CA2294672C

CA2294672C - Apparatus for assembling motor vehicle body

Info

Publication number: CA2294672C
Application number: CA 2294672
Authority: CA
Inventors: Shoichi Hirata; Toshio Semmyo; Takasi Kubo; Kenji Kusumegi; Jiro Sugawara; Gen Tsujii; Naoki Fukai
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1999-01-11
Filing date: 2000-01-10
Publication date: 2010-03-16
Anticipated expiration: 2020-01-10
Also published as: CA2294672A1

Abstract

An apparatus for assembling a vehicle body is provided with a movable base which is laterally movable, a setting jig for setting a side panel, and welding robots. A rotary frame is supported on the movable base. The setting jig is detachably mounted on the rotary frame. The welding robots are mounted on the rotary frame. The setting jig turns to an inward posture so as to assemble the side panel and other vehicle body constituting members. A cable supporting frame for supporting the cables for the welding robots are mounted on the rotary frame in a manner so as to project to a side opposite the setting jig. The cable supporting frame also functions as a balancing element to keep the rotary frame well balanced.

Description

APPARATUS FOR ASSEMBLING MOTOR VEHICLE BODY
BACKGROUND OF THE INVENTION

1. Field of the Invention The present invention relates to an apparatus for assembling a motor vehicle body in which right and left side panels are welded to other vehicle body constituting members such as a floor panel, a roof panel or the like.

2. Description of the Related Art This kind of apparatus is known from Japanese Published Unexamined Patent Application No. 124549/1993.
This apparatus comprises a movable frame which is provided on each of left and right side (i.e., on lateral side) portions of an assembly station into which vehicle body constituting members such as a floor panel, a roof panel, or the like other than side panels are transferred. The movable frame is movable between a laterally outward waiting position and a laterally inward welding position.
On this movable frame there are detachably mounted a setting jig on which each of the side panels is held in position, and a plurality of welding robots in a manner movable in the longitudinal (i.e., front and rear) direction. There is further provided a side panel feeding apparatus which moves a presetting jig for the side panel into, and out of, a space between the movable frame in the waiting position and the assembly station.

In this apparatus, the assembly of a motor vehicle body is performed in the following manner. Namely, the side panel which has been set in position in advance on the presetting jig is handed over from the presetting jig to the setting jig in a state in which the movable frame is moved to the waiting position. Thereafter, the movable frame is moved to the welding position. The side panel is thus welded to the other vehicle body constituting members by means of the welding robots.

According to this conventional apparatus, even if the welding points are changed due to the change in the kind of vehicles to be assembled, they can be dealt with by the movement of the welding robots. Therefore, the change in the kind of vehicles can be dealt with by changing the setting jig. As compared with a case in which a welding jig with a large number of welding guns mounted thereon is used, the cost for the setting jig is lower because the setting jig need not be provided with the welding guns. Even if several setting jigs must be provided to cope with the change in the kind of vehicles, the equipment cost can still be kept lower.

Depending on the kind of vehicles, there are cases where a side sill of the side panel is welded to the floor panel on its upper and lower sides. In this case, it is preferable to provide welding robots in a lower side portion of the assembly station so that the welding of the welding spots on the lower side of the sill can be performed with these welding robots to thereby shorten a cycle time. However, in the above-described conventional apparatus, it is necessary to secure, on both sides of the assembly station, a space for moving the side panel feeding apparatus. Therefore, this kind of welding robot cannot be disposed.

In view of the above-described points, the present invention has an object of providing an improved apparatus of the above-described conventional apparatus so that there is no need of providing a space for moving the side panel feeding apparatus on both sides of the assembly station.

SUMMARY OF THE INVENTION

In order to attain the above and other objects, the present invention is an apparatus for assembling a motor vehicle body in an assembly line which extends in a longitudinal direction by welding right and left side panels to other vehicle body constituting members such as a floor panel, a roof panel or the like. The apparatus comprises: a movable base provided on each of lateral side portions of an assembly station into which said other vehicle body constituting members are transferred, the movable base being movable between a laterally inward welding position and a laterally outward waiting position;
a rotary frame supported on the movable base so as to be rotatable about a longitudinally extending axis of rotation; a setting jig for holding a side panel, the setting jig being detachably mounted on the rotary frame such that the side panel can be set on the setting jig in a state in which the movable base is moved to the waiting position and in which the setting jig is turned by rotation of the rotary frame into an upward posture to look upward or an outward posture to look laterally outward and that the side panel and the other vehicle body constituting members can be welded together in a state in which the movable base is moved to the welding position and in which the setting jig is turned by rotation of the rotary frame into an inward posture to look laterally inward; a plurality of welding robots for welding the side panels and the other vehicle body constituting members together, the welding robots being mounted on the rotary frame so as to be longitudinally movable; and a cable supporting frame for supporting cables to be connected to the welding robots, the cable supporting frame being mounted on the rotary frame such that a turning moment which operates on the rotary frame in the inward posture due to a weight of the cable supporting frame cancels a turning moment due to a weight of the setting jig.

According to the present invention, it becomes possible to set the side panel onto the setting jig from an upper side or from a laterally outside by making the setting jig into the upward posture or into the outward posture. The space on the side of the assembly station for moving the side panel feeding apparatus therein is not required any more. As a result, welding robots can be disposed on a lower side portion of the assembly station so that the welding of the side panels to the floor panel can be assisted by these welding robots. The cycle time can thus be shortened.

The welding robots mounted on each of the rotary frames rotate around the axis of rotation by the rotation of the rotary frame. Here, since the cables for the welding robots are supported on the cable supporting frame which is mounted on the rotary frame, there is no possibility that the cables get entangled with each other as a result of rotation of the welding robots. In addition, since the cable supporting frame functions as a balancing element to keep the rotary frame well balanced, the rotary frame can be rotated smoothly.

By the way, as welding robots to be mounted on the rotary frame, there will be required upper part welding robots for welding the side panels to upper vehicle body constituting members such as a roof panel or the like, and lower part welding robots for welding the side panels to the floor panel. In this case, it is also considered to provide the rotary frame with a pair of upper and lower bar members which are longitudinally elongated. Then, the upper part welding robots are mounted on the upper bar member and the lower part welding robots are mounted on the lower bar member. In this arrangement, however, the positions of mounting the welding robots are away from the axis of rotation of the rotary frame. As a result, an inertia force of rotation of the welding robots due to the rotation of the rotary frame becomes large and, at the time of stopping the rotation of the rotary frame, an excessive force will be applied to the portion at which each of the welding robots is engaged with the rotary frame. On the other hand, if the apparatus further comprises a bar member provided on the rotary frame so as to extend along the axis of rotation of the rotary frame, and the plurality of welding robots are divided into two sets, one set of welding robots and the other set of welding robots being mounted, in postures opposite to each other, on those upper and lower surfaces, respectively, of the bar member which face upward and downward in the inward posture of the rotary frame, the position of mounting each of the welding robots becomes as close to the axis of rotation as possible. The inertia force of rotation of each of the welding robots due to the rotation of the rotary frame thus becomes small, and the force to be applied, at the time of stopping the rotation of the rotary frame, to the portion in which each of the welding robots is engaged with the rotary frame also becomes small. Therefore, there will occur no such a disadvantage as a poor positioning accuracy of the welding robots due to the deformation at the portions of engagement.

In this case, in order to prevent the cables for the above-described one set of welding robots from getting entangled with the cables for the other set of the welding robots, it is preferable to constitute the cable supporting frame by: an upper frame portion for supporting cables for the above-described one set of welding robots mounted on the upper surface of the bar member, the upper frame portion being longitudinally elongated in a position laterally outward, and above, the bar member in the inward posture of the rotary frame; and a lower frame portion for supporting cables for the other set of welding robots mounted on the lower surface of the bar member, the lower frame portion being longitudinally elongated in a position laterally outward, and below, the bar member in the inward posture of the rotary frame.

