Title:
Rapid heating, cooling and massaging for car seats using integrated shape memory alloy actuators and thermoelectric devices
Kind Code:
A1


Abstract:
An apparatus and method for providing controlled heating, cooling and motion, in a device such as an active robotic automobile seat, are disclosed. A shape memory alloy (SMA) element, which changes shape upon application of a temperature change to the SMA element, is coupled to a thermoelectric device. Heat flows through the TED upon application of an electrical current through the TED. The apparatus is operable in one of a plurality of modes. In a first mode, a current is applied through the TED to cause a temperature change in the SMA element to change the shape of the SMA element. In a second mode, a current is applied to the TED to cause heat flow in a space adjacent to the apparatus. By controlling application of current to the TED, controlled motion, heating and cooling are achieved in the seat.



Inventors:
Asada, Harry H. (Lincoln, MA, US)
Cho, Kyu-jin (Cambridge, MA, US)
Roy, Binayak (Cambridge, MA, US)
Application Number:
11/116002
Publication Date:
11/17/2005
Filing Date:
04/27/2005
Assignee:
Massachusetts Institute of Technology
Primary Class:
International Classes:
A47C7/72; B60N2/56; B60N2/90; (IPC1-7): A47C7/72
View Patent Images:
Related US Applications:
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20080079304Personalized raised-relief inlayApril, 2008Isaac
20090179468ACTIVE HEAD RESTRAINT SYSTEM FOR AN AUTOMOTIVE VEHICLE SEATJuly, 2009Orzelski et al.
20060071519Furniture combination useful for hiding pet productsApril, 2006Heide et al.
20090058164Footrest ApparatusMarch, 2009Ton
20090096260Kozy babyApril, 2009Long et al.
20050269860Constraint device for the releasable fastening of a child safety seat to a motor vehicle seatDecember, 2005Borghi
20090235451Interchangeable upholstered furniture frame systemSeptember, 2009Gorkin
20030107246Portable gun benchJune, 2003Smyers



Primary Examiner:
NELSON JR, MILTON
Attorney, Agent or Firm:
BURNS & LEVINSON, LLP (BOSTON, MA, US)
Claims:
1. An apparatus, comprising: a shape memory alloy (SMA) element, the SMA element changing shape upon application of a temperature change to the SMA element; a thermoelectric device (TED) coupled to the SMA element, heat flowing through the TED upon application of an electrical current through the TED; wherein: the apparatus is operable in one of a plurality of modes; in a first mode, a current is applied through the TED to cause a temperature change in the SMA element to change the shape of the SMA element; and in a second mode, a current is applied to the TED to cause heat flow in a space adjacent to the apparatus.

2. The apparatus of claim 1, wherein, in the second mode, the space is heated.

3. The apparatus of claim 1, wherein, in the second mode, the space is cooled.

4. The apparatus of claim 1, wherein the current flowing in the TED in the first mode is in a reverse direction to that of the current flowing in the TED in the second mode.

5. The apparatus of claim 1, wherein the SMA element is disposed between first and second TEDs.

6. The apparatus of claim 1, wherein the SMA element is in the form of a wire in thermal communication with the TED, such that, upon application of a current to the TED, the wire SMA element shortens.

7. The apparatus of claim 6, wherein the wire SMA element is connected to at least one actuating member to provide actuation of the actuating member upon application of the current to the TED.

8. The apparatus of claim 1, wherein the apparatus is located within a seat.

9. The apparatus of claim 8, wherein, in the second mode, the current applied to the TED effects heating of the seat.

10. The apparatus of claim 8, wherein, in the second mode, the current applied to the TED effects cooling of the seat.

11. The apparatus of claim 8, wherein the seat comprises an actuating member, the SMA element being coupled to the actuating member to provide actuation of the actuating member upon application of the current to the TED.

12. The apparatus of claim 11, wherein the actuating member provides a rising motion to at least a portion of the seat.

13. The apparatus of claim 11, wherein the actuating member provides a sinking motion to at least a portion of the seat.

14. The apparatus of claim 11, further comprising a plurality of actuating members coupled to at least one SMA element to provide actuation of the actuating members upon application of the current to the TED.

15. The apparatus of claim 14, wherein the actuation provides motion in a predetermined pattern in the seat.

16. The apparatus of claim 15, wherein the predetermined pattern is a wave motion.

17. The apparatus of claim 15, wherein the predetermined pattern is a pattern of at least one of rising motions and sinking motions.

18. The apparatus of claim 17, wherein the seat is an automobile seat.

19. A seat comprising: a plurality of actuation regions at which motion can be effected in the seat; an actuation device coupled to the actuation regions, the actuation device comprising: a shape memory alloy element (SMA), the SMA element changing shape upon application of a temperature change to the SMA element, and a thermoelectric device (TED) coupled to the SMA element, heat flowing through the TED upon application of an electrical current through the TED; wherein: the seat is operable in one of a plurality of modes; in a first mode, a current is applied through the TED to cause a temperature change in the SMA element to change the shape of the SMA element to actuate at least one of the actuation regions to effect motion in the seat; and in a second mode, a current is applied to the TED to cause heat flow in the seat.

20. The seat of claim 19, wherein, in the second mode, the seat is heated.

21. The seat of claim 19, wherein, in the second mode, the seat is cooled.

22. The seat of claim 19, wherein, the current flowing in the TED in the first mode is in a reverse direction to that of the current flowing in the TED in the second mode.

23. The seat of claim 19, wherein the SMA element is disposed between first and second TEDs.

24. The seat of claim 19, wherein the SMA element is in the form of a wire in thermal communication with the TED, such that, upon application of a current to the TED, the wire SMA element shortens.

25. The seat of claim 19, wherein the actuation device provides a rising motion to at least a portion of the seat.

26. The seat of claim 19, wherein the actuation device provides a sinking motion to at least a portion of the seat.

27. The seat of claim 19, wherein the actuation device provides motion in a predetermined pattern in the seat.

28. The seat of claim 27, wherein the predetermined pattern is a wave motion.

29. The seat of claim 27, wherein the predetermined pattern is a pattern of at least one of rising motions and sinking motions.

30. The seat of claim 19, wherein the seat is an automobile seat.

31. A method, comprising: providing a shape memory alloy (SMA) element, the SMA element changing shape upon application of a temperature change to the SMA element; providing a thermoelectric device (TED) coupled to the SMA element, heat flowing through the TED upon application of an electrical current through the TED; performing one of two operations in one of two respective modes, wherein: in a first mode, a current is applied through the TED to cause a temperature change in the SMA element to change the shape of the SMA element; and in a second mode, a current is applied to the TED to cause heat flow in a space adjacent to the apparatus.

32. The method of claim 31, wherein, in the second mode, the space is heated.

33. The method of claim 31, wherein, in the second mode, the space is cooled.

34. The method of claim 31, wherein the current flowing in the TED in the first mode is in a reverse direction to that of the current flowing in the TED in the second mode.

35. The method of claim 31, wherein the SMA element is disposed between first and second TEDs.

36. The method of claim 31, wherein the SMA element is in the form of a wire in thermal communication with the TED, such that, upon application of a current to the TED, the wire SMA element shortens.

