JP2003140498A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem wherein fixing performance gets unstable because of the change of room temperature in environment where an image forming apparatus is put in the conventional fixing device. SOLUTION: In the image forming apparatus, an image is fixed by the fixing device, at least, where recording material having an unfixed image is held and transported in a press-contact part formed by a pair of fixing rotary bodies disposed rotatably while press-contacting with each other so as to thermally fix the unfixed image on the recording material and oil is used as a releasing agent, and the ratio of the on-time and the off-time of a heater put for heating the fixing roller in the fixing roller is changed to an appropriate ratio in accordance with the room temperature in the environment where the image forming apparatus is put by changing the idly rotating speed of the fixing roller according to the room temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus which forms a latent image on an image bearing member, selectively adheres toner to the latent image to form a visible image, and then transfers the visible image to a recording sheet or the like. , Specifically, electrophotographic recording, electrostatic recording, ionography,
The present invention relates to an image forming apparatus that uses a magnetic latent image or the like.

[0002]

2. Description of the Related Art A conventional electrophotographic apparatus for forming a color image forming apparatus is shown in FIG.

The color electrophotographic apparatus shown in FIG. 2 is provided with a drum type electrophotographic photosensitive member (hereinafter referred to as photosensitive drum) 1 as an image bearing member.

The photosensitive drum 1 is rotationally driven in the arrow direction R1 (counterclockwise direction) by a drive manual throw (not shown).

Around the photosensitive drum 1, a charging device 2 for uniformly charging the surface of the photosensitive drum 1 in order according to its rotation direction, a laser beam is irradiated based on image information to form an electrostatic latent image on the photosensitive drum 1. An exposing device 3 for forming, a developing device 4 for developing a toner image by adhering toner to an electrostatic latent image, a toner image on the photosensitive drum 1 is primarily transferred, and is transferred to a transfer material S such as a recording medium such as paper. A transfer unit 5 for the next transfer, a cleaning device 6 for removing the transfer residual toner remaining on the surface of the photosensitive drum 1 after the primary transfer, and the like are provided.

Further, the transfer material S is fed toward the transfer unit 5 in order from the upstream side in the conveying direction of the transfer material S, and at the same time, the feeding / conveying section 7 for conveying the transfer material S and the transfer material S after the secondary transfer. A fixing device 208 for fixing the toner image onto the sheet, and a sheet discharge section 9
Is provided.

The photosensitive drum 1, the charging device 2, and the cleaning device 6 are integrally formed into a cartridge to form a process cartridge B, which can be attached to and detached from the apparatus main body 210 of the image forming apparatus A.

The photosensitive drum 1 will be described in detail below.

The photosensitive drum 1 includes an organic photoconductor layer (O) on the outer peripheral surface of an aluminum shilling having a diameter of about 47 mm, for example.
PC photoconductor) is applied.

Both ends of the photosensitive drum 1 are rotatably supported by support members, and a driving force from a drive motor (not shown) is transmitted to one end of the photosensitive drum 1,
It is rotationally driven in the arrow Rl direction (counterclockwise direction).

As the charging device 2, for example, Japanese Patent Application Laid-Open No. 63-
A so-called contact charging type as disclosed in Japanese Patent No. 149669 can be used.

The charging member is a conductive roller formed in the shape of a roller. By bringing this roller into contact with the surface of the photosensitive drum 1 and applying a charging bias voltage to this roller by a power source (not shown), The surface of the photosensitive drum 1 is uniformly charged.

The exposure device 3 has a polygon mirror 3a, and the polygon mirror 3a is irradiated with image light corresponding to an image signal by a laser diode (not shown).

The polygon mirror 3a is rotated at a high speed by a scanner motor (not shown), and the reflected image light is selectively exposed on the surface of the charged photosensitive drum 1 through the imaging lens 3b, the reflection mirror 3c and the like. To form an electrostatic latent image.

The developing device 4 accommodates a rotating body 4A which can be indexed and rotated about a shaft 4d, and four developing devices mounted on the rotating body, that is, yellow, magenta, cyan and black toners, respectively. Developing devices 4Y, 4M, 4C, 4B
equipped with k.

During development of the electrostatic latent image on the photosensitive drum 1,
A predetermined developing device for the color to be attached to the electrostatic latent image is arranged at the phenomenon position.

