JP2001282019A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the paper passing ability of a fixing device by eliminating the influence of the attraction of a recording medium on the surface of a fixing member caused by the electrification of the surface of the fixing member. SOLUTION: This fixing device 40 is equipped with a surface potential detecting device 49 detecting the surface electrification potential VS of at least either of a pair of fixing members 41A and 41B and a fixing condition adjusting device 64 adjusting a fixing condition in accordance with the surface electrification potential VS detected by the device 49. The fixing condition includes press- contact force between a pair of fixing members 41A and 41B, the supply time interval of a recording medium 35 supplied to a contact part 48 between the members 41A and 41B, and a releasing agent supply amount supplied to the surfaces of the members 41A and 41B.

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 this type of fixing device, as shown in FIGS. 23 and 24, a pair of fixing rollers 3, 4; a heating device 5 for heating these fixing rollers 3, 4; And a plurality of separation claws 7 and 8 arranged in the axial direction of the fixing rollers 3 and 4, respectively. It has been 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 recording medium 12 is conveyed to a contact portion (nip portion 11) between the pair of fixing rollers 3 and 4, and the developer on the recording medium 12 is
The recording medium 12 is melted and pressurized by the heat supplied from the recording medium 12. The leading end of the recording medium 12 that has passed through the nip 11 is guided by the separation claws 7 and 8, and separated from the fixing rollers 3 and 4.

[0003]

In the nip portion 11, the surface of the fixing rollers 3 and 4 comes into contact with the recording medium 12, so that the surface of the fixing rollers 3 and 4 and the recording medium 12 are charged due to friction or the like. For example, when the elastic member 10 is made of silicone rubber and the elastic recording medium 12 is a transfer paper mainly made of cellulose, the surfaces of the fixing rollers 3 and 4 are negatively charged, and the recording medium 12 is positively charged. Charges. As a result, the surfaces of the fixing rollers 3 and 4 and the recording medium 12
Between the fixing rollers 3 and 4, the electrostatic attraction force acts between the fixing rollers 3 and 4. In particular, when the surface charging potential of the fixing rollers 3 and 4 becomes high, the portion of the recording medium 12 that has passed through the nip portion 11 is
4 and causes paper jams and the like, and the paper passing property is reduced.

On the other hand, if the tips of the separation claws 7, 8 are always kept in contact with the surfaces of the fixing rollers 3, 4, the recording medium 12 is electrostatically charged on the surfaces of the fixing rollers 3, 4 by charging as described above. The recording medium 12 can be reliably separated from the fixing rollers 3 and 4 even if the recording medium 12 is sucked. However, if the tips of the separation claws 7 and 8 are always in contact with the surfaces of the fixing rollers 3 and 4, there are the following problems particularly when the image to be fixed is a full-color image. 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 tips of the separation claws 7 and 8 and the fixing rollers 3 and 4 are used.
The release agent accumulates between the surfaces of the recording medium 12, and the recording medium 12 is soiled by the release agent. Further, the fixing rollers 3 and 4 are
The separation claws 7 and 8 come into contact with the image portion, which causes image noise. Further, the surfaces of the fixing rollers 3 and 4 are scratched by the tips of the separation claws 7 and 8, and the scratches shorten the service life of the fixing rollers 3 and 4 and cause image noise.

Accordingly, an object of the present invention is to improve the paper passing property by removing the influence of the adsorption of the recording medium to the fixing member surface due to the charging of the fixing member surface.

[0006]

According to a first aspect of the present invention, there is provided 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; A driving device for driving at least one of the pair of fixing members, wherein the recording medium passes through a contact portion between the pair of fixing members, whereby the developer carried on the recording medium is heated and melted, and the recording medium is melted. A surface potential detecting device that detects a surface charging potential of at least one of the pair of fixing members, and adjusting a fixing condition according to the surface charging potential detected by the surface potential detecting device. And a fixing condition adjusting device. The fixing conditions include a pressing force between the pair of fixing members, a time interval for supplying the recording medium to a contact portion between the fixing members, and a supply amount of the release agent to the surface of the fixing member.

More specifically, the fixing condition adjusting device reduces the pressing force acting between the pair of fixing members as the surface charging potential detected by the surface potential detecting device increases. The higher the surface charging potential of the fixing member, the stronger the electrostatic attraction acting between the surface of the fixing member and the recording medium, so that the recording medium is less likely to be separated from the surface of the fixing member. On the other hand, if the pressing force between the fixing members is reduced, the dimension of the contact portion between the fixing members is reduced,
The contact time between the recording medium and the surface of the fixing member is shortened, and as a result, the surface charging potential of the fixing member is attenuated. Therefore,
The recording medium is reliably separated from the surface of the fixing member by reducing the pressing force between the fixing members as the surface charging potential increases.

Further, the fixing condition adjusting device may be arranged such that the higher the surface charging potential detected by the surface potential detecting device, the longer the time interval for supplying the recording medium to the contact portion between the pair of fixing members. . As the time interval of supplying the recording medium to the contact portion between the fixing members is longer, the amount of discharge from the surface of the fixing member is increased, and the surface charging potential is attenuated. Therefore,
By increasing the supply time interval of the recording medium as the surface charging potential increases, the recording medium is reliably separated from the surface of the fixing member.

Further, when the surface charging potential detected by the surface potential detecting device exceeds a predetermined value, the fixing condition adjusting device stops the supply of the recording medium to the contact portion between the pair of fixing members for a predetermined time. It may be something that causes it. If the supply of the recording medium is stopped for a certain period of time, the discharge time from the surface of the fixing member is sufficiently ensured, so that the surface charging potential of the fixing member is more reliably attenuated. Note that while the supply of the recording medium is stopped, the fixing member may be driven by a driving device, or the driving device may be stopped and the fixing member may be in a non-driving state.

