Vehicle energy harvesting device having a continuous loop of shape memory alloy material

An energy harvesting system includes a heat engine and a component. The heat engine includes first and second regions, a conduit, and a shape memory alloy (SMA) material. The conduit extends along a central axis. The SMA material surrounds the conduit and is disposed in one of the regions. The SMA material is radially spaced from a secondary axis that surrounds the central axis. A localized region of the SMA material changes crystallographic phase from martensite to austenite and contract in response to exposure to the first temperature. The localized region of the SMA material also changes crystallographic phase from austenite to martensite and expands in response to exposure to the second temperature. The SMA material rotates about the secondary axis in response to the contraction and expansion of the localized region of the SMA material. Rotation of the SMA material about the secondary axis drives the component.

TECHNICAL FIELD

The present invention generally relates to a vehicle, and more specifically, to an energy source for the vehicle and vehicle accessories.

BACKGROUND

Vehicles are traditionally powered by engines and/or batteries, which power the vehicle and provide the power to charge a battery of the vehicle. The battery provides power for starting the engine and for operating various vehicle accessories. During operation, the engine produces a large quantity of excess heat, i.e., excess thermal energy that is typically dissipated into the atmosphere and lost. Advancements in technology and desire for driver conveniences have led to additional power loads from the accessory systems. The increased power loads have led to greater demand on the vehicle power sources. In addition, a large portion of the power from the vehicle's power sources is lost as heat.

However, arrangements for extending the fuel economy of a vehicle are desirable in light of the growing concern for fuel efficient vehicles. Therefore, arrangements that reduce the power load and/or increase the efficiency of the vehicle's traditional power sources, such as the battery and the engine are desirable.

SUMMARY

A heat engine is configured to be operatively connected to a component. The heat engine includes a first region, a second region, a conduit, and at least one piece of shape memory alloy material. The first region is at one of a first temperature and a second temperature. The second region is spaced from the first region and is at the other of the first temperature and the second temperature. The conduit is disposed in the first region and extends along a central axis. The at least one piece of shape memory alloy material circumferentially surrounds the conduit about the central axis and is configured to be at least partially disposed in one of the first region and the second region. The at least one piece of shape memory alloy material is radially spaced from a secondary axis that circumferentially surrounds the central axis. The at least one localized region of the at least one piece of shape memory alloy material is configured to selectively change crystallographic phase from martensite to austenite and thereby circumferentially contract in response to exposure to the first temperature. The at least one localized region of the at least one piece of shape memory alloy material is also configured to selectively change crystallographic phase from austenite to martensite and thereby circumferentially expand in response to exposure to the second temperature. The at least one piece of shape memory alloy material is configured to rotate about the secondary axis in response to the contraction and expansion of the at least one localized region of the at least one piece of shape memory alloy material such that the at least one localized region of the at least one piece of shape memory alloy material moves into and out of the first and second regions.

An energy harvesting system includes a heat engine and a component. The heat engine includes a first region, a second region, a conduit, and at least one piece of shape memory alloy material. The first region is at one of a first temperature and a second temperature. The second region is spaced from the first region and is at the other of the first temperature and the second temperature. The conduit is disposed in the first region and extends along a central axis. The at least one piece of shape memory alloy material circumferentially surrounds the conduit about the central axis and is configured to be at least partially disposed in one of the first region and the second region. The at least one piece of shape memory alloy material is radially spaced from a secondary axis that circumferentially surrounds the central axis. The at least one localized region of the at least one piece of shape memory alloy material is configured to selectively change crystallographic phase from martensite to austenite and thereby circumferentially contract in response to exposure to the first temperature. The at least one localized region of the at least one piece of shape memory alloy material is also configured to selectively change crystallographic phase from austenite to martensite and thereby circumferentially expand in response to exposure to the second temperature. The at least one piece of shape memory alloy material is configured to rotate about the secondary axis in response to the contraction and expansion of the at least one localized region of the at least one piece of shape memory alloy material such that the at least one localized region of the at least one piece of shape memory alloy material moves into and out of the first and second regions. The component is operatively connected to the at least one shape memory alloy material such that rotation of the shape memory alloy material about the secondary axis drives the component.

