Compensating for incomplete reversal in mechanisms incorporating shape memory alloy wire
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
F01B-029/10
F02G-001/04
F01P-007/10
F03G-007/06
출원번호
US-0600337
(2012-08-31)
등록번호
US-9021801
(2015-05-05)
발명자
/ 주소
Gao, Xiujie
McKnight, Geoffrey P.
Herrera, Guillermo A.
Churchill, Christopher B
Johnson, Nancy L.
Browne, Alan L.
Sarosi, Peter Maxwell
Alexander, Paul W.
출원인 / 주소
GM Global Technology Operations LLC
대리인 / 주소
Reising Ethington P.C.
인용정보
피인용 횟수 :
4인용 특허 :
4
초록▼
Shape memory alloy (SMA) actuating elements are commonly simpler and of lower mass than alternative actuator designs and may find particular application in the transportation industry. Such SMA-powered devices are usually reliable and long-lived but the phase transformations which occur in the SMA a
Shape memory alloy (SMA) actuating elements are commonly simpler and of lower mass than alternative actuator designs and may find particular application in the transportation industry. Such SMA-powered devices are usually reliable and long-lived but the phase transformations which occur in the SMA alloy and are responsible for its utility are not totally reversible. This irreversibility, a consequence of irrecoverable strain, may progressively degrade the long-term actuator performance as the irrecoverable strain accumulates over many operating cycles. Methods and devices for compensating for these effects and extending the useful cycle life of SMA actuators are described.
대표청구항▼
1. An actuator for operating a device with one or more moveable components, the actuator comprising a linear Shape Memory Alloy (SMA) element with an axis and two ends, and a return spring with two ends, the SMA element having an active length and being initially taut when in a lower temperature pha
1. An actuator for operating a device with one or more moveable components, the actuator comprising a linear Shape Memory Alloy (SMA) element with an axis and two ends, and a return spring with two ends, the SMA element having an active length and being initially taut when in a lower temperature phase; a first end of each of the SMA element and the return spring each being attachable to the moveable component of the device, or to an attachment adapted to engage the moveable component of the device, the second end of the return spring being attachable to a fixed support, the SMA element, return spring and moveable component or attachment being arranged so that the return spring tensions the SMA wire;the SMA element being adapted to shorten, and thereby extend the return spring to displace the moveable component, or the attachment, from an initial configuration and operate the device when the SMA element is heated and adopts a higher temperature phase, the SMA element being adapted to be deformed and lengthened by the return spring when the SMA element is cooled and adopts the lower temperature phase;the actuator also comprising a stop, the stop limiting the lengthening of the SMA element by the return spring to enforce a predetermined lengthening of the SMA element when the element is in its lower temperature phase, the predetermined lengthening of the SMA element being selected to return the moveable component, or the attachment, to its initial configuration and ready the device for further operation, the SMA element progressively lengthening under repeated use so that the SMA element develops slack and loses its initial tautness when in its lower temperature phase;the actuator further comprising a tensioner for minimizing developed slack in the SMA element and maintaining the tautness of the SMA element, the tensioner having two inter-engaging parts, a moveable part attached to the second end of the SMA element, the moveable part engaging a tensioning spring which engages a stationary part of the tensioner secured to a support, the stationary part being spaced apart from the moveable part along the axis of the SMA element, the tensioning spring and the tensioner parts being arranged so that the tensioning spring acts to displace the moveable part, and the second end of the SMA element, along the SMA element axis and extend the SMA element to remove slack in the SMA element and restore the SMA element to its initially-taut configuration when the SMA element is in its low temperature phase; and,the stationary and moveable parts of the tensioner each having mutually-engageable features adapted to secure the moveable part to the stationary part and oppose any relative motion of the stationary and moveable parts of the tensioner in a direction which might produce slack in the SMA element while enabling repeated relative motion of the moveable and stationary parts in a direction for removing slack in the SMA element. 2. The SMA actuator of claim 1 in which the tensioning spring is one of a coil spring, a leaf spring, a polymer compression spring, a clock spring and a gas spring. 3. The SMA actuator of claim 1 in which the stationary part of the tensioner comprises a first toothed rack and the moveable part comprises a second toothed rack of complementary geometry. 4. The SMA actuator of claim 1 in which the stationary part of the tensioner comprises a toothed rack, and the end moveable part comprises at least a pivoting tooth. 5. The SMA actuator of claim 1 in which the first stationary part of the tensioner comprises a shaft with an axis and the second moveable part comprises a hold open washer comprising a washer section with an opening, the opening being sized to slide freely on the shaft when the washer is generally perpendicular to the shaft axis, and to engage the shaft when the washer is inclined to the shaft axis, the washer further comprising an outwardly-angled section for attachment to the SMA element. 6. The SMA actuator of claim 1 in which the first stationary part of the tensioner comprises an elongated threaded member with an axis and having a first continuous helical thread disposed about its axis, the stationary part being free to rotate about its axis but restrained against motion along its axis by engagement with a support, the moveable part having a second helical thread, complementary to the first thread, the stationary and moveable parts being threadably engaged, the stationary part being torqued by a pre-tensioned torsional spring. 