JPH11327227A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of preventing toner from being excessively electrified or toner from being insufficiently supplied by controlling toner concentration in a developing unit while adjusting the degree of forcible toner consumption in accordance with the density of an original with simple constitution. SOLUTION: In this developing device; two-component developer consisting of carrier and the toner is used, and development is executed by stirring the developer and electrifying the toner, and further the toner is supplied so that the toner concentration inside the device may be kept at a specified value. In the device; toner consumption to image forming time is calculated based on printed image data and the toner consumption is forcibly controlled in accordance with the calculated result so that the specified toner consumption may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
In particular, the present invention relates to controlling the density of developed toner in an image forming apparatus such as a digital copying machine.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile, a so-called magnetic brush developing method has been used as a developing method. In this method, a two-component developer composed of a carrier and toner is used to form a magnetic brush of the developer on the surface of a developing roller having a magnet therein, which rubs the photoreceptor. The development is performed by stirring the developer, that is, the toner, and the magnetized carrier in the container and charging the toner to a predetermined amount.

However, there is a difference in the amount of toner consumed from the developing device depending on the density of the document on which an image is formed,
The stirring state of the toner in the developing device changes. If the density of the original is low and the amount of consumed toner is small, the same toner stays in the developing device for a long time, resulting in excessive stirring. Then, the toner is overcharged, the electrical coupling between the toner and the carrier becomes too strong, and the toner supplied later passes through the developing device without being mixed with the carrier in the developing device. This causes background fog on the image.

As a countermeasure, conventionally, toner is forcibly applied to a portion other than the image forming area on the photoreceptor, for example, a portion between papers to be continuously transferred, that is, between papers. By consuming the toner, the toner in the developing device is replaced to prevent the toner from being overcharged.

[0005]

However, when toner is forcibly consumed in the above-described configuration, when the density of the document is high, a large amount of toner is consumed on the document and the force is increased. Toner consumption is also performed, the toner consumption exceeds the toner replenishment amount, and the toner replenishment may not catch up. In view of this problem, if the degree of forced toner consumption (width and frequency of applying toner outside the image forming area) is set to be not excessive, if the density of the document is extremely low, On the contrary, the toner consumption becomes insufficient and the effect cannot be obtained.

The present invention has been made in view of the above problems, and has a simple structure to control toner concentration in a developing device while controlling the degree of forced toner consumption in accordance with the density of a document to thereby reduce toner excess. An object of the present invention is to provide a developing device that prevents charging and insufficient toner supply.

[0007]

In order to achieve the above object, the present invention uses a two-component developer consisting of a carrier and a toner, stirs the developer, charges the toner, and performs development. In a developing device, a developing device that replenishes toner so as to maintain the toner density inside the device at a predetermined value calculates a toner consumption amount with respect to an image forming time based on image data to be printed, and according to the calculated amount, The configuration is such that the toner consumption is forcibly controlled so as to be the toner consumption.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view schematically showing the entire configuration of an embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a photosensitive drum that rotates at a constant speed. The photosensitive drum 1 is formed by evaporating, for example, a selenium-based photosensitive material on a surface of a drum base made of a material such as aluminum. Have been. Around the photosensitive drum 1, a main charging unit 2, an exposing unit 3, a developing unit 4, a transfer unit 8, and the like are provided in this order along the rotation direction. The left side of the photosensitive drum 1 is not shown.

The charging section 2 brings a charge wire 2b disposed in a U-shaped case 2a close to the surface of the photosensitive drum 1 along the axial direction. A high voltage is applied to the charge wire 2b, and the surface of the photosensitive drum 1 is charged by the high voltage. When the charged portion is exposed in the next exposure section 3 as shown by an arrow A, the surface potential of the exposed portion decreases in accordance with the exposure amount. As a result, an electrostatic latent image is formed.

The developing device 4 mixes and agitates the toner supplied from the main hopper 13 with the developer by the agitating rollers 6 and 7 and transfers the toner to the surface of the developing roller 5. The photosensitive drum 1 adheres toner to the surface thereof in accordance with the electrostatic latent image. As a result, a visible image is formed. The toner having formed the visible image is transferred to the fed paper (not shown) by the transfer unit 8. On the other hand, the toner supplied to the rear part of the main hopper 13 through the supply hopper 14 as shown by the arrow C is conveyed to the front part of the main hopper 13 as shown by the arrow E, where the rotation of the supply roller 9 near the toner outlet is performed. , As described above, the developing device 4
Will be replenished.

The developing device 4 is provided with a toner sensor 10 for detecting the magnetic permeability of the developer inside, thereby detecting the toner concentration T / D (toner / developer), that is, the ratio of the toner contained in the developer. The toner is replenished from the main hopper 13 to the developing device 4 by rotating the supply roller 9 at the time when the measured density becomes lower than the predetermined density. At this time, if the amount of toner consumption from the developing device 4 is large, the decrease in the toner concentration is fast, and if the amount is small, the decrease in the toner concentration is slow, and the toner supply operation fluctuates accordingly.

In the above configuration, the function of the present invention is to prevent the toner charge amount from becoming excessively charged in an image forming apparatus such as a digital copying machine which performs printing based on image data. In addition, when toner is forcibly consumed, that is, when toner is forcibly put on the photosensitive drum 1, the toner is not uniformly applied as described in the above-described conventional technique, but is applied to the photosensitive drum 1. The toner consumption is calculated based on the image data to be printed.

That is, the white / black ratio is calculated from the image data, and the toner consumption with respect to the image forming time is obtained based on parameters such as the number of originals and the number of copies. In response to this, the width and frequency of the toner to be put on the photosensitive drum 1 (how many sheets are processed each time) is controlled to adjust the toner consumption.

When the density of the document is high, the toner is consumed a lot and the toner is replenished quickly, so that the toner is not overcharged even without forcibly consuming the toner. Conversely, when the density of the original is low, the consumption of toner is small,
Since toner replenishment is delayed, by determining that,
By controlling the toner consumption forcibly, the consumption of the toner is increased and the overcharge is prevented.

[0015]

As described above, according to the present invention,
Provide a developing device that prevents overcharging of the toner and insufficient replenishment of the toner by controlling the toner concentration in the developing device while adjusting the degree of forced toner consumption according to the density of the original with a simple configuration. You can do it.

[Brief description of the drawings]

FIG. 1 is a side cross-sectional view schematically showing an entire configuration of an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum 2 main charging unit 3 exposure unit 4 developing unit 5 developing roller 6, 7 stirring roller 8 transfer unit 9 supply roller 10 toner sensor 13 main hopper 14 supply hopper

Claims (1)

[Claims] 1. A developing device which uses a two-component developer composed of a carrier and a toner to stir the developer and charge the toner to perform development, wherein the toner concentration inside the device is set to a predetermined value. In the developing device that replenishes toner so as to maintain the toner consumption, the amount of toner consumed with respect to the image forming time is calculated based on the image data to be printed, and the toner consumption is forcibly controlled so that the predetermined amount of toner is consumed accordingly. A developing device.