JP2002082569A - Image fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image fixing device capable of preventing unevenness in temperature distribution liable to be caused on a fixing belt to the utmost even with a simple configuration. SOLUTION: (1) The image fixing device has the fixing belt rotatably supported, a rotatable pressure roller provided on the outside of the fixing belt so as to be nearer to/away from the fixing belt, and a temperature controlling roller rotating while abutting on the pressure roller. (2) The image forming device is constituted so that the temperature controlling roller is made to abut on the rotatable pressure roller provided to contact with/separate from the fixing belt and the pressure roller is driven to be rotated by the driving mechanism of the image forming device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image fixing apparatus and an image forming apparatus for fixing a toner image formed by a copying machine, a printer or the like on a transfer material.

[0002]

2. Description of the Related Art A transfer material (hereinafter referred to as paper) carrying an unfixed toner image such that the toner image surface faces a surface of an endless fixing belt maintained at a predetermined temperature range.
While pressing the paper against the fixing belt with a pair of pressure rollers and the like arranged opposite to each other with the fixing belt interposed therebetween, through the heating and pressurization by the fixing belt and the pressure roller, An image fixing device configured to fix the toner image on paper (hereinafter simply referred to as a fixing device including the description of the present embodiment), and a copier and a printer having such a fixing device And the like are known.

[0003]

However, in a fixing device of the type using a fixing belt as described above,
A support roller for supporting the fixing belt is generally made of a metal material, and is configured by a cylindrical roller portion and a shaft penetrating therethrough, and the shaft is mounted on a frame via a bearing. It is structured to be attached to a predetermined position.

In the above structure, the heat applied to the fixing belt by the action of the heat source flows out through a roller portion such as a support roller or a pressure roller or a bearing portion, so that the surface temperature of the fixing belt is unnecessarily reduced. For example, when the fixing process must be performed immediately after the start of the fixing process, there is a problem that the fixing processing capability is reduced.

[0005] In order to suppress the above-mentioned heat outflow as much as possible, for example, it is conceivable that the support roller is formed of resin, or the cylindrical roller portion is formed of a column like an umbrella bone.

Further, a configuration in which a wire is stretched between left and right flanges integrally formed by a shaft and a suitable number of wires are stretched in the circumferential direction of the flange to form a cage roller is also disclosed in the present application. The inventor has considered.

Although such a configuration is useful for considerably reducing the problem of heat outflow of the conventional support roller, it has not been sufficiently satisfactory in a continuous fixing process.

Particularly, when the width of the sheet in the transport direction is smaller than the width of the fixing belt (for example, the fixing process is performed as compared with the case where the width of the fixing belt is slightly longer than the long side of the A4 size). When the sheet has a long side of A5 in the belt width direction), the heat on the fixing belt corresponding to the sheet width is taken by the sheet, but the taken heat is generated by a heat source having a heating area in the width direction of the fixing belt. By this control, the fixing temperature is maintained, but heat is accumulated at the widthwise end of the fixing belt not in contact with the sheet, so that heat is not taken away.

Therefore, after the continuous fixing process as described above,
For example, when A4 size paper is conveyed with its long side in the width direction of the fixing belt and heated and pressed, uneven gloss is generated at a boundary between heat and the like, and image quality is deteriorated. was there.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its main object an image fixing apparatus which has a simple structure and which can prevent non-uniformity of temperature distribution which tends to occur on a fixing belt as much as possible. To provide.

[0011]

The object of the present invention can be achieved by the following constitutions.

(1) A fixing belt rotatably supported, a rotatable pressure roller provided outside the fixing belt so as to be able to contact and separate from the fixing belt, An image fixing device comprising: a temperature control roller that rotates while rotating.

(2) A temperature control roller is brought into contact with a rotatable pressure roller provided so as to be able to contact and separate from the fixing belt, and the rotation of the pressure roller is controlled by a drive mechanism of the image forming apparatus. An image forming apparatus comprising:

[0014]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus comprising a color printer, and FIG. 2 is a schematic diagram of a fixing device partially enlarged.

