JPH0764422A - Fixing device - Google Patents

Abstract

PURPOSE:To provide a fixing device which can save energy by reducing fast- print time. CONSTITUTION:A heat insulating member (or armoring member) 40 covering a fixing roller 51 and a pressure roller 52 is provided with an openable fixing- device shutter 41; in sleep mode which is non-printing mode, the fixing-device shutter 41 is closed to prevent heat from diffusing outside the fixing device so as to enhance a heat insulating effect, and fast-print time is reduced during conversion to print mode so as to reduce the power consumed. In the print mode, paper is passed with the fixing-device shutter 41 opened, to obtain a fixed image from a paper outlet on the back of the device.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art An example of a conventional reversal development type image forming apparatus is shown in FIG. The photosensitive drum 1 having the photosensitive layer 1a on the conductive base material 1b such as a grounded metal is driven and rotated in the direction of arrow A, and the elastic layer 2a is formed on the core metal 2b to which a voltage is applied from the charging bias power source 11. Is uniformly and uniformly charged to a predetermined potential (dark potential) by the charging roller 2 having the above, and is exposed to the exposure light 3 such as a laser beam to have a predetermined potential (bright potential) to form an electrostatic latent image. . The electrostatic latent image is visualized by the toner of the developing device 4 including the developing sleeve 4a to which a voltage is applied from the developing bias power source 12.

Here, the recording material 61 in the paper feed cassette 14
Are taken out of the paper feed cassette 14 one by one, guided by the transfer entrance guide 6, and the transfer roller 5 having the elastic layer 5a on the core metal 5b to which the voltage is applied from the transfer bias power source 13 and the photosensitive drum. 1, the toner image on the photosensitive drum 1 is transferred onto the recording material 61, and the recording material 61 carrying the toner image is guided by the conveyance guide 8 and introduced into the fixing device 9 to form the toner image. Is fixed on the recording material 61.

The untransferred toner on the photosensitive drum 1 that has completed the transfer process is removed from the photosensitive drum 1 by the cleaning blade 7a and collected by the cleaning device 7, and the cleaned photosensitive drum 1 is sequentially restarted from the charging process. The image forming operation is performed by repeating the image forming process.

Conventionally, the fixing device 9 used in the image forming apparatus as described above has a structure as shown in FIG. In FIG. 8, a fixing roller 51 is provided with a releasable resin layer 54 such as PFA or PTFE on a core metal 53 such as aluminum or iron, and is heated by a heater 50 provided inside.

On the other hand, reference numeral 52 is a pressure roller that rotates in pressure contact with the fixing roller 51, and is made of metal such as iron or stainless steel.
6, an elastic layer 57 is provided on the elastic layer 57, and a release layer 59 made of silicone rubber, fluororubber or the like having a good releasing property is provided on the elastic layer 57.
Is formed.

The recording material 61 carrying the toner image 60 is guided to the nip portion between the fixing roller 51 and the pressure roller 52 by the fixing inlet guide 63 and is heated and pressed to record the toner image 60. It is fixed on the material 61. After that, the recording material 61 is separated from the fixing roller 5 by the separating claw 55.
The sheet is separated from the sheet No. 1 and discharged by the fixing sheet discharging roller 64 via the fixing sheet discharging guide 65.

Reference numeral 62 is a cleaning pad for cleaning the toner adhering to the fixing roller,
Reference numeral 40 denotes a heat retaining member of the fixing device or an exterior member configured so that the user does not directly touch a high temperature portion such as the fixing roller with a hand.

A temperature detecting element 58 for detecting the temperature of the surface of the fixing roller 51 is installed at the end of the fixing roller. When the fixing roller 51 is arranged so as to be close to or in contact with the central portion of the fixing roller 51 in the axial direction, toner or paper dust adheres to the surface of the temperature detecting element 58 as a result of long-term use, and the surface of the fixing roller 51 is exposed. This is because the release layer is worn and scratched, resulting in black streaks on the image.

To control the temperature of the fixing roller, the surface temperature of the fixing roller is measured by the temperature detecting element 58, and the power supply to the fixing heater 50 is turned on / off by a temperature adjusting circuit (not shown). By turning on the power supply when the surface temperature of the fixing roller is lower than the set temperature and turning off the power supply when the surface temperature is higher than the set temperature, the surface temperature of the fixing roller is kept constant.

