JPH0561294A - Image forming device - Google Patents

Abstract

PURPOSE:To improve the fixability of an OHP sheet with a simple configuration and further, with excellent operability, without using a fixing device for the OHP only by providing a second paper feeding port directly carrying a sheet of a fixing part without passing a transfer part. CONSTITUTION:A first paper feeding port 17 is provided on the lower part in front of a laser printer main body 10, and the sheet 19 on a paper feeding tray 18 is supplied to an image forming part 11 by a paper feeding roller 20. The second paper feeding port 26 is provided between the first paper feeding port 17 and a paper ejecting port 24. A paper feeding path reaching a fixing unit 22 is formed inside the paper feeding port 26. When the sheet is fed from the first paper feeding port 17, a transfer is performed on a transfer part 16, fixing is executed on the fixing unit 22, and then, the sheet is ejected from the paper ejecting port 24. When the ejected sheet is the OHP sheet, the ejected sheet is refed from the second paper feeding port 26, so that the ejected sheet is directly carried to the fixing unit 22 without passing the transfer part 16, to have refixing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus, and is particularly suitable for a color digital copying machine or a color laser printer which forms a color image using a color developing device.

[0002]

2. Description of the Related Art In an image forming apparatus for forming a color image using a color toner by an electrophotographic method, when an OHP sheet is used as a transfer material, the light transmittance of the toner after fixing is not good. Therefore, a satisfactory transferred image could not be obtained. Therefore, conventionally, a fixing device (OHP fuser) for exclusive use of OHP is used, and the OHP sheet once output is further passed through the OHP fuser to increase the light transmittance, or the transfer unit is transferred from the same paper feed port or manual paper feed port. It was re-fed to the fixing section via the paper.

[0003]

The object of the present invention is to provide an OH
It is possible to improve the fixing property of an OHP sheet with a simple configuration and good operability without using a fixing device dedicated to P and without performing wasteful conveyance such as feeding to a transfer unit. Especially.

[0004]

The image forming apparatus according to the present invention includes, in addition to the first paper feed port for feeding the sheet to the transfer section,
Second, which directly conveys the sheet to the fixing unit without passing through the transfer unit
It is characterized in that a paper feed port of is provided.

In this image forming apparatus, a sheet detecting means for detecting that a sheet has been inserted into the second sheet feeding port,
The image forming apparatus may include a conveyance unit that automatically conveys the sheet from the second sheet feed port to the fixing unit when the sheet detection unit detects the sheet in the ready state. The second paper feed port is preferably provided on the front surface of the main body of the image forming apparatus, like the first paper feed port and the paper ejection port.

[0006]

When a sheet is fed from the first sheet feeding port, it is transferred at the transfer section, fixed at the fixing section, and then discharged from the sheet discharge port. When the ejected sheet is an OHP sheet, the sheet is re-fed from the second sheet feeding port, so that the sheet can be directly conveyed to the fixing section without passing through the transfer section and re-fixed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of an internal configuration of a laser printer to which the present invention is applied. In the figure, reference numeral 10 is a laser printer main body, and 11 is an image forming section united with a photoconductor drum 12 as a center, a developing device 13, a primary charger 14, and the like. Reference numeral 15 is a developing roller of the developing device 13, and 16 is a transfer charger, which are arranged around the photosensitive drum 12. The developing device 13 contains, for example, blue toner. Reference numeral 17 denotes a first paper feed port for feeding the paper 19 on the paper feed tray 18 to the image forming unit 11 by the paper feed roller 20, and is provided in the lower front portion of the laser printer body 10. Reference numeral 21 denotes a laser unit which exposes and scans the photosensitive drum 12 using an image signal as a light modulation pulse. 22
Is a fixing device having a heater 23 built therein. Reference numeral 24 denotes a paper ejection port for ejecting the paper having passed through the fixing device 22 to the outside of the apparatus by a paper ejection roller 25, which is provided on the front upper part of the laser printer body 10.

In this laser printer, in addition to the above configuration, the first paper feed port 1 is provided on the front surface of the printer body 10.
A second sheet feeding port 26 is provided between the sheet feeding device 7 and the sheet discharging port 24. As shown in FIG. 2, a paper feed path 29 leading to the fixing device 22 is formed inside the paper feed opening 26 by the opposite conveyance guides 27 and 28, and the sheet detection means 30 and the sheet detection means 30 are provided in the middle of the paper feed path 29. A paper feed roller 31 is provided.

FIG. 3 shows a circuit configuration example of the control system. In the figure, reference numeral 32 is a control unit that controls the overall arithmetic control, and includes a microcomputer, a program memory, and an RA.
M, a laser control digital logic IC, a timer, and the like. Reference numeral 33 is an AC driver that controls an AC load 34 such as a lamp / heater, 35 is a motor control unit that controls a main motor 36, 37 is a load such as a solenoid, a clutch, and a fan, 38 is an alarm buzzer, and 39 is an operation display unit. ,
Reference numeral 40 is a development control unit. Further, 41 is a power switch for an AC power source, 42 is a DC power source for supplying power to the control unit 32, and 43 is a sensor. Reference numeral 44 is a high-voltage generator, which includes a primary charger 14, a transfer charger 16, and a developing roller 15.
Apply a high voltage to. The control unit 32 also controls the laser unit 21 in addition to the various devices described above. 45 is
It is a font ROM that stores character data, screen pattern data, and the like.

