Differential anti-pinch capacitive sensor

• US 7,319,301 B2
• Filed: 12/17/2004
• Issued: 01/15/2008
• Est. Priority Date: 12/18/2003
• Status: Expired due to Fees

• Current Assignee: Intier Automotive Closures, Inc.
• Original Assignee: Intier Automotive Closures, Inc.
• Inventors: Pribisic, Mirko
• Primary Examiner(s): Ro; Bentsu
• Application Number:
  US10/583,431
• Publication Number:
  US 20070183182A1
• Time in Patent Office: 1,124 Days
• Field of Search: 318/130, 318/434, 318466-469, 49/26, 49/27, 737/63, 737/74, 737/80, 200/61.42, 200/61.43, 200/61.44, 324/658, 324/686
• US Class Current: 318/468
• CPC Class Codes: E05F 15/46 responsive to changes in electrical capacitance
• CPC Class Codes: E05Y 2900/548 Trunk lids
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 2217/960725 Charge-transfer

Abstract

A proximity sensor for sensing an object in the path of or proximate to a closure panel such as a vehicle window. First and second electrodes encased in a non-conductive casing are mounted on the metallic structure near the closing edge of the aperture. The two electrodes define a capacitance CE1/2 therebetween, and parasitic capacitances CE1 and CE2 between the first electrode and chassis ground and the second electrode and chassis ground, respectively. A controller cyclically connects (1) the second electrode to a voltage reference source (V_ref1) and the first electrode to chassis ground and (2) the second electrode to chassis ground and the first electrode to the reference capacitor, thereby periodically charging the capacitance CE1/2 and transferring the charge stored thereon to the reference capacitor whilst short-circuiting the parasitic capacitances. The charge on the reference capacitor, the time period required to charge the reference capacitor to a specified voltage, or a calculated value for CE1/2 are then compared against a reference value in order to derive an obstruction signal.

Claims

1. A proximity sensor mountable adjacent to an aperture of a metallic motor vehicle for determining the presence of an object in the path of or proximate to a closure panel that moves between a fully open position and a closed position, the sensor comprising:

first and second electrodes encased in a non-conductive casing mountable on the vehicle, the two electrodes defining a capacitance CE1/2 therebetween;

a reference capacitor (C1);

a first switch for selectively connecting the first electrode to the reference capacitor or to chassis ground;

a second switch for selectively connecting the second electrode to a first voltage reference source (V_ref1) or to chassis ground;

a controller for controlling the first and second switches in order to periodically charge the capacitance CE1/2 and transfer the charge stored thereon to the reference capacitor.

2. A proximity sensor according to claim 1, wherein the controller transfers charge from the capacitance CE1/2 to the reference capacitor for a fixed number of periods for each charge and discharge cycle of the reference capacitor.

3. A proximity sensor according to claim 2, wherein the controller measures the voltage level of the reference capacitor.

4. A proximity sensor according to claim 2, wherein the controller calculates the value of capacitance CE1/2 according to the following formula:

CE1/2=(C1*V_ref2)/(N*V_ref1).

5. A proximity sensor according to claim 1, wherein the controller transfers charge from the capacitance CE1/2 to the reference capacitor for a variable number of periods for each charge and discharge cycle of the reference capacitor.

6. A proximity sensor according to claim 5, wherein the controller records the number of periods, N, required to transfer charge from capacitance CE1/2 to the reference capacitor until it reaches a voltage equal to a second voltage reference (V_re2).

7. A proximity sensor according to claim 1, wherein the reference capacitor (C1) forms part of a charge integrator circuit connectable to the first switch.

8. A proximity sensor according to claim 7, wherein the integrator circuit includes a switch controllable by said controller in order to dissipate charge from the reference capacitor (C1).

9. A proximity sensor according to claim 8, including a signal amplifier connected between the charge integrator circuit and the controller.

10. A proximity sensor mountable adjacent to an aperture of a metallic motor vehicle for determining the presence of an object in the path of or proximate to a closure panel that moves between a fully open position and a closed position, the sensor comprising:

first and second electrodes encased in a non-conductive casing mountable on the vehicle, the two electrodes defining a capacitance CE1/2 therebetween, a capacitance CE1 between the first electrode and chassis ground, and a capacitance CE2 between the second electrode and chassis ground;

a reference capacitor (C1);

a first switch for selectively connecting the first electrode to the reference capacitor or to chassis ground;

a second switch for selectively connecting the second electrode to a first voltage reference source (V_ref1) or to chassis ground;

circuitry for controlling the first and second switches in order to periodically charge the capacitance CE1/2 and transfer the charge stored thereon to the reference capacitor without transferring substantially any charge stored on the capacitances CE1 and CE2 to the reference capacitor.

11. An anti-pinch assembly for a closure device of a motor vehicle, said assembly comprising:

a closure panel, supported by the motor vehicle, and moveable between a fully open position and a closed position;

a controller operatively connected to the closure panel for controlling the operation thereof, said controller including a proximity sensor mountable adjacent to an aperture of the vehicle for determining the presence of an object in the path of the closure panel, the sensor comprising;

first and second electrodes encased in a non-conductive casing mountable on the vehicle, the two electrodes defining a capacitance CE1/2 therebetween;

a reference capacitor (C1),

a first switch for selectively connecting the first electrode to the reference capacitor or to chassis ground,

a second switch for selectively connecting the second electrode to a first voltage reference source (V_ref1) or to chassis ground, and

circuitry for controlling the first and second switches in order to periodically charge the capacitance CE1/2 and transfer the charge stored thereon to the reference capacitor;

said sensor providing an obstruction signal to the controller for preventing the movement of the closure panel when an object is sensed in the closure path.

12. A method of sensing the presence of an object in the path of or proximate to a closure panel, mounted in a metallic structure that moves in an aperture between a fully open position and a closed position, the method including:

mounting first and second electrodes encased in a non-conductive casing on the structure near the closing edge of the aperture, whereby the two electrodes define a capacitance CE1/2 therebetween, a parasitic capacitance CE1 between the first electrode and chassis ground, and a parasitic capacitance CE2 between the second electrode and chassis ground;

provisioning a reference capacitor (C1);

cyclically connecting (a) the second electrode to a voltage reference source (V_ref1) and the first electrode to a chassis ground and (b) the second electrode to chassis ground and the first electrode to the reference capacitor, thereby periodically charging the capacitance CE1/2 and transferring the charge stored thereon to the reference capacitor whilst short-circuiting the parasitic capacitances; and

comparing the charge on the reference capacitor, the time period required to charge the reference capacitor to a specified voltage, or a calculated value for CE1/2 against a reference value in order to derive an obstruction signal.

13. A sensing method according to claim 12, wherein the value of capacitance CE1/2 is calculated according to the following formula:

CE1/2=(C1*V_C1)/(N*V_ref1),

wherein V_C1 is the voltage on the reference capacitor.

14. A sensing method according to claim 12, wherein the reference capacitor (C1) forms part of a charge integrator circuit connectable to the first electrode.

15. A proximity sensor according to claim 14, wherein the integrator circuit includes a switch in order to periodically dissipate charge from the reference capacitor (C1).