Thermoelastic controller with a compact design

Abstract

The invention relates to a thermoelastic controller (1) for providing an, in particular rotational, control movement, comprising: a control element (4) for performing the, in particular rotational, control movement; an antagonistic actuator unit (2) that is coupled to the control element (4) in order to convert a translational movement into the, in particular rotational, control movement; wherein the antagonistic actuator unit (2) comprises: at least two electrically, separately activatable thermoelastic actuator elements (21, 21a, 21b) which are arranged in an extension direction (R) between a first end and a second end and in parallel with one another; a carriage element (24) that is moveably guided in the extension direction (R), wherein the thermoelastic actuator elements (21, 21a, 21b) are each connected to the carriage element (24) at the second end, such that, with a change in geometry upon activating one of the actuator elements (21, 21a, 21b), a traction force is exerted on the carriage element in order to translationally move the carriage element (24); and an electrical connection between the first ends of the actuator elements (21, 21a, 21b) connected to the carriage element (24) such that the actuator elements (21, 21a, 21b) can be applied with a common electrical potential.

Description

[0001] Thermoelastic position sensor in compact design

[0002] Technical area

[0003] The invention relates to thermoelastic position sensors, and in particular to position sensors with thermoelastic actuator elements in a compact design.

[0004] Technical background

[0005] Actuators for converting an electrical control into a mechanical actuating movement are used in a variety of technical devices, such as motor vehicles, household appliances, and the like. Such electromechanical actuators enable elements within a device to be moved and / or force applied to them in a controlled manner.

[0006] Typically, actuators are designed with electromotive actuators, which are usually designed as rotary electric motors. These actuators must be controlled with position control when adjusting a control element in order to specify a specific position of the actuator.

[0007] Another group of position sensors are those with thermoelastic actuator elements as the active element. Thermoelastic actuator elements are usually made of a thermoelastic material (also known as an elastocaloric or mechanocaloric material), e.g., a shape memory alloy, which undergoes a change in shape when the temperature changes, and vice versa. The thermoelastic materials change their microstructure when exposed to temperature, which leads to a change in geometry or the exertion of force. In particular, thermoelastic elements can reduce their dimensions when heated and, for example, exert a tensile force. Thermoelastic elements designed as actuator elements can contract when exposed to heat, thereby causing an actuating movement. When cooled, the thermoelastic element returns to its original shape, particularly when a corresponding restoring force is present.

[0008] However, position sensors with thermoelastic actuator elements have the disadvantage that they are not compact due to the required length of the thermoelastic actuator elements and therefore cannot be used in a variety of possible applications due to their size.

[0009] It is therefore an object of the present invention to provide an improved thermoelastic position sensor which is compact, robust and has a long service life and a high cycle stability.

[0010] Disclosure of the invention

[0011] This object is achieved by the thermoelastic position sensor according to claim 1.

[0012] Further embodiments are specified in the dependent claims.

[0013] According to a first aspect, a thermoelastic actuator for providing a rotary actuating movement is provided, comprising: an actuating element for outputting the rotary actuating movement; an antagonistic actuator unit coupled to the actuating element for converting a translatory movement into the rotary actuating movement;

[0014] - wherein the antagonistic actuator unit comprises: o at least two electrically activatable thermoelastic actuator elements, each extending in a direction of extension between a first end and a second end and arranged parallel to one another; o a slide element which is movably guided in the direction of extension, wherein the thermoelastic actuator elements are each connected to the slide element by the second end, so that in the event of a change in geometry upon activation of one of the actuator elements, a tensile force is exerted on the slide element in order to move the slide element translationally; o an electrical connection between the first ends of the actuator elements connected to the slide element, so that a common electrical potential can be applied to the actuator elements via the slide element.

