WO2019202569A1 - Assembly line for assembling vehicle body subassemblies - Google Patents

Abstract

A method for assembling vehicle body subassemblies in an assembly line (1) comprising a plurality of robotized work stations (3) arranged in succession one after the other, a plurality of handling robots (6) for moving the body subassemblies being processed from the each work station (3) to the following station, and a plurality of specific tools (13) for supporting and locking the subassemblies in the work stations (3), wherein the specific tools (13) are configured for producing a given subassembly model and are replaceable for reconfiguring the assembly line (1) for the production of at least one other subassembly model; the method comprises the step of moving the tools (13) from and to the work stations (3) by means of at least one automatic guide vehicle (55).

Description

ASSEMBLY LINE FOR ASSEMBLING VEHICLE BODY SUBASSEMBLIES

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority from Italian patent application no. 102018000004759 filed on 20/04/2018, the entire disclosure of which is incorporated herein by reference .

TECHNICAL FIELD

The invention relates to an assembly line for assembling vehicle body subassemblies, such as doors, body sides, floors, etc.

BACKGROUND ART

It is known to assemble vehicle body subassemblies by means of a series of operations (mainly welding operations) carried out in successive work stations along a production line .

In particular, with reference to a specific station, the subassembly being assembled is supplied by means of a first pick-and-place robot, which picks it up from the previous station, subjected to the operation (s) to be carried out by means of a plurality of work robots, for example welding robots, and removed from the station by means of a second pick-and-place robot, which supplies it to the next station .

Since the use of dedicated lines for each subassembly would lead to the use of a large number of lines, with consequences in terms of costs and space taken up, the current tendency of automotive manufacturers is that of using flexible assembly lines, which are capable of assembling a given number of different models (usually up to four) with a random mix. Lines of this type are known, for example, from WO 2017/109557 A1. These assembly lines allow for the production of vehicles "on demand".

Even though said flexible lines solve the above- mentioned problems caused by dedicated assembly lines, they are not free from drawbacks.

In particular, these lines require large machines (rotary drums, slides etc.) for the reconfiguration of the fixtures in the different stations and, therefore, they are very complicated, expensive and large.

The high degree of complexity leads to a relative high likelihood of faults and consequent production standstills.

A further direct consequence of the complexity of the aforesaid lines is that of requiring a very high initial investment upon installation of the line itself, regardless of the number of models that can be produced at first. Therefore, in case the line, at first, is used for the production of one single model, which is what usually happens, the production costs of said model are relatively high . Another problem arising from the use of known lines is the non-efficient use of manpower. Indeed, since the operations to be carried out in the stations of the line are completely automatic, operators only have to perform auxiliary manual operations, such as, for example, loading pieces into a station. These operations only last a fraction of the cycle-time, which means that operators are inactive for the remaining part of the cycle-time, waiting for the automatic operations to be completed.

A further problem of known lines is the loss of production due to the long standstills needed to for the introduction of following models.

DISCLOSURE OF INVENTION

The object of the invention is to provide an assembly line for assembling vehicle body subassemblies, which solves the problems of known lines described above.

The aforesaid object is reached by a line according to claim 1.

The use of automatic guided vehicles (AGV) for the replacement of specific support tools allows manufacturers to avoid having to use complicated and expensive fixtures, thus minimizing the investment for the fixtures dedicated to one single model and the probability of faults.

Furthermore, according to a preferred embodiment of the invention, the use of a logistics area associated with the line, where all auxiliary manual operations are carried out allows for a complete use of the operators' time.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, a detailed description of a preferred embodiment is provided hereafter by way of non-limiting example, with reference to the accompanying drawings, wherein:

figure 1 is a schematic, partial view from the top of a production line according to the invention;

figure 2 is a perspective view from the top of a work station of figure 1;

figure 3 is a side elevation view of the station of figure 2;

figure 4 is a perspective view from the top of a tool for supporting and locking a body subassembly in a station of the line;

figure 5 is an exploded, perspective view of the tool of figure 4;

figures 6, 7, 8, 9 and 10 are diagrams showing steps carried out to centre and place the tool of figure 5;

