Method for Winding a Winding Material via a Brake Roller onto a Winding Body having a Non-Circular Cross Section

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of winding machines, in particular machines for winding wire onto winding bodies having non-circular cross sections or asymmetrical geometries and, more particularly, to a method for winding a winding material via a brake roller onto a winding body having a non-circular cross section for influencing a tensile force characteristic of the winding material.

2. Description of the Related Art

Winding machines, in particular machines for winding wire onto winding bodies having non-circular cross sections or asymmetrical geometries, are commonly used in the manufacture of electric motors and transformers, where wire is intended to be wound onto coils with as constant a tensile force as possible in order to ensure the quality and efficiency of the electrical components. In addition to the winding of wire, there are a large number of other materials that are wound in a similar manner. For example, films or tapes, such as in particular plastic films or metal tapes or adhesive tapes, are wound onto winding bodies. Uniform winding ensures that the materials have no creases or damage during later processing or use.

Particularly for battery cell production, electrode webs are wound onto rectangular bodies, which are also subject to high requirements for a constantly prevailing tensile stress during winding. Even in the case of composite materials in the manufacture of composites or filaments made of plastics, such as PLA or ABS, which are used in 3D printers, winding with a uniform tensile stress is necessary in order to be able to produce high-quality parts. Non-circular coil geometries are also used for needle winding and the kinematic system performing the winding on must still meet the high requirements for uniform stress when a wire is being wound on.

In conventional wire winding machines, the wire is wound onto a winding body with the help of a brake. The brake is operated with torque control and provides a constant torque in the opposite direction to the wire unwinding direction. The torque setpoint value is constant and corresponds to the desired tensile force. However, in the case of a non-rotationally symmetrical winding body and a constant speed of the winding body, the wire unwinding speed is not constant and the brake is accelerated and braked. During an acceleration phase, the wire is therefore stretched; during a braking phase, the wire is compressed, or is temporarily tension-free, such that no constant tensile stress is applied overall.

Furthermore, it is known from the prior art to calculate and control a speed characteristic for the brake with the help of a geometric model of the winding body. The tensile force results from a position offset between the brake and the winding body together with the wire stiffness. The position offset is controlled by an upstream force controller. However, a complex model is required for this and the procedure is susceptible to deviations between model and reality, this leading to fluctuations in tensile force, because any small deviation in the position of the brake is weighted with the wire stiffness due to model inaccuracies or lack of controller dynamics.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention to provide a method that improves winding of a winding material onto an asymmetric coil body.

This and other objects and advantages are achieved in accordance with the invention by a method for winding a winding material via a brake roller onto a winding body having a non-circular cross section for influencing a tensile force characteristic of the winding material, where the method includes ascertaining a torque value via a torque balance of the brake roller in dependence on a winding material speed, and specifying the ascertained torque value for the drive of the brake roller.

The winding material, such as a wire, is pulled, for example, by a movement of the winding body, here a winding body having a non-circular cross section, such as an approximately rectangular coil core. For example, the winding body is electrically driven and controlled by at least one servo axis. Here, the winding material is intended to be wound onto a non-circular object, for example, via a winding machine with a defined force.

For example, in some implementations, use is made of kinematic systems or robots that wind a wire supplied via the brake onto a non-moving winding body. For example, use is made of needle winders which wind a wire onto a rectangular coil core.

The winding material is unwound via the brake roller or, in other words, made available to the winding process via a brake. The brake roller is also typically electrically driven and controlled by a servo axis.

Depending on the winding material used and on the mechanical structure, for example, a web of goods or a wire is deflected and guided between the brake and the winding body. For example, all deflecting and guiding elements are fixed and do not cause any change in the wire length. In alternative configurations, guiding elements cause the winding movement onto a fixed winding body.

The inventive method keeps the tensile force, which is acting on the winding material, in a range in which the tensile force neither becomes too low, such that the winding material would no longer be wound onto the coil in a defined manner, nor becomes too high, such that the winding material plastically deforms and the resistance of the coil would be too great or would even damage an insulation layer of the wire, for example.

