WO2001014676A1

WO2001014676A1 - Closure sensor

Info

Publication number: WO2001014676A1
Application number: PCT/GB2000/003204
Authority: WO
Inventors: Harald Philipp
Original assignee: Harald Philipp
Priority date: 1999-08-20
Filing date: 2000-08-18
Publication date: 2001-03-01
Also published as: GB9919728D0; AU6708100A

Abstract

A car door (1) has a window (2) with a lift motor (3) arranged to lift the window via a linkage (4). The door has a capacitive electrode (5) installed in the upper window guide (6). Via a cable (7), the electrode is connected to a charge transfer capacitance measurement circuit (CTCMC) (11) mounted in the body (not shown) of the car. The CTCMC and an UP/DOWN switch (12) is connected to a motor controller (14) for supplying power from the car's battery to the motor. In the event of a hand H - or other object - being in the window aperture (8) between the window (2) and the top (9) of the door carrying the electrode (5) and the guide (6), the CTCMC (11) measures an unusually high capacitance to ground, i.e. the car's chassis, and the controller stops the motor (3) from lifting the window, even although the UP button on the switch (12) is depressed.

Description

CLOSURE SENSOR

The present invention relates to a capacitive closure sensor, in particular but not exclusively for sensing obstruction to closing of a closure on a vehicle, such as a window of a car

Electric windows of a car can painfully trap a fingers or hands accidentally in the window aperture whilst the window is being closed

The object of the present invention is to provide a sensor to alleviate this problem

According to the invention, there is provided a sensor unit for use with a capacitive electrode arranged adjacent an end of an aperture to be closed in conjunction with a closure and a motor for driving the closure to close the aperture, the sensor unit comprising

• means for measuring capacitance between the capacitive electrode and an electric ground, and

• means for controlling the motor to stop advance of the closure in the event of an abnormal capacitance measurement indicating presence of an unusual object in or adjacent the aperture

The closure can be a door or a shutter or the like, however, it will normally be a window

In the event of an abnormal capacitance, the motor may be controlled merely to stop advance of the closure However, preferably, the control means controls the motor to reverse the advance of the closure in the event of an abnormal capacitance measurement. The reverse may be to open the closure fully, or merely to reverse it for a predetermined amount If the abnormal capacitance is detected at the beginning of closure, it may be permitted to occur to a certain extent, or it may be stopped altogether Normally, the sensor unit will include a memory of normal measured capacitance - of the window glass with the capacitive electrode - as a function of closure advance, the motor being stopped in event of abnormal deviation of the capacitance measurement from the memorised normal measurement However, since the presence of a human body part in the window aperture close to the top of the window will normally cause a capacitance measurement in excess of that of the window, it may be satisfactory merely to detect the abnormality on the basis of the absolute value of the measured capacitance

Whilst other capacitance measurement methods may be used, particularly those using high frequency, preferably the capacitance measurement means includes a charge transfer measurement circuit The latter can be as described in the applicant's prior US Patent No 5,730, 165

Preferably, the charge transfer measurement circuit includes a charge pulse generator having a narrow pulse width, that is to say conveniently between 50nsec and 200nsec. This is of advantage in avoiding erroneous readings such as might otherwise be introduced by moisture

The sensor electrode will normally be a metal strip, stripe or wire For testing its integrity, it may have connections to both ends with the sensor unit being adapted to test for electrical conductivity from one end to the other Whilst this can be done by testing for resistance between the ends of the sensor electrode, it can also be done by testing for capacitance. Provided the same capacitance is seen at both ends, the electrode can be inferred to be intact If it is not, a fault indication is triggered

The sensor unit may be duplicated where a car has two windows for instance. However, preferably a single sensor unit is provided with a multiplexing unit for addressing the sensor electrodes and sensor motors of two or more windows In addition, the sensor unit can be arranged to sense other things In particular, the window UP/DOWN switch can be a capacitive switch, having UP and DOWN capacitive sensor plates addressed by the sensor unit To help understanding of the invention, a specific embodiment thereof with variants will now be described by way of example and with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic view of a car door and window winding system, including a sensor unit in accordance with the invention,

Figure 2 is a block diagram of the sensor unit of Figure 1 ;

Figure 3 is a circuit diagram of a window drive controller an d associated circuitry for the sensor unit of Figure 1 ;

Figure 4 is a circuit diagram of charge transfer circuit and a m icroprocessor for the sensor unit;

Figure 5 is a circuit diagram for a simplified alternative sens or unit; and

Figure 6 is a block diagram similar to Figure 2 showing a sen sor unit having a multiplexing unit for four windows.