[0015] The core of the above thermoelastic position sensor is an antagonistic actuator unit in which two thermoelastic actuator elements act as counterparts on a slide element. The slide element is guided so as to be movable in a translational direction in one direction of extension and is thus moved by a first of the actuator elements through contraction in a first direction and by a second of the actuator elements through contraction in a second direction of extension opposite to the first. By alternately electrically controlling the actuator elements, they can be heated alternately, while the other actuator element cools down due to the cooler ambient temperature or is / has been cooled down. Thus, the controlled actuator element of the antagonistic actuator unit can move the slide element optionally in the first or the second opposite direction of extension, whereby the inactive actuator element is stretched.

[0016] Since the first end of the actuator elements is firmly connected to the housing, a force acting upon activation of one of the actuator elements can be absorbed in the housing and transmitted to the slide element.

[0017] The actuator elements are controlled electrically, i.e., by supplying electrical energy to heat the corresponding actuator element. To do this, a corresponding electrical current is passed through the entire length of the actuator element. The heating causes a contraction, which causes the slide element to move translationally.

[0018] To ensure antagonistic control of the actuator elements, they can be electrically connected to one another via a central connection. This means that the actuator elements are electrically connected to one another at one of their ends. The first and second actuator elements can be designed as wire bundle actuator elements. This has the advantage that the larger surface area ensures good heat dissipation to the environment, and a high actuating force can be exerted by such an actuator element.

[0019] Preferably, the slide element can be accommodated essentially between the actuator elements. The actuator elements are thus arranged essentially parallel to one another with their extension directions to achieve a compact design. Alternatively, the actuator elements and the slide element can also be arranged side by side.

[0020] According to one embodiment, the slide element and / or the housing may have through-openings in the form of slots, holes or a lattice structure to enable heat from the actuator elements to be dissipated by convection or an introduced air flow.

[0021] According to one embodiment, an electrically conductive connecting conductor can be arranged in or on the slide element in order to electrically connect the second ends of the thermoelastic actuator elements connected to the slide element to one another.

[0022] The slide element is electrically conductive or has a connecting conductor provided on or in the slide element. The electrically conductive connection electrically connects the contact points of the two actuator elements on the slide element, so that the first and second actuator elements can be supplied with a common potential via the slide element as a central connection.

[0023] A contacting device with a spring contact or a sliding contact can be provided to electrically contact the movable connecting conductor. The spring contact and the sliding contact have the advantage that a wire connection, which is prone to failure due to repeated movement stress, can be omitted. Selective energization of one of the actuator elements can be ensured by a connecting device to the slide element, with which a first terminal of the actuator elements can be connected to a predetermined first voltage potential. The other second electrical terminal of the actuator elements can then be controlled by selectively connecting it to a corresponding further voltage potential in order to achieve a current flow and a resulting contraction.

[0024] The actuator elements are energized alternately. Typically, only one of the two actuator elements is energized at a time, causing it to contract and move the slide element. The other actuator element is stretched by the resulting movement of the slide element. The contraction of the energized actuator element is thus transferred to the non-activated actuator element via the movable slide element.

[0025] The first and / or second ends of the actuator elements can have retaining elements with through-openings for receiving a respective fixing element. In particular, the fixing elements can be electrically conductive in order to supply current to the actuator elements via the received retaining elements.

[0026] The translational movement of the slide element can be transmitted via a gear to an actuating element that is designed for either a translational or a rotational movement.

[0027] Furthermore, the actuating element can be coupled to a braking device in order to hold the actuating element against a predetermined constant or variable holding torque.

[0028] Brief description of the drawings

[0029] Embodiments are explained in more detail below with reference to the accompanying drawings. Figure 1 shows a perspective view of the thermoelastic position sensor with an open housing;

[0030] Figure 2 is a plan view of the thermoelastic actuator of Figure 1;

[0031] Figure 3 is a sectional view through the thermoelastic actuator of Figure 1 along section line BB;

[0032] Figure 4 is a perspective view of the thermoelastic position sensor with closed housing;

[0033] Figure 5 is a sectional view through the thermoelastic actuator of Figure 1 along section line AA;

[0034] Figure 6 is an exploded view of the thermoelastic actuator of Figure 1; and

[0035] Figure ? a view of the underside of the circuit board of the thermoelastic position sensor of Figure 1.

