WO2003029538A2

WO2003029538A2 - Friction false twisting device and method for operating a friction false twisting device

Info

Publication number: WO2003029538A2
Application number: PCT/EP2002/010566
Authority: WO
Inventors: Reinhard Lieber; Michael Klug; Thomas Wortmann
Original assignee: Saurer Gmbh & Co. Kg
Priority date: 2001-09-27
Filing date: 2002-09-20
Publication date: 2003-04-10
Also published as: CN1617959A; WO2003029538A3; TWM283852U; EP1430171A2

Abstract

The invention relates to a friction false twisting device for false-twist texturing synthetic yarns and a method for operating said friction false twisting device. Said friction false twisting device comprises at least one friction false twisting unit having a separate electric motor drive, supplied by a common controllable electric power supply system, for driving a friction means. According to the present invention, the rotational speed of the electric motor or friction means is detected by a speed sensor. The measurement signal of the speed sensor, which is integrated in the friction false twisting unit, is outwardly led to an external evaluation device. The speed of each friction false twisting unit can thus be evaluated and, in case of too strong a speed drop, only the corresponding friction false twisting unit can be switched off or a warning message can be transmitted to the operator. Speed monitoring prevents overloads of the friction false twisting units and permits defects, such as yarn windings or storage damages, to be detected. By averaging the speed values, the determined mean value can be input, as a controlled variable, in speed regulators comprised in said controllable electric power supply system.

Description

Frictional false twist device and method for operating a frictional false twist device

The invention relates to a friction false twist device according to the preamble of claim 1 and a method for operating the friction false twist device.

A friction false twist device includes friction false twist units, as are known, for example, from EP 0 744 480, and their power supply. The well-known friction false twist unit for false twist texturing of synthetic threads contains a friction agent with stacks of overlapping disks rotating in the same direction, which are arranged on shafts arranged in parallel in the corner points of an equilateral triangle and on which a twist due to the gussets formed between the disks by rotation Thread is exercised.

The three rotatably mounted stacks of friction disks are coupled to one another via a belt or the like in such a way that the stacks of friction disks rotate in the same direction and at the same speed. The drive takes place via an electric motor drive assigned to the friction means and connected to the friction disk stacks. As a rule, an asynchronous motor is used for this purpose, which is operated together with the motors of other friction false twist units on a common controllable power supply, usually a converter.

To protect against damage due to overload, each motor must have its own protective device that protects the electrical system against both short-term overcurrents and long-term overloading. For this purpose, for example, a fusible link and a bimetallic fuse are used for each false friction swirl unit. In terms of a safer false twist texturing process and a documented, uniformly good quality of the thread, the exclusive protection of the unit against damage is not sufficient.

It is therefore an object of the invention to further develop a frictional false twist device of the type mentioned at the outset such that the purely protective function of the electrical system also allows impending functional changes in the frictional false twist aggregates to be recognized and documented or reported, and to develop a suitable method for operating the frictional false twist device.

This object is achieved according to the invention in that the friction false twist assemblies contained in the friction false twist device have a speed sensor connected to the drive or to the friction means, so that a continuous evaluation of the signal of the speed sensor is possible.

The advantage of the invention is that both suddenly occurring and continuously emerging disturbances can be easily detected. The invention takes advantage of the fact that the electric motors that are possible for a friction false twist unit have a falling speed-torque characteristic. If a friction false twist unit is now loaded with an additional braking torque due to a malfunction, this is noticeable by a decrease in the speed, which can easily be detected by a speed sensor.

The signal of the speed sensor is passed on to the outside for the purpose of external further processing, without it being evaluated within the friction false twist unit in terms of regulation, control or monitoring.

It is particularly advantageous to use the speed sensor in conjunction with an asynchronous motor, since there is a defined relationship between the load torque and the slip, the slip being easily derived from the field frequency and the measured speed can be determined. However, direct current motors or synchronous motors are also suitable for driving the friction means. Driven, overlapping friction disk stacks or friction belts or combinations of friction disks and friction belts can be used as the friction means.

