Abstract:
The present invention is directed to a new and improved method and apparatus for monitoring torque and joint conditions during the manufacturing process, particularly in the automobile industry. For a desired assembly of automobile members and fasteners is encountered during manufacturing, the optimal torque data and optimal joint data are retrieved from the data storage device. The tension sensor and the rotation sensor monitor the torque condition and joint condition and direct a controller to send torque instruction until the optimal torque condition and optimal joint condition are achieved.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to inspection of manufactured assemblies, more specifically to the inspection of torque specifications and joint specifications in manufactured automobile assemblies. 
       BACKGROUND OF THE INVENTION 
       [0002]    There is a need for additional error-checking in the automobile assembly process. The automobile assembly process requires joining hundreds to thousands of components, in a precise manner, into the final product. Imprecise assembly leads to loss of time, money, and convenience for the manufacturer and the consumer. For the manufacturer, time and expense is lost in repairing the defectively joined components during the warranty period. For the consumer, time and convenience are lost when defectively joined components are repaired under warranty. Moreover, defectively joined components have a shorter than expected life span. 
         [0003]    One of the key steps in automobile assembly is joining pluralities of automobile components. For the highest quality product, some types of automobiles components must be joined in a precise manner. Some of the necessary precision involves joining the components at precise torque and joint specifications. For example, if two components are supposed to be rotatably joined, too much torque in fastening the components may lead to poor rotation. Conversely, too little torque may lead to premature separation of the unit containing the joined assembly. Human senses and memory lack the capacity to consistently join components at a precise torque and prior manufacturing processes do not use all means to check for suboptimal torque and joint conditions. Thus it would be desirable to increase quality in the assembly of the automobile components by improving current error-checking means and adding new error-checking means. Furthermore, it would be advantageous to add error-checking means which can be refined over time to produce even more higher quality assembled articles. This invention addresses that issue. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention is directed to a new and improved method and apparatus for monitoring torque and joint conditions during the manufacturing process, particularly in the automobile industry. For a given desired assembly of automobile members and fasteners, an optimal torque and optimal joint condition is determined and placed in a data storage device. When the desired assembly of automobile members and fasteners is encountered during manufacturing, the optimal torque data and optimal joint data are retrieved from the data storage device by the processor. The tension sensor and the rotation sensor monitor the torque condition and joint condition and direct a controller to send torque instruction until the optimal torque condition and optimal joint condition are achieved. The sensed torque is determined from the torque fastener as a condition of time, from the torque fastener&#39;s visual coordinates over a period of time. The sensed joint condition is determined by the processor&#39;s analysis of the current assembly compared with the optimal joint data. If the either the torque condition or the joint condition are not optimum, the controller will communicate instructions to the torque fastener to increase or decrease torque until the optimal torque and optimal joint conditions are present. When the optimal torque condition and joint condition are achieved, the controller signals the operator that the desired assembly is complete. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  shows a plan view of an embodiment of the invention at an automobile assembly station. 
           [0006]      FIG. 2  shows a logic diagram of an embodiment of the invention. 
           [0007]      FIG. 3  shows a top view of a rotation sensor with an automobile member. 
           [0008]      FIG. 4  shows a top view of a rotation sensor with an automobile member. 
           [0009]      FIG. 5  shows a top view of an alternate rotation sensor with an automobile member. 
           [0010]      FIGS. 6A and 6B  show a top view of a rotation sensor and fastening device with reference marks at two different timepoints. 
           [0011]      FIG. 7  shows a graph of an optimal torque condition. 
           [0012]      FIGS. 8A ,  8 B, and  8 C show graphs of suboptimal torque conditions. 
           [0013]      FIG. 9  shows a top view of an optimal joint condition. 
           [0014]      FIG. 10  shows a top view of a suboptimal/malformed joint condition. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
         [0016]      FIG. 1  depicts an embodiment of the invention as it may exist in a manufacturing environment. Disclosed are automobile members  20   a ,  20   b , a fastener  24 , fastening device  28 , and a rotation sensor  30 . The automobile members  20   a ,  20   b  can be any plurality of members used to manufacture an automobile. The automobile member  20   a ,  20   b  may include any article that is necessary in the manufacture of an automobile. For example, one automobile member may be a door  20   a ′ and a second automobile member may be a door handle  20   b ′. Typically, the plurality of automobile members  20   a ,  20   b  would constitute a pair. Although automobile members  20   a ,  20   b  are illustrated as a door  20   a ′ and door handle  20   b ′, one skilled in the art would appreciate that the invention may be used to monitor torque conditions in the assembly of members in other industries. 
