JPH1020579A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device constituted so that the density of a recorded image can be uniformized even when the shape error and the rotational fluctuation of a photoreceptor drum, an intermediate transfer body, an electrifying unit, a developing unit and a transfer roll are caused. SOLUTION: This image forming device is provided with the photoreceptor drums 2A, 2B, 2C and 2D, the electrifying units 3A, 3B, 3C and 3D whose diamters are identical to the drums and which is rotated at an identical speed to the drums, the developing rolls 4A, 4B, 4C and AD and the transfer rolls 5A, 5B, 5C and 5D. Then, the turning-on time of exposure units 1A, 1B, 1C and 1D are corrected based on the cycle of the fluctuation of the density obtained by detecting the density of a transferred image transferred on an intermediate transfer belt 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus, and more particularly, to a method for synchronizing a cycle of occurrence of uneven charging, uneven developing, or uneven transferring caused by rotation of a charger, a photoreceptor, a developing unit, and a transfer unit. The present invention relates to an image recording apparatus in which the density of a recorded image is prevented from being changed.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus,
As a method of suppressing the density fluctuation of the recorded image, at the time of power-on or before image formation, a toner-developed development patch in a predetermined pattern is formed on a photosensitive drum and transferred to an intermediate transfer body or recording paper, Based on the density measurement result obtained by detecting the density of the development patch by the optical sensor, control parameters such as the output of the charger, the exposure amount of the light beam irradiated from the exposure unit, the development voltage and the supply amount of the developer are set. Set properly.

[0003] However, the photosensitive drum and the intermediate transfer member rotate with a slight fluctuation in rotation, and the rotation of the photosensitive drum and the intermediate transfer member must be completely synchronized even if the control parameters are appropriately set. Therefore, the density fluctuation may occur at irregular intervals in the recorded image.

Japanese Patent Application Laid-Open No. Hei 6-20249 discloses an image forming apparatus which eliminates the asynchronous rotation of the photosensitive drum and the intermediate transfer member.
There is one disclosed in Japanese Patent Publication No. 2 (JP-A) No. 2 (1994). This image forming apparatus synchronizes the rotation of the photosensitive drum and the intermediate transfer body by setting the outer diameters of the photosensitive drum and the intermediate transfer body in a relationship of an integer ratio, so that the density fluctuation is the same on one image. I'm trying to make it happen in place.

[0005]

However, Japanese Patent Laid-Open No. 6-2 / 1994
According to the image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 02492, the density fluctuation is periodically generated based on the rotation of the photosensitive drum and the intermediate transfer member. For example, the rotation of a charging roll or a developing roll contacting the photosensitive drum is controlled. If a shape error or rotation fluctuation occurs in the body, there is a problem that the synchronization between the photosensitive drum and the intermediate transfer body is lost and a density fluctuation occurs. Accordingly, an object of the present invention is to provide an image forming apparatus capable of making the density of a recorded image uniform even if there is a shape error or rotation fluctuation of the photosensitive drum, the intermediate transfer member, the charger, the developing device, and the transfer roll. Is to provide.

[0006]

In order to achieve the above object, the present invention provides a charging means for applying a predetermined potential to a drum or a belt-like photoconductor, and a charging means for applying the predetermined potential to the photoconductor. An exposure unit that scans a light beam corresponding to image information to form an electrostatic latent image, a developing unit that develops the electrostatic latent image formed on the photoconductor with toner to form a toner image, and the toner Transfer means for transferring an image to a transfer body or recording paper to form a transfer image; drive means for rotating the photoconductor at a predetermined rotation cycle; and detecting the density of the toner image or the transferred image to change the density. Density fluctuation detecting means for calculating the cycle of the density fluctuation, and correcting at least one operation parameter of the charging means, the exposure means, the developing means, and the transfer means based on the cycle of the density fluctuation, and Before To provide an image forming apparatus having a control means for controlling an integer multiple or single integer fraction of said predetermined rotation period of the photosensitive member.

In the above arrangement, the control means may change the lighting time of the exposure means based on the period of the density fluctuation of the toner image or the transferred image. The charging unit includes a charging roll that applies a predetermined potential to the photoconductor, and the charging roll may have the same outer diameter as the photoconductor. Further, the charging means may be a scorotron provided at a predetermined distance from the photoconductor.
The developing unit includes a developing roll that contacts the photoconductor and adheres the toner to the electrostatic latent image, and the developing roll may be formed with the same outer diameter as the photoconductor. The transfer unit includes a transfer roll that presses the transfer body or the recording paper against the photoconductor, and the transfer roll may have the same outer diameter as the photoconductor. Further, the transfer unit may be a corotron provided at a predetermined distance from the photoconductor via the transfer body or the recording paper. It is preferable that the density fluctuation detecting means detects the density of the toner image or the transferred image at power-on or before image formation, and calculates the period of the density fluctuation.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 shows an image forming apparatus according to an embodiment of the present invention, which emits light beams corresponding to image data of K (black), Y (yellow), M (magenta) and C (cyan). Laser scanner type exposure unit 1A,
1B, 1C, and 1D, photoconductor drums 2A, 2B, 2C, and 2D that form an electrostatic latent image based on scanning of a light beam, and photoconductor drums 2A, 2B, 2C, and 2D before exposure to a predetermined potential Transfer rolls 3A, 3 charged up to
B, 3C and 3D, and the photosensitive drums 2A, 2B and 2C
Rolls 4A, 4B, 4C and 4D for developing the electrostatic latent images formed on the toner image and the 2D, and a transfer roll 5 for transferring the toner image developed on the intermediate transfer belt 6
A, 5B, 5C and 5D, a driving roll 7 for rotatingly driving the intermediate transfer belt 6, support rolls 8A, 8B and 8C for rotatably supporting the intermediate transfer belt 6 with a predetermined tension, and a recording paper 9A. Paper cassette 9 to be stored, and paper roll 10 for carrying out paper 9A from paper cassette 9
And a secondary transfer roll 11 provided at a secondary transfer position where the support roll 8B is located to transfer the toner image from the intermediate transfer belt 6 to the sheet 9A, and a fixing unit 12 for fixing the toner image transferred to the sheet 9A. And an image sensor type density detector 13 for detecting the toner image transferred to the intermediate transfer belt 6, and a density detection signal input to the exposure units 1A, 1
A correction coefficient calculator 14 for calculating a correction coefficient for the lighting time of B, 1C and 1D; an exposure unit controller 15 for controlling the lighting time of the exposure units 1A, 1B, 1C and 1D based on the calculated correction coefficient; Having.

FIG. 2 shows a photosensitive drum 2A, a charging roll 3
A, the developing roll 4A, and illustrates the transfer roller 5A, the outer diameter D _p of the photosensitive drum 2A, the outer diameter D _d of the developing roller 4A, the outer diameter D _c of the charging roller 3A, and a transfer roll 5
Outer diameter D _t of A is configured to rotate at the same being formed with an outer diameter of the photosensitive drum 2A and the same rotational speed.

In the present embodiment, D _p , D _d , and D
_c is formed at 30 mm, and the outer peripheral length of the photosensitive drum is set to about 95 mm.
mm, not-shown photosensitive drums 2B, 2C and 2D, charging rolls 3B, 3C and 3D, developing rolls 4B, 4C and 4D, and transfer rolls 5B and 5C.
And 5D are also formed with the same outer diameter.

FIG. 3 shows a density detecting section 13, a housing 13B provided with a slit 13A on the upper surface, and a light source 1 provided inside the housing 13B for irradiating a transfer image 16 with measurement light.
3C and a lens 13 for collecting light reflected from the transfer image 16
D, and a light receiving element 13E for receiving the condensed reflected light.

