JP2003280427A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a fixing device capable of obtaining a satisfactory quality image regardless of a state of the surface of a transfer material and regardless of a case where images of thick accumulation of toner, such as solid images, or toners of monochrome halftone or the like are interspatially attached to the transfer material. <P>SOLUTION: The fixing device has a rotary body having a heat source, and a pressure member which forms a pressure contact portion together with the rotary body. The fixing device transports a recording material through the pressure contact portion while sandwiching it between them and thus thermally fixes a toner image, electrostatically formed on the surface of the recording material, onto the recording material. In the fixing device, a voltage is applied to the rotary body or the pressure member, and the value of the applied voltage is changed according to a state of the surface of the recording material. Specifically, the value of the applied voltage is increased in the case where the roughness of the recording material is large, but the value of it is decreased in the case where the roughness is small. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device and an image forming apparatus such as a copying machine, a laser printer, a facsimile or the like having the fixing device.

[0002]

2. Description of the Related Art A conventional image forming apparatus will be described with reference to the drawings.

FIG. 6 is a sectional view of a conventional full-color image forming apparatus capable of obtaining a full-color image by superposing four color toners.

The image forming apparatus shown in FIG. 6 includes a photosensitive drum 1 as an image carrier. First, the surface of the photosensitive drum 1 is uniformly charged by the charging device 2, and then the exposure device 3 performs scanning exposure with a laser beam whose ON / OFF is controlled according to the first image information. , An electrostatic latent image is formed.

The electrostatic latent image thus formed is visualized by the developing device 4. The developing device 4 includes a first developing device 4a containing black toner as the first color toner, a second developing device 4b containing magenta toner as the second color toner, and a third color toner. As
The third developing unit 4c which cyan toner is contained as toner of a fourth color, and a fourth developing device 4d in which yellow toner is contained, it was mounted rotatably in the arrow D ₁ direction rotary support It has and. This rotary support is indicated by arrow D
By rotating in _one direction, the developing device used for development is sequentially arranged at the developing position facing the photosensitive drum 1.

The above-mentioned first electrostatic latent image is a first developing device 4a containing black toner as the toner of the first color.
Is developed as a black toner image. The developed first toner image is primarily transferred onto an intermediate transfer belt (intermediate transfer member) 5 a forming a part of the transfer unit 5.

The intermediate transfer belt 5a is pressed against the surface of the photosensitive drum 1 with a predetermined pressing force by the primary transfer roller 6 disposed inside the intermediate transfer belt 5a, and a primary transfer nip portion T ₁ is formed between the intermediate transfer belt 5a and the photosensitive drum 1. Is forming. The intermediate transfer belt 5a is rotationally driven in the rotational direction of the photosensitive drum 1 (direction of arrow D ₂ ) at substantially the same speed as the peripheral speed of the photosensitive drum 1.
The toner image formed on the surface of the photosensitive drum 1 described above has a voltage (primary transfer bias) having a polarity opposite to the charging polarity of the toner applied to the primary transfer roller 6 by a primary transfer bias application power source (not shown). By being applied, electrostatically primary transfer is performed on the surface of the intermediate transfer belt 5a. The cleaning device 7 removes a small amount of the primary transfer residual toner remaining on the surface of the photosensitive drum 1 after the primary transfer.

Subsequently, the series of image forming steps described above, that is, the primary charging, the exposure, the development, the primary transfer and the cleaning are repeated for the remaining three colors, and each time, the second toner image developed with magenta toner, cyan. The third toner image developed with the toner and the fourth toner image developed with the yellow toner are sequentially primary-transferred onto the surface of the intermediate transfer belt 5a and superposed.

After that, the secondary transfer roller 8 which is in a separated state from the surface of the intermediate transfer belt 5a is pressed against the surface of the intermediate transfer belt 5a with a predetermined pressing force, and a secondary transfer nip is formed between the secondary transfer roller 8 and the intermediate transfer belt 5a. Form part T ₂ . The secondary transfer roller 8 is driven to rotate in the direction of the arrow D ₃ , and a voltage (secondary transfer bias) having a polarity opposite to the charging polarity of the toner is applied by the secondary transfer bias applying means (not shown). , The intermediate transfer belt 5 on the surface of the transfer material P conveyed to the secondary transfer nip portion T ₂ at a predetermined timing.
The toner images of four colors superposed on the surface a are secondarily transferred at once.

