Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT Application No. PCT/US2009/052799, filed Aug. 5, 2009 which claims the benefit of Japanese Application No. 2008-201834 filed Aug. 5, 2008, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a self-piercing rivet fastening device, and more particularly to a self-piercing rivet fastening device that can prevent self-piercing rivet dry-firing. 
     One example of a self-piercing rivet fastening device is described in JP 2007-530287, Gazette (Patent Literature 1). A self-piercing rivet comprises a flange-shaped head and a hollow tubular leg that extends downward from the head. When this rivet is driven into a plurality of members being fastened, such as two panels or the like, for example, the leg perforates the panels, and, while that is occurring, the leg deforms so that the tip thereof expands, whereupon the plurality of members being fastened is joined together by the deformed and expanded leg and the head. Self-piercing rivets are suitable for joining aluminum bodies which are not amenable to welding, and, in view of the fact that aluminum bodies are being adopted for automobile bodies as lighter weights are now being sought, the demand therefor is expected to grow. 
     The self-piercing rivet fastening device cited in Patent Literature 1 has a C-shaped frame, a punch disposed at one end of the C-shaped frame, and a die disposed at the other end so as to be opposed to the punch. At the one end of the C-shaped frame, a receiver is disposed for accepting self-piercing rivets fed from the self-piercing rivet feeder, and a feeder tube extending from the feeder is connected to the receiver. The punch is attached so as to drive in, toward the die, a self-piercing rivet sent to a driving chamber in the receiver. A self-piercing rivet driven in by the punch is driven into a plurality of members being fastened, those being disposed between the punch and the die, while perforating those members, whereupon the plurality of members being fastened is fastened together. 
     Patent Literature 1: PCT (WO) 2007-530287, Gazette 
     Patent Literature 2: TOKKAI [Unexamined Patent Application] No. H6-039650 
     In the self-piercing rivet fastening device of Patent Literature 1, sensors (281, 283) for detecting the presence of a self-piercing rivet are provided in the feeder tube between the feeder and the receiver. These sensors are supposed to prevent dry-firing by the punch when there is no self-piercing rivet in the receiver. This detection of the presence of a self-piercing rivet is desirable because it prevents punch dry-firing, but is to detect the presence of a self-piercing rivet inside the feeder tube, and is not to detect the presence of a self-piercing rivet that has arrived in the driving chamber of the receiver. Wherefore, there is room for improvement in the self-piercing rivet fastening device of Patent Literature 1 from the perspective of preventing punch dry-firing. 
     Patent Literature 2 describes a self-piercing rivet fastening device wherein the presence of members being fastened is detected and whereby, when there is no member being fastened between the punch and the die, self-piercing rivet driving is prevented. In Patent Literature 2, there is no description of any detection of the presence of a self-piercing rivet in the receiver. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to detect whether or not a self-piercing rivet is in the driving chamber of the receiver and definitely prevent punch dry-firing. 
     In order to attain said object, the self-piercing rivet fastening device pertaining to the present invention is a self-piercing rivet fastening device with a C-shaped frame, wherein a punch is disposed on one end of that C-shaped frame, a die is disposed on the other end thereof so as to oppose the punch, a receiver for accepting a self-piercing rivet fed from a self-piercing rivet feeder is deployed on the first-mentioned end of the C-shaped frame, a feeder tube extending from the feeder is connected to that receiver, the punch is attached so as to drive in, toward the die, a self-piercing rivet sent to a driving chamber of the receiver, a self-piercing rivet driven in by the punch opens holes in and is driven into a plurality of members being fastened that are deployed between the punch and the die, so that the plurality of members being fastened is fastened together, being configured such that a rivet arrival detection sensor is provided in the receiver for detecting whether or not a self-piercing rivet is present in the driving chamber, and, when the rivet arrival detection sensor has detected that no self-piercing rivet is present in the driving chamber, the drive for the punch is prevented in response to a signal from that sensor. 
     As noted above, in the receiver, a rivet arrival detection sensor is provided for detecting whether or not a self-piercing rivet is present in the driving chamber, and, when the punch is [to be] driven, if the rivet arrival detection sensor detects that no self-piercing rivet is present in the driving chamber, the punch is prevented, in response to a signal from the sensor, from being driven. Because the device is so configured, punch dry-firing is definitely prevented. 