Further, in a coordinate system at rest relative to the rotary frame, let a longitudinally extending coordinate axis be defined as an X-axis, and laterally extending and vertically extending coordinate axes in the inward posture of the rotary frame be, respectively, defined as a Y-axis and a Z-axis. It is then preferable to constitute each of the welding robots in each of the sets by: a robot main body movably supported on a guide rail which is elongated in the X-axis direction on each of the upper surface and the lower surface of the bar member;

an articulated member supported on the robot main body so as to be rotatable about an axis of rotation in the X-axis direction in a position away in the Z-axis direction from the guide rail; a robot arm elongated in a U-axis direction and supported on the articulated member so as to be movable in the U-axis direction, the U-axis being defined as that coordinate axis in the coordinate system at rest relative to the articulated member which is parallel to the Y-axis in a neutral position of rotation of the articulated member; and a welding gun mounted on an inner end in the U-axis direction of the robot arm through a wrist. The welding robot can thus be made smaller in weight and size than a Cartesian coordinate type of robot in which the movable range of the welding gun is made equal to each other. Preferably, each of the upper and lower frame portions is disposed so as to be positioned outside, in a swinging direction, of the robot arm relative to a position of an outer end in the U-axis direction of the robot arm, in a state: in which the robot arm of each welding robot in respective sets is moved to an outer stroke end in the U-axis direction; and in which the robot arm is swung by rotation of the articulated member to a swinging end at which the outer end in the U-axis direction of the robot arm lies away from the guide rail in the Z-axis direction. If there is further provided a cable holding member which is capable of bending two-dimensionally for holding cables which are taken out of each of the upper and lower frame portions, and if the cable holding member is disposed between each of the upper and lower frame portions and the robot main body of each of the welding robots so as to be capable of bending on a plane which is parallel to the X-axis and the U-axis at the swinging end, the plane being positioned outside the robot arm at the swinging end as seen in the swinging direction, then, the space for laying out the cables to be taken out of each of the frame portions can be made as small as possible without disturbing the movements of the robot main body and the robot arm.

By the way, in order to avoid an interference of the welding robots and the cable supporting frame with the movable bases when the rotary frame is rotated, it is desirable to constitute each of the movable bases by a pair of movable members which are disposed at a longitudinal distance from each other and to rotatably support the rotary frame between both the movable members.
In this case, a synchronizing apparatus to synchronize both the movable members becomes necessary. As a solution, it is preferable to provide: a hollow synchronizing shaft which is extended to bridge both the movable members; a pinion coupled to each end of the synchronizing shaft so as to be engaged with a stationary rack which is disposed along each of travel passages of both the movable members; and a self-aligning bearing for rotatably supporting the synchronizing shaft on each of the movable members. In this arrangement, if both the movable members get out of synchronization with each other, there will occur a difference in the angles of rotation of the pinions on both ends of the synchronizing shaft, whereby the synchronizing shaft is twisted. Then, the asynchronism of both the movable members is corrected by means of a reaction force against twisting. Further, if both the movable members get out of synchronization with each other, the synchronizing shaft tends to be inclined in the direction of movement of the movable members. It follows that, if the synchronizing shaft is rotatably supported by ordinary bearings, a bending moment will be operated on the synchronizing shaft. A
synchronizing shaft made of a hollow member to make it smaller in weight will decrease in the bending rigidity of the synchronizing shaft, resulting in the deformation thereof. On the other hand, in the above arrangement, the inclination of the synchronizing shaft is allowed by the self-aligning bearings. Therefore, the bending moment will not be operated on the synchronizing shaft, and it is only the twisting moment that is operated thereon.
Accordingly, even if the synchronizing shaft is made of a hollow construction, it is not subject to deformation.
The synchronizing apparatus can thus be made smaller in weight.

An apparatus for assembling a motor vehicle body is sometimes further provided with: a floor panel feeding station disposed on an upstream side of the assembly station in the assembly line; a roof panel feeding station disposed between the floor panel feeding station and the assembly station; and a transfer apparatus provided to transfer a floor panel fed into the floor panel feeding station to the assembly station by allowing it to pass through the roof panel feeding station. In an ordinary transfer apparatus, a transfer jig for supporting the workpiece is provided on a lifting frame which extends over the entire length of the workpiece transfer region such that the transfer jig to support the workpiece can be moved back and forth. In the transfer apparatus for transferring the floor panel from the floor panel feeding station to the assembly station, however, the range in which the lifting frame is extended is sometimes limited to the roof panel feeding station, which lies in an intermediate position, in order to avoid an interference with pieces of equipment which are disposed in the floor panel feeding station and the assembly station. In such a case, it is considered to make the following arrangement.
Namely, a movable frame which is supported on the lifting frame is provided so as to be movable in the longitudinal direction of the assembly line. A transfer jig is supported on the movable frame so as to be movable in the longitudinal direction of the assembly line. By moving the movable frame and the transfer jig to an upstream side of the assembly line relative to the lifting frame and the movable frame, respectively, the transfer jig is returned to the floor panel feeding station in a manner overhung from the lifting frame toward the upstream side of the assembly line, and by moving the movable frame and the transfer jig to a downstream side of the assembly line relative to the lifting frame and the movable frame, respectively, the transfer jig is moved forward to the assembly station in a manner overhung from the lifting frame toward the downstream side of the assembly line.
Here, the lifting frame of the transfer apparatus is moved up and down by synchronizing a plurality of driving sources such as cylinders or the like which are disposed in a plurality of portions at a distance from each other in the longitudinal direction of the assembly line. In order to reduce the equipment cost, it is preferable to drive the lifting frame by a single driving source.

However, in the above-described transfer apparatus in which the range of extending the lifting frame is limited to the roof panel feeding station, there is the following disadvantage. Namely, when the workpiece is lifted by moving up the lifting frame in a state in which the transfer jig is returned to the floor panel feeding station, the lifting frame is likely to be inclined downward toward the upstream side of the assembly line due to the load to operate on the transfer jig which is overhung toward the upstream side of the assembly line.
Therefore, it becomes difficult to smoothly move up the lifting frame by a single driving source.

In order to solve this kind of problem, it is preferable to arrange that the roof panel feeding station has: a plurality of guide frames for supporting the lifting frame so as to be movable up and down at a plurality of points as seen in the longitudinal direction of the assembly line; and a rotary shaft extending in the longitudinal direction of the assembly line. The lifting frame is thus vertically moved by rotation of the rotary shaft in a normal direction and in the opposite direction through motion converting mechanisms disposed at a plurality of points as seen in the longitudinal direction of the assembly line. A single driving motor for driving' the rotary shaft is connected to that end of the rotary shaft which is disposed on the upstream side of the assembly line.

According to an aspect of the present invention there is provided an apparatus for assembling a motor vehicle body in an assembly line which extends in a longitudinal direction by welding right and left side panels to other vehicle body constituting members, said apparatus comprising:

a movable base provided on each of lateral side portions of an assembly station into which said other vehicle body constituting members are transferred, said movable base being movable between a laterally inward welding position and a laterally outward waiting position;
a rotary frame supported on said movable base so as to be rotatable about a longitudinally extending axis of rotation;

a setting jig for holding a side panel, said setting jig being detachably mounted on said rotary frame wherein the side panel can be set on said setting jig in a state in which said movable base is moved to the waiting position and in which said setting jig is turned by rotation of said rotary frame into an upward posture to look upward or an outward posture to look laterally outward, and wherein the side panel and the other vehicle body constituting members can be welded together in a state in which said movable base is moved to the welding position and in which said setting jig is turned by rotation of said rotary frame into an inward posture to look laterally inward;
a plurality of welding robots for welding the side panels and the other vehicle body constituting members together, said welding robots being mounted on said rotary frame so as to be longitudinally movable; and a cable supporting frame for supporting cables to be connected to said welding robots, said cable supporting frame being mounted on said rotary frame such that a turning moment which operates on said rotary frame in the inward posture due to a weight of said cable supporting frame cancels a turning moment due to a weight of said setting jig.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and the attendant advantages of the present invention will become readily apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view of a vehicle body assembly line which is provided with the apparatus of the present invention;

