JPS6026878B2 - Paper machine control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to paper machines, and to an improved control system for paper machines.

FIG. 1 shows the general configuration of a paper machine.

That is, the raw material pulp liquid is transferred from the raw material tank 1 to the papermaking section 2.
It is continuously discharged onto the paper screen 3. The plow silk 3 is moved by a driving electric motor 14, and the moisture in the pulp liquid is naturally fallen due to its own weight, and a partially arranged suction box 4 and a suction couch roll 5 are used.
During the process of passing over the pulp, the suction function of both of them causes it to be forcibly dehydrated and become a pulp sheet. This pulp sheet is further passed through the rolls 7 of the pressing section 6, dehydrated, and then sent to the drying section 8, where it is dried by passing over the rolls 9 which are internally heated by steam heat. The paper thus obtained is polished by a calender 10 and finally wound onto a reel 11. A pump 12 supplies pulp liquid to the raw material tank 1, and is called a fan pump.

13 is its driving motor.

One of the factors that determines the quality of paper is its texture.

Formation is a term that refers to the uniformity of fiber distribution in paper, and is important for paper strength, printability, processing suitability, etc. As is well known, in order to maintain a uniform pooling, it is important that the ratio V, /V2 between the velocity V at which the pulp liquid flows out from the raw material tank 1 and the operating speed y2 of the plow silk section 2 is constant. This is called the jet wire ratio, V is called the jet speed, and V2 is called the wire speed. V is given by the following equation, where g is the gravitational acceleration and g is the discharge pressure of the pulp liquid, that is, the pressure at the bottom of the raw material tank 1. V, = 誼 ……
{The 11th is the sum of the pressure determined by the level of the pulp liquid in the raw material tank 1 and the pressure of the gas phase, and is called the total head.

Furthermore, if the jet wire ratio changes, the pulp weight per unit area on the plow silk section 2 will change, so it is clear that the paper will be thick and thin, making it impossible to produce a homogeneous product.

Therefore, each part of the paper machine from the plow section 2 to the reel 11 and the fan pump 12 employs a drive device whose speed is controlled with high accuracy, such as a thyristor Leonard drive device using a DC motor. FIG. 2 shows a subordinate drive device for the fan pump 12. As shown in FIG.

Reference numeral 16 denotes a rotation speed setting device for the fan pump 12, which sets a reference rotation speed determined by operating conditions.

On the other hand, the detection signal of the speed detector 15 directly connected to the drive motor, e.g., the DC motor 13, is used as feedback and is sent to the point of the power amplifier 18, e.g., the thyristor element, through the speed control circuit 17 so that the deviation becomes zero. Control the arc phase so that the speed remains constant. In reality, pressure fluctuations in the pulp liquid supplied to the fan pump 12,
The total head date varies due to pressure fluctuations in the gas phase within the raw material tank 1. Therefore, the detection signal of the total head detector 19 is added as a correction signal of the speed setting device 16, and this is controlled as the target fan pump rotation speed to be actually controlled. The total head detector 19 is
A commercially available diaphragm type differential pressure converter detects the total head as the differential pressure between the detection side pressure and atmospheric pressure.

Generally, the output is often pneumatic. This pressure is also converted into an electrical signal by the pneumatic converter 20'. Also, 2
1 is a signal converter for level matching this signal with the speed reference voltage of the fan pump 12;
This outputs the deviation from the standard total head date determined by Equation 1. The principle diagram of the diaphragm type differential pressure converter which is the total head detector 19 is as shown in FIG.

The diaphragm 31 converts the pressure difference between the high pressure side Hp and the low pressure side Lp into force, and the force applied to the lower end of the rod 32 is transferred to the support 3.
The distance between the nozzle 34 and the flapper 35 is reduced by a pulling force at point A using point 3 as a fulcrum. control relay 3
6, a pressure change also occurs in the output air in the direction of higher pressure. Here, R represents the supply air and K represents the air output. This output air pressure is converted into force by the bellows 37, and the point B is used as a retraction point, and the point A is used as a pullback point to the right.
When balanced with the force pulling left from the diaphragm 31, the output air pressure is the air pressure converted from the differential pressure applied to the diaphragm 31. A mechanism in which the gap between the nozzle 34 and the flapper 35 is opened in advance so that no output is produced unless a certain level of differential pressure is applied is called an elevation mechanism.

