Pneumatic valve

Abstract

Pneumatic valve with a first port (A), a second port (R1), a third port (P) and a fourth port (R2), with a valve chamber (14) having a first opening (VH1) connected to the first port (A), a second opening (VH2) connected to the second port (R1), a third opening (VP) connected to the third port (P), and a fourth opening (VT) connected to the fourth port (R2), with an actuator (16) which is formed with at least one SMA wire (SMA) and an actuating element (B), wherein a first sealing element (E) is arranged on the actuating element (B), which is pressed against the fourth opening (VT) by the actuating element (B) in the unactuated state of the actuator (16) and releases the fourth opening (VT) in the actuated state of the actuator (16), with a diaphragm (M) that divides the valve chamber (14) into two areas, wherein a first area (1) is connected to the first opening (VH1) and the second opening (VH2) and a second area (2) is connected via a through-hole (D, KG) to the third opening (VP) and to the fourth opening (VT), wherein the diaphragm (M) is clamped with its edge between a cup-shaped element (G) forming the valve chamber (14) and a cover element (K) inserted therein, and in the unpressurized state of the second region (2) of the valve chamber (14) releases the first opening (VH1) due to at least its intrinsic tension and, when the actuator (16) is not actuated and air is supplied through the third opening (VP) into the second region (2), is pressed against the first opening (VH1) and closes it.

Description

[0001] The invention relates to a pneumatic valve with a valve chamber divided into two separate sections by a diaphragm. In a first section, the diaphragm can connect or separate a first opening and a second opening of the valve chamber, thereby forming a 2 / 2-NO valve, i.e., the valve is open when the diaphragm is relaxed. The second section can be connected to or separated from ambient pressure by means of a shape memory alloy (SMA) actuator, whereby, in the non-actuated state of the actuator, a connecting opening of the second section of the valve chamber to ambient pressure is closed.

[0002] In vehicles, inflatable, elastic cushions are used to shape seat contours. These cushions are typically filled with air. Electrically operated valves are used to control the air pressure. Shape memory alloy (SMA) wire, which shortens in length when an electric current flows and it heats up, is increasingly used as the actuator for such valves.

[0003] The high flow rates required for some functions (e.g., cushion adjustment depending on driving dynamics) necessitate large valve cross-sections and therefore high actuation and sealing forces. An SMA actuator capable of providing these forces requires a correspondingly large size, which increases costs and installation space requirements.

[0004] For high-flow valves, the following options are known according to the state of the art: Documents DE 43 31 568 C2 and DE 43 31 515 A1 disclose servo or pilot solenoid valves operated by auxiliary flow, which control a larger pressure or flow rate with minimal actuation effort.

[0005] The unpublished publication DE 10 2023 208 359 A1 describes a valve with an SMA actuator, wherein the actuator switches an auxiliary valve which, by means of a pre-pressure, opens a main valve. The diaphragm has a narrow through-hole to achieve pressure equalization between both sides of the diaphragm when deactivated. The working air and at least a portion of the air to be switched are connected.

[0006] Furthermore, the German patent application DE 10 2019 208 051 B4 describes a valve with an SMA actuator, wherein the pivot point of a bending device and the SMA wire are arranged on opposite sides of a printed circuit board. The SMA wire and the printed circuit board are at ambient pressure.

[0007] German patent DE 102017 125 283 A1 relates to a valve system for a fuel tank that enables the controlled introduction and release of gases or hydrocarbon-enriched air. It comprises a housing with connections for the tank, activated carbon filter, and filler pipe, with main and secondary vent channels containing corresponding valves regulating the fluid connections. The main vent valve and a valve group in the secondary vent channel selectively control the opening or closing of the respective flow paths.

[0008] US Patent 2014 / 0117262A1 relates to a self-holding valve that includes a valve seal movable between two positions to selectively open a fluid passage between an inlet and an outlet port. Two pilot valve seals control whether pressurized fluid is introduced into or discharged from a control chamber, thereby forcing the main valve seal into a specific position. The pilot valves are actuated by shape-memory elements that deform when heated above a transformation temperature, thus influencing the valve position.

[0009] The object of the invention is to provide a compact pneumatic valve with a large nozzle cross-section, in which an SMA actuator is subjected to the lowest possible load in terms of force and displacement for actuation. The SMA actuator is also to be located at ambient pressure. Furthermore, the working air should be independent of the airflow to be switched, so that the valve can also be used for venting a consumer.

[0010] The problem is solved by a pneumatic valve with a first port, a second port, a third port and a fourth port, with a valve chamber having a first opening connected to the first port, a second opening connected to the second port, a third opening connected to the third port and a fourth opening connected to the fourth port, with an actuator formed with at least one SMA wire and an actuating element, wherein a first sealing element is arranged on the actuating element, which is pressed against the fourth opening by the actuating element in the unactuated state of the actuator and releases the fourth opening in the actuated state of the actuator, with a diaphragm that divides the valve chamber into two areas.wherein a first area is connected to the first opening and the second opening and a second area is connected via a through-opening to the third opening and to the fourth opening, wherein the diaphragm is clamped with its edge between a cup-shaped element forming the valve chamber and a lid element inserted therein, and in the unpressurized state of the second area of ​​the valve chamber, due to at least its intrinsic tension, releases the first opening and, when the actuator is not actuated and air is supplied through the third opening into the second area, is pressed against the first opening and closes it.

[0011] In the pneumatic valve according to the invention, one side of a diaphragm can be connected to a pressure supply via a small through-hole and to the environment via a trigger valve actuated by the SMA actuator. A main valve on the other side of the diaphragm is open when the valve is depressurized, and its ports do not need to be connected to the pressure supply. The main valve formed by the first and second openings of the valve chamber can therefore be closed by means of a pressure supply and opened by actuating the SMA actuator. This advantageously reduces the force required by the SMA actuator.

[0012] In one embodiment of the pneumatic valve, the diaphragm has a thickening in its center, which acts as a second sealing element to close the first opening. The second sealing element can therefore advantageously be formed as part of the diaphragm.

[0013] Stops can be formed on the diaphragm to provide support against the cover element, which prevents the diaphragm from being subjected to excessive bending stress when a higher pressure is applied to the main valve.

[0014] To support the membrane's inherent tension, a spring element can preferably be arranged between the first opening and the membrane, exerting a force on the membrane directed away from the first opening. Since the membrane, in its relaxed state, exposes the first opening, the restoring force of the membrane's inherent tension would cause the first opening to open. The spring element can advantageously assist this process.

[0015] In one possible embodiment of the pneumatic valve, the through-hole can be formed by a channel in the cup-shaped element and a groove in the edge of the diaphragm. The channel in the cup-shaped element can have any cross-section, while the groove in the edge of the diaphragm preferably has a small cross-section corresponding to a bore < 0.5 mm, typically approximately 0.3 mm.

[0016] However, the opening can also be formed in other ways, such as a channel within the cup-shaped element and the lid element, a depression in the cup-shaped element and the lid element in the area of ​​the clamping of the membrane between these two parts, a depression on the edge of the membrane or a bead formed on it in the area of ​​the clamping between the lid element and the cup-shaped element, a raised area on the cup-shaped element and the lid element in the area of ​​the clamping of the membrane, or a raised area on the edge of the membrane in the area of ​​the clamping between the lid element and the cup-shaped element.

[0017] The contours mentioned can each be used in different combinations.

[0018] The pneumatic valve can advantageously be formed with a housing in which the first port, the second port, the third port, the fourth port, the valve chamber and the actuator are formed or arranged, wherein the actuator is formed with a return element and a circuit board arranged in an actuator space, in addition to the SMA wire and the actuating element.