An energy harvesting system includes a heat engine and a component. The heat engine includes a first region, a second region, a conduit, and at least one wire. The first region is at one of a first temperature and a second temperature. The second region is spaced from the first region and is at the other of the first temperature and the second temperature. The conduit is disposed in the first region and extends along a central axis. The at least one wire forms a continuous loop and circumferentially surrounds the conduit about the central axis. The wire is configured to be at least partially disposed in one of the first region and the second region. The wire is radially spaced from a secondary axis that circumferentially surrounds the central axis. At least one localized region of the at least one wire is configured to selectively change crystallographic phase from martensite to austenite and thereby circumferentially contract in response to exposure to the first temperature. The at least one localized region of the at least one wire is also configured to selectively change crystallographic phase from austenite to martensite and thereby circumferentially expand in response to exposure to the second temperature. The at least one wire is configured to rotate about the secondary axis in response to the contraction and expansion of the at least one localized region of the at least one wire such that the at least one localized region of the at least one wire moves into and out of the first and second regions. The component is operatively connected to the at least one wire such that rotation of the wire about the secondary axis drives the component.

DETAILED DESCRIPTION

Referring to the Figures, wherein like reference numerals refer to like elements, a vehicle is shown generally at10inFIG. 1. The vehicle10includes an energy harvesting system12. The energy harvesting system12may include a heat engine14and a driven component16.

Referring to theFIG. 2, the heat engine14includes a shape memory alloy material22and is operatively disposed in a first region18and a second region20. The heat engine14is configured to convert thermal energy, e.g., heat, to mechanical energy and from mechanical energy to electrical energy. More specifically, the energy harvesting system12utilizes a temperature differential between the first region18and the second region20to generate mechanical and/or electrical energy via the shape memory alloy material22, as explained in more detail below.

Referring again toFIG. 1, the vehicle10defines a compartment24which may house power and drive sources for the vehicle10, i.e., an engine and transmission (not shown), which generate heat. The compartment24may or may not be enclosed from the surrounding environment, and may include one or more regions and components such as an exhaust pipe, a catalytic converter, shock absorbers, brakes, and any other region where energy is dissipated, such as in a passenger compartment or a battery compartment, i.e., in an electric vehicle.

The energy harvesting system12is located at least partially within the compartment24. The compartment24includes the first region18, having a first temperature, and the second region20, having a second temperature, different from the first temperature. The first temperature may be greater than the second temperature.

The first region18and the second region20may be spaced from one another, or be separated by a sufficient heat exchange barrier26, such as a heat shield, a Peltier device, and the like. The heat exchange barrier26may be employed to separate the compartment24into the first region18and the second region20such that a desired temperature differential between the first region18and the second region20is achieved. Fluid within the first region18and the second region20of the energy harvesting system12may be gas, liquid, or combinations thereof. It should be appreciated that the regions18,20are not limited to using fluid to promote heat transfer between the regions18,20and the shape memory alloy material22. Instead, the regions18,20may also be configured as one or more objects, i.e., a surface and the like, that promotes heat transfer between the object(s) having the different fluid regions18,20and the to the shape memory alloy material22. When the heat exchange barrier26disposed between the first and second regions18,20is a Peltier device, the heat exchange barrier26is configured to generate heat on one side of the barrier26and to cool on an opposing side of the barrier26. The first and second regions18,20may be fluidly connected to a pair of cylinder heads (not shown) that capture the energy given off from the respective region18,20. A pump may be disposed in fluid communication with at least one of the first and second regions18,20and the cylinder heads to circulate and move the fluid. The energy harvesting system12may be configured to utilize temperature differentials between the first and second regions18,20in the vehicle10in areas such as, proximate a catalytic converter, a vehicle battery, a transmission, brakes, suspension components, i.e., a shock absorber, and/or a heat exchanger, i.e., a radiator. Additionally, the energy harvesting system12may be configured to utilize temperature differentials between the first and second regions18,20in the vehicle10within a battery compartment24for an electric vehicle or within the heat exchanger. It should be appreciated that the energy harvesting system12may be configured to utilize temperature differentials in other areas of the vehicle, as known to those skilled in the art. One skilled in the art would be able to determine areas having an associated temperature differential and an appropriate position for the heat engine14of the energy harvesting system12to take advantage of the temperature differentials.

