Pneumatic valve with an SMA actuator

Abstract

A pneumatic valve is proposed, comprising a fluid supply port (P), a fluid outlet port (A), and a fluid drain port (R), a valve chamber (14) with a fluid supply port (FZ) connected to the fluid supply port (P), a fluid outlet port (VH) connected to the fluid outlet port (A), and a trigger port (VT) connected to an actuator chamber (15) of the valve, which includes the fluid drain port (R), an actuator (16) which, in the unactuated state of the actuator (16), presses a sealing element (E) against the trigger port (VT) and, in the actuated state of the actuator (16), releases the trigger port (VT), and a diaphragm (M) which divides the valve chamber (14) into two areas, a first area (1) being connected to the trigger port (VZ) and a second area (2) being connected to the fluid outlet port (VH), wherein the diaphragm (M) is connected to a The plunger (S) is connected,which is pressed against the fluid drain opening (VH) by a spring force in the unactuated state and releases the fluid drain opening (VH) in the actuated state of the actuator (16), wherein the diaphragm (M) has at least one through-opening (D) through which fluid can flow from the first region (1) to the second region (2), wherein the through-opening (D) has a smaller cross-section than the trigger opening (VT).

Description

[0001] The invention relates to a pneumatic valve with a fluid supply port, a fluid outlet port, and a fluid discharge port. The valve chamber includes a fluid supply port connected to the fluid supply port, a fluid outlet port connected to the fluid outlet port, and a trigger port connected to an actuator chamber of the valve, which includes the fluid discharge port. The valve is formed with an actuator comprising an SMA wire, an actuating element, a return element, and a circuit board arranged in the actuator chamber.The valve also has a diaphragm that divides the valve chamber into two regions, a first region communicating with the trigger opening and a second region communicating with the fluid discharge opening. The diaphragm is connected to a plunger that, due to a spring force, is pressed against a fluid opening when the actuator is not actuated, closing it. When the actuator is actuated, the plunger releases the fluid opening from a fluid flowing through the fluid supply opening. The diaphragm has at least one through-opening through which fluid can flow from the second region into the first region.

[0002] Such a pneumatic valve is known from DE 10 2019 208 051 B4. There, the diaphragm closes the fluid supply opening of the valve chamber, while the fluid outlet opening is constantly open. A plunger actuated by the leaf spring protrudes through the trigger opening and is connected to the diaphragm to press it against the fluid supply opening when not actuated. The trigger opening is closed by the diaphragm when the actuator is actuated, but the trigger opening is open when not actuated, so that fluid from a consumer connected to the fluid outlet connection, for example a bladder to be filled with fluid - for example, air - is discharged via the fluid outlet connection, holes in the diaphragm and the trigger opening into the actuator chamber and from there via the fluid outlet opening into the environment. It is therefore a 3 / 2 NC valve.

[0003] In a similarly constructed valve according to DE 10 2018 216 874 A1, the air must also flow serially through two nozzle openings during the filling process, so that the additional flow resistance reduces the flow compared to a single nozzle passage.

[0004] Such pneumatic valves are used to control a fluid flow for filling elastic cushions in vehicles to shape seat contours. The elastic cushions are usually filled with air as the fluid.

[0005] Shape memory wire (SMA = shape memory alloy) is increasingly being used as an actuator for such valves; this wire shortens in length when current flows and the resulting heating occurs.

[0006] The high flow required for certain functions, such as cushion adjustment depending on driving dynamics, requires large valve cross-sections and thus high actuation and sealing forces. An SMA actuator capable of providing these forces requires correspondingly large dimensions, which increases costs and installation space requirements.

[0007] For high-flow valves, the following options are known according to the state of the art: By connecting several individual valves in parallel, the flow rate can be scaled. However, this also increases costs and installation space accordingly.

[0008] As examples of a wide range of industrial valves, DE 43 31 568 C2 and DE 43 31 515 A1 show servo or pilot solenoid valves operated with auxiliary flow, which control a larger pressure or flow with little actuation effort.

[0009] US 9,080,682 B2 shows a valve in which SMA wires control two pilot valves via a diverter to actuate a main valve. The diverter is guided through a sealing element that reduces the available actuation force of the SMA wire.