13a FIG. 2 is a side view of the vehicle body assembly station;

FIG. 3 is a front view of an assembly line as seen along the line III-III in FIG. 2;

13b FIG. 4 is an enlarged side view, partly shown in section, taken along the line IV-IV in FIG. 2;

FIG. 5 is a sectional view as seen along the line V-V in FIG. 4;

FIG. 6 is a sectional view taken along the line VI-VI in FIG. 5;

FIG. 7 is an enlarged sectional view taken along the line VII-VII in FIG. 2;

FIG. 8 is a sectional view taken along the line VIII-VIII in FIG. 7;

FIG. 9 is a sectional view taken along the line IX-IX in FIG. 7;

FIG. 10 is an enlarged sectional view taken along the line X-X in FIG. 3;

FIG. 11 is an enlarged side view of a first transfer apparatus as seen from the side opposite to that in FIG.
2;

FIG. 12 is a plan view of the first transfer apparatus; and FIG. 13 is a front view of the first transfer apparatus as seen from the left side in FIG. 11.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1 and 2 show a vehicle body assembly line in which a floor panel feeding station 1, a roof panel feeding station 2, an assembly station 3, and an idling station 4 are disposed in the order mentioned toward the front end of the assembly line (i.e., from an upstream side to a downstream side of the assembly line). In this specification, unless otherwise noted, the line along which the floor panel feeding station 1 through the idling station 4 are disposed in the assembly line is called a "longitudinal direction" and a direction at right angles thereto is called a "lateral direction." Further, in the following detailed explanations, reference is sometimes made to only one set where there are provided a pair of sets such as setting jigs, side panels, guide rails, or the like. However, it should be understood that the same explanation also applies to the other set, where applicable.

In the floor panel feeding station 1, there is disposed a supporting base 5 for placing thereon a floor panel W1. The floor panel W1 to be discharged from a floor panel working line (not illustrated) which is located on the upstream side of the assembly line can be supported on the supporting base 5 by a plurality of workpiece receiving members 5a which are vertically provided on the supporting base 5. As shown in FIG. 3, the assembly station 3 is also provided with a supporting base 6 having thereon a plurality of workpiece receiving members 6a for holding the floor panel Wi after placing it in position. The floor panel W1 that has been placed on the supporting base 5 in the floor panel feeding station 1 is transferred by a first transfer apparatus 71 from the floor panel feeding station 1 to the assembly station 3 by allowing it to pass through the roof panel feeding station 2 (i.e., without performing work therein), to thereby place it on the supporting base 6 in the assembly station 3.

Above the assembly line, there is provided a travelling frame 8 which can be moved back and forth (i.e., longitudinally) between the roof panel feeding station 2 and the assembly station 3. Holding jigs 91, 92, 93 for holding a roof panel W2, a rear roof rail W3 and a dashboard upper panel W4, respectively, are hung from the travelling frame 8 in a manner to be movable up and down.
Three members of the roof panel W2, the rear roof rail W3 and the dashboard upper panel W4 to be fed by a transfer device (not illustrated) from side portions of the roof panel feeding station 2 are caused to be received by the respective holding jigs 91, 9Z, 93. These three members are then transferred into the assembly station 3 by moving the travelling frame 8 forward to the assembly station 3.

In the assembly station 3, the right and left side panels W5, W5 are combined by welding to the floor panel W1 which is held on the supporting base 6. Also, both end portions of the rear roof rail W3 and the dashboard upper panel W4 are combined by welding to both the side panels W5, W5. Further, the roof panel W2 is inserted from an upper side into a space between the upper edge portions of both the side panels W5, W5 to thereby set it in position.

The roof panel W2 and the side panels W5 are thus combined together by welding. A motor vehicle body W thus assembled is discharged by a second transfer apparatus 72 from the assembly station 3 to a reinforce-welding line (not illustrated) which is located on the downstream side of the assembly line by allowing it to pass through the idling station 4.

On each of the left and right (i.e., lateral) side portions of the assembly station 3, there is disposed a movable base 10 which can be moved back and forth (i.e., laterally) between a welding position which lies laterally inward as shown in the left half portion of FIG. 3 and a waiting position which lies laterally outward as shown in the right half portion of FIG. 3. A pair of supporting columns 10a, l0a which are disposed at a longitudinal distance from each other are vertically provided in each of the movable bases 10 to support therebetween a rotary frame 11 which is capable of rotation about an axis of rotation which extends in the longitudinal direction of the assembly line. Each of the rotary frames 11 is provided with a setting jig 12 for the side panel W5. The setting jig 12 is capable of turning in position by rotation of the rotary frame 11 between an inward posture in which the setting jig 12 looks laterally inward (a posture as shown in the left half of FIG. 3) and an upward posture in which the setting jig 12 looks upward (a posture as shown in the right half of FIG. 3). The setting jig 12 is constituted by mounting thereon a plurality of workpiece receiving members 12a and clamping members 12b for positioning and holding the side panels W5 on a jig frame of a framed construction. The setting jigs 12 are omitted in FIG. 1.

The rotary frame 11 is provided with a bar member llb which extends along the axis of rotation lla, and flange members llc, llc on the longitudinally opposite (i.e., front and rear) ends of the bar member llb. An electric motor lld and a coaxial reduction gear lle are mounted on each of the supporting columns l0a in line with the above-described axis of rotation lla. Each of the flanges llc, llc is coupled to an output end of the reduction gear ile so that the rotary frame 11 can be rotated. Front and rear end portions of the above-described setting jig 12 are detachably coupled to the flanges lic, llc so that the setting jig 12 can be exchanged depending on the change in the kind of the motor vehicle body.

In addition, a plurality of welding robots 13, each having a welding gun G attached to a working end thereof, are mounted on the following two surfaces in a vertically opposite manner (i.e., in postures which are opposite to each other). The two surfaces in question are those upper surface and lower surface, respectively, of the bar member 11 which face upward and downward, respectively, when the rotary frame 11 is rotated to a phase in which the setting jig 12 becomes the above-described inward posture. In this embodiment, the bar member llb is constituted by combining two square pipes llbl, llbl with a plurality of coupling pieces 11b2 which are provided at a longitudinal distance from one another. However, the bar member may also be made by a single pipe or a solid bar member.
Each of the rotary frames 11 is further provided with a cable supporting frame 14 for supporting the cables or the like to be connected to the welding robots 13. The cable supporting frame 14 is made up of an upper frame portion 14a, a lower frame portion 14b, a pair of front and rear vertical frame portions 14c, 14c and a projected portion 14d, as explained in more detail hereinbelow. The following explanation is based on a state in which the rotary frame 11 is rotated to the phase in which the setting jig 12 is in the inward posture. In this state, the upper frame portion 14a, which is of a duct shape, lies laterally outward, and also above, the bar member llb in a manner to extend in the longitudinal direction. The upper frame portion 14a is to insert therethrough and support the cables or the like for the welding robots 13 that are mounted on the upper surface of the bar member llb. The lower frame portion 14b, which is of a duct shape, lies laterally outward, and also below, the bar member llb in a manner to extend in the longitudinal direction. The lower frame portion 14b is to insert therethrough and support the cables or the like for the welding robots 13 that are mounted on the lower surface of the bar member llb. The pair of front and rear vertical frame portions 14c, 14c, each being of a duct shape, connect both longitudinal end portions of the upper and lower frame portions 14a, 14b, respectively. The projected portion 14d, which is of a duct shape, projects from the upper end portion of each of the vertical frame portions 14c outwardly in the longitudinal (i.e., in the front and rear) direction of the respective supporting columns 10a. The cable supporting frame 14 is coupled at each of the vertical frame portions 14c to the respective flange members lic. On each of the outer sides, as seen in the longitudinal direction of the assembly line, in the moving space of the movable base 10, there is disposed a cable holding member 15 and one end thereof is coupled to the projected portion 14d. Among the cables or the like to be taken out of the cable holding member 15, those cables or the like for the welding robots 13 that are mounted on the upper surface of the bar member lib are inserted into the upper frame portion 14a through the projected portion 14d, and those cables or the like for the welding robots 13 that are mounted on the lower surface of the bar member llb are inserted into the lower frame portion 14a through the projected portion 14d and the vertical frame portion 14c. Cable holding members 13a are disposed between each of the upper and lower frames 14a, 14b and each of the welding robots 13. The cables or the like taken out of each of the frame portions 14a, 14b are held by the cable holding members 13a and are connected to the respective welding robots 13.