Further, the fixing condition adjusting device may increase the supply amount of the releasing agent to the surface of the fixing member as the surface charging potential detected by the surface potential detecting device increases. As described above, the higher the surface charging potential of the fixing member, the more difficult it is to separate the recording medium. On the other hand, when the supply amount of the releasing agent to the surface of the fixing member increases, the friction between the fixing member and the recording medium is reduced, so that the recording medium is easily separated from the fixing member. Therefore, the recording medium is reliably separated from the surface of the fixing member by increasing the release agent supply amount as the surface charging potential of the fixing member increases.

A 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 fixing device comprising: a surface potential detecting device for detecting at least one surface charging potential; and a separation condition adjusting device for adjusting a separation condition in accordance with the surface charging potential detected by the surface potential detecting device. is there. The above separation conditions include
There are a position of a separation member such as a separation claw with respect to the fixing member, a position of the sheet ejection guide plate with respect to the fixing member, and an inclination of the pair of fixing members with respect to the recording medium conveyance direction.

More specifically, the separating condition adjusting device moves the leading end of the separating member closer to the fixing member as the surface charging potential detected by the surface potential detecting device is higher. The higher the surface charging potential of the fixing member, the stronger the electrostatic attraction acting between the surface of the fixing member and the recording medium, so that the recording medium is less likely to be separated from the surface of the fixing member. On the other hand, the closer the leading end of the separating member is to the fixing member, the more reliably the leading end of the recording medium is guided by the separating member. Therefore, as the surface charging potential becomes higher, the recording medium is more reliably separated from the surface of the fixing member by bringing the leading end of the separating member closer to the fixing member.

[0013] Further, the separation condition adjusting device sets the separation member out of contact with the fixing member if the surface charge potential detected by the surface potential detection device is equal to or less than a predetermined value.
When the value exceeds a predetermined value, the tip of the separation member may be brought into contact with the fixing member.

Further, the separation condition adjusting device may be such that the higher the surface charging potential detected by the surface potential detecting device is, the closer the paper ejection guide plate is to the fixing member. The closer the discharge guide plate is to the fixing member, the more reliably the recording medium is guided by the discharge guide plate. Therefore, as the surface charging potential becomes higher, the recording medium is more reliably separated from the surface of the fixing member by bringing the leading end of the separating member closer to the fixing member.

Further, in the separation condition adjusting device, the higher the surface charge potential detected by the surface potential detection device, the more the inclination of the pair of fixing members with respect to the recording medium conveyance direction and the more the front end of the separation member fixes the inclination. The member may be adjusted so as to approach the member.

As the surface potential detecting device, for example,
There is a surface potential sensor. Further, the surface potential detecting device may be a device that detects a current value flowing between the fixing member and the ground portion, or a device that detects a leak current value from the fixing member to the separating member.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) As shown in FIG. 1, a copying machine, which is an image forming apparatus having a fixing device of the present invention, has a document placing section 21 and a document placing section 21 mounted on the document placing section 21. An optical scanning device 22 for reading a placed document (not shown) is provided. The image data read by the optical scanning device 22 is stored in the image recording unit 23 and then sent to the exposure device 24. The exposure device 24 exposes the surface of the photoconductor 25, which is an image carrier, with laser light based on the image data.

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 photosensitive member 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 of the first embodiment shown in FIGS. 2 to 5 is adapted to adjust the fixing conditions in accordance with the surface charging potential of the fixing roller. As shown in the figure, the fixing device 40 includes 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 driving motor 47 is connected to the lower fixing roller 41B. Further, the fixing rollers 41A and 41B are pressed against each other by a pressing force adjusting mechanism 61 (see FIGS. 4 and 5) described later, and a contact portion (nip portion 48) extending in the axial direction is formed. When the fixing roller drive motor 47 operates, the lower fixing roller 41B
Rotates clockwise in the figure, and the upper fixing roller 41
A is driven to rotate.

A surface potential sensor 49, which is a surface potential detecting device, is disposed slightly apart from the surface of the upper fixing roller 41A. When the surface of the fixing roller 41A is charged by contact with the recording medium 35 at the nip portion 48, the surface potential sensor 49 detects the charging potential (surface charging potential V _S ) of the surface of the fixing roller 41A.

In this embodiment, the fixing roller 41A
Is provided with an elastic member 43 made of silicone rubber, so that the outer periphery of the fixing roller 41A is charged to a negative polarity by contact with the recording medium 35, and the recording medium 35 is charged to a positive polarity. Around the upper fixing roller 41A, a fixing roller 4 is provided.
Release agent (silicone oil in this embodiment) on the surface of 1A
Release agent application device 50 for applying the toner, cleaning roller 51 including a felt roller, and thermistor 52A
Is arranged.

The release agent application device 50 includes a release agent tank 50a in which a 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 supply 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 53b described later. Therefore, when the release agent supply device drive motor 50e operates and the pumping roller 50b rotates, the release agent application roller 50c
Is driven by the pumping roller 50b, and the release agent tank 5
The release agent 0a is supplied to the surface of the fixing roller 41A via the suction roller 50b and the release agent application roller 50c.

