JP2001013808A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain an entrance guide and to make steadily performable satisfactory image formation for a long time, by forming, in the vicinity of a solenoid, an air duct for cooling it. SOLUTION: An electromagnetic solenoid 18 is provided near an entrance guide 17, on a base 23 outside the rear side plate 22 of the device. Also, a spring is provided below the entrance guide 17, and the entrance guide 17 is always deviated toward a fixing roller situated above. In the case where stiff transfer materials of a small size are consecutively carried to a fixing device, the electromagnetic solenoid 18 is kept energized for a long time, a gradual temperature increase occurs, the resistance value of the coils of the electromagnetic solenoid 18 changes and attractive force decreases. Consequently, the entrance guide 17 cannot be kept in a high position and a jam or the like is caused. Therefore, air is forcibly exhausted by providing a duct 30 for covering the electromagnetic solenoid 18 and providing a fan 21 at its outer end. This prevents temperature increase of the electromagnetic solenoid 18 and makes it possible to carry out steady fixing at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a copying machine and a printer.

[0002]

2. Description of the Related Art The operation of a known image forming apparatus as described above will be briefly described. When copying is started, a document image read by an image reading unit is rotated by a normal rotation provided in the image forming unit. An electrostatic latent image is formed on a cylindrical image carrier.

Then, toner is applied to the latent image at a developing site to be visualized to form a toner image. When the toner image reaches the next transfer site, transfer of paper or the like to the transfer site is completed by this time. The material is supplied, and the toner image on the image carrier side is transferred to the transfer material by the action of the transfer bias.

After the transfer, the transfer material carrying the toner image is separated from the image carrier, reaches a fixing portion via a traveling path, where the toner image electrostatically formed on the transfer material is transferred. The hard copy formed and fixed on the material is discharged outside the machine.

After the transfer, the fixing portion where the transfer material enters is
Usually, a fixing roller heated by an appropriate heat source and a pressure roller pressed against the fixing roller are arranged, and the transfer material enters a contact nip portion between both rollers.

An entrance guide is provided on the entrance side so that the transfer material can smoothly enter the nip portion. The on / off of a solenoid connected to the entrance guide is switched to increase the height of the entrance guide ( (The angle of incidence on the fixing device) can be switched. Normally, the height of the entrance guide is set at a position higher than the nip portion by the action of a spring.

When the length of the transfer material in the traveling direction is long, the height of the entrance guide is at the high position as described above, and when the transfer material entering the fixing portion is deformed into a waveform, the entrance guide enters the nip portion. To reduce image shock such as image blurring and toner scattering.

However, with such a configuration, for example, A
In the case of a small transfer material having a size of 5 or less, or a small and strong transfer material such as a postcard, if the position of the entrance guide is set high as described above, the transfer of the transfer material may be hindered. .

This will be described below. After the transfer, the transfer material is conveyed to the fixing portion via the traveling path as described above, but the traveling path is usually composed of an endless belt provided with a number of small holes, and the belt is moved by the suction fan arranged inside. The transfer material on the outer surface is suctioned and transported in a stable state.

If the entrance guide of the fixing device is set high as described above, in the case of a stiff transfer material, the incident angle to the fixing device becomes large, so that the leading end portion of the transfer material that comes into contact with the fixing roller is transported by the conveyor belt. There is a problem in that only the rear end portion comes into contact with the conveyor belt and the conveyance force is weakened, and a jam is likely to occur.

To cope with such a problem, the end of the entrance guide to the fixing device on the side of the fixing device is made freely movable up and down, and this is connected to a solenoid. There has been proposed an apparatus in which a solenoid is energized to lower the position of the leading end of an entrance guide so that a transfer material can easily enter a fixing portion.

With this configuration, a certain effect is obtained for the transfer material to smoothly enter the fixing portion. However, when a large number of strong transfer materials are continuously copied, the transfer to the solenoid is performed. As the energization time becomes longer, the temperature rises, the resistance value of the solenoid winding increases, the suction force decreases, and it is not possible to maintain the lower position of the entrance guide, and the transfer material can smoothly enter the fixing part. The inconvenience of being unable to do so will occur.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in order to cope with such a situation.
In an image forming apparatus in which the height of the entrance guide to the fixing device can be adjusted by turning the solenoid on and off, the entrance guide is maintained by configuring the adjustment solenoid to be forcibly evacuated and cooled. It is an object of the present invention to provide an image forming apparatus capable of stably and favorably performing image formation over a wide range.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a method for forming an electrostatic latent image on an image carrier, applying a toner to the latent image to form a toner image, and transferring the toner image to a transfer material. Thereafter, the transfer material is conveyed to the fixing device, and the relative position of the entrance guide of the transfer material to the fixing device and the fixing device side is changed by the deenergization of the solenoid. An image forming apparatus (1), wherein an air path for cooling the solenoid is formed around the solenoid, or in the above (1), the air path forming member includes a solenoid. In the image forming apparatus (2) or (1) or (2), wherein a detachable lid is provided at an opposing portion, the air path is inside the image forming apparatus main body. Air exhaust system. The image forming apparatus according to claim (3).

[0015]

FIG. 1 is a schematic sectional side view of an image forming apparatus showing an embodiment of the present invention, and FIG. 2 is a plan view of a main part of the image forming apparatus.

The image forming apparatus 1 includes an image reading unit A disposed at an upper part and an image forming part B disposed at a lower part. A document image placed on the top surface of the image forming apparatus is read by an image reading unit, and a laser beam image-modulated according to the document image is converted into a rotating cylindrical image carrier having an axis perpendicular to the paper surface. 5 and an electrostatic latent image is formed on the photosensitive surface as the surface.

