JP3502547B2 - Fixing device for image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an unfixed sheet (paper) which is a recording medium provided in an image forming apparatus such as a copying machine, a laser beam printer, a facsimile machine or the like using an electrophotographic system. The present invention relates to a fixing device that heats and fixes toner.

[0002]

2. Description of the Related Art An image forming apparatus using an electrophotographic system visualizes a latent image formed on a photoreceptor having a photosensitive layer as a recording medium with powder toner and visualizes it. The toner image is transferred onto a sheet-shaped sheet that is a recording medium. Since the transferred toner image is unfixed,
In order to fix the toner on the paper, the toner is melted by heat and pressed to fuse the toner on the paper. Therefore, a heat fixing device is provided on the downstream side of the sheet conveyance path that passes through the image forming area, for example, in front of the sheet discharge section.

In this fixing device, the paper is brought into pressure contact with the heat roller, which is usually heated to a temperature at which the toner is melted, so that the unfixed toner on the paper is melted and fixed with pressure. It is configured. Therefore, the toner adheres to the heat roller during fixing.
In order to prevent this, the heat roller is covered with a member or the like having good releasability to toner, and if necessary, silicone oil or the like, which is a release agent for preventing toner adhesion, is applied. .

[0004] In contrast, in order to obtain a color image, a plurality of different colors, for example yellow, magenta, cyan, to reproduce the desired color appropriately superimposed black (black) optionally Tei It Therefore, the adhesion of the toner to the fixing device, especially the heat roller tends to increase. Further, since the color toner has a lower melt viscosity than the black toner, it tends to adhere to the heat roller more easily than the black toner. Therefore, it is necessary to increase the coating amount of the silicone oil by several steps as compared with the case of black toner.

Therefore, an example of a conventional fixing device for melting and fixing color toner is shown in FIG. This Figure 5
The fixing device is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-30132.

In FIG. 5, a fixing device 50 includes a heat roller 52 having a heater lamp 51, which is a halogen lamp as a heat source, therein, and a heating roller 52 which is pressed with a predetermined pressing force. It is composed of a pressure roller 53. Then, in this fixing device 50,
A sheet carrying toner is guided to a nip portion where the heat roller 52 and the pressure roller 53 are brought into pressure contact with each other through a guide 54 provided on the upstream side, and the toner image carried on the sheet is fixed. .

Further, in order to prevent the toner image from adhering to the heat roller 52 side, a silicone oil applying roller 55 is provided so as to be in pressure contact with the heat roller 52. Silicone oil is supplied to the coating roller 55 from a nozzle 58 from an oil tank 56 via a pump 57. Therefore, by rotating the application roller 55 in the direction of the arrow, the silicone oil on the surface of the application roller 55 is transferred to the surface of the heat roller 52 and applied.

At this time, the amount of silicone oil adhered to the application roller 55 is made uniform by the regulating blade 59 that is pressed against the application roller 55, and the excess oil is transmitted to the bottom surface of the oil case 60 and the oil tank 56. It is supposed to be collected.

As described above, the silicone oil is uniformly applied to the application roller 55, and the uniform application is performed by the uniform transfer to the heat roller 52. This prevents the toner from adhering to the heat roller 52.

[0010]

According to the fixing device 50 as shown in FIG. 5 described in the above-mentioned publication, the silicone oil can be uniformly applied to the heat roller 52 by the blade 59 or the like. Therefore, it is possible to prevent the toner from adhering to the heat roller 52 and prevent the offset phenomenon in which the toner adhering to the sheet is transferred by the rotation of the heat roller.

If the amount of silicone oil applied regulated by the blade 59 is not uniform (even in the rotation axis direction and around the applying roller 55), the surface of the heat roller 52 cannot be applied uniformly. Therefore, the coating roller 5
If the amount of silicone oil supplied to No. 5 is small, coating unevenness occurs and uniform coating cannot be performed. Therefore, as shown in FIG. 5, the oil sump member 61 is provided so as to be in pressure contact with the coating roller 55, and the space surrounded by the oil sump member 61 and the blade 59 is used as an oil sump, so that a sufficient amount of silicone oil can be obtained. It can be supplied to the coating roller 55.

However, if the supply becomes excessive, the blade 5
Even if 9 is provided, uneven application of oil to the application roller 55 and oil streaks occur, and uniform application cannot be performed. Furthermore, if a surplus, the number oil application amount to the heat roller 52, the sheet base <br/> convex rather silicone oil. In addition, it is a portion other than the fixing device becomes oil leaks and this dirty with oil. Further, a large amount is also supplied to the pressure roller 53 side, and the back surface of the sheet may be soiled with oil.

Therefore, on the side of the pressure roller 53, a cleaning blade 62 for removing the silicone oil transferred from the heat roller 52 is brought into pressure contact, and a tray 63 for receiving the removed silicone oil, an oil absorber 64, etc. are provided. It is configured to prevent oil from leaking out. Therefore, the structure of the entire fixing device is complicated,
And tends to grow.