[0019] In an advantageous embodiment of the pneumatic valve, a further valve with a further valve chamber and a further actuator can be formed in the housing, wherein the housing has a fifth port, wherein a first opening of the further valve chamber is connected to the first port of the housing, a second opening to the fifth port, a third opening to the fifth port and a fourth opening to the fourth port, wherein the further valve chamber has a further spring element which, in the unactuated state of the further valve, presses a further diaphragm of the further valve against the first opening of the further valve chamber.

[0020] This creates a 3 / 3 NC (normally closed) valve, through which, for example, an air-filled cushion connected to the first port in a vehicle can be filled via the fifth port and emptied via the second port. The supplied compressed air serves both to inflate the cushion and to close the first opening of the valve chamber.

[0021] During training, the second and fourth connections may be connected to the ambient air.

[0022] Furthermore, the third and fifth connections can be connected together. Therefore, only one compressed air connection is required.

[0023] The invention is described in more detail below with reference to exemplary embodiments and the aid of figures. These figures show... Fig. 1 a detailed representation of a longitudinal section through the valve chamber, Fig. 2 a cross-section through the valve chamber, Fig. 3 a pneumatic valve with a valve chamber and an actuator in a housing, Fig. 4 the pneumatic valve of the Fig. 3 in a closed state using compressed air, Fig. 5 the pneumatic valve of the Fig. 3 in a state opened by actuating the actuator, and Fig. 6 a 3 / 3-NC valve with a compressed air-operated outlet valve chamber.

[0024] In the detailed representation of a valve chamber 14 with an SMA actuator 16 of a pneumatic valve (see Fig. 3) The valve chamber 14 is formed by a cup-shaped element G molded onto a housing part of the valve, with a cover element K that closes and seals this element. An elastic diaphragm M divides the valve chamber 14 of the valve into a first area 1 and a second area 2. The second area 2 is connected to a third (pressure) port P of the valve via a narrow through-opening D and a channel KG, which forms a third opening VP of the valve chamber 14.

[0025] The connection between the third port P and the second area 2 of the valve chamber 14 can be implemented in various ways. As described above, all possible combinations of channels, depressions, or protrusions in the cup-shaped element G – i.e., the valve chamber wall – and depressions or protrusions in the edge region of the diaphragm M, i.e., the area clamped between the cup-shaped element G and the cover element K, are suitable. Crucially, a pressure equalization channel of average width must exist between the third opening VP of the valve chamber 14, or the third port of the valve, and the second area 2 of the valve chamber 14. This channel allows the pressure in the second area 2 to increase when the fourth opening VT is closed, thus pressing the diaphragm M against the first opening VH1 and sealing it.

[0026] The membrane M exhibits in the Fig. In the embodiment shown in Figure 1, a central thickening is provided, on the underside of which a sealing surface may be formed to press against the nozzle seat of the first opening VH1 in the lower end position of the diaphragm M and thus close a main valve VH1, VH2, M formed by the first and second openings VH1, VH2. The thickening can be manufactured integrally with the diaphragm M from an elastic material or it can be a component assembled with the diaphragm M.

[0027] The first and second openings VH1, VH2 of valve chamber 14 do not need to be connected to a pressure supply, or at least not directly. In particular, pressure can be present at one or both openings via the first or second connection, which may be independent of and, in particular, lower than the pressure of a pressure supply (inlet pressure). This allows the valve to function as a 2 / 2 valve.

[0028] In a first state, the pressure in the second section 2 of valve chamber 14 should be in the range of ambient pressure. This is the case when the fourth opening VT of valve chamber 14 is open. Since the fourth opening VT has a larger cross-section than the through-hole D, a lower pressure is established in the second section 2 (this is also the case when there is no pressure supply). The diaphragm M is then in an upper, relaxed position, in which the first opening VH1 and the second opening VH2 of valve chamber 14 – i.e., the main valve VH1, VH2, M – are pressurized together, meaning the valve is open. The diaphragm M can be held in this position by its own tension or by an optional elastic element (e.g., a spring element, not shown) that exerts an upward force.