figure 11 is a schematic, perspective view from the top of a logistics area of the line of figure 1; and

figure 12 is a schematic, perspective view from the top of a manual piece loading area;

figures 13 and 14 are perspective views from the top and from the bottom respectively, of a first type of automatic guided vehicle used in the line of the invention; figures 15 and 16 are a plan view from the top and a side elevation view, respectively, of a base of a support and contact tool and of an automatic guided vehicle associated with it;

figure 17 is an elevation view corresponding to the one of figure 16, in a different operating condition;

figure 18 schematically shows a sequence of model- change operations in a work station of the line;

figure 19 shows a detail of a loading station of the line;

figures 20 and 21 are perspective views from the top and from the bottom, respectively, of a second type of automatic guided vehicle used in the line of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to figure 1, number 1 indicates, as a whole, a multi-functional assembly line for assembling vehicle body subassemblies. The line is capable of assembling different models (for example, inner body sides/outer body sides; central floor/rear floor) with a batch production logic, as described more in detail below. The line can also be used to assemble models of different vehicles, as long as the technological parameters are compatible.

Hereinafter, the term "subassembly" identifies a body subassembly, namely a physical product, regardless of its state of assembly. On the other hand, the term "model" identifies the type of subassembly, as opposed to other models that can be produced with the line.

The line 1 comprises an initial loading station 2, where the components of the model to be assembled are loaded, a plurality of work stations 3, and a final discharging station 4, from which the finished model is picked up. The line 1 can further comprise one or more intermediate loading stations 2, in case it is not possible or practical to introduce all components in the initial loading station 2. The initial or intermediate loading station can also be a work station.

The subassembly being assembled is transferred from a station to the following station by means of pick-and-place robots 6, which are interposed between each pair of successive stations.

The robots 6 (figure 1) conveniently are all the same and, in particular, are provided with a universal gripping tool (or "hand") 7 (figure 2) .

Each work station 3 (figures 2 and 3) comprises a work station 11, which houses a fixed supporting and positioning tool 12, which is the same for all stations and is adapted to receive a specific supporting and locking tool 13 for the model being produced (hereinafter referred to as "the specific tool 13"), described more in detail below. The station 3 further comprises a waiting area 14 adjacent to the work area 11, where a specific tool 13 can be left while waiting for it to be subsequently used or picked up.

The work station 3 comprises two series of work robots 15, 16 (in the example shown herein, three robots for each series) arranged on opposite sides of the work station. In particular, a first series of work robots 15 is arranged on a platform 17 located on a side of the work area 11 opposite the waiting area 14; the second series of work robots 16 is arranged on a gantry 18 located on the opposite side of the work station 11 relative to the first series of work robots 15. Hence, the work robots 16 are in a higher position, above the waiting area 14, so as to allow the specific tools 13 to go from the waiting area 14 to the work area 11 and vice versa .

On the platform 17 and on the gantry 18 there also are, besides the respective robots 15 and 16, a plurality of cabinets 19 housing systems and controls for the work robots 15, 16, for a pick-and-place robot 6 associated with the station 3 and for the welding processes.

The platform 17 and the gantry 18 are designed as pre assembled modules, complete with robots and relative systems .

Figure 2 shows the station 3 without specific tools. Figure 3 shows the station 3 with a specific tool 13A

(designed for a model A) arranged in the work area 11 on the fixed support tool 12, and a specific tool 13B (designed to a model B) arranged in the waiting area 14.

A specific tool 13 is shown in figures 4 and 5 (exploded view) and basically comprises a base 20, which is the same for all models, one or more system boxes 21, which are specific for the model, and a plurality of positioning and locking tools 22, which are adapted to support and lock the model being processed. Therefore, the specific tool 13 is also specific for the station, besides being specific for the model, as its features depend on the state of progression of the assembly.

The base 20 comprises a rectangular support plane 23 and four feet 24. At the opposite ends of the support plane 23 there are the system boxes 21. Furthermore, the positioning and locking tools 22 are mounted on the support surface 23, though they are not described in detail herein because they are not part of the invention.

