This application claims priority to European Patent Application EP 05254552.2 filed on Jul. 21, 2005.
The present invention relates generally to a power release mechanism. More particularly, the present invention relates to a power release mechanism for a vehicle door latch.
It is known to have vehicle door latches that employ a power actuator to release the latch. In such latches, a vehicle user does not directly provide the energy to release the latch via a mechanical linkage from a door handle. Instead, an actuator, such as an electric motor, provides the energy to release the latch. Power release mechanisms are typically used on higher specification vehicles to improve the convenience for the vehicle user, or where (because of a high seal load on the door) the energy required to manually release the latch is too high for the latch to be released by a vehicle user.
Nevertheless, for safety reasons, power release latches typically have a backup manual release mechanism to enable the latch to be released in the event the power actuation mechanism fails.
It is desirable to avoid back-driving of the power release actuator to reset the mechanism after release has occurred because this requires additional control functionality which increases costs. It is also desirable to avoid the need for additional switches in the mechanism to provide feedback on the position of the power release mechanism during a release cycle, which again increases cost. It is known to use stepper motors as actuators for power release mechanisms because these obviate the need for switches. However, stepper motors are still more expensive than a standard DC electric motor.
The present invention seeks to overcome, or at least mitigate, the problems of the prior art.
The present invention provides a power release mechanism for a vehicle door latch including a rotary claw having a mouth to releasably retain a striker, a pawl abutment and a cam surface. The power release mechanism includes a pivotably mounted pawl resiliently biased to contact the pawl abutment to retain the claw in a latched condition and to contact the cam surface when in a released condition. The power release mechanism also includes a power drive formation having an input member configured to receive drive from a power actuator and an output member. One of the input member and the output member includes first and second stall abutments, and the other of the input member and the output member includes a follower configured for contact with the first and second stall abutments during power release of the pawl. Each of the first and second stall abutments is configured to retain the follower and thereby stall the power actuator.
The first stall abutment is contactable by the follower to lift the pawl from the claw. The second stall abutment is contactable by the follower by virtue of the cam surface of the claw pivoting the output member away from the input member such that the follower disengages the first stall abutment, resulting in the retention of the follower at the second stall abutment until the pawl relatches with the claw.
Another aspect of the present invention provides a method of operating a power release mechanism of the type described in the preceding paragraph. The method includes the step of powering the input member until the mechanism stalls with the follower contacting the second stall abutment.
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:
As shown in
The pawl 20 is rotatably mounted about a pivot pin 76, which is also secured to the shut face portion 15b. The pawl 20 is resiliently biased into contact with the claw 22 by a spring (not shown).
As shown in
As shown in
The power release lever 25 further includes a radially extending release cam surface 43 terminating in a first stall abutment in the form of a first hook 44. The first hook 44 extends in a generally clockwise direction when viewed in
A second stall abutment in the form of a ‘L’ shaped second hook 46 is provided radially outwards from the first hook 44, and a pathway 48 in the form of a recess exists between the first hook 44 and the second hook 46 through which a follower in the form of an actuator pin 50 may pass.
The release operation is now discussed in relation to
In
Because the claw 22 is now no longer retained by the pawl 20, the claw 22 rotates counter-clockwise as shown in
As a result, the actuator pin 50 is free to rotate further and enters the passageway 48 between the first hook 44 and the second hook 46. By virtue of the arcuate path of the actuator pin 50, the actuator pin 50 is now retained by the second hook 46 and therefore causes the power release actuator motor 33 to stall for the second occasion. In a preferred embodiment, the controller 30 signals the power release actuator motor 33 to power for a predetermined time (e.g., 0.4 s) before power is stopped. This gives sufficient time for the power release actuator motor 33 to drive the actuator pin 50 from a rest position past the first hook 44 and to stall on the second hook 46 with the latch 12 fully released, but not long enough to damage the power release actuator motor 33. In other embodiments, the stalled state of the power release actuator motor 33 is detected by the controller 30 due to the increasing current passing through the power release actuator motor 33 or due to a door open switch that is triggered by the cam surface 82 of the claw 22. In all of the above embodiments, the internal logic of the controller 30 cuts power to the power release actuator motor 33 with the actuator pin 50 in a known position on its arcuate path.
With reference to
To repeat the release process, the controller 30 merely needs to power the power release actuator motor 33 for a predetermined period of time which is sufficient such that the actuator pin 50 rests against the second hook 46 when the supply of power to the power release actuator motor 33 is stopped.
It is therefore apparent that a reliable release procedure of the claw 22 can be achieved without requiring back-driving of the power release actuator motor 33, the use of springs to reverse the actuator motor drive, switches to detect the position of the mechanism at any point during the release procedure, or potentially the sensing of the stalling of the power release actuator motor 33.
The term “power release actuator” should be understood to encompass any actuator driven by a vehicle power source, such as a vehicle battery. Specifically, the term should not be understood to mean an actuator, such as a door handle, whose power source is a vehicle user. Terms such as “clockwise” and “counter-clockwise” should not be construed as limiting and are merely used for explanation purposes.
It will be understood that numerous changes may be made within the scope of the present invention. The actuator pin 50 could be resiliently biased in a clockwise direction with respect to the gear wheel 52, and as a result the power release lever 25 could be integral with the pawl 20. The hooks 44 and 46 could be provided on the gear wheel 52 and the actuator pin 50 on the power release lever 25. The latch 12 may omit the mechanical back-up functions described in relation to
The foregoing description is only exemplary of the principles of the invention. Many modifications and variations are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than using the example embodiments which have been specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.
Number | Date | Country | Kind |
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EP 05254552.2 | Jul 2005 | EP | regional |