JP2005247533A - Web conveyance mechanism for printing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain stabilization of web conveying property during continuous printing and to enhance printing quality immediately after starting of conveying by switching force of an elastic body so as to relax impact when a movable buffer and a web are contacted. <P>SOLUTION: A driving source capable of varying force of the elastic body of the movable buffer of the web conveyance mechanism is provided and the force of the elastic body of the movable buffer before starting of printing, during printing and after stopping of printing is controlled by driving the driving source. Further, a sensor for detecting the force of the elastic body is provided and width of the web, continuous amount information and the set value of the force of the elastic body can be changed from an operator panel by an operator. Thereby, the force of the elastic body meeting to the condition of the web may be controlled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a printing apparatus for forming an image on a continuously conveyed web, and in particular, a web conveying mechanism including a buffer mechanism that absorbs web length variation between a web conveying mechanism and a web discharging mechanism of a transfer unit. About.

  A printing apparatus that records and forms an image on a continuous web includes a transfer unit, a web conveyance mechanism that conveys the web to the transfer unit, and the toner transferred to the web in the transfer unit by heating and pressurizing and fixing the web to the web. However, it is difficult to make the web transport speed of the transfer portion and the web transport speed of the fixing mechanism completely coincide with each other. If the web transport speed of the web transport mechanism is faster than the transport speed of the fixing mechanism, web slack occurs between the transfer unit and the fixing mechanism, and the slack increases as the web is continuously transported. Conversely, if the web transport speed of the fixing mechanism is faster than the web transport speed of the web transport mechanism, the web supply from the transfer unit to the fixing mechanism will not be in time, and the web will eventually break. For this reason, the variation in the web length between the transfer unit and the fixing mechanism caused by the difference between the web conveying speed of the web conveying mechanism of the transfer unit and the web conveying speed of the fixing mechanism is absorbed. A buffer mechanism for controlling the transport speed has been invented.

  An example of a conventional buffer mechanism will be described with reference to FIG.

  In FIG. 3, the web 1 includes a web transport mechanism 3 that transports to a transfer unit 2, and a fixing mechanism 4 that includes a rotatable heating roll 4 a and a pressure roller 4 b having a drive source independent of the web transport mechanism 3. It is conveyed on the printing process by the rotation of the roller. In order to absorb the difference in web conveyance speed between the web conveyance mechanism 3 and the fixing mechanism 4, a buffer mechanism 5 including a spring 7 and a rotatable buffer 6 is provided between the web conveyance mechanism 3 and the fixing mechanism. The buffer mechanism 5 recognizes the inclination of the movable buffer 6 with a position sensor or the like, monitors the web transport speed difference between the web transport mechanism 3 and the fixing mechanism 4, and changes the speed of the drive source on the fixing mechanism 4 side. The web length between the transfer unit 2 and the fixing mechanism 4 is adjusted. The spring 7 of the buffer mechanism 5 applies a force in the direction in which the movable buffer 6 is pushed up the web 1, holds the movable buffer 6 and applies tension to the web 1. It is known that the stronger the web 1 is, the more difficult it is to meander, and the weaker it is, the easier it is to meander. Here, a case where the web conveyance speed of the fixing mechanism unit 4 is controlled by the rotation speeds of the heating roll 4a and the pressure roller 4b will be described. When it is detected that the position of the movable buffer 6 is higher than the specified position (the web length is longer than the specified value), the web length is shortened by increasing the rotation speed of the heating roll 4a. Tilt to the control target position. On the other hand, when it is detected that the position of the movable buffer 6 is lower than the specified position (the web length is shorter than the specified value), the rotation speed of the heating roll 4a is decreased. Thereby, since the web length becomes long, the movable buffer 6 rises to the control target.

  However, since the speed difference between the web transport mechanism 3 and the fixing mechanism 4 is large when the web transport is accelerated at the start of printing or when the web transport is decelerated when the printing is stopped, for example, when the web transport is accelerated at the start of printing, the fixing mechanism When the conveyance timing is slightly earlier than the web conveyance mechanism, the web conveyance mechanism 3 is stopped for a short time, but the movable buffer 6 is rapidly pushed by the web tension. For this reason, the movable buffer 6 moves more with the inertial force than the amount of change in which the web length between the transfer unit 2 and the fixing mechanism 4 becomes short, and the movable buffer 6 and the web 1 are separated. On the other hand, when the conveyance timing of the web conveyance mechanism is slightly earlier than the fixing mechanism, the fixing mechanism 4 is stopped for a short time, but the web 1 is conveyed onto the movable buffer 6. Since the web 1 is not discharged, the web 1 can be slackened on the movable buffer in a short time, and the movable buffer 6 cannot follow the speed at which the web 1 is slackened. For this reason, the movable buffer 6 and the web 1 are separated. The same applies when decelerating. Although there are large and small values depending on the web conveyance speed, acceleration time, and deceleration time, the web 1 and the movable buffer 6 are always separated during the web conveyance, and the movable buffer 6 may not act on the web 1 in some cases.

JP-A-9-146316

  As described above, when the web is separated from the movable buffer, the web is moved by the elastic force of the movable buffer which is set to be strong to suppress the meandering of the web during continuous printing when the web contacts the movable buffer again. Tap. The impact of the movable buffer hitting the web reaches the transfer section, the image is blurred at the time of transfer, and the print quality is deteriorated by the transfer blur at the start of printing.

  The problem to be solved by the present invention is to maintain the stability of web conveyance during continuous printing and to perform printing immediately after the start of conveyance by switching the force of the elastic body so as to reduce the impact when the movable buffer comes into contact with the web. It is to improve quality.

