EP0849014B1 - Method of controlling a transfer device for intermittent workpiece transport - Google Patents

Description

The invention relates to a method for switching a transfer device in Emergency operating mode with the features of the preamble of claim 1.

In particular, multi-station presses, for example body presses or the like Transfer devices with which workpieces are transported from stage to stage become. For this purpose, such transfer devices usually have two parallel ones Transfer rails, between which spaced crossbars with Holding means, such as, for example, suction spiders or the like, are held. The Workpiece transport takes place through a combined lifting, feeding and Lowering movement of the transfer rails (two-axis transfer).

In addition, transfer devices are known in which instead of Cross members on the transfer rails holding means are provided. The In addition to the lifting, lowering and feed movements, crossbeams also perform one Cross movement off (three-axis transfer with vertical movement for lifting / lowering, Longitudinal movement to perform a transfer step and cross movement to open and close).

A three-axis transfer is already known in which as drives for the movements in the three movement axes Linear motors are provided. The linear motors are controlled separately, with the linear motors one Transport rail synchronous to the linear motors of the other transport rail as well as press synchronized become.

While driving transfer rails with linear motors as direct drives at low cost, structurally leads simple transfer devices that are flexible Allow use, there is one possible Failure of individual system components the risk that the Transfer rail and / or other elements of the transfer device, such as cross beams, not the desired one Carry out movement and, for example, a work station Not picking up or storing a workpiece in time leave. In the case of multi-station presses, this can lead to one serious damage to the transfer rail or other Elements and, at worst, the whole Guide the transfer device and / or tools.

DE 44 22 719 A1 describes a safety device for a flexible transfer system for presses became known, in which the transfer rail one Three-axis transfers on a preloaded spring mechanism is stored. This is in its tensioned position in the idle state locked and generated when triggered a quick sideways movement of the transfer rail. To the A toggle lever system serves to lock the spring accumulator, that is triggered electromagnetically in the event of a fault. The now quick transverse movement of the transfer rail leads them out of the danger area.

There are usually several spring accumulators for a single transfer rail required, the overall a significant effort and a considerable cause additional mass to accelerate and brake it during transfer applies

Based on this, it is an object of the invention to provide a method for fail-safe transfer device that exhibits good dynamic behavior

This object is achieved by the method according to claim 1.

The transfer device, which can be designed as a two or three-axis transfer can, has at least one, preferably two mutually parallel transfer rails on, in at least one axial direction, for example in the "open / close" direction, the means towards and away from each other, actuated by means of direct electric drives become. The respective transfer rail becomes parallel in the transverse direction of several acting electric direct drives driven with their respective output attack the transfer rail. The direct drives are spaced apart and over distributed the length of the transfer rail e.g. are three or more direct drives for each Axis provided.

The control device provided for actuation controls the one axis associated direct drives to match, so that the transfer rail on their entire length performs the specified movement uniformly. Preferably, the Control device sensor signals, for example via the current position of the transfer rail, see above that position control can be obtained.

The control device has in addition to its regular Operating mode in which it causes the transfer rail (s), preferably in the specified cycle along one programmable or otherwise adjustable transfer curve to move to an emergency mode in which they at least one of the connected and to be operated synchronously Direct drives are essentially force-free switches free of forces. Such an error can exist, for example, if an assigned to the linear actuator in question Position sensor emits an invalid signal. Becomes recognized this, the assigned direct drive becomes very quickly switched off. This prevents that he works against the other direct drives and the Blocked or blocked movement of the transfer rail. If a single drive fails, the motion sequence can continued until a safe state is reached become.

The communication system (bus, star, ring) between central control and intelligent drives is designed so that if one individual fails Drive remains operational. The control device controls the remaining direct drives in the Emergency mode continues, however, so that the movement of the Transfer rail is continued at least until the Holding means led out of the workstations are. Because of the quick release of power from the This can be done with the direct drive affected by the accident remaining linear motors with sufficient speed done, which are designed for this. Especially if the transfer rail is in an axis of several, preferably more than three direct drives is the loss of performance in the event of failure and after activating a direct drive, low that the transfer rail is removed from the danger area can be. If necessary, the direct drives in the emergency operating mode also for a short time with excessive power operate. This is particularly the case if the Operation of the transfer device is not over a few cycles away but only continues until the transfer rails and / or the holding means in in a safe position.