37. The method of claim 36, wherein the wire SMA element is connected to at least one actuating member to provide actuation of the actuating member upon application of the current to the TED.

38. The method of claim 31, wherein the method is carried out within a seat.

39. The method of claim 38, wherein, in the second mode, the current applied to the TED effects heating of the seat.

40. The method of claim 38, wherein, in the second mode, the current applied to the TED effects cooling of the seat.

41. The method of claim 38, wherein the seat comprises an actuating member, the SMA element being coupled to the actuating member to provide actuation of the actuating member upon application of the current to the TED.

42. The method of claim 41, wherein the actuating member provides a rising motion to at least a portion of the seat.

43. The method of claim 41, wherein the actuating member provides a sinking motion to at least a portion of the seat.

44. The method of claim 41, wherein a plurality of actuating members are coupled to at least one SMA element to provide actuation of the actuating members upon application of the current to the TED.

45. The method of claim 44, wherein the actuation provides motion in a predetermined pattern in the seat.

46. The method of claim 45, wherein the predetermined pattern is a wave motion.

47. The method of claim 45, wherein the predetermined pattern is a pattern of at least one of rising motions and sinking motions.

48. The method of claim 47, wherein the seat is an automobile seat.

49. A method comprising: providing a plurality of actuation regions at which motion can be effected in a seat; providing an actuation device coupled to the actuation regions, the actuation device comprising: a shape memory alloy element (SMA), the SMA element changing shape upon application of a temperature change to the SMA element, and a thermoelectric device (TED) coupled to the SMA element, heat flowing through the TED upon application of an electrical current through the TED; wherein: the seat is operable in one of a plurality of modes; in a first mode, a current is applied through the TED to cause a temperature change in the SMA element to change the shape of the SMA element to actuate at least one of the actuation regions to effect motion in the seat; and in a second mode, a current is applied to the TED to cause heat flow in the seat.

50. The method of claim 49, wherein, in the second mode, the seat is heated.

51. The method of claim 49, wherein, in the second mode, the seat is cooled.

52. The method of claim 49, wherein, the current flowing in the TED in the first mode is in a reverse direction to that of the current flowing in the TED in the second mode.

53. The method of claim 49, wherein the SMA element is disposed between first and second TEDs.

54. The method of claim 49, wherein the SMA element is in the form of a wire in thermal communication with the TED, such that, upon application of a current to the TED, the wire SMA element shortens.

55. The method of claim 49, wherein the actuation device provides a rising motion to at least a portion of the seat.

56. The method of claim 49, wherein the actuation device provides a sinking motion to at least a portion of the seat.

57. The method of claim 49, wherein the actuation device provides motion in a predetermined pattern in the seat.

58. The method of claim 57, wherein the predetermined pattern is a wave motion.

59. The method of claim 57, wherein the predetermined pattern is a pattern of at least one of rising motions and sinking motions.

60. The method of claim 49, wherein the seat is an automobile seat.

Description:

RELATED APPLICATION

This application is based on U.S. Provisional Application Ser. No. 60/565,894, filed on Apr. 28, 2004, the contents of which are incorporated herein in their entirety by reference.

BACKGROUND OF THE INVENTION

Long hours of driving cause the driver's tissue at the thighs and hips to be pressurized for an extended period and result in considerable discomfort and driver fatigue. Capillary blood vessels may collapse under a pressure higher than 30 mmHg thereby interfering with blood perfusion and circulation when the driver is seated for a long time. Furthermore, continuous contact with the seat surface often causes heat and moisture accumulation at the contact surface. Periodically stimulating the tissue in contact with the car seat, as well as providing adequate ventilation and pressure relief may alleviate these problems. Automotive manufacturers are enhancing the value of luxury cars by adding more functionality to the car seats.

These car seats are instrumental in providing a relaxed and comfortable driving experience, especially during long trips. Heated car seats are available in many cars, and systems that have cooling as well as heating of the seat surface have also been developed. Embedding a massage function in car seats is another new feature that is gaining popularity.

A driver who is driving for an extended period of time can be fatigued due to inadequate blood perfusion at the tissue under persistent pressure. Stimulation of the tissue as well as pressure relief and ventilation, are desirable. This can reduce the fatigue of the driver, thereby reducing the risk of accidents caused by driver's fatigue. This can generally be accomplished by massage. However, the massage effect should not interfere with driving and, therefore, conventional massage is not generally applicable to driving an automobile.

There are three types of active car seats providing massage effects. One is a vibrating and kneading massage cushion for car seats. These are built with simple DC motors with eccentric weights in order to create vibration. Due to the nature of the DC motor, the frequency of the vibration is high, creating a rapid vibratory motion. But these fast vibrations could cause itchiness and other discomfort when applied for a long time.

Therapeutic massage chairs similar to home-use massagers have been applied to back seats and passenger side seats. These may interfere with driving, and are therefore not applicable to driver car seats. Bulky motors and mechanisms also make them unfavorable for car seat applications.

There is another type of massage car seat that uses air inflation to create bumps on the surface of the seat. The bumps created by air inflation are limited to a simple round shape. They are effective for redistributing pressure, but no sophisticated motion can be created.

SUMMARY OF THE INVENTION

The present invention is directed to an apparatus and method applied to, for example, an active robotic car seat, in which contact pressure on the tissue of the driver, such as the thighs and hips, is actively redistributed, thus providing relief to the weary driver. To accommodate the distributed nature of the surface actuation and space limitations in the car seat, a large number of small, lightweight actuators are used and are confined to a small volume. Integrated devices which include shape memory alloy (SMA) actuators and thermoelectric devices (TED) are used to provide the necessary actuation plus a rapid heating and cooling function. These devices are suited to the application of an active car seat, due to their high power-to-weight ratio. A matrix architecture is used for the actuator drive amplifier that can drive N2 actuator units using only 2N switches and is thus suitable for vast degree of freedom systems in terms of scalability. In one particular exemplary embodiment, the seat 11 uses 16 SMA actuator units, which are driven in a matrix architecture using eight switches. The actuators are compactly housed under the car seat, and the force and displacements are transmitted to the flexible seat surface through a novel routing scheme. A distributed lifting motion of the seat surface in order to stimulate the tissue is generated. A complementary distributed sinking motion of the seat surface is created in order to provide pressure relief and ventilation. Additional auxiliary motions of the side flaps of the backrest are also created.

The invention provides an active seat surface that creates wave motion. The wave motion is created using straps of fabric laid on the seat surface. The wave motion on the seat surface alters the pressure distribution on the driver and removes heat and moisture at the contacting surface.

The invention also provides an integrated shape memory alloy (SMA) actuator and thermoelectric device (TED). The thermoelectric devices provide heating and cooling for activating and deactivating the shape memory alloy actuators, as well as a local heating and cooling for the seat of the invention.

The device includes shape memory alloy actuators sandwiched between upper and lower thermoelectric devices. In one configuration, the thermoelectric devices are packaged in a box with inlets and outlets for airflow to provide for ventilation.

The device operates in an actuation mode, a cooling mode and a heating mode. In the actuation mode, the shape memory alloy actuators are activated to create controlled motion in the seat by generating heat towards the actuators using the thermoelectric devices on top and bottom of the shape memory alloy actuators. The actuators are deactivated by creating heat flow in the reverse direction.

