JPS63788B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a latent image developing method and a developing device using a two-component developer consisting of a carrier and toner for electronic copying machines, laser beam printers, image forming apparatuses using magnetic latent images, etc. .

Conventionally, as shown in FIG.
A device that detects when developer is replenished by applying a voltage from a power source 4 to a detector 5 and measuring changes in resistance or capacitance with and without developer between the electrodes. is known.

The applicant has already proposed the use of a power source that forms an alternating electric field as the bias power source E in FIG. 1 for a one-component developer.

However, in a developing device using a two-component developer consisting of carrier and toner, only a device using a DC bias is known as a developing bias. In this case, a two-component developer will cause fogging and will not produce a good quality image.

An object of the present invention is to improve copy image quality when a two-component developer is used.

The present invention provides a developing method that achieves this as a first invention, and a developing device that implements this developing method as a second invention, the configuration of which is as set forth in the claims.

To specifically explain the illustrated example, in FIG. 2, an electrode 3 is arranged inside the hopper 1, and 2
Using the sleeve roller 6 that supports the component developer and using the resistor 7 as a passive element, the three members 3, 7,
6 are connected in series, and an AC electric field is applied between the electrodes 3 and 6 using an AC bias power source E for preventing fog, which is applied between the sleeve 6 and the electrostatic image support (for example, a photosensitive drum) 8. It is something to do.

The sleeve 6 is made of stainless steel and has a diameter of, for example, 30 mm, and magnetic poles N and S of, for example, 700 gauss are provided on the fixed magnetic roller 6a inside the sleeve 6 in the vicinity immediately below the blade 9 and inwardly. The rotation of the sleeve 6 causes the developer to stand up, causing the sleeve to have, for example,
A developer layer of about 100μ is supported like a coating,
For example, an electrostatic image on the photoreceptor 8 located at a distance of about 250 μm, that is, at a position not in contact with the developer layer, is visualized. Bias power supply 4 (E) is, for example, 200Hz.
It is 800Vpp alternating current, and sometimes direct current, for example +200V, is superimposed. In this sense, an electric field generated by a power source including alternating current or alternating current and direct current is called an alternating electric field.

FIG. 3 shows an equivalent circuit of FIG. 2. Electrodes 3 and 6 can be regarded as capacitors C, and constitute a CR circuit, and the change in C is detected by a passive element 7.
(resistance R) is detected as a voltage change. The detection circuit 5 includes, for example, a comparator 10 and a one-shot multi-circuit 11, and inputs the output voltage V of the resistor 7 and the standard voltage V _R to the comparator 10.

If the capacitor capacity is Ct when there is developer between electrodes 3 and 6, and Ca is that when there is no developer, then Ct＞
Ca.The output voltage at that time is V(Ct)・V(Ca),
The standard voltage V _R is determined by the relationship V (Ca) < V _R < V (Ct).

With the above configuration, when there is developer, V(Ct)>V _R , so the shaded area in _FIG . The pulse is input to the one-shot multi-circuit 11, and the circuit 1
By setting the duration T ₂ of 1 to T ₂ > T ₁ , the output of the circuit 11 is turned on as shown in FIG. 4C,
The output is connected to a lamp display circuit to display the presence of developer by lighting.

When the developer is exhausted and V (Ca) < V _R , the fifth
The pulse signal disappears as shown in figure A, and
Since the input pulse to the multi-circuit 11 becomes 0 and the output of the multi-circuit 11 also becomes 0, the lamp goes out to notify that it is time to replenish the developer. Also, depending on the design of the detection circuit 5, in the case of a two-component developer, it is also possible to measure the ratio of toner to carrier.

In the embodiment, the sleeve 6 is used as one of the electrodes, but a dedicated one may be used as shown in FIG. Moreover, instead of the voltage output of the passive element 7, it can also be extracted as a change in current.

Since the developing method and apparatus of the present invention have the above-described configuration, the AC bias effect is sufficiently exerted on the two-component developer that is not in contact with the electrostatic image.
That is, due to the alternating current bias applied between the developer support means 6 and the electrostatic image support means 8, the toner in the two-component developer layer that is not in contact with the electrostatic image is vibrated to remove agglomeration and increase fluidity. As a result, the gradation of the image is increased, the edges of the image are made clearer, fogging is prevented, and good images are always obtained. The configuration in which the AC bias power source is also used for detecting the remaining amount of developer has the advantage of saving power supply parts and being effective in downsizing the apparatus.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a reference device related to the present invention;
FIG. 2 is a schematic diagram of a specific embodiment of the present invention, FIG. 3 is an equivalent circuit diagram of the developer detection means in FIG. 2, and FIG.
FIG. 5 is an operating curve diagram for developer detection. 1 is a hopper, 2 and 3 are electrodes, 7 is a passive element, 4
6 is an AC power supply, 6 is a developer support means, and 9 is an electrostatic image support means.

Claims (1)

[Scope of Claims] 1. A developing method for developing an electrostatic image on an electrostatic image supporting means for supporting an electrostatic image using a developer, wherein the electrostatic image supporting means and the developer include a carrier and a toner. A two-component developer layer that is thinner than the gap between the two-component developer supporting means that conveys the two-component developer is supported by the developer supporting means, and an alternating electric field is applied between the electrostatic image supporting means and the developer supporting means. . A developing method in which an electrostatic image is visualized using the toner of the two-component developer layer. 2. The developing method according to claim 1, wherein the alternating electric field is an electric field obtained by superimposing a DC bias on an AC bias. 3. A photosensitive drum that rotates while supporting an electrostatic image, a hopper that stores developer, a developer sleeve that supports and conveys the developer in the hopper, and a magnet roller that is fixedly provided within the sleeve. and a blade that regulates the developer supplied from within the hopper to form a developer layer on the surface of the developing sleeve, wherein the developer is a two-component developer consisting of toner and carrier; Above 2
a blade for forming a developer layer of the component developer into a developer layer thinner than the gap between the photosensitive drum and the developing sleeve, and a developing bias power source for applying an alternating electric field between the photosensitive drum and the developing sleeve; A developing device comprising: