JPH11102134A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which is miniaturized, whose throughput is enhanced and by which a good-quality image having no color slurring is formed. SOLUTION: The fixing device of a copying machine is provided with a pair of heat rollers 71 and 72 arranged to roll in contact with each other. An auxiliary roller 73 is arranged to roll in contact with the roller 71 in the vicinity of the end of the roller 71. An encoder 75 which detects the circumferential speed of the roller 71 by detecting the circumferential speed of the roller 73 is attached to the rotary shaft of the roller 73. The circumferential speed of the heat roller is regularly detected by the encoder 75 and the rotating speed of the heat roller is controlled in accordance with the traveling speed of a carrying belt.

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 such as a copying machine, and more particularly to a color copying machine having a plurality of photosensitive drums for forming images of respective colors based on color-separated image signals.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus for outputting a color image, a toner of each color of yellow (Y), magenta (M), cyan (C) and black (B) is based on a color-separated image signal. 2. Description of the Related Art A so-called four-tandem color copying machine having four image forming units for forming an image is known.

A copying machine of this type includes four photosensitive drums arranged in parallel with each other, each carrying four color toner images, a transport device for transporting a recording sheet as a medium to be transferred through each photosensitive drum, and this transport. A transfer device for sequentially transferring the toner images of the respective colors formed on the respective photosensitive drums onto the recording paper conveyed by the apparatus, and heating and pressing the recording paper onto which the toner images of the respective colors have been transferred by the transfer device. And a fixing device for fusing each color toner image on recording paper.

The fixing device has a pair of heat rollers which are rolled and contacted with each other at a predetermined pressure, and heats and presses the recording paper by passing the recording paper between the heat rollers to melt the toner image on the recording paper. And settle it. Each heat roller is formed by a rubber roller having a heater lamp inside.

When the fixing device is operated for a long time by continuously passing a plurality of recording papers, each heat roller is heated by the heat of the heater lamp, and the rubber roller portion is thermally expanded. As described above, when each heat roller is thermally expanded, the outer peripheral length of each heat roller increases, and when each roller is rotated at a constant angular velocity, the peripheral speed of each heat roller increases.

As described above, when the peripheral speed of the heat roller is increased, the peripheral speed of each photosensitive drum, the transport speed of the transport device, and the processing speed of the fixing device do not match, and the recording speed between the pair of heat rollers of the fixing device is reduced. When the leading edge of the recording paper is nipped, the leading edge of the recording paper is pulled, and if the trailing edge of the recording paper is passing through the image forming unit, the toner image of each color is displaced (superimposed) on the recording paper. Deviation).

For this reason, in the conventional color copying machine, the rotation reference value of the heat roller is set to a low value in advance in consideration of such thermal expansion of the heat roller over time, thereby preventing color misregistration. Was.

In addition, the distance between the black image forming section located at the most downstream side in the conveying direction of the recording paper and the fixing device is sufficiently provided, the processing speed of the fixing device is reduced, and the processing speed of the recording paper is reduced. The recording paper is bent when the leading end reaches the fixing device, and the recording paper is sent to the fixing device in this state.

[0009]

However, if the processing speed of the fixing device, that is, the peripheral speed of the heat roller is set to be lower than the peripheral speed of the photosensitive drum and the transport speed of the transport device, as in the prior art, There has been a problem that the process speed of the entire copying machine is reduced, and the processing capacity is reduced.

Further, if the distance between the black image forming section and the fixing device is increased, the size of the device cannot be reduced. The present invention has been made in view of the above points, and an object of the present invention is to provide an image forming apparatus capable of reducing the size of the apparatus, increasing the processing capability, and forming a high-quality image without color shift. is there.

[0011]

According to another aspect of the present invention, there is provided an image forming apparatus for forming an image with a hot-melt developer on an image carrier. Transport means for transporting the transfer medium to the developer image formed on the image carrier, transfer means for transferring the developer image onto the transfer medium transported by the transport means, and A first roller and a second roller which are disposed adjacent to the end in the transport direction and which are disposed so as to be in contact with each other, a driving means for rotating the first roller at a variable speed, and heating at least one of the first and second rollers; Heating means to perform
The transfer medium conveyed by the transfer means and onto which the developer image has been transferred by the transfer means passes between the first and second rollers, and the developer image is melted and fixed on the transfer medium. Fixing means, first detecting means for detecting a conveying speed of the medium to be transferred by the conveying means, second detecting means for detecting a peripheral speed of a first roller rotated by the driving means, Control means for controlling the driving means in accordance with the result of detection by the second detection means and adjusting the peripheral speed of the first roller to the conveyance speed of the medium to be transferred by the conveyance means.

