WO1996018017A1

WO1996018017A1 - A safety device for an electrically operated window

Info

Publication number: WO1996018017A1
Application number: PCT/GB1995/002811
Authority: WO
Inventors: Jeremy John Greenwood
Original assignee: Rover Group Limited
Priority date: 1994-12-03
Filing date: 1995-12-01
Publication date: 1996-06-13
Also published as: GB2310511A; GB9711054D0; AU3988695A; GB2310511B; GB9424464D0

Abstract

A safety device (10), for an electrically operated openable and closeable window, comprises pressure sensitive switch means (S1) operative to sense the presence of an obstruction to closing movement of said window and to activate switching means (T1). The switching means (T1) provides a demand signal for a drive system (30) of said window to cause opening movement of said window which opposes any other command signal for closing of said window. Prolonging means (C1, R2) is also provided operative to prolong said release demand signal for a predetermined length of time.

Description

A SAFETY DEVTCE FOR AM ELEgTR.CCJ-T-.LY OPERATED TNDQ

The present invention relates to a device for an electrically operated window, particularly but not exclusively, a safety device for an electrically operated window of a road vehicle.

Electrically operated windows have become a widespread alternative to the traditional manually operated windows in road vehicles, due to their convenience and ease of operation. However, on closing an electrically operated window, there is a risk of trapping and injuring fingers and other parts of the body in the diminishing gap between the upper edge of the window and the upper edge of the window frame. Therefore, it is known to provide a safety device in such electrically operated window systems.

Many safety devices for electrically operated window systems are activated by a contact switch housed within a rubber seal extending around the periphery of the window frame. Such a contact switch is disclosed in US Patent Nos. 3710050 and 3793772.

Some electrically operated window systems are operated via an electronic control unit of the vehicle. This enables various functions to be incorporated into the system, including a safety system with a contact switch. One system which has been proposed responds to sensing of an obstruction by lowering the window slightly to allow removal of the obstruction.

In GB 2 232 255 an anti-trap system is disclosed which uses a variable resistance sensor and a micro-controller with associated logic to derive a trap condition. This system further uses the micro-controller to control the operation of the window lift motor. On derivation of a trap condition during upward movement of the window, the controller switches off power to the motor and then applies a downward potential. It is necessary for it to power the window down to relieve the pressure on a trapped object, such pressure being applied through the trapped object to provide the compression necessary on the sensor to trigger a trap condition in the micro-controller. It is the inclusion of a micro-controller which provides the sophisticated functionality of this type of system but at a cost to vehicle manufacturers which discourages the application of such a system to models other than their upper ranges which command high prices and can absorb the associated cost.

It is expected that in the future, such lowering of the window will be made mandatory for all electrically operated window systems. However, at present, only a small proportion of vehicles possess electronic control units, due to considerations of cost and space. An object of the present invention is to provide a simple electronic system which is operable to detect an obstruction and thereupon stop an electrically operated window moving upwards. In this way, it will be possible for vehicles without sophisticated electronic control systems to be provided with electrically operated windows with a useful safety system.

According to the invention there is provided a safety device for an electrically operated openable and closeable window, comprising a drive motor operative to close said window in response to a closing potential supplied by a closing demand switch to a first pole of said motor and operative to open said window in response to an opening potential supplied by an opening demand switch to a second pole of said motor and further comprising control means including pressure sensitive switching means operative independently of said demand switches to sense the presence of an obstruction to closing movement of said window and to apply an obstruction potential to said second pole upon detection of said obstruction such that if said obstruction potential is applied to said second pole whilst said closing potential is being applied to said first pole, upward movement of the window will cease.

The obstruction potential may cause opening movement of said window after said closing demand switch is released. The control means may further comprise activating means activated by said pressure sensitive switching means to apply said obstruction potential.

The control means may further comprise prolonging means to prolong the activation of said activating means for a predetermined length of time after said pressure sensitive switching means is released.

The pressure sensitive switching means may be arranged so that mechanical contact therewith closes said pressure sensitive switching means.

The pressure sensitive switching means may be included within a draught excluding seal of a window frame.