FIG. 4 shows the relationship between the lighting time of the exposure units 1A, 1B, 1C and 1D and the image density. As the lighting time of the exposure unit increases, the exposure amount of the photosensitive drum increases, so that the recorded image is recorded. The density increases.

FIG. 5 shows the density fluctuation of an image during one rotation of the photoconductor drum. The density fluctuation has a periodicity in the process direction of the photoconductor drum, and the fluctuation in the axial direction is based on the surface shape of the photoconductor drum. Shading has occurred.

FIG. 6 shows the lighting time of the exposure unit corrected based on the density fluctuation of the image shown in FIG. 5. The correction coefficient calculating unit 14 calculates the density of the transferred image input from the density detecting unit 13. A correction coefficient is calculated based on the correction coefficient. The lighting time of the exposure unit is corrected by multiplying the lighting time of the exposure unit by the correction coefficient.

Hereinafter, the operation of the image forming apparatus of the present invention will be described with reference to the drawings. For the sake of simplicity, a description will be given of a monochrome image forming operation based on the image forming unit shown in FIG.

FIG. 7 shows a first color (black) image forming portion of the image forming apparatus of the present invention, in which the photosensitive drum 2 is scanned with a light beam from the exposure unit 1 via the reflection mirror 17.
The roller is stretched with a predetermined tension by a charging roll 3, a developing roll 4, and a transfer roll 5, which rotate at the same speed as the photosensitive drum 2 at the same outer diameter, a driving roll 7, and support rolls 8A, 8B, 8C. Intermediate transfer belt 6 and density detector 1 for detecting toner image 16 transferred to intermediate transfer belt 6
3

First, the charging roll 3 is set to -1.1 kV, the developing roll 4 is set to -300 V, and the transfer roll 5 is set to +500 kV.
After applying a voltage of V, a light beam based on an image having a different density is emitted from the exposure unit 1 based on the image data. At this time, the photosensitive drum 2 is charged to −500 V by the charging roll 3, and an electrostatic latent image is formed on the photosensitive drum 2 based on the scanning of the light beam reflected by the reflection mirror 17.

The electrostatic latent image is conveyed to a developing device based on the rotation of the photosensitive drum 2, and black toner is supplied from a developing roll 4 rotating at the same speed as the photosensitive drum 2 in the developing device. Is developed. The developed toner image is conveyed to a transfer position based on the rotation of the photosensitive drum 2, and is transferred to an intermediate transfer belt 6 pressed by a transfer roll 5 provided at the transfer position.

Transfer image 16 transferred to intermediate transfer belt 6
Is transported to the density detecting unit 13 and the density of the toner is measured. This measurement result is output to the correction coefficient calculation unit 14.

FIG. 8 shows the result of measuring the density of the toner image 16 transferred to the intermediate transfer belt 6, wherein the density of the toner image fluctuates at a predetermined cycle in the process direction of the photosensitive drum. The cycle of this density fluctuation substantially corresponds to the length of one rotation of the photosensitive drum.

The correction coefficient calculation unit 14 calculates a correction coefficient for the lighting time of the exposure unit 1A based on the density measurement result of the density detection unit 13 so that the image density becomes uniform.
The calculation result of the correction coefficient is output to the exposure unit control unit 15 and is multiplied by the lighting time of the exposure unit.

FIG. 9 shows the corrected lighting time of the exposure unit 1A. The lighting time of the exposure unit 1A is changed so that the corrected image density becomes 1.0 in the entire region.

The exposure unit control section 15 outputs a control signal to the exposure unit 1A based on the corrected lighting time, and the exposure unit 1A emits a light beam based on the corrected lighting time to produce a photosensitive drum 2A. Is scanned.

