Patent Application
20210396053
The present disclosure is related generally to latch assemblies for vehicles and, more particularly, to latch assemblies that utilize a shape memory alloy (SMA) actuator.
Shape memory alloy (SMA) actuators can be used to facilitate movement of one or more components in a latch assembly. For example, U.S. Pat. No. 10,435,918 to Weber et al. discloses a latch system that includes an SMA wire which contracts when current is applied to it. The contraction of the SMA wire pulls a rocker and ultimately rotates an engagement element to open the storage compartment. Strategic decoupling of the interface between the engagement element or striker and the SMA wire can improve performance of the latch assembly.
An illustrative latch assembly for a vehicle includes a shape memory alloy (SMA) actuator having an actuator housing, an SMA wire, and an actuator lever arm. The actuator lever arm is configured to pivotably rotate or linearly translate with respect to the actuator housing upon activation of the SMA wire. A connecting link is coupled to the actuator lever arm. The connecting link is configured to translate linearly along a connecting link axis when the actuator lever arm pivotably rotates or linearly translates. A striker is coupled to the connecting link, and the striker is configured to rotate about a striker axis to engage a closing surface.
In some embodiments, the connecting link includes a wrapping end to couple the actuator lever arm.
In some embodiments, at least a portion of the shape memory alloy (SMA) wire runs parallel to an actuator housing axis that extends along a longest length of the actuator housing.
In some embodiments, the actuator lever arm is configured to pivotably rotate with respect to the actuator housing.
In some embodiments, an actuation range for pivotable rotation of the actuator lever arm is between 10° and 25°, inclusive.
In some embodiments, the actuation range overlaps an actuator lever arm axis, and the actuator lever arm axis is orthogonal to the actuator housing axis.
In some embodiments, the actuator housing axis is aligned with the connecting link axis.
In some embodiments, the actuator lever arm linearly translates upon activation of the shape memory alloy (SMA) wire.
In some embodiments, there is a decoupled interface between the striker and the shape memory alloy (SMA) actuator, and the decoupled interface decouples movement of the striker from movement of the SMA wire.
In some embodiments, the shape memory alloy (SMA) actuator includes a return spring, and the decoupled interface allows for the return spring and the SMA wire to return to original positions at different rates of speed.
In some embodiments, the striker includes a locking pawl and a connection extension.
In some embodiments, the connection extension has an open track to slidingly accommodate the connecting link.
In some embodiments, a center console for a vehicle comprises a latch assembly.
In some embodiments, the closing surface is located on an armrest.
In some embodiments, a glovebox for a vehicle comprises a latch assembly.
It is contemplated that any number of the individual features of the above-described embodiments and of any other embodiments depicted in the drawings or description below can be combined in any combination to define an invention, except where features are incompatible.
Illustrative embodiments will hereinafter be described in conjunction with the following figures, wherein like numerals denote like elements, and wherein:
Described herein are embodiments of latch assemblies for use in various vehicle-based applications, such as with consoles, armrests, glove boxes, other storage compartments, and other implementations such as a headrest. The latch assemblies strategically employ a shape memory alloy (SMA) wire in an SMA actuator that cooperates with a connecting link and a striker to facilitate opening and/or closing of the vehicle compartment, for example. The SMA actuator disclosed herein can provide a cost-effective solution that also improves packaging and noise. As compared with a solenoid actuator, for example, the latch assembly with the SMA actuator described herein can be much quieter, lighter, and smaller. The arrangement and operability of the various components of the SMA actuator can result in improved performance of the latch assembly. A strategically decoupled interface between the SMA actuator and the striker of the latch assembly allows for a return spring and the SMA wire to return to their original positions at different rates without moving the striker. Furthermore, the temporary movement of the striker when the storage compartment is closed does not impact the SMA actuator.
In operation, when users desire to open the armrest 16 to access a storage compartment 36 in the center console 14, they can press a button or some other trigger, actuation device, etc. which will ultimately cause current to be applied to the SMA wire 28. As the SMA wire 28 contracts, it moves the actuator lever arm 30. The actuator lever arm 30 pulls the connecting link 32, which rotates the striker 34. The striker 34 engages a closing surface 38 on the inner side of the armrest 16. The closing surface 38 may include a small groove, recess, pocket, etc. for accommodating the striker 34. In the illustrated embodiment, the armrest 16 includes two panels 40, 42. In other embodiments, there may be only one panel, or more than two panels. The latch assembly 20 operates to facilitate opening and/or secure closing of the first panel 40. It is possible to include a second latch assembly to facilitate opening and/or secure closing of the second panel 42, or it may also be feasible to have one latch assembly that secures both panels 40, 42. Other lidded arrangements are certainly possible.