The recording material P carrying the toner image is conveyed through the entrance guide plate 9 while being heated and pressed by a fixing roller 10 and a pressure roller 11 having a heating source (not shown) inside, and is fixed. Finish. After the secondary transfer of the toner image, the secondary transfer residual toner slightly remaining on the surface of the intermediate transfer belt 5a is in contact with the surface of the intermediate transfer belt 5a at a predetermined timing by a driving unit (not shown). Is removed by the cleaning roller 21.

However, in the above arrangement, when fixing the toner image, a part of the toner image is fixed to the fixing roller 1.
In some cases, the offset image was generated because the toner was attracted to the 0 side and the toner was again discharged onto the transfer material P after one round of the fixing roller 10.

Here, the offset is usually the recording material P.
The toner charged to the negative polarity on the surface of the recording material P, which is held by the positive charge on the back surface, is formed by a fixing roller 10 having an insulating or semi-conductive surface and a pressure roller 11 having an insulating surface. (Hereafter, "fixing nip part")
When the surface potential of the fixing roller 10 in the vicinity of the fixing nip portion fluctuates in the positive direction, the recording medium P cannot be held due to the positive charge on the back surface of the recording material P and moves to the fixing roller 10 side. .

The adhered toner returns to the transfer material P again after one rotation of the fixing roller 10, and appears as an image defect on the transfer material P. This offset phenomenon
In particular, it becomes remarkable in a solid image in which two or more color toners are superposed in a color image forming apparatus in which two or more color toners are superposed to form a color image. That is, on the surface where the toner layer is thick and thick, it is difficult to hold all the toner due to the charges on the back surface of the transfer material P, and the offset phenomenon is likely to occur.

In order to prevent this phenomenon, it is conceivable that the surface of the fixing roller 10 is made conductive, but in this case, the negative electric charge of the toner will escape through the fixing roller, and the plus on the back of the paper. The electric charge makes it impossible to hold the toner. As a result, an offset phenomenon will eventually occur, which is not a fundamental solution.

On the other hand, in the conventional image forming apparatus, there is a method of applying a negative bias to the fixing roller 10 to generate a repulsive electric field between the fixing roller 10 and the toner to prevent the offset. Being tried.

FIG. 7 is a sectional view of a fixing device of a conventional image forming apparatus in which a negative bias is applied to the fixing roller 10.

In FIG. 7, a negative bias is applied to the fixing roller 10 from the bias power source 12, and the surface of the fixing roller 10 is negatively charged. As a result, a repulsive electric field is generated between the toner and the surface of the fixing roller 10, and an attempt has been made to prevent the offset phenomenon.

Further, in recent years, a bias is applied to the fixing roller 10, and a conductive paper discharge roller connected to the ground is provided immediately after the fixing nip portion, and the fixing roller 10 passes through the transfer material P to the paper discharge roller to the ground. There has been proposed a configuration in which an offset is prevented by forming a current path that flows. This configuration will be described in detail with reference to FIG.

In FIG. 8, reference numeral 17 is a bias applying means for applying a negative bias to the fixing roller. or,
The paper discharge roller 18 is electrically conductive and is connected to the ground. The bias applied from the bias applying unit 17 passes through the fixing roller 10 and the transfer material P, and the discharge roller 18
A current path is formed by flowing from the ground to the ground.

In this current path, the transfer material P is fed to the fixing nip portion.
Is more effectively formed by the generation of water vapor as it passes. That is, the current path is not generated by the bias applied to the fixing roller 10 directly penetrating to the back surface of the transfer material P in the fixing nip portion, but by the water vapor generated after the transfer material passes through the fixing nip portion. It occurs because the resistance of the transfer material P decreases.

Therefore, in a normal use condition, the transfer material P is provided on the upstream side of the fixing nip portion or in the fixing nip portion.
A current path is formed without damaging the transfer charge on the back surface.

By forming the current path in this manner, an electric field is formed between the surface of the toner layer and the back surface of the transfer material P. Due to this electric field, even when the toner is thick in volume, a force for pressing the toner particles to the transfer material side is generated, and a good image can be obtained without the uppermost toner layer adhering to the surface of the fixing roller.

[0023]

However, even in the above configuration, the offset phenomenon may still occur. In particular, the study by the present inventor has revealed that the conditions under which the offset occurs vary depending on the surface property of the transfer material P and the image pattern.

