JPH0922210A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a recording material from slipping at rotary bodies pair nip inlet in a low speed fixing mode, by reducing the speed of the rotary bodies pair, after the recording material is nipped by the nip of the rotary bodies pair. SOLUTION: At the time of fixing mode, the rotary bodies pair 51 and 52 are rotated at a high speed until the recording material is nipped by the nip N of the rotary bodies 51 and 52, and thereafter the rotary speed is reduced. Namely, on setting in a transparent laminated film mode as the second mode, copying operation is started by pushing of a copying key, the fixing rollers pair 51 and 52, and a transporting belt begins to rotate at a transporting speed for an ordinary paper of 140mm/sec to match with the speed of the main body image forming part. Then, after 60m.sec as a predetermined specific time when the transparent laminated film trailing end passed the last position and the leading end entered the fixing nip inlet, the speed of the fixing roller pair 51 and 52, and the transporting belt is reduce from 140mm/sec to 70mm/sec, and after completion of fixing, made to return to 140mm/sec again, and then paper discharge is performed.

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 having a fixing device for fixing an unfixed image by passing a recording material having an unfixed image through a nip between a pair of rotating bodies which are in pressure contact with each other. .

[0002]

2. Description of the Related Art As a fixing device of an image forming apparatus, a fixing roller and a pressure roller are pressed against each other to form a nip,
It is general that the recording material carrying the unfixed toner image is nipped and conveyed at this nip for fixing.

In this type of apparatus, when an image is formed on a recording material having a resin layer on at least the surface such as a transparent film for OHP or coated paper, the surface of the image after fixing is smoothed in order to improve the image quality. Therefore, the fixing ability is increased, more heat is applied to the toner, and the toner is sufficiently melted for fixing.

Even when the recording material is thick paper, a large amount of heat is absorbed by the paper, so that the fixing ability is increased and more heat is applied to the recording material for fixing.

[0005]

By the way, in order to improve the fixing ability, the fixing temperature may be raised, but it takes time to change the temperature, which is not preferable in terms of responsiveness.

From the viewpoint of responsiveness, it is preferable to lower the fixing speed to enhance the fixing ability. However, when the recording material is introduced into the roller pair which continues to rotate at a low speed and at a constant speed, the recording material is the nip entrance of the roller pair. There is a problem in that the paper may slip due to the slipping, and the paper may be jammed without being pinched by the roller pair.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-described problem when the fixing speed is changed to improve the fixing ability. The image forming means for forming an unfixed image on a recording material and the pressure contact with each other. A first mode in which a recording material carrying an unfixed image is sandwiched by the pair of rotating bodies and is conveyed at a first speed for fixing, and a first speed; In an image forming apparatus capable of performing a second mode in which the toner is conveyed and fixed at a slower second speed, in the second mode, the rotating body is moved from the second speed until the recording material is taught at the nip. It is characterized by rotating at a high speed and then changing to the second speed.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will now be described with reference to the drawings.
An embodiment will be described.

FIG. 6 is a sectional view of a full-color copying machine which is an image forming apparatus to which the present invention is applied, FIG. 7 is an enlarged view of the image forming portion of FIG. 6, and FIG. 8 is an enlarged view of the fixing portion of FIG.

First, a full-color copying machine will be briefly described with reference to FIGS.

As shown in FIG. 6, an electrophotographic photosensitive member (hereinafter referred to as a "photosensitive drum") which is a latent image carrier is provided with an image forming unit which is an image forming unit including a developing device and the like. The four images are provided on the photosensitive drum formed by each of the image forming stations, and the recording material such as the paper (hereinafter referred to as a transfer paper) on the conveying unit that moves and passes adjacent to the photosensitive drum. Yes) is transferred to P.

Above the image forming station, there is provided a reader unit for reading an original with a photoelectric conversion element such as a CCD.