The activating means may be dependent on a voltage or current supplied by said control means achieving a threshold level for its activation.

The control means may be operative to achieve said threshold level more quickly on said pressure sensitive switching means being closed than said voltage or current will decay to the point at which said activating means is de-activated after said pressure sensitive switching means is released.

The activating means may be a transistor. The control means may be at least part of a biasing circuit for said transistor.

The activating means may be used to switch a relay which has switching contacts in a drive circuit of said window.

The closing, opening and obstruction potentials may be of equal magnitude.

The opening or obstruction potential when applied to the second pole may be greater than the closing potential when applied to the first pole.

Said obstruction potential may over-ride said closing potential.

One embodiment of the invention will now be described by way of example, referring to the drawings in which:

Figure 1 shows a circuit system of a safety device according to the invention connected to a relay switched drive circuit for an electrically operated window system; and

Figure 2 shows a circuit diagram of the safety device of Figure 1 connected to a directly switched drive circuit.

Referring to Figure 1, a safety device 10 for an electrically operated vehicle window (not shown) comprises a control means consisting of a switch SI and a transistor biasing circuit formed by a potential divider between resistors Rl and R2 and a capacitor Cl . The safety device 10 further comprises activating means in the form of an n- channel enhancement MOSFET Tl which is under the control of the control circuit and is used to switch a relay coil LI which in turn switches its contacts S2A in the circuit of a window lift motor Ml to power motor Ml to wind down the windo .

The source of the n-channel enhancement MOSFET Tl is held to a ground potential GND. The capacitor Cl has two terminals, one of which is connected to the gate of MOSFET Tl, the other to ground GND. The resistor R2 is connected in parallel with capacitor Cl. The switch SI is a single pole normally-open contact switch and is provided within a seal of a window frame of a vehicle (not shown) . Switch SI is arranged to make contact and thus to conduct when pressure is applied to the seal. In use, one terminal of switch SI is held at a supply potential VDD. The other terminal is connected to the terminal of the resistor Rl, the other terminal of which is connected to the gate of MOSFET Tl. VDD is chosen to suit the characteristics of MOSFET Tl.

In use, contact switch SI is normally open. In this condition, resistor R2 holds the gate of MOSFET Tl at GND, and capacitor Cl in a discharged state. Hence, the gate- source voltage for MOSFET Tl is zero and therefore the MOSFET Tl is switched off. If contact switch SI is closed, the resistor Rl is able to conduct current. Current flows through resistor Rl to flow through resistor R2 and to charge capacitor Cl. The potential at the gate of MOSFET Tl consequently rises. Eventually the gate potential rises to such a level that the threshold gate-source voltage is reached, and MOSFET Tl is switched on and will conduct current. On release of the contact switch, the current is broken. Rl no longer conducts current. Discharge current from capacitor Cl flows through resistor R2. The gate voltage of MOSFET Tl gradually drops and eventually falls below the threshold voltage, at which point the MOSFET Tl switches off.

The resistor R2 and capacitor Cl form a prolonging means within the control means operative to delay the switching off of MOSFET Tl. On the opening of switch SI, capacitor Cl discharges through resistor R2 and maintains a voltage across resistor R2 which sustains the operation of MOSFET Tl for a period of time set by a discharge constant (C1R2) , until the voltage dropped across resistor R2 falls below the gate-source threshold level of MOSFET Tl whereupon the transistor turns off.

By simple circuit analysis and algebraic manipulation, it can be seen that the ratio of the time constants for discharging and charging respectively is 1+R2/R1.

Therefore, by selecting an appropriate value for R2/R1, the transistor may be maintained in an 'on' state for a predetermined time. If Rl is of a suitably small value, the capacitor Cl will charge quickly and so reach an effective maximum charge and thus effective maximum gate voltage quickly. The effective maximum gate voltage will be set by the potential across resistor R2, which is derived by V_R2= VDDxR2/ (R1+R2) and is made greater than the gate-source threshold voltage of MOSFET Tl . The value of R2 may be selected according to the desired discharge time constant (C1R2) .