Referring first to Figure 1, the car door 1 thereshown has a window 2 with a lift motor 3 arranged to lift the window via a linkage 4. The door has a capacitive electrode 5 installed in the upper window guide 6. Via a cable 7, the electrode is connected to a charge transfer capacitance measurement circuit (CTCMC) 1 1 mounted in the body (not shown) of the car. The CTCMC and an UP/DOWN switch 12 are connected to a motor controller 14 for supplying power from the car's battery to the motor. It should be noted that the CTCMC and the controller comprise a sensor unit of the invention. In the event of a hand H - or other object - being in the window aperture 8 between the window 2 and the top 9 of the door carrying the electrode 5 via the guide 6, the CTCMC 11 measures an unusually high capacitance to ground, i.e. the car's chassis, and the controller stops the motor 3 from lifting the window, even although the UP button on the switch 12 is depressed, or the controller is latched for window lifting following initial depression of the button, where the controller is programmed for this feature.

A memory 15 is associated with the controller as is a tooth counter 16, for counting gear teeth of the winding mechanism, whereby the normal capacitance of the electrode 5 to ground induced by the presence of the rising glass - in the absence of a foreign object - can be memorised in the memory. In the presence of an object such as the hand, the capacitance increases, due to coupling to the hand of the rest of the individual's body Comparison of the measured capacitance with the memorised value reveals the abnormality and the motor is stopped before the hand is painfully gripped between the window and the top of the door

Referring to Figure 2, the arrangement of the CTCMC and the motor controller is shown in more detail, in that the controller is comprised of a microprocessor 50 and a power transistor array 17 controlled by the micro-processor

Turning on to Figures 3 & 4, the circuitry is arranged on two printed circuit boards, a mother board circuit shown in Figure 3 and a daughter board circuit shown in Figure 4, the daughter board being referenced 40 in Figure 3 The power transistor array 17 includes six transistors Q1-Q6, arranged in an H-bridge (believed to require no further description) to switch unregulated electrical power on line 18 from the car's battery 19 to the motor-up line 20 or the motor-down line 21 in accordance with a control voltage from the respective lines 22,23 from the daughter board Whether the motor is driving the window up or down, its drive current is returned to ground via a low - 0.05Ω - resistor 24 A stall detection circuit 25 amplifies the voltage across this resistor, which rises in event of stall and applies the amplified in voltage to the daughter board on line 26.

Also shown in Figure 3 is the UP/DOWN switch 12 arranged to apply voltage to either the switch-up line 27 or the switch-down line 28 Finally a pulse generator circuit 29 is arranged to switch the polarity on the transfer gate line 30 positive during a short pulse - typically for 80nsec - when the signal on transfer drive line 31 becomes positive. This is under control of the micro-processor 50 on the daughter board and associated 20MHz clock 41, see Figure 3

The daughter board incorporates a power supply 42, an e² PROM embodying the memory 15, a two stage charge sample amplifier 44 and an analogue to digital converter 45. The CTCMC circuit 1 1 is arranged to transfer charge from the sensor electrode 5 to a sample capacitor 46 during each sampling period The signal from the tooth counter 16 is applied to the micro-processor on the line 47 In operation, the system is initialised by driving the window up and down fully. This is under control of the UP/DOWN switch 12, which via the microprocessor controls the voltage on the motor-up and motor-down lines 22,23 to cause the power transistor array to power the motor up and down The tooth counter 16 provides an indication of the window's position End of travel is indicated to the micro-processor by detection of stalling of the motor, whereupon the voltage on the motor-up or motor-down line 22,23 is switched off The normal capacitance of the window to the sensor electrode 5 is memorised in the memory 43 as a table of positions and capacitance values The latter are measured by means of amplifying the voltage across the sample capacitor 46, which accumulates from the sensor electrode during each sample period The voltage is amplified in the amplifier 44 and applied via the analogue to digital converter 45 to the microprocessor for memorisation

After initialisation, the capacitance is measured in the same way whenever the window is operated. If a significant difference between the memorised value and the measured value is detected, the control signal on the motor-up line 22 is switched off. Usually, it is replaced with a control signal on the motor-down line 23 and the window is wound down so that the driver is alerted to the need to remove the obstruction to window closure. The winding down can be total or for a predetermined number of tooth counts, typically corresponding to dropping the window by 25% of its travel If the window is fully open on detection, no signal will be sent to wind the window up. The micro-processor can be programmed to hold the window down for as long as the obstruction is detected and then - when the obstruction is removed - to close it. Alternatively, it can be programmed for operator closure, with the switch 12 when the obstruction is removed

Figure 5 shows an alternative circuit diagram to that shown in Figures 3 & 4, which the man skilled in the art will recognise to be a productionised variant of the essentially prototype circuit shown in Figures 3 & 4

