Vehicle lock controlled by a shape memory alloy actuator

A contractible shape memory alloy (SMA) wire is used to throw a lever in a latch. The SMA actuator provides weight and space savings. In one embodiment, the SMA actuator is incorporated in the handle of the latch in order to provide a child lock or double lock function. The handle has a lever which includes a relatively short slot leg and a relatively long slot leg. A toggle sits in the slot. At least one SMA wire is connected to the toggle to move it between the relatively short slot leg, wherein the lever is prevented from pivoting, and the relatively long slot leg, where the lever is enabled to pivot. In another embodiment, the SMA actuator is embedded in the latch itself, and used to throw a lever that controls the child lock function.

FIELD OF INVENTION

The invention generally relates to automobile locks and/or latches and more specifically to a vehicle lock controlled by a shape memory alloy actuator.

BACKGROUND OF INVENTION

Automobiles often include child locks for preventing doors, especially rear doors, from being opened from within the passenger compartment. Child locks are typically either manually activated or power actuated. Manually activated child locks typically have a lockout control mechanism that can only be accessed when the door is open. This creates an inconvenience in that if there is an adult in the rear seat and the child lock is engaged, then someone else must open the door for the adult passenger. Power child locks typically require an actuator and a lockout control mechanism which is located on the door latch. The main problem with these types of locks is the lack of packaging space in the door to facilitate the actuator and the lockout mechanism.

Accordingly, it would be desirable to have a remotely actuated child lock in which the driver can operate the rear child lock doors from the front seat. As the costs associated with a power child lock are high when compared to the value this feature adds to a vehicle, it is desirable to provide such a child lock at a minimum cost.

In addition, another desirable feature to include in a vehicle door latching or locking system is a “double lock”, wherein, when engaged, both the inside and outside release levers are simultaneously inactive. This feature has conventionally been incorporated into the design of the latch itself, which can often necessitate a very expensive redesign of a pre-existing latch. Since the functions of a child lock and a “double lock” feature are quite similar, it would be desirable to provide a single structure that could provide both functions and thus further reduce costs.

SUMMARY OF INVENTION

One aspect of the invention provides a handle assembly which functions to enable or disable the door handle from actuating a latch rather than installing a lock assembly on the latch itself. In order to reduce packaging requirements and still keep costs low, the actuating mechanism preferably employs a wire, formed from a shape memory alloy, which is able to contract and expand in order to activate the locking function.

In accordance with the foregoing aspect of the invention, a first embodiment of a handle assembly is described which includes a housing having a door handle lever pivotably mounted therein. The lever has a slot formed therein which includes a relatively short slot leg and a relatively long slot leg. A toggle is mounted to the housing. The toggle includes a tab which seats in the slot of the lever. At least one selectively contractible wire is connected to the toggle in order to move the tab between the relatively short slot leg, wherein the lever is prevented from pivoting, and the relatively long slot leg, wherein the lever is enabled to pivot. The handle assembly may be utilized for a child lock function or for a double lock function.

Preferably, the short slot leg is situated generally orthogonal to the relatively long slot leg. The toggle is pivotably mounted to the housing and includes an arm from which the tab depends. A spring is connected to the housing for biasing the toggle arm to first and second positions required to insert the tab into the short and long slot legs of the door handle lever. When the tab is situated in the relatively long slot leg of the fleet this, the handle is enabled to actuate a latch and the tab can ride in the long slot leg as the door handle lever is rotated. When the tab is situated in the short slot leg, the handle is disabled such that the door handle lever is prevented from moving and actuating the latch.

Preferably, the wire is formed from a shape memory alloy (SMA). A first section of the SMA wire is electrically connected between a first terminal and the toggle and a second section of the SMA wire is electrically connected between a second terminal and the toggle. A controller is provided for selectively contracting the first section of wire (and in the process lengthening the second section of wire) and selectively contracting the second section of wire (and in the process lengthening the first section of wire), thereby selecting moving the tab between the first and second legs of the lever slot.

A second embodiment of a handle assembly is also described wherein the door handle lever is always movable but may or may not be enabled to release the latch. According to this embodiment, the latch is directly coupled to an intermediate latch release lever and the door handle lever is selectively coupled to the intermediate release lever by a floating pin and a link/toggle lever which is actuated by one or more contractible wires.