Rather, depending on the winding application, a high-quality coil winding having an orthocyclic winding pattern is achieved, for example, which is vital for the fill factor and thus the quality of a winding. Moreover, the coil is prevented from becoming spherical, which would be disadvantageous for further processing, such as inserting it into an electric motor.

This is achieved by specifying a torque value at the drive of the brake roller, where the torque value is derived from the torque balance of the brake roller and is ascertained taking into account the speed of the winding material that varies within each winding cycle. In particular, the winding material speed is a wire speed of a wire that is to be wound on.

Compared to the prior art, the inventive method offers the advantage that no complex model calculations for calculating a speed characteristic for the brake based on complex models are necessary in order to describe the reality as accurately as possible, without being able to take this directly into account.

The present invention therefore allows winding with the tensile force characteristic accurately matched with a desired characteristic, even in the case of non-round winding bodies and high speeds.

In accordance with one embodiment, a torque characteristic curve as a torque setpoint value and current setpoint value derived therefrom is specified to a current controller for the specification of the ascertained torque value. A drive torque setpoint value for the brake drive is therefore specified. The brake roller is operated by a current controller and associated control loop, and a torque setpoint value that takes into account the varying speeds of the winding material is specified.

In accordance with another embodiment, a torque limit in the speed control loop is controlled using the ascertained torque value as a variable torque limit value for the specification of the ascertained torque value. A torque limit is set up that prevents a higher torque or, in the case of negative values, a lower torque than that set via the limit value on the brake roller from acting on the winding material. In some implementations, an upper and lower limit is provided, where an upper or lower limit value is reached and the upper or lower limit value is assigned the ascertained value accordingly, depending on the mechanical structure of the winding machine. The torque limit therefore varies within each winding cycle.

Compared to conventional wire winding machines with torque control, the brake does not accelerate without limitation in the case of the proposed specification of a torque limit in the speed control loop via the torque limit, such that safety is increased.

In accordance with a further embodiment, the brake roller is controlled using a specifiable speed. A speed that is to be specified is ascertained, for example, when the winding machine is designed. The selected speed ensures that the wire reaches the torque limit after a short start-up phase. The torque limit is then controlled and selected such that the acceleration phases of the wire or of the brake are compensated for.

In accordance with an embodiment, the speed of the winding body is specified from a speed characteristic. In configurations with a speed characteristic, such as in the case of extreme coil geometries, sufficient winding material is therefore made available for compensating purposes.

In accordance with another embodiment, the speed is directed in the opposite direction to an unwinding direction, i.e., the speed would ensure that the wire is wound back onto the brake without the winder being driven. This thus ensures that a torque setpoint value of the brake would, after some time, reach a permanently specified torque limit that was set as an upper or lower limit in dependence on the mechanics. The torque limit is controlled and selected such that the acceleration phases of the wire or the brake are compensated for. The specified speed is relevant in the phase before the torque limit is reached and before operation in torque limitation.

In accordance with a further embodiment, the torque limit value is ascertained via the torque balance with a counteracting tensile force component and an identically acting inertia component.

The inertia component is dependent on the angular acceleration of the brake and therefore on the wire acceleration and thus also on the wire speed. The inertia component is particularly dependent on an effective radius of the winding body. The effective radius is in particular a position-dependent, perpendicular distance between the winding material and the center of rotation of the winding body.

Here, in common configurations of a wire brake, the tensile force component is given as the product of the tensile force at the brake and of the radius of the brake. The product of the moment of inertia and the angular acceleration of the brake is a common inertia component. The angular acceleration of the brake can be replaced by the winding material acceleration divided by the radius of the brake. The winding material acceleration is in turn ascertained from the winding material speed.

In accordance with another embodiment, the winding material speed is ascertained via geometric information relating to the winding body. The winding material speed is, for example, calculated with the help of a geometric model. Here, for example, a rotational speed of the winding body and an effective radius, which results from the geometry of the winding body and a distance of the winding material from the center of the winding body, are used.

In accordance with another embodiment, the winding material speed is recorded via a test winding of the winding body with test conditions. For example, for complex coil geometries for which the effective radius cannot be calculated from user data, the characteristic of the effective radius is thus learnt via a test winding, for example, one or more revolutions of the coil body. For this purpose, for example, during a slow movement of the winding body, during which acceleration processes can be ignored, and a constant torque on the brake, the braking speed is recorded as a trace.

In yet a further embodiment, the torque limit is controlled in real time. The desired tensile force characteristic is therefore attained as quickly as possible and thus as accurately as possible.

In accordance with another embodiment, a tensile force or a tensile force characteristic is specified for the tensile force component. For example, a setpoint tensile force is incorporated into a torque balance in order to ascertain the torque limit therefrom. The desired tensile force is selected in particular in dependence on a material of the winding material, a wire diameter, etc. The tensile force is, for example, able to be parametrized and in particular fixedly selected depending on the application.

In accordance with another embodiment, an inertia is specified, in particular derived from a CAD system and specified, or measured, for the inertia component. Depending on the application, a variable that is easy to ascertain or that is easy to measure is thus able to be used for the inertia, which variable is included in the torque balance in order to ascertain the torque limit therefrom.

The objects and advantages are also achieved in accordance with the invention by a control unit for a brake roller for winding a winding material onto a winding body, where the control unit includes a process and memory and is configured to implement the method in accordance with disclosed embodiments.

The objects and advantages are also achieved in accordance with invention by a computer program, comprising commands which, when executed by a computer, cause the computer to perform the method as claimed in one of the forms above, where the computer program is executed in particular on a virtual controller.

Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below based on exemplary embodiments with reference to the figures, in which:

FIG. 1 shows a schematic illustration of a wire winding machine having a control concept in accordance with the prior art;

FIG. 2 shows a schematic illustration of a wire winding machine having a control concept in accordance with a first exemplary embodiment of the invention;

FIG. 3 shows a schematic illustration of a geometry of a non-circular winding body with relevant variables;

FIG. 4 shows a schematic illustration of a wire winding machine having a control concept in accordance with a second exemplary embodiment of the invention;

FIG. 5 shows a schematic illustration of a wire winding machine having a control concept in accordance with a third exemplary embodiment of the invention; and

FIG. 6 is a flowchart of the method in accordance with the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

In the figures, elements having the same function are provided with the same reference signs, unless stated otherwise.

FIG. 1 shows a wire winding machine in accordance with the prior art, which involves winding a copper wire D onto a rectangular coil W with a constant tensile force. A geometry of a non-round winding body WK is therefore used as a basis for the coil W. FIG. 1 intends to illustrate how a wire D is wound slip-free onto a brake B driven by a brake motor Mb and made available to the process by a movement of the brake B. As depicted, the wire D is deflected once on a deflection roller U1 and guided on a wire guide U2. The coil W rotates at a constant speed, driven by the winding motor Mw. An encoder on the winder Gw ensures feedback into a current control loop having a current controller R_i_w for controlling a constant speed on the winder, here the coil W.

A speed characteristic for the brake B is calculated and controlled with the help of a geometric model of the winding body WK. An encoder Gb outputs the actual speed. The tensile force results from a position offset between the brake B and the winding body WK together with the wire stiffness. The position offset is controlled by an upstream force controller.

In order to keep the tensile force on the wire D at a setpoint tensile force F-soll, a force controller having a force controller R_f_b and feedforward controller C_f is placed upstream of a controller of the brake motor Mb having a current controller R_i_b and upstream speed controller R_n_b.

