The present disclosure generally relates to a drying system for an interior space of a housing, such as for a lamp assembly.
Lenses of lamp assemblies, such as vehicle headlamp assemblies, may become fogged due to an accumulation of moisture within the assembly. Desiccants are sometimes used to absorb moisture in lamp assemblies. Desiccants reach a maximum capacity at which they are unable to further absorb moisture.
Rechargeable desiccants, sometimes referred to as regenerating desiccants or reusable desiccants, may be “recharged”, also referred to as “regenerated”, by heating the desiccant to release the absorbed moisture. The rechargeable desiccant then has capacity to continue absorbing moisture.
Configuring a drying system with a rechargeable desiccant is challenging in many applications due to space constraints. Minimizing power consumption and added weight are also considerations, especially in vehicle applications. Drying systems disclosed herein include a shape memory alloy actuator to control venting of an interior space of the assembly. A shape memory alloy actuator provides a low weight, and relatively low power consumption solution. In some embodiments, power consumption is minimized by integrating heating of the shape memory alloy actuator and the desiccant.
A drying system comprises an assembly that includes a housing defining an interior space. For example, the assembly may be a lamp assembly, such as for a vehicle lamp assembly having a lens mounted to the housing at the interior space. In other examples, the assembly may be a sensor assembly having an emitting or receiving component at the interior space for which moisture could affect performance or aesthetics.
The housing has an inner wall that divides the interior space into the inner chamber and the outer chamber. The inner wall has a first opening through which the inner chamber communicates with the outer chamber. The housing has an outer wall with the outer chamber between the inner wall and the outer wall, and with a second opening in the outer wall. A rechargeable desiccant is disposed in the outer chamber. A door is disposed in the outer chamber and is configured to be movable between a first position and a second position. The door is configured to at least partially seal the second opening and unseal the first opening when in the first position, and at least partially seal the first opening and unseal the second opening when in the second position. An actuator is operatively connected to the door and is configured to move the door between the first position and the second position. The actuator is formed from a shape memory alloy transitionable between a first state and a second state in response to a change in temperature of the shape memory alloy. In some cases, the change in temperature is due to electrical energizing of the actuator. The shape memory alloy transitions between the first state and the second state to move the door from the first position to the second position.
Accordingly, when the door is in the first position, the exterior environment is blocked from both chambers, and the desiccant removes humidity from both chambers. When the door is in the second position, the inner chamber is sealed, protecting the inner chamber from moisture, while the outer chamber is in communication with the exterior environment, allowing moisture released from the desiccant during regeneration of the desiccant to be expelled from the outer chamber to the exterior environment. In one or more embodiments, a biasing spring biases the door to the first position. Accordingly, the first position is maintained in the absence of any electrical power. In some of these embodiments, power remains on to the actuator, or at least intermittently on, to keep the door from returning to the first position during recharging of the desiccant.
In one or more embodiments, the actuator is configured as a wire that contracts in length in response to the change in temperature. For example, a first end of the actuator may be anchored to the housing and a second end of the actuator may be anchored to the door. The door may be pivotably secured to the housing and pivot about a pivot axis when the door moves from the first position to the second position. Such pivoting motion may be referred to as articulation.
In one or more embodiments, heating of the shape memory alloy actuator and the desiccant is integrated. For example, electrical power may be provided to the shape memory alloy to increase the temperature of the shape memory alloy to a predetermined temperature at or above which the shape memory alloy transitions from the first state to the second state. The rechargeable desiccant may be disposed in sufficient proximity to the actuator such that heat from the actuator heats the rechargeable desiccant to remove moisture absorbed by the rechargeable desiccant. Stated differently, heat that radiates from the heated actuator heats the rechargeable desiccant. No separate heating element for the desiccant is used, and, accordingly, no separate electric power circuit for heating the rechargeable desiccant is needed. Instead, a power source may be selectively connectable to the actuator to electrically energize the actuator, thereby heating the shape memory alloy such that the shape memory alloy transitions from the first state to the second state. An electronic controller is operable to selectively connect the power source to the actuator, such as when desiccant recharging is to be performed.
