CN1019651B - Method for damping control in offset press - Google Patents

Abstract

Method of regulating an amount of dampening medium on a printing plate of an offset printing machine, includes determining the amount of dampening medium on the printing plate, adjusting the rotational speed of a dampening ductor and/or the like to a given set value so as to regulate the amount of dampening medium on the printing plate and, for regulation deviations wherein the set value is greater than an actual value, driving a controller with a greater amplification factor than for regulation deviations wherein the set value is smaller than the actual value. For achieving a consistently good printing quality, it is of great importance that the control of the quantity of dampening liquid on the printing plate takes place very rapidly without this causing instabilities. Furthermore, the control should be capable of keeping the quantity of dampening liquid constant even under the influence of severe disturbing factors.

Description

Method for damping control in offset press

The present invention relates to a kind of amount of controlling wetting agent on the offset press forme, that is the method for wetting agent bed thickness, in the method, detect the amount of wetting agent on the forme, and the revolution by regulating water bucket roller and/or regulate similar parameter the amount of wetting agent is controlled on the ratings given in advance.

In offset printing, the quality of printing depends on the conveying of wetting agent fatefully.Thus, the problem of existence is that the amount of wetting agent will adapt with the working condition that changes.In addition, the amount of wetting agent has a very big influence to the growth of tone value, so, to the amount of wetting agent carry out desirable, regulate accordingly with corresponding operating condition, have very big meaning.

At documents and materials " Germany printing " (Nr.13,1986 W 235ff) in, a kind of control method of wetting agent of offset press is disclosed, wherein, the amount of the wetting agent on the forme is detected, by the revolution of regulating water bucket roller it is controlled on the ratings of a regulation then.This is used for wetting ratings is to know from a ratings table of being drawn by empirical data, and this form is based on the empirical value that the various combination for forme-paper predicts, particularly knows and makes from the printing release of front.This known control method all is unfavorable with regard to its program run and working result.

For this reason, task of the present invention is, a kind of amount of controlling wetting agent on the offset press forme is provided, that is the wetting agent bed thickness method, it can realize outstanding control characteristic, particularly has desirable sensitivity and does not have instability problem; In addition, the amount of wetting agent also can keep stable on sizable degree when strong interference effect attacks.

To this task, the present invention so solves, and when control deviation was a ratings greater than the situation of actual value, controller was with bigger amplification factor operation, and promptly amplification factor is greater than in the amplification factor of control deviation when being ratings less than the situation of actual value.By method of the present invention, just the ratings of the amount of wetting agent can be selected in this near near so-called set-off edge.So-called set-off edge, people are interpreted as the state of so wetting dosage, place that promptly should not have printing ink this moment on the forme has just begun to be stained with printing ink, if cause producing waste product once rubbing printing ink herein.Although ratings is adjusted near the set-off edge, because control method of the present invention can not run to undesirable state yet.In other words, there is not the excessive state of amount of wetting agent in the yet danger that does not exist Shuitu so to increase.Change amplification factor by the present invention, can make on the one hand controller with wetting dosage by the less wetting dosage of the rapid tuning of critical conditions, so that set-off danger recited above has reduced; On the other hand, by using less amplification factor, under the too much situation of the amount of wetting agent, the instable danger of control loop is avoided equally.It is verified to use the test that control method of the present invention does, and under the situation that inserts interference volume, this control method has splendid quality.Owing to adopting high relatively amplification factor to make controller reagentia soon, just can not cause reducing of water film thickness, thereby surmount the parameter bound of program because of inserting the interference effect amount.In case the interference effect amount of access has disappeared, because the present invention's this moment has used less amplification factor, a roughly long status transition also is non-critical, because danger of set-off at this moment or the danger that Shuitu so increases are non-existent.Simultaneously, an overreaction (overshoot oscillation) of controller has also been avoided, that is the danger of persistent oscillation also has been limited.Also have, when ratings was hop variation (last or following), based on technical scheme of the present invention, the operation characteristic of control also was very good.In a word, control method of the present invention can make ratings be adjusted in one on the favourable ratings of printing quality, simultaneously, this control procedure in the critical zone with obviously fast response characteristic carry out like this, promptly be adjusted on the stable status.Slowly control reaction (finger) accordingly based on less amplification factor (basic amplification factor) and cause a kind of stable non-critical operating mode equally for the situation of ratings less than actual value.

