JP2003149906A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming device by which provides an optimum output for a recording medium to be used. SOLUTION: The whiteness of a recording medium P is detected by a detecting means 14, and is inputted to the A/D conversion input unit of a CPU 15. The CPU 15 generates a PWM output corresponding to an input value, and output it to a high voltage unit 16 to generate developing high voltage bias. The high voltage unit 16 generates a high voltage output corresponding to inputted PWM, and outputs to a developing unit 5a for yellow toner.

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention
The present invention relates to a color image forming apparatus capable of performing color printing with X or a copying machine. 2. Description of the Related Art A conventional color image forming apparatus does not have a correction / adjustment means corresponding to the whiteness of a recording medium.
When it is desired to obtain an optimum output, that is, to print a desired color on a recording medium, it is premised that a recording medium recommended by the color image forming apparatus is used. [0003] In a conventional image forming apparatus, when recycled paper, which is a recording medium that is not recommended, is used, the whiteness is often low. There has been a problem that the image is often more yellowish overall than expected as a whole. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problem, and conveys a recording medium to a position of an image forming unit, and the image forming unit applies a color image on the recording medium. In a color image forming apparatus for forming an image, detecting means for detecting the whiteness of a recording medium being conveyed between a position at which the feeding of the recording medium is started and a position of the image forming means, and A color image forming apparatus comprising: a control unit configured to control a condition of the image forming unit to be changed according to a detection value. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a color image forming apparatus of the present invention. The color image forming apparatus includes a rectangular parallelepiped housing 2 formed of a synthetic resin. At a substantially central portion of the housing 2, between the front and rear side plates made of a metal plate (not shown) arranged at a predetermined interval in the front-rear direction (a direction perpendicular to the paper surface in FIG. 1) within the housing 2. A photosensitive drum 3 as a toner image forming body is rotatably disposed. The photoreceptor drum 3 is driven to rotate by a gear transmission (not shown) in the direction indicated by an arrow in order through a charging area, an electrostatic latent image area, a developing area, an image transfer area, and a cleaning area. Around the photosensitive drum 3, a charging corona discharger 4 is provided in a charging area, a developing device 5 is provided in a developing area, an intermediate transfer body 6 as a toner image forming body is provided in an image transferring area, and a photosensitive drum 3 is provided in a cleaning area. Cleaning mechanisms 7 are provided. The developing device 5 includes a yellow toner developing unit 5a, a magenta toner developing unit 5b, a cyan toner developing unit 5c, and a black toner developing unit 5d. Further, the intermediate transfer member 6 includes the photosensitive drum 3
Similarly to the above, it is rotatably disposed between front and rear side plates disposed at predetermined intervals in the front-rear direction in the housing 2 and is driven to rotate in a direction shown by an arrow by a gear transmission (not shown). . A cleaning mechanism 8 for the intermediate transfer member 6 is provided at a lower left portion of the intermediate transfer member 6 in FIG. The cleaning mechanism 7 and the cleaning mechanism 8 may have a known configuration, and include a cleaning fur brush, a cleaning blade, and a transport screw in cleaning cases 71 and 81, respectively. [0007] A laser unit 9 as an electrostatic latent image forming means is provided in an upper portion of the housing 2. The laser unit 9 projects a laser beam based on image information output from an external device (computer) on the peripheral surface of the photosensitive drum 3 in an electrostatic latent image forming area between a charging area and a developing area. In the lower part of the housing 2,
A secondary transfer roller 10 is disposed below the intermediate transfer body 6, and a transport belt mechanism 11 and a fixing unit 12 are provided downstream (left side in FIG. 1) of the secondary transfer roller 10.
Are arranged. Next, the operation of the above-described color image forming apparatus will be briefly described. While the photosensitive drum 3 is rotated in the direction indicated by the arrow, the charging corona discharger 4 charges the photosensitive layer of the photosensitive drum 3 to a specific polarity. Next, in the electrostatic latent image forming area between the charging area in which the charging corona discharger 4 is provided and the developing area in which the developing device 5 is provided, laser light from the laser unit 9 is applied onto the photosensitive drum 3. The electrostatic latent image corresponding to the image information is formed on the peripheral surface of the photosensitive drum 3 by being projected. Thereafter, toner is applied to the electrostatic latent image on the photosensitive drum 3 by the developing device 5 to visualize the electrostatic latent image (to make it visible). The toner image formed on the photosensitive drum 3 in this manner is transferred to the intermediate transfer member 6 as a toner image carrier. In the case of color printing, charging of the photosensitive drum 3 by the charging corona discharger 4 for each color, exposure by the laser unit 9,
A developing unit 5a for yellow toner, a developing unit 5b for magenta toner, a developing unit 5c for cyan toner,
By performing the development by the black toner developing unit 5d and transferring the image to the intermediate transfer member 6 each time, a multicolor toner image corresponding to one image signal is transferred to the intermediate transfer member 6. On the other hand, the recording medium P fed from a sheet feeding device (not shown) is temporarily stopped by a pair of registration rollers 13 and is brought into timing with the intermediate transfer member 6 on which the toner image has been transferred. The sheet is conveyed to a secondary transfer area facing the next transfer roller 10. Recording medium P conveyed to secondary transfer area