Alternatively, in one or more other embodiments where heating of the shape memory alloy actuator and the desiccant is integrated, a heating element is disposed in the outer chamber and is electrically energizable to heat the rechargeable desiccant sufficiently to remove moisture absorbed by the rechargeable desiccant. The actuator is disposed in sufficient proximity to the heating element such that the shape memory alloy is transitionable from the first state to the second state in response to heat from the heating element. Stated differently, heat that radiates from the heating element to heat the rechargeable desiccant also causes a temperature change in the shape memory alloy to cause the transition to the second state, and the resulting movement of the door to the second position. No separate electric power circuit for heating the shape memory alloy is needed. Instead, a power source is selectively connectable to the heating element to electrically energize the heating element, and an electronic controller is operable to selectively connect the power source to the heating element.
In one or more embodiments, the rechargeable desiccant and the shape memory alloy are separately electrically energized. For example, the drying system may include a heating element disposed in the outer chamber and electrically energizable to heat the rechargeable desiccant sufficiently to remove moisture absorbed by the rechargeable desiccant. A power source may be selectively connectable to the actuator to electrically energize the actuator, thereby heating the shape memory alloy such that the shape memory alloy transitions from the first state to the second state, so that the door is in the second position when the heating element is energized. The power source may be selectively connectable to the heating element separately from the actuator to electrically energize the heating element. An electronic controller may be operable to selectively connect the power source to the actuator, and to separately selectively connect the power source to the heating element.
In other embodiments, the drying system is configured so that the power need not remain on to the actuator in order to keep the door in the first position. For example, a bi-stable spring and antagonistic shape memory actuators may be used. In one or more embodiments the actuator is a first actuator, and the assembly further comprises a second actuator that is operatively connected to the door and is configured to move the door between the second position and the first position. The second actuator is formed from a shape memory alloy transitionable between a first state and a second state in response to a change in temperature of the shape memory alloy of the second actuator, and the shape memory alloy of the second actuator transitions between the first state and the second state to move the door from the second position to the first position. A bi-stable spring is operatively connected to the door and biases the door to the first position when the door is in the first position, and biases the door to the second position when the door is in the second position. Accordingly, power is provided to one or the other actuator to move the door, and then the bi-stable spring will retain the door in the desired first or second position until the other actuator is powered.
In another example of a drying system that is configured so that the power need not remain on to the actuator in order to keep the door in the first position, the drying system comprises a releasable latch that is configured to latch the door in the second position. Accordingly, once the actuator is activated to move the door to the second position, the latch will retain the door in the second position, and electrical power to the actuator can be off. Stated differently, the drying system may include a power source selectively connectable to the actuator to electrically energize the actuator, thereby heating the actuator such that the shape memory alloy transitions from the first state to the second state. The power source is disconnected from the actuator when the releasable latch holds the door in the second position.
In some embodiments, the releasable latch is configured so that a subsequent actuation of the actuator will cause the door to be released from the releasable latch. Accordingly, when the door is held in the second position by the releasable latch and the power source is connected to the actuator to electrically energize the actuator, the releasable latch is configured to release the door.
In other embodiments, the drying system includes a separate shape memory alloy actuator to release the releasable latch from the door. For example, the actuator that moves the door is a first actuator, and the assembly may further include a second actuator operatively connected to the releasable latch. The second actuator is formed from a shape memory alloy transitionable between a first state and a second state in response to a change in temperature of the shape memory alloy of the second actuator, and the shape memory alloy of the second actuator transitions between the first state and the second state to release the releasable latch from the door. A heating element may be disposed in the outer chamber and may be electrically energizable to heat the rechargeable desiccant sufficiently to remove moisture absorbed by the rechargeable desiccant. The power source may be selectively connectable to the second actuator to electrically energize the second actuator, thereby heating the second actuator such that the shape memory alloy of the second actuator transitions from the first state to the second state. The power source may be separately selectively connectable to the heating element to electrically energize the heating element. An electronic controller may be operable to separately selectively connect the power source to the first actuator, to the second actuator, and to the heating element.
