JP3735261B2 - Web tension control device and web tension control method for rotary printing press - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device and a control method for tension control of a web in a rotary printing press.
[0002]
[Prior art]
FIG. 2 is a schematic configuration diagram for explaining a main part of a general commercial web offset printing press. As shown in FIG. 2, a typical commercial web offset printing press includes a paper feeding unit 1, an infeed unit 2, a printing device unit (also simply referred to as a printing unit) 3, a drying unit 4, a cooling unit 5, a web. A pass unit 6, a folding unit 7 and a control unit 8 for appropriately controlling them are provided as essential parts.
[0003]
The paper feeding unit 1 includes a reel stand (not shown) on which roll-shaped webs 11 and 12 are mounted. In the course of printing, the new and old webs are connected to each other and the web 10 is continuously fed. It works as much as possible. Here, the web 12 is in use and the web 11 is prepared for the next use. Each of the webs 11 and 12 is provided with a paper feed brake for restricting paper feed.
[0004]
The infeed unit 2 is a part that continuously pulls out the web 10 from the webs 11 and 12, and an infeed drag (infeed roller) 21 that sandwiches and rotates the web 10, and a web tension ( A dancer roller 22 (see FIG. 3, provided between the infeed drag 21 and the infeed tension pick 92 shown in FIG. 2) as a means for appropriately controlling the web tension) is provided. Reference numeral 23 denotes a tension fluctuation absorbing damper.
[0005]
The infeed drag 21 is connected via a continuously variable transmission 82 to a main drive shaft 81 that links the entire printing press, and a rotational driving force from the main drive shaft 81 is transmitted. The operation of the main drive shaft 81 and the continuously variable transmission 82 is controlled by the control unit 8.
As shown in FIG. 3, the dancer roller 22 is rotatably attached to a rotating shaft 22a disposed in parallel with the web 10 in a direction perpendicular to the traveling direction of the web 10 via an arm 22b. The air cylinder 22c is elastically supported in the up-down direction (that is, the direction in which the web 10 is separated from and contacting the traveling surface).
[0006]
Such a dancer roller 22 is provided between the guide rolls 24a and 24b, and the web 10 travels while being wound in the order of the guide roll 24a, the dancer roller 22, and the guide roll 24b. Is lowered to increase the tension of the web 10, and if the tension of the web 10 is strong, the dancer roller 22 rises against the air cylinder 22 c to decrease the tension of the web 10.
[0007]
In the printing unit 3, a plurality of sets of printing devices 31a to 31d having different normal ink colors are arranged in parallel along the web running direction. In this printing unit 3, the web 10 is sequentially passed to the printing devices 31a to 31d. Multi-color printing can be performed by using paper.
The web 10 that has been printed in the printing unit 3 is heated and dried in the drying unit 4 in the next process, then cooled in the cooling unit 5, transferred to the web pass unit 6, cut in the folding unit 7, and folded. It is done. The cooling unit 5 is equipped with a cooling drag 51, and the web path unit 6 is equipped with a web pass drag 61.
[0008]
Similarly to the infeed drag 21, the cooling drag 51 is also connected via a main drive shaft 81 and a continuously variable transmission 83 that interlock the entire printing press, and the rotational drive force from the main drive shaft 81 is transmitted. It has become so. The web pass drag 61 is also connected to a main drive shaft 81 that links the entire printing press via a continuously variable transmission 84, and the rotational drive force from the main drive shaft 81 is transmitted. The operation of the continuously variable transmissions 83 and 84 is also controlled by the control unit 8.
[0009]
Further, the infeed drag 21, the cooling drag 51, and the web pass drag 61 can be switched between a state in which a paper presser is attached and a state in which the paper presser is removed.
The web 10 in the folding unit 7 is folded in two vertically through a triangular plate (forming) 71, and then sequentially passes through a lead-in roller 72 and a folding machine drag (nipping roller) 73, by a saw cylinder 74 and a folding cylinder 75. The sheet is cut at a predetermined position and folded to be formed into a target signature, and then is carried out to the outside.
[0010]
As means for detecting the tension state (web tension) of the web 10, a paper feed tension pick 91 provided immediately upstream of the infeed drag 21 and an infeed tension pick provided immediately downstream of the infeed drag 21. 92, a cooling tension pick 93 provided immediately upstream of the cooling drag 51, and a cooling / web path tension pick 94 provided immediately upstream of the web path drag 61 are provided.