Hereinafter, FIG. 1 will be mainly used for the description. In FIG. 1, reference numeral 10 denotes a photosensitive drum (hereinafter, simply referred to as a drum) as an image carrier (image forming body); 11, a scorotron charger as a charging unit for each color; and 12, an image writing unit for each color. An exposure optical system, 13 is a developing device as a developing unit for each color, and 14 is a transfer belt.

The drum 10 is formed, for example, by forming a transparent conductive layer, an a-Si layer, an organic photosensitive layer (OPC), etc. on the outer periphery of a cylindrical base formed of a transparent member such as optical glass or transparent acrylic resin. Photosensitive layer (also called photoconductive layer)
And rotated clockwise as indicated by the arrow in FIG. 1 with the conductive layer grounded.

The scorotron charger 11, the exposure optical system 12, and the developing device 13 are used as a set to form a yellow (Y), magenta (M), cyan (C) and black (K) image processing means ( Hereafter, four sets are provided as image forming means), and are arranged in the rotation direction of the drum 10 in the order of Y, M, C, and K.

Since the mechanical structure of the four sets of image forming means is basically the same, the details thereof will be covered below by describing the structure of one set.

The scorotron charger 11 has a control grid maintained at a predetermined potential and a discharge electrode 11a composed of, for example, a sawtooth electrode.
The toner is attached to face the photosensitive layer of No. 0 and charged (corresponding to negative charge in the present embodiment) by corona discharge having the same polarity as the toner, and a uniform potential is applied to the surface of the drum 10.

The exposure optical system 12 is fixedly disposed inside the drum 10 so as to be located on the downstream side in the rotation direction of the drum 10 with respect to the scorotron charger 11 described above.

The exposure optical system 12 is a light-emitting element for emitting image exposure light arranged in the main scanning direction in parallel with the drum axis.
A linear exposure element 12a in which a plurality of EDs (light emitting diodes) are arranged in an array, and a light converging light transmitting body (trade name: Selfoc lens array, drawing out reference numeral 12 in the figure) as an imaging element This is an exposure unit composed of a portion where a line is projected) and a lens holder (not shown), and is attached to the holding member 120.

In addition to the exposure optical system 12 for each color, the transfer simultaneous exposure device 12
d and the uniform exposure device 12e are mounted and integrally housed inside the substrate of the drum 10.

The exposure optical system 12 performs image exposure of the photosensitive layer of the drum 10 from the back side in accordance with image data read by a separate image reading device and stored in a memory, and forms an electrostatic latent image on the drum 10. Form.

The emission wavelength of the exposure element is usually Y, M,
A toner having a high transmittance in the range of 780 to 900 nm for the C toner is used. However, in this embodiment, since the image is exposed from the back surface, the toner does not have sufficient transmittance for the color toner. 400-780 shorter than this
nm wavelength.

The developing unit 13 is formed of a cylindrical non-magnetic stainless steel or aluminum material which keeps a predetermined gap with respect to the peripheral surface of the drum 10 and rotates in the forward direction with respect to the rotation direction of the drum 10. It has a developing sleeve 131 and a developing casing 138, and a one-component or two-component developer of yellow (Y), magenta (M), cyan (C), and black (K) is provided inside the developing casing 138, respectively. Accommodating.

The developing device 13 is kept in non-contact with the drum 10 with a predetermined gap.
By applying a developing bias in which a DC voltage and an AC voltage are superimposed on No. 1, non-contact reversal development is performed, and a toner image is formed on the drum 10.

14a and 14b are the transfer belt 14
The transfer belt 14a receives power from a drive source (not shown) and rotates the transfer belt in the direction of the arrow.

Reference numerals 15 and 16 denote a transfer unit and a static eliminator arranged opposite to the drum 10 with the transfer belt 14 interposed therebetween; 17, an AC static eliminator for eliminating the charge of the drum 10 after the transfer step; A cleaning device that cleans the drum surface after the charge is removed;
80.

Reference numeral 20 denotes a cassette containing paper P on which the toner image formed on the drum 10 is transferred,
Reference numeral 5 denotes a paper feed roller.