Turning on, Figure 6 shows a sensor unit having a single microprocessor 150, a single CTCMC 111, a single memory 115, a multiplexing unit 151 The latter connects to multiple sensor electrodes 1051 , 1052, 1053, 1054 for four doors. Also the UP/DOWN switches are configured as multiple pairs of capacitive plates 112U1/112D1, 112U2/112D2, 1 12U3/112D3, 1 12U4/1 12D4 These are connected to the microprocessor via the multiplexing unit Further, via a separate portion of the multiplexing unit, four power transistor arrays 1 141, 1 142,1 143, 1 144 are provided for the four window motors (not shown) The multiplexing unit successively addresses the capacitive switches If an operator's finger is placed on one - via a cover - its capacitance to ground will change and the CTCMC will detect this The multiplexing unit will then pass to the appropriate power transistor array a signal appropriate for desired opening or closing of the window The relevant sensor electrode will then be addressed to guard against obstruction during closing

It should be noted that both ends of the sensor electrodes are connected to the multiplexing unit, whereby continuity of the electrode can be tested for in accordance with whether the same capacitance is measured at both ends If not a fault light is illuminated, suitably on the car's dashboard (not shown) via line 160 Where the car has a fault message system, the signal on line 160 can be encoded to identify the particular electrode at fault

In Figure 6, there are also shown additional control switches 170 and adjustment motors 171 for other parts of the car such as door mirrors, all connected to the multiplexing unit These do not require obstruction sensors If the sunroof is to be controlled in this way, it does

The invention is not intended to be restricted to the details of the above described embodiment For instance the initialisation can be up dated with use, to compensate for changes in apparent capacitance of the window with age

The sensor electrode can be embodied in a variety of forms It can be a metal strip or wire embedded in the window guide Alternatively, it can be a screen printed deposit on the window guide Also it can be applied via a self-adhesive backing Whilst the invention is expected to find application primarily with windows, it is also applicable to sun-roofs, electrically powered bonnet and boot lids and other closures in cars. Again, it is not restricted to cars and is applicable to other automobiles and indeed other vehicles, for instance a lift or railway carriage door In this instance, the sensor electrode can be installed in a seal, either on the door or on the door jamb

Claims

1 A sensor unit for use with a capacitive electrode arranged adjacent an end of an aperture to be closed in conjunction with a closure and a motor for driving the closure to close the aperture, the sensor unit comprising • means for measuring capacitance between the capacitive electrode and an electric ground, and • means for controlling the motor to stop advance of the closui e in the event of an abnormal capacitance measurement indicating presence of an unusual object in or adjacent the aperture 2 A sensor unit as claimed in claim 1 , wherein the contiol means is adapted to control the motor to reverse the advance of the closure in the event of an abnormal capacitance measurement, preferably by a predetermined proportion of the closure travel

3 A sensor unit as claimed in any preceding claim, wherein the controller is programmed to complete closing of the closure when the abnormal capacitance measurement ceases

4 A sensor unit as claimed in claim 1, claim 2 or claim 3, wherein the sensor unit includes a memory of normal measured capacitance as a function of closure advance, the motoi being stopped in event of abnormal deviation of the capacitance measurement from the memorised normal measurement

5 A sensor unit as claimed in any preceding claim, wherein the capacitance measurement means includes a charge transfer measurement circuit

6 A sensor unit as claimed in claim 5, including a charge pulse genei atoi having a narrow pulse width 7 A sensor unit as claimed in any preceding claim, wherein the sensor unit includes means foi testing the sensor electrode for continuity and means for alarming in the event of lack of continuity

8 A sensor unit as claimed in any preceding claim, including a multiplexing unit arranged to address a plurality of sensor electrodes and a corresponding plurality of closure motors

9 A sensor unit as claimed in any preceding claim, wherein the closure is a window in an automotive vehicle door, the motor is a window lift motor and the sensor electrode is arranged at the top of the door 10 A sensor unit as claimed in claim 9, wherein

11 A sensor unit as claimed in claim 8 or either of claims 9 and 10 as appendant to claim 8, wherein the multiplexing unit is additionally arranged to address capacitive closure open/close switches 12 A sensor unit as claimed in claim 1 1 , wherein the multiplexing unit is further arranged to address other capacitive switches and adjustment motors

13 A closure sensor comprising

• a sensor unit as claimed in any preceding claim and

• one or more capacitive sensor electrode arrangeable adjacent an end of the or each aperture to be closed in conjunction with the or each closure

14 A closure sensor as claimed in claim 13, wherein the or each sensor electrode is incorporated in a respective window guide

15 A closure sensor as claimed in claim 13 or claim 14, wherein the or each sensor electrode is a respective metal strip, stripe or wire 16 A closure system including

• a closure sensor as claimed in claim 13

• one or more closure switch associated with the or each aperture and

• one or more motor for driving the or each closure to close the or each aperture

17 A closure system as claimed in claim 16, wherein the or each closure switch comprises capacitive open/close sensor plates addressed by the sensor unit

18 A closure system as claimed in claim 17, including the multiplexing unit of claim 8 and additional capacitive switches and adjustment motors arranged to be addressed by the multiplexing unit