JP2003295672A - Fixing device and image forming apparatus having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of detecting an alteration in pressing force between a pair of rotary bodies and to provide an image forming apparatus having the fixing device. <P>SOLUTION: The fixing device having a pressing-force altering means which alters a pressing force between the rotary bodies is provided with: a power supply means that abuts on the conductive layers of the rotary bodies, and a conductive member so constituted as to be brought into contact with the conductive layers and separated therefrom. The conductive member abuts on the conductive layers linked with the pressing-force altering means, and detects the voltage of the conductive member to detect an alteration in pressing force. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, as a fixing device used in an image forming apparatus, a roller member having an elastic layer is press-contacted to a heat fixing means such as a roller or a film having a heat source inside and a heat fixing means is formed between the heat fixing means and the heat fixing means. 2. Description of the Related Art There is a widespread apparatus in which a recording material carrying an unfixed image is carried and conveyed in a nip portion to be formed and heated and pressed to obtain a fixed image.

In such a thermal fixing device, the outer diameter of the roller member is set so that the paper can be stably conveyed and at the same time, a predetermined nip width is obtained in order to secure the fixing property of the image.
Hardness and pressure are determined.

In recent years, as the number of types of recording paper used in the image forming apparatus has increased, there is a device in which the pressing force can be selected according to the type of recording paper.

For example, when paper wrinkles are likely to occur when the pressure is large such as an envelope or thin paper (70 g / m ^ 2 or less), the user can operate the lever or the like to reduce the pressure. There is a fixing device.

On the contrary, in the case of a paper having a large unevenness on the surface of the paper, there is a device capable of setting a large pressing force in order to improve the adhesion to the paper.

Conventionally, there has been no means for detecting such a change in the pressing force.

[0008]

However, in the above-mentioned conventional example, after the user changes the applied pressure and uses it,
It was necessary to return the applied pressure to the original strength, but there were cases where the user forgot to return it and continued to use it. As a result, the following problems may occur.

When the pressure is set stronger than usual and the pressure roller is used for a long period of time, the hardness of the pressure roller is rapidly decreased, and the life of the pressure roller is shortened. In particular, with a roller having a sponge elastic layer, foam breakage progresses and the elastic force is lost. Further, an increase in the nip width with the heat fixing unit causes frequent conveyance defects such as paper wrinkles and paper trailing edge jumps on long paper.

When the pressing force is set to be weaker than usual and the sheet is used for a long period of time, the fixing property of plain paper or thick paper is not sufficient, and an image defect due to so-called cold offset occurs. Therefore, the cold offset toner adheres to the pressure roller and the transport roller downstream of the fixing nip and appears as toner on the discharged paper. It also causes a jam. Particularly, in a device in which a separating roller is arranged using a soft roller having a rubber elastic layer below the release layer as the fixing roller, a large amount of toner adheres to the separating claw, and an accordion jam easily occurs. Could cause fatal damage to.

The problem caused by forgetting to reset the pressing force as described above becomes a particular problem in a network-compatible device in which one image forming device is shared by a plurality of personal computers as in recent years.

As a means for preventing the user from forgetting to return the pressing force, there is a device that automatically changes the pressing force by using a large electromagnetic solenoid or motor, but the device is inevitably large and costly. .

An object of the present invention is to provide a fixing device having a relatively inexpensive structure and capable of detecting a change in pressure between a pair of rotating bodies, and an image forming apparatus equipped with this fixing device. Is.

[0014]

In order to achieve the above object, a recording paper on which an unfixed toner image is placed is carried between a pair of rotating bodies and heated and pressed to form an unfixed toner image. In a fixing device for fixing on a recording paper, at least one rotating body has a conductive layer, and a feeding member contacting the conductive layer, a conductive member capable of contacting and separating from the conductive layer, and a rotating member between the rotating body. With a pressing force changing means capable of adjusting the pressure,
The conductive member is characterized in that the contact state with the conductive layer changes in conjunction with the pressing force changing means.

