WO2008080558A1

WO2008080558A1 - Transport system for workpieces

Info

Publication number: WO2008080558A1
Application number: PCT/EP2007/011157
Authority: WO
Inventors: Sigmund Kumeth
Original assignee: Sigmund Kumeth
Priority date: 2006-12-29
Filing date: 2007-12-19
Publication date: 2008-07-10
Also published as: DE102006062530B4; DE102006062530A1

Abstract

The present invention relates to a transport system for workpieces. Moreover, the invention relates to a method for transporting workpieces. In order to enable a particularly precise positioning of workpieces, a transport system is suggested having a drive (2), a drive means (3) which works with the drive (2) in a frictional manner, a number of workpiece receivers (5) which can be moved by the drive means (3), a measuring unit (7) for determining a position of at least one of the workpiece receivers (5) and/or a position of the drive means (3), and a control unit (8) for controlling the drive (2) according to the determination of position.

Description

description

Transport system for workpieces

The present invention relates to a transport system, in particular a transport system for an assembly and / or processing plant, for objects of any kind to be mounted or machined (hereinafter referred to as "workpieces") Furthermore, the invention relates to a method for transporting workpieces, in particular The workpieces are, for example, components or assemblies to be assembled or machined, or other objects to be mounted or processed, such as paper to be printed.

Assembly and processing systems are known in different versions. In particular, assembly systems are known in which workpiece holders are moved past on a closed conveyor line at several workstations at which the production or assembly of the components or assemblies is then carried out in several steps, on these recordings, this each with high precision at each workstation must be positioned

From the prior art, the use of a frictional or non-positive power transmission for a variety of systems is known (for example, so-called "transmission systems")., However, it is always assumed that such transmission systems not for positionally accurate transmission of forces or torques In particular, because it inevitably occurs a slip between the belt and pulley.

For control tasks and / or positioning, therefore, form-fitting transmissions (such as traction drives, such as chain drives or toothed belt drives) have always been used in the prior art in which a force or torque is transmitted by wheels with a corresponding form-fitting profiling (eg gear) ,

Accordingly, various rotary indexing and longitudinal transfer systems are known from the prior art, which can be used for the transport of workpieces and for the positioning of workpiece holders on such workstations. Usually, a belt in the form of a toothed belt is controlled by means of a switching stepping device or the like. The number of available target positions is u.a. determined by the step used. The deviations in the strip length resulting during tightening of the strip can only be partially compensated by adjusting the switching step. Thus, the desired and actual achievable target positions often do not match exactly. In other words, in the solutions known from the state of the art, the error tolerances of the belt and the shift pawl add up in a manner which makes high-precision positioning of workpieces very difficult.

If a drive chain is used instead of a toothed belt, nothing fundamentally changes in the cause of the fault. In this case, the error tolerances of the individual chain links add up to a total error. In summary, high-precision positioning of workpieces with the known from the prior art solutions due to design is not possible.

An object of the present invention is a

To provide a transport system for workpieces, with the particularly accurate positioning of the workpieces is possible. This object is achieved by a transport system according to claim 1 or by a method according to claim 10.

Thereafter, the transport system according to the invention comprises a drive, a frictionally cooperating with the drive drive means, a number by means of the drive means movable workpiece holders, a measuring unit for determining a position at least one of the workpiece holders and / or a position of the drive means and a control unit for controlling the drive in Dependence on the position determination.

The process according to the invention which can be carried out with the aid of this transport system comprises the following steps:

Determining a first position of the workpiece holder and / or the drive means with the aid of the measuring unit,

Moving the workpiece holder by means of the drive; determining a second position of the workpiece holder and / or the drive means with the aid of the measuring unit and

- Controlling the drive in dependence on the position determination by means of the control unit.

A first basic idea of the invention is to use a drive means in the manner of a frictional traction mechanism drive for the transport of the workpiece holders. However, while traction drives are gearboxes where a torque is transmitted between two axially parallel waves by means of a both shaft ends wrapped around the traction means, here only a drive of the "traction means" takes place through a first shaft, without it depends on a torque transmission to a second shaft.