In accordance with the present teachings, a lamp drying system may comprise a lamp assembly including a housing and a lens mounted to the housing such that the housing and the lens define an interior space. The housing has an inner wall dividing the interior space into an inner chamber and an outer chamber, and the lens is mounted to the housing at the inner chamber. The inner wall has a first opening through which the inner chamber communicates with the outer chamber. A rechargeable desiccant is disposed in the outer chamber. A door is disposed in the outer chamber and is configured to be movable between a first position and a second position. The door is configured to at least partially seal the second opening and unseal the first opening when in the first position, and at least partially seal the first opening and unseal the second opening when in the second position. An actuator is operatively connected to the door and is configured to move the door between the first position and the second position. The actuator is formed from a shape memory alloy transitionable between a first state and a second state in response to a change in temperature of the shape memory alloy. The shape memory alloy transitions between the first state and the second state to move the door from the first position to the second position. The rechargeable desiccant is disposed in sufficient proximity to the actuator such that electrical energizing of only one of the actuator or the rechargeable desiccant is sufficient to both cause the shape memory alloy to transition from the first state to the second state and remove moisture absorbed by the rechargeable desiccant.
The above features and advantages and other features and advantages of the present disclosure are readily apparent from the following detailed description of the best modes for carrying out the disclosure when taken in connection with the accompanying drawings.
Referring to the drawings, wherein like reference numbers refer to like components throughout the views,
The actuator 16 may be referred to as an SMA actuator. The use of a rechargeable desiccant 12 extends the ability to dry the interior of the lamp assembly 14, alleviating condensation or fogging of a lens 20. The use of a shape memory alloy actuator 16 is smaller, lighter, and may present cost savings as well as reduce the number of components.
The lamp assembly 14 as shown is a vehicle lamp assembly, such as a headlight assembly, and is positioned in a vehicle 15 (represented only in part) adjacent to an engine compartment such that the engine compartment is an exterior environment 22 of the lamp assembly 14. The exterior environment 22 is indicated in part. Instead of a headlight assembly, the lamp assembly 14 could be other vehicle lamp assemblies, such as taillight or even an interior lamp assembly. In other examples, the assembly may be a sensor assembly having an emitting or receiving component at the interior space for which moisture could affect performance or aesthetics. Accordingly, the systems 10, 110, 210, 310, 410, and assemblies 14, 114, 214, 314, 414 are not limited to a vehicle application or a lamp application.
The vehicle may be autonomous or driven by a human, and may include, but not be limited to a mobile platform in the form of a commercial vehicle (car, truck, sport utility vehicle, etc.), industrial vehicle (bus, etc.), agricultural vehicle, passenger vehicle, aircraft, watercraft, train, all-terrain vehicle, personal movement apparatus, robot and the like to accomplish the purposes of this disclosure.