[0036] Description of embodiments

[0037] Figures 1 to 7 show various views of an exemplary thermoelastic position sensor 1 with an antagonistic actuator unit 2, a gear 3, and a movable actuating element 4, at which a mechanical movement, a force, or a moment can be decoupled from the position sensor 1. The thermoelastic position sensor 1 is enclosed in a housing 5, in which the antagonistic actuator unit 2, the gear 3, the actuating element 4, and a printed circuit board 6 are provided to ensure electronic control and electrical contacting of the actuator unit 2.

[0038] The antagonistic actuator unit 2 has two actuator elements 21, which are designed as thermoelastic actuator elements 21. The thermoelastic actuator elements 21 correspond to conductive actuator elements 21 made of a conductive thermoelastic material, which is preferably formed with or from a shape memory alloy.

[0039] The actuator elements 21 can be designed as wire bundle actuator elements, each comprising a plurality of actuator wires 23 running parallel to one another between two holding elements 22. The holding elements 22 at the ends of the actuator elements 21 serve to enable force extraction from the elongated actuator elements 21. The holding elements 22 fix the actuator wires 23 in place so that they do not come loose even when subjected to force.

[0040] As can be seen from the figures, the actuator unit 21 is formed with a first actuator element 21a and a second actuator element 21b, which extend substantially parallel to one another in an extension direction R and between which a slide element 24 is arranged in a sandwich-like manner. The slide element 24 can be held in the housing 5 via suitable guide devices 51, so that the slide element 24 can preferably only move in a translational movement substantially in the extension direction R of the extension of the actuator elements 21a, 21b.

[0041] The actuator elements 21a, 21b have a length that allows for a significant change in length in order to decouple a force for adjusting the actuator 1. For example, the actuator elements 21a, 21b can have a length between 5 cm and 25 cm.

[0042] The slide element 24 may have through-openings 241, in particular in the form of slots, holes or a framework structure, in order to enable heat from the actuator elements 21a, 21b to be dissipated by convection.

[0043] Furthermore, a first of the holding elements 22a of the first actuator element 21, 21a is fixed in the housing 5 via a fixing element 25, which in the illustrated embodiment can be designed as a first holding pin 25a that can be inserted into the housing 5, so that a force acting in the direction of extension R can be absorbed by the housing 5. Similarly, a first of the holding elements 22a of the second actuator element 21, 21b is fixed in the housing 5 via a fixing element 25, which in the illustrated embodiment can be designed as a fourth holding pin 25d that can be inserted into the housing 5, so that a force acting in the direction of extension R can be absorbed in the housing 5. Instead of the first and fourth holding pins 25a, 25d, fixing screws or similar fixing devices can also be used.

[0044] A second of the holding elements 22b of the first actuator element 21a, which is opposite the first holding element 21a, is connected to the particularly elongated slide element 24, which is movably guided in the direction of extension R, so that the first actuator element 21a extends at least partially parallel to the slide element 24. A second of the holding elements 22b of the second actuator element 21b, which is opposite the first holding element 21b, is connected to the particularly elongated slide element 24, which is movably guided in the direction of extension R, so that the second actuator element 21b extends at least partially parallel to the slide element 24. For reasons of compactness, the slide element

[0045] 24 are completely covered by the respective actuator element 21, 21a, 21b in the direction of extension R. For this purpose, the second holding element 22b of each of the actuator elements 21a, 21b can be coupled to the slide element 24 via a corresponding fixing element 25 at an end of the respective actuator element 21a, 21b opposite the first holding element 22a. The corresponding second and third holding pins 25b, 25c, used as an example for the fixing element 25, and the second holding elements 22b attached thereto are each connected to the slide element 24 and are not stationary with respect to the housing 5. The second and third holding pins 25b, 25c and the second holding elements 22b attached thereto move together with the slide element 24 and relative to the housing 5.

