JP2002174978A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device for a color electrophotographic device capable of realizing a high-quality image free from irregular fixation by preventing the deformation of silicone rubber from occurring even when a fixing machine constituted of a fixing roller and a pressure roller covered with the silicone rubber is left as it is for a long time. SOLUTION: A pressuring force holding member whose width is larger than a gap between the core bars of both of the fixing roller and the pressure roller in a non-heating state and smaller than the gap between both of them in a heating state is provided between a core bar part not covered with the silicone rubber at the end of the fixing roller and that at the end of the pressure roller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus provided with a fixing device for pressing and compressing a recording medium such as paper on which toner images have been weighed together.

[0002]

2. Description of the Related Art There are many known systems for recording a color image in accordance with image information from a computer or the like.
Among these recording methods, an electrophotographic method capable of recording a high-quality color image at a relatively high speed is known to be effective.

In the color image recording using electrophotography, yellow, magenta, cyan, and black toner images are formed on a recording medium as a photoreceptor, and the formed toner images are recorded on a recording medium such as paper. After superimposing and synthesizing,
The image is fixed on the recording medium by passing the recording medium through a fixing device including a fixing roller having a built-in heater and a pressing roller that presses against the fixing roller to form a color image.

The fixing device of such a color electrophotographic apparatus comprises a fixing roller and a pressure roller, and an elastic roller in which a hollow core is covered with an elastic material such as silicone rubber. The nip is secured by the contact, and a sufficient amount of heat is applied to the toner layered in the nip portion to fix the toner.

[0005]

However, in the fixing device using the elastic roller as described above, if the rollers are left for a long time in a state where the rollers are pressed, the silicone rubber is formed at the contact portion of the roller. However, there is a problem that sufficient fixing performance cannot be obtained because the shape cannot be restored to the original shape even when starting is started. Further, the deformation of the silicone rubber recovers with the passage of time, but it takes time to recover, which is not practical.

As described above, when the fixing device is left for a long time, it is most desirable that the fixing roller and the pressure roller do not come into contact with each other. However, in the prior arts of Japanese Utility Model Laid-Open No. 5-84867 and Japanese Patent Application Laid-Open No. 11-14432, a pressing force between both rollers is reduced by providing a lever for releasing pressure between the fixing roller and the pressing roller. It is described that the silicone rubber is released to prevent deformation of the silicone rubber. However, in these prior arts, when a device such as a printer or a copying machine is left for a long time, the user intentionally releases the pressing force. This means that the user must always be aware of the neglected state for a long time, which is practically impossible.

An object of the present invention is to provide a member for holding a pressing force between a fixing roller and a pressing roller, thereby preventing deformation of silicone rubber even when a device such as a printer or a copying machine is left for a long time. An object of the present invention is to provide a fixing device of an electrophotographic apparatus capable of obtaining a quality image.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an intermediate transfer member on which a toner image on a photosensitive member is transferred, and a recording medium on which the toner image on the intermediate transfer member is transferred by a fixing roller and a pressure roller. The fixing roller and the pressure roller are formed by covering a metal shaft with rubber, and the metal shafts of both rollers are provided. This is achieved by providing a pressing force holding member between the bodies.

Further, the width of the pressing force holding member is achieved by making the width of the pressing roller larger than the gap between the metal shaft portions in a state where the both rollers are not heated.

Further, the width of the pressing force holding member is achieved by making the width of the pressing roller smaller than the gap between the metal shaft portions when both rollers are heated.

The pressing force holding member is achieved by being rotatably provided on the fixing roller.

Further, by the rotation of the pressing force holding member,
The pressing roller is moved in the direction opposite to the pressing direction, and the pressing force holding member is a member that releases the contact between the fixing roller and the pressing roller.

[0013] Further, the linear expansion coefficient of the pressing force holding member is achieved by being smaller than the linear expansion coefficient of the silicone rubber.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a color laser printer 1 provided with the present invention. In FIG. 1, 1 is
It is a color laser printer main body. Reference numeral 21 denotes a driven roller that also serves as a driving roller 22 and a tension roller that applies tension to the belt. Reference numeral 2 denotes a photosensitive belt that is stretched in the vertical direction by the driven roller 21 and rotates at a constant speed in the direction of the arrow. Reference numeral 3 denotes an intermediate transfer member that is arranged in contact with the photosensitive belt 2. Reference numeral 4 denotes a charger for uniformly charging the surface of the photoreceptor belt 2. Reference numeral 5 denotes an exposure device for exposing the uniformly charged surface of the photoreceptor belt 2 to form an electrostatic latent image on the surface.

