JPH06149029A - Developing device - Google Patents

Abstract

PURPOSE:To provide the developing device where a stable image output can be obtained from the initial period of use by controlling the aging time by detecting the fetching state of the toner to a fur brush by an electrical means. CONSTITUTION:In the developing device feeding the toner 5 to a developing roller 3 from a fur brush 2 rotated in contact with a developing roller 3, specified voltage is impressed on the fur brush 2, the current flowing from the fur brush 2 to the developing roller 3 is detected by a current detector 7 and the toner 5 is replenished to the fur brush 2 until the value of the current is a specified value. With this constitution, the quantity of the toner took in the fur brush 2 at the initial period of use of the developing device can be electrically detected. By this detection of the toner quantity, since the time of aging operation at the initial period of use can be freely controlled until the specified quantity of the toner is fetched, the stable image output can be obtained from the initial period of use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device in an image forming apparatus such as a copying machine, and more particularly to a developing device configured to supply toner from a fur brush to a developing roller using a one-component toner.

[0002]

2. Description of the Related Art Conventionally, in a developing device that supplies a predetermined amount of toner from a fur brush onto a developing roller, there is a problem that the density of an image varies depending on the amount of toner taken into the fur brush. It was necessary to perform aging operation for a certain period of time at the beginning of use. As shown in FIG. 4, by rotating the fur brush 21 and stirring the toner 24 replenished in the toner tank 23, a sufficient amount of toner is taken into the fur brush 21 and the toner 24 is sufficiently supplied. This is for rubbing the developing roller 22 with the included fur brush 21 and supplying a predetermined amount of toner to the peripheral surface of the developing roller 22. Developing roller 2
By forming a uniform toner layer on the surface 2, the amount of toner given from the developing roller 22 to the electrostatic latent image on the photoconductor 25 is stabilized, and an image output without uneven development can be obtained.

[0003]

However, since the aging operation in the conventional developing device using the fur brush is performed for the aging time which is empirically determined, the stable image output in the initial stage of use is constant. There was a problem that was not realized. That is, since the amount of toner taken into the fur brush is influenced by the toner state, the environmental state, etc., there are cases where the predetermined aging time is not appropriate. This state is caused by the excess or deficiency of the toner supply amount to the fur brush. The present invention was devised in view of the above problems, and a stable image output can be obtained from the initial stage of use by detecting the toner intake state into the fur brush by an electric means and controlling the aging time. An object is to provide a developing device.

[0004]

In order to achieve the above object, the means adopted by the present invention is a developing device for supplying toner to a developing roller from a fur brush rotating in contact with the developing roller. A developing device characterized in that a predetermined voltage is applied to the fur brush to detect a current flowing from the fur brush to the developing roller, and toner is supplied to the fur brush until the current value reaches a predetermined value. To be done.

[0005]

According to the present invention, it is possible to electrically detect the amount of toner taken into the fur brush at the beginning of use of the developing device. By detecting the toner amount, the aging operation time at the beginning of use can be controlled by the time until a predetermined amount of toner is taken into the fur brush, so that stable image output can be obtained from the beginning of use. In order to electrically detect the toner amount, a predetermined voltage is applied to the fur brush,
The current flowing from the fur brush to the developing roller is detected. Since the resistance value of the fur brush increases as the amount of toner taken in increases, the value of the current flowing from the fur brush to the developing roller changes depending on the amount of toner taken in by the fur brush. Therefore, a constant amount of toner taken into the fur brush can be obtained by replenishing the toner and performing the aging operation until the detected current value reaches the current value in the state of the preset predetermined toner amount.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. still,
The following example is an example embodying the present invention and does not limit the technical scope of the present invention. Figure 1
1 is a schematic diagram of a developing device according to an embodiment of the present invention, FIG. 2 is an equivalent circuit diagram of an electrical configuration for detecting the amount of toner taken into the fur brush shown in FIG. 1, and FIG. 3 is used for the configuration shown in FIG. It is a characteristic graph of the constant voltage diode used. In FIG. 1, the developing device 1 includes a fur brush 2 that agitates the toner 5 replenished in the toner tank 4 and takes it into the brush, and rubs against the developing roller 3 to supply the toner to the developing roller 3.
The toner supplied from the fur brush 2 is formed into a uniform thin layer on the peripheral surface and is conveyed to the photosensitive drum 6,
And a developing roller 3 which visualizes the electrostatic latent image formed thereon. Further, a constant voltage diode 8 for making a constant potential of the developing roller 3 is inserted between the ground of the developing roller 3 and the fur brush 2 has a predetermined voltage E exceeding the Zener voltage of the constant voltage diode 8. Is provided, and a current detector 7 that detects the amount of reverse current of the constant voltage diode 8 from the fur brush 2 through the developing roller 3 by this voltage application is provided. In the developing device 1 using the fur brush 2 having the above-described configuration, in order to make the fur brush 2 take in a predetermined amount of toner 5, at the beginning of use, the toner 5 is replenished in the toner tank 4 and the aging operation is performed. Then, the toner is taken into the brush while stirring the toner 5 by the fur brush 2.
This aging operation needs to be performed until a predetermined amount of toner 5 is taken into the fur brush 2, and by rubbing the developing roller 3 with the fur brush 2 sufficiently containing the toner 5, the developing roller 3 A predetermined amount of toner is supplied to the surface, and stable image output can be obtained from the beginning of use. The amount of the toner 5 taken into the fur brush 2 can be known from the change in the current detected by the current detector 7. That is, since the resistance value of the fur brush 2 increases as the amount of the toner 5 taken into the fur brush 2 increases, the toner taken-in amount can be detected by detecting the current value flowing from the fur brush 2 to the developing roller 3. An equivalent circuit for electrically detecting the amount of the toner 5 taken into the fur brush 2 can be represented as shown in FIG. The variable resistance R in the figure corresponds to the fur brush 2, and the resistance value changes depending on the amount of toner taken in. E is a voltage applied to the fur brush 2, Vz is a zener voltage of the constant voltage diode 8, and Iz is a reverse current flowing through the constant voltage diode 8, that is, a current value to be detected. As is well known in the characteristics of the constant voltage diode 8, when a reverse voltage is applied as shown in FIG. 3, a breakdown phenomenon occurs in which the reverse current sharply increases from around a certain specific voltage value (zener voltage Vz). Using this phenomenon,
If the reverse voltage applied to the constant voltage diode 8 is set to exceed the Zener voltage Vz when the value of the resistance R until the amount of toner taken into the fur brush 2 reaches a predetermined amount is R ₁ or less, the amount of toner taken in is set. The reverse current flows until the amount reaches the predetermined amount, and when the toner intake amount reaches the predetermined amount and the value of the resistance R becomes R ₂ , the reverse current Iz sharply decreases.
Therefore, the time of the aging operation can be controlled by detecting the change in the reverse current Iz of the constant voltage diode 8.
The detection of the reverse current Iz can be detected as a rapid current change from the characteristics of the constant voltage diode 8. Therefore, by setting the current change point at the time when the amount of toner taken into the fur brush 2 reaches a predetermined amount, when the detected value of the current detector 7 suddenly decreases, the amount of toner taken into the fur brush 2 is determined. Since it can be determined that the amount has been quantified, the aging operation ends. As described above, since the amount of the toner 5 taken into the fur brush 2 appears as a change in the resistance value of the fur brush 2, the fur brush 2 is simply used in addition to the configuration of the above embodiment.
Can be detected as the change value of the current passing through.

[0007]

As described above, according to the present invention, in the developing device for supplying the toner from the fur brush to the developing roller, the amount of toner taken into the fur brush at the initial stage of use of the developing device is electrically detected. You can By detecting this toner amount, the aging time at the beginning of use is
Since it can be controlled by the time until a predetermined amount of toner is taken into the fur brush, stable image output can be obtained from the beginning of use. Therefore, in the past, since the aging operation time was set by empirical judgment, the problem that the amount of toner taken into the fur brush was not constant and stable image output could not be obtained at the beginning of use was solved, and it was always stable. It is possible to provide a developing device that realizes the above-described image output.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a developing device according to an embodiment of the present invention.

FIG. 2 is an electrical equivalent circuit diagram of the configuration shown in FIG.

FIG. 3 is a characteristic graph of a constant voltage diode.

FIG. 4 is a schematic diagram showing a configuration of a developing device according to a conventional example.

[Explanation of symbols]

 1-Developing device 2-Fur brush 3-Developing roller 5-Toner 7-Current detector

Claims (1)

[Claims] 1. A developing device that supplies toner to a developing roller from a fur brush that rotates in contact with the developing roller, and applies a predetermined voltage to the fur brush to apply a current flowing from the fur brush to the developing roller. A developing device characterized in that toner is supplied to the fur brush until it is detected and the current value reaches a predetermined value.