JPS63131152A - Control method for image formation condition of image forming device - Google Patents

Abstract

PURPOSE:To places the quantity of toner stuck on an electrostatic latent image formed on a latent image carrier invariably to a standard state and to perform control so that the deviation between the standard value and an operation control object value is eliminated by holding the initial electrostatic charging potential of the latent image carrier and a developing bias potential constant at all times. CONSTITUTION:A photosensitive drum 1 as the latent image carrier is rotated by a motor as shown by an arrow, charged electrostatically and uniformly by a corona charger 2, and exposed by an exposure device 3 to a light image to obtain an electrostatic latent image, which is visualized by a developing device 4. The amount of toner stuck on the electrostatic latent image on the drum 1 is detected by light emission on the drum 1 and the density detector composed of photodetecting elements 25 and 26. Further, the output of the density detector is applied to a toner supply control circuit 29, and a comparing circuit 38 compares the amount of stuck toner in the standard state to the amount of toner stuck on the image and controls a charging current control circuit 6 to maintain conditions for an invariably excellent image state.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for controlling image forming conditions of an image forming apparatus, and particularly to a method for controlling an electrostatic latent image formed on a latent image carrier under a predetermined developing bias voltage. The present invention relates to a method of controlling image forming conditions for an image forming apparatus that performs image forming by developing toner.

(Prior Art) In various image forming devices such as electrophotographic recording devices, an electrostatic latent image is formed by exposing a photoreceptor drum or other latent image carrier, and this electrostatic latent image is transferred to a developing device. Accordingly, an image is formed by developing the toner under a predetermined developing bias voltage to obtain a developed image, thereby forming an image of a predetermined density. In this case, the final image state is adjusted by controlling various image forming conditions such as the charging potential of the latent image carrier, the developing bias voltage value, and the exposure date.

However, the various image forming conditions described above vary due to changes in the photoreceptor drum over time, etc., and the image condition cannot be properly controlled. It often happens that it becomes impossible to do so. In other words, the potential charged on the photoreceptor drum varies due to changes in various environmental conditions such as changes in the photoreceptor drum itself over time. It is not possible to perform control corresponding to variations in the image quality, which may result in unexpected deterioration of the final image.

(Objective) Therefore, the present invention provides a method for controlling image forming conditions for an image forming apparatus, which solves the problems of the conventional image forming condition control method and makes it possible to always obtain a good image condition. The purpose is to

(Structure) In order to achieve the above object, the present invention develops an electrostatic latent image formed on a latent image carrier with toner under a predetermined development bias voltage to form an image, thereby obtaining a predetermined image. In the method for controlling image forming conditions of an image forming apparatus, the surface potential of the latent image carrier is brought to approximately zero potential, and then a predetermined reverse development bias voltage is applied to perform toner development, thereby obtaining a After reading the toner adhesion of the developed image as an image formation reference value, the surface of the latent image bearing member is uniformly charged to a predetermined potential, and the electrostatic latent image formed at the charged potential is rotated in a normal order. Toner development is performed under an image bias voltage, and the toner adhesion amount of the resulting developed image is read as the image formation control target value, and the deviation between the image formation reference value and the image formation control target value of these developed images is eliminated. It is characterized by controlling various image forming conditions.

In a control method having such a configuration, the difference between the initial charging potential of the latent image carrier and the developing bias potential is always maintained constant, and toner adhesion to the electrostatic latent image formed on the latent image carrier is prevented. The amount itself will be controlled so that it is always in the reference state.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an example of an electrophotographic copying machine for carrying out the charging current control procedure according to the embodiment of the present invention shown in FIG. In this embodiment, the normal copying mode and the charging potential control mode are performed separately, and the charging potential control mode is performed during the pre-operation, post-operation, and after turning on the main switch of the copying mode.

In a normal copying mode, a photosensitive drum 1 as a latent image carrier that is used repeatedly is uniformly charged by a charging corona discharger 2 while being rotationally driven in the direction of the arrow by a motor. Thereafter, the exposure device 3 exposes the light image to form an electrostatic latent image, and the developing device 4 visualizes this electrostatic latent image.

A charging current is output from the high-voltage power supply 5 via a charging current control circuit 6, thereby driving the charging corona discharger 2.

The developing device 4 has a developing tank 8 that stores a two-component developer 7 consisting of toner and carrier. Due to friction with the carrier, it is charged to a polarity opposite to that of the electrostatic latent image. This developer is transferred from the pumping roller 11 to the developing roller 12 and is transferred to the photosensitive drum 1.
The electrostatic latent image on the photoreceptor drum 1 is visualized by adhesion of toner. The developer on the developing roller 12 is scraped off from the developing roller 12 by a scraper 13 after passing through the developing position, and the toner is replenished to the developer 7 by a toner replenishing device 14 .

