Abstract:
A method and apparatus for evaluating window regulators of the type having a reversible electric motor connected to a-slide/carrier plate by means of cables. The apparatus comprises a first transducer such as a piezoelectric accelerometer or a laser for generating a first signal quantity related to periodic noise produced by the motor during operation thereof, a second transducer such as a piezoelectric accelerometer for producing a second signal quantity representing transient noise produced by irregularities in the slide/carrier plate assembly during travel of the carrier plate along the slide, and a processor for decoding the first and second waveforms and using data derived therefrom as a basis for identifying unacceptably noisy window regulator assemblies. The method comprises placing the window regulators on a test fixture, operating the window regulator with a simulated glass load, and generating and processing the first and second signal quantities as described above.

Description:
FIELD OF THE INVENTION 
   This invention relates to automotive window regulators and more particularly to a method and apparatus for evaluating automotive window regulators during pre-installation operation thereof to identify window regulators which are unacceptably noisy. 
   BACKGROUND OF THE INVENTION 
   An automotive window regulator generally comprises the combination of a relatively small electric motor which is connected through a reduction drive, a drum and two or more cables to at least one slide/carrier plate assembly to which the window glass is attached when assembled into an automobile door or hatch. When the motor is operated it winds and unwinds the cables so as to cause the carrier plate or plates to travel along the slide or slides. When a window is attached to the carrier plate or plates, it moves in the open or close directions according to the direction of motor travel. 
   Manufacturing defects occasionally make such window regulators unacceptably noisy such that operation thereof in an automobile is displeasing to the owner. Noise can be the result of a number of different factors including motor armature imbalance, defective motor bearings, irregular motor commutator surfaces causing brush bounce or rattle, and surface imperfections such as dents and burrs in the finish of the metal slide where it is contacted by the carrier plate. 
   Noise produced by an installed window regulator tends to be amplified by the automobile door panels and, therefore, a regulator which may not sound particularly noisy before installation may be unacceptably noisy after installation. There is a significant advantage in identifying unacceptably noisy window regulators prior to installation into the automobile since replacement of the regulator after installation is more costly than discarding a faulty regulator prior to assembly into an automobile. 
   To our knowledge, window regulators have not been routinely tested for noise on the factory floor during the assembly process. We believe that this is due to the fact that ambient noise levels are too high in most factories to use microphonic pickups for noise detection. While this problem could be solved by removing the regulator to a noise-insulated test camber, it is impractical to do this with every regulator made in a mass-production facility. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the present invention, window regulators motors can be efficiently evaluated for noise/vibration characteristics on the factory floor by placing the motor on a support such as a test fixture or assembly-line pallet, operating the motor and arranging a suitable transducer in exclusive energy transfer relationship with the motor housing so as to generate a waveform representing periodic noise/vibration components emanating only from the motor. This waveform may be processed on-line to identify all window regulator motors which are unacceptably noisy. 
   As hereinafter set forth, transducers which can be disposed in exclusive energy transfer relationship with a chosen target such as a motor housing include single-axis accelerometers and lasers. 
   According to a second aspect of the invention a window regulator slide/carrier plate assembly is efficiently evaluated for operating noise characteristics by placing the assembly on a support such as a test fixture or assembly-line pallet, operating the carrier plate with a simulated glass load to cause it to travel along the slide, and, arranging a suitable transducer such as single axis accelerometer in exclusive energy transfer relationship with the carrier plate so as to generate a waveform representing transient noise components occuring during operation of the assembly. This waveform can be processed to identify unacceptably noisy assemblies prior to installation. 
   According to a third aspect of the invention the foregoing first and second aspects are used in combination by placing window regulator assemblies of a type comprising a motor, a slide/carrier plate combination and a cable drive on a support such as a test fixture or assembly-line pallet, operatively associating first and second noise/vibration transducers with the motor housing and the carrier plate respectively, operating the window regulator assembly and generating first and second waveforms representing the periodic and transient noise characteristics produced by operation of the assembly. These two waveforms are processed to identify unacceptably noisy window regulator assemblies according to any of a number of different criteria. 
