extends past the circuit board  64  which is equipped with the second detection component  35 . 
     The first detection component  34  is expediently arranged at the free end region of the base section  43 , so that given the deflection movement  48  it covers a relatively large pivoting path which benefits a precise position detection. 
     It is to be understood that the two detection components  34 ,  35  can just as well both be arranged within the device housing  3  and in particular in the contacting chamber  49 . 
     Concerning the illustrated embodiment example, the first detection component  34  is formed by a permanent magnet and the second detection component  35  by a sensor, in particular a Hall sensor, which responds to the magnetic field of the permanent magnet. This arrangement can also be exchanged. Likewise, other contact-free measuring principles can also be applied for the position detection, for example inductively, capacitively or optically. 
     The electronic control device  8  expediently comprises an internal closed-loop control unit  77  for carrying out the closed-loop control measures which are described further above. 
     The electronic control device  8  is further expediently provided with input means  78  via which at least one setpoint of the pivoting position of the base section  43  which is to be set, or of the volume of the fluid chamber  5  which is to be set, can be inputted. This setpoint in the closed-loop control unit  77  is compared to the actual values which are determined by the position detection device  33 , in order to output an operating voltage to the electrode arrangement  57  via the electrical leads  66  in dependence on the results of the comparison, by way of which operating voltage the piezoactuator  7  is deformed such that the pivoting position of the base section  43  and thus the volume of the fluid chamber  5  is set to the desired setpoint. 
     Concerning the exemplary fluid device  1 , for this reason there is the advantageous possibility of deforming the membrane working section  27  in a manner closed-loop controlled with regard to the distance and accordingly of indirectly also carrying out a closed-loop control of the volume which is defined by the fluid chamber  5 . 
     In the illustrated exemplary design as a fluid suction device  1   a , a first fluid channel  81  and a second fluid channel  82  are connected to the fluid chamber  5 , of which by way of example the first fluid channel  81  forms an exit channel and the second fluid channel  82  an entry channel. 
     The first fluid channel  81  leads to a delivery opening  83 , at which a desired fluid quantity can be delivered. On using the fluid suction device  1   a , the fluid chamber  5  and the first fluid channel  81  are normally completely filled with fluid. 
     The second fluid channel  82  leads to a fluid source  84 , concerning which it is for example a fluid reservoir, for example a liquid reservoir. 
     A delivery pump  85  is preferably connected into the course of the second fluid channel  82  and is capable of feeding fluid which is provided by the fluid source  84 , through the second fluid channel  82  into the fluid chamber  5 . 
     Preferably, a shut-off unit  86  is arranged in the course of the second fluid channel  82  in the channel section between the fluid chamber  5  and the delivery pump  85 , concerning which shut off unit by way of example it is a shut-off valve which in particular has a 2/2-way valve function. The shut-off unit  86  is expediently connected onto the electronic control device  8  via an electrical control lead  87  and can be actuated by way of this according to requirements. By way of example, the shut-off unit  86  can be selectively switched into a shut-off position which is evident from  FIG.  1    or into an open position. A fluid passage through the second fluid channel  82  is possible in the open position, whereas the second fluid channel  82  is blocked in the shut-off position of the second fluid channel  82 , in order to prevent a flow of fluid into the fluid chamber  5 . 
     Concerning a preferred operating manner of the fluid suction device  1   a , the shut-off unit  86  in a first operating phase is switched into the open position, wherein the delivery pump  85  which is in operation delivers a fluid out of the fluid source  84  through the second fluid channel  82 , the fluid chamber  5  and the first fluid channel  81  to the delivery opening  83 . The fluid exits at the delivery opening  83  for the designated use. 
     The fluid transport and the fluid delivery take place until the shut-off unit  86  is switched over into the shut-off position by the control device  8 . Here, the fluid flow and the fluid delivery at the delivery opening  83  are then stopped. 
     Evidently, a metered fluid delivery at the delivery opening  83  can be effected during the time intervals which are selected between the open position and the shut-off position of the shut-off unit  86 . Inasmuch as this is concerned, the fluid suction device  1   a  can be advantageously used in a metering device  2  according to the illustrated embodiment example. 
     The changeability of the volume of the fluid chamber  5  in the case of the outlined metering application can be used in the second operating phase which is evident in  FIG.  1   , to prevent a subsequent undesired dripping-out of fluid at the delivery opening  83 . For this, the volume of the fluid chamber  5  can be enlarged after the switching-over of the shut-off unit  86  into the shut-off position by way of a corresponding actuation of the piezoactuator  7 , so that a underpressure arises in the fluid chamber  5 , such resulting in fluid which is situated in the first fluid channel  81  being sucked back into the fluid chamber  5 . By way of this, the fluid column which is located in the first fluid channel  81  is drawn back and an intermediate space which is filled with air and which prevents a fluid exit forms between this fluid column and the delivery opening  83 . 
     The exemplary fluid suction device  1   a  in particular can be used to the extent that the piezoactuator  7  during a first operating phase, in which the shut-off unit assumes the open position, is activated by way of applying an operating voltage such that the membrane working section  27  is deflected in the direction of the fluid chamber  5  and the fluid chamber  5  is set to a reduced chamber volume. This corresponds to the operating state which is shown in  FIG.  5   . In order to generate the desired underpressure, in a second operating phase according to  FIG.  4    the operating voltage is reduced for the piezoactuator  7  or the piezoactuator  7  is discharged, so that the membrane working section  27  is moved somewhat in the direction of the non-deflected home position according to  FIG.  4    or completely returns into this non-deflected home position which entails an increase of the volume of the fluid chamber  5  which causes a underpressure and entails the previously outlined fluid back-sucking effect. 
     The desired volume of the fluid chamber  56  or the desired volume change can be set and specified in a very precise manner with the help of the electronic control device  8 . In this manner, one can specify in a very exact manner the quantity of fluid which is to be sucked back. 
     The fluid suction device  1   a  by way of example can be used in the context of a metering device  2  which is used to apply the necessary photoresist on semiconductor manufacture. Another possible application is for example is a metered delivery of liquid into the cavities of micro titration plates in laboratory application. 
     The two fluid channels  81 ,  82  run out with channel mouths  81   a ,  82   a  which are separate from one another, into the fluid chamber  5  independently of one another. These channel mouths  81   a ,  82   a  by way of example are formed on a lower housing wall  88  which delimits the fluid chamber  5  at the lower side  63  and through which longitudinal sections of the first and second fluid channels  81 ,  82  pass. Further length sections of the fluid channels  81 ,  82  by way of example pass through the channel plate  9 , wherein they run out at the carrier surface  10  such that they communicate with the length sections of the fluid channels  81 ,  82  which pass through the lower housing wall  88 . 
     The two channel mouths  81   a ,  82   a  are expediently arranged distanced to one another in the longitudinal direction  19  and in particular each lie in one of the two axial end regions of the fluid chamber  5 , so that the fluid covers a long as possible flow path on flowing through the fluid chamber  5 , so that a uniform fluid flow is ensured. 
     By way of example, a delivery nozzle  91 , through which the first fluid channel  81  passes and on which the delivery opening  83  is formed is attached to the channel plate  9 . Furthermore, for example a connection device  92  which is assigned to the second fluid channel  82  and on which a fluid conduit  93  which forms a length section of the second fluid channel can be connected is arranged on the channel plate  9 , said fluid conduit in the illustrated embodiment example leading to the shut-off unit  86 . 
     The fluid chamber  5  does not necessarily need to communicate with two fluid channels  81 ,  82  for the designated use of the fluid device  1 . For example, only a single fluid channel can be connected onto the fluid chamber  5 , said fluid channel for its part being connected onto a further fluid channel, wherein this further fluid channel extends between the fluid source  84  and the delivery opening  83 . In this case too, a sucking-back of fluid can be created by way of actuating the fluid device  1 . 
     Expediently, a pressing frame  94  which is indicated in  FIG.  3    in a dot-dashed manner is formed as one piece on the inner surface of the second housing part  30  which faces the fluid chamber  5 , said pressing frame acting upon the peripheral edge section  17  of the membrane element  4  all around, in order to clamp this element to the first housing part  29 . 
     Apart from the drawing back of a metered liquid, the fluid device  1  yet permits a further possibility for fluid handling. If on drawing back the liquids, it is not air which is received into the delivery nozzle  91  but a second liquid, then a through-mixing of both liquids can be carried out within the delivery nozzle  91  by way of an oscillating stroke movement of the membrane element  4 , in particular if the first fluid channel  81  is formed in the delivery nozzle  01  in a stepwise manner, which given the fluid oscillation permits an better through-mixing due to the formation of turbulence at the step edges.