JPH01288886A - Fixing device - Google Patents

Abstract

PURPOSE:To extend the life of fixing rolls and a separating member by separating the separating member from fixing roll after the front end of a sheet-shaped recording material existing between fixing rolls reaches a carrying roll below. CONSTITUTION:When the front end of a copy paper after fixing is caught between a pair of paper ejecting rolls 8A and 8B, the copy paper pushes up a roll 9A and an actuator 9B cuts off a photo interrupter 9C. Then, a solenoid 6A is operated to separate a separating pawl 6 from a fixing roll 1. When the rear end of the copy paper passes between the pair of paper ejecting rolls 8A and 8B, the roll 9A falls by its own weight to release cut-off of the photo interrupter 9C, and the solenoid 6A is turned off by its signal, and the separating claw 6 is brought into contact with the fixing roll. Thus, the life of the fixing roll and the separating pawl is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is utilized in the field of technology for preventing sheet-like members from wrapping around a rotating body, and particularly for preventing sheet-like recording materials from wrapping around a fixing roller. The present invention relates to a fixing device designed to achieve this.

[Prior Art] In a device that conveys a sheet-like member under pressure between a pair of rotating bodies and, for example, in a roller fixing device such as an electrophotographic device, an image support material such as paper as a sheet-like recording material is After fixing the toner image, the image support material often adheres to and wraps around the fixing roller during fixing, and to prevent this, a wrap prevention piece is provided on the roller so as to be in contact therewith. The roller pair described above has a surface layer coated with a heat-resistant release rubber such as silicone rubber, fluorosilicone rubber, or fluorosilicone rubber, or coated with tetrafluoroethylene, so that toner is not deposited on the roller surface during fixing. Care is taken to prevent adhesion, or so-called offset, from occurring.

In order to increase the effect of the anti-wrapping piece, it is preferable to increase the contact pressure with the roller; however, the anti-wrapping piece is in contact with the roller surface for a long time due to the contact pressure. And because the contact is always made in the same position,
Coupled with the fact that the material of the surface layer is not very hard, the toner adhering to the wrapping prevention piece 1F causes damage to the roller surface! I was supposed to go to school.

Therefore, in order to solve this problem, we decided to
Japanese Patent No. 237 discloses a method in which the anti-wrapping piece is moved in the axial direction of the roller while in contact with the roller, thereby moving the contact position and shortening the contact time at the same location.

[Problems to be Solved by the Invention] However, this method has the following problems due to the fact that the anti-wrapping piece is moved while being in contact with the roller.

α) Since the anti-wrapping piece was moved in the axial direction with toner still attached to the contact portion with the roller, there were cases where the roller surface was scratched in the axial direction.

■Since the anti-wrapping piece moves in the axial direction while in contact with the roller, the anti-wrapping piece tilts by the amount of play on the rotating shaft and contacts the roller at the corner, resulting in so-called uneven contact. This may damage the roller surface.

As described in (2), since the anti-wrapping piece hits unevenly, the recording material cannot be separated sufficiently, which may cause a jam.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device having a sheet-like member wrapping prevention device that solves the above-mentioned conventional problems.

[Means for Solving the Problems] According to the present invention, the above object is to convey a recording material having an unfixed toner image on the surface thereof under pressure between a pair of heated fixing rollers. In a fixing device that fixes the toner image on a recording material by fixing the toner image on the recording material, the fixing device includes a separation member that is in contact with the circumferential surface of at least one roller of the pair of L rollers, and the recording material is present between the pair of rollers for fixing. and a separating means for separating the separating member from the roller after at least the leading end of the recording material reaches a pair of conveying rollers located downstream from the pair of rollers in the direction of the conveying force of the recording material. , achieved by.

Further, in this case, the separating means is set so that when the separating member is brought into contact with the fixing roller again after being separated, it is brought into contact at a different position from the position where it was in contact before being separated. It is preferable to do so.

[Function] In the present invention as described above, when at least the leading edge of the recording material reaches the pair of transport rollers while the recording material is being conveyed under pressure between the pair of fixing rollers, the separating member separates the recording material from the fixing roller. Leave. Then, when the next recording material is fixed, it contacts the fixing roller again.

Further, in the preferred embodiment of the present invention, when the separating member contacts the fixing roller again, the separation member contacts the fixing roller at a different position than the previous time. Note that the fixing roller has stopped F.
When in this state, the separation member is in contact with the fixing roller.
It is preferable to have C.

