JP2001350296A - Double-sided printing device - Google Patents

Abstract

(57) [Problem] In a color image forming method using a tandem method, there is a problem that the whole apparatus becomes large and is not practical especially when realizing double-sided printing on continuous paper at high speed. According to the present invention, two printing stations in which a plurality of printing units having a completely equivalent configuration are arranged in the vertical direction are symmetrically installed, and the conveyance path of the recording paper is formed in a double U-shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-sided printing apparatus for performing a two-sided recording of a color image for forming a color image on both sides of continuous paper in an electrophotographic method.

[0002]

2. Description of the Related Art As a conventional full-color recording system in an electrophotographic system, there is known a method in which a photosensitive member as a recording member is rotated four times and one color is developed at each rotation. This method has a disadvantage that the time required for color printing is four times as long as that for single-color printing because the photoconductor rotates four times. Another drawback is that it is difficult to use continuous paper. A so-called tandem system, in which four photoreceptors are linearly arranged in a horizontal or vertical direction, developed one by one with each photoreceptor, and printed at the same speed as monochrome printing, has been well known as a method for improving these. ing. As a method of printing a color image on both sides of continuous paper, Japanese Patent Application Laid-Open No. 7-72776 discloses that four photoconductors for cyan, magenta, yellow, and black are used.
A method is shown in which a total of eight sets are successively arranged in the vertical direction, continuous paper is passed therebetween, and a color image is printed on both sides of the continuous paper in one process. Although this method is excellent in performing double-sided color printing in a single housing, it uses a staggered photoconductor arrangement, but prints at a higher speed because eight photoconductors are arranged in a substantially straight line. If an attempt is made to increase the diameter of the photoconductor, the height of the apparatus increases, making it difficult to replace, adjust, and maintain the consumables of the upper printing unit.
As a result, there is a problem that it is difficult to increase the printing speed.

[0003]

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a double-sided printing apparatus for forming a color image on both sides of continuous paper, in which the entire apparatus is compact and capable of high-speed recording. A printing device is provided. It is another object of the present invention to provide a two-sided printing apparatus for color images in which the construction of each printing unit is equivalent.

[0004]

SUMMARY OF THE INVENTION In a double-sided printing apparatus for forming a color image on both sides of a continuous recording sheet, the apparatus comprises a plurality of printing units each including at least a photoreceptor, a charging section, a developing section and a transfer section. Are arranged in two rows symmetrically with respect to the floor, and the first and second printing stations are arranged between the first and second printing stations. The recording paper that has been loaded from above is U-shaped first.
After the direction is changed to the station side and the toner image is transferred to the recording paper at the transfer section of the first printing station,
It is folded back into a U-shape, again folded into a U-shape, transported to the transfer section of the second printing station, and then the toner image is transferred to the recording paper, and then a conveyance path for the recording paper sent to the fixing device is provided. This is a two-sided printing device.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a printing unit used in the duplex printing apparatus of the present invention. In the printing unit 2, the photoconductive recording body 21 negatively charged by the charger 22 rotates clockwise to form a negative electrostatic latent image by the laser beam 24 emitted from the optical system 23, and then develops the image. Transported to The developing device 25 contains a so-called two-component developer 251 composed of a magnetic carrier and a toner. The electrostatic latent image is formed on a developing roll 252 of the developing device 25 by a developer having a negatively charged toner. The toner image is formed on the surface of the recording medium 21 by being developed by the magnetic brush 251. This toner image is electrostatically transferred to the recording paper 3 by the positive corona discharge of the transfer unit 26. The residual charge on the surface of the recording medium 21 is removed by the eraser 27, and the residual toner is removed by the cleaner 28. The recording paper 3 after the transfer is sent to a fixing device.

A first embodiment of the present invention will be described with reference to FIG. The figure shows a full-color duplex printing apparatus using continuous paper according to the present invention. A first printing station 11 and a second printing station 12, each having four printing units each having cyan, magenta, yellow, and black toners arranged vertically, are installed in parallel. The second printing station 12 has a line-symmetric configuration with respect to the first printing station 11. For simplicity, the recording unit 21, the developing device 25, and the transfer device 2
Only 6 was described. The first printing station and the second printing station are arranged such that the arrangement of the developing device and the rotation direction of the photoconductor are symmetrical between the first printing station and the second printing station. I have. The recording paper 3, which is a continuous paper that has been carried in between the first printing station 11 and the second printing station 12 from above, is transferred by the transfer unit of the first printing station 11 when turning in a U-shape. The cyan, magenta, yellow, and black toner images formed on the individual recording bodies 21 are sequentially superimposed on the front surface and transferred to form a full-color image. The toner images of cyan, magenta, yellow, and black formed on the four recording bodies 21 on the back surface of the recording paper 3 are sequentially superimposed sequentially on the back surface of the recording paper 3 by the transfer device of the second printing station 12 after being transported along the mold path. The image is transferred to form a full-color image, and is transported upward. The toner images 4 formed on both sides of the recording paper 3 are fixed on the recording paper 3 by the fixing device 5 and stored in the paper storage means.

The fixing device 5 includes a pair of rollers each having a heat source as shown in FIG. 1 or a pair of a heating roller and a pressure roller to fix unfixed toner on both surfaces. Are arranged so as to hit both sides. A pair of two heating rollers is good for miniaturizing the entire apparatus.