The base 20 is adapted to be laid on the fixed support tool 12, which is substantially C-shaped (figure 5), by means of a centring and positioning system, which is designed to ensure a relative one-way positioning as described below.

More in particular, the fixed tool 12 comprises a pair of parallel plates 25 facing one another, which are adapted to be fixed to the floor, and a crosspiece 26, which is perpendicular to the plates 25 and connects respective ends of the plates to one another. In use, the fixed tool 12 is fixed in the work area 11 of the station 3 by means of foundation bolts 28, so that the crosspiece 26 is arranged parallel to a horizontal axis X, which is longitudinal relative to the line, and the plates 25 are parallel to a horizontal axis Y, which is perpendicular to the axis X.

Close their ends opposite the crosspiece 26, the plates 25 have respective upper supports 27 for the base 20.

Each one of the plates 25 has, close to the crosspiece 26, a respective centring and positioning assembly 30 consisting of a conical pin 31, which is tapered upwards, and a pair of rollers 32, which have axes C parallel to one another and to the axis X and are carried by respective pins 33, which are fixed to the plates 25 and project from them.

The pairs of rollers 32 are adapted to cooperate with respective lower projections 34 (which are not visible in figure 5, but are schematically shown in figures 6 to 10) of the base 20, so as to obtain a relative centring in direction Y.

Similarly, the crosspiece 26 further has, along its middle line, a centring assembly 35 comprising a pair of rollers 36, which are identical to the rollers 32, but have axes that are parallel to the axis Y and are designed to cooperate with a lower projection (not shown) of the base

20, so as to carry out a centring in direction X.

The conical pin 31 of one of the centring and positioning assemblies 30 is adapted to engage a hole made in a centring element 37 (figures 6-10), which is fixed in a corresponding position under the base 20 and has an inner diameter that allows it to be engaged by the base of the projection 31 without clearance.

The conical pin 31 of the other one of the centring and positioning assemblies 30 is adapted to engage a slot made in a centring element (nor shown) , which is fixed in a corresponding position under the base 20 and extends in direction X.

Owing to the above, when the base 20 is placed on top of the fixed tool, there is, at first, a relative centring in directions X and Y thanks to the rollers 32, 36 and, then, an engagement of the conical pins 31 in the hole 37 and in the non-shown slot, respectively.

This is shown in detail, with reference to one of the centring and positioning assemblies 30, in the sequence of figures 6-10, where the rollers 32 and the pin 31 are misaligned to the side in order to avoid overlaps, though it is clear that the respective symmetry planes M coincide.

After a first approaching phase in a relative undetermined position (figure 6), the projection 34 of the base 20, in case it is misaligned, comes into contact with one of the rollers 32 (figure 7) and tends to be dragged to a centred position as the base 20 lowers relative to the fixed tool 12.

The centring and positioning assembly 30 is sized so that the conical pin 31 can get into the hole 37 only when the relative centring is sufficient (figure 10) . Going on with the relative approach between the base 20 and the fixed tool 12, there is the progressive engagement of the conical pin 31 in the hole 37 (figure 11), until the hole 37 is coupled to the base of the conical pin 31 eliminating any clearance (figure 12), when the base 20 rests on the fixed tool 12.

Please, note that the presence of a slot instead of a hole in the other centring and positioning assembly 30 and the absence of the conical pin in the centring assembly 35 allows for an isostatic constraint between the base 20 and the fixed tool 12.

As already mentioned above, the subassemblies are transferred from a station to the other by means of universal pick-and-place robots 6. In order to adjust the standard "hand" of the robots 6 to the specific model, a gripping tool 40 or "gripper" (figures 4 and 5) needs to be used, which is specific for every model and for every pair of stations . The gripper 40 is provided with an interface flange 41 which is adapted to cooperate with the hand of the robots 6 and actually is an extension of the hand itself, which is adapted to allow a universal hand to pick up and place different models.

The gripper 40 basically consists of a support truss 42 provided with gripping and supporting organs 43 for the subassembly being processed.

