JP3126631B2 - Image forming device - Google Patents

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 a non-fixed image by passing a recording material having an unfixed image through a nip of a pair of rotating members 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.
In general, a recording material carrying an unfixed toner image is nipped and conveyed by the nip to perform 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, in order to improve the image quality, the image surface after fixing is smoothed. Therefore, the fixing ability is increased, more heat is applied to the toner, and the toner is sufficiently melted to perform fixing.

Further, 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 fixing is performed by giving more heat to the recording material.

[0005]

In order to increase the fixing ability, it is necessary to increase the fixing temperature. However, it takes a long time to change the temperature, which is not preferable in terms of responsiveness.

From the viewpoint of responsiveness, it is preferable to increase the fixing ability by lowering the fixing speed. However, when the recording material is caused to enter a pair of rollers that continuously rotates at a constant speed at a low speed, the recording material is moved to the nip entrance of the roller pair. In such a case, there is a problem that paper jam occurs without being pinched by the roller pair.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-described problem of increasing the fixing ability by changing the fixing speed. The image forming means for forming an unfixed image on a recording material is pressed against each other. A pair of rotating bodies forming a nip,
A first fixing unit for nipping a recording material carrying an unfixed image at the nip and conveying the recording material at a first speed to fix the unfixed image on the recording material;
An image forming apparatus capable of performing a second mode in which an unfixed image is fixed on a recording material by being conveyed at a second speed lower than the first speed. It rotates at a speed higher than the second speed until the leading end is pinched by the nip and comes out of the nip, and thereafter the speed is changed to the second speed. An unfixed image forming unit for forming, a nip for nipping and conveying the recording material, a fixing unit for fixing the unfixed image on the recording material at the nip, and a conveying unit for conveying the recording material to the fixing unit, The conveying means is capable of conveying the recording material at a first speed or at a second speed lower than the first speed, and the first portion is held until the leading end of the recording material is sandwiched by the nip and comes out of the nip. Note with speed Transporting the timber, it is characterized in that for conveying the recording material in a subsequent second speed.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment will be described.

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

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

As shown in FIG. 6, an image forming stay as an image forming means including a developing device is provided around an electrophotographic photosensitive member (hereinafter, referred to as a "photosensitive drum") as a latent image carrier. An image on the photosensitive drum formed at each of the image forming stations is provided with a recording material such as a sheet of paper (hereinafter referred to as transfer paper) on a conveying means which moves and passes adjacent to the photosensitive drum. ) Is transferred to P.

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

As shown in FIG. 7, photosensitive drums 1a, 1b, 1c and 1d are provided at image forming stations Pa, Pb, Pc and Pd for forming images of magenta, cyan, yellow and black, respectively. Each photosensitive drum is rotatable in the direction of the arrow. further,
Around each photosensitive drum 1a, 1b, 1c, 1d, chargers 12a, 12b, 12c, 12d, a laser scanning unit, developing devices 2a, 2b, 2c, 2d, and a cleaner 4
a, 4b, 4c, and 4d are sequentially arranged along the rotation direction of the photosensitive drum, and a transfer section 3 is arranged below each photosensitive drum. The transfer unit 3 includes a transfer belt 31 serving as 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 a paper feed cassette 61 as a recording material supply means shown in FIG. 1 is supported on a transfer belt 31 and conveyed to each image forming station, and a toner image of each color formed on each photosensitive drum is formed. Are sequentially transferred. When the transfer process is completed, the paper P is separated from the transfer belt 31 and is conveyed to the fixing device 5 by the conveyance belt 62 serving as a recording material guiding unit.

The fixing device 5 includes, as shown in detail in FIG.
A fixing roller 51 rotatably disposed as a fixing rotating body.
A pressurizing roller 52 serving as a pressurizing rotating body which rotates while being pressed against the fixing roller 51; a release agent applying device 53 serving as a release agent supplying / applying 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 provided respectively. Further, the fixing roller 51
And the pressure roller 52 are provided with thermistors 58 and 59, respectively.
The temperature of the surface of the fixing roller 51 and the pressure roller 52 is controlled by controlling the voltage to the heater 56 and the heater 57 via a temperature control circuit.