The direct drives assigned to an axis point preferably uniform performance, so that emergency operation in the event of failure of any direct drive leads to tolerable conditions. The direct drives are preferably efficient dimensioned so that if a direct drive fails the full required total output or at least provide sufficient performance.

The transfer rail of the transfer device according to the invention is preferably particularly rigid, to ensure that even if a Direct drive no elastic bends occur, leading to a collision between transfer rail and Tool. The bending stiffness, for example, in Lateral direction is increased so far that the natural frequency a mounting rail section, which extends from one worker over a fancy to that next working direct drive extends, is larger than the lowest excitation frequency resulting from the lateral movement in the emergency mode results.

The movement of the transfer rail can be in the emergency mode deviate from the motion curve that the Transfer rail runs during normal operation. In particular can the movement curve during emergency operation be determined that the fastest possible exit from the Workstations is made possible. This may happen with a pure lateral movement of the transfer rail can be achieved. Usually, however, too attempted during emergency operation, which during regular operation passing curve at least within a predetermined Tolerance to follow.

The direct drives are preferably electrical Linear motors, but also hydraulic or others electrically controllable direct drives are used can.

To detect failures at the sensors, the Direct drives or the control device can Monitor device for the detection of error states be provided. The monitor device can be part of the Control device or formed separately from this and is used in the event of a system failure direct drive that can no longer be controlled correctly and the emergency mode with the other direct drives initiate.

A further increase in operational security will by using a redundant communication system between the central control and the intelligent Drives reached. Reliability is further increased through redundant execution of the central Control.

The control device preferably contains separate ones Control units, each assigned to a direct drive are. The control units subordinate to a central unit communicate with each other and with the Central unit via a data transmission system, the one Can have ring structure or bus structure. To avoid of subsequent failures of larger system parts failed transmission sections switched to inactive become. You can also use the entire system or parts of which can be designed redundantly by stand-by units be provided, the operation in the event of a fault take.

The advantages of the method result accordingly for a multi-station press when switching in the emergency mode.

Fig. 1

eine Mehrstationenpresse mit Dreiachstransfer, in schematisierter, ausschnittsweiser Darstellung unter Weglassung der Stößelführungen und der Stößelantriebe,

Fig. 2

den Dreiachstransfer nach Fig. 1 mit als Direktantrieb dienenden Linearmotoren, in perspektivischer, schematisierter Darstellung,

Fig 3

einen Asynchron-Linearmotor, wie er als Direktantrieb für den Dreiachstransfer nach Fig 2 verwendbar ist, in schematisierter, vereinfachter Schnittdarstellung,

Fig. 4

eine Transferschiene des Dreiachstransfers mit ausgefallenem Linearantrieb, in einer Draufsicht, unter überhöhter Darstellung möglicher dynamischer Übergangsvorgänge,

Fig. 5

eine die linearmotoren ansteuernde Steuereinrichtung mit mehreren Steuereinheiten, im Blockschaltbild,

Fig. 6

ein Polardiagramm zur Darstellung der zeitlichen bzw. phasenmäßigen Zuordnung von Bewegungen des Dreiachstransfers in Bezug auf einen Pressenumlauf,

Fig. 6A

Zeitverläufe der Bewegung der Transferschienen und des Pressenstößels, und

Fig. 7

einen mittels elektrischer Linearmotoren angetriebenen Zweiachstransfer in perspektivischer Prinzipdarstellung.