Longitudinally extending stationary frames 16, 17 are provided at both upper and lower portions on each of the left and right sides of the assembly station 3.
Welding robots 18, 19, each having a welding gun G at each operating end thereof, are mounted on each of the stationary frames 16, 17 so as to be movable in the longitudinal direction. In the figures, reference numerals 18a, 19a denote cable holding members for holding the cables or the like for the welding robots 18, 19, respectively. In FIG. 1, the cable holding members 15, 13a, 18a, 19a are omitted.

In assembling the motor vehicle body W, the following steps are taken. Namely, the movable base 10 is first moved to the waiting position, and the setting jig 12 is turned to the upward posture by the rotation of the rotary frame 11. In this state, a side panel W5 is set in position from an upper side onto the setting jig 12 by a transfer device (not illustrated), and a floor panel W1, a roof panel W2, a rear roof rail W3 and a dashboard upper panel W4 are transferred into the assembly station 3.
Then, the setting jig 12 is turned into the inward posture, and the movable base 10 is moved to the welding position. The side panel W5 is connected from a side to the floor panel W1 as well as to the rear roof rail W3 and the dashboard upper panel W4 that have been respectively lowered to the predetermined assembly positions. In this state, by means of those welding robots 13 for welding the lower portions which are mounted on the lower surface of the bar member lib of the rotary frame 11, the side panel W5 is welded to the floor panel W1, and by means of those welding robots 13 for welding the upper portions which are mounted on the upper surface of the bar member llb, the end portions of the rear roof rail W3 and the dashboard upper panel W4 are welded to the side panel W5. Further, the roof panel W2 is set in position from an upper side into a space between the left and right side panels W5, W5. The side panels W5 are welded to the roof panel W2 by means of the welding robots 13 for welding the upper portions.

By the way, each of the above-described welding robots 13 is to weld a plurality of welding points. In that kind of vehicle body which has a large number of welding points, the cycle time becomes long. In such a case, the welding of the side panels W5 to the floor panel Wl and the roof panel W2 is assisted by the welding robots 18, 19 that are respectively mounted on the upper and lower stationary frames 16, 17 to thereby shorten the cycle time.

When the assembling of the motor vehicle body W has been finished as explained above, the holding of the side panel W5 by the setting jig 12 is released. The movable base 10 is moved to the waiting position and the setting jig 12 is turned into the upward posture. The next side panel W5 is then set onto the setting jig 12. Also, the motor vehicle body W is discharged from the assembly station 3, and the next floor panel W1, roof panel W2, rear roof rail W3 and dashboard upper panel W4 are transferred into the assembly station 3. By repeating the above steps, the motor vehicle bodies W are assembled in a continuous manner.

The following way is also possible. Namely, by turning the setting jig 12 into the outward posture in which it looks laterally outward, the side panel W5 is set onto the setting jig 12 from a laterally outer side.
Furthermore, without assembling the side panel W5 in advance, the constituting elements of the side panel W5 are set onto the setting jig 12 in a predetermined positional relationship. These side panel constituting elements are then combined by welding by means of the welding robots 13 mounted on the rotary frame 11 to thereby assemble the side panel W5.

The welding robots 13 mounted on the rotary frame 11 rotate about an axis of rotation lla by the rotation of the rotary frame 11. However, since the cables or the like for the welding robots 13 are supported by the cable supporting frame 14 mounted on the rotary frame 11, the cables or the like do not get entangled with each other even if the welding robots 13 rotate about the axis of rotation lla. Furthermore, it is so arranged that, in a state in which the rotary frame 11 is rotated into the phase in which the setting jig 12 becomes the inward posture, the center of gravity of the cable supporting frame 14 is located laterally outside relative to the axis of rotation lla. Therefore, the turning moment due to the weight of the cable supporting frame 14 operates in a direction to cancel the turning moment due to the weight of the setting jig 12. In other words, the cable supporting frame 14 functions as a balancing element to keep the rotary frame 11 well balanced and, therefore, the rotary frame 11 can be rotated smoothly.

In addition, if that inertia force of rotation of the welding robots 13 which is generated by the rotation of the rotary frame 11 becomes large, a large force will be operated on the portion of engagement of the welding robots 13 with the rotary frame 11 at the time of stopping the rotation of the rotary frame 11 when the setting jig 12 has been in the inward posture and in the upward posture. This may result in a deformation of the above-described portion of engagement. In the present embodiment, on the other hand, the two sets of upper and lower welding robots 13 are mounted, in posture opposite to each other, i.e., one set in the upward posture and the other set in the downward posture, respectively, on the upper and lower surfaces of the bar member lib which extends along the axis of rotation lla of the rotary frame 11. Therefore, the position of mounting each of the welding robots 13 becomes as close to the axis of rotation lla as possible and, as a consequence, the inertia force of rotation of each of the welding robots 13 due to the rotation of the rotary frame 11 becomes small. As a result, the force to act on the portion of engagement of each of the welding robots 13 with the rotary frame 11 at the time of stopping of rotation of the rotary frame 11 also becomes small. There is thus no disadvantage that the positioning accuracy of each of the welding robots 13 becomes poor due to the deformation of the portion of engagement.

With reference to FIG. 4, the following definition is made. Namely, in a coordinate system at rest relative to the rotary frame 11, a coordinate axis in the longitudinal direction (also called a longitudinally extending coordinate axis) is defined as an X-axis, and a coordinate axis in the lateral direction and a coordinate axis in a vertical direction (also called a laterally extending coordinate axis and a vertically extending coordinate axis), in a state in which the setting jig 12 is in the inward posture, are defined as a Y-axis and a Z-axis, respectively. Each welding robot 13 is made up of:
a robot main body 131 which is movably supported on a pair of guide rails 130, 130 which are provided on the upper surface or the lower surface of the bar member llb so as to extend longitudinally (i.e., in the X-axis direction), each pair of guide rails 130, 130 being disposed at a lateral distance (i.e., in the Y-axis direction) from each other; an articulated member 132 which is supported on the robot main body 131 at a position away from the guide rails 130 in the Z-axis direction so as to be rotatable about an axis of rotation extending in the X-axis direction; a robot arm 133 which is elongated in a U-axis direction and is supported on the articulated member 132 so as to be movable in the U-axis direction, the U-axis being defined as that coordinate axis in the coordinate system at rest relative to the articulated member 132 which is parallel to the Y-axis in a neutral position of rotation of the articulated member 132; and a welding gun G which is mounted on an inner end, as seen in the U-axis direction, of the robot arm 133 through a wrist 134.
According to this arrangement, the welding gun G can be moved in a wide range by swinging the robot arm 133 as a result of rotation of the articulated member 132 and by moving the robot arm 133 in the direction of the U-axis.

This welding robot 13 can be made smaller in size and weight than a Cartesian-coordinate type of robot with an equal movable range of the welding gun G.

The upper and lower frame portions 14a, 14b of the cable supporting frame 14 are disposed, as seen in the direction of swinging of the robot arm 133, to lie outside relative to the outer end position of the robot arm 133 as seen in the U-axis direction in the following states, i.e., in a state in which the robot arm 133 of each of the welding robots 13 for welding the upper portion and the lower portion, respectively, is moved to an outer stroke end in the U-axis direction, and also in a state in which the robot arm 133 is swung by the rotation of the articulated member to a swinging end at which the outer end in the U-axis direction of the robot arm 133 lies away from the guide rails 130 in the Z-axis direction. A cable receiver 135 which projects outward in the swinging direction of the robot arm 133 is mounted on the robot main body 131 of each of the welding robots 13. The above-described cable holding member 13a which can be bent in two dimensions for holding the cables or the like which are taken out of each of the upper and lower frame portions 14a, 14b is disposed between each of the upper and lower frames 14a, 14b and the cable receiver 135 of each of the welding robots 13. The cable holding member 13a is arranged to be capable of bending on a plane which is parallel to the X-axis and the U-axis at the above-described swinging end and which is also outside the swinging direction of the robot arm 133 which lies at the above-described swinging end. According to this arrangement, the space for laying out the cables or the like to be taken out of each of the frame portions 14a, 14b can be made as small as possible without interfering with the movement of the robot main body 131 and the robot arm 133.