That is, in the case of the transfer material P having a rough surface, the toner enters the unevenness of the transfer material, and due to the unevenness of the transfer material, a gap (air layer is present between the fixing roller and the toner layer). ) Will occur. Since this air layer functions as a heat insulating layer, the toner is in an insufficiently melted state, and a larger bias value is required to prevent the offset phenomenon. In this case, as described above, it becomes remarkable when a solid image or a color image is formed by superposing toner images of two or more colors. This is because when toner is stacked thickly, more energy is required for melting the toner, so that the amount of toner attracted to the fixing roller 10 in an insufficiently fixed state increases.

On the contrary, in the case of the transfer material P having a smooth surface, for example, the toner of only one color is on the transfer material P with a gap (for example, a monochromatic halftone image corresponds to this). By applying an excessive bias, the contact portion between the fixing roller 10 and the toner particles is increased, so that the toner particles are very strongly and negatively charged, rather the repulsive force between the toner particles is increased, and the offset phenomenon is caused. It tends to occur.

Further, in the case of a monochromatic halftone image on the transfer material P having a smooth surface, the contact area between the transfer material P and the fixing roller is large, and an electric current is easily generated in the fixing nip portion in a direction penetrating the transfer material P. The positive charge held on the back surface of the transfer material P and the negative charge due to the fixing bias cancel each other, and the charge on the back surface of the transfer material P is easily lost before the toner image enters the fixing nip portion.

As a result, the negatively charged toner retained by the positive charge on the back surface of the transfer material P loses the force retained by the transfer material P and is attracted to the fixing roller 10 side to cause an offset phenomenon. There was a problem that it would end up.

The present invention has been made in view of the above problems, and the object of the present invention is, regardless of the surface state of the transfer material,
A fixing device and an image forming device that can obtain a high-quality image without offset regardless of whether a thick image such as a solid image is accumulated or a toner such as a monochromatic halftone is left on a transfer material with a gap. To provide a device.

[0029]

In order to achieve the above object, the present invention comprises a rotating body having a heating source and a pressure member forming a pressure contact portion of the rotating body, and recording on the pressure contact portion. In a fixing device in which a material is nipped and conveyed and a toner image electrostatically formed on the surface of the recording material is thermally fixed on the recording material, a voltage is applied to the rotating body or the pressure member. The value of the applied voltage is changed according to the surface condition of the recording material.

Further, according to the present invention, a latent image carrier for carrying a latent image, a carrying section for carrying a recording material in a predetermined direction, a developing means for developing a toner image on the latent image carrying body, and the carrying section. An image forming apparatus is configured to include a transfer unit that transfers an image onto a recording medium that is conveyed by the fixing unit and the fixing device.

[0031]

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

<First Embodiment> FIG. 1 is a sectional view of an image forming apparatus according to a first embodiment of the present invention. As the image forming apparatus according to the present exemplary embodiment, a full color image forming apparatus that can obtain a full color image by overlapping toners of four colors is used.

The image forming apparatus shown in FIG. 1 includes a photosensitive drum 1 as an image carrier. The surface of the photosensitive drum 1 is first uniformly charged by the charging roller 2 as a charging device, and then, the exposure exposure is performed by the laser beam ON / OFF controlled by the exposure device 3 according to the first image information. By performing the above, an electrostatic latent image is formed.

The electrostatic latent image thus formed is visualized by the developing device 4. The developing device 4 includes a first developing device 4a containing black toner as the first color toner, a second developing device 4b containing magenta toner as the second color toner, and a third color toner. , A third developing device 4c containing cyan toner, a fourth developing device 4d containing yellow toner as a fourth color toner, and a rotatably supporting member for mounting them in the direction of arrow D1. It has a body. This rotary support is indicated by arrow D1
By rotating in the direction, the developing device provided for development is arranged in order at the developing position facing the photosensitive drum 1.

The above-mentioned first electrostatic latent image is a first developing device 4a containing black toner as the toner of the first color.
Is developed as a black toner image. The developed first toner image is primarily transferred onto an intermediate transfer belt (intermediate transfer member) 5 a forming a part of the transfer unit 5. The intermediate transfer belt 5a is, for example, PVdF adjusted to have a thickness of 50 to 200 μm and a volume resistivity of 10 ⁸ to 10 ¹⁴ Ω · cm,
It is made of a resin such as PET, polycarbonate, polyethylene, or silicone.

Further, the thickness is 0.3 to 2 mm and the volume resistivity is 10
Thickness of 2 to 2 on elastic base layer such as urethane rubber, hydrin rubber, NBR, EPDM etc. adjusted to ⁴ to 10 ⁸ Ω · cm
A rubber or resin adjusted to have a volume resistivity of 10 ⁸ to 10 ¹⁴ Ω · cm may be provided as the surface layer. The peripheral length of the intermediate transfer belt 5a is set to 441 mm, and the intermediate transfer belt 5a is stretched around the rollers 5b, 5c, and 5d.