   In the preferred form, the apparatus for carrying out the invention comprises an assembly-line conveyor pallet forming a support surface for a test fixture on which window regulator assemblies are placed during and/or as part of an overall assembly operation on the factory floor, i.e., because the pickups are essentially exclusive, no sound chamber is required for isolation. The conveyor is such as to cause the pallet and window regulator assembly disposed thereon to pass through a test station where a first transducer, such as a single axis accelerometer, is magnetically attached to the motor housing. In addition, a second accelerometer supported on a bracket which is detachable relative to a hanger assembly is positioned where it will be picked up by the carrier plate and carried along with the carrier plate during operation of the window regulator assembly. A weight is attached by cable or the like to the bracket on which the second accelerometer is mounted to simulate a glass load when the carrier plate fits into and moves with the accelerometer support bracket during operation of the window regulator assembly. Two waveforms are generated by the transducers representing periodic and aperiodic or transient noise components. These waveforms are processed to identify unacceptably noisy window regulator assemblies before they are assembled into automobile doors. 
   In the preferred form the data from the processor is transferred to a memory module on the pallet so that it stays with the individual window regulator for use in sorting regulators at a terminal point on the assembly line. 
   As further disclosed herein a laser ray be substituted for the motor accelerometer to permit, for example, evaluation of motors having non-ferromagnetic housings. Doppler-shift principles are used to create frequency components representing the noise/vibration of the motor housing during operation thereof. 
   As used herein the terms “noise” and “vibration” are interchangeable and synonymous; i.e. they are used together and separately to refer to periodic and transient accelerations of the structure under test. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
       FIG. 1  is a perspective view of a window regulator assembly on a conveyor pallet in a test location for testing both the window regulator motor and the carrier/slide for noise, 
       FIG. 2  is a side view of the apparatus of  FIG. 1  with the carrier plate of the window regulator assembly moving toward engagement with the transducer bracket; 
       FIG. 3  is a side view of the apparatus of  FIG. 1  with the carrier plate in engagement with the transducer bracket; 
       FIG. 4  is a side view of the apparatus of  FIG. 1  with the carrier plate in engagement with the transducer bracket and with the bracket detached from the hanger; 
       FIG. 5  is a perspective view of the carrier plate transducer hanger and bracket, 
       FIG. 6  is a diagramatic side view of a conveyor for handling the pallets of FIG.  1  and causing a series of pallets to move through a series of assembly stations as well as the test station; and 
       FIG. 7  is a diagrammatic representation fo a laser transducer for use as a motor vibration pickup. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows an apparatus  10  for evaluating window regulators  12  for noise and vibration characteristics as they are assembled on the factory floor. The apparatus  10  comprises a pallet  14  which in this case defines a test fixture mounted for intermittent movement along a conveyor  16  between multiple assembly stations and the test station represented in FIG.  1 . Further details of the conveyor are shown in FIG.  6 . 
   The window regulator  12  is representative and comprises a DC electric motor  18  having a ferromagnetic housing  20  connected to a reduction drive unit  22  and a drum housing  24 . Cables  26  and  28  connect the drum in housing  24  to an assembly comprising a carrier plate  30  adapted to receive automotive window glass (not shown) and to travel along a bowed metal slide  32  having attached feet  80 . Other types of regulators can also be tested using the principles discussed herein in example, regulators used for large heavy glass panels often have two carrier plate and slide assemblies. 