The lamp assembly 14 includes a housing 24. The lens 20 is mounted to the housing 24 such that the housing and the lens together define an interior space 26A, 26B that has an inner chamber 26A and an outer chamber 26B. The housing 24 has an upper wall 24A, a lower wall 24B, an inner wall 24C, an outer wall 24D, and first and second sidewalls 24E, 24F. The sidewalls 24E, 24F are best shown in
The inner wall 24C has a first opening 28 through which the inner chamber 26A communicates with the outer chamber 26B. The outer chamber 26B is between the inner wall 24C and the outer wall 24D. The outer wall 24D has a second opening 30 with which the outer chamber 26B communicates with the exterior environment 22. The first opening 28 may be referred to as an inner opening, and the second opening 30 may be referred to as an outer opening. The rechargeable desiccant 12 is disposed in the outer chamber 26B. In the example shown, the rechargeable desiccant 12 is contained within a container 32 that is secured to the upper wall 24A within the outer chamber 26B. The container 32 allows the desiccant 12 to be exposed to the air in the outer chamber 26B. For example, the container 32 may include vents so that air in the outer chamber 26B reaches the rechargeable desiccant 12. The container 32 may also be integrally formed with the upper wall 24A. The rechargeable desiccant 12 may be a commercially available absorbent salt or a mixture of salts that absorb moisture such as but not limited to calcium chloride, or magnesium chloride.
As discussed herein, the lamp system 10 includes a door 18 that is selectively moveable by the SMA actuator 16 to at least partially alternately block and seal the first opening 28 and the second opening 30 in coordination with drying of the interior space 26A, 26B by the desiccant 12.
The SMA actuator 16 is operatively connected to the door 18, which is disposed in the outer chamber 26B and is configured to be movable by the SMA actuator 16 between a first position shown in
The SMA actuator 16 may be configured as a wire with a first end 16A anchored to the housing 24, and a second end 16B anchored to the door 18. The second end 16B may be secured to an extension 18D of the door 18, best shown in
The door 18 is pivotably secured to the housing 24 and pivots about a pivot axis 31 when the door 18 moves from the first position to the second position. Such pivoting motion may be referred to as articulation. As best shown in
A biasing spring 40 biases the door 18 to the first position. Accordingly, the door 18 is maintained in the first position by the mechanical force of the spring 40 and in the absence of any electrical power. The biasing spring 40 is shown as a torsion spring centered around the lower end 18C of the door 18, and has one end secured to the door and the other end secured to the outer wall 24D. Other types of biasing springs may be used within the scope of the present teachings. Pivoting of the door 18 counter-clockwise in
In the wire form, the SMA actuator 16 contracts in length in response to a sufficient increase in temperature. For example, the SMA actuator 16 is formed from a shape memory alloy transitionable between a first state (
In the lamp drying system 10 of
As used herein, the terminology “shape memory alloy” refers to an alloy that exhibits a shape memory effect and has the capability to quickly change properties in terms of stiffness, spring rate, and/or form stability. That is, the shape memory alloy may undergo a solid state crystallographic phase change via molecular or crystalline rearrangement to shift between a martensite phase, i.e., “martensite”, and an austenite phase, i.e., “austenite”. That is, the shape memory alloy may undergo a displacive transformation rather than a diffusional transformation to shift between martensite and austenite. A displacive transformation is defined as a structural change that occurs by a coordinated movement of atoms or groups of atoms relative to neighboring atoms or groups of atoms. Further, the martensite phase generally refers to a comparatively lower-temperature phase and is often more deformable than the comparatively higher-temperature austenite phase.
The temperature at which the shape memory alloy begins to change from the austenite phase to the martensite phase is characterized as the martensite start temperature, Ms. The temperature at which the shape memory alloy completes the change from the austenite phase to the martensite phase is characterized as the martensite finish temperature, Mf Similarly, as the shape memory alloy is heated, the temperature at which the shape memory alloy begins to change from the martensite phase to the austenite phase is characterized as the austenite start temperature, As. The temperature at which the shape memory alloy completes the change from the martensite phase to the austenite phase is characterized as the austenite finish temperature, Af.
The shape memory alloy may have a suitable form, i.e., shape. For example, the SMA actuator 16 may be configured as a shape-changing element such as a wire (
Therefore, in one non-limiting example illustrated in
In one example, the change in temperature at which the SMA actuators described herein transition from the first state to the second state and the temperature at which the desiccant is regenerated are the same, or are compatible such that heat released from one activates the other as described herein. For example, the SMA actuator may transition from the first state to the second state when the temperature rises from an ambient temperature to 110 degrees Celsius, and the desiccant 12 may be regenerated at a temperature of 110 degrees Celsius or at a temperature that occurs in the vicinity of the SMA actuator 16 when it is heated to 110 degrees Celsius.
