JP2001282030A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize not only the prevention of the damage of the surface of a fixing member caused when a separating member abuts on the fixing member but also excellent paper passing ability in the fixing device. SOLUTION: This fixing device 40 is equipped with the separating members 56 and 57 which are arranged on a downstream side in the carrying direction of a recording medium 35 from a contact part 48 between a pair of separating members 41A and 41B and whose tips are opposed by leaving space in between with respect to the members 41A and 41B, an image mode detecting device 23 detecting an image mode, and a separating condition adjusting device 70 adjusting the positions of the members 56 and 57 to the contact part 48 in accordance with the image mode detected by an image mode detecting device 23. The device 70 can adjust the positions of the members 55 and 57 to the contact part 48 based on image density, the outside diameter of a roller, the kind of the recording medium, and the carrying speed or the humidity of the recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer and a facsimile, which heats and melts a developer image transferred from a surface of an image carrier to a recording medium such as a transfer paper or an OHP sheet. And a fixing device for performing fixing.

[0002]

2. Description of the Related Art As a fixing device used in a full-color image forming apparatus, as shown in FIGS. 28 and 29, a pair of fixing rollers 3, 4 and a heating device 5 for heating these fixing rollers 3, 4 are used. A driving device 6 for rotating and driving at least one of the fixing rollers 4, a spring (not shown) for pressing the fixing rollers 3 and 4 against each other with a fixed pressing force, and an axial direction of the fixing rollers 3 and 4. A plurality of separating claws 7,
8 are known. Each of the fixing rollers 3 and 4 includes a cylindrical core 9 and an elastic member 10 provided on a peripheral surface of the core 9. The pair of fixing rollers 3 and 4
The recording medium 12 is conveyed to the contact portion (nip portion 11). The developer on the recording medium 12 is melted and heated by the heat supplied from the fixing rollers 3 and 4 and is fixed on the recording medium 12 by being pressed. Recording medium 12 that has passed through nip portion 11
Is separated from the fixing rollers 3 and 4 with its leading end guided by separation claws 7 and 8.

[0003]

If the tips of the separation claws 7 and 8 are always kept in contact with the surfaces of the fixing rollers 3 and 4,
The recording medium 12 that has passed through the nip 11 can be reliably separated from the fixing rollers 3 and 4. Accordingly, in the case of a fixing device used in a relatively hard monochrome image forming apparatus in which a fluororesin layer such as Teflon (registered trademark) is provided on the surface of the cored bar, the separation claw is usually attached to the fixing roller. Always in contact.

However, when the surfaces of the fixing rollers 3 and 4 are made of the elastic member 10 as in the fixing devices shown in FIGS. 28 and 29, the tips of the separation claws 7 and 8 are brought into contact with the surfaces of the fixing rollers 3 and 4. Then, there is the following problem. First, in the case of a full-color image, since the amount of the release agent applied to the surfaces of the fixing rollers 3 and 4 is large, the release agent is provided between the tips of the separation claws 7 and 8 and the surfaces of the fixing rollers 3 and 4. Accumulates, and the recording medium 12 is soiled by the release agent. Further, the separation claws 7 and 8 come into contact with the image portion of the recording medium 12, which causes image noise. Further, the tips of the separation claws 7 and 8 scratch the surfaces of the fixing rollers 3 and 4, which cause image noise and
The service life of the fixing rollers 3 and 4 is shortened.

On the other hand, if the separation claws 7 and 8 are not brought into contact with the fixing rollers 3 and 4, the problems such as scratches on the surfaces of the fixing rollers 3 and 4 are reduced, but the recording medium 12 is fixed to the fixing members 3 and 4. In some cases, the paper may not be separated by being wrapped around No. 4, and the paper passing property is not good.

As described above, if the separating member is always brought into contact with the fixing member, the recording medium is surely separated from the fixing member and the paper passing property is good, but the image noise and the service life of the fixing member are shortened. There's a problem. On the other hand, if the separation member is not in contact with the fixing member, the image noise and the service life of the fixing member are good, but the paper passing property is not good.

SUMMARY OF THE INVENTION Accordingly, the present invention is directed to a separation member that is not in contact with the fixing member, which is adjusted according to various factors related to the ease of winding the recording medium around the fixing member. It is an object of the present invention to prevent both the occurrence of scratches and the like on the surface of the fixing member due to contact with the fixing member, and to realize both excellent paper-passing properties.

[0008]

According to a first aspect of the present invention, a pair of fixing members pressed against each other are provided.
A heating device that heats at least one of the pair of fixing members, and a driving device that drives at least one of the pair of fixing members, and a recording medium passes through a contact portion between the pair of fixing members, A fixing device in which the developer carried on the recording medium is heated and melted and fixed on the recording medium, the fixing device being disposed downstream of the contact portion in the conveying direction of the recording medium, and having a leading end attached to the fixing member. A separating member facing at an interval, an image mode detecting device for detecting an image mode, and a contact portion between at least the fixing member of the separating member according to the image mode detected by the image mode detecting device. And a separation condition adjusting device for adjusting a position with respect to the fixing device.

Specifically, when the image mode is the monochrome mode, the distance between the tip of the separating member and the contact portion is a first value, and the image mode is the color mode. If the distance between the tip of the separation member and the contact portion is smaller than the second value,
The position of the separating member with respect to the contact portion is adjusted so that

In the fixing device according to the first aspect of the present invention, since the leading end of the separating member faces the fixing member at an interval,
Dirt on the recording medium due to accumulation of the release agent between the leading end of the separating member and the surface of the fixing member, image noise due to the leading end of the separating member contacting the image area of the recording medium, and the leading end of the separating claw. It is possible to prevent image noise due to scratches on the surface of the fixing member and shortening of the service life of the fixing member.

Generally, the amount of the developer adhered to the recording medium is larger when the image mode is the color mode than when the image mode is the monochrome mode. Then, as the amount of the applied developer increases, the adhesive force acting between the recording medium and the fixing member increases, so that the recording medium is likely to be wound around the fixing member. On the other hand, the closer the leading end of the separating member is to the contact portion between the fixing members, the more reliably the recording medium is guided by the separating member. In the fixing device according to the first aspect, the distance between the leading end of the separation member and the contact portion between the fixing members in the color mode is set smaller than that in the monochrome mode. It is surely separated from the member.

The second invention comprises a pair of fixing members which are pressed against each other, a heating device for heating at least one of the pair of fixing members, and a driving device for driving at least one of the pair of fixing members. A fixing device in which the developer carried on the recording medium is heated and melted by the recording medium passing through a contact portion between the pair of fixing members, and is fixed to the recording medium. A separating member that is disposed downstream in the transport direction of the recording medium, and whose tip faces the fixing member at an interval, and an image density detection device that detects the image density of an image formed on the recording medium. A separation condition adjusting device that adjusts at least a position of the separation member with respect to a contact portion between the fixing members according to an image density detected by the image density detection device. Is shall.

Specifically, the separation condition adjusting device adjusts the position of the separation member with respect to the contact portion such that the higher the image density, the closer the tip of the separation member approaches the contact portion.

In the fixing device according to the second aspect of the present invention, since the leading end of the separating member faces the fixing member at an interval,
It is possible to prevent the recording medium from being stained by the release agent, image noise, and shortening the service life of the fixing member.

The higher the image density, the greater the amount of developer attached per unit area of the recording medium, and the greater the adhesive force of the developer acting between the recording medium and the fixing member, so that the recording medium adheres to the fixing member. Winding easily occurs. On the other hand, the closer the leading end of the separation member is to the contact portion of the fixing member, the more reliably the recording medium is guided by the separation member. In the fixing device according to the second aspect of the present invention, the higher the image density, the closer the tip of the separating member approaches the contact portion. Therefore, even when the image density is high, the recording medium is reliably separated from the fixing member.

The third invention comprises a pair of fixing members which are pressed against each other, a heating device for heating at least one of the pair of fixing members, and a driving device for driving at least one of the pair of fixing members. A fixing device in which the developer carried on the recording medium is heated and melted by the recording medium passing through a contact portion between the pair of fixing members, and is fixed to the recording medium; Is a fixing roller, which is disposed downstream of the contact portion in the direction of conveyance of the recording medium, and has a separation member whose front end faces the fixing member at an interval, and an outer diameter of the fixing roller. And a position of at least the separating member with respect to the contact portion between the fixing rollers is adjusted according to the outer diameter of the fixing roller detected by the roller outer diameter detecting device. It is to provide a fixing device and a releasing condition adjusting device.

Specifically, the separation condition adjusting device adjusts the position of the separation member with respect to the contact portion such that the larger the outer diameter of the fixing roller, the closer the tip of the separation member approaches the contact portion. .