         [0017]    The fastener  24  preferably is a mechanical fastener  24  which can be any plurality of fasteners  24  used to join the automobile members  20   a ,  20   b . The mechanical fastener  24  may be a bolt, a bolt and nut combination, a screw, a rivet, a pin, or other mechanical fasteners known in the art. The illustrated embodiment depicts a mechanical fastener  24  and an automobile member  20   b , the mechanical fastener  22  adapted for rotation by the fastening device  28 . 
         [0018]    The fastening device  28  can be any device adapted for applying rotational torque to the mechanical fastener  24 . Preferably, the fastening device  28  should be able to provide varying levels of instantaneous torque incrementally. Additionally, the fastening device  28  as is generally understood, may be pneumatically or electromagnetically powered. The fastening device  28  is also adapted for electromagnetic communication with the tension sensor  30 . While, the preferred embodiment provides for electromagnetic communication, the communication may occur via a physical or nonphysical connection. 
         [0019]    A tension sensing device  30 , also referred to herein as a tension sensor, is illustrated in  FIG. 1  and generally includes a controller  52  in communication with a rotation sensor  60  also referred to herein as an imager. The tension sensor  30  is adapted for communication with the fastening device  28  through the controller  52 . 
         [0020]    As generally understood, the controller  52  may be any electronic processor  54  based system adapted for executing programmed instructions pursuant to an instruction set such as that illustrated in  FIG. 2 . Preferably, a general purpose programmable microprocessor would contain the instruction set for the controller  52 . Additionally, the controller  52  preferably has an input/output device, an electronic retrievable storage device  56  adapted for storing data, an embedded or programmed instruction set and communications interfaces for operably communicating with various associated devices. For example, the controller  52  should be adapted for a communications interface with the rotation sensor  30 , a communications interface with the fastening device  28 , and a communications interface with the electronic retrievable data storage device  56 . The controller  52  generally operates according to an exemplary instruction set represented by the logic diagram in  FIG. 2 . 
         [0021]    The interface from the controller  52  to both the rotation sensor  30  and the fastening device  28  may be a physical or nonphysical interface. A physical interface would be represented by an electrically or light conductive cable, where the controller  52  would send and receive signals to and from the rotation sensor  30  and the fastening device  28 . A nonphysical interface would be represented by electromagnetic or light communication, where the controller  52  would send and receive electrical signals to and from the rotation sensor  30  and the fastening device  28 . Through each type of interface, the controller  52  would send and receive information, such as instructions or data, to and from the fastening device  28  and the rotation sensor  30 . 
         [0022]    The rotation sensor  30  includes a light source or projector  62  for propagating light  64  across a member  20   b  and an imager  66  that receives the propagated light  64 , as depicted in  FIGS. 3 ,  4 , and  5 . Discussion of such a device is disclosed in U.S. Pat. No. 6,522,777, which is hereby incorporated by reference. 
         [0023]    Referring to  FIGS. 1-4 , the rotation sensor  30  in communication with the controller  52  via the processor  54  uses two dimensional and three dimensional information to analyze the visual condition of the automobile member  20   a . Such analysis may include visual characteristics of the automobile member including the dimensions, color, reflectiveness, depth, and other visual characteristics. 
         [0024]    As further illustrated, the rotation sensor  30  includes an imager  66  and projector  62  which are moved relative to the automobile member  20   a  positioned within a zone of visual range associated with the rotation sensor  30 . A projected pattern of light  64 , such as a pattern of stripes or lines, is scanned across the surface of the automobile member  20   a , which is analyzed based upon the reflected light and which is used to acquire and map out a three dimensional surface associated with the automobile member  20   a . The pattern projector  62  projects a pattern of lines and an imager  66  includes a trilinear-array camera  66 ′ as an imager. The camera  66 ′ and at least one pattern projector  66 ′ are maintained in fixed relation to each other. The trilinear-array camera  66 ′ includes a plurality of linear detector elements  80 , each linear detector element  80  having the same fixed number of pixels and each linear detector element  80  extending in a direction parallel with the pattern of light lines  64 . The geometry of the imager  66  and projector  62  are arranged such that each linear detector element  80  picks up a different phase in the line pattern projected by the pattern projector  62 . As the imager  66  and projector  62  are scanned across the object of interest (namely the automobile member  20   a ), the linear detector elements  80  communicate the visual data back to the processor  54 . Relative depth at each point on the automobile member  20   a  is determined from the intensity reading obtained from each of the linear detector elements  80  that correspond to the same point on the automobile member  20   a . Data on each of these points is communicated and a visual field is formed from the collection of points. Alternatively, this aspect of the rotation sensor can use a different system, such as a Moire interferometry sensor system, to acquire a visual field. A Moire interferometry sensor system is depicted in  FIG. 5 . 
