WO1999061729A1

WO1999061729A1 - Vehicle door latch

Info

Publication number: WO1999061729A1
Application number: PCT/GB1999/001595
Authority: WO
Inventors: Sydney Edward Fisher
Original assignee: Meritor Light Vehicle Systems (Uk) Ltd.
Priority date: 1998-05-22
Filing date: 1999-05-20
Publication date: 1999-12-02
Also published as: GB9810972D0; GB2337555A

Abstract

A vehicle door latch power actuator for door power closure as hereinbefore defined, said actuator including a motor (14) drivingly connected to a power output shaft (20), and a drive transmitting element on the output shaft for operative connection to a latching element of the latch to power a bolt thereof for drawing the associated door from the first safety position to its fully shut position characterised in that the drive transmitting element is a crank arm (24) whose radially outer end is operatively connected to the latching element by a coupling (10), the arm being angularly disposed so that the force applied to the latching element progressively increases as it is shifted from the first safety position by the turning of the arm (24) bringing the longitudinal axis of the coupling (10) closer to the axis of rotation of the shaft.

Description

VEHICLE DOOR LATCH

This invention relates to latches for vehicle doors, particularly for light passenger and goods vehicles, and more specifically to actuators for powered closing of said doors by operation of their latches.

The term "powered closure" is used herein to mean powered operation of the door latch mechanism to draw the door to its fully shut and latched condition from the first safety position of the door at which the latch bolt, commonly a rotating claw, has first engaged a co-acting striker on moving the door towards its closed position. Thus the only manual operation needed is to swing the door gently to the first safety position so that the bolt and striker engage. Thereafter, either automatically or by manual switching, the actuator of the latch mechanism operates the bolt, eg by rotating the claw, to force the door shut against its weather seals and for fully engaging the latch to secure it shut.

Powered closure is becoming desirable both for convenience of the user, in reducing the noise nuisance and wear and tear resulting from slam closing of vehicle doors, to ensure the door is properly closed in a fail-safe manner, and to permit development of more effective weather sealing and variations in door styling and fitting, as for reducing wind noise and resistance at speed, without the inhibitions on door design previously imposed by manual slam closing.

One example of a latch mechanism providing power closure is described and claimed in our co-pending patent application GB9710602.5 dated 23rd May 1997.

The object of the invention is to provide improvements in vehicle door latch mechanisms, in particular their power actuators for effecting power closure, in particular improvements in reliability, durability, operation and ease of manufacture and assembly.

According to the invention there is provided a vehicle door latch power actuator for power closure as defined by claim 1 of the appended claims and preferably or conveniently having some one or more of the subsidiary or optional features defined by other of those claims.

An example of the invention is now more particularly described with reference to the accompanying drawings wherein:-

Fig.l is an exploded perspective view of parts of a vehicle latch power actuator for effecting power closure; Figs.2a and b are views showing an output lever of the mechanism in start and finish positions and;

Fig.3 is a graph of power output of the actuator.

The latch mechanism incorporating provision for power closure is generally as described in our said co-pending patent application 9710602.5 to which reference is made for further detail. In order to effect power closure a latch bolt in the form of a conventional rotating latch claw has to be turned by angular movement of a power input lever carrying a latching pawl which self-engages with the claw, the input lever being driven by connection of an arm thereof to a power actuator by means of a pull cable 10.

The power actuator 4 operating this cable is constructed as a single unit having a housing 12, eg a plastics moulding, locating and enclosing the actuator mechanism and its related electrical components.

An electrical drive motor 14 has a worm 16 on its output shaft meshing with a toothed sector 18 secured on a transverse output shaft 20 journalled in housing 12.

Shaft 20 is located by a gear box cover plate 22 of the housing, one end of the shaft projecting therethrough and the gearing being contained within a sealed compartment defined by the left-hand part of housing 12 as viewed in Fig.l. Said end of shaft 20 mounts an output crank 24 to which cable 10 is connected.

The right-hand part of housing 12 as viewed in Fig.l contains and locates an electric circuit board or module 26 behind a further sealed cover plate 28.

The inner end of shaft 20 carries a radially extending sensor arm 30 mounting a magnet 32 at its distal end.

The electric control circuit for motor 14 in or on module 26 includes a pair of Hall effect sensors 34a, 34b on a mounting 36 in spaced relationship to arm 30 so that the sensors co-act with magnet 32 at respective angular positions of shaft 20.

Referring to Figs.2a and b it will be seen that crank 24 is angularly positioned on shaft 20 so that at a start position, with cable 10 retracted with respect to a fixed cable guide 38 said crank is substantially at right- angles to the direction of pull on the cable, whereas when shaft 20 has rotated anti-clockwise as viewed in the drawings to draw cable 10 to the finish position shown in Fig.2b, the line of pull is close to the axis of rotation of shaft 20.

This arrangement progressively increases the force applied through cable 10 and hence to the claw as the actuator crank 24 approaches said finish position, thus matching the actuator power output with the progressively increasing force needed to close the door against its weather seals as it moves from the first safety position, corresponding to the start position of Fig.2a.

Fig.3 is a graph representing the power output of a sample of the described actuator in relation to the distance of travel of cable 10 from the start position (left-hand side of the graph) to the finish position (right-hand side of the graph) at which the door has been shut fully and retained by the latch mechanism.

This arrangement ensures reliable operation along with the most efficient and effective use of the energy available for driving the actuator.

The position sensors 34a, 34b are positioned to corresponding to said start and finish positions of shaft 20 and operate to limit angular movement thereof to the range of those positions by turning motor 14 on and off through the logic built into module 26. It will be appreciated that other types of position sensors could be utilised eg Reed switches or other forms of micro-switch. As magnet 32 is mounted directly on shaft 20 which in turn carries output crank 24 the position sensing is particularly positive giving exact tracking of movement. The sensors can be positioned to suit the range of operation required. As there are no physical limit stops controlling the range of movement noise and stress on the mechanism is reduced. As there is no physical contact between the moving element and the position sensors assembly tolerances are less critical, the operation is unaffected by wear, and the electrical components of the actuator can be wholly separated from the mechanical parts for increased durability and reliability.

Claims

1. A vehicle door latch power actuator for door power closure as hereinbefore defined, said actuator including a motor drivingly connected to a power output shaft, and a drive transmitting element on the output shaft for operative connection to a latching element of the latch to power a- bolt thereof for drawing the associated door from the first safety position to its fully shut position characterised in that the drive transmitting element is a crank arm whose radially outer end is operatively connected to the latching element by a coupling, the arm being angularly disposed so that the force applied to the latching element progressively increases as it is shifted from the first safety position by the turning of the arm bringing the longitudinal axis of the coupling closer to the axis of rotation of the shaft.

2. An actuator as in claim 1 including an electrical module for controlling operation of the motor, and position sensing means including sensors responsive to the angular position of the output shaft to control the motor so as to determine the limits of operative travel of the crank arm.

3. An actuator as in claim 2 wherein the position sensing means includes a magnet carried on the shaft for angular displacement therewith and a pair of Hall effect or other position responsive sensors positioned to co-act with the magnet.

4. An actuator as in claim 1, 2 or 3 including a housing locating the motor and in which the shaft is journalled, said housing also enclosing electrical circuitry for controlling operation of the motor.

5. A power actuator as substantially as hereinbefore described with reference to and as shown in Figs.l and 2 of the accompanying drawings.

6. A vehicle door latch assembly including an actuator as in any preceding claim.

7. A vehicle including an actuator or a latch assembly as defined by any one of the preceding claims.