As shown in FIG. 7, the photosensitive drums 1a, 1b, 1c and 1d are respectively provided in the image forming stations Pa, Pb, Pc and Pd which form images of magenta, cyan, yellow and black, respectively. The photosensitive drums are arranged so as to be rotatable in the arrow directions. further,
Around the photosensitive drums 1a, 1b, 1c, 1d, chargers 12a, 12b, 12c, 12d, a laser scanning unit, developing devices 2a, 2b, 2c, 2d, and a cleaner 4 are provided.
a, 4b, 4c, and 4d are sequentially arranged along the rotation direction of the photosensitive drum, and the transfer section 3 is arranged below each photosensitive drum. The transfer unit 3 includes a transfer belt 31 which is a recording material conveying unit common to each image forming station.
And transfer chargers 3a, 3b, 3c, 3d.

In the copying machine as described above, FIGS.
The transfer paper P supplied from the paper supply cassette 61, which is a recording material supply means, is supported on the transfer belt 31 and conveyed to each image forming station, and the toner image of each color formed on each photosensitive drum is formed. Are sequentially transferred. When this transfer step is completed, the paper P is separated from the transfer belt 31 and is conveyed to the fixing device 5 by a conveyor belt 62 which is a recording material guide means.

The fixing device 5, as shown in detail in FIG.
A fixing roller 51 that is a rotatably arranged rotating body for fixing.
A pressure roller 52, which is a rotating body for pressure, which rotates while being in pressure contact with the fixing roller 51, a release agent application device 53, which is a release agent supply application means, and roller cleaning devices 54 and 55.
Is provided. Inside the fixing roller 51 and the pressure roller 52, a heater 56 such as a halogen lamp,
57 are arranged respectively. In addition, the fixing roller 51
The pressure roller 52 and the pressure roller 52 have thermistors 58 and 59, respectively.
Are arranged so as to come into contact with each other, and the temperature of the surfaces of the fixing roller 51 and the pressure roller 52 is adjusted by controlling the voltage to the heater 56 and the heater 57 via the temperature adjusting circuit.

A cleaning device 54 and a release agent applying device 53 are attached to the fixing roller 51, and the cleaning device 54 cleans the toner and the like offset on the fixing roller 51.
The releasing agent applying device 53 applies silicone oil or the like as a releasing agent to the fixing roller 51, and the fixing roller 51
The transfer paper P is easily separated from the toner and the offset of the toner is prevented.

The cleaning device 54 includes a cleaning web 54a made of a band-shaped heat-resistant nonwoven fabric, and a pressing roller 5 for pressing the cleaning web 54a against the fixing roller 51.
4b, an unwinding roller 54c that unwinds a new cleaning web 54a, and a winding roller 54d that gradually winds up the cleaning web 54a that has deteriorated cleaning ability due to toner or the like. The cleaning device 54 is provided on the upstream side of the thermistor 58 in the rotation direction of the fixing roller 51 so that the offset toner does not adhere to the thermistor 58 and the detection failure occurs in the thermistor 58.

The mold release agent applying device 53 includes an oil tank 53a having a mold release agent such as silicone oil, and a roller 5 for drawing up a mold release agent oil from the oil tank 53a.
3b and 53c, and an application roller 53d that applies oil from the scooping rollers 53b and 53c to the fixing roller 51.
And a blade 53e for controlling the amount of oil applied from the applying roller 53d. Particularly, in order to achieve uniform oil application to the fixing roller 51, the releasing agent applying device 53 is provided in the thermistor 58. On the other hand, the fixing roller 51
Is disposed on the downstream side in the rotation direction. The application roller 53d is a rotatable roller in which the surface of sponge rubber is covered with silicone rubber, and if necessary, the fixing roller 5d.
1 to apply oil to the fixing roller 51.

The pressure roller 52 is also attached to the fixing roller 1.
Cleaning web 5 similar to the cleaning device 54 of
5a, a pressing roller 55b, an unwinding roller 55c, a take-up roller 55d and the like are attached, and the toner adhering to the pressure roller 52 via the fixing roller 51 is cleaned.

The pressure roller 52 includes a pressure roller 5
An oil removing blade 60, which is an elastic body for removing the release agent that removes the excess release agent remaining on the surface 2, is in contact. If the oil removing blade 60 is not provided, the excess release agent collects in the nip between the fixing roller 51 and the pressure roller 52 and causes stains on the recording material, or the transparent laminating film for OHP slips to cause the nip. Entry failure occurs. As the material of the oil removing blade 60, Si rubber, fluororubber, or the like is used, and these blades are in contact with the pressing roller 52 in the forward direction or the reverse direction with an appropriate amount of advance.