A fixing device for carrying and conveying a recording paper carrying an unfixed toner image between a pair of rotating bodies and fixing the unfixed toner image on the recording paper by heating and pressurizing the recording paper. One of the rotating bodies has a conductive layer, and is provided with a power feeding member that can be brought into contact with and separated from the conductive layer, a conductive member that comes into contact with the conductive layer, and a pressing force changing unit capable of adjusting the pressing force between the rotating bodies. , The power feeding means is interlocked with the pressing force changing means,
It is characterized in that the contact / separation state with respect to the conductive layer changes.

An image forming apparatus equipped with the above fixing device is
It is characterized in that it is provided with a voltage detecting means for detecting the voltage of the conductive member, and the output of the voltage detecting means can detect that the pressure applied between the rotating bodies is changed.

As a result, it is possible to prevent a problem that occurs when the device is used without changing the pressing force and is used while the pressing force is changed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing a schematic structure of a laser beam printer (process speed 150 mm / s) using negative toner and capable of reversal development, which can pass up to A4 horizontal size.

In the figure, reference numeral 1 is a scanner unit having an optical means for irradiating and scanning a laser beam emitted according to image information and a scanning means. Further, 10 is a process cartridge containing a main image forming means,
The photosensitive drum 3 as an image holding member, a roller charger 4 made of semi-conductive rubber, a developing device 5 for developing the toner 6 on the photosensitive drum 3, a cleaner 8 for removing waste toner from the photosensitive drum 3, and the like. Has been done.

The photosensitive drum 3 in the process cartridge 10 rotates in the direction of the arrow, and the roller charger 4
Thus, the surface is uniformly charged, and then the laser light emitted from the scanner unit 1 is irradiated through the mirror 2 to form an electrostatic latent image on the surface. ing. Then, the electrostatic latent image is visualized as a toner image by the toner supplied by the developing device 5.

On the other hand, the paper 14 in the paper feed cassette 12 is separated and fed one by one by the paper feed roller 13 and a separation pad (not shown) provided facing the paper feed roller 13. The fed paper 14 is conveyed to the pair of registration rollers 15 along the upper and lower guides 13a. The registration roller 15 is stopped until the paper 14 arrives, and the leading end of the paper 14 abuts against the registration roller 15 to correct the skew of the paper 14. Next, the registration roller 15 conveys the paper 14 to the transfer portion in synchronization with the leading edge of the image formed on the photosensitive drum 103. A paper feed sensor (not shown) is installed near the registration roller 15 to detect the paper passing state, jam, and paper length.

The paper 1 conveyed to the transfer section as described above
Reference numeral 4 denotes a paper 14 which is charged with electric charges having a polarity opposite to that of the toner from the transfer roller 7.
The toner image formed on the photosensitive drum 3 is transferred to the paper 14 from the back side of the paper. The paper 14 having the toner image transferred thereon is conveyed by the conveying roller 16a and the conveying guide 1.
6b is conveyed to the fixing device 17, and the fixing device 17
Is a recorded image by melting and fixing the toner image on the paper 14 with heat and pressure. Then, the paper 14 after the image fixing is ejected to the ejection tray 18 through the respective conveyance rollers selected by the flapper (not shown).

Further, the laser printer has a printer control unit (not shown) for controlling the printer, which is connected to an external device such as a personal computer through an interface (not shown).

Next, the fixing device of this embodiment will be described with reference to the drawings.

The fixing device of the present embodiment is provided with a pressing force changing lever which is a pressing force changing means, and the pressing force can be adjusted by appropriately operating the pressing force changing lever according to the recording paper used by the user. There is.

FIG. 1A is a view showing a pressure state of the fixing device of the present embodiment when printing out plain paper, and the total pressure 196 is set by the spring 66 and the pressure stay 65.
By applying a pressure of N to the pressure roller 52, a nip having a width of 6 mm is formed between the pressure roller 52 and the fixing roller 51, and good fixing property and stable paper conveyance can be performed. The configuration will be described below.