[0010] EP 3 078 890 B1 also shows a pilot valve actuated by an SMA wire. The SMA wire is located in the pressure range of the main valve's working port; therefore, the associated electrical contacts must be hermetically sealed, which increases the complexity and thus the costs.

[0011] The object of the invention is therefore to provide a compact pneumatic valve with a large nozzle cross-section. The SMA actuator for actuation should be subjected to as little force and travel as possible. Furthermore, sealing the SMA actuator's connections should be eliminated.

[0012] The object is achieved by a pneumatic valve according to claim 1. Advantageous developments of the pneumatic valve are specified in the subclaims.

[0013] Accordingly, the pneumatic valve according to the invention is formed with a fluid supply port, a fluid outlet port, and a fluid discharge opening. It has a valve chamber with a fluid supply port connected to the fluid supply port, with a fluid outlet port connected to the fluid outlet port, and with a trigger opening connected to an actuator chamber of the valve, which has the fluid discharge opening. It is also formed with an actuator formed with an SMA wire, an actuating element, a reset element, and a circuit board arranged in the actuator chamber. A sealing element is arranged on a movable part of the actuating element, which sealing element is pressed against the trigger opening by the reset element when the actuator is not actuated and releases the trigger opening when the actuator is actuated.The valve chamber is divided into two regions by a membrane, a first region being connected to the trigger opening and a second region being connected to the fluid outlet opening, the membrane being connected to a plunger which, due to a spring force, is pressed against the fluid outlet opening in the unactuated state of the actuator and closes it, and in the actuated state of the actuator is pressed away from the fluid outlet opening by a fluid flowing through the fluid supply opening and opens the fluid outlet opening, the membrane having at least one through-opening through which fluid can flow from the first region into the second region, the through-opening having a smaller cross-section than the trigger opening.

[0014] In the unactuated state, the valve chamber of the pneumatic valve is therefore connected to the air supply via the fluid supply connection, whereby the same pressure is established in both the first and second areas of the valve chamber due to the through-hole in the diaphragm, thus preventing any stress on the diaphragm. In the actuated state, the actuator opens the trigger opening so that air can escape from the first area into the actuator chamber and from there into the environment. Due to the higher pressure in the second area, the effective area of ​​the diaphragm causes the connected plunger to be lifted from the outlet opening against the spring force, allowing air to flow through the valve into a connected consumer - for example, a pillow. Only a small force is therefore required to actuate the SMA actuator, since the pressure of the incoming air is used to open the valve.Since the through opening has a smaller cross-section than the trigger opening, the compressed air flowing into the second area cannot reach the first area quickly enough, so that there is a higher pressure in the second area as long as the trigger opening is open.

[0015] The actuating element can be designed as a leaf spring, which also acts as a return element. A fixed end of the actuating element (bend section) can be connected to the circuit board, and the movable end (actuating section) can be connected to the SMA wire.

[0016] It is also possible to design the return element with a spiral spring, as shown, for example, in DE 10 2018 216 874 A1.

[0017] In one embodiment of the pneumatic valve, the valve chamber is formed with a cover element containing the trigger opening. This cover element can be locked into a housing wall forming the valve chamber, thus forming a sealed chamber that can also absorb the forces of the spring.

[0018] The spring force acting on the plunger can be generated in one embodiment of the pneumatic valve by a coil spring arranged between the plunger and the cover element. However, it is also conceivable to design the diaphragm as a spring element. The spring force must be dimensioned such that, on the one hand, the outlet opening can be securely closed, while, on the other hand, the pressure of the incoming air is sufficient to lift the plunger from the outlet opening when the trigger opening is released.

[0019] Advantageously, the entire fluid line from the pressure supply up to and including the fluid supply opening has a larger cross-section than the outlet opening, so that the pressure in the first area of ​​the valve chamber largely corresponds to the pressure of the incoming air even when the outlet opening is open.

[0020] In a further embodiment of the pneumatic valve, the plunger can have a cup-shaped region in which the coil spring is mounted. Alternatively, the plunger can have a pin-shaped region around which the coil spring is arranged.