When the latent image reaches a developing site where the developing device 3 is disposed to face as the image carrier 5 rotates,
Toner is supplied from the developing device 3 via a developing sleeve 7 and is applied to the latent image to be visualized as a toner image.

When the image carrier further rotates and the toner image arrives at a transfer site where the transfer roller 6 is opposed, the cassettes 2a and 2b disposed below the image forming unit by this time. The transfer material S taken out of the printer waits at the position of the registration roller 4 and is supplied to the transfer portion in time with the arrival of the toner image at the transfer portion.

When the transfer material reaches the transfer portion, a transfer bias is applied to the transfer roller, and the toner image on the image carrier is transferred to the transfer material by the action of the electric field formed thereby.

After the transfer, the transfer material S carrying the toner image
Is separated from the image carrier 5, passes through the transport path 11, and is supplied to the fixing device 12 via the entrance guide 17. The fixing device is provided with a fixing roller 12a and a pressure roller 12b, and the transfer material is supplied to a pressure contact nip between both rollers.

The transfer material supplied to the nip portion is heated and pressurized here to fix the toner image on the transfer material to form a hard copy, and is discharged to a tray 14 through a pair of discharge rollers 13 and 16. Is done.

The entrance guide 17 disposed on the transfer material entry side of the fixing device 12 has its end on the side of the transport path 11 rotatably supported by a pin 20, and the end on the side of the fixing device 12 moves up and down. I'm going to do it.

In the vicinity of the entrance guide 17, the rear plate 2 of the apparatus
An electromagnetic solenoid 18 is disposed on the outer base 23, and a spring 19 is disposed below the entrance guide 17, so that the entrance guide 17 is always located above the fixing roller 12a. It is biased.

As shown in FIG. 2, the solenoid 1
The tip of the iron core 27 of FIG. 8 and the arm 25 are clean with pins (not shown). A relief spring 24 is attached to the arm 25, and the tip of the spring 24 contacts the entrance guide 17. I have.

When the transfer material conveyed from the side of the traveling path 11 is longer than a predetermined length, for example, A4 width, the solenoid 18 is kept deenergized. Thus, the entrance guide 17 is held at a high position by the action of the spring 19.

If the transferred transfer material is shorter than a predetermined length, the control means (not shown) detects the detected state and urges the solenoid 18. As a result, the iron core 27 is pulled, the arm 25 is pushed down about the support shaft 26 as a rotation center, and the relief spring 24 lowers the entrance guide 17.

According to such a configuration, the direction of the transfer material entering the fixing device can be properly determined according to the difference in size of the transfer material supplied to the fixing device and the strength of the waist, thereby deteriorating the image quality. It is possible to have a certain effect on prevention.

When a small-sized, stiff transfer material is continuously conveyed to the fixing device, the solenoid is kept energized for a long time, so that the temperature gradually rises and the resistance value of the solenoid winding changes. As a result, the traction force is reduced, and the entrance guide 17 cannot be maintained at a high position, causing problems such as occurrence of jam.

In the present invention, as shown in the figure, a duct 30 is provided so as to cover the solenoid 18 and a fan 21 is provided at the outer end thereof to forcibly exhaust air. It is possible to perform stable fixing at all times by preventing the occurrence of such a function.

FIG. 3 shows another embodiment of the present invention. In this apparatus, a detachable lid 28 is attached to a portion of the duct 30 facing the solenoid 18 in the apparatus of the above embodiment. Is provided so that the solenoid 18 can be replaced promptly when the solenoid 18 fails. The lid 28 is provided with an engaging claw 28a, and when the lid is mounted, an engaging portion (not shown) on the duct main body side is to be engaged.

FIG. 4 is a plan view of a main part showing still another embodiment. In this apparatus, a duct 30 is formed to extend to a position of a heat exhaust port 29 formed in the apparatus main body. It is configured to contribute not only to the vicinity of the solenoid 18 but also to exhaust inside the apparatus main body. With this configuration, the entire image forming apparatus can be more effectively discarded.

[0032]

As described above, according to the present invention,
Image formation in which the height of the transfer material entering the fixing part of the entrance guide arranged on the entrance side of the fixing device for receiving the transfer material after transfer is changed according to the size of the transfer material, the strength of the waist, etc. In the device, the temperature rise of the solenoid for displacing the position of the entrance guide is prevented, so that good image forming work can be performed over a long period without causing jams and deteriorating image quality that can always exhibit its function stably. I can do it.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view of an image forming apparatus showing an embodiment of the present invention.

FIG. 2 is a plan view of an essential part of the embodiment.

FIG. 3 is a plan view of a main part showing another embodiment.

FIG. 4 is a plan view of a main part showing still another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2a, 2b Cassette 3 Developing device 4 Registration roller 5 Image carrier 6 Transfer roller 7 Developing sleeve 11 Transport path 12 Fixing device 12a Fixing roller 12b Pressure roller 13, 16 Discharge roller pair 17 Entrance guide 18 Electromagnetic solenoid Reference Signs List 21 cooling fan 19 spring 23 base 24 relief spring 25 arm 27 iron core 30 duct

Claims (3)

[Claims] An electrostatic latent image is formed on an image carrier, toner is applied to the latent image to form a toner image, and the toner image is transferred to a transfer material, and then the transfer material is conveyed to a fixing device. In the image forming apparatus, the relative position of the entrance guide of the transfer material to the fixing device and the fixing device side is changed by the deenergization of the solenoid. An image forming apparatus characterized by forming an air passage for cooling. 2. The image forming apparatus according to claim 1, wherein a detachable lid is provided at a portion of the air path forming member facing the solenoid. 3. The image forming apparatus according to claim 1, wherein said air passage exhausts the inside of the image forming apparatus main body.
Alternatively, the image forming apparatus according to claim 2.