[0014] In particular, as a sheet on which the toner image is formed, plain paper der lever, is consumed is absorbed part of the oil which is applied to the heat roller 52, not a coating plethora of silicone oil. However, the OHP sheet does not absorb the silicone oil and consumes almost no oil. Therefore, if image formation using the OHP sheet continues, the amount of oil becomes excessive, the above-mentioned coating unevenness occurs, oil streaks occur, and improper fixing occurs.

In order to solve the above-mentioned problems, an object of the present invention is to limit the coating amount of a release agent having a good releasability to toner with a simple structure and at the same time, enable uniform coating. The present invention provides a fixing device having a coating device having various configurations.

Another object of the present invention is to fix the color toner excellently, and to prevent the offset phenomenon, the amount of the release agent applied to the heat roller can be controlled according to the material of the recording medium. Another object is to provide a fixing device.

[0017]

SUMMARY OF THE INVENTION According to the present invention, a fixing device of an image forming apparatus for achieving the above-mentioned object is provided with a heat roller whose surface is heated to a desired temperature and a pressure roller which feeds the heat roller. And a pressure roller for bringing the recording medium carrying an unfixed image coming in close contact with the heat roller side, and passing the recording medium between the heat roller and the pressure roller to thereby fix the unfixed image. In a fixing device of an image forming apparatus that fixes an image and forms an image, a coating device is provided to prevent the unfixed image carried on the recording medium from adhering to the heat roller. A first coating means for pressing the heat roller to coat the release agent, and a coating amount of the first coating means .
Remote consists of a number the second application means, said second coating
The cloth means is provided below the first application means, and the second means is provided.
A tank for storing the release agent is arranged below the coating means,
The release agent in the tank is applied to the first and second applying means.
It is characterized in that first and second coating members for supplying and coating are provided, and the first coating means and the second coating means are selectively used according to the material of the recording medium.

[0018] With this configuration, it can be arbitrarily set the coating amount, it is possible to control according to the type of the recording medium. As a result, when the recording medium is a sheet such as OHP, less coating amount, always to be possible good fixing can be prevented from becoming coated excessive release agent.

[0019] Therefore, in the apparatus, characterized in the above-described configuration, the first application means comprises a first application roller for applying the releasing agent is pressed against the said heat roller, said
In order to supply and apply the release agent to the first coating roller,
The end is dipped in the release agent in the tank and the other end is the first
The first coating member in contact with the first coating roller, and regulates the supplied release agent on the surface of the first coating roller in a uniform state.
Comprising a first regulating blade and said second application means, the second coating roller, the release agent is supplied to the second coating roller for coating of applying a release agent to the heat roller
One end is immersed in the release agent in the tank and the other end is
Second coating member formed in contact with the second applicator roller, Ru Bei <br/> give a second regulating blade to make uniform the amount of the supplied release agent. Further , the surface roughness of the second coating roller is set to be rougher than the surface roughness of the first coating roller. The surface roughness Rz of the first coating roller is set to 10 μm or less, and the surface roughness Rz of the second coating roller is set to be 5 μm rougher than the roughness of the first coating roller.
With such a configuration, it is possible to uniformly apply the release agent according to the material of the recording medium. For example, if the recording medium is a plain paper sheet, it is necessary to increase the coating amount of the release agent. Therefore, it is possible to deal with it by selectively using the second coating means, and stable fixing can be achieved. If the recording medium is a sheet of OHP or the like, if the first coating means is selectively used, it is possible to prevent the release agent from being over-coated and to always perform stable fixing. Particularly, when the toner image formed on the recording medium is a color image, it is necessary to apply the release agent uniformly, but at the same time as the uniform application, the minimum amount of the release agent can be applied and stable fixing can be achieved. Can be maintained.

In addition, in the apparatus having the above-mentioned configuration, the first or second coating means is used for the first or second coating in order to selectively use the recording medium to be used according to the material. The roller can be contacted and separated from the heat roller, or the release agent is applied and applied to the first and second application rollers.
By providing the first and second application members so that they can be brought into contact with and separated from each other, application control can be easily performed according to the material of the recording medium, for example, plain paper or OHP sheet.

[0021]

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a fixing device for explaining a first embodiment according to the present invention, and in particular, shows the entire structure of the fixing device including a device for applying a release agent to a heat roller which comes into contact with toner constituting the fixing device. It is sectional drawing shown. 2 is an enlarged view for explaining an example of controlling the coating amount of the release agent in the fixing device in FIG. 1, and FIG. 3 is an image forming apparatus equipped with the fixing device according to the present invention shown in FIG. FIG. 1 is a diagram showing an overall structure of a color image forming apparatus (color printer).

First, the overall structure of a color image forming apparatus having the fixing device of the present invention will be described with reference to FIG.

The color image forming apparatus shown in FIG. 3 stocks and supplies a sheet, which is a recording medium on which an image is finally formed with toner, and a transfer section 2 that transfers a toner image onto the sheet. The image forming section 3 includes a developing device that forms a toner image, and the fixing device 4 according to the present invention that melts and fuses the toner image transferred onto the sheet to fix the toner image.