In the cooling mode, cool air is transferred to the seat. First, heat flow is generated using the thermoelectric devices such that the heat is extracted from the top surface to the bottom surface of the thermoelectric devices. Airflow is created on the top surface, and a valve is opened such that the outlet of the air channel that flows through the top surface goes to the seats.

In the heating mode, hot air is transferred to the seat. First, heat flow is generated using the thermoelectric devices such that the heat is extracted from the bottom surface to the top surface of the thermoelectric device. Airflow is created on the top surface, and a valve is opened such that the outlet of the sir channel that flows through the top surface goes to the seats.

The invention also provides a lifting and sinking apparatus and method for a seat. Multiple lifting motions are created sequentially to alter the pressure distribution on the tissue and remove heat and moisture at the contacting surface. The lifting and sinking motions are also created by straps laid under the fabric of the seat. Pulling of the fabric reduces the length of the strap and thereby lifts the strap creating pressure on the body. In order to create this motion, side panels to hold the edges of the strap are used. These change the direction of the force or displacement from lateral to vertical. The sinking motion is created by pulling down certain points of the seat. The sinking motion creates crater-like depressurized zones that enhance the blood circulation and enhance ventilation at the sinking points.

In accordance with the invention, auxiliary motion in the seat is also created. The displacement of the SMA wires is further used for auxiliary motions of the side flaps for a car backrest. The side flaps can be used to cradle the body better, especially during turning. The side flaps are actuated by transmitting the motion of SMA actuator units from the actuator box, which is placed under the car seat. The issue of limited displacement of SMA actuators is overcome in the invention by using a ratcheting mechanism. The position of the side flaps is controlled in small discrete steps, thereby eliminating the need to control the position of the individual SMA actuator units. A routing scheme, using Kevlar wires and cable housing, from the actuator box to the point of actuation is also used.

In one aspect, the invention is directed to an apparatus which includes a shape memory alloy (SMA) element which changes shape upon application of a temperature change to the SMA element. A thermoelectric device (TED) is coupled to the SMA element. Heat flows through the TED upon application of an electrical current through the TED. The apparatus is operable in one of a plurality of modes. In a first mode, a current is applied through the TED to cause a temperature change in the SMA element to change the shape of the SMA element. In a second mode, a current is applied to the TED to cause heat flow in a space adjacent to the apparatus.

In one embodiment, in the second mode, the space is heated. Alternatively, in the second mode, the space is cooled. The current flowing in the TED in the first mode is in a reverse direction to that of the current flowing in the TED in the second mode.

In one embodiment, the SMA element is disposed between first and second TEDs.

In one embodiment, the SMA element is in the form of a wire in thermal communication with the TED, such that, upon application of a current to the TED, the wire SMA element shortens. In one embodiment, the wire SMA element is connected to at least one actuating member to provide actuation of the actuating member upon application of the current to the TED.

In one embodiment, the apparatus is located within a seat. In one embodiment, in the second mode, the current applied to the TED effects heating of the seat. In one embodiment, in the second mode, the current applied to the TED effects cooling of the seat. In one embodiment, the seat comprises an actuating member, the SMA element being coupled to the actuating member to provide actuation of the actuating member upon application of the current to the TED. In one embodiment, the actuating member provides a rising motion to at least a portion of the seat. In one embodiment, the actuating member provides a sinking motion to at least a portion of the seat. In one embodiment, a plurality of actuating members are coupled to at least one SMA element to provide actuation of the actuating members upon application of the current to the TED. In one embodiment, the actuation provides motion in a predetermined pattern in the seat.

In one embodiment, the predetermined pattern is a wave motion. In one embodiment, the predetermined pattern is a pattern of at least one of rising motions and sinking motions. The seat can be an automobile seat.

In another aspect, the invention is directed to a seat having a plurality of actuation regions at which motion can be effected in the seat. An actuation device is coupled to the actuation regions, the actuation device comprising: (i) a shape memory alloy element (SMA), the SMA element changing shape upon application of a temperature change to the SMA element, and (ii) a thermoelectric device (TED) coupled to the SMA element, heat flowing through the TED upon application of an electrical current through the TED. In one embodiment, the seat is operable in one of a plurality of modes. In a first mode, a current is applied through the TED to cause a temperature change in the SMA element to change the shape of the SMA element to actuate at least one of the actuation regions to effect motion in the seat. In a second mode, a current is applied to the TED to cause heat flow in the seat.

In one embodiment, in the second mode, the seat is heated. In one embodiment, in the second mode, the seat is cooled. In one embodiment, the current flowing in the TED in the first mode is in a reverse direction to that of the current flowing in the TED in the second mode. In one embodiment, the SMA element is disposed between first and second TEDs. In one embodiment, the SMA element is in the form of a wire in thermal communication with the TED, such that, upon application of a current to the TED, the wire SMA element shortens. In one embodiment, the actuation device provides a rising motion to at least a portion of the seat. In one embodiment, the actuation device provides a sinking motion to at least a portion of the seat. In one embodiment, the actuation device provides motion in a predetermined pattern in the seat. In one embodiment, the predetermined pattern is a wave motion. In one embodiment, the predetermined pattern is a pattern of at least one of rising motions and sinking motions.

In one embodiment, the seat is an automobile seat.

In another aspect, the invention is directed to a method comprising: (i) providing a shape memory alloy (SMA) element, the SMA element changing shape upon application of a temperature change to the SMA element, (ii) providing a thermoelectric device (TED) coupled to the SMA element, heat flowing through the TED upon application of an electrical current through the TED, and (iii) performing one of two operations in one of two respective modes. In a first mode, a current is applied through the TED to cause a temperature change in the SMA element to change the shape of the SMA element. In a second mode, a current is applied to the TED to cause heat flow in a space adjacent to the apparatus.

In one embodiment, in the second mode, the space is heated. In one embodiment, in the second mode, the space is cooled. In one embodiment, the current flowing in the TED in the first mode is in a reverse direction to that of the current flowing in the TED in the second mode. In one embodiment, the SMA element is disposed between first and second TEDs.

In one embodiment, the SMA element is in the form of a wire in thermal communication with the TED, such that, upon application of a current to the TED, the wire SMA element shortens. In one embodiment, the wire SMA element is connected to at least one actuating member to provide actuation of the actuating member upon application of the current to the TED.

In one embodiment, the method is carried out within a seat. In one embodiment, in the second mode, the current applied to the TED effects heating of the seat. In one embodiment,, in the second mode, the current applied to the TED effects cooling of the seat. In one embodiment, the seat comprises an actuating member, the SMA element being coupled to the actuating member to provide actuation of the actuating member upon application of the current to the TED. In one embodiment, the actuating member provides a rising motion to at least a portion of the seat. In one embodiment, the actuating member provides a sinking motion to at least a portion of the seat. In one embodiment, a plurality of actuating members are coupled to at least one SMA element to provide actuation of the actuating members upon application of the current to the TED. In one embodiment, the actuation provides motion in a predetermined pattern in the seat. In one embodiment, the predetermined pattern is a wave motion. In one embodiment, the predetermined pattern is a pattern of at least one of rising motions and sinking motions.