As with friction-locking Zumitteltriebe, which are also referred to as positive traction mechanism drives, it is essential in the invention that a torque through the in the contact surface between the belt and drive pulley

(Pulley) acting frictional forces is transmitted. This is the case in particular with flat belts or V-belts. The size of the frictional forces depends on the preload, which can be adjusted by means of a tension pulley or over the length of the belt.

A belt is understood to mean an elongated strip of a more or less flexible material, the two ends of which are connected and which is used to transmit forces or torques. Flat belts achieve a particularly high degree of efficiency. In order to prevent that flat belts from the discs (drive pulley, clamping pulley) run, they can be made more or less spherical. The belts then center automatically. As used herein, the terms "belt" and "belt" are used interchangeably.

Instead of a flat belt and a V-belt can be used. V-belts can transmit much larger forces than flat belts with the same footprint. Due to the higher friction and the forces on the bearings are much lower. Instead of a drive pulley with a flat pad is often used to drive a V-belt a disc with a wedge-shaped groove.

In addition, intermediate forms of the belt are possible, wherein it is essential to the invention that the involved

Components are free of component-specific positioning elements (e.g., teeth or holes in the belt, etc.). Essential to the invention is that the belt can take any position without being limited by predetermined positioning elements in its free position choice.

By determining the position of the tape or the workpiece holders and the corresponding control of the drive is a highly accurate and not by

Positioning elements rigidly fixed positioning of the workpiece holders according to the requirements of each case possible.

Further advantages of the frictional transmission and the

Using a belt as a drive means quiet and quiet running, low maintenance (no lubrication), comparatively low cost, short-term overload capability (belt slippage) and high rotational speeds (rotational speeds).

By using a frictional transmission, no high-precision components are required according to the invention. Simply by controlling the drive means the desired high-precision positioning can be achieved. In other words, all components can have tolerances. In particular, the drive means (belt, belt) can have a length tolerance of up to several millimeters demonstrate. Also, the tensioning of the belt has no influence on the precision of the transport system. The decisive factor is that after the tensioning of the belt, an initialization of the transport path is made. For this purpose, the position of at least one of the workpiece holders (and / or the belt) is determined by a measuring unit. Subsequently, the tape runs a full revolution or a plurality of revolutions until the original position of the workpiece holder (or the band) is reached again. Thus, the length of the tape and thus the total existing transport path is determined and can be used in the control unit of the drive for an assignment of motor rotation (rotation of the drive pulley) on the one hand and movement of the drive means (belt, belt) on the other.

Another basic idea of the invention is to use a direct drive as the drive. This means that the drive pulley is part of the engine and eliminates an additional gear for transmitting the torque from the engine to the drive pulley. The motor is designed to operate directly with the speed of the drive pulley. The use of such a direct drive not only eliminates a gearbox, which reduces wear, noise and oil loss of the drive. At the same time, the required space is reduced by the integrated design.

Further advantageous embodiments of the invention are specified in the dependent claims and are described in more detail using an exemplary embodiment with the aid of the figures. These show: 1 is a schematic representation of a transport system according to the invention,

2 shows an inventive transport system (perspective from above),

3 shows the transport system according to the invention from FIG. 2 (perspective from below), FIG.

Fig. 4 shows the transport system according to the invention from Fig. 2 (top view) and

Fig. 5 is a detail view of a workpiece holder with tape

(Sectional view).

The figures show the invention only schematically. Design details are only to the extent necessary for the understanding of the invention.