[Example] Hereinafter, the details of the present invention will be explained with reference to Examples.

FIG. 1 is a cross-sectional view showing an example of a heat roller fixing device for fixing a l-toner image T formed by electrophotography to a paper sheet P serving as a recording material, as a first embodiment of the present invention. .

In the figure, l is a heating heater such as a halogen heater.
The fixing roller 3B is rotated C11 in the direction of the arrow by receiving driving force from a drive motor (not shown). 2 is a heater 3 for low heating such as a sheathed heater
A pressure roller C is installed in the roller L and is in pressure contact with the roller L so as to rotate due to friction.

The fixing roller 1 has an elastic layer IB made of silicone rubber, fluororubber, fluorosilicone rubber, etc. on the outer peripheral surface of a hollow roller core IA made of metal such as aluminum, copper, or stainless steel.
is preferably provided with a thickness of 0.065 to 0.75 m+s, and more preferably, the upper layer is provided with a thickness of 0.010 to 0.75 m+s.
070 inch 1) TFE or PFΔ coated IC.

On the other hand, the pressure roller 2 has silicone rubber, fluororubber, fluorosilicone rubber, etc. on the outer peripheral surface of the metal roller core 2A.
The elastic layer 2B, such as EPDM, preferably has a thickness of 2 to IOm+
*Provided with a thickness of *, more preferably, the upper layer is o,
It consists of a PTFE or PFA coating with a thickness of oio to 0.100 mm and a tube 2C.

A temperature detection element 4 such as a thermistor or thermocouple is placed in contact with the outer peripheral surface of the fixing roller 1, and the detection signal thereof is guided to a known control means (not shown) to control the heaters 3A and 3B. The temperature of the outer peripheral surface of the fixing roller l is maintained at the toner image melting temperature.

Reference numeral 5 denotes an anti-offset liquid coating neck which also serves as a cleaning device for removing foreign matter such as offset toner and paper powder adhering to the surface of the fixing roller from the surface of the fixing roller, and is wound in a roll on the supply roller 5A. The heat-resistant web 5B made of Nomex, Himeron, etc. is impregnated with an anti-offset liquid such as dimethyl silicone oil, methylphenyl silicone oil, fluorosilicone oil, amino-modified silicone oil, etc.

The cleaning web 5B is brought into contact with the fixing roller by an elastic pressing roller 5C.

Further, the web 5B is moved by being pulled out from the web roll little by little by the take-up roller 5D under the rotational driving force, and always has a new surface in contact with the fixing roller.

6.7 is a separating member (separating claw) that comes into contact with the fixing roller and the pressure roller, and it separates the copy paper that is the recording material after fixing.
A plurality of rollers are provided along the axial direction of the rollers to be reliably separated from the fixing roller l and the pressure roller 2. The separation claw 6 on the fixing roller side is the ON-O of the solenoid 6A.
The FF is configured to be able to approach and separate from the surface of the fixing roller using position 6B as a rotational fulcrum.

After the fixing, the copy paper P is ejected from the apparatus while being held between a pair of ejecting rollers 8A and 8B, which serve as a pair of conveying rollers in the ejecting section. The distance between the paper ejection roller pair 8A, 8B, the fixing roller 1 and the pressure roller 2 is determined by the shortest distance among the various lengths of the conveyed recording material, for example, the length of a postcard (AS size length). It is set. Note that the circumferential speed of the pair of paper ejection rollers may theoretically be the same as the circumferential speed of the fixing roller, but if it is faster than this, it is possible to completely avoid wrapping of the recording material around the fixing roller due to slack. It is preferable.

A jam detection means 9 is provided in the paper discharge section as a separating means, and the detection means 9 is composed of a roller 9A, an actuator 9B, and a photointerrupter 9C. In the paper ejecting section, when copy paper is gripped by the paper ejecting roller pair 8A, 8B, the roller 9A rotates clockwise about the rotational fulcrum 9D, and as a result, the other side of the actuator 9B on the opposite side of the roller 9D rotates clockwise. The end portion i3 cuts off the photointerrupter 9C. In the jam detecting means 9, when the copy paper passes, the roller 9A returns to the lowered position by its own weight, and the blocking of the photo interrupter 9C by the actuator 9B is released. If the photointerrupter 9C is not shut off within a predetermined time after the copy signal is issued, it is determined that the copy paper has not reached the paper ejection section, and a jam signal is issued. Further, if the photointerrupter 9C is not released even after a predetermined period of time has elapsed after the photointerrupter 9C has been cut off, a jam signal is also generated.