On the moving path of the paper P, there are provided a pair of conveying rollers R1 to R6, a fixing device 30 including a transfer belt 14, and a fixing belt 300 driven at the same linear speed as the moving speed of the paper P. is there.

Reference numeral 44 denotes an AC static eliminator for separating paper, which is disposed to face the roller 14a with the transfer belt 14 interposed therebetween.

The fixing device 30 includes a housing (outer frame) 303 for shielding a member (means) described later from the outside, and an endless fixing belt 30 formed by applying silicon rubber to a metal base.
0, a first support roller 310 and a second support roller 320 that rotatably support the fixing belt, and a rotatable and position fixing member provided inside the fixing belt and on the first support roller 310 side. A pressure roller (hereinafter, referred to as a first pressure roller) 330, a heating source H including a halogen heater provided between the first pressure roller 330 and the second support roller 320, and the heating source H A reflecting plate 350 provided between the fixing belt 300 and the second support roller 320;
A pressure roller disposed opposite to the first pressure roller and rotatable and capable of moving toward and away from the fixing belt by moving vertically. 340), and a rotatable rotatable metal material having good thermal conductivity such as aluminum or aluminum alloy provided so as to always contact (press) the second pressure roller 340. It is composed of a temperature control roller 345 and the like.

Further, when the heat pipe is used as a temperature control roller, higher heat conductivity can be obtained.

The surface of the temperature controlling roller 345 is provided with a thin layer of a releasable material such as fluororesin or a thin tube made of PFA (perfluoroalkoxy) resin to prevent contamination. Is preferable.

In the above configuration, the second support roller 3
Reference numeral 20 is connected to a driving system provided on the image forming apparatus main body side, and functions as a driving roller of the fixing belt 300.

The first pressure roller 330 and the second pressure roller 340 are also connected to an appropriate driving mechanism provided on the image forming apparatus main body side, and are used not only during the fixing process but also during the non-fixing process (idling). ), The motive power is transmitted to rotate.

As shown in FIG. 2, which is a partially enlarged view, the fixing belt 300 is not tensioned during the non-fixing process, but is stretched (hanged) on the first support roller 310 and the second support roller 320 with a slack. In this state, the first pressure roller 330 is fixed to the fixing belt 3.
00 is in contact with the portion forming the upper part of the loop
The pressure roller 340 is located at a position separated from the fixing belt 300.

In the first pressure roller 330 having the above-described structure, the surface layer has a low thermal conductivity and a low heat capacity, and has a surface temperature substantially equal to the surface temperature of the fixing belt 300 during the fixing process.

The second pressure roller 340 is controlled, for example, by an appropriate control unit S for controlling the sequence of the entire apparatus. At the time of the fixing process, the second pressing roller 340 is moved from the position shown in FIG. It is configured to move to a position where it is pressed against the first pressure roller 330.

The position moving mechanism of the second pressure roller 340 can use a known technique. The relationship between the fixing belt and the pressure roller during the fixing process is shown in the schematic diagram of FIG.

Reference numeral 50 denotes an oil application unit for preventing toner from adhering. 500 is a web impregnated with oil, 510 is a web original roll, 520 is a take-up core, and 530 is a vertical direction. The pressing roller is provided so as to be movable on the surface.

The oil applying means 50 also functions as a cleaning means for the surface of the fixing belt as described later.

The pressing roller 530 is disposed to face the first pressure roller 330 via the fixing belt 300 and the web 500, and contacts the web 500 with the fixing belt 300 during non-fixing processing including preheating. The fixing position is set to a release position where the web is not brought into contact with the fixing belt, and comes to an operation position where the web contacts the fixing belt during the fixing process.

The web 500 is intermittently driven to apply an appropriate amount of oil applied onto the fixing belt 300 and to remove dust or toner powder adhering to the fixing belt and carry it away therefrom. It is designed to be wound around the winding core 520.

The web 500 may be wound by continuous driving instead of the intermittent driving described above, and the winding amount (synonymous with the moving amount of the web per unit time) is appropriately determined in consideration of various factors. be able to.

