JPS62127776A - Developing device - Google Patents

Abstract

PURPOSE:To perform stable development, by directly controlling the temperature of the developing agent in a developing tank. CONSTITUTION:Driving of heaters 11 and 12 is controlled by a temperature controlling circuit, which controls the power supply to the heaters 11 and 12 in accordance with detecting signals of a detecting means 13 that detects the temperature of the developing agent 2 in a developing tank 1. The detecting means 13 is constituted of, for example, a thermistor, etc., whose resistance value changes as the temperature changes, and the temperature controlling circuit compares the detecting signals with a reference signal and controls the heaters 11 and 12 so as to make the detecting signals coincident with the reference signals. The thermistor 13 is provided closely to a developing roller 7, especially, and before the developing agent 2 is carried to a developing area in the developing tank 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a developing device that develops an electrostatic latent image formed on a recording medium into a visible image.

<Prior Art> In electrophotographic copying machines, laser printers, etc., a developing device is provided to form an electrostatic latent image on a recording medium and to visualize this latent image. This developing device includes, for example, a developing tank containing developer and a developing roller configured by providing a magnet within a cylindrical sleeve made of a non-magnetic material. The developing roller attracts the developer to the sleeve surface using the magnetic force of the magnet, and by rotating the sleeve,
conveying the developer to a development area facing the recording medium;
Developing.

In the above-mentioned developing device, changes in temperature, humidity, etc. cause, in particular, clumping of colored toner, changes in charge amount, fluidity, etc., and adversely affect development. For example, image density, reproducibility of capri and fine lines, etc. change significantly. Further, due to changes in fluidity and the like, the concentration of the developer cannot be controlled normally, and the above-mentioned changes become more noticeable. Moreover, deterioration of the developer itself is also accelerated.

Therefore, in the past, a heating source was provided in the developing device itself.
A device that controls the temperature of the developing device using this heat source is disclosed in JP-A-51-111340, “Developing device for electrostatic copying machine.”
is shown. Although this is effective to some extent, since the heating source is installed outside the developer tank,
Thermal efficiency is very poor, making it impossible to directly control the temperature of the developer.

Therefore, sometimes the image may be seriously affected.

OBJECTIVES> The present invention provides an apparatus that effectively controls the temperature of the developer in the developing device and does not cause any change in image quality.

<Example> FIG. 1 is a sectional view showing an outline of a developing device according to the present invention. The developing device stores a certain amount of developer 2 in a developing tank 1 . For example, the developer 2 is composed of a carrier' made of a magnetic material and a toner made of a colored pigment. toner 3
is stored in a toner hopper 4 provided at a replenishment port provided at the upper part of the developer tank L, and the developer tank! will be replenished within. Opposite the toner 3 replenishment position,
A stirring roller 6 for stirring the developer 2 in the developer tank is rotatably provided in the developer tank l.

A developing roller 7 is provided in the developer tank 1 so as to face a recording medium (not shown). The developing roller 7 includes a cylindrical sleeve 8 made of a non-magnetic material, and the sleeve 8.
It consists of one magnet 9 provided inside. magnet 9
is usually fixed in the state shown in the figure, and the sleeve 8 around it is configured to rotate. Therefore, as the sleeve 8 rotates, the developer 2 attracted to the surface of the sleeve 8 by the magnetic force of the magnet 9 is transported to the development area facing the recording medium, and returned to the developer tank 1 after development.

The magnet of the developing roller 7 is fixed to the outer circumferential surface of the cylindrical roll 10, and six poles facing the sleeve 8 are provided so as to be sequentially different from each other. Inside the roll 10 is a developer tank! A rod-shaped heater 10 is provided to heat the developer 2 inside. This rod-shaped heater 11 directly heats the developer 2 via the developing roller 7 and controls the developer 2 to be maintained at a predetermined temperature. A rod-shaped heater 12 is also provided inside the hollow cylindrical portion 14 of the rotating stirring roller 6 to heat the developer 2 .