Further, a cleaning device 54 and a release agent applying device 53 are attached to the fixing roller 51. The cleaning device 54 cleans the toner and the like offset on the fixing roller 51.
A release agent application device 53 applies a release agent, such as silicone oil, to the fixing roller 51.
This facilitates the separation of the transfer paper P from the paper and prevents the toner from being offset.

The cleaning device 54 includes a cleaning web 54 a made of a belt-shaped heat-resistant nonwoven fabric, and a pressing roller 5 for pressing the cleaning web 54 a 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 the cleaning web 54a having a reduced cleaning ability due to the adhesion of toner and the like. This cleaning device 54 is provided upstream 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 to cause a detection failure in the thermistor 58.

The release agent applying device 53 includes an oil tank 53a having a release agent such as silicone oil, and a roller 5 for pumping oil as a release agent from the oil tank 53a.
3b, 53c and an application roller 53d for applying oil from the pumping rollers 53b, 53c to the fixing roller 51
And a blade 53e for controlling the amount of oil applied from the application roller 53d. In particular, in order to uniformly apply oil to the fixing roller 51, the release agent application device 53 is provided with a 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 sponge rubber is coated with silicone rubber on its surface.
1 to apply oil to the fixing roller 51.

The pressing roller 52 is also provided with the fixing roller 1.
Cleaning web 5 similar to the cleaning device 54 of FIG.
A cleaning device 55 such as 5 a, a pressing roller 55 b, an unwinding roller 55 c, a winding roller 55 d, etc. is attached, and the toner attached to the pressing roller 52 via the fixing roller 51 is cleaned.

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

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

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

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

In FIG. 1, the horizontal axis indicates the time from the start of copying, and the vertical axis indicates the fixing speed and the conveying belt speed at that time. When the copy button is pressed and the copy operation is started, the fixing roller pair 51, 52 and the transport belt 62 are set to a plain paper (thickness of about 90 μm) in accordance with the speed of the main body image forming section.
The rotation is started at a conveying speed of 140 mm / sec in m).

After the rear end of the transparent laminated film has passed through the final transfer position and the front end has entered the fixing nip entrance, the speed of the pair of fixing rollers 51, 52 and the conveyor belt 62 is reduced 60 msec, which is a predetermined time set in advance. 140mm
/ Sec to 70 mm / sec, and after fixing,
The sheet was returned to 140 mm / sec again and discharged. That is, the transport belt synchronizes with the roller pair and transports the recording material at the same speed.
FIG. 2 shows that the rotational speed (peripheral speed) of the fixing roller pair is 140 mm /
The state of the fixing nip when switching from sec to 70 mm / sec is shown. As shown in FIG. 2, in this embodiment, when the tip of the transparent laminate film reaches a position 60 m · sec after reaching the nip entrance, that is, the tip of the transparent laminate film is sandwiched by a pair of rollers. When the tip 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 exit
(= 8.4 mm-7.5 mm). In this embodiment, there is a leading edge margin (W) at which no image is formed at the leading end of the transparent laminated film at 13 mm, and when the leading end of the transparent laminated film is at the position, the trailing end of the leading margin, that is, the leading end of the image area is a nip. Has not entered.

As described above, according to the present embodiment, in the case of a transparent laminate film, the fixing speed is reduced to 70 mm / sec to improve the fixability, so that the image surface formed on the transparent laminate film is smoothed. In particular, 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 reduced to a low speed and remains at the speed during normal image formation. Therefore, the transparent laminated film can be securely held.

According to this embodiment, the speed of the transport belt for transporting the transparent laminate film to the fixing roller pair is also high (140 mm) when the recording material enters the nip entrance.
/ Sec), the transparent laminate film can be conveyed to the nip with momentum, so that the slip when the transparent laminate film enters the nip of the roller pair can be more reliably prevented.

In this embodiment, the fixing speed of the transparent laminated film is reduced before the image area enters the nip, so that the fixing property of the image is not deteriorated.

In this embodiment, the deceleration is performed 60 msec after the leading end of the transparent laminate film enters the fixing nip. However, since this value varies depending on the main body speed, it is not necessarily limited to this value. at least,
It suffices if it is a little later than when the tip of the transparent laminate film enters the fixing nip.

FIG. 3 illustrates a comparative example of the present embodiment.

In FIG. 3, the rear end of the transparent laminated film passes through the final transfer position, and is 140 to 70 mm / sec before the front end enters the fixing nip.
Slow down. In this case, when the transparent laminated film enters the fixing nip, the speed of the fixing roller pair and the conveying belt is 70 mm / sec.
Since the moment when the recording material enters the fixing nip becomes smaller than the timing shown in FIG. 7, the fixing nip entering slip may occur. As described above, at least when the leading end of the transparent laminate film decelerates at a timing later than when it enters the fixing nip, slippage at the time of entry is eliminated, and satisfactory fixing to the transparent laminate film can be performed. The speed change sequence of the present embodiment is not limited to a transparent laminated film, but is preferably applied to a recording material having a smooth surface such as a coated paper having at least a resin layer on the surface. In particular, the transparent laminated film and coated paper are slippery because the surface is resin,
Performing the shift sequence of the present embodiment is particularly effective.

Next, a reference example of the present invention will be described. The basic configuration of the apparatus is the same as that of the first embodiment, and different parts will be described.

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

In FIG. 4, the horizontal axis represents the time from the start of copying, and the vertical axis represents the fixing speed and the conveying belt speed at that time. When the copy button is pressed and another copy mode is started, the fixing roller pair 51, 52 and the transport belt 62 are set to the plain paper (thickness: about 40 mm) in accordance with the speed of the main body image forming section. Rotation is started at a transport speed of 140 mm / sec (90 μm).

Then, the rear end of the thick paper passes through the final transfer position,
After 26 msec, which is a predetermined time set after the leading end enters the fixing nip entrance, the fixing roller pair 51, 5
2. The speed of the conveyor belt 62 is increased from 140 mm / sec to 7
Decelerate to 0 mm / sec, and after fixing, 140 mm
/ Sec and discharged. FIG. 5 shows that the rotational speed (peripheral speed) of the fixing roller pair is changed from 140 mm / sec to 70 mm / sec.
3 shows the state of the fixing nip when switching to.

As shown in FIG. 5, in this embodiment, when the leading end of the cardboard arrives at a position 26 m · sec after the arrival at the nip entrance, that is, the leading end of the cardboard is pinched by a pair of rollers, Is in the nip, the rotational speed of the roller pair is switched from 140 mm / sec to 70 mm / sec. In this example, the nip (W) width is 7.5 m.
m about 3.6 mm from the nip entrance (# 14
(0 mm / sec × 26 m · sec), so that the switch is made when the tip comes to the approximate center of the nip. Also, in this reference example, the leading edge margin (W) where no image is formed at the leading edge of the thick paper
Is 4 mm, and when the front end of the transparent laminate film is at the position of, the rear end of the front margin, that is, the front end of the image area does not enter the nip.

As described above, according to the present embodiment, in the case of thick paper, the fixing speed is reduced to 70 mm / sec to improve the fixing property. Therefore, even with thick paper, sufficient heat and pressure are applied to the entire recording material. In particular, according to this reference example, 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 not reduced. Since the cardboard remains as it is, the thick paper can be reliably held.

Further, according to this embodiment, the speed of the conveyor belt for conveying the thick paper to the fixing roller pair remains at a high speed (140 mm / sec) when the thick paper enters the nip entrance. And the slip when the thick paper enters the nip of the roller pair can be more reliably prevented.

In this embodiment, the leading end of the cardboard is pinched,
Since the fixing speed is reduced before the image area enters the nip, the fixing property of the image does not deteriorate. In this embodiment, the deceleration was performed 26 m · sec after the leading end of the thick paper entered the fixing nip. However, since this value varies depending on the main body speed, it is not necessarily limited to this value. It's better if it's a bit later than when you go into the nip.

In the first embodiment and the reference example, the rotation speed of the pair of fixing rollers 51 and 52 when the transparent laminate film and the thick paper enter the fixing nip is slightly faster than the rotation speed of the conveyor belt 62. Since the rotating member produces a pulling effect of the fixing nip, the rush slip can be more reliably prevented.

[0041]

The deceleration sequence of the first embodiment and the reference example 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. In the case where the roller pair is decelerated to improve the fixing property even for plain paper, it is preferable to perform the same deceleration sequence as that in the first embodiment and the reference example from the viewpoint of slip prevention.

In the first embodiment and the reference example described above, the copy operation is started by setting the transparent laminate film mode (or cardboard mode) and pressing the copy button. When a film (or thick paper) is fed into the apparatus, the feeding may be detected and the copying operation may be automatically performed. Also, 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 simply by feeding the paper without the user setting the type and thickness of the recording material. The deceleration sequence according to the first embodiment and the reference example described above for the material can be performed.

[0044]

As described above, according to the present invention, after the recording material is nipped by the nip of the pair of rotating bodies, the pair of rotating bodies is decelerated. Even in the case where the performance is enhanced, the recording material does not slip at the entrance of the rotating body pair, and the jam of the recording material can be prevented.

[Brief description of the drawings]

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

FIG. 2 is a view for explaining the first embodiment;

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

FIG. 4 is a timing chart showing a reference example of the present invention.

FIG. 5 is a diagram illustrating a reference example.

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

FIG. 7 is an enlarged view of the image forming unit in FIG. 6;

FIG. 8 is an enlarged view of a fixing unit in FIG. 6;

[Explanation of symbols]

 51 fixing roller 52 pressure roller N nip P recording material

Continuation of front page (56) References JP-A-6-208262 (JP, A) JP-A-49-73141 (JP, A) JP-A-3-211568 (JP, A) JP-A-63-311360 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/20 G03G 15/00 303 G03G 15/20 G03G 21/00 370-502

Claims (6)

(57) [Claims] 1. An image forming means for forming an unfixed image on a recording material, and a pair of rotating bodies which press each other to form a nip, wherein the nip holds a recording material carrying an unfixed image. A first mode in which the unfixed image is fixed on the recording material by conveying at a first speed, and a second mode in which the unfixed image is fixed on the recording material by conveying at a second speed lower than the first speed. In the image forming apparatus, the rotator rotates at a speed higher than the second speed until the leading end of the recording material is sandwiched by the nip and comes out of the nip, and thereafter, at the second speed. An image forming apparatus characterized by being changed. 2. The image forming apparatus according to claim 1, wherein the rotating body is changed to the second speed a predetermined time after the leading end of the recording material enters 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 cardboard having at least a resin layer on a surface. 4. A transporting device for transporting a recording material on which an unfixed image is formed by the image forming device to the pair of rotating members, wherein the transporting device is synchronized with the rotating member in the second mode. 2. The image forming apparatus according to claim 1, wherein the recording material is conveyed at the same speed. 5. The image forming apparatus according to claim 1, wherein a speed higher than the second speed is the first speed. 6. An unfixed image forming means for forming an unfixed image on a recording material, and a nip for nipping and conveying the recording material,
An image forming apparatus comprising: a fixing unit configured to fix an unfixed image on a recording material at the nip; and a conveyance unit configured to convey the recording material to the fixing unit. The recording material can be conveyed at a lower second speed, and the recording material is conveyed at the first speed until the leading end of the recording material is nipped by the nip and comes out of the nip, and then conveyed at the second speed. An image forming apparatus comprising: