JPH0451179A - image forming device - Google Patents

Abstract

PURPOSE:To uniformize the temperature distribution of a fixing device by selectively sending air to the image supporting material non-passing part of the fixing device. CONSTITUTION:A toner image formed on a photosensitive drum 5 is transferred to a transfer material by a transfer discharger 12. Thereafter, a transfer material separated from a photosensitive drum 5 by a separation charger 13 is guided to the fixing device 15 by a carrying belt 14. In such a case, the air is blown off only to the non-passing part of the transfer material 9 to cool the fixing device 15 by controlling and sending the air in a direction (f) to the device 15 through the transfer material 9 by a fan 17 and a duct 16. Meanwhile, the transfer material guided to the device 15 is heated, fixed and ejected. In this case, the fan 17 is driven by the control of a DC controller and only when the transfer material 9 advances to the device 15. Thus, the temperature at the transfer material non-passing part of the fixing device is prevented from excessively rising.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a cooling device for a fixing device of an image forming apparatus that heats and fixes a toner image on an image support material.

``Prior Art'' Conventionally, a fixing device used in this type of apparatus uses a heating roller maintained at a predetermined temperature and a pressure roller having an elastic layer that presses against the heating roller to remove unfixed images. A fixed fixing method using heated rollers is often used, in which a transfer material on which a toner image has been formed is sandwiched and heated while being conveyed.

Furthermore, a belt fixing system described in US Pat. No. 3,578,797 is known.

There is also a fixing method described in Japanese Patent Publication No. 313182/1982. This is a fixing means that heats and fixes a transfer material on which an unfixed toner image is formed via a film that is pressed against a fixedly supported heating body.

"Problems to be Solved by the Invention" However, in the conventional heat fixing method described above, heat is absorbed by the transfer material as it passes through the fixing device.

Therefore, a heater is used to secure the temperature necessary for fixing. However, when continuous copying is performed, the heater is used more frequently, and although this makes it possible to maintain a temperature in the area where the transfer material passes, at the same time an excessive temperature rise occurs in the area where the transfer material does not pass. This temperature rise causes ■ thermal deterioration of the parts used.

■ Toner offset may occur due to high temperature.

■ Malfunction due to thermal deformation of used parts.

■ Malfunctions due to heat of surrounding parts, etc.

■ The fixing method described in Japanese Patent Publication No. 63-313182 usually requires controlling the deviation of the film when it is driven.
It becomes difficult to control this deviation due to thermal expansion of the pressure roller in the area where the transfer material does not pass.

There were other drawbacks.

Conventionally, these have been adjusted by the arrangement of heaters and the distribution of heat capacity.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of an image forming apparatus having a fixing device that performs heat fixing, and to provide an image forming apparatus in which the temperature distribution of the fixing device is made uniform by a cooling means.

"Means for Solving the Problems" The present invention provides an image forming apparatus having a fixing device that heats and fixes an image support material supporting an unfixed visible image, in which air is selectively blown to a portion of the fixing device through which the image support material does not pass. This is an image forming apparatus characterized by being provided with an air blower.

"Example" Embodiments of the present invention will be described below with reference to the drawings.

Before describing each embodiment of the present invention, an outline of an image forming apparatus implementing the present invention will be explained.

FIG. 2 is a side view schematically showing the image forming apparatus. An image of a document placed on a document table 1 made of a transparent member such as glass is illuminated by an illumination lamp 2, and the reflected light image is slit-exposed onto a photosensitive drum 5 via a group of mirrors 3 and a lens 4. . Furthermore, the wide charger 6 charges the photosensitive drum 5 uniformly. The photosensitive drum 5 is rotated in the direction of arrow a, uniformly charged, and then exposed to the slit to form an electrostatic latent image.

This electrostatic latent image is visualized by a developing device 7 using a material (made of a resin or the like that softens and melts when heated). - The transfer material 9 stored in the monthly paper feed cassette 8 is moved by a paper feed roller 10 and a pair of transport rollers 11 that are rotated while being pressed vertically in synchronization with the image on the photosensitive drum 5. It is fed onto the photosensitive drum 5.

Then, the toner image formed on the photosensitive drum 5 by the transfer discharger 12 is transferred onto the transfer material. Thereafter, the transfer material separated from the photosensitive drum 5 by a separation charger 13 or known separation means is guided to a fixing device 15 by a conveyor belt 14. At this time, by controlling the fan 17 and duct 16 to send air in the direction f through the transfer material 9 to the fixing device 15, air is blown only to the area where the transfer material 9 does not pass, thereby cooling the fixing device 15. do. On the other hand, fixing device 1
The transfer material guided to 5 is heated and fixed and discharged. still,
After transferring the toner image, residual toner on the photosensitive drum 5 is removed by a cleaning device 18.

The fixing device 15 consists of a heating roller 15a equipped with a heater (not shown) inside, and a pressure roller 15b that is in pressure contact with the heating roller 15a. When these rollers rotate, the toner image on the surface of the transfer material is transferred to the heating roller. It is heated and melted by the heat of 15a and fixed to the transfer material. The heating roller 15a and the heater are larger than the width of the maximum transfer material and are provided so as to uniformly heat the maximum transfer material. Therefore, when the paper is not being passed, the temperature of the heating roller 15a rises uniformly in the longitudinal direction, but the pressure roller 15a in contact with it rises in temperature uniformly.
5b is also heated uniformly in the longitudinal direction by heat conduction from the heating roller 15a.

Embodiment 1 FIG. 1 is a drawing showing the features of the present invention, and is a perspective view of the duct 16 and fixing device 15 shown in FIG. 2.