Next, a concrete example will be shown with numerical values regarding the device of this embodiment.

First, the fixing roller l is provided with a heat-vulcanized silicone rubber layer 1B, which is a 0.25 mmH elastic layer, on an aluminum core metal IA, which is a hollow roller core, and a 20 mmH silicone rubber layer 1B on the upper layer.
The pressure roller 2 is formed as a roller with an outer diameter of 60 mm and is provided with a thick PTFE coating, while the pressure roller 2 is made of a heat-vulcanized elastic layer having a thickness of 5 mm and 1 mm on an iron core 2A as a metal roller core. A mold silicone rubber layer 2B is provided.

Furthermore, it is formed as a roller with an outer diameter of 60 mm with a 20 gts thick fluororubber latex covering "1Q2C" on the upper layer, and the fixing roller speed (peripheral speed) is 480 arms.
/sec.

The copying speed was 80 sheets/minute and A4 paper was passed.

The temperature of the fixing roller was maintained at 185°C.

Further, as shown in FIG. 2, from the time the copy paper P is held between the pair of paper ejection rollers 8A and 8B until the trailing edge of the copy paper completely passes the pair of fixing rollers 1.2, the solenoid 6A
was operated to separate the separation claw 6 from the fixing roller.

The above operation can be performed using the jam detection means 9, for example.

That is, the leading edge of the copy paper after fixing is the paper ejection roller pair 8A,
When the actuator 9B interrupts the photo interface 9C by pushing up the copy paper roller 98, the solenoid 6A is operated to separate the separating claw 6 from the fixing roller 1. After that, when the trailing edge of the copy paper passes the paper ejection roller pair 8A, 8B, the roller 98 descends under its own weight, the photo interrupter 9C is unblocked, the solenoid 6A is turned OFF by the signal, and the separation claw 6 is connected to the fixing roller. 8
come into contact with

Under the above conditions, 300,000 sheets were passed without cleaning the pair of fixing rollers, separation claws, etc., and no problems occurred and good results were obtained.

After passing 300,000 sheets, there was little wear on the surface of the fixing roller, and it was possible to pass more sheets. Also, the jam rate at the fixing section is 0.
, 002%, a good result was obtained. Further, in this embodiment, the operation signal for the solenoid 6A is obtained from the jam detection member in the paper ejecting section, but the present invention is not limited to this. For example, the solenoid may be operated after a predetermined number of clocks have been measured from the copy signal using microcomputer control. good.

Next, a conventional method will be shown as a comparative example in comparison with a specific example of the actual implementation.

Comparative Example 1> Paper was passed under the same conditions as in the specific example of this example except that the separation claw 6 was brought into constant contact with the fixing roller l. In that case, the experiment was discontinued after approximately 150,000 sheets had been passed due to frequent jams.

The fixing roller 1 and the separation claw 6 showed considerable wear, and toner fusion to the separation claw was significant, and the use limit was reached. Also, the jam rate before jams occur frequently is 0.0
3%, which is 15 times that in the case of this example.

Comparative Example 2> Paper passing was carried out under the same conditions as in the specific example of this example, except that the separating claws were brought into contact and separated under the following conditions.

Conditions for contact and separation of the separation claw: After the copy paper was fixed and the leading edge of the copy paper passed through the separation claw, the separation claw was separated.

After passing approximately 100,000 sheets, a jam occurred and the fixing roller was damaged, so the experiment was discontinued.

Until then, the jam rate was as high as 0.05%, and there were many jams that got caught in the fixing roller from the middle of the copy paper.

Next, a second embodiment of the present invention will be described.

FIG. 3 is a front view of the fixing device showing this second embodiment, and FIG.
The figure is a perspective view of the device.

In addition, the same reference numerals are given to the parts in the drawings that are common to the apparatus of the previous embodiment, and the description thereof will be omitted.

In the figure, l is a rotatable type with heating means inside.
A fixing roller similar to that of the previous embodiment is provided with a pressure roller 2 pressed against the fixing roller l from below and subjected to driven rotation.