In one embodiment, the seat is an automobile seat.

In another aspect, the invention is directed to a method comprising: (i) providing a plurality of actuation regions at which motion can be effected in a seat, (ii) providing an actuation device coupled to the actuation regions. The actuation device includes: (i) a shape memory alloy element (SMA), the SMA element changing shape upon application of a temperature change to the SMA element, and (ii) a thermoelectric device (TED) coupled to the SMA element, heat flowing through the TED upon application of an electrical current through the TED. The seat is operable in one of a plurality of modes. In a first mode, a current is applied through the TED to cause a temperature change in the SMA element to change the shape of the SMA element to actuate at least one of the actuation regions to effect motion in the seat. In a second mode, a current is applied to the TED to cause heat flow in the seat.

In one embodiment, in the second mode, the seat is heated. In one embodiment, in the second mode, the seat is cooled. In one embodiment,, the current flowing in the TED in the first mode is in a reverse direction to that of the current flowing in the TED in the second mode.

In one embodiment, the SMA element is disposed between first and second TEDs.

In one embodiment, the SMA element is in the form of a wire in thermal communication with the TED, such that, upon application of a current to the TED, the wire SMA element shortens.

In one embodiment, the actuation device provides a rising motion to at least a portion of the seat. In one embodiment, the actuation device provides a sinking motion to at least a portion of the seat.

In one embodiment, the actuation device provides motion in a predetermined pattern in the seat. In one embodiment, the predetermined pattern is a wave motion. In one embodiment, the predetermined pattern is a pattern of at least one of rising motions and sinking motions.

In one embodiment, the seat is an automobile seat.

Hence, the invention is directed to a new approach to car seat design for alleviating long-drive fatigue. To enhance blood circulation as well as to keep the skin temperature and moisture at desired levels, an active control of the seat surface is accomplished with the use of Shape Memory Alloy (SMA) wire actuators. Since SMA actuators have high power-to-weight ratio, a multitude of SMA actuators can be embedded in a limited space.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the invention will be apparent from the more particular description of preferred aspects of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

FIG. 1 contains a schematic diagram of an active seat surface for altering pressure distribution on a person in accordance with an embodiment of the invention.

FIG. 2 contains a schematic diagram of the active seat surface of the invention shown in FIG. 1, illustrating propagating surface waves for removing hot, humid air.

FIG. 3 contains a schematic diagram of the integrated SMA and TED device used with an active car seat in accordance with an embodiment of the invention.

FIG. 4 contains a schematic diagram of the active car seat of the invention in the actuation mode, according to an embodiment of the invention.

FIG. 5 contains a schematic diagram of the active car seat of the invention in the cooling mode, according to an embodiment of the invention.

FIG. 6 contains a schematic diagram of the active car seat of the invention in the heating mode, according to an embodiment of the invention.

FIG. 7 contains a schematic diagram illustrating the lifting motion according to an embodiment of the invention.

FIG. 8 contains a schematic diagram illustrating the geometry of the lifting motion mechanism, in accordance with the invention.

FIG. 9 is a curve showing variation of lifting height H as W changes from 10 inches to 14 inches, according to the invention.

FIG. 10 contains a schematic diagram illustrating the sinking motion according to an embodiment of the invention.

FIG. 11 is an image which schematically illustrates the positions of the pulling down points for creating the depressurized zones in the active car seat according to one particular illustrative embodiment, for the sinking motion of the invention.

FIG. 12 contains an image illustrating an uncovered active car seat 11 in accordance with an embodiment, of the invention, illustrating one embodiment of the lifting motion mechanism of the invention.

FIG. 13 contains an image illustrating the uncovered car seat of FIG. 12, with the sinking points of the invention also illustrated.

FIG. 14 is an image illustrating a model of one embodiment of an actuator box in accordance with the invention.

FIG. 15 is an image containing an illustration of a portion of an active car seat of the invention mounted over the actuator box of the invention.

FIG. 16 contains an image of the robotic car seat of the invention covered with automotive upholstery.

FIG. 17 comprises an image of detailed hardware used in the actuator box of the invention.

FIG. 18 is an image illustrating detail of the routing done by assembly of bicycle brake cable housings and noodles, in accordance with the invention.

FIG. 19 is a schematic diagram illustrating the architecture of the matrix drive system in accordance with the invention.

FIG. 20 contains an image of the locking mechanism used to eliminate slack in accordance with the invention.

FIG. 21 is an image illustrating the use of pulleys to increase the displacement provided by the actuators, in accordance with the invention.

FIG. 22 is a schematic perspective view of a continuous pulley in accordance with an embodiment of the invention.

FIG. 23 is a view of the menu of the controller software according to the invention.

FIG. 24 contains a schematic diagram of a portion of the thermoelectric devices (TED) used in the integrated SMA/TED actuator devices of the invention.

FIG. 25 contains a schematic diagram of a partially cut-away assembled thermoelectric device according to the invention.

FIG. 26 contains a schematic diagram of one thermoelectric device in accordance with the invention.

FIG. 27 contains a schematic diagram of an integrated SMA/TED actuator in accordance with the invention.

FIG. 28 is a graph of the rate of heat added to the hot side of a TED versus hot side temperature according to the invention.

FIG. 29 is a schematic diagram of the integrated SMA/TED actuator device of the invention in the actuation mode.

FIG. 30 is a schematic diagram of the integrated SMA/TED actuator device of the invention in the rapid cooling mode.

FIG. 31 is a schematic diagram of the integrated SMA/TED actuator device of the invention in the heating mode.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 contains a schematic diagram of an active seat surface 11 for altering pressure distribution on a person in accordance with an embodiment of the invention. As illustrated in the figure, the body of the user, illustrated by human tissue 10, is supported at different areas of contact, so that the pressurized tissue areas may be changed. The figure shows a wave pattern of crests and troughs that are altered periodically. Referring to the “before” and “after” views, the motion of the wave pattern of crests and troughs is observed.

FIG. 2 contains a schematic diagram of the active seat surface 11 of the invention shown in FIG. 1, illustrating propagating surface waves for removing hot, humid air. To remove heat and moisture at the contact area, the air gap between the crest and the trough is relatively large. Furthermore, if the wave propagates, as shown in FIG. 2, the air of high moisture and temperature that is captured between the human skin and the trough may be transferred sideways and removed from the contact surface. This enhances the ventilation effect.

Pressure relief and ventilation are the two major functional requirements for enhancing long-drive comfort and alleviating fatigue. The surface activation method described above directly controls the contacting surface and meets the functional requirements. To implement the surface activation method, a new type of actuator system in accordance with the invention is used. The distributed nature of surface activation requires a large number of degrees of freedom. Considering the limited space for actuators, actuators are of high energy density, i.e., compact and powerful. To this end, shape memory alloy (SMA) actuators, for activating many points on the seat surface, are used.

To create a wave motion on the seat surface and actuation for other purposes related to the car seat or chair, a device that integrates the shape memory alloy actuators with the thermoelectric device is provided. The device includes shape memory alloy actuators placed between the two thermoelectric devices. The thermoelectric devices provide heating and cooling for activating and deactivating the shape memory alloy actuators, as well as a local heating and cooling for the chairs.