Further, according to the image forming apparatus of the present invention, the second detecting means detects the peripheral speed near the axial end of the first roller through which the transfer medium does not pass. It is characterized by.

According to another aspect of the present invention, there is provided an image forming apparatus comprising: a plurality of photosensitive drums arranged in parallel with each other;
Image forming means for forming an image of each color with a hot-melt developer on the surface of each photosensitive drum based on the color-separated image signal, and a state in which the image forming means is in rolling contact with the surfaces of the plurality of photosensitive drums Transport means for holding a medium to be transferred on the transport belt and transporting the developer images of the respective colors formed on the photosensitive drums, and transporting the developer by the transport means. Transfer means for sequentially superimposing and superimposing developer images of the respective colors on the transfer-receiving medium to be transferred, and first and second transfer means arranged adjacent to the end of the transfer means in the transfer direction and arranged in contact with each other. A roller, driving means for rotating the first roller at a variable speed, and heating means for heating at least one of the first and second rollers,
The transfer medium conveyed by the conveying means and having the developer image of each color polymerized and transferred by the transfer means is passed between the first and second rollers, and the developer image of each color polymerized and transferred is melted. Fixing means for fixing the transfer belt on the transfer medium, first detecting means for detecting a traveling speed of the transport belt, second detecting means for detecting a peripheral speed of a first roller rotated by the driving means, Control means for controlling the drive means in accordance with the detection results of the first and second detection means, and adjusting the peripheral speed of the first roller to the traveling speed of the transport belt.

According to the image forming apparatus of the present invention, the second detecting means detects a peripheral speed near an axial end of the first roller through which the transfer medium does not pass. It is characterized by.

According to a fifth aspect of the present invention, there is provided an image forming apparatus, comprising: an image forming means for forming an image with a hot-melt developer on an image carrier; and a developer formed on the image carrier. A transfer unit that transfers the transfer medium to the image, a transfer unit that transfers the developer image onto the transfer medium that is transferred by the transfer unit, and a transfer unit that is disposed adjacent to an end of the transfer unit in the transfer direction, and First and second rollers arranged in rolling contact,
A driving unit configured to rotate the first roller at a variable speed; and a heating unit configured to heat at least one of the first and second rollers. A transfer unit that transfers the transferred transfer medium between the first and second rollers, melts the developer image, and fixes the transfer device on the transfer medium; and detects a transfer speed of the transfer medium by the transfer unit. A first detecting unit, an auxiliary roller which is disposed in rolling contact with the first roller rotated by the driving unit, and a second detecting unit which detects a peripheral speed of the first roller by detecting a peripheral speed of the auxiliary roller. 2 detecting means, and control means for controlling the driving means in accordance with the detection results by the first and second detecting means, and for adjusting the peripheral speed of the first roller to the conveying speed of the medium to be transferred by the conveying means. ing.

According to the image forming apparatus of the present invention, the auxiliary roller is formed by an aluminum roller having a roughened surface and a high friction coefficient.

According to the image forming apparatus of the present invention, the auxiliary roller is disposed so as to be rolled and contacted near the axial end of the first roller through which the transfer medium does not pass. It is characterized by.

Further, according to the image forming apparatus of the present invention, the second detecting means is an encoder attached to a rotation shaft of the auxiliary roller.

According to the image forming apparatus of the present invention, the control means periodically controls the peripheral speed of the first roller at predetermined time intervals via the second detecting means. And controlling the driving means.