Basically, there are two kinds of set temperatures of the fixing device of the conventional image forming apparatus: a set temperature in the standby mode (standby temperature) and a set temperature in the print mode (print temperature). When the main switch of the image forming apparatus is turned on, the fixing roller is maintained at the standby temperature by the temperature adjusting circuit, and when the print data is input to the image forming apparatus from the host device, the fixing roller is changed by the temperature adjusting circuit to the print temperature. Is controlled to start printing the image, and the toner image is fixed on the recording material. After the printing is completed, the fixing device is maintained at the standby temperature again.

The print temperature is determined by the toner melting point, the process speed, etc. Normally, the standby temperature is the print temperature in consideration of the time until the image forming apparatus starts the print operation after the print data is input. Than 1
The temperature is set low by about 0 ° C.

As described above, in the conventional heat fixing type image forming apparatus, when the main power source of the apparatus is turned on, the print data is input to the image forming apparatus so that the image can be immediately formed. In order to keep the temperature of (1) constant at the standby temperature (standby state), the heater of the fixing device is repeatedly turned ON / OFF.

With the recent energy saving, for example, when the image forming apparatus does not shift to the print mode after the standby state continues for 5 minutes, the "sleep mode" in which the fixing device heater is completely turned off is adopted. Image forming apparatuses have also been proposed.

[0015]

However, the above-mentioned conventional example has the following problems.

(1) Even when trying to raise the temperature of the fixing device to the print temperature when shifting from the sleep mode to the print mode, the time until the print temperature is reached by the escape of heat from the opening of the heat retaining member 40. (First print time) becomes long, and there is a problem of wasting energy.

(2) Further, in the conventional image forming apparatus of this type, it is general to use several kinds of recording materials having different sizes. For example, the maximum A3 (sheet passing width 297 m) is used.
m) image forming apparatus capable of vertical feeding
4 (sheet passing width 211 mm) or B5 (sheet passing width 182 mm),
When a narrow recording material such as an envelope (paper passing width 105 mm) or a business card (paper passing width 55 mm) is continuously passed, a non-paper passing portion is generated in the fixing unit of the fixing device, and a heat amount is generated in the non-paper passing portion. Since it is not absorbed by the recording material, the fixing roller and the pressure roller in the non-sheet passing area become high in temperature, which causes a problem of “temperature rise in non-sheet passing area”. The outline of this problem is explained below.

In the non-sheet passing portion, the temperature of the fixing roller becomes high, and the rubber material of the pressure roller deteriorates. The thermal expansion of the pressure roller becomes uneven between the paper passing portion and the non-paper passing portion, and a difference in roller outer diameter in the longitudinal direction occurs, so that wrinkles or skewing of the recording material occurs. The fixing roller in the non-sheet-passing area becomes higher than the set temperature after the small-sized recording material is passed, so when the larger-sized recording material is passed after the small-sized recording material is passed. In the non-sheet passing portion, the toner is in an excessively melted state and hot offset occurs.

This is the case where the temperature detecting element is installed in the paper passing area, and when the temperature detecting element is installed in the non-paper passing area, the temperature of the paper passing area becomes lower than the set temperature. Poor fixing or cold offset occurs. As a measure to prevent the temperature rise in the non-sheet passing area, a method has been proposed in which the distance between recording materials is made larger than that in normal continuous paper feeding to prevent the local temperature rise of the fixing roller. With the method, when printing small size paper, it takes a very long time and the printing speed becomes slow.

(3) Normally, when a recording material is passed through the fixing device, the water content of the recording material evaporates and water droplets adhere to the inside of the fixing device, which stains the recording material after fixing or fixing. There is a problem that corrosion (such as rust) due to moisture of the metal member of the device occurs.

(4) Further, due to the heat of the fixing device, the waste toner accumulated in the cleaning device 7 is hardened in the vicinity of the cleaning blade 7a and does not go into the depth of the cleaning device 7 to cause a cleaning failure, which is a blocking phenomenon. There are various problems caused by the temperature rise inside the image forming apparatus such as occurrence of the above.