[0046] The holding elements 22, 22a, 22b preferably have a receiving opening through which the holding pins 25a, 25b, 25c, 25d protrude in the assembled state, thus securing the holding elements 22, 22a, 22b. Such a connection has the advantage that it is detachable, and thus the actuator elements 21a, 21b can be easily replaced if necessary by removing them from the holding pins 25 and replacing them. If necessary, the actuator elements 21 can be secured with snap rings or other securing devices before being detached from the fixing elements.

[0047] 25. In particular, the first holding element 22a of the first actuator element 21a is connected to the housing 5 via a first holding pin 25a, the second holding element 22a of the first actuator element 21a is connected to the slide element 24 via a second holding pin 25b, the first holding element 22a of the second actuator element 21b is connected to the slide element 24 via a third holding pin 25c, and the second holding element 22b of the second actuator element 21b is connected to the housing 5 via a fourth holding pin 25d. The second and third holding pins 25b, 25c are received in the slide element 24, preferably inserted therein.

[0048] The actuator elements 21, 21b are activated by energization, i.e., via the electrically conductive fixing elements 25a-25d, which are connected to the actuator elements 21a, 21b via the corresponding holding elements 22, 22a, 22b. To activate the actuator elements 21, 21b, a voltage is applied to them, which leads to a current flow and to electrical power being converted in the respective actuator element 21, 21b. The power is dimensioned such that the respective actuator element 21a, 21b is heated, which, due to the thermoelastic material, leads to a contraction of the respective actuator element 21, 21b.

[0049] Electronic circuits for implementing functions for controlling and communicating with external devices can be provided on the circuit board 6. For example, a communication interface for communication via a bus system, such as Ethernet, CAN, LIN, and the like, can be implemented, allowing actuation of the actuating element 4 to be executed based on corresponding received commands. Furthermore, position information regarding the position of the actuating element or other moving components can be communicated externally to the actuator 1 via the communication interface. The functions can also include diagnostic and / or monitoring functions.

[0050] The actuator elements 21a, 21b can be alternately controlled via appropriate wiring or electronics on the circuit board 6. For this purpose, the first holding element 22a of the first actuator element 21a is electrically contacted via the first holding pin 25a, and the first holding element 22a of the second actuator element is electrically contacted via the fourth holding pin 25d, and is electrically firmly connected to the circuit board 6. For this purpose, the first and fourth holding pins 25a, 25d are received in corresponding through-openings 61 of the circuit board 6 and can be applied with an electrical voltage potential there by suitable electrical contact.

[0051] The fixation of the fixing elements 25 in the housing 5 or the circuit board 6 and in the slide element 24 ensures that the actuator elements 21, the fixing elements 25, and the holding elements 22 are not subjected to transverse forces or relative movements, apart from forces acting in the direction of extension, thereby reducing material fatigue in these components. In particular, the electrical contact of the first and fourth holding pins 25a, 25d is thus not subjected to any stress due to movement.

[0052] The first and second actuator elements 21a, 21b are electrically connected to one another. For this purpose, the second holding element 22b of the first actuator element 21a is electrically connected to the second holding element 22b of the second actuator element 21b by the slide element 24. For this purpose, the slide element 24 can be completely electrically conductive or can be designed with an electrically applied or embedded connecting conductor 27. The connecting conductor 27 ensures the electrical connection between the second holding pin 25b and the third holding pin 25c. For example, as shown in the cross-sectional view of Figure 3, the slide element 24 can be provided as an injection-molded part with an electrically conductive connecting conductor 27 embedded by overmolding, so that the connecting conductor is embedded as a core in the slide element 24.

