JP3363700B2 - Fixing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing an unfixed image (toner image) on the surface of a material to be heated by heating.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus for forming an image by an electrophotographic method, as a fixing apparatus for fixing a visible image on a recording material, a heat roller method having a heating body inside is known. There is.

This heat roller type fixing device can be widely used from low speed machines to high speed machines, and has an advantage that it is easy to handle in terms of design and maintenance.

However, this heat roller type fixing device consumes a large amount of power and may take a long time to reach a fixable temperature, that is, a so-called warm-up time. 63-3131
A fixing method using a heat resistant film as disclosed in Japanese Patent Publication No. 82 has been proposed.

This film type fixing device includes a thin heat-resistant film, a driving roller for the film, and a heating body fixedly supported so as to be in sliding contact with the inner peripheral surface of the film.
A pressurizing means arranged so as to come into contact with the outer peripheral surface of the film and to press-contact the heating body via the film, wherein the film and the pressurizing means constituting the heating means are: At least during image fixing, the recording material is rotated at the same speed as the conveying speed of the recording material.

Therefore, the recording material is nipped and conveyed by the pressure contact portion (hereinafter referred to as the fixing nip portion) of the heating member and the pressure applying means formed via the film, so that an unfixed image (toner image) on the recording material is obtained. ) Is applied with the heat energy of the heating body, the unfixed image is softened / welded, and the recording material is discharged from the fixing nip portion, so that the unfixed image is cooled and solidified and fixed on the recording material. .

According to such a film type fixing device, since the film and the heating body have a low heat capacity, the warm-up time is not required, and the thermal efficiency can be improved because the distance between the toner image and the heating body is short. it can.

However, in both the heat roller system and the film system, unfixed toner may adhere to the surface of the pressure roller normally used as the pressure unit. In some cases, this toner re-transferred to the recording material to cause a so-called offset phenomenon.

Therefore, conventionally, the residual toner on the surface of the pressure roller is removed by bringing various types of cleaning means into contact with the pressure roller, and the recording material is contaminated by the contamination of the pressure roller. Measures are taken to prevent it.

For example, a cleaning method generally used in the above fixing device includes a fixing cleaner having a web made of aramid fiber impregnated with silicone oil having a high cleaning (foreign matter removal) ability. There are a method of contacting the pressure roller and a method of contacting a cleaning roller or the like as a low heat capacity cleaning means with the pressure roller.

In the method using a web, since the cleaner performance is low if the web is not warm, it is necessary to energize the heating element to warm the web before the fixing operation is started, and the warm-up time is not required. It is not possible to take full advantage of the fixing method using a film.

On the other hand, the method of bringing a cleaning means such as a cleaning roller into contact with the pressure roller is cheaper than the case of using a web, and the cleaning means itself does not need to be heated. , It does not affect the warm-up time.

Further, if the cleaning means is made of a material having high thermal conductivity, the cleaning means is brought into contact with the pressure roller so that not only the surface of the pressure roller is cleaned but also the temperature distribution is made uniform. It is possible to exhibit effects such as suppressing excessive temperature rise in the non-sheet passing portion when continuous copying of small size paper and improving durability of the fixing film and the pressure roller.

However, the method of bringing the cleaning means such as a cleaning roller into contact with the pressure roller is such that the pressure roller and the paper or OH as the recording material to be conveyed.
The pressure roller surface may be charged to several kV due to friction with the P sheet (sheet material made of a resin material).

Therefore, when the conductor cleaning means is brought into contact with the surface of the pressure roller, a very large electric charge is accumulated in the cleaning means, and the electric charge is accumulated between the conductor cleaning means and other portions around the cleaning means. There is a problem in that there is a concern that the spark discharge may occur and the noise generated at that time may disturb the signals of the control system.

In particular, the surface of the pressure roller has a good releasability P.
When a fluororesin such as FA is used, the charging potential of the pressure roller due to friction is higher and has a negative polarity. Therefore, when a developer having a negative charge polarity is used, the cleaning means and the developer have the same polarity, which repel each other and the cleaning ability is significantly reduced.
There is a possibility that the residual toner may not be completely collected by the cleaning means and may stain the recording material.

