AU592719B2 - Paper making machine dryer section - Google Patents

Description

c.)lc~ r I mr~--m AUSTRALIA D PATENTS ACT 1952 COMPLETE SPECIFICATION 92 19 Form

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: ih; document contains the al-iy-dments made under Section 49 and is correct for printing.

Related Art: TO BE COMPLETED BY APPLICANT ,a a a a a Name of Applicant: Address of Applicant: KABUSHIKI KAISHA TOSHIBA 72 HORIKAWA-CHO

SAIWAI-KU

KAWASAKI-SHI

KANAGAWA-KEN

JAPAN

Actual Inventor: Address for Service: 4" t t GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

I 6 a Complete Specification for the invention entitled: PAPER MAKING MACHINE DRYER SECTION The following statement is a full description of this invention including the best method of performing it known to me:- 1A- Background of the Invention i. Field of the Invention The present invention relates to an improvement of a paper making machine dryer section and, more particularly, to a drive system for driving rolls of a dryer section.

2. Description of the Related Art U.S. Patent No. 3,815,256 discloses an example of paper making machine dryer section driver, but this type has various shortcomings such as its having a large number of parts.

A solution to the problems is proposed in U.S.

Paten Nos. 4,495,711 and 4,495,712; the disclosed dryer V Vt d section drivers comprise a plurality of motors for S 15 directly driving canvas rolls or cylinder rolls and controllers for controlling the motors in such a way that the rotational speeds of the individual rolls are S, synchronized with one another.

According to the structures as disclosed in those two U.S. patents, driven rolls are in synchronism with !isijone another and they have the same rotational speed.

A paper web is wet at the inlet of the dryer and is dry at the outlet, and it is desirable to vary the paper conveying speed even in a single dryer. With driven rolls being rotated in synchronism with one another, however, it is difficult to realize such a speed change.

Further, in the dryer section driver, a paper web may be 2 r 4 -2torn or wrinkled when a load applied to each motor varies due to some cause.

Summary of the Invention Accordingly, it is an object of this invention to provide a paper making machine dryer section in which driven rolls can be controlled at the proper speed and under the properly distributed load.

To achieve the object, there is provided a paper making machine dryer section which comprises: conveying means having a plurality of cylinder rolls (lA-iF), a plurality of canvas rolls (2A-2H) and canvases running between the cylinder rolls (IA-IF) and the canvas rolls (2A-2H), the conveying means for drying a paper web to be dried while conveying the I paper web a plurality of motors (4A-4H), coupled to associated rolls of the cylinder rolls (IA-IF) and the canvas rolls (2A-2H), each for driving at least one of the associated roll, whereby the paper web to be dried is conveyed in a predetermined path and is dried by the cylinder rolls (IA-IF) and the canvases and motor controllers (14A-14H), respectively provided to the motors (4A-4H), for individually controlling speeds and load distribution of the motors (4A-4H). With the above arrangement, the dryer section of this invention can separately control the motors for driving rollers in the proper mode, thereby preventing 3 a paper web to be dried from being torn or wrinkled.

Brief Description of the Drawings Fig. 1 is a diagram illustrating the arrangement of a dryer section according to the first embodiment of this invention; Fig. 2 is a diagram illustrating the arrangement of a dryer section according to the second embodiment of this invention; Fig. 3 is a diagram illustrating the arrangement of a dryer section according to the third embodiment of this invention; Fig. 4 is a diagram illustrating the arrangement of L a dryer section according to the fourth embodiment of ,this invention; 15 Fig. 5 is a diagram illustrating the arrangement of a dryer section according to the fifth embodiment of this invention; and Fig. 6 is a diagram for explaining a drooping function.

Detailed Description of the Preferred Embodiments 3A paper making machine dryer section according to the first embodiment of this invention will be described below with reference to Fig. 1.

Fig. 1 illustrates the arrangement of a dryer section according to the first embodiment of this invention. This dryer section is disposed at the back of wire and press sections of a paper making machine, -4and at the back of the dryer section are lJisposed a calender section and a reel section.

Pulp liquid is led to the wire section for dehydration and is pressed in the press section to become a wet paper. This wet paper is dried in the dryer section shown in Fig. 1, is finished in the calender section and is wound up in the reel section.

j In Fig. 1, three cylinder rolls 1A to 1C and four canvas rolls 2A to 2D are arranged in cooperative staggered fashion at a lower stage. Similarly, three cylinder rolls 1D to 1F and four canvas rolls 2E to 2H1 are arranged in cooperative staggered fashion at an upper stage. An upper canvas (felt) 3 for guiding the wet paper around the cylinder rolls and drying it is running between the upper rolls, and a lower canvas 3 is running between the lower rolls.

The wet paper fed out from the press section is sequentially alternately wound around the upper cylinder rolls 1 and the lower cylinder rolls 1. The paper, which is indicated by the broken line W in Fig. 1, is dried by heated cylinder rolls 1 and canvas 3.

Eight motors 4A-4H are provided to eight canvas rolls 2A-2H in one to one association. In this embodiment, motor 4A serves as a main motor with the others serving as auxiliary motors. The individual canvas rolls 2A-2H are coupled directly or through a decelerator to the respective motors 4A-4H. Canvases 3 are driven by canvas rolls 2A-2H, so are cylinder rolls IA-IF but indirectly. Motor controllers 14A-14H are provided to motors 4A-4H in one to one association.

As will be described later, main motor controller 14A controls the speed of main motor 4A and auxiliary motor controllers 14B-14H controls the load torques of auxiliary motors 4B-4H. The motor controllers 14A-14H separately control the associated motors 4A-4H.

Main motor controller 14A comprises a speed controller 7, an adder 9, a switching power source 6 including a switching controller 6A and a chopper 6B, and a current detector 8 for detecting the oiitput current of switching power source 6. Switching power

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source 6 has its input terminal coupled to, for example, a main power source PS and its output terminal coupled to main motor 4A. The rotational shaft of main motor 4A is coupled co a speed sensor 5, tacho-generator.

Speed sensor 5 outputs a speed signal SS (also a function of the speed of conveying the paper W) corresponding to the rotational speed of the motor. This speed signal SS is supplied to the minus input terminal of speed controlle r 7. A signal SREF representing the reference (system reference) of the paper conveying speed in this paper making machine is supplied through a draw adjuster 11 (voltage divider) to the plus input terminal of speed controller 7. An adjustment value of draw adjuster 11 is set in consideration of the draw 1 l' -6given to the dryer section, and the output signal. DREF of draw adjuster 11 represents the reference of of the I paper conveying speed in the dryer section. Speed controller 7 attains the difference between the speed signal SS and reference signal DREF and outputs a speed control signal SC corresponding to this difference. The speed control signal SC, also representing the amount of increase or decrease in the armature current that should be supplied to main motor 4A, is supplied to adder 9 which is also supplied with the output signal of current detector 8. The output signal of adder 9 is supplied to switching power source 6. Based on the input signal, switching controller GA of switching power source 6 controls the ON time (in the case of PWM), ON frequency (in the case of PFM), etc. of chopper GB to control the output current of the chopper, thereby controlling main motor 4A so that its rotational speed becomtes equal to the rotational speed defined by the reference signal DREF. Currenit detector 8 detects the effective (mean) current from main motor 4A and sends its corresponding signal to adder 9. Adder 9, switching power source 6 and current detector 8 forms a minor current loop.

Each ,of auxiliary motor controllers 14B-14H comprises a switching power source 6 including a switching controller GA and a chopper 6B, a current detector 8 and an adder 9. The speed control signal Sc from speed controller 7 of main motor controller 14A is 7 i| supplied to load adjusters 12B-12H, which are provided to auxiliary motors 4B-4H in one to one association.

