Valve with shape memory alloy wire

A valve (100) includes a housing (111) and the fluid port (121). A plunger (125) is configured to seal the fluid port (121) in a first position (91) and to unseal the fluid port (121) in a second position and to displace along a displacement direction (259) from its first position (91) towards its second position. The valve (100) also includes at least one shape memory alloy, SMA, actuator (151, 152) extending along the displacement direction (259) for at least 50% of its length and configured to exert an actuation force (155) on the plunger (125) to displace the plunger (125) from the first position (91) towards the second position.

TECHNICAL FIELD

Various examples relate to actuating a plunger of a valve using a shape memory alloy actuator. Various examples relate to an operating range of a shape memory alloy actuator for actuating the plunger.

BACKGROUND

Valves to switch a fluid flow are employed in various fields including automotive seating. Here, an example application includes switching the flow of pressurized air to implement functions such as lumbar support, bolster adjustment, and massage.

Traditionally, such valves are implemented using solenoid technology. However, respective valves are comparably bulky and heavy and, furthermore, cause a significant noise level during operation.

To overcome these issues, valves are sometimes equipped with an actuator employing a shape memory alloy (SMA) wire.

For example, a normally-open valve using a SMA wire is known from U.S. Pat. No. 7,815,161 B2. However, normally-open valves using SMA wires typically face the drawback that it is difficult to protect the SMA wire against overstress once the plunger of the valve seals the fluid port. Comparably complex designs may be required to implement an overstress protection.

Therefore, normally-closed valves are sometimes employed. An example is known from WO 2015/185 132 A2. Here, a lever-type mechanism is employed to translate the length change of the SMA wire into a displacement of the plunger.

However, SMA-actuated normally-closed valves according to reference implementations face certain restrictions and drawbacks. For example, these valves can be comparably complex and require many parts. Further, the respective valves can use housings having large dimensions such that they are difficult to integrate.

SUMMARY

Therefore, a need exists for advanced techniques of actuating valves employing a SMA wire. In particular, a need exists for such techniques which overcome or mitigate at least some of the above-identified restrictions and drawbacks.

This need is met by the features of the independent claims. The features of the dependent claims define embodiments.

According to an example, a valve includes a housing and a fluid port arranged in the housing. The valve also includes a plunger configured to seal the fluid port in a first position and to unseal the fluid port in a second position. The plunger is further configured to displace along the displacement direction from its first position towards its second position. The valve further includes at least one SMA actuator which extends along the displacement direction for at least 50% of its length. The SMA actuator is configured to exert an actuation force on the plunger to displace the plunger from the first position towards the second position.

According to an example, a seat includes a valve. The valve includes a housing and a fluid port arranged in the housing. The valve also includes a plunger configured to seal the fluid port in a first position and to unseal the fluid port in a second position. The plunger is further configured to displace along the displacement direction from its first position towards its second position. The valve further includes at least one SMA actuator which extends along the displacement direction for at least 50% of its length. The SMA actuator is configured to exert an actuation force on the plunger to displace the plunger from the first position towards the second position.

For example, the seat may be an automotive seat or an airplane seat. For example, the seat may include one or more fluid bladders. It is possible that the valve is used to switch the fluid flow to one or more fluid bladders.

According to an example, a system includes a housing, a first valve, and the second valve. The first valve includes a fluid port arranged in the housing, a plunger configured to seal the fluid port of the first valve in a first position and to unseal the fluid port of the first valve in a second position, and at least one SMA actuator configured to exert an actuation force on the plunger of the first valve to displace the plunger of the first valve from its first position towards its second position. The second valve includes a fluid port arranged in the housing, a plunger configured to seal the fluid port of the second valve in a first position and to unseal the fluid port of the second valve in a second position, and at least one SMA actuator configured to exert an actuation force on the plunger of the second valve to displace the plunger of the second valve from its first position towards its second position. The valve system also includes a fluid flow path between the first valve and the second valve. The SMA actuator of the first valve and the SMA actuator of the second valve may enclose an angle of not more than 50° with respect to each other.

According to an example, a seat includes a valve system. The valve system includes a housing, a first valve, and the second valve. The first valve includes a fluid port arranged in the housing, a plunger configured to seal the fluid port of the first valve in a first position and to unseal the fluid port of the first valve in a second position, and at least one SMA actuator configured to exert an actuation force on the plunger of the first valve to displace the plunger of the first valve from its first position towards its second position. The second valve includes a fluid port arranged in the housing, a plunger configured to seal the fluid port of the second valve in a first position and to unseal the fluid port of the second valve in a second position, and at least one SMA actuator configured to exert an actuation force on the plunger of the second valve to displace the plunger of the second valve from its first position towards its second position. The valve system also includes a fluid flow path between the first valve and the second valve. The SMA actuator of the first valve and the SMA actuator of the second valve may enclose an angle of not more than 50° with respect to each other.

For example, the seat may be an automotive seat or an airplane seat. For example, the seat may include one or more fluid bladders. It is possible that the valve is used to switch the fluid flow to the one or more fluid bladders.

According to an example, a valve includes a housing, a fluid port arranged in the housing, and a plunger configured to selectively seal the fluid port. The valve also includes a SMA actuator made of a Nickel-Titanium alloy and configured to actuate the plunger by transitioning between a contracted state and an elongated state. The valve is configured to operate the SMA actuator at stresses of not less than 160 MPa, optionally of not less than 173 MPa, further optionally of not less than 270 MPa.

According to an example, a seat includes a valve. The valve includes a housing, a fluid port arranged in the housing, and a plunger configured to selectively seal the fluid port. The valve also includes a SMA actuator made of a Nickel-Titanium alloy and configured to actuate the plunger by transitioning between a contracted state and an elongated state. The valve is configured to operate the SMA actuator at stresses of not less than 160 MPa, optionally of not less than 173 MPa, further optionally of not less than 270 MPa.

For example, the seat may be an automotive seat or an airplane seat. For example, the seat may include one or more fluid bladders. It is possible that the valve is used to switch the fluid flow to the one or more fluid bladders.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, techniques of switching a fluid flow are described. The fluid may be a gas or a liquid. To switch the fluid flow, a valve is employed. The valve includes a fluid port and a plunger. The plunger (sometimes also referred to as piston) is configured to selectively seal the fluid port. The plunger may include a sealing surface for this purpose. For example, the plunger may fully seal the fluid port in a first position (closed position) and fully unseal the fluid port in a second position (opened position). In other examples, also an intermediate position is conceivable where the plunger partially seals the fluid port, i.e., provides a certain flow resistance to the fluid. An example technique to reliably position the plunger in the intermediate position includes using a pulse-width modulated heating current applied to the SMA actuator using logic to set the duty cycle depending on the desired degree of flow resistance.

To displace the plunger, an actuator is employed. The actuator displaces the plunger between the opened position and the closed position. The plunger moves between the closed position and the opened position along a displacement direction.

