Lost motion cam actuating device

A lost motion cam assembly for a vehicle lock. The assembly includes a lever, pivotally mounted to the housing and movable between locked and unlocked positions. A motor drives a gear mounted to a shaft in the housing. A cam is also rotatably mounted to the shaft, and includes a pair of opposing cam arms. When a cam arm engages a first interaction surface on the lever, the lever actuates. A second interaction surface on the lever stops the cam. The cam is operably connected to the gear by a lost motion connection that defines a range of free travel of the cam relative to the gear. Manually pivoting the lever while one of the pair of cam arms is in contact with the first interaction surface on the lever causes the cam to rotate within the range of free travel.

FIELD OF THE INVENTION

The invention relates to a cam assembly for actuating a lever, such as a lock lever or a power release detent on a vehicle latch.

BACKGROUND OF THE INVENTION

Power locking/unlocking is a popular feature for vehicle door latches. Typically, power-locking latches are equipped with a DC motor that drives a series of gears and cams to actuate a lock lever between the locked and unlocked position. However, for both safety and convenience purposes, the latch must also be able to be locked and unlocked manually. Preferably, manual locking/unlocking should not back drive the power-locking drive train. Previously, it has been difficult and/or expensive to produce an actuating device that allowed both manual and power locking and unlocking. In addition to power locking/unlocking, other components of the latch are becoming motorized. For example, some latches are now equipped with a power release feature. In a latch equipped with power release, the pawl is typically spring-biased against the ratchet. A DC motor drives the gear train to actuate the pawl into the released position. Once released, the motor must disengage to allow mechanical latching.

One solution is to provide a cam that can actuate the lock lever when the motor is engaged, but remains clear of the lock lever's motion path when the motor is disengaged. In this fashion, the lock lever can be manually actuated without difficulty. However, in practice it has been found that such systems do not always move fully clear of the lock lever's travel path. For example, when a cam is forced to stop rotating, it may bounce back into the path of the lock lever. In this case, the cam may partially or fully hinder manual actuation of the lock lever.

What is desired is an actuating device for a vehicle door latch that provides power locking/unlocking and reliably allows for manual locking/unlocking without manually back driving the drive train. What is also desired is an actuating device for a vehicle door latch that provides power release and allows manual latching. Additionally, the actuating device should be inexpensive to assemble.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided an actuating device, particularly for a vehicle lock. The actuating device includes a lever, pivotally movable between two positions. The lever has a first interaction surface such as a fork, and a second interaction surface, such as a stop. The actuating device also includes a gear, selectively rotatable about an axis, and a cam, rotatable about an axis. The cam has a pair of cam arms for actuating or otherwise kinematically coupling with the lever such that one of the cam arms engages the first interaction surface to pivot the lever, and the other of the two cam arms engages the second interaction surface to stop the rotation of the cam. A lost motion connection is provided between the gear and the cam. The lost motion connection reduces the counter-rotation or “bounce-back” of the cam caused by engagement of the other of the two cam arms with the second interaction surface.

DETAILED DESCRIPTION OF THE INVENTION

Referring now toFIG. 1, a latch is shown generally at10. Latch10includes a molded housing12, preferably formed from a high-impact plastic. A lock lever14is pivotally mounted to a post16integrally formed from and extending out of the inner surface of housing12. Pivoting lock lever14actuates a lock link lever (not shown) that moves latch10into either a locked or an unlocked state. An arm18extends from lock lever14and terminates in a claw19. The end of a door rod (not shown) connected to the inside lock lever (also not shown) is looped around claw19. Thus, locking/unlocking the inside lock lever manually actuates lock lever14. The angular travel of lock lever14is delimited by shoulders20and22integrally formed in housing12. Lock lever14is movable between a “locked” position, where arm18abuts shoulder20, and an “unlocked” position where arm18abuts shoulder22. To reduce noise and wear, a lock lever bumper23is preferably mounted around arm18. When lock lever14moves into either the locked or the unlocked position, bumper23abuts one of shoulder20and22. Lock lever14further includes an indented region24located between two cam shoulders25. Indented region24and cam shoulders25are used to power-actuate lock lever14and are described in greater detail below.

Lock lever14is power-actuated by the power-locking drive train. In the current embodiment, this power-locking drive train includes a lock motor26mounted to housing12. Lock motor26is a DC motor, and reversibly drives a worm28. Worm28, in turn meshes with a cluster gear30, rotatably mounted around pin31. In turn, cluster gear30meshes a lock gear32. As will be apparent to those of skill in the art, different gear arrangements between lock motor26and lock gear32can be used for the power-locking drive train, and are within the scope of the invention.

Lock gear32is rotatable about an axis defined by a shaft34, located in a hole (not shown) in housing12. Preferably, shaft34is fixed in the hole via friction or the like so that it does not rotate under normal use. As can be seen inFIG. 2, shaft34passes through a central hole36in an annular post38extending out from a planar surface of lock gear32. Lock gear32includes a cavity40formed between annular post38and a teeth wall42. A rubber ring44is mounted around annular post38, and includes two resilient bumpers46aand46b. The two bumpers46abut against a lug48that extends out of lock gear32into cavity40.

