JP2000075565A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device automatically executing the control of transfer bias and temperature of a fixing device or the like in accordance with the thickness of paper. SOLUTION: This device sends the paper to be conveyed to a conveying means 11, and the deflection of the paper is formed by a resist roller 7 and the top end of the paper are aligned. The device possesses a deflection detection switch 13 arranged at a deflection space 12 where the paper is deflected and a slipping means by which the deflection is not caused because thick paper and a driving roller 11a are slipped even in the state of abutting on the resist roller 7 in the case that the feeding means 11 is constituted of the driving roller 11a and a driven roller 11b and the thick paper of a specified thickness is conveyed. Then, the control exclusive to the thick paper is executed for succeeding image forming in the case that the deflection detection switch 13 does not detect the deflection by the actuation of the slipping means though the paper is sent by the feeding means 11.

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 for controlling a transfer bias and a fixing temperature according to the thickness of a sheet, and more particularly to an image forming apparatus for controlling a transfer bias and a fixing temperature by recognizing the thickness of a sheet. Regarding improvement.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus, a technique for controlling a transfer bias and a fixing temperature in accordance with the thickness of a sheet in order to prevent a transfer failure and a fixing failure has been known. Is generally controlled by setting a thick mode or a thin mode on the operation panel by a user in advance.

As another method, a contact transfer roller system is employed, and when a sheet passes through a nip portion between the photosensitive drum and the transfer roller, a current flowing into the photosensitive drum via the thickness resistance of the sheet is used. Detection is performed to control the transfer current and the fixing temperature. Further, as another method, it is also known to detect a roller distortion due to a thickness of a sheet by a transport roller that transports the sheet to a registration roller side, measure the thickness, and control a transfer roller and a fixing temperature.

[0004]

However, when a thick mode or the like is set on the operation panel, it is necessary to check the type of paper loaded in the paper cassette one by one. Problem also arises. Further, when the control is performed by the transfer roller, the control is performed after entering the nip portion of the transfer roller, so that the control is performed with a delay from the leading edge of the sheet, which causes a problem of poor transfer. Furthermore, when detecting the thickness by the distortion of the transport roller,
Significant accuracy is required and expensive. Moreover,
It is known that when the paper is thick paper, the guide for entering the photosensitive drum before the transfer cannot be controlled, and a transfer failure occurs at the transfer roller nip, causing image deterioration (horizontal stripe unevenness).

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and detects the thickness of a sheet with a simple configuration.
An object of the present invention is to provide an image forming apparatus capable of performing stable transfer bias and fixing temperature control on thick paper without erroneous operation.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention sends out a sheet housed in a sheet feeding housing section toward a registration roller by a conveying means, and uses the registration roller to move the leading end of the sheet. Abutting, and furthermore, by sending it out by the transporting means, to form a flexure to align the leading ends, and thereafter, the resist roller enters a transfer section via a transport guide, and applies a predetermined transfer bias to apply toner to the paper. In the image forming apparatus configured to send the sheet on which the toner image has been transferred to a fixing device that fixes the sheet by applying a predetermined temperature or pressure, the sheet before the registration roller is transferred to the transfer apparatus. A bending detection switch that detects a bent sheet in a space to be bent, and a drive roller that drives one of the transport units by themselves, and the other is a driving roller. When a sheet having a predetermined thickness is conveyed while being constituted by a driven roller or a friction plate having no movement, even if the front end of the sheet comes into contact with a registration roller, the sheet is further conveyed by the conveying means. And a slip means configured not to generate a deflection by slipping on the drive roller, and the slip detection switch operates to cause the deflection detection switch to bend even though the paper is fed by the transport means. In the case where is not detected, the angle at which the sheet enters the transfer section of the transport guide is reduced, and the transfer bias and the temperature or pressure of the fixing device are increased. As a result, the paper of a predetermined thickness slips, so that the thickness of the paper can be easily determined, and the conveyance guide, the transfer bias, the fixing temperature, and the pressure control for the subsequent image formation can be performed by the control dedicated to the thick paper. It is.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an outline of the present invention, and FIG. 2 is an explanatory diagram for explaining a transport device for sending out to a registration roller. Reference numeral 1 denotes an image forming apparatus according to the present invention, which includes a photoreceptor 2, a charger 3, an exposure unit indicated by an arrow, a developing unit 4, a transfer unit 5, and a cleaning unit 6 around the photoreceptor 2. Reference numeral 8 denotes a fixing device having a halogen lamp 8a inside. The fixing device 8 may be configured by melting the toner by heat, may be fixed by pressure, or may be used for both. Reference numeral 7 denotes a registration roller, which makes contact with the leading end of the sheet sent from the sheet feeding cassette 9 by the sheet feeding roller 10 and sends out the sheet sandwiched between the conveying rollers 11 to form a predetermined nip.

As shown in FIG. 2, reference numeral 14 denotes a guide plate, and the fed sheet comes into contact with the registration roller 7,
Further, when the transport roller 11 is rotationally driven, a bending is formed in the bending space 12 as shown in the figure, and the guide 14 is lifted. The reason for this configuration is that the guide 14 descends, so that when the leading edge of the sheet enters the registration roller 7, the sheet can be successfully brought into contact with the registration roller 7.
If the guide 14 is not provided, a paper transport trajectory is drawn in the bending space 12, and a sufficient bending space cannot be obtained even if the leading edge of the paper is brought into contact with the registration roller 7 and bent in this state. .