As a speed sensor, for example, a sensor operating on the tachogenerator principle or similar is conceivable, which emits an analog measurement signal that is essentially proportional to the speed.

Another advantageous variant of the speed sensor emits a fixed number of pulses per revolution of the drive or, for example, the friction disk stack. These pulse sequences can be read in and processed further very simply and precisely by digital signal processing devices. In the case of an asynchronous motor, the evaluation is particularly simple when the speed sensor generates the same number of pulses per motor revolution as the motor has pole pairs. In this case, a characteristic value proportional to the slip can be formed by simply forming a difference between the sensor pulse frequency and the converter frequency.

In the friction false twist device according to the invention, the monitoring of the rotational speed in the friction false twist units is realized particularly simply and economically if the signals of the speed sensors of a plurality of friction false twist units are evaluated jointly by an evaluation device.

The speed sensors are particularly advantageously connected to the evaluation device via a local fieldbus system when carrying out the electrical installation.

When using friction disk stacks as the friction means, the speed sensor can also advantageously be used directly with the friction disk stack or with assign shafts connected to the friction disk stacks.

In the method according to the invention for operating a friction false twist device according to the invention, the rotational speed or a value derived from the rotational speed, such as the slip, is continuously monitored. Continuous monitoring does not mean that this has to be done continuously. Rather, it makes economic sense to query and monitor these cyclically one after the other when monitoring a large number of signals from the speed sensors.

If the method detects that a characteristic value formed from the rotational speed, such as the slip, exceeds a limit value by a predetermined amount of deviation, the method assumes a malfunction due to stiffness or blockage and switches off the frictional false twist unit concerned. This corresponds to the motor protection by a fuse.

A further development of the method additionally monitors for tighter limit values taking into account the duration and the amount of the exceedance. As a result, the drive can be effectively protected against overheating with less stiffness. This corresponds to motor protection with a bi-metal fuse. A sensible monitoring strategy is based on the fact that the motor overtemperature results from the power loss minus a cooling capacity multiplied by the duration of the overload. If the characteristic value lies above a threshold value, the difference between the characteristic value and the threshold value can be calculated as an integral by integrating or adding up the excess amount over time, and an error can be identified by comparing the integral thus obtained with a limit value.

In an additional advantageous variant of the method, the historical development of the speed characteristic value, for example the slip, is used for monitoring. A slip that increases steadily in a short time can indicate, for example, a thread winder forming around a friction disc stack. An increasing slip over a longer period of time can can be caused, for example, by bearing damage in the friction false twist unit. Here the method responds accordingly by generating an error signal.

The method uses different reactions depending on the type of error signal. In the event of serious errors that can damage the friction false twist unit on the drive or on the friction disk stacks, the drive of the friction false twist unit concerned must be stopped immediately. This applies if the slip exceeds a high threshold value for a short time or a low threshold value over a longer period. In the case of a thread winder forming around a friction disc stack, the unit must also be stopped.

In other situations, only the operating personnel are alerted with a malfunction indicator in order to rectify the malfunction at the appropriate time.

In an advantageous development of the invention, the error signals or characteristic values formed from the error signals are stored and taken into account in a quality assessment of the yarn. For example, a yarn in which one of the above-mentioned errors occurred during further processing is downgraded to the quality level. This also applies to errors in which the friction false twist unit has not been switched off.

In a further advantageous development of the invention, the speed values of all the friction counter-rotation units that are collectively driven in the friction false-twist device by a converter are averaged and fed to the converter in the sense of a regulation. This has the advantage that when the setpoint speeds for the friction false twist units are set, the actually realized speed is usually not known and can only be estimated or must be fine-tuned later when the process is optimized. In contrast, with averaging and feedback to the converter and regulation of the average speed, it is ensured that the specified speed actually averages is achieved. Due to the generally sufficiently high number of friction false twist units which are operated on one converter, a significant decrease in the speed of an individual unit has only a slight influence on the average speed, so that the following control intervention changes the speed of the other friction false twist units only slightly increased.