FIG. 3 contains a schematic diagram of the integrated SMA and TED device used with an active car seat 11 in accordance with an embodiment of the invention. The device includes multiple axis of SMA actuators placed perpendicular to air flow inlets 16, 17 and outlets 18, 19. Air flows through the top and bottom surfaces of the integrated SMA/TED device. A valve 20 is used to control the direction of the air flow that passes the top surface of the seat 11. As shown in FIG. 3, in the actuation mode, the valve 20 is positioned such that any air flowing into inlets 16 and 17 flows out only through outlet 18. Thermoelectric devices 21 and 22 are mounted within the seat 11 facing each other as shown. The SMA actuators 26 in the shape of wires are interposed between and in thermal contact with surfaces of the thermoelectric devices 21, 22. The TEDs operate to create a temperature difference between their top and bottom surfaces, and, therefore, heat flow between the surfaces, upon application of an electrical potential across the surfaces. Upon application of a potential of a first polarity orientation, heat flows in a first direction from one surface to the other. Potential applied across the device in the opposite polarity orientation causes heat flow in the opposite direction. The SMA actuators 26 are activated when the TEDs 21, 22 on top and bottom of the SMA actuators 26 all generate heat towards the actuators. The heat applied to the actuators 26 interposed between the TEDs causes the shape of the SMA actuators to change, such as by increasing or decreasing their length. This actuation motion is coupled throughout the active seat and controlled as needed to provide the sinking, lifting, wave and other motions provided in the seat 11.

FIG. 4 contains a schematic diagram of the active car seat 11 of the invention in the actuation mode, according to an embodiment of the invention. The SMA material reaches temperatures well above austenite finish temperature by using the sandwiched configuration illustrated, i.e., the SMA actuators 26 being interposed between the TEDs. By applying potential to both TEDs 21, 22 in the polarity orientation that causes heat to flow toward the SMA actuators 26 from both top and bottom TEDs 21, 22, the temperature of the SMA actuators rises sufficiently to provide the required seat actuation motion. The SAM actuators 26 are deactivated by reversing the polarity of the potential applied to the TEDs to move the heat that is gathered in the center of the device towards the outer surface of the device.

The device of the invention can be used to generate cold or hot air for local cooling and heating of the seat 11, without activating the actuators. FIG. 5 contains a schematic diagram of the active car seat 11 of the invention in the cooling mode, according to an embodiment of the invention. By generating the heat flow using the thermoelectric devices 21, 22 such that the heat flows from the top surface to the bottom surface of the integrated SMA/TED device, as indicated by arrows 27. The air that enters at the top surface at inlet 16 cools, and is sent to the top surface of the car seat 11 for local cooling. Enough cooling can be done without activating the actuators, since the temperatures of the shape memory alloys are kept below the austenite starting temperature even though the top surface is sufficiently cooled. In the cooling mode, air enters the top of the seat through inlet 16 and flows along the top surface of the car seat 11 to cool it. The cooling air then exits through the outlet 19. The valve 20 is set to allow the air to exit through the outlet 19. Air also enters the bottom region of the car seat 11 through inlet 17 and flows along the bottom heated surface of the integrated SMA/TED device to remove heat from the interior of the seat 11. Air carrying the heat away exits the seat 11 through the outlet 18.

FIG. 6 contains a schematic diagram of the active car seat 11 of the invention in the heating mode, according to an embodiment of the invention. The heating mode is essentially functionally opposite of the cooling mode. That is, in the heating mode, the TEDs 21, 22 are activated by applied potential to cause heat to flow from the bottom surface to the top surface of the integrated SMA/TED device, as indicated by arrows 27. The heat is transmitted via the TEDs 21, 22 from the bottom surface to the top surface, thereby creating a hot area at the top surface. The air that enters the seat 11 at inlet 16 is heated for local heating of the seat. The valve 20 is again set to permit the warm air to exit the seat 11 at outlet 19.

The massage functions of the active car seat of the invention are unique in that they do not interfere with driving. The massage function provides pressure redistribution and enhanced ventilation through active control of the seat surface. The redistribution of pressure does not interfere with the driver's driving capability. Many points of the seat 11, which are wide enough to cover the whole bottom part of the body, are activated. The mechanism is not perceptible when the massage is not being performed. The actuator mechanism is light enough to be installed in a car, where the weight of the system is directly related to the fuel efficiency. Although light, the actuator mechanism has enough power to pressurize the body so as to provide enough stimulation.

In accordance with the invention, two complementary motions fulfill the fundamental requirements of pressure redistribution and ventilation. These are generically called the lifting motion and the sinking motion. The purpose of the lifting motion is to redistribute the pressure on the thighs and the hips of the driver, and the purpose of the sinking motion is to provide ventilation. By combining these motions to create a large gap between the seat and the body surface, the ventilation effect is enhanced. Both motions are created by pulling the end of a cable or a strap of fabric that is placed on the bottom foam of the car seat 11. The cables are connected to the integrated SMA/TED devices such that selective and controlled activation of those devices provides the desired lifting and sinking motions. Rigid mechanical components are not used for the mechanism such that considerable weight reduction is realized. Furthermore, the system complies with the shape of the human body. Thus the mechanism is imperceptible to the driver when it is not being used.

FIG. 7 contains a schematic diagram illustrating the lifting motion according to an embodiment of the invention. FIG. 7 schematically illustrates the driver's thighs 10 in cross-section over the mechanism for providing the lifting. The mechanism of the invention, through activation of the integrated SMA/TED devices, pulls on a cable or strap 30, preferably at both ends of the strap 30, to provide the lifting motion to the driver's legs and thighs. The pulling of the fabric lifts the strap creating pressure on the body. In order to create this motion, side panels to hold the edges of the strap are used. These change the direction of the force or displacement from lateral to vertical.

FIG. 8 contains a schematic diagram illustrating the geometry of the lifting motion mechanism. The height h of the sidebar 31, the width of the thighs, and the width of the chair all contribute to the amount of lifting height when the fabric is pulled a certain length. Referring to FIG. 8, the straps 30 are assumed to be a straight line and maintained straight with a width of W throughout the operation. Although actual shape of the strap would be a shape of the hip or thigh of the person sitting on it, the straight line of the strap is regarded as a virtual line that connects the two end points of the contact between the strap and the human body. In one embodiment, to prevent the lifting motion from interfering with the driver's driving capability, lifting height H is limited to less than 1 inch. The required displacement d, of the SMA actuator, given the required lifting height of H, is d=2(h-H)2+(L-W2)2-h2+(L-W2)2(1)
where L is the width of the chair, h is the height of the sidebar, and W is the width of the thigh or hip of the person sitting on the chair. Based on measurements of an average person, and from the requirement that the lifting motion should not interfere with the driving, the width of the thighs used for design was 12 inches, and required lifting height was chosen to be 0.75 inches. From the given specifications, the displacement of the actuator needed is 0.89 inches. This is achieved by using a SMA wire of length 12.82 inches.