[0011]
The web path unit 6 is equipped with a compensator roll 62.
Next, control of a conventional rotary printing press will be described.
In the rotary printing press, when the printing of the current order is completed, the machine is stopped and washed, the printing wound around the plate cylinder is replaced, and other preparations for the next order are performed. In this case, since the engagement (clamping) of the blanket cylinder and the nipping roller 73 of the folding unit 7 is released, the web pass line on which the web 10 travels becomes free.
[0012]
Therefore, there is no tension acting on the web 10 that has been passed through, and the middle of the web 10 is in a relaxed state. When the printing is resumed from such a state, there is a problem that the printing position is shifted in the vertical direction or the processing position is shifted for a long time when the web 10 is cut or folded in the folding unit 7. .
[0013]
Therefore, in the conventional apparatus, the following operation is performed at the start of printing (start of reprinting accompanying an order change or the like).
First, the paper feed brake 12 is turned on to restrict paper feed. Then, the slow motion operation is started in which the web 10 is run at an extremely low speed with the paper feed of the infeed drag 21, the cooling drag 51, and the web path drag 61 being removed. At this time, the speeds of the drags 21, 51, 61 are set equal to those during normal printing.
[0014]
When the slow motion operation is started, the slow motion operation is continued until the state of the web 10 in the printing press is stabilized (the slack is eliminated and the meandering is corrected).
When the state of the web 10 in the printing press is stabilized, the web traveling speed is increased to the lowest operation speed (40 to 80 rpm) of the apparatus.
When the speed is increased to the minimum operation speed, the paper pressers of the in-feed drag 21, the cooling drag 51, and the web path drag 61 are put on.
[0015]
Thereafter, the normal operation state is entered and printing is started. At the time of printing, the drags of the infeed drag 21, the cooling drag 51, and the web path drag 61 operate as follows.
The infeed drag 21 is configured so that the tension of the web 10 (web tension) is in a predetermined state based on the detection information from the paper feed tension pick 91 or the angle of the dancer roller 22 (the swing angle of the arm 22b in the vertical direction). The peripheral speed is controlled (tension control).
[0016]
The peripheral speed of the cooling drag 51 is controlled (draw control) so as to be a drag peripheral speed ratio set by the user (for example, about 100.12% assuming that the printing speed is 100%).
The web pass drag 61 is also controlled (draw control) so as to have a drag peripheral speed ratio set by the user (for example, about 100.12% assuming that the print speed is 100%).
[0017]
[Problems to be solved by the invention]
However, in the control of the above-described conventional rotary printing press, it takes a long time for the web to sag and the meandering is corrected, and the web to run stably. ) The web 11 becomes all waste paper. At the same time, the waiting time until the web 11 runs stably is wasted.
[0018]
Further, until the web is stretched, the behavior of the web in the printing press becomes unstable due to meandering, which causes troubles such as a paper jam.
That is, the conventional apparatus has a problem that not only productivity is lowered but also loss of materials (winding paper) is increased, resulting in high production cost.
In addition, if the web is accelerated or decelerated due to disturbance during printing, the web tension will fluctuate. In this case, the suppression of the tension fluctuation depends on the paper damper characteristics and the drag roller slipping. When fluctuation occurs, it takes time to stabilize the tension.
[0019]
By the way, Japanese Patent Application Laid-Open No. 6-122188 discloses a technique for tension-controlling the speed of each drag only when it is less than the minimum speed of the machine. However, in the case of such tension control, at the start of printing, the web loosens relatively quickly and the web runs stably. During normal operation (during printing), the same drag control as before is used. Therefore, when acceleration / deceleration occurs in the web due to disturbance or the like and the web tension changes, the problem that it takes time to stabilize the tension remains.
[0020]
Japanese Patent Laid-Open No. 2000-127352 discloses a technique for tension-controlling the speed of each drag over the entire operating speed of the machine. This technology can quickly eliminate the effects of web tension fluctuations, but control hunting occurs because it tries to control web tension fluctuations caused by compensator movements and pasters by a cut-off controller. There is a fear.