With reference to FIGS. 5 and 6, the robot main body 131 of each of the welding robots 13 is formed into an L-shape having: a base portion 131a which is slidably engaged with both the guide rails 130, 130; and a rising portion 131b which rises in the Z-axis direction from an end portion at one side, as seen in the X-axis direction, of the base portion 131a. The robot main body 131 has a recessed portion 131c which recedes in the central portion, as seen in the Y-axis direction, into the space between both the guide rails 130, 130. Inside the base portion 131a, there is contained a driving motor 132a for the articulated member 132 in a posture parallel to the X-axis direction so as to enter into the recessed portion 131c. The articulated member 132 is supported, on that side surface of the rising portion 131b which faces the other side, as seen in the X-axis direction, in a cantilevered manner through a coaxial harmonic drive type of reduction gear 132b which is positioned in line with the axis of rotation of the articulated member 132. The driving motor 132a and the reduction gear 132b are coupled together by a timing belt 132c which serves as a winding type of power transmission means. In addition, the articulated member 132 is formed into a plate shape which is flat as seen in the X-axis direction. The robot arm 133 is supported on the side surface which faces the other side, as seen in the X-axis direction, of the articulated member 132 so as to be slidable in the U-axis direction along a guide rail 133a which is provided on the robot arm 133. According to this arrangement, the reduction gear 132b, the articulated member 132 and the robot arm 133 are disposed in sequence from the rising portion 131b of the robot main body 131 toward the other side in the X-axis direction. Here, the other side in the X-axis direction coincides with the direction in which the base portion 131a of the robot main body 131 is bent relative to the rising portion 131b. Therefore, it becomes possible to dispose the reduction gear 132b, the articulated member 132 and the robot arm 133 in a manner overlapped with each other in the X-axis direction relative to that driving motor 132a for the articulated member 132 which is contained inside the base portion 131a. In addition, that portion of the articulated member 132 which supports the robot arm 133 can be disposed without projecting it in the Z-axis direction of the robot main body 131. Further, by disposing the driving motor 132a for the articulated member 132 in a manner contained in the recessed portion 131c of the base portion 131a of the robot main body 131, the height in the Z-axis direction of the base portion 131a can be made smaller. In this manner, the dimensions of the welding robot 13 in the X-axis direction and in the Z-axis direction can be shortened and the welding robot 13 can be made small to the best extent possible.

On the outer side, as seen in the Y-axis direction, of the robot main body 131, there is mounted a driving motor 131d for the robot main body 131. A pinion 131f which is coupled to the electric motor 131d through a coaxial reduction gear 131e is engaged with a rack 131g which is fixed to the bar member lib so that the robot main body 131 can be moved in the X-axis direction. The articulated member 132 is provided with a projected portion which projects in the U-axis direction. On that side surface of this projected portion which faces the above-described one side as seen in the X-axis direction, there is mounted a driving motor 133b for the robot arm 133 in a posture parallel to the X-axis direction so that the driving motor 133b lies in an overlapped relationship with the reduction gear 132b and the rising portion 131b.
A pinion 133d which is coupled to the electric motor 133b through a coaxial reduction gear 133c is engaged with a rack 133e which is fixed to the robot arm 133 so that the robot arm 133 can be moved in the U-axis direction.

The wrist 134 of each of the above-described welding robots 13 is constituted into a three-axis construction having: a first wrist portion 1341 which is rotatable about the U-axis; a second wrist portion 1342 which is rotatable about a V-axis which crosses the U-axis at right angles;
and a third wrist portion 1343 which is rotatable about a W-axis which crosses the V-axis at right angles. The welding gun G is attached to the third wrist portion 1343.
On an outer end, as seen in the U-axis direction, of the robot arm 133, there are mounted a driving motor 1341a for the first wrist portion 1341 and a driving motor 1342a for the second wrist portion 1342. A hollow rotary shaft 1341d which is coupled to the driving motor 1341 through a coaxial reduction gear 1341b and a gear 1341c is inserted into a hollow portion of the robot arm 133, and the first wrist portion 1341 is coupled to the front end of the rotary shaft 1341d. A rotary shaft 1342b which is directly coupled to the diving motor 1342a is inserted into a hollow portion of the rotary shaft 1341d. The second wrist portion 1342 is coupled to the front end of the rotary shaft 1342b through a bevel gear 1342c inside the first wrist portion 1341 and a coaxial reduction gear 1342d. In addition, a driving motor 1343a for the third wrist portion 1343 is mounted on the second wrist portion 1342, and the third wrist portion 1343 is coupled to this motor 1343a through the coaxial reduction gear 1343b.

Among the cables or the like to be held by the cable holding member 13a, the cables or the like for the driving motor 131d for the robot main body 131 and the cables or the like for the driving motor 132a for the articulated member 132 are branched at the above-described cable receiver 135 and are connected to the motors 131d, 132a.
The remaining cables or the like C are disposed with a slack between the cable receiver 135 and a cable distribution board 136 mounted on the articulated member 132. Among these cables, the cables or the like for the driving motor 133b for the robot arm 133 are branched at the cable distribution board 136 and are connected to the motor 133b. Other remaining cables or the like are held by a cable holding member 137 which is disposed between the cable distribution board 136 and an outward end, as seen in the U-axis direction, of the robot arm 133 and which can be bent on a plane parallel to the U-axis and the Z-axis. Among the cables or the like to be held by this cable holding member 137, the cables or the like for the driving motors 1341a, 1342a for the first and second wrist portions 1341, 1342 are branched at the connection end, on the side of the robot arm 133, of the cable holding member 137 and are connected to the motors 1341a, 1342a. The remaining cables or the like CM for the driving motor 1343a for the third wrist portion 1343 and the cables or the like CG for the welding gun G are respectively disposed to lie along the robot arm 133 in a state in which they are contained inside each of recessed grooves 133f, 133g which are formed on an outside surface of the respective robot arms 133. These cables or the like are taken out of the robot arm 133 near the inner end, as seen in the U-axis direction, of the robot arm 133 and are connected to the driving motor 1343a and the welding gun G.
By the way, on the outer end as seen in the U-axis direction of the robot arm 133, there is provided a changeover valve GV to connect, out of the cables or the like CG for the welding gun G. air piping for pressurizing cylinders for the welding gun G. The air piping between the welding gun G and the changeover valve GV is thus shortened so that the welding gun G can be controlled to be opened and closed at a good response.

In the base portion 131a of the robot main body 131, there are formed perforated portions 131h for inserting therethrough covers 130a for the guide rails 130. A pair of pinching rollers 131i, 131i to pinch the cover 130a from both sides in the Z-axis direction are provided on one end in the X-axis direction of the base portion 131a, and a supporting roller 130J for supporting the cover 130a from the inner side as seen in the Z-axis direction is mounted on the other side, as seen in the X-axis direction, of the base portion 131a. It is thus so arranged that the cover 130a does not come into contact with the inner surface of the penetrating hole portion 131h. The cover 130a is divided into plural pieces in accordance with the range of movement in the X-axis direction of the respective welding robots 13 which are mounted on the guide rail 130. Adjoining covers 130a are connected together by connection pieces 130b. By releasing this connection, each of the welding robots 13 can be removed from the guide rail 130 together with the cover 130a.