Further, in recent years, the fixing roller 51 shown in FIG.
Conventionally, the core metal 53 had a wall thickness of about 3 mm, but the wall thickness of the core metal 53 was reduced to about 0.7 mm to improve the start-up speed by using a “thin wall fixing roller” or heat resistance as shown in FIG. Heating device "Film fixing system" in which a heating element is adhered to one side of the heat-resistant film and a material to be heated is adhered to multiple sides, and the heat energy of the heating element is applied to the material to be heated through the heat resistant film.
Is proposed.

In the film fixing system, the endless belt-shaped fixing film 24 shown in FIG. 9 is stretched around the driving roller 25, the driven roller 26 and three members of the low heat capacity linear heating element 20 as heating elements which are parallel to each other. The pressure roller 28, which is provided and is pressed against the fixing film 24, is rotationally driven at the same speed as the conveying speed of the recording material 61, and the recording material 61 carrying the unfixed toner image 60 is conveyed to the nip portion N. The toner image 60 is introduced onto the recording material 61 and is heated and pressurized to fix the toner image 60 on the recording material 61. The low heating capacity linear heating element 20 as a heating element is a glass layer 3 for the purpose of insulation and protection.
The heater substrate 21 is provided with an electric heating element 22 having 0 as a surface layer, a temperature detecting element 23, and the like, and is fixedly supported by heating element supports 27 and 27a having rigidity, heat resistance, and heat retention.

According to the above-mentioned "thin-wall fixing roller" and "film fixing method", there is an advantage that the fixing device is easily warmed up and printing can be started immediately when the power is turned on, but the heat capacity of the fixing roller and the fixing film is high. Therefore, the problem of the temperature rise in the non-sheet-passing area becomes very remarkable, and the temperature difference between the sheet-passing area and the non-sheet-passing area reaches 200 ° C. in some cases.

The present invention solves the above problems and saves energy in the fixing device, shortens the first print time, causes a blocking phenomenon due to the temperature rise inside the machine, raises the temperature of the non-sheet passing portion,
An object of the present invention is to provide a fixing device that can prevent water droplets from adhering to the inside of the fixing device.

[0026]

According to the present invention, the above object is to provide a nipping / conveying means for nipping and conveying a recording material, and a developer image on the recording material via the nipping / conveying means or directly. In a fixing device provided with a heating means for heating and a heat retaining member or an exterior member covering the sandwiching and conveying means and the heating means, a shutter member which can be opened and closed is provided in a part of the heat retaining member or the exterior member. Achieved by

[0027]

According to the present invention, since a shutter member that can be opened and closed is provided on a part of the heat insulating member or the exterior member, the shutter member can be opened and closed at any time to prevent heat from escaping and wasteful energy. The consumption is suppressed, the blocking phenomenon is prevented, or conversely, the heat is released to prevent the temperature rise of the non-sheet passing portion, and further prevent the adhesion of water droplets in the fixing device.

[0028]

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

<Embodiment 1> First, Embodiment 1 of the present invention will be described with reference to FIG. In the fixing device of FIG. 1, the fixing roller 51 and the pressure roller 52 have a heat insulating member (or an exterior member) 4.
It is covered with 0, and a part of the heat insulating member 40 serves as a fixing device shutter 41. The fixing device shutter 41
Is openable and closable, and the fixing device shutter 41 is closed in the sleep mode, which is the time of non-printing.
Prevents heat diffusion to the outside of the fixing device. As a result, the heat retention effect can be improved, the first print time at the time of shifting to the print mode can be shortened, and the power consumption can be reduced. Further, in the print mode, the fixing device shutter 41 is opened to allow the paper to pass therethrough, and the fixed image is obtained from the paper discharge port on the rear surface.