In the above-described image forming apparatus, the photosensitive drum, the charging roll, the developing roll, and the transfer roll are formed with the same outer diameter and are driven at the same speed. , The rotation cycles of the developing roll and the transfer roll coincide, and the occurrence cycle of the shape error and the rotation fluctuation becomes equal. As a result, the density fluctuation of the recorded image also occurs in synchronization with the rotation of the photosensitive drum, the charging roll, the developing roll, and the transfer roll, and accordingly, the lighting time of the exposure unit 1A according to the density fluctuation of one rotation of the photosensitive drum. Is corrected, an image having a uniform density over the entire image area can be obtained.

Therefore, the second color, the third color, and the fourth color
Similarly, for the color image forming unit, the toner image formed by forming the photosensitive drum, charging roll, developing roll, and transfer roll with the same outer diameter and driving at the same speed is also used as the density detecting unit. By calculating the correction coefficient of the lighting time of the exposure unit based on the density measurement result obtained in the above, so that the image density becomes uniform, there is no change in hue, and the density is uniform over the entire image area. Image can be obtained.

FIG. 10 shows another embodiment of the present invention, in which a scorotron 18 for charging the photosensitive drum 2 and a toner image formed on the photosensitive drum 2 are transferred to the intermediate transfer belt 6.
And the other configuration and function are the same as those of the image forming unit shown in FIG. 7, and therefore, duplicated description will be omitted.

In the above configuration, the discharge wire of the scorotron 18 is -5.0 kV, and the grid electrode is -520 kV.
After applying a voltage of -300 V to the developing roll 4 and a voltage of +5.0 kV to the discharge wire of the corotron 19, a light beam based on an image having a different density is emitted from the exposure unit 1 based on the image data. At this time, the photosensitive drum 2 is charged to -500 V by the scorotron 18, and
An electrostatic latent image is formed on the photosensitive drum 2 based on the scanning of the light beam reflected by the reflection mirror 17.

This electrostatic latent image is conveyed to the developing device based on the rotation of the photosensitive drum 2, and black toner is supplied from the developing roll 4 rotating at the same speed as the photosensitive drum 2 in the developing device. Is developed. The developed toner image is conveyed to a transfer position based on the rotation of the photosensitive drum 2, and is electrostatically transferred to the intermediate transfer belt 6 by a corotron 19 provided at the transfer position.

Toner image 1 transferred to intermediate transfer belt 6
6 is conveyed to the density detector 13 and the density of the toner is measured. This measurement result is output to the correction coefficient calculation unit 14.

FIG. 11 shows the result of measuring the density of the toner image 16 transferred to the intermediate transfer belt 6, where the density of the toner image fluctuates at a predetermined cycle in the process direction of the photosensitive drum. This period of density fluctuation occurs because the distance from the scorotron 18 changes due to the eccentricity of the photosensitive drum.
The length substantially corresponds to the length of one rotation of the photosensitive drum. When the scorotron 18 and the corotron 19 were used, there was no change in shading in the axial direction of the photosensitive drum.

As described above, even when the scorotron for charging the photosensitive drum and the corotron for electrostatically transferring the toner image formed on the photosensitive drum to the intermediate transfer belt are provided, the density fluctuation of the recorded image is not affected. Can be given periodicity. For this reason, by correcting the lighting time of the exposure unit in accordance with the density fluctuation for one rotation of the photosensitive drum, an image having a uniform density over the entire image area can be obtained.

In the above embodiment, an image forming apparatus using a photosensitive drum has been described. However, the present invention can be applied to an image forming apparatus using a photosensitive belt.

[0034]

As described above, according to the image forming apparatus of the present invention, the photosensitive drum, the charging roll, the developing roll,
And the transfer roll is formed with the same outer diameter, and the lighting time of the exposure unit is corrected based on the density fluctuation of the recorded image generated by driving at the same speed. The density of the recorded image can be made uniform even if there is a shape error or rotation fluctuation of the developing device and the transfer roll.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a configuration of a photosensitive drum, a charging roll, a developing roll, and a transfer roll according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a configuration of a density detection unit 13 according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram illustrating a relationship between an image density and a lighting time of an exposure unit.

