JPS61238076A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent staining or image disorder due to a liquid pool by rotating a couple of rotating bodies temporarily at a higher peripheral speed of rotation than the speed of fixation to a recording material before the front end of the recording material reaches the couple of rotating bodies. CONSTITUTION:Plungers 14 and 15 are turned on and felt 30 for applying releasing oil abuts on a coating roller 13. Then, when a sheet is separated from a transfer drum 5 after processes of electrostatic charging, exposure, development, and transfer for image formation, a fixing roller 13, the roller 13, and a pressure roller 12 rotate fast and a plunger 18 is put in operation at the same time to bring a web 27 into contact with the surface of the fixing roller 11. Oil pools 221 and 222 formed right before contacting parts of the respective rollers are recovered to the surface of the roller 13 by the fast rotation of the rollers and also absorbed by the web 27. Then, the approach of a sheet to the roller 11 is detected and the speed of the roller 11 is switched from the fast speed to a speed for fixation to perform a fixing process. Thus, liquid staining and image disorder are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to fixing a pair of rotating bodies such as belts and rollers used in recording devices such as copying machines, printers, printing machines, and composite devices thereof. The present invention relates to a fixing device including means for applying an anti-offset liquid to one surface of the pair of rotating bodies.

(Prior Art) A fixing device is generally provided with a pair of rollers and a member for applying an anti-offset liquid such as silicone oil to one of the pair of rollers. The amount of coating applied by this coating member varies somewhat depending on the recording speed of the recording apparatus in which the fixing device is installed, but is generally large.

Particularly, in color image recording devices and high-speed recording devices in which toner images are formed using a plurality of developers, a large amount of anti-offset liquid is applied. It is also known that the application means is provided with a contact/separation mechanism so that a large amount of application is performed only during the fixing operation.

However, even when this contact/separation mechanism is not provided, even if it is provided, an oil pool of offset prevention liquid is formed between the pair of fixing rollers, which stains the recording material sheet. In particular, when a sheet with a non-absorbent surface such as a resin sheet is used as a recording material, the anti-offset liquid may flow onto the surface of the sheet, disturbing the toner image or forming an oil flow pattern. If you put it away, special problems will occur.

Conventionally, the rotational speed of the roller pair has been changed for special purposes, but in such devices, slowing down the rotational speed causes more liquid pools to form, which increases the inconvenience. Resulting in.

(Objective of the Present Invention) The present invention aims to solve the problems of the recording material caused by the liquid pool 9, and provides a fixing device that can form recorded images without stains or image disturbances caused by the liquid pool.

Another object of the present invention is to provide a fixing device that can form a color image on a resin sheet without disturbing the image of a desired color due to liquid pooling, and that can provide excellent fixing performance.

(Summary of the Present Invention) The present invention is designed to significantly reduce oil accumulation between the pair of fixing rotors when the recording material reaches directly between the pair of fixing rotors. It has a rotation control means for rotating the pair of rotors by temporarily setting the rotation peripheral speed of one pair of rotors higher than the fixing speed to the recording material before reaching the pair of rotors, and when fixing the recording material, the fixing speed is adjusted. This is a fixing device characterized by fixing images.

(Examples of the present invention) The present invention will be further described below with reference to Examples.

FIG. 2 shows a sectional view of essential parts of an electrophotographic copying machine for forming full-color copied images to which the present invention can be applied.

In the figure, a photosensitive drum 1, which is a latent image carrier, rotates in the direction of the arrow. A charger 2, an exposure optical system 3, a developing device 4, a transfer system 5, and a cleaning device 6 are arranged around it. The optical system 3 includes a document scanning section 3a and a color separation filter portion 3b. The developing devices 4 include a yellow developer 4Y using yellow toner, a magenta developer 4M using magenta toner, a magenta developer 4C using cyan toner, and a black developer 4 using black toner.
It has 8K in one piece. As disclosed in Japanese Patent Publication No. 55-20579 by the applicant of the present invention, each developing device is prevented from scattering toner by the action of a magnetic field, and is removably held on a support 4a as shown in the figure, and centered around a central axis 4b. By rotating, the developing device is replaced with respect to the developing position. On the other hand, the transfer section 5 includes a drum 5b having a gripper 5a and a transfer discharger 5c inside the drum 5b.

A full-color image is formed by sequentially transferring toner onto a sheet supported on the transfer drum, as in conventional copying machines. This sheet is supplied from a cassette 7, and after the transfer process is completed, it is separated from the transfer section 5 by a separation means 8. Thereafter, the sheet is conveyed by the conveying means 31 and reaches the position Lf'+10 (via the fixing device 9).