Figure 4 shows the relationship between the measurement range that is the maximum measurable value of differential pressure, the differential pressure when the measurement range (span) is set by the elevation function, and the output air pressure. represents the measurement span. Note that the low pressure side is generally kept at atmospheric pressure as it is. By the way, the accuracy of commercially available differential pressure converters is ±0.5 of the measurement range.
It is about %. Therefore, if the measurement span is wide, the measurement error will also be wide, making it impossible to accurately control the fan pump. As mentioned above, the limit to which the weight of pulp per unit area of the product, which is an element of quality control, can be kept constant is determined as follows.

BD=A. C. pnoagH. ．． ．．・・・
・■V2 However, BD: Pulp weight per unit area C: Pulp liquid concentration P: Pulp density A: Area of the discharge port of the raw material tank.

In formula '21, once the operating conditions are determined, A, C, pV
2 days is constant, so the total head detection error is △
If it is day, then the error ΔBD of BD is as {2''.

△BD: K no Oguchi ・・・・・・・・・
Go' Now, the measurement accuracy of the differential pressure transducer is 100.5 of the measurement range.
%, and if the measurement span is 1/4 of the measurement range, the measurement error will be 0.125%.

Therefore, (from the 2r formula, △BD = ±0.35%. Generally, it is required for quality control to control △BD to within 0.2%. Therefore, it is necessary to realize such control. However, once the range of change in V2 is determined from the operating conditions, the range of change in the total head is determined, so there is a limit to how small the measurement span can be.However, there is a limit to how small the measurement span can be. If some form of external pressure is applied to the pressure on the low pressure side of the converter in response to changes in V2, the measurement span can be increased up to the range of fluctuations caused by operational disturbances by 4.
・You will be able to set the height. The present invention was made based on the above reasons, and by applying pressure to the low pressure side of the differential pressure converter according to the operating speed of the paper machine, the detection accuracy of the total head detector is kept constant over the entire operating range, and the detection accuracy of the total head detector is kept constant over the entire operating range. The present invention, which aims to provide a control device for a paper machine with improved quality, will be described below based on an embodiment shown in FIG.

40 is an air source, and 41 and 43 are pressure reducing valves. In the same figure, the required total head detection range is divided into two sections depending on the operating conditions of the paper machine, and two are installed on the low pressure side of the total head detector 19.
This shows a case where two different air pressures are supplied.

In FIG. 4, the low pressure side supply pressures in the case of straight lines 2 and 3 are shown to be P2 and P3. Straight line 1 indicates a state in which the low-pressure side gas differential pressure is open. 42 and 44 are solenoid valves that are selected depending on the operating speed of the paper machine.

Further, 7001 is a fan pump control device, which outputs selection commands for the solenoid valves 42 and 44 and operating speed commands for the fan pump 12 and the paper machine. 60 is a setting device for setting the jet wire ratio V, /V2, 61 is a setting device for setting the weight (basis weight) per unit area of paper, and 62 is a paper machine operating speed setting device.

With this configuration, the rotational speed n of the sieve section 2 is detected by the speed detector 51 directly connected to the driving electric motor 14, and the speed of the sieve section 2 is calculated by the following equation by the speed calculator 72.

V2 double Dn ,. ．．
、． ．． [3} Where D: drive roll number n: drive roll rotation speed.

From the set value y of the jet wire ratio setting device 60, the jet speed V is determined by the following equation.

71 is a jet wire speed calculator.

V,=mDn・y...
[4} A comparator 73 performs the following three comparisons.

