JPH05107944A - Image forming device - Google Patents

Abstract

PURPOSE:To inexpensively form an excellent image at any time irrespective of the change in resistance value caused by the quality and humidity of a recording sheet. CONSTITUTION:A constant voltage is applied to a paper feeding guide 42 by a high voltage power source 45 and the resistance value of a recording sheet carried between the paper feeding guides 41 and 42 is detected by a detecting part 47b. When the resistance value of the recording sheet is judged to be great by the output of the detecting part 47b, a control part 46 switches a change-over switch 44 to the earth side and a paper carrying guide 43 is earthed. On the other hand, when the resistance value is judged to be small, the change-over switch 44 is switched to the high voltage power source 45 side to connect the high voltage power source 45 to the paper carrying guide 43. Then, a high voltage is applied from the high voltage power source 45.

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 such as an electronic copying machine for forming an image on a sheet of recording paper.

[0002]

2. Description of the Related Art Conventionally, electronic copying machines have been susceptible to changes in the quality and humidity of the recording paper used. That is, when the humidity is high, the resistance value of the recording paper decreases, so that good copying cannot be performed on the recording paper having such a low resistance value.

In order to prevent this, an electronic copying machine has been developed which is provided with a high voltage power source for constantly applying a voltage to a paper conveyance guide during copying. However, in an electronic copying machine that applies a high voltage to the paper transport guide, if the backside of the recording paper becomes dirty or the resistance of the recording paper is high, the guide may There were drawbacks such as clinging to each other and poor transport.

On the other hand, as a device for handling recording paper having a high resistance value, an electronic copying machine has been developed in which a paper transport guide is always connected to the ground. However, in the case of this copying machine, there is a drawback that transfer omission occurs when the resistance value of the recording paper becomes low.

Therefore, a constant voltage from a constant voltage source is applied to the paper feed guide, which is read as a change in the current value flowing through the resistance value of the recording paper being conveyed, and the resistance value of the read recording paper is read according to the read resistance value. An electronic copying machine has been devised in which the application of a voltage from a high-voltage power supply to the paper conveyance guide in the subsequent stage and the connection to the ground side are switched.

However, in the case of this copying machine, a constant voltage source for applying a constant voltage to the paper feed guide and a high voltage power source for applying a voltage to the paper transport guide are prepared separately, and accordingly, that amount. However, there was a drawback that the cost was high.

[0007]

As described above, in the prior art, a constant voltage source for applying a constant voltage to the paper feed guide and a high voltage power source for applying a voltage to the paper transport guide are separately provided. Since it was prepared, there was a drawback that the cost would increase accordingly.

Therefore, according to the present invention, it is possible to always perform good image formation without impairing the conveyance ability of the recording paper, and to reduce the cost, regardless of whether the recording paper has a high resistance value or a low resistance value. An image forming apparatus is provided.

[0009]

In order to achieve the above object, in the image forming apparatus of the present invention, a constant voltage from a constant voltage source is applied to a paper feed guide, and recording is carried there. The resistance value of the paper is read as a change in the flowing current value, and according to the read resistance value of the recording paper, the application of the voltage from the high voltage power supply to the paper conveyance guide in the subsequent stage and the connection to the ground electrode are switched. In the above configuration, the constant voltage source that applies a constant voltage to the paper feed guide is also used as the high voltage power source that applies a voltage to the paper transport guide.

[0010]

According to the present invention, since the power source to be prepared can be made one by the above means, the cost can be reduced accordingly.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows the internal structure of the electronic copying machine according to the present invention.

That is, the photoconductor drum 12 is arranged in the substantial center of the main body 11 of the electronic copying machine 10. Around the photosensitive drum 12, a charging device 13, an exposure position 14a by the optical device 14, a developing device 16, a transfer peeling charger 17, a cleaning device 18, and a charge eliminating lamp 20 are provided.

On the right side of the main body 11, a cassette 21 for accommodating the sheet-shaped recording paper P is provided. The recording paper P in the cassette 21 is sequentially fed to a transfer portion between the photosensitive drum 12 and the transfer peeling charger 17 via a paper feeding portion.

That is, in the main body 11, the cassette 21
From the pickup roller 22, the recording paper P fed through the paper feed section is guided through the transfer section of the photoconductor drum 12 to the paper discharge path 23 on the left side of the main body 11, and a paper conveyance path 24. Are formed.