The release agent applying device 50 has a release agent supply amount adjusting mechanism 53. The release agent supply amount adjusting mechanism 53 includes a spring 5 having one end connected to the rotation shaft side of the release agent application roller 50c and the other end connected to the cam plate 53a.
3b and an eccentric cam 53c pressed against the cam plate 53a. The eccentric cam 53c is connected to a release agent supply amount adjusting motor 53d. The eccentric cam 53c is shown in FIG.
When the release agent application amount adjusting motor 53d rotates the eccentric cam 53c clockwise in the figure at the angular position shown in FIG. 7, the pressure contact force between the release agent application roller 50c and the fixing roller 41A increases. The dimensions of the contact area of
As a result, the amount of the release agent applied to the fixing roller 41A increases. On the other hand, when the eccentric cam 53c rotates counterclockwise in the drawing, the release agent applying roller 50c and the fixing roller 41c are rotated.
Since the pressure contact force of A decreases, the dimension of the contact portion between the two decreases, and as a result, the amount of the release agent applied to the fixing roller 41A decreases. The amount of the release agent applied to the lower fixing roller 41B increases or decreases according to the amount of the release agent applied to the upper fixing roller 41A.

Around the lower fixing rollers 41A and 41B, there are arranged a fluorine rubber leveling blade 54 and a thermistor 52B for leveling the release agent on the peripheral surfaces of the fixing rollers 41A and 41B.

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. Further, on the downstream side of the separation claws 56 and 57 in the transport direction of the recording medium 35, a pair of discharge rollers 58A and 58A for transporting the recording medium 35 to the discharge tray 33 shown in FIG.
58B are arranged. These paper discharge rollers 58A, 58
B are pressed against each other, and a lower discharge roller 58B in the figure is connected to a discharge roller driving motor 59. When the discharge roller drive motor 59 operates, the discharge rollers 58A and 58B rotate, and the discharge rollers 58A and 58B
The recording medium 35 supplied to the contact portion is carried out of the fixing device 40.

As shown in FIG. 4 and FIG.
Is provided with a pressing force adjusting mechanism 61 for adjusting the pressing force of the fixing rollers 41A and 41B. The press-contact force adjusting mechanism 61 includes a press-contact member 61b whose base end is rotatably supported by a pivot pin 61a. This pressing member 61
b is engaged with the lower portion of the rotating shaft 62 of the lower fixing roller 41B. The upper fixing roller 41A has a fixed vertical position in the figure, and the lower fixing roller 41A has a fixed position.
1B is movable in the vertical direction in the figure.

The pressing force adjusting mechanism 61 includes a lever 61d whose base end is rotatably supported by a pivot pin 61c.
It has. An eccentric cam 61f, which is rotationally driven by a pressing force adjusting motor 61e, is in contact with a lower side of the lever 61d in the drawing. The tip of the lever 61d and the tip of the press contact member 61b are connected by a spring 61g.

For example, when the eccentric cam 61f is at the angular position shown in FIG. 4, the lever 61d is substantially horizontal in the figure, and the tip of the pressing member 61b is a spring 61g.
It is pulled up stronger. Therefore, when the eccentric cam 61f is at the angular position shown in FIG. 4, a strong pressing force acts between the fixing rollers 41A and 41B, and the width of the nip portion 48 (the dimension in the transport direction of the recording medium 35) is large. .

On the other hand, when the eccentric cam 61f is at the rotation angle position shown in FIG. 5, the tip of the cam plate is lowered downward in the figure, so that the force of the spring 61g to pull up the tip of the press contact member 61b is weakened. Therefore, when the eccentric cam 61f is at the rotational position shown in FIG. 5, the pressing force between the fixing rollers 41A and 41B decreases, and the nip portion 48
Width shrinks.

The fixing device 40 includes a controller 64 shown in FIGS. The controller 64 has a surface charging potential V detected by the surface potential sensor 49.
_S and the temperature detected by the thermistors 52A and 52B are input. The controller 64 controls the fixing roller drive motor 47, the release agent supply device drive motor 50e, and the paper discharge roller drive motor 59 based on these inputs and the like. Further, the controller 64 determines that the surface charging potential V _S
The release agent supply amount adjusting motor 53d and the pressing force adjusting motor 61e are controlled in accordance with. Further, the controller 64 includes a sheet passing sequence controller 65 (FIG. 3) for controlling the supply of the recording medium 35 from the transfer device 29 to the fixing device 40.
Is shown only in FIG. ) Is connected, depending on the surface charge potential V _S which is the input, and controls the sheet passing sequence controller 65.

The operation of the fixing device 40 will be described.
7. The release agent supply device drive motor 50e and the paper discharge roller drive motor 59 are operating. In FIG. 2, the developer image 66 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 66 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 58A and 58B.

Next, the adjustment of the fixing conditions executed by the controller 64 will be described with reference to the flowchart of FIG. 6 and Table 1 below.

[0035]

[Table 1]

First, in step S6-1, the surface potential V of the fixing roller 41A is detected by the surface potential sensor 49.
_S is detected. Next, at step S6-2, the following absolute value of the surface charge potential V _S is 1.5 kV, that is, the surface charge potential V _S is greater than 0 kV, -1.5
If kV or less, the process proceeds to step S6-3.

In step S6-3, the fixing condition is set to "fixing condition 1" which is a standard fixing condition. If the absolute value of the surface charge potential V _S as described above 1.5kV or less, because weak charge of the fixing roller 41A due to contact with the recording medium 35, the electrostatic acting between the recording medium 35 fixing roller 41A The winding of the recording medium 35 around the fixing roller 41A due to the electric attraction force is relatively unlikely to occur. For this reason, in the “fixing condition 1” of step S6-3, the setting is made such that the printing condition and the like are more important than the fixing condition.

Specifically, in the "fixing condition 1", the pressing force between the fixing rollers 41A and 41B is set to a standard value of 40 kg by the pressing force adjusting mechanism 61. In addition, the sheet passing sequence controller 65 controls one sheet of the recording medium 3.
5 reaches the nip portion 48 and then the next recording medium 3
The time interval (the supply time interval of the recording medium 35) until the leading end of No. 5 reaches the nip portion 48 is set to a standard value of 8 seconds. Further, the amount of the release agent applied to the fixing roller 41A by the release agent application amount adjusting mechanism 53 is a standard value A
The amount is set to 10 mg per one of the four sizes of the recording medium 35. Next, if the copy is completed in step S6-4, the copy operation is completed.
Return to 6-1.