Preferably, the handle assembly according to the second embodiment includes a housing and a door handle lever pivotably mounted to the housing. The door handle lever has a slot and therein which includes a first slot leg (short slot leg) and a comparatively longer second slot leg (long slot leg). An intermediate latch release lever having a slot therein is pivotably mounted to the housing. A link/toggle lever having a slot therein is also pivotably mounted to the housing and movable between first and second positions. A pin is floatingly disposed in the slots of the door handle lever, the intermediate latch release, and the link/toggle lever. At least one selectively contractible wire is connected to the link/toggle lever in order to move it between the first position, wherein the pin is forced into the short slot leg so as to kinematically couple the door handle lever to the intermediate latch release lever, and the second position, wherein the pin is forced into the long slot leg such that the door handle lever is not kinematically coupled to the intermediate latch release lever.

A second aspect of the invention relates to an improved latch having a built-in child lock or double lock mechanism which is activated by throwing a lever, the improvement comprising at least one contractible wire for throwing the lever.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1shows a door handle and child lock assembly10according to a first preferred embodiment which includes a housing12mountable to an automobile door as well known in the art. The assembly10includes a door handle lever14, which is shown in isolation inFIG. 4. The door handle lever14includes a pin16that extends upwardly from a planar structure18of lever14. The pin16seats in an aperture of the housing12, as seen best inFIG. 1A, thereby enabling the door handle lever14to pivot from a rest position shown inFIG. 1to a pulled (or activated) position shown inFIG. 2, provided the handle is enabled as discussed in greater detail below. The door handle lever14includes a connector20which is used to affix a control rod or other linkage (not shown) between the door handle lever14and the latch of the vehicle door (not shown). Thus, in this embodiment, rotation of the door handle lever14will unlatch the door. In what follows, the assembly10is described in the context of a child lock in which case the child lock is said to be “disengaged” when the handle is enabled and “engaged” when the handle is disabled. Those skilled in the art will understand from the description that follows that the assembly10can be readily employed for use in a double lock function.

In order to provide a lockout, the door handle lever door14includes a slot24(seen best inFIG. 4) having a first leg24aand a second leg24bwhich is disposed generally orthogonal to the first leg24a. The child lock includes an actuator30(FIG. 1) comprising a plate32mounted to the housing12. A toggle34comprising a sleeve33is pivotably mounted to a post35extending from the plate32. The toggle34includes two arms36and38integrally formed with the sleeve33. Arm38includes a pin or tab40which extends through an aperture42formed in the plate32in order to engage slot24of handle lever14. The aperture42of plate32is sized and oriented similar to the first leg24aof slot24. Arm36is connected to one end of a spring44which has the other end thereof attached to the plate32. The toggle34pivots between first and second positions. In the first position as shown inFIG. 1, the tab42is located at a first end42aof aperture42and the child lock is disengaged. In the second position as shown inFIG. 3, the tab42is located at an opposite and42bof the aperture42and the child lock is engaged. The toggle34is forced into these two positions only as a result of the spring44. More particularly, as seen inFIG. 5, arm36follows an arcuate path as indicated by the stippled line. When the arm36is at the midpoint of its travel path, the distance x between the arm36and a fixation point45of the spring of44is at its shortest point. At this position the spring44is compressed and thus the arm36is urged to one side or the other of the midpoint until the arm36reaches at the end of its arcuate path of travel. At the end of travel, the distance y between arm36and the fixation point45of spring44is such that that the spring is in its rest state. It will be understood that as soon as the toggle34is actuated to move past the midpoint x it will be urged to reach its closest end of travel position.

The actuator30includes a wire50constructed from a shape memory alloy (SMA) that is able to contract and expand and is used to set or position the toggle34. The SMA wire50is fixed at its two ends to two terminals52aand52bthat are electrically isolated from one another. The wire50is also fixedly wound around the electrically conductive sleeve30of toggle34. In its rest state the sleeve/terminal33and each of the terminals52aand52bare connected to a voltage source (typically the vehicle battery). In order to actuate the child lock, a controller (not shown) selectively connects one of the terminals52aor52bto ground. For example, if terminal52ais connected to ground then the section of SMA wire50extending from the sleeve/terminal33to terminal52awill contract (and in the process expand or lengthen the other section of wire50), causing the toggle34to pivot such that tab40is moved from aperture end42ato end42b, as shown inFIG. 3. When this happens, the tab40is situated within the first leg24aof the door handle lever14. This engages the child lock. In this position, the door handle lever14cannot be moved or rotated as a result of tab40being lodged in the short leg24a,and consequently the latch cannot be unlatched by pulling on the door handle lever14.