The intermediate transfer belt 5a is pressed against the surface of the photosensitive drum 1 with a predetermined pressing force by the primary transfer roller 6 disposed inside the intermediate transfer belt 5a, and a primary transfer nip portion T1 is formed between the intermediate transfer belt 5a and the photosensitive drum 1. is doing. The intermediate transfer belt 5a is rotationally driven in the rotation direction of the photosensitive drum 1 (direction of arrow D2) at substantially the same speed as the peripheral speed of the photosensitive drum 1.

The toner image formed on the surface of the photosensitive drum 1 is applied to the above-mentioned primary transfer roller 6 by a primary transfer bias application power source (not shown) with a voltage (primary transfer) having a polarity opposite to the charging polarity of the toner. By applying a bias, electrostatically primary transfer is performed on the surface of the intermediate transfer belt 5a. The cleaning device 7 removes a small amount of the primary transfer residual toner remaining on the surface of the photosensitive drum 1 after the primary transfer.

Subsequently, the series of image forming steps described above, that is, the primary charging, the exposure, the development, the primary transfer, and the cleaning are repeated for the remaining three colors, and the second toner image developed with the magenta toner each time. Similarly, the third toner image developed with cyan toner and the fourth toner image developed with yellow toner are transferred to the intermediate transfer belt 5a.
It is primarily transferred to the surface and superposed.

After that, the secondary transfer roller, which has been separated from the surface of the intermediate transfer belt 5a, is brought into pressure contact with the surface of the intermediate transfer belt 5a with a predetermined pressing force, and the secondary transfer nip portion is formed between the secondary transfer roller and the surface of the intermediate transfer belt 5a. Form T2. The secondary transfer roller is rotationally driven in the direction of arrow D3, and a voltage (secondary transfer bias) having a polarity opposite to the charging polarity of the toner is applied by a secondary transfer bias applying unit (not shown), The toner images of the four colors superposed on the surface of the intermediate transfer belt 5a are secondarily transferred onto the surface of the transfer material P conveyed to the next transfer nip portion T2 at a predetermined timing.

The transfer material P after the secondary transfer of the toner image is indicated by an arrow D.
It is conveyed to the fixing device in four directions, where it is heated and pressed to be fixed as a permanent image, and then discharged outside the apparatus (outside the main body of the image forming apparatus).

After the secondary transfer of the toner image, the intermediate transfer belt 5a has a small amount of secondary transfer residual toner remaining on the surface of the intermediate transfer belt 5a on the surface of the intermediate transfer belt 5a at a predetermined timing by a driving means (not shown). It is removed by the cleaning roller 21 in the contact state. The cleaning roller 21 has, for example, a surface layer of rubber, resin, or the like, which is adjusted to have a thickness of ² to ⁶ mm and a volume resistivity of 10 ⁴ to 10 ⁶ Ω · cm around a core metal, and is formed on the surface of the photosensitive drum 1. When the toner images are sequentially primary-transferred onto the surface of the intermediate transfer belt 5a, they are separated from the surface of the intermediate transfer belt 5a, and the toner image on the surface of the intermediate transfer belt 5a is brought into contact with the surface of the transfer material P,
A bias is applied by a high voltage power supply (not shown).

As a result, the secondary transfer residual toner remaining on the surface of the intermediate transfer belt 5a is charged to a charging polarity opposite to the original charging polarity, and the first color black of the subsequent image forming process is continuously performed. At the same time that the first toner image of the toner is primarily transferred from the surface of the photosensitive drum 1 to the surface of the intermediate transfer belt 5a, it is reversely transferred from the surface of the intermediate transfer belt 5a to the surface of the photosensitive drum 1 at the primary transfer nip portion T1. The cleaning process of the surface of the transfer belt 5a is completed.

Next, the fixing device according to the present embodiment will be described in detail with reference to FIG.

In FIG. 2, the fixing roller 10 has an outer diameter of 30.
A surface layer 10-b of a fluororesin such as PFA having a thickness of about 30 μm is provided on an aluminum cylinder 10-a having a thickness of 2 mm and a thickness of 2 mm. Further, a halogen heater (not shown) is provided as a heating body inside, and heats the fixing roller 10 to a proper temperature by a predetermined control.