Therefore, for embodiments in which the SMA actuator 16 is configured as the wire, the wire may contract in length in response to the change in temperature that results from energizing the SMA actuator 16 (
In other words, as the shape memory alloy warms, the SMA actuator 16 contracts in length and pulls the door 18 where it is connected to the door 18 at its second end 16B. Because the second end 16B is offset from the pivot axis 31, this causes the door 18 to pivot to the second position of
Accordingly, when the door 18 is in the first position, the exterior environment 22 is blocked from both chambers 26A, 26B, the first chamber 26A is in communication with the second chamber 26B through the first opening 28, and the desiccant 12 removes moisture M from both chambers 26A, 26B as shown in
The lamp drying system 10 may be referred to as a “power on” system, as power is provided to the SMA actuator 16 to counteract the biasing force of the spring 40 and keep the door 18 in the second position during regeneration of the rechargeable desiccant 12. The power may be kept on continuously during the regeneration until the desiccant 12 is fully regenerated, or, due to the switch 34, may be intermittently shut off, but not for a long enough period to allow the door 18 to shift significantly from the opening 28. For example, the switch 34 may be a normally-closed switch. In
When the door 18 is in the second position, the controller C causes the power source P to direct electrical energy to the heating element 44 disposed in the second chamber 16B adjacent to the desiccant 12. The heating element 44 may be a conductive material heated by resistive heating, for example. The controller C may close a switch within the power source P or between the power source P and the heating element 44 to direct electrical energy to the heating element 44. As indicated in
When the desiccant 12 is sufficiently dry, power to the heating element 44 is terminated, and the SMA wire 16 cools, returning the door 18 to its nominally closed position (the first position of
The heating element 44 and the SMA actuator 16 are thus separately electrically energized in the lamp drying system 10 of
In other embodiments, heating of the SMA actuator 16 (and the resulting articulation of the door 18) and heating of the rechargeable desiccant 12 may be integrated to reduce the number of components and/or the complexity of the electrical connections. For example, in
The bi-stable spring 340 is operatively connected to the door 18. More specifically, one end of the bi-stable spring 340 is connected to the door 18, and the other end is fixed to the housing, such as to the sidewall 24E at a point midway between the first and second positions of the door 18, as shown in
A second SMA actuator 416 has one end 416A connected to the housing 24 and a second end 416B connected to the releasable latch 460. The SMA actuator 416 is formed from a shape memory alloy is transitionable between a first state (
In
When the door 18 is latched in the second position of
The releasable latch 560 is shown from a viewpoint generally looking toward the side wall 24E of the housing 24, with the post 18E in cross-sectional view. A first electrical energizing of the SMA actuator 16 moves the door 18 from the first position to the second position, and the post 18E of the door 18 slides along a first cam surface 561 in a first track 562 of the releasable latch 560 as the SMA actuator 16 is contracting until it rests against the latch 560 at a stop 563 (post represented as 18E1) due to the biasing force of the spring 40, so that the door 18 does not return to the first position even with power to the SMA actuator 16 then terminated.
When the desiccant 12 is sufficiently dried, and the door 18 is to be returned to the first position to close the opening 30, the power source P again electrically energizes the SMA actuator 16. The contracting SMA actuator 16 then causes the post 18E to slide along a second cam surface 564 in a second track 565 of the releasable latch 560, with the post represented as 18E2. The first cam surface 561 is such that the path of the post 18E in the first track 562 is generally in the X-Y plane in
While the best modes for carrying out the disclosure have been described in detail, those familiar with the art to which this disclosure relates will recognize various alternative designs and embodiments for practicing the disclosure within the scope of the appended claims.