The sheet feeding section 1 is detachably attached to the lowermost portion of the main body of the image forming apparatus, and is particularly arranged so that it can be pulled out from the front side or the right side (front side of the apparatus) in the drawing and stocks sheets. 5 and the front of the apparatus main body, that is, the right side in the drawing, is provided with a manual insertion portion 6 for manually inserting a sheet. Then, a pickup roller 7 for feeding the sheets stored in the paper feeding cassette 5 one by one from the uppermost one, a PF roller 8 for conveying the sheets fed by the pickup roller 7, and a manual insertion portion 6 are inserted. A manual feed roller 9 that conveys the sheet to be formed is provided. Further, a pre-curl roller 10 for curling the sheet conveyed by the PF roller 8 and the manual feed roller 9 in advance is provided.

The above-mentioned sheet feeding unit 1 is constituted by these. The sheet feeding unit 1 feeds the sheet to the transfer unit 2 in accordance with an image forming command.

The sheet feeding cassette 5 is provided with a pushing-up member biased upward by a spring or the like, that is, a sheet placing table 5a in the drawing, and a sheet is placed on the sheet placing table 5a. It has become. This allows
The uppermost part of the sheets stocked in the paper feed cassette 5 faces the pickup roller 7, and the picked-up roller 7 is driven to rotate once in the direction of the arrow to come into contact with the uppermost sheet, so that one sheet is not fed out. Done. And
The fed sheet is conveyed to the pre-curl roller 10 via the PF roller 8.

The sheet paper inserted from the manual insertion section 6 is also pre-curled by the manual insertion roller 9
Be transported to.

The pre-curl roller 10 pre-curls the sheet conveyed as described above. This is for facilitating the sheet to be adsorbed and held on the surface of the cylindrical transfer drum 11 provided in the transfer unit 2, and is provided for that purpose.

The transfer section 2 is provided with a cylindrical transfer drum 11 as transfer means as described above. Around the transfer drum 11, a ground roller 12 serving as a grounded electrode member, a guide member 13 for guiding the sheet so as not to fall from the transfer drum 11, and a sheet adsorbed on the transfer drum 11 are forcibly peeled off. Peeling nail 14
Etc. are arranged. The peeling claw 14 is provided so as to come in contact with and separate from the surface of the transfer drum 11, and peels the sheet from the transfer drum 11 after the transfer is completed.

Further, the image forming section 3 is provided with a photoconductor drum 15 as an image carrier which is brought into pressure contact with the transfer drum 11, and the photoconductor drum 15 is a grounded conductive aluminum element tube. 15a, and an OPC film (organic photoconductive film) is applied to the surface thereof.

Further, around the photosensitive drum 15,
The developing units 16, 17, 18, and 19 containing yellow, magenta, cyan, and black toners are sequentially arranged in a radial pattern, and the charging unit 20 that charges the surface of the photosensitive drum 15 and the remaining surface of the photosensitive drum 15 are charged. A cleaning blade 21 for scraping and removing the toner is provided. In the image forming unit 3, for each of the toners,
A toner image is formed on the photosensitive drum 15 and is sequentially transferred to the sheet wound around the transfer drum 11 described above. Therefore, according to the photoconductor drum 15, a toner image of a desired color is formed on the sheet by repeatedly performing charging, exposure, development, and transfer for each color.

Therefore, when a color toner image is formed on a sheet, each time the transfer drum 11 makes one rotation, the toner image is transferred one color to the sheet electrostatically attracted to the transfer drum 11, and a maximum of four rotations are made. It is possible to obtain a color image with one toner in which the respective colors are superposed.

The photosensitive drum 15 and the transfer drum 11
In terms of transfer efficiency and image quality, is pressed so that a pressure of, for example, about 8 kg is applied at a transfer portion, particularly a contact portion.

[0035] Therefore, the toner image formed on the sheet in the manner described above is unfixed, in order to finish it as a permanent image, the peeling claw 14 corresponds to the provided et the position of the transfer drum 11 Thus, the fixing device 4 for performing the heat fixing of the present invention is provided.

The fixing device 4, which will be described in detail later, is peeled off from the transfer roller 11 and the heat roller 41 for fixing the toner image carried on the sheet by a predetermined temperature and pressure through the peeling claw 14. A fixing guide 22 for guiding the sheet to the heat roller 41 is provided.

A discharge roller 23 is provided at the sheet exit of the fixing device 4, that is, on the downstream side of the sheet conveyance, and the fixed sheet is a discharge tray provided outside the image forming apparatus main body. Is discharged onto 24. As shown in the figure, the discharge tray 24 is located above the image forming apparatus and is provided in an inclined state.

Therefore, the fixing device 4 of the present invention will be described in detail with reference to FIG. 1. On the surface of the cylindrical cored bar 31 made of aluminum Al or the like, for example, silicone excellent in releasability from toner is used. Rubber coating layer 32 such as rubber
Is provided with a heat roller 41 configured by being bonded and fixed with an adhesive called a primer, for example. Inside the core metal 31 of the heat roller 41, the heat roller 41
A heater lamp 43 including a halogen lamp or the like serving as a heating source for maintaining the surface temperature of the sheet at a fixing temperature (set temperature) is provided.