The pressure roller 11 has an outer diameter of 24 mm and an outer diameter of 1
An elastic layer 11-b of silicone sponge is provided on a core metal 11-a of 2 mm, and a nip that gives a sufficient amount of heat for fixing is pressed against the fixing roller. or,
The outermost layer of the pressure roller 11 is formed of a PFA tube 11-c having a thickness of 30 μm to improve releasability.

Here, a conductive agent is dispersed in the surface layer 10-b of the fixing roller, and the volume resistance value is from 10 ⁵ Ω · cm to
It is adjusted to about 10 ¹³ Ω · cm. On the other hand, the PFA tube which is the outermost layer of the pressure roller 11 has a resistance of 10 ¹⁴ Ω.
-Fixing roller surface layer 10 having a volume resistance value of cm or more
It has a higher resistance value than -b.

As the conductive agent dispersed in the surface layer of the fixing roller, an arbitrary conductive agent such as an ion conductive conductive agent such as an organic phosphorus salt or an organic salt containing a perfluoroalkyl group, or an electronic conductive conductive agent such as carbon is used. Can be used. In this embodiment, carbon is dispersed in the surface layer of the fixing roller in an amount of 5% by weight to reduce the volume resistance to about 1.
It is formed to be 0 ⁹ Ω · cm.

The aluminum cylinder as the fixing roller base is connected to the ground. Entrance guide plate 9
Determines the position where the recording material P enters the fixing nip portion, and prevents paper wrinkles and the like.

Further, the aluminum cylinder 10-a is connected to the bias power source 12, and the bias power source 12 can apply an arbitrary voltage. The voltage applied from the bias power source 12 to the fixing roller 10 is controlled by the CPU 13 in the image forming apparatus. The bias power supply of the present embodiment can change the voltage in the range of 0V to -1kV.

Three types of rough paper (A, B, C) such as bond paper are used as transfer materials for image output in the present embodiment.
3 types of plain paper (D, E, F), 3 types of smooth paper (G,
H, I) were prepared respectively. Table 1 shows the results of measuring the Beck smoothness of each paper type.

The measuring method of Beck's smoothness is JIS-P-
Based on 8119. That is, the time (unit: second) during which 10 ml of air passes between the glass surface having an area of 10 square centimeters (diameter 37.4 mm) and the paper surface is measured.
In this test method, paper with a rough surface has a low numerical value, and paper with a smooth surface has a high numerical value.

[0053]

[Table 1] The following three types of image patterns were used for image output.

A pattern in which a so-called secondary color solid image, in which a solid image of cyan and magenta is superimposed, is drawn on a portion between the tip 5 mm to 80 mm, and the latter half is a solid white image. This image is considered the most severe, as electrostatic offset is more noticeable in the thick toner buildup.

A pattern in which a halftone of a single color of magenta is printed on the portion between 5 mm and 80 mm at the leading end, and a solid white image is formed in the latter half. In a single-color halftone image, the toner distribution is sparse, so it is considered that the image is the most severe against charging to the toner and penetrating negative charges into the back surface of the transfer material P in the nip portion.

Practical image. Specifically, an image including a solid portion of a secondary color and a halftone image of a single color in an appropriate ratio by a combination of a graph and characters. We prepared images that are considered to be commonly used in actual user usage.

In the image forming apparatus according to the present embodiment, the user can select three modes (rough paper mode,
The plain paper mode and the smooth paper mode) are set so that any mode can be selected.

The fixing bias value at this time was set to -1000V in the rough paper mode, -500V in the plain paper mode, and -100V in the smooth paper mode. The mode is selected from the operation panel (not shown) of the image forming apparatus.

Table 2 shows the evaluation results of the offset levels of the secondary color solid and the monochromatic halftone when the image is output in each mode for each paper type.

[0060]

[Table 2] In the table, ∘: a level without any problem, Δ: an offset is seen, but there is no problem with a practical image, x: a level with a severe offset, which is not acceptable in a practical image.

From this table, the level of the secondary color offset is not improved unless the bias is increased as the surface of the transfer material is rough, and conversely, the level of the single color offset is biased as the surface of the transfer material is smoother. It can be seen that there is no improvement unless lowering. In summary, it can be seen that it is appropriate to print in the rough paper mode for Beck smoothness of 10 seconds or less, in the plain paper mode from 11 seconds to 51 seconds, and in the smooth paper mode for 52 seconds or more.