[0021]
In other words, when tension control is actually performed, there is a delay time from when the drag speed is adjusted until this adjustment is reflected in the tension, and this delay time is the paper path length (between the drag and the tension detector) and Varies with printing speed. For this reason, control control hunting is likely to occur when tension control is performed against web tension fluctuations caused by compensator movement, pasta, or the like.
[0022]
The present invention has been devised in view of the above problems, and can provide a web tension control device and a web tension control method for a rotary printing press capable of stabilizing the running of the web during operation under various conditions. The purpose is to provide.
[0023]
[Means for Solving the Problems]
  In order to achieve the above-mentioned target, the web tension control device (Claim 1) of the rotary printing press according to the present invention includes a printing device section, and upstream that drives the web upstream and downstream of the printing device section. In a rotary printing press having a side drag and a downstream drag, a control device for controlling the tension of the web, the web tension detection detecting the tension state of the web between the upstream drag and the downstream drag And the feedback feedback control of the operating speed of the upstream drag and / or the downstream drag so that the detected web tension value becomes a predetermined target web tension value based on the detection information from the web tension detecting means and the web tension detecting means. Control means, and change the mode of tension feedback control by the control means according to the operating state of the rotary printing press Equipped with a control change meansThe control changing means is a control time constant changing means for changing the control time constant of the tension feedback control by the control means so that the response is accelerated in proportion to the printing speed.It is characterized by that.
[0025]
  Also,A web tension control device for a rotary printing press according to the present invention (Claim 2) includes a printing device section, and an upstream drag and a downstream drag for driving the web upstream and downstream of the printing device section. And a web tension detecting means for detecting a tension state of the web between the upstream drag and the downstream drag, and a web tension detection device. Control means for performing tension feedback control on the operating speed of the upstream drag and / or the downstream drag so that the detected web tension value becomes a predetermined target web tension value based on detection information from the means; Comprising a control changing means for changing the mode of tension feedback control by the control means in accordance with the operating state of the rotary printing press;The control change means includesThe control time constant of the tension feedback control by the control means is changed so as to increase the response in proportion to the printing speed except when a predetermined functional element of the rotary printing press capable of changing the detected web tension value is operated. By changing the aspect of the tension feedback control described above,During operation of a predetermined functional element of the rotary printing press capable of changing the detected web tension valueIs, Change the control time constant of the tension feedback control by the control meansIt is characterized by that.
  A web tension control device for a rotary printing press according to the present invention (Claim 3) includes a printing device unit, and an upstream drag and a downstream drag for driving the web on the upstream side and the downstream side of the printing device unit. And a web tension detecting means for detecting a tension state of the web between the upstream drag and the downstream drag, and a web tension detection device. Control means for performing tension feedback control on the operating speed of the upstream drag and / or the downstream drag so that the detected web tension value becomes a predetermined target web tension value based on detection information from the means; Comprising a control changing means for changing the mode of tension feedback control by the control means in accordance with the operating state of the rotary printing press;The control change means includesThe control time constant of the tension feedback control by the control means is changed so as to increase the response in proportion to the printing speed except when a predetermined functional element of the rotary printing press capable of changing the detected web tension value is operated. By changing the aspect of the tension feedback control described above,During operation of a predetermined functional element of the rotary printing press capable of changing the detected web tension valueIs, Temporarily hold the tension feedback control by the control meansIt is characterized by that.
[0026]
  The upstream drag is an infeed drag provided in a paper feeding unit upstream of the printing device unit, and the downstream drag is a cooling drag provided in a cooling unit downstream of the printing device unit and It is preferable that the web path drag is provided in a web path section downstream of the cooling section.4).
  A web tension control method for a rotary printing press according to the present invention (claims)5) Is a control for controlling the tension of the web in a rotary printing press having a printing device section and having an upstream drag and a downstream drag for driving the web upstream and downstream from the printing apparatus section. A method of detecting a tension state of the web between the upstream drag and the downstream drag and adjusting the detected web tension value to a predetermined target web tension value based on the detection information. Tension feedback control is performed on the operating speed of the side drag and / or the downstream drag, and during the tension feedback control,By changing the control time constant of the tension feedback control so that the response is accelerated in proportion to the printing speed,The aspect of the tension feedback control by the control means is changed according to the operating state of the rotary printing press.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a web tension control device and a web tension control method of a rotary printing press as one embodiment of the present invention. A schematic configuration diagram of the drive system, (b) is a schematic control block diagram of the drag drive system. The rotary printing press according to this embodiment will be described with reference to FIGS.