In the drawing, an embodiment of the invention is shown. Show it:

Fig. 1

a multi-station press with three-axis transfer, in a schematic, partial representation, omitting the ram guides and the ram drives,

Fig. 2

1 with linear motors serving as direct drive, in a perspective, schematic representation,

Fig. 3

an asynchronous linear motor, as it can be used as a direct drive for the three-axis transfer according to FIG. 2, in a schematic, simplified sectional view,

Fig. 4

a transfer rail of the three-axis transfer with failed linear drive, in a plan view, with an excessive representation of possible dynamic transition processes,

Fig. 5

a control device controlling the linear motors with several control units, in the block diagram,

Fig. 6

a polar diagram to show the temporal or phase assignment of movements of the three-axis transfer in relation to a press cycle,

Figure 6A

Timings of the movement of the transfer rails and the press ram, and

Fig. 7

a two-axis transfer driven by means of electric linear motors in a perspective basic illustration.

description

In Fig. 1, a multi-station press 1 is schematic indicated, the several in the direction of T in succession arranged press stations 2, 3, 4 and possibly has further press stations, not shown. To improve clarity are the Workstations 3, 4 assigned plungers 6, 7 only indicated in dashed lines, with tappet guides, Ram drives and press frames for simplification are omitted. The press frame is just through stands 8, 9 shown by way of example and in section, 10 indicated.

For transporting workpieces from the press station Press station in which tools 12, 13, 14 are arranged are a three-axis transfer device 15. The Workpiece transport may take place between the press stations 2, 3, 4 arranged intermediate shelves 17, 18, 19.

The transfer device 15 has two along the Passage direction T extending, parallel to each other Transfer rails 21, 22, the holding means 23 for Carrying and storing the workpieces. The transfer rails 21, 22 are with respect to a vertical longitudinal median plane the multi-station press 1 inclusive their drives are mirror-symmetrical to each other. The following description of the transfer rail 21 applies therefore correspondingly for the transfer rail 22.

The transfer rail 21 is in the direction of T as well as in the vertical direction V and on the center of the multi-station press 1 to and from this, that is in Transverse direction Q, movably mounted. For storage and Guide the transfer rail 21 in the longitudinal direction (clock direction T) is used for a longitudinal slide guide. This will formed by a longitudinal beam 25 on which the transfer rail 21 is mounted for longitudinal displacement. For the drive the transfer rail 21 in the longitudinal direction serve electrical Linear motors between the side members 25 and the transfer rail 21 act and as direct drives are trained. Over the length of the side member 25 can be distributed over several linear motors. In principle are also controlled or regulated hydraulic drives possible. For position control are position-sensing Sensors are provided which determine the relative position of the Characteristic transfer rail 21 with respect to the longitudinal beam 25 Give signal.

The longitudinal beam 25 is of several, in the longitudinal direction spaced-apart cross slides 26, 27 worn, the output of linear motors 28, 29 for form the transverse direction Q. The linear motors 28, 29 are provided with sensors, not shown, a Issue position signal.

To raise and lower the transfer rail 21 are the Linear motors 28, 29 each on lifting units 31, 32 kept, also by means of electric linear motors or other direct drives can be operated. The transfer device is used to improve clarity 15 separately illustrated in FIG. 2, wherein deviating from the transfer device described above on the longitudinal member 25, which is divided several times here not a continuous transfer rail, but individual ones Carriage units 33 are mounted for longitudinal displacement, each with its own linear drive are driven. Each carriage unit 33 registers Holding means 23.

3, the linear motor 28 is illustrated. He has a primary part serving as an output 281 and a secondary part 282 formed as a stator, the in corresponding grooves of the ferromagnetic stator Short circuit conductor 283 contains. In grooves of the ferromagnetic Primary part 281 embedded windings phase-shifted (U, V, W; U ', V', W '). If necessary can instead of such a single comb motor also a double comb motor, a solenoid motor or a Synchronous motor with permanent magnetic excitation is used become. The advantage of the asynchronous motor is in the fact that it is particularly easy to switch off leaves.

As from the schematic view from FIG. 4 emerges, access the transfer rail 21, for example Movement in the transverse direction Q (opening and closing) next to the mentioned linear motors 28, 29 further linear motors 28a, 29a, 29b, 29c, 29d, which are controlled synchronously become. For this purpose, one shown in FIG. 5 is used Control device 36, the press controller 37 is subordinate. The control device 36 has one Central unit 38 to which via an optical fiber ring line 39 control units 41, 42, 43, 44 and 45 as well as other control units, not shown are. The optical fiber ring line 39 is used for data exchange between the central unit 38 and the control units 41 to 45. Each control unit 41 to 45 controls an electric linear motor 28, 29, for position feedback, each with a linear position measuring unit 46, 47 is provided.

On the control units 41 to 45 and / or on the Central unit 38 is a monitor unit M in each case trained the correct functioning of each Unit of the connected linear drive (28, 29) and connected sensors (46, 47) are monitored. The Monitor unit M can also be part of control units 41 to 45 or the central unit 38. E.g. can the Monitor function from the control unit or from one Program section to be provided, which becomes a program the control or central unit 41 to 35, 38 belongs.

If the sensors of the linear motors function properly the power supply and the control units 41 to 45 and the central unit 38 influence the Monitor units M the operation of the control device 36 Not. The control units 41 to 45 received from the Central processing unit 38 via the optical fiber ring line 39 control signals for positioning the transfer rail 21. The control units 41 to 45 set this Control commands and regulate the respectively connected Linear motors so that the specified movement is achieved becomes.

Figures 6 and 6A illustrate relative to FIG a press revolution angular ranges in which the transfer device 15 completed movements must and their timings. More than a half Angular range 51 taking eccentric shaft revolution indicates the downward stroke of the press ram e.g. in a drawing stage or in another press stage. The remaining angular range 52 characterizes the Return stroke of the ram. The control is on this movement the linear drives synchronized. The transfer rails 21, 22 guide a feed stroke in an angular range 53 out of a workpiece in the open tool leads. The transfer rails begin before the feed stroke ends 21, 22 in the angular range 54. As soon as the workpiece is placed on the lower tool at "S" is, the transfer rails 21, 22 begin in the Angular range 55 to move away from each other to release the closing tool. During the stamp is moved further downwards, begins during the Opening movement (angular range 55) of the transfer rails 21, 22 whose return stroke 66 at an angular position of about 110 °. Even during the return stroke 66 Tranferschienen 21, 22, these begin with themselves opening tool in an angular range 57 again close to grasp the workpiece and open Raise die in area 58 and in the next cycle continue to convey in the angular range 53.

The angular range proves to be particularly critical 55, in which the opening transfer rails the Must have left the working area of the ram while the tool closes. If this does not succeed, can the press ram because of the relatively large flywheels do not stop abruptly, so that there is a collision between the tool and the transfer rails 21, 22 or the holding means 23 comes.

To damage the tools in such cases and to avoid the transfer device 15, monitor the monitor devices M the correct function of the Transfer device 15. It is found that, for example, a single linear motor is not working correctly or correctly is controlled so that there is a collision could enter the monitor device in question Error signal to the relevant control unit and / or the entire system. Such a triggering error can For example, a sensor signal from the linear displacement measuring device 47 be that with respect to the other sensor signals is outside a specified tolerance. In In this case, the control device 36 goes into an emergency operating mode about. This serves, in particular in the Angular range 55, the transfer notes 21, 22 and connected holding means 23 from the closing The tool. For this the of Error affected linear drive (in the example the linear motor 29) De-energized while the others Linear motors continue to operate at full power. The linear motors are dimensioned so that even if a linear motor fails, it is used for acceleration and braking the transfer rail 21 required force be applied by the remaining linear motors can.

In the simplest case, one is in the emergency mode Reliable, i.e. collision-free, Position P of the transfer rails 21, 22 set, after which the transfer device 15 and the main press drive to be stopped. The safe or collision-free position P can on the movement curve can be achieved, which otherwise also with proper Operation is going through. The definition of different Curves KN for emergency operation, on which a collision-free Position P faster or with less effort is achievable is possible. With the emergency operation achieved that only a small security angle between the removal of the holding means 23 from the Tool and closing the tool required is. Then the working speed of the press increase.

