EP0751244A2 - Method for controlling yarn tension - Google Patents

Abstract

The method for controlling yarn tension after the friction twisting head (6) on a false twist texturing machine comprises using: (i) a controller (12) with control constants (I,P) which converts the deviation of the measured yarn tension (T) from a required value arising from a disturbance of magnitude (Z) into a correction signal (VS) to adjust the setting (S) of the twisting head (6); where: (a) during the control process the control constants (I,P) are corrected according to the magnitude (Z) of the disturbing factors.

Description

The invention relates to a method for regulating the thread tension according to the preamble of claim 1.

Such methods are known.

DE 306 594 A1 describes a method for false twist texturing, in which the twist moment transmitted from the friction false twist unit to the thread is adjusted as a function of the tensile force by adjusting the contact pressure of two surfaces acting on the thread accordingly. With this method the thread tension can be adjusted to a constant value. The disadvantage of this method is that fluctuations in the mean value no longer appear and therefore, under certain circumstances, errors which should be detected by the thread tension measurement can no longer be detected. Thread tension changes can e.g. occur due to wear of a delivery plant or due to errors in the temperature control of the texturing zone; however, these errors cannot be detected using the known method; rather, these errors are corrected and thereby covered.

EP 0 439 183 B1 describes a method for monitoring the thread tension of a running thread in the texturing zone of a false twist crimping machine, in which the thread tension is thereby It is corrected that this is converted into an adjustment signal via a time filter and through this the size and / or the component distribution of the frictional force of the false twist unit on the thread is controlled, the adjustment signal being used as the signal representing the current average of the current measured value for quality monitoring. The adjustment signal, by means of which the thread tension is corrected, is thus monitored to determine whether it leaves the predetermined range between the upper limit value and the lower limit value. These limit values are used to output an alarm signal when the adjustment signal leaves the area between these limit values. In addition, the difference between the currently measured thread tension after appropriate shaping can be compared with the adjustment signal and an alarm signal can be issued if the difference signal leaves a predetermined range between an upper limit value and a lower limit value.

The method described in WO 92/11532 for regulating the thread tension of a running thread behind a friction false twist unit of a false twist crimping machine is based on the method of adjustment described in EP 0 439 183 B1 for regulating the thread tension in the twist zone. A twist / feed ratio (R / Y) defined as the quotient of the effective radius of the friction false twist unit and the thread speed is set by setting the point of application of the thread on the friction false twist unit or / and the thread speed.

Furthermore, a method for monitoring the thread quality of the running thread is described in EP 0 207 471 D1. This method serves primarily the purpose of uncovering the errors occurring in the method described in DE 33 06 594 A1.

With all the known methods and the devices of the prior art working with these methods, it has now been shown that the numerous individual friction-false twist units present in a false twist crimping machine all have the same structure, but surprisingly a variation of the thread tension on different ones Positions, ie different friction false twist aggregates or also occurs over time. As a result, it is impossible to achieve crimped threads of the same quality produced with just a single false twist crimping machine.

It is therefore the object of the invention to provide a method for regulating the thread tension of a running thread behind a friction false twist unit of a false twist crimping machine, in which local and temporal variations in the crimp quality of the thread can be minimized.

This object is achieved by a method with the features according to claim 1. Advantageous further developments and refinements of the method are the subject of the subclaims.

The method according to the invention for regulating the thread tension of a running thread behind a friction-wrong unit of a false twist crimping machine is characterized in that the regulator constant of the regulator is corrected while the process is running, ie during regulation. The particular advantage of this procedure is the fact that each work station individually to the environmental conditions, such as. B. device tolerances, wear, thread speed, etc., which act as disturbances.