     In the self-piercing rivet fastening device described above, the receiver has an intake passageway for receiving a self-piercing rivet sent from the feeder tube, and a driving chamber, the latter being formed at a position at which self-piercing rivets are received from the intake passageway and at which a drive passageway of the punch is crossed and the self-piercing rivets are impacted by the punch and the rivet arrival detection sensor is disposed adjacent to the driving chamber at a position where the intake passageway will not be obstructed. In this fastening device, a turnable gate is provided in the receiver whereby the intake passageway and the driving chamber can be partially opened; said gate is configured so that the intake passageway and the driving chamber are normally closed but can be turned so as to partially open the intake passageway and the driving chamber for the removal of a jammed self-piercing rivet. In that fastening device, the rivet arrival detection sensor is disposed in a position where the opening and closing of the gate will not be obstructed, that being a position also where the intake passageway is opposed. In order to detect a self-piercing rivet that is sent from the self-piercing rivet feeder, a rivet arrival detection sensor is provided either at the discharge port of the feeder or at the intake of the feeder tube. Whether the feeding of a self-piercing rivet from the feeder tube to a point just short of the driving chamber is proper or improper can be detected. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a configuration diagram of a self-piercing rivet fastening device relating to one embodiment of the present invention. 
         FIG. 2  is a section of the receiver and the punch portions of the self-piercing rivet fastening device diagrammed in  FIG. 1 . 
         FIG. 3  is a partially cutaway diagonal view of the receiver and punch portions of the self-piercing rivet fastening device diagrammed in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of the present invention is now described.  FIG. 1  is an overall diagram of a self-piercing rivet fastening device  1  relating to the embodiment of the present invention. In  FIG. 1 , the self-piercing rivet fastening device  1  has a C-shaped frame  5  which has a connecting part  3  for connecting to an articulated robot arm  2 . The C-shaped frame  5  is a rigid member wherein an upper horizontal arm  6 , a vertical arm wherein the connecting part  3  is disposed, and a lower horizontal arm  7  are integrally formed. One end of the C-shaped frame  5 , that is, the upper horizontal arm  6  end, is secured to a tubular shaped punch drive  11 , constituting punch drive means, for driving a punch  9  formed so as to hold a self-piercing rivet  8  ( FIG. 2 ), and so as to press the rivet toward a die  10  therebelow, at the time of a fastening action. In this embodiment, the punch drive  11  comprises an electric motor, a spindle that is turned by that electric motor and which moves up and down, and a rod or the like extending from the spindle to the punch  9 . By the turning of the electric motor, the spindle moves downward and powerfully pushes the self-piercing rivet  8  held by the punch  9  to the die  10  side. The punch  9  can be retracted by the reverse turning of the electric motor. The punch drive  11  may be hydraulic, air-pressure or other drive means. The die  10  is disposed at the other end of the C-shaped frame  5 , that is, at the lower horizontal arm  7  end so as to oppose the punch  9 , being disposed so as to receive the leg of a self-piercing rivet driven in by the punch  9 . 
     To the self-piercing rivet fastening device  1  is connected a controller  13 , which controller  13  controls the action of the punch drive  11 . To the self-piercing rivet fastening device  1  is also connected a feeder tube  15  that extends from the self-piercing rivet feeder  14  and feeds self-piercing rivets one at a time to a point below the punch  9 . In the portion of the upper horizontal arm  6  of the C-shaped frame  5  where the punch  9  is disposed, a receiver  17  is disposed for receiving self-piercing rivets and holding the self-piercing rivets at the position where they are driven in. The feeder tube  15  is connected to the receiver  17 . The self-piercing rivet feeder  14  is controlled by the controller  13 , which controls the drive of the punch  9  and the feeding of the self-piercing rivets so that such drive and feeding are proper. 