Therefore, in order to prevent the cleaning means from being electrified, a method of grounding the cleaning means has been proposed, and the cleaning ability is improved to prevent image deterioration and the durability of the pressure roller is improved. At the same time, the stability of device control was improved.

However, even when the cleaning member is grounded as described above, the heat roller of the heat roller type and the heat resistant film of the film type are not liable to be heated due to friction in the fixing process.
The developer is charged in the opposite polarity to the developer, the attraction of the developer to the recording material weakens, and the unfixed image (toner image) softened at the fixing nip part peels off from the recording material. In some cases, the heat roller and the heat resistant film in the case of the film method may cause an offset to cause an offset. Further, after that, when the heat roller or the heat-resistant film is rotated again, when it comes into contact with the recording material again, the adsorbed developer may be transferred onto the recording material this time, causing image deterioration. .

Therefore, by applying a bias having a polarity opposite to that of the developer to the pressure roller, the adsorbing force of the developer to the recording material is improved, so that the unfixed image (toner image) from the recording material is applied. A method for preventing peeling (offset) has been proposed.

[0020]

However, in the above-mentioned conventional example, the unevenness of the internal resistance of the pressure roller or the unevenness of the resistance due to the film thickness of the insulating tube coated on the pressure roller, and the unevenness of the pressure roller are applied. The applied voltage of the bias for preventing the offset becomes unstable due to the change of the contact area with the conductive cleaning means in contact with the image, and the image may be offset and the image may be deteriorated. In particular, when a pinhole is formed in the insulating tube during the pressure roller manufacturing process or the fixing device assembling process, the phenomenon may become more remarkable. Further, the instability of the applied voltage may cause uneven fixing property, partial decrease in cleaning ability, and shortening of the life of the pressure roller.

Therefore, the present invention makes it possible to stabilize the fixing property, improve the cleaning ability to prevent image deterioration, and improve the durability of the pressing means such as the pressing roller. The purpose is to provide a device.

[0022]

According to a first aspect of the present application, there is provided a means for solving] The object is achieved by a heating means having a moving surface that will be heated, disposed opposite to the heating means, the moving surface pressure member forming a nip for nipping and conveying the recording material between
And a DC voltage of the opposite polarity to the toner is applied to the conductive layer of the pressure member.
And voltage applying means for pressurizing, and contact the pressure member, the pressure member
In the fixing device having a cleaning member conductive for cleaning the surface, the pressure roller have the insulating layer on the outer layer of the conductive layer
And contact the insulating layer to eliminate the charge on the insulating layer.
This is achieved by the grounded cleaning member having a high-resistance resistor interposed between the cleaning member and the ground .

According to the second invention of the present application,
With the above object, the resistance value of the resistor of the first invention is 200
It is achieved by having kΩ or more.

Further, according to the third invention of the present application, the above-mentioned object is the heating means of the first invention or the second invention, wherein the heating member and the heat of the heating member are applied to the material to be heated. And a film member that requires a moving surface for transmission.

According to the fourth invention of the present application,
The above object can be achieved by the heating means of the first invention or the second invention, which is a roller member having a heating body inside.

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

That is, in the first aspect of the present invention, since the cleaning means contacting the pressurizing means is formed of a conductive member and is grounded via a resistor having a high resistance value, the charge is not charged. Keeping the potential of the pressure means at a predetermined value by extending the time until it falls due to grounding , and pinhole the pressure roller.
Even if this occurs, the amount of grounded charges is reduced and the image deterioration due to the partial offset of the image does not occur.

In the second invention of the present application, since the resistance value of the resistor of the first invention is 200 kΩ or more, a predetermined bias voltage is applied to the pressurizing means, and the applied voltage is unstable. In this case, the electric potential of the pressurizing means is not drastically lowered, and the offset of the image is not generated.