Reference numerals 61, 62, 63, and 64 denote four developing machines which are arranged in contact with the horizontal surface of the photoreceptor belt 2 to develop an electrostatic latent image to form a toner image. Reference numeral 10 denotes a cassette that stores a transfer material such as paper. A paper feed roller 11 feeds a transfer material such as paper from the cassette 10. Reference numeral 12 denotes a registration roller for correcting the posture of a transfer material such as a sheet fed from the cassette 10. Reference numeral 13 denotes a transfer roller for transferring the toner image to a transfer material such as paper.
Numeral 14 denotes a fixing device which comprises a pair of elastic rollers and fixes a toner image transferred onto a transfer material such as paper. Reference numeral 17 denotes a sheet discharge unit that stores a transfer material such as a sheet fixed and discharged outside the apparatus. Reference numeral 8 denotes a blade for removing toner remaining on the surface of the photosensitive belt 2 after the transfer. Reference numeral 9 denotes an erase lamp for removing charges remaining on the surface of the photoreceptor belt 2 after transfer of the toner image. Fifteen
Is a cleaner for removing toner remaining on the surface of the intermediate transfer member 3. Reference numeral 16 denotes sheets stacked in the cassette 10.

Next, the operation of forming a color image by the present apparatus will be described. First, after the power is turned on, when a print signal is sent from an information processing apparatus (not shown) to the printer 1 in a print standby state, the exposure device 5 emits a laser beam corresponding to the toner image in accordance with the signal. 4 irradiates the photoreceptor belt 2 uniformly charged, and an electrostatic latent image is formed on the photoreceptor belt 2. Next, an electrostatic latent image corresponding to the yellow toner image is formed on the photoreceptor belt 2 by the exposure device 2, and is developed by the yellow developing device 61 to form a toner image. Here, 61 is a developing machine using yellow toner, 62 is a developing machine using magenta toner, 63 is a developing machine using cyan toner, and 64 is a black toner. The developing function is given or eliminated by controlling the bias voltage to each developing machine. The toner image formed on the photoreceptor belt 2 is transferred to the surface of the intermediate transfer member 3 at a contact portion with the intermediate transfer member 3, and is held on the surface.

On the other hand, on the photoreceptor belt 2 after the transfer of the toner image, the toner remaining without being transferred is removed by a blade 8, and then the charge remaining on the surface of the photoreceptor belt 2 is erased.
It is designed to be removed by a slump 9. After the process of returning the surface of the photoreceptor belt 2 to the initial state is completed, a magenta toner image of the next color is similarly formed on the surface of the photoreceptor belt 2 and held on the surface of the intermediate transfer member 3. The toner image is superimposed on the yellow toner image and transferred to the intermediate transfer member 3. The same process is repeated for the cyan and black colors, so that the four color toner images are superimposed on the intermediate transfer member 3 and simultaneously held on the surface.

In order to transfer the four-color toner images formed on the surface of the intermediate transfer member 3 onto the paper 16,
The sheet feed roller 11 is rotated to separate the sheets 16 stored in the cassette 10 one by one, conveyed to the registration roller 12, corrected for skew of the sheet 16, and then stopped.

Next, the rotation of the registration roller 12 is started at a timing that matches the toner image on the intermediate transfer member 3. At the same time that the leading edge of the conveyed paper comes into contact with the intermediate transfer member 3, the transfer roller 13 is pressed from the back of the paper,
The four-color toner images on the surface of the intermediate transfer member 3 are formed on a sheet 16 at a time.
Electrostatic transfer on top. The four-color toner images formed on the paper 16 in this manner are heated and pressed by the fixing device 14.
Then, the paper is fixed on the paper 16 by being passed between the printer 1 and the paper 16 and is discharged to the paper discharge unit 17 on the upper part of the printer 1.

FIG. 2 is a diagram showing details of the fixing portion.
In FIG. 2, the fixing machine includes a fixing roller 143 having a core metal 141 coated with a silicone rubber 142 and a pressing roller 146 having a core metal 144 coated with a silicone rubber 145. It receives a pressing force from 31 and is placed in pressure contact. At this time, the nip 1 is formed at the contact portion of both rollers by the deformation of the silicone rubber due to pressure
47 are formed. Paper 16 with unfixed toner image
Passes through the nip 147, the toner image is fixed on the sheet under the heat and pressure. When the image formation is completed, the fixing roller 143 and the pressure roller 146 stop rotating.