In the fixing device according to the third aspect of the present invention, since the leading end of the separating member faces the fixing member at an interval.
It is possible to prevent the recording medium from being stained by the release agent, image noise, and shortening the service life of the fixing member.

When the fixing roller expands due to heat and its outer diameter increases, the dimension of the contact portion in the recording medium transport direction (the width of the contact portion) increases, and the time required for the recording medium to pass through the fixing member is increased. That is, the contact time between the recording medium and the fixing member becomes longer. As a result, the charging potential of the recording medium and the fixing member caused by the contact increases, and the electrostatic attraction acting between the recording medium and the fixing member increases, so that the fixing member easily winds around the fixing roller. On the other hand, the closer the leading end of the separating member is to the contact portion between the fixing rollers, the more reliably the recording medium is guided by the separating member. In the fixing device according to the third aspect of the present invention, the larger the outer diameter of the fixing roller, the closer the tip of the separating member approaches the contact portion. Is reliably separated from

The fourth invention comprises a pair of fixing members which are pressed against each other, a heating device for heating at least one of the pair of fixing members, and a driving device for driving at least one of the pair of fixing members. A fixing device in which the developer carried on the recording medium is heated and melted by the recording medium passing through a contact portion between the pair of fixing members, and is fixed to the recording medium. A separating member that is disposed downstream of the recording medium in the conveying direction and whose leading end faces the fixing member at an interval, a recording medium detection device that detects the type of the recording medium, and the recording medium detection device And a separation condition adjusting device that adjusts at least the position of the separation member with respect to the contact portion between the fixing members in accordance with the type of recording medium detected by the fixing device.

Specifically, when the recording medium is a cardboard or an OHP sheet, the distance between the leading end of the separating member and the contact portion is a first value.
If the recording medium is plain paper, the position of the separation member with respect to the contact portion is adjusted so that the distance between the tip of the separation member and the contact portion becomes a second value smaller than the first value. Adjust.

In the fixing device according to the fourth aspect of the present invention, since the leading end of the separating member faces the fixing member at an interval,
It is possible to prevent the recording medium from being stained by the release agent, image noise, and shortening the service life of the fixing member.

In general, plain paper is weaker in elasticity than thick paper and OHP sheets, and is therefore easily wound around a fixing member. On the other hand, the closer the leading end of the separating member is to the contact portion between the fixing members, the more reliably the recording medium is guided by the separating member. In the fixing device according to the fourth aspect of the invention, when the recording medium is plain paper, the distance between the leading end of the separation member and the contact portion is set smaller than when the recording medium is thick paper or an OHP sheet. Even paper is reliably separated from the fixing member.

The fifth invention comprises a pair of fixing members which are pressed against each other, a heating device for heating at least one of the pair of fixing members, and a driving device for driving at least one of the pair of fixing members. A fixing device in which the developer carried on the recording medium is heated and melted by the recording medium passing through a contact portion between the pair of fixing members, and is fixed to the recording medium. A separating member disposed at the downstream side in the conveying direction of the recording medium, and having a leading end opposed to the fixing member at an interval, and a conveying speed detecting device for detecting a conveying speed of the recording medium to the contact portion. A separation condition adjusting device that adjusts at least a position of the separation member with respect to a contact portion between the fixing members according to a conveyance speed of the recording medium detected by the conveyance speed detection device. It is intended to provide.

Specifically, the separation condition adjusting device adjusts the position of the separation member with respect to the contact portion such that the lower the transport speed of the recording medium, the closer the tip of the separation member approaches the contact portion. I do.

In the fixing device according to the fifth aspect of the present invention, the leading end of the separating member faces the fixing member at an interval.
It is possible to prevent the recording medium from being stained by the release agent, image noise, and shortening the service life of the fixing member.

The slower the transport speed of the recording medium, the longer the time required for the recording medium to pass through the contact portion, that is, the longer the contact time between the recording medium and the fixing member. As a result, the charging potential of the recording medium and the fixing member caused by the contact increases,
Because the electrostatic attraction acting between them increases,
The fixing member is easily wound around the fixing roller. On the other hand, the closer the leading end of the separation member is to the contact portion of the fixing member, the more reliably the recording medium is guided by the separation member. In the fixing device according to the fifth aspect of the present invention, the lower the transport speed of the recording medium, the closer the leading end of the separation member approaches the contact portion. Therefore, even when the transport speed is low, the recording medium is reliably separated from the fixing member.

The sixth invention comprises a pair of fixing members which are pressed against each other, a heating device for heating at least one of the pair of fixing members, and a driving device for driving at least one of the pair of fixing members. A fixing device in which the developer carried on the recording medium is heated and melted by the recording medium passing through a contact portion between the pair of fixing members, and is fixed to the recording medium. A separating member that is disposed downstream of the recording medium in the transport direction, and whose leading end faces the fixing member at an interval, a humidity detecting device that detects humidity, and a humidity that is detected by the humidity detecting device. A fixing condition adjusting device that adjusts at least the position of the separating member with respect to the contact portion between the fixing members.

Specifically, the separation condition adjusting device adjusts the position of the separation member with respect to the contact portion such that the tip of the separation member approaches the contact portion as the humidity increases.

In the fixing device according to the sixth aspect of the present invention, the leading end of the separating member faces the fixing member at an interval.
It is possible to prevent the recording medium from being stained by the release agent, image noise, and shortening the service life of the fixing member.

Generally, as the humidity increases, the amount of water absorbed by the recording medium increases, and the elasticity of the recording medium decreases.
The separation member is easily wound around the fixing member. On the other hand, the closer the leading end of the separation member is to the contact portion of the fixing member, the more reliably the recording medium is guided by the separation member. In the fixing device according to the sixth aspect, the tip of the separation member approaches the contact portion as the humidity increases, so that the recording medium is reliably separated from the fixing member even when the humidity is high.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention shown in the drawings will be described in detail. (First Embodiment) As shown in FIG. 1, a copying machine which is an image forming apparatus provided with a fixing device of the present invention includes
And an optical scanning device 22 that reads a document (not shown) placed on the document placing portion 21. The image data read by the optical scanning device 22 is stored in an image recording unit 23.
And then sent to the exposure device 24. Exposure device 2
Reference numeral 4 denotes a photosensitive member 25 serving as an image carrier based on image data.
Is exposed with a laser beam.

Around the photosensitive member 25, a charging device 27, developing devices 28A, 28B, 28
C, 28D, a transfer device 29, a cleaning device 30, and a charge removing device 31 are provided. Also, the paper cassette 3
2. Recording media 3 such as transfer paper and OHP sheets stored in
A paper feed path 37 is provided to supply the transfer sheet 5 to a transfer area where the photoconductor 25 and the transfer device 29 face each other.

When the surface of the photoreceptor 25 uniformly charged by the charging device 27 is exposed to the laser light, an electrostatic latent image is formed. This electrostatic latent image is developed by developing devices 28A-2
8D is visualized by the developer supplied to form a developer image. This developer image is electrostatically transferred by the transfer device 29 to the recording medium 35 supplied from the paper feed cassette 32. The recording medium 35 onto which the developer image has been transferred is
0 to the paper discharge tray 33.

The fixing device 40 according to the first embodiment shown in FIGS. 2 to 6 has a pair of fixing rollers 41A and 41A as fixing members.
1B. These fixing rollers 41A, 41B
Is provided with an elastic member 43 made of silicon rubber around a metal core 42 made of an aluminum cylinder. A halogen lamp 44, which is a heating device, is housed inside the core metal 42 of each of the fixing rollers 41A and 41B. A fixing roller drive motor 47 is connected to the lower fixing roller 41B. The fixing rollers 41A and 41B are pressed against each other by a spring 65e, which will be described later, to form a contact portion (nip portion 48) extending in the axial direction. When the fixing roller driving motor 47 operates, the lower fixing roller 41B rotates clockwise in the drawing, and the upper fixing roller 41A rotates following.

Around a periphery of the upper fixing roller 41A, a releasing agent application device 50 for applying a releasing agent (silicone oil in this embodiment) to the surface of the fixing roller 41A, a cleaning roller 51 including a felt roller, and The thermistor 52A is provided.