In FIG. 1, 51 is a φ40 fixing roller, which has a thickness of 50 μ on an aluminum core metal 11 of 1 mm.
m fluororesin layer is provided via a primer. A halogen heater 53 as a heat source is provided inside the fixing roller.
(700 W), the fixing roller 51 is heated from the inside.

On the other hand, 52 is pressed against the fixing roller 51 by a spring spring 66 which is a pressing means and forms a fixing nip N1 (6 mm) with the fixing roller 51 φ3.
0 pressure roller. The pressure roller 52 has a heat-resistant silicone rubber elastic layer formed on an aluminum cored bar, and a fluororesin layer which is a conductive release layer formed on the elastic layer.
It is an elastic roller having a sker-C hardness of 54 degrees.

Reference numeral 54 denotes a thermistor for detecting the surface temperature of the fixing roller 51. The thermistor 54 is in contact with the surface of the fixing roller with a predetermined contact pressure, and a heater is provided to keep the temperature of the fixing roller surface constant during printing. Is turned on / off (the electric circuit that turns on / off the current is not shown).
In the fixing device having the cleaning mechanism, the thermistor 5
4 can be provided in the recording material sheet passing area, but in the fixing device having no cleaning mechanism as in the present embodiment, it is provided in the edge non-sheet passing area in order to avoid image contamination.

The fixing roller 51 is driven by a driving means (not shown) installed in the main body, and the recording paper 14 carrying the unfixed toner 6 is heated and pressed at the fixing nip N1 to form a fixed image. A fixing cover 67 heat-insulates the fixing device.

In the present embodiment, in order to prevent offset and scattering in the fixing device 17, a potential difference is provided in a direction in which the toner is pressed against the paper at the fixing nip N1. Specifically, the core metal of the fixing roller is grounded, the conductive brush 57 as a power feeding member is brought into contact with the conductive release layer on the surface of the pressure roller, and the bias (+600 V) of the same polarity as that of the toner 6 is applied. In order to stably supply a bias (+600 V) to the surface of the pressure roller, the resistance value of the conductive release layer is set to 1 × 10.
It is preferably set to 6Ω or less. This bias is applied in synchronization with the driving of the fixing roller 51.

Further, the pressure roller 52 is provided with a bearing 55 at the end of the core metal, and the bearing 55 is made of a PPS resin bearing 56 which also has heat insulating properties.
9 supported. The pressure stay 59 is a spring spring 6 which is a pressure means arranged in the paper discharge direction of the pressure roller 52 around a fulcrum 58 fixed to the fixing frame 65.
By the action of the force point of 6, the fixing roller 51 is pressed in the substantially central direction.

On the other hand, FIG. 1 (b) is a view showing a pressurizing state when the envelope is printed out. By raising the pressurizing force changing lever 63, the pressurizing stay 59 is pressed downward and the pressurizing stay 59 is pressed. The force applied to the pressure roller 52 is restricted to 98N. As a result, the nip width N2 formed between the fixing roller 51 and the fixing roller 51 is 4.5 mm, and wrinkles and image deviation do not occur even when the envelope is passed.
The pressure applied when the envelope is printed out is preferably a pressure compatible with both fixability and wrinkles and image shifts.
In this embodiment, good results were obtained when the force applied to the pressure roller was 98N.

When the pressing force changing lever 63 is lifted, the thickness t = conductive member is connected through the connecting bar 62.
One end of the 0.2 mm SUS plate 60 is configured to be in contact with the conductive release layer on the surface of the pressure roller about the fulcrum 61. S
The US plate 60 is brought into contact with the surface of the pressure roller with a force of about 0.98 N in the non-sheet passing area of the end portion, and damage to the surface of the pressure roller is reduced. A conducting wire is connected to the other end of the SUS plate 60, and is guided to the main body electrical equipment board through a connector (not shown) to detect a voltage.