With reference to FIGS. 7 and 8, each of the welding robots 18 to be mounted on each of the above-described stationary frames 16 on the upper portion of the assembly station 3 has the following construction. In these figures, the longitudinal direction of the assembly line is defined as the X-axis direction, the vertical direction is defined as the Y-axis direction, and the lateral direction is defined as the Z-axis direction. The welding robot 18 is made up of: a robot main body 181 which is movably supported by a pair of guide rails 180, 180 which are parallelly provided on the side surface so as to extend in the X-axis direction, the pair of guide rails 180, 180 being disposed at a vertical distance from each other (i.e., in the Y-axis direction); a first robot arm 182 which is supported on the robot main body 18 so as to be swingable about a first axis of rotation which extends in the X-axis direction; and a second robot arm 183 which is supported on the front end portion of the first robot arm 182 so as to be swingable about a second axis of rotation which extends in the X-axis direction. A welding gun G is mounted on the front end of the second robot arm 183 through a wrist 184.

Here, the robot main body 181 is arranged to have: a base plate portion 181a which is slidably engaged with the guide rails 180, 180; and a case portion 181b which is provided so as to project in the Z-axis direction from one half portion, as seen in the X-axis direction, of the base plate portion 181a. On the other side surface, as seen in the X-axis direction, of the case portion 181b, there is supported the first robot arm 182 in a cantilevered manner through a coaxial reduction gear 182a which is positioned to lie on the first axis of rotation. A driving motor 182b for the first robot arm 182 is mounted on one circumferential side surface of the case portion 181b in a posture crossing the X-axis at right angles. As shown in FIG. 9, a bevel gear mechanism 182c which couples the driving motor 182b to the reduction gear 182a is contained inside the case portion 181b. Further, on that side surface at the front end portion of the first robot arm 182 which faces one side in the X-axis direction, there is supported the second robot arm 183 in a cantilevered manner through a coaxial reduction gear 183a which is positioned on the second axis of rotation. On that side surface of the first robot arm 182 which faces one side and in an intermediate portion of the first robot am 182, there is provided a driving motor 183b for the second robot arm 183 in a posture parallel to the X-axis. This motor 183b and the reduction gear 183a are coupled to each other by means of a timing belt 183c which serves as a winding type of power transmission means. According to this arrangement, the first robot arm 182, its driving mechanism, the second robot arm 183 and its driving mechanism can all be contained within the width, as seen in the X-axis direction, of the robot main body 181. A
portion projected in the X-axis direction relative to the robot main body 181 can thus be eliminated and, therefore, the width of the welding robot 18 in the X-axis direction can be made to the smallest extent possible.

On an outside, as seen in the Y-axis direction, of the robot main body 181, there is mounted a driving motor 181c for the robot main body 181. A pinion 181e which is coupled to the driving motor 181c through a coaxial reduction gear 181d is engaged with a rack 181f which is fixed to the stationary frame 16 so that the robot main body 181 can be moved in the X-axis direction. Further, the wrist 184 is constituted, like in the wrist 134 of the above-described welding robot 13, into a three-axis construction having: a first wrist portion 1841 which is rotatable about the U-axis which extends in the direction in which the second robot arm 183 extends; a second wrist portion 1842 which is rotatable about a V-axis which crosses the U-axis at right angles; and a third wrist portion 1843 which is rotatable about a W-axis which crosses the V-axis at right angles. The welding gun G is attached to the third wrist portion 1843. On a rear end of the second robot arm 183, there are mounted a driving motor 1841a for the first wrist portion 1841 and a driving motor 1842a for the second wrist portion 1842. A hollow rotary shaft 1841d which is coupled to the driving motor 1841a through a coaxial reduction gear 1841b and a gear 1841c is inserted into a hollow portion of the second robot arm 183 to thereby couple the first wrist portion 1841 to the front end of the rotary shaft 1841d. A rotary shaft 1842b which is directly coupled to the diving motor 1842a is inserted into a hollow portion of the rotary shaft 1841d. The second wrist portion 1842 is coupled to the front end of the rotary shaft 1842b through a bevel gear 184zc inside the first wrist portion 1841 and a coaxial reduction gear 1842d. Further, a driving motor 1843a for the third wrist portion 1843 is mounted on the second wrist portion 1842, and the third wrist portion 1843 is coupled to this driving motor 1843a through a coaxial reduction gear 1843b.

Each of the cable holding members 18a for the welding robots 18 is coupled to a cable receiving member 185 which is attached to the root main body 181. Among the cables or the like to be held by the cable holding member 18a, those cables or the like for the driving motors 181c, 182b for the robot main body 181 and the first robot arm 182, respectively, are branched at the cable receiving member 185 and are connected to these driving motors 181c, 182b. The remaining cables or the like are disposed around the circumference of the first axis of rotation of the case portion 181b of the robot main body 181 and are bridged to one side surface, as seen in the swinging direction, of the first robot arm 182.

The cables or the like for the driving motor 183b for the second robot arm 183 are branched therein and are connected to the driving motor 183b. Further, the remaining cables or the like are disposed along the above-described one side surface, as seen in the swinging direction, of the first robot arm 182 and then around the circumference of the second axis of rotation at the front end of the first robot arm 182, and are then bridged to the rear end portion of the second robot arm 183. The cables or the like for the driving motors 1841a, 1842a for the first wrist portion 1841 and the second wrist portion 1842a, respectively, are branched therein and are connected to the driving motors 1841a, 1842a. The cables or the like CM for the driving motor 1843a for the third wrist portion 1843 and the cables or the like CG for the welding gun G

are respectively disposed along the second robot arm 183 in a state in which they are contained inside each of recessed groves 183d, 183e which are formed on the outer surface of the second robot arm 183. These cables or the like are taken out of the second robot arm 183 near the front end thereof and are connected to the driving motor 1843 and to the welding gun G. The cables or the like CG
for the welding guns are held by cable clamping members 186 from the circumferential surface of the case portion 181b of the robot main body 181 up to the circumference at the front end portion of the first robot arm 182. The cables or the like CM for each of the driving motors 183b, 1841a, 1842a, 1843a are contained inside recessed grooves 181g, 182d which are formed on the circumference of the case portion 181b as well as on the side surface and the circumference at the front end of the second robot arm 182.

According to the above-described arrangement, the cables or the like can be disposed at a good space efficiency along the robot main body 181 and the first robot arm 182 so that they can be contained within the width thereof as seen in the X-axis direction. Further, at the portions of bridging the cables or the like between the robot main body 181 and the first robot arm 182 as well as between the first robot arm 182 and the second robot arm 183, the cables or the like are extended from the circumference of the case portion 181b of the robot main body 181 and the circumference of the front end portion of the first robot arm 182 toward the swinging direction of the first robot arm 182 and the second robot arm 183, respectively. Therefore, these extended portions can be bent into a U-shape toward the first robot arm 182 and the second robot arm 183, respectively, in order to allow for slacking thereof at the bridged portions. As a result, the bridged portions move regularly to follow the swinging movements of the first robot arm 182 and the second robot arm 183, respectively. The cables or the like can thus be prevented from getting entangled with the first robot arm 182 and the second robot arm 183 at the bridged portions.

At the rear end of the second robot arm 183, there is provided a changeover valve GV to connect, among the cables or the like CG, air piping for a pressurizing cylinder for the welding gun G. In the base portion 181a of the robot main body 181, there are formed perforated portions 181h for inserting therethrough covers 180a for the guide rails 180. A pair of pinching rollers 181i, 1811 for pinching each of the covers 180a from both sides, as seen in the Z-axis direction, are provided on one end, as seen in the X-axis direction, of the base portion 181a.
A supporting roller 180J for supporting each of the covers 180a from the inner side, as seen in the Z-axis direction, is mounted on the other side, as seen in the X-axis direction, of the base portion 181a. This arrangement is similar to that of the above-described welding robot 13.
The welding robots 19 to be mounted on each of the above-described stationary frames 17 on the lower portion of the assembly station 3 has the same construction as that of the above-described welding robots 13. Therefore, their detailed explanations are omitted.