The valves described herein may find application in various fields. For example, the valves may be employed in seats, e.g., office chairs or automotive seats. Here, bladders in the seats may be selectively filled with pressurized air. This increases the seating comfort. Massage functionality may be possible.

For example, a control unit may be provided which is configured to control the actuation of the valve. The control unit may be implemented by a microcontroller, a field-programmable array (FPGA), or an application-specific integrated circuit (ASIC).

According to examples, the actuator is implemented by an SMA actuator. For example, the SMA actuator may be implemented by a wire-shaped SMA material or by a belt-shaped SMA material. The SMA actuator may provide a length change depending on its temperature. For example, an SMA actuator can be configured to reversibly change its shape due to thermal activation between an extended state and a contracted state. The extended and contracted states may correspond with the closed and opened positions of the piston, respectively. The SMA actuator may provide such a shape change due to phase transformation between two or more solid-state phases. Typically, the transformation is between a low-temperature phase/martensitic phase to a high-temperature phase/austenitic phase. Typically, the phase transformation is reversible and independent of time. According to various examples, the SMA actuator can employ the so-called extrinsic two-way effect. Here, the SMA actuator can be continuously held under a mechanical bias, e.g., provided by a resilient member. For example, heating the SMA actuator typically results in contraction and, thereby, displacement of the plunger. The contraction is typically related to the phase transformation, e.g., from de-twinned martensitic to austenitic in some SMA materials. A pseudo-plastic deformation may result where the extension of the SMA material is from austenitic to de-twinned martensitic directly, i.e., not via twinned martensitic.

It is possible to activate the SMA actuator by feeding a heating current to the SMA material. Due to the current flow, the SMA material is heated. The change in temperature causes the length change. In other examples, external heating elements arranged adjacent to the SMA actuator could be employed, e.g., separate current-carrying wires, etc.

In the various examples described herein, different materials may be used for the SMA actuator. Examples include a Nickel-Titanium (NiTi) alloy—e.g., binary NiTi alloys—such as the one sold under the tradename 90° FLEXINOL of DYNALLOY, Inc., Irvine, Calif. For example, ternary or quaternary elements may be added to such a NiTi-based SMA actuator, for example including carbon, oxide, copper, chromium, etc. Other examples for SMA actuators include copper-based alloys such as CuZnAl or CuAINi.

According to some examples, a normally-closed valve is provided. Hence, activation of the SMA actuator—due to contraction—exerts a respective actuation force on the plunger to unseal a fluid port and to displace the plunger from its closed position to its opened position. It is possible that the displacement of the plunger, i.e., the contraction of the SMA actuator, is not limited by a stop etc. if the normally-closed valve is used. In particular, the displacement of the plunger may not be limited by the plunger coming into contact with a sealing surface of a fluid port upon contract of the SMA actuator. This may help to avoid an excessive load on the SMA actuator.

The techniques described herein enable the implementation of a linear geometry of the SMA actuator with respect to the displacement direction of the plunger. As such, a coaxial linear motion of the plunger and the longitudinal axis of the SMA actuator can be implemented. For example, the SMA actuator can extend along the displacement direction for at least 50% of its length, optionally for at least 80% of its length, further optionally of at least 90% of its length, further optionally of at least 95% of its length, further optionally of at least 99% of its length, further optionally of 100% of its length. Such a linear geometry enables to highly integrate the valve using compact dimensions for the housing. In particular, bulky lever-type arrangements are avoided. Furthermore, if compared to lever-type arrangements or generally a rotational sealing, a particular tight sealing of a fluid port may be achieved. This may be due to a sealing surface of the plunger engaging tightly and uniformly with a fluid port.

I) Valve Design

FIG. 1illustrates aspects with respect to a valve100employing a SMA wire151to actuate a plunger125. The valve100, according to the example ofFIG. 1, can implement a 2/2 valve functionality.FIG. 1illustrates a one-way valve; here, a single plunger125is actuated. InFIG. 1, the closed position91of the plunger125is illustrated in which the plunger125seals a fluid port121.

FIG. 1illustrates a linear geometry. Here, the SMA wire151extends along a longitudinal axis111A of the housing111for 100% of its length251, albeit generally it would also be possible that the SMA wire151only extends along the axis111for a smaller fraction of its length251. The housing111includes two long side surfaces1111,1112and two short side surfaces1113,1114. The sealable fluid port121is arranged in the short side surface1113. Likewise, the other fluid port122is arranged in the opposing short side surface1114, albeit it could also be arranged in one of the long side surfaces1111,1112. In between the fluid ports121,122, there is defined a fluid flow path116. As is apparent fromFIG. 1, the linear shape of the housing111correlates with the linear arrangement of the SMA wire151.

The SMA wire151has two ends351,352. The end351is coupled with the plunger125. The end352is at a fixed position with respect to the reference frame of the housing111. For this, a connection piece such as a crimp connection or adhesive connection may be employed. Thus, a length change of the SMA wire151results in a displacement of the plunger125away from a fluid port121(not shown inFIG. 1).

In the example ofFIG. 1, the SMA wire151extends along its entire length251between the fluid ports121,122defining the fluid flow path116. In other words, the SMA wire151extends between the opposing sides1113,1114of the housing111in which the fluid ports121,122are arranged. Generally speaking, the SMA wire151may extend along at least 20%, optionally at least 50%, further optionally at least 90% of its entire length251between the fluid ports121,122. This facilitates a compact design of the valve100—in particular if compared to scenarios where the SMA wire151extends away from the fluid flow path116. Also, a tight engagement between a sealing surface of the plunger125and, e.g., an O-ring of the fluid port121can be facilitated.

FIG. 2illustrates aspects with respect to the valve100according to the example ofFIG. 1. However, inFIG. 2, the opened position92of the plunger125is illustrated in which the plunger125does not seal the fluid port121. Thus, a fluid may enter or exit the inner part of the housing111via the fluid port121.

InFIG. 2, a displacement direction259of the plunger125is illustrated. When the SMA wire151contracts, it exerts an actuation force155on the plunger125. The SMA wire151pulls the plunger125along the displacement direction259(horizontally, towards the left inFIG. 2). This actuation force155causes the plunger125to move/displace along the displacement direction259. The respective displacement99of the plunger125from the closed position91to the open position92is illustrated inFIG. 2. This displacement99is parallel to the displacement direction259. For example, to guide the displacement99along the displacement direction259, guide slots, a dovetail guide, or other guide members may be provided (not shown inFIG. 2).

The SMA wire151, in the example ofFIG. 2, extends along the displacement direction259for 100% of its length—hence, a fully linear design is implemented; in other examples, the SMA wire151could extend along the displacement direction259for a smaller fraction of its length251, e.g., for at least 50% of its length251, optionally for at least 90% of its length, further optionally for at least 95% of its length.

Such a fully or partly linear geometry enables to implement the valve100with a small footprint. Also, the actuation force is efficiently transmitted from the SMA wire151to the plunger125. Furthermore, complex lever-type geometry is not required and a tight sealing engagement between the plunger125and the fluid port121can be achieved.