The release agent application device 50 includes a release agent tank 50a in which the release agent is stored, a pump 50b made of an aluminum roller, a release agent application roller 50c made of a silicone rubber roller, and a release agent application roller. A release agent regulating blade 50d for regulating the thickness of the release agent layer on the surface 50c is provided.
A part of the pumping roller 50b is immersed in the release agent in the release agent tank 50a. Further, a release agent applying device driving motor 50e is connected to the pumping roller 50b. Further, the pumping roller 50b and the release agent applying roller 50c are pressed against each other. Further, the release agent applying roller 50c is pressed against the surface of the fixing roller 41A by a spring (not shown). for that reason,
When the release agent application device drive motor 50e operates and the pumping roller 50b rotates, the release agent application roller 50c is driven to rotate, and the release agent in the release agent tank 50a is drawn up by the suction roller 50b and the release agent application roller 50c. Through the fixing roller 41A.

On the other hand, around the lower fixing roller 41B, a leveling blade 54 made of fluoro rubber and a thermistor 52B for leveling the release agent on the peripheral surface of the fixing roller 41B.
Is arranged.

The fixing rollers 41 are located downstream of the nip 48 in the direction of conveyance of the recording medium 35 indicated by the arrow A.
A, a plurality of separation claws 56, 57 serving as separation members for each 41B
Are arranged in the axial direction of the fixing rollers 41A and 41B. The ends of the separation claws 56 and 57 are fixed to the fixing roller 4.
It faces the peripheral surface of 1A, 41B at intervals.

A plurality of separation claws 56 corresponding to the upper fixing roller 41A in FIG.
With 0, it is possible to move in the left-right direction (horizontal direction) in the figure. The separation claw moving mechanism 60 will be described. First, a plurality of separation claws 56 corresponding to the upper fixing roller 41A are attached to one frame 60a, and this frame 60a is a lower end of a rod 60b extending vertically in the drawing. It is fixed to. A cylindrical member 60c is fixed to the upper end of the rod 60b. A horizontally extending shaft 60d supported rotatably and immovably in the axial direction is provided.
Od is inserted through the cylindrical member 60c. A male screw formed on the inner peripheral surface of the cylindrical member 60c is engaged with a male screw formed on the outer peripheral surface of the shaft 60d. A gear 60e fixed to one end of the shaft 60d is engaged with a gear 60g fixed to the output shaft of the separation claw driving motor 60f. Therefore, when the separation claw driving motor 60f rotates, the cylindrical member 60c moves in the horizontal direction on the shaft 60d according to the rotation direction, and accordingly, the separation claw 56 approaches and separates from the fixing roller 41A.

The pair of paper discharge guide plates 62A and 62B can be moved in the horizontal direction by a paper discharge guide plate moving mechanism 63 shown in FIG. The paper ejection guide plate moving mechanism 63 will be described first.
A and 62B are rods 63a extending vertically in the figure.
Is fixed to the upper end. A cylindrical member 63b is fixed to a lower end of the rod 63a. A horizontally extending shaft 63 supported rotatably and immovably in the axial direction.
The shaft 63c is inserted through the cylindrical member 63b. A female screw formed on the inner peripheral surface of the cylindrical member 63b is engaged with a male screw formed on the outer peripheral surface of the shaft 63c. The gear 63d fixed to one end of the shaft 63c is
3e is engaged with a gear 63f fixed to the output shaft.
Therefore, when the discharge guide plate driving motor 63e rotates,
The cylindrical member 63 is placed on the shaft 63c according to the rotation direction.
b moves in the horizontal direction, and the discharge guide plate 6
2A and 62B move toward and away from the fixing rollers 41A and 41B.

The inclination angle θ of the line L connecting the rotation centers C1 and C2 of the pair of fixing rollers 41A and 41B with respect to the conveying direction of the recording medium 35 can be adjusted by the fixing roller posture adjusting mechanism 65 shown in FIG. The fixing roller attitude adjusting mechanism 65 will be described first.
A gear 65a is rotatably attached to one end of the rotation shaft 66 of 1B. A sliding member 65c is provided on a frame 65b provided integrally with the gear 65a. The rotating shaft 66 of the upper fixing roller 41A in the figure is rotatably supported by the sliding member 65c. Further, a spring receiving portion 65d is provided at an upper end portion in the drawing of the frame 65b, and the spring receiving portion 65d and the sliding member 65c are provided.
The spring 65e is arranged in a compressed state between them. Due to the urging force of the spring 65e, the fixing rollers 41A, 41B
Are pressed against each other. The gear 65a includes a gear 65
The rotation of the fixing roller attitude adjusting motor 65h is transmitted via f and 65g. This fixing roller attitude adjusting motor 65
h, the gear 65a rotates about the rotation shaft 66 in accordance with the direction of rotation, and the frame 65
b also rotates about the rotation axis 66. Therefore, the tilt angle θ can be adjusted by operating the fixing roller attitude adjusting motor 65h.

As shown in FIG. 2, the separation claws 56, 57
And the recording medium 35 than the discharge guide plates 62A and 62B.
A pair of paper discharge rollers 68 for transporting the recording medium 35 to the paper discharge tray 33 shown in FIG.
A, 68B are arranged. The discharge rollers 68A,
68B are pressed against each other, and a lower discharge roller 68B in the figure is connected to a discharge roller driving motor 69. When the discharge roller drive motor 69 operates, the discharge rollers 68A and 68B rotate, and the discharge rollers 68A and 68B.
The recording medium 35 supplied to the contact portion B is carried out of the fixing device 40.

The fixing device 40 includes a controller 70 shown in FIGS. This controller 70
It functions as the image mode detecting device and the separation condition adjusting device in the first invention. The controller 70 receives the image data from the image recording unit 23 and the temperatures detected by the thermistors 52A and 52B. Also,
The controller 70 controls the fixing roller driving motor 47 and the release agent applying device driving motor 50 based on these inputs and the like.
e, controlling the discharge roller drive motor 69; Further, the controller 70 determines whether the image mode is the monochrome mode or the color mode based on the image data input from the image recording unit 23. further,
The controller 70 controls the separation claw drive motor 60f, the paper ejection guide plate drive motor 63e, and the fixing roller attitude adjustment motor 65h in accordance with the determined image mode, and
6 and the positions of the discharge guide plates 62A and 62B with respect to the nip portion 48 are adjusted.

The operation of the fixing device 40 will be described.
7. The release agent application device drive motor 50e and the paper discharge roller drive motor 69 are operating. In FIG. 2, the developer image 72 is recorded on the recording medium 35 conveyed to the fixing device 40 from the left side.
Are formed. When the recording medium 35 passes through the nip portion 48, the developer is heated and melted, and the developer image 72 is fixed on the recording medium 35. The recording medium 35 that has passed through the nip 48 is separated by the fixing claws 56 and 57 into fixing rollers 41A and 41A.
The sheet is separated from the sheet 41B and is conveyed to the sheet discharge tray 33 by the sheet discharge rollers 62A and 62B.

In the fixing device 40 of the first embodiment, since the leading ends of the separation claws 56 and 57 are opposed to the fixing rollers 41A and 41B with an interval, the leading ends of the separating portions 56 and 57 and the fixing roller 41A. Of the recording medium 35 due to accumulation of the release agent between the surface of the recording medium 35 and the separation claws 56, 5B.
7, the image noise caused by the tip of the recording medium 35 contacting the image area of the recording medium 35, and the image noise and the fixing roller 41A caused by the tip of the separation claws 56, 57 scratching the elastic member 43 on the surface of the fixing rollers 41A, 41B. , 41B can be prevented from being shortened.

Next, the adjustment of the separation condition performed by the controller 70 will be described with reference to the flowchart of FIG. 7 and Table 1 below.

[0048]

[Table 1]

First, in step S7-1, the controller 70 determines whether the developer image 72 on the recording medium 35 is a monochrome image or a color image based on the image data input from the image recording section 23, that is, It is determined whether the image mode is the monochrome mode or the color mode.

Next, in step S7-2, if the image mode is the monochrome mode, the process proceeds to step S7-3. In step S7-3, the separation condition is set to "separation condition 1" which is a standard separation condition. When the image mode is the monochrome mode, the amount of the developer attached to the recording medium 35 is relatively small.
1A is relatively weak, and the fixing roller 4
Winding of the recording medium 35 around 1A is unlikely to occur. Therefore, in the "separation condition 1" of step S7-3, the setting is made such that the separation condition is given more importance to prevention of image noise than paper passing property.

Specifically, in the “separation condition 1”, the distance d1 of the tip of the separation claw 56 to the nip 48 by the separation claw moving mechanism 60 is set to a standard value of 17 mm. The distance d2 between the paper discharge guide plates 62A and 62B and the nip 48 by the paper discharge guide plate moving mechanism 63 is:
The standard value is set to 24 mm. Further, the inclination angle θ of the line L connecting the rotation centers C1 and C2 of the fixing rollers 41A and 41B with respect to the conveyance direction of the recording medium 35 is set to a standard value of 90 degrees as shown in FIG. Is done.