Further, in the third invention according to the present application, the heating means of the first invention or the second invention comprises a heating body and a moving surface for transferring the heat of the heating body to the material to be heated. Since the necessary film member is provided, fixing without offset is performed as described above, and fixing with low power consumption is performed without warm-up time.

Further, in the fourth invention according to the present application, the heating means of the first invention or the second invention is a roller member having a heating body inside, so that the fixing without offset as described above can be performed. In addition to being performed, the maintainability is improved, and the fixing is performed in a wide range of speeds from low speed to high speed.

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a diagram illustrating a configuration of a fixing device 60 in the present embodiment, and FIG. 2 is a schematic configuration diagram of an example of an electrophotographic image forming apparatus G1 using the fixing device 60.

First, the image forming apparatus G1 will be described with reference to FIG. In FIG. 2, reference numeral 20 denotes a document table glass fixedly arranged, and the document 1 is placed on the document table glass 20.
9 is placed and the required copying conditions are set, and then the copy start key is pressed, whereby the photosensitive drum 39 is rotationally driven in the clockwise direction indicated by the arrow at a predetermined peripheral speed, and the following image forming operation is performed. Is started.

First, the light source 21, together with the reflection shade 22 and the first mirror 23, moves from the home position on the left side of the glass to the right side of the glass along the lower surface of the platen glass 20 at a predetermined speed V, and then the second mirror. By moving 24 and the third mirror 25 in the same direction at a speed of V / 2, the downward image surface of the document 19 placed on the document glass 20 is illuminated and scanned from the left side to the right side. Then, the light reflected from the original surface of the illumination scanning light is image-formed and exposed (slit exposure) on the surface of the rotating photosensitive drum 39 via the image-forming lens 29, the fixed fourth, fifth and sixth mirrors 26, 27 and 28. To be done.

Next, before the exposure, the surface of the photosensitive drum 39 uniformly charged to a predetermined positive or negative potential by the primary charger 30 has a pattern corresponding to the original image by the exposure. An electrostatic latent image is sequentially formed, and the electrostatic latent image is conveyed to a portion facing the developing roller 32 of the developing device 31 as the photosensitive drum 39 rotates in the arrow direction.

Then, the developing roller 32 which rotates while carrying the toner (not shown) contained in the developing device 31.
Since a predetermined developing bias is applied between the photosensitive drum 39 and the photosensitive drum 39, the toner on the developing roller 32 is transferred to the electrostatic latent image on the photosensitive drum 39, and the electrostatic latent image is transferred. The image is visualized as a toner image.

On the other hand, the recording material P is fed by the paper feed roller 51 in synchronism with the above-described image development process, and the recording material P passes through the guide 33 and is transferred and charged onto the photosensitive drum 39 at a predetermined timing. It is introduced into the transfer section between the container and the container. Then, the recording material P is brought into contact with the photosensitive drum 39 by receiving the transfer corona at the transfer portion, and the toner visible images on the surface of the photosensitive drum 39 are sequentially transferred to the upper surface of the recording material P.

Next, the recording material P that has passed through this transfer portion is
While being subjected to back surface charge removal by the charge removal needle 35, the charge is sequentially separated from the surface of the photoconductor drum 39, introduced into the fixing device 60 via the transport unit 38 and the inlet guide 10, and subjected to toner image fixing as described later, and the image is fixed. It is discharged out of the machine as a formed product.

Incidentally, the surface of the photosensitive drum 39 after the transfer is cleaned and removed by the cleaning blade 37 of the cleaning device 36 to remove stains such as residual toner, and is repeatedly used for image formation.

Further, the moving optical members 21 to 25, which have moved on the outward path as described above, are set so as to move on the return path when reaching a predetermined outward path end point, return to the initial home position, and then perform the next copy. Wait until the start of the cycle.

Next, the fixing device 60 used in the image forming apparatus G1 will be described in detail with reference to FIG. In FIG. 1, reference numeral 6 denotes an endless belt-shaped fixing film as a film member that constitutes a heating means. The fixing film 6 includes a left driving roller 7 and a right driven roller 8.
It is stretched between a low heat capacity linear heater 1 as a heating body fixedly arranged below the rollers 7 and 8.