In the various examples described herein, the connection piece between the SMA wire151and the plunger125does not provide a transmission ratio larger than 1:1±10—optionally 1:1±2%, further optionally 1:1±1%—where the transmission ratio is defined by the length change of the SMA wire151with respect to the displacement99of the plunger125. For example, the transmission ratio can be 1:1; i.e., a length change of 2 mm of the SMA wire151results in a displacement of 2 mm of the plunger125. This provides a simple and robust setup. The coupling can be a simple crimped connection, etc. Lever concepts using a pivotably arranged rod or the like which amplify the SMA contraction are not required.

Typically, the absolute length change of the SMA wire151is limited to some value in order to avoid non-elastic deformation and damage. The length change corresponds to strain. For example, typical strain may be limited to 3-7%. In order to nonetheless provide a sufficiently large displacement99of the plunger125, the length251of the SMA wire151can be dimensioned sufficiently large. Then, even a small strain results in a significant displacement99. Example implementations provide a length251of the SMA wire151in the range of 10 millimeters—50 millimeters, optionally in the range of 25 millimeters—35 millimeters. For example, here, a 2% length change of the SMA wire151results in a displacement of approximately 0.6 millimeters.

As illustrated inFIG. 2, the valve100further includes a resilient member161. Example implementations of the resilient member161include a leaf spring and a coil spring or another elastic element such as a rubber element, etc. The resilient member161is configured to exert a bias force161A onto the plunger125. The bias force161A generally urges the plunger125into the closed position91, because in the example ofFIGS. 1 and 2a normally-closed valve100is provided. The bias force161A generally opposes the actuation force155of the SMA wire151. During displacement from the closed position91towards the opened position92, the actuation force155is larger in magnitude than the bias force161A. This causes the plunger125to move. In the opened position92, the bias force161A and the actuation force155may be in equilibrium. Alternatively or additionally, a stop member could be provided physically limiting further displacement of the plunger125beyond the opened position92.

In the example ofFIG. 2, the resilient member161is arranged on the same side of the plunger125as the SMA wire151. Here, the bias force161A may result from a compression of the resilient member161. In other examples, it would also be possible that the resilient member161is arranged in between the plunger125and the fluid port121, i.e., on the opposing side of the plunger125if compared to the SMA wire151. Then, the bias force161A may result from an extension of the resilient member161.

The valve100according to the example ofFIGS. 1 and 2can be modified in other examples. For example, it would be possible to use more than a single SMA wire151.

FIG. 3Aillustrates aspects with respect to a valve100employing two SMA wires151,152to actuate the plunger125. Aside from the use of multiple SMA wires151,152, the valve100according to the example ofFIG. 3Agenerally corresponds to the valve100according to the example ofFIGS. 1 and 2.

The end351of the SMA wire151is coupled with the plunger125. The end353of the SMA wire152is likewise coupled with the plunger125. The end352of the SMA wire151is fixed with respect to the reference frame of the housing111. Likewise, the end354of the SMA wire152is fixed with respect to the reference frame of the housing111.

In other examples, it would be possible to use an even larger number of SMA wires in order to actuate the plunger125. For example, a count of 3 or 4 or 5 SMA wires could be used. Generally, the various SMA wires can be arranged in parallel with respect to each other. The use of multiple SMA wires enables to increase the actuation force155provided by the multiple SMA wires; while avoiding overload with respect to each individual SMA wire. The stress per SMA wire can be reduced. It would also be possible to increase the total force provided by the multiple SMA wires, while the stress on each individual SMA wire remains constant. Such various design options can also be combined.

FIG. 3Billustrates aspects with respect to a valve100employing a single SMA wire151. In the example ofFIG. 3B, the SMA wire151is arranged in a U-shape. In other words, the SMA wire151includes two sections which are arranged anti-parallel with respect to each other (upper and lower part of the SMA wire151inFIG. 3B).

Both ends351,352of the SMA wire151are coupled to the plunger125. In a middle region355of the SMA wire151—arranged in between the end351,352—the SMA wire151is wound about a fixture157-1fixedly arranged with respect to the reference frame of the housing111. The example scenario illustrated inFIG. 3Ballows to provide a significant actuation force155and/or a significant displacement99due to the U-shaped arrangement of the SMA wire151; at the same time, the number of electrical contacts to feed the heating current into the SMA wire151is limited (in particular if compared to the scenario ofFIG. 3Ausing multiple distinct SMA wires). This simplifies the arrangement.

FIG. 3Cillustrates aspects with respect to a valve100employing a single SMA wire151. The example ofFIG. 3Cgenerally corresponds to the example ofFIG. 3B, but employs a somewhat inverted geometry. Here, the fixture157-1is coupled with the plunger125and the ends351,352of the U-shaped SMA wire151are fixed in the reference frame of the housing111. For example, the fixture157-1may be built into the plunger125and may, optionally, be formed integrally with the plunger125.

FIG. 3Dillustrates aspects with respect to a valve100employing two SMA wires151,152to actuate the plunger125. The example ofFIG. 3Dgenerally corresponds to the example ofFIG. 3A. However, the two SMA wires151,152are connected by a segment360at the respective ends opposing the plunger125. For example, the segment360could be implemented by a belt of an elastic material. The segment360may be or may not be electrically conductive. The segment360is wound about a fixture157-1fixed in the reference frame of the housing111.

The segment360may be elastic. In particular, in may be possible that the segment360has an elasticity which is larger than the elasticity of the SMA wires151,152. Thereby, additional tolerances can be provided when assembling the valve100. In particular, offsets in the length251of the SMA wires151,152may be compensated by the segment360which can extend or contract accordingly. Here, it is not required that the segment360includes the SMA material. The material of the segment360may be generally different from the material of the SMA wires151,152. E.g., a polymer or plastic material may be used.

A further effect of the segment360can be to load the SMA wires151,152appropriately. For example, the segment360could be crimped to the SMA wires151,152after being pulled to the correct tension such that the SMA wires151,152are loaded appropriately.

FIG. 4illustrates aspects with respect to the valve100employing a single SMA wire151. However, examples discussed with respect toFIG. 4could also be applied for valves including multiple SMA wires. In the example ofFIG. 4, the SMA wire151encloses an angle with respect to the displacement direction259. For example, the angle enclosed by the SMA wire151and the displacement direction259could be less than 20°, optionally less than 5°, further optionally less than 1°.

In the example ofFIG. 4(as well as in some of the further FIGS.), the longitudinal axis111A of the housing111is aligned with the displacement direction259of the plunger125; hence, the SMA wire151encloses the respective angle also with the longitudinal axis111A. Here, the transmission ratio between the length change of the SMA wire151and the displacement99of the plunger125of less than 1:1. For example, a length change of the SMA wire151amounting to 2 millimeters can result in a displacement99of the plunger125of less than 2 millimeters. This is because the projection of the axis of the SMA wire151onto the displacement direction259defines the displacement99.