[0028]
First, a rotary printing press according to the present embodiment will be described with reference to FIGS.
As a rotary printing press according to the present embodiment, a conventional general commercial offset rotary printing press can be used. As shown in FIG. 2, a paper feeding unit 1, an infeed unit 2, a printing device unit (printing unit) 3) A drying unit 4, a cooling unit 5, a web path unit 6, a folding unit 7, and a control unit 8 for appropriately controlling them are provided as the main components. Since each of these parts has already been described, the description will focus on the part relating to web tension control.
[0029]
The apparatus constituent elements related to the conveyance control of the web (printing paper) 10 at the start of operation include an element that drives (or brakes) the web 10, an element that detects the tension state (web tension) of the web 10, and a detection element And a control system element (control means) for controlling the web driving element from the above information.
Elements for driving or braking the web 10 include a paper feed brake (not shown) provided on the shafts of the roll-shaped webs 11 and 12 of the paper supply unit 1, and an infeed drag (in) provided in the infeed unit 2. Feed roller) 21, cooling drag 51 provided in the cooling unit 5, web pass drag 61 provided in the web pass unit 6, folding drag (nipping roller) 73 provided in the folding unit 7, There is.
[0030]
These drags (drag rollers) 21, 51, 61, 71 can adjust the rotation speed independently. For example, the in-feed drag 21 and the web path drag 61 are shown in FIG. As described above, the rotation speed is controlled independently by the electric motors 21A and 61A.
Elements for detecting the tension state (web tension) of the web 10 include a paper feed tension pick 91 provided immediately upstream of the infeed drag 21 and an infeed tension pick 92 provided immediately downstream of the infeed drag 21. And a cooling tension pick 93 provided immediately upstream of the cooling drag 51 and a cooling / web path tension pick 94 provided immediately upstream of the web path drag 61.
[0031]
  A control unit 8 is a control system element (control means).
  In the control unit 8, during operation, the infeed drag 21 and the cooling drag 51 detected by the infeed tension pick 92ofBased on the tension state (web tension) of the web 10 between them, or the tension state (web tension) of the web 10 between the cooling drag 51 and the web path drag 61 detected by the cooling / web path tension pick 94. The rotation states of the in-feed drag 21 and the web path drag 61 are controlled through the motors 21A and 61A, and the web tension is controlled to a predetermined tension state.
[0032]
For this reason, as shown in FIG.1 (b), the motor control amount is set to the control part 8 based on the difference (TEa-TE) of the detected web tension value TE and the target web tension value TEa. A controller 8A and a motor controller 8B that operates the motors 21A and 61A based on the motor control amount set by the controller 8A are provided. The controller 8A controls the rotation of the motors 21A and 61A through the motor controller 8B so that the web tension is in a predetermined state by tension feedback control (for example, PI control) based on the difference (TEa-TE).
[0033]
  By the way, the control unit 8 sets the control time constant T for setting the control amount by the controller 8A to the machine operating state.InControl time constant changing means (control changing means) 8C which changes in response is provided. That is, in feedback control such as PI control, control responsiveness (control sensitivity) is determined according to the control time constant T. However, in the control time constant changing means 8C, according to the speed of the printing press (here, the printing speed). The control time constant T is set so that the control response is accelerated in proportion to Vp.
[0034]
Further, in this control time constant changing means 8C, control responsiveness (control sensitivity) at the time of operation of a predetermined functional element (for example, movement of a compensator by a cut-off controller or a paster) capable of changing the detected web tension value. ) Is set so that the control time constant T greatly decreases.
Note that the tension feedback control is temporarily held (time constant infinite) when a predetermined functional element of the rotary printing press that can change the detected web tension value (for example, movement of a compensator by a cut-off controller or a paster) is activated. The control change means 8 may be configured as described above.
[0035]
Since the web tension control device and web tension control method of a rotary printing press as one embodiment of the present invention are configured in this way, an in-feed drag that is an upstream drag of the printing machine unit 3 during the operation of the machine. 21 and the web path drag 61 that is the downstream drag of the printing machine unit 3 are detected by an in-feed tension pick 92, and the difference between the detected web tension value TE and the target web tension value TEa (TEa Based on -TE), feedback control is performed so that this difference (TEa-TE) becomes zero.