According to an improvement project of the present invention, so be provided with, promptly bigger amplification factor approximately is 1.2 to 2 times of basic amplification factor, preferably 1.5 times, this value proves particularly advantageous.

Also can so take measures, that is, have only when the difference between ratings and the actual value is in beyond the tolerance range of regulation, just to have one regulating the control procedure that parametric variable works.According to such measure, have only when crossing the tolerance range of regulation, this controller just provides a control voltage quantities.As if this controller work in the hysteresis mode.The advantage that this working method had is, the random vibration of measuring-signal (actual value or the relevant value of value) therewith can not consider, thereby useless control action can not take place, and in addition, regulating device is because less protection of loading.(ratings is greater than actual value: amplification factor is big on the basis of the mentioned in front selection of amplification factor being carried out relevant sign; Ratings is less than actual value: amplification factor is little), difference between ratings and the actual value is controlled within the tolerance range scope by mentioned above although be, also still can make respond timely reactivity worth with accurate measurement of controling appliance, and the skew of unallowed big numerical value can not occur.

This program run can also so be improved, and promptly interference volume with well-known function of stack compensates control in control procedure.The result that this program mode (PM) causes is, interference volume effect with known properties needn't compensate on whole parameters by control loop, and this interference volume or (a plurality of) compensation that interference volume carried out only are used for the parameter regulation to that all are a basic new duty.Simultaneously, so carry out, promptly this control procedure always is in continuous reactiveness in compensation process.The interference volume that compensates by described compensating action can be the variable of print speed printing speed, printing ink input, temperature or airflow etc.Alleged disturbance variable compensation effect preferably so realizes, i.e. stack compensation parameter on the controller output parameter, and this compensation parameter is by measurement the interference volume that the conveying of wetting agent has well-known function to be known.

Can also carry out like this, promptly one of stack compensates parameter on the controller output parameter, and this compensation parameter obtains by only measuring an interference volume.If want to use several disturbance variable compensations, will carry out the measurement of respective number so, realize the stack of the compensation parameter of respective number thereupon.

Yet other or both select for the moment and may scheme be, the compensation Parameters Calculation come out or from the form that stores and search acquisition in the family curve, such form or family curve can be for example to be stored in the corresponding program run computing machine, and the calculating of compensation parameter then can realize by a computing machine.

For obtaining outstanding printing quality, the programmed control that can adopt the band ratings to regulate, and the adjusting of ratings is carried out near the set-off edge.

Verified, it is effectively special using the PI-controller.

For detecting actual value, show that the actual value that obtains on the light path by optical reflectance measurements is favourable.This actual value then is to weigh the amount of wetting agent or a yardstick of wetting agent bed thickness.

The present invention is described in detail by accompanying drawing below.

Fig. 1 is a regulating device sketch of implementing the inventive method;

Fig. 2 is the square wiring diagram of regulating loop;

Fig. 3 has shown in the scope at set-off edge ratings and actual value curve over time with the sketch formula;

Fig. 4 shows ratings and actual value curve over time under the situation that inserts interference volume;

Fig. 5 shows the steering characteristic sketch under ratings sudden change situation;

Fig. 6 is inserting interference volume and is considering ratings under the situation of tolerance range of ratings and actual value and the sketch of actual value;

Fig. 7 A shows a square wiring diagram

Fig. 7 B is the continuity sketch of a band ratings and actual value tolerance range;

Fig. 8 shows under the situation of considering ratings-actual value tolerance range when ratings suddenlys change the sketch about steering characteristic;

Fig. 9 shows under the situation of the compensation that realizes the known disturbances amount by superposing control ratings and actual value curve sketch over time.

