GB2433768A

GB2433768A - Latch mechanism

Info

Publication number: GB2433768A
Application number: GB0526546A
Authority: GB
Inventors: Denis Cavallucci; Gurbinder Singh Kalsi; Chris Rhodes; Nigel Victor Spurr; Sylvain Rehi Chonavel; David Peatey; Paul Moore; Robert Frank Tolley; Jean-Vincent Olivier; Robert James Clawley
Original assignee: ArvinMeritor Light Vehicle Systems France SA
Current assignee: Inteva Products France SAS
Priority date: 2005-12-29
Filing date: 2005-12-29
Publication date: 2007-07-04
Also published as: GB0526546D0

Abstract

A latch mechanism including: ```a latch bolt 14 rotatable on a latch chassis 12 and having an open position corresponding to an ```open condition of the latch and a closed position corresponding to a closed condition of ```the latch, ```a toggle link 26 pivotally mounted on the chassis, ```a pawl 32 for selectively retaining the latch bolt in the closed position, ```and an index wheel 36, ```wherein the pawl 32 is pivotally mounted at 30 on the toggle link 26, ```the index wheel 36 being capable of moving the toggle link 26 from a first position (fig.2) in which ```the pawl is retracted from the latch bolt to a second position (fig.1) in which the pawl is able ```to retain the latch bolt in the closed position.

Description

Latch Mechanism This invention relates to vehicle door latches and in

particular, but not exclusively to power opening vehicle door latches.

It is known to provide vehicle door latches with a power opening feature in order to reduce the load which the user must apply to the latch handle in order to open the door. This is of particular importance as the opening and closure loads reacted by vehicle door latches rise in line with increasing door seal loads. The door seal load is that load applied to the door by the door seal which is under compression between the door and the vehicle body.

Generally speaking, the greater the door seal load, the better the isolation of the passenger cabin from outside environmental factors, such as tyre and wind noise. Another source of high door seal load can be as a result of a road traffic accident which results in distortion of the door or frame.

In order to prevent the door from opening under the seal load, the load is reacted by the latch mechanism, and in particular a latch bolt and pawl arrangement. Thus, the higher the seal load the greater the reaction load observed in the latch mechanism.

In known latch mechanisms, the pawl is rotated from engagement with the latch bolt in order to open the latch mechanism. However, in order for the pawl to release the latch bolt, the friction between the latch bolt and the pawl, generated by the reaction to the seal load between the pawl and the latch bolt, must be overcome. Consequently, the higher the seal load, the greater the demand placed on the passenger in order to open the door.

It is known to provide a power opening latch in order to reduce the manual effort required to open the door. However, this does not solve the problem of the high friction load which must be overcome to open the latch.

it is advantageous therefore to provide a latch mechanism which has a reduced friction load which must be overcome to open the latch since this reduces the power required to drive the power opening mechanism.

It is an object of the current invention to at least mitigate some of the problems outlined above.

According to the present invention there is provided a latch mechanism including: a latch bolt rotatable on a latch chassis and having an open position corresponding to an open condition in the latch and a closed position corresponding to a closed condition in the latch, a toggle link pivotally mounted on the chassis, the toggle link carrying a pawl rotatable with respect to the toggle link, the pawl for selectively retaining the latch bolt in the closed position to close the latch mechanism, the latch mechanism further including an index wheel for selectively moving the toggle link so as to move the pawl between a first position in which the pawl is permitted to retain the latch bolt in the closed position, and a second position in which the pawl retracts from the latch bolt to open the latch.

The invention will now be described with reference to the following drawings, in which:-Figure 1 is a schematic plan view of the latch mechanism of the current invention, shown in its closed condition.

Figure 2 is a schematic plan view of the latch mechanism of claim 1, showing the pawl retracted from the latch bolt so as to allow opening of the latch.

Figure 3 is a schematic plan view of the latch mechanism of figure 2 showing the latch bolt in its open position, Figure 4 is a schematic plan view of the latch mechanism of figure 3, showing the latch bolt in its open position with the latch mechanism reset in readiness for closure of the latch mechanism, Figure 5 is a schematic plan view of the latch mechanism of figure 4 showing the latch mechanism in its first safety condition.

In figure 1 a latch mechanism 10 is shown having a latch chassis 12, on which is mounted a latch bolt 14, a toggle link 26, a pawl 32 and an index wheel 36, the operation of which will be described in further detail shortly. The latch mechanism 10 is typically mounted in a vehicle door and is arranged to co-operate with a striker (not shown for clarity) mounted on a vehicle body.