That is, the predetermined developing device stops at the developing position facing the photosensitive drum 1 by the indexing rotation of the rotating body 4A,
Further, after the developing sleeve 4b of the developing device is positioned so as to face the photosensitive drum 1 with a minute gap (about 300 μm), the electrostatic latent image on the photosensitive drum 1 is developed.

This development is performed as follows.

The toner in the container of the developing device corresponding to the color to be developed is fed to the coating roller 4a by the feeding mechanism, and a thin layer of toner is formed on the outer circumference of the rotating developing sleeve 4b by the rotating coating roller 4a and toner regulating blade 4c. The toner is applied and charged to the toner (triboelectric charging).

By applying a developing bias between the developing sleeve 4b and the photosensitive drum 1 on which the electrostatic latent image is formed, a toner image is attached to the electrostatic latent image and developed as a toner image. .

Further, each developing device 4Y, 4M, 4C, 4Bk
The developing sleeve 4b is connected to a high-voltage power source (not shown) for developing each color provided in the apparatus main body 210 when each developing device is placed at the developing position. A voltage is selectively applied to.

The developing devices 4Y, 4M, 4C and 4Bk
Are configured to be attached to and detached from the rotating body 4A individually, and the rotating body 4A can be attached to and detached from the apparatus main body 210, respectively.

The transfer unit 5 secondary-transfers a plurality of toner images, which are sequentially primary-transferred from the photosensitive drum 1 and superposed, to the transfer material S at once.

The transfer unit 5 is equipped with an intermediate transfer belt 5a running in the direction of arrow R5.

The intermediate transfer belt 5a of this embodiment is an endless belt having a peripheral length of about 440 mm, and is composed of the drive roller 5a.
b, the secondary transfer counter roller 5c, and the driven roller 5d are wound around, and the driving roller 5b rotates to travel in the direction of arrow R5.

The transfer unit 5 includes a driven roller 5
and a pressing roller (primary transfer roller) 5e that moves backward so that the intermediate transfer belt 5a is pressed to the photosensitive drum 1 in the vicinity of d, and the intermediate transfer belt 5a is moved away from the photosensitive drum 1. The secondary transfer roller 5f is provided so as to be freely contactable with the secondary transfer counter roller 5c via 5a.

At a predetermined position outside the intermediate transfer belt 5a, a cleaning unit 5g that can be brought into contact with and separated from the surface of the intermediate transfer belt 5a is provided, and the transfer residual toner remaining on the transfer material S after the secondary transfer at once. To remove.

In the cleaning unit 5g, the charging roller 5h is brought into contact with the intermediate transfer belt 5a to give the toner an electric charge opposite to that at the time of transfer.

The toner to which the opposite charge is applied is electrostatically attached to the photosensitive drum 1 and then collected by the cleaning device 6 for the photosensitive drum 1.

The cleaning method of the intermediate transfer belt 5a is not limited to the electrostatic cleaning described above, but may be a mechanical method such as a blade or a fur brush, or a combination thereof.

The cleaning device 6 is a so-called transfer residual toner that remains on the surface of the photosensitive drum 1 without being primary transferred after the toner developed on the photosensitive drum 1 by the developing device 4 is primarily transferred to the intermediate transfer belt 5a. Is to be removed.

The feeding / conveying unit 7 transfers the transfer material S to the transfer unit 5.
The feeding cassette 7 that stores a plurality of transfer materials S and is loaded in the lower portion of the apparatus main body 210.
a.

During image formation, the pick-up member 7b, the paper feed roller 7c, and the transport roller 7d are driven and rotated in accordance with the image forming operation to separate and feed the transfer materials S in the feed cassette 7a one by one, and to guide the guide plate. Guided by 7e,
The sheet is fed to the intermediate transfer belt 5a through the registration roller 7f.

The fixing device 208 is for fixing the toner image secondarily transferred onto the transfer material S, and is a fixing roller 21 as a fixing rotating member driven and rotated by a motor (not shown).
1 and a pressure roller 212 as a pressure rotating member that rotates in pressure contact with the transfer material S to apply pressure to the transfer material S.

Next, the image forming operation of the image forming apparatus A having the above structure will be described.

First, the photosensitive drum 1 is rotated in the direction of arrow Rl (counterclockwise) in FIG. 2 in synchronization with the rotation of the intermediate transfer belt 5a, and the surface of the photosensitive drum 1 is uniformly charged by the charging device 2. The exposure device 3 irradiates a yellow image with light to form a yellow electrostatic latent image on the photosensitive drum 1.

