JP4866069B2 - Duplex printing device - Google Patents

Description

  The present invention relates to a duplex printing apparatus that forms images on both sides of a web that is continuously conveyed.

  In a printing apparatus that forms an image on a continuous web, a web is conveyed by driving a tractor mechanism by engaging a pin member of a tractor mechanism mounted on the printing apparatus with a paper feed hole. If a web with feed holes is used, it is necessary to cut both ends of the web with feed holes after printing. Use a web that does not have feed holes and change the web transport to a tractor mechanism. Devices that do not require the work of cutting both ends of the web by using a roller mechanism have been put into practical use. These printing apparatuses have fixing means for fixing the toner transferred to the web by the image forming means to the web. The fixing means includes contact fixing such as a NIP roller for heating and pressing the toner, and flash fixing. Various methods have been developed such as non-contact fixing such as oven fixing.

  The need for double-sided printing is also increasing, and it is also common to place two printing devices side by side, perform image formation and fixing on one side, then flip the web outside the device and print the other side on the second side. In this method, shrinkage or deformation occurs in the heated web in the first fixing, causing a paper jam in the second printing apparatus or causing image formation failure or fixing failure. . As a means for solving this problem, there is also known a double-sided printing apparatus in which two image forming units and two fixing units are arranged in one printing apparatus, and after image formation on both sides is performed, fixing is performed at once.

  3 and 4 show the double-sided printing apparatus according to the above method, FIG. 3 shows a tractor feeding method, and FIG. 4 shows a conveying roller feeding method. 3 and 4, the same reference numerals as those in FIGS. 1 and 2 denote the same members, and the description of the members is substituted by the description of FIGS.

JP 2000-298413 A

  In the tractor feeding system shown in FIG. 3, in the case of a web having a feed hole, the web is transported by controlling the web transport speed by engaging the feed hole with the pin member of the tractor, but the downstream also transports by the tractor. It is difficult. In other words, since there are unfixed toner images on both sides of the web before the fixing unit, the tractor cannot be arranged, and the downstream tractor must be arranged after the fixing unit. Then, since the upstream tractor and the downstream tractor are driven by different drive sources, it is difficult to match the conveyance speeds. If the transport speed of the downstream tractor is higher than that of the upstream tractor, the web tension becomes strong and breaks. If the transport speed of the downstream tractor is slow, the web is slackened. Therefore, the downstream side is not a tractor, and a slip roller is used that slips between the web and the roller surface. Secured. The web tension depends on the frictional force between the slip roller and the web, and is determined by the characteristics of the web (particularly the coefficient of friction of the web surface). Further, since the roller is always slid, the surface of the roller is worn, and the frictional force changes with time. That is, it is difficult to secure a stable tension, and the behavior of the web is not stabilized due to the fluctuation of the tension, and the printing quality is deteriorated.

  This is the same in the case of the transport roller feeding method of FIG.

The present invention includes a first image forming unit that forms an image on one surface of a web to be transported, a second image forming unit that forms an image on the other surface of the web, and a web transport for transporting the web A double-sided printing apparatus having a fixing means for fixing the image to the web, and a web discharging means for discharging the web;
The web conveying means is located in a preceding stage of the first second image forming means, and has a driving means controlled by a web feed speed to the first second image forming means, and the fixing means A fixing means that is not in contact with the web, and is displaced between the fixing means and the web discharging means according to the length of the web between the first and second image forming means and the discharging means; And a tension applying means position detecting means for detecting the position of the tension applying means. Based on the position information from the tension applying means position detecting means, the first second image is provided. Web discharge means control means for controlling the conveying speed of the drive means of the web discharge means so that the web length between the forming means and the web discharge means is constant, and the first second image forming means and the web discharge means Tensioning of the web is characterized in that only the roller not having tensioning means and the drive means in.
The web conveying means is a tractor mechanism.
The web conveying means is a conveying roller mechanism.
Further, the tension applying means includes a buffer plate and a torsion coil spring.
In addition, the web discharge unit includes a pressing roller and a discharge roller driven by the driving unit.

  According to the present invention, the web tension of the double-sided printing apparatus can be stabilized and the printing quality can be ensured regardless of the medium conditions including the characteristics of the web, and as a result, a high-quality apparatus can be provided.

The purpose of stabilizing the web tension of the duplex printing apparatus and ensuring the printing quality was achieved regardless of the media conditions including the web characteristics.

  An embodiment of the duplex printing apparatus according to the present invention will be described.