As described above, since the SUS plate 60 can be brought into contact with and separated from the surface of the pressure roller in conjunction with the pressing force changing lever 63, the voltage applied to the SUS plate 60 can be detected by detecting the voltage. It is possible to detect which position the pressure changing lever 63 is in.

The timing of detecting the voltage of the SUS plate 60 may be when the fixing roller 51 is driven and a bias is applied to the pressure roller 52, or the fixing roller 5 is used.
A bias may be applied to read the voltage when 1 is stopped.

Also, when the user specifies the paper size,
The user may be warned if the pressing force detection results of the present embodiment are different. For example, if the detection result of the pressing force change lever corresponds to an envelope,
When the paper size specified by the user is plain paper,
Information of "size mismatch" can be sent to the personal computer through an interface (not shown) to notify the change of the paper size or the change of the pressing force changing lever.

In this embodiment, the SUS plate 60 is made to interlock with the pressing force changing lever 63 which is the pressing force changing means, but the SUS plate 60 may be made to interlock with the movement of the pressure stay 59.

(Embodiment 2) This embodiment shows an example applied to a fixing device capable of strongly setting a pressing force.

FIG. 2 is a sectional view showing the fixing device of the present embodiment. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 2A is a view showing a cross section of the fixing device when printing plain paper. In this example, a screw member 73 that can adjust the gap with the fixing frame is used as the pressing force changing unit.

As shown in FIG. 2, the screw member 73 penetrates the pressure spring 66 and the pressure stay 58, and is inserted into the fixing frame 74 having a screw groove. The pressure spring spring 66 presses the pressure stay 58 against the fixing roller 51 by pressing the pressure stay 58 with the screw member as a supporting surface. The position of the screw member 73 is adjusted to a predetermined position by a tool such as a screwdriver at the time of shipment. The predetermined position is a nip width N1 that provides sufficient fixability when printing plain paper, and in this example, N1 = 6 mm.

On the other hand, FIG. 2B is a view showing a cross section of the fixing device in the case of printing thick paper or recording paper having large irregularities on the surface.
It is possible to change the pressing force by rotating the to shorten the distance from the fixing frame 74 and obtain a desired nip width N3.

In the vicinity of the pressure roller, there is provided an SUS plate 71 which can be brought into contact with the surface of the pressure roller about a fulcrum 71a. The SUS plate 71 has a distance between the fixing frame and the screw member 73 within a predetermined range. In the following cases, the surface of the pressure roller is brought into contact with the surface of the pressure roller, and it can be detected that the pressure is set strongly. 72
Is a spring that biases the SUS plate 71 in the direction of separating it from the surface of the pressure roller. In this example, when the nip width N3 is 8 mm or more, the SUS plate 71 contacts the surface of the pressure roller.

Conventionally, in a device for changing a pressing force using a screw member, once the screw member is rotated, it becomes unclear what value the pressing force is set to, and the pressing force is left to be set strongly. I was afraid. In this embodiment,
Since it is possible to detect when the pressing force reaches a predetermined value or more, it is possible to prevent deterioration of the paper conveyance such as shortening of the life of the pressure roller and wrinkles and curls due to forgetting to return. Further, it can be used as a guide when the applied pressure is strengthened or returned to the normal applied pressure.

(Third Embodiment) In the conventional fixing device, the main body power switch is turned on with the recording paper wound around the roller.
When turned off, it was impossible to judge whether the recording paper was wrapped around the roller. Therefore, the power switch is O
When the fixing device is driven N and the fixing device is driven, the recording paper is further wound around the roller, which makes it difficult for the user to perform the jam processing.

Therefore, a fixing device provided with a winding detection mechanism for bringing a conductive member into contact with the paper passing area of a roller having a conductive layer on the surface and detecting the potential of the conductive member to determine whether the paper is wound around the roller is provided. is there.

The separating means of such a device is preferably installed in a non-contact manner in order to protect the conductive layer on the surface.

