JP3835654B2 - Electrophotographic apparatus for double-sided recording - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic apparatus, and more particularly to an electrophotographic apparatus suitable for printing a mono-black or color toner image on both sides of continuous paper at high speed.
[0002]
[Prior art]
As a typical method of double-sided printing using a conventionally known electrophotographic technique, when the recording paper is cut paper, one or a plurality of photoconductors are used, and a toner image is transferred from the photoconductor to the front surface of the recording paper. A method is known in which the recording paper is fixed once after transfer, and the recording paper is turned upside down, and the toner image is transferred from the photosensitive member to the back side of the recording paper again and fixed.
[0003]
When the recording paper is continuous paper, for example, as disclosed in Japanese Patent Laid-Open No. 7-72776, one set of four photosensitive members for cyan, magenta, yellow, and black is used, and two sets for front and back printing. A total of 8 photoconductors are continuously arranged in a staggered pattern, and the recording paper, which is continuous paper, is transported between them. The photoconductor is driven by the recording paper to perform color printing on both sides of the recording paper in one process. A method for printing an image is known. However, in this method, since the photosensitive member rotates following the recording paper, there is a problem in that when printing at high speed, the load on the recording paper increases and the recording paper breaks.
[0004]
[Problems to be solved by the invention]
In view of the circumstances described above, an object of the present invention is to transfer toner images from a toner carrier such as a photosensitive member or an intermediate transfer member arranged on the front side and the back side of a recording sheet, which is a continuous sheet, on both sides of the recording sheet. In a double-sided recording electrophotographic apparatus that transfers and fixes both sides simultaneously, the toner carrier and the recording paper are driven independently, and at that time, a recording paper buffer section generated upstream of contact-type fixing means such as a heating roller It is an object of the present invention to provide an electrophotographic apparatus for double-sided recording, which can prevent the sag and vibration of the recording sheet from being transmitted to the fixing means as it is and causing image distortion.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is the final stage in an electrophotographic apparatus for double-sided recording, in which a toner image formed on the front and back surfaces of a recording sheet that is continuous paper is fixed by a fixing unit. Between the paper driving means and the fixing means, there is provided a paper holding means that rotates following the recording paper so as not to disturb the toner image in the unfixed state. Is to prevent the occurrence of
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the front surface recording printing station is named the first printing station, and the back surface recording printing station is named the second printing station. Embodiments of the present invention will be described below with reference to the drawings.
[0007]
A first embodiment of the present invention will be described with reference to FIG. The figure shows an example of a schematic configuration of an electrophotographic apparatus for double-sided mono black printing using the continuous paper of the present invention.
[0008]
The black first toner image 12 formed on the first toner carrier 11 of the first printing station 1 is transferred to the front surface of the recording paper 3 which is continuous paper by the first transfer means 13. Then, the black second toner image 22 formed on the second toner carrier 21 of the second printing station 2 is transferred to the back surface of the recording paper 3 by the second transfer means 23 to record the recording paper. 3 to form toner images on both sides. Next, the toner images formed on both sides of the recording paper 3 are simultaneously fixed by the fixing unit 4 including the two heating rollers 41 to complete double-sided printing.
[0009]
A printing process in the first printing station 1 will be described. The first toner carrier 11 made of a drum-shaped photoconductor charged by the first charger 14 rotates clockwise, forms an electrostatic latent image with the first laser beam 15, and then transports it to the developing unit. It is. This electrostatic latent image is developed by the negatively charged toner of the first developing device 16 to form a first toner image 12 on the surface of the first toner carrier 11. This is electrostatically transferred to the recording paper 3 by the first transfer means 13 which is a corona discharger. Residual charges on the surface of the first toner carrier 11 are neutralized by the first eraser 17, and residual toner is removed by the first cleaner 18.
[0010]
Similarly, in the second printing station 2, the second toner carrier 22 made of a drum-like photoconductor charged by the second charger 24 rotates counterclockwise, and the second laser beam 25 After forming the electrostatic latent image, it is carried to the developing unit. This electrostatic latent image is developed by the positively charged toner of the second developing machine 26 to form a second toner image 22 on the surface of the second toner carrier 22. This is electrostatically transferred onto the recording paper 3 by the second transfer means 23. Residual charges on the surface of the toner carrier 22 are neutralized by the second eraser 27, and residual toner is removed by the second cleaner 28.