As the width of the thighs or hips are different from person to person, the lifting height changes as a function of W. FIG. 9 is a curve showing variation of lifting height H as W changes from 10 inches to 14 inches. The lifting height becomes smaller as the width of the thighs becomes larger. Specifically, the lifting height changes from 0.82 to 0.49 inches, as the width changes from 10 to 14 inches.

FIG. 10 contains a schematic diagram illustrating the sinking motion according to an embodiment of the invention. FIG. 10 schematically illustrates the driver's thighs 10 in cross-section over the mechanism for providing the sinking in the surface of the seat 11. FIG. 10 shows the sinking motion created by pulling down certain points of the seat 11. Sinking motion creates crater-like depressurized zones 33 that enhance the blood circulation at the point and also enhance the ventilation at the points. In one particular illustrative embodiment, two depressurizing zones 33 are used at the thighs and three depressurized zones 33 are used along the center of the hips, where ventilation is most effective. The mechanism of the invention, through activation of the integrated SMA/TED devices, pulls on a cable, or strap that is attached to the underside of the seat surface at the depressurized zones 33.

FIG. 11 is an image which schematically illustrates the positions of the pulling down points for creating the depressurized zones 33 according to one particular illustrative embodiment, for the sinking motion of the invention. In this particular embodiment, five sinking points are illustrated. It will be understood that any number of sinking point can be used in accordance with the invention. The pulling down points are connected to the SMA actuators in the actuator box 40 via wires or cables 41. The displacement provided by activation of the SMA actuators is transferred to the pulling down points via the wires or cables 41. In one embodiment, these wires or cables 41 are Kevlar wires routed to the actuator box 40 via tumbuckles. The tensions in the Kevlar wires can be adjusted by means of the tumbuckles, thus preventing slack.

FIG. 12 contains an image illustrating an uncovered active car seat 11 in accordance with an embodiment, of the invention, illustrating one embodiment of the lifting motion mechanism of the invention. FIG. 12 shows the arrangement of straps 30 disposed over the seat 11 for the lifting motion. In one particular embodiment, the straps include six ⅜-inch wide straps made out of polyethylene fibers to create the lifting motions. The straps are attached to the Kevlar wires 41 coming out of the actuator box 40 by means of tumbuckles. The tensions of the Kevlar wires can be adjusted by means of the tumbuckles, thus preventing slack. The other end of the strap is attached to another length adjustment mechanism that makes it possible to adjust to different weights of the person sitting on the seat.

FIG. 13 contains an image illustrating the uncovered car seat 11 of FIG. 12, with the sinking points of the invention also illustrated. As shown in FIG. 13, the sinking points are distributed on the base of car seat 11. The sinking points are created by passing the Kevlar wires into the base foam of the seat 11 and connecting them to the SMA actuators 26 in the actuator box 40. When the actuators are activated, the wires pull down the sinking points and this results in crater-like depressions on the base foam. This gives rise to pressure relief and enhanced ventilation.

FIG. 14 is an image illustrating a model of one embodiment of an actuator box in accordance with an embodiment of the invention, and FIG. 15 is an image containing an illustration of a portion of an active car seat 11 of the invention mounted over the actuator box 40 of the invention.

In accordance with the invention, auxiliary motion is also provided to the active car seat 11 of the invention. According to the auxiliary motion, side flaps in the upper backrest portion of the seat are moved over an angular range of about 30 degrees. Discrete motion of the flaps is achieved in small steps. The SMA actuators are used to move the flaps. This requires substantial displacement for the individual SMA actuator units. The mechanism uses, in one embodiment, four SMA actuator units in a pair-wise antagonistic fashion. A ratcheting mechanism with locking is used to respond to the limited amount of displacement provided by the SMA actuators.

Thus, in accordance with the invention, active control of the car seat surface is achieved. According to the invention, the actuator units are housed in a compact actuator box 40 under the car seat 11, and cables or wires are used to transmit the force and displacements to the actuation points on the seat surface. A distributed lifting and sinking motion on the surface of the car seat is achieved in order to enhance blood circulation by pressure redistribution as well as to keep the skin temperature and moisture at desired levels.

FIG. 16 contains an image of the robotic car seat 11 of the invention covered with automotive upholstery. The robotic seat 11 includes an actuator box 40 that has, in one embodiment, sixteen SMA actuators and fits under the car seat 11. A routing mechanism 43 transmits the forces and displacements from the actuator box 40 to the desired actuation points in the seat. The lifting and the sinking motions described above can be accomplished with this set-up.

FIG. 17 comprises an image of detailed hardware used in the actuator box 40. As noted above, the actuator box 40 includes sixteen SMA actuators. Each actuator includes multiple SMA wires attached to a Printed Circuit Board (PCB). Although the SMA wires are mechanically in parallel, they are configured in a mix of serial and parallel connections electrically. If all the wires are connected in parallel electrically, the total resistance of the actuator becomes too low. This makes it difficult to design the drive circuitry. Therefore the SMA wires are electrically configured in order to maintain the resistance of the actuator to be between 1 to 10 ohms. By reconfiguring the wires electrically, all the necessary electrical wirings can be done at one end, making it simple to design mechanical parts at the moving end of the actuator.

In one embodiment, the length of each SMA tendon cable or wire is 12.5 inches, and each wire has a diameter of 0.015″ or 0.01″. Each tendon cable provides 110 to 220 N of force and a 12 mm stroke. Six of the actuators are designed for a force requirement of 36 kgf in order to be used for lifting motion. All other actuators are designed with a force requirement of 10 kgf. The actuators are cooled by an array of fans that are placed under them. A bias spring is connected at the ends of each actuator to ensure that they return to their natural length when the current is turned off. A pulley system is attached at the end of the moving PCB in order to amplify the limited displacement provided by the SMA. Kevlar wires are used to transmit the force and displacement generated by the actuator to each mechanism. Kevlar has a breaking strength that is five times greater than steel wire, but is much lighter.

In one embodiment, each actuator of the sixteen actuators includes 12 to 36 actuator wires or tendon cables, depending on the force requirement. For the lifting motion actuators, there are 36 0.38 mm diameter SMA wires or tendon cables, providing a force of 72 kgf with 36 kgf being due to pulleys. The displacement is 20 mm actual due to stress. The actuators operate at 1 ohm and 16 Amps. The actuators for sinking motion and the auxiliary flap motion include 24 0.25 diameter SMA wires or tendon cables. A force of 22.5 kgf, 11.25 kgf due to pulleys, is generated. The displacement is 20 mm. The actuators operate at 10 ohms and 2 Amps.

FIG. 18 is an image illustrating detail of the routing done by assembly of bicycle brake cable housings and noodles. The Kevlar wires are contained in a cable housing that is inextensible, in order to ensure the perfect transmission of the displacement generated by the SMA wire.

In order to make the system more compact and efficient in terms of power related resources, in one embodiment, a matrix drive system is used. Wires and drive amplifiers are shared among the actuators, instead of having a dedicated wire and power amplifier for each actuator. FIG. 19 is a schematic diagram illustrating the architecture of the matrix drive system. Since the robotic car seat does not require all of the actuators to be turned on at the same time, it is reasonable to use a matrix drive architecture. 2N number of switches and wires are used to activate N2 number of actuators. By activating the appropriate pair of switches in each column and each row of the matrix, one can turn on any actuator in the network at any instant. By turning on the switch for the mth row and the nth column, the actuator on the corresponding row and column, denoted Amn, will be turned on. For example when both switches from the third row and the second column of the matrix are connected to the power source, only actuator A32 will be turned on.