Be provided with by the structure of Fig. 1 below control method of the present invention is elaborated.The offset machine of being described 1 has a printing unit 2 and an other printing unit 3.Only study print couple 2 and control device herein below in great detail.Printing unit 3 is equipped a control corresponding device too.

With the 4 corresponding upper inking roller of not depicting of some and several the other dampener 5 of being provided with of the plate cylinder with forme in the printing unit 2.Dampener 5 ' and wetting agent memory 6 collaborative works.The revolution of the dampener 5 ' that is provided with as immersing roller can change herein.This point is to show by the arrow that points to them.By an effective coupling arrangement 8 revolution is descended from impression cylinder 7, and be delivered on the rotating speed signalling generator 9.This impression cylinder 7 is equipped with a selsyn transmitter 10, and it can detect angle position.

Also be provided with following peripheral unit among this external Fig. 1: 12, one computing machines 13 of 11, one floppy disks drive unit of an evaluation circuit and a measurement data dissection process unit 14.In order to detect the thickness of wetting agent layer, carry out optical scanning with the surface that 15 pairs of sensors are installed in the forme on the plate cylinder 4, this sensor 15 is connected with evaluation circuit 11 by lead 16.The evaluation circuit then is connected with computing machine by line 17.Computing machine is connected with floppy disk drive unit and measurement data dissection process unit with 19 by lead 18.Selsyn transmitter 10 is communicated with measurement data dissection process unit 14 by lead 20, and rotating speed signalling generator 9 is connected with measurement data dissection process unit 14 equally by lead 21.At last, lead 22 makes measurement data dissection process unit 14 be connected with the gearing of the dampener of not depicting 5 '.

Note a little just can obtaining following mechanism: sensor 15 detects the wetting agent bed thickness on the forme, then it is sent into evaluation circuit 11, and this circuit 11 just carries out corresponding data processing.The actual value of wetting agent bed thickness is brought with giving earlier given ratings and is compared, and ratings is so selected, and promptly it is relatively near so-called set-off edge.The value that this set-off edge flag corresponding wetting agent is wetting agent bed thickness value in other words, and when reaching this value, place that should not have printing ink on the forme just in time begins to receive printing ink.The advantage that primary action had of this ratings is to reach outstanding especially printing effect.These peripheral units of offset machine 1 just constitute a kind of control loop like this at present, (this also will describe in detail below): the wetting agent bed thickness of knowing from sensor 15 (actual value) will cause the revolution of dampener 5 ' to regulate (the adjusting nT that immerses the roller revolution) with respect to the deviation of the ratings of regulation.Simultaneously, according to invention, will carry out like this in control method, promptly controller carries out work according to state status with different amplification factors.In addition, as can be seen from Figure 1, a kind of measure that influences of depending on print speed printing speed is set, this point can be achieved by the velocity voltage of being imported by the lead 21 that is connected on the measurement data dissection process unit 14 from rotating speed signalling generator 9.To explain in detail below about the details here.When arriving a certain definite machine location, the measurement request signal is sent out (with degree or step-by-step counting), so that the position that measuring head is stipulated on forme is measured.This zero pulse only plays the effect that counter f is resetted, and the effect of determining the machine instantaneous position is then played in step-by-step counting.

Fig. 2 is the square wiring diagram that the front has been stated control loop.The ratings Swsoll of the amount of wetting agent (perhaps wetting agent bed thickness) is transported to an addition position 23.Simultaneously, the actual value Swixt of this wetting dosage (wetting agent bed thickness in other words) is input to this 23 places, addition position equally with negative sign.Difference (control deviation Xd) Swsoll-Swist synthetic by these two values then is input in the controller 24.And controller output end is connected with the dampening device 26 of offset press 1 by an addition position 25.Come the immersion roller revolution nT of dampening device 26 is regulated according to the output valve of controller 24.What the square that draws on dampening device 26 next doors was represented is forme 27, and it places on the plate cylinder 4 of offset press 1.Then be an other addition position 28, its output numerical value has embodied the actual wetting agent bed thickness on the forme.These arrow 29 expressions of pointing to addition position 28 influence the interference volume of wetting agent bed thickness.This interference volume is that back input or the variation of temperature owing to the flowing of air, printing ink produces.