In this embodiment, the air outlet 16b of the duct 16 is connected to the fixing device 1.
It is provided on the entry side of the transfer material 9 and facing the path of the transfer material 9 in No. 5, and the blowing direction of the blowing outlet 16b is set to be the direction in which the air blown onto the surface of the heating roller 15a is directed.

To control the fan 17 and duct 16 to send air to the fixing device 15 in the direction f through the transfer material 9 only when the transfer material 9 is entering the fixing device 15 as shown in FIG. As a result, the wind is blown only on the portion of the fixing device 15 where the transfer material 9 does not pass, thereby preventing excessive temperature rise in the portion of the fixing device 15 where the transfer material 9 does not pass.

The fan 17 is driven only when the transfer material 9 is entering the fixing device 15 under the control of the DC controller.

In this embodiment, since the air is blown only while the transfer material 9 is passing through the fixing device, it is certain that the air flow hits only the portions of the transfer material 9 that are not passing through. Furthermore, the structure is simple and does not get in the way of the conveyor belt.

"Example 2" The duct 16 is partitioned on the inside as shown in Fig. 3, and the width of the duct 19 is 2 mm.
It is provided at a pitch of ~5 mm. The duct 16 has a suction port 16a below the conveyor belt 14, and the pressure roller 15
An air outlet 16b is provided below and is divided into left and right sides.

The cross-flow fan 17 is partitioned off by a plate at the same position as each partition 19. The method of partitioning is to use one impeller and partition the impeller with a disc, or to arrange multiple impellers in parallel on the same axis and insert a partition between the impellers in the casing (not shown).

In this embodiment, the transfer material 9 after transfer is conveyed in the direction of the arrow e and partially blocks the suction port 16a of the duct 16.The blocked part is C1, the unblocked part is d, and the sections 19 are separated from each other. Since air flows through the area, no air flow occurs in the air passage corresponding to the part C blocked by the transfer material, but an air flow in the direction of the arrow A occurs in the air passage corresponding to the part d of the duct 16 where the transfer material does not pass. is generated and sprayed onto the transfer material non-passing portions d at both ends of the fixing device 15.

On the other hand, the transfer material 9 is further conveyed in the direction of the arrow e, and is sandwiched between the fixing device 15 and fixed. At this time, the transfer material 9 passes through a portion C of the fixing device 15, and the heat of this portion is removed. .

However, part d is not affected by heat. When paper is continuously fed, the temperature difference between parts C and d (7:l rM becomes large).The thermistor 20 detects the temperature of part C and keeps the temperature of this part constant, so the temperature of part d rises. However, since air is selectively blown from the duct 16 to the portion d, the temperature rise in the non-sheet passing portion of the fixing device 15 can be suppressed without affecting other portions. It is controlled to operate only when the transfer material 9 passes over the opening 16a.In this embodiment, cooling air can be selectively sent to the fixing device without using an electrical method to detect the paper width.
Furthermore, the transfer material can be attracted to the conveyor belt at the same time.

"Example 3" FIG. 4 shows that air is sent from the air outlet 16b in the direction f using the fan 17 and duct 16 of the fixing device 15 to the part of the heating roller 15a and the pressure roller 15b where the transfer material 9 does not pass. At this time, the air outlet 16b of the duct 16 is provided with a shutter 21, which will be described next.
Based on information about the size of the transfer material, such as from cassette detection, the position of the shutter is determined so that the wind hits only the portion of the transfer material 9 that does not pass through.

FIGS. 5 and 6 are detailed views of this shutter portion. For example, two sliding shutters 21 that are guided by the upper and lower edges of the air outlet 16b and can slide laterally are provided, one end of the spring 23 is connected to the end of the shutter 23 on the mating side, and the other end of each spring 23 is provided. is the side 16 opposite to the door stop of the air outlet 16b when the shutter to which the spring 23 is connected is closed.
c, and connect one end of the wire 22 to the mutually distant door stop side of the shutter 21, and connect the two wires 22
The other end is wound around the shaft end of the motor 24 in the same direction. The wires 22 are hung on rope pulleys 26 at the portions where each direction changes.

By controlling the motor 24 with the DC controller based on the information on the size of the transfer material, the shutter 21 position is changed, and the air outlet 16b of the duct 16 is opened only in the part corresponding to the part where the transfer material 9 does not pass. It has become.

The effect of this embodiment is that wind is neither blown directly onto the transfer material nor sucked, so there is no fear of adverse effects on the transfer material.

[Advantageous Effects of the Invention 1] As explained above, by cooling the portion of the fixing device through which the transfer material does not pass, an excessive temperature rise in the portion of the fixing device through which the transfer material does not pass can be prevented. ■ By preventing thermal deterioration of the parts used, it is effective in preventing troubles before they occur.

■ The heat resistance of the parts used can be lowered, and there is no need to use heat-resistant materials, resulting in cost reduction.

■ Since there are no high temperature parts, the life of the parts used can be extended.

■ Trouble caused by high temperature offset can be prevented.

■ Thermal deformation of parts is suppressed and malfunctions can be prevented.

There are other effects.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the conveyance and fixing section of the first embodiment, FIG. 2 is a side view showing an outline of the image forming apparatus of the embodiment of the present invention, and FIG.
4 is a side view of Embodiment 3, FIG. 5 is a perspective view of Embodiment 3, and FIG. 6 is a front view of Embodiment 3. 15.Fixing device 15a.Heating roller 16.Duct 16a.Intake port 16b.Blowout port 17.
・Fan 21... Shutter patent applicant Canon Co., Ltd. Agent Part 1 Figure 4v! A Figure 3 Figure 5 Figure 6

Claims (1)

[Claims] 1. An image forming apparatus having a fixing device that heats and fixes an image support material supporting an unfixed visible image, characterized in that an air blower is provided for selectively blowing air to a portion of the fixing device through which the image support material does not pass. Image forming device.