  The above-described problem is to provide a drive source that can vary the force of the elastic body of the movable buffer of the web conveyance mechanism, and to move the drive source by the force of the elastic body of the movable buffer before printing, during printing, and after printing stops. This is solved by controlling the force of the elastic body of the movable buffer. In addition, by providing a sensor for detecting the force of the elastic body, and by allowing the operator to change the setting value of the elastic body force from the operator panel, the width of the web and the amount information, and the operator can change the web conditions. You may control the force of the elastic body.

  According to the present invention, a drive source capable of changing the force of the elastic body of the buffer mechanism is provided, and the force of the elastic body immediately after the start of printing in which the movable buffer and the web are separated and recontacted is weakened. By striking the web, the impact is reduced, the impact of the web toward the transfer portion is reduced, and the impact is attenuated while reaching the transfer portion, so that transfer blur immediately after the start of web conveyance can be reduced. Further, during continuous printing, the force of the elastic body is set and controlled to a force necessary to suppress the meandering of the web, so that the web transportability can be maintained. As a result, by reducing the transfer blur, it is possible to provide a printing apparatus with high print quality and stable web conveyance over the entire printing.

  An embodiment of the present invention is shown in FIG. The web 1 is rotated by a roller of a fixing mechanism 4 including a web transport mechanism 3 transported to the transfer unit 2, a rotatable heating roll 4 a having a drive source independent of the web transport mechanism 3, and a pressure roller 4 b. Is conveyed on the printing process. In order to absorb the difference in web conveyance speed between the web conveyance mechanism 3 and the fixing mechanism 4, a buffer mechanism 5 including a spring 7 and a rotatable movable buffer 6 is provided between the web conveyance mechanism 3 and the fixing mechanism 4. Yes. Since the operation of the buffer mechanism 5 is the same as that of the prior art, description thereof is omitted.

  In this embodiment, the spring 7 is constituted by a tension coil spring. A hook on the other side of the spring 7, one side of which is fixed to the movable buffer 6, is connected via a idler pulley 8 to a drive pulley 10 directly connected to a rotating shaft of a drive source 9 by a wire 11. A spring force detection sensor 12 that detects the length of the spring 7 by detecting the rotational position of the drive source 9 is attached to the rotation shaft of the drive source 9. Based on the length of the spring 7 and the spring coefficient, the spring force is calculated by the control device of the printing apparatus.

The web tension control method will be described with reference to FIG. The spring force when printing is stopped is F ₁ [N], and the web is tensioned with a spring force weaker than the spring force F ₂ [N] during printing, the printing operation is started, and the web conveyance speed is 0 [m / s]. Is accelerated to V ₁ [m / s] (process speed) from time t ₁ [s] at the timing when the web conveyance speed reaches V ₁ [m / s], or at t ₂ [s] at a timing later than the spring. The force is gradually increased from F ₁ [N] to F ₂ [N] (eg, spring force during conventional printing), and the web tension during continuous printing is kept constant by the spring force of F ₂ [N]. When printing is stopped, the spring force is decreased from F ₂ [N] to F ₁ [N] at t ₃ [s] at the same timing or earlier than the web conveyance deceleration timing t ₄ [s], and the spring of F ₁ [N] Apply tension to the web when printing stops. The spring force F ₁ [N] is preferably determined by experiment or the like because there is an appropriate value that does not cause transfer blur depending on the web conveyance process speed V ₁ [m / s] of the printing apparatus. In this embodiment, F ₁ [N] can be made variable but fixed. The spring force of the movable buffer 6 during continuous printing, the information such as the width and thickness of the web, the automatic detection or by operator inputs from the operator panel, the spring force F _{2 [N]} to F ₃ [ N] or F4 ₂ [N] can be changed to make web conveyance more stable.

1 is a schematic configuration diagram illustrating an embodiment of a printing apparatus according to the present invention. FIG. 3 is a control timing chart showing an embodiment of the printing apparatus of the present invention. It is a schematic block diagram which shows the conventional printing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Web, 2 ... Transfer part, 3 ... Web conveyance mechanism, 4 ... Fixing mechanism, 4a ... Heating roller, 4b ... Pressure roller, 5 ... Buffer mechanism, 6 ... Movable buffer, 7 ... Spring, 8 ... Idler pulley, 9 ... Driving source, 10 ... Drive pulley, 11 ... Wire, 12 ... Spring force detection sensor

Claims (4)

  A printing apparatus for forming an image on a web to be conveyed, the transfer unit recording and forming an image on the web, a web conveyance mechanism for conveying the web to the transfer unit, and discharging the web on which the image is placed by the transfer unit Absorbing the web length variation between the web discharging mechanism and the web discharging mechanism generated by the difference between the web conveying mechanism and the web conveying speed of the web conveying mechanism and the web conveying speed of the web discharging mechanism; And a buffer mechanism that applies tension to the web. The buffer mechanism includes a movable buffer and an elastic body that is connected to the movable buffer and applies tension to the web. The elastic body includes a drive source. A web transport mechanism of a printing apparatus, wherein members are connected.   The printing apparatus according to claim 2, wherein the movable buffer includes a spring force detection sensor that detects a position of a member having the drive source, and controls the force of the elastic body according to an output of the sensor. Web transport mechanism.   The web transport mechanism of a printing apparatus according to claim 2, wherein the movable buffer controls the force of the elastic body before printing, during printing, and after printing is stopped according to information such as web width and thickness. . 4. The web transport mechanism of a printing apparatus according to claim 3, wherein information such as the width and thickness of the web is obtained from an operator panel.

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