Next, if the copy is completed in step S7-4, the copy operation is completed, and if not, the process returns to step S7-1.

On the other hand, if it is determined in step S7-2 that the image mode is the color mode, the process proceeds to step S7-5. In step S7-5, the separation condition is set to "separation condition 2." When the image mode is the color mode, the amount of the developer attached to the recording medium 35 is larger than in the monochrome mode, and the recording medium 35 and the fixing roller 41A are attached.
And a relatively strong adhesive force acts between them, so that the recording medium 35 is likely to be wound around the fixing roller 41A. Therefore, the “separation condition 2” in step S7-4 is set with emphasis on sheet passing properties.

Specifically, in the “separation condition 2”, the separation claw 56 is moved by the separation claw moving mechanism 60 in a direction approaching the nip portion 48, and the tip of the separation claw 56 and the nip portion 4 are moved.
8 is reduced to 15 mm.

In the "separation condition 2", the paper discharge guide plates 62A and 62B are moved by the paper discharge guide plate moving mechanism 63 in a direction approaching the fixing rollers 41A and 41B.
Distance d2 between the tip of paper ejection guide plate 68A and nip portion 48
Is reduced to 22 mm. Discharge guide plates 62A, 62B
Is closer to the fixing rollers 41A and 41B, the recording medium 35 is more reliably guided by the paper discharge guide plates 62A and 62B. Therefore, the recording medium 35 is reliably separated from the surfaces of the fixing rollers 41A and 41B by bringing the sheet discharge guide plates 62A and 62B closer to the fixing rollers 41A and 41B.

Further, in the "separation condition 2", the fixing roller attitude adjusting mechanism 65 causes the fixing rollers 41A, 41
B, the tip of the separation claw 56 is
A is adjusted to approach A. Specifically, as shown in FIG. 6B, the inclination angle θ is set to 86 degrees, and the tip of the separation claw 56 approaches the fixing roller 41A.
As described above, the separation claw 56 approaches the fixing roller 41A,
Further, as the inclination angle θ changes, the distance d1 from the tip of the separation claw 56 to the nip 48 is reduced to 15 mm. The closer the leading end of the separation claw 56 is to the fixing roller 41A, the more reliably the leading end of the recording medium 35 is guided by the separation claw 56. Therefore, by bringing the tip of the separation claw 56 closer to the fixing roller 41A, the recording medium 35 is reliably separated from the surface of the fixing roller 41A.

As described above, in the fixing device 40 of the first embodiment, the distance d1 between the tip of the separation claw 56 and the nip portion 48 and the distance d2 between the paper discharge guide plate 62A and the nip portion 48 in the color mode are set as follows. Since the setting is made smaller than in the monochrome mode, the recording medium 35 is reliably separated from the fixing rollers 41A and 41B even in the color mode.

The distances d1 and d2 and the inclination angle θ may be adjusted according to the image mode input by the user from a control panel (not shown).

(Second Embodiment) In the fixing device 40 of the second embodiment, the recording medium 35 is more advanced than the fixing rollers 41A and 41B.
An image density detecting CCD 74 (shown in FIGS. 1 and 8), which is an image density detecting device according to the second invention, is provided on the upstream side in the conveyance direction. This image density detecting CCD 7
Reference numeral 4 captures the developer image 72 in the leading end area of the recording medium 35 on the transport direction side (in this embodiment, an area within 3 cm from the leading end of the recording medium 35 on the transport direction side). The image density detecting CCD 74 is connected to the controller 70,
The controller 70 calculates an image density D _t at the tip portion of the conveying direction of the recording medium 35 based on the signal input from the image density detection CCD 74. Further, the controller 70 adjusts the separation conditions in accordance with the calculated image density D _t.

The other structure of the fixing device 40 of the second embodiment is the same as that of the fixing device 40 of the first embodiment (see FIGS. 1 and 2).
), And the description is omitted.

Next, the adjustment of the separation condition performed by the controller 70 will be described with reference to the flowchart of FIG. 9 and Table 2 below.

[0062]

[Table 2]

First, in step S9-1, the controller 70 calculates the image density in the area on the leading end side in the transport direction of the recording medium 35 based on the signal input from the image density detecting CCD 74.

Next, at step S9-2, the image density D _t is less than 8 g / m ^2, if step S9-
Move to 3.

In step S9-3, the separation condition is set to "separation condition 1" which is a standard separation condition. If the image density D _t is less than 8 g / m ^2, since the amount of deposition of the developer in the conveying direction leading end of the area of the recording medium 35 is relatively small, the adhesive force acting between the recording medium 35 fixing roller 41A Is relatively weak, and the winding of the recording medium 35 around the fixing roller 41A is unlikely to occur. Therefore, in the “separation condition 1” of step S9-3, the setting is made such that the separation condition is given more importance to prevention of image noise than to the paper passing property.

Specifically, in the “separation condition 1”, the distance d1 of the separation claw 56 to the nip 48 by the separation claw moving mechanism 60 is set to a standard value of 17 mm. Further, the paper ejection guide plate 62 is moved by the paper ejection guide plate moving mechanism 63.
The distance d2 of A to the nip 48 is set to a standard value of 24 mm. Further, the inclination angle θ of the fixing rollers 41A and 41B is set to a standard value of 90 degrees by the fixing roller posture adjusting mechanism 65.

Next, if the copy is completed in step S9-4, the copy operation is completed, and if not, the process returns to step S9-1.

Meanwhile, in step S9-2, if the image density D _t is 8 g / m ² or more, if the step S
Move on to 9-5. In step S9-5, the separation condition is set to "separation condition 2." Image density _Dt is 8 g / m ²
In the case described above, the amount of the developer attached to the recording medium 35 in the region at the leading end in the transport direction is large, and the recording medium 35 and the fixing roller 4
1A, a relatively strong adhesive force acts on the recording medium 3A.
5 is in a state where it is likely to be wound around the fixing roller 41A. Therefore, the “separation condition 2” of step S9-5 is set with emphasis on the paper passing property.

Specifically, under the “separation condition 2”, the separation claw 56 is moved by the separation claw moving mechanism 60 in a direction approaching the nip portion 48, and the distance d1 is reduced to 15 mm.

In the "separation condition 2", the discharge guide plate moving mechanism 63 moves the discharge guide plates 62A and 62B in a direction approaching the fixing rollers 41A and 41B.
The distance d2 is reduced to 22 mm.

Further, in the "separation condition 2", the fixing roller attitude adjusting mechanism 72 causes the fixing rollers 41A, 41
The inclination angle θ of B is set to 86 degrees, and the distance d1 from the tip of the separation claw 56 to the nip 48 is reduced to 15 mm.

As described above, in the fixing device 40 of the second embodiment, as the image density _Dt is higher, the distance d1 between the tip of the separation claw 56 and the nip 48 and the distance d2 between the paper ejection guide plate 62A and the nip 48 are increased. Is set small, the image density D
Even when _t is high, the recording medium 35 is fixed to the fixing rollers 41A and 41A.
1B. Further, since the leading ends of the separation claws 56 and 57 are opposed to the fixing rollers 41A and 41B with a space therebetween, the recording medium 35 is not stained by the release agent.
Image noise and shortening of the service life of the fixing rollers 41A and 41B can be prevented.

Note that, without providing an image density detection CCD,
Controller 70 may estimate the image density D _t based on the image data input from the image recording unit 23. Further, continuously distances d1, it may be adjusted d2 and the inclination angle θ in accordance with the image density D _t.

(Third Embodiment) A fixing device 40 according to a third embodiment of the present invention shown in FIGS.
A laser type outer diameter measuring device 75 for measuring the outer diameter (roller outer diameter OD) of 1A (constituting the roller outer diameter detecting device in the third invention) is provided. This laser type outer diameter measuring device 7
5 is connected to the controller 70. The outer diameter of the fixing rollers 41A and 41B increases and decreases due to thermal expansion.
The controller 70 adjusts the separation condition according to a change in the outer diameter OD of the fixing roller 41A detected by the laser outer diameter measuring device 75.

The other configuration of the fixing device 40 according to the third embodiment is the same as that of the fixing device 40 according to the first embodiment, and thus the description thereof is omitted.

Next, the adjustment of the separation condition performed by the controller 70 will be described with reference to the flowchart of FIG. 12 and Table 3 below.

[0077]

[Table 3]

First, in step S12-1, the laser type outer diameter measuring device 75 detects the outer diameter OD of the fixing roller 41A.

Next, in step S12-2, if the roller outer diameter OD is less than 61.1 mm, the flow proceeds to step S12-3.