A separation roller 25 and a registration roller pair 26 are provided on the upstream side of the photosensitive drum 12 in the sheet transport path 24, and a transport belt 27, a fixing roller pair 28, and a discharge roller pair 30 are provided on the downstream side. Is provided.

On the other hand, on the upper surface of the main body 11, a document table (transparent glass) 34 on which a document D is placed, a white platen sheet 35a, and a document cover 35 for covering the document table 34 are provided and operated. A panel (not shown) is provided. A document scale 32 that serves as a guide when the document D is placed is provided on the leading edge side (sheet discharge side) around the document table 34.

The optical device 14 includes an exposure lamp 36, mirrors 37a, 37b, 37c, 37d and 37.
e, 37f, and a lens block 15 for zooming.

The exposure lamp 36 and the mirror 37a,
37b and 37c are moved in the direction of arrow S in the figure along the lower surface of the document table 34, and the document D on the document table 34 is exposed and scanned in accordance with this movement. in this case,
The mirrors 37b and 37c move at half the speed of the mirror 37a so as to maintain the optical path length.

The lens block 15 is moved to a position corresponding to a copy magnification set on an operation panel (not shown) during zooming. The mirrors 37d and 37e are automatically moved to the focus position according to the moving amount of the lens block 15.

The document D placed on the document table 34 is irradiated with light from the exposure lamp 36 as the optical system moves. The reflected light from the original D is reflected by the mirror 3
7a, 37b, 37c, the lens block 15, and the mirrors 37d, 37e, 37f in this order to the exposure position 14a of the photosensitive drum 12, and the surface of the photosensitive drum 12 is uniformly charged by the charging device 13. Is imaged.

Then, the image is slit-exposed at the exposure position 14a to form an electrostatic latent image on the surface. This electrostatic latent image is visualized by the toner attached by the developing device 16. On the other hand, in synchronism with this, the recording paper P taken out from the cassette 21 is sent toward the photosensitive drum 12 by the registration roller pair 26.

On the recording paper P, the toner image on the photosensitive drum 12 is transferred by the action of the transfer peeling charger 17 at the transfer portion. The transferred recording paper P is sent to the fixing roller pair 28 by the conveyor belt 27, where the transfer image is fixed, and then discharged to the discharge tray 23 outside the main body 11 by the discharge roller pair 30. To be done.

The photosensitive drum 12 after the transfer is returned to the initial state by removing the residual toner on the surface by the cleaning device 18 and erasing the residual image by the charge eliminating lamp 20. FIG. 1 shows in more detail the structure around the above-mentioned paper feeding unit.

As described above, the recording paper P taken out from the cassette 21 is fed from the direction of the arrow in the figure, passes between the paper feed guides 41 and 42 in order, and is temporarily set to the registration roller pair 26.
Is stopped at the position. After this, this registration roller pair 2
6 is guided on the paper conveyance guide 43 and guided to the transfer portion between the photoconductor drum 12 and the transfer peeling charger 17.

At this time, the above-mentioned paper transport guide 43 is
According to the resistance value of the recording paper P, its potential is dropped to the ground (ground electrode) side, or a voltage is applied to itself. That is, the movable contact piece 44a of the changeover switch 44 is connected to the paper conveyance guide 43, the first fixed contact 44b of the changeover switch 44 is grounded to the ground side, and the second fixed contact 44c is connected to the second fixed contact 44c. A high voltage power supply 45 is connected. These changeover switches 44
The high voltage power supply 45 is operated by a switching signal or an operation signal from the control unit 46.

On the other hand, a paper resistance detecting section 47 is provided at a predetermined portion of the above-mentioned paper feeding section. This paper resistance detector 4
Reference numeral 7 detects the resistance value of the recording paper P fed between the paper feed guides 41 and 42. For example, the paper feed guide 42 to which a constant voltage is applied from the high-voltage power supply 45, the paper feed guide 41, and A grounding resistor 47a connected to the grounding resistor 47a and a detecting unit 47 for detecting a change in voltage across the grounding resistor 47a.
b.

The detection section 47b detects a change in the value of the current flowing according to the resistance value of the recording paper P as a change in the voltage across the ground resistance 47a, and this detection output is supplied to the control section 46. It is supposed to be done. Next, the operation of the above configuration will be described.