The transport system 1 according to the invention for an assembly and / or processing system for workpieces comprises, as shown in FIG. 1, a drive 2, a drive means 3 interacting frictionally with the drive 2 and a number of workpiece receivers 5 movable in the transport direction 4 by means of the drive means 3 (In Fig. 1, drive means and workpiece holders, etc. are summarized as "transport mechanism" 6), a measuring unit 7 for determining the position of at least one of the workpiece holders 5 and / or a position of the drive means 3, and a control unit 8 for controlling the drive 2 in The control unit 8 has a powerful microprocessor and is connected via a fieldbus system 9 with the Drive 2 on the one hand and the measuring unit 7 on the other hand connected.

By way of example, a simple concentricity transport system is shown (cf., FIGS. 2 to 4), in which twelve

Workpiece receivers 5 in the form of receiving carriage with the help of four guide rollers 11 on .einer guide or support rail 12 are guided. The course of the mounting rail 12 indicates the path of movement of the workpiece holders 5. The support rail 12 has a cross-section on a sword profile and is located between two pairs of guide rollers of a receiving carriage (see Fig. 5). One of the outer guide rollers 11 has a projection 13 to which a vertically downwardly extending holder 14 is attached. On the inside 15 of the holder 14, two clamping pieces 16 are provided, which are bolted to the holder 14. Between the inner sides 17 of the clamping pieces 16 and the inner side 15 of the holder 14 serving as a drive means 3 steel band is clamped, as shown by way of example in Fig. 5. The steel strip 3 acts frictionally with the drive pulley 18 of the drive 2, here an electric motor, together.

The use of steel, especially spring steel, as strip material reduces the sensitivity to external influences (oil, gas, temperature, dirt, water, dust). Spring steel bands are particularly durable, light and hardly stretchy. In particular, the tensile slip is drastically reduced by the use of steel as strip material. Therefore, a steel strip is well suited for precision positioning as in the present case. The steel strip 3 is designed in the present example as a flat band. The surfaces of the drive pulley 18 and des Bandes 3 are essentially smooth. In any case, they have no subdivisions or positioning elements.

The vertical distance between the clamping pieces 16 to each other is selected such that the drive pulley 18 and the drive pulley 18 opposite clamping disc 19 engage in the resulting gap 21 and the Band 3 can drive via a friction. Since the band 3 is firmly clamped to the holder 14, the twelve receiving carriage 5 are taken in the transport direction 4 by the movement of the belt 3. The tensioning of the belt 3 is effected by a displacement of the tensioning pulley 19. The tensioning pulley 19 also serves for deflecting the steel belt 3 during operation. Alternatively, it is possible to tension the band 3 by a corresponding displacement of the drive pulley 18.

The drive pulley 18 is formed in the illustrated embodiment as part of a direct drive. The direct drive is usually a special form of servo drive, usually in the form of a three-phase, brushless synchronous motor with permanent excitation. In direct drive technology, the desired movements take place directly, ie without prior

Transformation of the rotating motion sequence. In other words, loads are directly driven without a mechanical reduction. Thus not only high accelerations can be achieved, but also the dynamics of such drives (ie the ratio of the maximum to the minimum)

Speed) is particularly high. In addition, direct drives are characterized by a long service life, fewer wear parts and high efficiency and a high Reliability and are also compact and small in size.

For the present invention, a direct drive 2 is preferably a "switched reluctance machine".

(Edge effect reluctance machine) used. In particular, a high-pole edge effect reluctance machine is used. The motor used is a brushless servomotor without permanent magnets. It is equipped with a cross roller bearing with high rigidity and accuracy as well as a lifetime lubrication and thus offers high availability and maintenance-free operation. Motor 2 and control unit 8 of the motor 2 are designed so that they allow a motor drive with a resolution of several 100,000 pulses per revolution. As a result, any desired rotational position of the motor 2 can be approached with a very high repeatability of a few angular seconds. With the aid of the motor 2, accelerations on the order of 80 to 120 s ^"2 can preferably also be realized.

By controlling pulses, any division is possible. For example, the system may be sized to require about ten revolutions of the drive pulley 18 for a belt revolution. For example

800,000 pulses per drive wheel revolution, this would correspond to a figure of approximately 8,000,000 pulses per belt revolution. In other words, the tape 3 can be stopped at 8,000,000 different target positions.

During initial commissioning, so after installation of the transport system 1 and the tensioning of the belt 3, first a reference travel takes place, in which the length of the Bandes 3 and thus the future target positions are set in relation to the control pulses of the motor 2. The measuring unit 7 determines for this purpose the position of a selected workpiece carrier X '. Thus, a "zero position" is defined After passing through one revolution, this zero position is again reached by the workpiece carrier X 'The workpiece carrier X' is again detected by the measuring unit 7. Thus, the number of pulses for one revolution is defined "Zero position" does not necessarily require a fixed "stop", however, such a fixed stop may be provided.

As measuring unit 7 different measuring systems can be used. Magnetic systems, for example, in which magnetic strips attached to the workpiece holders 5 have been detected by a stationary sensor, have proven to be useful. In the present example, an optical measuring unit 7 is used, which forms an "optical probe" for detecting a workpiece holder 5 with the aid of a combined laser transmitter / receiver unit 22

Measurement results of the measuring unit 7 are transmitted to the control unit 8 and there - possibly after signal conversion, etc. - processed and used to control the motor 2 in dependence on the position determination.

The workpiece holders 5 are firmly connected to the band 3, ie not articulated or the like. The once defined positions of the individual workpiece carriers on the belt therefore no longer change. A future control of the target positions of the workpiece holders 5 can thus take place solely on the basis of the tape position, ie by the control of the motor 2 with a certain number of control pulses by the control unit 8. Particularly simple is the positioning of the individual workpiece holders 5, if they are connected at regular intervals with the band 3. However, it is also possible to determine the position of each workpiece holder 5 on the belt 3 with the aid of the measuring unit 7 and to deposit a corresponding individual position information in the control unit 8.

For control purposes, it is provided with the aid of the measuring unit 7, a position determination of

Werkstückaufnähme (s) 5 and the band 3 at regular intervals, for example, after each tape circulation to make and compare this position information in the control unit 8 with the previous control information as well as possibly to adjust and correct. Thus, for example, any change in the tape length can be compensated for directly and automatically, for example by an automatic adaptation of the number of control pulses required for the respective positioning by the control unit 8.

With the present invention, the mechanical error is reduced solely to the tolerance of the drive pulley 18. A possible slippage of the belt 3 is prevented by suitable material (steel). Some residual slippage is nevertheless acceptable, since the transport system 1 is a self-controlling system in which the measuring unit 7 determines the position of at least one workpiece holder 5 or of the band 3 at regular intervals (for example at each cycle). As a result, an automatic correction of the slip is possible with the aid of an electronic control 8. This self-control preferably takes place at each start-up of the transport system 1 and at the same time even in a number of predefined occasions, for example, when shifted by collision workpiece holders 5 or the like.

In comparison to the prior art, the complexity of the drive train as a whole is reduced. In particular, the rotational angle of the drive need not - as in the prior art - be known in advance. They are rather freely programmable, so that any positions can be approached. Retooling and downtime, which were required in conventional systems with angular changes, can be eliminated. New target positions can be defined in a simple and fast way by reprogramming the control unit.

Preferably, the direct drive 2 also has a built-in position sensor 23 (see Fig. 1), with the aid of the control unit 8, the current position of the drive pulley 18 is transmitted in each case. Thus, and with the respectively determined position of the workpiece holders 5 and the band 3, a completely closed control loop is provided, with the aid of which previously unknown positioning accuracies can be achieved.

With such a transport system 1, for example, the complete production of a complicated component or a complex assembly or editing, for example, a printing of workpieces made of paper, cloth or other material to successively arranged printing machines with high timing and precision done. At the individual stations (target positions), a check can be made in addition to or instead of an assembly and / or a processing. With the present invention, preferably ring and oval guide systems can be realized when using appropriate guide or support rails 12, wherein the workpiece holders (slide), for example, run on a rectangular or oval course with arbitrarily long lines. Among other things, machine parts, electrical or optical components, electronic components, semiconductor components, etc. may be used as workpieces.