FIG. 5illustrates aspects with respect to the valve100employing a single SMA wire151. In the example ofFIG. 5, the valve100includes a screen112which extends along the SMA wire151. The screen112delimits the inner compartment115of the housing111in which the SMA wire151is arranged from the fluid flow path116. The fluid flow path116is defined by openings112-1in the screen112that are arranged adjacent to the fluid port121. In particular, the openings112-1are arranged in between the plunger125and the fluid port121if the plunger125is in the opened position92. Then, the fluid passing through the fluid port121also passes through the openings112-1. While in the example ofFIG. 5a count of two openings112-1to both sides of the fluid port121is illustrated, in other examples, it would also be possible that a larger count of openings is employed.

By using the screen112, it is possible to reduce the wearout of the SMA wire151. In particular, friction between the flowing fluid and the SMA wire151can be reduced, because the fluid can be guided offset and away from the SMA wire151. Furthermore, by using the screen112, it may also possible to avoid localized temperature changes in the surrounding of the SMA wire151. For example, a cold fluid flow in the direct vicinity of the SMA wire151may be avoided; this can increase the durability of the SMA wire151. Also, any hot airflow, e.g., from a pumpline, could adversely affect the transition temperature for actuating the SMA wire151; this is avoided by use of the screen112. To achieve such effects, it is generally not required that the inner compartment115is completely sealed off from the fluid flow path116. Hence, it is generally possible that the inner compartment115is fluidly coupled with the fluid flow path116(illustrated inFIG. 5by the offset125X of the plunger125from the screen112). This simplifies the inner design and reduces the required footprint.

FIG. 6illustrates aspects with respect to the force profile of the resilient member161. In particular,FIG. 6illustrates the bias force161A exerted by the resilient member161on the plunger125—and, via the plunger125, on the SMA wire151,152—as a function of the length251of the SMA wire151,152. As illustrated with respect to the various examples described herein, typically, the length251of the SMA wire151,152directly translates into the displacement99of the plunger125. As such, inFIG. 6, also the closed position91and the opened position92are illustrated (for example, the opened position92corresponds to the contracted state of the SMA wire151having a comparably short length251).

InFIG. 6, a forward force bias (dashed line) and a reverse force bias (full line) are illustrated. Here, the forward force bias corresponds to the following scenario: as the length251of the SMA wire151,152decreases, the bias force161A of the resilient member161increases. For example, if a conventional coil spring is used as the resilient member161, this dependency corresponds to Hook's law where larger deviations from the rest position of the coil spring—due to elongation or compression—result in larger bias forces161A.

According to various examples, it would also be possible that the resilient member161is configured to provide a reversed force profile. Here, the bias force161A is larger (smaller) for larger (smaller) lengths of the SMA wire151,152. Here, the respective linear dependency ofFIG. 6is an illustrative example only. More complex dependencies also including a change of sign of the derivative of the bias force151A as a function of the length251could be implemented. The reversed force profile may result in reduced wearout of the SMA wire151,152.

Generally, various different techniques are conceivable in order to implement the reversed force profile. In one example, the reversed force profile may be provided by an appropriately shaped leaf spring implementing the resilient member161.

FIG. 7illustrates aspects with respect to the resilient member161.FIG. 7is a perspective view of an example valve100(inFIG. 7, the housing111is not illustrated). InFIG. 7, the sealing surface of the plunger125is arranged on the left-hand side. The SMA wire151is U-shaped. A fixture157-1is arranged adjacent to the sealing surface of the plunger125(cf.FIG. 3C).

In the example ofFIG. 7, the resilient member161is implemented by a leaf spring161. Sometimes, the leaf spring may be referred to as semi-elliptical spring. A longitudinal axis10of the leaf spring161is aligned with the SMA wire151and the displacement direction259. When the plunger125displaces from its closed position (inFIG. 7to the left) towards its opened position (inFIG. 7to the right), the leaf spring161is compressed. Here, the larger the compression, the smaller the bias force; thereby, defining the reversed force profile. By means of the leaf spring161, it is possible to provide a reversed force profile at a comparably small package, i.e., using comparable small dimensions of the housing111. For example, outer dimensions of the housing111may be less than 15 mm for the short sides1113,1114, optionally less than 10 mm, further optionally less than 7 mm. The outer dimensions of the housing111may be less than 150 mm for the long sides1111,1112, optionally less than 100 mm, further optionally less than 70 mm.

Compression of the leaf spring161results in a deflection of the leaf spring161. In order to facilitate the deflection of the leaf spring161, the leaf spring161may be made out of a material having a sufficient elasticity, i.e., providing material-induced elasticity. Further, as illustrated in the example ofFIG. 7, the leaf spring161includes a tapered middle portion161B. The tapered middle portion161B may provide shape-induced elasticity. Alternatively or additionally, the tapered middle portion161B may be designed to reduce the spring force of the leaf spring161. The tapered middle portion161B is optional. In other examples, the leaf spring161may be designed without the tapered middle portion161B.

FIG. 8illustrates aspects with respect to the resilient member161.FIG. 8is a side view of the resilient member161implemented by the leaf spring according to the example ofFIG. 7. InFIG. 8, the deflection161C of the leaf spring161towards the SMA wire151is depicted. Such an arrangement allows integrating the leaf spring161into a small footprint of the housing111.

In an alternative scenario, it would also be possible that the deflection161C of the leaf spring161is oriented away from the SM wire151.

FIG. 8Aillustrates aspects with respect to the resilient member161. In the example ofFIG. 8A, the resilient member161is implemented as a leaf spring. As such, the scenario ofFIG. 8Agenerally corresponds to the scenario ofFIG. 7. This helps to achieve a reversed force profile for the SMA wire151,152. It has been found that the particular shape of the leaf spring161according to the scenario ofFIG. 8Ahelps to provide the reversed force profile for the SMA wire151,152; as well as provides for limited wearout of the leaf spring161such that many activation cycles can be endured before damage to the material of the leaf spring161.

In the scenarioFIG. 8A, the leaf spring161again extends along a longitudinal axis161D. This axis can be aligned with the displacement direction259as explained, e.g., in connection withFIG. 7. This helps to reduce the footprint required.

The leaf spring161has a middle portion161B arranged in between the two end parts811. The middle portion161B is widened. Hence, a width of the leaf spring161increases towards the middle part161B, as seen from one of the end parts811.

FIG. 8Bis a cross-sectional view of the leaf spring161of the scenarioFIG. 8A, taken along the line A-A′ ofFIG. 8A. Here, it is apparent that the leaf spring includes a center part805and edge parts801,802forming wings. Specifically, these wings801,802are deflected/tilted if compared to the center part805. The wings801,802are curved away from the plane of the center part805. The wings801,802extend from the center part805which may or may not be of larger thickness (up-down direction ofFIG. 8B) if compared to the wings801,802.

As a general rule, the wings801,802may be bent upwards or downwards if compared to the center part805.