The load adjusters 12B-12H subject the received speed control signal SC to voltage division in accordance with the loads of the individual motors and send the resultant signals MSC as a current indication signal to the respective adders 9 each supplied with the output signal of its associated current detector 8. The switching controller 6A of switching power source 6 controls the ON time, ON frequency, etc. of the chopper 6B in accordance with the output signal of adder 9. Current detector 8 detects the output current of power source 6 and sends its output signal to adder 9.

So 9 It is assumed in this embodiment that the overall °0o 15 dryer section needs 100 KW of driving force and the main motor has 30 KW of driving force and each auxiliary 4, motor has 10 KW of driving force. In this case, the signal output to input ratios of load adjusters 12B-12H are set to 1/3 (10/30). With the signal SREF indicating 600 m/min, for example, the output signal DREF of draw adjuster 11 is set to a value indicating 596 m/min.

A description will now be given of the operation of 4 the dryer section arranged as shown in Fig. 1.

Canvas rolls 2A-2H are rotated by motors 4A-4H, and 'cylinder rolls 1A-1F and canvases 3 are indirectly driven by the motors. The wet paper W fed from the press section alternately passes between the upper

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r i i i 27 8 cylinder rolls ID-1F and the upper canvas 3 and the lower cylinder rolls IA-IC and the lower canvas 3 and is dried during this conveyance. The dried paper W is then sent to the calender section.

In this embodiment, in the normal state, main motor 4A and each of auxiliary motors 4B-4H respectively share KW and 10 KW loads, and the wet paper W is conveyed on canvas roll 2A at the speed of 596 m/min.

Let us consider the case where the paper conveying i0 speed becomes lower than what is indicated by the reference signal DREF due to an increase in load. Speed controller 7 attains the difference between the reference signal DREF and speed signal SS and outputs the speed control signal SC of a positive level corresponding to the difference. Adder 9 adds the speed control signal SC and the signal indicating the current which is presently supplied to main motor 4A and is detected by current detector 8. Based on the output signal of adder 9, switching controller 6A controls the ON time, on frequency, etc. of the chopper 6B. In this example, the level of the speed control signal SC is positive. The level of the output signal of adder 9 is greater by the level of the speed control signal SC than the one corresponding to the effective value of the current presently supplied to main motor 4A. Therefore, switching controller 6A increases the ON time, ON frequency, etc. of the chopper 6B to thereby increase the effective value ii

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i l! i t I 9 of the current that is to be supplied to main motor 4A.

Current detector 8 detects the effective current supplied to main motor 4A and supplies the corresponding signal to adder 9 to thereby execute the current minor loop control. The above control operation is repeated until the level of the speed control signal SC becomes zero. The control system becomes stable when the effective value of the current supplied to main motor 4A increase, the torque of the motor 4A increases ac:ordingly, and the rotational speed of the motor 4A increases to become the speed indicated by the reference signal DREF. As a result, main motor 4A is driven at a constant speed as defined by the reference signal DREF.

As said earlier, in this embodiment, the signal output to input ratios of load adjusters 12B-12H are set to 1/3, so that the level of the speed control signal SC from speed controller 7 is reduced to 1/3 and is supplied as the signal MSC to adders 9 of auxiliary motor controllers 14B-14H. Adders 9 are also supplied with the signals from current detectors 8 which indicates the values of the currents generated from switching power sources 6. In this example, the level of the speed control signal SC is positive, and the levels of the output signals of adders 9 are greater by the level of the signal MSC than the one corresponding to the effective values of the currents presently supplied to auxiliary motors 4A-4H. The switching controllers 6A of r I 00 i S- i0 power sources 6 increase the ON time, ON frequency, etc.

i of the choppers 6B to thereby increase the effective values of the currents supplied to auxiliary motors 4B-4H. The amount of the current increase here differs from that of main motor controller 14A. Accordingly, the drive current control (torque control) is executed.

The above operation is repeated until the level of the speed control signal SC becomes zero. The control system becomes stable when the rotational speed of main 1 0 motor 4A equals the one indicated by the reference signal DREF Assume now that the paper conveying speed becomes 0I greater than what is indicated by the reference signal 14 2 DREF due to a decrease in load. Let us consider the operation of main motor controller 14A in this case.

