GB2167482A - Door locking system - Google Patents

Abstract

A door locking system for a motor vehicle comprising at least one switch (20) reversably movable between a closed position and an open position; at least one electric motor (24) associated with a corresponding door lock for actuating the door lock between a locked position and an unlocked position; and a control circuit (22) comprising monitoring means for monitoring a change in voltage produced by a change in the position of the switch or one of the switches and for producing an output signal corresponding to the last operation of the switch or one of the switches, and actuating means responsive to a change in the output signal from the monitoring means for actuating the electric motor or electric motors associated with the or each door lock. <IMAGE>

Description

SPECIFICATION Door locking system This invention relates to a door locking system for a motor vehicle or the like.

In known electrically operated door locking systems for motor vehicles which have multipoint switching, a problem has been encountered because each switch needs its own associated electronic circuitry. This is because the known systems monitor each switch in both its open and its closed position, and the associated electronic circuitry reacts to a change in switch position using an engage/inhibit arrangement. It is not possible to connect more than one switch to one circuit.

It is an object of the present invention to overcome this disadvantage.

According to the present invention, a door locking system for a motor vehicle comprises at least one switch reversably movable between a closed position and an open position; at least one electric motor associated with a corresponding door lock for actuating the door lock between a locked position and an unlocked position; and a control circuit comprising monitoring means for monitoring a change in voltage produced by a change in the po- sition of the switch or one of the switches and for producing an output signal corresponding to the last operation of the switch or one of the switches, and actuating means responsive to a change in the output signal from the monitoring means for actuating the electric motor or electric motors associated with the or each door lock.

Unlike the previously known arrangement, the door locking system of the present invention monitors any change in voltage on one of the poles of a switch due to a change in position of the switch; rather than if the switch is in its open or its closed position. As a consequence, the number of connections between each switch and the electronic circuitry can be reduced from two to one, and the control circuit can be made to respond to any number of switches.

The monitoring means preferably comprises a resistor network which produces a voltage step for each change in position of the switch or one of the switches; a voltage step in one direction (upwards) corresponding to the switch or one of the switches being moved to an open position; a voltage step in the other direction (downwards) corresponding to the switch or one of the switches being moved to a closed position. Preferably the voltage steps are of constant value.

The monitoring means is preferably such that the output signal it produces only changes if consecutive voltage steps are in opposite directions. In this case, the monitoring means preferably comprises first and second operational amplifiers and a seti reset latch circuit. Preferably the set/reset latch circuit has two outputs; a first at logic level 1 when the second is at logic level 0; and the second at logic level 1 when the first is at logic level 0; the logic levels being determined by a change in position of the switch or one of the switches.The first and second operational amplifiers are preferably connected to the switch or switches with a first resistor-capacitor network preferably connected between the positive input terminal of the first operational amplifier and the resistor network, a second resistor-capacitor network connected between the negative input terminal of the second operational amplifier and the resistor network, and the other input terminals of the first and second operational amplifiers being connected directly to the resistor network. With this arrangement, when the switch or one of the switches is moved to an open position, the resistor network produces a voltage step in the upwards direction.The presence of the first resistor-capacitor network means that the voltage step signal is registered at the negative input terminal of the first operational amplifier before it is registered at the positive input terminal (the first resistor-capacitor network delays the transmission of the voltage step signal), and a negative pulse is produced in the output of the first operational amplifier indicating that a switch has been opened. As the input terminals of the second operational amplifier are connected in the opposite manner to that of the first operational amplifier, no pulse is produced in the output of the second operational amplifier.However, if the switch or one of the switches is moved to a closed position, a voltage step in the downward direction is produced by the resistor network, resulting in a negative pulse in the output of the second operational amplifier, but no change in the output of the first operational amplifer. The set/reset latch circuit preferably comprises a third and a fourth operational amplifier interconnected in such a way that the output from the fourth operational amplifier is connected to the negative input terminal of the third operational amplifier and that the output from the third operational amplifier is connected to the negative input terminal of the fourth operational amplifier.The output of the first operational amplifier is preferably connected to the positive input terminal of the third operational amplifier and the output of the second operational amplifier is connected to the positive input terminal of the fourth operational amplifier. If a negative output pulse is produced by the first operational amplifier, the output (the first output) from the third operational amplifier is held at or moved to logic level 0 and (due to the interconnection of the third and fourth operational amplifiers) the output (the second output) from the fourth operational amplifier is held at or moved to logic level 1.Similarly, if a negative output pulse is produced by the second operational amplifier the output (the second output) from the fourth operational amplifier is held at or moved to logic level 0 and the output (the first output) from the third operational amplifier is held at or moved to logic level 1. In this case, the set/reset latch circuit acts as a NAND circuit. It will be appreciated therefore that in a series of switching operations (no matter how rapid) the logic level outputs of the third and fourth operational amplifiers will only be reversed if two consecutive switch movements are in opposite directions. The last switch operation is also memorised in that the logic levels are held after the last switch operation, thereby ensuring correct final actuation of the motor or motors.It will be appreciated that the wiring configurations of the operational amplifiers may be reversed such that the first and second operational amplifiers produce positive output pulses if the switch or one of the switches is moved to an open or a closed position respectively, and such that opposite changes in logic level are produced for changes in switch position. In this case the set/reset latch circuit acts as a NOR circuit. The first, second, third and fourth operational amplifiers are preferably integrally formed as a single chip integrated circuit (a programmable operational amplifier).

