Abstract:
An anti-pinch system for a vehicle opening device, such as a window regulator, that includes a pressure sensitive resistive coupler located between a gear and a damper plate in the vehicle opening device. When the load is increased on the vehicle opening device, the resistive coupler compresses, altering its electrical resistance. An electrical circuit runs through the resistive coupler, and the circuits resistance is measured. A controller for the device&#39;s motor is operable to adjust the velocity of the motor based upon changes in resistance in the damper. Preferably, the controller compares changes in measured resistance to an expected change in resistance based upon the opening device&#39;s position to determine whether a pinch condition has occurred.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to powered window regulators for motor vehicles. More specifically, the present invention relates to safety devices used to detect pinching conditions in order to protect both individuals and the motor vehicle.  
       BACKGROUND OF THE INVENTION  
       [0002]     Power window are a popular feature on many vehicles. Typically, a user activates a switch to engage an electric motor that raises or lowers the window glass a vehicle door. However, there is a risk of harm to individuals, objects and the window glass when obstacles are caught between the moving window and the doorframe. To mitigate harm to both individuals and objects, anti-pinching systems have become an important safety feature. Current window regulator anti-pinch technology typically relies upon hall-effect sensors to determine the position of the window glass relative to its fully open or closed position. This signal can be integrated to calculate the velocity of the window glass. When used in conjunction with motor current measurement, the instantaneous output torque of the motor can be calculated within a reasonable margin of error. The instantaneous torque of the motor can be compared to a position vs. torque matrix, to determine if the motor is producing normal or excess torque at this position. If the torque output is excessive, the controller will stop or even reverse the motor to prevent damage from occurring to either the window regulator system or the obstacle in its path.  
         [0003]     While anti-pinch technology using hall-effects sensors and current-sensing circuitry can provide a degree of protection, it is not without its drawbacks. The use of hall-effects and current sensing circuitry drives up the cost of the window regulator controller, as a more powerful microprocessor is required. In addition, the calculated instantaneous torque provides a relatively incomplete picture of the window regulator load performance, from which a “go/no go” decision must be made. The need to respond quickly to infrequently updated torque data is a major contributor to false tripping of the anti-pinch circuit. It is therefore desirable to provide a more responsive, reliable and less expensive anti-pinching system for a window regulator.  
       SUMMARY OF THE INVENTION  
       [0004]     According to a first aspect of the invention, there is provided an apparatus for detecting a pinch condition in a vehicle opening device, comprising  
         [0005]     an electric motor;  
         [0006]     a gear, driven by the electric motor;  
         [0007]     a damper plate, driven by the gear and operatively coupled to the vehicle opening device to move the vehicle opening device between an open and a closed position;  
         [0008]     a pressure sensitive resistive coupler connecting the gear to the damper plate, the resistive coupler varying its electrical resistance when compressed by the motion of the damper plate relative to the gear;  
         [0009]     at least two electrical terminals interconnected by the resistive coupler to form a circuit;  
         [0010]     a controller for the electric motor, operable to measure at least one operating characteristic in the circuit and compare a measured value for the operating characteristic against a predetermined value to determine whether a pinch condition exists.  
         [0011]     According to a second aspect of the invention, there is provided a method for detecting a pinch condition in a vehicle closure device, comprising:  
         [0012]     measuring the electrical resistance in a pressure sensitive resistive coupler that varies its electrical resistance due to compression, and where increasing the load on the vehicle closure device compresses the resistive coupler; and  
         [0013]     comparing changes in the measured electrical resistance to a predetermined threshold to determine if a pinch condition exists.  
         [0014]     The present invention eliminates the need to calculate window glass velocity or to measure motor current in order to measure torque in the window regulator. Instead, the invention measures electrical resistance as it corresponds to torque. In addition, the invention provides a quicker response than prior art anti-pinch systems at a reduced cost.  