The latch bolt 14 is rotatably mounted on the latch chassis 12 by way of a latch bolt pivot 16. The latch bolt 14 is biased in a clockwise direction by a latch bolt spring (not shown for clarity) in a known manner. The latch bolt 14 has a U-shaped slot 20 for receiving the striker, and for retaining the striker in the closed position as shown in figure 1. The striker accesses the latch bolt 14 by way of a mouth 18 cut into the latch chassis 12. The latch bolt 14 has a first safety abutment 22, a closure abutment 24, and a peripheral region 46, the purpose of which will be described in further detail shortly.

Also mounted for rotation on the latch chassis 12 is the toggle link 26 which is rotatable with respect to the latch chassis 12 by way of a toggle link pivot 28. The toggle link pivot 28 is arranged at a first end 26A of the toggle link 26. The toggle link 26 is biased in a clockwise direction by a toggle link spring which is not shown for clarity but which acts between the toggle link and the chassis. A second end 26B of the toggle link 26 defines a pawl pivot 30 on which is rotatably mounted the pawl 32. The pawl 32 is biased in an anticlockwise direction by way of a pawl spring, which is also not shown for clarity, but which acts between the toggle link and the pawl. In an alternative embodiment a pawl spring is provided which acts between the pawl and the latch chassis. Anticlockwise rotation of the pawl 32 is limited by a pawl stop (not shown for clarity) which acts between the pawl 32 and the toggle link 26 to prevent anticlockwise rotation of the pawl 32 relative to the toggle link 26 beyond the position shown in figure 2. The second end 26B of the toggle link 26 also defines an abutment 34 for engaging the index wheel 36 as will be described in further detail shortly.

The pawl 32 is provided to selectively engage the latch bolt 14 as follows. The pawl 32 has a pawl tooth 33 which is shown in figure 1 in engagement with the closure abutment 22 of the latch bolt 14. With the closure abutment 22 so engaged, the latch bolt 14 is retained in the closed position so as to hold the striker in the U-shaped slot 20.

The index wheel 36 is mounted on an index wheel pivot 38 and is driven by an electric motor which is not shown for clarity. The index wheel 36 includes an inner annular portion 40 and a series of radial projections in the form of teeth 42. Between the teeth 42 are arranged a series of recesses 44. In this particular embodiment, six teeth 42 (and six recesses 44) are shown, although it will be appreciated that a different number of teeth may be employed on the index wheel 36 within the scope of the invention. With the latch mechanism 10 in the closed condition of figure 1, a first tooth 42A is in engagement with the abutment 34 of the toggle link 26. As a result, the toggle link 26 is held against the action of the toggle link spring so as to allow the pawl tooth 33 to engage the latch bolt 14, thereby retaining the latch mechanism 10 in the closed condition.

In summary, figure 1 shows the latch mechanism 10 in the closed condition in which a striker (not shown) is retained within the U-shaped slot 20 in order to hold the vehicle door closed.

When the user wishes to open the vehicle door, he may actuate a manual release, for example, an outside door handle. A signal is sent from the outside door handle to the electric motor, to instruct the electric motor to drive the index wheel 36 from its figure 1 position to its figure 2 position. Reference to figure 2 shows that the index wheel 36 has rotated in a clockwise direction from its figure 1 position to allow the abutment 34 of the toggle link 26 to disengage from the first tooth 48A. As shown in figure 2, the abutment 34 now rests in a first recess 44A arranged between the first tooth 42A and a second tooth 42B. The toggle link 26 has moved from its figure 1 position to its figure 2 position under the action of the toggle link spring, and also under the action of the latch bolt which is rotated by its relative movement with respect to the striker so as to drive the pawl out of its path of rotation and thereby displace the toggle link. The effect of this is to move the paw! pivot 30 in an upward direction so as to disengage the pawl tooth 33 from the closure abutment 24.

Since the latch is able to drive the toggle link from its figure 1 position to its figure 2 position it follows that in an alternative embodiment of latch mechanism, the toggle link is not provided with a toggle link spring. Rotation of the toggle link in the anticlockwise direction upon opening of the latch in this embodiment is dependent on the action of the latch bolt on the pawl.

Figure 2 therefore shows a transient position, in which, for example, an outside door handle has just been actuated. As soon as the pawl tooth 33 retracts from the closure abutment 24, the latch bolt 14 will begin to rotate in a clockwise direction under the action of the latch bolt spring and the door seal.