On the other hand, in step S6-2, if the absolute value of the surface charging potential V _S exceeds 1.5 kV, that is, if the surface charging potential V _S exceeds -1.5 kV, the process proceeds to step S6-4. Transition.

In step S6-4, the fixing condition is set to "fixing condition 2". As described above, the surface charging potential V _S
Is greater than 1.5 kV, the recording medium 35
Since the fixing roller 41A is strongly charged due to contact with the recording medium 35, the recording medium 35 acting between the recording medium 35 and the fixing roller 41A is electrostatically attracted. ing. Therefore, the “fixing condition 2” in step S6-4 is set with emphasis on paper passing.

More specifically, in the "fixing condition 2", the pressing force between the fixing rollers 41A and 41B is reduced by the pressing force adjusting mechanism 61, and is set to 30 kg. Fixing roller 41
If the pressing force between A and 41B is reduced, the width of the nip portion 48 is reduced, so that the recording medium 35 and the fixing rollers 41A,
41B, the contact time with the surface of the fixing roller 41B is reduced.
A, the surface charge potential V _S of 41B attenuated. Therefore, the recording medium 35 is reliably separated from the surfaces of the fixing rollers 41A and 41B by reducing the pressure contact force between the fixing rollers 41A and 41B.

In the “fixing condition 2”, the time interval for supplying the recording medium 35 to the fixing device 40 is expanded by the sheet passing sequence controller 65 and set to 16 seconds.
Recording medium 3 to nip between fixing rollers 41A and 41B
More supply time interval 5 is long, the discharge time from the surface of the fixing member 41A to the air is increased, the discharge amount is increased, the surface charge potential V _S is attenuated. Therefore, the recording medium 3
5, the recording medium 35 is extended.
Is reliably separated from the surfaces of the fixing rollers 41A and 41B.

Further, in the "fixing condition 2", the release agent application amount adjusting mechanism 53 increases the amount of the release agent applied to the fixing roller 41A, and sets the amount to 20 mg per A4-size recording medium 35. Is done. When the amount of release agent supplied to the surfaces of the fixing rollers 41A and 41B increases, the fixing rollers 41A and 41B
Since the friction between B and the recording medium 35 is reduced, the recording medium 35 is easily separated from the fixing rollers 41A and 41B. Therefore, by increasing the release agent supply amount,
The recording medium 35 is reliably separated from the surface of the fixing roller 41A.

Next, at step S6-5, if the absolute value of the surface charge potential Vs exceeds 2.0 kV, i.e. the surface charge potential V _S exceeds the -2.0kV is
The process moves to step S6-6.

[0045] Since the absolute value of the surface charge potential V _S as described above in the case of more than 2.0kV, the fixing roller 41A is charged very strongly, the fixing of the recording medium 35 roller 4
It is in a state where winding around 1A is more likely to occur. Therefore, in step S6-6, the paper passing sequence controller 65 sends the recording medium 35 to the fixing device 40.
Is stopped for a certain time (for example, 10 seconds). While the supply of the recording medium 35 is stopped, the fixing roller 41
Since the charges on the surfaces of A and 41B are discharged into the air, the surface charging potential V _S is attenuated. While the supply of the recording medium 35 is stopped in step S6-6, the fixing roller driving motor 47 may be operated to keep the fixing rollers 41A and 41B idle, or the fixing roller driving motor 47 may be stopped to stop the fixing roller 41A. The rotation of 41A, 41B may be stopped. After the elapse of the predetermined time, the flow shifts to step S6-4.

Meanwhile, at step S6-5, if the absolute value of the surface charge potential V _S is less than 2.0 kV, that is, the surface charge potential V _S exceeds the -1.5kV is -2.
If it is 0 kV or less, the process proceeds to step S6-4.

The structure of the release agent application amount adjusting mechanism 53 is not particularly limited as long as the application amount of the release agent to the fixing rollers 41A and 41B can be adjusted. For example, in the release agent application amount adjusting mechanism 53 shown in FIG. 7, a part of the release agent regulating blade 50d is rotatably supported, and a lever 53e rotatable around the base end side is provided. Also, the release agent application roller 50 of the release agent regulating blade 50d.
c and the end of the lever 53e are connected to a spring 53f.
Are connected by Further, an eccentric cam 53g is in contact with the lever 53e. When the lever 53e is at the angular position shown in FIG.
When the eccentric cam 53g is rotated clockwise in FIG. 3d by 3d, the clearance between the release agent regulating blade 50d and the release agent application roller 50c increases.
The thickness of the release agent layer on the c surface increases, and as a result, the amount of the release agent applied to the fixing roller 41A increases. On the other hand, when the eccentric cam 53g rotates counterclockwise in the drawing, the gap between the release agent regulating blade 50d and the release agent application roller 50c decreases, and thus the thickness of the release agent layer on the surface of the release agent application roller 50c. As a result, the amount of the release agent applied to the fixing roller 41A decreases.

(Second Embodiment) A fixing device 40 according to a second embodiment of the present invention shown in FIGS.
A, depending on the surface charge potential V _S of 41B, it is adapted to adjust the separation conditions. The separation conditions include the position of the separation claw 56 with respect to the fixing roller 41A and the fixing rollers 41A and 41B of the sheet discharge guide plates 68A and 68B, as described later.
And the inclination of the fixing rollers 41A and 41B with respect to the conveying direction of the recording medium 35.