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0015]     Preferred embodiments of the present invention are described in detail below with reference to the accompanying illustrations in which:  
         [0016]      FIG. 1  shows a vehicle door for a vehicle equipped with a window regulator;  
         [0017]      FIG. 2  shows a dis-assembled view of the motor assembly for the window regulator shown in  FIG. 1 ;  
         [0018]      FIG. 3  shows a plan view of a first side of the worm gear shown in  FIG. 2 ;  
         [0019]      FIG. 4  shows a plan view of the second side of the worm gear shown in  FIG. 2 ;  
         [0020]      FIGS. 5   a  and  5   b  show a partial sectional view of the motor assembly shown in  FIG. 2  under no load and load conditions; and  
         [0021]      FIG. 6  shows a diagrammatic view of a controller for the motor assembly shown in  FIG. 2 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     Referring now to  FIG. 1 , a vehicle door  10  is shown, having a movable window glass  12 . Window glass  12  is raised or lowered by a window regulator  14 , and moves between an open and a closed position. In the presently illustrated embodiment, window regulator  14  includes a pair of lift plates  16  that slide along a pair of rails  18 . Window glass  12  is mounted into the two lift plates  16 . An electric motor assembly  20  rotates a cable drum(not shown), thereby raising or lowering the lift plates  16  via cables  22 . The implementation of window regulator  14  is not particularly limited. For instance, window regulator  14  could use single or dual rails  18 . Instead of dual lift plates, window regulator  14  could use a single lift plate  16  spanning between two rails  18  Alternatively, window regulator  14  could use a scissor configuration. Other types of window regulators will occur to those of skill in the art.  
         [0023]     Referring now to  FIG. 2 , motor assembly  20  is shown in greater detail. Motor assembly  20  includes a plastic housing  23  and a reversible DC motor  24 . DC motor  24  drives a worm  26 . Worm  26  intermeshes with a set of teeth  28  located on a gear, namely, plastic worm wheel  30 . Worm wheel  30  is rotably mounted around annular post  32  within a gear chamber  34  in housing  23 . Worm wheel  30  provides a first surface  36  facing housing  23  and a second opposed surface  38 . A central aperture  40  is provided in the middle of worm wheel  30 . As can best be seen in  FIG. 3 , a conductive inner slip ring  42  and an outer slip ring  44  are concentrically mounted on first surface  36  around central aperture  40 . Outer slip ring  44  includes a number of evenly-spaced outwardly extending teeth  46 .  
         [0024]     As can best be seen in  FIG. 4 , a recessed region  48  is provided in second surface  38  between an outer annular wall  50  and an inner annular wall  52  that defines the periphery of central aperture  40 . A number of evenly distributed radial walls  54  extend out from inner annular wall  52  towards outer annular wall  50 , partially dividing recessed region  48  into a number of equally sized sectors  55 . The radial walls  54  do not extend all the way to outer ring wall  50 , but instead leave a gap therebetween. Within each sector  55  is a pair of conductive strips  57  and  59  along second surface  38 . Conductive strips  57  and  59  are electrically isolated from each other, but are in electrical contact with inner slip ring  42  and outer slip ring  44 , respectively, via terminal connectors that extend through worm wheel  30 .  
         [0025]     A pressure-sensitive coupler ring  56  is mounted within recessed region  48 . Coupler ring  56  is manufactured from a pressure sensitive conductive rubber such as Zoflex™ that varies in its electrical resistance when compressed. In the present embodiment, the electrical resistance of coupler ring  56  decreases as pressure is applied. Coupler ring  56  includes contoured scallops  58  that are fitted around radial walls  54 , providing a tight fit. A plurality of concave divots  60  are provided on the surface of coupler ring  56 , facing away from worm wheel  30 . While coupler ring  56  is described here as an integral ring, it could also be subdivided into a number of arc segments arranged together to fill recessed region  48 .  
         [0026]     A damper plate  62  ( FIG. 2 ) abuts against coupler ring  56 . Damper plate  62  is a substantially flat disk, having a plurality of studs  64  extending from the surface of damper plate  62  and spaced as to be located within divots  60  in coupler ring  56 . A ring of teeth  66  is provided in damper plate  62  around the edges of a central aperture  68 . A shaft  69  from the cable drum (not shown) is sized as to extend through apertures  40  and  68 , and mesh with ring of teeth  66  on damper plate  62 .  
         [0027]     A pair of electrically connected feelers arms  70 ,  72  is mounted to the surface of housing  23  within gear chamber  34 . Feeler arms  70 ,  72  are spring-loaded and biased away from housing  23  to abut against inner slip ring  42  and outer slip ring  46  respectively. The coupler ring  56  extends between inner slip ring  42  and outer slip ring  46 , thus forming a circuit between feeler arms  70 , 72 . The feeler arms  70 ,  72  are connected to a resistance sensor  74  ( FIG. 5 ) that measures the resistance in coupler ring  56  between inner slip ring  42  and outer slip ring  44 . Alternatively, other operating characteristics of the circuit, such as voltage or current could be measured by a sensor connected to one of the feeler arms  70 ,  72 . Another feeler arm  76  (not shown) is connected to a position sensor  78  ( FIG. 6 ) and is positioned as to be in periodic contact with teeth  46  on outer slip ring  44  when worm wheel  30  rotates. Since feeler arm  72  provides constant power through outer slip ring  44 , position sensor  78  pulses on every time feeler arm  76  contacts one of the teeth  46 .  