The actuation means preferably comprises first and second cross-linked, edge-triggerable monostable multivibrators, preferably integrally formed as a single chip integrated circuit, and a switched relay associated with each multivibrator, one relay actuating the motor or motors to lock the door or doors, and the other relay actuating the motor or motors to unlock the door or doors. Where the set/ reset latch circuit has two outputs, the first output is preferably fed to the input of the first multivibrator, the second output is preferably fed to the input of the second multivibrator, and both multivibrators are either negative edge triggerable or positive edge triggerable.It will be appreciated that if the switch or one of the switches is moved and the logic levels in the first output and the second output are changed as a result, because the logic levels change in opposite directions and because the multivibrators are triggerable in the same direction, only one of the multivibrators produces an output pulse, hence only one of the relays is actuated, and the motor or motors move in one direction only. If switch movement does not produce a change in logic levels (when two consecutive switch movements are in the same direction), neither of the relays is actuated. Preferably the multivibrators have a common timing circuit of a resistor and a capacitor. This is possible because at any one time only one of the relays may be actuated.The time constant of the timing circuit governs the length of the output pulses from the multivibrators, and hence the length of time the motor or motors are actuated. The second multivibrator preferably actuates its associated relay to lock the door or doors, and the first multivibrator actuates its associated relay to unlock the door or doors.

As a door locking system of this type must be permanently activated, problems can occur due to the continuous flow of current through the switch contacts which may produce oxide layers thereon.

In a door locking system in accordance with this invention, the system normally operates at 1mA or less (higher values can lead to degradation of the battery), and preferably the system comprises means by which a higher current (preferably approximately 20 mA) is fed intermittently to the contacts to burn off any oxide layers formed.

Preferably the higher current is fed to the contacts when the motor or motors are actuated.

Preferably the door locking system also comprises a crash sensor circuit which senses impacts above a predetermined level on the motor vehicle, and which on sensing such an impact overrides the monitoring means to activate the actuating means to unlock the door or doors. Preferably the crash sensor circuit is only operable when the motor vehicle ignition is switched on.The crash sensor circuit preferably includes a g, sensor which is preferably triggered due to a deceleration above 60 m/s2 This invention is now described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an illustration of a known arrangement for a door locking system; Figure 2 is an illustration of a door locking system in accordance with the present invention; Figure 3 is a circuit diagram of the control circuit of the system in Figure 2; and Figures 4A and 4B illustrate the variations in input and output from the components in Figure 3 for variations in switch position.

Referring to Figure 1, the known door locking system comprises a switch 2 having an open pole S and a closed pole S'; a motor 4 for actuating a door lock (not shown); and a control circuit 6. The control circuit 6 comprises a terminal 8 for connection to the motor vehicle battery (not shown); a power supply protection circuit 10; and, for each pole S, S' of the switch 2, a transient protection network 12, 12', a timer 14, 14' and a switched relay 16, 16'. If the switch 2 is moved to pole S, the transient protection network 12 triggers the. timer 14 to close the switched relay 16, which actuates the motor 4 to unlock the door. Similarly, movement of the switch 2 to pole S' will lock the door.

The timers 14, 14' are interlinked by an engage/inhibit arrangement which prevents them actuating the motor 4 at the same time. However, no more than one switch can be connected to this circuit 6.

The door locking system shown in Figure 2 is for a five door motor vehicle (four side doors and a tailgate). Each door has a locking switch, three of which, 20, are electrically connected to a control circuit 22. The control circuit 22 is also electrically connected to motors 24 associated with each door lock 26.