The wiring for the 16 SMA actuators for the actuator box 40 for the robotic car seat uses a matrix drive system. By using matrix drive system, the number of drive amplifiers was reduced to 8 from 16. The wiring was also simplified by connecting 8 wires onto each actuator and the drive circuitry connected to the nearest actuator, instead of 16 wires being connected one by one from each actuator to the drive circuitry. Although the actuators are not placed in matrix architecture, they are electrically connected in matrix architecture. The actuators are placed side by side, with 8 wires connecting all sixteen actuators from each actuator to another actuator, creating a daisy chain like structure. Four wires correspond to the row wires and the other four wires correspond to the column wires. Although they are physically connected to all the actuators, each actuator is electrically connected to one row wire and one column wire. For example, actuator A12 is electrically connected to 1st row wire and 2nd column wire. So, by turning on the switch for row 1 and column 2, actuator A12 will be activated.

Hence, an active control of the car seat surface, using SMA actuator units has been implemented. The actuator units are housed in a compact actuator box 40 under the car seat 11, and cables are used to transmit the force and displacements to the actuation points on the seat surface. The SMA actuator units are driven using a scalable matrix architecture, which uses 2N switches to drive N2 actuator units.

According to the invention, actuation is done with a soft fabric, and the fabric is placed on a flexible cushion. The depth of the cushion change under loading of different person causes change of initial position of the actuator, causing slack in the actuator. Due to this slack, when the SMA wire is actuated, the displacement is used to reduce the slack, instead of being used to activate the fabric actuators. In order to eliminate this slack problem, a locking mechanism is used. FIG. 20 contains an image of the locking mechanism used to eliminate this slack. Each fabric actuator strap has a break pad 51 attached at the end, and the break pad is attached to a spring 53. The spring 53 is attached to a fixed frame. When a person sits on the seat, there will be a different displacement of all the fabric actuator straps. The locking bar is locked with a locking knob 55 after a person sits on the chair, providing a initial position of the fabric actuator straps 30 by fixing the one end without any slacks at the actuator end.

In one particular exemplary embodiment, the displacement of each actuator is 20 mm. This displacement is translated into upper lift motion and pulling down motion. In order to increase the displacement for larger pressurizing effect, pulleys are used. By using one more pulley per actuator, their displacement can be doubled, thereby increasing the displacement to 40 mm. FIG. 21 is an image illustrating the use of pulleys to increase the displacement provided by the actuators.

Another alternative is to use a continuous pulley. FIG. 22 is a schematic perspective view of a continuous pulley in accordance with an embodiment of the invention. By using a continuous pulley, the ratio of displacement increase can be controlled by changing the ratio of the diameter of the hub that each actuator passes by. For example by setting the ratio of R2 to R1 to be 3, displacement can be multiplied three times the displacement created by the actuator. This component creates larger displacement increase while using less space.

In one embodiment, the side bar is separate from the seat foam and are placed outside of the foam. Alternatively, the structure that supports the actuators can be incorporated inside the foam. The molding of the foam can be done with the structure included in the casting mold.

Software for controlling the car seat actuator was developed using Microsoft Visual Basic 6.0 and Measurement Studio for Visual Studio 6.0. FIG. 23 is a view of the menu of the controller software. In order to facilitate the experiment of the car seat actuator, there are two types of motions that can be created with the controller. In accordance with one illustrative exemplary embodiment, first, each actuator can be actuated separately by designating the actuator to be activated. Actuators A1 to A4 are designated for activating the Flap mechanism, and Actuators C2, C3 and D1 to D4 are designated for lifting motion, where D4 is the actuator closest to the front end of the chair, and C2 is the inner most actuator for lifting motion. Actuators B2, B3, C1 are the actuators for sinking motion placed at the center of the seat, and actuators B4 and C4 are actuators for sinking motion at the leg part, left and right respectively. The period of actuation can be determined by changing the value labeled period, and the duty ratio can be changed by sliding the Duty Ratio slide bar. Then, the On-time and Off-time of the actuator that was chosen is shown at the textboxes. After choosing the actuator and setting the On-time and Off-time, operation can be initiated by pressing “Start”. The chosen actuator will be activated until the “Stop” button is pressed.

Three sets of continuous wave motions can also be created using the software. Flap motion can be created by checking the Move in or Move out button, and then Flap motion button. The On-time and Off-time can also be controlled. Continuous wave of lifting motion is created by pressing the lift wave motion button and setting the On-time factor and Off-time factor. Similarly, sinking wave motion is created by pressing the sink wave motion and setting the On-time and Off-time.

FIG. 24 contains a schematic diagram of a portion of the thermoelectric devices (TED) used in the integrated SMA/TED actuator devices of the invention. The TEDs include multiple Peltier elements 61, 62 electrically connected in series by conductors 63. Each Peltier element includes a thermoelectric material which experiences heat flow in a particular direction upon application of an electrical current in a particular direction. In the invention, N-type Peltier elements 62 are connected in series in an alternating fashion with P-type elements 61. As indicated in FIG. 24, a voltage is applied across positive terminal 65 and negative terminal 64 of the illustrated exemplary device. As a result, electron current flows from negative terminal 64, through the Peltier elements 61,62, to the positive terminal 65. Also, hole current flows from the positive terminal 65, through the elements 61, 62, to the negative terminal 64. As illustrated in the figure, in N-type Peltier material, heat flows in the direction of the electron current, and, in P-type Peltier material, heat flows in the direction of the hole current. As a result, with the applied voltage having the indicated polarity with regard to the terminals 64 and 65, heat is released at the top surface of the device, and heat is absorbed at the bottom surface of the device. Accordingly, the top surface has a higher temperature than the bottom surface. If the polarity of the voltage applied to terminals 64 and 65 is reversed, then the heat flows in the opposite direction, i.e., the top surface of the device is cooled, and the bottom surface is heated.

FIG. 25 contains a schematic diagram of a partially cut-away assembled thermoelectric device . As shown in the figure, the device includes an array of both P-type (61) and N-type (62) Peltier “pellets” or elements connected together by conductors 63. An upper ceramic substrate 66 is formed over the device, and a lower ceramic substrate 67 is formed at the bottom side of the device.

As described above, the integrated SMA/TED actuator of the device uses TEDs or Peltier devices to apply heat to the shape memory alloy material of the SMA actuator to cause the material to change its shape and, as a result, provide the actuation motions used by the active car seat of the invention. A certain amount of heat is required to be transferred by the TED to provide the required temperature applied to the SMA actuator. In one embodiment, the single-axis SMA actuator should provide 700N of force and 12 mm of displacement. From these requirements, the mass of the SMA actuator can be calculated according to the following.
Area=Force/Maximum stress of SMA=700N/200 Mpa=3.5 mm2
Length=Displacement/0.04=300 mm
Volume=Area*Length=1.05*10−6 m3
Mass (MSMA)=Volume*Density=1.05*10−6*6450 kg=6.77 g

The heat needed to increase the temperature of the SMA up to 100° C. is calculated in accordance with the following.
−Heat=Cp*ΔT*MSMA+Δh*MSMA
Cp: Specific heat=450 J/kg° C.
ΔT: temperature increase=75° C.
Δh: latent heat of transformation=32,000 J/kg
From these calculations, it is determined that to raise the temperature of the SMA actuator to 100° C., the heat required is given by ESMA=356.4 J/axis.

