GB1355657A - Control circuits for vehicle window lift mechanism - Google Patents

Abstract

1355657 Control of D.C. motors JOSEPH LUCAS (INDUSTRIES) Ltd 28 Sept 1971 [13 Oct 1970 12 Jan 1971] 48497/70 and 1396/71 Heading H2J [Also in Division E2] A control circuit for a vehicle window lift mechanism comprises a manually operable switch 18 having an off position, a first position in which its movable contact engages a fixed contact 19 and a D.C. motor 17 is driven to lift the window, and a second position in which the movable contact engages fixed contact 21 to reverse the motor to lower the window, a limit switch 24 which closes in the event of an obstruction being placed in the path of movement of the window while it is being lifted, a relay having normally-open contacts 15a, 15b and an operating coil 15 energized by conduction of a transistor 14 and a relay having changeover contacts 16a, 16b and an operating coil 16, the arrangement being such that closure of the switch 24 reverses the direction of operation of the motor 17, even though the switch 18 remains in its first position, and the motor is operated for a predetermined time to lower the window after which it stops until the switch 18 is moved to its off position and then restored to its first position. During lifting the motor 17 is energized through circuit elements 19, 16b, 16a, a resistor 23 being in parallel with its armature. Movement of switch 18 to engage the contact 21 causes the transistor 14 to turn on and energize the coil 15, closure of whose contact 15a energizes the coil 16 to changeover contacts 16a, 16b and so complete the motor supply circuit through circuit elements 15a, 16a, 16b and 15b. Closure of switch 24 also turns on the transistor 14 and rapidly charges a capacitor 27. Members 15, 16 operate as before to reverse the motor 17 until the capacitor 27 has discharged and transistor 14 turns off to de-energize the coil 15, the coil 16 remaining energized through its contact 16a, resistors 23, 25, 26 and contacts 18, 19 to prevent further operation of the motor. The coil 16 is de-energized by movement of the switch 18 to its off position. The switch 24 may be supplied through the switch contacts 18, 19 to ensure that it is only effective during a lifting operation and so prevent inadvertent actuation by other causes from lowering the window and/ or stalling the motor. A control circuit including this modification is described, Fig. 2 (not shown), and includes an RC circuit associated with the switch 24 to ensure that inadvertent movement of the switch 18 to its off position, before the switch 24 has been closed long enough to turn on the transistor 14 and charge the capacitor 27, does not cause mal-operation of the circuit. A diode may be connected in series with the resistor 23, Fig. 2 (not shown) to prevent the motor being stalled with the window open, should pressure be applied to the switch 24 before the switch 18 is moved from its first position, with the pressure then being maintained indefinitely.