JP2686284B2 - Unwinding web tension control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an improvement of a web tension control method when a web, for example, a sublimation type color film used in a thermal transfer color printer or the like is unwound from an original roll.

[Prior art]

Generally, the tension control of the web when the web printed by rotary printing is unwound from the unwinding shaft is performed by using the dancer roller, and the control method is to adjust the position (displacement amount) of the dancer roller. In proportion to this, the voltage applied to the electromagnetic brake attached to the unwinding shaft is changed to obtain a braking force commensurate with the winding diameter of the original roll on the unwinding shaft. That is, assuming that the displacement amount of the dancer roller is x, the proportional constant is a, and the voltage is y, y = ax.

[Problems to be solved by the invention]

By the way, when the web is a thin film of several microns, such as the color film for the thermal transfer printer as described above, the following problems occur. That is, when the web is unwound from the original roll and wound onto the small bobbin by the small winding machine, the small winding machine frequently repeats stopping, operating and stopping, and the tension applied to the color film is small. However, when the roll diameter of the original roll is large, the color film may flow out due to the inertial force when the operation of the small winding machine is stopped. In addition, when the winding diameter of the original roll is small, there is a problem that when the small winding machine shifts from stop to operation, hunting occurs even with a slight voltage change. With respect to the above problem, it is necessary to increase the proportional constant a of the voltage applied to the electromagnetic brake attached to the unwinding shaft, and to reduce the latter, the proportional constant a must be decreased. Since it is necessary to take contradictory means, conventionally, the value of the proportional constant a is unavoidably set to an intermediate value. For this reason, it has not been possible to sufficiently prevent the web from flowing out or causing hunting. On the other hand, as disclosed in, for example, Japanese Patent Laid-Open No. 56-122757, in a brake device of an unwinder, the total brake torque applied to the core shaft of the unwinding roll is approximately the square of the unwinding diameter. Some have been designed so that they can be gradually reduced in proportion. However, the brake device of this unwinder cannot apply a braking torque that is exactly proportional to the square of the unwinding diameter, and the tension of the web unwound from the unwinding roll suddenly fluctuates. In this case, since the braking force is simply applied to the core shaft, there is a problem in that it is not possible to absorb the rapid fluctuation of the tension and perform proper tension control.

[Object of the invention]

The present invention has been made in view of the above problems of the prior art, in which inertia force is applied to the unwinding shaft by applying a brake torque to the unwinding shaft that is exactly proportional to the square of the unwinding diameter. Therefore, the web does not flow out, or hunting does not occur due to a slight voltage change during operation from stop to operation, and even if the tension applied to the web fluctuates rapidly, this is absorbed and proper control is performed. It is an object of the present invention to provide a method of controlling the tension of an unwinding web that can be used.

[Means for Solving the Problems]

The present invention is a method for controlling the tension of a web unwound from the unwinding shaft by giving resistance to the rotation of the unwinding shaft by an electromagnetic brake, while unwinding the web through a dancer roller, and The object is achieved by detecting the displacement amount of the dancer roller and increasing or decreasing the voltage applied to the electromagnetic brake in proportion to the square of the displacement amount of the dancer roller.

[Action]

In the present invention, the voltage applied to the electromagnetic brake is increased / decreased in proportion to the square of the displacement amount of the dancer roller, that is, the square of the unwinding diameter. Therefore, even when the winding diameter is large, When the small winding machine shifts from operation to stop, it suppresses the web from flowing out due to inertial force with sufficient braking force, and when the winding diameter is small, the small winding machine changes from stop to operation. When moving, the braking force is small and hunting is suppressed. Further, since the web is unwound through the dancer roller that detects the winding diameter of the web, even if a sudden change in the tension applied to the web occurs, it can be absorbed and the tension can be properly controlled.

【Example】

A method for controlling the tension of an unwinding web according to the present invention will be described below with reference to the drawings showing an apparatus for carrying out the method. This device, as shown in FIG.
An electromagnetic brake 14 attached to the unwinding shaft 12, a control device 16 for controlling a current voltage supplied to the electromagnetic brake 14, and a displacement amount of a dancer roller 18 are detected, and the detected value is controlled as described above. And a displacement detection device 20 for outputting to the device 16. As shown in FIG. 2, the control device 16 supplies the current from the AC power source 22 with the supply voltage, that is, the brake voltage y = ax ²
(X = displacement amount of dancer roller, a is a constant). The dancer roller 18 is rotatably attached to the tip of a swing lever 26 pivotally supported by a pin 24. The swing lever 26 is pulled in the counterclockwise direction in FIG.
The web 30 is tensioned via the. The displacement detecting device 20 is composed of a potentiometer, a rotary encoder, etc., and includes a pin 24 of the swing lever 26.
The amount of displacement x of the dancer roller 18 is detected from the swing displacement centered at, and output to the control device 16. The electromagnetic brake 14 is one in which magnetic powder is arranged between the rotating member on the side of the unwinding shaft 12 and the stationary member, and an electromagnetic force is applied to this magnetic powder to obtain a braking force. Therefore, detailed description will be omitted. Reference numerals 32A and 32B in FIG. 1 denote guide rollers for guiding the web 30, respectively. In this embodiment, the displacement detection device 20 detects the displacement amount x of the dancer roller 18, and based on the detected value x, the control device 16 sets the brake voltage y of the electromagnetic brake 14 to y = ax ² . Therefore, when the roll diameter of the original roll 10 is large, that is, when the displacement amount x of the dancer roller 18 is large, the brake voltage y (brake force) is increased in proportion to the square of x. It is possible to sufficiently prevent the web 30 from flowing out by sufficiently suppressing the excessive rotation due to the inertial force of the original roll 10 when the web roll 30 is stopped from the winding operation (not shown). When the winding diameter of the original roll 10 is small, that is, when the displacement amount x of the dancer roll 18 is small, the brake voltage y
(Braking force) is much smaller than when the winding diameter of the original roll 10 is large, so when the small winding machine shifts from stop to operation, overbraking does not occur and hunting does not easily occur. Become. Furthermore, since the web 30 is unwound from the original fabric roll 10 via the dancer roller 18, even if the tension applied to the web 30 suddenly fluctuates, the dancer roller 18 absorbs this and the proper tension is obtained. Control can be performed. In the above embodiment, as the displacement amount detecting means of the dancer roll 18, a displacement detecting device 20 such as a potentiometer is attached to the rocking lever 26, but this means other means, for example, an air cylinder device. The displacement amount of the dancer roller 18 may be detected from the displacement amount of 28.

【The invention's effect】

Since the present invention is configured as described above, it is possible to apply a brake torque that is exactly proportional to the square of the unwinding diameter to the unwinding shaft, and when the unrolled roll has a large winding diameter, stop from the unwinding state. It is possible to suppress the outflow of the web due to inertial force when shifting to the state, and to suppress hunting when shifting from the unwinding state to the operating state when the winding diameter of the original roll is small, and to dance to the web by the dancer roller. Even if the tension suddenly fluctuates, it is absorbed, and an appropriate effect that the tension control can be appropriately performed is provided.

[Brief description of the drawings]

1 is a schematic front view including a partial block diagram showing an apparatus for carrying out a tension control method for an unwinding web according to the present invention, and FIG. 2 is a relationship between a brake voltage and a dancer roller displacement in the apparatus. FIG. 10 …… Original roll, 12 …… Unwinding shaft, 14 …… Electromagnetic brake, 16 …… Control device.

Claims (1)

(57) [Claims] 1. A method for controlling tension of a web unwound from the unwinding shaft by applying resistance to rotation of the unwinding shaft by an electromagnetic brake, and unwinding the web through a dancer roller, A tension control method for an unwinding web, wherein the displacement amount of the dancer roller is detected, and the voltage applied to the electromagnetic brake is increased or decreased in proportion to the square of the displacement amount of the dancer roller.