Next, the operation will be described. When the power switch 41 is turned on, first, various sensors detect whether or not an abnormality has occurred in the machine. For example, when it is determined that the paper remains in the fixing device 22 in the machine, the operation display unit 39 displays that the paper is jammed and prompts the user to remove the paper.

If there is no abnormality, the heater 23 of the fixing device 22
And waits for the fixing roller to reach a predetermined temperature at which fixing can be performed (wait state). When the temperature of the fixing roller reaches a predetermined temperature, the main motor 36 is energized for a certain period of time to drive the photosensitive drum 12, the fixing device 22 and the like, and the temperature of the roller of the fixing device 22 is made uniform (wait state is released). After that, the main motor 36 is stopped and the printer stands by in a printable state (ready state). When the image data is input from the host computer in this state, the printing operation starts.

The main motor 36 rotates in response to the print command, the photosensitive drum 12 starts to rotate in the direction of the arrow in FIG. 1, and a high voltage is supplied to the primary charger 14 from the high voltage generator 44 to cause the photosensitive drum 12 to rotate. The surface is charged. After that, an image signal is written by the laser unit 21 and an electrostatic latent image is formed on the photosensitive drum 12. Next, the latent image is developed by the developing device 13, transferred to the paper at the transfer portion by the transfer charger 16, and then the paper is separated from the photosensitive drum 12. Next, the residual toner remaining on the photosensitive drum 12 is collected by the cleaner 46, and the print cycle is repeated again.

The sheet on which the toner image is transferred is separated from the photosensitive drum 12 and conveyed to the fixing device 22. Fixing device 2
In No. 2, the temperature sensor disposed on the surface of the fixing roller and the heater 23 control the surface of the fixing roller to a predetermined temperature, the toner image is fixed on the sheet, and then the sheet discharge roller 25 discharges the sheet 24. Is ejected to the paper ejection section outside the machine.

In such fixing and discharging, the fixing property is still insufficient when the paper is an OHP sheet. Therefore, the OHP sheet discharged from the paper discharge port 24 is inserted from the second paper feed port 26. At this time, the control unit 32 detects that the OHP sheet is inserted into the second paper feed port 26 by the sheet detection unit 30 and rotates the paper feed roller 31.
At the same time, the fixing roller also starts to rotate, and the OHP sheet is sucked into the machine, guided to the fixing device 22, fixed again by the fixing device 22, and then discharged from the paper discharge port 24. The paper feed roller 31 is
After the sheet detection unit 30 detects the rear end of the OHP sheet, the sheet is rotated for a predetermined time and then stopped to prevent the user from being accidentally caught in a finger or clothes. Further, even if the paper feeding roller 31 is rotated for a predetermined time, the sheet detecting means 3
When 0 does not detect the trailing edge of the sheet, it is determined that a jam has occurred, and the fact is displayed on the operation display unit 39.

[0015]

As described above, according to the present invention, the fixing property of the OHP sheet can be improved with a simple structure in which the second paper feed port is provided. Further, by providing the sheet detecting means so that the OHP sheet can be automatically sucked into the machine, a troublesome insertion operation can be eliminated. Furthermore,
The operability is improved by providing the second paper feed port on the front surface of the image forming apparatus main body like the first paper feed port and the paper ejection port.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a laser printer to which the present invention is applied.

FIG. 2 is an enlarged configuration diagram of a second paper feed port of the laser printer and its inside.

FIG. 3 is a block diagram showing a circuit configuration of a control system.

[Explanation of symbols]

 10 Laser Printer Main Body 12 Photosensitive Drum 16 Transfer Charger 17 First Paper Feeding Port 22 Fixing Device 24 Paper Ejecting Port 26 Second Paper Feeding Port 29 Paper Feeding Path 30 Sheet Detecting Means 31 Paper Feeding Roller

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[Procedure amendment]

[Submission date] November 5, 1991

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G03G 15/20 102 6830-2H 15/22 106 6830-2H

Claims (3)

[Claims] 1. An electrophotographic image forming apparatus in which a latent image on a photoconductor is visualized with toner, the toner image is transferred onto a sheet by a transfer unit, then fixed by a fixing unit, and discharged from a paper discharge port. In the above, there is provided a first paper feed port for carrying the sheet to the transfer unit, and a second paper feed port for carrying the sheet directly to the fixing unit without passing through the transfer unit. Image forming apparatus. 2. A sheet detecting means for detecting that a sheet has been inserted into the second sheet feeding port, and the sheet detecting means for detecting a sheet when the image forming apparatus is in a ready state. The image forming apparatus according to claim 1, further comprising: a conveyance unit that automatically conveys a sheet from the two paper feed ports to the fixing unit. 3. The image forming apparatus main body according to claim 1, wherein the first sheet feeding port, the second sheet feeding port, and the sheet discharging port are all provided on a front surface of the image forming apparatus main body. Image forming device.