In the previously known methods for regulating the thread tension, a specific regulator constant that has been specified has always been used. This regulator constant is e.g. B. was obtained by measuring a route characteristic field. The best possible controller constant has only been set for a certain operating point. In practice, however, it has been found that the relationship between the manipulated variable at the false twist unit and the thread tension at each work station is different. Furthermore, the operational changes in the disturbance variables, such as. B. wear and thread speed, are also taken into account. Since a new static operating state arises when the manipulated variable or disturbance variable changes after a dynamic transition, no optimal control has been achieved so far. This is achieved by the method according to the invention, since the regulator constant is corrected during the regulation as a function of the disturbance variable acting on the friction false twist unit or a controlled system. The influence of the disturbance variable can be determined from the relationship between the thread tension and the disturbance variable at the current operating point or from the relationship between the thread tension and the adjustment signal at the operating point. A corrected controller constant can be determined on the basis of a predetermined controller map. The controller map shows the relationship between the controller constant and the slope, which is obtained by dividing the difference in thread tension between two times and the difference between the manipulated variables and the adjustment signals at these times. The controller map is determined by measurement or empirical calculations and given to the machine. From this, the corrected controller constant associated with this operating point, which is supplied to the controller as a corrected value, can then be determined with the new slope value. It is thus achieved that the dependencies between manipulated variable and controller variable, which differ from work station to work station, as well as the dependence on the disturbance variables, are different do not affect the thread quality. This means that the controllers of each texturing point have individual controller constants. The controller constant is not determined continuously, but if necessary or according to certain time patterns.

In the method for regulating the thread tension of a running thread, the angle between the thread running direction and the direction of movement of the friction surface of the friction false twist unit is preferably measured as a manipulated variable. In addition to the angle as a manipulated variable, the distance between the axes of the Frikton shafts can also be measured as a manipulated variable. Since the contact pressure of the friction surfaces has an influence on the thread tensile force of a running thread, it is proposed that the contact pressure of the friction surfaces be measured as a manipulated variable. According to a further advantageous idea, it is proposed that the thread speed of the thread is measured as a disturbance variable.

The correction in the controller constant takes place via a control, the control deviation of the thread tension being controlled as a function of the control constant. A PI controller is preferably used to regulate the thread tension. The PI controller has an integration factor and a proportionality factor, which influence the behavior of the controller. The influence of the two factors on the controller is different. If the PI controller is too sensitive, this sensitivity can be influenced by changing the integration factor. If the controller is too slow, the proportionality factor can be increased. It should be noted that on the one hand the controller does not become unstable or on the other hand it does not become too slow and sluggish.

In a preferred exemplary embodiment, the control behavior of the PI controller is influenced at defined time intervals, which are very large can be, which means that the influence can be very slow. Ideally, in a further preferred exemplary embodiment, the control behavior of the PI controller can be influenced automatically via a control.

Further advantages and possible applications of the invention will now be explained in detail with reference to the accompanying drawings.

Fig. 1

ein Diagramm der Abhängigkeit der Fadenspannung von der Stellgröße S, daß die Unterschiede einzelner Friktionsfalschdrall-Aggregate veranschaulicht;

Fig. 2

ein Diagramm der Fadenspannung über der Stellgröße S, daß eine zeitliche Veränderung der Fadenspannung an einem Friktionsfalschdrall-Aggregat veranschaulicht;

Fig. 3

ein Diagramm der Fadenspannung über dem Verstellsignal VS in Abhängigkeit von der Fadengeschwindigkeit;

Fig. 4

ein Reglerkennfeld;

Fig. 5

ein Diagramm der Abhängigkeit des Proportionalitätsfaktors des Reglers in Abhängigkeit von der Steigung ΔT/(ΔD/Y);

Fig. 6

die Abhängigkeit des Integrationsfaktors des Reglers von der Steigerung ΔT/(ΔD/Y);

Fig. 7

eine Bearbeitungsstelle einer Falschzwirnkräuselmaschine in schematischer Darstellung gemäß der Erfindung;

Fig. 8

ein Ausführungsbeispiel eines Friktionsfalschdrall-Aggregats;

Fig. 9

das Friktionsfalschdrall-Aggregat in der Draufsicht.