In this state, when the transfer paper P is conveyed, the fixing roller 51 and the pressure roller 52 rotate, silicone oil is applied to the surface of the fixing roller 51 as a release agent, and the transfer paper P is fixed. Roller 51 and pressure roller 52
When passing between the two, the unfixed toner image on the surface of the paper is melted and fixed by being pressed and heated from both the front and back sides at a substantially constant pressure and temperature, and a full-color image is formed on the transfer paper P.
The transfer sheet P on which the image is fixed is separated from the pressure roller 52 by the lower separation claw 68 and is discharged to the outside of the machine.

When the recording material is plain paper (first mode), the recording material is conveyed at a constant speed (140 mm / sec) by the transfer belt, the conveying belt, and the fixing roller pair.

Next, a fixing operation when a transparent laminate film for OHP which is a recording material having at least a resin layer on its surface is used as the recording material will be described with reference to FIG.

In FIG. 1, the horizontal axis represents the time from the start of copying, and the vertical axis represents the fixing speed and the transport belt speed at that time. When the transparent laminate film mode, which is the second mode, is set, the copy button is pressed, and the copy operation starts, the fixing roller pairs 51 and 52 and the conveyor belt 62 are set to plain paper (thickness of about 90 μm according to the speed of the main body image forming unit).
The rotation starts at 140 mm / sec which is the transport speed of m).

After the rear end of the transparent laminated film has passed through the final transfer position and the front end has entered the entrance of the fixing nip, the speed of the fixing roller pair 51, 52 and the conveyor belt 62 is changed 60 msec after the preset time. 140 mm
/ Sec to 70mm / sec, and after fixing,
The paper was returned to 140 mm / sec and discharged. That is, the conveyor belt synchronizes with the roller pair and conveys the recording material at the same speed.
In FIG. 2, the rotation speed (peripheral speed) of the fixing roller pair is 140 mm /
The state of the fixing nip portion at the time of switching from sec to 70 mm / sec is shown. As shown in FIG. 2, in the present embodiment, when the tip of the transparent laminated film reaches a position 60 msec after the tip reaches the nip entrance, that is, the tip of the transparent laminated film is nipped by the roller pair. When the tip of the roller comes out of the nip, the rotation speed of the roller pair is switched from 140 mm / sec to 70 mm / sec. In this embodiment, the nip (N) width is 7.5 mm, and the transparent laminated film is 8.4 mm (= 140 mm / sec × 60 m · s) from the nip entrance.
ec) As it advances, the tip is 0.9 mm from the nip outlet.
(= 8.4mm-7.5mm) It switches when it goes out. Further, in the present embodiment, the leading edge (W) where no image is formed is 13 mm at the leading edge of the transparent laminated film, and when the leading edge of the transparent laminated film is at the position, the trailing edge of the leading edge margin, that is, the leading edge of the image area is the nip. It has not entered inside.

As described above, according to this embodiment, in the case of the transparent laminated film, the fixing speed is slowed down to 70 mm / sec to improve the fixing property, so that the image surface formed on the transparent laminated film is made smooth. Although the image quality can be improved, particularly according to the present embodiment, at the moment when the transparent laminate film enters the fixing nip, the rotation speed of the roller pair is not decreased to the low speed and the speed at the normal image formation is maintained. Therefore, the transparent laminate film can be reliably sandwiched.

Further, according to this embodiment, the speed of the conveyor belt for conveying the transparent laminated film to the fixing roller pair is high (140 mm when the recording material enters the nip entrance).
/ Sec), it is possible to convey the transparent laminated film to the nip with a force, and it is possible to more reliably prevent slipping when the transparent laminated film rushes into the nip of the roller pair.

Further, in this embodiment, since the leading end of the transparent laminate film is sandwiched and the fixing speed becomes slow before the image area enters the nip, the fixing property of the image does not deteriorate.