An embodiment is described below with reference to the accompanying drawings.

They represent:

1 shows a friction false twist unit of the friction false twist device according to the invention,

2 a friction false twist device according to the invention,

3 shows the time course of the speed characteristic value in the event of a fault,

Fig. 4 shows the time course of the speed parameter in another fault.

FIG. 1 shows a friction false twist unit of the friction false twist device according to the invention. The friction swirl unit 1 has a friction medium consisting of a plurality of friction disc stacks 2.2 and a plurality of shafts 2.1 connected to the friction disc stack. The thread, not shown here, is passed through the gusset formed between the disks 3 mounted on the friction disk stacks 2.2 and twisted through the peripheral surfaces of the disks 3 rotating in the same direction and at the same speed. The axes of the friction disc stacks 2.2 span a prism with an equilateral triangle as the base. The friction disk stacks 2.2 are rotatably mounted on the shafts 2.1 in the bearing block 4. On the other side of the bearing block 4, the shafts 2.1 driving the friction disk stacks 2.2 protrude and are connected to one another by a belt drive 5 in such a way that the friction disk stacks 2.2 rotate in the same direction and at the same speed. In addition, one of the shafts 2.1 is connected to a further belt drive 6, which connects the shaft to an electric motor 7. The interaction of the two belt drives 5 and 6 causes the electric motor 7 to drive all of the friction disk stacks 2.2.

The invention is not limited to a connection of the shafts 2.1 by means of belt drives. Other transmission techniques are known to the person skilled in the art and can likewise be used in the sense of the invention. Other friction means such as friction belt drives can also be used. '

The voltage supply line 8 connects the electric motor 7 to a controllable voltage source, not shown here, preferably to a converter. An asynchronous motor is preferably considered as a motor, but other electric motors, for example direct current motors or synchronous motors, are also conceivable.

A speed sensor 10 is installed on the shaft of the electric motor 7. Also conceivable and in the sense of the invention is an installation of the speed sensor 10 in the area of the friction medium, for example the friction disk stack 2.2, as shown in FIG. 1 as an alternative with a broken line. The speed sensor could also be installed on one of the shafts 2.1 or by coupling it into its own pulley on one of the belt drives 5 or 6. The speed sensor 10 supplies either a signal proportional to the speed or a pulse train which is proportional to the speed. This is advantageous if an asynchronous motor is used. This is particularly the case when the speed-frequency ratio of the sensor matches that of the motor. The signal that is present on the signal line 11 is either an analog voltage or current signal that is proportional to the speed or one that is proportional to the speed. proportional frequency. However, it is also conceivable that the speed sensor 10 contains a conversion module for a local area network. In this case, the signal line 11 is the connection to the next network connection.

FIG. 2 schematically shows a friction false twist device according to the invention with several friction false twist units 1. A controllable voltage supply, in this example a converter 13, generates a supply voltage which determines the speed of the friction false twist units and is output via the voltage supply network 12. Each of the friction false twist units 1 is connected with its voltage supply line 8 to the voltage supply network 12. The signal line 11 of the friction false twist units are either connected in a star shape to a speed signal evaluation 16. In the case of a large number of friction false twist units 1, a high amount of wiring is to be expected. In this case, it is advantageous if a network connection is used for the signal lines 11, so that the signal lines 11 only have to be coupled into the signal line network 15 at a branch 14.

The signal line network 15 passes the speed signals to a speed signal evaluation 16. There, the individual speed signals are evaluated either by continuously monitoring all speed signals simultaneously or by cyclically querying and evaluating the individual speed values. In addition, depending on the further processing of the data, the measured speed can be converted into a slip value.