Instead of a rectangular or oval course, however, the band 3 may also be circular or S-shaped in further embodiments of the invention. An S-shaped course of the band 3 would be particularly useful for example for a transport of workpieces in a drying chamber for paints or the like.

In addition, the attachment of the band 3 to the workpiece holders 5 vary. Particularly in the case of an S-shaped course of the band 3, the clamping of the band takes place

3 preferably only on one hinge side. In the example of FIG. 5, the clamping of the band 3 would then be done, for example, only one side between the inner side 17 of the upper clamping piece 16 and the inner side 15 of a greatly shortened holder 14, which terminates substantially with the lower edge of the clamping piece 16.

All figures show the invention only schematically and with its essential components. In particular, the type of transport system 1, the number and shape of the

Workpiece holders 5, the type of guide 12, etc. differ from the example shown here. For example, the used guide 12 is not continuous, but only provided on sections of the band.

All in the description, the following claims and the drawings illustrated features may be essential to the invention both individually and in any combination.

LIST OF REFERENCE NUMBERS

1 transport system

2 drive, electric motor

3 drive means, steel band

4 transport direction 5 workpiece holder, receiving carriage

6 Transport mechanics

7 measuring unit

8 control unit

9 fieldbus 10 (free)

11 leadership role

12 mounting rail

13 approach

14 holder 15 holder inside

16 clamping piece

17 clamping piece inside

18 drive pulley

19 clamping disc 20 (free)

21 gap

22 laser unit

23 position transmitter

Claims

claims

1. transport system (1) for workpieces,

- with a drive (2), - with a with the drive (2) frictionally cooperating drive means (3),

- With a number by means of the drive means (3) movable workpiece holders (5),

- With a measuring unit (7) for determining a position of at least one of the workpiece holders (5) and / or a position of the drive means (3) and

- With a control unit (8) for controlling the drive (2) in dependence on the position determination.

2. Transport system (1) according to claim I _7, characterized in that the drive (2) is a direct drive.

3. Transport system (1) according to claim 1 or 2, characterized in that the drive (2) for cooperation with the drive means (3) has a rotatable drive pulley (18).

4. Transport system (1) according to one of claims 1 to 3, characterized in that the drive means (3) is a belt.

5. Transport system (1) according to claim 4, characterized in that the belt is a flat belt.

6. Transport system (1) according to claim 4 or 5, characterized in that the belt is a steel band.

7. Transport system (1) according to one of claims 1 to 6, characterized in that the workpiece holders (5) are fixedly connected to the drive means (3).

8. Transport system (1) according to one of claims 1 to 7, characterized in that the workpiece holders (5) by means of a guide system (12) are guided on a movement path.

9. Transport system (1) according to one of claims 1 to 8, characterized in that the measuring unit (7) for determining the position of a workpiece holder (5) relative to the drive means (3) and / or for determining the absolute position of the workpiece holder (5 ) or the drive means (3) is formed.

10. A method of transporting workpieces with a transport system, the transport system comprising:

a drive (2), a drive means (3) interacting with the drive (2) in a friction-locked manner,

a number of workpiece holders (5) movable by means of the drive means (3),

a measuring unit (7) for determining a position of at least one of the workpiece holders (5) and / or a position of the

Drive means (3) and

- A control unit (8) for controlling the drive (2) in response to the position determination, and the method comprises the following steps: - Determining a first position of the workpiece holder (5) and / or the drive means (3) by means of the measuring unit ( 7), Moving the workpiece holder (5) by means of the drive (2),

- Determining a second position of the workpiece holder (5) and / or the drive means (3) by means of the measuring unit (7) and

- Controlling the drive (2) in dependence on the position determination by means of the control unit (7).