JPH1172978A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device which controls image density properly without an AIDC(automatic image-density-control) control sensor which is low reliable. SOLUTION: The digital copying machine drives a laser scan optical unit 5 based on original-document image information read by an image reader 1, forms a latent image on a photoreceptor drum 11, and develops the latent image by means of a developing unit 13. In the case, an estimated amount of toner consumption is stored in a memory 22, also an amount of toner replenishment is stored in a memory 36, and conditions under which the image is formed are corrected by the comparison of both the values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus for forming an electrostatic latent image on an image carrier based on image information and developing the latent image with toner.

[0002]

2. Description of the Related Art Conventionally, in the field of electrophotographic copying machines and laser printers, in order to stabilize an image, a test pattern is formed on a photoreceptor under predetermined image forming conditions, and toner adhered to the test pattern is formed. AIDC (auto-ima) which feeds back to image forming conditions (photoconductor charging voltage, exposure light amount, developing bias voltage, etc.) by optically detecting the amount of
ge-density-control) control was used.

However, in the AIDC control, the detection value of the toner adhesion amount varies depending on the degree of contamination of the toner adhesion amount detection sensor, the variation in the detection value due to the temperature / humidity characteristics, or the variation in the characteristics of the sensor itself. There was a problem that incorrect correction was performed. In particular, since the sensor is disposed immediately below the developing device, the sensor is easily stained with toner. A method of detecting the dirt state and correcting the output value of the sensor has been considered. However, when the dirt becomes severe, the dynamic range of the detection area is narrowed, and the accuracy is extremely reduced.

[0004] Therefore, an object of the present invention is to provide a low reliability A
An object of the present invention is to provide an image forming apparatus capable of appropriately controlling image density without using an IDC control sensor.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, an image forming apparatus according to the present invention comprises a replenishing amount accumulating means for accumulating a replenishing amount of toner based on a toner concentration detection result in a developer; A predicted consumption amount accumulating means for accumulating a predicted toner consumption amount based on the included density information; and an operation on the image carrier based on respective accumulated values of the replenishment amount accumulating means and the predicted consumption amount accumulating means. Control means for correcting the image condition.

Preferably, the replenishing amount accumulating means is a memory for accumulating a driving time of a toner replenishing motor, and the predicted consumption amount accumulating means is a memory for accumulating exposure data based on digitized image information. preferable.

In the present invention, the control means compares the accumulated value of the replenishment amount with the accumulated value of the predicted consumption amount, that is, estimates the history of the image density up to now, and from the estimation result, the image on the image carrier. Correct the image forming conditions and optimize the image density. For example, if the replenishment amount accumulation value is smaller than the predicted consumption amount accumulation value, it is considered that the toner is unlikely to adhere due to a deterioration phenomenon of the image carrier, and the image forming condition is corrected to a higher adhesion amount. The image forming conditions corrected at this time are, for example, at least one of an image carrier charging voltage, an exposure light amount, and a developing bias voltage.

As is apparent from the above description, according to the present invention, the image forming condition on the image carrier is corrected based on the accumulated toner supply amount and the estimated toner consumption amount. As a result, the image density can be optimized and stabilized. Moreover, since an AIDC sensor that directly detects the amount of toner adhered on the image carrier is not used, it is possible to eliminate the adverse effect of the detection error caused by the sensor.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, an image forming apparatus is configured as a digital electrophotographic copying machine. Generally, an image reader 1 reads an original image, and a laser light source is modulated based on the read image information to expose the image. Body drum 11
Laser scanning optical unit 5 for forming an image (latent image) thereon
And an image forming unit 10 having a photosensitive drum 11 as a center.

The image forming unit 10 includes a scorotron-type charging charger 12, a developing unit 13, a transfer charger 14, and a photosensitive drum 11 which is driven to rotate in the direction of arrow a.
A cleaner 15 for residual toner and an eraser lamp 16 for residual charge are provided. For the photosensitive drum 11,
First, it is uniformly charged to a predetermined voltage by the charging charger 12, and an electrostatic latent image is formed by a laser beam emitted from the laser scanning optical unit 5. This latent image is
3 and is transferred onto the sheet S conveyed in the direction of arrow b by the electric field emitted from the transfer charger 14. The toner image transferred on the sheet S is
The sheet is fixed by a fixing unit (not shown) and discharged outside the apparatus.

The image information of the original read by the image reader 1 is transferred to an image processing circuit 21.
The image processing circuit 21 performs necessary image correction processing such as shading correction and γ correction, and transfers the data to the laser scanning optical unit 5 as exposure data. The image processing circuit 2
In step 1, the number of print dots (density information) is counted from the exposure data, and the count value is output to the toner consumption memory 22. The exposure data corresponds to the estimated toner consumption, and the value is stored in the memory 22.

On the other hand, an ATDC sensor 31 for detecting, for example, magnetically, the toner concentration in the developer is provided in the developing device 13.
Is installed. The toner density detection circuit 32 is ATDC
The output voltage of the sensor 31 is converted into a toner density to calculate a drive time of the supply motor 34 corresponding to a necessary toner supply amount, and outputs the calculated drive time to the drive circuit 33. The replenishing motor 34 is driven to rotate for the above-described driving time, and replenishes toner from the hopper 35 to the developing tank. The drive circuit 33 outputs the drive time of the supply motor 34 to the toner supply amount memory 36. The driving time corresponds to the toner supply amount, and the value is stored in the memory 36.

