JP2545135B2 - Fixing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device of an image forming apparatus that heats and fixes a toner image on a recording material.

[Conventional technology]

Conventionally, as a means for fixing the toner image on the recording material,
A heat roller method using a heat roller maintained at a predetermined temperature has been generally used. However, in the heat roller method, the time required to reach the fixing temperature, that is,
Since the wait time is long and the temperature of the heating roller needs to be constantly maintained at a predetermined value, there are drawbacks such as high power consumption.

Therefore, recently, as a solution to the above-mentioned drawbacks, the present applicant has proposed a fixing device for fixing a toner image on a recording material by heating and fusing it through a heat-resistant endless fixing film.

[Problems to be Solved by the Invention]

However, in the fixing device of the above proposal, the toner image is heated and fixed, so that there is a problem as described below due to the temperature rise of each part.

For example, when the fixing device is used repeatedly or continuously, the driving roller located on the downstream side of the heating element heats up considerably and accumulates heat. In particular, when a recording material narrower than the width of the heating body, for example, paper is passed through, it is remarkable due to the temperature rise in the non-paper passing portion. Further, when the small-sized recording material as described above is passed through the heating body without being distributed, the non-sheet passing portion is deviated to either side and a temperature distribution is generated in the drive roller. In addition, a temperature distribution may occur in the drive roller due to the influence of a heat source of the image forming apparatus body including the fixing device, for example, an electric component section.

When the temperature distribution is generated in the driving roller in this way, the roller diameter is distributed in the longitudinal direction due to the difference in thermal expansion of the driving roller. In such a case, the fixing film may be greatly affected, and the fixing film may be broken and damaged even though some means for preventing the deviation is provided. If the roller diameter is not uniform, the fixing film may be wrinkled and damaged.

In addition to these, even when there is no distribution in the drive roller diameter in the longitudinal direction, the drive roller diameter increases due to the temperature rise and expansion of the drive roller, and the feeding speed of the fixing film, that is,
The recording material conveyance speed changes. At this time, in the case of an image forming apparatus in which the portion for transferring the toner image on the recording material is close to the fixing device, the image may be disturbed.

According to the experiments conducted by the present inventors, a driving roller having a diameter of 20 mm and a rubber thickness of 1 mm showed a diameter increase of about 0.04 mm at a temperature increase of 25 ° C., which greatly disturbed the deviated balance.

The present invention is intended to solve the above problems. That is, it is an object of the present invention to provide a fixing device capable of suppressing a temperature rise of a drive roller, preventing damage of a fixing film due to misalignment and wrinkles, and at the same time preventing image distortion. It is a thing.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a heating body, an endless film that slides with the heating body, a pressure member that forms a nip with the heating body through the film, and a movement of the film. A drive roller that contacts the film and drives the film downstream of the nip with respect to direction;
In a fixing device having a recording material carrying an unfixed image in the nip and carrying out heat fixing, the drive roller is provided with a rubber layer on the surface, and an inlet is provided in the vicinity of the drive roller. It is assumed to have an exhaust means for drawing wind from the vicinity of.

[Action]

According to the present invention, at least the driving roller of the appropriate number of rollers for driving the fixing film is cooled by the cooling means and the temperature rise of the roller is suppressed, so that the film is deviated and damaged by wrinkles. Is also prevented, and image disturbance is prevented.

〔Example〕

FIG. 1 shows a first embodiment of the present invention, and FIG. 2 shows an example of an image forming apparatus using the fixing device of FIG.

First, in FIG. 2, reference numeral 1 denotes an original placing table made of a transparent member such as glass, which reciprocates in the direction of arrow a to scan the original. A short-focus small-diameter image-forming element array 2 is arranged immediately below the document table 1, and a document image placed on the document table 1 is illuminated by an illumination lamp 3 and a reflected light image thereof is produced by the array 2. Slit exposure is performed on the photosensitive drum 4. The photosensitive drum 4 rotates in the direction of arrow b. Further, 5 is a charger, for example, uniformly charging the photosensitive drum 4 coated with a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer. On the photosensitive drum 4 uniformly charged by the charger 5, an electrostatic image formed by image exposure by the array 2 is formed. This electrostatic image (electrostatic latent image) is visualized by the developing device 6 using a toner made of a resin or the like that is softened and melted by heating. On the other hand, the recording material (sheet) P stored in the cassette S is a pair of conveyances which are rotated in pressure contact with each other in the vertical direction at a timing so as to be synchronized with the image on the feeding roller 7 and the photosensitive drum 4. It is fed onto the photosensitive drum 4 by the roller 8. Then, the transfer discharger 9 transfers the toner image formed on the photosensitive drum 4 onto the recording material P. afterwards,
The recording material P separated from the photosensitive drum 4 by the known separating means is guided to the fixing device 11 by the conveyance guide 10.
After heat fixing processing, the sheet is discharged onto the tray 12. After the toner image is transferred, the residual toner on the photosensitive drum 4 is removed by the cleaner 13.