Show it:

Fig. 1

a diagram of the dependence of the thread tension on the manipulated variable S that illustrates the differences between individual friction false twist units;

Fig. 2

a diagram of the thread tension over the manipulated variable S, which illustrates a temporal change in the thread tension on a friction false twist unit;

Fig. 3

a diagram of the thread tension over the adjustment signal VS as a function of the thread speed;

Fig. 4

a controller map;

Fig. 5

a diagram of the dependence of the proportionality factor of the controller as a function of the slope ΔT / (ΔD / Y);

Fig. 6

the dependence of the integration factor of the controller on the increase ΔT / (ΔD / Y);

Fig. 7

a processing point of a false twist crimping machine in a schematic representation according to the invention;

Fig. 8

an embodiment of a friction false twist unit;

Fig. 9

top view of the friction false twist unit.

1 shows a diagram of the thread tension over the manipulated variable S, which illustrates for the position curves indicated as parameters in the diagram that different curves of the thread tension over the manipulated variable S result for different friction false twist units of a false twist crimping machine. This surprising result is all the more remarkable since the same components and the same type of control were used for all friction false twist units. 1 also shows the determination of the slope D at the operating point B1. The slope D is formed by the quotient from the difference between the thread tension ΔT and ΔS. The slope D can also be formed as a differential of the thread tension T as a function of the manipulated variable S at the operating point B1.

Similarly, Fig. 2 shows a diagram of the thread tension T over the manipulated variable S. This diagram shows that when a new friction false twist unit is put into operation, the relationship between the thread tension and the manipulated variable S is approximately hyperbolic, during this course after an operating time of 20 hours is clearly stretched and more closely approximated to a straight line.

3 shows a diagram which shows the dependence of the thread tension T on the adjustment signal VS. The thread tension decreases with increasing adjustment signal VS. From the diagram it can also be seen that at a constant adjustment signal VS the thread tension increases with increasing thread speed.

Fig. 4 shows a controller map that shows the relationship between the controller constant K and the slope D. The controller map is determined by measurement or empirical calculations and given to the machine. From the controller map, the newly determined slope D can then be used to determine the controller constant K associated with this operating point, which is then supplied to the controller as a corrected value KR.

5 shows a diagram which shows the dependency of the proportionality factor of the controller on the quotients ΔT / (ΔD / Y), which is referred to as the slope. From this diagram it can be seen that the proportionality factor not only rises sharply with the slope, but also rises very sharply with falling yarn speed. The quotient defined as the slope expresses the change in thread tension as a function of the change in the twist / conveying ratio, the latter being the ratio of the effective diameter of the disks of the friction false twist unit to the thread running speed.

6 shows a diagram to illustrate the integration factor of the controller on the slope. The integration factor increases as a function of the thread running speed, the integration factor falling with increasing gradient. It can be seen from FIGS. 5 and 6 that with increasing thread running speed, based on a defined pitch D, the proportionality factor P decreases, while the integration factor I increases.

Fig. 7 shows a schematic representation of a processing point of a false twist crimping machine. The synthetic thread 1 is by the Input delivery unit 3 subtracted from the supply spool 2. The texturing zone is formed between the input delivery unit 3 and the take-off delivery unit 9. It mainly comprises a heating rail 4, a cooling rail 5 and the friction false twist unit 6. The friction false twist unit has endlessly moving surfaces which are moved transversely to the thread axis and against which the thread lies. These endlessly moving surfaces are preferably designed as discs that are rounded on the outer edges. These surfaces give the thread a twist in the direction of the input delivery unit, which dissolves again in the direction of the output delivery unit 9.

A measuring device 8 for measuring the thread tension, which outputs the thread tension T from the output signal, is arranged between the friction false twist unit 6 and the output delivery mechanism 9. Not shown in FIG. 5 is a winder arranged behind the output delivery unit 9 or also an intermediate treatment by heating, which may be necessary there.