This endless belt-shaped fixing film 6
Is repeatedly used for heating and fixing the toner image,
It has excellent heat resistance, releasability, and durability.
Generally, a thin film having a thickness of 100 μm or less, preferably 40 μm or less is used.

As an example, a highly heat-resistant resin such as polyimide, polyetherimide, polyethersulfone, or polyetheretherketone having a thickness of 20 μm or nickel,
PTF is applied to the outer peripheral surface of a thin metal endless belt such as SUS
Low surface energy resin such as E (tetrafluoroethylene resin), PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin), or a release coating layer in which a conductive material such as carbon black is added to these resins It is possible to use an endless belt-shaped fixing film having a layer thickness of 30 μm in which 10 μm is applied.

Further, the heater 1 having a low heat capacity as a heating body which constitutes the heating means together with the fixing film 6 has, for example, a thickness of 1.0 mm, a width of 10 mm and a longitudinal length of 340 m.
m of alumina substrate 2 is coated with a resistance material such as silver palladium or ruthenium oxide to have a thickness of 10 μm and a width of 1.0 mm to form a heat generating layer 3, and the heat generating layer 3 is further laminated on the heat generating layer 3. A protective layer 4 made of glass or the like in consideration of movement is formed, and is fixedly supported by being attached and held on the heater support 11.

The heater support 11 has a heat insulating property, a high heat resistance, and rigidity for adiabatically supporting the fixing device 60 of the heater 1 and the image forming apparatus. For example, PPS (polyphenylene sulfide) or PEEK (polyether ether). (Ketone), a liquid crystal polymer, or other high heat resistant resin, or a composite material of these resins and ceramics or metal.

The heat generating layer 3 of the heater 1 is energized with AC 100 V from both ends in the longitudinal direction, and is made of NTC which is adhered or pressure-bonded or integrally formed on the back surface of the substrate 2 with a heat conductive silicone rubber adhesive or the like. The energization is controlled by the control means (not shown) according to the temperature detected by the thermistor 5.

Further, the driven roller 8 is the fixing film 6
The fixing film 6 also serves as a tension roller for applying a tension in the direction of stretching outward, and the fixing film 6 is rotated clockwise in accordance with the clockwise rotation of the driving roller 7 whose surface has been coated with silicone rubber or the like to increase the friction coefficient. It is driven at a predetermined peripheral speed without wrinkling, meandering or speed delay.

Further, 9 is a pressurizing means, the surface of which is covered with an insulating layer, for example, an insulating tube 9a made of fluororesin such as PFA having excellent releasability and durability, and the inside is electrically conductive as a conductive member. Made of flexible rubber layer 9b, longitudinal direction 380m
m is a pressure roller having a diameter of 25 mm. The lower film portion of the endless belt-shaped fixing film 6 is sandwiched between the heater 1 and the lower surface of the heater 1 by a biasing means such as a spring. For example, they are pressed against each other with an abutting force of 5 to 10 kgf, and rotate in the forward counterclockwise direction in the conveyance direction of the recording material P.

In the fixing device 60 having the above-described structure, the recording material P as the heated material, to which the unfixed toner image T as the developer image is transferred on the upper surface, is guided by the image forming operation as described above. When the toner 1 is guided by the fixing film 6 and enters the pressure contact portion (hereinafter, referred to as a fixing nip portion) N between the heater 1 and the pressure roller 9 which is formed via the fixing film 6, the unfixed toner image T is formed on the lower surface of the fixing film 6. Adhesion to the fixing film 6 without causing surface misalignment, wrinkles, or deviation
The fixing nip portion N passes through the fixing nip portion N while receiving a clamping pressure.

At this time, the toner image bearing surface of the recording material P receives the heat of the heat generating layer 3 through the fixing film 6 while passing through the fixing nip portion N in the pressure fixing state on the surface of the fixing film 6, and the toner is held. The image T is melted at a high temperature and softened on the surface of the recording material P to form a toner image Ta which is adhered.