The SMA actuator 24 includes an actuator housing 26, an SMA wire 28, and an actuator lever arm 30. One embodiment of an actuator housing 26 is illustrated in
The SMA wire 28 is constructed from a shape memory alloy material, which varies in length depending on the temperature of the material. Thus, when a current is applied to the SMA wire 28, it heats and contracts, which pulls the actuator lever arm 30. The shape memory alloy material reversibly switches material states (e.g., between martensite and austenite) to cause the contraction and motion of the actuator lever arm 30. Cooling of the SMA wire 28 causes the wire to return to its original position. The original position 58 is shown in
The SMA wire 28 is mounted on the PCB 50 such that it loops around or is otherwise attached to an anchor 62 on the actuator lever arm 30. At least a portion of the SMA wire 28 runs parallel to the actuator housing axis AH. The anchor 62 for coupling the SMA wire 28 to the lever arm 30 is a washer; however, other ways to anchor the wire 28 to the lever arm 30 are certainly possible. When the SMA wire 28 contracts, the anchor 62 is pulled by the SMA wire and the actuator lever arm 30 rotates at the pivot point 64. Thus, the actuator lever arm 30 is configured as an output-stage lever arm to pivotably rotate with respect to the actuator housing 26 upon activation of the SMA wire 28. An actuation range 66 for pivotable movement of the actuator lever arm 30 is at least partially defined by a return spring 68 and an end stop 70. The return spring 68 is a bias spring which aids in retraction of the lever arm 30 and wire 28 when the voltage is turned off. The actuation range 66 for pivotable rotation of the actuator lever arm 30 is advantageously between 10° and 25°, inclusive. In the illustrated embodiment, the actuation range 66 is 14°. The actuation range 66 overlaps an actuator lever arm axis AL, which is an axis that lengthwise divides the actuator lever arm 30 along its longest length or extent when the lever arm is at its original position 58. The actuator lever arm axis AL is orthogonal to the actuator housing axis AH in the original position 58. Additionally, in the original position 58, the anchor 62 and the pivot point 64 are both aligned along the actuator lever arm axis AL. This arrangement, where the actuator lever arm axis AL is orthogonal to the actuator housing axis AH at the original position 58, can provide for improved mounting of the latch assembly 20. Further, having the actuator lever arm 30 extend orthogonally from the housing 26 along the actuator lever arm axis AL can help regulate the force output while maintaining a smaller, thinner overall package for fitting into a compact area.
In this embodiment, the SMA wire 28 contracts a few millimeters (about 3-5% of its length) when actuated. Actuation of the SMA wire 28 may be triggered by a button on the console 14, on the instrument panel, or by some other operable means (e.g., voice activation). Power may be supplied to the SMA actuator 24 and the SMA wire 28 through the vehicle power supply or through a separate low voltage battery, to cite a few examples. The arrangement of the actuator lever arm 30 with respect to the housing 26 and the SMA wire 28 multiplies the stroke to achieve an output stroke of approximately 10 mm. The output force at the end of the lever arm 30 is approximately 10 N. After contraction, the SMA wire 28 retracts to its original position within about 5 seconds, aided by the return spring 68. In one example embodiment, the SMA wire 28 is activated with about 3-15V (Vcc). Higher voltages have the potential of decreasing actuation time. With the Vcc and ground leads connected, a logic-level signal is sent to a MOSFET transistor driver circuit. The driver applies the desired voltage (Vcc) to the SMA wire 28. The signal can also be pulse-width-modulated (PWM) to simulate a voltage lower than Vcc. To help prevent the application of a high voltage that could burn out the wire 28, the end stop 70 along with a second end stop 72 help to electromechanically limit the applied voltage. When the lever arm 30 reaches the predetermined end of its stroke or the end of the actuation range 66, one of the end stops 70, 72 will be contacted by the lever arm. This signals to the control electronics 74, which are advantageously housed within the housing 26, to momentarily stop the voltage and then reapply the voltage. This on-and-off modulation can help prevent the SMA wire 28 from overheating. Other mechanisms for cooling the SMA wire 28 may also be included, such as a cooling jacket, heat sink, etc.
The decoupled interface 44 between the SMA wire 28 and the striker 34 allows for the SMA wire 28 to retract/extend without affecting the striker 34. This allows the return spring 68 and the SMA wire 28 to return to their original positions at different rates without impacting the latch assembly 20. Further, when the panel 40 of the armrest 16 is closed, the striker 34 temporarily moves until it engages with a notch or the like in the closing surface 38 and the latch assembly 20 locks again. This temporary movement does not impact the SMA actuator 24 given the decoupled interface 44. To form the decoupled interface 44, the actuator lever arm 30 is coupled to the connecting link 32 which is then coupled to the striker 34.
The connecting link 32 has a main rod body 76 situated between a wrapping end 78 and a striker interface end 80. The wrapping end 78 is operably coupled to the actuator lever arm 30. A fastener may extend through an attachment recess 82 located in a distal end of the actuator lever arm 30 and arms 84, 86 of the wrapping end 78 may extend around the fastener in order to couple the wrapping end and the actuator lever arm. With particular reference to
It is to be understood that the foregoing is a description of one or more embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.
As used in this specification and claims, the terms “e.g.,” “for example,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation. In addition, the term “and/or” is to be construed as an inclusive OR. Therefore, for example, the phrase “A, B, and/or C” is to be interpreted as covering all the following: “A”; “B”; “C”; “A and B”; “A and C”; “B and C”; and “A, B, and C.”