The toner image formed on the peripheral surface of the intermediate transfer member 6 is transferred to the surface of the intermediate transfer member 6 by the operation of the transfer roller 10. The recording medium P on which the toner image has been transferred is peeled off from the intermediate transfer body 6 and is conveyed to a fixing unit 12 by a conveying belt mechanism 11 where the toner image is heated and fixed on the surface of the recording medium P. It is discharged outside. [0010] After the toner image is transferred from the photosensitive drum 3 to the intermediate transfer member 6, the residual toner attached to the surface of the photosensitive drum 3 is removed by the cleaning mechanism 7. On the other hand, the residual toner adhering to the surface of the intermediate transfer member 6 after transferring the toner image from the intermediate transfer member 6 to the recording medium P is removed by the cleaning mechanism 8. Then, the removed residual toner is supplied to the cleaning case 7.
The toner is discharged to the toner collecting device 20 by the transport screw disposed in the inside of the toner collecting device 81 and collected in the residual toner collecting container 21. In the present invention, detecting means 14 for detecting the whiteness of the recording medium is provided between a position (not shown) at which the feeding of the recording medium is started (not shown) and a secondary transfer position.
The above-described conditions of the image forming means are controlled so as to be variable in accordance with the detected value of. In the present embodiment, the detection unit 14 is provided at a position immediately before the registration roller pair 13 on the transport path. Hereinafter, a case where the developing high voltage bias of the yellow toner developing unit 5a is controlled in accordance with the detection value of the detecting means 14 will be described with reference to FIG. First, the detection means 14 detects the whiteness of the recording medium P. In the detecting means 14, the light is emitted to the recording medium P by the light emitting means by the optical sensor, and the reflected light is taken in by the light receiving means. Then, a value corresponding to whiteness, which is a value obtained for the reflected light, is amplified as necessary,
15 A / D conversion input devices. The CPU 15 generates a PWM output according to the input value, and outputs the PWM output to the high-voltage unit 16 that generates a developing high-voltage bias. High pressure unit 1
At 6, a high voltage output corresponding to the input PWM output is generated and output to the yellow toner developing unit 5a. With such control, it is possible to change the image forming conditions according to the whiteness of the recording medium P and to set the optimum image forming conditions. The generation of the PWM output according to the present embodiment includes a method of referring to a predetermined look-up table and a method of performing processing by a predetermined operation, and any method may be used. Further, in the present embodiment, a description has been given of variable conditions for the yellow toner developing unit 5a.
This is because, by adjusting the yellow toner developing unit 5a as a countermeasure against the yellowish impression, a natural color output can be obtained without enhancing yellow. However, in addition to changing the toner charge amount of the yellow toner developing unit 5a of this embodiment, other image forming conditions such as the charge amount of the photosensitive drum 3 or the exposure amount of the laser unit 9 may be changed. May be controlled. Further, the following may be performed as another embodiment. (1) When the high voltage to be fed back is only the DC component, the value obtained from the detection means 14 is amplified without the intervention of the CPU 15 to generate a high voltage output. (2) Add a conditional branch. For example, if it is desired to use the same processing (same high-voltage output) for paper having a whiteness of 85% or more, a condition branch of whiteness determination is inserted after whiteness measurement, and whiteness in a range to be corrected is inserted. Performs the same processing as in FIG. 2, and performs processing with a fixed value when correction is not necessary. (3) Whiteness information is input via a front panel or a driver screen of the color image forming apparatus, and corresponding processing is performed. Further, at the position of the detecting means 14 in this embodiment, when the recording medium P reaches the detecting means 14, a toner image may already be formed on the intermediate transfer member 6. Therefore, it is preferable to dispose the detecting means 14 as far upstream as possible in the sheet feeding direction. Further, even if the first recording medium P is in time, information on the first recording medium P is stored, and when the same recording medium P is fed after the second sheet, the above-described control is performed. It may be performed. As described above, according to the color image forming apparatus of the present invention, the condition of the image forming means is changed according to the whiteness of the recording medium to be used. And a color image forming apparatus that obtains an optimum output.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a color image forming apparatus of the present invention. FIG. 2 is a diagram showing a processing procedure of the color image forming apparatus of the present invention. [Description of Signs] 2: Housing 3: Photoconductor drum 4: Corona discharger 5 for charging: Developing device 5a: Developing unit 5b for yellow toner: Developing unit 5c for magenta toner: Developing unit 5d for cyan toner 5d: For black toner Developing unit 6: Intermediate transfer members 7, 8: Cleaning mechanism 9: Laser unit 10: Secondary transfer roller 11: Conveying belt mechanism 12: Fixing unit 13: Registration roller pair 14: Detecting means 15: CPU 16: High pressure unit

Claims (1)

1. A color image forming apparatus which conveys a recording medium to a position of an image forming means and forms a color image on the recording medium by said image forming means. Detecting means for detecting the whiteness of the recording medium being conveyed from the start position to the position of the image forming means; and changing the condition of the image forming means in accordance with the detection value of the detecting means. A color image forming apparatus, comprising: a control unit for controlling the color image forming apparatus.