FIG. 26 contains a schematic diagram of one thermoelectric device 21, 22 in accordance with the invention. The heat transfer calculations for the TED are in accordance with the following.

The rate of heat extracted from the cold side QC is given by
QC=S*I*TC−I2R/2−(TH−TC)/θTED

The rate of heat added to the hot side QH is given by
QH=S*I*TC+I2R/2−(TH−TC)/θTED

In these equations,

    • R: electrical resistance of TED
    • I: current
    • S: Seebeck coefficient [Volts/Kelvin]
    • S=Sm*2Nc
    • Nc: Number of p-n element pairs in TED
    • Sm: Material Seebeck coefficient
    • Sm=S0+S1* T+S2*T
    • S0=2.2224*10−5
    • S1=9.306*10−7
    • S2=−9.905*10−10
    • θTED: TED thermal resistance [Kelvin/Watts]
    • θTED=λ/2KmNc
    • λ=L/A: Form factor
    • Km: Material thermal conductivity [Watts/Kelvin*cm]

FIG. 27 contains a schematic diagram of an integrated SMA/TED actuator in accordance with the invention. As illustrated in the figure, the device includes an upper thermoelectric device 21 and a lower thermoelectric device 22. The TEDs 21 and 22 are positioned facing each other with the shape memory alloy (SMA) actuator wire 26 disposed between them. Heat is applied to the SMA actuator 26 by the TEDs to change it length to provide the actuation motion. As illustrated by arrows 79, both TEDs 21 and 22 are biased to provide heat flow toward their inner surfaces 72, 74 and away from their outer surfaces 71, 73, respectively. As a result, heat is applied to the SMA actuator 26 to change its length and provide the required pulling motion. In one embodiment, at least the inner surfaces 72 and 74 of the TEDs 21, 22, respectively, are made of a ceramic material.

In one embodiment, the SMA actuator wire is about 7 mm by 300 mm. In one embodiment, this calls for a TED to be 10 mm by 300 mm is size.

The total heat needed Eneeded is given by
Eneeded=ESMA+Eceramic+Emiscellaneous=(1156.4 α)J

In this equation,

    • ESMA: Heat needed for activating the SMA=356.4 J
    • Eceramic: Heat needed to increase the temperature of the ceramic plate of the TED=800 J
    • Emiscellaneous: Other heat losses (through side openings, etc.)

FIG. 28 is a graph of the rate of heat added to the hot side QH versus hot side temperature with I=10 A, R=3.26 ohms, TC=25° C. and TH=25° C. to 100° C. The rate of heat temperature, and TH increases from 25° C. to 100° C., and TC is assumed to be constant at 25° C. Since the SMA actuator is sandwiched between two elements, the total heat transfer rate is twice the calculated value. In one embodiment, the average QH is about 600 Watts.

FIG. 29 is a schematic diagram of the integrated SMA/TED actuator device of the invention in the actuation mode. As illustrated by the arrows, in the actuation mode, both TEDs 21 and 22 are biased to transfer heat toward their inner surfaces, where the SMA actuator wire 26 is located. As a result, the SMA actuator 26 is heated and changes shape. As illustrated, the cold temperature at the outer surfaces of the TEDs 21, 22 is about 25° C., and the hot temperature at the inner surfaces of both TEDs is about 100° C. Because heat flows from both TEDs 21, 22 toward the SMA actuator 26, the temperature of the actuator 26 is sufficiently high, e.g., 100° C., to cause the SMA actuator 26 to change shape and create the desired actuation motion.

FIG. 30 is a schematic diagram of the integrated SMA/TED actuator device of the invention in the rapid cooling mode. As shown in the figure, in the rapid cooling mode, both TEDs 21 and 22 are biased to cause heat flow from their top surfaces 71, 74 to their bottom surfaces 72, 73. The result is a total net flow of heat away from the top surface of the device, to cool the seat 11. As a result, the temperature at the top surface 71 of the device is about 5° C., the temperature in the middle of the device is about 35° C., and the temperature at the bottom surface 73 of the device is about 81° C. Thus, with both TEDs biased to flow heat toward the bottom of the device, rapid cooling is realized.

As noted above, the rate of heat extracted from the cold side is given by
QC=S*I*TC−I2R/2−(TH−TC)/θTED
Referring to FIG. 30, QC1, the heat extracted from the cold side 71 in TED 21, is given by
QC1=S*I*TC−I2R/2−(TM−TC)/θTED
And the heat extracted from the cold side 74 in TED 22 is given by
QC2=S*I*TM−I2R/2−(TH−TM)/θTED
QC!=QC2
Since QC is dependent on TH an TC, temperature difference of TC and TM is not equal to the temperature difference of TM and TH. For I=5 A, about 54 Watts=170 Btu/hour of cooling power can be achieved with a single axis.

As shown in FIG. 30, heat flows in TED 21 toward the SMA actuator 26, but, heat flows in the TED 22 away from the SMA actuator 26. This results in the temperature at the actuator 26 being at some intermediate level, e.g., 35° C. Because this intermediate temperature at the actuator 26 is relatively low, the actuator 26 does not change shape, and no actuation motion is produced. Hence, in accordance with the invention, in the cooling mode, no actuation motion takes place.

FIG. 31 is a schematic diagram of the integrated SMA/TED actuator device of the invention in the heating mode. As shown in the figure, in the heating mode, both TEDs 21 and 22 are biased to cause heat flow from their bottom surfaces 72, 73 to their top surfaces 71, 74. The result is a total net flow of heat toward the top surface of the device, to heat the seat 11. As a result, the temperature at the top surface 71 of the device is about 81° C., the temperature in the middle of the device is about 35° C., and the temperature at the bottom surface 73 of the device is about 5° C. Thus, with both TEDs biased to flow heat toward the top of the device, heating is realized.

As noted above, the rate of heat added to the hot side is given by
QH=S*I*TC+I2R/2−(TH−TC)/θTED
Referring to FIG. 31, QH1, the heat added to the hot side 74 in TED 22, is given by
QH1=S*I*TC+I2R/2−(TM−TC)/θTED
And the heat added to the hot side 71 in TED 21 is given by
QH2=S*I*TM+I2R/2−(TH−TM)/θTED
QH1=QH2
For I=5 A, about 135 Watts of heating power can be achieved with a single axis.

As shown in FIG. 31, heat flows in TED 22 toward the SMA actuator 26, but, heat flows in the TED 21 away from the SMA actuator 26. This results in the temperature at the actuator 26 being at some intermediate level, e.g., 35° C. Because this intermediate temperature at the actuator 26 is relatively low, the actuator 26 does not change shape, and no actuation motion is produced. Hence, in accordance with the invention, in the heating mode, no actuation motion takes place.

While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made herein without departing from the spirit and scope of the invention as defined in the appended claims.