The surface of the fixing roller I is in elastic contact with the tip 12A of a separation claw 12 as a wrapping member, which is rotatably mounted around a shaft 11 extending parallel to the axis of the fixing roller I. ing. Further, the above-mentioned elastic contact is made by the torque applied by the torsion coil spring 13. The separating claw 12 is made of pps, for example, in order to easily slide without damaging the surface of the fixing roller l and to ensure strength.
It is made of heat-resistant materials such as polyamide-imide and polyimide, or relatively soft metals, or their surfaces coated with mold release resin such as PTFE. It has a wide triangular cross section. The separation claw 12 and its rotation center shaft 11 are held by a claw support member 14. The claw support member 14 is fixed to a claw support member fixing plate 15, and an arm l [i is attached to the claw support member fixing plate t5, and a side plate 17.1
An arrow 20 is centered around a rotation shaft 19 rotatably held at 8.
In the axial direction, both ends are fixed to the rotating shaft 19 by thrust stop members 21, and are constantly biased in the direction of arrow 23 by a compression coil spring 22.

The arm 16 is connected to another arm 25 via a link 24, and the arm 25 is rotatable about the central axis 2SA, and the other end is connected to a solenoid 26.

With the above configuration, the claw support member 14 is urged in the direction of the arrow 28 by the tension spring 27, and the positioning portion 14A abuts against the positioning portion 29 such as a fixing device and is fixed, and in this state, the claw tip 1
2A is in contact with the surface of the fixing roller l.

Further, one end 19A of the rotation shaft 19 has a hemispherical shape, and is brought into contact with the wound surface 30A of the cam 30 by the force of the above-mentioned spring 22. Being forced.

A rotating shaft 33 fixed to the cam is rotatably held by side plates 34 and 17 and rotates together with the cam. A lever 35 including a one-way clutch is fitted onto this rotating shaft 33, and a tip 35A of this lever 35 is connected to an opening 15A provided in the F2 claw support member fixing plate 15.

The operation of the apparatus of this embodiment having the configuration described above will be explained below.

As mentioned above, normally, the separation claw 12 is held in position in contact with the positioning part 14A of the claw support member 14 or the positioning part 29 of the fixing device etc. by the force of the spring 27, as shown in FIGS. 3 and 4. In this state, the claw tip 12A is in contact with the roller.

Next, when a separating claw separation signal is input from the control means 36 under certain conditions, the solenoid 26 is turned on, the arm Z5 is pulled in the direction of the arrow 37, and the arm 25 rotates about 25A. Accordingly, the claw support member fixing plate 15 and the claw support member 14 rotate in the direction of the arrow 38 about the rotation shaft 19 via the link 24 and the arm 16, and the claw 12 engaged with the claw support member 14 moves. Therefore, the claw tip 12A moves to a position of 128" and separates from the roller surface.

At the same time, the following operation is also performed.

As the claw support member fixing plate 15 moves in the direction of arrow 37, the lever 35 rotates in the direction of arrow 38 about the rotation shaft 33 due to the engagement of the tip end 35A of the lever 35 and the opening 15A. As mentioned above, since the lever 35 is integrated with the one-way clutch, the direction of the arrow 38 is locked due to the above-mentioned movement, so the rotating shaft 33 rotates in the direction of the arrow 38 and becomes integrated with the shaft. Cam 30 also rotates in the same direction.

This movement causes the rotation shaft 19 to move in the direction of arrow 39 while being guided by the cam surface.

By the above-described movement, the claw tip 12A is simultaneously separated from the roller surface and moved in the axial direction.

Next, when the control means 36 sends an 8-contact signal to the roller at the tip of the claw, the solenoid 26 is turned off, and the solenoid 26 enters the above-mentioned state of contact with the roller. The aforementioned lever 35 then rotates in the opposite direction.

As mentioned above, the lever 35 is equipped with a one-way clutch, and the direction of the arrow 40 is the idling direction, and the rotation shaft 33
The shaft 33 does not rotate because the cam 30, which is integral with the shaft, is held down by the brake 32. That is, in this operation, the pawl did not move in the axial direction, but only came into contact with the roller.

According to this embodiment as described above, it is possible to move the claws toward and away from each other and to move them in the axial direction with a simple configuration.

In addition, in this configuration, the tip 12A of the separation claw 12 is normally in contact with the surface of the fixing roller, and the claw separates from the roller only when the solenoid is turned on. Since the tip 12A of the separating claw 12 is in contact with the surface of the roller, it is easy to clear the jam.

Furthermore, although the brake 32 is used to prevent the cam from rotating, it is also possible to use a ratchet mechanism that acts to restrict the direction or a method that provides another one-way clutch.