When the leaf spring161is compressed/bent, then there may be a force acting to move the wings801,802into the plane of the center part805. Hence, there may be a tendency to flatten the wings801,802upon compression of the leaf spring161. This helps to provide the reverse force bias.

This configuration including the wings801,802was found to provide a reversed force profile which is helpful to reduce wearout of the SMA wire151,152(not illustrated inFIGS. 8A and 8B).

As a general rule, whileFIG. 8Billustrates a scenario in which the leaf spring161has the widened middle portion161B, in other scenarios it would be possible to provide the wings801,802for a tapered middle portion161B (cf.FIG. 7) or for a leaf spring without width variation along its longitudinal axis161D.

As a further general rule, instead of relying on a pair of wings801,802, it would be possible to include a single wing on either side of the center part805. Hence, the leaf spring161may include one or more wings801,802.

FIG. 8Cis a perspective view of the leaf spring161ofFIG. 8AinFIG. 8B.FIG. 8Cillustrates the end parts811that can be used to fix the leaf spring161at the plunger and the housing.

FIG. 9Aillustrates aspects with respect to a valve100. The valve100according to the example ofFIG. 9Aincludes two plungers125-1,125-2. The plunger125-1selectively seals the fluid port121; while the plunger125-2selectively seals the fluid port122. Thereby, the valve100ofFIG. 9Aimplements a two-way valve functionality. Here, the plunger125-1is actuated by the SMA wire151in a manner comparable to the other examples described herein.

For example, the valve100according to the example ofFIG. 9Amay provide a 3/2 valve functionality. For this, an additional fluid port may be provided (not shown inFIG. 9Afor sake of simplicity). For example, the additional fluid port may be arranged on one of the long side surfaces1111,1112or on one of the short side surfaces1113,1114. The fluid can be exhausted via the additional fluid port.

Additionally, a coupling126is provided between the plunger125-1and the plunger125-2. Thereby, the displacement99-1of the plunger125-1correlates with the corresponding displacement of the plunger125-2. According to the example ofFIG. 9A, the plunger125-1is in its opened position92while the plunger125-2is in its closed position91.

For example, the displacement99-1of the plunger125-1may translate one-to-one into the displacement of the plunger125-2. In would also be possible that the displacement99-1of the plunger125-1does not translate one-to-one into the displacement of the plunger125-2. For example, it would be possible that one of the plungers125-1,125-2reaches a stop—e.g., when coming into contact with the respective fluid port—and the other one of the plungers125-1,125-2then continues to displace.

FIG. 9Billustrates aspects with respect to the valve100according to the example ofFIG. 9A. However, in the example ofFIG. 9B, the plunger125-1is in the closed position91while the plunger125-2is in the opened position92. From a comparison ofFIGS. 9A and 9B, the alternating configuration of the plungers125-1,125-2is apparent. Such an alternating configuration of the plungers125-1,125-2with respect to the corresponding closed and opened positions is achieved by the coupling126.

Next, details of the functioning of the coupling126are explained. The coupling126is configured to at least partially translate the displacement99-1of the plunger125-1into the displacement99-2of the plunger125-2. The displacement99-2is also oriented along the displacement direction259, but is opposing the displacement99-1. In some examples, the coupling126may be a two-way coupling; i.e., the coupling126may be configured to rigidly couple the plungers125-1,125-2and fully transfer any displacement99-1,99-2there between. However, in the example ofFIG. 9B, a one-way coupling126is employed (illustrated by the arrow adjacent to the coupling126inFIG. 9B). Here, only a force directed to urge the plunger125-1into its closed position91—e.g., the bias force161A—is transferred by the coupling126to the plunger125-2. Differently, any force directed to urge the plunger125-1into its opened position92—e.g., the actuation force155of the SMA wire151—is not transferred by the coupling126to the plunger125-2. Such a one-way configuration of the coupling126avoids overload imposed on the SMA wire151. In particular, it is avoided that the SMA wire151has to exert an actuation force155sufficiently large to actuate, both, the plunger125-1and the plunger125-2.

To reliably actuate the plunger125-2between its closed position91and its opened position92, a further resilient member162is provided. The resilient member162is associated with the plunger125-2. The resilient member161may be implemented as a leaf spring; while the resilient member162may be implemented by a coil spring. The resilient member162is configured to exert the bias force162A urging the plunger125-2into its closed position91. In particular, it is possible that the bias force162A is dimensioned smaller than the bias force161A. Then, the following can be achieved: considering a scenario where the plunger125-1is in the opened position92and the plunger125-2is in the closed position91(cf.FIG. 9A). If the heating current to the SMA wire151is cut, the temperature in the SMA wire151decreases and the SMA wire151does not provide the actuation force155anymore. Then, the bias force161A urges the plunger125-1towards its closed position91. Because the bias force161A is dimensioned larger than the bias force162A, the bias force161A is also sufficient to displace the plunger125-2to its opened position92. After a while, the SMA wire151may be heated again to cause contraction. Then, the actuation force155acts on the plunger125-1, but the resulting force—now oriented to urge the plunger into its opened position92—is not transmitted towards the plunger125-2by the one-way coupling126. However, the bias force162A urges the plunger125-2towards its closed position91(cf.FIG. 9B).

FIG. 10illustrates aspects with respect to the coupling126. In particular,FIG. 10illustrates an example implementation of the one-way coupling126according to the example ofFIG. 9B. In the example ofFIG. 10, the plunger125-1includes an extension126-1configured to engage with an interrelated extension126-2of the plunger125-2. Respective engagement surfaces126-3face each other. Such a configuration is facilitated by the coaxial alignment of the displacement directions99-1,99-2of the plungers125-1,125-2. This, in turn, is facilitated by the arrangement of the fluid ports121,122on opposing short side surfaces of the housing111.

If the actuation force155moves the plunger125-1towards its opened position (to the left inFIG. 10) the engagement surfaces126-3disengage. Then, the resilient member162exerts the bias force162A so that the plunger125-2also displaces to the left. Differently, if the bias force161A moves the plunger125-1towards its closed position (to the right inFIG. 10), the engagement surfaces126-3engage. Because the bias force161A is dimensioned to be larger than the bias force162A, the plunger125-2follows and also displaces to the right, i.e., towards its opened position92.

FIG. 11illustrates aspects with respect to the coupling126. In particular,FIG. 11is a perspective view of the one-way coupling126according to the examples ofFIGS. 9A, 9B, andFIG. 10.

InFIG. 11, an extension rod125-5of the plunger125-2is illustrated; here, a coil spring could be mounted to provide the bias force162A.

FIGS. 11A-11Cillustrate aspects with respect to a valve100. The valve100according to these examples includes two plungers125-1,125-2. Specifically,FIGS. 11A-11Cillustrate an example implementation of the scenario according toFIGS. 9A, 9B, and 10.FIGS. 11A-11Cillustrate aspects with respect to the coupling126.