A cam50is also rotatably mounted to shaft34, adjacent lock gear32. Shaft34passes through a central hole51in an annular post52that is integrally formed from cam50. Preferably, hole51provides a tighter frictional fit for shaft34than hole36on lock gear32, so that cam50rotates less easily than lock gear32. Cam50also includes a curved depending sidewall54that is adapted to fit within cavity40and is concentric with teeth wall42. Depending sidewall54provides a lost motion connection between lock gear32and cam50. The arc length of depending sidewall54between its edges56aand56bis shorter than the arc formed in cavity40between the two bumpers46aand46bso that cam50can rotate around shaft34independent of lock gear36between the two bumpers46. Thus, the difference in arc length between bumpers46aand46band edges56aandbdefine a range of free travel of cam50relative to lock gear32. Cam50further includes two opposing cam arms58aand58bthat extend out from annular post52towards the circumference of cam50. At the distal end of each cam arm54is a pair of opposing involute edges60. As will be described in greater detail below, the profile of involute edges60are complementary to the edge of lock lever14within indented region24.

Power locking of latch10will now be described with additional references made toFIGS. 3 to 8. Rotation of lock lever14, lock gear32and cam50are indicated by arrows labeled ‘L’, ‘G’, and ‘C’, respectively. To power-lock latch10, engaging lock motor26drives worm16, which in turn drives cluster gear18. The lock gear32is driven by lock motor26in clockwise direction (FIG. 3). Cam50does not move yet due to the lost motion connection (i.e., bumper46ais not yet in contact with edge56aon depending sidewall54yet).

Once the lost motion is finished and the edge56aon depending sidewall54abuts against the bumper46a, lug48begins to transmit rotation force to depending sidewall54(FIG. 2), so that lock gear32and cam50rotate together in clockwise direction (FIG. 4). Cam arm58arotates into indented region24and the leading involute edge60abegins to interact with a first engagement surface62formed on the edge of indented region24on lock lever14, pivoting lock lever14in counterclockwise direction. First engagement surface62has an involute profile complementary to involute edges60, reducing friction between lock lever14and cam arms58.

Lock gear32and cam50continue moving lock lever14until it reaches its full travel (FIG. 5) and moves into the locked position. Cam arm58adisengages from lock lever14, and lock gear32and cam50continue to rotate until the cam arm58bhits a second engagement surface64located on shoulder25on the lock lever14(FIG. 6). As resistance from the second engagement surface64is encountered, bumper46b(FIG. 2) is compressed and lock motor26stalls.

Once lock motor26is no longer driving lock gear32, the energy accumulated in the compressed bumper46bcauses lock gear32to rebound and rotate in a counterclockwise direction, i.e., in the direction opposite to its previous travel (FIG. 7), back driving cluster gear30and worm28. Friction between cam50and shaft34substantially prevents cam50from rotating with lock gear32until the end of lost motion is reached and bumper46b(FIG. 2) abuts against edge56bon depending sidewall54.

Once edge56bon depending sidewall54abuts against bumper46b, cam50begins to move with lock gear32counterclockwise (FIG. 8). The friction between cam50and shaft34slows down both cam50and locking gear32.FIG. 8shows the approximate position where cam50and locking gear32stop after rebound. With cam50and locking gear32in this position, locking lever14can be manually moved between the locked and unlocked positions without moving cam50, locking gear32or motor26. Additionally, all three are ready for next locking or unlocking power cycle.

If cam50and locking gear32keep moving in the rebound direction past the position shown inFIG. 8, cam50will eventually end up in indented region24of locking lever14(FIG. 9). In this condition, locking lever14can still be operated manually because of the lost motion connection between cam50and locking gear32. Locking lever14is rotated manually in clockwise direction until the first engagement surface62along indented region24engages involute edge60on cam arm58b. Because of the lost motion between locking gear32and cam50, cam50rotates within its range of free travel, but locking gear32remains in place (FIG. 10). Thus there is no back drive of motor26. Locking lever14has reached its full travel into the unlocked position. It can now be rotated manually back and forth without increased efforts caused by moving locking gear32and motor26. Power cycle can also be started in any direction.

Referring now toFIG. 11, a second embodiment of the invention is shown in greater detail. A friction spring70is located around a post72formed in the surface of housing12. Arms74aand74bare biased against a perimeter sidewall76in cam50. When cam50rotates, friction spring70remains stationary due to being looped around post72. Friction created between perimeter sidewall76and spring arms74aand74breduces bounce-back of cam50at the end of travel after one of the cam arms58aor58bhits second engagement shoulder64. The drag caused by friction spring70is not sufficient to significantly hinder movement of cam50during power lock/unlock via lock motor26or by manual lock/unlock via pivoting lo lock lever14.

While the present embodiment of the invention relates to using a lost-motion actuating device to actuate a locking lever, it will be understood that the actuating device can be used to actuate other latch components. For example, the actuating device could be used to actuate a pawl for a power release feature. The pawl is spring-biased against a ratchet (which engages a striker bar to latch the door). Activating the power-release motor causes the cam to pivot the pawl and release the ratchet. When the latch is manually actuated, the pawl can pivot freely between without back-driving the motor. Other uses of the lost-motion actuating device will occur to those of skill in the art. The above-described embodiments of the invention are intended to be examples of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention which is defined solely by the claims appended hereto.