JPH01133084A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To execute optimum transfer control according to the moisture absorbing condition of paper which is a transfer member and to stabilize image quality by providing a control means for at least either of the exposure of an exposing means or the impressed voltage of a transfer device by the leak current flowing to the transfer member by the corona discharge of the transfer device. CONSTITUTION:The leak current passed to the transfer member 6 by the corona discharge of the transfer device 4 is detected via a paper carrying member 7. The control means of at least either of the means for controlling the exposure of the 2nd exposing device 15 installed between a developing device 3 and the transfer device 4 by the detected current and the means for controlling the impressed voltage of the transfer device 4 is provided. The always stable image quality is thereby obtd. even with any kind of paper, i.e., moisture absorptive paper, normally moist paper and further high-resistance paper.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic apparatus, and more particularly, the present invention relates to an electrophotographic apparatus, and more particularly, the moisture absorption state of paper that is a transfer member, that is, whether the paper is moisture absorption paper, normal humidity paper, or even high humidity paper. The present invention relates to an electrophotographic apparatus that can always achieve optimal transfer control and stabilize image quality regardless of the type of resistive paper used.

[Conventional technology]

The structure of an electrophotographic apparatus is generally such that charging, exposure, development, and transfer devices are sequentially arranged around a photoconductive photosensitive drum.

However, in conventional electrophotographic devices, when the actual measured relative 5% density exceeds 70%, the image density decreases significantly.
A problem has been raised that good image quality cannot be obtained.

The reason for this is that as the relative humidity increases, the electrical resistance of paper that has absorbed moisture decreases, and the amount of charge also decreases, giving the paper enough Coulomb force to overcome the electrical adsorption force between the photosensitive drum and toner. This is because it is not possible.

To explain this in more detail, especially during the rainy season, when paper absorbs moisture and is exposed to high humidity for a long period of time, toner transfer efficiency decreases significantly and image quality deteriorates. The electric charge flows through the paper into the paper conveying member, that is, the grounded paper strip member.

As a countermeasure to this problem, a method has been considered in which the paper transport member is insulated from ground in order to prevent electric charges from flowing into the paper transport member through the paper.

We are also considering a method of performing a second exposure at a constant exposure amount after development to weaken the attraction between the photosensitive drum and the toner, and to enable transfer even to moisture-absorbing paper with a small amount of charge. It will be done.

Note that prior art related to electrophotographic devices is described in, for example, Japanese Patent Application Laid-Open Nos. 61-32667 and 61-290461.

[Problem that the invention seeks to solve]

However, according to the former method, a large area needs to be insulated and the product price becomes expensive. For paper or high-resistance paper, electric discharge occurs between the paper and the photosensitive drum, resulting in a new problem of poor image quality.

The present invention was made as a result of studies to solve the problems of the prior art described above, and its purpose is to determine the moisture absorption state of paper that is a transfer member, that is, whether the paper is moisture absorbent paper or normal moisture paper. Furthermore, even in the case of high-resistance paper, optimal transfer control can always be performed according to the resistance state of the paper, and image quality can be stabilized. The object of the present invention is to provide an improved electrophotographic device that is particularly easy to use.

[Means for solving problems]

The purpose is to charge, expose, and charge the area around the photoconductive photosensitive drum.
In an electrophotographic apparatus in which developing and transfer devices are sequentially arranged, leakage current flowing to the transfer member due to corona discharge of the transfer device is detected via a paper conveying member, and this detected current is used to connect the developing device and the transfer device. This is achieved by providing at least one of a means for controlling the exposure amount of the second exposure device installed between the processes and a means for controlling the voltage applied to the transfer device.

That is, the present invention provides at least one of a means for performing exposure again after the development process and a means for changing the voltage applied to the transfer device in order to change the attraction force between the photosensitive drum and the toner in accordance with the moisture absorption state of the paper. or at the same time as adding one vehicle.

The current flowing through the paper is detected as a change in leakage current to the paper conveyance member, and the amount of exposure of the exposure device and the voltage applied to the transfer device are controlled based on the amount of change in current.