The above described safety device 10 is connected to a relay switched drive circuit 20 for a window lift motor Ml which opens and closes a window in said window frame of the vehicle. The drive circuit 20 includes two relays with coils LI and L2 as shown with switching contacts S2A and S3A respectively. The drain of the MOSFET Tl is connected to one end of the coil LI, and the other end of the coil LI is connected to the supply potential VDD. In use, relay coil LI switches the drive circuit 20 to drive the motor Ml in an opening direction by supplying an opening potential in the form of VDD to a pole P2 of said motor Ml, and relay coil L2 switches the drive circuit 20 to drive the motor Ml in a closing direction by supplying a closing potential in the form of VDD to a pole PI of motor Ml .

Opening and closing demand switch means are provided in the form of single pole, normally-open switches S2 and S3 respectively. One terminal of each switch is connected to ground (GND) . The other terminal of switch S2 is connected to the drain of MOSFET Tl. The other terminal of switch S3 is connected to one end of relay coil L2, the other end of which is connected to the supply potential VDD.

It can be seen that closing of switch S3 will energise relay coil L2, which will in turn switch its contacts S3A to supply a closing potential to pole PI . As pole P2 is connected to ground GND, current will flow through Ml in a closing direction and cause it to drive the window in a closing direction. In similar fashion, closing of switch S2 or switching on of MOSFET Tl will energise relay coil LI and activate the drive circuit 20 to supply VDD as an opening potential to pole P2 of motor Ml . Hence switch S2 and MOSFET Tl act as simple single throw switches connected in parallel . Thus a demand for the window to open can originate from an operator of the 'down' switch S2 or from the safety device 10. If, while switch S3 is closed, the contact switch SI is closed, the window will cease moving in a closing direction because potential VDD will be supplied to poles PI and P2 simultaneously and there will be no resultant electromotive force. When S3 is released, the safety device 10 will cause opening movement of the window because pole PI will be connected to ground GND and current can flow through the motor Ml in an opening direction.

The drive circuit 30 of Figure 2 is a switched device. Relay coil LI is connected to the MOSFET Tl of the safety device 10 as in Figure 1. Relay coil LI operates a single pole, two-way changeover switch S4.

A motor Ml is illustrated to show the way in which the drive circuit 30 is activated by the safety system.

Opening and closing demand switches are provided in the form of single pole, two-way changeover switches S2 and S3. In use, the pole of each switch is normally switched to ground GND. Operation of one of the switches S2, S3 will switch the pole to a supply potential V_x. Switching switch S3 represents a demand signal from an operator for the window to be driven in a closing direction. Switching switch S2 represents a demand signal from an operator for the window to be driven in an opening direction. The pole of switch S3 is connected to a pole PI of the motor Ml. The other pole P2 of the motor Ml is connected to the pole of the relay switch S4. The contact of relay switch S4 which the pole thereof contacts when the relay coil LI is not energised, is connected to the pole of switch S2.

Hence, when relay coil LI is not energised, the potential at the pole of switch S2 is developed to pole P2 of the motor. The potential at the pole of switch S3 is developed to pole PI of the motor Ml, regardless of the state of the relay coil LI. Therefore, if the pole of S2 is switched to the supply potential V₁ and switch S3 is switched to ground GND, then the motor Ml will wind the window open. Alternatively, if the pole of S3 is switched to the supply potential V_x and switch S2 is switched to ground GND and relay coil LI is not activated, then the motor Ml will wind the window closed. If switches S2 and S3 are both switched to V_x at the same time, the motor Ml will not operate or if it is already operating it will cease operation, as both poles PI and P2 will be at supply potential V_x and there will be no resultant electromotive force across the poles PI and P2 to drive motor Ml. If the relay coil LI is energised due to activation of contact switch SI, then the pole of S4 will switch to the other contact. This contact is held at supply potential V₂. Hence if the pole of S3 is switched to V₁₍ then (if V_x = V₂) the motor Ml will cease operation, and on release of switch S3, the motor Ml will wind in an opening direction, driven by potential V₂ which is developed to pole P2.

This particular embodiment is advantageous because the safety device 10 is electrically isolated from the drive circuit 30. In addition to this, the device can be made at low cost as only one additional relay is required for its implementation.