[0021] In a further development of the pneumatic valve, the valve chamber has a projection in the area next to the trigger opening, against which the area of ​​the membrane in which the through opening is located is pressed by the inflowing fluid in the activated state of the actuator.

[0022] This reduces the working air flow and thus also the pressure difference between the second and first areas, until the pressure force and spring force reach equilibrium. However, even when the through-hole is in contact with the projection, the design must ensure that a minimum working air flow is maintained, which is important for the rapid completion of the filling process. When the valve is not actuated, the arrangement also consumes no working air.

[0023] Advantageously, the SMA wire and a bending section of the actuating element - for example a leaf spring - can be arranged on opposite sides of the circuit board.

[0024] In a further development of the pneumatic valve, the membrane is clamped between the cover element and a cup-shaped element of the valve chamber that receives the cover element, thereby achieving simple assembly.

[0025] For particularly good sealing, the cover element can have a projection on its edge that is in contact with the membrane, whereby the membrane is additionally held in place by a positive fit.

[0026] The diaphragm can be connected to the tappet as a single piece. However, the diaphragm and tappet can also be made of separate parts that are joined together.

[0027] The cross-section of the trigger opening is advantageously smaller than the cross-section of the outlet opening. This allows the associated SMA actuator to travel a short distance and require limited force for actuation. This benefits the service life (especially the number of actuation cycles) of the SMA wire.

[0028] In a further design of the pneumatic valve, the effective area of ​​the diaphragm is larger than the cross-section of the outlet opening. This allows the main valve to be opened against a high pre-pressure and the force of the spring, even when the consumer is depressurized. The pressure supply provides the additional energy for opening. The pre-pressure can vary over a wide range; it must simply be at least large enough for the pressure force acting on the diaphragm to exceed the return force of the spring.

[0029] In a further development of the pneumatic valve, the outlet opening of the valve chamber is connected to the fluid outlet port via an additional valve element. This allows for the realization of a 3 / 3 valve.

[0030] When the further valve element is open in its unactuated state, the pneumatic valve is realized as a 3 / 3 NO valve.

[0031] If, however, the other valve element is closed in its unactuated state, the pneumatic valve is formed as a 3 / 3 NC valve.

[0032] The invention will be explained in more detail below using exemplary embodiments with the aid of figures. Fig. 1 a pneumatic valve according to the invention, Fig. 2 the valve chamber in a detailed view, Fig. 3 the pneumatic valve in the deactivated state, Fig. 4 the pneumatic valve in the activated state, Fig. 5 the pneumatic valve as a 3 / 3 NC valve in the venting state, Fig. 6 the pneumatic valve as 3 / 3 NO valve, Fig. 7 the valve chamber with a variant of the diaphragm-tappet connection and Fig. 8 the valve chamber with a variant of the spring retainer of the tappet.

[0033] The Fig. 1 shows, in a first exemplary embodiment, a pneumatic valve in a cross-sectional view, which is formed with a housing 10 having a first housing part 11, which in the illustrated exemplary embodiment is designed as a base plate. The housing 10 also has a second housing part 12, which is designed as a cover, and finally a third cup-shaped housing part 13, which is designed as an insert between the first and second housing parts 11, 12 and onto which a fluid supply connection P and a fluid outlet connection A are formed. A fluid drain opening R is formed in the second housing part 12, which connects an actuator chamber 15, which is formed between the second housing part 12 and the third housing part 13 and in which an actuator 16 is arranged, with the environment, so that openings for electrical connections of the actuator do not have to be sealed.

[0034] An air chamber 14 is formed on the third housing part 13 by having a cup-shaped portion into which a cover element K is inserted as the cover of the air chamber 14. The air chamber 14 has a fluid supply opening FZ, a fluid outlet opening VH acting as the main valve, and a trigger opening VT. In the illustrated embodiment, the fluid supply opening FZ and the fluid outlet opening VH are formed in the third housing part 13, and the trigger opening VT is formed in the end part K that closes off the air chamber 2.

[0035] Compressed air can therefore be fed into the housing 10 via the fluid supply opening FZ, for example from a compressor, wherein the compressed air can reach the air chamber 14 via the fluid supply opening FZ and from there via the fluid outlet opening VH and the fluid outlet connection A into a consumer that can be connected thereto, for example an air cushion.