The compartment24may be an engine compartment, where fluid within the first region18and the second region20is air. However, it should be appreciated that other fluids, as known to those skilled in the art, may also be used within the compartment24. Further, the heat engine14and the component16may be surrounded by a vented housing28. The housing28may define cavities (not shown) through which electronic components, such as wires may pass.

Referring toFIG. 2, the shape memory alloy material22is disposed in thermal contact, or heat exchange relationship, with each of the first and second regions18,20. The shape memory alloy material22of the heat engine14has a crystallographic phase changeable between austenite and martensite in response to exposure to the first and second temperatures of the first and second regions18,20. As used herein, the terminology “shape memory alloy” (SMA) refers to alloys which exhibit a shape memory effect. That is, the shape memory alloy material22may undergo a solid state phase change via molecular rearrangement to shift between a martensite phase, i.e., “martensite”, and an austenite phase, i.e., “austenite”. Stated differently, the shape memory alloy material22may undergo a displacive transformation rather than a diffusional transformation to shift between martensite and austenite. A displacive transformation is when a structural change occurs by the coordinated movement of atoms (or groups of atoms) relative to their neighbors. In general, the martensite phase refers to the comparatively lower-temperature phase and is often more deformable than the comparatively higher-temperature austenite phase. The temperature at which the shape memory alloy material22begins to change from the austenite phase to the martensite phase is known as the martensite start temperature, Ms. The temperature at which the shape memory alloy material22completes the change from the austenite phase to the martensite phase is known as the martensite finish temperature, Mf. Similarly, as the shape memory alloy material22is heated, the temperature at which the shape memory alloy material22begins to change from the martensite phase to the austenite phase is known as the austenite start temperature, As. The temperature at which the shape memory alloy material22completes the change from the martensite phase to the austenite phase is known as the austenite finish temperature, Af.

Therefore, the shape memory alloy material22may be characterized by a cold state, i.e., when a temperature of the shape memory alloy material22is below the martensite finish temperature Mfof the shape memory alloy material22. Likewise, the shape memory alloy material22may also be characterized by a hot state, i.e., when the temperature of the shape memory alloy material22is above the austenite finish temperature Afof the shape memory alloy material22.

In operation, shape memory alloy material22that is pre-strained or subjected to tensile stress can change dimension upon changing crystallographic phase to thereby convert thermal energy to mechanical energy. That is, the shape memory alloy material22may change crystallographic phase from martensite to austenite and thereby dimensionally contract if pseudoplastically pre-strained so as to convert thermal energy to mechanical energy. Conversely, the shape memory alloy material22may change crystallographic phase from austenite to martensite and if under stress thereby dimensionally expand so as to also convert thermal energy to mechanical energy.

Pseudoplastically pre-strained refers to stretching the shape memory alloy material22while in the martensite phase so that the strain exhibited by the shape memory alloy material22under that loading condition is not fully recovered when unloaded, where purely elastic strain would be fully recovered. In the case of shape memory alloy material22, it is possible to load the material such that the elastic strain limit is surpassed and deformation takes place in the martensitic crystal structure of the material prior to exceeding the true plastic strain limit of the material. Strain of this type, between those two limits, is pseudoplastic strain, called such because upon unloading it appears to have plastically deformed, but when heated to the point that the shape memory alloy material22transforms to its austenite phase, that strain can be recovered, returning the shape memory alloy material22to the original length observed prior to any load was applied. Shape memory alloy material22may be stretched before installation into the heat engine14, such that a nominal length of the shape memory alloy material22includes that recoverable pseudoplastic strain, which provides the motion used for actuating/driving the heat engine14. Without pre-stretching the shape memory alloy material22, little deformation would be seen during phase transformation.

The shape memory alloy material22may have any suitable composition. In particular, the shape memory alloy material22may include an element selected from the group including cobalt, nickel, titanium, indium, manganese, iron, palladium, zinc, copper, silver, gold, cadmium, tin, silicon, platinum, gallium, and combinations thereof. For example, suitable shape memory alloys22may include nickel-titanium based alloys, nickel-aluminum based alloys, nickel-gallium based alloys, indium-titanium based alloys, indium-cadmium based alloys, nickel-cobalt-aluminum based alloys, nickel-manganese-gallium based alloys, copper based alloys (e.g., copper-zinc alloys, copper-aluminum alloys, copper-gold alloys, and copper-tin alloys), gold-cadmium based alloys, silver-cadmium based alloys, manganese-copper based alloys, iron-platinum based alloys, iron-palladium based alloys, and combinations thereof. The shape memory alloy material22can be binary, ternary, or any higher order so long as the shape memory alloy material22exhibits a shape memory effect, e.g., a change in shape orientation, damping capacity, and the like. A skilled artisan may select the shape memory alloy material22according to desired operating temperatures within the compartment24(FIG. 1), as set forth in more detail below. In one specific example, the shape memory alloy material22may include nickel and titanium.