With reference to FIG. 10, each of the movable bases 10, 10 is constituted by a pair of front and rear movable members 100, 100 which are disposed at a longitudinal distance from each other (i.e., at a distance from each other in the longitudinal direction) and in each of which the above-described supporting column l0a is vertically provided. Each of the movable members 100 is slidably engaged with a pair of guide rails 102, 102 which are disposed at a longitudinal distance from each other on each of stationary frames 101, 101. The stationary frames 101, 101 are provided in a pair at a longitudinal distance from each other on a side of the assembly station 3 so as to be elongated in the lateral (left and right) direction.
On each stationary frame 101, there is provided a threaded bar 105 which is rotated by an electric motor 103 in one and the opposite directions through a timing belt 104 which serves as a winding type of power transmission means. A nut 106 to be engaged in a screwed manner with the threaded bar 105 is fixed to the movable member 100.
Each of the movable members 100 is thus arranged to be linearly movable in the lateral direction by the respective electric motors 103.

As a synchronizing apparatus to laterally move in a synchronized manner the pair of front and rear movable members 100, 100, a hollow synchronizing shaft 107 is provided to bridge both the movable members 100, 100.

Pinions 107a, 107a to be engaged with stationary racks 108 which are mounted on the front and rear stationary frames 101, 101 are coupled to both ends of the synchronizing shaft 107. The synchronizing shaft 107 is rotatably supported on both the movable members 100, 100 through self-aligning ball bearings 107b, 107b. According to this arrangement, when both the movable members 100, 100 get out of synchronization with each other, there will occur a difference in the angles of rotation of the pinions 107a, 107a on both ends of the synchronizing shaft 107, resulting in twisting of the synchronizing shaft 107. Due to a consequent twisting reaction force, both the movable members 100, 100 are corrected back to the synchronized state. Here, if both the movable members 100, 100 get out of synchronization with each other, the synchronizing shaft 107 is likely to be inclined toward the direction of movement of the movable members 100, 100. In this case, if the synchronizing shaft 107 is rotatably supported on both the movable members 100, 100 through ordinary bearings, there will occur the following disadvantage.
Namely, a bending moment will be operated on the synchronizing shaft 107 and, therefore, the synchronizing shaft 107 formed into a hollow construction will be insufficient in the bending rigidity, resulting in the deformation of the synchronizing shaft 107. In this embodiment, on the other hand, the inclination of the synchronizing shaft 107 is allowed by the self-aligning ball bearings 107b, 107b and, therefore, a bending moment will not be operated on the synchronizing shaft 107. It is thus only a twisting moment that will be operated on the synchronizing shaft 107. Therefore, even if the synchronizing shaft 107 is made into a hollow construction, it will not be deformed and thus contributes to the reduction in weight of the synchronizing apparatus as well as to the reduction in the driving load of the movable bases 10.

With reference to FIGS. 11 through 13, the first transfer apparatus 71 is provided with: a lifting frame 71 which is disposed in a vertically movable manner on a base 70 provided in the roof panel feeding station 2; a movable frame 72 which is supported on the lifting frame 71 so as to be movable in the front and rear direction which is the longitudinal direction of the assembly line; and a transfer jig 73 which is supported on the movable frame 72 so as to be movable in the longitudinal direction. The transfer jig 73 is provided thereon with a plurality of workpiece receiving members 73a which are vertically disposed to hold in position and support the floor panel W1. Guide rails 73b, 73b which are elongated in the longitudinal direction are mounted on an upper edge on the left and right sides of the movable frame 72. The transfer jig 73 is supported, in a manner to roll over the guide rails 73b, 73b, on a large number of rollers 73c which are mounted on both left and right sides of the lower portion of the transfer jig 73. Further, the transfer jig 73 has mounted thereon an electric motor 73f which is coupled to a pinion 73e to be engaged with a rack 73d which is fixed to the movable frame 72 so that the transfer jig 73 can be moved in the longitudinal direction relative to the movable frame 72.

Guide rails 72a, 72a which are elongated in the longitudinal direction are provided on a lower edge on left and right sides of the movable frame 72. Rollers 72b for supporting the guide rails 72a are provided on brackets 71a which are vertically provided in a plurality of portions in the longitudinal direction on the left and right sides of the lifting frame 71. Further, an electric motor 72e is mounted on the lifting frame 71. The electric motor 72e has coupled thereto a pinion 72d which is engaged with a rack 72c fixed to the movable frame 72.
The movable frame 72 is thus arranged to be movable in the longitudinal direction relative to the lifting frame 7.
By moving the movable frame 72 and the transfer jig 73 rearward, which is on the upstream side of the assembly line, relative to the lifting frame 71 and the movable frame 72, respectively, the transfer jig 73 can be returned to the floor panel feeding station 1 in a manner overhung in the rearward direction from the lifting frame 71. Also, by moving the movable frame 72 and the transfer jig 73 to the forward, which is the downstream side of the assembly line, relative to the lifting frame 71 and the movable frame 72, respectively, the transfer jig 73 can be moved forward to the assembly station 3 in a manner overhung in the forward direction from the lifting frame 71. When the floor panel W1 is transferred from the floor panel feeding station 1 to the assembly station 3, the transfer jig 73 is returned to the floor panel feeding station 1 and the lifting frame 71 is lifted. The floor panel W1 is thus lifted from the supporting base 5 in the floor panel feeding station 1. The transfer jig 73 is then moved forward to the assembly station 3 and the lifting frame 71 is lowered. The floor panel W1 can thus be set onto the supporting base 6 in the assembly station 3.

The lifting frame 71 is provided with vertically extending leg pieces 71b at a plurality of portions as seen in the longitudinal direction. Guide frames 70a are vertically disposed in a plurality of portions, as seen in the longitudinal direction, of the base 70. Vertically elongated guide rails 71c which are attached to the respective leg pieces 71b are slidably engaged with linear guides 71d which are mounted on each of the guide frames 70a so that the lifting frames 71 can be moved up and down. Further, a rotary shaft 71e which is elongated in the longitudinal direction is mounted on the base 70.
Pinions 71g to be engaged with racks 71f which are fixed to the leg pieces 71b are mounted at a plurality of positions in the longitudinal direction of the rotary shaft 71e. Further, a single electric motor 71h for driving the rotary shaft 71e is coupled to the rear end, which is on the upstream end of the assembly line, of the rotary shaft 71e. By rotating the rotary shaft 71e in one and the opposite directions by the electric motor 71h, the lifting frame 71 is moved up and down through a motion converting mechanism made up of rack and pinion mechanisms 71f, 71g which are provided at a plurality of portions in the longitudinal direction. On the base 70, there are further disposed balance cylinders 71i which are disposed at a plurality of portions in the longitudinal direction and are coupled to the lifting frame 71, and a plurality of locking cylinders which are disposed at a plurality of portions in the longitudinal direction of the lifting frame 71 to lock the lifting frame 71 at a lowered position (illustrated position) and a lifted position by fitting, at the above plurality of positions, lock pins 71k into respective locking holes 71j formed at an upper portion and lower portion of the respective leg pieces 71b.

When the lifting frame 71 is lifted in a state in which the transfer jig 73 is returned to the floor panel feeding station 1, the transfer jig 73 is overhung from the lifting frame 71 in the rearward direction.

Therefore, a large load is operated on the rear end portion of the lifting frame 71 through the motion conversion mechanism on the rear end of the lifting frame 71. Therefore, if the driving motor 71h is coupled to the front end of the rotary shaft 71e, there will occur a twisting in the rotary shaft 71e, with the result that the lifting of the lifting frame 71 on the rear side delays.
As a result, the lifting frame 71 inclines downward in the rear direction. Consequently, there will occur a wrenching or gouging effect to the guide frame 70a, i.e., wrenching or gouging between the guide rail 71c and the linear guide 71d, and the lifting frame 71 cannot be lifted smoothly any more. In this embodiment, on the other hand, since the driving motor 71h is coupled to the rear end of the rotary shaft 71e, the twisting of the rotary shaft 71e, i.e., the inclination of the lifting frame 71 can be restricted. Therefore, the lifting frame 71 can be lifted smoothly without the occurrence of gouging to the guide frames 70a. In this manner, the driving source for the lifting frame 71 can be constituted by a single driving motor 71h with a reduction in cost.
The second transfer apparatus 7z has a similar construction as that of the first transfer apparatus 71.
Therefore, the same reference numerals are attached to those members that are the same as those of the first transfer apparatus 71, and their explanations have been omitted.

