Patent Application
20110023280
The present invention relates to inspection of manufactured assemblies, more specifically to the inspection of torque specifications and joint specifications in manufactured automobile assemblies.
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.
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.
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's visual coordinates over a period of time. The sensed joint condition is determined by the processor'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.
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.
The fastener 24 preferably is a mechanical fastener 24 which can be any plurality of fasteners 24 used to join the automobile members 20a, 20b. 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 20b, the mechanical fastener 22 adapted for rotation by the fastening device 28.
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.
A tension sensing device 30, also referred to herein as a tension sensor, is illustrated in
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
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.
The rotation sensor 30 includes a light source or projector 62 for propagating light 64 across a member 20b and an imager 66 that receives the propagated light 64, as depicted in
Referring to
As further illustrated, the rotation sensor 30 includes an imager 66 and projector 62 which are moved relative to the automobile member 20a 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 20a, 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 20a. 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 20a), the linear detector elements 80 communicate the visual data back to the processor 54. Relative depth at each point on the automobile member 20a 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 20a. 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
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 28a, 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 20a, 20b, as is depicted in
In addition to the tension sensing, the rotation sensor 30 in the present embodiment monitors joined surfaces. After the automobile members 20a, 20b 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 20a, 20b 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.
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 20a, 20b 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.
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 20a, 20b 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.
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 20a, 20b 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.
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.
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.
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.
Referring generally to the logic diagram in
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.
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's 30 continuous transmission of the fastening device'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.
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.