In step S12-3, the separation condition is set to "separation condition 1" which is a standard separation condition. When the roller outer diameter OD is less than 61.1 mm, the time required for the recording medium 35 to pass through the nip 48 is relatively short because the width of the nip 48 is relatively small. Therefore, in this case, the contact time between the recording medium 35 and the fixing rollers 41A and 41B in the nip portion 48 is relatively short. If the contact time between the recording medium 35 and the fixing rollers 41A, 41B is short, the recording medium 35 and the fixing rollers 41A, 41A,
The charging of the recording medium 3B due to this charging is relatively weak.
Since the electrostatic attraction acting between the roller 5 and the surfaces of the fixing rollers 41A and 41B is weak, the recording medium 35 is hardly wound around the fixing roller 41A. For this reason, in the "separation condition 1" of step S12-3, the setting is made such that the separation condition is given more importance to preventing image noise than to the paper-passing property.

Specifically, in the “separation condition 1”, the distance d1 of the separation claw 56 to the nip 48 by the separation claw moving mechanism 60 is set to a standard value of 17 mm. Further, the distance d of the paper ejection guide plate 62A to the nip portion 48 is set.
2 is set to a standard value of 24 mm by the paper ejection guide plate moving mechanism 63. Further, the fixing roller 41
A, 41B is the inclination angle θ of the fixing roller attitude adjusting mechanism 6.
5 is set to a standard value of 90 degrees.

In this embodiment, the fixing roller 41
The fixing rollers 41A and 41B are negatively charged and the recording medium 35 is positively charged because the surfaces A and 41B are provided with an elastic member 43 made of silicone rubber on the surface.

Next, if the copy is completed in step S12-4, the copy operation is completed, and if not, the process returns to step S12-1.

On the other hand, in step S12-2,
If the roller outer diameter OD is 61.1 mm or more, the process proceeds to step S12-5. In step S12-5, the separation condition is set to "separation condition 2." When the roller outer diameter OD is 61.1 mm or more, the width of the nip 48 is relatively large, so that the contact time between the recording medium 35 and the fixing rollers 41A and 41B in the nip 48 is also long. Therefore, the recording medium 35 and the fixing rollers 41A, 41B are strongly charged by the contact, and the recording medium 35 is separated from the fixing rollers 41A, 41 by an electrostatic attraction force acting between them.
B is easily wrapped around. For this reason, the “separation condition 2” of step S11-5 is set with emphasis on paper passage.

More specifically, under the “separation condition 2”, the separation claw 56 is moved by the separation claw moving mechanism 60 in a direction approaching the nip 48, and the distance d1 is reduced to 15 mm.

In the "separation condition 2", the paper ejection guide plates 62A and 62B are moved by the paper ejection guide plate moving mechanism 63 in a direction approaching the fixing rollers 41A and 41B.
The distance d2 is reduced to 22 mm.

Further, in the “separation condition 2”, the fixing roller attitude adjusting mechanism 72 controls the fixing rollers 41A and 41A.
The inclination angle θ of B is set to 86 degrees, and the distance d1 from the tip of the separation claw 56 to the nip 48 is reduced to 15 mm.

As described above, in the fixing device 40 of the third embodiment, as the roller outer diameter OD is larger, the distance d1 between the tip of the separation claw 56 and the nip portion 48 and the distance d2 between the paper discharge guide plate 62A and the nip portion 48 are increased. Is set small, the recording medium 35 is reliably separated from the fixing rollers 41A and 41B even when the roller outer diameter OD is increased due to thermal expansion. Further, the tips of the separation claws 56 and 57 are fixed to the fixing roller 41.
Since the recording medium 35 is opposed to A and 41B with an interval, it is possible to prevent contamination of the recording medium 35 due to the release agent, image noise, and shortening of the service life of the fixing rollers 41A and 41B.

The distances d1 and d2 and the inclination angle θ may be continuously adjusted according to the roller outer diameter OD.

(Fourth Embodiment) As shown in FIGS. 1 and 13, the fixing device 40 of the fourth embodiment determines whether the recording medium 35 is plain paper, thick paper, or an OHP sheet. The recording medium discrimination sensor 76 (constituting the recording medium detecting device in the fourth invention) is provided on the paper feed path 37. This recording medium discrimination sensor 76 is connected to a controller 70 which is a separation condition adjusting device, and the controller 70 adjusts the separation conditions according to the type of the recording medium 35.

The other components of the fixing device 40 of the second embodiment are the same as those of the fixing device 40 of the first embodiment (see FIGS. 1 and 2).
), And the description is omitted.

Next, the adjustment of the separation condition performed by the controller 70 will be described with reference to the flowchart of FIG. 14 and Table 4 below.

[0093]

[Table 4]

First, in step S14-1, the recording medium discrimination sensor 76 detects the type of the recording medium 35.

Next, in step S14-2, if the recording medium 35 is thick paper or an OHP sheet, step S14-2 is executed.
It moves to 14-3. In step S14-3, the separation condition is set to "separation condition 1" which is a standard separation condition. If the recording medium 35 is a thick paper or an OHP sheet, the elasticity is relatively strong. Therefore, even if the adhesive force by the developer or the electrostatic suction force due to the charging of the recording medium 35 and the fixing rollers 41A and 41B acts, the fixing is performed. Recording medium 3 on roller 41A
5 is hardly wrapped. Therefore, this step S
In the "separation condition 1" of 14-3, the separation condition is set so that prevention of image noise and the like is more important than paper passing property.

Specifically, in the “separation condition 1”, the distance d1 of the separation claw 56 to the nip 48 by the separation claw moving mechanism 60 is set to a standard value of 17 mm. Further, the paper ejection guide plate 62 is moved by the paper ejection guide plate moving mechanism 63.
The distance d2 of A to the nip 48 is set to a standard value of 24 mm. Further, the inclination angle θ of the fixing rollers 41A and 41B is set to a standard value of 90 degrees by the fixing roller posture adjusting mechanism 65.

Next, if the copy is completed in step S14-4, the copy operation is completed, and if not, the process returns to step S14-1.

On the other hand, in step S14-2,
If the recording medium 35 is plain paper, the process proceeds to step S14-5. In step S14-5, the separation condition is set to "separation condition 2." Since plain paper has lower elasticity than thick paper and OHP sheets, if the recording medium 35 is plain paper, electrostatic attraction by the developer and charging of the recording medium 35 and the fixing rollers 41A and 41B by electrostatic charge. The recording medium 35 is easily wound around the fixing roller 41A due to the force. Therefore, the “separation condition 2” of step S14-5 is set with emphasis on the paper passing property.

Specifically, under the “separation condition 2”, the separation claw 56 is moved by the separation claw moving mechanism 60 in a direction approaching the nip portion 48, and the distance d1 is reduced to 15 mm.

In the "separation condition 2", the paper discharge guide plates 62A and 62B are moved by the paper discharge guide plate moving mechanism 63 in a direction approaching the fixing rollers 41A and 41B.
The distance d2 is reduced to 22 mm.

Further, in the "separation condition 2", the fixing rollers 41A and 41A are
The inclination angle θ of B is set to 86 degrees, and the distance d1 from the tip of the separation claw 56 to the nip 48 is reduced to 15 mm.

As described above, in the fixing device 40 of the second embodiment, when the recording medium 35 is plain paper having relatively low elasticity, the distance d1 between the tip of the separation claw 56 and the nip portion 48 is set.
And the distance d2 between the paper discharge guide plate 62A and the nip portion 48.
However, if the recording medium 35 is made of cardboard or OHP
Therefore, even if the recording medium 35 is plain paper, the fixing rollers 41A, 41B
Is reliably separated from Further, since the leading ends of the separation claws 56 and 57 are opposed to the fixing rollers 41A and 41B at intervals, the contamination of the recording medium 35 due to the release agent, image noise, and the service life of the fixing rollers 41A and 41B are reduced. Shortening can be prevented.

The distances d1, d2 and the inclination angle θ may be adjusted according to the type of the recording medium input by the user from a control panel (not shown) without providing the recording medium discrimination sensor 78.

(Fifth Embodiment) As shown in FIG. 1 and FIG.
A speed sensor 78 for detecting the transport speed V _R of the recording medium 35, on the upstream side of the recording medium 35 in the transport direction of the recording medium 35 from A and 41B.
(Constituting the transport speed detecting device according to the fifth invention). The speed sensor 78 is connected to the controller 70 is separated conditioning apparatus, the controller 70 adjusts the separation conditions in accordance with the conveyance velocity V _R of the recording medium 35 detected by the speed sensor 78.

The other structure of the fixing device 40 of the fifth embodiment is the same as that of the fixing device 40 of the first embodiment (see FIGS. 1 and 2).
), And the description is omitted.