         [0025]    Discussion of tension sensing methods is disclosed in U.S. Pat. No. 4,738,145, which is hereby incorporated by reference. The fastening device  28  may include a mechanical tension sensor  28   a , but a tension sensing method used in the current embodiment utilizes the processor  54  to analyze visual feedback from the rotation sensor  30  and the torque provided from the fastening device  28 . In this tension sensing method, the rotation sensor  60  is able to monitor the fastening device  28  while it fastens the automobile members  20   a ,  20   b , as is depicted in  FIGS. 6A and 6B . The rotation sensor  60  allows for monitoring the rotational distance traveled by the mechanical fastener  24  as a result of torque applied by the fastening device  28 . Concurrently, the fastening device  28  provides feedback to the controller  52  regarding the applied torque. With the rotational information and the torque feedback, the processor  54  can monitor the torque over time and thus analyze and predict various torque scenarios. 
         [0026]      FIG. 7  depicts a sample graph of time versus torque and represents optimal torque data, having no indications of abnormal torque during the fastening period.  FIGS. 8A ,  8 B, and  8 C represent suboptimal torque data, having indications of abnormal torque during the fastening period. These indicators of an abnormal torque may include frequently changing slopes or sinusoidally changing torques. 
         [0027]    In addition to the tension sensing, the rotation sensor  30  in the present embodiment monitors joined surfaces. After the automobile members  20   a ,  20   b  are joined via the fastener  24 , a joint is formed at the joined surfaces. Monitoring the status of the joint, in addition to the torque, provides an advantage over single focused techniques. For instance, manufacturing tolerances for typical mechanical fasteners used during the automobile assembly process may present limited understanding of the joined surface and may not detect a suboptimal fastening event. For example, the bolt  24  used to fasten automobile members  20   a ,  20   b  may lead to inconsistent manufacturing tolerances which may lead to inconsistent thread density. This different thread density would require a different optimal rotational distance, which in turn would require additional torque for an optimal joint. In this way traditional applications would provide limited advance detection of suboptimal joint which may lead to premature failures in relation to the improved rotation sensor application in the present invention. 
         [0028]    The processor  54 , in communication with the data storage device  56  and the rotation sensor  30  allows for early detection of suboptimal joints. After the automobile members  20   a ,  20   b  are joined by the fastener  24 , the rotation sensor  30  records the visual field, including the joint located between the joined surfaces. The rotation sensor  30  then transmits this information to the processor  54  for analysis and retrievable storage by the storage device  56 . 
         [0029]    The processor  54 , in communication with the data storage device  56 , analyzes the characteristics of the visual field and matches the characteristics with known characteristics stored within the data storage device to assess the nature of the joined members  20   a ,  20   b  and  22  present within the observed visual field. By way of example, the communicated visual field may include certain geometric shapes and other characteristics and visual data. The processor  54  may analyze the recorded visual field and compare those shapes with the shapes in the data retrieved from the data storage device  56 . When a match in the shapes occurs, the processor  54 , in cooperation with the data storage device  56 , can correlate that shape to a particular type of automobile member or a particular type of fastener. The processor  54  iterates through the visual field data until all automobile members and fasteners in the visual field are identified. Although shapes were used as the “key” or “index” to the data, one skilled in the art would appreciate that other visual data, individually or in combination, may be used to identify automobile members  20  and fasteners  22 . 
         [0030]    Then the processor  54 , in communication with the data storage device  56 , retrieves the optimal joint data from the data retrievably stored within the data storage device for the given automobile members  20   a ,  20   b  and fasteners  24  in the visual field, using the joined surface combination as the key the optimal joint data. As the fastening device  28  provides torque to the fastener  24 , the processor  54 , in communication with the rotation sensor  30 , compares the optimal joint data with the joint data of the assembly in the visual field. 