In this example, tests were conducted in the same manner as in the previous example, and the results will be shown here with specific numerical values.

Paper was passed using the separating device L under the same conditions as the fixing roller pair, copying speed, etc., as in the first embodiment.

Further, the approach and separation of the separation claw and the movement in the axial direction were performed as follows.

As in the case of the first embodiment, the solenoid 26 is operated and the separating claw 1
2 was separated from the fixing roller.

The shape of the cam 30 was set so that when the solenoid 26 was turned off immediately after the copy paper passed, the separation claw 12 came into contact with the fixing roller with a deviation of 0.1 mm in the axial direction.

Further, the movement width of the separation claw in the axial direction was set to be three times the width of the separation claw.

As a result, 1 million sheets were passed without cleaning the pair of fixing rollers, separation claws, etc., and no problems occurred and good results were obtained. After 1 million sheets had been passed, the surface of the fixing roller showed some wear or was in a state where the paper had not been passed many times. Also,
The jam rate in the fixing section was 0.0022%, which is almost the same value as in the first example.

Next, a third embodiment of the present invention will be described with reference to a specific example.

In this example, paper was passed through the same fixing section and under the same fixing conditions as in the second example, except that the timing of contact and separation of the separating claws was changed.

In that case, the separation claw approaches and separates in the same way as in the second embodiment in the case of single copying, and once every 50 sheets of paper passes in the case of continuous copying, as shown in FIG. While the trailing edge of the copy paper is still in the nip between the pair of fixing rollers, the solenoid 26 is operated to separate it from the fixing roller, which is a separating claw, and separate it just before the leading edge of the next copy paper reaches the nip. The nail was brought into contact with the fixing roller. This is particularly effective in high-speed machines or printers with small space between pages, since it takes time for the mechanism to complete its operation after the above-mentioned operation signal is issued.

One million sheets were passed using the following operation timings, and good results were obtained, almost the same as in the second embodiment.

This is because the wear of the fixing roller caused by the separation claw occurs mainly in the transient state where acceleration is applied when the roller rotation starts (and stops) and transitions from static friction to dynamic friction, so during continuous copying, intermittent copying This is due to the fact that the amount of wear is less than when

Furthermore, in the case of a fixing device that rotates for a predetermined period of time after the power is turned on until the wait is completed, it is more preferable to separate the separating claws during that time.

In addition, even more stable and good results can be obtained by operating the solenoid to separate the separating claw from the fixing roller for a predetermined time selected from a time shorter than the time it takes for the copy paper to reach the fixing unit at the same time as the copy signal. .

[Effects of the Invention] As described above, in the present invention, a sheet-like member or another rotating body that exists between a pair of fixing rollers and at least the leading end of the sheet-like recording material is located downstream of the rollers. Since the separating member was separated from the fixing roller after reaching the pair of barrel conveying rollers, the following effects were obtained.

It becomes possible to significantly extend the life of the rollers used for medium-tone wear.

(2) It becomes possible to significantly extend the life of the separation member.

■It can reduce contamination of the separation member (toner fusion) and greatly reduce the jam rate of recording materials, providing a highly reliable device.

[Phase]) Maintenance intervals can be significantly extended and costs for servicing the equipment can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional front view of the general configuration of the apparatus according to the first embodiment of the present invention, showing the state when paper is not passing through, FIG. 2 is a diagram showing the apparatus in FIG. The figure is a front view of the device of the second embodiment.
FIG. 4 is a perspective view of the apparatus shown in FIG. 3 with the fixing roller and pressure roller omitted, and FIG. 5 is a front view showing the general configuration of the third embodiment of the individual package when paper is passed through. 1.2... Fixing roller pair

Claims (2)

[Claims] (1) The recording material having an unfixed toner image on the surface of the recording material is conveyed under pressure between a pair of heated fixing rollers to fix the toner image on the recording material, and at least In a fixing device having a separating member in contact with the circumferential surface of one of the rollers, a recording material is present between the pair of fixing rollers, and at least a leading end of the recording material is A fixing device comprising: a separating means for separating the separating member from the rollers after reaching a pair of conveying rollers located downstream of the pair of rollers in the conveying direction. (2) The separating means is configured such that when the separating member is brought into contact with the fixing roller again after being separated, the separating member is brought into contact with a position different from the position where the separating member was in contact with the fixing roller before being separated. The fixing device according to (1).