However, in a device that separates recording paper while keeping a constant gap from the surface of the pressure roller, if the pressure is changed by the pressure changing means, the distance between the roller surface and the tip of the separating means increases, so that the error is erroneous. However, there is a problem in that, when plain paper is passed through, jamming and winding around rollers easily occur.

The present embodiment is characterized in that the pressurization force change detection and the recording paper winding around the roller can be detected by the same member, and the occurrence of jams and winding around the roller due to plain paper is reduced. .

FIG. 3 is a sectional view of the fixing device of the present embodiment. In FIG. 3, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 3A, reference numeral 68 is a pressure separation guide supported by the fixing frame 65, and is brought into contact with the surface of the pressure roller by a roller (not shown) with a gap of G1 = 0.3 mm. There is. The SUS sheet metal 60 is supported by a heat-resistant resin support member 70, and is arranged on the downstream side of the pressure separation guide 68 in the recording paper passage area. The support member 70 is provided with rotatable fulcrums at both ends in the roller longitudinal direction, and is supported by the pressure stay 59. The other end 70a of the supporting member 70 to which the SUS sheet metal 60 is attached
A ferrite shaft 70b that can be turned on and off by an electromagnetic solenoid (not shown) is coupled to the SUS sheet metal 6
0 is configured so as to be able to come into contact with or separate from the surface of the pressure roller about the fulcrum of the support member 70.

Normally, when the main body power switch is turned on,
At the same time when the power feeding bias is applied, the electromagnetic solenoid operates, and the SUS sheet metal 60 makes contact with the surface of the pressure roller. Then, it is possible to detect the potential of the SUS sheet metal 60 and determine whether the recording paper is wound around the roller.

Here, the method of detecting the wrapping of the paper around the pressure roller is performed by the following wrapping detection circuit (not shown). That is, the winding detection circuit is composed of a control unit including a high-voltage circuit unit and a CPU, and divides the high-voltage bias applied to the pressure roller into one terminal of the comparator in the high-voltage circuit unit and inputs the divided voltage as a reference voltage. The voltage detected by the SUS plate, which is a conductive member, is divided into one terminal and input as a detection voltage. The detection voltage is compared with the reference voltage, and a High / 1ow signal is sent to the CPU to determine whether the paper wound around the roller is present or absent. Specifically, when the detected voltage becomes 85% or less of the reference voltage, a High signal is sent to the CPU to judge that the paper is wrapped around.

On the other hand, when the envelope is printed out, the pressing force changing lever 63 is lifted by the user as shown in FIG. 3 (b). As a result, the pressure separation guide 68 supported by the fixing frame 65 and the pressure roller 5 are
Since the gap between the two surfaces expands to G2 = 0.5mm,
In the conventional apparatus having no means for detecting the change in the pressing force, when the plain paper is mistakenly passed, the winding around the roller occurs.

In this embodiment, the projection 69 made of PET resin attached to the pressure stay presses one end 70a of the support member 70 downward, so that the SUS sheet metal 60 is added regardless of the operation of the electromagnetic solenoid. It is configured to contact the surface of the pressure roller with a force of about 0.98N. As a result, it is possible to detect the position of the pressing force changing lever 63.

That is, the conditions for the pressure change detection and the winding detection are determined as follows.

When the power switch is turned on, power is supplied to the pressure roller by the high voltage power source.

If the potential of the SUS sheet metal 60 is 85% or more, it is judged that the pressure is weakened, and the user is notified that the pressure has been changed.

If the electric potential of the SUS sheet metal 60 does not reach 85%, it is judged that the applied pressure is in a normal state and the electromagnetic solenoid is driven.

With the electromagnetic solenoid driven, S
If the potential of the US sheet metal 60 is 85% or more, it is determined that the recording paper is not wound around the roller, and the normal printing operation is performed.

With the electromagnetic solenoid driven, S
If the potential of the US sheet metal 60 does not reach 85%, it is determined that the recording paper is wrapped around the roller and a warning is issued.