When terminal52bis connected to ground, the section of SMA wire50extending from the sleeve/terminal33to terminal52bis contracted (and in the process expanding or lengthening the other section of the wire50), causing the tab40to move back to position, as shown inFIG. 1. In this position the tab40is located in leg24bof slot24. This disengages the child lock. In this position, the handle lever14may be rotated (as shown inFIG. 2) as a result of the relatively long length of leg24bin which tab40rides. Rotation of the door handle lever14will unlatch the latch, as previously described.

In the embodiment described above, the door handle lever14is prevented from moving when the child lock is engaged. In a second embodiment described below with reference toFIGS. 6-10, the door handle lever is always movable. This is made possible by directly coupling of the latch to an intermediate latch release lever and selectively coupling the door handle lever to the intermediate release lever via a link lever and the floating pin. When the child lock is engaged, the door handle lever is kinematically coupled to the latch release lever (and thus enabled) and when the child lock is disengaged the door handle lever is kinematically uncoupled from the latch release lever (and thus disabled).

More particularly,FIGS. 6-10show a door handle and child lock assembly58in which door handle lever14is connected to a latch release lever60and a link/toggle lever70via a floating pin80. The latch release lever60is pivotally mounted to the pin16of housing12, which is the same point about which the door handle lever14pivots. In this embodiment, however, the control rod, cable or linkage that is used to unlatch the latch (not shown) is connected to the latch release lever60via a rivet62mounted in aperture64. The pin80rides in slot66of the latch release lever60. A washer82is welded or otherwise fixed to the pin80above lever60.

The link/toggle lever70is pivotally mounted to a post85located on housing12via a sleeve76integrally formed with lever70. The link/toggle lever70includes an extending arm74and spring44is connected between this arm and housing12in order to provide a toggle mechanism similar to that described above which forces the link/toggle lever70into one of two positions, described in greater detail below. An SMA wire50is wrapped around the sleeve76and is mounted to two electrically isolated end terminals (not shown), providing contractible wire sections151and152. The pin80is fitted into a slotted aperture72of lever70and a second washer84is welded to or otherwise fixed to the pin80below lever70.

The pin80also rides in the dual-legged slot24of handle release lever14.

FIG. 7shows the assembly58with the handle release lever14enabled (i.e., the child lock is disengaged) and in the closed position. In this state, the toggle/link lever70is in a first position which forces the pin80into the short slot leg24aof the handle release lever14. In this position, the pin80is located in a first end66aof slot66of latch release lever60. When the handle release lever14is pulled, wall section24xof slot leg24apushes against the pin80which, in turn, pushes against wall section66xof the latch release lever60. Consequently, the latch release lever60will pivot as indicated, causing the pin80to ride in and along slot72of the link/toggle lever70until the pin80reaches the end of the slot72, as shown inFIG. 8.

FIG. 9shows the assembly58with the handle release lever14disabled (i.e., the child lock is engaged) and in the closed position. In this state, the toggle/link lever70is in a second position in which the pin80is forced into the long slot leg24bof the handle release lever14. In this position, the pin80is located in a second end66bof slot66of the latch release lever60. When the handle release lever114is pulled, the pin80stays stationary because it is located in the log slot leg24bwhich does not have a wall to push the pin, and thus as the handle release lever114is pulled the slot leg24bmoves relative to the stationary pin80as shown inFIG. 10, without moving the latch release lever60.

In a manner similar to the first embodiment described above, the sleeve76is set to a predetermined voltage and the end terminal of each wire section151,152is selectively switched between this voltage or ground. The switches are controlled by a controller (not shown) which establishes the current flow in wire sections151and152in order to selectively actuate the link/toggle lever60to the first or second positions in accordance with a command signal.

Referring now toFIGS. 11,12aand12b, a third embodiment of the invention is shown. In this embodiment, the shaped memory actuator is mounted to the latch housing and directly pivots a child lock lever between a locked and an unlocked position. Latch160includes a child lock lever162pivotally mounted to latch housing164via a child lock pin166. Child lock lever162is movable between a locked and an unlocked position. As can more clearly be seen inFIG. 12a, a claw168on child lock lever162retains an end of a lock link lever (not shown). By pivoting child lock lever162between the locked and unlocked positions, the lock link lever kinematically couples or decouples the inner door handle from the release lever (also not shown). The inner door handle can also be decoupled in order to provide a double-locking feature, if desired. A toggle spring (not shown) may be used to bias the child lock lever162to the locked or unlocked positions, if desired.