Simultaneously with the formation of the electrostatic latent image, the developing device 4 is driven to position the yellow developing device 4Y at the developing position, so that the yellow toner adheres to the electrostatic latent image on the photosensitive drum 1. By applying a voltage having the same polarity as that of the charging polarity and having substantially the same potential, yellow toner is attached to the electrostatic latent image to develop the latent image.

Then, the pressing roller (primary transfer roller) 5
A voltage having a polarity opposite to that of the toner is applied to e to primarily transfer the yellow toner image on the photosensitive drum 1 onto the intermediate transfer belt 5a.

When the primary transfer of the yellow toner image is completed as described above, the next developing device is rotationally moved and positioned at the developing position facing the photosensitive drum 1, and magenta and cyan are used in the same manner as in the case of yellow. Then, for each color of black, electrostatic latent image formation, development, and primary transfer are sequentially performed, and four color toner images are superimposed on the intermediate transfer belt 5a.

During this time, the secondary transfer roller 5f is separated from the intermediate transfer belt 5a and is in a non-contact state, and the charging roller 5h of the cleaning unit 5g is also separated from the intermediate transfer belt 5a and is in a non-contact state.

After the four color toner images have been formed on the intermediate transfer belt 5a, the secondary transfer roller 5f is pressed against the intermediate transfer belt 5a, and the registration roller pair 7f synchronizes with the rotation of the intermediate transfer belt 5a. Transfer material S that was waiting
Is sent out.

The transfer material S, to which the toner images have been secondarily transferred in this manner, is conveyed by the conveying belt 13 to reach the fixing device 208, and the fixing roller 211 and the pressure roller 21.
The full-color toner image is thermally fixed on the transfer material S by being pressed and heated between the two.

The transfer material S on which the full-color toner image is fixed is discharged to the paper discharge tray 14 by the paper discharge rollers 9a, 9b, 9c of the paper discharge unit 9, and a series of image forming operations is completed.

For example, as shown in FIG. 3, the fixing device 208 sandwiches the transfer material S having the unfixed toner image by the toner T transferred to the nip portion N between the fixing roller 211 and the pressure roller 212. The unconfirmed toner image is conveyed and the metallic cored bar 211a of the fixing roller 211 and the pressure roller 212,
Heaters 211b and 21 which are heating elements provided in 212a
The unfixed toner image can be fixed on the transfer material S as a permanently fixed image by heating and pressurizing at 2b.

In the fixing device shown in FIG. 3, the fixing roller 211 has a structure in which the surface of a metal cored bar 211a is covered with silicone rubber and fluororubber to a predetermined thickness.
It is rotationally driven in the arrow direction (clockwise direction) by the connected drive means (not shown).

A heater 211b such as a halogen lamp is included in the metal cored bar 211a.

Further, the fixing roller 211 is provided with a release agent applying device 215 and a cleaning device 216.

The release agent applying device 215 is a release agent container (oil pan) 2 containing a release agent E such as silicone oil.
15a, scooping rollers 215b and 215c for scooping up the release agent E from the release agent container 215a, a coating roller 215d for applying and releasing the release agent E to the fixing roller 211, and a release agent. It has a regulation blade 215e for controlling the coating amount of E.

A coating roller 215d rotatably supported.
The surface of sponge rubber is coated with silicone rubber, and the releasing agent E is applied to the fixing roller 211.

The regulating blade 215e is a coating roller 215.
It is fixed to the sheet metal at a constant angle with respect to d, and the application roller 2
It is pressed against 15d with a constant pressure.

Therefore, the coating amount of the release agent E drawn up by the drawing-up roller 215b is regulated.
The release agent E is uniformly applied from the front end to the rear end of the transfer material S, which is adjusted to be constant by 5e and is conveyed between the fixing roller 211 and the pressure roller 212.

The cleaning device 216 includes the fixing roller 2
The release agent E and the like on the fixing roller 211 are cleaned by the web 216a that abuts on the fixing roller 211.

The web 216a is made up of roller members 216b, 2
16c and 216d, and the roller member 216
The nickel web 216a is attached to the fixing roller 2 at the circumferential portion of d.
It is in contact with 11.

The pressure roller 212 is arranged so as to be in pressure contact with the fixing roller 211, and is axially supported so as to be rotated by the fixing roller 211.

The pressure roller 212 is a metal cored bar 212a.
The surface of the is covered with silicone rubber and fluororubber to a predetermined thickness, and a heater 212b such as a halogen lamp is provided inside the fixing roller 211 as in the fixing roller 211.