When the printer body 1 does not perform printing for a long time, the function of stopping the heating of the fixing device in order to reduce power consumption and performing heating again when the next print command comes is provided. Provided. In such a case, the fixing roller 143 and the pressure roller 146 stand by while being pressed. Further, even when the power of the printer body is turned off, the fixing roller 143 and the pressure roller 146 are left in a state of being pressed.

As described above, when the silicone rubber is left for a long time in a pressurized state, the silicone rubber remains deformed, and it takes a long time until the deformation returns to the original state. Further, if fixing is performed while the silicone rubber remains deformed, unevenness in gloss and the like occurs in the image corresponding to the deformed portion, causing a problem of deteriorating the image quality.

FIG. 3 is a partial perspective view of the fixing device viewed from an oblique direction. Note that the same reference numerals as those in FIG. 2 denote the same items, and a description thereof will be omitted. In FIG. 3, when the fixing device is left for a long time, the pressing force is changed to the silicone rubber 142,
The pressing force is maintained between the core metal part 141a at the end of the fixing roller 143 not coated with the silicone rubber and the core metal part 145a at the end of the pressure roller 146 so as not to be applied to the fixing roller 143. A member 20 is provided. The pressing force holding member 20 is a fixing roller,
And at both ends of the pressure roller.

FIG. 4 is a view showing the operation of the pressing force holding member 20 in a non-heated state. In FIG. 4, the pressing force holding member 20 is disposed with a width of L2 between the core end 141a of the fixing roller and the core end 145a of the pressure roller. Here, when the pressing force holding member 20 is not provided in the non-heating state, the two metal core ends 141a and 145a
In this case, the width L2 of the pressing force holding member 20 is set to be larger than L1.

Therefore, when left unheated,
For example, when the printer enters the low power consumption mode without a print command for a long time, or when the power supply of the printer body is turned off, the cores 141a and 145a and the silicone rubber 1
Since the rollers 42 and 144 contract, a gap of δ1 is formed between the fixing roller 143 and the pressure roller 146. For this reason, although the pressing force from the pressing lever 30 is applied in a direction to narrow the gap between the two rollers, the pressing force is blocked by the pressing force holding member 20, and the two rollers maintain the non-contact state. That is, the pressing force holding member 20 regulates the pressing force from the pressing lever 30 when left unheated, and prevents the fixing roller 143 from contacting the pressing roller 146. Therefore, the pressing force holding member 20 needs to be made of a material having a lower heat shrinkage than silicon rubber and a cored bar. As a result, even if the fixing device is left unheated for a long time, the silicone rubber does not deform.

FIG. 6 is a view showing the operation of the pressing force holding member 20 in the heating state. In FIG. 6, the fixing roller 143 and the pressure roller 146 have larger outer diameters than the non-heated state due to thermal expansion due to heating.
As the temperature rises, both rollers come into contact. Here, the fixing roller 143 has a back surface at the end of the cored bar 141 a to receive a pressing force from the pressing roller 146.
Since the roller is thermally expanded and the outer diameter increases, the pressing roller 146 pushes the pressing lever 30 to spread and retreats from the fixing roller 143. Therefore, when the fixing roller 143 is heated to a predetermined temperature,
Fixing roller core end 141a and pressure roller core end 14
The distance L3 from the gap 5a is larger than the distance L1 in the non-heated state. At this time, if the linear expansion coefficient of the pressing force holding member 20 is smaller than the linear expansion coefficients of the silicone rubber and the core metal constituting the fixing roller and the pressing roller, the width L2 of the pressing force holding member 20 after thermal expansion is reduced. The interval L3 between the core portions of both roller ends is larger than '(> L2), and a gap of δ2 is formed between the pressing force holding member 20 and the core portions of both roller ends. In such a state, the fixing roller 1
A predetermined pressing force received from the pressure lever 30 is applied between the pressure roller 43 and the pressure roller 146 to form a nip.

Further, as shown in FIG.
When the fixing roller 2 is provided at the fixing roller core end 141a in a rotatable shape, the interval between the fixing roller core end 141a and the pressure roller core end 145a can always be stably maintained. Further, in order to remove a jam or the like generated during printing, as shown in FIG.
By providing a handle 32a on the pressing force holding member 32 rotatably provided on the handle 41a, as shown in FIG.
2a is rotated in the direction of the arrow, and the pressing roller 146 is retracted from the fixing roller 143 at a portion having a width L4 larger than the interval L3 between both roller core ends of the pressing force holding member 32,
It is also possible to operate as a lever for releasing the pressing force between the fixing roller 143 and the pressure roller 146.

According to the above configuration, it is possible to prevent the pressing force from acting between the pressing roller and the pressing roller in the non-heating state, so that the silicone rubber remains deformed even when left in the non-heating state for a long time. Can be prevented. Further, by setting the linear expansion coefficient of the pressing force holding member to be smaller than that of the silicone rubber or the core metal, the pressing force can act on both in the heating state, so that a high quality fixed image can be obtained. Becomes

In other words, the width of the non-silicone rubber core at the end of the fixing roller and the width of the non-silicone rubber core at the end of the pressure roller are not heated. And a pressure holding member that is larger than the gap between the cores of both rollers and smaller than the gap between the cores of both rollers in the heated state.

Thus, according to the present invention, in a non-heated state such as when the apparatus is left unattended, the pressing force holding member receives the pressing force between the fixing roller and the pressing roller at the cored bar. No pressure will be applied,
Deformation of the silicone rubber can be prevented without intentionally releasing the pressing force.

On the other hand, when printing an image, the fixing roller and the pressure roller are in a heated state, the respective rollers thermally expand to increase the outer diameter, and the gap between the cores of the rollers is a pressing force holding member. Therefore, sufficient pressure acts on the silicone rubber portion to enable fixing. This makes it possible to provide an electrophotographic apparatus that has realized a high-quality image.

[0032]

According to the present invention, it is possible to provide an electrophotographic apparatus capable of preventing deformation of silicone rubber even when an apparatus such as a printer or a copying machine is left for a long time and obtaining a high quality image.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a general color laser printer.

FIG. 2 is a schematic configuration diagram of a general fixing device.

FIG. 3 is a partial perspective view of a fixing device provided with the present invention.

FIG. 4 is a schematic configuration diagram of a fixing device provided with the present invention.

FIG. 5 is a schematic diagram illustrating a contact state between a fixing roller and a pressure roller.

FIG. 6 is a schematic diagram of a fixing device provided with the present invention.

FIG. 7 is a partial perspective view of a fixing device provided with the present invention.

FIG. 8 is a schematic configuration diagram of a fixing device provided with the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Color laser printer, 2 ... Photoreceptor belt, 21 ...
Driven roller, 22 drive roller, 3 intermediate transfer belt, 4 charger, 5 optical device, 61 yellow developing machine, 62 magenta developing machine, 63 cyan developing machine, 64 ... Black developing machine, 8 ... Blade, 9 ...
Erase lamp, 10 paper cassette, 11 paper feed roller, 12 registration roller, 13 transfer roller, 14
Fixing machine, 15 cleaner, 16 paper, 17 discharge section,
Reference Signs List 20: pressure holding member, 30: pressure lever, 31: pressure spring, 141: core of fixing roller, 141a: end of core of fixing roller, 142: silicone rubber of fixing roller, 14
3: fixing roller, 144: silicone rubber of pressure roller, 145: pressure roller core, 145a: pressure roller core end, 146: pressure roller, 147: nip.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshio Ogiso 502 Kandate-cho, Tsuchiura-shi, Ibaraki Pref.Mechanical Research Laboratory, Inc. Within the Machinery Research Laboratory (72) Inventor Katsuyoshi Onose 1-1-1, Higashitaga-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi Taga Electronics Co., Ltd. FA03 GA02 GA54 HA53

Claims (6)

[Claims] An intermediate transfer member to which a toner image on a photosensitive member is transferred and a recording medium on which the toner image on the intermediate transfer member has been transferred are heated by passing between a fixing roller and a pressure roller. The fixing roller and the pressure roller are formed by coating a metal shaft with rubber, and a pressing force holding member is provided between the metal shafts of the two rollers. An electrophotographic apparatus characterized by being provided. 2. The electrophotographic apparatus according to claim 1, wherein the width of the pressing force holding member is larger than the gap between the metal shaft portions when the rollers are not heated. 3. The electrophotographic apparatus according to claim 1, wherein a width of said pressing force holding member is smaller than a gap between said metal shaft portions when said rollers are heated. 4. An electrophotographic apparatus according to claim 1, wherein said pressing force holding member is rotatably provided on said fixing roller. 5. The pressurizing roller is moved in a direction opposite to the pressurizing direction by the rotation of the pressurizing force retaining member, and the pressurizing force retaining member releases the contact between the fixing roller and the pressurizing roller. The electrophotographic apparatus according to claim 4, wherein the electrophotographic apparatus is a member. 6. The electrophotographic apparatus according to claim 1, wherein a linear expansion coefficient of said pressure holding member is smaller than a linear expansion coefficient of said silicone rubber.