Retained within latch housing164is a SMA subassembly170. SMA subassembly170provides a mounting structure for the SMA wires and terminals. While the SMA subassembly shown inFIG. 12is mounted to latch housing164, it is also contemplated that the SMA subassembly170could also be integrally formed from latch housing164. A power child lock lever172is pivotally mounted to SMA subassembly170via a post or pin173. A claw174on power child lock lever172is hooked around a post176extending from a planar surface of child lock lever162, kinematically coupling the motion of the two levers162,172so that pivoting one lever pivots the other lever as well. A SMA wire178and a SMA wire180are each connected to terminals181aand181bat a first end located on a terminal end182of SMA subassembly170, and at a second end to power child lock lever172respectively. Each of SMA wire178and SMA wire180are electrically isolated from each other, and can be selectively and alternatively grounded. Thus, by activating either SMA wire178or SMA wire180, power child lock lever172can be pivoted in a first or second direction to either the locked position disabling operation of the door handle lever or the unlocked position enabling operation of the door handle lever.

A manual child lock knob184extends out from a planar surface of child lock lever162through a hole (not shown) in latch housing164to the exterior of latch160. Child lock knob184includes a slot185, allowing child lock knob184and thus, child lock lever162to be manually rotated (typically with a slotted screwdriver). SMA wires178and180provide only minimal resistance to manually pivoting child lock lever162.

Referring now toFIGS. 13-15, a fourth embodiment of the invention is shown. In this embodiment, a SMA wire pair186and a SMA wire pair188run between terminal end182of SMA subassembly170and power child lock lever172. The two wires of each SMA wire pair186and188run substantially parallel to each other. At terminal end182, the ends of both wires in each of SMA wire pair186and188are connected to terminals (not shown) located in terminal receptacles183aand183brespectively. At power child lock lever172, the ends of both wires in each SMA wire pair186and188are connected to each other by a conductive metal crimp190held within a niche192in power child lock lever172, making each of SMA wire pairs186and188completed circuits. Actuation strength is thusly increased by pairing each of the SMA wires over using a single SMA wire. Additionally, since terminals are only required at terminal end182, the cost and complexity of latch160are reduced. In this embodiment, power child lock lever172pivots around SMA subassembly172on a pair of posts194, and is kinematically coupled with child lock lever162via an extending post196.

The child locks described above are electrically actuated and therefore can be remotely activated from anywhere inside or outside of the vehicle. This eliminates the need for the driver to get out of the car to open the rear doors from the outside. Instead, the driver can actuate a button located in the front passenger area or on a key fob remote controller. Another advantage provided by the first two embodiments described above is that the latch requires comparatively less packaging space because the child lock assembly is part of the inside release handle and is not located on the latch itself. There is more room to package the child lock in this part of the door. The use of the shape memory alloy actuator is also cost-effective in that it replaces the conventional electric actuator having a motor, gears and a housing. The preferred embodiments described above are also a satisfactory from a “craftsmanship” point of view since they have less moving parts and eliminate noise emanating from motors and gears of conventional power actuators. Furthermore, there are no levers that need to be manually operated.

The SMA wire is preferably formed from an alloy comprising nickel and titanium, commercially available under the trade name Nitinol™. Other types of alloys may be employed in the alternative. For example, a ternary shaped memory alloy comprising nickel, titanium and either palladium or hafnium could be used to form the SMA wire. It will also be understood that where one contiguous SMA wire has been shown wrapped around a toggle mechanism, two separate SMA wires be used in the alternative. For extended longevity of the SMA actuator, the latter option, two separate wires, is preferred. It has been found that the use of one long wire which is wrapped around a post or other structure tends to become brittle after many operational cycles, possibly due to the friction between the SMA wire and the post. Accordingly, in the most preferred embodiments it is desirable that the SMA wire is linearly routed so as to not contact any other part of the latch (except at the ends of the wire where electrical contact is made) in order to preclude this problem.

Those skilled in the art will understand that a variety of modifications may be made to the embodiments described herein without departing from the spirit of the invention.