According to a tenth aspect of the present invention, there is provided an image forming apparatus, comprising: a plurality of photosensitive drums juxtaposed with each other; It has image forming means for forming an image with the hot-melt developer of each color, and a transport belt which can run in a state of being in rolling contact with the surfaces of the plurality of photosensitive drums. A transport unit that holds and transports the developer image of each color formed on each of the photosensitive drums, and superimposes the developer images of each color sequentially on a transfer medium transported by the transport unit and polymerizes and transfers Transfer means,
A first roller and a second roller which are arranged adjacent to the end of the conveying means in the conveying direction and which are arranged so as to be in contact with each other; a driving means for rotating the first roller at a variable speed; And a heating unit for heating at least one of the first and second rollers. The transfer medium conveyed by the conveyance unit and onto which the developer images of the respective colors are polymerized and transferred by the transfer unit is passed between the first and second rollers. A fixing unit for melting the transferred developer images of the respective colors and fixing the transferred developer images on a transfer-receiving medium; a first detecting unit for detecting a traveling speed of the transport belt; and a first roller rotated by the driving unit. An auxiliary roller arranged in a rolling contact, a second detecting means for detecting a peripheral speed of the first roller by detecting a peripheral speed of the auxiliary roller, and a detecting means for detecting a peripheral speed of the first roller. Drive means Gyoshi, the peripheral speed of said first roller and a, and control means for matching the running speed of the conveyor belt.

According to the image forming apparatus of the present invention, the auxiliary roller is formed by an aluminum roller having a roughened surface and a high friction coefficient.

According to the image forming apparatus of the present invention, the auxiliary roller is disposed so as to be in contact with an axial end of the first roller through which the transfer medium does not pass. It is characterized by.

According to the image forming apparatus of the present invention, the second detecting means is an encoder mounted on a rotation shaft of the auxiliary roller.

Further, according to the image forming apparatus of the present invention, the control means periodically controls the first control means at predetermined time intervals via the second detection means.
The invention is characterized in that the peripheral speed of the roller is detected and the driving means is controlled.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a color copying machine 1 (hereinafter, referred to as an image forming apparatus) according to the present invention.
FIG. 2 is a perspective view of the copying machine 1 as viewed obliquely from the rear left side. FIG. 2 is a perspective view of the copying machine 1 viewed obliquely from the rear left side. First, the overall configuration of the copying machine 1 will be described with reference to FIGS.

As shown in FIG. 1, at the top of the copying machine 1,
A document table 2 on which a document is placed is provided. A document holder 3 for preventing the document from moving is provided on the document table 2 so as to be openable and closable in the direction of arrow a.

An operator panel 4 for setting and executing various instructions for the copying machine 1, such as a copy start switch, is provided on the upper front side of the copying machine 1. At the lower portion of the copying machine 1, paper cassettes 5a and 5b for mounting recording paper as a transfer medium are provided so as to be drawn out in the directions of arrows b and c with respect to the copying machine 1.

On the right side of the copying machine 1, an access cover 6 for jam clearance and a paper guide 7 for manual paper feed are provided so as to be openable and closable in the direction of arrow d with respect to the copying machine 1. .

As shown in FIG. 2, on the left side of the copying machine 1, a paper discharge port 8 for discharging the recording paper on which the image formation is completed, and the recording paper discharged through the paper discharge port 8 are provided. Is provided with a paper discharge tray 9 for receiving the document. The paper discharge tray 9 is detachably attached to the copying machine 1.

Also, on the back of the copying machine 1,
Power cord 10 for supplying power to the computer, I / F connector 1 for connecting to a computer device such as a personal computer
1. An I / F connector 12 for connecting to a facsimile is provided.

FIG. 3 is a sectional view showing the internal structure of the copying machine 1. FIG. 4 is an enlarged view of a main part of FIG. Here, a schematic configuration of the entire copying machine 1 will be described first, and a detailed configuration will be described later.

Copiers 1 are roughly classified into: 1) an original reading section 20 for digitally reading an image of an original to be copied and converting it into an image signal 2) an image forming section 303 using an electrophotographic system 3) It is divided into a sheet cassette 5a, 5b and a sheet feeding and transporting section 80 including a manual sheet feeding section.

The original reading section 20 includes an illumination lamp 2 for illuminating an original (not shown) placed on the original placing table 2.
1. A reflector (not shown) that converges light from the illumination lamp 21 toward the original, and guides the light reflected from the original to the light receiving element 24 using the reflection mirrors 22a, 22b, 22c, the imaging lens 23, and the like. An optical system 25, a light receiving element 24 such as a CCD for converting light from a document into an electric signal, and an image signal for each color of yellow, magenta, cyan, and black by color-separating the photoelectrically converted electric signal. Image processing device 26 for

The image forming section 30 applies a known electrophotographic method, and each color (yellow: Y, magenta: M,
An exposure device 40 for exposing a photosensitive drum (image carrier) provided for each of cyan (C) and black (B); an image forming mechanism 50 including a photosensitive drum for each color; a transfer mechanism 60;
It comprises a fixing device 70 and the like.