The result of the speed signal evaluation 16 can, for example, result in one of the friction false twist units 1 being switched off. For this purpose, the fault shutdown monitoring 17 outputs a signal on the shutdown signal network 19. As with signal line network 15 for the speed signal, it can also be either a star-shaped connection or a local network. From the switch-off signal branch 20, the switch-off signal line 21 is fed to a switch-off device 18, which the respective friction false twist unit 1 switches off in the event of a fault.

For the signal line network 15 for the speed signals and the shutdown signal network 19, in the case of a realization as a local network, it makes sense to physically provide both networks on a common network.

The result of the speed signal evaluation 16 can also lead, for example, to a message for the operator being output on a fault detector 22. The fault detector 22 can be arranged both centrally and decentrally. Thanks to an integrated display, the malfunction indicator can also provide special operating instructions, such as an indication of contamination of one of the friction false twist units 1.

The averaging of all speed signals is also integrated in the speed signal evaluation 16. It is self-evident for the person skilled in the art that speed signals recognized as having a fault are not used for averaging. The speed average value determined in this way is fed to the converter 13, in which case it is assumed that it is a converter with an integrated controller. The current output by the converter 13 via the voltage supply network is adapted in such a way that the speed average value corresponds to a predetermined setpoint.

In Figure 3, two different courses of a speed characteristic value are plotted over time. The slip is used here as the speed parameter. In the case of an asynchronous motor, the slip is the difference between the rotating field frequency and the measured speed related to the rotating field frequency, the rotating field frequency being assumed to be constant in the figures shown here.

In the case of a DC motor, the idling speed should be used here instead of the rotating field frequency.

The course of the slip signal 24.1 increases due to a defect. The Limit value 25 is stored in the speed signal evaluation 16 in FIG. 2 and represents the load limit of a drive for short-term overloads. As soon as the slip signal 24.1 exceeds the limit value, a signal is triggered which is forwarded to the fault shutdown monitoring 17 in FIG. 2, where the shutdown signal network is used 19, a switch-off signal is sent to the switch-off device 18 which is associated with the friction-triggering swirl unit 1 which triggers the fault and which switches off the friction-counter-swirl unit in question. In addition, a fault message can be displayed on the fault detector 22 in FIG. 2.

The course of the slip signal 24.2 exceeds a threshold value 26, which is set as a limit value for permanent overloads. The amount by which the slip signal exceeds the threshold of the limit value violation 26 is integrated into the integrated limit value violation 27. The integral is shown in FIG. 3 as a surface under the slip signal 24.2. As soon as this area exceeds a limit value at point 28, the friction false twist unit 1 in question is switched off, as explained above. The monitoring described here makes use of the knowledge that there is a constant relationship between slip, torque and power loss. The conversion of the power loss causes the drive to heat up so that the shutdown prevents overheating.

Figure 4 shows two further monitoring points. Two curves of the slip signal 24.3 and 24.4 are shown in the upper area. The lower area shows the time derivative of the slip signals 29 and 31. The slip signal 24.3 has a slow rise, the derivative 29 of which falls within a limit area 30. This limit area 30 is selected such that slowly increasing slip signals, such as those that occur in the event of bearing damage, can be detected. In this case, the malfunction with the possible cause is reported to the operator via the malfunction indicator 22 shown in FIG.

The slip signal 24.4 has a rapid rise, the derivative 31 of which falls into a higher limit area 32. This limit area 32 is selected such that for example, thread winder forming around the friction false twist unit 1 can be detected. In this situation, the friction false twist unit 1 in question must be switched off in the manner described above.

