JPH043769A - Image forming device - Google Patents

Abstract

PURPOSE:To effectively discharge the steam generated by a fixing device by providing a guide plate forming a passage communicated from the upper section of the fixing device to the inner space of a suction conveying unit. CONSTITUTION:A suction port 23 is bored on a wall at the portion near the upper section of the fixing device 9 of a suction conveying unit 15, and a duct is formed with a guide plate 24 between multiple openings 25 bored on the upper face of the casing of the fixing device 9 and the suction port 23. A transfer sheet 2 is heated when it passes the nip sections of the roller pair of the fixing device 9, the moisture contained in the transfer sheet 2 is evaporated to generate steam, then the steam rises to the guide plate 24 through the openings 25 bored at the upper section of the casing of the fixing device 9. The guide plate 24 forms a passage to a suction port 23 provided on the wall of a suction conveying unit 15, thus the steam is sucked by the negative pressure in the suction conveying unit 15, thus the steam is sucked by the negative pressure in the suction conveying unit 15 and discharged to the outside by a sucking fan 13.

Description

[Detailed description of the invention] 1 bunch of tateho light disaster The present invention relates to an electrophotographic image forming apparatus.

1A In image forming apparatuses using electrophotographic processes such as laser printers, electrophotographic copying machines, and facsimile machines, a toner image formed on a photoreceptor is transferred to transfer paper, separated from the photoreceptor, and then fixed. The image is transported to the device, fixed, and recorded.

With these recording devices, such as laser printers that do not require the document to be placed on a contact glass, it is easy to set the optical writing position to the photoconductor at the bottom of the photoconductor, and transfer is performed at the top of the photoconductor. By doing this, the transfer paper conveyance path is made straight and the transfer paper can be stacked with the transfer surface facing down, so the pages are stacked in order, making it easy to remove jammed paper and preventing unfixed toner from falling onto the transfer paper. Because of its various advantages, such as the fact that the transfer paper is transferred over the photoreceptor with its transfer surface facing down, the toner image is transferred on the upper part of the photoreceptor, and the unfixed toner image is retained until it reaches the fixing device. The so-called top conveyance method, in which the loaded surface is conveyed with the surface facing downward, has come to be adopted.

However, the photoreceptor and fixing device are designed in consideration of the influence of heat.
Since it is provided a certain distance in front, if the leading edge or trailing edge of the paper becomes cantilevered after it leaves the photoconductor until the leading edge reaches the fixing roller, the transfer paper will droop due to its own weight. The leading end may not be caught in the nip of the fixing roller, or the image surface at the rear end may be rubbed by another member, causing the image to be distorted. Therefore, in the top conveyance method, as a conveyance auxiliary means, a suction conveyance unit is provided with a large number of suction ports that are sucked by suction air from a suction fan on the upper side of the transfer paper conveyance path, and conveys the transfer paper while sucking the upper side of the transfer paper. Generally, devices equipped with

FIG. 2 is a diagram showing a schematic configuration of an example of a laser printer having an upper strip feeding device of this type.

The transfer paper 2 fed from the paper feeding device 1 in the six directions of the arrows is placed between the transfer charger 8 provided above the photosensitive drum 4 and the photosensitive drum 4 at a timing controlled by a pair of register rollers 3a and 3b. is transported to the transfer section. A charger 5 is provided below the photoreceptor drum 4, and a writing position by a laser optical system 6 and a developing device 7 are provided between this charger and the transfer section in the order of the rotational direction of the photoreceptor. The toner image formed on the photoreceptor drum 4 by these process devices is transferred to the transfer paper 2 under the action of the transfer charger 8.
After the transfer, the transfer paper is separated from the photoreceptor drum 4, and is transported to the fixing device 9 without sagging even when the front and rear ends of the transfer paper are in a cantilevered state, while the back surface is sucked by the suction transport unit 15. The sheet is fixed and discharged to the paper discharge tray 10 outside the machine in the direction of arrow B. On the other hand, the toner remaining on the transfer paper drum 4 after the transfer is removed by the cleaning device 11 and collected in a toner collection tank.

The laser printer in this example has a paper feed device 1 and a fixing device 1.
The upper part of the transfer paper conveyance path A-C-B excluding the fixing device W9 constitutes an upper unit 12a, and the lower unit 12 consisting of other parts is pivotally connected to each other at the left end in the figure. As shown by the chain line, the upper unit 12a can be flipped up and opened wide, making it easy to clear jams and maintain parts.

As shown in FIGS. 3 and 4, the suction conveyance unit 15, whose lower surface serves as a guide surface for the transfer paper suction conveyance device, has a suction fan 13 inside and a number of suction ports 16 on the lower wall. The transfer paper 2 is constructed in a box-like shape, and the inside becomes negative pressure by suction air from the suction fan 13, and the transfer paper 2 is sucked onto the guide surface 14 and conveyed. The conveyance guide surface 14 has a slightly downwardly concave shape,
This makes use of the stiffness of the paper to maintain its shape along the guide surface. The suction conveyance unit 15 has an upper unit 12a.
It is vertically movable by a shaft 17 fixed perpendicularly to the top surface of the machine frame and a spring 18 surrounding the shaft, and the lower end of the support section 19 of the suction conveyance unit 15 and the upper end of the support section 20 of the main body 12 are connected to each other. are in contact with each other, and the suction conveyance unit 15 is positioned with respect to the apparatus main body 12.

Now, the toner image transferred to the transfer paper is applied heat and pressure by the fixing device 9, and the toner is fused to the paper surface of the transfer paper and fixed. Water evaporates due to heat and becomes water vapor. This water vapor becomes dew and adheres to recording paper or metal members around the fixing device, causing rust and the like.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of conventional image forming apparatuses, the present invention utilizes an intake fan of a suction conveyance unit provided in a top conveyance type image forming apparatus to remove water vapor generated in a fixing device. It is an object of the present invention to provide a device that can effectively discharge the air to the outside of the machine.

Section Means for Solving In order to solve the above problems, the present invention provides an image forming apparatus of a top conveyance type having the above-mentioned configuration.
The present invention is characterized in that a guide plate is provided that forms a flow path communicating from the top of the fixing device to the internal space of the suction and conveyance unit.

Operation With the above configuration, when one image is formed, the water vapor generated from the transfer paper that is attracted to the conveyance guide surface by the action of the suction fan in the suction conveyance unit and conveyed to the fixing device, and heated by the fixing device is absorbed into the fixing device. The air is sucked into the internal space of the suction conveyance unit, which has a negative pressure, through the above-mentioned flow path, and is discharged outside the machine by the suction fan.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a side sectional view showing the structure of the vicinity of a suction conveyance unit and a fixing device in an embodiment in which the present invention is applied to the top conveyance type laser printer previously explained with reference to FIGS. 2 to 4;
That is, this is a diagram corresponding to FIG. 4 shown earlier. Therefore, members having the same functions will be described with the same reference numerals.

A suction port 23 is formed in the wall of the suction conveyance unit 15 near the top of the fixing device 9, and a suction port 23 is provided between the plurality of openings 25 formed in the upper surface of the casing of the fixing device 19 and the suction port 23. A duct is formed by the guide plate 24 .

Therefore, when the transfer paper 2 is heated as it passes through the nip between the pair of rollers of the fixing device 9, the moisture contained in the transfer paper evaporates and water vapor is generated. It passes through the opening 25 and rises to the guide plate 24.

Since the guide plate 24 forms a flow path up to the suction port 23 provided on the wall of the suction conveyance unit 15, the water vapor is sucked by the negative pressure inside the suction conveyance unit 15 and is discharged outside the machine by the suction fan 13. .

As described above, according to the present invention, the water vapor generated in the fixing device is sucked into the suction conveyance unit through the flow path formed by the guide plate, and is discharged outside the machine by the suction fan. This prevents dew from condensing and adhering to the transfer paper, or from adhering to the metal parts of the fixing device and causing rust.

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view showing the structure of the fixing device and the vicinity of the suction conveyance unit according to the embodiment of the present invention, and FIG. 3
The figure is a perspective view showing the external appearance of the suction conveyance unit, and FIG. 4 is a side sectional view thereof. 2... Transfer paper 4... Photosensitive drum 8... Transfer charger 9... Fixing device 13... Suction fan 14... ... Suction conveyance path guide surface 15 ... Suction transport unit 16 ... Suction port 23 ... Suction port 24 ... Guide plate 2ET ...・Opening diagram 1

Claims (1)

[Scope of Claims] A toner image formed on the surface of a photoreceptor is transferred onto a transfer paper above the photoreceptor, and the transfer paper separated from the photoreceptor is transported to a fixing device by suctioning its upper side. , an electrophotographic image forming apparatus having a suction conveyance unit which has a conveyance surface made of a wall surface with a large number of air intake ports on the lower side, and whose internal space is sucked in by a fan; An image forming apparatus characterized in that a guide plate is provided that forms a flow path communicating from the suction conveyance unit to the internal space of the suction conveyance unit.