The output signal T of the measuring device 8 for measuring the thread tension, which represents the thread tension T, is converted via a filter 11 into a long-term value LW. The long-term value LW is supplied to a control device 12 together with a target value. In the control device 12, the target value and the long-term value are compared with one another and converted into an adjustment variable VS. On the basis of this adjustment value, its control behavior is influenced by a PI controller 13 by taking into account the ratio of the change in the thread tension to the change in a current value corresponding to the adjustment variables, ie the proportionality factor and / or the integral factor of the controller are influenced. This adjustment variable corrected in this way is fed to an actuator 7 of the friction false twist unit 6, the actuator 7 being the Swirl transmission of the friction false twist unit 6 on the thread 1 controls. The output signal T of the measuring device 8 for measuring the thread tension as well as the adjustment signal is fed to an evaluation device 10. In the evaluation device 10, the adjustment signal represents the adjustment signal of the thread tension corrected by the PI controller 13 by the ratio ΔT / ΔI. The evaluation device 10 provides an evaluation of the current output signal T, which represents the currently measured thread tension, in accordance with the principles described in EP 207 471 A1.

This means that an upper limit value and a lower limit value for the adjustment signal VS (GOVS, GUVS) are stored in the evaluation device 10. If the adjustment signal VS exceeds one of these limit values, an alarm signal is preferably output. Furthermore, a difference value DU is formed in the evaluation device 10 between the current output signal T and the adjustment signal VS after both have previously been converted into compatible, comparable quantities. Finally, the upper limit value and the lower limit value of this difference signal DU (GODU; GUDU) are stored in the evaluation device 10, and an alarm signal A is preferably output when the difference signal DU between the adjustment signal and the currently measured output signal D is one of the limit values GODU, GUDU exceeds.

The friction false twist unit 6, as shown in FIGS. 8 and 9, has three parallel shafts 16, 17 and 18 arranged in the corner points of an equilateral triangle. The shafts 16, 17 and 18 are rotatably mounted in a frame 19. The shaft 16 serves as a drive shaft which is driven by a drive belt 20. The transmission of the rotary movement from the shaft 16 is carried out by two drive belts 21, 20, which are guided by pulleys 23, 24 and 25. The pulley 23 is on the shaft 17, the pulley 24 on the shaft 18 and the pulley 25 arranged on the shaft 16. The pulley 25 is designed as a double pulley, so that the drive belts 21, 22 are guided over it.

In the exemplary embodiment shown, the friction false twist unit 6 has two groups of disks 26, 27, 28; 29, 30, 31, the number of disks 26, 27, 28; 29, 30, 31 of each group corresponds to the number of rotating shafts 16, 17, 18. Accordingly, the first group of disks 26, 27, 28 and the second group of disks 29, 30, 31 comprises. The disks of each group follow each other in the thread running direction with the same distance.

The disks 26, 27, 28; 29, 30, 31 are connected to the shafts 16, 17, 18 in a non-positive or positive manner. However, each disc can be pulled off its shaft. In order to set and maintain the distance between the disks 26, 27, 28, 29, 30, 31 of a shaft 16, 17, 18, different sleeve-shaped spacers 32, 33, 34, 35, 36 are provided over each shaft 16, 17, 18 , 37 pushed. For axially fixing the spacers 32, 33, 34; 35, 36, 37 and the disks 26, 27, 28, 29, 30, 31 serve screws 38 in the head of each shaft, 16, 17, 18. The shaft distances and the disk diameter are designed so that - as in Fig. 9 - the disks 26, 27, 28 and the disks 29, 30, 31 overlap. Due to the overlap, a so-called "overlap triangle" with arc-shaped sides is formed. Between the sides of this triangle, the thread 1 is tensioned on its course by the friction false twist unit between the disk groups to form a helix. It is possible to use a friction false twist unit with more than three disks and therefore with more than three shafts each disk group.

Each disk 26, 27, 28, 29, 30, 31 has a friction surface 39.

In the method for regulating the thread tension of a running thread 1, the angle between the thread running direction and the direction of movement of the friction surface 39 is measured as a manipulated variable. In addition to the angle as a manipulated variable, the distance between the shafts 16, 17, 18 can also be measured as a manipulated variable. Since the contact pressure of the friction surfaces 39 has an influence on the thread tension of a running thread, the contact pressure of the friction surfaces can be measured as a manipulated variable.