7. The SMA actuator of claim 1 in which the stationary part of the tensioner comprises an elongated threaded member with an axis and having a first continuous helical thread disposed about its axis, the stationary part being free to rotate about its axis but restrained against motion along its axis by engagement with a support, the moveable part having a second helical thread, complementary to the first thread, the stationary and moveable parts being threadably engaged, the moveable part being torqued by a pre-tensioned torsional spring. 8. An SMA-actuated device incorporating one or more moveable components and an SMA actuator, the actuator comprising a linear Shape Memory Alloy (SMA) element with an axis and an active length, and a return spring, each of the SMA element and the return spring having two ends; one end of each of the SMA element and the return spring being attached to the moveable component of the device, or to an attachment adapted for engagement with the moveable component of the device, the SMA element, return spring, and moveable component, or attachment, being arranged so that the SMA wire is tensioned by the return spring;the SMA element being adapted to shorten and thereby extend the return spring to displace the moveable component, or the attachment, from an initial configuration and operate the device when the SMA element is in a higher temperature phase, the SMA element being adapted to be deformed and stretched by a predetermined return distance by the return spring when in a lower temperature phase to return the moveable component, or the attachment, to its initial configuration and ready the device for further operation;the actuator also comprising a stop, the stop enforcing the predetermined return distance to develop a predetermined extension in the SMA element when the element is in its lower temperature phase, the active length of the SMA element, initially taut when in its lower temperature phase, progressively extending and developing slack under repeated use;the actuator further comprising a tensioner for maintaining the tautness of the active length of the SMA element as the SMA element develops slack under repeated use, the tensioner having two parts, a stationary part attached to a fixed support, and a moveable part, spaced apart from the stationary part along the SMA element axis and attached to the second end of the SMA element, the stationary and moveable parts of the tensioner each being spring-loaded by a tensioning spring, the tensioning spring and the tensioner parts being arranged so that the tensioning spring acts to displace the moveable part by a distance sufficient to remove the slack in the SMA element so as to repeatedly restore the SMA element to its initially-taut configuration during extended use; and,the stationary and moveable parts of the tensioner having mutually-engageable features adapted to maintain the SMA element in its tautened configuration during subsequent operation of the device. 9. A device incorporating the SMA actuator of claim 8 in which the tensioning spring is one of a coil spring, a leaf spring, a polymer compression spring and a gas spring. 10. The device recited in claim 8 in which the SMA actuator is cycled between a first position and a second position. 11. The device recited in claim 10 in which the device is one of the group consisting of a retractable air dam, a latch and a clutch. 12. The device recited in claim 8 in which the SMA actuator may adopt any of a range of positions between a first position and a second position. 13. The device recited in claim 12 in which the device is one of the group consisting of an adjustable louver array, a fluid flow valve, a rearview mirror, a side mirror and a sun visor. 14. A tensioner for eliminating slack in an active length of linear shape memory alloy (SMA) element used in an SMA actuator, the active length of the SMA element having two ends, the active length of the SMA element being initially taut when in a lower temperature phase, but progressively lengthening, and thereby developing slack and loss of tautness in the active length, when in the lower temperature phase during continuing use, the tensioner comprising: a moveable part engaging the SMA element, a fixed part, and a tensioning spring engaging the moveable part;the fixed part being secured to a fixed support and engaging either, the SMA element or the moveable part, to establish an end of the active length;the moveable part, under the urging of the tensioning spring, being moveable in a direction to take up any slack in the SMA element;the moveable part and the fixed part cooperating to eliminate slack in the SMA element when in its lower temperature phase while maintaining the locations of the ends of the active length of the SMA element during operation of the actuator as the SMA element is first heated to adopt a higher temperature phase and then cooled to again adopt the lower temperature phase. 15. The tensioner of claim 14 in which the fixed part comprises a releasable clamp for engaging and securing the taut SMA element. 16. The tensioner of claim 14 in which the moveable part comprises a pulley with a ratchet and a pawl, the pulley supporting and securing the SMA element, the pulley being secured to a support. 17. The tensioner of claim 14 in which one of the parts is a toothed rack. 18. The SMA actuator of claim 14 in which the first part of the tensioner comprises a shaft with an axis and the second part comprises a hold open washer comprising a washer section with an opening, the opening being sized to slide freely on the shaft when the washer is generally perpendicular to the shaft axis, and to engage the shaft when the washer is inclined to the shaft axis, the washer further comprising an outwardly-angled section for attachment to the SMA element. 19. The tensioner of claim 14 in which the moveable and fixed parts mutually engage. 20. The tensioner of claim 19 comprising an elongated, threaded member moveable part with an axis and having a first continuous helical thread disposed about its axis, the moveable part being free to rotate about its axis but restrained against motion along its axis by threadable engagement with a fixed part having a second helical thread, complementary to the first thread, the second part being torqued by a pre-tensioned torsional spring.
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이 특허에 인용된 특허 (4)
Browne, Alan L.; Johnson, Nancy L.; Aase, Jan H.; Brown, James H., Active material actuated louver system.
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