Next, the adjustment of the separation condition executed by the controller 64 will be described with reference to the flowchart of FIG. 16 and Table 5 below.

[0107]

[Table 5]

[0108] First, in step S16-1, the speed sensor 78 detects the conveying velocity V _R of the recording medium 35.

[0109] Next, step S16 if in step S16-2, the conveying speed V _R is 120 mm / s or more
-3.

In step S16-3, the separation condition is set to "separation condition 1" which is a standard separation condition. When the transport speed V _R of the recording medium 35 is 120 mm / s or more,
The recording medium 35 passes through the nip 48 relatively quickly,
Recording medium 35 and fixing roller 41 in nip portion 48
The contact time of A and 41B is relatively short. Therefore, the charging of the recording medium 35 and the fixing rollers 41A and 41B due to the contact is relatively weak, and the recording medium 35 is hardly wrapped around the fixing roller 41A due to the electrostatic attraction acting between them. Therefore, in the "separation condition 1" of step S16-3, the separation condition is set so that prevention of image noise or the like is more important than paper passing property.

Specifically, in the “separation condition 1”, the distance d1 of the separation claw 56 to the nip 48 by the separation claw moving mechanism 60 is set to a standard value of 17 mm. Further, the paper ejection guide plate 62 is moved by the paper ejection guide plate moving mechanism 63.
The distance d2 of A to the nip 48 is set to a standard value of 24 mm. Further, the inclination angle θ of the fixing rollers 41A and 41B is set to a standard value of 90 degrees by the fixing roller posture adjusting mechanism 65.

Next, if the copy is completed in step S16-4, the copy operation is completed, and if not, the process returns to step S16-1.

On the other hand, in step S16-2,
Conveying speed V _R is less than 120 mm / s, the process proceeds to step S16-5. In step S16-5, the separation condition is set to "separation condition 2." The conveying speed V _R is 1
If it is less than 20 mm / s, the recording medium 35
8 takes longer and the nip 4
8, the contact time between the recording medium 35 and the fixing rollers 41A and 41B becomes longer. Therefore, the recording medium 3
5 and the fixing rollers 41A and 41B are relatively strongly charged, and the fixing roller 41 due to electrostatic attraction acting between them.
A is in a state where the recording medium 35 is easily wound around A. Therefore, in the “separation condition 2” of step S16-5, the setting is made with emphasis on the paper passing property.

Specifically, under the “separation condition 2”, the separation claw 56 is moved by the separation claw moving mechanism 60 in a direction approaching the nip portion 48, and the distance d1 is reduced to 15 mm.

In the "separation condition 2", the paper ejection guide plates 62A and 62B are moved by the paper ejection guide plate moving mechanism 63 in a direction approaching the fixing rollers 41A and 41B.
The distance d2 is reduced to 22 mm.

Further, in the “separation condition 2”, the fixing roller attitude adjusting mechanism 72 causes the fixing rollers 41A and 41
The inclination angle θ of B is set to 86 degrees, and the distance from the tip of the separation claw 56 to the nip 48 is reduced to 15 mm.

[0117] In this way the fixing device of the fifth embodiment 40, slower conveying speed V _R of the recording medium 35 is, separating claw 5
The distance d2 between the distance d1 and the discharge guide plate 62A and the nip portion 48 between the tip and the nip 48 of 6 is set small, the fixing roller 41A even when the recording medium 35 is a slow conveying speed V _R, the 41B Separated reliably. Further, since the leading ends of the separation claws 56 and 57 are opposed to the fixing rollers 41A and 41B with a space therebetween, dirt on the recording medium 35 due to the release agent, image noise, and the fixing rollers 41A and 4B.
1B can be prevented from being shortened.

The position at which the speed sensor 78 is mounted is not particularly limited. Further, the controller 70 may estimate the conveying speed V _R from the rotational speed of the fixing roller drive motor 47. Furthermore, continuous distance d in accordance with the conveyance velocity V _R
1, d2 and the inclination angle θ may be adjusted.

(Sixth Embodiment) As shown in FIGS. 1 and 17, a fixing device 40 according to a sixth embodiment
2 is provided with a humidity sensor 79 (humidity detecting device according to the sixth invention) for detecting the humidity in the apparatus. The humidity sensor 79 is connected to a controller 70 which is a separation condition adjusting device, and the controller 70 adjusts the separation condition according to the humidity H detected by the humidity sensor 79.

The fixing device 40 according to the sixth embodiment has the other configuration except for the fixing device 40 according to the first embodiment (see FIGS. 1 and 2).
), And the description is omitted.

Next, the adjustment of the separation condition performed by the controller 70 will be described with reference to the flowchart of FIG. 18 and Table 6 below.

[0122]

[Table 6]

First, in step S18-1, the humidity sensor 79 detects the humidity in the sheet cassette 32.

Next, in step S18-2, if the humidity H is less than 70%, the flow shifts to step S18-3.

In step S18-3, the separation condition is set to "separation condition 1" which is a standard separation condition. Humidity H
Is less than 70%, even if the recording medium 35 is thick paper or plain paper, the amount of water absorbed is relatively small, so that the elasticity of the recording medium 35 due to the absorption of water is small. Therefore, in this case, the recording medium 35 is hardly wrapped around the fixing roller 41A even when the adhesive force of the developer or the electrostatic attraction force due to the charging of the recording medium 35 and the fixing rollers 41A and 41B acts. For this reason, in the “separation condition 1” of step S18-3, the setting is made such that the separation condition is given more importance to prevention of image noise and the like than paper passing property.

Specifically, in the “separation condition 1”, the distance d1 of the separation claw 56 to the nip 48 by the separation claw moving mechanism 60 is set to a standard value of 17 mm. Further, the paper ejection guide plate 62 is moved by the paper ejection guide plate moving mechanism 63.
The distance d2 of A to the nip 48 is set to a standard value of 24 mm. Further, the inclination angle θ of the fixing rollers 41A and 41B is set to a standard value of 90 degrees by the fixing roller posture adjusting mechanism 65.

Next, if the copy is completed in step S18-4, the copy operation is completed, and if not, the process returns to step S18-1.

On the other hand, in step S18-2,
If the humidity H is 70% or more, the process proceeds to step S18-5. In step S18-5, the separation condition is set to "separation condition 2." When the humidity H is 70% or more, if the recording medium 35 is thick paper or plain paper, it absorbs a relatively large amount of water and the elasticity is reduced. Therefore, in this case, the recording medium 35 is likely to be wound around the fixing roller 41A due to the adhesive force of the developer or the electrostatic attraction force due to charging. Therefore, the “separation condition 2” in step S18-5 is set with emphasis on paper passing properties.

Specifically, under the “separation condition 2”, the separation claw 56 is moved by the separation claw moving mechanism 60 in the direction approaching the nip portion 48, and the distance d1 is reduced to 15 mm.

In the "separation condition 2", the paper discharge guide plates 62A and 62B are moved by the paper discharge guide plate moving mechanism 63 in a direction approaching the fixing rollers 41A and 41B.
The distance d2 is reduced to 22 mm.

Further, in the "separation condition 2", the fixing roller attitude adjusting mechanism 65 causes the fixing rollers 41A, 41A to be used.
The inclination angle θ of B is set to 86 degrees, and the distance from the tip of the separation claw 56 to the outer peripheral surface of the fixing roller 41A is reduced to 15 mm.

As described above, in the fixing device 40 of the fifth embodiment, as the humidity H increases, the tip of the separation claw 56 and the nip 4
8 and the discharge guide plate 62A and the nip portion 48.
The distance d2 from the fixing rollers 41A and 41B is reliably separated from the fixing rollers 41A and 41B even when the humidity H is high and the recording medium 35 absorbs a large amount of water. Further, since the leading ends of the separation claws 56 and 57 are opposed to the fixing rollers 41A and 41B with a space therebetween, dirt on the recording medium 35 due to the release agent, image noise, and the fixing rollers 41A and 41B.
Can be prevented from being shortened.

The position at which the humidity sensor 79 is mounted is not limited to the sheet cassette 32. Further, the distances d1 and d2 and the inclination angle θ are continuously determined according to the detected humidity H.
May be adjusted.