A considerable contact width (nip width) is formed on the heat roller 41 in order to efficiently fix the toner image on the sheet between the heat roller 41 and the sheet paper P on the heat roller 41 side. To make the
A pressure roller 42 constituted by coating a PFA tube 34 on a silicon rubber or sponge having a wall thickness or low hardness or both is provided on a cored bar 33 rotatably supported. As described above, the pressure roller 42 is provided with the thick coating layer 34 so as to improve the heat insulating property and to reduce the temperature drop on the surface of the heat roller 41 on the image side. As described above, the nip width in the transport direction in contact with the heat roller 41 is increased.

On the other hand, in order to maintain the surface temperature of the heat roller 41 at a predetermined set temperature, the power supply to the heater lamp 43 is controlled. Therefore, a temperature detection sensor 35 including a thermistor or the like arranged so as to contact the surface of the heat roller 41 is provided. The power supply to the heater lamp 43 is controlled according to the output of the temperature detection sensor 56.

Although a halogen lamp is used as the heater lamp 43 in the heat roller 41 of the fixing device 4, other heating means such as a sheet heating element may be used.
A ceramic heater, a xenon lamp, a self-temperature control type ceramic heater (PTC), etc. can be used.

The planar heating element is a heating element having a heating element such as a nichrome wire formed in a planar shape, and the surface thereof is covered with an insulating material such as ethylene tetrafluoride or polyimide to insulate the surface. It is preferable that the shape and the smoothness can be secured. When applied as a heat source of the fixing device of the present invention, the heat transfer efficiency is maximized by directly contacting with the heat roller 41 for heating, but the heat rollers 41 may be arranged apart from each other by several mm. For example, the sheet heating element is provided by being directly attached to the inner peripheral surface of the cored bar 31 which constitutes the heat roller 41.

The ceramic heater is formed by printing an MO-type planar heating resistor on an alumina ceramic substrate and printing and laminating a glass coat on it. The ceramic heater can be quickly heated to a predetermined heating temperature by energizing the heating resistor, and the heating surface is arranged close to or in contact with the outer peripheral surface of the heat roller 41.

The xenon lamp is a flash lamp including a xenon gas, the application of a high DC pulse voltage across the electrodes of the tube, it is also of that occur radiant energy having a strong peak at a wavelength of 566 nm, a heat The efficiency of heating the roller 41 from the outside is high. Therefore, it is arranged so as to face the outer peripheral surface of the heat roller 41 without being provided inside the heat roller 41.

Further, the self-temperature control type ceramic heater is a ceramic heater and is an element which generates heat up to a constant value of the current flowing therein when a voltage is applied. Therefore, by selecting the material, the surface temperature of the heating element when the predetermined voltage is applied can be maintained at the predetermined temperature.
This self-temperature control type ceramic heater is applied to the heat roller 4
The heat roller 41 can be heated from the outside by bringing it close to or in contact with 1.

(First Embodiment of the Present Invention) A pair of heat roller 41 and pressure roller 4 of the fixing device 4 according to the present invention.
In order to enable high image quality, especially color image quality, the heat roller 41 for fixing the toner image in contact with the unfixed toner image is provided with the coating layer 32 coated with silicon rubber or the like as described above. It enables high image quality.

Further, in order to perform the fixing, it is necessary to keep the surface temperature of the heat roller 41 constant, and further, the nip width of the pressure contact portion between the pair of rollers 41 and 42 (the width at which the rollers contact each other). Will be needed. These settings, that is, the set temperature of the surface of the heat roller 41, the nip width, and the like vary depending on the sheet conveying speed of the image forming apparatus and the toner characteristics used, but the set temperature of the heat roller 41 is normally set. The temperature is controlled so that fixing failure does not occur and high temperature offset does not occur.

The fixing device 4 having the structure described above.
In order to positively prevent the toner from adhering to the surface of the heat roller 41 and prevent the offset phenomenon from occurring, for example, silicone oil having releasability with respect to the toner is used in the coating device of the present invention. It is applied through.

First, the structure of the first embodiment is shown in FIG.
Will be described in detail with reference to. The coating device uniformly coats a release agent such as silicone oil on the surface of the heat roller 41. The release agent is supplied from the oil supply bottle 36 into the lower oil tank 37, and then the tank 37 is supplied. I try to store it. Therefore, the oil supply bottle 36 is detachably attached to the tank 37 and is replaced when the oil in the bottle is exhausted.

The oil surface of the oil tank 37 is detected by a sensor (not shown), and the oil is supplied from the bottle 36 into the tank 37 according to the detection, so that the oil surface is always maintained at a constant level. Controlled to be done. The silicone oil 40, which is a release agent stored in the oil tank 37, is provided with an oil supplying coating member 44 having one end immersed for sucking up by utilizing the capillary phenomenon. The other end of the coating member 44 is pressed against the peripheral surface of the coating roller 45 rotated with the heat roller 41 in a predetermined region (length).

Since one end of the coating member 44 is immersed in the silicone oil 40 stored in the tank 37, the opposite end of the coating member 44 comes into contact with the surface of the coating roller 54, so that the silicone oil 40 is capillarized. It is sucked up and supplied by. Therefore, at the contact position of the coating member 44 with the coating roller 45, the coating roller 45 is located at the heat roller 4
It is set so as to be on the opposite side of the position where it is pressed against 1.