V, SV, n・mln...(technique)
V, n・minSV, SV,n・max×……(
kalpa) V, n・maxSV, ... (&) However, V,
n・min is the maximum value of V that can be taken by solenoid number n=1, 2, etc., and V, n・max is the maximum value that can be taken by solenoid number n=1, 2, etc. This value indicates the maximum value of V, and is stored in advance.

The selection signal from the comparator 73 excites the solenoids 42 and 44 via the solenoid operating circuit 74, and selects the low pressure side supply pressure of the total head detector 19. On the other hand,
The set rotation speed of the fan pump is determined from the set values of the setters 60 to 62 as follows. That is, first, the discharge flow rate Q of the fan pump is determined via the calculator 75 using the following equation. Q=W・A・p・V2y・BDS/C=K・
V2・y・BDS・・・・・・【
61 However, W: Width dimension of the paper machine V2: Set speed of the paper machine BDS: Basis weight set value y: Jet wire ratio K: Proportionality constant (K=W・A・p/C) 76 is calculated via the calculator 75 This is a fan pump rotation speed calculation unit that determines the fan pump rotation speed from the fan pump discharge flow rate determined by the fan pump discharge flow rate.

That is, the flow rate characteristic with the rotation speed of the fan pump as a parameter is stored in advance, and the fan pump rotation speed is calculated from the output side of the calculator 75 determined by the formula '6) and sent to the fan pump speed setting device 16. outputs a speed command. The following operations are the same as those shown in FIG. 2, so the explanation will be omitted. On the other hand, from the set value of the paper machine operating speed setter 62, the speed standard of the paper machine driving motor from the plowing section 2 to the reel is output. 50 is a control device for the drive motor of the plow silk section 2.

As described below, according to the present invention, even if the operating conditions change, the wire speed can be constantly monitored and operation can be continued continuously by automatically setting the measurement span of the total head detector to the minimum value. .

Therefore, since the total head can be detected with high precision over the entire operating range, quality such as formation and basis weight can be uniformly controlled.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the configuration of the paper machine, Fig. 2 is a block diagram of the control device for the subsidiary fan pump, Fig. 3 is an explanatory diagram of the principle of the differential pressure converter, and Fig. 4 is the operation of the differential pressure converter. The characteristic diagram, FIG. 5, is a block diagram showing an embodiment of the present invention. 1...Raw material tank, 2...Sukikinu department, 3.
...Plow net, 4...Suction pockets, 5...
Suction couch roll, 6... Pressing section, 7...
...Press roll, 8...Drying section, 9...
Drying roll, 10... power render, 11... reel,
12...Fan pump, 13,14...Drive motor, 15,51...Speed detector, 16...
... Rotation speed setting device, 17 ... Speed control circuit,
18...Power amplifier, 19...Total head detector, 20...Pneumatic converter, 21...
... Level converter, 40 ... Air source, 41, 43
......Pressure reducing valve, 42, 44... Solenoid valve, 60...... Driving amount motor control device for the screen section, 60...... Jet wire ratio setting device, 61・
...Basic weight setting device, 62...Paper machine operating speed setting device, 700...Fan pump control device,
71. Core... Jet speed calculator, 72... Screen section speed calculator, 73... Comparator, 74...
... Solenoid operation circuit, 75... Raw material flow rate calculator, 76... Fan pump rotation speed calculator. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A differential pressure transducer installed in the raw material tank of the paper machine to detect the total head, and a depressurizer that divides the total head detection range required by the operating conditions of the paper machine into two and supplies different air pressures to the differential pressure transducer. a solenoid valve that sends the supply air pressure outputted through the pressure reducing valve to the differential pressure converter, a speed detector that detects the number of revolutions of the screen section of the paper machine, a wire ratio setting device, and a basis weight setting device. and a paper machine operating speed setting device, the outputs of these setting devices, and the output of the speed detector are input, a series of calculations are performed, and a selection command for the solenoid valve and a speed command for the fan pump and paper machine are output. What is claimed is: 1. A control device for a paper machine, comprising a fan pump control device, and controlling the operation while maintaining constant detection accuracy of the differential pressure converter for detecting the total head.