The plunger125-1(extending left-right inFIGS. 11A-11C) is configured to selectively seal the fluid port121(the fluid port121is not illustrated inFIGS. 11A-11C). The plunger125-1is activated by the SMA wire151in a manner comparable to other examples described herein. Upon actuation, the actuation force155displaces the plunger125-1along the displacement direction259. The bias force161A urges the plunger125-1in its closed position91.FIG. 11Aillustrates the closed position91;

FIG. 11Cillustrates the opened position92; inFIG. 11Billustrates an intermediate position of the plunger125-1.

In the scenario ofFIGS. 11A-11C, the coupling126includes a lever701. The lever701includes an engagement surface126-3that engages, in the closed position91of the plunger125-1, with a protrusion125-1R of the plunger125-1. Instead of the protrusion125-1R, other means of engagement of the plunger125-1with the lever701may be relied upon, e.g., indentations, etc.

A compression spring162is provided. The compression spring162is coupled with the plunger125-2via the coupling126, i.e., via the lever701. This helps to reduce the footprint required for the coupling126, the compression spring162, and the plunger125-2.

Instead of a compression spring162, other types of resilient members may be used, e.g., a leaf spring (not illustrated).

The compression spring126is configured to exert a bias force162A on the plunger125-2. The bias force162A urges the plunger125-2into its closed position92. The bias force162A is also transferred, at least in parts, via the engagement surface126-3onto the plunger125-1when the plunger125-1is in the closed position91; the transferred part of the bias force162A opposes the bias force161A.

The bias force161A is larger than the bias force162A. Therefore, the plunger125-1is not released from its closed position91, unless the SMA wire151is actuated to contract. Further, the plunger125-2is not released from its opened position92, unless the SMA wire151is actuated to contract.

The lever701is free to displace the plunger125-2once the plunger125-1is displaced along the displacement direction259by actuation of the SMA wire151. This is illustrated in FIG.11B and in FIG.11C, where the protrusion125-1R disengages with the lever701. This is due to a stop provided to the lever701. Thus, in the contracted state of the SMA wire151—when the plunger125-1is in the opened position92—, the bias force162A is not transferred by the coupling701towards the plunger125-1. This helps to reduce the force exerted on the SMA wire151and the contracted state; thereby a reduced wearout of the SMA wire151may be obtained. For example, a reversed force profile may be supported.

Due to the asymmetric engagement of the protrusion125-1R and the engagement surface126-3of the lever701of the coupling126, the bias force161A is transmitted from the plunger125-1to the plunger125-2; however, the actuation force155is not transmitted (cf.FIG. 10). This limits the load imposed on the SMA wire151; thereby mitigating overstress in the SMA wire151.

As illustrated inFIG. 11A-FIG.11C, the displacement direction259of the plunger125-1is rotated vis-à-vis the displacement direction of the plunger125-2, by approximately 90°. Generally, the displacement direction of the plunger125-2may be rotated with respect to the displacement direction259of the plunger125-1by 90°±45°, optionally 90°±25°. The plunger125-2displaces including translational motion and rotational motion. This is due to the lever701of the coupling126. Such an arrangement provides a reduced footprint of the coupling126and the plunger125-2. This may be particularly helpful where a 3/2-valve functionality is implemented using such an arrangement of the coupling126including the lever701.

FIG. 12illustrates aspects with respect to the valve100. The valve100, according to the example ofFIG. 12, includes three fluid ports121-123. For example, the valve100could implement a 3/2 valve functionality. The plungers125-1,125-2are coupled via the coupling126. The resilient member161is implemented as a leaf spring; while the resilient member162is implemented by a coil spring. In particular, because the bias force162A does not act on the SMA wire151(due to the one-way coupling126), here, no reverse force bias is required; hence, it is not required to use a leaf spring for the resilient member162.

An example application of the 3/2 valve functionality may be with respect to a massage functionality of a vehicle seat using air bladders. Here, it would be possible that the exhaust port123is for the bladder/output, and the fluid port122is for deflate/exhaust of the air.

FIG. 13illustrates aspects with respect to a valve100. The valve100according to the example ofFIG. 13includes two SMA wires151,152running in parallel and arranged within an inner compartment115formed within the housing111by the screen112.

FIG. 14is a detailed view of the valve100of the example ofFIG. 13. In particular,FIG. 14illustrates the ends352,354of the SMA wires151,152arranged remote from the plunger125. The ends352,354are implemented by a crimped connection of the SMA wires151,152to a segment360wound about a fixture157-1. Here, the segment360is non-conductive such that a heating current cannot flow via the segment360. The segment360may have a large elasticity to provide additional tolerances; in particular the elasticity of the segment360may be larger than the elasticity of the SMA wires151,152. In other examples, it would also be possible that the elasticity of the segment360is about the same as the elasticity of the SM wires151,152or even less.

The crimped connection of the SMA wires151,152also implements electrical contacts158,159. These electrical contacts158,159may be associated with different voltages such that the voltage difference drives the heating current. Hence, the heating current is fed to the SMA wires151,152via the electrical contacts implemented by the crimped connection. While in the example ofFIG. 13the electrical contacts158,159are implemented by the crimped connection, in other examples, dedicated electrical contacts remote from the crimped contacts could be provided.

In order to support the heating current to flow between the electrical contacts of the two SMA wires151,152, the SMA wires151,152can be electrically connected at the respective ends close to the plunger125. This is illustrated inFIG. 15.FIG. 15is a detailed view of the valve100of the example ofFIGS. 13 and 14. In particular,FIG. 15illustrates the ends351,353of the SMA wires151,152arranged adjacent to the plunger125. For example, the ends351,353could be implemented by a crimped connection with the plunger125.

FIG. 15illustrates aspects with respect to a limit switch250. The limit switch250selectively provides the electric connection between the ends351,353depending on the displacement99of the plunger125. If the limit switch250is activated—i.e., if the electrical contact is broken or cut—, the heating current is cut. For this, a conductor157is arranged between the ends351,353and rigidly coupled with the plunger125. For example, the plunger125is moved beyond the open position92, the conductor157loses contact with at least one of the ends351,353due to the displacement99; then, the heating current cannot flow between the electrical contacts associated with the SMA wires151,152. This causes a reduction of the temperature of the SMA wires151,152and thereby a reduction of the actuation force155. Due to the bias force161A, there is a tendency for the plunger125to return to its closed position91. By activating the limit switch250directly via the displacement of the plunger125, a simple yet effective and failsafe overload protection mechanism can be implemented.

For example, the conductor157may provide shape-induced and/or material-induced elasticity. Thereby, a spring-loaded limit switch250may be implemented. This may help to reliably actuate the limit switch250.

FIGS. 16 and 17illustrate aspects with respect to the limit switch250. Again, in the example ofFIGS. 16 and 17, the limit switch250is actuated by the displacement99of the plunger125.FIGS. 16 and 17illustrate an example where a single U-shaped SMA wire151is employed. The ends351,352of the SMA wire151are both coupled with the plunger125.