The heaters 11 and 12 are driven and controlled by a temperature control circuit (not shown), and the temperature control circuit operates the heaters based on a detection signal from a detection means 13 that detects the temperature of the developer 2 in the developer tank l. 11 and 12 are controlled. The detection means 13 is composed of, for example, an ohmister whose resistance value changes depending on the temperature, and a temperature control circuit compares this signal with a reference signal and controls heaters I+ and +2 so that both signals are always constant.
The thermistor I3, which controls the developer tank i
Among these, it is located particularly close to the developing roller 7 and at a position where the developer 2 is detected before it is conveyed to the developing area.

For example, the temperature control circuit stops energizing the heaters 11 and 12 when the temperature of the developer 2 reaches 20°C or more,
If it is below, it is Heater II.

12 is controlled to be energized.

In the figure, reference numeral 15 denotes a sensor for detecting the concentration of the developer 2, and the sensor 15 detects the magnetic permeability of the developer 2.

In response to the detection signal of the sensor 15, the toner hopper 4
Replenishment of the toner 3 contained therein is controlled. As a result, the amount of developer 2 in developer tank 1 is maintained at a constant amount, and at the same time, its concentration is controlled to be constant.

According to the developing device configured as described above, the temperature of the developer 2 in the developer tank 1 is always controlled within a predetermined temperature range. Therefore, the fluidity and charge amount of the developer 2 do not change due to changes in temperature or humidity. Therefore, stable development is always possible. In particular, according to the developing device of the present invention, the thermistor 13 and the like are provided in the developer tank, and the developer 2 is directly detected and heated by the heating means, so heating efficiency is high and stable control is possible. o Moreover, the temperature is detected before the developer 2 is conveyed to the development area, and the temperature is detected before the developer 2 is transported to the development area.
Since the temperature of the developer 2 is detected, the developer 2 used for development is directly controlled, allowing more effective control.

Here, the characteristic diagram shown in FIG. 2 is a comparison between the one according to the present invention and the conventional one.

In the figure, the vertical axis represents the copy density (image density) during development, and the horizontal axis represents the number of copies. Furthermore, the broken line shows the experimental results of developing using a developing device configured as shown in Figure 1, and the solid line shows the experimental results of developing using a developing device without a heater, and the ambient temperature is 5°C This is data under 30% humidity. As shown in the figure,
In the conventional method, as the number of copies gradually increases, the copy density decreases significantly. However, according to the developing device of the present invention, no change in copy density was observed even if the number of copies increased.

Further, the diagram shown in FIG. 3 is a characteristic diagram showing changes due to concentration control of the developer 2 between the developing device according to the present invention as shown in FIG. 1 and the conventional developing device not having a heater. In this figure as well, the vertical axis represents the toner concentration of the developer 2, and the horizontal axis represents the number of copies. Furthermore, the broken line indicates the data according to the present invention, and the solid line indicates the conventional data, and the data is obtained at an ambient temperature of 5° C. and a humidity of 30%.

As shown in the above, according to the developing device of the present invention, the toner concentration of the developer 2 is always kept constant regardless of the number of copies. As a result, the image quality resulting from development is stabilized. However, in the case of conventional printers, the toner density changes greatly as the number of copies increases. As a result, the image quality resulting from development becomes unstable compared to the present invention.

<Effects> According to the developing device of the present invention, since the temperature of the developer in the developer tank can be directly controlled, the characteristics of the developer are stabilized and stable development can be performed at all times. Furthermore, since the developer is directly heated, heating efficiency is improved and temperature control of the developer is stabilized.

As a result, developer density control is stabilized, and images are always stabilized.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a specific example of a developing device according to the present invention, and FIGS. 2 and 3 are characteristic diagrams for comparing the developing device of the present invention and a conventional developing device. 1: Developing tank 2: Developer 3: Toner 6: Stirring roller 7: Developing roller II, +2: Heater 13: Temperature detection means agent Patent attorney Yoshihiko Fukushi (and 2 others) Figure 1: One sheet IL (X1000#c) Figure 3

Claims (1)

[Claims] 1. In a developing device having a developing means for conveying a developer to a developing area facing a recording medium and a developing tank equipped with the developing means and containing the developer, the amount of water in the developing tank is The present invention is characterized by comprising a heat source for heating the developer, a detection means for detecting the temperature of the developer in the developer tank, and a control means for controlling energization of the heat source in accordance with a detection signal from the detection means. Developing device.