Further, in the standby mode until the next sheet is passed after printing, the fixing device shutter 41 is used.
Is closed and the fixing device shutter is opened only when the paper passes through the fixing device, so that heat radiation from the fixing device to the outside in the standby mode is prevented and the heat retention effect is improved. Therefore, the power consumption in the standby mode can be reduced, and further, the heat dissipation to the outside of the fixing device can be prevented, and the temperature inside the image forming apparatus can be lowered, and the photosensitive drum 1, the transfer roller 5, etc. can be reduced. The problems caused by the heat deterioration of the device, the blocking phenomenon of the cleaning device, and the like and the rise in temperature inside the device are also solved.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, in order to further improve the heat retention effect of the first embodiment, the opening width of the fixing device shutter 41 of the first embodiment is set to the sheet passing size detected by the paper size detecting mechanism (not shown). It is variable according to the situation. As a result, it is possible to prevent the heat radiation to the outside and further improve the heat retention effect and reduce the power consumption.

For example, when passing a small size sheet such as an envelope, only the fixing device shutter 42b is opened and A3
When passing size paper, the fixing device shutter 42
The heat retaining effect is improved by forming the openings a and 42b. There are two opening widths in this embodiment,
A plurality of opening widths may be adjustable depending on the size of the paper to be passed.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

When a small-sized sheet such as an envelope is passed through the fixing device, a non-sheet passing portion is generated in the fixing section. However, when the temperature detecting element is in the sheet passing area, the heat amount is absorbed in the sheet in the non-sheet passing section. As a result, the fixing roller and the pressure roller in the non-sheet passing area become high in temperature, which causes a problem of "temperature rise in non-sheet passing portion". In particular, the temperature rise in the non-sheet passing portion is remarkable in the case of a thin fixing roller having a small heat capacity or a film fixing method.

As a measure for preventing the temperature rise in the non-sheet passing portion,
In this embodiment, as shown in FIG. 3, the fixing device shutter 43, which is a part of the heat retaining member corresponding to the non-sheet passing portion, is opened to keep the heat of the fixing roller 51 and the pressure roller 52 in the non-sheet passing portion. By reducing the effect and cooling the non-sheet passing portion, it is possible to prevent the temperature rise of the non-sheet passing portion.

Actually, the temperature distribution of the fixing roller is measured,
FIG. 4 shows a temperature distribution K when the conventional small-sized paper is continuously fed, and a temperature distribution L when the “fixing device shutter 43” method of this embodiment is used.

K in FIG. 4 shows a case where a small-size paper sheet is continuously passed from the center to the right half on the T2 side in the image forming apparatus with one side reference on the T2 side (a temperature detection element is installed in the sheet passing area). The fixing roller in the non-sheet passing portion on the T1 side from the center is much higher than the set temperature Tf.

FIG. 4L shows the case where the heat-retaining member corresponding to the non-sheet passing portion is opened by using the "fixing device shutter 43" method of the present embodiment, and small-size paper is continuously fed. The set temperature Tf is maintained in the entire region.

Further, if an air passage is provided on the upper surface of the fixing device by means of an exhaust fan or the like, the cooling effect becomes large.

In the present embodiment, the one-sided reference image forming apparatus has been described.
When small-sized paper is passed through the center, the heat insulating members at both ends of the fixing device may be used as fixing device shutters so that both ends are opened. Further, although the fixing roller side is cooled in this embodiment, the heat insulating member on the lower surface side of the fixing device may be opened to cool the non-sheet passing portion of the pressure roller. It is advisable to arbitrarily set the opening width and the opening position depending on the degree of temperature rise in the paper portion.

As described above, by applying the fixing shutter as a cooling device for the non-sheet passing portion as in this embodiment,
It was possible to obtain a clear image forming apparatus capable of preventing the temperature rise in the non-sheet passing portion, degrading the pressure roller, and free of wrinkles of the recording material, hot offset, and the like. Furthermore, since continuous paper can be passed, the printing speed of small size paper is also improved, especially
When applied to the above-mentioned "thin-wall fixing roller" or "film fixing method", the effect of preventing the temperature rise of the non-sheet passing portion is great.

In the present embodiment, the throughput of paper is not reduced by cooling the temperature rising part in the non-paper feed area.
It is possible to prevent the temperature rise in the non-sheet passing portion.