The specific tool 13, as shown in figure 4, is configured so as to also support the gripper 40, besides the subassembly, and - therefore - it can act like a "magazine" for the gripper 40 when not it use.

Figure 10 shows a logistics area 45, which is part of the line 1 and is conveniently arranged at an end of the line .

The logistics area 45, in turn, is divided into two areas :

- a tool magazine 46, where the specific tools 13 are deposited when the relative model is not being produced or about to be produced; and

- a manual component loading or "kitting" area, indicated with number 47 and shown more in detail in figure 12.

The kitting area 47 is used to manually load the components making up the subassembly onto carts 48, which are going to be sent to the loading station 2 of the line 1. The carts 48 (see also figure 19) are provided with a support plane 49, which carries a plurality of reference elements 50 for the positioning of the components. The carts 48 are further provided with support feet, which allow the support plane 49 to be spaced apart from the floor.

The components are manually picked up from containers 53 and loaded onto the carts 48 in the form of kits arranged in layers, so that they can be picked up by means of one or more pick-and-place robots in the loading station 2. Hence, each cart 48 is specific for a model and is provided with a a plurality of component kits on top of one another, which are adapted to be picked up in succession.

The loading station 2 is conveniently provided with a picking area 53 and with a waiting area 54, which are adapted to receive respective carts 48 (figure 19) .

The picking area 53 is conveniently provided with position reference means for the carts 48, similarly to what described above for the position reference of the specific tools 13 in the work area of the stations 3. The picking area 53 contains the specific cart 48 for the model being produced .

The waiting area 54 is adapted to contain a cart 48 for the model following the one currently being produced, in case a model change is about to happen, or, according to figure 19, an empty cart 48 after its replacement with a full cart in the picking area 53.

According to the invention, the specific tools 13 are moved by means of automatic guided vehicles, hereinafter referred to, for the sake of brevity, as "AGVs".

In particular, the specific tools 13 are moved by means of a first plurality of AGVs 55 having a flat and oblong shape (figures 13 and 14), which are capable of being arranged under the base 20 of the specific tools 13 and of lifting it .

An example of AGV which can be used for this purpose is the AGV called MR-Q9-LD300A (H) produced by Hangzhou Hikrobot Technology Co., Ltd (China).

The AGV 55 is provided, at the bottom, with four sets of independent motorized wheels 56 and with a sensor 57 for the detection of the path (for example, an optical sensor) .

The AGV 55 is further provided, at the top, with a pair of lifting elements 58, which are parallel to one another and extend transversely to the main size of the AGV. These lifting elements 58 are adapted to be lifted due to the thrust of an electric actuator, which is not shown herein. The lifting elements are each provided with a pair of loading areas 59 arranged at the respective ends and adapted to come into contact with the base 20.

The AGV 55 finally comprises an upper sensor 60, for example an optical sensor, which is adapted to "read" a corresponding identification code arranged under the base 20 of a specific tool 13 in order to correctly identify the tool .

The vertical space taken up by the AGV 55 in the rest position, in which the lifting elements 58 are lowered, is slightly smaller than the free height under the support plane 23 of the base 20.

For example, the carrying capacity of the AGV is around 3000 kg and the lifting stroke is around 100 mm.

Figures 15, 16 and 17 show an AGV 55 arranged under a base 20. According to figure 15, the space taken up by the AGV 55, in plan view, is substantially equal to the one of the support surface 23.

In figure 16, the AGV is in a rest position, in which the feet 24 of the base 20 of the specific tool 13 rest on the floor. In figure 17, the AGV 55 is in the lifting position, in which the base 20 is lifted from the ground and the AGV 55 can transport the specific tool 13.

In a substantially similar manner, according to a preferred embodiment of the invention, the carts 48 are moved by means of a second plurality of AGVs 61 (figures 20 and 21), which are capable of being arranged under the carts 48 and of lifting them.

An example of AGV which can be used for this purpose is the AGV called MR-Q7-LR050C produced by Hangzhou Hikrobot Technology Co., Ltd (China).

The AGV 61 is provided, at the bottom, with four sets of independent motorized wheels 62 and with a sensor 63 for the detection of the path (for example, an optical sensor) .