It will be noted that since the toggle link 26 is biased in a clockwise direction, and the pawl 32 is biased in an anticlockwise direction, the effect of rotating the index wheel 36 to release the toggle link 26 causes the pawl tooth 33 not only to rotate out of engagement with the closure abutment 24 as in conventional pawl arrangements, but to retract from the closure abutment 24 in a direction at 45 degrees to a tangent of the axis of rotation of the latch bolt. This is achieved under a combination of clockwise rotation of the toggle link 26 and anticlockwise rotation of the pawl 36, the resulting direction of movement annotated at A in figure 2. In this way, the pawl tooth 33 is able to disengage the closure abutment 24 rapidly, and with the minimum of friction generated between the pawl tooth 33 and the closure abutment 24. Furthermore, substantial advantage is gained by way of the geometry of the latch mechanism when it is in the closed condition as shown in figure 1. The majority of the load passing from the latch bolt closure abutment 34 to the pawl tooth 33 is transferred to the latch chassis 12 via the pawl pivot 30 and toggle link pivot 28. This results from the near alignment of the pawl tooth 33, pawl pivot 30 and toggle link 28.

Some of the load is transferred to the latch chassis 12 by the toggle link abutment 34 and index wheel 36 but this load is substantially smaller than that transferred by the toggle link pivot. Consequently, the friction generated between the abutment 34 and the index wheel 36 (i.e. that friction which must be overcome to open the latch mechanism of the current invention) is for less than that generated between the pawl tooth and latch bolt (i.e. that friction which must be overcome to open conventional latch mechanisms).

As mentioned above, figure 2 shows a transient position in which the latch bolt 14 has just been released from engagement with the pawl 32. Upon opening of the vehicle door and under the action of the latch bolt spring, the latch bolt 14 rapidly rotates in the clockwise direction from the transient position shown in figure 2 to the open position shown in figure 3. It will be noted that the toggle link 26, pawl 32 and index wheel 36 have not moved from their figure 2 position. Only the latch bolt 14 has rotated in order to release the striker from the U-shaped slot 20 to allow the opening of the latch. With the latch mechanism 10 in its figure 3 position, the vehicle door is now open.

However, it will be appreciated that if the toggle link 26, pawl 32 and index wheel 36 were to remain in their figure 3 positions, it would not be possible to close the latch mechanism upon closure of the vehicle door since the pawl 32 would not be able to engage either the first safety abutment 22 or the closure abutment 24 of the latch bolt 14.

In order to allow subsequent closure of the latch mechanism 10, the index wheel 36 is driven by the electric motor in the clockwise direction as soon as the latch bolt is in its open position as shown in figure 3.

In driving the index wheel 36, the electric motor moves the index wheel 36 from its figure 3 position to its figure 4 position. In figure 4, it will be noted that the second tooth 42B has driven the abutment 34 to rotate the toggle link 26 against its toggle link spring in order to rotate the toggle link 26 in the clockwise direction allowing the second tooth 42B to engage a tip 35 of the abutment 34 as shown in figure 4. It will be appreciated that the angle through which the index wheel 36 must be driven by the electric motor to move from the figure 2 position to the figure 3 position and onto the figure 4 position is half the angle between the first tooth 42A and second tooth 42B.

With the toggle link 26 in its figure 4 position, the pawl pivot 30 has been moved downwards with respect to the figure 3 position causing the pawl 32 to rotate in the clockwise direction against the action of the pawl spring. This rotation is achieved since the pawl tooth 33 rests against a peripheral region 46 of the latch bolt 14.

The latch mechanism 10 is now reset so that upon closure of the vehicle door, the pawl tooth 33 will be able to retain the latch bolt 14 by way of the first safety abutment 22 and closure abutment 24. This is achieved upon rotation of the latch bolt 14 in an anticlockwise direction under the action of the striker.

Turning now to figure 5, the vehicle door has been closed by the user so that the striker has rotated the latch bolt in an anticlockwise direction from figure 4 so as to allow the pawl tooth 33 to engage the first safety abutment 22. In moving from the figure 4 position to the figure 5 position, the pawl 32 has rotated in the anticlockwise direction under the action of the pawl spring to move off the peripheral region 46 to engage the first safety abutment 22.