Wetting agent bed thickness on forme 27 is predicted by sensor 15, and its numerical value is flowed in the evaluation circuit 11, and this evaluation circuit is to handle mean value by square 30(measured value in Fig. 2) explain.The output valve of this measured value treating apparatus is exactly the actual value Swist that is input on the addition position 23.

Control deviation Xd is imported in the square 32, and its access will exert an influence to controller 24, and wherein, amplification factor KR is influenced.The present invention regulation comparing under the situation that a bigger ratings Swsoll is arranged with actual value Swist, adopt bigger amplification factor, promptly than being that ratings Swsoll is big less than the amplification factor under the situation of actual value Swist in control deviation.Best, this higher amplification factor approximately is 1.5 times of low amplification factor (basic amplification factor).This controller 24 preferably is arranged to the PI-controller.

In Fig. 2, also has a compensating circuit 33 in addition.For example it can carry out a velocity compensation, in other words, comes the print routine parameter generating is influenced by changing print speed printing speed.But also can consider to compensate with other the parameter that occurs as interference volume, all these interference volumes all can predict, because their effect is known, so that they can be known by measuring, calculating or find out according to impact effect from form and family curve.Return on the embodiment among Fig. 2, in compensating circuit 33, import the amount that the speed in the printing process is changed.This variable quantity is represented with Um.By a dampening device compensation characteristic curve, just can find parameter Uk, it has shown the voltage of a velocity compensation.This voltage is imported into 25 places, addition position.A kind of like this arrangement (instruction) just causes the variation of print speed printing speed to control by control loop, but on the contrary velocity compensation is added on the control loop as controlled quentity controlled variable.Just can realize that by jointly controlling of this and described compensation system (compensating circuit 33) a kind of more stable constant substantially wetting agent carries, i.e. the method that does not adopt control one to disturb to combine than people but to carry out the situation of balance adjustment with this interference volume more stable.The present invention just can regulate the skew with respect to ratings quite rapidly according to this.Known in the prior art compensation system is to carry out work as pure control device, and its shortcoming is that additional interference parameter has defective owing to regulating device and can not control.This shortcoming has then been eliminated by superposing control in apparatus of the present invention.

According to the foregoing description, the present invention a kind ofly is used to control greater than 0 or less than the different control characteristics of 0 deviation by adopting different amplification factor KR to be provided with.As a kind of control device, preferably above-mentioned a kind of like this control method is superimposed with the disturbance variable compensation method of having described, this interference parameter has known effect.Bigger amplification factor is preferably elected 1.5 times of basic amplification factor as.

About the structure setting of sensor 15, can from the following examples, know:

It has a lighting device, and lighting device is mapped on the surface of forme by the light of an illumination optics device with orientation.The light that reflects from forme is just received by row's photodiode.Owing to used this photodiode, thereby just existed such possibility, can on this row's length, measure the distribution of whole scattered lights.According to the transmitted intensity that on the single diode in the in a row diode, detects, in the evaluation circuit 11 that output terminal connects, just calculate an amount or a wetting agent bed thickness corresponding parameter Sw with wetting agent.