[0011]
The recording paper 3 with feed holes at the end of the paper is held and pulled at both ends by a first paper drive means 51 and a second paper drive means 52 comprising a rotating belt so-called tractor with pins adapted to the feed holes. Transport. The tractor is provided with a sheet presser cover 53 to prevent the recording sheet 3 from coming off the tractor.
[0012]
Since the recording paper 3 is also pulled by the heating roller 41, the heating roller 41 and the second paper driving means 52 allow the recording paper 3 to have a slack between the heating roller 41 and the second paper driving means 52 so as not to break. The conveyance speed of the recording paper 3 is controlled.
[0013]
Between the second paper driving means 52 and the heating roller 41, a paper holding means 6 comprising a pinned roller 61 which holds both ends of the recording paper 3 and rotates following the recording paper 3 is installed at a fixed position. . The roller 61 with a pin is provided with a load means 60 that applies a load with respect to the rotation of the roller 61 with a pin, that is, a mechanical or electrical load with respect to the conveyance of the recording paper 3. Therefore, sagging of the recording paper 3 occurs between the paper holding means 6 and the second paper driving means 52, and does not occur between the heating roller 41 and the paper holding means 6. For this reason, since the recording paper 3 does not come into contact with the heating roller 41 in a slack or vibrated state, image disturbance due to offset or the like can be prevented. Further, the pinned roller 61 holding both ends of the recording paper 3 can be prevented from wrinkling in the recording paper 3 by applying tension to the outside by an elastic body such as a spring and pulling the recording paper 3 in the width direction. .
[0014]
The sagging state of the recording paper 3 between the pin roller 61 and the second paper driving means 52 is observed by an optical sensor, and the conveyance speed of the recording paper 3 by the heating roller 41 and the second paper driving means 52 is determined. Control.
[0015]
According to the present embodiment, since the end of the recording paper 3 is held by the second paper driving means 52 and the paper holding means 6, unfixed toner images on both sides of the recording paper 3 are not disturbed.
[0016]
A second embodiment of the present invention will be described with reference to FIG. FIG. 2 shows the second printing station 2 and its downstream part. In this embodiment, instead of the pin-equipped roller 61 used in the first embodiment as the paper holding means 6, a bias roller that contacts the full width of the back surface of the recording paper 3 and rotates around a fixed position following the recording paper 3. 62 is used. The bias roller 62 is provided with a rubber layer or a resin layer on a metal cylinder, and is used to prevent the toner having a positive charge adhering to the back surface of the recording paper 3 from adhering to the bias roller 62. A positive voltage is applied to the cylinder, and a negative corona discharge is applied to the front surface of the recording paper 3 by the charger 33 to record on the toner having a positive charge attached to the back surface of the recording paper 3. An electrostatic force in the direction of attracting the sheet 3 is applied. As the bias roller 62, a charge may be applied to the surface of the roller by corona charging. A cleaner 63 for removing a small amount of adhering toner on the surface of the bias roller 62 is in contact with the bias roller 62 and rotates. By rotating the rotation direction of the cleaner 63 in the same direction as the rotation direction (counterclockwise direction) of the bias roller 62, the moving direction on the contact surface is reversed, and the cleaner 63 serves as a load means for the rotation of the bias roller 62. Next to the bias roller 62, there is provided a sheet pressing roller 7 having the same structure as the pinned roller 61, adapted to the feed hole of the recording sheet 3, holding both ends, driven by the recording sheet 3 and rotated around a fixed position. The recording paper 3 is brought into close contact with the bias roller 62. In this embodiment, since the bias roller 62 that contacts the entire width of the back surface of the recording paper 3 is used as the paper holding means 6, the recording paper 3 is applied with a uniform force without sagging, and wrinkles of the recording paper 3 are generated. Therefore, there is an advantage that it is suitable for high-speed recording.