Although the winding direction (moving direction) in the present embodiment is opposite to the rotating direction of the fixing belt at the point of contact with the fixing belt, a predetermined function can be obtained. In this case, the direction may be forward.

The first support roller 310 described above is
As shown in FIG. 4, a wire is stretched between left and right support members (hereinafter, referred to as flanges) so as to be concentric with the center of the rotation axis, and adjacent wires are stretched so as to be substantially parallel to each other. It constitutes a shape.

FIG. 4 is a conceptual diagram for explaining the structure of the first support roller, particularly, the structure of extending a wire.

In the figure, 311 is a left flange, 31
Reference numeral 2 denotes a right flange, J1 denotes a shaft integrally formed with the flange to position the left flange 311 at a predetermined position of a frame (described later), and J2 denotes a right flange to perform the same function as the shaft J1. This is an integrated shaft.

As is apparent from the figure, the left and right flanges 31
There is no shaft between 1 and 312 for integrally configuring the two.

W is a wire, left and right flanges 311, 3
12 and extending substantially parallel to the center of the flanges at predetermined intervals on a concentric circle.

In the embodiment, a number of small holes 315 and 317 are formed at equal intervals in the circumferential direction of a circle having a predetermined diameter at the center of the shaft. For example, one end of a wire is screwed on the left flange 311. After having been fixed with the like, the other end is passed through one of the small holes, and passed through one of the small holes of the right flange 312,
Next, after turning back through the adjacent small hole, the work of passing through the small hole of the left flange at the same angle (meaning that the position of the small hole corresponds) is repeated, and finally the other end of the wire is connected. By fixing on one of the flanges with a screw or the like, a cage-shaped first support roller can be obtained when assembly is completed.

In the above embodiment, the left and right flanges are integrated by a wire, and are handled independently up to that time. Therefore, when the wire is stretched, an appropriate jig is used to reduce the distance between the two flanges. It is essential to work as specified and work in a fixed arrangement.

When the first support roller is incorporated into the frame of the fixing device, the position of the flange is controlled so that a predetermined tension is applied, or the tension is applied by a spring or the like.

As a material constituting the wire W, a metal wire such as a steel wire can provide a predetermined effect, but a resin fiber material having high strength, high heat resistance, low heat conductivity, low specific heat, and low elongation is used. If used, even higher effects can be obtained, for example, aromatic polyamide fibers are preferred.

In this embodiment, the circumference is 314 m.
m, width 320 mm, tension 20 to 30 N (Newton) or less, using a fixing belt 300 of 400 denier aromatic polyamide fiber, the number of bridges (the number of wires in the circumferential direction of the flange) 24 wires W 20
By fixing with a tension of 30N, the diameter 30
The first support roller 310 corresponding to mm was constructed.

It is appropriate that the number of the wires W to be installed is 8 to 30, the thickness of the wires W is 100 to 1000 denier, and the tension of the wires W is 10 to 50 N (Newton).

As described above, one wire W may be reciprocated a required number of times and stretched, or a plurality of wires W may be individually wound on the flange member 31.
It is also possible to extend between 1 and 312, and the degree of freedom of design is wide.

The structure of the second support roller is changed to the first support roller 3.
In the case of the same configuration as 10, it is preferable to connect (connect) both shafts integral with the left and right flanges of the second support roller to the drive system on the apparatus side. Twisting can be prevented and it is sufficient to input a drive to only one flange.

When the second support roller is a roller having a shaft as in the prior art, the amount of heat radiation is large, but the amount of heat radiation from the first support roller 310 is kept small, and more stable. Belt drive is realized.

Further, the driving force may be applied to all of the left and right flanges of the first support roller 310 and the second support roller 320 from the apparatus side. One or both of the same sides may be connected by a timing belt or the like.

Returning to FIG. 1, a conventionally known method can be used to control the energization of the heating source H to maintain the surface temperature of the fixing belt 300 within a predetermined temperature range.

In the drawing, G is a guide plate, and 46 is a separation claw, which has a function of surely separating the sheet P after transfer transferred integrally with the transfer belt 14, and a transfer belt on the roller 14a. The tip is positioned close to the 14 surfaces.