FIG. 16illustrates a state in which the plunger125is in the closed position91. Here, the fluid port121is sealed. Furthermore, the ends351,352are in contact with static electrical contacts158,159. A voltage difference may be present between the electrical contacts158,159. Then, the heating current is fed to the SMA wire151via the electrical contacts158,159.

This causes contraction of the SMA wire151. The plunger125is moved to the opened position92, as illustrated inFIG. 17. The electrical contacts158,159remain stationary within the reference frame of the housing111; then, eventually, the ends351,352lose contact with the electrical contacts158,159such that the heating current is cut. For example, the arrangement of the electrical contacts158,159with respect to the ends351,352can be such that the limit switch250is actuated by displacement of the plunger125beyond the opened position92. This helps to avoid overstress imposed on the SMA wire151.

FIG. 18illustrates an example stress-strain characteristic according to which the various valves100described herein may operate.FIG. 18illustrates the stress imposed on the SMA material as a function of the strain. In particular,FIG. 18illustrates the stress-strain characteristic for different temperatures. Here, different temperatures can correspond to different solid-state phases.FIG. 18illustrates an example stress-strain characteristic of the SMA material formed into a SMA wire having a diameter of 76 μm. The SMA material is a NiTi alloy.

FIG. 18illustrates two reference stress-strain characteristics. A first reference stress-strain characteristic is labeled as “cold” (dashed-dotted line) and corresponds to the stress-strain characteristic observed if the temperature is below a transition temperature such that the entire SMA material adheres a first solid-state phase. For example, typical SMA materials may implement the “cold” stress-strain characteristic in a fully martensitic phase. A second reference stress-strain characteristic is labeled as “hot” (dashed-dotted-dotted line) and corresponds to the stress-strain characteristic observed if the temperature is above the transition temperature such that the entire SMA material adheres to the second solid-state phase different from the first solid-state phase. For example, typical SMA materials may implement the “hot” stress-strain characteristic in a fully austenitic phase. From a comparison of the first and second reference stress-strain characteristics, it is apparent that the SMA material contracts for increasing temperature: the strain reduces. For temperatures close to the transition temperature, a mix between the first and second solid-state phases may be observed in the SMA material (not illustrated inFIG. 18)

FromFIG. 18, it is apparent that there is a tendency that the stress increases for increasing strain. Typically, if the stress exceeds a certain threshold, the deformation of the SMA material is non-reversible and damage occurs. Therefore, according to examples, the operating range600according to which the valve100is operated is tailored so that the stress remains below an appropriate threshold. For example, it has been observed that care should be taken to not situate the operating range600beyond a certain safety margin (dotted line inFIG. 18) with respect to the hot curve. In particular, for large cycle counts there can be a tendency towards damage otherwise.

FromFIG. 18it is, furthermore, apparent that the deformation of the SMA material exhibits a hysteresis. Often, this hysteresis is considered in system design, but not necessarily employed to tailor the actuation of the valve.

FIG. 18illustrates the operating range600of the SMA wire151,152according to example implementations of the valve100. InFIG. 18, the stress-strain states corresponding to the closed position91and the opened position92of the plunger125,125-1are illustrated. For example, a smaller strain corresponds to a shorter length251of the SMA wire151,152. Increasing the strain of the SMA wire151,152corresponds to increasing the length251of the SMA wire151,152—and, thereby, reducing the actuation force155on the plunger125,125-1. For example, the transition from the opened position91to the closed position92can be achieved by heating the SMA wire151,152; and the transition from the closed position92to the opened position91can be achieved by reducing the temperature the SMA wire92.

In the example ofFIG. 18, the stress experienced by the SMA wire151,152is tailored by the geometry of the resilient member161as well as tailored by the arrangement of the resilient member161with respect to the plunger125,125-1and/or the SMA wire151,152. In particular, as illustrated inFIG. 18, the stress remains relatively constant in the range of approximately 270 MPa-310 MPa. Generally, for a single-sided valve, the stress may be in the range of 173 MPa-245 MPa; and for a double-sided valve, the stress may be in the range of 270 MPa-310 MPa. Generally, it would be possible to operate the SMA wire151,152at stresses of not less than 160 MPa, optionally of not less than 173 MPa. At the same time, damage to the SMA wire151,152due to over-stress is avoided.

The flat stress profile may be achieved by tailoring the bias force161A to match the general stress-strain characteristics of the SMA material. The general stress-strain characteristics define that a reduction of the length251of the SMA wire151,152due to the phase transition results in a reduction of the strain (e.g., as can be seen from a comparison of the cold curve with the hot curve). At the same time—due to the forward force bias—the bias force161increases if the length251reduces. Thus, the general reduction of the strain due to heating is approximately compensated by the increase of the bias force161which causes a flat stress dependency on the strain.

By appropriately tailoring the operating range600with respect to the stress, it is possible to obtain higher activation temperatures and/or higher deactivation temperatures for switching the valve100. This may be of particular help in an automotive requirement where generally high temperatures can be observed.

In the example ofFIG. 18, the operating range600covers strains in the range of 3.7-5.4%. Generally, the valve100may be configured to operate the SMA wire151,152it strains in the range of 2%-7%, optionally in the range of 3%-6%, further optionally in the range of 3.5%-5.5%.

For example, the change of the strain covered by the operating range600(1.7% in the example ofFIG. 18) may correlate with the change of the length251of the SMA wire151,152, e.g., in a one-to-one manner.

InFIG. 18, the safety margin is illustrated by the dotted line. The safety margin is offset from the hot curve by approximately 1 percentage points of strain. For example, the valve100may be configured to operate the SMA wire151,152at the operating range600which is offset at least 0.2 percentage points of strain from the hot curve, optionally at least 0.7 percentage points, further optionally at least one percentage point. This avoids damage even in presence of tolerances in high-volume production including variation from part to part. Thereby, fully reversible operation according to the extrinsic two-way effect can be achieved.

FIG. 19illustrates an example stress-strain characteristic of the SMA material formed into a SMA wire having a diameter of 76 μm. The example ofFIG. 19generally corresponds to the example ofFIG. 18. However, in the example ofFIG. 19, a resilient member161providing a reversed force profile is used. For this reason, with decreasing length also the bias force161A decreases (as illustrated by the parallel arrows inFIG. 19). This decreasing bias force161A causes a reduction in the stress for increasing temperatures and decreasing strains. Thereby, the operating range600—while still maintaining the safety margin—has a width of 3.2%-5.4% strain: this is significantly larger than achievable for the forward force bias (cf.FIG. 19). Thus, larger changes of the length251or higher stresses of the SMA wire151,152may be achieved.

III) Valve Systems

Above, various examples have been described with respect to a single valve100. For example, the single valve100could be a one-way valve or a two-way valve. For example, the single valve100could implement 2/2 valve functionality or 3/2 valve functionality.