The coating roller 45 is rotatably provided so as to follow the rotation of the heat roller 41, for example. Therefore, when the image forming apparatus starts the operation for forming the image, the fixing device 4 starts the operation, and the heat roller 41 is rotated, so that the coating roller 45 is driven to rotate. . The coating roller 45 may be driven to rotate in the same direction without being driven, and the rotation speed or the like may be set arbitrarily.

Further, the coating device removes the excess silicone oil 40 coated by the coating member 44 on the downstream side in the rotation direction of the coating roller 45 from the tip end portion of the coating member 44 which comes into contact with the coating roller 45, and coats it. The roller 45 is provided with a regulating blade 46 for forming a uniform layer (film thickness) of the releasing agent on a predetermined amount. The blade 46 is provided such that the edge portion at the tip thereof contacts the coating roller 45, scrapes off the silicone oil 40 supplied to the coating roller 45, and coats the surface of the coating roller 54 that has passed through the blade 46. That is, the film thickness of the release agent that adheres is made uniform over the entire area in the rotation axis direction.

In the heat roller 41, a surface of a raw tube (core bar) 31 made of aluminum or the like is coated with a silicone rubber layer 32 having a slightly high rubber hardness and a high thermal conductivity. further,
LTV (low temprerature) with good releasability on its surface
vulcanizing) A rubber layer is formed. The surface of the heat roller 41 is brought into contact with the coating roller 45 in which the silicone oil 40 is regulated in a uniform state,
The silicone oil 40 layer is applied uniformly. As a result, the toner image comes in contact with the color toner image formed on the sheet, and due to the pressure contact action of the pressure roller 42, the toner image is melted and fixed by the heat of the heat roller 41.

In the fixing process in this case, since the heat roller 41 is uniformly applied to the silicone oil 40 as described above, it is possible to positively prevent the toner from adhering to the heat roller 41.

The coating member 44 has a fiber bundle structure such as felt and takes up the silicone oil 40 by utilizing the capillary phenomenon between the fibers. This uses a conventionally known one. Further, the blade 46 is integrally formed of fluororubber on an elastic support plate (not shown) made of, for example, stainless steel so as to cover the tip end side. The opposite side of the support plate is fixed to a support member 46a that is rotatably supported by a frame such as an exterior constituting the fixing device 4, and is pressed against the support member 46a via a biasing means (not shown). . Therefore, the tip end of the blade 46 is pressed against the coating roller 45 with an appropriate pressure by the elastic force of the support plate and the biasing means. In particular, the tip end surface of the blade 46 that comes into contact with the coating roller 45 is smoothed so that the silicone oil 40 has a uniform film thickness.

Further, in the coating device, it is preferable that the tip of the coating member 44 is arranged close to the tip of the blade 46. In particular, the tip of the coating member 44 and the blade 4
6 contact with the tip, or at least about 2 mm, preferably
It is arranged close to set the distance within 1mm.

According to this structure, the silicone oil 40 is sufficiently sucked up (raised) by the coating member 44 and uniformly coated on the surface of the heat roller 41 via the coating roller 45, while the silicone oil 40 is formed by the conventional method. It is possible to supply the required amount of silicone oil 40 without performing such circulation such as supply and recovery, and it is possible to eliminate dripping of the release agent due to excessive supply of silicone oil 40, that is, leakage.

That is, the tip of the coating member 44 and the blade 46
Since the tip end is in close proximity, the coating roller 45 is rotated by the start of the fixing process operation, and the silicone oil 40 sucked up by the coating member 44 is immediately formed by the blade 46 into a uniform silicone oil 40 film. Form. At this time, the excess silicone oil 40 scraped off by the blade 46 exists in a state of being impregnated at the tip of the coating member 44, and the silicone oil 40 impregnated at that portion is saturated.

Therefore, since the tip of the coating member 44 is saturated, it is no longer possible to suck up and supply the silicone oil by the capillary force. As a result, the silicone oil 4 voluntarily
Supply and stop of 0 are adjusted and extra silicone oil 4
0 is not supplied while the coating roller 54 continues to rotate. As a result, a sufficient and surplus silicone oil 40 does not collect in the contact area of the blade 46, so that the problem that the release agent drips can be solved. However, if there is excess silicone oil 40,
As shown in the figure, the recovery member 4 provided on the back surface of the coating member 44.
4a is sucked and recovered to the oil tank 37 side, or a part thereof is re-supplied from the lower end portion to the coating member 44 again. Therefore, the end portion of the recovery member 44a has the tank 37
It is separated from the liquid surface of the silicone oil 40.

According to the present invention, the coating roller 45 described above is used.
The silicone oil is uniformly applied to the heat roller 41 by. The coating roller 45 is configured such that the surface thereof is supplied with silicone oil by the coating member 44 and coated. Then, the silicone oil 40 supplied and applied by the regulation blade 45
Coating amount, that is, the oil layer is made uniform.

Therefore, in order to make the coating state even and thinner and to prevent excessive coating, the surface roughness of the coating roller 45 is more preferably 10 μm or less according to JIS standard. Is Rz5μ
It is about m. In this respect, the conventional coating roller 45
At present, the surface roughness Rz is set to 15 μm or more.