[0053] The electrical connecting conductor 27 in the slide element 24 can be connected to an electrical voltage potential via the circuit board 6, so that alternate control of the actuator elements 21a, 21b is possible by selectively energizing the first or second actuator element 21a, 21b. A contacting element 62 for electrically contacting the connecting conductor 27 can be designed as a spring contact between the circuit board 6 and the slide element 24, which is pressed against an electrical contacting surface 28 of the slide element 24. The electrical contacting surface 28 is electrically connected to the connecting conductor 27 inside the slide element 24. The contacting element 62 is attached to the circuit board 6 and is applied there with a fixed voltage potential.The contacting element 62 can alternatively be designed as a sliding contact with a sliding bridge curved toward the slide element 24, in particular as a spring-elastic, electrically conductive bracket. The force with which the contacting element 62 acts on the contact surface 28 is selected such that displacement of the slide element 24 is not impeded, but sufficiently reliable electrical contact is nevertheless enabled.

[0054] The design of the contacting element 62 as a spring contact makes it possible to avoid wire contact with the slide element 24. Wire contact has the disadvantage that, due to the cyclical movement of the slide element 24, a continuous mechanical movement load acts on such a wire contact, which can lead to a breakage of the connecting wire and thus to a reduced cycle stability of the position sensor.

[0055] The slide element 24 is provided with a rack section 29, which is coupled to the actuating element 4 via the gear 3. The gear 3 enables the translational movement of the slide element 24 to be converted into a rotational movement of the actuating element 4. The gear 3 has a first gear element 31 as a pivoting lever, which has a toothed section 32 for engaging the rack section 29 and a toothed section 33 provided on a protruding end of the pivoting lever, which engages a pinion 41 of the actuating element 4. When the slide element 24 moves, the first gear element 31 pivots, and the actuating element 4 rotates.

[0056] The actuating element 4 can be provided with a braking device 42 designed to hold the actuating element 4 in its last approached position with a predetermined holding torque when the active control of the actuator elements 21 is no longer active. For this purpose, the braking device 42 can be implemented, for example, with a braking element 44 that bears against a circular segment-shaped outer surface 43 in order to hold the actuating element 4 with a holding torque through static friction against an externally acting torque. The braking device 42 can be designed to provide the same or different holding torque for different directions of rotation. The outer surface 43 can be designed with micro-toothing that engages with a corresponding micro-toothing on the braking element 44. The holding torque is achieved by a locking of the micro-toothing, the engagement of which is overcome when a maximum holding torque is exceeded.By means of asymmetric tooth angles on the outer surface 43, different holding torques can be realized in different directions of rotation of the actuating element 4.

[0057] Alternatively or additionally, a corresponding braking device can also be arranged on the carriage element 24 and / or on the first gear element 31.

[0058] The circuit board 6 can be arranged laterally offset from the thermoelastic actuator unit 2 in the housing 5. The circuit board 6 can be configured to accommodate electrical components in a desired configuration. The circuit board 6 can be contacted via a connector 63, so that the electrical power for energizing the actuator elements 21 can also be supplied via the connector 63. The connector 63 is accessible via an opening 54 in the housing 5.

[0059] Furthermore, the housing 5 can be provided with ventilation slots 52 to ensure heat dissipation from at least one of the actuator elements 21. The ventilation slots 52 are located directly opposite the respective actuator element 21 to ensure air circulation so that the heat generated by activating the actuator elements 21 can be quickly dissipated into the environment of the position sensor 1.

[0060] The actuating element 4 is rotatably mounted in the housing 5 and protrudes axially through the circuit board 6. To determine the position (angular position) of the actuating element 4, it can be coupled to a potentiometer 65 or another position sensor in order to detect the current rotational position of the actuating element 4. Alternatively, the position of the actuating element 4 can also be detected by the current lengths of the thermoelastic actuator elements 21a, 21b. For this purpose, a resistance measurement of the actuator elements 21a, 21b can be performed. The position of the actuating element 4 can be determined from the dependence of the ohmic resistance on the current length of the actuator elements 21a, 21b. In a further embodiment, the position of the actuating element 4 can be derived from a position of the slide element 24. The position of the slide element 24 can be detected by sensors in a suitable manner.