Fig. 3 shows a sketch, and nominal time T on its horizontal ordinate is labeled as wetting agent bed thickness Sw on its ordinate.Dot-and-dash line is represented the set-off edge.Mark the ratings Swsoll of wetting agent bed thickness above this set-off edge, and this value is desirable for the present invention.The actual value Swist of wetting agent bed thickness then swings along its time coordinate round ratings Swsoll, simultaneously as can be seen, for example owing to disturb the influence of parameter, control skew occurs greater than 0 with less than 0 situation, in other words, in the place of ratings greater than actual value, control deviation is greater than 0, just should adopt the amplification factor of an increase this moment, and in the place of ratings less than actual value, control deviation is exactly one will use such amplification factor less than 0 value for this reason, and it is less than the amplification factor in the described situation in front.These different states have all been done to show in Fig. 3.Also can know from Fig. 3 in addition, constituted a critical section between ratings Swsoll and set-off edge, in other words, existing controller vibration has the danger that causes making because of set-off the print result breaking-up in this section.It above ratings Swsoll so-called non-critical district.If actual value is in this zone, though exist on forme than desired more moisture content, this state but is not very serious for the degenerating of print result.In order to leave this critical zone as much as possible, the present invention is provided with a control amplification factor that the basic amplification factor of ratio is higher in the critical section.If enter non-critical zone, for program run, just allow to insert a less amplification factor so, so that can leave non-critical district more slowly, still, as what described, this is to printing the effect that do not cause damage.

Fig. 4 is illustrated in ratings Swsoll and the time dependent curve of actual value Swist under the situation that inserts interference volume.At time point t place in order to test, for example with one airflow delivery that produces by exhaust blower to the surface of forme, in other words, quickened the vaporization of wetting agent, water film thickness reduces thereupon, this just is attended by the danger that enters the set-off zone.But, owing to increased amplification factor according to the present invention, above-mentioned this tendency will be resisted very soon, thereby actual value Swist is moved to again on the ratings Swsoll, and almost parallel ground is close to ratings in change curve subsequently.At time point t, this interference volume is interrupted, and in other words, in described this experiment, the conveying of airflow is interrupted.In view of the above, the bed thickness of wetting agent film at first increases on the forme, so that actual value Swist has surpassed ratings Swsoll.Like this, controller just is operated in (comparison diagram 3) in the non-critical district, and only be that basic amplification factor KR enters operation this moment.In change curve subsequently, actual value Swist is just along with corresponding time constant moves towards the direction of ratings Swsoll again.

Fig. 5 represents actual value and ratings curve over time, and this curve map is used to describe to control operation characteristic.Shown emphatically that herein ratings has the situation of unexpected variation.Under the situation of big ratings Swsoll, controller is just very promptly followed the tracks of in ratings Swsoll hop, operates with bigger amplification factor because be herein.Yet this district is the critical section, and in this district, ratings Swsoll knock-ons again to definite value Swsoll.But can occur the situation of of short duration ratings less than actual value herein, in other words, with amplification factor KR operation, it is corresponding with basic amplification factor to (KR).According to this, this operational process is just correspondingly slower, simultaneously, according to the selection to basic amplification factor numerical value, just can make inevitable overshoot oscillation (part that is represented by dotted lines in Fig. 5) can not reach the degree of crossing the set-off boundary.In practice, the danger of this set-off also can reduce further, and wherein, people change for such ratings, is not that requirement is all making it effective on the height at once, but little by little makes it effective on whole height.To this measure that is fit to is known control technology.

Fig. 6 to Fig. 8 corresponding to a kind of method of operation of control device of the present invention under the situation of the tolerance range of using ratings and actual value.This means that this controller is with a kind of mode work of hysteresis, because have only when the difference between ratings and the actual value is in outside the tolerance range of regulation, the control voltage of this controller just changes.This expression, this controller just reacts with the adjusting parametric variable when crossing the predetermined tolerance of control deviation.Particularly do not consider the random vibration of measuring-signal herein, this just causes whole process relatively more balanced.

Simultaneously, be performed such, that is, between controller 24 and addition position 23, insert lag element 34 according to Fig. 7 A.Control deviation Xd of input is as input value in this lag element 34, and a controlling value Xd* who has revised is exported by this device as output voltage.Can in the sketch of Fig. 7 B, find out in the funtcional relationship between Xd and the Xd*.From true origin, when Xd be constantly become big on the occasion of the time, the control deviation Xd* of correction always is in 0 value.Have only when surmounting boundary value S1, the control deviation Xd* of this correction is just on hop to definite value, and from then on value is opened and cheated the linear funtcional relationship with Xd.If control deviation begins to diminish from here, the control deviation value Xd* of this correction just gets back to 0 along straight line so.If control deviation Xd crosses 0 value, that is to say, when it will become negative value, so just will produce the family curve of a corresponding symmetry.At this moment ,-the Xd* value only just has hop when crossing a boundary value S2.

The total effect that is produced on the basis of this set is, is not just to carry out a kind of control action for deviation less between ratings and the actual value, but with only just carrying out this control action crossing corresponding boundary value S1 or S2.It is the positive acting effect that this point just makes overall system.

Fig. 6 is corresponding with Fig. 4 and Fig. 5 with Fig. 8, at this moment the hysteresis characteristic described with the front of this controller and working.Operation based on this hysteresis, just compare and to find out with corresponding figure, bigger control deviation is only done the principle adjustment, however, this process is still with enough carrying out with stable fast, and its advantage is that this controller is introjection not too often, for this reason, adjusting gear has needed with regard to less.

Fig. 9 has shown the actual value to control structure stack compensation control time that the front described and the effect situation of ratings.At t constantly, for example print speed printing speed from per hour 4000 pages bring up to 6000 pages, and t constantly printing efficiency print/per hour be reduced to from 6,000 4000 print/per hour.Compensation by this speed, will cause actual value Swist to have only a relatively shorter damped oscillation, at this moment as previously described around ratings Swsoll, change because eliminate basic parameter, so this controller only needs a very small control action by superposing control.Utilize method of the present invention just can realize a desirable program run in a word.

All that mention at instructions and new technical features that describe in the accompanying drawings all are substances of the present invention, even their propose protection clearly in claims.

Claims (10)

1, the method of the amount (or wetting agent bed thickness) of the wetting agent on the control offset press forme, in the method, the amount of the wetting agent on the forme is detected to be known, revolution by regulating water bucket roller and/or regulate similar parameter and the amount of wetting agent is controlled on the ratings given in advance then, it is characterized in that: in control deviation (Xd) is under the situation of ratings (Swsoll) greater than actual value (Swist), controller (24) is that ratings (Swsoll) is big less than the amplification factor under the situation of actual value (Swist) (KR) than control deviation (Xd) promptly with a bigger amplification factor (KR) operation.

2, according to the method for claim 1, it is characterized in that: bigger amplification factor (KR) is approximately elected 1.2 times to 2 times of basic amplification factor (KR grund) as.

3, according to the method for claim 2, it is characterized in that: bigger amplification factor (KR) is elected 1.5 times of basic amplification factor (KR grund) as.

4, by the method for aforementioned claim 1, it is characterized in that: only when the difference of ratings and actual value is in outside the tolerance range of regulation, just have an effect to regulating control procedure that parametric variable works for one.

5, by the method for aforementioned claim 1, it is characterized in that: control method of stack in this control method is used for the interference volume (z) with well-known function is compensated.

6, by the method for claim 5, it is characterized in that: a compensation of stack parameter on the controller output parameter, this compensation parameter draws by measurement interference volume (z).

7, claim 5 or 6 method is characterized in that: this compensation parameter can calculate or from the form that stores and search in the family curve and know independently.

8, by the method for aforementioned claim 1, it is characterized in that: ratings (Swsoll) is selected near the set-off edge of printing process.

9, by the method for aforementioned claim 1, it is characterized in that: adopt a PI-controller (24).

10, by the method for aforementioned claim 1, it is characterized in that: the actual value of indicated wetting dosage (Swist) is known by optical reflectance measurements with optical approach.

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