In the present embodiment, the transparent laminated film tip rushes into the fixing nip and decelerates after 60 m · sec. However, this value varies depending on the speed of the main body and is not necessarily limited to this value. at least,
It may be a little later than when the leading edge of the transparent laminated film enters the fixing nip.

A comparative example of this embodiment will be described with reference to FIG.

In FIG. 3, the rear end of the transparent laminated film passes through the final transfer position, and 140 mm / sec to 70 mm / sec before the front end enters the fixing nip.
Decelerated to. In this case, when the transparent laminated film rushes into the fixing nip, the speed of the fixing roller pair and the conveying belt is 70 mm / sec.
Since the momentum when the recording material plunges into the fixing nip is smaller than the timing shown in (4), a slip in the fixing nip may occur. As described above, at least the leading edge of the transparent laminate film is decelerated at a timing later than when it enters the fixing nip, so that slipping at the time of entry can be eliminated and good fixing to the transparent laminate film can be performed. Further, the speed change sequence of the present embodiment is not limited to the transparent laminated film, and is preferably applied to a recording material having a smooth surface such as coated paper having a resin layer on at least the surface. In particular, the transparent laminated film and coated paper have a resin surface, so they are slippery,
It is particularly effective to carry out the shift sequence of this embodiment.

Next, a second embodiment of the present invention will be described. The basic device configuration is similar to that of the first embodiment, and only different parts will be described.

In the present embodiment, a shift sequence when the recording material is thick paper will be described with reference to FIGS. 4 and 5.

In FIG. 4, the horizontal axis represents the time from the start of copying, and the vertical axis represents the fixing speed and the transport belt speed at that time. When another thick paper mode, which is the second mode, is set, the copy button is pressed, and the copy operation starts, the fixing roller pairs 51 and 52 and the conveying belt 62 are set to the plain paper (thickness approximately equal to the thickness of the main body image forming unit). The rotation starts at 140 mm / sec of the conveyance speed of 90 μm).

Then, the rear end of the thick paper passes through the final transfer position,
After the tip enters the fixing nip entrance, the fixing roller pair 51, 5 is reached after 26 m · sec which is a preset predetermined time.
2. The speed of the conveyor belt 62 is changed from 140 mm / sec to 7
After decelerating to 0 mm / sec and fixing, 140 mm again
The paper was returned to / sec and discharged. FIG. 5 shows the rotation speed (peripheral speed) of the fixing roller pair from 140 mm / sec to 70 mm / sec.
The state of the fixing nip portion when switching to is shown.

As shown in FIG. 5, in the present embodiment, when the leading edge of the thick paper reaches a position 26 msec after the leading edge of the thick paper arrives, that is, the leading edge of the thick paper is nipped by a pair of rollers, , The rotational speed of the roller pair is switched from 140 mm / sec to 70 mm / sec. In this embodiment, the nip (W) width is 7.
5 mm, and for thick paper, about 3.6 mm (≈
140 mm / sec × 26 m · sec), so that the tip is switched when it comes to the approximate center of the nip. Further, in the present embodiment, the leading edge margin (W) where an image is not formed is 4 mm at the leading edge of the thick paper, and when the leading edge of the transparent laminate film is at the position, the trailing edge of the leading edge margin, that is, the leading edge of the image area is within the nip. I have not entered.

As described above, according to the present embodiment, in the case of thick paper, the fixing speed is slowed down to 70 mm / sec to improve the fixability, so that even with thick paper, sufficient heat and pressure are applied to the entire recording material. However, according to the present embodiment, especially at the moment when the thick paper enters the fixing nip, the rotation speed of the roller pair is not reduced to a low speed, and the speed at the time of normal image formation is reduced. Since it is still there, it is possible to reliably hold thick paper.

Further, according to the present embodiment, the speed of the conveyor belt for conveying the thick paper to the pair of fixing rollers is also high (140 mm / sec) when the thick paper enters the nip entrance, so that the thick paper is given momentum. It is possible to more reliably prevent slipping when thick paper enters the nip of the roller pair.

Further, in this embodiment, since the leading edge of the thick paper is pinched and the fixing speed becomes slow before the image area enters the nip, the fixing property of the image does not deteriorate. In this embodiment, the tip of the thick paper is projected into the fixing nip to reach 26 m · se.
Although deceleration was performed after c, this value is not necessarily limited to this value because it varies depending on the speed of the main body, and at least a little later than when the leading edge of the thick paper enters the fixing nip.

Further, in the first and second embodiments, the rotational speed of the fixing roller pair 51, 52 when the transparent laminated film and the cardboard plunge into the fixing nip is slightly faster than the rotational speed of the conveyor belt 62. Since the rotation of the fixing nip has a pulling effect on the fixing nip, the rush slip can be prevented more reliably.

Specifically for the first and second embodiments, the rotation speed of the conveyor belt 62 is 70 mm / se.
The rotation speed of the fixing roller pair 51 and 52 is 71 to
It is preferably set to about 73 mm / sec.

The deceleration sequence of the first and second embodiments described above is not limited to a recording material having a resin layer on the surface such as a transparent laminated film or coated paper, or a thick recording material. When decelerating the roller pair to improve the fixing property even on plain paper, it is preferable from the viewpoint of slip prevention that the deceleration sequence similar to that of the first and second embodiments described above is performed.

In the above-described first and second embodiments, the transparent laminated film mode (or cardboard mode) is used.
Copy operation was started by setting the and pressing the copy button, but when a transparent laminated film (or thick paper) was fed into the machine by manual feeding etc., the feeding operation is detected and the copying operation is automatically performed. It may be carried out at. Further, at this time, if a recording material detecting means for detecting the type and thickness of the fed recording material is provided in the apparatus, the recording can be performed by simply feeding the recording material without the user setting the type and thickness of the recording material. The deceleration sequence of the above-described first and second embodiments suitable for the material can be performed.

[0044]

As described above, according to the present invention, after the recording material is sandwiched by the nip of the pair of rotating bodies, the pair of rotating bodies is decelerated, so that the speed of the pair of rotating bodies is reduced and the fixing is performed. Even when improving the property, the recording material does not slip at the entrance of the pair of rotating bodies, and the jamming of the recording material can be prevented.

[Brief description of drawings]

FIG. 1 is a timing chart showing a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the first embodiment.

FIG. 3 is a timing chart of a comparative example.

FIG. 4 is a timing chart showing a second embodiment of the present invention.

FIG. 5 is a diagram for explaining the second embodiment.

FIG. 6 is a sectional view of an image forming apparatus to which the present invention is applied.

7 is an enlarged view of the image forming unit in FIG.

FIG. 8 is an enlarged view of the fixing unit in FIG.

[Explanation of symbols]

 51 fixing roller 52 pressure roller N nip P recording material

Claims (5)

[Claims] 1. A recording material carrying an unfixed image, comprising: an image forming means for forming an unfixed image on the recording material; and a pair of rotating bodies that are in pressure contact with each other to form a nip. In the image forming apparatus, it is possible to perform a first mode of nipping and carrying at a first speed for fixing, and a second mode of carrying at a second speed slower than the first speed for fixing. In the mode, the image forming apparatus is characterized in that the rotating body rotates at a speed higher than the second speed until the recording material is nipped by the nip, and then is changed to the second speed. 2. The image forming apparatus according to claim 1, wherein the rotating body is changed to the second speed after a predetermined time has elapsed since the leading edge of the recording material entered the nip. 3. The image forming apparatus according to claim 1, wherein the second mode is a case where recording is performed on a recording material or a cardboard having a resin layer on at least a surface thereof. 4. A transporting means for transporting a recording material on which an unfixed image is formed by the image forming means to the pair of rotating bodies, wherein the transporting means is synchronized with the rotating body in the second mode. The image forming apparatus according to claim 1, wherein the recording material is conveyed at the same speed. 5. A conveyance unit configured to convey a recording material on which an unfixed image is formed by the image forming unit to the rotating body pair, and when the leading end of the recording material enters the nip, the rotating body is configured to The image forming apparatus according to claim 1, wherein the image forming apparatus is faster than the speed of the conveying means.