Here, a resistor of 390 kΩ is used as the ground resistance, and the surface potential of the photosensitive drum 12 is 700 to 900.
At about 1,400 V from the high voltage power supply 45 to the paper transport guide 43.
A case where V is applied will be described.

For example, suppose that the copying operation has just started. Then, first, the high voltage power supply 45 is operated by the operation signal from the control unit 46. Then, by the operation of the high voltage power supply 45, a constant voltage is applied to the paper feed guide 42.

After that, when the recording paper P taken out from the cassette 21 reaches the space between the paper feed guides 41 and 42, the paper feed guide 42, the recording paper P, the paper feed guide 41, A current flows in the path of the ground resistance 47a. Here, when the resistance value of the recording paper P changes, the current value changes, and the change in the current value is detected by the detection unit 47b as a voltage change across the ground resistance 47a.

The output of the detector 47b is sent to the controller 46, and the switching of the changeover switch 44 and the ON / OFF of the high-voltage power supply 45 are controlled according to the detection result of the resistance value of the recording paper P.

For example, the resistance value of the recording paper P is 500 MΩ.
Is larger than the movable contact piece 4 of the changeover switch 44,
4a is switched to the first fixed contact 44b side, and the paper transport guide 43 is connected to the ground side. At this time, the operation of the high-voltage power supply 45 is stopped, which causes the paper conveyance guide 43 to move.
The static electricity of will be removed. As a result, the recording paper P having a large resistance value is satisfactorily conveyed without sticking to the guide 43. Further, in this case, it is possible to prevent the toner from scattering on the paper conveyance guide 43, and it is possible to perform good transfer without stain on the back surface of the recording paper P.

On the other hand, for example, the resistance value of the recording paper P is 500.
If it is less than MΩ, the movable contact piece 44 of the changeover switch 44
A is switched to the second fixed contact 44c side to connect the paper conveyance guide 43 to the high-voltage power supply 45 side, and during that time, the high-voltage power supply 45 is continuously operated. As a result, good transfer is performed on the recording paper P having a small resistance value without causing a transfer omission. As described above, only one power supply is required to detect the resistance value of the recording paper and apply the voltage to the paper conveyance guide according to the change.

That is, a constant-voltage power supply applied to the paper feed guide for detecting the resistance value of the recording paper is used to apply a high voltage to the paper conveyance guide when the recording paper having a low resistance value is conveyed. I am trying to use it for both. This allows
Since a dedicated constant voltage source is unnecessary, the cost can be reduced accordingly. Therefore, it is possible to form an image under optimum conditions regardless of the paper quality, humidity, etc., and it is possible to reduce the cost.

In the above embodiment, the case where the paper transport guide is directly connected to the ground side has been described.
The connection is not limited to this, and the connection may be made via, for example, a resistor or a Zener diode. Of course, various modifications can be made without departing from the spirit of the invention.

[0036]

As described above in detail, according to the present invention, good image formation can be always performed without impairing the recording paper transporting ability regardless of whether the recording paper has a high resistance value or a low resistance value. Therefore, it is possible to provide an image forming apparatus that can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a diagram showing a main part of a configuration according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the internal structure of the copying machine.

[Explanation of symbols]

11 ... Main body, 12 ... Photosensitive drum, 13 ... Charging device, 1
4 ... Optical device, 15 ... Lens block, 16 ... Developing device, 17 ... Transfer peeling charger, 21 ... Cassette, 26
... registration roller pair, 28 ... fixing roller pair, 34 ... document table, 41, 42 ... paper feed guide, 43 ... paper transport guide, 4
4 ... Changeover switch, 45 ... High-voltage power supply, 46 ... Control unit, 4
7 ... Paper resistance detector, 47b ... Detector.

Claims (1)

[Claims] 1. A constant voltage from a constant voltage source is applied to a paper feed guide, which is read as a change in a current value flowing through a resistance value of a recording paper conveyed, and the resistance value of the read recording paper is read according to the read resistance value. In an image forming apparatus configured to switch the application of a voltage from a high-voltage power supply to the paper conveyance guide in the subsequent stage and the connection to the ground electrode, the constant voltage source for applying a constant voltage to the paper feed guide is the paper feed guide. An image forming apparatus, wherein the high-voltage power supply for applying a voltage to a conveyance guide is also used.