The control circuit 22 (see Figure 3) has eight ter minals; a terminal Si, S2, Sa for each switch 20, a ground terminal GND, a battery terminal B+, a terminal IGN connected to the ignition of the motor vehicle, and terminals M1, M2 for connection to the door lock motors 24 for actuating the motors to unlock and lock the doors respectively. The input circuit 28 from the battery terminal comprises a diode D, and a voltage regular circuit 30. Diode D, acts to protect the remainder of the control circuit 22 from transients and prevents the Darlington resistors Ti and T2 associated with relays RL, and RL2 from conducting under reverse bias. The voltage regulator circuit 30 comprises a transistor T3, two Zener diodes ZD1, ZD2, a resistor R" and a capacitor Ci. The voltage regulator circuit 30 provides a fixed voltage output VDD for the rest of the control circuit; VDD remaining constant despite any fluctuations in battery voltage.

The control circuit 22 also comprises monitoring means 32 and actuating means 34. The monitoring means 32 comprises a resistor network 36 comprising five resistors Ra, Ra, R4, R5 and R6 and a diode D2. This arrangement is such that any change in voltage on any one of the terminals Si, S2, S3 due to one of the switches 20 being opened or closed produces a constant voltage step at connection points 38, 39, 40; the height of the voltage step being determined by the values of the resistors Ra to R5. If a switch is opened, a voltage step in the upwards direction is produced. If a switch is closed a voltage step in the downwards direction is produced.Diode D2 provides a fixed voltage drop across it which is monitored by the remainder of the monitoring means 32. Capacitors C2, C3 provide protection against transients for the monitoring means 32. Resistors R7, Ra, Ra guarantee voltage VOD is provided on the monitoring means 32 side of terminals S,, S2, S3. The remainder of the monitoring means comprises four operational amplifiers 42,44,46,48 and two resistor-capacitor networks 50,52. The positve in put terminal 54 of the first operational amplifier 42 is connected via the first resistor-capacitor network 50 to connection point 40 of the resistor network 36. The negative input terminal 56 of the first operational amplifier 42 is connected directly to connection point 39 of the resistor network 36.The negative input terminal 58 of the second operational amplifier 44 is connected via the second resistor-capacitor network 52 to connection point 38 of the resistor network 36. The positive input terminal 60 of the second operational amplifier is connected directly to connection point 40 of the resistor network 36. Under stable conditions, when no switch movement is occurring, the voltage level at input terminals 54 and 60 is above that at input terminals 56,58 and as a consequence a constant voltage is produced at the output terminals 62,64 of the first and second operational amplifiers 42,44 respectively.If one of the switches 20 is opened a positive voltage step is produced at connection points 38,39,40, which, due to the predetermined value of the resistors R2 to R5, is greater than the difference in voltage at input terminals 54 and 56 of the first operational amplifier. Because of the positive voltage step produced at connection points 39,40, the voltage at input terminal 56 rises substantially instantaneously to a value above that previously on input terminal 54, and the voltage terminal 54 also rises by the same amount but, due to the first resistor-capacitor network 50 the rise is exponential. As a consequence, for a period of time determined by the time constant factor of the first resistor capacitor network 50, the voltage on input terminal 56 is above that on input terminal 54 and a negative pulse is produced in the voltage level at output 62.The positive voltage step has no effect on the voltage level at the output terminal 64 of the second operational amplifer 44 as the voltage level at input terminal 60 always remains above the voltage level of the input terminal 58.

In a similar manner, if one of the switches 20 is closed, a negative pulse is produced in the voltage at the output terminal 64 of the second operational amplifier 44, whereas the voltage at the output terminal 62 of the first operational amplifier remains unchanged.