  FIG. 1 is a diagram illustrating an overall configuration of a double-sided printing apparatus. The web 3 (continuous paper) is fed to the image forming unit 1 including the first and second image forming units 1a and 1b by the transport tractor 10 to form a toner image, and then the first and second fixing units 2a. The image is fixed on the web 3 by the fixing means 2 comprising 2b. An unfixed toner image is present on both sides of the web 3 after passing through the second image forming unit 1b, and the toner image is disturbed when it comes into contact with the member. Therefore, it is difficult to place the member between them.

Fixing means 2, Ru noncontact fixing means der such as flash fixing and oven fixing for fixing the toner without contacting the web 3. In the printing apparatus, the web 3 is usually paper, but is not necessarily paper, and a plastic film or the like may be used. The web conveyance speed of the image forming unit 1 is determined by the web feed speed of the tractor 10.

  Therefore, a buffer mechanism that displaces according to the web length between the image forming unit 1 and the web discharge roller 8 and applies tension to the web 3 is provided downstream of the fixing unit 2. The buffer plate 4 is swingably supported by the printer housing, and is normally pushed up by the spring force of the torsion coil spring 5 and is pressed against the web 3. Secure.

  The displacement of the buffer plate 4 is detected by the buffer position detection means 6, the conveyance speed of the web discharge roller 8 is controlled via the discharge roller control means 7, and the web length between the image forming means 1 and the discharge roller 8 becomes constant. To control. As the spring constant of the torsion coil spring 5 is smaller, the tension applied to the web 3 can be kept stable without being affected by the displacement of the buffer plate 4. According to the present invention, the web conveyance speed of the image forming unit 1 that affects the print quality can be controlled by the conveyance tractor 10, and at the same time, the tension of the web 3 can be kept stable by suppressing fluctuations. Can be prevented.

  FIG. 2 shows an example in which a transport roller 11 and a pressing roll 12 are used instead of the transport tractor 10 in order to use a web having no feed holes.

  In FIG. 2, the web conveyance speed of the image forming unit 1 is controlled by the conveyance roller 11, and the web tension is determined by the spring force of the torsion coil spring 5 that pushes up the buffer plate 4. This tension can suppress the influence of the wear on the surface of the conveying roller 11 and the web surface state. Further, the web conveyance speed of the discharge roller 8 is controlled according to the displacement of the buffer plate, and does not affect the conveyance speed and tension of the image forming unit 1.

  According to the present invention, it is possible to provide a high-quality double-sided printing apparatus that can secure a stable tension regardless of the presence or absence of a web feed hole.

It is a schematic block diagram which shows the Example of this invention. It is a schematic block diagram which shows the Example of this invention. It is a schematic block diagram which shows an example of a prior art. It is a schematic block diagram which shows an example of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Image forming means 1a: First image forming means 1b: Second image forming means 2: Fixing means 2a: First fixing means 2b: Second fixing means 3: Web 4: Movable buffer 5: Torsion coil spring 6: Buffer Position detection means 7: discharge roller control means 8: discharge roller 9: pressure roll 10: transport tractor 11: transport roller 12: pressure roll 13: slip roller

Claims (5)

First image forming means for forming an image on one side of a web to be conveyed;
Second image forming means for forming an image on the other surface of the web;
A web conveying means for conveying the web, which is located in a preceding stage of the first second image forming means;
In the double-sided printing apparatus, which is located at the subsequent stage of the first and second image forming means and has a fixing means for fixing the image on the web and a web discharge means for discharging the web
The web conveying means has a driving means controlled by a web feed speed to the first second image forming means,
The fixing unit is a fixing unit that is not in contact with the web;
Between the fixing unit and the web discharging unit, there is provided a tension applying unit that is displaced according to the web length between the first and second image forming units and the discharging unit and applies tension to the web. ,
A tension applying means position detecting means for detecting the position of the tension applying means;
Based on the position information from the tension applying unit position detecting unit, the conveying speed of the driving unit of the web discharging unit is controlled so that the web length between the first image forming unit and the web discharging unit is constant. Web discharge means control means,
The double-sided printing apparatus according to claim 1, wherein the tension applied to the web between the first second image forming unit and the web discharging unit is only a roller that does not include the tension applying unit and the driving unit .   The double-sided printing apparatus according to claim 1, wherein the web conveying unit is a tractor mechanism.   The double-sided printing apparatus according to claim 1, wherein the web conveyance unit is a conveyance roller mechanism.   The double-sided printing apparatus according to claim 1, wherein the tension applying unit includes a buffer plate and a torsion coil spring.   5. The duplex printing apparatus according to claim 1, wherein the web discharge unit includes a pressing roller and a discharge roller driven by the driving unit.

Images