 FIG. 3 shows the fixing device 11 of FIG. 2 in an enlarged manner.

In FIG. 3, reference numeral 20 denotes a low-heat-capacity linear heating element fixedly supported by the apparatus. For example, an alumina substrate 21 having a thickness of 1.0 mm, a width of 10 mm, and a length of 240 mm is coated with a resistance material 22 in a width of 1.0 mm. The electric current is applied from both ends in the longitudinal direction. Energization is a pulsed waveform with a direct current of 100 V and a cycle of 20 msec, and a pulse controlled according to a desired temperature and energy release amount controlled by the temperature measuring element 23 is given by changing its pulse width. The pulse width is approximately 0.5-5 msec.

In this way, the energy and temperature-controlled low heat capacity linear heating element 20 is brought into contact with the fixing film in the direction of the arrow in the figure.
24 moves. As an example of this fixing film 24, the thickness
20μ heat resistant film, such as polyimide, polyetherimide, PES, PFA, PTFE, PFA at least on the image contact surface
It is an endless film in which a release layer made by adding a conductive material to a fluororesin such as 10 .mu.m is coated. Generally a total thickness of 100
μ, and more preferably less than 40 μ.

The film is driven in the direction of the arrow by the driving and tension of the driving roller 25 and the driven roller 26.

Reference numeral 27 denotes a pressure roller having a rubber elastic layer having a good releasability such as silicon rubber, which presses the heating body 20 through the fixing film 24 with a total pressure of 4 to 7 kg to rotate in pressure contact with the fixing film.

The unfixed toner 29 on the recording material 28 is introduced from the entrance guide 30 to the fixing section, and a fixed image is obtained by the above heating.

The image forming apparatus is applicable to all fixing devices such as copying machines, printers, and faxes that form an image using toner.

By the way, generally, in the fixing device 11 using the endless fixing film 24 of such a heat-resistant thin film, a deviation prevention mechanism of the fixing film 24 is provided. In this embodiment, as an example, the deviation of the fixing film 24 is detected by an optical sensor, and the result is fed back to the driven roller 26.
By moving up and down, fix the film within a certain range.
An example configured to suppress the deviation of 24 will be described.

4 and 5 are cross-sectional views of the side surface of the fixing device embodying the above example as seen from the back side.

The bearing 35 of the driven roller 26 is slidable in the vertical direction.
And one end of the driven roller 26 is rotatably supported, and the other end of the driven roller 26 is rotatably supported by a bearing (not shown) provided on the side plate 47.

The fixing member 36 attached to the side plate 46 supports one end of a spring 37 for pushing up the bearing 35, and the lower end of the bearing 35 is a spring.
The other end of 37 is pressed. The spring clutch 38 includes an input hub (not shown), a coil spring (not shown) having a control claw (not shown), a control collar 40a provided to hold the control claw, and an output hub 41. When the control collar 40a is configured and is stopped by engaging the engaging claw 40b or 40c with the lever claw 44 as shown in FIGS. 4 and 5, the power of the input hub is transferred to the output hub 41. Not transmitted. When the lever claw 44 is separated from the engaging claw 40b or 40c, the control collar 40a becomes rotatable and power is transmitted from the input hub to the output hub 41. Rotational force is constantly transmitted to the input hub in the direction of arrow J via a gear (not shown). A cam 39 having a different radius depending on the angle is fixed to the output hub 41 so as to rotate integrally. As shown in FIG. 4, when the engaging claw 40b and the lever claw 44 are engaged, the lower radius of the cam 39 is the maximum,
As shown in the drawing, when the engagement claw 40c and the lever claw 44 are engaged, the radius of the lower side of the cam 39 is minimum, and in other positions, there is a smooth connection therebetween.

Therefore, in the state where the engaging claw 40b is engaged with the lever claw 44, the maximum radius portion of the cam 39 pushes the bearing 35 downward,
When the engagement claw 40c is engaged with the lever claw 44, the bearing 35 is pushed upward by the spring 37.

The lever 43 is rotatably supported by a support shaft 42 planted in a side plate 46, a lever claw 44 is formed at the other end, and the other end is connected to an operating rod of a solenoid 45. Solenoid 45
Is turned on for a predetermined time in response to signals from the sensors 48 and 49, as will be described later.

The sensors 48 and 49 detect that the fixing film 24 has moved to the back side or the front side of a predetermined position.
The output signals of the sensors 48 and 49 are sent to the microcomputer, and the solenoid 45 is turned on according to a predetermined sequence.
・ Turn off.