[0036] As detailed in the Fig. As can be seen in Figure 2, an elastic membrane M divides the valve chamber 14 into a lower, first region 1 and an upper, second region 2. The first region 1 is connected to the fluid supply opening FZ and thus to the fluid supply connection P. The second region 2 is sealed off from the actuator chamber 15 and thus from the environment by a cover element K. The membrane M has a small through-opening D, which allows a limited air flow (working air) from the first region 1 into the second region 2 of the valve chamber 14.

[0037] The diaphragm M is connected to a plunger S. The plunger S has a sealing surface on its underside in order to close the nozzle seat of the fluid outlet opening VH in its lower end position. The plunger S can be made in one piece with the diaphragm M from an elastic material or it can be a component assembled with the plunger S. An elastic element F, e.g. a spring, which is mounted between the cover element K and the plunger S, generates a restoring force for closing the fluid outlet opening VH by means of the plunger S. The elastic element F can optionally also be formed with the diaphragm M, which pulls the plunger S through its internal tension into the lower end position closing the fluid outlet opening VH.

[0038] A corresponding SMA actuator consists of a leaf spring B and an SMA wire SMA. The leaf spring B has a bending section and an actuating section, each of which is arranged on opposite sides of an electrical circuit board 17 and at ambient pressure in the actuator chamber 15. The cover element K has the trigger opening VT, which functions as a trigger valve. A sealing element E is attached to the underside of an actuating section of the leaf spring B, which can seal the trigger opening VT.

[0039] In the Fig. Figures 3 to 5 depict a pneumatic valve as a 3 / 3 NC valve with two valve elements V1 and V2 in three different switching states. The first valve element V1 is formed with a valve chamber 14 as described above, and the second valve element V2 is formed as a simple valve with only one valve opening 22, actuated by an SMA actuator 21. A sealing element 22 arranged on the SMA actuator 21 closes the valve opening 22 in the unactuated state and releases it in the actuated state.

[0040] In the Fig. 3 shown state “Hold” (ie the SMA actuator 16 of the first valve element V1 is not activated, see Fig. 3, right) the trigger opening VT is closed by the sealing element E. The lower 1 and the upper area 2 of the valve chamber 14 are connected to one another via the through-opening D, so that pressure equalization takes place. Thus, no pneumatic force acts on the diaphragm M, even at high or variable pressure of the pressure supply at the fluid supply port P. The elastic element F, designed as a spiral spring, now presses the plunger S connected to the diaphragm M against the nozzle seat of the fluid outlet opening VH and seals it. The force of the elastic element F is designed such that it can apply pressure and sealing forces in the most unfavorable case (e.g. max. consumer pressure and min. supply pressure).

[0041] The second valve element V2 is not actuated in this state, i.e. in a closed state.

[0042] At the beginning of the “Filling” state, as described in the Fig. 4 (ie the SMA actuator 16 of the first valve element V1 is activated, see Fig. 4, right), the trigger opening VT is open. The cross-section of the trigger opening VT is preferably as small as possible, but nevertheless significantly larger than the cross-section of the through-opening D. As a result, the pressure in the second region 2 of the valve chamber 14 drops and approaches the ambient pressure. The pressure difference to the supply pressure in the first region 1 of the valve chamber 14 now exerts an upward force on the diaphragm M, causing the plunger S to open the fluid outlet opening VH and thus the main valve.

[0043] Due to the small cross-section of the trigger opening VT compared to the cross-section of the trigger opening VH, the associated SMA actuator 16 requires only a short travel and limited force for actuation. This benefits the service life (especially the number of actuation cycles) of the SMA wire SMA.

[0044] Preferably, the effective area of ​​the diaphragm M is significantly larger than the cross-section of the fluid outlet opening VH. Thus, the fluid outlet opening VH can be opened against a high pre-pressure and against the force of the elastic element F, even when the consumer at the fluid outlet connection A is depressurized. The pressure supply provides the additional energy for opening ("servo valve"). The pre-pressure can vary over a wide range; it must simply be at least large enough that the pressure force on the diaphragm M is greater than the restoring force of the elastic element F.