In the present embodiment, the color image forming apparatus has been described as an example, but of course, the present invention can be applied to a monochrome image forming apparatus using only a single color. or,
In this embodiment, three types of modes, that is, a rough paper mode, a plain paper mode, and a smooth paper mode are provided, but an image forming apparatus having two kinds of modes or an image forming apparatus having four or more kinds of modes is also available. Naturally conceivable. Further, in addition to performing the mode setting from the operation panel of the image forming apparatus main body, when the image forming apparatus is connected to the host computer, the mode setting command is transmitted from the computer and the mode is changed in response to the command. It may be configured to perform.

<Second Embodiment> FIG. 3 shows a sectional view of an image forming apparatus according to a second embodiment of the present invention.

The feature of this embodiment is that it is the same as the first embodiment.
Allows the user to manually input the transfer material type, but the sensor provided in the image forming device can automatically detect the surface property of the transfer material and select an appropriate fixing bias mode. There is a point.

In this embodiment, the image forming process itself is the same as that in the first embodiment, but the transfer material surface property detecting member 14 is provided on the transfer material conveying path. Transfer material surface property detection member 14 in the present embodiment
As shown in FIG. 3, the transfer material P is installed on the upstream side of the secondary transfer nip portion T2 and is in a state where an image is not printed.
The surface property of the transfer material P is detected by irradiating the surface with light and detecting the output of reflected light.

The transfer material surface property detecting member will be described in detail with reference to FIG.

In FIG. 4, the upper surface position of the transfer material P is detected by a sensor (not shown) and is always kept at a constant height.

Further, 41 is a light source which is always kept at a constant amount of light, and 42 is a lens which makes the light from the light source 41 parallel light. The light from the light source 41 is reflected by the transfer material P, and the reflected light is The light passes through the lens 43 and is detected by the light receiving element 44. Then, the light receiving element 44 receives the light from the light source 41 at an angle of θ.

In the case of a transfer material having a rough surface,
The amount of reflected light on the transfer material is small, and the amount of reflected light is large when the surface is not rough.

Using this transfer material surface property detecting member 41,
Table 3 shows the outputs detected by the light receiving element 44 for the transfer materials A to I of the first embodiment.

From this result, it is understood that the surface property of the transfer material P can be detected by the output of the light receiving element 44.

Based on this result, when the output of the light receiving element 44 is 0.36 V or less, the rough paper mode is used, when the output is 0.37 V to 0.6 V, the plain paper mode is used.
When the output is 0.61 V or higher, the image forming apparatus is set to enter the smooth paper mode.

[0073]

[Table 3] Using the image forming apparatus according to the present embodiment, an image is output using the same paper type as that of the first embodiment. As a result, an appropriate fixing bias mode is entered for each of rough paper, plain paper, and smooth paper. Similar to the first embodiment, a good image without offset could be obtained.

In the present embodiment, the optical surface property detecting means by irradiating the surface of the transfer material with light and measuring the reflectance of the light is used, but a contact member is provided on the surface of the transfer material during conveyance. By contacting and detecting the vibration of the contact member,
It is of course possible to use a contact type transfer material surface property detecting means for detecting the surface property of the transfer material.

<Third Embodiment> The present embodiment is characterized in that a film fixing device is used as the fixing device.

Referring to FIG. 5, the film fixing device according to this embodiment will be described in detail.

The film type heat fixing device comprises a polyimide film 22 having a release layer made of a fluororesin and having a thickness of about 50 μm, a film guide 20, a resistance heating element, electrodes and a protective glass on a ceramic substrate. And a heater unit including a thermistor 23 arranged on the back surface of the heater and a pressure roller 1 that is pressed against the heater unit by a pressure unit (not shown).
1 is a basic configuration.

The film fixing device according to this embodiment will be described in detail with reference to FIG.

The fixing device according to the present embodiment is disclosed in Japanese Patent Laid-Open No.
It is a film heating system / pressure roller drive system / tensionless type heat fixing device using a cylindrical fixing film disclosed in, for example, JP-A-44075 to 44083.

The fixing member is composed of a heating body 19, a heat insulating stay holder 20, a fixing film 22 and the like. The pressure member is the elastic pressure roller 11. The heating element 19 is a thin-walled and horizontally-long ceramic heater (hereinafter abbreviated as a heater).
Is.

The heat insulating stay holder 20 is a member that holds the heater 19 and prevents heat radiation in the direction opposite to the fixing nip portion, and is made of liquid crystal polymer, phenol resin, PPS, PEE.
It is formed of K or the like. The heat-insulating stay holder 20 is a gutter-shaped gutter-shaped lateral cross section, is heat-resistant and electrically insulating, and is a member that can withstand a high load. The surface side is exposed downward in a groove portion provided along the longitudinal direction and is fitted and fixedly supported.