As the vehicle door continues to close, the latch mechanism 10 moves from the condition shown in figure 5, to a position virtually identical to that shown in figure 1, with the exception that the second tooth 42B is now in the position assumed by the first tooth 42A in figure 1.

The next time the latch mechanism 10 is opened, a third tooth 42C will be brought into engagement with the abutment in order to reset the latch mechanism 10. In this way, the electric motor ratchets the index wheel 36 each time the latch mechanism 10 is opened and is therefore only ever required to drive the index wheel 36 in a single direction. This substantially increases the motor life, and thereby the reliability of the latch mechanism 10.

It will also be appreciated that, as shown in all the figures and accordingly all latch mechanism conditions, the pawl pivot 30 lies above an imaginary line between the pawl tooth 33 and the toggle pivot 28. In other words the pawl pivot 30 is overcentre the pawl tooth 33 and toggle pivot 28.

In one alternative embodiment of latch mechanism, a single tooth is provided on the index wheel inner annular portion 40 rather than the six teeth of the above described embodiment. In this embodiment, each time the latch mechanism is released, the index wheel is rotated a full 360 degrees in order to reset the mechanism. In a further alternative embodiment, two teeth are provided and the index wheel rotates 180 degrees to reset the mechanism. The embodiment with six teeth rotates 60 degrees in order to reset the mechanism. The more teeth, the less rotation required to reset the latch mechanism and consequently the less power used by the motor. The maximum number of teeth is limited by the width of the recess between the teeth being sufficient to accept the toggle link abutment 34.

The latches shown in figures 1 to 5 are electrically opened by rotation of the index wheel.

In further embodiments, it is possible to provide a manual backup in addition to electrical operation. Thus, a mechanical transmission path can be provided between pawl 32 and an inside door handle, and/or an outside door handle. Operation of the door handle will cause the transmission path to rotate pawl 32 in a clockwise direction as shown in figure 1, thereby releasing the latch. The transmission path typically might include a bowden cable and/or various levers and linkages.

Claims

Claims 1. A latch mechanism including: a latch bolt rotatable on a

latch chassis and having an open position corresponding to an open condition of the latch and a closed position corresponding to a closed condition of the latch, a toggle link pivotally mounted on the chassis, a pawl for selectively retaining the latch bolt in the closed position, and an index wheel, wherein the pawl is pivotally mounted on the toggle link, the index wheel being capable of moving the toggle link from a first position in which the pawl is retracted from the latch bolt to a second position in which the pawl is able to retain the latch bolt in the closed position.

2. The latch mechanism according to claim I wherein a first end of the toggle link is pivoted on the latch chassis, and a second end of the toggle link carries the pawl.

3. The latch mechanism according to claim I or 2 wherein the toggle link is biased in a clockwise direction with respect to the chassis.

4. The latch mechanism according to any preceding claim wherein the pawl is biased in an anticlockwise direction with respect to the toggle link.

5. The latch mechanism of any preceding claim wherein the latch bolt is biased in an anticlockwise direction with respect to the latch chassis.

6. The latch mechanism of any preceding claim wherein the pawl includes a pawl tooth for engaging the latch bolt.

7. The latch mechanism of claim 6 wherein an axis of rotation of the pawl is over centre the pawl tooth and an axis of rotation of the toggle link.

8. The latch mechanism according to claim 7 wherein the axis of rotation of the pawl is over centre the pawl tooth and axis of rotation of the toggle link in a direction towards an axis of rotation of the index wheel.

9. The latch mechanism of any preceding claim wherein the index wheel rotates in a single direction to selectively move the toggle link.

10. The latch mechanism of any preceding claim wherein the index wheel defines a series of circumferentially spaced projections.

11. The latch mechanism according to any preceding claim wherein the toggle link includes an abutment for engaging index wheel.

12. The latch mechanism according to claim 11 when dependent on claim 10 wherein the abutment rests on an index wheel projection when the latch mechanism is in the closed condition.

13. The latch mechanism according to claim 12 wherein the index wheel includes a series of circumferential recesses arranged between the projections, the abutment resting transiently in one of the recesses when the latch mechanism is opened.

14. The latch mechanism according to claim 6, or any one of claims 7 to 13 when dependent on claim 6, wherein a direction of retraction of the pawl tooth upon opening of the latch mechanism is at substantially 45 degrees to a tangent of an axis of rotation of the latch bolt.

15. The latch mechanism according to claim 10, or any one of claims 11 to 14 when dependent on claim 10, wherein the index wheel has six projections.