The image forming means before the transfer section including the transfer drum is driven by a drive motor M, and the conveyance means 3
1 and the rollers in the fixing device 9 are driven by a drive means 26 (such as a motor) that is separate from the motor M.

Here, the configuration inside the fixing device 9 will be explained using FIG. 2. 1
A fixing roller 12 has a silicone rubber surface that contacts the sheet and heats and melts the toner image on the sheet and fixes it. A fixing roller 12 that contacts the silicone rubber 5110-11 supplies heat and heats the back side of the sheet at the same time. A pressure roller 213 having a resin surface made of 4-dollar ethylene and having a built-in roller 20 is in contact with the fixing roller 213 to replenish oil, heat, and apply pressure.
2 is a fer l- for contacting the application roller 13 and applying the mold release oil;
0 is a heat source housed in the application roller 19, and 21 is a separating claw for separating the sheet from the roller.

27 is a cleaning web that fixes the sheet either when the sheet is a resin sheet (hereinafter referred to as a trap pen) or when the fixing roller pressure roller becomes faster than the fixing speed determined depending on the sheet (when removing the oil reservoir). The web 27 comes into contact with the surface of the roller 11 to clean the surface of the fixing roller.The web 27 is moved by a pressure roller 28 that is moved by the operation of the plunger 18, and the contact position of the web 27 is set to clean the surface of the fixing roller. In order to facilitate the application, the rollers are brought into contact with and separated from each other on the sheet entry side and between the application roller 213, the fixing roller 11, and the pressure contact portion of the pressure roller ()XZ. Further, the web 27 is driven in steps by a motor (not shown), and the moving directions of the web 27 and the circumferential surface of the roller are relatively opposite at the contact portion of the fixing roller 11.

The plunger 15 presses the pressure roller 12 against the fixing roller by rotating the pressure roller 16 around the fulcrum 17, and the plunger 14 causes the felt 30 to approach and separate from the application roller 13. These outside plungers 14 s 15 operate when a copy signal is input and abut the felt,
Pressure is applied to the pressure roller 12.

In this example, the fixing speed and fixing temperature for a sheet of plain paper are set as speed v1 and set temperature T, and the fixing speed and fixing temperature for a trap pen are set as speed V and (η×η set temperature T).
*('rt<T1). This has the effect of improving the fixability to the trap pen, improving the color mixing properties (colors) of the image, and preventing offset.

Below, using the flowchart in Figure 3, the rollers 13.11,
The rotation control means 25 that controls the peripheral rotational speed of the rotor 12 will be explained. In addition, 131 and 121 are rollers 13*', respectively.
The driving gear 912 rotates by receiving the driving force from the driving means 26, and the circumferential speeds of the rollers 13, 11, and 12 are made to be the same speed through a driven drive.

Main switch is on and off, and predetermined image forming conditions (fixing roller temperature, photosensitive drum surface potential, presence/absence of sheet, etc.)
When it is satisfied, it goes into standby mode. At this time, after the sheet to be fixed is selected on the panel P using the designation keys T and F, when the copy switch C is turned on, this flowchart is activated.

First, in determination 40, the recording sheet is determined, and the fixing speed and fixing temperature are set according to the sheet.

In this example, we distinguish between Trapen T and plain paper F, and when the previous condition setting is Trapen, speed V1, temperature T! (setting 41), speed η and temperature TI (setting 42) for plain paper. Hereinafter, since the process in the Trapen mode and the process for plain paper F are almost the same, the explanation will be based on the Trapen mode. Note that the subscripts of numbers in the flowchart indicate plain paper.

After the setting of the fixing condition is changed (performed by a known reference value changing means or the like), the plungers 14 and 15 are turned on, and the felt DEG 30 is brought into contact with the application roller 131C. Thereafter, three or four color toners are transferred onto the sheet through the processes of image formation, charging, exposure, development, and transfer. After this transfer is completed, the sheet is separated from the transfer drum 5 (at this time, it can be further confirmed that the sheet is a trap pen by detecting transmitted light by the light source 23 and sensor 24 and by the signal from the grip s & ), the fixing roller 11, application roller 13, and pressure roller 12 are rotated at high speed (velocity V, , V, higher speed), and at the same time, the plunger 18 is operated and the web 27 hits the surface of the fixing roller 211. be touched. Due to this high-speed rotation, the oil reservoir 5221.22 formed just before the contact portion of each roller is conveyed by the circumferential surface of each roller and collected on the surface of the application row 213, decreasing in size. Since the liquid is absorbed into the liquid-absorbing member, the oil pool 22 between the fixing roller and the pressure roller can be almost completely eliminated. This high speed is preferably at least twice the fixing speed, and in this example, the speed is 2 times higher than the fixing speed.
It was set to ~3 times as much.