The fixing film 22 is a cylindrical heat-resistant film, and is loosely fitted to the heat insulating stay holder 20 including the heater with a margin in the circumferential length.
The heat insulating stay holder 20 supports the fixing film 22 from the inner surface.

The fixing film 22 has a small heat capacity, and has a total thickness of 100 in order to enable quick start.
Polyimide, polyamideimide, PEEK, PES, PPS, P having heat resistance and thermoplasticity with a thickness of μm or less
It is a film that uses FA, PTFE, FEP, or the like alone or as a base layer by mixing them.

Further, a film having a total thickness of 20 μm or more is required as a film having sufficient strength and excellent durability to constitute a long-life heat fixing device. Therefore, the total thickness of the fixing film 22 is optimally 20 μm or more and 100 μm or less. Furthermore, in order to prevent offset and ensure the separability of the recording material, PFA, PTFE, FE are used on the surface layer.
A heat-resistant resin having a good releasing property such as P or silicone resin is mixed or coated alone.

A conductive primer layer is provided between the base layer film and the surface layer. This enhances the adhesiveness between the base layer and the surface and at the same time, plays a role similar to that of the conductive substrate in the fixing roller when applying a bias.

The elastic pressure roller 11 as a pressure member is
The heat insulating stay holder 20 is held by a bearing member (not shown).
The fixing film 22 is sandwiched between the downward surface of the heater 19 which is fixedly supported on the lower surface side of the sheet, and a fixing nip portion necessary for heat fixing is formed from both ends in the longitudinal direction by a pressurizing unit (not shown). Pressurized.

The pressure roller 11 is rotationally driven in the counterclockwise direction indicated by the arrow by a driving means (not shown) (pressurizing rotor driving method). A rotational force acts on the fixing film 22 by the pressure contact frictional force between the outer surface of the pressure roller 11 and the outer surface of the fixing film 22 at the fixing nip portion due to the rotational driving of the pressure roller 11, so that the inner surface of the fixing film 22 is fixed. While closely contacting and sliding on the downward surface of the heater 19 in the nip portion, the outer circumference of the heat insulating stay holder 20 is driven to rotate in a clockwise direction indicated by an arrow at a peripheral speed substantially corresponding to the peripheral speed of rotation of the pressure roller 11.

In this case, in the cylindrical fixing film 22 which is driven to rotate around the outside of the heat insulating stay holder 20, the fixing film portion other than the fixing nip portion of the circumference and the fixing film portion in the vicinity thereof is tension-free (the tension is not applied). There is no state).

The inner surface of the fixing film 22 is the heater 1
9 and a part of the outer surface of the heat insulating stay holder 20 are rotated while rubbing against each other, it is necessary to suppress the frictional resistance between the heater 19 and the heat insulating stay holder 20 and the fixing film 22 to be small. For this reason, a small amount of lubricant such as heat resistant grease is provided on the surfaces of the heater 19 and the heat insulating stay holder 20. This allows the fixing film 22 to rotate smoothly.

The pressure roller 11 is rotatably driven, and the cylindrical fixing film 22 is moved along with the rotation of the pressure roller 11.
When the outer circumference of 0 is driven to rotate, the heater 19 is energized, and the temperature of the fixing nip portion rises to a predetermined temperature due to the generated heat, and an unfixed toner image is formed and carried on the fixing nip portion. The recording material P thus introduced is introduced along the fixing inlet guide plate 9, and the unfixed toner image bearing surface side of the recording material P adheres to the outer surface of the fixing film 22 in the fixing nip portion and the fixing nip portion together with the fixing film 22. Is sandwiched and conveyed.

In the sandwiching and conveying process of the recording material P, the heat of the heater 19 is applied to the recording material P through the fixing film 22, and the unfixed toner image on the recording material P is fixed by heat and pressure.

A bias power source is applied from the power source to the conductive primer portion of the fixing film, and the third embodiment
Different bias voltages are applied based on the information from the transfer material surface property detection member similar to the above.

Using the image forming apparatus according to this embodiment, an image is output using the same paper type as in the first embodiment.
By entering an appropriate fixing bias mode, a good image without offset could be obtained as in the first embodiment.