Referring again toFIGS. 1 and 2, the driven component16of the energy harvesting system12may be configured to be driven by the mechanical energy or power generated from the conversion of thermal energy to mechanical energy within the heat engine14. In particular, the aforementioned dimensional contraction and the dimensional expansion of the shape memory alloy material22may drive the component16. The component16may be a simple mechanical device, such as a generator, a fan, a clutch, a blower, a pump, a compressor, and combinations thereof. It should be appreciated that the component16is not limited to these devices, as any other device known to those skilled in the art may also be used. The component16may be operatively connected to the heat engine14such that the component16is driven by the heat engine14. More specifically, the component16may be part of an existing system within the vehicle10such as a heating or cooling system and the like. Alternatively, heat engine14may be configured such that the component16is at least partially incorporated therein. More specifically, heat engine14may be configured such that the component16is not an entirely separate device. The mechanical energy provided by the shape memory alloy material22, as described above, may drive the component16or may provide assistance to other systems of the vehicle10in driving the component16. Driving the component16with mechanical energy provided by the heat engine14may also allow an associated existing system within the vehicle10to be decreased in size and/or capacity or eliminated entirely. For example, the heat engine14may be configured to assist in driving a fan for the heating and/or cooling system, allowing a capacity of the main heating and cooling system to be decreased, while providing weight and energy savings. Additionally, the mechanical energy produced by the energy harvesting system12may be used to directly drive the component16or be stored for later use. Therefore, the energy harvesting system12may be configured to provide additional energy to operate the vehicle10and reduce the load on a main energy source for driving the vehicle10. Thus, the energy harvesting system12increases the fuel economy and range of the vehicle10. Also, the energy harvesting system12may be configured to operate autonomously such that no input from the vehicle10is required.

When the component16is a generator, the component/generator16may be configured to convert mechanical energy from the heat engine14to electricity, as shown as30inFIGS. 1 and 2. The component/generator16may be any suitable device configured to convert mechanical energy to electricity30. For example, the component/generator16may be an electrical generator that converts mechanical energy to electricity30using electromagnetic induction. The component/generator16may include a rotor (not shown) that rotates with respect to a stator (not shown) to generate electricity30. The electricity30generated by the component/generator16may then be used to assist in powering one or more systems within the vehicle10.

Additionally, referring toFIG. 1, the energy harvesting system12may include an electric control unit32(ECU) that is configured to control the first and second temperature of the fluid in the first and second regions18,20, respectively. The ECU32may be operatively connected to the vehicle10. The ECU32may be a computer that electronically communicates with one or more controls and/or sensors of the energy harvesting system12. For example, the ECU32may communicate with temperature sensors within the first and/or second regions18,20, a speed regulator of the component16, fluid flow sensors, and/or meters configured for monitoring electricity30generation of the component/generator16. Additionally, the ECU32may be configured to control the harvesting of energy under predetermined conditions of the vehicle10, e.g., after the vehicle10has operated for a sufficient period of time such that a temperature differential between the first region18and the second region20is at an optimal differential. It should be appreciated that other predetermined conditions of the vehicle10may also be used, as known to those skilled in the art. The ECU32may also be configured to provide an option to manually override the heat engine14and allow the energy harvesting system12to be turned off. A clutch (not shown) may also be controlled by the ECU32to selectively disengage the heat engine14from the component16.

As also shown inFIG. 1, the energy harvesting system12may also include a transfer medium34configured to convey electricity30from the energy harvesting system12. In particular, the transfer medium34may convey electricity30from the component16. The transfer medium34may be, for example, a power line or an electrically-conductive cable. The transfer medium34may convey electricity30from the generator16to a storage device36, e.g., a battery for the vehicle. The storage device36may be located proximate to, but separate from, the vehicle10. Such a storage device36may allow the energy harvesting system12to be utilized, for example, with a parked vehicle10. In another example, the energy harvesting system12may be configured to take advantage of a temperature differential created by a sun load on a hood for the corresponding compartment24and convert the mechanical energy created from the temperature differential into electrical energy30to be stored within the storage device36.