       FIGS. 2 and 3  are a vertical section and partially cutaway diagonal view of the portions of the self-piercing rivet fastening device  1  where the receiver  17  and punch  9  are located. The receiver  17  has an intake passageway  18  for receiving self-piercing rivets sent from the feeder tube  15  and a driving chamber  21  for receiving self-piercing rivets from the intake passageway  18 , formed at a position which crosses a drive passageway  19  of the punch  9  and at which the self-piercing rivets  8  are impacted by the punch  9 . Downward from the driving chamber  21 , a nose  22  that forms the drive passageway  19  is disposed. The self-piercing rivets  8  that are sent through the feeder tube  15  are automatically fed, by compressed air or the like, for example, in a proper attitude in the intake passageway  18  and driving chamber  21  of the receiver  17 . The self-piercing rivets  8  that are held in a proper attitude in the driving chamber  21  are driven in toward the die  10  ( FIG. 1 ) by the descending of the punch  9 , and self-piercing rivets  8  driven by the punch  9  are driven into the plurality of members being fastened (not shown in the drawings) while perforating them, whereupon the plurality of members being fastened is fastened together. The legs of the self-piercing rivets  8 , in the lowermost member being fastened, do not punch through that member being fastened but expand outwardly in the radial direction just short of the lower surface thereof, and the driving-in terminates just short of the lower surface without penetrating through the lower surface. 
     In the receiver  17 , a rivet arrival detection sensor  23  is provided for detecting whether or not a self-piercing rivet  8  is present in the driving chamber  21 . The sensor  23  is disposed at a position that is adjacent to the driving chamber  21  and at which the intake passageway  18  will not be obstructed. In the embodiment diagrammed, as indicated in  FIG. 3 , in the receiver  17  is provided a turnable gate  25  capable of partially opening the intake passageway  18  and partially opening the driving chamber  21 . The gate  25  is configured so as normally to close the intake passageway  18  and driving chamber  21 , but can be turned so as to partially open the intake passageway  18  and partially open the driving chamber  21 . When such a gate  25  is present, the rivet arrival detection sensor  23  is disposed at a position where the opening and closing of the gate  25  will not be obstructed. In order to satisfy these conditions, in the embodiment diagrammed, the rivet arrival detection sensor  23 , as indicated in  FIGS. 2 and 3 , is deployed at a position that is adjacent to the driving chamber  21  and also opposes the driving chamber  21 . The rivet arrival detection sensor  23  will typically be an optical sensor, but it may be some other sensor, such as one that employs a proximity switch, for example. Output signals from the rivet arrival detection sensor  23  are input via a signal line  27  to the controller  13 . 
     Furthermore, as diagrammed in  FIG. 1 , a rivet feed detection sensor  26  is provided either in the vicinity of the discharge port of the self-piercing rivet feeder  14  or in the vicinity of the intake of the feeder tube  15 . This rivet feed detection sensor  26  detects that a self-piercing rivet has been sent from the feeder  14  to the receiver  17 . The rivet feed detection sensor  26  will typically be a sensor that uses the impedance of an electromagnetic coil, but a sensor that employs a proximity switch may also be used. The output signals from the rivet feed detection sensor  26  are input, via another signal line  29 , together with other signals, to the controller  13 . 
     The controller  13  is configured so that, when the rivet arrival sensor  23  has detected that no self-piercing rivet  8  is present in the driving chamber  21  of the receiver  17 , the drive (driving-in) of the punch  9  is prevented in response to a signal from the rivet arrival sensor  23 . Thus, if the rivet arrival sensor  23  detects that no self-piercing rivet  8  is present in the driving chamber  21 , then the drive of the punch  9  will be prevented so that dry firing of the punch  9  is definitely prevented. Moreover, when the controller  13 , after first receiving a self-piercing rivet feed signal from the rivet feed detection sensor  26 , then detects a self-piercing rivet arrival signal from the rivet arrival detection sensor  23 , the controller  13  recognizes a proper feed of a self-piercing rivet  8 . But, when that feed time exceeds a certain time period, then the controller  13  can detect that the feed was improper. That is, by using the rivet arrival detection sensor  23  and the rivet feed detection sensor  26 , the controller  13  can determine whether the feed of a self-piercing rivet  8  from the feeder tube  15  to the driving chamber  21  is proper or improper. 
     It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only, and not in any limiting sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.

Technology Category: 4