Speed controller 7 outputs a speed control signal SC of a negative level. The level of the output signal of V adder 9 is smaller by the level of the speed control signal SC than the one corresponding to the effective value of the current presently supplied to main motor 7 4A. Switching controller 6A reduces the ON time, ON frequency, etc. of chopper 6B to decrease the effective value of the current supplied to main motor 4A. Let us now consider the operation of auxiliary motor controllers 14B-14H. The level of the output signal of each adder 9 is smaller by the level of the signal MSC than the one corresponding to the effective value of the 11 current presently supplied to the associated one of auxiliary motors 4B-4H. The switching controller of each switching power source 6 reduces the ON time and ON frequency of the associated chopper to decrease the effective value of the current supplied to the associated auxiliary motor. This operation is repeated until the level of the speed control signal SC becomes zero.

With the above arrangement, even a load varies, main motor 4A can be controlled to be driven at a constant speed. The torques of auxiliary motors 4B-4H are increased or decreased in accordance with the sharing ratio of the load among auxiliary motors 4B-4H.

Accordingly, the individual motors are always driven in the proper states, thus ensuring conveyance a paper to be dried without tearing or wrinkling the paper.

The second embodiment of this invention will be described below referring to Fig. 2. In Fig. 2, those components shown in Fig. 1 are given the same numerals to omit their redundant explanation. Also, a minor structure is omitted from Fig. 2 for diagrammatic simplicity. The feature of the second embodiment lies in that cylinder rolls IA-1F are separately driven by motors 4A-4F. The control operation in this embodiment is substantially the same as that in the first embodiment although specific control parameters should be changed.

Referring to Fig. 3, a description will now be 12 7 given of the third embodiment which corresponds to a combination of the first and second embodiments as shown in Figs. 1 and 2. Motors 4A and 4E are respectively coupled to cylinder rolls IA and ID. Motors 4B-4D and motors 4F-4H are respectively coupled to canvas rolls 2B-2D and 2F-2H. In this case, the values of the currents supplied to the individual mcors and the values of load adjusters 12 are set in view of the difference in speed and torque of the motors and the 1, 0 shared loads of the motors, which are originated from the difference in diameter of the involved rolls.

Referring to Fig. 4, a description will now be given of the fourth embodiment which is a modification of the third embodiment. In this embodiment, motors are provided to canvas rolls 2B-2D and 2F-2H in one to one association. Cylinder rolls 1A and ID are mechanically coupled by means of a gear 13 and are driven by one motor 4A. The fourth embodiment is the same as the first one in that motor 4A serves as a main motor subjected to speed control while the other motors 4B-4H serve as auxiliary motors subjected to torque control in consideration of the load sharing.

Referring to Fig. 5, a description will now be given of the fifth embodiment. While the main motor is subjected to speed control and the auxiliary motors are subjected to torque control in consideration of the load sharing in the first through fourth embodiments, all the 'i, 1 r 13 motors are subjected to speed control in the fifth i embodiment.

In this embodiment, motors 4A-4H are respectively provided to canvas rolls 2A-2H, and speed detectors 5A-5H and motor controllers 14A-14H are provided to the motors 4A-4H in one to one association. The structures of motor controllers 14A-14H are substantially the same as the structure of motor controller 4A shown in Fig. 1.

These motor controllers 14A-14H commonly receive the reference signal DREF from draw adjuster 11. Speed controller 7 of each of motor controllers 14A-14H outputs a speed control signal SC based on the reference signal DREF and the speed signal SS from the associated one of speed detectors 5A-5H. Adder 9 attains the sum of the speed control signal SC and the signal indicating the effective current from the associated current I( detector 8. In accordance with the output signal from adder 9, the pulse width and pulse frequency of the associated switching power source 6 are controlled.

j§ 20 That motor controller 14 is selected which has a function to reduce the motor speed drooping function) with an increase in load torque as shown in Fig. 6. This function reduces the motor speed when a i load becomes greater, thereby properly maintaining the load shared between canvas rolls 2A-2H.