In accordance with a first exemplary embodiment, the brake B is controlled at a constant speed. FIG. 2 illustrates the exemplary embodiment, where the structure of the winder W having the deflection roller U1 and the wire guide U2 is identical to the structure shown in FIG. 1. The selected constant speed of the brake B is directed in the opposite direction to the unwinding direction, i.e., the speed would ensure that the wire D would be wound back onto the brake B. This ensures that the torque setpoint value of the brake B reaches the torque limit very quickly. The torque limit is controlled and selected in real time such that the acceleration phases of the wire D or of the brake B are compensated for.

The acceleration force to be compensated for is derived from the wire acceleration. The wire acceleration is obtained from the wire speed and this is calculated with the help of a geometric model:

v W ⁢ i ⁢ r ⁢ e ( t ) = r ⁡ ( θ ) ⁢ θ ˙

Where θ is the angle of rotation of the winding body WK and r(θ) is the effective radius. Both variables are explained with reference to FIG. 3.

FIG. 3 shows a non-round winding body WK around which a wire D is wound. The winding body WK rotates around a point o which at the same time forms the origin of a coordinate system, drawn for illustrative purposes, with an x-axis and a y-axis in the plane of rotation. The effective radius r(θ) is the shortest distance between the center of rotation o of the winding body WK and the wire D. In the case of a simple geometry, such as a rectangle, this function can be concluded from user data.

The wire acceleration is obtained from the wire speed.

a W ⁢ i ⁢ r ⁢ e ( t ) = r ⁡ ( θ ) ⁢ θ ¨ + d ⁢ r d ⁢ θ ⁢ ( θ ) ⁢ θ ˙ 2

The following torque balance applies to a rotating brake:

F z ⁢ u ⁢ g ⁢ r B = J B ⁢ θ ¨ B + M ist B

Where r_B is the radius of the brake, F_Zug is the tensile force acting on the wire, J_B is the inertia of the brake and {umlaut over (θ)}_B is the angular acceleration of the brake.

The angular acceleration of the brake can be replaced by the wire acceleration divided by the radius of the brake.

M ist B = F z ⁢ u ⁢ g ⁢ r B - J B r B [ r ⁡ ( θ ) ⁢ θ ¨ + d ⁢ r d ⁢ θ ⁢ ( θ ) ⁢ θ ˙ 2 ]

The value M_ist_B ascertained in this way is then used as the torque limit value M_G, as illustrated in FIG. 2. The torque limit value M_G is controlled and is consistently reached at the provided torque limit G. Consequently, this limit is output as the setpoint to the current controller R_i_b. The conversion into a setpoint current that is specified to the motor takes place. In addition, a PI controller PI is provided in the speed control loop, for example.

In accordance with a second exemplary embodiment, instead of the torque limit with a controlled limit value, a torque setpoint value M_soll_b is specified to the current controller R_i_b. The value M_ist_B, as was ascertained in connection with the first exemplary embodiment described, is used as the torque setpoint value M_soll_b. In particular, this is a torque setpoint value characteristic which repeats itself almost in each cycle.

In accordance with the second exemplary embodiment, separator films and electrode films are wound onto a core for manufacturing a battery cell. Only one of the films that is to be wound one on top of another in layers is depicted.

In accordance with a third exemplary embodiment of the invention, the described concept of the torque value ascertained via the torque balance is used for the brake drive in a winding machine, in which the winding body WK of a coil or the like does not rotate but rather a kinematic system K winds the winding material onto the winding body WK. This can be advantageous, for example, in the case of flexibly interchangeable coil bodies in which the movement of the kinematic system K can compensate for the various geometries.

FIG. 6 is a flowchart of the method for winding a winding material D via a brake roller B onto a winding body WK having a non-circular cross section for influencing a tensile force characteristic of the winding material D.

The method comprises ascertaining a torque value via a torque balance of the brake roller B in dependence on a winding material speed, as indicated in step 610.

Next, the ascertained torque value for the drive Mb of the brake roller B is specified, as indicated in step 620.

Thus, while there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the methods described and the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps that perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.