         [0028]      FIG. 5   a  shows the worm wheel  30  and damper plate  62  operating under a normal, non-load condition.  FIG. 5   b  shows the worm wheel  30  and damper plate  62  operating under a load condition of 200 N. Engaging DC motor  24  drives worm  26  in the direction indicated by arrow A. Worm  26 , in turn, drives worm wheel  30 . Worm wheel  30  drives damper plate  62 , which in turn, drives window regulator  14 . The resistance of coupler ring  56  is measured by resistance sensor  74  as approximately 2 Mohms. When a load is applied to window glass  12  (i.e., a potential pinch condition occurs), the load is transferred through window regulator  14  to damper plate  62  in the direction indicated by arrow B. Studs  64  compress a portion of ring  56  against radial walls  64 . Under compression, the electrical resistance of coupler ring  56  drops from approximately 2 Mohms to 1 Mohms.  
         [0029]     By measuring the number of pulses in feeler arm  76 , position sensor  78  can track the total rotational distance of worm wheel  30 , and by extension, the position of window glass  12 . The total travel distance of window glass  12  between its open and its closed position can be divided into a number of regions  80   n , ( FIG. 1 ) that each correspond to one full rotation of worm wheel  30 . The size of each region  80   n  is not particularly limited, and each region  80   n , can be sized to be a different multiple number of rotations of worm wheel  30 . Alternatively, if smaller regions are desired, each region  80   n  can be sized to be a fraction of a rotation of worm wheel  30 . Rotating worm wheel  30  in a direction to raise window glass  12  increases the region count and rotating worm wheel  30  in the opposite direction to lower window glass  12  decreases the region count.  
         [0030]     Referring now to  FIG. 6 , resistance sensor  74  and position sensor  78  are located within, or otherwise implemented by, a controller  82 . Controller  82  includes a processor  84 , which can be a microprocessor, micro-controller or application specific integrated circuit (ASIC), and a memory unit  86 , which can be any non-volatile memory, such as ROM, EEPROM or FLASH memory. Controller  82  receives or calculates the resistance values from resistance sensor  74  for each region  80   n  and calculates a resistance delta  90   n  between the current window regions  80   n  and the previous window region  80   n-1 . The resistance delta  90   n  is stored in an array  88  within memory unit  86 . Array  88  also contains expected resistance deltas  92   n  for each region  80   n . As motor assembly  20  raises window glass  12 , processor  84  compares resistance delta  90   n  to the expected resistance delta  92   n . If resistance delta  90   n  is varies from (in the preferred embodiment, is less than) the expected resistance delta  92   n  by more than a predetermined threshold, a pinch condition has been detected. Depending on the severity of the pinch condition detected, processor  84  can slow, stop or even reverse the direction of DC motor  24 . It is contemplated that processor&#39;s response to the detected pinch condition could vary depending on which region  80  window glass  12  is currently located in. For instance, DC motor  24  could slow down if window glass  12  relatively far from its closed position, stop if window glass  12  is close to its closed position, and reverse if window glass  12  is within its final window region  80 .  
         [0031]     Temperature changes, particularly the extremes of winter and summer, have been known to temporally alter resistance values for window regulator  14 . Rubber seals expand and contract, and ice can form between the seals and window glass  12 . Thus, processor  84  may temporally adjust the expected resistance delta  92   n  in array  88  by a specific amount based upon information provided by an external temperature sensor (not shown). In addition to temporary seasonal variances, resistance deltas for the window regulator  14  in different region  80   n  may drift due to wear and tear on the vehicle. Rubber seals may harden or contract, worm efficiency may deteriorate, cabling may begin to slip, etc. Thus, array  88  can maintain a column of previously measured resistance deltas  94   n  for each region  80   n . As the resistance values for each region  80   n  change, controller  82  may update the expected resistance delta  90   n  in array  88  in order to prevent both false or premature pinch detections or belated pinch detections. It should also be appreciated that the expected or resistance values may be dynamically calculated during operation of the window regulator  14 . It should also be appreciated that the invention is not particularly limited and can be applied to opening devices other than window regulators, such as power lift gates, etc. Other opening devices will occur to those of skill in the art.