According to the first to fifth embodiments, with the driving capacities of the individual motors being -14properly set, the drive system can continue its operation even if one motor or one motor controller becomes inoperable. Assume now that, for the conventional dryer section in which a single motor drives all the rolls, the driving capacity needed for this motor is 100 KW.

If canvas rolls are driven by six motors each having a driving capacity of 22 KW, then the total driving i capacity is 6 x 22 132 KW. Even if one motor or motor controller becomes inoperable, the total driving capalo. 10 city of the remaining motors is 110 KW which is greater Sothan the necessary driving capacity. With this arrangement, therefore, even if a motor or a motor controller becomes inoperable, the paper making process can continue.

In the above embodiments, speed deviation is attained and the effective value of a current output from a chopper is varied in accordance with the speed thereby performing the speed control and torque control.

This invention is not, however, restricted to these embodiments. The motor controllers for executing the speed control and torque control of motors may have other known types of structures than that described above. For instance, switching power source 6 may be replaced by an ordinary variable power source or may not serve as a chopper. This invention may use DC motoxs and DC power sources as well as AC motors and AC power sources. For instance, ordinary structures for speed

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-7 control and torque control of motors can be utilized; a frequency controller may replace switching power source 6 for controlling the speed of an AC motor.

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77 37 7 7 3.7 7 7 7* 77 7 33

Claims (13)

1. A paper making machine dryer section comprising: I conveying means having a plurality of cylinder rolls, a plurality of canvas rolls and canvases running t between said cylinder rolls and said canvas rolls, said conveying means for drying a paper web to be dried while r conveying said paper web; 0 ,a plurality of motors, coupled to associated rolls of said cylinder rolls and said canvas rolls, each for I"p driving at least one of said associated rolls to thereby convey and dry said paper web to be dried in a predeter- mined path; and motor controllers, respectively provided to said t 15 motors, for individually controlling speeds and load distribution of said motors wherein a speed detector for detecting a rotational speed of a first motor in said plurality of motors is coupled to said first motor; and wherein a first motor controller for controlling said first motor controls the rotational speed of said first motor based on an output signal of said speed detector and a reference signal in view of a draw in such a way that said rotational speed of said first motor equals what is indicated by said reference signal.

S2. The dryer section according to claim 1 wherein 17 those motor controllers other than said first motor controller control torques of associated motors in accordance with load sharing ratios of said associated motors.

3. The dryer section according to claim 1 wherein said first motor controller includes: speed difference detecting means for attaining a difference between a rotational speed indicated by said o~o reference signal and an actual rotational speed of said 00 C, o6 10 first motor based on said output signal of said speed o odetector and said reference signal, and outputting a 0o speed control signal corresponding to said difference; and speed control means for controlling a speed of said 15 first motor based on said speed control signal. 60 0 o

4. The dryer section according to claim 3 wherein each of said motor controllers other than said first motor controller includes: orootr compensation means for compensating said speed 20 control signal from said speed difference detecting ~Li means of said first motor controller in accordance with a load sharing of an associated motor; and control means for controlling a current to be supplied to said associated motor based on a compensated speed control signal.

The dryer section according to claim 4 'wherein W given that a load of said associated motor being X KW Uj p.-1 1, F 18 and a load of said first motor being Y KW, each of said compensation means includes: means for multiplying said speed control signal from said first motor controller by X/Y; and torque control means for controlling an associated armature current based on said X/Y-multiplied speed control signal.

6. The dryer section according to claim 1, wherein each of said motors is coupled with a speed detector for 0 10 detecting a rotational speed of an associated motor; and wherein each of said motor controllers controls o 9 o said associated motor based on an output signal of an associated one of said speed detectors and a reference signal in consideration of a draw, in such a way that a 15 rotational speed of said associated motor equals a rotational speed defined by said reference signal.