On the other hand, the transfer paper is transferred from the paper feed cassette 15 to the paper feed roller 16,
The original image is transferred from the photosensitive drum 1 to the transfer paper by one transfer corona discharger, which is conveyed by conveyance rollers 17 and 18. The toner is fixed on this transfer paper by a fixing device 20, and the paper is discharged onto a tray 21. Furthermore, after the image transfer, residual charges are removed from the photosensitive drum 1 by a charge-eliminating corona discharger 22 and a charge-eliminating lamp 23, and residual toner is removed by a cleaning device 24.

Further, the exposure device 3 not only illuminates the original placed on the original table and projects the light image onto the photosensitive drum 1, but also is provided outside the original image projection area of the original table at a different timing. A reference pattern having a specified reference density is illuminated, and the reflected light is projected onto the photoreceptor drum 1. Therefore, an electrostatic latent image of the reference pattern is also formed on the photosensitive drum 1, and this electrostatic latent image is visualized by the developing device 4. A density detector consisting of a light emitting element 25 and a light receiving element 26 detects the amount of toner adhering to the photoreceptor drum 1 (density).
It has a function to detect. On the other hand, the concentration detection circuit 27
is driven by a timing signal from the timing generation circuit 28, and has a function of converting the output signal from the density detector for the above-mentioned image into a voltage. The toner replenishment control circuit 29 compares the output value with a reference value when the output signal of the density detection circuit 27 is input to the toner replenishment control circuit 29 via the switch 30, and determines the output of the density detection circuit 27. When the signal becomes larger than the reference voltage (when the toner adhesion amount falls below the reference value), toner replenishing device 1
4 to control the developing ability of the developing device 4 to a constant level. The developing roller 12 also serves as a developing electrode, and a predetermined developing bias voltage from a bias power supply circuit 31 is applied to the developing roller 12 .

On the other hand, in the charging potential control mode, as shown in FIG. ■), the entire surface of the photoreceptor drum 1 is erased (step knee ■). As a result, the surface potential of the photosensitive drum 1 is uniformly brought to approximately zero potential. Following this, the developing device 4 is driven (step T
-■> At the same time, the developing bias voltage is switched from the normal forward bias voltage a to the reverse bias voltage (step knee ■). This switching operation of the developing bias voltage is as follows:
The bias power supply circuit 31 is switched from the bias switching control circuit 32 based on the timing signal from the timing circuit 28.
This is done by a switching signal issued to In this case, the reverse development bias voltage value b (b<O) is set to a standard voltage value that allows a good image to be obtained.

The reference pattern is developed under such a reverse development bias voltage (steps ■-■), and the toner adhesion mM8 of the developed image thus obtained is read by the density detection circuit 27 through the density detectors 25 and 26. (of Stepney). The read toner adhesion ffi M e is converted into a predetermined signal by the A/D converter 33 from the switch 30 and then output to the first memory 35 through the switch 34 operated by the timing generation circuit 28 . Then, the toner adheres to the first memory 35 ff1.
M8 is stored (steps ■-■). This stored toner adhesion amount M8 is used as an image forming reference value in subsequent control operations.

Subsequently, as a second stage control operation, the developing bias voltage is first switched from the reverse bias voltage to the normally used forward bias voltage a (steps 1-2). Roughly speaking, a charging current of a predetermined value is output from the high-voltage power supply 5 via the charging current control circuit 6, and the charging corona discharger 2 is thereby driven (steps ■-■).
The potential V at which the surface of is normally used. It is uniformly charged at .

This charging potential ■. Variations occur due to changes in the photoreceptor drum 1 over time. In this uniformly charged state, the erase lamp 36 is partially activated to erase the periphery (steps 1-2), and a reference pattern is formed. Then, the forward development bias voltage a as described above is applied.
Toner development of the reference pattern is performed under (steps 1-2). The toner adhesion amount of the developed image thus obtained is sent to the density detection circuit 2 through density detectors 25 and 26.
7 (steps ■-■).

The read "toner adhesion" is outputted from the switch 30 through the A/D converter 33 to the second memory 37 from the switch 34 operated by the timing generation circuit 28, and is stored in the second memory 37. (step ■−■). This toner adhesion amount MA is hereinafter treated as a value to be controlled for image formation.

The toner adhesion data M8 and MA stored in the first memory 35 and second memory 37, respectively, are outputted to the comparison circuit 38 and compared (steps ■-■).
Both toner adhesion amounts M8. If the MAs are equal to each other and M8=MA, the control operation is ended (steps ①-②).

For both toners, M and M are different from each other, and M8≠B
If the value of the charging current that charges the photoreceptor drum 1 is changed by the charging current control circuit 6 (steps ■-■), the second stage control operation is repeated, and the image forming control is performed. The charging current is adjusted until it becomes equal to the actual toner adhesion amount which is the target value or toner adhesion ff1M which is the image forming reference value, that is, so that there is no deviation between the two values M8°.