         [0031]    The data storage device  56  contains data on plural automobiles members and plural automobile fasteners. The stored data may be arranged as a database, a table, a series, or either or both in which a row may contain a plurality of automobile members, a plurality of fasteners, optimal torque data for desired assemblies of pluralities of automobile members, pluralities of fasteners, the rotational distance to achieve the optimum torque specification for desired assemblies of automobile members  20  and fasteners  24 , and visual indicators of the optimal joint condition. 
         [0032]    Portions of the data on the data storage device  56  would be pre-populated prior to distribution and activation within an assembly process. For each automobile member  20  used in the assembly process, a unique identifier and a visual representation of it may be retrievably stored on the storage device  56 . For each fastener  24  used in the assembly process, a unique identifier and a visual representation of it would be stored. For each desired assembly of automobile members  20  and fasteners  24  in the manufacturing process, a visual representation or numerical representation corresponding to a visual representation of the joined assembly in optimal torque and optimal joint conditions may be stored for retrieval, analysis, and comparison with observed conditions. 
         [0033]    Over time, the data on the data storage device  56  would be updated or increased based upon the recorded observations. Even with quality engineering, optimal joint condition may be refined over time. As given assemblies of automobile members and fasteners are produced and exposed to operational conditions, optimal torque data and optimal joint data may be refined. Over time, the data would be enhanced with subsequent visual representations of torque and joint conditions in combination with warranty or other external data. This additional refinement of optimal torque and optimal joint data leads to less suboptimal assemblies in future manufactured assemblies. 
         [0034]    Referring generally to the logic diagram in  FIG. 2 , the processor  54  may contain instruction related to this invention. In accordance with the illustrated instructions, the storage device  56  would be populated with automobile member and fastener information. Next the automobile members  20   a ,  20   b  and the fasteners  22  within the observed visual field would be scanned  104 ,  112  and then the processor  54  would identify  106 ,  114  the automobile members  20   a ,  20   b  and the fasteners  24 . The rotation sensor  30  then records the visual field containing the automobile members  20   a ,  20   b  and/or fasteners  24  transmitting the information to the storage device  56  through the processor  54 . The processor  54  uses characteristics from the observed visual field such as dimensions, color, emissivity, depth, and other visual characteristics or information to match  108 ,  116  the observed information with the previously recorded information on the data storage device  56 . The processor  54  repeats this step for every item within the visual field until all members and all fasteners have been identified  110 ,  118 . 
         [0035]    The processor  54  retrieves  120  the assembly data from the storage device  56  for the corresponding assembled automobile members  20  and fasteners  24 . The processor  54  uses the combination of the automobile members  20  and fasteners  22  in the visual field as a key to retrieve the assembly information  120  from the data on the data storage device  54 . The retrieved information for a given desired assembly includes the optimal torque data  126  and optimal joint data  128  to be used in fastening the automobile members. 
         [0036]    The automobile members, fasteners, and fastening device are then engaged  122 . As instructed by the processor  54 , the controller  52 , sends  124  torque instructions to the fastening device  28 . Concurrently, the processor  54  receives visual information from the rotation sensor  30 . The processor  54  uses the specified torque provided by the fastening device  28  combined with the rotational distance traveled by fastening device  28 , which is determined from the rotation sensor&#39;s  30  continuous transmission of the fastening device&#39;s  28  position. The processor  54  monitors the torque condition and joint condition and directs the controller  52  to send torque instructions  124  while the torque condition and joint condition are outside the optimal torque specifications and optimal joint specifications retrievably stored within the data storage device  56 . Once the processor  54  determines that an optimal torque condition exists  126 , the processor  54  then determines if an optimal joint condition exists  128 , if not, the controller continues to make adjustments until both an optimal torque condition exists  126  and an optimal joint condition exists  128 . In evaluating the joint condition, the rotation sensor  30  records and transmits the visual field, including the joint condition, for evaluation by the processor  54 . The processor  54  then compares the data of the newly assembled joint to the optimal joint data retrieved from the data storage device  56 . If the conditions are within an acceptable range, the controller  52  signals a successful condition and the fastening device  28  is operably disengaged. 
         [0037]    While the foregoing detailed description has disclosed several embodiments of the invention, it is to be understood that the above description is illustrative only and not limiting of the disclosed invention. It will be appreciated that the discussed embodiments and other unmentioned embodiments may be within the scope of the invention.