Further, the pressure roller 212 is also provided with a cleaning device 217, and the release agent E and the like on the pressure roller 211 are cleaned by the web 217a which is in contact with the pressure roller 212.

The web 217a is composed of roller members 217b, 2
The roller member 217 is stretched by 17c and 217d.
The web 217a is in contact with the pressure roller 212 at the circumferential portion of d.

In FIG. 3, 218 and 219 are temperature sensors, and 220 is a regulating blade.

Then, the fixing device 2 is used at the time of image formation described above.
When the transfer material S is conveyed to 08, the fixing roller 211
And the pressure roller 212 rotate at a constant speed, and when the transfer material S passes between the fixing roller 211 and the pressure roller 212, the transfer material S is pressed and heated at a substantially constant pressure and temperature from both front and back surfaces and carried on the surface. The unfixed toner T is melted and fixed.

[0060]

In the image forming apparatus, the fixing heater of the fixing roller constituting the fixing device is generally controlled to be turned on / off by the temperature of the fixing roller.

For example, when the temperature of the fixing roller is adjusted at 170 ° C., the heater is turned on at 169 ° C. and the temperature is 171 ° C.
It is supposed to FF.

In such control, the on-time of the heater normally lasts for about 10 seconds and then the off-time lasts for about 120 seconds.

Therefore, in the conventional fixing device, the fixing performance may become unstable due to a change in the room temperature of the environment in which the image forming apparatus is placed.

The present invention has been made in view of the above points, and an object of the present invention is to turn on a heater placed in the fixing roller for heating the fixing roller and heat the fixing roller, The ratio of the time when the heater is turned off and the fixing roller is not heated is changed to an optimum ratio according to the room temperature of the environment where the copying machine is placed by changing the idling speed of the fixing roller according to the room temperature. A fixing device that can be controlled to

[0065]

Therefore, in the present invention, an image forming apparatus shown in either of the following items (1) and (2) is provided to achieve the above-mentioned goal. Is.

(1) At least at a pressure contact portion formed by a pair of fixing rotators which are rotatably arranged in pressure contact with each other, a recording material having an unfixed image is conveyed at a narrow pressure and is transferred onto the recording material. In an image forming apparatus in which an unfixed image is heat-fixed and fixed by using a fixing device that uses oil as a release agent, in the fixing roller, the closing time and the opening time of a heater placed for heating the fixing roller are set. The fixing device is characterized in that the ratio can be controlled so as to change to an appropriate ratio in accordance with the room temperature of the environment where the image forming apparatus is placed by changing the idling speed of the fixing roller in accordance with the room temperature. .

(2) The ratio of the closing time and the opening time of the heater for heating the fixing roller is 1: 3 when the room temperature of the environment in which the image forming apparatus is placed is less than 15 ° C. and 15 ° C.
The fixing device described in (1) is characterized in that the temperature is 1: 6 when the temperature is lower than 20 ° C.

[0068]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment) In this embodiment, in an image forming apparatus (hereinafter referred to as a copying machine), the idling speed of a fixing roller (fixing rotary member) is set to the environment in which the copying machine is placed. A fixing device capable of improving the fixing performance by changing the temperature according to the room temperature will be described.

In FIG. 1, 101 is a fixing roller and 10 is a fixing roller.
Reference numeral 2 is a heater (hereinafter referred to as heater) placed for heating the fixing roller, 103 is a core metal, and 104 is rubber.

In general, the fixing performance (the ability to heat toner to fix it on paper) has the same temperature on the surface of the fixing roller 101, and the rubber 104 on the surface layer of the fixing roller 101.
The higher the temperature of the core metal 103 existing inside the core, the better.

FIG. 1 shows the reason.

As shown in FIG. 1, the higher the temperature of the core metal 103, the larger the amount of heat transferred to the paper and the higher the fixing performance.

If the temperature of the surface of the fixing roller 101 itself is raised, the rubber 104 of the fixing roller 101 may be peeled off, and therefore the temperature of the surface of the fixing roller 101 must be kept low.

To raise the temperature of the core metal 103 while keeping the surface temperature of the fixing roller 101 constant, the fixing roller 1
There is a method in which 01 is idled.

By idle rotation, the surface of the fixing roller 101 radiates heat to the outside, the temperature drops, and the heater 102 lights up (turns on).

On the other hand, since the core metal 103 is on the inner side, it is not greatly affected.

Therefore, the temperature of the cored bar 103 rises.

In this case, the higher the idling speed,
The heat radiation effect is also large, and the ratio of the time when the heater is turned on (on) becomes large.

As a result, the temperature rise of the cored bar 103 becomes large and the fixing performance is improved.

Normally, the fixing roller 101 is stationary during standby after the copying machine is started up.

As a result of measuring the on / off time of the heater 102 at that time, after the on-time continued for about 10 seconds,
The off time lasted about 120 seconds.

In this state, the fixing performance test was conducted under the condition of a low temperature of 15 ° C. to a normal temperature of 23 ° C.

The test method was carried out by a method in which after about 2 colors of toner were placed and fixed, a bending test was performed to determine whether the toner came off.

The results are shown in Table 1.

[0085]

[Table 1]

Therefore, we tried to improve the fixing performance by increasing the on-time ratio of the heater 102 by performing idle rotation during standby.

The idling speed is changed from 0 mm / s to 200
When the same fixing property test was carried out with various changes up to mm / s, the results shown in Table 2 were obtained.

[0088]

[Table 2]

Based on this result, when the room temperature of the environment where the copying machine is placed is less than 20 ° C., idle rotation is performed at 200 mm / s, and when the temperature is 20 ° C. or more and less than 23 ° C., idle rotation is performed at 100 mm / s. Then, it was controlled to stand still when the temperature was 23 ° C. or higher.

As a result, good fixing performance could be obtained.

This control can be used only when the fixing is severe and immediately after the copying machine is started up, for example, 1 hour after the start-up.

By properly adjusting and using it, it is possible to prevent a great burden on energy saving.

[0093]

According to the present invention, at least the above-mentioned object is to press a recording material having an unfixed image at a pressure contact portion formed by a pair of fixing rotators rotatably arranged in pressure contact with each other. In an image forming apparatus that conveys and fixes an unfixed image on the recording material by heating, and fixing is performed by using a fixing device that uses oil as a releasing agent, in a fixing roller that is a fixing rotating body, a fixing roller is provided. The ratio of the time for turning on the heater placed for heating and heating the fixing roller to the time for turning off the heater and not heating the fixing roller changes the idling speed of the fixing roller according to the room temperature. It has been achieved by providing a fixing device characterized in that it can be controlled to change to an optimum ratio according to the room temperature of the environment where the image forming apparatus is placed.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a relationship between a fixing roller surface temperature and a core metal temperature, which influences fixing performance.

FIG. 2 is a schematic cross-sectional view showing an image forming apparatus including a conventional fixing device.

FIG. 3 is a schematic sectional view showing a fixing device in a conventional example.

[Explanation of symbols]

A image forming apparatus E Release agent S transfer material N Nip part T toner 101 fixing roller 102 heater 103 core metal 104 rubber 208 fixing device 210 Device body 211 fixing roller 211a, 212a Metal core bar 211b, 212b heater 212 Pressure roller 215 Release agent coating device 215a oil pan 215b, 215c pumping roller 215d coating roller 215e Regulation blade 216 Cleaning device 216a Web 216b, 216c, 216d roller members 217 Cleaning device 217a Web 217b, 217c, 217d Roller members 218,219 Temperature sensor 220 Regulator blade

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H027 DA11 DA12 DA16 ED25 EE03                       EF04                 2H033 AA03 AA32 BA24 BA30 BA41                       BA51 CA03 CA08 CA32 CA40                       CA45                 3K058 AA54 AA71 BA18 CA12 CA26                       CB19 DA02

Claims (2)

[Claims] 1. A recording material having an unfixed image is conveyed at a narrow pressure by at least a pressure contact portion formed by a pair of fixing rotators that are rotatably arranged while being in pressure contact with each other, and the recording material is undetermined on the recording material. In an image forming apparatus that heats and fixes a deposited image and uses a fixing device that uses oil as a release agent, the ratio of the closing time and the opening time of the heater placed inside the fixing roller for heating the fixing roller. However, by changing the idling speed of the fixing roller according to the room temperature, the fixing device can be controlled so as to change to an appropriate ratio according to the room temperature of the environment in which the image forming apparatus is placed. 2. The ratio of the closing time and the opening time of the heater for heating the fixing roller is 1: 3 when the room temperature of the environment where the image forming apparatus is placed is less than 15 ° C., and is 15 ° C. or more. When the temperature is lower than 20 ° C, the ratio is 1: 6.
The fixing device described in 1.