[0094]

As is apparent from the above description, according to the present invention, a rotary member having a heating source and a pressure member forming a press contact portion for the rotary member are provided, and recording is performed on the press contact portion. In a fixing device in which a material is nipped and conveyed and a toner image electrostatically formed on the surface of the recording material is thermally fixed on the recording material, a voltage is applied to the rotating body or the pressure member. Since the value of the applied voltage is changed according to the surface condition of the recording material, an appropriate fixing bias value is selected according to the surface property of the transfer material, and the offset phenomenon A good image that does not occur can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a color image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the fixing device according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional view of an image forming apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram of a transfer material surface property detection member according to a second embodiment of the present invention.

FIG. 5 is a sectional view of a film fixing device according to a third embodiment of the present invention.

FIG. 6 is a schematic sectional view of a conventional image forming apparatus.

FIG. 7 is a schematic cross-sectional view of a conventional fixing device.

FIG. 8 is a schematic sectional view of a conventional fixing device (forming a current path by a fixing bias).

FIG. 9 is a graph showing the relationship between Beck's smoothness and the light-receiving element output.

[Explanation of symbols]

1 photosensitive drum 2 Primary charging mechanism (charging roller) 3 Exposure device (laser scanner) 4 Developing device 4a Black developer 4b Cyan developing device 4c magenta developer 4d yellow developer 5a Intermediate transfer belt 5b to 5d Intermediate transfer belt suspension roller 6 Primary transfer roller 7 Cleaning device 8 Secondary transfer roller 9 Fixing entrance guide plate 10 fixing roller 10-a Fixing roller base (aluminum cylinder) 10-b fixing roller surface layer 11 Pressure roller 11-a Pressure roller core metal 11-b Pressure roller elastic layer 11-c Pressure roller surface layer 12 Bias power supply 14 Transfer material surface property detection member 18 Conductive paper ejection roller 19 heater 20 Thermal insulation stay holder 22 Fixing film 23 Thermistor

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masato Yoshioka             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation (72) Inventor Masahide Hirai             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation F-term (reference) 2H033 AA09 BA13 BA59 BE03 CA16                       CA26                 2H300 EB02 EB12 EC05 EC09 ED01                       ED07 EF08 EH16 EH25 EJ09                       EJ15 EK01 EK03 EK07 EK09                       EK10 GG01 GG02 GG03 GG29                       HH16 KK03 KK06 KK07 KK13                       MM25 NN04 PP02 PP07 QQ03                       QQ10 QQ28 RR22 RR48 RR50

Claims (10)

[Claims] 1. A rotating body having a heating source and a pressure member for forming a pressure contact portion of the rotating body, the recording material being nipped and conveyed by the pressure contact portion, and electrostatically transferred onto the surface of the recording material. In a fixing device for thermally fixing the toner image adhered and formed on the recording material, a voltage is applied to the rotating body or the pressure member, and the value of the applied voltage is changed according to the surface condition of the recording material. Fixing device characterized by changing the temperature. 2. The value of the applied voltage is increased when the surface roughness of the recording material is large, and the value of the applied voltage is decreased when the surface roughness of the recording material is small. The fixing device according to item 1. 3. The fixing device according to claim 1, wherein the applied voltage is increased when the surface smoothness of the recording material is a Beck smoothness of 10 seconds or less. 4. The fixing device according to claim 1, wherein the applied voltage is lowered when the surface smoothness of the recording material is 52 seconds or more in terms of Bekk smoothness. 5. A surface property detecting member for the recording material is provided before the recording material enters the pressure contact portion, and the value of the applied voltage is changed according to the output of the surface property detecting member. The fixing device according to any one of claims 1 to 4. 6. The surface property detection member has a contact member that comes into contact with the recording material, and the surface property of the recording material is detected by detecting vibration of the contact member. The fixing device described. 7. The fixing device according to claim 5, wherein the surface property detecting member irradiates the recording material with light and detects the reflected light to detect the surface property of the recording material. . 8. A heat generating means fixed to the surface of the film guide, a heat resistant fixing film rotatable along the film guide, and a pressing means for pressing a recording material against the fixing film. The fixing device according to claim 1, wherein the fixing device is configured as a film-type fixing device having a temperature detecting means for detecting a temperature as a basic configuration. 9. A latent image carrier that carries a latent image, a transport unit that transports a recording material in a predetermined direction, a developing unit that develops a toner image on the latent image carrier, and a transport unit. An image forming apparatus comprising: a transfer unit that transfers an image onto a recording medium; and the fixing device according to claim 1. 10. The image forming apparatus according to claim 9, wherein the image forming apparatus is a color image forming apparatus that forms a color image by superposing toner images of two or more colors.