GB2434401A

GB2434401A - Latch arrangement remaining in half-latched position under maximum power

Info

Publication number: GB2434401A
Application number: GB0601344A
Authority: GB
Inventors: John Phillip Chevalier
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-01-23
Filing date: 2006-01-23
Publication date: 2007-07-25
Anticipated expiration: 2026-01-23
Also published as: GB0601344D0; GB2434401B

Abstract

A latch arrangement for an automotive door or other closure, for releasably retaining a striker, comprising: a rotary latch bolt 1 being spring-biased towards an open position, a pawl 3 being spring-biased towards a latching position and an electric motor 6 having an output drive coupled for selectively actuating the pawl 3 to move it against its spring bias from its latching to a releasing position. The power supplied to the electric motor is controlled such that under normal operation the motor 6 is operated under less than full power to limit the speed of actuation of the pawl 3, to allow the latch bolt 1 to rotate from its fully-latched position past a half-latched position to ensure that it continues to its open position. The electric motor 6, the latch bolt 1, the pawl 3 and the spring-biasing of the latch bolt and the pawl are such that under maximum output drive, as a result of a failure of the control means to limit the power supply, the pawl is allowed by the output drive to return its latching position before the latch bolt has reached its half-latching position, to ensure that it stays half latched, preventing opening of the door or other closure.

Description

I

M&C Folio: GBP93599 Document: 1138461

LATCH ARRANGEMENT

This invention relates to a latch arrangement for an automotive door or other closure such as a tail gate or a cupboard or container, and whilst the invention is particularly useful in an automotive door application, it is not limited to automotive use.

Automotive door latches controlled by electric motors and control circuitry are well known, and examples are described in my patent applications WO 98/27301 and GB-A-2415990.

Safety is of course paramount in automotive vehicle applications, and door latches in particular have to function safely in a wide variety of fault conditions. Door latches should be prevented from opening whilst the vehicle is in motion, or when there is an electrical fault condition in the control circuitry which drives the electric motor within the latch.

The present invention provides a latch arrangement for an automotive door or other closure, for releasably detaining a striker, comprising: a rotary latch bolt shaped to retain the striker at a fully-latching position and at a half-latching position and to release the striker at an open position of the latch bolt; a paw! mounted for movement between a latching position, at which it retains the latch bolt at its fully-latching or its half-latching position, and a releasing position, at which it allows the latch bolt to move to its open position; the latch bolt being spring-biased towards its open position and the paw! being spring-biased towards its latching position; and an electric motor having an output drive coupled for selectively actuating the pawl to move it against its spring bias from its latching to its releasing position to cause the latch-bolt to release the striker; and control means for controlling the power supplied to the electric motor such that under normal operation the motor is operated under less than full power to limit the speed of actuation of the pawl, to allow the latch bolt to rotate from its fully-latched position past its half-latched position to ensure that it continues to its open position, to allow the door or other closure to open; wherein the electric motor, the latch bolt, the pawl and the spring-biasing of the latch bolt and the pawl are such that under maximum output drive, as a result of a failure of the control means to limit the power supply, the pawl is allowed by the output drive to return its latching position before the latch bolt has reached its half-latching position, to ensure that it stays half-latched, preventing opening of the door or other closure.

The invention provides a form of mechanical override which ensures half-latching, and thus preventing of the opening of the door or other closure, in the event of an electrical fault in the electrical power supply to the motor. If full power from the vehicle battery is supplied to the motor, in a latch of the type described, then, without the benefit of the invention, there would be a danger of the paw! being swung away from its latching V position long enough for the latch bolt to have rotated to its open position, allowing the door or other closure to open.

Whilst it is possible to use a slow speed motor or drive mechanism to ensure full release of the door, slow acting electrical door release would, in most cases, negate the advantage of having electrical power door opening as a comfort feature in modern cars.

If the power door release is not fast enough, as is the case with most latches on the market today, the door is often opened mechanically, because the electrical drive mechanism has insufficient time to react to manual activation of a door handle.