[0029] In a second state, the pressure of a pressure supply should be present at the third port P in the second area 2. This is the case when the trigger valve is closed. If the average pressure at both ports of the main valve VH1, VH2, M is lower than the inlet pressure, the resulting pressure difference exerts a downward force on the diaphragm M. This forces it into a lower position, in which the main valve VH1, VH2, M is closed.

[0030] In the Fig. Figure 2 shows a cross-sectional view of the valve chamber. The channel KG in the valve chamber wall and the through-opening D in the ridge of the diaphragm M's edge are particularly visible.

[0031] As especially in the Fig. As shown in Figures 3 to 5, an associated SMA actuator 16 consists of at least one actuating element B and one SMA wire SMA, wherein the actuating element B, according to DE 10 2019 208 051 B4, has a bending section and an actuating section, which are each arranged on opposite sides of an electrical circuit board 17 and at ambient pressure. The fourth opening VT of the valve chamber 14 is formed in the cover element K and, together with the SMA actuator 16, forms a trigger valve. A sealing element E is attached to the underside of the actuating element B, which can seal the trigger valve VT.

[0032] In the Fig. Figures 3 to 5 are identical parts with the same reference numerals, although for clarity not all reference numerals are used in every figure. The valves shown are identical and are only depicted in different switching states.

[0033] Thus, in Fig. Figure 3 shows the state in which the trigger valve VT, 16 is closed, but since there is no pressure at the third opening VP or at the third port P, the main valve VH1, VH2, M is open, so that air could flow from the first port A to the second port R1, for example to vent a cushion connected to the first port A.

[0034] In the Fig. Figure 4 shows a state in which a higher pressure is present at the third port P, so that air flows through the third opening VP, i.e., the channel KG and the through-hole D, into the second area 2 of the valve chamber 14. This presses the diaphragm against the first opening VH1 or its sealing seat, so that the main valve VH1, VH2, M is closed.

[0035] The Fig. Figure 5 now shows a state in which the actuator 16 is actuated, thereby opening the fourth opening VT – i.e., the trigger valve. As a result, the air in the second area 2 of the valve chamber 14 escapes into the environment through the fourth port R2, and the diaphragm M, due to its own tension or the spring force of a spring element (not shown), reopens the first opening VH1.

[0036] The pressure difference between the first area 1 (e.g., consumer pressure) and the second area 2 (near ambient pressure) of the valve chamber 14 can exert an upward force on the diaphragm M. Therefore, the upward stroke of the diaphragm M is limited by stops 18 to prevent overstretching of the diaphragm M.

[0037] Due to the small cross-section of the fourth opening VT compared to the cross-section of the first opening VH1, the associated SMA actuator 16 requires only a short distance and limited force for actuation. This benefits the service life (especially the number of actuation cycles) of the SMA wire.

[0038] During the open state, a limited working airflow from a pressurized supply at the third port P through the duct KG, the through-opening D and the open fourth opening VT through the fourth port R2 into the environment.

[0039] This can be done easily in the Fig. Combine valve V1 shown in sections 3 to 5 with another valve V2 to fill a consumer at the first connection A, as shown in Fig.Figure 6 shows the behavior of the valve arrangement. The depicted behavior thus corresponds to a 3 / 3 NC (normally closed) valve. The first two ports P for pressure supply shown here can also be combined into a single port by suitable channel routing, as can the second port R1 and fourth port R2 to the environment. The additional valve V2 has another SMA actuator 16' and another diaphragm M'. This diaphragm is pressed onto the nozzle seat of the associated first opening VH1' by another spring element F' when not actuated.

[0040] The proposed valve V1 can also be used for fluidically connecting and disconnecting two consumers (e.g. for targeted pressure equalization), pressure sources or the like, since the valve connections can be completely separated from the working air.

[0041] Likewise, the device shown can also be operated as a pure actuator by using the stroke movement of the diaphragm to actuate other mechanical components.

[0042] The proposed pneumatic valve has the advantage that a single, lightly loaded SMA actuator 16 can actuate a large valve cross-section for venting thanks to the implemented servo function. This increases the actuator's service life. Furthermore, parallel-connected valves are not required, thus reducing installation space and costs.