As described above, when the conductive member that can be brought into contact with and separated from the roller surface in the sheet passing area is made to interlock with the pressurizing force changing means, when the pressurizing force is changed, the user may mistakenly perform normal operation. It is possible to prevent the paper from passing through. Therefore, it is possible to prevent the occurrence of cold offset due to plain paper and at the same time reduce the winding around the roller.

(Embodiment 4) A fourth embodiment of the present invention will be described with reference to FIG. The same members as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, in the fixing device provided with the winding detection means, the bias is applied by the power feeding means in which the pressure varying lever which is the pressure varying means and the power feeding brush which is the power feeding member are integrated. It is characterized by having done.

FIG. 4 is a perspective view of the fixing device of the present embodiment, and shows a normal pressure state for printing plain paper.

In the non-sheet passing area of both ends of the pressure roller having a conductive layer on its surface, the power feeding brush integrated with the pressing force changing lever comes into contact with the roller surface, and +500 V from the high voltage power source connected to the power feeding brush. Bias is applied.

On the other hand, in the central sheet passing area of the pressure roller, a SUS plate, which is a conductive member, is arranged on the downstream side of the rotation of the pressure separation guide, and is brought into contact with the surface of the pressure roller by an electromagnetic solenoid (not shown).・ Separation is performed. Then, as described in the third embodiment, the potential of the SUS plate is detected, and it is possible to determine whether the recording paper is wrapped around the roller by comparing it with the power supply bias.

In the present embodiment, when the pressing force changing lever which is the pressing force changing means is lifted, the feeding brush is separated from the roller surface, so that the feeding bias is not induced in the SUS plate and the pressing force is changed. Can be detected. Further, in the device in which the pressurizing force changing levers are arranged at both ends as shown in FIG. 4, if only one pressurizing force changing lever is forgotten to be returned, the detection voltage of the SUS plate changes and the pressurizing force is changed independently. Can be detected. Further, when the fixing device is rotationally driven, it is not necessary to bring the SUS plate into contact with the conductive layer on the roller surface, so that the roller is not damaged.

(Fifth Embodiment) A fifth embodiment of the present invention will be described.

The present embodiment is an example in which the pressure roller is applied to a roller whose surface is covered with an insulating fluororesin.

FIG. 5 (a) shows a pressing force state of 196N of this embodiment, and FIG. 5 (b) shows a state in which the pressing force is changed to 98N by the pressing force changing means. 5, the same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In FIGS. 5 (a) and 5 (b), 52 'is an iron cored bar on which a 3 mm thick silicone rubber elastic layer is formed, and the surface of which is coated with PFA resin as an insulating fluororesin. The pressure roller is a release layer.

A carbon chip (not shown) is provided on the core metal of the pressure roller 52 'as a contact, and a +50 from a high voltage power source is provided.
+2 is applied between fixing roller 51 and 0V bias.
The potential difference of 00V can be maintained.

In this embodiment, as shown in FIG. 5B, when the pressing force changing lever 63 is lifted up, the connecting bar 71 causes the SUS sheet metal 60, which is a conductive member, to be the center of the fulcrum 61 and the pressing roller 52 '. It is configured to be able to contact the core metal.

At this time, the change in the voltage detected by the SUS sheet metal 60 is read to determine that the pressing force is changed.

The present embodiment has an advantage that the applicable roller can have a higher degree of freedom than the first and second embodiments.

For example, as the surface insulating PFA resin,
It may be coated with a fluororesin such as PFA, FEP, or PTFE, or may be formed by molding the fluororesin into a tube shape and adhering it to the rubber elastic layer via a primer. Also, if a silicone rubber elastic layer is mixed with a conductive agent to make it conductive and the surface is coated with a fluororesin of medium resistance, the electrostatic capacity of the pressure roller increases, and the fixing roller is used even for continuous printing. Since it is possible to secure the potential contrast between the above and the other, it is possible to prevent image defects such as offset.