The AGV 55 is further provided, at the top, with an annular lifting element 64, which is adapted to be lifted due to the thrust of an electric actuator, which is not shown herein, and with a sensor 65 for the correct identification of the cart 48.

The vertical space taken up by the AGV 55 in the rest position, in which the lifting element 64 is lowered, is slightly smaller than the free height under the support plane 49 of the cart 48.

For example, the carrying capacity of the AGV is around 500 kg and the lifting stroke is around 60 mm.

As already mentioned above, the AGVs 55, 61 are responsible for moving the specific tools 13 and the carts 48 between the logistics area 46 and the work stations 3 and, respectively, the loading station 2 of the line 1.

This movement takes place along a dedicated lane 65, which is arranged beside the line 1 and to which operators have to access, hereinafter referred to as AGV lane 65 (figures 2 and 11) .

The line 1 finally comprises a control system 66, which can be programmed to control the AGVs 55 and 61. The control system 66 conveniently comprises a line controller 67, which is connected, through a field network, to the controllers of the single stations 2, 3, 4 and, in a wireless mode, to the AGVs 55 and 61. The line controller 67 controls the transport of the specific tools between the tool magazine and the work stations 3 and the replacement of the specific tools.

The AGVs 61 can be controlled by the line controller 67 or by a different controller, if necessary shared by different lines, in which case the control is carried out through a wireless plant network.

The operation of the line 1, which already is partly evident from the description above, is the following.

During the production of a subassembly model, for example model A, the corresponding cart 48 provided with the components of the model is placed in the picking area 53 in the lading station (s) 2. In the work stations 3, the specific tool 13A of the model being produced is placed in the work area 11.

In the loading station 2, the components are loaded onto a gripper 40; furthermore, the gluing with adhesives is carried out (by means of dedicated robots), when needed.

The first pick-and-place robot 6 transfers the model from the loading station 2 to the first work station 3 by means of the gripper 40. In the work station 3, the model is locked on the specific tool 13 in order to carry out welding operations. Then, the gripper 40 is moved back to the loading station 2 for the following cycle.

At the end of the welding operations, the model is picked up from the work station 3 and transferred to the following one by means of the following pick-and-place robot 6, using another gripper, and so on for all the work stations 3 of the line.

In the discharge station 4, the model is discharged from the line.

In the waiting areas 14 of the work stations 3 there are specific tools 13B for the following model to be produced. In the waiting areas 54 of the loading stations 2 there is a cart 48 for the following model to be produced or for the same model, if the number of kits present in the cart 48 standing in the picking area 53 is not sufficient to complete the batch.

In preparation for a model change, for example from model A to model B, the tools 13A in the work stations 3 must be replaced with the tools 13B present in the waiting stations 14. The replacement is carried out by means of two AGVs 55, in succession for all the stations.

Figure 18 shows, in detail the sequence of operations needed for the purpose. The sequence is shown starting from a condition in which the two AGVs 55 are under the respective tools 13A, 13B. Therefore, for the sake of clarity, said

AGVs are hereinafter identified as AGV 55A and AGV 55B (provided that the AGVs are standard, non-specific devices) .

The sequence of the operations is the following:

1) The two AGVs 55A, 55B lift the respective tools 13A,

13B;

2) The tool 13B is moved to the AGV lane 65 by means of the AGV 55A;

3) The tool 13B is moved along the AGV lane 65 by means of the AGV 55B so as to free the extraction path for the tool 13A;

4) The tool 13A is moved to the AGV lane 65 by means of the AGV 55A;

5) Both tools 13A, 13B are moved along the AGV lane 65 by means of the respective AGVs 55A, 55B so as to align the tool 13B with the axis of the station;

6) The tool 13B is moved to the work area 11 by means of the AGV 55A;

7) The tool 13A is moved along the AGV lane 65 by means of the AGV 55A so as to align it with the axis of the station;

8) The tool 13B is moved to the waiting area 14 by means of the AGV 55B;

9) The AGV 55A is removed from the tool 13A and moved to the AGV lane 65; 10) The AGV 55A is moved along the AGV lane 65;

11) The AGV 55A is removed from the tool 13A and moved to the AGV lane 65.