After this, the sheet is near the fixing roller for a time determined by the conveyance speed or by actual detection of the leading edge of the sheet (sensor 2
4', the light source 23' is detected, and the roller speed is switched from the high speed η for removing the oil pool to the speed corresponding to the fixing trap sheet, and the fixing process is performed (Steps 47 and 48).
．． 50).

During this fixing process, since the sheet does not pass through the oil reservoir 22, image drift due to the oil reservoir is prevented, and oil stains on the sheet can also be reduced.

After this, when fusing is performed on the same sheet continuously (single sheet copying), this flow can be repeated, and if there is a second sheet of continuous copying, there is no need to remove the oil pool. Therefore, it is sufficient to perform steps 48 and 50 (in the flowchart in Fig. 3, this is shown to mean that high-speed rotation is not performed).

In addition, when in plain paper mode, steps 42 and 43'.

After performing steps 44'...49', the web 27 is
is separated from the fixing roller and the roller speed is set to a fixing speed η suitable for plain paper to perform the fixing process. This suppresses the consumption of the cleaning web 27 and indicates that it is a cleaning means exclusively for the trap mode.

In this embodiment, the removal of oil spots on plain paper was also performed, but if the fixing speed of plain paper is not slow or if the oil spots are ignored, it is also possible to remove curls on plain paper. At this time, the roller high speed may be set to match the fixing speed of plain paper.

In any case, if a problem occurs due to a liquid accumulation such as an oil accumulation between the pair of rollers, the roller pair should be rotated at high speed to disperse the accumulation, preferably by bringing another liquid absorbing member into contact with it. Increasing the effectiveness will solve the above problem.

When a liquid absorbing member such as the web 27 is used to assist, it is sufficient to perform the above-mentioned high-speed rotation until the oil pool is absorbed by the liquid absorbing member.

According to the above embodiment, during fixing, the image is rotated at high speed in advance;
By absorbing excess oil with the cleaning member, it is effective to reduce oil accumulation at the fixing roller nip portion and prevent image blur due to oil accumulation at the leading edge of the OHP film.

The roller in the above embodiment may be a belt (and the cleaning web may be a liquid-absorbing felt, etc.).

The present invention is particularly effective when the fixing speed is reduced for sheets that are non-absorbent or have poor liquid absorbency. It is something to play.

The present invention is not limited to the above-mentioned embodiments, but includes everything that appropriately utilizes the technical idea of the present invention.

(Effects of the Invention) The present invention can reduce the amount of liquid contamination and turbulence caused by the liquid because the high-speed rotation process is performed before the recording material reaches the pair of fixing rotors, and the amount of liquid accumulation of the offset prevention liquid can be reduced. can be prevented.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of main parts of an embodiment of the fixing device of the present invention, FIG. 2 is a schematic diagram of a color copying machine incorporating FIG. 1 and showing a particularly preferred embodiment of the present invention, and FIG. 3 is a diagram similar to that of FIG. Example 70
-It is a chart. 11 is a fixing roller, 12 is a pressure roller, 13 is an applicator roller, 22, 2211-j is a fi pool, 27 is a cleaning web, 14, 15, and 18 are solenoids, 25 is a rotation control means, and 1 is for removing an oil pool. High speed, pickled is Trapen fixing speed, ■ is plain paper fixing speed.

Claims (2)

[Claims] (1) A pair of fixing rotors for gripping and conveying a recording material to fix a toner image on the recording material, means for pressing the pair of rotors against each other, and at least offset prevention on one surface of the pair of rotors. A fixing device comprising means for applying a liquid, a driving means for rotating the pair of rotating bodies under pressure during fixing, and a means for conveying the recording material to the pair of rotating bodies, wherein the leading end of the recording material is connected to the rotating body. The rotation control means rotates the pair of rotors by temporarily setting the peripheral speed of the pair of rotors higher than the fixing speed for the recording material before reaching the pair of rotors, and when fixing the recording material, the pair of rotors is rotated. A fixing device characterized by fast fixing. (2) The driving means has means for changing the fixing speed according to the type of the recording material, and the rotation control means fixes the fixing speed to a paper sheet where the recording material is a resin sheet and has the fixing speed. 2. The fixing device according to claim 1, wherein the fixing device operates when the rotational speed is lower than the rotational speed, and the high rotation peripheral speed is faster than the fixing speed to the resin sheet.