REFERENCE SIGN LIST

1

thread

2nd

Supply spool

3rd

Incoming delivery plant

4th

Heating rail

5

Cooling rail

6

Frictional false twister

7

Actuator

8th

Thread tension meter

9

Output plant

10th

Evaluation device

11

filter

12th

Control device, PI controller

13

Converter

14

Measuring device

15

Timer

16.17, 18

wave

19th

frame

20,21,22

Drive belt

23,24,25

Pulley

26,27,28

disc

29.30.31

disc

32,33,34

Spacers

35,36,37

Spacers

38

screw

39

Friction surface

A

evaluation

F

filter

VS

Adjustment signal

GOVS

upper limit for the VS

GUVS

lower limit for the VS

B1

Operating point

D

Slope at the operating point

I.

Controller constant

KR

Controller constant

P

Controller constant

S

Manipulated variable

T

Thread tension

Z.

Disturbance variable

Claims (16)

Method for controlling the thread tension of a running thread behind a friction false twist unit of a false twist machine, in which the thread tension (T) behind the friction false twist unit (6) is measured and regulated by the fact that the deviation of the thread tension caused by a disturbance variable (Z) ( T) is converted from a predetermined target value of the thread tension by means of a control device with a predetermined controller constant (s) (I, P) into an adjustment signal (VS) for controlling a manipulated variable (S) of the friction false twist unit (6),
characterized,
that the regulator constant (s) (I, P) is corrected during the regulation as a function of the disturbance variable (Z) acting on the friction false twist unit (6) or a controlled system. Method according to Claim 1, in which the influence of the disturbance variable (Z) is determined from the ratio between the thread tension (T) and the manipulated variable (S) at the current operating point (B). Method according to Claim 1, in which the influence of the disturbance variable (S) is determined from the ratio between the thread tension (T) and the adjustment signal (VS) at the current operating point (B). Method according to Claim 2 or 3, in which the correction of the controller constant (s) (I, P) is carried out in the following steps: a) Measurement of the manipulated variable (S1) or the adjustment signal (VS1) and the thread tension (T1) at the time (t1). b) Measurement of the manipulated variable (S2) or the adjustment signal (VS2) and the thread tension (T2) at the time (t2). c) Determination of the slope $\text{D = (T1-T2) / (S1-S2)}$

or $\text{D = (T1-T2) / (VS1-VS2)}$

. d) Determination of a corrected controller constant (KR) from a given controller map (KD). Method according to Claim 3 or 4, in which the controller map (K-D) is determined empirically by measurement or calculation. Method according to one of Claims 2 to 5, in which the rotational speed of the friction false twist unit (6) or the ratio rotational speed / thread speed is measured as a manipulated variable (S). Method according to one of Claims 2 to 5, in which the angle between the thread running direction and the direction of movement of the friction surface (s) (39) of the friction false twist unit (6) is measured as a manipulated variable (S). Method according to one of Claims 2 to 5, in which the center distance between the friction shafts (16, 17, 18) is measured as a manipulated variable (S). Method according to one of claims 2 to 5, in which the contact pressure of the friction surfaces (39) is measured as a manipulated variable (S). Method according to one of Claims 2 to 5, in which the entry angle between the friction surface (39) and the thread (1) is measured as a manipulated variable (S). Method according to Claim 1, in which the thread speed is measured as a disturbance variable (Z). Method according to Claim 11, in which the correction of the controller constant (I, P) is carried out in the following steps: a) Measurement of the thread tension (T) and the thread speed (V) at an operating point (B). b) Determination of the slope (D) from the controlled system characteristic field (T-VS). c) Determination of a corrected controller constant (KR) from a predetermined controller map (KD). Method according to one of the preceding claims, in which the correction of the regulator constant (s) (I, P) takes place at defined time intervals. Method according to one of Claims 1 to 12, in which the correction of the regulator constant (s) is carried out via a regulation. Method according to Claim 14, in which the control deviation of the thread tension is controlled as a function of the control constant. Method according to one of Claims 1 to 15, in which a PI regulator (12) with the regulator constants (P) and (I) is used to regulate the thread tension.

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