The third and fourth operational amplifiers 46,48 are interconnected in such a way as to act as a set/ reset latch circuit. The positive input terminal 66 of the third operational amplifier 46 is connected to the output terminal 62 of the first operational amplifier 42. The negative terminal 68 of the third operational amplifier 46 is connected via a resistor network comprising resistors R10, Rii and R12 to the output terminal 76 of the fourth operational amplifier 48. Similarly, the positive input terminal 70 of the fourth operational amplifier 48 is connected to the output terminal 64 of the second operational amplifier 44.The negative input terminal 72 of the fourth operational amplifier is connected via a resistor network comprising resistors R,3,R,4,R15 to the output terminal 74 of the third operational amplifier 46. In this arrangement, the voltage at the output terminals 74,76 switch between two levels (logic level 1 and logic level 0). If output terminal 74 is at logic level 1, then output terminal 76 is at logic level 0, and vice versa. If a negative pulse is produced in the voltage at the output terminal 62 of the first operational amplifier 42, the negative pulse received at the positive in put terminal 66 of the third operational amplifier 46 causes the voltage level at the output terminal 74 to move to logic level 0 (assuming it was previously at logic level 1).This causes the negative input terminal 72 of the fourth operational amplifier 48 to go low, and the voltage level at the output terminal 76 to move to logic level 1. If the voltage level at output terminal 74 is already at logic level 0, then no change occurs when a negative pulse is produced at output terminal 62. Similarly, if a negative pulse is produced at the output terminal 64 of the second operational amplifier 44, the voltage level at the output terminal 76 of the fourth operational amplifier 48 is moved to or held at logic level 0, and the voltage level at the output terminal 74 of the third operational amplifier 46 is correspondingly moved to or held at logic level 1. The changes in logic level are used to activate the actuating means 34.

The four operational amplifiers 42,44,46,48 are integrally formed on a single chip integrated circuit (for example, a circuit sold by Motorola under the serial no. MC 14573). The value of resistor R,6 is chosen to ensure the four operational amplifiers 42,44,46,48 operate at a low current (to prevent degradation of the battery) and to restrict the slew rate (to protect the circuit against noise).

The actuating means 34 comprises two interconnected, negative-edge triggerable, monostable multivibrators 78,80 and the two relays RL, and RL2. The multivibrators 78,80 are integrally formed as a single chip integrated circuit, for example as sold by Motorola under the serial no. MC 14538.

Actuation of relay RL, actuates the motors 24 to unlock the doors. Actuation of relay RL2 actuates the motors to lock the doors. The output terminal 74 of the third operational amplifier 46 is connected to the trigger input terminal 82 of the first multivibrator 78, and the output terminal 76 of the fourth operational amplifier 48 is connected to the trigger input terminal 84 of the second multivibrator 80. The output terminal 86 of the first multivibrator 78 is connected to the base of Darlington transistor Ti, the collector of which is connected to relay RL1. Similarly, the output terminal 88 of the second multivibrator 8C is connected via Darlington transistor T2 to relay RL2.As the multivibrators 78,80 are negative-edge triggerable, an output pulse is only generated when the output at third and fourth operational amplifiers 46,48 drops from logic level 1 to logic level 0. Hence, multivibrator 78 only generates an output pulse, and hence only actuates relay RL1, when a switch 20 is opened.

Similarly, multivibrator 80 only actuates relay RL2 when a switch 20 is closed. The length of the output pulses, and hence the length of time the motors 24 are actuated is governed by the values of resistance R17 and capacitor C4. A common resistance R,7 and capacitance C4 can be used on the timing circuit because, at any one time, only one of the multivibrators 78,80 will be generating an output pulse. Diodes D3, D4 are connected between the output terminal 86,88 of one multivibrator 78,80 and the input terminal 82,84 of the other multivibrator 78,80. When an output pulse is generated by a multivibrator 78,80, this diode feedback sends a high signal from the multivibrator to the input of the other multivibrator, to thereby store the next event.Resistor R,8,capacitor C6 and diode D6 set the R-C time constant on the reset line and prevent the voltage level at the reset input terminals 90,92 going above VOID.

The changes in voltage at the input and output terminals of the operational amplifiers and multivibrators for a switch 20 being opened and a switch 20 being closed is shown in Figures 4A and 4B respectively.

When the motors 24 are actuated, a high current (approximately 20 mA) is sent from the motor drive circuit 94 through resistors R,,,R,, and diodes D6,D7,D8 to the switch 20 contacts. This high current substantially removes any oxide layer formed on the switch 20 contacts, and keeps the contacts substantially clean.

The control circuit 22 also comprises a crash sensor circuit 96 comprising a resistor R2, and a g sensor 98 connected between the IGN terminal of the control circuit and the negative input terminal 68 of the third operational amplifier 46. The crash sensor circuit 96 only operates when the ignition of the motor vehicle is switched on. If the g sensor 98 detects a rapid deceleration (due to the motor vehicle being in a crash) above a predetermined level (preferably 60 m/sec2), the g sensor 98 shorts out and a high voltage is automatically applied to the negative input terminal 68 of the third operational amplifier 46. This high voltage overrides any signal from the switches 20, and sends the output terminal 74 of the third operational amplifier 46 to logic level 0 (assuming it is not already there) which triggers multivibrator 78, and hence relay RL1, to actuate the motors 24 to unlock the doors.

A door locking system in accordance with the present invention has the advantage over known systems that it can react to rapid switching of the switches. All the necessary components are readily available, and, therefore, the control circuit can be easily and cheaply manufactured. Arrangements can easily be provided for contact cleaning and crash sensing. More than one switch can be connected to a control circuit.

Claims (17)

1. A door locking system for a motor vehicle comprising at least one switch reversably movable between a closed position and an open position; at least one electric motor associated with a corresponding door lock for actuating the door lock between a locked position and an unlocked position; and a control circuit comprising monitoring means for monitoring a change in voltage produced by a change in the position of the switch or one of the switches and for producing an output signal corresponding to the last operation of the switch or one of the switches, and actuating means responsive to a change in the output signal from the monitoring means for actuating the electric motor or electric motors associated with the or each door lock.

2. A door locking system as claimed in Claim 1, in which the monitoring means comprises a resistor network which produces a voltage step for each change in position of the switch or one of the switches; a voltage step in one direction corresponding to the switch or one of the switches being moved to an open position; a voltage step in the other direction corresponding to the switch or one of the switches being moved to a closed position.

3. A door locking system as claimed in Claim 2, in which the voltage steps are of substantially constant value.

4. A door locking system as claimed in Claim 2 or Claim 3, in which the monitoring means is such that the output signal it produces only changes if consecutive voltage steps are in opposite directions.

5. A door locking system as claimed in Claim 4, in which the monitoring means comprises first and second operational amplifiers and a set/reset latch circuit.

6. A door locking system as claimed in Claim 5, in which the set/reset latch circuit has two outputs; a first at logic level 1 when the second is at logic level 0; and the second at logic level 1 when the first is at logic level 0; the logic levels being determined by a change in position of the switch or one of the switches.

7. A door locking system as claimed in Claim 5 or Claim 6, in which the first and second operational amplifiers are connected to the switch or switches with a first resistor-capacitor network connected between the positive input terminal of the first operational amplifier and the resistor network, a second resistor-capacitor network connected between the negative input terminal of the second operational amplifier and the resistor network, and the other input terminals of the first and second operational amplifiers being connected directly to the resistor network.

8. A door locking system as claimed in Claim 7, in which the set/reset latch circuit comprises a third and a fourth operational amplifier interconnected in such a way that the output from the fourth operational amplifier is connected to the negative input terminal of the third operational amplifier; the output from the third operational amplifier is connected to the negative input terminal of the fourth operational amplifier; the output of the first operational amplifier is connected to the positive input terminal of the third operational amplifier; and the output of the second operational amplifier is connected to the positive input terminal of the fourth operational amplifier.

9. A door locking system as claimed in Claim 8, in which the operational amplifiers are integrally formed as a single chip integrated circuit.

10. A door locking system as claimed in any one of Claims 1 to 9, in which the actuating means comprises first and second cross-linked, edge-triggerable monostable multivibrators, and a switched relay associated with each multivibrator, one relay actuating the motor or motors to lock the door or doors, and the other relay actuating the motor or motors to unlock the door or doors.

11. A door locking system as claimed in Claim 10 comprising monitoring means comprising a set/ reset latch circuit having two outputs, in which the first output is fed to the trigger input of the first multivibrator, the second output is fed to the trigger input of the second multivibrator, and both multivibrators are either negative edge-triggerable or positive edge-triggerable.

12. A door locking system as claimed in Claim 10 or Claim 11, in which the multivibrators have a common timing circuit of a resistor and a capacitor.

13. A door locking system as claimed in any one of Claims 1 to 12 comprising means by which a high current is fed intermittently to the switch contacts to clean the contacts.

14. A door locking system as claimed in Claim 13, in which the high current is fed to the contacts when the motor or motors are actuated.

15. A door locking system as claimed in any one of Claims 1 to 14 comprising a crash sensor circuit which, on sensing an impact above a predetermined level, overrides the monitoring means to activate the actuating means to unlock the door or doors.

16. A door locking system as claimed in Claim 15, in which the crash sensor circuit is only operable when the motor vehicle ignition is switched on.

17. A door locking system substantially as hereinbefore described with reference to, and as shown in, Figures 2 to 4 of the accompanying drawings.