A plurality of separating 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 70 will be described. First, a plurality of separation claws 56 corresponding to the upper fixing roller 41A are attached to one frame 70a, and this frame 70a is a lower end of a rod 70b extending vertically in the figure. It is fixed to. A cylindrical member 70c is fixed to an upper end of the rod 70b. A horizontally extending shaft 70c supported rotatably and immovably in the axial direction is provided.
Od is inserted through the cylindrical member 70c. A male screw formed on the inner peripheral surface of the cylindrical member 70c is engaged with a male screw formed on the outer peripheral surface of the shaft 70d. A gear 70e fixed to one end of the shaft 70d is engaged with a gear 70g fixed to the output shaft of the separation claw drive motor 70f. Therefore, when the separation claw drive motor 70f rotates, the cylindrical member 70c moves on the shaft 70d in the left-right direction (horizontal direction) in the figure according to the rotation direction, and accordingly, the separation claw 56 moves with respect to the fixing roller 41A. Approach and leave.

The pair of paper discharge guide plates 68A, 68B can be moved in the left-right direction (horizontal direction) in the figure by a paper discharge guide plate moving mechanism 71 shown in FIG. The paper ejection guide plate moving mechanism 71 will be described. First, the paper ejection guide plates 68A and 68B are fixed to the upper end of a rod 71a extending in the vertical direction in the figure.
A cylindrical member 71b is fixed to a lower end of the rod 71a. A horizontally extending shaft 71c supported rotatably and immovably in the axial direction is provided, and this shaft 71c is inserted through the cylindrical member 70c. A female screw formed on the inner peripheral surface of the cylindrical member 71b is engaged with a male screw formed on the outer peripheral surface of the shaft 71c. A gear 71 fixed to one end of the shaft 71c
d is engaged with a gear 71f fixed to the output shaft of the paper ejection guide plate drive motor 71e. Therefore, when the paper ejection guide plate driving motor 71e rotates, the cylindrical member 71b moves in the horizontal direction on the shaft 71c in accordance with the rotation direction, and the paper ejection guide plates 68A, 68B move the fixing rollers 41A, 41B accordingly. Approaching and moving away from

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 72 shown in FIG. The fixing roller attitude adjusting mechanism 72 will be described. First, a gear 72a is rotatably attached to one end of a rotating shaft 62 of the lower fixing roller 41B in the figure. A sliding member 72c is provided on a frame 72b provided integrally with the gear 72a. The rotating shaft 62 of the upper fixing roller 41A in the figure is rotatably supported by the sliding member 72c.
A spring receiving portion 72d is provided at the upper end in the drawing of the frame 72b, and a spring 72e is arranged in a compressed state between the spring receiving portion 72d and the sliding member 72c. Due to the urging force of the spring 72e, the fixing roller 4
1A and 41B are pressed against each other. Gear 72a
The rotation of the fixing roller attitude adjusting motor 72h is transmitted to the motor via gears 72f and 72g. When the fixing roller attitude adjusting motor 72h operates, the gear 72a rotates about the rotation shaft 62 in accordance with the rotation direction, and accordingly, the frame 72b also rotates about the rotation shaft 62. Therefore, the inclination angle θ can be adjusted by operating the fixing roller attitude adjusting motor 72h.

The controller 64 shown in FIGS. 8 and 9 has a surface charging potential V detected by the surface potential sensor 49.
_S and the temperature detected by the thermistors 52A and 52B are input. The controller 64 controls the fixing roller drive motor 47, the release agent supply device drive motor 50e, and the paper discharge roller drive motor 59 based on these inputs and the like. Further, the controller 64 determines that the surface charging potential V _S
, The separation claw driving motor 70f, the paper ejection guide plate driving motor 71e, and the fixing roller attitude adjusting motor 72h are driven. In the fixing device 40 of the second embodiment, the release agent application device 50 does not include the release agent application amount adjusting device 53 (see FIG. 2), and a fixed amount of the release agent is applied to the surface of the fixing roller 41A. Is supplied.

The other configuration of the fixing device 40 of the second embodiment is the same as that of the first embodiment, and therefore, the same components are denoted by the same reference characters and description thereof is omitted.

The operation of the fixing device 40 of the second embodiment will be described. During the operation of the fixing device 40, the fixing roller drive motor 47, the release agent supply device drive motor 50e, and the paper discharge roller drive motor 59 operate. ing. In FIG. 8, a developer image 66 is formed on the recording medium 35 conveyed to the fixing device 40 from the left side. When the recording medium 35 passes through the nip 48, the developer is heated and melted, and the developer image is fixed on the recording medium 35. After the recording medium 35 that has passed through the nip portion 48 is separated from the fixing rollers 41A and 41B by the separation claws 56 and 57, the recording medium guide plate 68
A, 68B, and the paper discharge rollers 58A, 58B
Is conveyed to the paper discharge tray 33 via the.

Next, the adjustment of the separation condition performed by the fixing device 40 will be described with reference to the flowchart of FIG. 13 and Table 2 below.

[0056]

[Table 2]

[0057] First, in step S13-1, the surface charge potential V _S of the fixing roller 41A is detected by the surface potential sensor 49. Then, in step S13-2, the following absolute value of the surface charge potential V _S is 1.5 kV, that is, the surface charge potential V _S is greater than 0 kV,
If it is equal to or lower than -1.5 kV, the process proceeds to step S6-3.

In step S13-3, the fixing condition is set to "separation condition 1" which is a standard fixing condition. If the absolute value is less than 1.5kV surface charge potential V _S, relatively weak charge of the fixing roller 41A due to contact with the recording medium 35, winding of the recording medium 35 to the fixing roller 41A it is difficult to relatively occur . Therefore, this step S13
In the "separation condition 1" of -3, the separation condition is set so that the printing speed and the like are more important than the paper passing property.