In the first embodiment of the present invention, by making the surface roughness of the coating roller 45 fine, the oil layer of the silicone oil on the coating roller 45 by the blade 46 can be made uniform and thin. This is the coating roller 4
Since the surface roughness Rz of 5 is very fine and the unevenness is small,
Due to the pressure contact with the blade 46, the silicone oil 40 easily fits in and the layer thickness can be reduced. As a result, the coating layer of the silicone oil 40 on the heat roller 41 can be made uniform and thin, and even when an OHP sheet is used as the recording medium, there is no excess oil and there is no problem of stickiness with oil. The toner image can be fixed. At this time, since there is no excess oil, uneven coating on the surface of the heat roller 41, oil streaks, etc. do not occur, and deterioration of image quality due to defective fixing can be prevented.

In order to regulate the amount of silicone oil applied to the application roller 45, the blade 46 is brought into pressure contact. The amount of silicone oil applied to the application roller 45 can be controlled by changing the pressure contact state. Therefore, as the above-mentioned sheet, not only the toner image of only the sheet such as OHP sheet but also the sheet of plain paper can be fixed.

Particularly, when the recording medium is a plain paper sheet, it is necessary to increase the amount of the silicone oil 40 applied to the application roller 45 to some extent. That is, the OHP sheet hardly absorbs the silicone oil by itself, so that in the case of the plain paper sheet, it is necessary to increase the coating amount of the silicone oil.

For this purpose, it is possible to control the angle θ at which the tip of the blade 46 is pressed against the coating roller 45 according to the material of the sheet used. For example, in FIG.
As shown in, the tangent line of the point where the tip of the blade 46 contacts the coating roller 45 and the blade 46 when the tip contacts
The angle formed by the application roller 45 and the antinode surface is θ. By increasing the angle θ, the coating roller 45
The uniform application amount of silicone oil can be reduced, and the smaller application amount of silicone oil can be increased.

For example, in the case of fixing the image forming on the OHP sheet, the angle θ is
For example, if it is set to 32 ° (± 3 °) or 16 ° (± 3 °) for a plain paper sheet, it is possible to cope with an OHP sheet or a plain paper sheet and to achieve better fixing. it can.

With this arrangement, the contact angle θ of the blade 46 can be adjusted so that good fixing can be achieved for each sheet. In particular, it is possible to perform uniform application, and it is possible to achieve good fixing without application unevenness due to excessive silicone oil and oil streaks.

(Second Embodiment of the Present Invention) On the other hand, in the first embodiment of the present invention, an application roller 45 is provided,
In order to uniformly apply the silicone oil to the heat roller 41 by the application roller 45, the surface roughness Rz of the application roller 45 is set to 10 μm or less.

Therefore, as described above, the surface roughness Rz of the coating roller 45 is set to 10 μm or less, preferably about 5 μm so that the color toner image formed on the OHP sheet can be well fixed. There is. In the case where the color toner image formed on the plain paper sheet is fixed, the contact angle θ of the blade 46 is controlled in order to increase the amount of silicone oil applied. Instead of the blade 46 that is controlled each time according to the type of sheet to be used, an embodiment having the configuration described below can be implemented.

As shown in FIG. 1, on the downstream side of the rotation of the heat roller 41, that is, on the side close to the nip portion in pressure contact with the pressure roller 42, the first roller having the same structure as the coating roller 45 described in the first embodiment is formed. Two coating rollers 47 are provided, and the coating roller 45 or the coating roller 47 is selectively used.

That is, the coating member 44, the coating roller 45, and the regulating blade 46 described in the first embodiment.
And the like to form the first coating unit, and the second coating unit including the above-described second coating roller 47 described below is separately installed in parallel to configure the coating device. Any one of the coating means is selected and used according to the material of the recording medium.

Therefore, also in the second coating roller 47, a coating member 48 for supplying and coating silicone oil.
And a regulating blade 49 for equalizing the layer of the silicone oil applied in the same manner are similarly provided to constitute the second applying means. In addition, in order to return excess silicone oil to the oil tank 37, the coating member 4
A recovery member 48a is provided on the back surface of the device 8.

The second coating roller 47, the coating member 48, the regulating blade 49, etc. constitute a second coating means, and a uniform silicone oil layer is formed on the surface of the second coating roller 47. The heat roller 41 is formed.
It is applied evenly on. Also in the second applying means, as with the first applying means, the materials for the second applying roller 47, the applying member 48, and the regulating blade 49,
The structure is the same.

In the second coating means, especially the second
The surface roughness Rz of the coating roller 47 is roughened by about 5 μm with respect to the surface roughness Rz of the first coating roller 45 constituting the first coating unit according to the first embodiment. this is,
This is to support fixing of plain paper sheets. That is,
The plain paper sheet also absorbs silicone oil, and unlike the OHP sheet, it tends to absorb the silicone oil applied to the heat roller 41 and gradually decrease. In order to compensate for this, the amount of silicone oil applied to the heat roller 41 is increased to prevent toner from adhering and at the same time prevent excessive application of silicone oil.

In the blade 49 as well, the pressure contact tip portion is provided close to the contact tip of the coating member 48.