When such a control operation is performed, even if variations occur in the initial charging potential of the photoreceptor drum 1 due to changes in the photoreceptor drum 1 over time, the toner-attached Wl of the image can always be maintained at a good level. .

That is, the initial charging potential of the photoreceptor drum 1 is V.

When the binding and developing bias voltage value is VB, the toner adhesion amount M due to development is a function of (Vo-V, >, and is expressed as M=f (Vo V8). Therefore, (■o- If the value of VB) is constant, the toner adhesion amount M is also kept constant.The toner adhesion amount M is determined by the density detectors 25 and 26, as described above.

Here, as in the above embodiment, in the first step, the charging potential of the photoreceptor drum 1 is set to zero, the developing bias voltage at that time is set to b (b<O), and the toner adhesion under these image forming conditions ffl M 8 Detect. As a second step, the charging potential of the photosensitive drum 1 is set to vol and the developing bias voltage at that time is set to a (a>0), and the toner adhesion amount under these image forming conditions is detected. Then, when controlling so that both of these toner adhesion amounts and M are equal, M8=
From MA, M=f (Vo-a)=f (0-b), and (1) o=a-b=constant is obtained. As a result, the initial charging potential V of the photoreceptor drum 1 remains unchanged regardless of changes in the photoreceptor drum 1 over time. is always kept constant, and the image is also kept constant. for example,
In order to maintain Vo at 850V, a is 550■, b
One possibility is to set the voltage to -300V.

In the embodiment shown in FIG. 3, the image forming conditions are controlled by:
A developing bias voltage is used. That is, in FIG. 3, in which the same steps as those in the embodiment shown in FIG. 1 are represented by the same reference numerals, and in FIG. When each toner adhesion amount and MA stored in the memory 35 and the second memory 37 are outputted to the comparison circuit 38 and compared (step -Cj:5), both toner adhesion amounts M8゜M are equal to each other. If MB=MA, the control operation is terminated (step ①-Kabura).

If both toner attachment 1fiM and M are different from each other and MB≠AMA, the developing bias voltage value a is changed by the bias potential control circuit 40 (step ■-φ), and then the second stage control operation is performed. is repeated, and the actual toner adhesion amount is changed to the toner adhesion amount M, which is the image forming reference value for development.
, that is, both values M8. The developing bias voltage +111ia is adjusted so that there is no deviation in MA.

Even in such an embodiment, the same actions and effects as in the above embodiment can be obtained. In addition to this, it is also possible to control image formation by, for example, the amount of exposure light or the transfer voltage.

(Effects) As described above, in the method for controlling image forming conditions of an image forming apparatus according to the present invention, as the first control step, the charging potential of the latent image carrier is set to zero, and the charging potential of the latent image carrier is set to zero, and the charging potential of the latent image carrier is set to zero, and the charging potential of the latent image carrier is set to zero, and the charging potential of the latent image carrier is set to zero, and the charging potential of the latent image carrier is set to zero. In addition to detecting the toner adhesion amount M8 of the developed image obtained by development, as a second control step, the charging potential of the latent image carrier is set to the actual use potential vo, and the charging potential is set to the actual use order under the development bias voltage. Since the toner adhesion amount MA of the developed image obtained by development is detected and the image forming conditions are controlled so that both toner adhesion IM8 and MA are equal, accurate image formation control can be achieved with a simple structure. Even if variations occur in the initial charging potential of the latent image carrier due to changes in the latent image carrier over time, the amount of toner adhering to the image can always be maintained at a good level.

[Brief explanation of the drawing]

FIGS. 1 and 2 are flow charts and tack diagrams respectively showing a control procedure and a control device in an embodiment of the present invention, and FIGS. 3 and 4 are diagrams. 1... Photosensitive drum, 2... Corona charger, 4...
・Developing device, 25.26...Concentration detector, 31...
Development bias power supply circuit. Figure 7 Figure Z

Claims (1)

[Claims] In an image forming condition control method for an image forming apparatus, the electrostatic latent image formed on a latent image carrier is developed with toner under a predetermined developing bias voltage to form an image, and a predetermined image is obtained. After setting the surface potential of the latent image carrier to almost zero potential, toner development is performed while applying a predetermined reverse development bias voltage, and the amount of toner adhesion in the resulting developed image is read to determine the image formation reference value. After that, the surface of the latent image carrier was uniformly charged to a predetermined potential, and the electrostatic latent image formed at the charged potential was developed with toner under a normal forward development bias voltage. The amount of toner adhering to each developed image is read as the image forming control target value, and various image forming conditions are controlled so that there is no deviation between the image forming reference value, which is the amount of toner adhering to each of these developing images, and the image forming control object value. An image forming condition control method for an image forming apparatus, characterized in that: