JPS62280871A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent a ground stain and to easily execute an image adjustment by adjusting the supply voltage of an original lamp in accordance with the degree of fatigue of a photosensitive body, and correcting automatically a developing bias potential, when the supply voltage reaches a prescribed value. CONSTITUTION:Even when the supply voltage of an original lamp of F5 is 69V at the time point of copying of 20,000 sheets, a bright part potential VL value becomes -200V. In such case, when a user adjusts an F5 shift key 10 again, an adjusting means, first of all, raises the original lamp supply voltage to 69V of a prescribed value by a lamp regulator 13, and switches it automatically to a developing bias DC portion by a microcomputer 15. That is to say, it is switched to a high voltage transformer 27 side being a correcting means for correcting a developing bias potential. Accordingly, the original lamp supply voltage becomes 69V of the upper limit, and -250V adding -30V to -220V of the initial developing bias DC portion is applied to a developing sleeve 32. In such way, a correct image being free from fog is obtained.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus that reduces background stains due to fatigue of a photoreceptor in an electrophotographic copying apparatus.

(Prior Art) Conventionally, in an electrophotographic copying apparatus that repeatedly uses a photoreceptor, particularly an OPC photoreceptor, charging and exposure are required.

As the trough processes of development, transfer, printing, and fatigue recovery are repeated continuously, as the number of repetitions increases, under -ffi exposure conditions, the background stains on the copied material become noticeable. come. This is due to the fact that as the number of times the photoreceptor is used repeatedly, that is, the number of copies is increased, the surface potential at the bright area on the photoreceptor becomes higher or lower. For example, after uniformly charging a Todoroki OPC photoreceptor, it was exposed imagewise and the surface potentials of its dark and bright areas were measured, and the comparison was 1,650 V in the dark area and 1,170 V in the bright area. Then, when 10,000 sheets were continuously copied and measurements were taken in the same manner after t, the voltage was -650V in the dark area and -270V in the bright area. This is a result of the surface potential of the bright area increasing almost linearly in proportion to the number of copies, which causes an increase in the background density of the copies.

For this reason, in the past, a method has been adopted in which the exposure amount or developing bias potential is adjusted to prevent fatigue of the photoreceptor, that is, background staining due to an increase or decrease in residual potential.

(Problem to be Solved by the Invention) By the way, in the method described above in which the surface potential of bright areas is corrected by adjusting the exposure amount in order to prevent background stains, the correction limit is determined by the margin of the exposure amount. is restricted. For example, when a Halodan lamp with a rating of 80 V and 200 W is used as a document illumination lamp, the bright area is -170 V'1 to initially reproduce a standard document (ground density 0.07) as a proper image with an OPC photoreceptor. Yes, the lamp lighting voltage requires 64V, but when copying newspapers etc. where the background of the original has a reflection density of about 0.3, fog-free images are required.The standard lighting voltage of 64V is required. It is necessary to add IIV to the voltage and maintain it up to f475V.

Therefore, when correcting the exposure amount for the increase in bright area potential due to fatigue of the photoreceptor, the standard lighting voltage + IIV must be taken into account, but the rated 80V halon lamp
Only the SVa degree from 64V to 69Vl can be corrected. This is an increase of about 30% in terms of light intensity, and the bright area potential changes from -170V to -127V after 20,000 continuous copies.
In the case of the OPC photoconductor which has been changed to 0V, the voltage decreases only to -220V. As a result, when the bright area potential is 1220V, the background density of the copy increases compared to the initial state of the OPC photoconductor, and fogging occurs, but there is no margin for exposure, and at this point the photoconductor There was a problem in that the father had to be changed. However, in actual use mode, 20,000 sheets are rarely copied continuously, and the photoreceptor is normally used by repeating one copy and one copy, so the increase in bright area potential will be large as described above. It is almost impossible to get all the values.

-1. In the method of correcting the surface potential of bright areas by adjusting the developing bias potential, as the developing bias potential increases, the image density becomes thinner, and inversion fog occurs where toner adheres to the bright areas. There is a problem that
o Furthermore, there is a correction method in which the exposure amount and the developing bias potential can be adjusted independently, but this has the problem that image adjustment becomes complicated for the user.

Therefore, the present invention has been made to solve the above-mentioned problems of the conventional example, and its purpose is to form an image that prevents background stains and allows easy image adjustment. The goal is to provide equipment.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention 1c adjusts the supply voltage of the original lamp by the adjustment means in accordance with the degree of fatigue of the photoreceptor, and It is constructed by switching to a correcting means that automatically corrects the developing bias potential at a fixed time when the supply voltage reaches a predetermined value.

(Function) In the present invention, the original lamp lighting voltage is adjusted by the adjusting means in accordance with the degree of fatigue of the photoreceptor, and when the original lamp supply voltage reaches a predetermined value, the original lamp supply voltage reaches the predetermined value. The system automatically switches to correction of the developing bias potential.

(Embodiment) An embodiment of an image forming apparatus according to the invention will be described below based on the drawings.

The present invention is applied to FIG. 3 and 7'! : 'Niko photocopying apparatus is schematically shown, and its configuration will be explained below. 1 is a document, 2 is a Halodan lamp as an example of the next original height lamp that illuminates the document 1, and 3 is a final lamp. This is an image optical system.

Reference numeral 4 denotes an OPC photosensitive drum, which is rotatably supported in the direction indicated by the arrow in FIG.
A secondary distortion device 5, a developing device 6, a transfer charger 7, and a cleaner 8 are provided. Additionally, a light source for pre-exposure, a light source for non-image area exposure, a fixing device, etc. are arranged around the photosensitive drum 4, but these are omitted for the sake of convenience. In the figure, 9 is a transfer material.

FIG. 1 shows an image forming condition control means that controls image forming conditions by controlling the light amount and developing bias of a document illumination lamp, and this image forming condition control means consists of an operation section 11 and a DC controller. 12 and Lampregu v-%13.

It consists of a high voltage transformer 27. The operation section 11 is equipped with a plurality of digital density adjustment keys 14, and the digital density adjustment key 14 is a digital density adjustment key 14. -14 Image forming conditions are set by performing all operations. Digital density adjustment key 14 is D
The microcomputer 15 is connected to the microcomputer 15 of the C controller 12, and the microcomputer 15 outputs the next original lamp dimming signal (LINT) via the D/A converter 16 in response to the operated digital density adjustment key 14. At the same time, a lamp regulator operating signal (LRD) is outputted via the operational amplifier 18 during copy operation.

The original lamp dimming signal (LINT) is inputted to the differential amplifier circuit 19 of the lamp regulator 13, and the lamp regulator activation signal (LRD) is inputted to the lambda computer switch circuit 20. The differential amplifier circuit 19 amplifies the voltage difference between the constant voltage signal output from the power source' voltage fluctuation detection circuit 21 and the document lamp dimming signal (LINT), and adjusts the phase control circuit 22 according to the voltage difference. Then, the runner-up circuit 23 is controlled using a triac or the like, and the original lamp supply voltage supplied to the original lamp 2 is adjusted. Lamp regulator 1 circuit 20U, lamp regulator operation signal (L
RD) turns on/off the supply of 24V power to the phase control circuit 22. 24 is the manufacturing fuse, 25 is 10
A 0 VACt source is shown in each case.

The density value set by the digital density adjustment key 14 is based on the standard density F5, and the density value at which the density becomes maximum is FO1, which is the density value at which the density becomes maximum light, t-F10.
There are 11 stages: FO-+F1...F4→F5→...F9→FIO. The light intensity ratio of Flo and F5 is set to FIO so that the density is set to FIO so that the newspaper will fly.
IO/F5 is set to 1.7. However, for the light intensity ratio of FO and F5, set the density to FO and just in case, reflect f! degree 0.
FO/F5 is set to 0.79 so that the reproducibility of the original No. 2 can be equal to or higher than the reproducibility of the original with a reflection density of 0.3 at F5.