[0043] The proposed valve causes a connected consumer to vent automatically when the pressure supply is switched off, thus eliminating the need for active control of a venting process (e.g. to protect connected air chambers in a parked vehicle from overpressure due to heat).

[0044] Other possible uses for the device include as a universal 2 / 2 valve or as a mechanical actuator.

[0045] In its resting position, the servo valve consumes no working air.

[0046] The servo actuation works within a wide pressure range of the pre-pressure, provided the pre-pressure is greater than the switched pressure.

[0047] The described servo valve can be extended to a 3 / 3 NC valve using an additional SMA actuator, according to the state of the art.

[0048] The SMA actuator and the associated circuit board with electronics are not located in the pressure area and therefore do not need to be sealed.

Claims

[1] Pneumatic valve with a first port (A), a second port (R1), a third port (P) and a fourth port (R2), with a valve chamber (14) having a first opening (VH1) connected to the first port (A), a second opening (VH2) connected to the second port (R1), a third opening (VP) connected to the third port (P), and a fourth opening (VT) connected to the fourth port (R2), with an actuator (16) which is formed with at least one SMA wire (SMA) and an actuating element (B), wherein a first sealing element (E) is arranged on the actuating element (B), which is pressed against the fourth opening (VT) by the actuating element (B) in the unactuated state of the actuator (16) and releases the fourth opening (VT) in the actuated state of the actuator (16), with a diaphragm (M) that divides the valve chamber (14) into two areas, wherein a first area (1) is connected to the first opening (VH1) and the second opening (VH2) and a second area (2) is connected via a through-hole (D, KG) to the third opening (VP) and to the fourth opening (VT), wherein the diaphragm (M) is clamped with its edge between a cup-shaped element (G) forming the valve chamber (14) and a cover element (K) inserted therein, and in the unpressurized state of the second region (2) of the valve chamber (14) releases the first opening (VH1) due to at least its intrinsic tension and, when the actuator (16) is not actuated and air is supplied through the third opening (VP) into the second region (2), is pressed against the first opening (VH1) and closes it. [2] Pneumatic valve according to claim 1, wherein the diaphragm (M) has a thickening in its center which acts as a second sealing element for closing the first opening (VH1). [3] Pneumatic valve according to claim 1 or 2, wherein stops (18) are formed on the diaphragm (M) for support against the cover element (K). [4] Pneumatic valve according to one of the preceding claims, wherein a spring element is arranged on the diaphragm (M) which assists in lifting the diaphragm (M) away from the first opening (VH1). [5] Pneumatic valve according to one of the preceding claims, wherein the through-opening (D) is formed with a channel (KG) in the cup-shaped element (G) and with a groove in the edge of the diaphragm (M). [6] Pneumatic valve according to one of the preceding claims, comprising a housing in which the first port (A), the second port (R1), the third port (P), the fourth port (R2), the valve chamber (14) and the actuator (16) are arranged, wherein the actuator (16) is formed in addition to the SMA wire (SMA) and the actuating element (B) with a return element and with a circuit board (17) arranged in an actuator space (15). [7] Pneumatic valve according to claim 6, in which a further valve (V2) with a further valve chamber (14') and an SMA actuator (16') is formed in the housing, where the housing has a fifth connector (P'), in which a first opening (VH1') of the further valve chamber (14') is connected to the first port (A) of the housing, a second opening (VH2') to the fifth port (P'), a third opening (VP') to the fifth port (P') and a fourth opening (VT') to the fourth port (R2), in which the further valve chamber (14') has a further spring element (F') which, in the unactuated state of the further valve (V2), presses a further diaphragm (M') of the further valve (V2) against the first opening (VH1') of the further valve chamber (14'). [8] Pneumatic valve according to claim 6 or 7, wherein the second and fourth ports (R1, R2) are connected to the ambient air. [9] Pneumatic valve according to any one of claims 6 to 8, wherein the third port (P) and the fifth port (P') are connected to each other.

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