Accordingly, in a preferred embodiment, the latch and the power release drive mechanism have been designed, and the motor selected, to allow very fast unlatching of the latch bolt (6 to 10 milliseconds). If the motor is powered directly without control, the pawl would move away from the latch bolt engaging position and return under its return spring to engage the latch bolt this time in its half-latch or secondary latching position, i.e. the claw will not have enough time to rotate past its half latch positionlsecondary latching position. This will have the effect of preventing the door from moving to its free and fully open position.

The door then remains secure, as the secondary latching position is by design intended to provide a safeguard against accidental door opening (due to accidental impact or mechanical shock).

The pawl is driven out from the latch bolt engaging position and held up for a predetermined period of time at a position at which the latch bolt is free to rotate. This is achieved by slowing down an otherwise fast motor (the typical motor speed being greater than 10,000 rpm). The speed of the motor is slowed down using e.g. PWM as one possible means. This would allow the latch bolt sufficient time to rotate freely to its fully unlatched position under the effect of the force of its return spring and the door weather seal reaction force (typically between 300N and 500N).

V The motor is powered at varying speeds so as to allow very fast actuation initially towards the latch bolt releasing position. It is then slowed down to ensure the latch bolt has moved freely past its secondary latching position. From there onwards the latch bolt is free and the paw! is released to return to a position whereby it is once again capable of engaging the latch bolt in one of its two latching positions.

When the motor is powered without control of its speed (and particularly due to the fast speed of actuation) the pawl will swing up and immediately be freed to return back to a latch bolt engaging position under its return spring. The paw! intercepts the latch bolt just before it reaches its secondary latching position, and so prevents the door from becoming open. The works in exactly the same manner as under mechanical shock whereby the latch bolt is released but recaptured in its secondary latching position in time to prevent the door from opening.

In order that the invention may be better understood, preferred embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a partial perspective view of components of the latch arrangement of an automotive door latch embodying the invention; Figure 2 is a partial plan view of the latch of Figure 1, with the latch bolt in its fully-latched position; Figure 3 is a partial perspective view corresponding to Figure 2, but with the latch bolt in its half-latched position; Figure 4 corresponds to Figure 8 of my above-mentioned publication GB-A-24 15990, and illustrates an alternative embodiment of the invention which provides for powered door closing as well as electrical door opening; and Figure 5 is a schematic diagram of a control circuit for the latch of Figures ito 4.

A first embodiment of the invention will now be described with reference to Figures 1 to 3.

An automotive door latch, of the type described in my above-mentioned patent publications, has a rotary latch bolt 1 mounted for pivotal movement about a pivot 2 fixed to a frame 100. The latch bolt 1 has a typical claw shape, shown more clearly in Figures 2 and 3, for retaining a u-shaped striker (not shown) in the body of the vehicle.

The latch bolt is of steel, with a plastics coating over its surface except for the extremities such as projections 101 and 102 which define notches at fully-latched and half-latched rotary positions.

A pawl 3 is mounted on a pivot point 4 secured to the frame 100, for rotary movement between a latching position as shown in Figures 2 and 3, at which its tip engages into one of the notches 101, 102 of the latch bolt; and a releasing position (not showing) at which it allows the latch bolt to rotate, and its tip may slide along the arcuate edge of the latch bolt.

The latch bolt 1 is spring-biased (not shown) mounted on the pivot point 2, to bias the latch bolt towards its open position: by virtue of a reaction force against the striker, this spring biasing also tends to force the door open, but the weather seal around the door also assists in this action, since the weather seal is resiliently compressed when the door is closed.

The paw! 3 is spring biased by another torsion spring (not shown) mounted on the pivot point 4, biasing the paw! towards its latching position.

Electrical control for the opening of the door is provided by an electric motor 6 having an output drive spindle 7 whose gear drives a gear wheel 8 which in turn drives an indexing gear 9, the arrangement together providing a significant speed reduction from the motor to the indexing gear.

