Accelerating cooling in active material actuators using heat sinks

• US 8,567,188 B2
• Filed: 06/02/2010
• Issued: 10/29/2013
• Est. Priority Date: 10/13/2008
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Mankame, Nilesh D., Usoro, Patrick B., Browne, Alan L., Skurkis, Richard J., Johnson, Nancy L., Gao, Xiujie
• Primary Examiner(s): Bomberg, Kenneth
• Assistant Examiner(s): JETTON, CHRISTOPHER M
• Application Number:
  US12/792,120
• Publication Number:
  US 20100236236A1
• Time in Patent Office: 1,245 Days
• Field of Search: 60527-529
• US Class Current: 60/528
• CPC Class Codes: F03G 7/065 using a shape memory element

Abstract

An actuator includes a thermally activated active material element, such as at least one shape memory alloy wire, and a heat sink configured to operatively engage the element and accelerate cooling after activation, so as to improve bandwidth.

Claims

1. A thermally activated active material actuator adapted for increasing bandwidth, said actuator comprising:

an active material actuator element operable to undergo a reversible change in fundamental property, when exposed to or occluded from a thermal activation signal, so as to heat and activate the element or enable the element to be cooled and deactivated, respectively,

wherein the element presents an ambient rate of cooling when occluded from the signal after being activated, and a first cooling period based upon the ambient rate; and

a heat sink including at least one flexible bowed structure, the heat sink presenting a rate of thermal conductivity greater than the ambient rate, and autonomously engaging the element when the element is activated, so as to present a second cooling period shorter than the first period;

wherein the change causes the sink to autonomously engage or increase engagement with the actuator element and causes the structure to further bow towards and engage the actuator element, and the sink defines an exposed surface area.

2. The actuator as claimed in claim 1, further comprising at least one shape memory alloy wire included with the actuator element.

3. The actuator as claimed in claim 1, further comprising a cooling pad attached to the structure and configured to engage the element as a result of the change, and the pad increases the exposed surface area.

4. A thermally activated active material actuator adapted for increasing bandwidth, said actuator comprising:

an active material actuator element operable to undergo a reversible change in fundamental property, when exposed to or occluded from a thermal activation signal, so as to heat and activate the element or enable the element to be cooled and deactivated, respectively,

wherein the element presents an ambient rate of cooling when occluded from the signal after being activated, and a first cooling period based upon the ambient rate;

a heat sink presenting a rate of thermal conductivity greater than the ambient rate, and autonomously engaging the element when the element is activated, so as to present a second cooling period shorter than the first period; and

a separate drive element communicatively coupled and dedicated to the sink, and configured to cause the sink to autonomously engage the actuator element.

5. The actuator as claimed in claim 4, further comprising an active material auxiliary element included with the drive element operable to undergo a second reversible change in fundamental property when exposed to or occluded from an activation signal, so as to be activated or deactivated respectively.

6. The actuator as claimed in claim 5, wherein the auxiliary element is thermally activated, and the sink is configured to concurrently engage the actuator and auxiliary elements, so as to accelerate heat transfer from both.

7. The actuator as claimed in claim 5, wherein the auxiliary element is thermally activated, and the actuator and auxiliary elements are cooperatively configured and relatively positioned such that the actuator element passively activates the auxiliary element.

8. The actuator as claimed in claim 5, further comprising a pivot arm fixedly attached to the sink, and the second change is operable to cause the arm to pivot towards the actuator element.

9. The actuator as claimed in claim 5, further comprising at least one shape memory alloy wire included with both the auxiliary and actuator elements, and the wires are cooperatively configured such that the actuator wire is fully activated prior to activating the auxiliary wire.

10. The actuator as claimed in claim 9, wherein the actuator element presents a first total cross-sectional area, and the auxiliary element presents a second total cross-sectional area greater than the first total cross-sectional area.

11. The actuator as claimed in claim 9, wherein the actuator element presents a first transformation temperature, and the auxiliary element presents a second transformation temperature greater than the first transformation temperature.

12. The actuator as claimed in claim 9, wherein said at least one actuator and auxiliary wires are connected in series, so as to be activated by a common current.

13. The actuator as claimed in claim 4, wherein the sink is comprised of materials selected from the group consisting essentially of copper, copper alloys, aluminum, and aluminum alloys.

15. The actuator as claimed in claim 4, wherein the sink defines at least one fluid opening.

16. The actuator as claimed in claim 4, further comprising a rack and pinion transmission intermediately coupling the sink and element, and driven by the change.

14. A thermally activated active material actuator adapted for increasing bandwidth, said actuator comprising:

an active material actuator element operable to undergo a reversible change in fundamental property, when exposed to or occluded from a thermal activation signal, so as to heat and activate the element or enable the element to be cooled and deactivated, respectively,

wherein the element presents an ambient rate of cooling when occluded from the signal after being activated, and a first cooling period based upon the ambient rate; and

a heat sink presenting a rate of thermal conductivity greater than the ambient rate, and autonomously engaging the element when the element is activated, so as to present a second cooling period shorter than the first period;

wherein the element defines a first length and width, and the sink presents a second width greater than the first width, and a second length not less than 25% of the first length so as to define a contact area of engagement.

17. A thermally activated active material actuator adapted for increasing bandwidth, said actuator comprising:

an active material actuator element including at least one shape memory wire operable to undergo a reversible change in fundamental property, when exposed to or occluded from a thermal activation signal, so as to heat and activate the element or enable the element to be cooled and deactivated, respectively,

wherein the element presents an ambient rate of cooling when occluded from the signal after being activated, and a first cooling period based upon the ambient rate; and

a heat sink presenting a rate of thermal conductivity greater than the ambient rate, and autonomously engaging the element when the element is activated, so as to present a second cooling period shorter than the first period;

wherein the element and sink define a contact area of engagement and the sink defines at least one groove or channel configured to increase the contact area of engagement.

18. The actuator as claimed in claim 17, further comprising a plurality of wires, and the sink defines a plurality of grooves or channels, and the grooves or channels are further configured to space the wires.

19. The actuator as claimed in claim 18, further comprising plural sets of stackable mated parts included with the sink, wherein the wires are oriented to define plural rows and each set is configured to buttress a row, so as to space adjacent rows when stacked.

20. The actuator as claimed in claim 17, wherein the sink defines a surface area exposed to ambient conditions, and presents at least one fin configured to increase the surface area.