Transport control method, a transport apparatus, and a printing apparatus

Abstract

A transport control method for use in transporting a medium in a predetermined direction by an upstream drive roller and a downstream drive roller, to operate the downstream drive roller by using PID control based on a detection value of a tension sensor disposed downstream of the upstream drive roller and upstream of the downstream drive roller for detecting tension. The transport control method includes a stable state determining step for determining, at time of the operation, whether a difference between the detection value of the tension sensors and a target value is within a stable width to make a stable state which maintains a stability time; and a gain decreasing step for decreasing a gain of the PID control to be less than an initial value when the difference is determined to be in the stable state.

Description

BACKGROUND OF THE INVENTION(1) Field of the Invention[0001]This invention relates to a transport control method, a transport apparatus, and a printing apparatus for transporting an elongate printing medium in a predetermined direction.(2) Description of the Related Art[0002]Conventionally, a printing apparatus having this type of transport apparatus includes a paper feeder, a printing station, a takeup roller and the transport apparatus (see Japanese Unexamined Patent Publication No. 2014-24266 (FIG. 1), for example).[0003]The above transport apparatus includes a first drive roller, a second drive roller, a third drive roller, and a fourth drive roller. The first drive roller is disposed downstream of the paper feeder, which supplies elongate printing paper, and has a nip roller for feeding the printing paper from the paper feeder. The second drive roller has a nip roller for feeding the printing paper sent by the first drive roller into a printing area directly under the printing s...

AI Technical Summary

Benefits of technology

[0008]This invention has been made having regard to the state of the art noted above, and its object is to provide a transport control method, a transport apparatus, and a printing apparatus which can inhibit transport irregularities, while suppressing tension variations at the time of acceleration, by rendering a gain variable according to a stability level of tension control.

[0012]The tension is unstable at times of acceleration and deceleration. By performing the control with the initial value instead of a small gain, therefore, the control amount is increased to be able to inhibit tension variations at the times of acceleration and deceleration.

[0014]The gain is enlarged to increase the control amount at the time of nonstable state. This can stabilize tension even at times of large tension variations.

[0018]Setting the minimum gain as a lower limit can avoid an excessively small gain lowering sensitivity too much, which would cause an inconvenience in tension adjustment.

[0020]Setting the maximum gain as an upper limit can avoid an excessively large gain raising sensitivity too high, which would cause an inconvenience in tension adjustment.

[0026]According to this invention, when the drive control unit operates the downstream drive roller by PID control, the stable state determining unit determines whether or not the difference between the detection value of the tension sensor and the target value is in a stable width to make a stable state which maintains a stability time. When the stable state is established, the gain adjusting unit makes the gain of PID control smaller than an initial value. Therefore, when tension control is not stable such as at a time of acceleration, PID control is carried out with the gain at the initial value. Only when tension control is stable, PID control is carried out with sensitivity lowered by a small gain. As a result, when tension control is unstable as at the time of acceleration, for example, the control amount becomes large. The control amount becomes small when tension control is stable as in a constant speed state. Thus, transport irregularities of the printing medium can be inhibited while inhibiting tension variations at the time of acceleration. As a result, the quality of printing on the printing medium by the printing station can be improved.

Problems solved by technology

As a result, when tension control is unstable as at the time of acceleration, for example, the control amount becomes large.

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