The indexing gear 9 rotates integrally with a radial projection 10 on a pivot axis 11 mounted on the frame 100. The projection 10, shown in Figure 2, is arranged to provide linear actuation to a reciprocating linear actuator 5, which is constrained to move lengthwise of the latch frame 100, by means of a pair of slots formed in its body, and cooperating projections from the latch frame. The opposite end of the actuator 5 is positioned to abut against a boss 31 of the surface of the paw! 3, to rotate the pawl clockwise in Figures 2 and 3, to move the pawl to its releasing position. A further projection 13 mounted on the pivot 11, and appropriately spring baised, returns the actuator 5 to its neutral position as shown in Figure 2. Both projections 10, 13 act on a laterally-projecting tooth 12 of the actuator. Opposite this tooth 12 is a further tooth 14, which cooperates with a further rotary actuator 15 arranged to be driven, against a spring bias, by a cable from a door handle, for manually opening the door. The arrangement thus provides independent manual and electrical door opening.

The door latch is shown in its fully-latched position in Figure 2, with the pawl engaging the notch 101 of the latch bolt. Under the control of circuitry described below with reference to Figure 5, the electric motor may then be energised, for electrical door opening, and the projection 10 may then very rapidly be caused to slide the actuator 5 to release the paw! 3 from the latch bolt. The latch bolt 1 is then accelerated from rest by its spring bias, in a clockwise sense as shown in Figures 2 and 3. Under normal operation, with limited power supplied to the electric motor, the pawl will have been moved sufficiently slowly by the actuator 5 that the latch bolt will have rotated clockwise past the half-latching position shown in Figure 3, such that the pawl is able to slide against the long arcuate surface of the latch bolt until the latch bolt reaches its fully open position.

However, under a fault condition, where the electric motor is supplied with greater power than it should be, for example full power, then the actuator 5 is moved more rapidly, with the result that the pawl 3 begins its acceleration, under its spring bias, earlier in the sequence back to its latching position. Under such conditions, the pawl 3 engages into the half-latching notch 102, as shown in Figure 3, preventing further movement of the latch bolt towards its open position. This is a safety feature which ensures that the door remains closed, albeit at a half-latched position of latch, in the event of an electrical fault.

In order to achieve this result, that normal electrical drive causes the latch bolt to open, but a fault condition in the electrical drive causes half-latching, it is necessary to select appropriately the spring force of the torsion springs on both the latch bolt and the pawl, in relation to their moments of inertia; thus to determine the relative rotary accelerations. It is also necessary to provide the appropriate dimensions of the pawl 3 in relation to the positions of the notches 101, 102 on the latch bolt. Further still, these parameters have to be determined in relation to the power output of the electric motor 6 under its different supply conditions, since this affects the acceleration of the actuator 5.

This combination of parameters may be determined empirically, in any specific configuration of components.

A second embodiment of the latch arrangement is shown in Figure 4, and this is described more fully in my above-mentioned publication GB-A-2415990. In this arrangement, the electric motor 9 has an output drive including a centrifugal clutch 901 and a gear 902 driving a large gear 903 corresponding to gear 8 of Figure 1. Large gear 903 has a pinion 904 driving an indexing gear 905 corresponding to gear 9 of Figure 1.

Coupled to gear 905 is a gear 906 with four angularly-spaced radial projections or teeth which actuate different components of the latch for opening and locking. A first segment gear 907 is also coupled on the same pivotal arrangement to the indexing gear 905, and this drives a second segment gear 908 over part of the angular range of movement of the indexing gear 905. The second segment gear 908 has a projection 909 which drives the latch bolt 1, corresponding to the latch bolt of Figures 1 to 3. This latch bolt 1 has similar notches 203, 204 for latching it.

This drive mechanism selectively couples the indexing gear to the latch bolt to drive it rotationally from a half-latching position to a fully-latching position, to complete the closure of the door under the power of the electric motor.

The latch motor control circuitry is shown schematically in Figure 5. A micro-controller contains program code for controlling the operation of the latch of Figures 1 to 3 or Figure 4, by providing a control signal to a motor driver which supplies electrical power from a 12 volt motor supply to the motor. The micro controller receives input signals indicating the status of the motor driver and the voltage supplied to the motor. It also receives a signal from a handle switch, i.e. a micro-switch positioned in or adjacent to a door handle, for initiating electrical door opening. The micro-controller receives power from a 12 volt permanent supply and signals from a Local Interconnect Network (LIN), through LiN interface (JIF) and voltage regulation circuitry as shown.

The latch mechanism requires a slower actuation speed to release the door than the motor will normally provide under full electrical power. The power to the motor is therefore controlled in order to reduce the actuation speed to a level that allows the latch to open safely and controllably. The power level is controlled using software in the micro-controller. This software may use one or more of the following algorithms: 1. Proportional integral derivative (PID) control, such that the velocity and angular position of the output drive of the motor may be controlled; 2. Pulse width modulation (PWM) or pulse code modulation (PCM), controlling the speed of the motor; and 3. Linear analogue motor control, in which the circuitry uses a potentiometer or certain predetermined register circuits to control output power.

If the controlling circuitry malfunctions and applies full power to the motor, then the latch will not fully release. Equally, if the motor is powered erroneously as a result of a short circuit, the latch cannot fblly release.

Claims

CLAIMS: I. A latch arrangement for an automotive door or other closure,

for releasably detaining a striker, comprising: a rotary latch bolt shaped to retain the striker at a fully-latching position and at a half-latching position and to release the striker at an open position of the latch bolt; a pawl mounted for movement between a latching position, at which it retains the latch bolt at its fully-latching or its half-latching position, and a releasing position, at which it allows the latch bolt to move to its open position; the latch bolt being spring-biased towards its open position and the pawl being spring-biased towards its latching position; and an electric motor having an output drive coupled for selectively actuating the pawl to move it against its spring bias from its latching to its releasing position to cause the latch-bolt to release the striker; and control means for controlling the power supplied to the electric motor such that under normal operation the motor is operated under less than full power to limit the speed of actuation of the pawl, to allow the latch bolt to rotate from its fully-latched position past its half-latched position to ensure that it continues to its open position, to allow the door or other closure to open; wherein the electric motor, the latch bolt, the paw! and the spring-biasing of the latch bolt and the paw! are such that under maximum output drive, as a result of a failure of the control means to limit the power supply, the paw! is allowed by the output drive to return its latching position before the latch bolt has reached its half-latching position, to ensure that it stays half-latched, preventing opening of the door or other closure.

2. A latch arrangement according to Claim 1, in which the output drive comprises an indexing gear with at least one radial projection and an actuating member arranged to couple the rotary drive from the radial projection to the pawl.

3. A latch arrangement according to Claim 2, comprising a drive mechanism selectively coupling the indexing gear to the latch bolt, to drive the latch bolt from its half-latching position to its fullylatching position, to complete closure of the door or other closure.

4. A latch arrangement according to Claim 2 or Claim 3, further comprising a locking mechanism for locking the pawl, coupled to a further radial projection from the indexing gear, angularly spaced from the said projection, for selective electric locking and unlocking in sequence with the releasing of the paw! for the opening of the door or other closure.

5. A latch arrangement according to any preceding claim, in which the paw! is mounted for pivotal movement and is spring-biased by a torsion spring on its pivot axis.

6. A latch arrangement according to any preceding claim, in which the latch bolt is formed with angularly-spaced notches engagable by the pawl at the fully-latching and half-latching position to hold the latch bolt against its spring bias.

7. A latch arrangement according to any preceding claim, in which the control means comprises a PID control circuit provided with feedback from the motor output drive, to control the speed of the output drive.

8. A latch arrangement according to any preceding claim, in which the control means comprises PWM, PCM or another modulation technique to limit the power suppiy to the electric motor.

9. A latch arrangement according to any preceding claim, in which the control means comprises linear analogue motor control circuitry to limit the power supplied to the electric motor.

10. A latch arrangement substantially as described herein with reference to the accompanying drawings.