[0017]
A third embodiment of the present invention will be described with reference to FIG. FIG. 3 shows the second printing station 2 and its downstream part. In this embodiment, in order to further adapt to high-speed recording, the heating roller 41 and two parallel heat plates 42 installed so as to sandwich the recording paper 3 are used together as the fixing unit 4. In this embodiment, the same bias roller 62 as that in the second embodiment is used. A rotary cleaner 63 acts as a load means in the same direction as the rotation direction of the bias roller 62. In addition, an idler roller 8 with a pin that rotates in response to the recording paper 3 is provided in the slack portion of the recording paper 3 so as to be fitted to the feed hole of the recording paper 3 and hold both ends. The idler roller 8 moves according to the degree of sagging of the recording paper 3 and applies a constant tension to the recording paper 3. Since the position of the idler roller 8 can be measured accurately, the conveyance speed of the recording paper 3 by the heating roller 41 and the second paper driving means 52 can be controlled more accurately. In this embodiment, there is an advantage that higher speed recording is possible.
[0018]
In the present invention, the printing station for recording the front surface of the recording paper 3 is named the first printing station, and the printing station for recording the back surface is named the second printing station. The arrangement and configuration of the printing station and the second printing station are not limited to those described in the embodiments of the present invention, and there are many variations. An example is shown in FIG. In FIG. 4, for simplicity, only the toner carrier among the components of the printing station is indicated by a circle.
[0019]
(A) is an example of a double-sided mono black printing apparatus configuration in which the recording paper 3 is conveyed linearly and the first printing station 1 and the second printing station 2 are installed on both sides thereof.
[0020]
(B) is an example of a double-sided mono black printing apparatus configuration in which a front / back reversing device 9 for the recording paper 3 is provided between the first printing station 1 and the second printing station 2.
[0021]
(C) shows a first printing station 1 including an intermediate transfer drum having four photosensitive members for forming cyan, magenta, yellow, and black toner images on both sides of the recording paper 3 conveyed linearly. 2 is an example of an apparatus configuration for double-sided full-color printing in which two printing stations 2 are installed.
[0022]
(D) is an example of a double-sided full-color printing apparatus configuration in which the recording paper 3 is conveyed in a U-shape and each of the first printing station 1 and the second printing station 2 has four toner carriers.
[0023]
In these examples, the recording paper is mainly conveyed in the horizontal direction, but there are many variations such as a configuration in which the recording paper is conveyed in the vertical direction.
[0024]
【The invention's effect】
As described above, according to the present invention, in the electrophotographic apparatus for double-sided recording, the toner carrier and the recording paper are driven independently, and the recording that occurs upstream of the fixing means such as a heating roller at that time. There is an effect that it is possible to prevent the sag and vibration of the recording paper in the paper buffer section from being transmitted to the fixing means as they are, and the occurrence of image distortion.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a duplex printing apparatus showing an embodiment of the present invention.
FIG. 2 is a configuration diagram of a duplex printing apparatus showing a second embodiment of the present invention.
FIG. 3 is a configuration diagram of a duplex printing apparatus showing a third embodiment of the present invention.
FIG. 4 is a configuration diagram of a printing apparatus showing a modification of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... 1st printing station, 2 ... 2nd printing station, 3 ... Recording paper, 4 ... Fixing means, 6 ... Paper holding means, 7 ... Paper pressing roller, 8 ... Idler roller, 11 ... 1st toner carrying Body, 12 ... first toner image, 41 ... heating roller, 42 ... heat plate, 51 ... first paper driving means, 52 ... second paper driving means, 60 ... loading means, 61 ... roller with pin, 62 ... Bias roller, 63 ... Cleaner.

Claims (4)

The toner images formed by the first printing station on the front surface of the recording paper, which is continuous paper, and the second printing station on the back surface, are fixed by fixing means for holding and heating the recording paper. In the electrophotographic apparatus for double-sided recording, the recording sheet is driven to rotate at a fixed position between the sheet driving unit and the fixing unit provided on the downstream side of the second printing station, and a load is applied to the rotation. An electrophotographic apparatus comprising a sheet holding unit having a load unit. 2. The electrophotographic apparatus according to claim 1, wherein the recording sheet is a sheet with a feed hole at an end, and the sheet holding means is a rotating member with a pin that fits the feed hole of the recording sheet. . 3. The electrostatic discharge device according to claim 1, wherein the sheet holding unit is in contact with the entire width of the surface of the recording sheet and presses the unfixed toner image in contact with the sheet holding unit against the surface side of the recording sheet. An electrophotographic apparatus characterized by being a bias roller to which a voltage is applied so as to give a sufficient force. 4. The electrophotographic apparatus according to claim 3, wherein the load means for the bias roller is a cleaner that contacts the bias roller and rotates in the same direction as the rotation direction of the bias roller.

Images