Specifically, in the “separation condition 1”, the tip of the separation claw 56 is fixed to the fixing roller 41 by the separation claw moving mechanism 70.
A distance d1 from the outer peripheral surface of A is set to a standard value of 2.5 mm. Further, the distance d2 between the leading end of the discharge guide plate 68A and the peripheral surface of the fixing roller 41A is set to a standard value of 7 mm by the discharge guide plate moving mechanism 71. Further, the rotation centers C1, C of the fixing rollers 41A, 41B are set.
The inclination angle θ of the line L connecting 2 with respect to the transport direction of the recording medium 35 is a standard value of 9 as shown in FIG.
Set to 0 degrees.

Next, if the copy is completed in step S13-4, the copy operation is completed, and if not, the process returns to step S13-1.

On the other hand, in step S13-2,
When the absolute value of the surface charging potential V _S exceeds 1.5 kV,
That surface charge potential V _S is the case above the -1.5kV, the process proceeds to step S13-5.

In step S13-5, the separation condition is set to "separation condition 2". If the absolute value of the surface charge potential V _S exceeds 1.5kV, since the fixing roller 41A is strongly charged by contact with the recording medium 35, an electrostatic acting between the recording medium 35 fixing roller 41A The recording medium 35 is likely to be wound around the fixing roller 41 </ b> A due to the attractive force. Therefore, in the “separation condition 2” of step S6-4, the separation condition is set with emphasis on paper passage.

More specifically, in the “separation condition 2”, the separation claw 56 is moved in the direction approaching the fixing roller 41A by the separation claw moving mechanism 70, and the tip of the separation claw 56 and the outer peripheral surface of the fixing roller 41A are moved. Is reduced to 1.0 mm.

In the "separation condition 2", the paper discharge guide plates 68A and 68B are moved by the paper discharge guide plate moving mechanism 71 in a direction approaching the fixing rollers 41A and 41B.
The distance d2 between the tip of the paper ejection guide plate 68A and the outer peripheral surface of the fixing roller 41A is reduced to 3.5 mm. The closer the paper ejection guide plates 68A and 68B are to the fixing rollers 41A and 41B, the more reliably the recording medium 35 is discharged.
Guided by 68B. Therefore, the paper ejection guide plate 68
The recording medium 35 is reliably separated from the surfaces of the fixing rollers 41A and 41B by bringing the A and 68B closer to the fixing rollers 41A and 41B.

Further, under the “separation condition 2”, 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. 12B, 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,
In addition, as the inclination angle θ changes, the distance from the tip of the separation claw 56 to the outer peripheral surface of the fixing roller 41A becomes 1.0.
mm. The tip of the separation claw 56 is fixed to the fixing roller 41.
The closer to A, the more reliably the leading end of the recording medium 35 is guided by the separation claw 56. Therefore, the surface charging potential V _S
Is higher, the leading end of the separation claw 56 is brought closer to the fixing roller 41A, whereby the recording medium 35 is reliably separated from the surface of the fixing roller 41A. Other operations of the fixing device 40 of the second embodiment are the same as those of the above-described first embodiment, and a description thereof will be omitted.

As shown in FIG. 14, in the second embodiment, the separation claw moving mechanism 7 is provided for each of the plurality of separation claw 56.
0-1 to 70-5 may be provided, and the individual separation claws 56 may be moved independently. In this case, a sensor for detecting a dimension (width) of the recording medium 35 in a direction perpendicular to the conveying direction of the recording medium 35 is provided in the paper feed path 37 (see FIG. 1), and a plurality of sensors are provided in accordance with the width of the recording medium 35 detected by the sensor. A part or all of the separation claw 56 may be moved.

For example, if 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 any, is operated all the separation claw moving mechanism 70-1～70-5 according to the surface charge potential V _S, if the dimension of the short side of A4-size, some according to the surface charge potential V _S Only the separation claw moving mechanisms 70-2 to 70-4 are operated. 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 There dimension of the long side of the A4 size, all separation claw moving mechanism according to the surface charge potential V _S 70-1~7
Activate 0-5 and if it is the dimension of the short side of A4 size,
Some of the separation claw moving mechanisms 70- depend on the surface charging potential VS.
Activate only 1-70-3.

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 according to the width of the recording medium 35 as shown in FIG. 14, the recording medium 35 is prevented from being stained and image noise is generated, and the recording medium is charged by the fixing roller 41A. 35 can be reliably prevented from being wound.

As shown in FIG. 15, the separating claw moving mechanism 70 may move the separating claw 56 vertically in the drawing.

As shown in FIG. 16, the separation claw moving mechanism 70 may move the separation claw 56 in the tangential direction of the fixing roller 41A.

Further, as shown in FIG. 17, the separation claw moving mechanism 70 may move the separation claw 56 in the circumferential direction of the fixing roller 41A. This separation claw moving mechanism 7
0 is the rotation shaft 62 of the upper fixing roller 41A in the figure.
Equipped with a gear 70g rotatably attached to
The separation claw 56 is attached to the gear 70g. The rotation of the separation claw drive motor 70f is transmitted to the gear 70g via the gears 70h and 70i.

[0072] FIG 15 any separation claw moving mechanism 70 in FIG. 17 also, the fixing roller 41A surface charge potential V _S is separated as indicated by the arrow B1 reaches a predetermined value or more nails 56
Is moved in a direction approaching the fixing roller 41A, and when the surface charging potential VS falls below a predetermined value, the separation claw 56 is moved in a direction away from the fixing roller 41A as indicated by an arrow B2.

In the second embodiment, one fixing roller 41
Although only separation claw 56 corresponding to A is moved in accordance with the surface charge potential V _S, may be moved only separation claw 56 corresponding to the other of the fixing roller 41B, both of the fixing roller 41A, 41B May be moved according to the surface charging potential V _S.