As can be seen from FIG. 4, they form one another spaced linear motors 28, 28a, 29 to 29d force introduction points, which are spaced apart. The Transfer rail 21 has such a lateral rigidity on that they are relative at the occurring large accelerations in the direction of the Q axis deflects significantly. In addition, it has a stiffness reserve on, which prevents the transfer rail 21 in the event of failure of a linear motor, e.g. the Linear motor 29, due to the now larger distance between the active linear motors 28 and 29a at the side Accelerate bends elastically, as at 61 indicated. The increased rigidity of the transfer rail 21 thus enables that in the event of a linear motor failure its driving force from the neighboring linear motors 28, 29a and the other linear motors and is introduced into the transfer rail 21.

The control device takes a similar emergency operation 36 in the event of failure of parts of the optical fiber ring line 39 a, with appropriate interpretation of the information transmission system only for failure one or fewer drive units. The Linear motors that remain active go into emergency operation over and pose during the particularly critical opening phase (55 in Fig. 6) collision-free operation for sure.

In Fig. 7 is a modified, as a two-axis transfer trained transfer device 15 'illustrates in which the transfer rails 21, 22 only in the direction of passage T and in the vertical direction V are movable. For driving in the direction of travel T and as a lifting unit for Lifting and lowering in the vertical direction serve electrical purposes Linear drives, as in principle and as an example in Fig. 3 illustrates. Between the transfer rails 21, 22 cross-members 62 are held, with suction spiders 63 are provided. With such a two-axis transfer device 15 'it depends on the holding means 23 (suction spiders 63) in the event of an error when closing the To bring the tool out of it in time. While this is essentially the case with the three-axis transfer Direction of the Q axis takes place with the biaxial Transfer device 15 'in emergency operation with the remaining ones Linear drives one stroke in the transfer direction in one safe, collision-free position performed, after which the press is shut down.

A controller 36 for direct electric drives 28, 29 of a transfer device 15 contains at least one Monitor device M, the malfunction of a direct drive 28, 29 the control device 36 in an emergency operating mode toggles. The switches in the emergency mode Control device 36 to those affected by the error Linear drive is powerless and controls the remaining ones Direct drives preferably with full or slightly excessive Performance so that there is no collision between the forming tool and the transfer device 15 after which the press is preferably shut down becomes.

Claims (4)

1. Method of controlling a transfer apparatus (15) for the transport of workpieces along a plurality of work stations, in particular press stations (2, 3, 4), in an emergency operating mode,

   having at least one transfer rail (21), the longitudinal extent of which essentially corresponds to a direction (T) in which the workpieces are to be transported in a cyclic manner and which is provided with devices (23) for receiving or retaining the workpieces,

   having a plurality of electric direct drives (28, 29), the outputs of which are connected to the transfer rail (21) and which drive the transfer rail (21) with corresponding direction of force, so that the electric direct drives (28, 29) form a drive group for a predetermined axis direction (Q),

   having a control device (36) which activates the direct drives (28, 29) belonging to the drive group in an essentially corresponding manner and which assumes an emergency operating mode in the event of a hazard caused by a failure of a direct drive (28, 29) or of parts of the control device (36) which are assigned to this direct drive (28, 29), characterized in that the control device (36), in the emergency operating mode, essentially neutralizes that direct drive (28, 28a, 29 to 29d) of the drive group which is affected by the failure,

   and in that the control device (36), in the emergency operating mode, continues to activate the remaining direct drives (28a, 29 to 29d) and leads the transfer rail (21) and its retaining means (23) out of the work stations (2, 3, 4).
2. Method according to Claim 1, characterized in that the control device, in the emergency operating mode, activates the remaining direct drives (28, 28a, 29 to 29d) in such a way that the movement of the transfer rail (21), at least in sections within a predetermined tolerance, follows a time characteristic run through during regular operation.
3. Method according to Claim 1, characterized in that a monitor device (M), for error detection, monitors signals which have been transmitted by sensors (46, 47) and/or instruments belonging to the control device.
4. Method according to Claim 1, characterized in that the control device (36) stops the transfer rail (21) as soon as the transfer rail (21) has reached a safe position in the emergency operating mode.

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