<Fourth Embodiment> Next, a fourth embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 5 is a vertical sectional view of a conventional fixing device. In the fixing device of FIG. 5, when the paper 61 carrying the toner image 60 is passed and inserted into the nip portion between the fixing roller 51 and the pressure roller 52, the separation claw 55 and the fixing roller are separated by the curvature separation. After that, the sheet is discharged from the sheet discharge guide 65 through the fixing sheet discharge roller 64 to the outside of the machine. At this time,
Water droplets 44 adhere to the inside of the heat insulating member on the rear surface of the fixing roller. In particular, plain paper contains a lot of water,
In the fixing section, it becomes water vapor and adheres to the inside of the heat insulating member as water droplets, which causes problems such as soiling the paper after fixing and rusting on the metal member of the fixing device. In view of this, in the present embodiment, as shown in FIG. 6, a portion 45 of the heat retaining member (or exterior member) above the back surface of the fixing roller is used as the fixing device shutter, and the fixing shutter 45 is opened when the fixing device passes through the fixing device 45. Releases water vapor to the outside, and in the sleep mode and standby mode, the fixing shutter 4
By closing 5 to improve the heat retention effect, it is possible to reduce power consumption and shorten the first print time, and further to prevent water droplets from adhering to the fixing device.

Of course, the above-mentioned first to fourth embodiments may be used in combination depending on the degree of the problem and the application.

[0047]

As described above, according to the present invention,
A part of the heat retaining member (exterior member) of the fixing device serves as a shutter of the fixing device to automatically open and close, thereby improving the heat retaining effect and reducing the power consumption of the fixing device.
Fast printing and time reduction, prevention of blocking phenomenon by prevention of temperature rise in the machine, prevention of thermal deterioration of components in the image forming apparatus, further prevention of temperature rise at the end by cooling effect, and opening / closing of the fixing-type fixing device It is possible to provide a fixing device and an image forming apparatus that can realize the prevention of water droplet adhesion in the fixing device and can obtain a clear fixed image for a long period of time.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating a fixing device according to a first exemplary embodiment of the present invention.

FIG. 2 is a perspective view illustrating a fixing device according to a second exemplary embodiment of the present invention.

FIG. 3 is a perspective view illustrating a fixing device according to a third exemplary embodiment of the present invention.

FIG. 4 is a diagram showing a temperature distribution on a surface of a fixing roller in a longitudinal direction.

FIG. 5 is a diagram illustrating a problem of a conventional fixing device.

FIG. 6 is a cross-sectional view of a fixing device according to a fourth exemplary embodiment of the present invention.

FIG. 7 is a vertical sectional view of an example of a conventional image forming apparatus.

FIG. 8 is a vertical cross-sectional view of an example of a conventional fixing device.

FIG. 9 is a vertical sectional view of an example of a conventional film fixing device.

[Explanation of symbols]

9 Fixing device 20 Low heat capacity linear heating element (heating means) 24 Fixing film (sandwiching and conveying member) 28 Pressure roller (sandwiching and conveying means) 40 Heat retaining member or exterior member 41 Fixing device entrance opening / closing shutter (shutter member) 42a, 42b Multiple size fixing device entrance shutter (shutter member) 43 Fixing device end temperature rise prevention shutter (shutter member) 45 Fixing device water vapor exhaust shutter (shutter member) 50 Heater (heating means) 51 Fixing roller (sandwiching means) 52 pressure roller (sandwiching / conveying means) 60 toner (developer) 61 recording material

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Hiroaki Sakai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Minoru Matsukuma 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Masaharu Okubo, 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) In-house, Takayasu Yukino, 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (4)

[Claims] 1. A nipping and conveying means for nipping and conveying a recording material,
In the fixing device, a heating device for heating the developer image on the recording material via the sandwiching / conveying means or directly, and a heat retaining member or an exterior member for covering the sandwiching / conveying means and the heating means are used. A fixing device, wherein a shutter member that can be opened and closed is provided on a part of the member or the exterior member. 2. The fixing device according to claim 1, wherein the shutter member is set to open and close in response to a fixing operation. 3. The fixing device according to claim 1, wherein the shutter member is set so as to change its opening / closing position or size according to the size of the recording material. 4. The fixing device according to claim 1, wherein the shutter member is provided on the recording material entrance side of the fixing device and is located in the recording material conveying path.