[Effect]

In the above configuration, the current value flowing into the paper conveying member is
It changes depending on the moisture absorption state of the paper. That is, in the case of low-resistance paper, the value of current flowing into the paper conveyance member is large, and in the case of high-resistance paper, the value of current flowing into the paper conveyance member is small. Therefore, by detecting the current value from the paper conveyance member and changing the exposure amount of the exposure device and the applied voltage of the transfer device based on this current value, it is possible to Even with resistive paper, stable image quality can always be obtained. For example, if paper is left in an environment with relative humidity of 80%, the leakage current to the paper transport member will increase, so depending on the current value, the amount of exposure after development may be increased or the voltage applied to the transfer device may be increased. This improves the transfer of toner to paper. On the other hand, in the case of low-humidity paper, since the leakage current to the paper conveying member is small, good image quality can be obtained by lowering the exposure amount after development or by lowering the voltage applied to the transfer device.

〔Example〕

Hereinafter, the present invention will be explained based on FIGS. 1, 2, and 5. FIG. 1 is an explanatory diagram of the overall configuration of an embodiment of an electrophotographic apparatus according to the present invention, and FIG. FIG. 5 is a partially enlarged detailed view of FIG. 1, which is the main part of the invention, and FIG. 5 is a characteristic diagram of toner attraction force, leakage current, and exposure lamp light amount variation obtained by the apparatus of the present invention.

In FIG. 1, 1 is a photoconductive photosensitive drum, 2 is a charger, 21 is a laser beam from an exposure device (not shown), 3 is a developing device, 4 is a transfer device, and 5 is a paper conveyance roller 5. .

16 is a leakage current detection circuit whose details will be described later; 7 is a leakage current detection plate; and 15 is a second exposure lamp unit installed between the developing device 3 and the transfer device 4.

Here, each structure of the leakage current detection circuit 16, the leakage current detection@7, and the exposure lamp unit 15 will be explained in detail.

The leakage current detection plate 7 has a function as a guide for conveying the transfer member 6, similar to the conventional improved electrophotographic apparatus.

Also, one end of the leakage current detection plate 7 is configured to be grounded via a voltage dividing resistor 8°9, and from the branch point of the voltage dividing resistors 8 and 9,
An input signal of a leakage current detection circuit 16 constituted by a resistor 10.11 and an amplifier 12 is sent.

Furthermore, the output signal of the leakage current detection circuit 16 is as follows.

This is an input signal to a transistor 14 that controls the amount of light from the exposure lamp unit 15 via a resistor 13.

Next, the operation of the above embodiment will be explained.

In FIG. 1, an electrostatic latent image is formed by the laser beam 21 on the surface of the photosensitive drum 1 which has been negatively charged by the charger 2, and due to the developing action of the imager 3, an electrostatic latent image is formed as shown in FIG. , 1-ner particles 19 adhere to the surface of the photosensitive drum 1 by an attractive force Fo (see FIG. 5). At the same time, the transfer member 6 sent out by the paper conveyance roller 5 passes through the leakage current detection plate 7 and reaches the transfer device 4 . Then, a negative electric field is applied to the transfer member 6 near the opening of the transfer device 4, as also shown in FIG.
As a result, at the same time that the negative charge 20 is placed on the surface of the transfer member 6, a portion of the negative charge 20 flows to the ground side via the leakage current detection plate 7 and the resistors 8 and 9. Due to this phenomenon, a leakage current flows into the transfer member 6 from the ground side in the opposite direction to the flow direction of the charge, and the leakage current causes a potential difference in the resistor 9, and this potential difference Vt is used as an input signal. , a resistor 10, 11, and an amplifying element 12 perform amplification. As a result, an output voltage v2 is obtained, which causes the transistor 14 to operate via the resistor 13. When the transistor 14 operates, the exposure lamp power supply E
A current flows through the exposure lamp unit 15, and the surface of the photosensitive drum 1 is irradiated with a light amount Lw (see FIG. 5) corresponding to the leakage current Is. When the toner particles 19 adhering to the surface of the photosensitive drum 1 receive the lamp light intensity Lw, the attraction force increases to FD' as shown in FIG.
When the toner particles 19 further reach the transfer device 4, the toner particles 9 are attracted by the attraction force FP due to the negative charge of the transfer member 6 and the toner particles 19, as shown in FIGS. 2 and 5. Attraction force FD' between photosensitive drum 1
is transferred to the transfer member 6 due to the attraction force of the difference F between the two, and thus the leakage current Is to the transfer member 6 is detected,
By controlling the light amount Lw of the exposure lamp, the toner particles 19 can be transferred to the transfer member 6 with a suction force F with little variation.

FIG. 3 shows a second embodiment of the invention.

In FIG. 1, it is desirable that the exposure lamp unit 15 be installed at a position closest to the mounting position of the transfer device 4. The reason is that before the exposure lamp unit 15 operates,
The toner particles 19 on the surface of the photosensitive drum 1 have already been transferred to the transfer device 4.
When reaching the opening, at the front edge of the transfer member 6,
The above effects cannot be obtained. That is, due to some design circumstances, space cannot be secured around the transfer device 4, and the exposure lamp unit 15 is installed at the transfer device 4.
If the location is far away from the location, it becomes difficult to obtain the above-mentioned effects.

On the other hand, as shown in FIG. 3, a second transfer device 17 is provided to apply a negative electric field to the transfer member 6, and the distance Hs between the transfer devices 4 and the second transfer device 17 is The relationship with the distance HL between the antishock light lamp units 15 is expressed as H
By allocating so that s > HL, the effects of the present invention described above can be fully enjoyed.

Further, as shown in FIG. 4, the present invention also enables the exposure lamp unit 15 to be controlled by feeding back the detection/amplification signal v2 of the leakage current Is to the transfer member 6 to the power control of the bias power supply 18 of the transfer device 4. Effects similar to those obtained by controlling the amount of light can be obtained, and in this case, the problem with the leading edge of the transfer member 6 described above does not occur.

Further, in the present invention, both the above-described exposure lamp light amount control and transfer device bias control can be used together.

〔Effect of the invention〕

The present invention is as described above, and as is clear from the explanation of the illustrated embodiments, according to the present invention, the moisture absorption state of the paper that is the transfer member, that is, whether the paper is moisture absorption paper, ordinary paper, or even high resistance Regardless of the type of paper, it is possible to always perform optimal transfer control according to the resistance state of the paper, and to stabilize the image quality. An electrophotographic device can be obtained.

[Brief explanation of the drawing]

1 and 2 show an embodiment of an electrophotographic apparatus according to the present invention, FIG. 1 is an explanatory diagram of its overall configuration, and FIG. 2 is an enlarged detail of a portion of FIG. 1, which is the main part of the present invention. FIG. 3 is an explanatory diagram of the main part configuration showing the second embodiment of the device of the present invention, and FIG.
The figure is an overall configuration explanatory diagram showing a third embodiment of the device of the present invention,
FIG. 5 is a characteristic diagram of toner attraction force, leakage current, and exposure lamp light amount variation obtained by the apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 2... Charger, 3... @ image device, 4... Transfer device, 6... Transfer member, 7... Leakage current detection plate, 15... Exposure lamp unit, 16...
- Leakage current detection circuit, 17... second transfer device, 21.
...Laser light.

Claims (1)

[Scope of Claims] 1. In an electrophotographic device in which charging, exposure, development, and transfer devices are sequentially arranged around a photoconductive photosensitive drum, leakage flowing to a transfer member due to corona discharge of the transfer device A current is detected through a paper conveying member, and the detected current controls the exposure amount control means of a second exposure device installed between the developing device and the transfer device and the voltage applied to the transfer device. An electrophotographic apparatus comprising at least one control means among the means. 2. In the invention described in claim 1, a second exposure device is installed between the developing device and the transfer device, and a paper transport system is located on the paper feeding side with respect to the transfer device. A second transfer device that applies the same electric field to the transfer member as that of the transfer device is provided midway, and the distance H_L between the second exposure device and the transfer device and the distance H_L between the second exposure device and the second transfer device are
An electrophotographic apparatus in which the distance H_S between transfer devices is in the relationship H_L<H_S.