(Third Embodiment) FIG. 18 shows a third embodiment of the present invention.
1 illustrates a fixing device 40 according to an embodiment. This fixing device 4
No. 0 includes a separation claw positioning mechanism 80 that switches between a state in which the separation claw 56 is brought into contact with the fixing member 41A and a state in which the separation claw is not brought into contact with the fixing member 41A.

The separation claw positioning mechanism 80 includes a frame 80a to which a plurality of separation claws 56 are attached. The frame 80a has a pin 80 near the center in the longitudinal direction.
b is fixed to a lower end of a lever 80c rotatably supported by b. An eccentric cam 80e, which is rotationally driven by a separation claw positioning motor 80d, is provided on the upper end of the lever 80c.
Is in contact. Also, the lever 80c is connected to the eccentric cam 80e.
The spring support 80f and the lever 80c.
And a spring 80g is compressed between them.

In the third embodiment, in the case of the “separation condition 1” of step S13-3 in FIG. 13, ie, when the absolute value of the surface charging potential V _S detected by the surface potential sensor 49 is 1.5 kV or less, If so, the rotational position of the eccentric cam 80e is set to the position shown in FIG. In this case, the separation claw 5
6 is opposed to the outer peripheral surface of the fixing roller 41A at an interval. On the other hand, step S13-5 in FIG.
In the case of “separation condition 2”, the absolute value of the surface charging potential VS detected by the surface potential sensor 49 is 1.5 kV
In the case where the rotation angle exceeds the range, the eccentric cam 80e driven by the separation claw positioning motor 80d rotates 180 degrees from the angular position shown in FIG. As a result, the lever 80c is
The tip of the separation claw 56 comes into contact with the outer peripheral surface of the fixing roller 41A by rotating in the direction of arrow D by the urging force of g.

If the tip of the separation claw 56 is in contact with the fixing roller 41A, the tip of the recording medium 35 is surely
And is separated from the fixing roller 41A. Accordingly, when the surface charging potential is high as in the third embodiment, if the tip of the separation claw 56 is brought into contact with the fixing roller 41A, the recording medium 35 is reliably separated from the surface of the fixing roller. Further, when the surface charge potential V _S in the third embodiment is low, to a non-contact separation claw 56 with respect to the fixing roller 41A, the release agent is accumulated that between the separation claw 56 fixing roller 41A , And the occurrence of image noise due to the separation claw 56 coming into contact with the fixing roller 41A or the image portion of the recording medium 35 can be suppressed.

Since the other configuration and operation of the third embodiment are the same as those of the second embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

(Fourth Embodiment) A fixing device 40 according to a fourth embodiment of the present invention shown in FIG. 19 extends parallel to the shaft 70d of the separation claw moving mechanism 70, and is supported rotatably and immovably in the axial direction. Shaft 70j. The shaft 70j is inserted through the cylindrical member 70k, and a female screw formed on the inner peripheral surface of the cylindrical member 70k and the shaft 70k.
A male screw formed on the outer peripheral surface of j is engaged. Also,
A gear 70m fixed to one end of the shaft 70j is a gear 70g fixed to the rotation shaft of the separation claw driving motor 70f.
Is engaged. Rods 70n extending downward from the cylindrical member 70k in FIG.
B is attached. When the separation claw driving motor 70f operates and the separation claw 56 approaches or separates from the fixing roller 41A, the paper discharge rollers 58A and 58B are synchronized with the movement.
Approaches or separates from the fixing roller 41A. Therefore, regardless of the position of the separation claw 56, the distance between the separation claw 56 and the paper discharge rollers 58A, 58B is kept constant, and the recording medium 3
5 is reliably discharged from the fixing device 40.

The other configuration and operation of the fourth embodiment are the same as those of the second embodiment. Therefore, the same elements are denoted by the same reference numerals and description thereof will be omitted.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, as shown in FIG. 20A, an ammeter 86 for detecting a current flowing between the metal core 42 of the fixing roller 41A and the ground 85 is provided, and a controller is provided based on the current value detected by the ammeter 86. 64 is
The surface charging potential V _S of the fixing rollers 41A and 41B may be estimated. As shown in FIG. 20B, an ammeter 87 is provided for detecting a leak current flowing between the separation claw 56 corresponding to one of the fixing rollers 41A and the ground 85, and the current detected by the ammeter 87 is provided. The controller 64 may estimate the surface charging potential V _S based on the value.

Further, as shown in FIG. 21, the fixing device 40 of the second embodiment uses one of the fixing members
0A, 100B and a belt-type fixing member 1 composed of a belt 101 stretched between the rolls 100A, 100B.
02, or both fixing members may be belt-type fixing members 102, as shown in FIG. Similarly,
In the fixing device 40 of the first, third, and fourth embodiments, one or both fixing members may be the belt-type fixing member 102.

Further, the adjustment of the fixing condition according to the surface charging potential V _S of the first embodiment and the adjustment of the separation condition according to the surface charging potential V _S of the second to fourth embodiments are performed by one fixing device. May go

[0084]

As is apparent from the above description, in the fixing device of the first invention, the pressing force between the fixing members and the contact between the fixing members are determined in accordance with the surface charging potential detected by the surface potential detecting device. Since the fixing condition adjusting device adjusts the fixing condition, which is the supply interval of the recording medium to the fixing portion and the supply amount of the release agent to the surface of the fixing member, the static electricity acting between the surface charging potential of the fixing member and the recording medium. It is possible to reliably prevent the recording medium from being wound around the fixing member due to the electric attraction force, and to obtain good paper passing properties.