According to the linear design in which the SMA wire151,152is substantially parallel to the displacement direction259along a significant fraction of its length251or even along its entire length251, it is possible to reduce the footprint of the housing111. Furthermore, a characteristic geometry can be achieved for the housing111: the housing111may be elongated having the long side surfaces1111,1112extending along the SMA wire151,152. One or more fluid ports121-123can be arranged on the short side surfaces1113,1114of the housing111. Then, the SMA wire151,152can be substantially parallel to a longitudinal axis111A of the housing111, e.g., along a significant fraction of its length251or even along its entire length251.

Beyond the inherently small footprint of such a housing111, it is also possible to implement valve systems using a plurality of such valves100. Such valve systems—due to the elongated shape of the housing111—can be implemented with a particularly small footprint, as well.

FIG. 20illustrates aspects with respect to a valve system500. The valve system500includes a first valve100-1and a second valve100-2. For example, the valve system500could implement a 2×2/2 valve functionality.

Each valve100-1,100-2could be implemented according to techniques described herein, i.e., using a linear design of the SMA wire (not shown inFIG. 20) with respect to the displacement direction defined by the displacement of the respective plunger. Each valve100-1,100-2could employ a stress-strain operating range600as discussed above.

For example, the valve100-1includes the fluid port121-1. The valve100-1implements a one-way valve. In some examples, it could also be possible that the valve100-1includes one or more additional fluid ports (not illustrated inFIG. 20). A plunger can be actuated by a SMA wire in order to selectively seal the fluid port121-1. For this, techniques can be implemented as described herein with respect to the valve100.

The valve100-2also includes a fluid port122-1. The valve100-2implements a one-way valve. For this, a plunger can be actuated by a SMA wire in order to selectively seal the fluid port122-1. For this, techniques can be implemented as described herein with respect to the valve100. The valve100-2also includes the fluid port122-2. The fluid port122-2, in the example ofFIG. 20, is unsealed independent of the position of the plunger of the valve100-2.

InFIG. 20, the valve system500includes a fluid flow path116. The fluid flow path116is in between the valves100-1,100-2. The fluid flow path116is arranged in between the valves100-1,100-2. The fluid flow path116connects the various fluid ports121-1,122-1,122-2.

In the example ofFIG. 20, the SMA wires of the valves100-1,100-2are arranged substantially in parallel, i.e., include an angle of approximately 0° with respect to each other. Generally, it would be possible that the SMA wires of the valves of the valve system include an angle of not more than 50° with each other, optionally of not more than 5°, further optionally of not more than 1°.

As will be appreciated fromFIG. 20, due to the elongated shape of each one of the valves100-1,100-2implementing the linear design in which the SMA wires extends substantially in parallel to the displacement direction of the respective plunger, it becomes possible to implement the housing111of the valve system500having comparably small dimensions. The height of the configuration can be less than 15 mm, optionally less than 10 mm, further optionally less than 6 mm.

Furthermore, the design offers the potential of increased modularity. For example, it could be desired to implement another valve functionality instead of the 2×2/2 valve functionality of the valve system500according to the example ofFIG. 20. This can be done by reconfiguring the screens112-5,112-6used in order to define the fluid flow path116. For example, the implementation ofFIG. 20employs two screens112-5,112-6. The screen112-5extends along the SMA wire of the valve100-1(inFIG. 20the SMA wire is not illustrated). The screen112-6extends along the SMA wire of the valve100-2(inFIG. 20the SMA wire is not illustrated). The screen112-5includes an opening112-1adjacent to the fluid port121-1; depending on the respective plunger position, the fluid flow path116is then selectively coupled with the fluid port121-1. Likewise, the screen112-6includes an opening112-1adjacent to the fluid port122-1; depending on the respective plunger position, the fluid flow path116is then selectively coupled with the fluid port122-1. The fluid port122-2is coupled with the fluid flow path116independent of the position of the plunger.

FIG. 21illustrates aspects with respect to the valve system500. Here, the general shape and design of the housing111corresponds to the general shape and design of the housing111of the valve system500according to the example ofFIG. 20. However, the interior design of the valve system500in the example ofFIG. 21is different from the interior design of the valve system500in the example ofFIG. 20. Here, the valve100-2is a two-way valve including two plungers configured to selectively seal the fluid ports122-1,122-2. For implementing the two-way valve100-2, for example, techniques as described herein using a coupling in between the respective plungers could be used. Also, the screen112-6includes an additional opening112-1adjacent to the fluid port122-2. The valve system500of the example ofFIG. 21implements a 3/2 into 2/2 valve functionality.

FIG. 22illustrates aspects with respect to the valve system500. Here, the general shape and design of the housing111corresponds to the general shape and design of the housing111of the valve system500according to the example ofFIG. 20. However, the interior architecture of the valve system500in the example ofFIG. 22is different from the interior architecture of the valve system500in the example ofFIG. 20. Here, the valve100-1, as well as the valve100-2are two-way valves, each including two plungers configured to selectively seal the fluid ports121-1,121-2and122-1,122-2, respectively. The valve system500of the example ofFIG. 22implements a 4/4 valve functionality.

FIG. 23illustrates aspects with respect to a valve module1500. In some examples, it would also be possible to combine a plurality of the valves100and/or a plurality of the valve systems500as discussed herein in order to implement the valve module1500. Here, it is not required that fluid flow paths interconnect the valves of different valve systems.

The valve module1500includes a common fluid port1521. For example, pressurized air could be provided via the fluid port1521to each one of the valves100or valve systems500. The valve module1500also includes data interfaces in order to receive control data which enables the system to individually switch each one of the valves100or valve systems500. A common baseplate1550, e.g., a printed circuit board (PCB), is provided which may provide fixture functionality to the plurality of valves100or valve systems500. It would also be possible that the valves100of the valve system500have incorporated fixtures such as clip features such that the baseplate1550is not the load-bearing connection. Optionally, a microcontroller or another control logic for individually controlling the valves100or valve systems500may be attached to the common baseplate1550.

The valves100and/or valve systems550are arranged adjacent to the common baseplate1550. If the common baseplate1550includes electronic circuitry, the housings111of the valves100and/or valve systems500may provide protection functionality to the electronic circuitry.

For example, while above various examples have been described with respect to SMA wires, similar techniques may also be employed for other kinds and types of SMA actuators such as SMA belts or SMA plates, etc.

For example, while above various examples have been described with respect to valves having a fully opened and a fully closed position of the plunger, also valves employing positions which partially obstruct the fluid flow can be implemented using the techniques described herein.

LIST OF REFERENCE NUMERALS

99displacement of plunger

99-1displacement of plunger

99-2displacement of plunger

111A longitudinal axis of housing

116fluid flow path

125-5extension rod of plunger

126-1extension of plunger

126-2extension of plunger

158electrical contact

159electrical contact

161A bias force

161B leaf spring middle portion

161C leaf spring deflection

161D leaf spring longitudinal axis

162A bias force

251length of SMA wire

351end of SMA wire

352end of SMA wire

353end of SMA wire

354end of SMA wire

355middle region of SMA wire

1111long side surface of housing

1112long side surface of housing

1113short side surface of housing

1114short side surface of housing