[0036]
For example, if the detected web tension value TE is lower than the target web tension value TEa, the rotation speed of the in-feed drag 21 is decreased and / or the rotation speed of the web path drag 61 is increased. If the detected web tension value TE is higher than the target web tension value TEa, the rotational speed of the in-feed drag 21 is increased and / or the rotational speed of the web path drag 61 is decreased.
[0037]
In this way, the web tension can always be in an optimum state. However, if such control is performed when the web tension changes due to compensator movement or pasta by the cut-off controller, the paper path length (drag and tension detection) Control hunting may occur due to the response delay time that varies depending on the printing speed.
[0038]
On the other hand, in this apparatus, the control time constant changing means (control changing means) 8C sets the control time constant T so that the control response is increased in proportion to the printing speed Vp, for example, according to the speed of the printing press. Therefore, the response delay time does not change depending on the printing speed. In addition, when the control time constant changing means 8C operates a predetermined functional element (for example, movement of a compensator by a cut-off controller or a paster) capable of changing the detected web tension value, control response (control sensitivity) Since the control time constant T is set so as to greatly decrease, control hunting is less likely to occur when the web tension changes due to movement of the compensator by the cut-off controller or pasta.
[0039]
Alternatively, the control hunting can be eliminated if the tension feedback control is temporarily held (time constant infinite) when the compensator is moved by the cut-off controller or the paster is operated.
Moreover, since this apparatus is based on constant tension control at all times, it is possible to reduce the waiting time until the web 10 runs stably at the time of starting, and the time until the web 10 is stretched is short. The cause of trouble such as a paper jam can be prevented without becoming unstable due to meandering.
[0040]
Therefore, productivity is improved, loss of materials (winding paper) is reduced, and reduction of various production costs can be promoted.
Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and various modifications can be made without departing from the spirit of the present invention.
[0041]
For example, the web tension is controlled by controlling the rotational speeds of the infeed drag 21 and the web path drag 61 by controlling the driving means (motors 21A, 61A), but between the infeed drag 21 and the cooling drag 51 The web tension may be controlled by controlling the rotational speed, or the web tension may be controlled by controlling the rotational speeds of the in-feed drag 21, the cooling drag 51, and the web pass drag 61.
[0042]
In this case, the cooling drag 51 may be driven by a single motor. Of the drags (drag rollers) 21, 51, 61, 71, it suffices that the speeds of this control can be adjusted independently of each other. May be.
As for the tension pick, a paper feed tension pick 91, a cooling tension pick 93, etc. may be used as necessary, and the web tension may be detected using other means.
[0043]
In any case, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-127352, if the configuration of the present invention is applied to a technique for tension controlling the speed of each drag over the entire operating speed of the machine, it is always stable. Control performance can be obtained.
[0044]
【The invention's effect】
  As detailed above, claims 1 to4The web tension control device of the rotary printing press according to the present invention and the claim5According to the web tension control method of the rotary printing press of the present invention described above, the machine is started from the start to the normal operation.MachineIn addition to being able to operate with the web tension in the printing machine stabilized from low speed to high speed, it is possible to prevent control hunting due to high and low printing speed and specific operation of the machine such as compensator movement and pasta. Stable control performance can always be obtained with respect to tension.
In addition, since the tension control is always based, it is possible to reduce the waiting time until the web runs stably at the time of start-up, and since the time until the web stretches is short, the web behavior in the printing machine snakes. Thus, there is an effect that the cause of the trouble such as a paper jam can be prevented without becoming unstable.
[Brief description of the drawings]
1A and 1B are diagrams for explaining a web tension control device and a web tension control method for a rotary printing press according to an embodiment of the present invention. FIG. 1A is a schematic configuration diagram of the drag drive system, and FIG. It is a typical control block diagram of the drag drive system.
FIG. 2 is a schematic side view showing a device configuration of a general rotary printing press according to an embodiment of the present invention.
FIG. 3 is a schematic side view showing a main configuration of a general rotary printing press according to an embodiment of the present invention.