In a further embodiment of the invention disclosed herein, the safety device 10 can be made operable to over¬ ride the closing operation of switch S3, rather than stop the motor at the position it has reached when switch SI is closed. This will ensure that the window is lowered at least far enough to open switch SI without the need for switch S3 to be released, such as might be desirable if a child was standing on switch S3 with its fingers trapped in the window aperture by a closing window. One way of achieving the over-ride feature would be to make potential V₂ (or indeed potential V_x) developed to pole P2 greater than a closing potential V_close developed to pole PI. In this way, if switch SI was to be closed while closing potential V_close was being applied to pole PI, the window would always be driven open (until switch SI opened) by a potential of (V₂ - V_close) developed to pole P2 (or if appropriate by V_x - V_close) . The opening movement of the window would be prolonged beyond the opening of switch SI by the prolonging means of safety device 10, as described with reference to figure 1. To achieve this it would only be necessary to include a potential divider (not shown) between switch S3 and ground GND with pole PI tapping off a potential V_close lower than V₁₍ the resistors forming such a potential divider being selected to lower the potential developed to pole PI enough to cause the window to move downward in a trap condition, without reducing the potential available to pole PI by enough to slow the upward movement to the point of customer complaint. For example, the potential divider could consist of a pair of series resistors of 2Ω and 10Ω, with the 2Ω resistor being included between switch S3 and pole PI and the 10Ω resistor being provided in parallel with the motor Ml between pole PI and ground GND. If V-_L and V₂ were set at 12V, the window would be driven closed by 10V and open by 12V or in the case of an obstruction the window would be driven open by a potential of 2V (i.e. 12V-10V) until after switch SI opened. This feature would provide added safety for minimal cost. A more sophisticated embodiment could regulate V_x and V₂ separately.

Claims

1. A safety device for an electrically operated openable and closeable window, comprising a drive motor operative to close said window in response to a closing potential supplied by a closing demand switch to a first pole of said motor and operative to open said window in response to an opening potential supplied by an opening demand switch to a second pole of said motor and further comprising control means including pressure sensitive switching means operative independently of said demand switches to sense the presence of an obstruction to closing movement of said window and to apply an obstruction potential to said second pole upon detection of said obstruction such that if said obstruction potential is applied to said second pole whilst said closing potential is being applied to said first pole, upward movement of the window will cease.

2. The device of claim 1 wherein said obstruction potential will cause opening movement of said window after said closing demand switch is released.

3. The device of claims 1 or 2 wherein the control means further comprises activating means activated by said pressure sensitive switching means to apply said obstruction potential.

4. The device of claim 3 wherein said control means further comprises prolonging means to prolong the activation of said activating means for a predetermined length of time after said pressure sensitive switching means is released.

5. The device of any preceding claim wherein said pressure sensitive switching means is arranged so that mechanical contact therewith closes said pressure sensitive switching means.

6. The device of any preceding claim wherein said pressure sensitive switching means is included within a draught excluding seal of a window frame.

7. The device of any of claims 3 to 6 wherein said activating means is dependent on a voltage or current supplied by said control means achieving a threshold level for its activation.

8. The device of claim 7 wherein the control means is operative to achieve said threshold more quickly on said pressure sensitive switching means being closed than said voltage or current will decay to the point at which said activating means is de-activated after said pressure sensitive switching means is released.

9. The device of claim 3 or any dependent claim wherein said activating means is a transistor.

10. The device of claim 9 wherein said control means is at least part of a biasing circuit for said transistor.

11. The device of claim 9 or claim 10 wherein said activating means is used to switch a relay which has switching contacts in a drive circuit of said window.

12. The device of any preceding claim wherein the closing, opening and obstruction potentials are of equal magnitude.

13. The device of any preceding claim wherein the opening or obstruction potential when applied to the second pole is greater than the closing potential when applied to the first pole.

14. A device according to any preceding claim wherein said obstruction potential over-rides said closing potential.

15. A safety device substantially as described herein with reference to figure 1 or figure 2 of the accompanying drawings.