Therefore, the above-described first and second coating units are selectively used according to the type of sheet used. Therefore, the heat roller 41 on the side of the second coating means
Supply or shut off the supply of silicone oil to the. As an example thereof, as shown in FIG. 4A, the second coating roller 47 is provided so as to be able to come into contact with and separate from the heat roller 41. Therefore, when performing fixing of plain paper on the sheet, the second coating roller 47 is contacted as shown in Figure 1 with respect to the heat roller 41. As a result, the amount of silicone oil applied to the heat roller 41 can be increased. Therefore, a good color toner image can be fixed to the plain paper sheet.

In this case, the first application roller 45, which is the first application unit, is separated from the heat roller 41. Further, even if they are brought into contact with each other as they are, the second application roller 47 only applies more silicone oil, and the amount applied by the second application roller 47 should be set small in anticipation of this. May be.

When the OHP sheet is fixed, the second coating roller 47 is separated from the heat roller 41 as shown in FIG. 4 (a). As a result, by uniformly applying the silicone oil to the heat roller 41 by the applying roller 45 constituting the first applying means, uneven application of the surface of the heat roller 41 and oil streaks are eliminated by excessive supply.

On the other hand, another method is conceivable as means for cutting off the application state of the silicone oil to the heat roller 41 without directly contacting and separating the second application roller 47 from the heat roller 41. That is to cut off the supply of silicone oil to the second coating roller 47. For that purpose, the supply coating member 48 is provided so as to be able to come into contact with and separate from the second coating roller 47 as shown in FIG. 4B. With this configuration, in the case of the plain paper sheet as in the case of the fourth (a), as shown in FIG.
The sheet P is separated from the application roller 47 as shown in FIG. This allows plain paper or OHP
The color toner image is satisfactorily fixed on the sheet. Also in this case, the coating member 44 constituting the first coating means is provided so as to be able to come into contact with and separate from the coating roller 45 so that the sheet is in contact with an OHP sheet and is separated from a plain sheet. To do.

Here, regarding the surface roughness Rz of the second coating roller 47, when the first and second coating means are selected and used, the surface roughness Rz of the first coating roller 45.
To about 5 μm. Therefore, at least R
z is set to less than 15 μm. When the thickness is preferably 10 μm, the silicone oil layer applied to the second applying roller 47 can be made uniform by the regulating blade 49.

When forming a color image using a plain paper sheet or an OHP sheet, the operator selects the operation key on the operation panel to control the supply of the sheet oil by the above-mentioned second application means. It can be done by That is, by selectively operating the operation key of the plain paper sheet or the OHP sheet, the supply or non-supply of the silicone oil can be controlled according to the operation. In addition, in order to perform automatically, a plain paper sheet or an OH
It is also possible to provide a sensor for determining whether the sheet is a P sheet and control the supply or non-supply of the silicone oil described above according to the output from the sensor.

Such control controls the contact angle θ of the blade 46 that regulates the coating amount when uniform coating is performed by the first coating roller 45 in FIG. 1 without providing the second coating means. What can be done is as described in the first embodiment.

As described above, the experimental results are shown below in order to confirm the effect of the coating apparatus described in the first and second embodiments of the present invention.

The surface roughness Rz of the first coating roller 45 is set to 5
μm, the surface roughness Rz of the second coating roller 47 is 10 μm
And Then, the first and second coating rollers 45, 47
Hardness of 40 to 70 degrees (hardness of Asker C). At this time, the pressure of the first and second coating rollers 45, 47 contacting the heat roller 41 was set to a total pressure of 1.5 to 3 kg. Further, in the regulation blades 46 and 49, a silicone rubber having a hardness of 40 to 70 degrees (hardness of Asker C) is coated with a fluororesin (polytetrafluoroethylene tape) having a thickness of about 80 μm.
5, 47 are pressed against each other at a pressure of 500 to 1800 g.

When the A4 size OHP sheet thus constructed was passed through the fixing device 4, the consumption of silicone oil was confirmed to be 5 to 10 mg. Also,
In the case of A4 size plain paper sheet, the consumption of silicone oil was 10 to 20 mg. OH
In the case of the P sheet, the second application roller 47 is separated and the supply of the silicone oil is cut off. In the case of a plain paper sheet, the first application roller 45 is separated and the silicone oil is supplied. Feed application was turned off.

On the other hand, as the coating means of the comparative example,
Using only the coating roller 45, the surface roughness Rz at that time is 15
μm, and the hardness of the silicone rubber roller was 80 degrees (the hardness of Asker C). The pressure contact force of the coating roller 45 to the heat roller 41, the material and hardness of the blade 46, and the pressure contact force to the coating roller 45 were the same as those of the present invention.

As a result, the amount of silicone oil consumed by the A4 size plain paper sheet is 20 to 90 mg, which is larger than that of the present invention. Therefore, when the toner was fixed to the OHP sheet, the silicone oil was excessively supplied, and uneven coating on the heat roller 41 and generation of oil streaks were gradually observed. The above results are shown in detail in Table 1.