LIST OF REFERENCE NUMBERS

1 friction false twist unit

2.1 Stack of friction disks

2.2 wave

3 friction disc

4 bearing block

5 belt drive

6 belt drive

7 electric motor

8 power supply line

9 housing

10 speed sensor

11 signal line

12 power supply network

13 Controllable power supply

14 branching

15 signal line network

16 Speed signal evaluation

17 Fault shutdown monitoring

18 switch-off device

19 Shutdown signal network

20 switch-off signal branch

21 shutdown signal line

22 malfunction detectors

23 Average speed value

24.1 slip signal

24.2 Slip signal

24.3 Slip signal

24.4 slip signal

25 limit Threshold Integrated limit exceeded Limit differentiated slip signal limit range Differentiated slip signal limit range

Claims

claims

1. Frictional false twist device for false twist texturing of endless threads, comprising several frictional false twist units (1), each with one

Friction means (2.1, 2.2) for twisting the thread, and with an electric motor (7) for driving the friction means (2.1, 2.2), as well as containing a controllable power supply (13) which is connected to the electric motors (7) of the friction false twist units (1) characterized in that the friction false twist units (1) each have a speed sensor (10) connected to the electric motor (7) or to the friction means (2.1, 2.2).

2. Frictional false twist device according to claim 1, characterized in that the frictional false twist units (1) each have an external signal line

(11), at which the signal of the speed sensor (10) is output.

3. Frictional false twist device according to claim 1 or 2, characterized in that the electric motors (7) are formed by asynchronous motors.

4. Frictional false twist device according to one of claims 1 to 3, characterized in that a signal proportional to the speed is present on the signal lines (11) of the speed sensors (10).

5. Frictional false twist device according to one of claims 1 to 3, characterized in that the signal lines (11) of the speed sensors (10) each have a pulse sequence corresponding to the speed or a multiple of the speed.

6. Frictional false twist device according to claim 5, characterized in that that the number of pulses generated per revolution by the speed sensors (10) corresponds to the number of machine pole pairs of the asynchronous motors (7).

7. Frictional false twist device according to one of claims 1 to 6, characterized in that a speed signal evaluation (16) is provided, which is connected to the speed sensors (10) of the frictional false twist units (1).

8. Frictional false twist device according to claim 7, characterized in that the speed sensors (10) of the frictional false twist units (1) and the speed signal evaluation (16) are connected to one another by a fieldbus system.

9. Frictional false twist device according to one of the preceding claims, characterized in that the friction means have a plurality of coaxial friction disc stacks (2.2) arranged on parallel shafts (2.1), which shafts (2.1) are connected to the electric motor (7), and that the speed sensor (10) is assigned to the friction disc stacks (2.2).

10. A method for operating a friction false twist device according to one of the preceding claims, characterized by the method steps:

10.1. Interrogation of the signal of the speed sensor (10) in each case of a friction false twist unit (1);

10.2. Formation of a speed characteristic value in each case;

10.3. Comparison of the respective speed characteristic value with a comparison value and determination of the deviation and

10.4. Generation of an error signal if the deviations exceed a limit.

11. The method according to claim 10, characterized in that the comparison value is a target speed and that the limit value is a permissible deviation from the target speed.

12. The method according to claim 10, characterized by the additional method steps:

12.1. Consideration of the deviation only in one direction;

12.2. Formation of the integral (27) of the deviation over time;

12.3. Comparison of the integral with a limit value and

12.4. Generation of an error signal if the integral exceeds the limit.

13. The method according to any one of claims 10 to 12, characterized in that the comparison value is determined from one or more previously determined speed parameters and that an error signal is generated after the speed has decreased continuously over a defined period of time.

14. The method according to any one of claims 10 to 13, characterized in that with the generation of an error signal, the associated friction false twist unit (1) is switched off.

15. The method according to any one of claims 10 to 14, characterized in that with the generation of an error signal, a fault detector (22) active fourth.

16. The method according to any one of claims 10 to 15, characterized in that with the generation of an error signal, this is assigned to the yarn processed by the respectively assigned friction false twist unit (1), stored and consulted during a quality assessment of the yarn.

17. The method according to any one of claims 10 to 15 or the preamble of claim 10, characterized by the method steps:

17.1. Querying the signals of the speed sensors (10) of all friction false twist units (1);

17.2. Averaging the signals and

17.3. Regulation of the mean value by changing the voltage supply to the electric motors (7).