At the end of this operation, the work station 3 is operative and can start working on the new model. The total production standstill time, which is needed to complete the operations 1-10 described above, does not exceed 90 s.

At this point, the AGVs 55A, 55B can be moved towards the following station 3 and placed under the two tools 13A, 13B. This step is not indicated in figure 18, because it takes place in masked time, with both work stations 3 in operating conditions. The standstill time of the following station starts with operation 1.

Since, during the fixture change in a work station 3, the other stations keep normally working, the total production standstill time equals the standstill time of one single station (the standstill time is a sort of discontinuity which "propagates" from station to station) .

The exchange of the carts 48 standing in the picking station 53 and in the waiting station 54 and the replacement of an empty cart 48 with a full cart take place by means of two AGvs 61, in ways that are similar to the ones described for the specific tools 13. The sequence of the operations is not described in detail herein.

A close analysis of the assembling method according the invention and of the line 1 disclosed herein reveals the advantages of the invention relative to the prior art.

The use of AGVs for moving the specific tools 13 allows the structure of the line to be significantly simplified, since there is no need any longer for complicated model change mechanisms, such as rotary drums, slides etc.

As a consequence, the initial cost of the structure of the line is reduced and the costs of the fixtures are "spread" over different models. Therefore, in case the line, at first, is used for the production of one single model, the latter does is not affected by high costs.

The introduction of new models does not determine long production interruptions, which is what happens in the prior art. Once the specific tools for the new model are available in the tool magazine, the model change is performed in a very quick manner by means of the AGV, as described above. Since the structure of the line is absolutely neutral, the number of models that can be produced potentially is unlimited .

The production standstill caused by a model change can be compared with the cycle time. Therefore, the line 1 is not designed for a production in "random mix" mode, but it is suited for a batch production.

However, considering the greater simplicity of the line compared to the prior art, the incidence of faults is practically irrelevant. As a consequence, the number of subassemblies per batch is fairly high (for example, corresponding to at least one hour of production) , the production losses due to a model change are compensated by the smaller production losses causes by technical problems compared to known flexible lines.

Finally, since the operators work in a logistics area separated from the work stations 3 and, therefore, are subjected to machine-times, the invention allows for an elimination of waiting times and, hence, for a saturation of the use of manpower.

Claims

1. A method for assembling vehicle body subassemblies in an assembly line (1) comprising:

- a plurality of robotized work stations (3) arranged in succession one after the other;

- a plurality of handling robots (6) each being arranged between a first and a second work station (3) adjacent to one another for moving the body subassemblies in process from the first station to the second station, and

- a plurality of specific tools (13) for supporting and locking the subassemblies in the work stations (3), said specific tools (13) being configured for producing a determined subassembly model and being replaceable for reconfiguring the assembly line (1) for the production of at least one other subassembly model,

the method being characterised by comprising the step of moving the specific tools (13) from and to the work stations (3) by means of at least an automatic guide vehicle (55) .

2. The method as claimed in claim 1, characterised in that the step of moving the specific tools (13) comprises, for each station, the operation of arranging a first specific tool (13) for a first body subassembly model in a working area (11) of the station, arranging a second specific tool (13) for a second body subassembly model in a waiting area

(14) of the station, and replacing the first specific tool (13) with the second specific tool (13) when the assembly line (1) is converted from a first configuration adapted to produce the first body subassembly model to a second configuration adapted to produce the second body subassembly model .

3. The method as claimed in claim 1, characterised in that the step of moving the specific tools (13) comprises, for each work station (3), the operation of transporting the specific tools (13) between said station and a tool magazine (46) .

4. The method as claimed in claim 3, characterised in that said transport operation is carried out by using a lane (65) dedicated to the automatic guide vehicles (55, 61) and placed beside the assembly line (1) .

5. The method as claimed in any one of the preceding claims, characterised by comprising the step of providing the components to be assembled at a loading station (2) of the assembly line (1) on carts (48) moved by at least one automatic guide vehicle (61) .