FIG. 6 shows the driven roller 26 and the driving roller 25 as seen from the paper feeding side.
FIG. As mentioned above,
When the minimum radius of the cam 39 shown in the figure faces the bearing 35,
The end of the driven roller 26 is pushed up by the spring 37, and the driven roller 26 is moved to the upper right position as shown in FIG.
At this time, the fixing film 24 moves to the right (back side) direction. As described above, when the bearing 35 is pushed down by the cam 39, the fixing film 24 can be moved in the leftward (frontward) direction.

That is, by moving the driven roller 26 with a cam mechanism or the like by the output signals of the sensors 48, 49,
Usually, the fixing film 24 can be stably run at a position close to a certain range.

As described above, FIG. 1 shows the first embodiment of the present invention and is a side sectional view of the fixing device 11 as seen from the front side.

In FIG. 1, 101 is a cross flow fan which is an exhaust means, which is driven by a dedicated small DC motor. The fan 101 rotates in the direction of arrow A to generate an air flow in the directions of arrows B and C. As a result, a negative pressure is applied to the portion D, so that a wind flow as indicated by an arrow E is generated to draw the wind from the vicinity of the drive roller 25, and the drive roller 25 is cooled.

FIG. 7 shows a second embodiment of the present invention. This second
In the embodiment, when there is a margin in the structure of the image forming apparatus main body, as is clear from the figure, the wind near the drive roller 25 is blown from the inlet side of the cross flow fan 102 near the drive roller 25 by the arrows F and G. Like

In either case, the cross flow fans 101, 102
May also be used for other temperature raising parts of the image forming apparatus main body, for example, for preventing temperature rise of the main motor part and the electrical equipment part, and for discharging ozone generated in the process unit part out of the machine. .

By the way, in the fixing device of this configuration, unlike the heating roller of the fixing device of the heat roller type, it does not matter even if the fixing film 24 is cooled. The reason is that the toner image on the recording material is
This is because the nip portion is rapidly heated and pressed to be fixed, and thus the fixing property and offset resistance do not depend on the temperature of the fixing film 24 other than the nip part. Further, the required amount of electric power does not increase due to the cooling of the fixing film 24.

FIG. 8 shows a third embodiment of the present invention. That is, FIG. 8 is an elevational view of the fixing device 11 as seen from the paper discharge side.

In FIG. 8, 103 is an axial flow type small fan, which is driven by a dedicated small DC motor or the like, and causes wind in the direction of arrow H. The driving roller 25 has a surface made of silicone rubber baked on the pipe material in order to increase the frictional force with the fixing film 24. Then, flanges 107 and 108 having holes are attached to both ends of the drive roller 25 so as not to block the air passage, and are respectively received by bearings. The fan 103
When is rotated, a wind flow is generated in the drive roller 25 in the direction of arrow I, and the temperature rise of the drive roller 25 is prevented. In order to improve efficiency, a hood 106 having a shape connecting the fan 103 and the drive roller 25 is provided. A fan may be provided inside the pipe of the drive roller 25 in order to enhance the heat radiation / cooling effect.

The fan 103 may be rotated coaxially with the driving roller 25 instead of being driven by a motor.

〔The invention's effect〕

As described above, according to the present invention, the drive roller that has the rubber layer on the surface and drives the fixing film, that is, the drive roller that has the most thermal adverse effect on the fixing film is cooled by the cooling means. As a result, the temperature rise of the roller is suppressed, so that there is an effect of preventing damage due to the abnormal deviation of the balance of the fixing film near the fixing film and damage due to wrinkles. In addition to these, since the transport speed of the fixing film can be kept constant, there is an effect of preventing the occurrence of image distortion.

[Brief description of drawings]

FIG. 1 is a sectional side view showing a first embodiment of the present invention, and FIG.
1 is a sectional side view of an image forming apparatus using the fixing device shown in FIG. 1, FIG. 3 is an enlarged sectional side view of the fixing device shown in FIG. 2, and FIG. 4 is a fixing film shift prevention mechanism 1 shown in FIG. FIG. 5 is a sectional side view showing two states, FIG. 5 is a sectional side view showing the other state, FIG. 6 is an explanatory view of the movement of the fixing film by the mechanism shown in FIGS. 4 and 5, and FIG. Is a sectional side view showing a second embodiment of the present invention, and FIG. 8 is an elevational view showing the same embodiment of FIG. 11 …… Fixing device 20 …… Low heat capacity Linear heating element 24 …… Fixing film, 25 …… Drive roller 26 …… Following roller, 27 …… Pressing roller 101,102 …… Cross flow fan 103 …… Axial flow type compact fan

Claims (1)

(57) [Claims] 1. A heating body, an endless film that slides on the heating body, a pressure member that forms a nip with the heating body via the film, and a downstream side of the nip with respect to the moving direction of the film. In a fixing device having a driving roller that is in contact with the film and drives the film, and nipping and transporting a recording material carrying an unfixed image in the nip to perform heat fixing, the driving roller has a rubber layer on the surface, A fixing device characterized in that the inlet has an exhaust means provided near the drive roller to draw air from the vicinity of the drive roller.