[0045] Advantageously, the entire fluid line from the pressure supply up to and including the fluid supply opening FZ has a larger cross-section than the fluid outlet opening VH, so that the pressure in the first region 1 of the valve chamber 14 largely corresponds to the pressure of the pressure supply even when the fluid outlet opening VH is open.

[0046] During the "filling" state, a limited working air flow flows from the pressure supply through the through-hole D and the open trigger opening VT into the atmosphere. With the diaphragm M at its maximum deflection, the through-hole D optionally approaches a projection KS in the cover element K. This reduces the working air flow and thus also the pressure difference between the lower 1 and upper area 2 until the pressure force and the spring force reach equilibrium.

[0047] Even when the through-hole D is in contact with the web KS, the design must ensure that a minimum working air flow is maintained, which is important for the rapid completion of the filling process. When the valve is not actuated, the arrangement also does not consume any working air.

[0048] At the end of the filling process (ie the SMA actuator 16 of the first valve element V1 is deactivated, see Fig. 3, right), the trigger opening VT is closed again. Pressure equalization now occurs between the first 1 and the second 2 areas of the valve chamber 14 via the through-opening D.

[0049] The force of the elastic element F consequently also closes the fluid outlet opening VH again.

[0050] The first valve element V1 can be easily combined with a second valve element V2 to vent a consumer in a known manner, as shown in Fig. 5. The behavior of the valve arrangement shown corresponds to a 3 / 3 NC valve (normally closed).

[0051] In the venting state, the second valve element V2 is actuated via the associated SMA actuator 21 with SMA wire and leaf spring. A sealing element 22, also attached to the leaf spring, then opens the corresponding nozzle seat (left). This allows air to flow from the consumer into the environment.

[0052] Likewise, the proposed first valve element V1 can be combined with a pot valve V2' (see Fig. 6, left). The additional pot valve V2', also equipped with a state-of-the-art SMA actuator, connects a consumer connected to the fluid outlet port A to the environment via the fluid outlet port R in the idle state (not activated). When the SMA actuator is activated, a plunger closes the nozzle seat of the vent valve with its sealing element at the top. The behavior of the valve arrangement shown thus corresponds to 3 / 3 NO (normally open).

[0053] The optimized valve designs described below can also be used advantageously: As in the Fig. 7 and Fig. As shown in Figure 8, the membrane M can be placed at the level of the sealing surface on the underside of the plunger S. This has the advantage that the plunger D is guided more precisely in its lower position and is less susceptible to possible tilting.

[0054] The cover element K can advantageously have a lateral projection 23 as a mechanical stop during installation (e.g. pressing in) into the pot of the valve chamber 14.

[0055] This ensures that the vertical position of the nozzle seat of the trigger opening VT is precisely maintained, while simultaneously clamping the bead on the outer edge of the diaphragm M. This avoids unnecessary tolerances in the mechanical and pneumatic properties of the pneumatic valve.

[0056] To seal the membrane M against the cover element K, the latter can also have a narrow ring-shaped elevation KRV, which presses into the edge of the membrane M and thus seals ( Fig. 7).

[0057] The elastic element F can be guided not only in a hollow cylinder SB of the plunger S, but alternatively also through a pin-shaped extension SZ of the same, as in the Fig. 8. This pin-shaped extension SZ can advantageously also serve as the upper end stop of the tappet and has a corresponding notch on its upper side which, in the upper position of the tappet, still allows working air to escape from the second region 2 of the valve chamber 14 through the nozzle seat of the trigger opening VT.