[0089]

[Table 1]

As shown in Table 1, when the surface roughness Rz of the coating roller 45 according to the comparative example is set to 15 μm or more, the amount of silicone oil consumed by the plain paper sheet increases, and the silicone oil is used in the initial stage of image formation. Although there was no problem in supplying the oil, the supply of silicone oil to the heat roller 41 gradually became excessive, and the occurrence of oil streaks and coating unevenness was observed. That is, the surface roughness Rz by the coating roller 45 is not 15 μm or more as in the conventional case, but at least the surface roughness Rz of the coating roller 45 is 1 or more.
By setting it to 0 μm or less, preferably 5 μm, O
Good fixing with the HP sheet can be made possible.

Also in the plain paper sheet, the second coating roller 47 and the like are provided, and the surface roughness thereof is set to be about 5 μm rougher than the surface roughness Rz of the first coating roller 45. The consumption can be reduced and good fixing can be maintained.

In Table 1, the contact angle θ by the blade 46 is shown when only the first coating roller 45 is provided. That is, by setting the contact angle θ of each of the OHP sheet and the plain paper sheet to the indicated value, it is possible to equalize the consumption of silicone oil by each sheet when the second coating roller 47 is not provided.

[0093]

According to the fixing device of the present invention, in the application of the release agent for preventing offset, the first and the first and second application apparatuses are provided with different application amounts so as to eliminate excessive supply of the release agent .
The material of the recording medium to be used is composed of two coating means.
The OH is selectively used according to
The fixing of the toner image on the P sheet can be always maintained in a good state.

Further, by controlling the supply of the release agent by the second coating roller which constitutes the second coating means so as to be able to deal with the plain paper sheet, too much release agent is similarly supplied. Therefore, good toner image fixing can be maintained.

As a toner image, particularly in the fixing of a color toner image which requires a large amount of a releasing agent, it is possible to maintain a good fixing state without excessive supply.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a schematic structure of a fixing device equipped with a coating device for explaining a first embodiment of a fixing device of the present invention.

FIG. 2 is an enlarged view for explaining an example for controlling a coating amount by a coating device in the fixing device shown in FIG.

FIG. 3 is a configuration diagram showing an internal structure of a color image forming apparatus including the fixing device shown in FIG.

FIG. 4 shows an operation example when controlling the coating amount according to the material of the sheet used in the coating device for explaining the second embodiment of the fixing device of the present invention,
FIG. 7A is a diagram showing an example in which a coating roller is provided so that it can be brought into contact with and separated from each other, and FIG.

FIG. 5 is a configuration diagram showing a schematic structure of a conventional fixing device.

[Explanation of symbols]

3 Image forming section 4 fixing device 15 Photosensitive drum 36 Silicone Oil Supply Bottle 37 oil tank 40 Silicone oil (release agent) 41 Heat roller 42 Pressure roller 43 Heater lamp (heating source) 44 Coating member 45 coating roller 46 regulation blade 47 Second coating roller (second coating means) 48 coating member (second coating means) 49 Control blade (second coating means)

Claims (5)

(57) [Claims] 1. A heat roller, the surface of which is heated to a desired temperature, and a pressure for adhering a recording medium bearing an unfixed image, which is pressed and sent to the heat roller, to the heat roller side. A fixing device of an image forming apparatus for fixing the unfixed image by passing the recording medium between the heat roller and the pressure roller to form an image. A coating device is provided to prevent the unfixed image carried on the recording medium from adhering, and the coating device includes a first coating unit that is pressed against the heat roller to coat the release agent, and And a second coating unit having a coating amount greater than that of the first coating unit . The second coating unit is provided below the first coating unit.
Only, tanks for storing the release agent below the second coating means
The release agent in the tank is disposed in the first and second applying means.
First and second coating members for supplying and coating the first recording medium and the second coating member are provided, depending on the material of the recording medium.
A fixing device for an image forming apparatus, which is characterized in that it selectively uses the coating means of. Wherein said first coating means was applied to supply the first coating roller for applying the releasing agent is pressed against the said heat roller, and to said first coating roller a release agent
One end is immersed in the release agent inside the tank and the other end
A first coating member that is in contact with the first coating roller, a first regulating blade that regulates the supplied release agent on the surface of the first coating roller in a uniform state, and the second coating described above. The means is a second coating roller for coating the heat roller with a release agent, and one end for supplying the release agent to the second coating roller for coating is a release agent in the tank.
And the other end side is in contact with the second coating roller.
The second coating member to make the amount of the release agent supplied uniform.
A second regulating blade is provided, and the second regulating blade is provided.
The image forming apparatus described. 3. The first or second coating means can selectively contact the heat roller with the first and second coating rollers for selective use according to the material of the recording medium to be used. 3. The fixing of the image forming apparatus according to claim 2, wherein the first and second coating members for supplying and coating the release agent are provided so as to be in contact with and separated from the first and second coating rollers. apparatus. 4. The fixing device for an image forming apparatus according to claim 2, wherein the surface roughness of the second coating roller is set to be rougher than the surface roughness of the first coating roller. 5. The surface roughness Rz of the first coating roller is set to 10 μm or less, and the surface roughness Rz of the second coating roller is set to be 5 μm rougher than the roughness of the first coating roller. The fixing device for an image forming apparatus according to claim 4, wherein