The image forming process in the image forming apparatus having the above configuration is as follows.

After the warming-up is completed, a drum drive motor (not shown) is started by the start of image formation, the drum 10 is rotated clockwise as indicated by an arrow in FIG. 1, and at the same time, the yellow (Y) scorotron charger 11 is operated. Thus, a predetermined potential is applied to the drum 10.

Subsequently, the image writing by the first color signal, ie, the electric signal corresponding to the Y image data is started via the Y exposure optical system 12, and the Y image of the original image is formed on the surface of the drum 10. A corresponding electrostatic latent image is formed.

The electrostatic latent image is reversely developed in a non-contact state by a Y developing unit 13, and a yellow (Y) toner image is formed on the drum 10.

Next, a potential is applied to the drum 10 from above the Y toner image by the charging action of the magenta (M) scorotron charger 11, and the second color signal, that is, the M image is applied by the M exposure optical system 12. An electrostatic latent image corresponding to the M image is formed by writing an image using an electric signal corresponding to the data, and is formed on the yellow (Y) toner image by non-contact reversal development by the M developing unit 13. A magenta (M) toner image is formed to overlap.

By the same process, the cyan (C) toner image corresponding to the third color signal is superimposed by the cyan (C) scorotron charger 11, the exposure optical system 12 of C, and the developing device 13 of C. The black (K) toner image corresponding to the fourth color signal is sequentially superimposed thereon by a black (K) scorotron charger 11, a K exposure optical system 12, and a K developing device 13. A superposed color toner image of four colors of yellow (Y), magenta (M), cyan (C) and black (K) is formed on the peripheral surface within one rotation of the photosensitive drum 10. .

These Y, M, C and K exposure optical systems 1
2 for writing an image on the photosensitive layer of the drum 10
It is performed from the inside of the drum 10 through the above-mentioned translucent substrate.

Therefore, the writing of the images corresponding to the second, third and fourth color signals is performed without any influence from the previously formed toner image, and corresponds to the first color signal. It is possible to form an electrostatic latent image equivalent to an image.

The superimposed color toner image formed on the drum 10 as the image carrier by the above-described image forming process is transferred by the transfer device 15 in the transfer area.
The images are collectively transferred onto the sheet P conveyed at a proper timing.

At this time, it is preferable to perform uniform exposure by energizing the simultaneous transfer exposure device 12d provided inside the drum 10 so that good transfer is performed.

After the transfer process is completed, the toner remaining on the peripheral surface of the drum 10 is subjected to a charge removing operation by the AC charge remover 17 and then cleaned by a cleaning device 18, whereby the surface of the drum 10 is moved to the next position. Provided for image formation.

In the embodiment, after cleaning and before the next charging, the uniform exposure device 12e using, for example, a light emitting diode is operated to eliminate the history of the preceding image formation on the drum surface.

On the other hand, the sheet P on which the color toner image has been transferred
After being separated from the drum 10 by the action of the static eliminator 16, the transfer belt 1 is conveyed by the transfer belt 14, and the transfer belt 1 is separated by the static elimination action of the AC static eliminator 44 and the separation claw 46.
4 and then guided to the fixing device 30.

Prior to the fixing process, the fixing belt 30
0 is maintained at a predetermined temperature for fixing the toner image, and the second pressure roller 340 is connected to the first pressure roller 330 via the fixing belt 300 as shown in FIG. As described above, the toner image surface side of the sheet P comes into a pressure contact state with the surface of the fixing belt 300, and the toner (image) receives a heating action on the sheet P as described above. The sheets are sequentially fixed and discharged.

With the above configuration, for example, even if the paper P having a size smaller than the width of the fixing belt is used and the fixing process is continuously performed, the both ends of the fixing belt 300 which do not come into contact with the paper are not contacted. Since heat is taken by the temperature control roller via both ends of the second pressure roller 340, the temperature of the fixing belt is maintained in a certain range regardless of the presence or absence of the sheet.