7. The dryer section according to claim 6 wherein each of said motor controllers includes: speed difference detecting means for attaining a difference between a rotational speed indicated by said reference signal and an actual rotational speed of an associated motor based on said output signal of an associated one of said speed detectors and said reference signal and outputting a speed control signal corresponding to said difference; and speed control means for controlling a speed of said pL14 associated motor based on said speed control signal. $1L 9 19

8. The dryer section according to claim 6 wherein said motor controllers each have a drooping function for reducing a rotational speed with an increase in torque.

9. The dryer section according to claim 1, wherein at least two of said canvas rolls and cylinder rolls are mechanically coupled together and one of said plurality of motors drives said two coupled rolls.

The dryer section according to claim i, wherein a sum of driving capacities of those of said 1 0 plurality of motors other than arbitrary one of said lmotors exceeds a driving capacity necessary for driving t I said plurality of canvas and cylinder rolls.

11. In a paper making machine dryer section comprising an upper stage having a plurality of cylinder *II 15 rolls, a plurality of canvas rolls arranged in staggered fashion with said cylinder rolls, a canvas for running between said cylinder rolls and said canvas rolls, and a lower stage having a plurality of cylinder rolls, a plurality of canvas rolls arranged in staggered fashion with said cylinder rolls, a canvas for running between said cylinder rolls and said canvas rolls, a paper to be dried, in use, being sequentially alternately wound around said cylinder rolls of said upper stage and said cylinder rolls of said lower stage and being dried by said cylinder rolls and said canvas, a driver, for driving said cylinder and canvas rolls, comprising: a plurality of motors, coupled to associated at V 20 least one of said canvas rolls and said cylinder rolls, for driving the associated roll; a first mrtor controller having a speed detector for detecting a rotational speed of one of said plural- ity of motor, means for comparing an output signal of said speed detector with a reference signal determined in advance in consideration of a draw, attaining a difference between an actual rotational speed of said r r cne motor and a rotational speed defined by said refer- ence signal, and speed control means for controlling an associated motor based on a signal corresponding to said difference so as to cause said rotational speed of said one motor equal to said reference signal; and second motor controllers, provided to those of said 15 plurality of motors other than said one motor in one to €t one association and each having compensation means for receiving and compensating a speed control signal from said first motor controller based on a ration of a load of an associated motor and a load of said first motor and outputting said compensated speed control signal, and control means for controlling a current supplied to said associated motor based on said compensated speed control signal, thereby controlling a torque of said associated motor.

12. In a paper making machine dryer section comprising an upper stage having a plurality of cylinder rolls, a plurality of canvas rolls arranged in staggered 21 fashion with said cylinder rolls, a canvas for running between said cylinder rolls and said canvas rolls, and a lower stage having a plurality of cylinder rolls, a plurality of canvas rolls arranged in staggerc3 fashion with said cylinder rolls, a canvas for running between said cylinder rolls and said canvas rolls, a paper to be dried, in use, being sequentially alternately wound around said 0 cylinder rolls of said upper stage and said cylinder oseO ,rolls of said lower stage and being dried by said cylinder rolls and said canvas, a driver, for driving said cylinder and canvas rolls, comprising: a plurality of motors, coupled to associated at least one of said cylinder rolls and said canvas rolls, for driving the associated roll; 4 P 15 speed detectors, respectively provided for said motors, for detecting rotational speeds of associated motors; and motor controllers, respectively provided for said motors and each having means for attaining a difference A 20 between an output signal of an associated one of said speed detectors and a reference signal in consideration of a draw and outputting a speed control signal corre- sponding to said difference and means for changing a rotational speed of an associated one of said motors in accordance with said speed control signal so as to cause S a rotation speed of said associated motor equal to a II rotational speed defined by said reference signal. r 'N i I I 22

13. A paper making machine dryer section, substan- tially as hereinbefore described with reference to the accompanying drawings. DATED this 12th day of October, 1989 KABUSHIKI KAISHA TOSHIBA By its Patent Attorneys: GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. 4t#r ILr *r I tt II *r UA c 1 I