7. Rated 80V, 200W as a document illumination lamp.
When using the front lamp 2, the supply voltage of the second lamp 2 is 64V at the standard density F5, and the voltage is set to F5 so as to satisfy the above light intensity ratio of FO/F5/FIO. The FO is 6■ low, and the IIV supply voltage is high in the FIO. When the OPC photosensitive drum 4 is new,
When the original lamp supply voltage is 64V, the bright area potential VL = −
Ensure 170V is applied to the developing cylinder 32 at this time.
The developing bias and [, te 1500Hz, 130
0 Vpp and a DC component of 220 V were applied, and a proper image without fogging was obtained.

Here, Fig. 2 is a graph showing the relationship between the original lamp supply voltage and the surface potential.
■ indicates the characteristics after 10,000 continuous copies were made.

In the initial characteristics, the original lamp supply voltage of F5 is 64
V, the bright area potential VL is 1170 V (A+). As shown in (2), this increases to -220V due to the increase in the bright area potential vL when the light is lit at 64V. This correction can be performed by the user adjusting the F5 shift key 10 of the operation unit 11, and the bright area potential vL can be corrected according to the image exposure amount up to the original lamp supply voltage of 69V. Then, ■→
Even if it changes to You will get it.

In addition, in Fig. 2, the characteristic after 20,000 copies is 0, and even if the F5 original lamp supply voltage is 69V, the bright area potential VL value is -200V (C+), which is the appropriate bright area potential. -30V has increased compared to -170VK. At this time, the user gets 1 again! When jF5 shift -+-10 is adjusted, the adjusting means first increases the document lamp supply voltage by a predetermined value +7)69VK by the lamp regulator 13, and at this point the microcomputer 15 automatically switches to the developing bias DC component. That is, the switch is made to the high voltage transformer 27 side, which serves as a correction means for correcting the development/arm potential.

A correction means for correcting the DC component of the developing bias will be explained based on FIG. 1. In the figure, a DC controller 12 corresponds to the F5 shift key 10 and outputs an fcDC bias control signal (D'cBC), and also outputs an AC bias timing pulse (ACBTP) at the time of starting copying. In the high voltage transformer 27, when the AC bias timing voltage (ACBTP) is "0", the AC bias switch circuit 28 is turned off, so the output of the 1500 Hz silk generator circuit 29 is amplified by the current amplifier circuit 30. Further A
After being boosted (to 1300 Vpp) by the C transformer 31, the voltage is supplied to the developing cylinder 32 of the developing device 6. Further, the high voltage transformer 27 outputs a DC bar (7, C control signal (DCBC) t
- Supplying a DC voltage (to which the differential amplifier circuit 33 and the oscillation circuit 35 are connected, AC as a DC bias via the DC-DC inverter transformer 34) to the lance 31 to control the voltage supplied to the developing cylinder 32; K, υ, it becomes possible to correct the bright area potential vLag. Therefore, 20
When the user operates the F5 shift key 10 at the time of copying ,000 sheets, the original lamp supply voltage becomes the upper limit of 69V, and the bright area potential VL value at this time is -200V.
Initial developing bias DC component: 1220V to 130Vt-
By applying the sum of 7'j-250V to the developing sleeve 32, a proper image without fogging can be obtained.

In this embodiment, a type in which the bright area potential increases as the photoreceptor becomes fatigued will be described; however, the present invention can of course be applied to a type in which the bright area potential decreases as the photoreceptor has the opposite characteristics.

(Effects of the Invention) The image forming apparatus according to the present invention has the above-described structure and operation, and can always obtain a proper image without fogging or reverse fogging, and can easily perform image adjustment. be effective.

[Brief explanation of the drawing]

FIG. 1 is a Glock diagram showing an embodiment of an image forming apparatus according to the present invention, FIG. 2 is a graph showing the relationship between original lamp supply voltage and surface potential in the same embodiment, and FIG. 3 is a graph to which the present invention is applied. 1 is a schematic diagram of a nine electrophotographic copying apparatus. Explanation of symbols 10...F5 shift key 11...Operation unit 12...
・DC controller

Claims (1)

[Claims] The adjusting means adjusts the voltage supplied to the document lamp in accordance with the degree of fatigue of the photoreceptor, and when the supplied voltage reaches a predetermined value, the system automatically switches to the correcting means for correcting the developing bias potential. image forming device.