   At the right side of the apparatus shown in  FIG. 1  a first transducer support assembly  34  is secured to the conveyor bed so it is in a fixed location relative to pallet  14  when it arrives in the test station. Assembly  34  comprises a bracket  36  connected to a vertically moveable elevator plate  38  carrying clamp fingers  40  and  42  which releasably clamp to and hold a first transducer in the form of a single axis piezoelectric pick up  44  having a permanent magnet base  46 . In the arrangement shown in  FIG. 1 , the pallet  14  with the window regulator assembly  12  mounted thereon for assembly and test purposes arrives at and is temporarily locked into the test station by conventional means (not shown). In this position the motor housing  20  is directly under the piezoelectric pick up  44  such that operation of the elevator  38  in the downward direction shown by the double ended arrow brings the transducer  46  into contact with the flat top of the motor housing  20 . When this is achieved the clamp fingers  40  and  42  are released to place the pickup  44  in exclusive energy transfer relationship with the motor housing. 
   The motor  18  has a power head  47  which is connectable to a dc power plug  49  such that the motor can be run in both directions while in the test location. Vibration caused by any of the factors described above will cause periodic displacement of the motor housing  20  along the sensitive axis of the piezoelectric transducer  44 ; i.e., the vertical axis as shown in  FIGS. 1-4 , to produce a periodic output waveform from the transducer  44 . This waveform is connected by way of signal line  48  to a fixed conveyor-side data processor  50 . When the fingers  40  and  42  are actuated to release their grip on the transducer  44 , the transducer is in exclusive energy transfer relationship with the motor housing  20  so as to pick up and respond to vibration thereof exclusive of all other noise which might be generated in the factory area around the test location. It will be appreciated by those skilled in the art that the motor armature (not shown) within the housing  20  is mounted for rotation about an axis which is orthogonal to the sensitive axis of the transducer  44  such that rotation of the motor armature unless perfectly balanced in good bearings causes a periodic reciprocal movement of the motor housing along the sensitive axis of the piezoelectric transducer  44 . The fundamental frequency of the vibration is related to the rotation speed of the motor  18  but, as will be understood by those skilled in motor technology, there will be other frequencies, usually multiples of the motor rotation frequency, to which the accelerometer  44  will respond and which will result in other waveform components to be analyzed. These frequencies, as mentioned above, may occur at multiples of the fundamental frequency wherein the multiplying factor is the number of commutator segments in a particular motor design. Moreover, there will be sum and difference components in the waveform where multiple frequency components, including harmonics, are present. 
   The motor housing  20  shown in  FIG. 1  has flat top and bottom surfaces and curved side surfaces. Therefore the contact surface of the magnet  46  is also preferably flat. In the event it is desirable to maintain contact between the transducer  44  and a non-flat motor housing, the magnet may be machined to the contour of the motor housing to maintain good magnetic association. 
   Continuing with the description of the apparatus  10  shown in  FIG. 1 , a second support assembly  52  is mounted in a fixed location on the conveyor bed on the left side of the pallet  14  as shown in FIG.  1 . Assembly  52  comprises a hanger  54  which is connected to the bracket  52  by means of a pneumatic elevator  56  such that the bracket may be raised and lowered relative to the path of the carrier plate  30  as it slides along the slide mechanism  32 . Hanger  54  releasably receives a bracket  58  having fingers  64  and a horizontal slot  65  to receive the carrier plate  30  edgewise therein when the carrier plate moves toward the bracket  58  and the bracket is at the correct elevation as determined by the elevator  56 . Bracket  58  has a pedestal portion  66  on which a second single axis piezoelectric transducer  68  is removably magnetically attached. Transducer  68  is responsive to vibration displacement along its sensitive axis to produce an electrical signal waveform which is connected by signal line  70  to the data processor  50 . 
   The test location represented by the pallet  14  in  FIG. 1  is further provided with releasable clamps  76  and  78  to hold the slide  32  in place during assembly and test thereof. As will be apparent to those skilled in the conveyor and transfer machinery arts, clamps are preferably provided for several parts of the window regulator  12  during test and those clamps are preferably automatically operated by pneumatic actuators. 