Here, the image forming section 30 will be described in detail. The transfer mechanism 60 has an endless transport belt 61 that transports the recording paper, and an image forming unit that forms an image of each color of yellow, magenta, cyan, and black from the right on the upper surface side of the transport belt 61. 50Y,
50M, 50C, and 50B are arranged at equal intervals.

A fiber sensor 61a (first detecting means) for detecting the traveling speed of the conveyor belt 61 is provided above the conveyor belt 61 and on the left side of the image forming unit 50B for black in the drawing. It is arranged at a predetermined distance from 61. Fiber sensor 61a
Is configured to detect the traveling speed of the conveyor belt 61 by reading a test pattern formed on the conveyor belt 61.

Further, above these, an exposure device 40
Is provided. The exposure device 40 has laser light sources 42Y, 42M, 42C, and 42B that are driven according to image signals for each color created by the image processing device 26. Each of the laser light sources 42Y, 42M, 42C, and 42B emits laser light 41Y, 41M, 41M according to the color-separated image signal.
C and 41B are emitted, and the image forming units 50Y, 50M, 5M, and 5B are emitted through the polygon mirror 43 shown in FIG.
Photoreceptor drums 51Y and 51 provided in OC and 50B.
An electrostatic latent image is formed on M, 51C, and 51B.

The transfer mechanism 60 includes a transfer device 62.
Y, 62M, 62C, and 62B are the respective photosensitive drums 51Y,
It is provided facing 51M, 51C, 51B. The drive roller 63 is rotated in a direction indicated by an arrow by a motor (not shown) so that the transport belt 61 runs at a predetermined speed in a direction indicated by an arrow. A predetermined tension is applied to the driven roller 64 in a direction away from the driving roller 63 by a pressing mechanism (not shown).
1 is not sagging.

On the transport belt 61, a paper feed guide device 65 for feeding the recording paper onto the transport belt 61 so as not to be shifted, and a cleaning device 66 for cleaning the surface of the transport belt 61 are provided. I have.

Each image forming unit 50Y, 50M, 50
C and 50B have the same configuration, and form an image corresponding to each color by a known electrophotographic process.

As shown in detail in FIG.
1Y, 51M, 51C, and 51B, the charging devices 52Y, 52M, 52C, and 52 along the rotation direction.
B, developing devices 53Y, 53M, 53C, 53B, transfer devices 62Y, 62M, 62C, 62B (see FIG. 3), cleaning devices 54Y, 54M, 54C, 54B, and static eliminators 55Y, 55M, 55C, 55B, respectively. The exposure device 4 is arranged according to the image signals separated for each color.
Laser light 41Y, 41M, 41C, 4
A color image corresponding to 1B is formed.

The fixing device 70 has an upper heat roller 71 (first roller) and a lower heat roller 72 (second roller) which are rolled and contacted at a predetermined pressure and heated to a predetermined temperature. Then, each of the heat rollers 71, 7
By passing the recording paper between the two, the toner transferred onto the recording paper is melted and fixed to the recording paper.

Next, the sheet feeding / conveying section 80 will be described.
Below the transfer mechanism 60, sheet cassettes 5a and 5b for stacking and storing a plurality of sheets of recording paper, and recording sheets taken out of each of the sheet cassettes 5a and 5b are stored in the image forming unit 30.
Is provided with a paper feeding unit 82 for feeding and transporting the paper.

The paper feed section 82 has a paper feed roller 83 for picking up recording paper from each of the paper cassettes 5a and 5b.
a and 83b, a pair of transport rollers 84a and 84b for guiding the recording paper onto the transport belt 61, and a pair of aligning rollers 85 for adjusting the timing of feeding the recording paper.

On the upstream side of the aligning roller 85, there is provided a manual paper feeder 86 for guiding the recording paper manually fed via the paper guide 7 (see FIG. 1) onto the conveyor belt 61. ing. When the recording paper is placed on the upper surface of the paper guide 7 with the paper guide 7 opened, the pickup roller 87
Is rotated, and the leading end of the recording paper is aligned with the aligning roller pair 85.
To be sent to.

