JPH0343624B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus having a transfer means for applying an electric field to a transfer material when an image on an image support is transferred to a transfer material.

A corona charger is used as a transfer means for applying the above electric field. When this corona charger is driven by a constant-voltage high-voltage power supply, the amount of corona discharge changes due to changes in temperature, humidity, atmospheric pressure, dirt on the discharge electrode, etc., and the electric field acting on the image support and transfer material also changes, causing transfer. was unstable. In addition, when the corona charger is driven by a constant current high voltage power supply, the amount of corona discharge does not change due to changes in temperature, humidity, atmospheric pressure, etc. However, the resistance value of transfer materials such as paper changes depending on humidity. Although the transfer was more stable than the previous case, the transfer was still insufficient.

Therefore, in order to improve transfer performance under high humidity, the transfer material transport path from the paper feed position to the transfer position is insulated, and a bias voltage with the same polarity as the transfer charge is applied to the transport path. Prevents leaks from the material. However, sufficient transfer performance could not be obtained under high humidity conditions. In addition, a heater has been proposed in the paper feed cassette to prevent the transfer material from absorbing moisture. There were drawbacks such as wrinkles appearing on the transfer material when it was passed between a heating roller and a pressure roller to be fixed.

In addition, as described above, when transferring by applying an electric field to the transfer material, a sudden change in the electric field occurs when the transfer material separates from the image support after transfer, and the image on the transfer material (electrostatic image or (unfixed visible image after development) is disturbed. Therefore, conventionally, a charge eliminating means is applied to the transfer material immediately after transfer to eliminate the electric charge on the transfer material to prevent the above-mentioned image disturbance.

The present invention utilizes the fact that the static eliminating current flowing through the static eliminating means changes depending on the change in the electric field acting on the transfer material, and controls the transfer means that supplies the electric field, thereby forming an image in which a stable transferred image can be obtained. The purpose is to provide equipment.

Hereinafter, details of the present invention will be explained with reference to embodiments shown in the drawings. FIG. 1 is a diagram explaining the principle of the image forming apparatus of the present invention. The image support 1 has a photoreceptor 2 formed by sequentially laminating, for example, a conductive support, a photoconductive layer, and an insulating layer on the circumferential surface of a drum, and is rotatable around a shaft 3 on a body (not shown). installed on. According to this rotation, an electrostatic image is formed on the surface of the photoreceptor by the well-known electrophotographic process disclosed in, for example, Japanese Patent Publication No. 42-23910. Transfer material 4
is conveyed by conveying means such as a pair of feeding rollers 11 and 12 and a guide roller 13, and comes into contact with the photoreceptor surface of the image support 1 at the transfer position. An electric field is applied to the transfer material 4 by the transfer promoting corona charger 5 disposed corresponding to this contact position, and the image on the image support is transferred onto the transfer material 4.

Immediately after this transfer, the charge on the transfer material 4 is eliminated through a ground electrode 6 serving as a charge eliminating means. This ground electrode 6
is made of stainless steel with a thickness of 0.2 mm, for example, and has a thickness of 5 to 10 mm relative to the transfer material 4 as shown in Figure 2.
They are placed at some distance apart. Further, in order to promote discharge from the transfer material 4, convex portions (discharge tips) 6a having an opening angle of 50 degrees are arranged in parallel at 5 mm intervals on the surface of the ground electrode 6 facing the transfer material.

When paper is used as transfer material 4, the relative humidity is 55
% environmental volume resistivity 2×10 ¹² Ω・cm (water content 6
%), 5×10 ¹³ Ω・cm (moisture content 3) in a 25% environment
%), 2×10 ¹¹ Ω・cm (moisture content 8
%), 10 ⁹ Ω・cm or less in an 80% environment (moisture content 13
%) and physical property values varied greatly. For this reason, the transfer acceleration corona charger 5 has a voltage of 6 kV and a total current of 200 μA.
When transfer was performed by supplying electric power, the value of the static elimination current flowing through the ground electrode 6 had the relationship shown in FIG. 3 in response to changes in environmental humidity.

In the present invention, in order to detect the value of the static elimination current flowing through the ground electrode 6, the ground electrode 6 is grounded via a resistor 7, and the ground electrode surface A of the resistor 7 is connected via an amplifier 9 to a high voltage current 10. This is the configuration connected to.
With this configuration, the value of the static elimination current flowing to the ground electrode 6 is detected, and the high voltage power supply 10 is controlled based on this detected value, so that the value of the static elimination current flowing to the ground electrode 6 is controlled regardless of environmental changes such as humidity. Set it to 10μA at normal humidity and 65%.

FIG. 4 is a diagram showing the relationship between the total transfer output current of the high-voltage power supply 10 and the relative humidity controlled in this way.
This is opposite to the slope of the graph in FIG.

As mentioned above, by varying the output of the high-voltage power supply supplied to the transfer accelerating corona charger according to environmental changes such as humidity, it is possible to maintain the electric field applied to the transfer material so that it always maintains appropriate transfer conditions. can. As a result, a stable transferred image can be obtained without partial transfer omissions or thin images.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of the image forming apparatus of the present invention, Fig. 2 is a front view of the ground electrode, Fig. 3 is a diagram showing the relationship between relative humidity and current flowing through the ground electrode, and Fig. 4 is a diagram showing the relationship between relative humidity and high voltage. FIG. 3 is a diagram showing the relationship between power supply outputs. 1 is an image support, 4 is a transfer material, 5 is a corona charger, 6 is a ground electrode, 7 is a resistor, 8 is ground, 9 is an amplifier, and 10 is a high voltage power source.

Claims (1)

[Claims] 1 Image formation in which the image on the image support is transferred to the transfer material by applying an electric field to the transfer material by a transfer means, and then the charge held by the transferred transfer material is removed by a charge removal means having a discharging tip. In the device,
An image forming apparatus characterized in that an output of the transfer means is controlled according to a value of a current flowing through the charge eliminator when the transfer material having post-transfer charges faces the charge eliminator.