[Explanation of symbols]
1 Paper feeder
2 Infeed section
3 Printing device section (printing section)
4 Drying section
5 Cooling section
6 Web Pass Club
7 Folding machine part
8 Control unit (control means)
8A controller
8B motor controller
8C Control time constant changing means as control changing means
10 Web
11,12 Rolled paper
21 Infeed drag (Infeed roller)
21A motor (drive means)
22 Dancer Roller
23 Damper for absorbing tension fluctuation
31a to 31d printing apparatus
51 Cooling drag
61 Web Pass Drag
61A motor (drive means)
62 Compensator Roll
71 Triangular plate (forming)
72 Lead-in Roller
73 Folding machine drag (nipping roller)
74 saw barrel
75 Folding body
81 Main drive shaft (Drag drive means)
82-84 continuously variable transmission
91 Feeding tension pick (web tension detecting means)
92 In-feed tension pick (web tension detection means)
93 Cooling tension pick (web tension detection means)
94 Cooling / Web path tension pick (web tension detection means)

Claims (5)

A control device that controls a tension of a web in a rotary printing press that includes a printing device and includes an upstream drag and a downstream drag that drive the web upstream and downstream of the printing device. And
Web tension detecting means for detecting a tension state of the web between the upstream drag and the downstream drag;
Control means for performing tension feedback control on the operating speed of the upstream drag and / or the downstream drag so that the detected web tension value becomes a predetermined target web tension value based on detection information from the web tension detection means; As well as
Comprising a control changing means for changing the mode of tension feedback control by the control means in accordance with the operating state of the rotary printing press;
The control changing means changes the tension feedback control mode by changing the control time constant of the tension feedback control by the control means so as to increase the response in proportion to the printing speed. Web tension control device for rotary printing press. A control device that controls a tension of a web in a rotary printing press that includes a printing device and includes an upstream drag and a downstream drag that drive the web upstream and downstream of the printing device. And
Web tension detecting means for detecting a tension state of the web between the upstream drag and the downstream drag;
Control means for performing tension feedback control on the operating speed of the upstream drag and / or the downstream drag so that the detected web tension value becomes a predetermined target web tension value based on detection information from the web tension detection means; As well as
Comprising a control changing means for changing the mode of tension feedback control by the control means in accordance with the operating state of the rotary printing press;
The control changing means responds with a control time constant of tension feedback control by the control means in proportion to the printing speed except when a predetermined functional element of the rotary printing press capable of changing the detected web tension value is operated. When the predetermined functional element of the rotary printing press capable of changing the detected web tension value is changed, the tension feedback control mode by the control means is changed. A web tension control device for a rotary printing press, wherein the control time constant is changed. A control device that controls a tension of a web in a rotary printing press that includes a printing device and includes an upstream drag and a downstream drag that drive the web upstream and downstream of the printing device. And
Web tension detecting means for detecting a tension state of the web between the upstream drag and the downstream drag;
Control means for performing tension feedback control on the operating speed of the upstream drag and / or the downstream drag so that the detected web tension value becomes a predetermined target web tension value based on detection information from the web tension detection means; As well as
Comprising a control changing means for changing the mode of tension feedback control by the control means in accordance with the operating state of the rotary printing press;
The control changing means responds with a control time constant of tension feedback control by the control means in proportion to the printing speed except when a predetermined functional element of the rotary printing press capable of changing the detected web tension value is operated. By changing the tension feedback control mode to change the detected web tension value, the tension feedback control by the control means is performed when a predetermined functional element of the rotary printing press that can change the detected web tension value is changed. A web tension control device for a rotary printing press, wherein the web tension control device is temporarily held. The upstream drag is an infeed drag provided in a paper feeding unit upstream of the printing apparatus unit, and the downstream drag is a cooling drag and / or provided in a cooling unit downstream of the printing apparatus unit. The web tension control device for a rotary printing press according to any one of claims 1 to 3 , wherein the web path drag is provided in a web path section downstream of the cooling section. This is a control method for controlling the tension of a web in a rotary printing press having a printing apparatus section and having an upstream drag and a downstream drag for driving the web upstream and downstream of the printing apparatus section. And
Detecting the tension state of the web between the upstream drag and the downstream drag;
Tension feedback control is performed on the operating speed of the upstream drag and / or the downstream drag so that the detected web tension value becomes a predetermined target web tension value based on the detection information,
At the time of the tension feedback control, a mode of tension feedback control by the control means according to the operating state of the rotary printing press by changing the control time constant of the tension feedback control so that the response is accelerated in proportion to the printing speed. A web tension control method for a rotary printing press, characterized in that:

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