6. The method as claimed in claim 5, characterised in that the step of providing the components to be assembled at the loading station (2) comprises the step of manually loading the components on the carts (48) carried out manually in a logistics area (45) of the assembly line (1) and the step of moving the carts (48) between the logistics area (45) and said loading station (2) .

7. The method as claimed in claim 6, characterised in that the step of moving the carts (48) comprises the operation of arranging a first cart (48) containing the components for a first body subassembly model in a picking area (53) of the loading station (2), arranging a second cart (48) containing the components for a second body subassembly model in a waiting area (54) of the loading station, and replacing the first cart (48) with the second cart (48) when the assembly line (1) is converted from a first configuration adapted to produce the first body subassembly model to a second configuration adapted to produce the second body subassembly model.

8. The method as claimed in one of the claims from 5 to 7, characterised in that the step of moving the carts (48) comprises the operation of bringing back the empty carts (48) from the loading station (2) to the logistics area (45) .

9. An assembly line for assembling vehicle body subassemblies comprising:

- a plurality of robotized work stations (3) arranged in succession one after the other;

- a plurality of handling robots (6) each being arranged between a first and a second work stations (3) adjacent to one another for moving the body subassemblies in process from the first to the second work station (3) and

- a plurality of specific tools (13) for supporting and locking the subassemblies in the work stations (3), said tools being configured for the production of a determined subassembly model and being replaceable for reconfiguring the assembly line (1) for the production of another subassembly model,

characterised by comprising:

- a tool magazine (46) adapted to contain the specific tools (13) for the subassembly models of to be produced;

- a plurality of automatic guide vehicles (55); and

- a control system (66) for controlling the automatic guide vehicles (55), which can be programmed to control the transport of the specific tools (13) between the tool magazine and the work stations (3) and the replacement of the tools (3) for reconfiguring the assembly line (1) .

10. The assembly line as claimed in claim 9, characterised by comprising:

- at least one loading station (2) for loading components to be assembled;

- a plurality of carts (48) each configured to support components for a determined model of subassembly;

- a logistics area (46) adapted to store and manually load said carts (48) ;

the control system of the automatic guide vehicles being programmable for controlling the transport of carts (48) between the logistics area (46) and said at least one loading station (2), and the replacement of the carts (48) in said at least one loading station (2) .

11. The assembly line as claimed in claim 9 or 10, characterised in that each work station (3) comprises a working area (11) and a waiting area (14) adapted to receive respective specific tools (13), said working area (11) being provided with position reference elements (30) adapted to cooperate with corresponding position reference elements of the specific tools (13) for defining the position of the latter in a unique manner.

12. The assembly line as claimed in claim 11, characterised in that said specific tools (13) comprise a base (20) which is the same for all the tools and is provided with said position reference elements, and a plurality of specific fixtures (22) carried by the base and configured to cooperate with the respective body subassembly.

13. The assembly line as claimed in one of the claims from 10 to 12, characterised in that said specific fixtures comprises a handling and support element (40) configured to support the body subassembly and to be picked by a handling robot (6) for transporting the body subassembly from a work station (3) to a following work station (3) .

14. The assembly line as claimed in one of the claims from 11 to 13, characterised in that in each work station

(3) the working area (11) and the waiting area (14) are arranged facing one another, the work station (3) comprising at least one first work robot (15) arranged at a first side of the working area (11) opposite the waiting area (14) and at least a second work robot arranged at a second side of the working area (11) on the side of the waiting area (14), the work station (3) comprising an elevated structure on which said at least one second robot is mounted, and configured to allow the specific tools (13) to pass from the working area (11) to the waiting area (14) and vice versa.

15. The assembly line as claimed in one of claims 10 to 14, characterised by comprising at least one loading station (2) provided with a picking area (53) and a waiting area (54) configured to receive respective carts (48) in a pre-set reference position.

16. The assembly line as claimed in claim 15, characterised by comprising a movement lane (65) for the automatic guide vehicles (55, 61) adjacent to the waiting areas (14, 54) of the work stations (3) and the loading station (2 ) .