Although the structure in which the conductive member is brought into contact with the pressure roller has been described above, the present invention can also be applied to a structure in which the conductive layer of the heat fixing means such as the fixing roller or the fixing film is contacted to detect the change in the pressing force. .

[0081]

As described above, according to the present invention,
Since the conductive member interlocking with the pressurizing force changing means can be connected to and separated from the conductive layer of the pressure roller so that the pressurizing force change can be detected from the voltage of the conductive member, the conventional pressurizing force change detecting means is provided. It is possible to prevent a problem that occurs when the pressure force is changed with a device which does not exist. Specifically, the life of the roller can be shortened by using it while the applied pressure is kept strong, and image defects due to paper wrinkles and paper trailing edge can be prevented. Alternatively, it has become possible to prevent toner adhesion to the roller, which has occurred due to use with the applied pressure weakened. Further, in a device capable of continuously adjusting the pressing force by using a screw member, it was conventionally difficult to return the pressing force to the original strength, but by the interlocking of the conductive member with the pressing force changing means, It can be detected electrically.

Further, in the device capable of detecting the wrapping around the roller, the wrapping around the roller and the pressure change detection can be detected by the same member.

[Brief description of drawings]

FIG. 1A is a sectional view showing a fixing device in a normal pressure state according to a first embodiment. FIG. 3B is a cross-sectional view showing the fixing device according to the first embodiment in a pressed state in which the applied pressure is weakened.

FIG. 2A is a sectional view showing a fixing device in a normal pressure state according to a second embodiment. FIG. 6B is a cross-sectional view showing the fixing device according to the second embodiment in a pressurized state where the applied pressure is increased.

FIG. 3A is a sectional view showing a fixing device in a normal pressure state according to a third embodiment. FIG. 6B is a cross-sectional view showing the fixing device according to the third embodiment in a pressed state in which the applied pressure is weakened.

FIG. 4 is a perspective view of a fixing device according to a fourth exemplary embodiment.

FIG. 5A is a sectional view showing a fixing device in a normal pressure state according to a fifth embodiment. FIG. 9B is a cross-sectional view showing the fixing device according to the fifth embodiment in a pressed state in which the applied pressure is weakened.

FIG. 6 is a sectional view of the image forming apparatus main body according to the present embodiment.

[Explanation of symbols]

52 Pressure roller whose surface is coated with a conductive layer 57 Metal brush that is a power feeding means 59 Pressure stay 60 SUS plate which is a conductive member 63 Pressurization change lever which is a pressing force change means 66 spring

Claims (3)

[Claims] 1. A fixing device which carries and conveys a recording paper carrying an unfixed toner image between a pair of rotating bodies and fixes the unfixed toner image on the recording paper by heating and pressurizing the recording paper. One of the rotating bodies has a conductive layer, and includes a power feeding member that abuts on the conductive layer, a conductive member that can contact and separate from the conductive layer, and a pressing force changing unit that can adjust a pressing force between the rotating bodies. The fixing device is characterized in that the conductive member changes its contact / separation state with respect to the conductive layer in conjunction with the pressing force changing means. 2. A fixing device for fixing and carrying an unfixed toner image on a recording paper by carrying and conveying a recording paper carrying an unfixed toner image between a pair of rotating bodies, and heating and pressing the recording paper. One of the rotating bodies has a conductive layer, and is provided with a power feeding member that can be brought into contact with and separated from the conductive layer, a conductive member that is brought into contact with the conductive layer, and a pressing force changing unit capable of adjusting a pressing force between the rotating bodies. The fixing device is characterized in that the power feeding means is interlocked with the pressure changing means to change the contact / separation state with respect to the conductive layer. 3. A voltage detecting means for detecting the voltage of the conductive member according to claim 1 is provided, and it is possible to detect that the pressure applied between the rotating bodies is changed by the output of the voltage detecting means. A characteristic image forming apparatus.