Further, the recording material P that has passed through the fixing nip portion N is cooled while being guided by the guide 12, and the image Ta that has been softened and adhered is the fixed image Tb fixed on the toner image bearing surface of the recording material P. Becomes

In the present embodiment, the heater 1
Of these, the heat capacity of the heat generating layer 3 and the substrate 2 is small, and these are adiabatically supported by the heater support 11. Therefore, the surface temperature at the fixing nip portion N of the heater 1 is sufficient for the melting point of the toner in a short time. It is not necessary to raise the temperature of the heater 1 to a very high temperature in advance (so-called standby temperature adjustment), energy can be saved, and the temperature inside the machine can be prevented.

However, even in such a fixing device, the fixing film 6 is charged with a polarity opposite to that of the developer due to friction in the fixing process, and the attracting force of the toner to the recording material P is weakened, so that the fixing nip portion is formed. In some cases, the unfixed image (toner image) Ta softened by N was peeled off from the recording material and adsorbed to the fixing film 6 to cause offset. Further, after that, when the fixing film 6 is rotated, when the recording material P comes into contact with the recording material P again, the adsorbed toner now absorbs the recording material P.
There is a case where the image is transferred onto the upper surface to cause image deterioration.

Therefore, in the present embodiment, the pressure roller 9 is provided with 1.
A constant voltage power supply 62 applies a bias of 5 kV.

Further, 13 is a cleaning roller as a cleaning means arranged so as to be in pressure contact with the pressure roller 9, and this cleaning roller 13 has a longitudinal direction 40.
The roller is made of aluminum and has a diameter of 0 mm and a diameter of 20 mm.
It is pressed against each other with a contact force of up to 2000 gf.

Further, the cleaning roller 1 of this embodiment
A roller 3 made of aluminum is grounded via a resistor 61 having a high resistance value of 200 MΩ.

By grounding the cleaning roller 13 in this manner, it is possible to prevent charges from being accumulated and to be discharged to other constituent members, and to prevent the noise of the discharge from disturbing the signals of the control system. be able to.

Further, even if there is a pinhole or the like in the insulating tube 9a which is the surface layer of the pressure roller 9, when the pinhole contacts the conductive cleaning roller 13, the potential of the pressure roller 9 suddenly drops. It is possible to prevent the deterioration of the adsorbing power of the developer to the recording material and prevent the image deterioration due to the offset of the image.

Further, in the present embodiment, the developer can be used regardless of whether the charging characteristics of the developer are positive or negative. As a result of an experiment, it was confirmed that the effect of the present invention is exhibited when the resistance value of the resistor 61 is 200 kΩ or more.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those of the first invention are designated by the same reference numerals and the description thereof will be omitted.

This embodiment is a modification of the first embodiment. As shown in FIG. 3, the aluminum cleaning roller 13 is provided with a varistor 63 as a constant voltage applying means. Grounded.

Therefore, even if there is a pinhole or the like in the insulating tube 9a which is the surface layer of the pressure roller 9, the potential of the pressure roller 9 drops when the pinhole contacts the conductive cleaning roller 13. It is possible to prevent the deterioration of the adsorbing force of the developer to the recording material P due to this, and to prevent the image deterioration due to the offset of the image.

The same effect can be obtained by using a constant voltage power source as the constant voltage applying means.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those of the first invention are designated by the same reference numerals and the description thereof will be omitted.

The present invention described above is for always keeping the pressure roller 9 at a certain potential or more, and is not related to the structure of the heating means. However, not only the fixing device using the fixing film 6 of the above-described embodiment but also the heating roller 64 as a heating means having the heat generating means 65 inside the roller member 66 as shown in FIG. There is no problem in applying it to a fixing device of a fixing type.