Next, the operation of the copying machine 1 configured as described above will be described. First, when a signal for performing copying is input via the operator panel 4, the document reading unit 20 starts operating, the illumination lamp 21 is turned on, and the optical system 25 is moved. The light reflected from the document passes through the optical system 25, is taken into the light receiving element 24, is converted into an electric signal, and is sent to the image processing device 26.

The image signal sent in this way is decomposed by the image processing device 26 into image signals for respective colors of yellow, magenta, cyan, and black, and sent to a writing image processing device (not shown).

A signal from the writing image processing control device is sent to the exposure device 40, and at the same time, the photosensitive drums 51Y and 51
M, 51C, 51B, the conveyance belt 61, the fixing device 70, etc. start to rotate.

The recording paper accommodated in the paper cassette 5a or 5b is picked up by paper feed rollers 83a and 83b or a pick-up roller 87 of a manual paper feed unit, conveyed by conveying roller pairs 84a and 84b, and aligned by an aligning roller. The timing is adjusted by the pair 85, and the sheet is sent onto the transport belt 61.

On the other hand, the image signal from the image writing control device is sent to the exposure device 40, and the laser light 4 corresponding to each color is transmitted.
Emitted as 1Y, 41M, 41C, 41B. Each laser beam is scanned by the polygon mirror 43 and guided to the corresponding photosensitive drum.

For example, with respect to the yellow signal, the exposure device 40 controls the laser light source 4 according to the yellow image signal.
2Y is energized to emit a laser beam 41Y. The laser beam 41Y is used to expose and scan the photosensitive drum 51Y uniformly charged by the charging device 52Y to form an electrostatic latent image according to a yellow image signal.

The photosensitive drum 51Y is rotating in the direction of arrow e (see FIG. 4), and the electrostatic latent image on the photosensitive drum 51Y is developed by the developing device 53Y to form a yellow toner image.

This yellow toner image is transferred to the transfer device 62Y
Is transferred to the recording paper on the conveyor belt 61. Thereafter, the yellow toner remaining on the surface of the photosensitive drum 51Y without being transferred is cleaned by the cleaning device 54Y.

Further, the residual potential on the photosensitive drum 51Y is reduced uniformly by the illumination of the charge removing device 55Y, so that the apparatus is ready for the next electrophotographic process. For magenta, cyan, and black, corresponding image signals are sent to the exposure device 40, and a laser beam 41
M, 41C, and 41B are ejected, and each image forming unit forms an image through the same process as the yellow image forming unit 50Y.

In the above-described image formation, while the recording paper is conveyed by the conveyance belt 61, the images of each color are transferred one after another, and then conveyed by separation by the curvature of the driving roller 63 or forced separation by separation claw (not shown). Belt 61
From the fixing device 70.

The recording paper is subjected to image fixing by heat and pressure in the fixing device 70, and thereafter is discharged onto a paper discharge tray 9 provided outside the copying machine 1 through a paper discharge port 8.

In the above-described color copying machine, generally, a plurality of continuous copies are input and input via the operator panel 4 for one document, and a predetermined number of copies are continuously performed. When such continuous copying is continued, thermal expansion occurs in the upper heat roller 71 and the lower heat roller 72 of the fixing device 70, and the heat rollers 71, 72
Increases with time.

As described above, when the diameter of each of the heat rollers 71 and 72 is increased, the peripheral speed of each of the heat rollers is faster than the peripheral speed of each of the photosensitive drums 51Y, 51M, 51C and 51B and the traveling speed of the conveyor belt 61. The leading end of the recording paper fed to the fixing device 70 is
It is pinched and pulled by. At this time, if the trailing end of the recording paper is in, for example, the magenta image forming unit, color misregistration occurs in images output by the image forming units after magenta.

In the case of a monochrome copying machine having a single photosensitive drum, such image deviation is inconspicuous. However, in the case of a quadruple tandem-type color copying machine as in the present embodiment, it is not so.
The deviation of the peripheral speed as described above causes a serious problem of color deviation.

For this reason, in this embodiment, a change in the peripheral speed due to the thermal expansion of the heat rollers 71 and 72 over time is periodically detected, and the peripheral speed of each heat roller is determined by each photosensitive drum and the conveyor belt. Was controlled to match the speed.

FIG. 5 shows a pair of heat rollers 71 and 72 and an upper heat roller 7 arranged in a fixing device 70.
1 shows the auxiliary roller 73 rolled and contacted. FIG. 6 is a side view of each roller of FIG. 5 as viewed from the axial direction.

At substantially the center of each of the heat rollers 71 and 72,
Heater lamps 71a and 72a are provided as heating means extending along the rotation axis of each roller. Rubber rollers 71b and 72b are provided around each heater lamp. Each heat roller 7 thus configured
1 and 72 are pressed against each other at a predetermined pressure by an urging mechanism (not shown), and are rotated by a motor 76 as a driving unit connected to a rotation shaft of the upper heat roller 71. Therefore, the upper heat roller 71 acts as a driving roller, and the lower heat roller 72 acts as a driven roller.

An auxiliary roller 73 is provided in a rolled state at an end of the upper heat roller 71 through which recording paper does not pass, that is, at a portion where the upper heat roller 71 is most likely to undergo thermal expansion. The auxiliary roller 73 is made of aluminum, and its surface is roughened to increase the friction coefficient.
A device for suppressing slippage with the upper heat roller 71 is provided. The auxiliary roller 73 is attached to the upper heat roller 71 via a spring 74. Therefore,
As described above, the three rollers that are rolled and contacted with each other have substantially the same peripheral speed.

Further, an encoder 75 as second detecting means for detecting the peripheral speed of each of the heat rollers 71 and 72 by detecting the peripheral speed of the auxiliary roller 73 is attached to the rotating shaft 73a of the auxiliary roller 73. Have been.

Hereinafter, referring to the flow chart shown in FIG.
A control operation when adjusting the peripheral speed of the lower heat roller 72 (and the lower heat roller 72) will be described.

First, when the number of copies and the like are set via the operator panel 4 and the copy start switch is pressed (step 1), the traveling speed of the transport belt 61 (that is, the photosensitive drum) is reduced via the fiber sensor 61a. It is measured (step 2) and this running speed is monitored.

Next, measurement of the peripheral speed of the upper heat roller 71 is started via the encoder 75 attached to the auxiliary roller 73 (step 3). When the peripheral speed of the upper heat roller 71 is measured a predetermined number of times, the average value is calculated (step 4).

Then, the running speed of the transport belt 61 monitored via the fiber sensor 61 and the average value of the peripheral speed of the upper heat roller 71 detected by the encoder 75 are:
The comparison is periodically made at preset time intervals (step 5), and it is determined whether the peripheral speed of the upper heat roller 71 is the same as the traveling speed of the transport belt 61 (step 6).

If it is determined in step 6 that the two speeds do not match, the upper heat roller 71
Is changed in accordance with the running speed of the conveyor belt 61 in accordance with the difference in speed (step 7). For example, when the peripheral speed of the upper heat roller 71 becomes faster than the traveling speed of the transport belt 61 due to thermal expansion of the upper heat roller 71 over time, the peripheral speed of the upper heat roller 71 is adjusted to the traveling speed of the transport belt 61. Speed is reduced.

On the other hand, if it is determined in step 6 that the traveling speed of the conveyor belt 61 is equal to the peripheral speed of the upper heat roller 71, the condition is that the copying operation is completed (step 8). Then, the monitoring of the traveling speed of the conveyor belt 61 by the fiber sensor 61a is terminated (step 9), and the measurement of the peripheral speed of the upper heat roller 71 by the encoder 75 is terminated (step 10).

When the copying operation is continued, the monitoring of the traveling speed of the conveyor belt 61 by the fiber sensor 61a (step 11) and the measurement of the peripheral speed of the upper heat roller 71 by the encoder 75 (step 12) are continued. .

As described above, according to the present embodiment, the peripheral speed of the pair of heat rollers 71, 72 of the fixing device 70 is periodically measured by the encoder 75, and the traveling speed of the transport belt 61 is measured by the fiber sensor 61a. And the peripheral speed of the heat roller was controlled to match the traveling speed of the conveyor belt 61. As a result, even when the heat rollers 71 and 72 undergo thermal expansion, the processing speed of the fixing device 70 can be kept constant, and a high-quality image without color shift can be formed. Also, the heat rollers 71 and 7
2, the distance between the black image forming unit 50B and the fixing device 70 can be shortened, the size of the entire copying machine can be reduced, and the processing capability of the device can be increased. it can. Note that the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

[0073]

As described above, since the image forming apparatus of the present invention has the above-described configuration and operation, the apparatus can be downsized and the processing capability can be increased.
High quality images without color shift can be formed.

[Brief description of the drawings]

FIG. 1 is a front perspective view showing a copying machine according to an embodiment of the present invention.

FIG. 2 is a rear perspective view showing the copying machine shown in FIG. 1;

FIG. 3 is a sectional view showing the internal configuration of the copying machine of FIG. 1 in detail.

FIG. 4 is an enlarged view showing a main part of the copying machine shown in FIG. 3 in an enlarged manner;

FIG. 5 is a schematic diagram partially showing an internal configuration of a fixing device incorporated in the copying machine of FIG. 1;

FIG. 6 is a side view of the configuration of FIG. 5 as viewed from the axial direction of each roller.

FIG. 7 is a flowchart illustrating a control operation for controlling the peripheral speed of the heat roller in accordance with the traveling speed of the transport belt.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Color copier, 2 ... Document stand, 3 ... Document holder, 4 ... Operator panel, 5a, 5b ... Paper cassette, 6 ... Access cover, 7 ... Paper guide, 8 ... Discharge port, 9 ... Discharge tray Reference Signs List 10 power supply cord 11 12 I / F connector 20 document reading section 21 illumination lamp 22a, 22b, 22c reflection mirror 23 imaging lens 24 light receiving element 25 optical system 26 image processing device 30 image forming unit 40 exposure device 41Y, 41M, 41C, 41B laser light 42Y, 42M, 42C, 42B laser light source 43 polygon mirror 50Y, 50M, 50C , 50B: image forming means, 51Y, 51M, 51C, 51B: photosensitive drum, 52Y, 52M, 52C, 52B: charging device, 53Y, 53M, 53 53B: developing device, 54Y, 54M, 54C, 54B: cleaning device, 55Y, 55M, 55C, 55B: static elimination device, 60: transfer means, 61: transport belt, 61a: fiber sensor, 62Y, 62M, 62C, 62B ... transfer device 63 drive roller 63a belt motor 64 driven roller 65 paper feed guide device 66 cleaning device 70 fixing device 71 72 heat roller 71a 72a heater lamp 71b, 72b: rubber roller, 73: auxiliary roller, 74: spring, 75: encoder, 80: paper feeder, 82: paper feeder, 83a, 83b: paper feed roller, 84a, 84b: transport roller pair, 85 ... Aligning roller pair, 86: manual feeder, 87: pickup roller

Claims (14)

[Claims] 1. An image forming means for forming an image with a hot-melt developer on an image carrier, a transport means for transporting a transfer medium to a developer image formed on the image carrier, and the transport Transfer means for transferring the developer image onto the transfer medium conveyed by the means, first and second rollers arranged adjacent to the end of the conveyance means in the conveyance direction and rolled and contacted with each other; A driving unit for rotating the first roller at a variable speed; and a heating unit for heating at least one of the first and second rollers. The developer image is transferred by the transfer unit and transferred by the transfer unit. Fixing means for passing the transferred transfer medium between the first and second rollers to fuse the developer image and fix the transfer medium on the transfer medium; and detecting a transfer speed of the transfer medium by the transfer means. 1 Rotating by the detecting means and the driving means A second detecting means for detecting a peripheral speed of the first roller, and a driving means for controlling the driving means in accordance with a detection result by the first and second detecting means, so that the peripheral speed of the first roller is controlled by the transfer means. An image forming apparatus, comprising: control means for adjusting to the transport speed of the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the second detecting means detects a peripheral speed near an axial end of the first roller through which the transfer medium does not pass. 3. A plurality of photosensitive drums juxtaposed to each other, and an image for forming an image by a heat-fusible developer of each color on the surface of each photosensitive drum based on color-separated image signals. Forming means, and a transport belt capable of running in a state of being in contact with the surfaces of the plurality of photosensitive drums, and holding the transfer-receiving medium on the transport belt, and forming each color formed on each of the photosensitive drums Conveying means for conveying the developer images of the respective colors, transfer means for superimposing and superimposing the developer images of the respective colors on the transfer medium conveyed by the conveying means, and adjacent to the end of the conveying means in the conveying direction. First and second rollers arranged in a rolling contact with each other, driving means for rotating the first roller at a variable speed, and heating means for heating at least one of the first and second rollers. And the transport means The transfer medium, which has been conveyed and transferred with the developer image of each color polymerized by the transfer means, passes between the first and second rollers, and melts the developer image of each color polymerized and transferred to transfer the medium. Fixing means for fixing on the upper side; first detecting means for detecting a traveling speed of the transport belt; second detecting means for detecting a peripheral speed of a first roller rotated by the driving means; An image forming apparatus comprising: a control unit that controls the driving unit according to a detection result of the second detection unit, and adjusts a peripheral speed of the first roller to a traveling speed of the transport belt. 4. An image forming apparatus according to claim 3, wherein said second detecting means detects a peripheral speed near an axial end of said first roller through which a transfer medium does not pass. 5. An image forming means for forming an image with a hot-melt developer on an image carrier, a transport means for transporting a transfer medium to a developer image formed on the image carrier, and the transport Transfer means for transferring the developer image onto the transfer medium conveyed by the means, first and second rollers arranged adjacent to the end of the conveyance means in the conveyance direction and rolled and contacted with each other; A driving unit for rotating the first roller at a variable speed; and a heating unit for heating at least one of the first and second rollers. The developer image is transferred by the transfer unit and transferred by the transfer unit. Fixing means for passing the transferred transfer medium between the first and second rollers to fuse the developer image and fix the transfer medium on the transfer medium; and detecting a transfer speed of the transfer medium by the transfer means. 1 Rotating by the detecting means and the driving means An auxiliary roller which is disposed in rolling contact with the first roller to be set, a second detecting means for detecting the peripheral speed of the first roller by detecting a peripheral speed of the auxiliary roller, and the first and second detecting means An image forming apparatus comprising: a control unit configured to control the driving unit in accordance with a detection result obtained by the control unit and adjust a peripheral speed of the first roller to a transport speed of the medium to be transferred by the transport unit. 6. The image forming apparatus according to claim 5, wherein said auxiliary roller is formed by an aluminum roller having a roughened surface and a high friction coefficient. 7. The image forming apparatus according to claim 5, wherein the auxiliary roller is disposed so as to roll near an axial end of the first roller through which the transfer medium does not pass. 8. The image forming apparatus according to claim 5, wherein said second detecting means is an encoder attached to a rotation shaft of said auxiliary roller. 9. The control means controls the drive means by periodically detecting the peripheral speed of the first roller at predetermined time intervals via the second detection means. The image forming apparatus according to claim 5. 10. A plurality of photosensitive drums juxtaposed to each other, and an image for forming an image of a heat-fusible developer of each color on the surface of each photosensitive drum based on color-separated image signals. Forming means, and a transport belt capable of running in a state of being in contact with the surfaces of the plurality of photosensitive drums, and holding the transfer-receiving medium on the transport belt, and forming each color formed on each of the photosensitive drums Conveying means for conveying the developer images of the respective colors, transfer means for superimposing and superimposing the developer images of the respective colors on the transfer medium conveyed by the conveying means, and adjacent to the end of the conveying means in the conveying direction. First and second rollers arranged in a rolling contact with each other, driving means for rotating the first roller at a variable speed, and heating means for heating at least one of the first and second rollers. And the above carrier The transfer medium transported by the transfer unit and having the developer image of each color polymerized and transferred by the transfer means passes between the first and second rollers, and the developer image of each color polymerized and transferred is melted and transferred. Fixing means for fixing on a medium; first detecting means for detecting a traveling speed of the transport belt; an auxiliary roller which is disposed in rolling contact with a first roller rotated by the driving means; Second detecting means for detecting the peripheral speed of the first roller by detecting the peripheral speed; and controlling the driving means in accordance with the detection results by the first and second detecting means, thereby controlling the peripheral speed of the first roller. An image forming apparatus comprising: a control unit configured to match the traveling speed of the transport belt. 11. The image forming apparatus according to claim 10, wherein the auxiliary roller is formed by an aluminum roller having a roughened surface and a high friction coefficient. 12. The image forming apparatus according to claim 10, wherein the auxiliary roller is disposed so as to be in contact with an axial end of the first roller through which the transfer medium does not pass. 13. An image forming apparatus according to claim 10, wherein said second detecting means is an encoder attached to a rotation shaft of said auxiliary roller. 14. The control means detects the peripheral speed of the first roller periodically at a preset time interval via the second detection means, and controls the driving means. The image forming apparatus according to claim 10.