   A weight  62  simulating a glass load is connected to the bracket  58  by means of a cable  60  which may pass through several pulleys before being attached to a free weight  62 . The path to the cable  60  is kept clear so that it imposes an inertial force on the bract  58  intending to hold the bracket  58  on the hanger  54  as shown in  FIGS. 1 and 5  and thereafter to simulate the weight of a window panel attached to the carrier plate  30 . 
   The data processor  50  processes the signal waveforms received by and on signal lines  48  and  70  and produces a complex output signal on line  74  which is connected to a transmitter  72  adjacent the conveyor path. The transmitter  72  communicates the intelligence or data content of the signal to a memory unit  73  which is associated with each pallet  14  in a series of pallets moving along conveyor  16 . The transmitter  72  and memory unit  73  are conventional devices and may operate with inductive or infrared or RF links. 
   As will be appreciated by those skilled in the waveform analysis and mathematics arts, the signals transmitted by lines  48  and  70  to the data processor  50  may take many forms depending on the type of noise and/or vibration signal under analysis. As earlier indicated, waveform coming to the data processor on line  48  is periodic in nature and is analyzed using classic frequency domain analysis principles. The analysis is preferably not model based; i.e., it is not based on vibration or noise signatures taken from a series of devices with known or prearranged defects. Rather, the analysis looks at specific frequency components and issues a pass/fail output according to the magnitudes of these components relative to an objective standard. The signal arriving at the data processor  50  on line  70  is transient or aperiodic in nature since it is derived from clicks, bumps and the like caused by surface irregularities in the slide structure  32  where it is contacted by the carrier plate  30 . Accordingly a simple time domain analysis may be employed for this portion of the signal. 
   The signal which is communicated to the units  72  and  73  is preferably of a complex character; i.e., having data components representing both the inputs on lines  48  and  70 . The ultimate termination is one of pass-fail but the signal communicated to the memory unit  73  has enough intelligence in it to determine whether the failure is based on the motor  18  or the carrier plate/slide assembly  30 ,  32  or both. 
     FIG. 2  is a side view of the  FIG. 1  apparatus showing the condition of the apparatus  10  when the transducer  44  is lowered into place on the motor housing  20  and the hanger  54  is lowered to the point that the bracket  58  has the slotted portion  64  on the same level as the slide plate  30  such that movement of the slide plate  30  from left-to-right as shown in  FIG. 2  will cause the plate to engage the receiver slot in the bracket  58 ,  66 . 
     FIG. 3  shows how the carrier plate  30 , when the motor  18  is running in the left-to-right direction as shown in  FIG. 3 , advances into physical engagement with the bracket  66 . As shown in  FIG. 4 , further advance of the carrier plate  30  causes the bracket  58 ,  66  to separate from the hanger  54  such that the piezoelectric transducer  68  is in exclusive energy transfer relationship with the carrier plate/slide assembly  30 ,  32 . Note that the drag line  60  is connected to the bracket  58  to resist the movement from left-to-right as shown in FIG.  4  and to assist in rehanging bracket  58 ,  66  on the hanger  54  when the motor  18  is reversed to cause the carrier plate  30  to travel from right-to-left as shown in FIG.  4 . Since noise transients can be directionally sensitive, the transducer  68  is operated to produce an output during both directions of travel along the slide  32 . 
     FIG. 5  shows the bracket  58 ,  66  in greater detail when in full engagement with the carrier plate  30 . The basket handle shaped portion of the bracket  58 ,  66  slides into the slot created by the fingers  102  of the hanger  54  and the weight attached to the cable  60  holds the bracket  58 ,  66  on the hanger after it reaches the hanger during the return stroke. The hanger  54  is thereafter lifted by the elevator mechanism  38  previously described. The magnet  82  is faceted such that it may be turned onto a stud (not shown) extending vertically from the base of pickup  68 . 
   The sequence of events is essentially as follows:
         1. The pallet  14  is advanced until it is in the text station shown in  FIG. 1 ; i.e., between the supports  34  and  52  on which the transducers  44  and  68  are mounted;   2. The motor  18  is connected to the power source plug  49 ;   3. The bracket  38  is lowered until the magnet  46  is in contact with the motor housing  20 ;   4. The clamp fingers  40  and  42  are released;   5. Th elevator  56  lowers the hanger  54  until the slotted portion  64 ,  65  is on the same elevation as the crier plate  30 ; note this may require the momentary operation of the motor  18  to move the carrier plate  30  to a clear position as shown in  FIG. 1 ;   6. The motor is operated to move the carrier plate from left-to-right as shown in  FIGS. 2 ,  3  and  4 . This produces an output waveform from transducer  44  which is communicated to the data processor  50  as previously described. In addition operation of the motor in the direction described above causes the carrier plate  30  to engage with bracket  58 ,  66  to disengage the bracket from the hanger  54  and move the bracket against the retarding force of the drag line  60  and the free weight  62 .   7. When the carrier plate reaches the right-hand limit of travel a proximity switch or limit switch ( 110 ) sends a signal to the data processor  50  which reverses the motor input signal polarity and causes the motor to reverse direction. This causes the carrier plate  30  to progress in the opposite direction. The bracket  58  is reinstalled on hanger  54 .   8. The transducer  68  is active to produce an output signal waveform on cable  70  to the data processor  50  during both directions of travel;   9. When a full-cycle of travel has been achieved the clamp fingers  40  and  42  are re-engaged to grasp the transducer  44 . Both elevator units are activated to lift the transducers and/or carrier assemblies thereof upwardly;   10. The result of the analysis is communicated by data processor to memory unit  73  by way of transmitter  72 ;   11. The elevator assemblies  38  and  54  raise the transducers  44  and relative to the regulator  12  to provide clearance for forward movement thereof; and   12. the pallet  14  is advanced to the next station.       

     FIG. 6  shows one possible conveyor setup for integrating window regulator assembly and test operations. The test location is shown by reference numeral  14  on the top surface of the conveyor table  16  with pallets moving from right-to-left as shown in the drawing. After exiting the test station represented by reference numeral  14 , the pallets move to a position  14   a . In this position they are dropped downwardly by an elevator assembly to position  14   b  whereupon they are conveyed from left-to-right along a roller assembly  90  to position  14   c . At this point a second elevator lifts each pallet to position  14   d  whereupon it is moved intermittently through assembly stations  14   e  and  14   f . It will be understood that the arrangement shown in  FIG. 6  is exemplary and diagrammatically portrayed. 
   Should the motor  18  not have a ferromagnetic housing, it is then not possible to achieve an exclusive energy transfer relationship between the housing and the transducer  44  by means of the permanent magnet  82  shown in FIG.  5 . As shown in  FIG. 7  this situation can be accommodated using a laser transceiver  112  in place of the single axis piezoelectric transducer  44 . The laser transceiver  112  is disposed on the bracket  34  but requires no elevator mechanism to raise and lower it out of contact with the motor  18 . Instead the laser transceiver  112  maintains a fixed spacing from the motor housing and, when activated, directs a fixed frequency light signal toward the motor housing. Reflections of this signal are picked up by the transceiver and are Doppler shifted according to the frequency of the vibratory movements or displacement of the motor housing along the line of sight axis of the laser transceiver  112 . These Doppler shifts in the basic laser frequency produce sum and difference signals according to the components of the vibration and resulting signals are analyzed by processor  50  in the manner described above. 
   It will be appreciated that the motor noise analysis process and the carrier plate/slide transient noise analysis process may be carried out individually; i.e., each without use of the other. Alternatively, as shown herein, they may be carried out in combination. For example, it may be desirable to test motors at the place of manufacture thereof before assembly into window regulators. Similarly carrier plate/side assemblies may be temporarily connected to a motor power source for operation independently of the final dedicated motor to which they are to be attached. 
   While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.