FIG. 5 is an explanatory diagram illustrating a density variation of an image for one rotation of the photosensitive drum according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a lighting time of an exposure unit which is corrected according to a density variation of the image shown in FIG. 5;

FIG. 7 is an explanatory diagram illustrating an image forming unit of the image forming apparatus according to the embodiment of the present invention.

FIG. 8 illustrates an intermediate transfer belt 6 according to the embodiment of the present invention.
FIG. 7 is an explanatory diagram showing a result of measuring the density of the toner image 16 transferred to the image forming apparatus.

FIG. 9 is an explanatory diagram showing a lighting time of an exposure unit which is corrected according to a density variation of the image shown in FIG. 8;

FIG. 10 is an explanatory diagram illustrating an image forming unit of an image forming apparatus according to another embodiment of the present invention.

FIG. 11 is an explanatory diagram showing a result of measuring the density of the toner image 16 transferred to the intermediate transfer belt 6 in another embodiment of the present invention.

[Explanation of symbols]

 1, 1A, 1B, 1C, 1D, exposure unit 2, 2A, 2B, 2C, 2D, photoreceptor drum 3, 3A, 3B, 3C, 3D, charging roll 4, 4A, 4B, 4C, 4D, developing roll 5 , 5A, 5B, 5C, 5D, transfer roll 6, intermediate transfer belt 7, drive roll 8A, 8B, 8C, support roll 9, paper feed cassette 9A, recording paper 10, paper feed roll 11, secondary transfer roll 12, Fixing unit 13, density detector 13A, slit 13B, housing 13C, light source 13D, lens 13E, light receiving element 14, correction coefficient calculator 15, exposure unit controller 16, transfer image 17, reflection mirror 18, scorotron 19, corotron

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location G03G 21/14

Claims (8)

[Claims] A charging unit configured to apply a predetermined potential to a drum or a belt-shaped photoconductor; and a light beam corresponding to image information is scanned on the photoconductor applied with the predetermined potential to form an electrostatic latent image. Exposure means for forming a toner image; developing means for developing the electrostatic latent image formed on the photoconductor with toner to form a toner image; transferring the toner image to a transfer body or recording paper to form a transfer image Transferring means for rotating the photoconductor at a predetermined rotation cycle; density fluctuation detecting means for detecting the density of the toner image or the transferred image to calculate a cycle of density fluctuation; At least one operation parameter of the charging unit, the exposing unit, the developing unit, and the transfer unit is corrected based on a cycle, and a cycle of the density fluctuation is an integral multiple or an integer of the predetermined rotation cycle of the photoconductor. An image forming apparatus comprising: a control unit for controlling the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein said control means changes a lighting time of said exposure means based on a cycle of said density fluctuation of said toner image or said transferred image. 3. The charging device according to claim 1, wherein the charging unit includes a charging roll that contacts the photoconductor to apply the predetermined potential, and the charging roll is formed to have the same outer diameter as the photoconductor. 2. The image forming apparatus according to claim 1. 4. The image forming apparatus according to claim 1, wherein said charging means is a scorotron provided at a predetermined distance from said photosensitive member. 5. The image forming apparatus according to claim 1, wherein the developing unit includes a developing roll that contacts the photoconductor and adheres toner to the electrostatic latent image, wherein the developing roll is formed to have the same outer diameter as the photoconductor. The image forming apparatus according to claim 1. 6. The image forming apparatus according to claim 1, wherein the transfer unit includes a transfer roll that presses the transfer body or the recording paper against the photoconductor, and the transfer roll is formed to have the same outer diameter as the photoconductor. 2. The image forming apparatus according to claim 1. 7. The image forming apparatus according to claim 1, wherein the transfer unit is a corotron provided at a predetermined distance from the photoconductor via the transfer body or the recording paper. 8. When the power supply is turned on, the density fluctuation detecting means includes:
2. The image forming apparatus according to claim 1, wherein the density of the toner image or the transferred image is detected before the image is formed, and the cycle of the density change is calculated.