JPH09197770A - Image forming device - Google Patents

Abstract

(57) Abstract: In an image forming apparatus using an electrophotographic process, the accuracy of the charging potential of an image carrier can be increased,
To make it possible to easily adjust the power supply system without lowering the accuracy of the charging potential. A constant current power supply 23 is provided for both charging and transfer devices, which is capable of constant current control by adjusting output current. The constant voltage element 15 for adjusting the voltage of the grid electrode 2a and the variable resistor 22 are connected in series to the casing of the charging device 2, and the constant voltage element 15 is connected to the casing of the transfer device 7. Transfer device 7 by adjusting the output current of constant current power supply 23
After adjusting the transfer current flowing through, the constant voltage element 15 and the variable resistor 22 adjust the potential applied to the grid electrode 2a of the charging device 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic process such as a copying machine, a printer and a fax machine, and more particularly to an improved image forming apparatus whose power supply circuit is adjusted.

[0002]

2. Description of the Related Art In recent years,
Image forming apparatuses using an electrophotographic process have been downsized and reduced in cost, and one means of reducing costs is to reduce the cost of power supply devices. On the other hand, in the image forming apparatus using the electrophotographic process, it is necessary to accurately control the value of the grid potential of the charging device. In this case, the potential can be accurately controlled by controlling with a constant voltage power source, but The cost will increase. Therefore, a method of controlling with a constant voltage element or a variable resistor has been proposed. For example, in Japanese Utility Model Laid-Open No. 63-21959, there is a technique in which the casing and the grid of a charging device are set to the same potential and grounded via a constant voltage element. A technique for grounding via a series circuit of an element and a variable resistor has been proposed.

FIG. 4 is a schematic diagram of an image forming apparatus having the above-mentioned configuration. In the figure, 1 is an image carrier, 2 is an image carrier 1.
2a is a grid electrode of the charging device, 3 is exposure from an exposure device for forming a latent image, and 4 is a latent image formed on the surface of the image carrier 1. A developing device for visualizing the image, 5 is an elastic invasion restricting member for restricting the intrusion of the transfer material, 6 is a charge restricting member for restricting the charge applied to the surface of the image carrier 1.
Reference numeral 7 is a transfer device, 8 is a cleaning device for removing the developer remaining after the transfer, 9 is a static eliminator for eliminating the residual potential of the image carrier 1, and 10 is the transfer material after separation to the fixing device 11. Is a conveyance guide member, 12 is a registration roller, 13 is a power supply of the charging device, 14 is a power supply of the transfer device, and 15 is a constant voltage element connected to the casing of the charging device and the grid electrode.

However, in the case where the casing of the charging device 2 and the grid electrode 2a are controlled by the grid potential only with the constant voltage element 15 as shown in FIG. 4, the voltage is changed as shown in FIG. Target center value V
_The potential fluctuates within the range around _GR0 (the range sandwiched by the dotted lines and shaded). As a result, the surface potential of the image carrier 1 also varies. Since variations in the surface potential of the image carrier 1 directly correspond to changes in the image, it is necessary to stabilize it as much as possible.

Further, in this type of image forming apparatus, since a high voltage power source is used for charging, developing, transferring, etc., cost reduction is proposed by making them common or integrated. For example, in Japanese Unexamined Patent Publication No. 61-126578, the charging and transfer power sources are shared, and the grid applies a required potential during image formation by the control means (constant voltage element and variable resistance connected in series). In this case, a technique has been proposed in which the application of electric potential is hindered (grounded).

In view of the conventional situation regarding cost reduction as described above, the present invention can improve the accuracy of the charging potential of the image carrier and can easily adjust the power supply system without lowering the accuracy of the charging potential. An object is to provide a forming device.

[0007]

An image forming apparatus according to the present invention is provided with a power source capable of controlling a constant current by adjusting an output current in common for a charging device and a transfer device, and is provided with a grid electrode of the charging device. In an image forming apparatus including an adjusting unit for adjusting a voltage, the adjusting unit including at least a constant voltage element and a variable resistor, the output current of the power source is adjusted to adjust the transfer current, and then the grid is adjusted by the adjusting unit. It is characterized in that the electric potential of the electrodes is adjusted.

In the image forming apparatus according to the present invention, a power source capable of constant current control by adjusting the output current is provided in common for the charging device and the transfer device, and the voltage of the grid electrode is adjusted in the casing of the charging device. An image forming apparatus in which a constant voltage element and a variable resistor are connected in series as adjusting means, and a constant voltage element is connected to the casing of the transfer apparatus, and the transfer current is adjusted by adjusting the output current of the power source. After that, the adjusting means adjusts the potential of the grid electrode.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the following, description will be made by assigning common reference numerals to parts common to the related art.

FIG. 1 shows an embodiment of an image forming apparatus according to the present invention. In the figure, 21 is a constant voltage element connected to the casing of the transfer device 7, 22 is a variable resistor connected to the casing of the charging device 2 and its grid electrode 2a, and 23 is a charging / charging device.
A constant current power source that is used for both transfer devices is shown. That is, like the device of FIG. 4, the casing of the charging device 2 and the grid electrode 2a
If the grid potential control of only the constant voltage element is carried out, the potential will fluctuate and the surface potential of the image carrier 1 will also fluctuate. Therefore, in the apparatus of FIG. By utilizing the change in the potential difference at both ends together with the change in the resistance value, the target center value V _GR0 of the voltage can be obtained. In FIG. 1, a part common to FIG. 4 is omitted, and a part that is not so important for the description of the present invention is omitted.

Specifically, the slope of the straight line shown by the solid line in FIG. 2 changes, and the intersection of the straight line with the current value actually flowing through the casing of the charging device 2 and the grid electrode 2a is the target V.
Adjust the resistance value so that it becomes _GR0 . As a result, the surface potential of the image carrier 1 can be controlled with high accuracy and a stable image can be formed.

Further, in the configuration as shown in FIG. 1, the charging device 2
In order to set the potential of the grid electrode 2a of 1 to a predetermined value, the variable resistor 22 is adjusted first, and then the output current of the constant current power supply 23 is adjusted so that the transfer current has a predetermined value.
The transfer device 7 side can be adjusted very accurately, but the current on the charging device 2 side also changes. The output of the constant current power supply 23 is determined by the output of the transfer device 7 side. The charging device 2 side can obtain the target grid potential and charging potential by adjusting the variable resistance as long as a certain amount of current flows. On the other hand, it is the easiest for the transfer side to adjust the output current of the power supply 23 in order to obtain an appropriate current value. However, as the current on the charging side changes, the grid electrode 2
Since the current flowing into a also changes, the variable resistor 22
The potential difference generated at both ends of the grid changes, and the set grid potential changes. Therefore, the surface charging potential of the image carrier 1 deviates from a predetermined value, and it becomes necessary to readjust the grid potential again.

Therefore, first, the output current of the constant current power supply 23 is adjusted so that the transfer current has a predetermined value, and then the variable resistor 22 is adjusted. By doing so, a predetermined grid potential can be obtained without significantly shifting the transfer current from the initial set value. The transfer current is within the range where the actual transfer efficiency hardly changes. The dependency of the transfer rate on the transfer current is as shown in FIG. 3. If the set value of the transfer current at the time of adjustment is set to I _T0 , even if it shifts to I _T1 by adjusting the grid potential, Since the characteristics are flat in the vicinity, the transferability is not significantly affected.

[0014]

The image forming apparatus according to the present invention adjusts the transfer current by adjusting the output current of the constant current controllable power source, and then adjusts the grid of the charging device by the adjusting means including the constant voltage element and the variable resistor. By clarifying the adjustment order so as to adjust the potential of the electrodes, without increasing the cost,
There is an effect that an appropriate transfer current and grid potential can be easily set.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a diagram showing a relationship between a grid voltage and a current flowing through a charging device in the embodiment shown in FIG.

FIG. 3 is a diagram showing a relationship between a transfer rate and a transfer current in the embodiment of FIG.

FIG. 4 is a diagram illustrating an example of a conventional image forming apparatus.

5 is a diagram showing the relationship between the grid voltage and the current flowing through the charging device in the apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 2 Charging device 2a Grid electrode of charging device 3 Exposure from exposure device 4 Developing device 5 Elastic ingress regulation member 6 Charge regulation member 7 Transfer device 8 Cleaning device 9 Static eliminator 10 Conveyance guide member 11 Fixing device 12 Registration roller 15 constant voltage element (for charging device) 21 constant voltage element (for transfer device) 22 variable resistor 23 constant current power supply

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Asami 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Manabu Mochizuki 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Inventor Noriyuki Usui 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (2)

[Claims] 1. A power source capable of controlling a constant current by adjusting an output current is commonly provided for a charging device and a transfer device, and an adjusting means for adjusting a voltage of a grid electrode of the charging device is provided. An image forming apparatus comprising at least a constant voltage element and a variable resistor, characterized in that after adjusting an output current of the power source to adjust a transfer current, the potential of the grid electrode is adjusted by the adjusting means. Image forming apparatus. 2. A power source capable of controlling a constant current by adjusting an output current is commonly provided for the charging device and the transfer device, and a constant voltage element is provided in a casing of the charging device as an adjusting means for adjusting a voltage of a grid electrode. An image forming apparatus in which a variable resistor is connected in series, and a constant voltage element is connected to a casing of the transfer device, wherein the output current of the power supply is adjusted to adjust the transfer current, and then the adjusting means described above is used. An image forming apparatus characterized by adjusting the potential of a grid electrode.