[0081]

As described above, the first aspect of the present application
According to the invention, since the cleaning means contacting the pressurizing means is formed of a conductive member and is grounded via a resistor having a high resistance value, the time until the charge drops due to grounding is increased.
The pressure roller to maintain the potential of the pressure means at a predetermined value.
Even if a pinhole occurs in the image, the amount of grounded electric charge can be reduced, and the occurrence of image deterioration due to partial offset of the image can be reliably prevented. Further, since the electric potential of the pressurizing unit does not fluctuate abruptly, it is possible to prevent the occurrence of nonuniformity in the fixing property, and it is also possible to prevent a partial decrease in the cleaning ability of the cleaning unit. Furthermore, the service life of the pressing means can be extended, that is, the service life of the fixing device itself can be extended.

According to the second invention of the present application,
Since the resistance value of the resistor of the first invention is 200 kΩ or more, even if a predetermined bias voltage is applied to the pressurizing means and the applied voltage becomes unstable, the potential of the pressurizing means is rapidly lowered. Thus, it is possible to reliably prevent the occurrence of image offset. Further, since the electric potential of the pressurizing means does not fluctuate abruptly, it is possible to prevent the occurrence of unevenness in the fixability, and it is also possible to prevent a partial decrease in the cleaning ability of the cleaning means. Furthermore, the service life of the pressing means can be extended, that is, the service life of the fixing device itself can be extended.

Further, according to the third invention of the present application, the heating means of the first invention or the second invention is a heating body and a moving surface for transferring the heat of the heating body to a material to be heated. Since it is provided with a film member that requires high temperature, good fixing can be performed without offset and unevenness as described above, and good fixing can be performed for a long period of time due to high cleaning ability. Fixing can be performed with low power consumption without uptime.

According to the fourth invention of the present application,
Since the heating means of the first invention or the second invention is a roller member having a heating body inside, it is possible to perform good fixing without offset and unevenness as described above, and it is also excellent due to high cleaning ability. The fixing can be performed for a long period of time, the maintainability is improved, and the fixing can be performed in a wide range of speeds from low speed to high speed.

[0085]

[0086]

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a fixing device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an image forming apparatus according to a first embodiment of the present invention.

FIG. 3 is a vertical sectional view of a fixing device according to a second embodiment of the present invention.

FIG. 4 is a vertical sectional view of a fixing device according to a third embodiment of the present invention.

[Explanation of symbols]

1 heater (heating means, heating element) 6 Fixing film (heating means, film member) 9 Pressure roller (pressurizing means) 9a Insulation tube (insulation layer) 9b Conductive rubber layer (conductive member) 13 Cleaning roller (cleaning means) 60 fixing device 61 resistor 63 Varistor (constant voltage applying means) 64 heating roller (heating means, roller member) G1 image forming apparatus N fixing nip part (press contact part) P Recording material (heated material) T, Ta toner image (developer image)

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-4-136880 (JP, A) JP-A-6-175520 (JP, A) JP-A-4-139476 (JP, A) JP-A-6- 337611 (JP, A) JP 4-14080 (JP, A) JP 4-335386 (JP, A) JP 3-255487 (JP, A) Actual flat 6-16965 (JP, U) 59-136651 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (4)

(57) [Claims] And 1. A heating means having a heated Ru moving surface, disposed opposite to the heating means, serial between the mobile surface
And a pressure member forming a nip for nipping and conveying the Rokuzai, pressurized
A voltage that applies a DC voltage of the opposite polarity to the toner is applied to the conductive layer of the member.
A pressure application means, abut the pressure member, the surface of the pressure member Kiyoshi
In the fixing device having a conductive cleaning member for scavenging, a pressure roller having an insulating layer on the outer layer of the conductive layer, the insulation
Grounded to contact the layer and eliminate the charge on the insulating layer
A fixing device , wherein the cleaning member has a high-resistance resistor interposed between the cleaning member and the ground . 2. The fixing device according to claim 1, wherein the resistance value of the resistor is 200 kΩ or more. 3. The fixing device according to claim 1, wherein the heating unit includes a heating body and a film member that requires a moving surface to transfer the heat of the heating body to the material to be heated. . 4. The fixing device according to claim 1, wherein the heating unit is a roller member having a heating body therein.