It is to be appreciated that for any of the aforementioned examples, the vehicle10and/or the energy harvesting system12may include a plurality of heat engines14and/or a plurality of component16. That is, one vehicle10may include more than one heat engine14and/or component16. For example, one heat engine14may drive more than one components16. Likewise, the vehicle10may be configured to include more than one energy harvesting system12, where each energy harvesting system12includes at least one heat engine14and at least one component16. The use of multiple heat engines14may take advantage of multiple regions of temperature differentials throughout the vehicle10. Whether the energy from the energy harvesting system12is used to drive a component16directly or is stored for later usage, the energy harvesting system12provides additional energy to the vehicle10and reduces the load on the main energy sources for driving the vehicle10. Thus, the energy harvesting system12increases the fuel economy and range for the vehicle10. As described above, the energy harvesting system12may operate autonomously requiring no input from the vehicle10.

Further, the shape memory alloy material22may change both modulus and dimension upon changing crystallographic phase to thereby convert thermal energy to mechanical energy. More specifically, the shape memory alloy material22, if pseudoplastically pre-strained, may dimensionally contract upon changing crystallographic phase from martensite to austenite and may dimensionally expand, if under tensile stress, upon changing crystallographic phase from austenite to martensite to thereby convert thermal energy to mechanical energy. Therefore, when a temperature differential exists between the first temperature of the first region18and the second temperature of the second region20, i.e., when the first region18and the second region20are not in thermal equilibrium, respective localized regions66,68of the shape memory alloy material22disposed within the first and/or second regions18,20may respectively dimensionally expand and contract upon changing crystallographic phase between martensite and austenite.

Referring to the energy harvesting system12ofFIG. 1, the component16is driven by the heat engine14. That is, mechanical energy resulting from the conversion of thermal energy by the shape memory alloy material22may drive the component16. In particular, the aforementioned dimensional contraction and the dimensional expansion of the shape memory alloy material22, coupled with the changes in modulus may drive the component16.

In one variation, shown inFIGS. 2 and 3, the heat engine14may include a conduit38and at least one wire40. The conduit38is disposed in the first region18and extends along a central axis42. The conduit38may be an exhaust pipe, or any other pipe, channel, and the like that is configured to radiate heat at the first temperature. The heat engine14may be arranged about the conduit38to take advantage of the temperature differential between the heat radially emitted from the conduit38, i.e., the first region18, and an exterior location44, i.e., the second region20, radially spaced from the conduit38. Fluid may flow through the conduit, as indicated by arrow39, to provide a heat source.

Each of a plurality of the wires40form a continuous loop and circumferentially surround the conduit38about the central axis42and are each configured to be at least partially disposed in one of the first and second regions18,20. The wires40may be configured to have any suitable cross-sectional shape. For example, each of the wires40may be formed as at least one elongated strand of wire40, where each elongated strand of wire50has a cross-section that is round, rectangular, octagonal, ribbon, strip, helical coils, or any other shape known to those skilled in the art. Additionally, the wires40may be formed as a braid, cable, and the like.

The plurality of wires40circumferentially surround conduit38as a continuous loop to form a torus46. The torus46is generally doughnut shaped and presents a surface48of revolution that is generated by revolving a circle about a central axis42. A cross-sectional view of the torus46ofFIG. 2, taken along line3-3, is shown inFIG. 3. A total of five wires40are illustrated inFIGS. 2 and 3. It should be appreciated, however, that more or less wires, as known to those skilled in the art, may also be used.

Referring toFIG. 3, the wires40are disposed on or near the surface48of the torus46and circumferentially surround a secondary axis50. More specifically, the torus46is configured to provide a structure that would allow the surface48to continuously rotate in a first axial direction52about the secondary axis50, relative to the conduit38, as indicated by the arrow inFIGS. 2 and 3, in response to the application of an initial force. More specifically, the torus includes a material56, or skin, that radially surrounds the secondary axis50. Each wire40is disposed in the material56. Accordingly, portions of the material56contract and expand along with the contraction and expansion of the respective localized regions66,68of the wires40. The secondary axis50may extend generally transverse to and surround the central axis42. The wires40may be embedded in the material56that is flexible, resilient, and/or attached to another structure that would allow the surface48to rotate, i.e., a looped spring, flexible cable housing, and the like. The wires40may be circumferentially spaced from one another to surround the secondary axis50. It should be appreciated that the proximity of the wires40to the surface48and/or the spacing of the wires40to one another may differ than that shown, as known to those skilled in the art.

The wires40are formed from the shape memory alloy material22. The wires40that are closest to the central axis42have a shorted length to provide a smaller diameter than the wires40that are farthest from the central axis42. This is because the wires40that are closest to the central axis42are contracted and those that are progressively farther away are stretched or expanded. When placed around the conduit38, the wires40that are closest to the central axis42and located within the first region18are heated at the first temperature and, therefore contract. Conversely, the wires40that are radially farther away from the central axis42and located within the second region20are at the second temperature, which is less than the first temperature, such that the wires40may be environmentally cooled and expanded. The wires40are configured to rotate along with the surface48of the torus46in the first axial direction52, about the secondary axis50, such that the wires40are continuously moving into and out of the first and second regions18,20as a result of being heated (contracted) and being cooled (expanded). More specifically, during rotation, the wires40closest to the central axis42continuously rotate about the secondary axis50to move further away from the central axis42, while the wires40that are farthest from the central axis42continuously rotate in the first axial direction52to move closer to the central axis42. Kinetic energy that results from this continuous rotation may be harvested from the surface48of the torus46, as known to those skilled in the art.

The torus46may move or roll axially along the conduit38, i.e., along the central axis42, during the continuous rotation about the secondary axis50. Alternatively, referring toFIG. 2, at least one restraining element58may be configured to prevent movement of the torus46along the conduit38in the direction of the central axis42. By way of a non-limiting example, protrusions60may be formed on an exterior of the conduit38and the torus46may be at least partially retained between the protrusions60. By way of another non-limiting example, the conduit38may define a groove or channel (not shown) that surrounds the central axis42and the torus46may be at least partially disposed and retained within the groove. The restraining element58may be any type of element configured to restrain the torus46to prevent axial movement, as known to those of skill in the art.

The torus46may alternatively be formed from a continuous thin film (not shown) of shape memory alloy material22, as known to those skilled in the art. The continuous thin film of the shape memory alloy material22may be resilient and configured to rotate about the secondary axis50in response to the expansion and contraction of the localized regions66,68of the shape memory alloy material22.

As the shape memory alloy material22moves between thermal contact or heat exchange relation with the first region18and the second region20, the shape memory alloy material22dimensionally expands and contracts. Additionally, the modulus of the shape memory alloy material22changes as the shape memory alloy material22moves between thermal contact or heat exchange relation with the first region18and the second region20. As described above, in response to the dimensionally expanding and contracting shape memory alloy material22and the accompanying changes in modulus, the surface48of the torus46is driven to rotate in the first axial direction52. It should be appreciated that the direction indicated for the first axial direction52may be opposite that indicated inFIGS. 2 and 3.

In operation, with reference to the energy harvesting system12ofFIG. 1, and described with respect to the example configuration of the shape memory alloy material22shown inFIGS. 2 and 3, at least one wire40including the shape memory alloy material22may be immersed in, or be in heat exchange relation with, the first region18while at least one other wire40may be immersed in, or be in heat exchange relation with, the second region20. As one wire40, that includes the shape memory alloy material22, dimensionally expands when under stress and in contact with the second region20, another wire40, that includes the shape memory alloy material22that is pseudoplastically pre-strained and in contact with the first region18, dimensionally contracts. Alternating dimensional contraction and expansion of the torus46form of the shape memory alloy material22, upon exposure to the temperature difference between the first region18and the second region20, may cause the shape memory alloy material22to convert potential mechanical energy to kinetic mechanical energy, thereby rotating the surface48of the torus46and converting thermal energy to mechanical energy to drive the component16.

Referring again toFIG. 2, the torus46may be connected to the component16such that the rotation of the torus46about the secondary axis50may drive the component16. Speed of rotation of the torus46about the secondary axis50, relative to the component16, may optionally be modified by one or more gear sets. By way of a non-limiting example, a driven member62may be configured for rotation about a tertiary axis64. The driven member62operatively interconnects the shape memory alloy material22and the component16. The driven component16rotatably engages the torus46such that rotation of the shape memory alloy material22about the secondary axis50rotates the driven component about the tertiary axis64to drive the component. The tertiary axis64may extend generally transverse to the secondary axis50and the central axis42. The driven member62may be a wheel, gear sets, or any other driven member62configured for translating rotation from the torus46to drive the component16, as known to one of skill in the art.

FIG. 4illustrates a second embodiment of a heat engine114for use with the energy harvesting system12for the vehicle10(shown inFIG. 1). The heat engine114has a similar arrangement to the heat engine14described above inFIGS. 2 and 3. The heat engine114may include a torus146where each of a plurality of wires140may extend as a continuous loop about the secondary axis50. The torus146presents a surface148of revolution that is generated by revolving a circle about the central axis42. More specifically, each of the wires140is formed as a circle. The circles are disposed in circumferentially spaced relationship to one another to surround the conduit38about the central axis42to form the torus146. The wires140are formed from the shape memory alloy material22. More specifically, the torus includes the material56that radially surrounds the secondary axis50. Each wire40is disposed in the skin material. Accordingly, portions of the material56contract and expand along with the contraction and expansion of the respective localized regions66,68of the wires40The conduit38is within the first region18at the first temperature. The wires140are configured such that localized regions66,68of each of the wires140are operatively disposed in each of the first and second regions18,20. In this embodiment, the portions of the wires140that are closest to the central axis42are heated (contracted) and the portions of the wire140that are further away from the central axis42are cooled (expanded) when the torus146surrounds the conduit38. When the initial force54is applied to the torus146, the torus146begins to rotate continuously in the first axial direction52. The kinetic energy that results from this continuous rotation may be harvested from the surface148of the torus146, as known to those skilled in the art. Fluid may flow through the conduit38, as indicated by the arrow39.

The torus146may move or roll axially along the conduit38, i.e., along the central axis42, during the continuous rotation about the secondary axis50. Alternatively, referring toFIG. 4, at least one restraining element158may be configured to prevent movement of the torus146along the conduit38in the direction of the central axis42. By way of a non-limiting example, protrusions160may be formed on an exterior of the conduit38and the torus146may be at least partially retained between the protrusions160. By way of another non-limiting example, the conduit38may define a groove or channel (not shown) that surrounds the central axis42and the torus146may be at least partially disposed and retained within the groove. The restraining element158may be any type of element configured to restrain the torus146to prevent axial movement, as known to those of skill in the art.

As the shape memory alloy material22moves between thermal contact or heat exchange relation with the first region18and the second region20, the shape memory alloy material22dimensionally expands and contracts. Additionally, the modulus of the shape memory alloy material22changes as the localized regions66,68of the shape memory alloy material22move between thermal contact or heat exchange relation with the first region18and the second region20. In response to dimensionally expanding and contracting the localized regions66,68of the shape memory alloy material22and the accompanying changes in modulus, the surface148of the torus146rotates about the secondary axis50, relative to the conduit38and the central axis42.

The torus146may be operatively connected to the component16such that the rotation of the surface148of the torus146about the secondary axis50may drive the component16, i.e., via a driven member162and the like. Speed of rotation of the surface148of the torus146, relative to the component16, may optionally be modified by one or more gear sets.

Referring again toFIG. 4, the torus146may be connected to the component16such that the rotation of the torus146about the secondary axis50drives the component16. Speed of rotation of the torus146about the secondary axis50, relative to the component16, may optionally be modified by one or more gear sets. By way of a non-limiting example, a driven member162may be configured for rotation about a tertiary axis164. The driven member162operatively interconnects the shape memory alloy material22and the component16. The driven component rotatably engages the torus146such that rotation of the shape memory alloy material22about the secondary axis50rotates the driven component about the tertiary axis164to drive the component16. The tertiary axis164may extend generally transverse to the secondary axis50and the central axis42. The driven member162may be a wheel, gear sets, or any other driven member162configured for translating rotation from the torus146to drive the component16, as known to one of skill in the art.