The accumulated values of the toner consumption memory 22 and the toner replenishment memory 36 are transferred to the CPU 40, where they are compared and calculated to correct image forming conditions. For example, if the toner replenishment amount accumulated value Mi stored in the memory 36 is smaller than the estimated toner consumption amount accumulated value Si stored in the memory 22 (Mi <Si), it means that the required amount of toner has not been consumed. I do. In this case, since the photoconductor may be deteriorated, the image forming condition is corrected in a direction in which the toner is highly adhered. On the other hand, in the opposite case (Mi> S
In i), since the toner is consumed in an amount larger than the required amount, the image forming condition is corrected in a direction in which the toner is reduced in adhesion.

The data is stored in the memories 22 and 36 each time the power of the copying machine is turned on.
6 is performed. The estimated toner consumption amount accumulated value Si is compared with the toner replenishment amount accumulated value Mi as “Si + α” to which the correction value α is added.

In the digital copying machine shown in FIG. 1, the image forming conditions include the amount of exposure light (power supplied to the laser diode) of the laser scanning optical unit 5, the current applied to the wire to the charger 12 (the output of the high voltage transformer 17). ), The grid voltage of the charging charger 12 (output of the high voltage transformer 18), and the developing bias voltage (output of the transformer 19) applied to the developing sleeve 13a of the developing device 13. The CPU 40 corrects at least one of them to execute optimization of the toner adhesion amount (image density).

In a digital copying machine that performs reversal development in which toner adheres to a low potential portion on a photoconductor, shifting to higher adhesion means increasing the amount of exposure light, increasing the photoconductor charging voltage (charger current or grid). Voltage increase), which means increasing the developing bias voltage. On the other hand, shifting to lower adhesion means performing the opposite correction.

FIG. 2 shows an example of image stabilization control in this embodiment. Here, when the number of copies is 4,000, the toner supply amount becomes smaller than the exposure data (the estimated toner consumption amount). Therefore, the grid voltage Vg is increased from 600 V to 650 V, and the developing bias voltage Vb is increased.
Was increased from 500 V to 550 V to shift to higher adhesion. By such correction of the image forming conditions, the toner adhesion amount (image density) in the subsequent copy processing maintains an appropriate value. Furthermore, when the number of copies is 8,000,
Similarly, since a decrease in the toner supply amount was determined, the grid voltage Vg was increased from 650 V to 700 V, and
The developing bias voltage Va was increased from 550 V to 600 V, and was shifted to higher adhesion. With this,
The toner adhesion amount (image density) maintained an appropriate value until the copy processing of 10,000 sheets.

FIG. 3 shows an outline of a control procedure of image forming conditions. When the power of the copier is turned on and the CPU 40 is reset and the program is started, first, the memories 22 and 36 are reset in step S1. Step S2
When the copy processing is executed in step S3, the memory 3
6 is calculated, and the estimated toner consumption accumulated value Si transferred to the memory 22 is calculated in step S4.

Next, at step S5, Mi> (Si + α)
It is determined in step S7 whether or not Mi <(Si + α). If NO in each case, the process returns to step S2. Mi
If> (Si + α), in step S6, the toner adhesion amount is shifted to lower adhesion. On the other hand, Mi <(Si + α)
If so, in step S8, the toner adhesion amount is shifted to higher adhesion.

The image forming apparatus according to the present invention is not limited to the above embodiment, but can be variously changed within the scope of the invention. In particular, the present invention is applicable not only to digital copying machines and printers as image forming apparatuses, but also to analog copying machines that perform normal development in which toner is adhered to a high potential portion on a photoconductor. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a digital copying machine according to an embodiment of the present invention.

FIG. 2 is a chart illustrating an example of control of image forming conditions in the digital copying machine.

FIG. 3 is a flowchart showing one control procedure of image forming conditions in the digital copying machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Image reader 5 ... Laser scanning optical unit 11 ... Photoreceptor drum 12 ... Charging charger 13 ... Developing unit 22, 36 ... Memory 31 ... ATDC sensor 34 ... Toner supply motor 40 ... CPU

Claims (4)

[Claims] 1. An image forming apparatus for forming an electrostatic latent image on an image carrier based on image information and developing the latent image with toner, the toner supply amount based on a toner concentration detection result in a developer. Replenishing amount accumulating means for accumulating the toner, estimated consumption amount accumulating means for accumulating the estimated toner consumption amount based on the density information included in the image information, and replenishing amount accumulating means and estimated consumption amount accumulating means. Control means for correcting image forming conditions on the image carrier based on the accumulated value. 2. The image forming apparatus according to claim 1, wherein said replenishing amount accumulating means is a memory for accumulating a driving time of a toner replenishing motor. 3. The image forming apparatus according to claim 1, wherein said predicted consumption amount storage means is a memory for storing exposure data based on digitized image information. 4. The image forming condition controlled by the control means is at least one of an image carrier charging voltage, an exposure light amount, and a developing bias voltage. The image forming apparatus as described in the above.