Abstract:
The invention concerns a cable drum having a non-cylindrical profile of its outer surface and the use of this cable drum in a window regulator system, particularly in a vehicle. The window regulator system may include a slider assembly adapted to engage a movable window and move along a pre-defined path, a cable assembly operatively engaging the slider assembly, a cable drum having a first end, an opposed second end, and an outer surface extending substantially from the first end to the second end, with the outer surface having a non-cylindrical profile about which a portion of the cable assembly wraps; and a drive unit operatively engaging the cable drum to selectively cause the cable drum to rotate.

Description:
BACKGROUND OF INVENTION  
       [0001]     The present invention relates generally to window regulators that are employed to raise and lower windows in vehicles.  
         [0002]     Window regulator assemblies are employed to raise and lower windows in vehicles. Such window regulator assemblies may employ a switch to operate a motor, which raises and lowers the window—commonly called a power window. Some power window systems use slider assemblies that are secured to the window and move up and down on guide rails. These slider assemblies may be pulled up and down by a cable assembly, which is driven by a cable drum mounted to the output shaft of the motor. The other ends of the cable assemblies attach to the slider assemblies. The cable drum has a generally cylindrical shape and the cables are wound onto and off of the drum by activating the motor in one direction or the other. Rotation of the cable drum, then, causes the cables to pull the slider assemblies up (to close the window) or to pull the slider assemblies down (to open the window). With a motor having a single speed, and the cable drum being cylindrical, the travel speed and the pull force are constant throughout the entire length of window travel.  
         [0003]     A constant travel speed and pull force may not be desirable for certain window opening/closing conditions. For example, it may be desirable to have a larger pull force at the end of upward (i.e., closing) travel to overcome window seal resistance. Also, it might be desirable to have a larger pull force at the beginning of downward (i.e., opening) travel to overcome seal resistance or release a frozen window. In addition, it might be desirable to increase the travel speed of the window in the mid-travel range, with a slower travel speed at each end of travel. There may be other types of variations in travel speed and pull force that may be desirable for the operation of a window regulator assembly. Such variation in the travel speed and/or pull force during window opening and closing may be possible by employing a controller with some type of a hardware and/or software control function that will provide for the variability desired. But this may increase the size of motor required, and would increase the number of parts and complexity of the window regulator assembly. Consequently, such a solution may be more costly and complex than is desired for a window regulator assembly.  
       SUMMARY OF INVENTION  
       [0004]     An embodiment of the present invention contemplates a window regulator system. The window regulator system may include a slider assembly adapted to engage a movable window and move along a pre-defined path, a cable assembly operatively engaging the slider assembly, a cable drum having a first end, an opposed second end, and an outer surface extending substantially from the first end to the second end, with the outer surface having a non-cylindrical profile about which a portion of the cable assembly wraps, and a drive unit operatively engaging the cable drum to selectively cause the cable drum to rotate.  
         [0005]     An embodiment according to the present invention may contemplate a cable drum for use in a window regulator system of a vehicle having a first end, an opposed second end, and an outer surface extending substantially from the first end to the second end, with the outer surface having a non-cylindrical profile, and with the non-cylindrical profile of the outer surface adapted to receive a portion of a cable assembly therearound.  
         [0006]     An advantage of an embodiment of the present invention is that the window regulator system can move the window with a variable travel speed and variable pull force. This ability to vary the travel speed and pull force is accomplished without requiring a controller with additional hardware and/or software, thus minimizing the cost and complexity of the window regulator system.  
         [0007]     An advantage of an embodiment of the present invention is that the motor size can be reduced by shaping the profile of the cable drum to reduce the maximum torque output required by the motor to produce the required pull force at each portion of window travel. A smaller motor may improve packaging, and reduce the mass and cost of the motor. For example, the pull force can be increased at the end of upward travel to overcome seal resistance, and/or at the beginning of downward travel to overcome seal resistance or release a frozen window. Additionally, the travel speed of the window can be increase in the mid-travel range to assure relatively quick movement between the fully closed and fully open positions. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0008]      FIG. 1  is a somewhat schematic, partially exploded, perspective view of a portion of window regulator system for a vehicle window, in accordance with the present invention.  
         [0009]      FIG. 2  is an enlarged view of a portion of the window regulator system of  FIG. 1 .  
         [0010]      FIG. 3  is a schematic view of a cable drum and cable of a window regulator system for a vehicle window, in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0011]      FIGS. 1-3  illustrate a window regulator system, indicated generally at  10 , for raising and lowering a vehicle window (not shown). The window regulator system  10  includes a first guide rail  12  and a second guide rail  14 , which mount to vehicle structure, such as a door (not shown), in a conventional manner.  
         [0012]     A first slider assembly  16  mounts to the first guide rail  12  and a second slider assembly  18  mounts to the second guide rail  14 . The guide rails  12 ,  14  define the paths along which the slider assemblies  16 ,  18  move. Each slider assembly  16  may include a slider  20  (mounted to a respective guide rail), a clamp plate  22 , a friction pad  24  that mounts between the slider  20  and clamp plate  22  and engages the window, and a lift plate  26 . The slider assemblies  16 ,  18  may be conventional and so will not be discussed or shown in greater detail herein.  
         [0013]     The first guide rail  12  may also have an upper pulley  28  and a lower pulley (not shown), and a down stop  34  mounted thereon, and the second guide rail  14  may have an upper pulley  30  and a lower pulley  32  mounted thereon. Alternatively, other mechanisms for redirecting and allowing a sliding motion of a stretched cable may be employed instead of the pulleys, if so desired.  
         [0014]     A cable assembly  42  may include a first cable  36 , a second cable  38  and a third cable  40 . The cables  36 ,  38 ,  40  may each have an outer casing and an inner core, as is known to those skilled in the art. The inner cores of the cables  36 ,  38  are not shown herein, and the inner core of the cable  40  is shown only in  FIG. 3 . The first cable  36  connects at a first end to the first slider assembly  16  and at a second end to the second slider assembly  18 . The first cable  36  also extends around the upper pulley  28  and the lower pulley  32 .  
         [0015]     The second and third cables  38 ,  40  in the cable assembly  42  include first ends that are attached to a cable drum  44  (discussed below), and wind around or unwind from the drum  44  depending upon the direction the drum rotates. The second cable  38  includes a second opposing end that is secured to the second slider assembly  18 , and is mounted around the upper pulley  30 . The third cable  40  includes a second opposing end that is secured to the first slider assembly  16 . Alternatively, the second and third cables  38 ,  40  connected to the cable drum  44  can be a single cable wrapped around the drum  44 , with first and second ends connected to respective slider assemblies  16 , 18 .  
         [0016]     The cable assembly, then, forms a pull-pull type of system between the cable drum  44  and the slider assemblies  16 ,  18 . That is, depending upon the direction of rotation of the motor  46 , the cables  36 ,  38 ,  40  will pull the slider assemblies  16 ,  18  up along the guide rails  12 ,  14  or will pull the slider assemblies  16 ,  18  down along the guide rails  12 ,  14 . The slider assemblies  16 ,  18 , cables  36 ,  38 ,  40  and pulleys  28 ,  30 ,  32  are operative in a known manner in response to the actuation of the motor  46  to raise and lower the slider assemblies  16 ,  18 , and thereby raise and lower the window, and so will not be discussed in greater detail herein.  
         [0017]     The window regulator system  10  also includes a drive unit  48 , which includes the bidirectional motor  46 . The drive unit  48  is fixed relative to the guide rails  12 ,  14 . The supply of power to and control of the motor  46  can be conventional and so will not be discussed further herein. The motor  46  has an output shaft  50 , with the cable drum  44  mounted to and driven by the output shaft  50  about an axis  54 . The drive unit  48  may also include a drum housing  52  that covers and protects the drum  44  and cables  38 ,  40 .  
         [0018]     The cable drum  44  has a first end  56  that mounts adjacent to the motor  46  and an opposed second end  58  facing away from the motor  46 . An outer surface  60  extends generally between the first and second ends  56 ,  58  (best seen in  FIG. 3 ). This outer surface  60  has a profile  62  that is a generally frustum-conical shape—being radially larger near the first end  56  and tapering down toward the second end  58 . For the motor  46  driving the drum  44  at a given speed, then, a cable winding on the drum  44  near the first end  56  will have greater travel speed but less pull force than when winding on the drum  44  near the second end  58 . Thus, this window regulator system  10  has a variable travel speed/pull force, even without employing special electronics or a variable speed motor—although, if so desired, one may add these features to the system as well.  
         [0019]     The outer surface  60  of the cable drum  44  may have a helical shaped cable groove  64  to receive the cable  40  as the drum  44  turns. This cable groove  64  causes the cable  40  to track in a predictable manner (i.e., preventing it from slipping up or down the drum profile  62 ), thus providing proper tensioning and travel speed/pull force for each position of the vehicle window (not shown). The depth, width and spacing of the cable groove  64  can be any suitable dimensions for assuring that the cable  40  tracks on the drum  44  in the desired manner. Alternatively, a different means for causing the cable to track around the drum in a predictable manner may be employed instead of the cable groove, if so desired.  
         [0020]     When referring to the profile  62  of the outer surface  60  herein, this refers to the overall general shape of this surface  60 , whether or not it includes the cable groove  64 . Accordingly, for a conventional cable drum, the profile is cylindrical (i.e., a generally constant diameter extending axially from near the first end to near the second end), whether or not the outer surface has a cable groove. In the example shown in  FIGS. 1-3 , then, the profile  62  of the outer surface  60  is considered to be frustum-conical (i.e., a larger diameter near the first end  56  tapering down to a smaller diameter near the second end  58 ), even though the outer surface  60  includes the cable groove  64 .  
         [0021]     As an alternative to the profile  62  illustrated in  FIGS. 1-3 , the profile of the cable drum  44  may radially taper down extending toward the motor  46  rather than as shown radially tapering down as it extends away from the motor  46 . As another alternative, the cable drum  44  may have other non-cylindrical outer surface profile shapes, as desired, to obtain the desired variations in window travel speed/pull force relative to corresponding window open positions. For example, the cable drum may have a profile shape being a pair of frustum-cones back-to-back, with the first frustum-cone being adjacent to the first end and extending toward the second end and the second frustum-cone being adjacent to the second end and extending toward the first end until it meets the first frustum-cone. In this example, if the pair of frustum-cones radially taper down from the middle out toward the first and second ends, respectively, then the window travel speed would vary slow-fast-slow. On the other hand, if, in this example, the pair of frustum-cones radially taper down from each end toward the middle, then the window travel speed would vary fast-slow-fast. Or, as a further alternative, the outer surface profile shape may have only a portion that is cylindrical and another portion that is not so that the overall profile is non-cylindrical, with the travel speed/pull force being constant over a portion of the window travel and varying over another portion of the window travel.  
         [0022]     While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.