[0058] The advantages of the above-mentioned designs compared to currently available state-of-the-art solutions are summarized below: • A single, lightly loaded SMA actuator 16 can actuate a large valve cross-section for filling thanks to its servo function. This increases the service life of the actuator 16. Furthermore, parallel valves are no longer required, reducing installation space and costs. • In the rest position the servo valve does not consume any working air. • The servo actuation works in a wide pressure range of the pre-pressure. • The servo valve can easily be expanded to a 3 / 3 valve NC and NO with another SMA actuator. • The SMA actuator 16 and the associated circuit board 17 with electronics are not located in the pressure area and therefore do not need to be sealed. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 208 051 B4

[0002] DE 10 2018 216 874 A1 [0003, 0016] DE 43 31 568 C2

[0008] DE 43 31 515 A1

[0008] US 9,080,682 B2

[0009] EP 3 078 890 B1

[0010]

Claims

[1] Pneumatic valve with a fluid supply port (P), a fluid outlet port (A) and a fluid drain port (R), with a valve chamber (14) with a fluid supply opening (FZ) connected to the fluid supply connection (P), with a fluid outlet opening (VH) connected to the fluid outlet connection (A) and with a trigger opening (VT) connected to an actuator chamber (15) of the valve having the fluid outlet opening (R), with an actuator (16) which is formed with an SMA wire (SMA), with an actuating element (B), a return element and with a circuit board (17) arranged in the actuator chamber (15), wherein a sealing element (E) is arranged on the actuating element (B), which sealing element is pressed against the trigger opening (VT) by the return element in the non-actuated state of the actuator (16) and releases the trigger opening (VT) in the actuated state of the actuator (16), with a membrane (M) which divides the valve chamber (14) into two areas, wherein a first area (1) is connected to the trigger opening (VZ) and a second area (2) is connected to the fluid outlet opening (VH), wherein the membrane (M) is connected to a plunger (S) which, due to a spring force, is pressed against the fluid discharge opening (VH) in the unactuated state of the actuator (16) and closes it, and in the actuated state of the actuator (16) is pushed away from the fluid discharge opening (VH) by a fluid flowing through the fluid supply opening (FZ) and releases the fluid discharge opening (VH), wherein the membrane (M) has at least one through-opening (D) through which fluid can flow from the first region (1) into the second region (2), wherein the through-opening (D) has a smaller cross-section than the trigger opening (VT). [2] Pneumatic valve according to claim 1, wherein the valve chamber (14) is formed with a cover element (K) having the trigger opening (VT). [3] Pneumatic valve according to claim 2, wherein the spring force acting on the tappet (S) is generated by a spiral spring arranged between the tappet (S) and the cover element (K). [4] Pneumatic valve according to one of the preceding claims, wherein the actuating element (B) is designed as a leaf spring having a bending section and an actuating section. [5] Pneumatic valve according to claim 4, wherein the bending portion and the actuating portion of the leaf spring are respectively arranged on opposite sides of the electrical circuit board (17). [6] Pneumatic valve according to one of the preceding claims, in which the valve chamber (14) has a projection in the area next to the trigger opening (VT) against which the area of ​​the membrane (M) in which the through opening (D) is located is pressed by the inflowing fluid in the activated state of the actuator (16). [7] Pneumatic valve according to one of the preceding claims, in which the membrane (M) is clamped between the cover element (K) and a cup-shaped element (18) of the valve chamber (14) receiving the cover element (K). [8] Pneumatic valve according to claim 7, wherein the cover element (K) has a projection (KRV) on its edge (KR) which is in contact with the membrane (M). [9] Pneumatic valve according to one of the preceding claims, in which the membrane (M) is integrally connected to the tappet (S). [10] Pneumatic valve according to one of the preceding claims, wherein the cross-section of the trigger opening (VT) is smaller than the cross-section of the outlet opening (VH). [11] Pneumatic valve according to one of the preceding claims, wherein the cross section of the fluid supply opening (FZ) is larger than the cross section of the outlet opening (VH). [12] Pneumatic valve according to one of the preceding claims, wherein the effective area of ​​the membrane (M) is larger than the cross section of the outlet opening (VH). [13] Pneumatic valve according to one of the preceding claims, wherein the outlet opening (VH) of the valve chamber (14) is connected to the fluid outlet connection (A) via a second valve element (V2). [14] Pneumatic valve according to claim 13, wherein the second valve element (V2) is open in its unactuated state, so that the pneumatic valve is a 3 / 3 NO valve. [15] Pneumatic valve according to claim 13, wherein the second valve element (V2) is closed in its unactuated state, so that the pneumatic valve is a 3 / 3 NC valve.

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