(Seventh Embodiment) A fixing device 40 according to a seventh embodiment of the present invention shown in FIG. 19 extends in parallel with the shaft 60d of the separation claw moving mechanism 60, and is supported rotatably and immovably in the axial direction. Shaft 60j. The shaft 60j is inserted into the cylindrical member 60k, and a female screw formed on the inner peripheral surface of the cylindrical member 60k and the shaft 60k.
A male screw formed on the outer peripheral surface of j is engaged. Also,
A gear 60m fixed to one end of the shaft 60j is a gear 60g fixed to the rotation shaft of the separation claw driving motor 60f.
Is engaged. Rods 60n extending downward in the drawing from the cylindrical member 60k are provided with paper discharge rollers 68A, 68A.
B is attached. When the separation claw 56 approaches or separates from the fixing roller 41A by operating the separation claw drive motor 60f, the paper discharge rollers 68A, 68B are synchronized with the movement.
Approaches or separates from the fixing rollers 41A and 41B. Therefore, regardless of the position of the separation claw 56, the distance between the separation claw 56 and the paper discharge rollers 58A and 58B is kept constant,
The recording medium 35 is reliably discharged from the fixing device 40.

Since the other configuration and operation of the seventh embodiment are the same as those of the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted. The fixing device 40 according to the second to sixth embodiments has the same configuration as the fixing claw 5.
6, the paper discharge rollers 68A and 68B may be moved in synchronization with the movement of the roller 6.

The present invention is not limited to the above embodiment, and various modifications can be made.

For example, as shown in FIG. 20, each of the plurality of separation claws 56 has a separation claw moving mechanism 60-1 to 60-60.
-5 may be provided to move the individual separation claws 56 independently. In this case, the recording medium 35 is placed in the paper feed path 37 (see FIG. 1).
A sensor for detecting a dimension (width) of the recording medium 35 in a direction orthogonal to the conveyance direction may be provided, and some or all of the plurality of separation claws 56 may be moved according to the width of the recording medium 35 detected by the sensor.

For example, when the recording medium 35 is the fixing roller 41A
If the center of the recording medium 35 is supplied to the nip portion 48 so that the center in the axial direction of the recording medium 35 coincides with the center in the width direction of the recording medium 35 (center reference sheet passing), the width of the recording medium 35 is the size of the long side of the A4 size If present, the image mode, image density D _t , roller outer diameter O
D, the type of the recording medium, all of the separation claw moving mechanism in accordance with the conveyance velocity V _R or humidity H of the recording medium 60-1～60-5
Is operated, and if it is the dimension of the short side of the A4 size, some separation claw moving mechanisms 70-2 to 70-
Only 4 is activated. When the recording medium 35 is supplied to the nip portion 48 such that one end in the axial direction of the fixing roller 41A coincides with one end in the width direction of the recording medium 35 (one-side reference sheet passing), the width of the recording medium 35 is reduced. If the is the dimension of the long side of the A4 size, all the separation claw moving mechanisms 60-1 to 60-5 are operated according to the image mode or the like. Accordingly, only some of the separation claw moving mechanisms 60-1 to 60-3 are operated.

When the separation claw 56 approaches the fixing roller 41A, the recording medium 35 is surely separated from the fixing roller 41A. However, the release agent is accumulated between the separation claw 56 and the fixing roller 41A, and the recording medium 35 becomes dirty. The possibility and the possibility that image noise occurs due to the tip of the separation claw 56 contacting the image portion of the recording medium 35 increase. Therefore, by moving only the necessary separation claws 56 in accordance with the width of the recording medium 35 as shown in FIG. 20, the recording medium 35 can be prevented from being stained and image noise can be prevented from being generated with respect to the fixing roller 41A. Winding can be reliably prevented.

As shown in FIG. 21, the separation claw moving mechanism 60
May move the separation claw 56 in the vertical direction (vertical direction) in the figure.

As shown in FIG. 22, the separation claw moving mechanism 60
May move the separation claw 56 in the tangential direction of the fixing roller 41A.

As shown in FIG. 23, the separation claw moving mechanism 60
May move the separation claw 56 in the circumferential direction of the fixing roller 41A. The separation claw moving mechanism 60 includes a gear 60p rotatably mounted on the rotation shaft 62 of the upper fixing roller 41A in the figure, and the separation claw 56 is mounted on the gear 60p. The rotation of the separation claw driving motor 60f is transmitted to the gear 60p via the gears 60q and 60r.

[0143] Any of the separation claw moving mechanism 60 in FIG. 23 from FIG 21, the image mode, the image density D _t, the outer diameter of the roller OD, the type of recording medium, in accordance with the conveyance velocity V _R or humidity H of the recording medium The separation claw 56 is moved in a direction approaching the fixing roller 41A as indicated by an arrow B1, or is moved away from the fixing roller 41A as indicated by an arrow B2.

Each of the separation claw moving mechanisms 60 in FIGS. 2, 21, 22 and 23 moves only the separation claw 56 corresponding to one fixing roller 41A, while the separation claw moving mechanism 60 is the other. Only the separation claw 57 corresponding to the fixing roller 41B may be moved.
The separation claws 56 and 57 corresponding to 1A and 41B may be moved.

As shown in FIGS. 24 and 25, the nip width adjusting mechanism 80 controls the nip portion 4 of the fixing rollers 41A and 41B.
8, the distance d1 between the tip of the separation claw 56 and the nip 48 may be adjusted. The nip width adjusting mechanism 80 includes a pressing member 80b whose base end is rotatably supported by a pivot pin 80a. This pressing member 8
0b is engaged with the lower part of the rotating shaft 66 of the lower fixing roller 41B. The upper fixing roller 41A is fixed in the vertical direction in the figure, and the lower fixing roller 41B is movable in the vertical direction in the figure.

The nip width adjusting mechanism 80 includes a lever 80 whose base end is rotatably supported by a pivot pin 80c.
d. An eccentric cam 80f rotationally driven by a nip width adjusting motor 80e is in contact with a lower side of the lever 80d in the drawing. The tip of the lever 80d and the tip of the press contact member 80b are connected by a spring 80g.

When the eccentric cam 80f is at the rotation angle position shown in FIG. 24, the lever 80d is substantially horizontal in the figure, and the tip of the pressing member 80b is strongly pulled upward by the spring 80g. Therefore, the eccentric cam 8
When 0f is at the angular position shown in FIG. 23, a strong pressing force acts between the fixing rollers 41A and 41B, and the width of the nip portion 48 is large. When the width of the nip portion 48 is large, the distance d1 from the tip of the separation claws 56 and 57 to the nip portion 48 becomes short.

On the other hand, when the eccentric cam 80f is at the rotation angle position shown in FIG. 24, the tip of the lever 80d is lowered downward in the figure, so that the force of the spring 80g pulling up the tip of the press contact member 80b is weakened. Therefore, when the eccentric cam 80f is at the rotation angle position shown in FIG. 24, the pressure contact force between the fixing rollers 41A and 41B is reduced, and the width of the nip 48 is reduced. And the nip part 4
When the width of 8 is reduced, the distance d1 from the tips of the separation claws 56 and 57 to the nip 48 increases.

Accordingly, the nip width adjusting mechanism 80 controls the image mode, image density, roller outer diameter, type of recording medium,
Fixing members 56, 5 according to the transport speed of the recording medium or humidity.
The distance d1 from the tip of the head 7 to the nip 48 can be adjusted.

As shown in FIG. 26, the fixing device 40 according to the first embodiment is configured such that one fixing member is connected to a pair of rolls 100A,
A belt-type fixing member 102 composed of 100B and a belt 101 stretched between the rolls 100A and 100B may be used, or both the fixing members may be belt-type fixing members 102 as shown in FIG. Similarly, in the fixing devices 40 of the second to sixth embodiments, one or both fixing members may be the belt-type fixing members 102.

Further, the separation condition may be adjusted based on two or more factors of the image mode, the image density, the roller outer diameter, the type of the recording medium, the conveying speed of the recording medium, and the humidity.

[0152]

As is apparent from the above description, in the fixing device of the present invention, since the leading end of the separating member faces the fixing member with a space therebetween, the leading end of the separating member and the surface of the fixing member. Contamination of the recording medium due to accumulation of the release agent between the recording medium, image noise caused by the tip of the separating member coming into contact with the recording medium, and image noise caused by scratching the surface of the fixing member at the tip of the separating claw. In addition, it is possible to prevent the service life of the fixing member from being shortened. In addition, the separation condition adjusting device allows the image mode, image density, outer diameter of the fixing roller,
The position of the separation member with respect to the contact portion between the fixing members is adjusted according to the type of the recording medium, the conveyance speed of the recording medium, or the humidity. Sex can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a copying machine that is an image forming apparatus including a fixing device of the present invention.

FIG. 2 is a schematic diagram illustrating a fixing device according to a first embodiment.

FIG. 3 is a block diagram illustrating a controller of the fixing device according to the first exemplary embodiment.

FIG. 4 is a schematic view showing a paper ejection guide plate moving mechanism.

FIG. 5 is a schematic view showing a fixing roller attitude adjusting mechanism.

FIGS. 6A and 6B are schematic diagrams illustrating inclination of a fixing roller with respect to a recording medium conveyance direction.

FIG. 7 is a flowchart illustrating an operation of the fixing device according to the first exemplary embodiment.

FIG. 8 is a block diagram illustrating a controller of a fixing device according to a second embodiment.

FIG. 9 is a flowchart illustrating an operation of the fixing device according to the second embodiment.

FIG. 10 is a schematic diagram illustrating a fixing device according to a third embodiment.

FIG. 11 is a block diagram illustrating a controller of a fixing device according to a third embodiment.

FIG. 12 is a flowchart illustrating an operation of a fixing device according to a third embodiment.

FIG. 13 is a block diagram illustrating a controller of a fixing device according to a fourth embodiment.

FIG. 14 is a flowchart illustrating an operation of a fixing device according to a fourth embodiment.

FIG. 15 is a block diagram illustrating a controller of a fixing device according to a fifth embodiment.

FIG. 16 is a flowchart illustrating an operation of a fixing device according to a fifth embodiment.

FIG. 17 is a block diagram illustrating a controller of a fixing device according to a sixth embodiment.

FIG. 18 is a flowchart illustrating an operation of a fixing device according to a sixth embodiment.

FIG. 19 is a schematic diagram illustrating a fixing device according to a seventh embodiment.

FIG. 20 is a plan view showing another example of the separation claw moving mechanism.

FIG. 21 is a schematic view showing another example of the separation claw moving mechanism.

FIG. 22 is a schematic view showing another example of the separation claw moving mechanism.

FIG. 23 is a schematic view showing another example of the separation claw moving mechanism.

FIG. 24 is a schematic view showing a nip width adjusting mechanism.

FIG. 25 is a schematic view showing a nip width adjusting mechanism.

FIG. 26 is a schematic view showing a modification of the present invention.

FIG. 27 is a schematic view showing a modification of the present invention.

FIG. 28 is a schematic view illustrating an example of a conventional fixing device.

FIG. 29 is a plan view of FIG. 28.

[Explanation of symbols]

 Reference Signs List 23 Image recording unit 32 Paper feed cassette 35 Recording medium 37 Paper feed path 40 Fixing device 41A, 41B Fixing roller 47 Fixing roller drive motor 48 Nip unit 50 Release agent applying device 56, 57 Separating claw 60 Separating claw moving mechanism 62A, 62B Discharge guide plate 63 Discharge guide plate moving mechanism 65 Fixing roller attitude adjusting mechanism 68A, 68B Discharge roller 69 Discharge roller drive motor 70 Controller 72 Developer image 74 Image density detection CCD 75 Laser type outer diameter measuring device 76 Recording Medium discrimination sensor 78 Speed sensor 79 Humidity sensor 80 Nip width adjustment mechanism 100A, 100B Roll 101 Belt 102 Belt-type fixing member

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuro Ito 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka F-term in Osaka International Building Minolta Co., Ltd. 2H033 AA16 BA15 BA16 BA20 BA21 BA42 BA43 BB01 BB03 BB06 BB29 BB33 BB34 BB37 CA01 CA11 CA16 CA18 CA26

Claims (12)

[Claims] 1. A fixing device comprising: a pair of fixing members pressed against each other; a heating device for heating at least one of the pair of fixing members; and a driving device for driving at least one of the pair of fixing members. A fixing device in which the developer carried on the recording medium is heated and melted by the recording medium passing through a contact portion between the fixing members, and is fixed to the recording medium. A separating member which is disposed downstream in the direction and has a leading end opposed to the fixing member at an interval, an image mode detecting device for detecting an image mode, and an image mode detected by the image mode detecting device. A fixing condition adjusting device that adjusts at least a position of the separating member with respect to a contact portion between the fixing members. 2. The separation condition adjusting apparatus according to claim 1, wherein the distance between the tip of the separation member and the contact portion is a first value when the image mode is the monochrome mode, and when the image mode is the color mode. 2. The fixing device according to claim 1, wherein a position of the separation member with respect to the contact portion is adjusted such that a distance between a tip of the separation member and the contact portion has a second value smaller than the first value. apparatus. 3. A fixing device comprising: a pair of fixing members pressed against each other; a heating device for heating at least one of the pair of fixing members; and a driving device for driving at least one of the pair of fixing members. A fixing device in which the developer carried on the recording medium is heated and melted by the recording medium passing through the contact portion between the fixing members, and is fixed to the recording medium. A separating member disposed downstream in the transport direction and having a leading end opposed to the fixing member at an interval, an image density detecting device for detecting an image density of an image formed on a recording medium, and the image density A fixing condition adjusting device that adjusts at least a position of the separating member with respect to a contact portion between the fixing members in accordance with an image density detected by the detecting device. 4. The separation condition adjusting device according to claim 3, wherein the position of the separation member with respect to the contact portion is adjusted such that the tip of the separation member approaches the contact portion as the image density increases. Fixing device. 5. A fixing device comprising: a pair of fixing members pressed against each other; a heating device for heating at least one of the pair of fixing members; and a driving device for driving at least one of the pair of fixing members. A fixing device wherein the developer carried on the recording medium is heated and melted by passing the recording medium through a contact portion between the fixing members, and is fixed to the recording medium. The pair of fixing members include a fixing roller A separating member disposed downstream of the contact portion in the conveying direction of the recording medium and having a leading end facing the fixing member at an interval, and a roller for detecting an outer diameter of the fixing roller. An outer diameter detecting device, and a separation condition adjusting device that adjusts at least a position of the separating member with respect to a contact portion between the fixing rollers according to an outer diameter of the fixing roller detected by the roller outer diameter detecting device. A fixing device and a device. 6. The separation condition adjusting device adjusts the position of the separation member with respect to the contact portion such that the larger the outer diameter of the fixing roller, the closer the tip of the separation member approaches the contact portion. 3. The fixing device according to claim 1. 7. A fixing device comprising: a pair of fixing members pressed against each other; a heating device for heating at least one of the pair of fixing members; and a driving device for driving at least one of the pair of fixing members. A fixing device in which the developer carried on the recording medium is heated and melted by the recording medium passing through the contact portion between the fixing members, and is fixed to the recording medium. A separating member that is disposed downstream in the transport direction and whose leading end faces the fixing member at an interval, a recording medium detection device that detects the type of recording medium, and a recording medium detection device that detects the type of the recording medium. A fixing condition adjusting device that adjusts at least a position of the separating member with respect to a contact portion between the fixing members according to a type of a recording medium. 8. The separation condition adjusting device according to claim 1, wherein if the recording medium is cardboard or an OHP sheet, the distance between the leading end of the separation member and the contact portion is a first value, and the recording medium is plain paper. If so, the position of the separation member with respect to the contact portion is adjusted so that the distance between the tip of the separation member and the contact portion becomes a second value smaller than the first value. The fixing device as described in the above. 9. A fixing device comprising: a pair of fixing members pressed against each other; a heating device for heating at least one of the pair of fixing members; and a driving device for driving at least one of the pair of fixing members. A fixing device in which the developer carried on the recording medium is heated and melted by the recording medium passing through the contact portion between the fixing members, and is fixed to the recording medium. A separation member that is disposed downstream in the conveyance direction and whose leading end faces the fixing member at an interval, a conveyance speed detection device that detects the conveyance speed of the recording medium to the contact portion, and the conveyance speed A fixing device comprising: a separation condition adjusting device that adjusts at least a position of the separation member with respect to a contact portion between the fixing members according to a conveyance speed of the recording medium detected by the detection device. 10. The separation condition adjusting device adjusts a position of the separation member with respect to the contact portion such that a lower end of the separation member approaches the contact portion as the conveyance speed of the recording medium is lower. 10. The fixing device according to item 9. 11. A pair of fixing members pressed against each other,
A heating device that heats at least one of the pair of fixing members, and a driving device that drives at least one of the pair of fixing members, are provided.A recording medium passes through a contact portion between the pair of fixing members. What is claimed is: 1. A fixing device, wherein a developer carried on a recording medium is heated and melted and fixed on the recording medium. A separating member opposed to the fixing member at an interval, and a humidity detecting device for detecting humidity. According to the humidity detected by the humidity detecting device, at least a position of the separating member with respect to a contact portion between the fixing members is determined. A fixing device comprising a separation condition adjusting device for adjusting. 12. The separation condition adjusting device according to claim 11, wherein the separation condition adjusting device adjusts the position of the separation member with respect to the contact portion such that the tip of the separation member approaches the contact portion as the humidity increases. Fixing device.