As can be seen from the above explanations, according to the present invention, the side panels can be set onto the setting jig by turning the setting jig to the upward posture or the outward posture by the rotation of the rotary frame. Therefore, it is not necessary to secure a space for moving the side panel feeding apparatus on the side portion of the assembly station. As a result, it becomes possible to dispose the welding robots for assisting the welding of the side panels to the floor panel in a side lower portion of the assembly station to thereby shorten the cycle time. Further, even if the welding robots mounted on the rotary frame are rotated about the axis of rotation by the rotation of the rotary frame, the cables or the like for the welding robots do not get entangled with each other because they are supported on the cable supporting frame. Still furthermore, since the cable supporting frame functions as a balancing element to keep the rotary frame well balanced, the rotary frame can be rotated smoothly.

It is readily apparent that the above-described apparatus for assembling a motor vehicle body meets all of the objects mentioned above and also has the advantage of wide commercial utility. It should be understood that the specific form of the invention hereinabove described is intended to be representative only, as certain modifications within the scope of these teachings will be apparent to those skilled in the art.

Accordingly, reference should be made to the following claims in determining the full scope of the invention.

Claims

1. An apparatus for assembling a motor vehicle body in an assembly line which extends in a longitudinal direction by welding right and left side panels to other vehicle body constituting members, said apparatus comprising:
a movable base provided on each of lateral side portions of an assembly station into which said other vehicle body constituting members are transferred, said movable base being movable between a laterally inward welding position -.and-a laterally outward waiting position;
a rotary frame supported on said movable base so as to be rotatable about a longitudinally extending axis of rotation;
a setting jig for holding a side panel, said setting jig being detachably mounted on said rotary frame wherein the side panel can be set on said setting jig in a state in which said movable base is moved to the waiting position and in which said setting jig is turned by rotation of said rotary frame into an upward posture to look upward or an outward posture to look laterally outward, and wherein the side panel and the other vehicle body constituting members can be welded together in a state in which said movable base is moved to the welding position and in which said setting jig is turned by rotation of said rotary frame into an inward posture to look laterally inward;
a plurality of welding robots for welding the side panels and the other vehicle body constituting members together, said welding robots being mounted on said rotary frame so as to be longitudinally movable; and a cable supporting frame for supporting cables to be connected to said welding robots, said cable supporting frame being mounted on said rotary frame such that a turning moment which operates on said rotary frame in the inward posture due to a weight of said cable supporting frame cancels a turning moment due to a weight of said setting jig.

2. An apparatus for assembling a motor vehicle body according to claim 1, further comprising a bar member provided on said rotary frame so as to extend along an axis of rotation of said rotary frame, wherein said plurality of welding robots are divided into two sets, one set of welding robots and another set of welding robots being mounted, in postures opposite to each other, on upper and lower surfaces, respectively, of said bar member which face upward and downward in the inward posture of said rotary frame .

3. An apparatus for assembling a motor vehicle body according to claim 2, wherein said cable supporting frame comprises:
an upper frame portion for supporting cables for said one set of welding robots mounted on the upper surface of said bar member, said upper frame portion being longitudinally elongated in a position laterally outward, and above, said bar member in the inward posture of said rotary frame; and a lower frame portion for supporting cables for said another set of welding robots mounted on the lower surface of said bar member, said lower frame portion being longitudinally elongated in a position laterally outward, and below, said bar member in the inward posture of said rotary frame.

4. An apparatus for assembling a motor vehicle body according to claim 3, wherein, in a coordinate system at rest relative to said rotary frame, a longitudinally extending coordinate axis is defined as an X-axis, and laterally extending and vertically extending coordinate axes in the inward posture of the rotary frame are, respectively, defined as a Y-axis and a Z-axis, each of said welding robots in each of said sets of welding robots comprising:
a robot main body movably supported on a guide rail which is elongated in the X-axis direction on each of said upper surface and said lower surface of said bar member;
an articulated member supported on said robot main body so as to be rotatable about an axis of rotation in the X-axis direction in a position away in the Z-axis direction from said guide rail;
a robot arm elongated in a U-axis direction and supported on said articulated member so as to be movable in the U-axis direction, the U-axis being defined as that coordinate axis in the coordinate system at rest relative to said articulated member which is parallel to the Y-axis in a neutral position of rotation of said articulated member; and a welding gun mounted on an inner end in the U-axis direction of said robot arm through a wrist, wherein each of said upper and lower frame portions is disposed so as to be positioned outside, in a swinging direction, of said robot arm relative to a position of an outer end in the U-axis direction of said robot arm, in a state in which said robot arm of each welding robot in respective sets is moved to an outer stroke end in the U-axis direction, and in which said robot arm is swung by rotation of said articulated member to a swinging end at which the outer end in the U-axis direction of said robot arm lies away from said guide rail in the Z-axis direction, and wherein said apparatus further comprises a cable holding member which is capable of bending two-dimensionally for holding cables which are taken out of each of said upper and lower frame portions, said cable holding member being disposed between each of said upper and lower frame portions and said robot main body of each of said welding robots so as to be capable of bending on a plane which is parallel to the X-axis and the U-axis at the swinging end, said plane being positioned outside said robot arm at the swinging end as seen in the swinging direction.

5. An apparatus for assembling a motor vehicle body according to claim 1, wherein each of said movable bases comprises:
a pair of movable members which are disposed at a longitudinal distance from each other so as to be laterally movable by an independent driving source;

a hollow synchronizing shaft which is extended to bridge both said movable members;
a pinion coupled to each end of said synchronizing shaft so as to be engaged with a stationary rack which is disposed along each of travel passages of both said movable members; and a self-aligning bearing for rotatably supporting said synchronizing shaft on each of said movable members.

6. An apparatus for assembling a motor vehicle body according to claim 1, wherein said other vehicle body constituting members comprise a floor panel and a roof panel, wherein a floor panel feeding station is disposed on an upstream side of the assembly station in the assembly line, a roof panel feeding station is disposed between the floor panel feeding station and the assembly station, and a transfer apparatus is provided to transfer a floor panel fed into the floor panel feeding station to the assembly station by allowing it to pass through the roof panel feeding station, and wherein said transfer apparatus comprises:

a lifting frame disposed in the roof panel feeding station so as to be vertically movable wherein said roof panel feeding station comprises a plurality of guide frames for supporting said lifting frame so as to be movable up and down at a plurality of points as seen in the longitudinal direction of the assembly line and a rotary shaft extending in the longitudinal direction of the assembly line, said lifting frame being vertically moved by rotation of said rotary shaft in a normal direction and in an opposite direction through motion converting mechanisms disposed at the plurality of points as seen in the longitudinal direction of the assembly line;

a movable frame supported on said lifting frame so as to be longitudinally movable;

a transfer jig for supporting the floor panel, said transfer jig being supported on said movable frame so as to be longitudinally movable, said transfer apparatus being arranged such that: (a) by moving said movable frame and said transfer jig to an upstream side of the assembly line relative to said lifting frame and said movable frame, respectively, the transfer jig is returned to the floor panel feeding station in a manner overhung from said lifting frame toward the upstream side of the assembly line; (b) by moving said movable frame and said transfer jig to a downstream side of the assembly line relative to said lifting frame and said movable frame, respectively, the transfer jig is moved forward to the assembly station in a manner overhung from said lifting frame toward the downstream side of the assembly line; (c) by returning said transfer jig to the floor panel feeding station and lifting said lifting frame, the floor panel is lifted; and (d) by forwarding said transfer jig to the assembly station and lowering said lifting frame, the floor panel is transferred into, and set in position in, the assembly station; and a single driving motor for driving said rotary shaft, said driving motor being connected to an upstream end of said rotary shaft which is disposed on the upstream side of the assembly line.