Similarly, in the fixing device of the second invention, the position of the separation member such as the separation claw with respect to the fixing member and the position of the sheet discharge guide with respect to the fixing member are determined in accordance with the surface charging potential detected by the surface potential detecting device. The separation condition, which is the inclination of the pair of fixing members with respect to the position and the conveying direction of the recording medium, is adjusted by the separation condition adjusting means, so that the electrostatic attraction force acting between the surface charging potential of the fixing member and the recording medium is reduced. As a result, it is possible to reliably prevent the recording medium from being wound around the fixing member, and to obtain good paper passing properties.

[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 of the present invention.

FIG. 3 is a block diagram showing a controller.

FIG. 4 is a schematic view showing a pressing force adjusting mechanism.

FIG. 5 is a schematic view showing a pressing force adjusting mechanism.

FIG. 6 is a flowchart illustrating an operation of the fixing device according to the first exemplary embodiment.

FIG. 7 is a schematic diagram showing another example of a supply agent application amount adjusting mechanism.

FIG. 8 is a schematic diagram illustrating a fixing device according to a second embodiment of the present invention.

FIG. 9 is a block diagram showing a controller.

FIG. 10 is a schematic view showing a paper ejection guide plate moving mechanism.

FIG. 11 is a schematic view showing a fixing roller attitude adjusting mechanism.

FIGS. 12A and 12B are schematic diagrams showing the inclination of the fixing roller with respect to the recording medium conveyance direction.

FIG. 13 is a flowchart illustrating an operation of the fixing device according to the second embodiment.

FIG. 14 is a plan view showing another example of the separation claw moving mechanism.

FIG. 15 is a schematic view showing another example of the separation claw moving mechanism.

FIG. 16 is a schematic view showing another example of the separation claw moving mechanism.

FIG. 17 is a schematic view showing another example of the separation claw moving mechanism.

FIG. 18 is a schematic diagram illustrating a fixing device according to a third embodiment of the present invention.

FIG. 19 is a schematic view showing a fixing device according to a fourth embodiment of the present invention.

FIGS. 20A and 20B are schematic diagrams showing another example of the surface potential detecting device.

FIG. 21 is a schematic view showing a modification of the present invention.

FIG. 22 is a schematic view showing a modification of the present invention.

FIG. 23 is a schematic view showing an example of a conventional fixing device.

FIG. 24 is a plan view of FIG.

[Explanation of symbols]

 Reference Signs List 35 recording medium 37 paper feed path 40 fixing device 41A, 41B fixing roller 42 metal core 43 elastic member 44 halogen lamp 47 fixing roller drive motor 48 nip portion 49 surface potential sensor 50 release agent applying device 51 cleaning roller 52A, 52B thermistor 53 Release agent supply amount adjusting mechanism 54 Leveling blade 56, 57 Separating claw 58A, 58B Discharge roller 59 Discharge roller drive motor 61 Pressure contact force adjusting mechanism 62 Rotating shaft 64 Controller 65 Paper passing sequence controller 66 Developer image 68A, 68B Discharge guide plate 70 Separating claw moving mechanism 71 Discharge guide plate moving mechanism 72 Fixing roller attitude adjusting mechanism 80 Separating claw positioning mechanism 86, 87 Ammeter 100A, 100B Roll 101 Belt 102 Belt-type fixing member

 ────────────────────────────────────────────────── ─── Continuing on 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 AA25 BA16 BA21 BA42 BA43 BA46 BB01 BB03 BB06 BB28 BB34 CA01 CA02 CA23 CA27 CA30

Claims (10)

[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 the contact portion between the fixing members, and is fixed to the recording medium, wherein at least one of the pair of fixing members is fixed. A fixing device comprising: a surface potential detecting device that detects a surface charging potential; and a fixing condition adjusting device that adjusts fixing conditions according to the surface charging potential detected by the surface potential detecting device. 2. The fixing condition adjusting device according to claim 1, wherein the higher the surface charging potential detected by the surface potential detecting device, the lower the pressing force acting between the pair of fixing members. Fixing device. 3. The fixing condition adjusting device according to claim 1, wherein the higher the surface charging potential detected by the surface potential detecting device, the longer the time interval for supplying the recording medium to the contact portion between the pair of fixing members. The fixing device according to claim 1. 4. The fixing condition adjusting device stops the supply of the recording medium to the contact portion between the pair of fixing members for a predetermined time when the surface charging potential detected by the surface potential detecting device exceeds a predetermined value. The fixing device according to claim 1, wherein 5. The fixing condition adjusting device according to claim 1, wherein the higher the surface charging potential detected by the surface potential detecting device, the greater the amount of release agent supplied to the surface of the fixing member. The fixing device as described in the above. 6. 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, wherein at least one of the pair of fixing members is fixed. A fixing device comprising: a surface potential detecting device that detects a surface charging potential; and a separation condition adjusting device that adjusts a separation condition according to the surface charging potential detected by the surface potential detecting device. 7. The fixing device according to claim 6, wherein the separation condition adjusting device moves the leading end of the separation member closer to the fixing member as the surface charge potential detected by the surface potential detection device increases. 8. The separation condition adjusting device sets the separation member in non-contact with the fixing member when the surface charge potential detected by the surface potential detection device is equal to or less than a predetermined value, and separates the separation member when the surface charge potential exceeds the predetermined value. 7. The fixing device according to claim 6, wherein a tip of the member is brought into contact with the fixing member. 9. The separation condition adjusting device according to claim 6, wherein the higher the surface charging potential detected by the surface potential detecting device is, the closer the discharge guide plate is to the fixing member.
3. The fixing device according to claim 1. 10. The separation condition adjusting device, the higher the surface charge potential detected by the surface potential detection device,
7. The fixing device according to claim 6, wherein the inclination of the pair of fixing members with respect to the conveyance direction of the recording medium is adjusted such that the leading end of the separation member approaches the fixing member.