FIG. 5illustrates a third embodiment of a heat engine214for use with the energy harvesting system12for the vehicle, shown inFIG. 1. In this embodiment, the heat engine214includes a continuously looped helical spring70that includes a plurality of coils72extending along the secondary axis50. The continuously looped helical spring70circumferentially extends about the conduit38and surrounds the central axis42. Therefore, the coils72surround the central axis42in generally circumferentially spaced relationship to one another. The continuously looped helical spring70is formed from wire240. The wire240is formed from the shape memory alloy material22. An inner portion74of the looped helical spring70that is closest to the central axis42, i.e., the localized region66, experiences less strain than an outer portion76of the looped helical spring70furthest away from the central axis42, i.e., another localized region68, providing a required strain gradient. As a result, when the continuously looped helical spring70surrounds the conduit38, the inner portion74attempts to contract, due to heating of the inner portion74. When an initial force54is applied to the continuously looped helical spring70, the coils72of the looped helical spring70begin to rotate about the secondary axis50in the first axial direction52, relative to the central axis42, such that the localized region66of the inner portion74is heated and contracted toward the central axis42, while the other localized region68of the outer portion76is cooled and stretched away from the central axis42. As the localized region66contracts, the other localized region68of the coil72that is expanded is pulled toward the central axis42while the localized region66of the coil72is expelled away from the central axis42.

To prevent this heat engine214from moving or rolling axially along the conduit38, the heat engine214may include a restraining element258that is configured to axially restrain the continuously looped helical spring70, as known to those skilled in the art. If the looped helical spring70is held axially stationary, relative to the central axis42, the coils72would snake or otherwise rotate about the central axis42in a second axial direction53, transverse to the direction of rotation of the first axial direction52, while providing another form of kinetic energy to be harvested. By way of a non-limiting example, protrusions260may be formed on an exterior of the conduit38and the continuously looped helical spring70may be at least partially retained between the protrusions260. By way of another non-limiting example, the conduit38may define a groove or channel (not shown) that surrounds the central axis42and the continuously looped helical spring70may be at least partially disposed and retained within the groove. The restraining element258may be any type of element configured to restrain the continuously looped helical spring70to prevent axial movement along the central axis42, as known to those of skill in the art.

As the shape memory alloy material22moves between thermal contact or heat exchange relation with the first region18and the second region20, the shape memory alloy material22dimensionally expands and contracts. Additionally, the modulus of the shape memory alloy material22changes as the shape memory alloy material22moves between thermal contact or heat exchange relation with the first region18and the second region20. In response to the dimensionally expanding and contracting shape memory alloy material22and the accompanying changes in modulus, the coils72of the looped helical spring rotate axially, relative to the central axis42.

The temperature differential between the first region18and the second region20causes the shape memory alloy to sufficiently dimensionally contract or expand in order to rotate the coils72of the looped helical spring, after the application of the initial force54to the coils72of the looped helical spring.

The looped helical spring may be operatively connected to the component16such that the rotation of the coils72of the looped helical spring may drive the component16. Speed of rotation of the coils72of the continuously looped helical spring70relative to the component16may optionally be modified by one or more gear sets (not shown).

Referring again toFIG. 5, the continuously looped helical spring70may be operatively connected to the component16such that the rotation of the continuously looped helical spring70about the secondary axis50may drive the component16. Speed of rotation of the continuously looped helical spring70about the secondary axis50, in the first axial direction52, and about the central axis42, in a second axial direction53, relative to the component16, may optionally be modified by one or more gear sets. By way of a non-limiting example, a driven member262may be configured for rotation about a tertiary axis264. The driven member262operatively interconnects the shape memory alloy material22and the component16. The driven component16rotatably engages the continuously looped helical spring70such that rotation of the shape memory alloy material22about the secondary axis50rotates the driven component16about the tertiary axis264to drive the component16. The tertiary axis264may extend generally parallel to the central axis42. The driven member262may be a pinion78having a plurality of radially extending teeth80that circumferentially surround the tertiary axis264. The teeth80are configured to mesh with corresponding coils72of the continuously looped helical spring70, as the continuously looped helical spring70rotates about the secondary axis50, in the first axial direction52, and about the central axis42, in the second axial direction53, to rotate the pinion78about the tertiary axis264. The pinion78is operatively connected to the component16such that rotation of the pinion78about the tertiary axis264drives the component16. It should be appreciated that any other driven member262configured for translating rotation from the continuously looped helical spring70to drive the component16, as known to one of skill in the art, may also be used.