Claims

Claims 1. Thermoelastic actuator (1) for providing a rotary actuation movement, in particular, comprising: an actuating element (4) for outputting the rotary actuation movement, in particular; an antagonistic actuator unit (2) coupled to the actuating element (4) to convert a translational movement into the rotary actuation movement; - wherein the antagonistic actuator unit (2) comprises: o at least two electrically separately activatable thermoelastic actuator elements (21, 21a, 21b) which extend in a direction of extension (R) between a first end and a second end and are arranged parallel to each other; o a slide element (24) which is movably guided in the direction of extension (R), wherein the thermoelastic actuator elements (21, 21a, 21b) are each connected at their second end to the slide element (24) such that, upon activation of one of the actuator elements (21, 21a, 21b) and a change in geometry, a tensile force is exerted on the slide element (24) to move the slide element (24) translationally; o an electrical connection between the first ends of the actuator elements (21, 21a, 21b) connected to the slide element (24), so that the actuator elements (21, 21a, 21b) can be subjected to a common electrical potential.

2. Thermoelastic actuator (1) according to claim 1, wherein the slide element (24) is wholly or at least partially accommodated between the actuator elements (21 , 21a, 21b). A thermoelastic actuator (1) according to claim 1 or 2, wherein the slide element (24) has through-openings, in particular in the form of slots, holes, or a truss structure, to allow heat dissipation from the actuator elements (21, 21a, 21b) by convection. A thermoelastic actuator (1) according to any one of claims 1 to 3, wherein an electrically conductive connecting conductor (27) is arranged in or on the slide element (24) to electrically connect the second ends of the thermoelastic actuator elements (21, 21a, 21b) connected to the slide element (24). A thermoelastic actuator (1) according to claim 4, wherein a contacting device (62) is provided with a spring contact or a sliding contact to electrically contact the connecting conductor (27), in particular via a circuit board (6) arranged laterally to the slide element (24).Thermoelastic actuator (1) according to any one of claims 1 to 5, wherein the actuator elements (21, 21a, 21b) are designed as wire bundle actuator elements. Thermoelastic actuator (1) according to any one of claims 1 to 6, wherein the first end of the actuator elements (21, 21a, 21b) is fixedly connected to a housing of the actuator, such that a force acting upon activation of one of the actuator elements (21, 21a, 21b) is absorbed in the housing and transmitted to the slide element (24). Thermoelastic actuator (1) according to any one of claims 1 to 7, wherein the first and / or second ends of the actuator elements (21, 21a, 21b) Retaining elements with through-openings to accommodate a respective fixing element (25, 25a, 25b, 25c, 25d). Thermoelastic actuator according to claim 8, wherein the fixing elements (25, 25a, 25b, 25c, 25d) are electrically conductive to energize the actuator elements (21, 21a, 21b) via the retaining elements. Thermoelastic actuator according to any one of claims 1 to 9, wherein the actuating element (4) is coupled to a braking device (42) to hold the actuating element (4) with a holding torque against an externally applied torque, wherein, in particular, the holding torque is the same or different for different directions of rotation of the actuating element (4).A thermoelastic actuator according to any one of claims 1 to 10, comprising a housing (5), wherein at least one of the actuator elements (21, 21a, 21b) extends directly along a housing wall of the housing (5), and wherein one or more ventilation slots (52) are provided in a region of the housing wall opposite the at least one actuator element (21, 21a, 21b). A thermoelastic actuator according to any one of claims 1 to 11, wherein the slide element (24) is provided with through-openings (241) to facilitate heat dissipation from the actuator element (21a, 21b), particularly by convection.

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