The transport roller 11 has a drive lower 11a.
And a driven roller 11b (not shown) to which spring pressure is applied to the drive lower 11a side. In the case of ordinary paper, after the leading end of the paper comes into contact with the registration roller 7, when the transport roller 11 is further driven to rotate, a flexure is formed in the flexure space 12 in order to catch and transport the paper firmly. Is done. However, when the paper of a predetermined thickness is formed, the gap between the rollers of the transport roller 11 is pushed up by the stiffness of the paper, so that the transport roller 11 cannot be caught firmly and slips (slip means). It is configured so that it cannot be formed. The paper having a predetermined thickness referred to in the present invention means, for example, a basis weight of 100 to 200 g / m ² including a postcard, an envelope and the like.
The ordinary paper is a so-called office paper having a basis weight of 60 to 90 g / m ² .

Reference numeral 13 denotes a bending detection switch, which forms a bending in the bending space 12 as shown in FIG. 2 and presses the lever of the bending detection switch 13 to determine that the sheet is a normal sheet. However, if the deflection detection switch 13 is not slipped and pushed up when the sheet has the above-described thickness, control of the transfer device and control of the fixing device are performed as described later.

Reference numeral 15 denotes a timing switch which kicks the leading edge of the fed sheet to thereby control image forming timing, registration roller rotation timing, transfer timing, and the like. Also, 1 in FIG.
Reference numeral 6 denotes a transfer guide (conveyance guide). When the above-mentioned paper is a thick paper, it is connected to a solenoid 17 so that the entrance angle at which the paper enters the nip portion of the transfer roller 5 is made smaller than that of ordinary paper to ensure the transfer. The transfer guide 16 can be moved so as to have an angle of entry that can be fed into the nip portion.

Next, the operation of the present invention will be described. The paper stored in the paper cassette 9 is sent out from the paper feed roller 10 and further transported by the transport roller 11 toward the registration roller 7. Then, when the leading edge of the sheet is detected by the timing switch 15, the image formation is started, the timing at which the registration roller 7 is conveyed to the transfer roller 5 is determined, and the registration roller 7 comes into contact with the registration roller 7, and is further moved.
The guide 14 is caused to bend while the guide 14 is being lifted by the rotation drive of 1. By turning on the deflection detection switch, this deflection is recognized as plain paper, the normal transfer guide 14 is arranged at an angle facing the photoconductor 2 side, and is controlled by the normal transfer bias and fixing temperature.

On the other hand, when the paper is thick paper, the paper comes into contact with the registration roller 11 and the transport roller 11 continues to rotate. However, since the paper is strong, the drive roller 11a which is a slip mechanism of the transport roller 11 is provided. Slip does not form deflection. If the deflection detection switch is not turned on even when the transfer timing of the transfer roller 5 is reached, it is determined that the sheet is thick paper, and the solenoid 17 moves the transfer guide 16 to reduce the angle of entry so that the thick paper just enters the nip portion of the transfer roller 5. The fixing roller 8 is moved to a position where it can be conveyed, the transfer bias is increased, and the heat of the halogen lamp 8a of the fixing roller 8 is increased. In this case, the roller pressure of the fixing device 8 may be increased.

[0014]

According to the above arrangement, it is possible to automatically control the transfer unit and the fixing unit by detecting that the thickness of the sheet is a predetermined thickness. The operation from the panel becomes unnecessary, the erroneous operation and the complexity for the operator are eliminated, and appropriate control is performed with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of the present invention.

FIG. 2 shows a main part of the invention.

[Explanation of symbols]

 1: Image forming apparatus 2: Photoreceptor 3: Charging device 4: Developing device 5: Transfer device 6: Cleaning device 7: Registration roller 8: Fixing device 8a: Halogen lamp 9: Paper cassette 10: Paper roller 11: Transport Roller 11a: Drive roller 11b: Follower roller 12: Flexure space 13: Flexure detection switch (transportation means, slip means) 14: Guide plate 15: Timing switch 16: Transfer guide (transportation guide) 17: Solenoid

Claims (1)

[Claims] 1. A sheet stored in a sheet storage unit is sent out to a registration roller by a conveying unit, the leading end of the sheet is brought into contact with the registration roller, and the sheet is sent out by the conveying unit to form a bend. To align the tips,
Then, the toner is transferred to a transfer device that transfers the toner to the paper by applying a predetermined transfer bias by applying a predetermined transfer bias to the transfer unit via the conveyance guide by the registration roller,
In an image forming apparatus configured to send a sheet on which the toner image has been transferred to a fixing device that applies a predetermined temperature or pressure to fix the sheet, a space that bends the sheet in front of the registration roller,
A deflection detection switch for detecting a bent sheet, and a drive roller for driving one of the transport means by itself, and a driven roller or a friction plate having no drive for the other, and transporting a sheet of a predetermined thickness. And a slip means configured to prevent the sheet from slipping on the drive roller and causing bending even after the leading edge of the sheet comes into contact with the registration roller even after being sent out by the transporting means. When the slip means operates and the bending detection switch does not detect the bending even though the paper is sent out by the transporting means, the paper entering angle of the transport guide to the transfer portion is reduced. And an image forming apparatus configured to increase the temperature or pressure of the transfer bias and the fixing device.