The heat at both ends of the fixing belt flows out to the temperature control roller 345 via the second pressure roller 340, and is transported in the axial direction by the large heat conduction of the temperature control roller. The surface temperature of the second pressure roller 340 in contact with the fixing roller is smoothed, while the second pressure roller 340 is in contact with the fixing belt 300 and the fixing belt in contact with the paper. Since the upper region is supplied with heat from the second pressure roller, the surface temperature in the width direction of the fixing belt can be suitably adjusted.

As a result, the amount of heat supplied from the heating source H for maintaining the temperature of the fixing belt 300 and supplying heat to the paper can be reduced as compared with an apparatus having no configuration as described above. Therefore, it is possible to easily prevent an excessive rise in temperature at the belt end.

When dust such as toner adheres to the fixing belt 300, the dust is wiped off by the web 500 constituting the oil applying means 50.

Incidentally, the structure of the fixing belt 300 will be described more specifically.
It is composed of three layers: a metal substrate of up to 80 μm such as nickel or stainless steel, an outer layer and an inner layer.

An outer layer formed by applying a silicone resin (rubber) having heat resistance and releasability to toner is formed on the outer peripheral surface of the metal substrate. The surface has an inner layer formed by applying a silicone resin in which carbon is dispersed.

That is, the inner layer of the fixing belt 300 is coated with a silicone resin in which carbon, which is an infrared absorbing material, is dispersed, has a high absorption of irradiation light, and is heated by a heating source H such as a halogen heater. The temperature can be raised to a predetermined temperature (for example, 190 ° C.) in a short time.

The silicone resin forming the inner layer is sufficiently thin (10 to 100 μm or less) and does not peel off due to bending of the fixing belt 300 during rotation.

Further, the fixing belt 300 is provided between the first support roller 310 and the second support roller 320 by 500 N.
/ M or less, more preferably 200 N / m or less, but may be loosened with zero tension.

Although the embodiment has been described above, the present invention is not limited to the embodiment, but includes a configuration that does not depart from the technical idea thereof.

[0089]

According to the present invention, even when a large number of transfer materials having a size smaller than the width of the fixing belt are continuously processed, the heat of the fixing belt end which does not contact the paper of the fixing belt flows out with a simple structure. Then, the fixing is carried out (the heat is fed back to the fixing belt again as a heat cycle), whereby a stable fixing process can be performed.

Further, the durability of the fixing belt can be expected to be high.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus including a color printer.

FIG. 2 is a schematic view of the fixing device shown in a partially enlarged manner.

FIG. 3 is a schematic diagram illustrating a relationship between a fixing belt and a pressure roller during a fixing process.

FIG. 4 is a conceptual diagram for explaining a configuration of a first support roller, particularly, a configuration of extending a wire.

DESCRIPTION OF SYMBOLS 30 Image fixing device 300 Fixing belt 310 First support roller 320 Second support roller 340 Pressure roller (second pressure roller) 345 Temperature control roller 50 Oil applying means 500 Web

Claims (9)

[Claims] A fixing belt rotatably supported; a rotatable pressure roller provided outside the fixing belt so as to be able to contact and separate from the fixing belt; An image fixing device, comprising: a rotating temperature control roller. 2. The image fixing device according to claim 1, wherein the pressure roller has a rubber layer. 3. The image fixing device according to claim 1, wherein the temperature control roller is a metal roller. 4. The temperature control roller is made of aluminum or an aluminum alloy.
3. The image fixing device according to claim 1. 5. The image fixing device according to claim 1, wherein the temperature control roller is a heat pipe. 6. The temperature control roller according to claim 1, wherein a surface of the roller is coated with a release layer.
An image fixing device according to any one of claims 1 to 5. 7. The image fixing device according to claim 6, wherein the release layer is made of a fluororesin. 8. A temperature control roller is brought into contact with a rotatable pressure roller provided so as to be able to contact and separate from the fixing belt, and the pressure roller is driven to rotate by a drive mechanism of the image forming apparatus. An image forming apparatus characterized by having such a configuration. 9. The image forming apparatus according to claim 8, wherein the rotation of the pressure roller is continued even in an idling state separated from the fixing belt.