As is apparent from the present embodiment, one of the features of the present invention is that four printing units are vertically arranged, so that the height can be reduced compared to a system in which eight printing units are arranged in a staggered manner. The point is that the entire recording apparatus becomes compact. The second feature of the present invention is that the configuration of eight printing units, that is, all the printing units are essentially equivalent. This is a great advantage in comparison with the method in which the printing units are not equivalent in terms of stability of print image quality, reliability of the entire apparatus, and apparatus cost. A third feature of the present invention is that the developing device can be installed below the recording body because the recording paper is transported upward from below and the toner image is transferred beside the printing unit. When the recording paper is conveyed from top to bottom, a developing device must be installed above the recording body on mounting, but a large developing device having a plurality of high-speed developing rolls above the recording body is required. It is quite difficult to design the loudspeaker. The fourth feature of the present invention is that, in the paper transport path of the present invention, all three transport rolls 6 for changing the transport direction of the recording paper are in contact with the surface of the recording paper 3 opposite to the toner image adhering surface. Unfixed transfer toner image transferred to the recording paper 3 is fixed by the fixing device 5 and is conveyed without touching the conveyance roll 6 which is a member for contacting the paper. For example, in the paper conveyance path where the transfer toner image contacts the roll, in order to prevent the transfer toner image from being disturbed by the contact or adhering to the conveyance roll, as the conveyance roll, the charged charge of the toner of the transfer toner image is used. It is necessary to use a so-called bias roll to which voltages of the same polarity are applied. In this case, advanced technology such as the configuration of the bias roll, the material, the voltage application method, and the cleaning method is required, which is a considerable disadvantage in cost and reliability.

As described above, according to the recording method of this embodiment, in a color duplex printing apparatus for continuous paper using a tandem method, the height of the entire apparatus can be suppressed low, and all printing units are equivalent. It has the advantage of being superior in cost, device reliability, ease of use, and print quality without the need for equipment such as bias rolls.

Next, a second embodiment of the present invention will be described with reference to FIG. In the figure, cyan, magenta, yellow, and black toner images formed on four recording bodies 21 at a first printing station 11 are sequentially superimposed and transferred to form a full-color image, and then folded in an inverted U-shape. Later first
The fixing device 41 fixes the toner image and sends it to the second printing station 12, where the second printing station 1
2, cyan, magenta, yellow, and black toner images formed on four recording members 21 on the back surface of the recording sheet 3 are sequentially superimposed and transferred to form a full-color image, and the direction is reversed by the reversing roll 61. Then, the toner image is fixed by the second fixing device 42 installed beside the second printing station 12 and is stored in the paper storage unit 7. The fixing device 4
Reference numerals 1 and 42 denote fixing devices using a heating roller and a pressure roller, respectively, and are arranged so that an unfixed toner image hits the heating roller.

In this embodiment, unlike the first embodiment, two fixing devices are required, but the toner image formed on the paper surface in contact with the reversing roll 61 is already in the first fixing device 41. Since the paper is fixed, the paper transport path is changed without using the bias roll to which the voltage is applied.
Is installed next to the printing station 12, and the recording paper is fixed after the conveyance direction is changed, so that the entire height of the double-sided recording apparatus can be reduced.
When the first fixing device 41 is not used, the reversing roll 6
No. 1 comes into contact with an unfixed toner image and needs to be a bias roll.

In the embodiment of the present invention, the transport path shown in FIG. 1 has been described as the transport path of the recording paper. However, a configuration in which the configuration in FIG. 1 is symmetrical to the left and right is completely equivalent. Although the embodiment of the present invention describes the case where an image is formed by an electrophotographic method, the present invention relates to a relationship between a printing unit and a recording sheet, and is applicable to other image forming methods using toner. it can.

[0013]

As described above, according to the present invention, all printing units can be made equivalent in a recording method of printing on both sides of continuous paper using two sets of printing stations in which printing units are linearly arranged. In addition, there is an effect that the recording apparatus can be made compact.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a printing apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a printing unit used in the present invention.

FIG. 3 is a configuration diagram of a printing apparatus showing another embodiment of the present invention.

[Explanation of symbols]

2 printing unit, 3 recording paper, 5 fixing device, 11
... first printing station, 12 ... second printing station, 21 ... recording medium.

Claims (3)

[Claims] 1. A double-sided printing apparatus comprising a plurality of printing units each including at least a photoconductor, a charging device, a developing device, and a transfer device, and forming a color image on both sides of recording paper as continuous paper. The printing stations arranged in the vertical direction with respect to the floor are arranged in two rows symmetrically to form first and second printing stations, respectively, and the space between the first printing station and the second printing station is carried in from above. The transferred recording paper is turned into a U-shape in the direction of the first station, the toner image is transferred to the recording paper by the transfer device of the first printing station, then folded back into an inverted U-shape, and then folded back into a U-shape. The transfer path of the recording paper, which is transferred to the transfer sheet of the second printing station after transferring the toner image to the recording paper, and then sent to the fixing device, is a double-sided printing apparatus. 2. A double-sided printing apparatus according to claim 1, wherein the printing station comprises four printing units corresponding to color materials of black, cyan, magenta and yellow. 3. The fixing device according to claim 1, further comprising: a fixing device provided in the course of recording paper conveyance from the first printing station to the second printing station, in addition to the fixing device.
A double-sided printing apparatus as described in the above.