JPH0362060A - Developing device - Google Patents

Abstract

PURPOSE:To provide the inexpensive device and to prevent the change in image density occurring in a change in temp. and humidity by fixing a developer layer thickness regulating member via a hygroscopic swelling resin to a developing housing member. CONSTITUTION:The developer layer thickness regulating member is fixed via the hygroscopic swelling resin to the developing housing member 3. The developer layer thickness regulating part interposing member 6 consisting of the hygroscopic swelling resin, therefore, expands or shrinks by an environmental change. The actual toner concn. is controlled by the value higher than a standard at the time of a high temp. and high humidity, but a doctor gap narrows and, therefore, the excessive increase of the image density is prevented. The actual toner concn. is controlled by the value lower than the standard at the time of a low temp. and low humidity, but the doctor gap widens and, therefore, the decrease of the image density is prevented. Thus, the change in the image density by the environmental change is prevented by the inexpensive method without using a costly temp. and humidity detecting element.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image density control device in an image forming apparatus such as an electrophotographic apparatus.

Conventional technology In an electrophotographic device using a two-component development method, changes in temperature and humidity change the characteristics of the electrostatic latent image carrier and the amount of triboelectric charge between the carrier in the developer and the toner in the developing device. , the image density changes. - Numerically speaking, when the temperature and humidity are low, the characteristics of the electrostatic latent image carrier deteriorate, and the amount of triboelectric charge between the carrier and toner in the developer increases, resulting in a decrease in image density. On the other hand, when the temperature is high and the humidity is high, the image density increases excessively. Conventionally, as a countermeasure against these problems, changes in image density have been prevented by detecting the temperature near the developing device and controlling the bias voltage applied to the developer carrier in the developing device according to the detected temperature. but,
According to this method, it is not possible to prevent changes in image density due to humidity, which are caused by changes in image density.

Problems to be Solved by the Invention Here, in order to correct the influence of humidity, it is possible to add a humidity detection means and control it to correct both temperature and humidity, but in these methods, Temperature and humidity detection elements (sensors and circuits) are required and expensive. Therefore, the present invention is an inexpensive device,
And temperature.

The purpose is to prevent changes in image density due to changes in humidity.

Means for Solving the Problems The technical means of the present invention for solving the above-mentioned problems is to fix the developer layer thickness regulating member to the developer housing member via a hygroscopic swelling resin. This prevents the image density from changing due to factors such as humidity, humidity, etc.

The developer layer thickness regulating part intervening member made of a hygroscopic swelling resin expands or contracts due to changes in the working environment (particularly humidity and temperature). Specifically, it expands when it is hot and humid, and contracts when it is cold and humid. As a result, the gap (hereinafter referred to as doctor gap) between the developer layer thickness regulating member and the developer carrier (hereinafter referred to as sleeve) becomes narrower when the temperature is high and humid, and widens when the temperature is low and humid.

In addition, toner concentration is generally determined by using a detection element that detects changes in magnetic permeability to determine the amount of carrier in the developer. The amount of triboelectric charge increases, and as a result,
A large amount of toner is absorbed by the carrier. As a result, the apparent amount of carriers decreases, and the magnetic permeability also decreases, making it appear as if the toner a degree has increased. Therefore, since toner concentration control is performed such that the output signal level of the detection element is always at the reference value, it works to lower the increased toner concentration, and as a result, the actual toner concentration decreases. On the other hand, in high temperature and high humidity conditions, the amount of frictional charging due to mixing and stirring of toner and carrier decreases, and as a result, it appears as if the toner concentration has decreased, and toner concentration control works in the direction of increasing toner concentration. As a result, the actual toner concentration increases too much. From the above explanation, when the temperature is low and humidity, the image density decreases, and when the temperature and humidity are high, the image density increases too much.

Therefore, by controlling the doctor gap as described above, it is possible to prevent changes in image density due to environmental changes.

EXAMPLE An example of the present invention will be described below with reference to the drawings. 1st
The figure shows a developing section of an electrophotographic apparatus according to the present invention. In FIG. 1, l denotes a photosensitive drum which is an electrostatic latent image carrier, and is connected to a developer carrier 2 (hereinafter referred to as a sleeve) which carries a developer, which is a mixed powder of toner 8 and carrier 7, on its surface. The toner 8 is deposited on the electrostatic latent image on the photosensitive drum 1. A constant developing bias voltage for controlling the amount of toner 8 deposited is generated and applied to the sleeve from a high voltage power supply for developing bias 13. ing.

The developer is triboelectrically charged by stirring by the developer stirring paddle 4, adheres to the sleeve 2, is smoothed to an appropriate layer thickness by the doctor blade 5, and is conveyed to the development area.

Said sleeve 2. A rotational drive source such as the photosensitive drum 1 receives driving force from an external motor via a gear train. 10
is a toner concentration detection element, and the doctor blade 5
The toner concentration in the developer flowing over the scraper 9 is detected. 12 is a hopper housing section for storing toner 8; by driving a hopper motor (not shown), the toner roll 11 provided in the hopper housing 12 is rotated, and the toner 8 is stored in the developing housing 3; Further, toner concentration control is performed such that the output signal level of the toner concentration detection element 10 is always kept constant.

Further, the doctor blade 5 is fixed to a developer layer thickness regulating part intervening member 6 made of polyamide resin such as nylon 6 by screwing or the like, and the intervening member 6 is fixed to the developer housing part 3.

If an environmental change occurs and the temperature becomes high and humid, the actual toner density will be controlled at a value higher than the standard, but the doctor gap will become narrower to prevent the image density from increasing too much. Furthermore, when the temperature is low and humidity is low, the actual toner density is controlled to a value lower than the standard, but the doctor gap becomes wider, which prevents the image density from decreasing.

Effects of the Invention The present invention prevents image density changes due to environmental changes in a simple manner by fixing the doctor blade to the developer housing member via a hygroscopic swelling resin, without using an expensive temperature/humidity sensing element. It is something.

[Brief explanation of drawings]

FIG. 1 is a main sectional view of a developing section of an electrophotographic apparatus according to the present invention. DESCRIPTION OF SYMBOLS 1...Photosensitive drum, 2...Developer carrier, 5...Doctor blade, 6...Layer thickness regulating portion intervening member.

Claims (1)

[Claims] A developer carrier is arranged relative to the image carrier, and is configured to be able to carry a developer on its surface and to be rotatable; A developing device having a developer layer thickness regulating member, wherein the developer layer thickness regulating member is fixed to a developing housing member via a hygroscopic swelling resin.