JP2006119425A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize the stress on a rubber layer of a roller of a fixing device and to achieve a longer lifetime with simple sequence without entailing an excessive cost and without the influence on fixability and paper sheet deformation. <P>SOLUTION: The fixing device is equipped with an automatic pressurization and decompression alienation mechanism for pressurizing, decompressing and alienating the fixing roller, a driving means for the same, and a control means for the same. The device pressurizes the roller during image fixing, alienates the roller in the specific state of the image forming apparatus including a power source off state, and decompresses the roller in cases other than the image fixing and the specific state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pressure / pressure reduction / separation mechanism that pressurizes / depressurizes / separates a fixing roller (or film) and a pressure roller (or film), and a fixing device and an image forming apparatus including the pressure / pressure reduction / separation mechanism. .

  In an image forming apparatus such as a copying machine or a printer, in order to make an unfixed toner image formed on a recording material a permanent image, a fixing roller heated by a heating source such as a heater and held at a high temperature state, A fixing device that conveys the recording material and heats and presses the recording material by a pressure roller that rotates in pressure contact with the recording medium is used.

  A general fixing device will be described with reference to FIG.

  In FIG. 8, the recording material 801 is conveyed from the direction C in the drawing and enters a nip portion formed by the pair of pressure roller 211 and fixing roller 210. The unfixed toner image formed on the recording material 801 that has entered the recording material 801 is applied with pressure and heat from a heater built in the fixing roller 210 while passing through the nip portion, and is melted and the like. The image is fixed to 801 and becomes a permanent image. The fixed recording material 801 is guided outside the apparatus by a paper discharge roller (not shown) disposed downstream of the fixing roller 210 and the pressure roller 211.

  The fixing roller and the pressure roller described above are in pressure contact with a very large force in order to improve the fixability of the toner image on the recording material 801. Then, by rotating in a pressed state, the heat of the fixing roller is conducted to the pressure roller, and the pressure roller is also warmed. By suppressing the temperature difference between the two rollers in this way, heat is lost to the pressure roller during continuous printing, preventing the paper from warming up and causing a decrease in fixing performance. It prevents curling and the like caused by the difference.

  As described above, since both the rollers are pressed with a large force, if the roller is left in that state when the power is turned off, the rubber layer called C set is deformed and the image quality is adversely affected. Further, when a jam occurs, a very large force is required to remove the recording material under pressure, which adversely affects usability. In view of this, the conventional fixing device has coped with the inconvenience by including an automatic pressure separation mechanism that automatically separates the fixing roller and the pressure roller when the power is turned off or when a jam occurs.

  Next, the automatic pressure separation mechanism of the fixing device in the conventional example will be described with reference to FIG.

  FIG. 9A is a view showing the fixing device in a pressurized state. In the figure, 101 is a side plate that holds the pressure roller 210, 102 is a pressure spring that presses the side plate 101 and pressurizes the pressure roller 211, 103 is a cam that switches between the pressure and separation states, and 904 is a pressure and separation state. It is an HP sensor that detects the home position (HP). The HP sensor includes a flag and a detector including a light emitting unit and a light receiving unit.

  FIG. 9B is a diagram illustrating the fixing device in a separated state. In this figure, the side plate 101 is pushed up by the cam 103 to separate the fixing roller 210 and the pressure roller 211 from each other.

  In addition, since the cam 103 is joined to the shaft of the fixing roller 210 by a one-way gear, when the fixing roller 210 is driven in the transport direction, the cam 103 is not driven and is driven in the direction opposite to the transport direction. Only when the cam 103 is driven, the pressurization and separation state can be switched.

  Next, the pressurizing process will be described with reference to the flowchart of FIG.

  First, it is determined whether the HP sensor is in a pressurized state (S1001). If already pressurized, the process is terminated. If it is in the separated state, the reverse rotation of the fixing motor is started (S1002). Next, it is determined whether the value of the HP sensor is in a pressurized state (S1003). It is determined whether a predetermined time has passed (S1004). About two processes of said S1003 and S1004, a process is repeated until either one conditions are satisfy | filled.

  If the value of the HP sensor is in a pressurized state within a predetermined time, the process waits until the center of the HP sensor flag is at the detector position, and the cam 103 is brought into a completely pressurized state (S1005). If the value of the HP sensor does not reach the pressurized state within the predetermined time, it is determined that the pressurizing process has failed (S1006). Finally, the fixing motor is stopped (S1007), and the process is terminated.

  Next, the relationship between the printer state and the pressure state of the roller in the conventional example will be described with reference to FIG.

As can be seen from the figure, in the conventional printer, the fixing roller and the pressure roller are in a pressurized state during normal processing such as warm-up, pre-printing, printing, post-printing, and standby. . The fixing roller and the pressure roller are in a separated state during special processing such as power-off, jamming, door opening, and sleep.
JP 2003-295676 A

  The conventional fixing device maintains the high temperature and high pressure state except for the separation in special cases such as when the power is turned off or when the jam occurs, as described above. The roller was rotated in a pressurized state.

  For this reason, the rubber layer, intermediate layer, adhesive layer, etc. of the roller are subjected to a great deal of stress, wrinkles occur due to aging, adversely affect the image, and rarely the rubber peels off due to aging. It may occur. When such a symptom occurs, it is handled that the fixing device has reached the end of its life, and the fixing device must be replaced. As a result, there is a problem that the running cost of the main body is increased.

  Fixing device and image formation that can achieve a longer service life by minimizing stress on the rubber layer of the roller with a simple sequence without incurring extra costs and without affecting the fixability and paper deformation. The object is to provide a device.

  In order to achieve the above object, a first invention according to the present application includes a fixing roller, an automatic pressurizing / depressing / separating mechanism that pressurizes, depressurizes and separates the roller, the roller and the autopressurizing / depressurizing mechanism. The image fixing apparatus includes a driving unit that drives a separation mechanism and a control unit that controls the driving unit, pressurizing the roller during image fixing, and separating the roller in a specific state of the image forming apparatus including a power-off state. The roller is decompressed at times and in cases other than the above specific state.

  According to a second aspect of the present application, there is provided a fixing roller, roller driving means for rotating the roller, an automatic pressurizing / depressurizing / separating mechanism for pressurizing, depressurizing and separating the roller, and the automatic pressurizing. An image forming unit including a mechanism driving unit that is independent of the roller driving unit that drives the decompression and separation mechanism; and a control unit that controls the roller driving unit and the mechanism driving unit. The roller is separated in a specific state of the apparatus, and the roller is decompressed at the time of fixing the image and in a case other than the specific state.

  According to a third aspect of the present application, there are provided a fixing roller, roller driving means for rotating the roller, an automatic pressurizing / depressing / separating mechanism for pressing, depressurizing and separating the roller, and the roller driving means. Switching means for driving the automatic pressurizing / decompressing / separating mechanism by switching power transmission, and control means for controlling the roller driving means and the switching means, and pressurizing the roller during image fixing, including a power-off state The roller is separated in a specific state of the image forming apparatus, and the roller is decompressed at the time of fixing the image and in a case other than the specific state.

  According to the first invention of the present application, by using the conventional pressure release mechanism and reducing the pressure except when the toner image is fixed on the fixing device, the fixing property and the sheet deformation can be achieved without extra cost. There is no influence of this, and a longer life can be achieved with a simple sequence.

  Further, according to the second invention of the present application, by providing a fixing roller and a cam rotation motor independently, a fixing device having a longer life can be provided without affecting the performance of first printout. It becomes possible to do.

  In addition, according to the third invention of the present application, by providing a cam drive clutch, it is possible to provide a fixing device having a longer cost and a longer life without affecting performance such as first printout. Is possible.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 2 is a schematic view of a laser beam printer as an image forming apparatus according to the present invention. As shown in FIG. 2, the image forming apparatus forms an electrostatic latent image with image light formed based on the image signal in the image forming unit, transfers the visible image to the recording material 201, and records the recording material 201. The image forming unit is composed of a photosensitive unit, a charging roller 202 as a primary charging unit, a cleaning unit, a developing unit, an intermediate transfer body 203, a sheet feeding unit, a transfer unit, and a fixing unit 204. The

  The photosensitive drum 205 is configured by applying an organic photoconductor layer to the outer periphery of an aluminum cylinder. The photosensitive drum 205 rotates when a driving force of a driving motor (not shown) is transmitted. The driving motor rotates the photosensitive drum 205 in a counterclockwise direction according to an image forming operation. The exposure light to the photosensitive drum 205 is sent from the scanner 206, and an electrostatic latent image is formed by selectively exposing the surface of the photosensitive drum 205.

  As a developing means, in order to make the electrostatic latent image visible, a developing device 207 that performs development is provided, and the developing device 207 is provided with a sleeve 208.

  The intermediate transfer member 203 is configured to come into contact with the photosensitive drum 205 and rotate with the rotation of the photosensitive drum 205. The intermediate transfer member 203 rotates in a clockwise direction during image formation and transfers a visible image from the photosensitive drum 205. Receive. Further, the intermediate transfer body 203 simultaneously transfers the visible image on the intermediate transfer body 203 to the recording material 201 by bringing the recording roller 201 into contact with a later-described transfer roller 209 during image formation.

  The transfer roller 209 is provided as a transfer charger that is supported so as to be in contact with the intermediate transfer member 203.

  While transferring the visible image onto the intermediate transfer member 203, the transfer roller 209 is spaced downward so as not to disturb the visible image. After the visible image is formed on the intermediate transfer member 203, the transfer roller 209 is positioned upward by a cam member (not shown) in accordance with the timing of transferring the visible image to the recording material 201. As a result, the transfer roller 209 is pressed against the intermediate transfer member 203 with a predetermined pressing force via the recording material 201, and a bias voltage is applied, so that a visible image on the intermediate transfer member 203 is transferred.

  The fixing unit 204 fixes the transferred visible image while conveying the recording material 201. As shown in FIG. 1, the fixing unit 210 heats the recording material 201 and presses the recording material 201 against the fixing roller 210. And a thermistor that monitors the temperature of the pressure roller 211 and the fixing roller. The recording material 201 holding the visible image is conveyed by the fixing roller 210 and the pressure roller 211, and the toner image is fixed on the surface by applying heat and pressure.

  The automatic pressurizing / depressurizing / separating mechanism, which is a feature of the present invention, will be described below with reference to FIG.

  In the figure, components having the same functions as those of the conventional example are denoted by the same reference numerals and description thereof is omitted. Reference numeral 104 denotes a control device such as a CPU for controlling the motor, and reference numeral 105 denotes a motor for driving the fixing roller and the cam. The motor 105 rotates forward in the same manner as in the conventional example, and rotates the fixing roller 210 via the one-way gear 106 for normal rotation to carry the paper. Further, the motor 105 rotates in the reverse direction to rotate the cam 103 of the automatic pressurizing / depressing / separating mechanism via the one-way gear 107 for reverse rotation.

  A is a location where the amount of pressing of the side plate 101 by the cam 103 is minimized, that is, a location where both rollers are in a pressurized state. B is a location where the amount of pressing down of the side plate 101 by the cam 103 is maximized, that is, a location where both rollers are separated.

  C is a location that is an intermediate position between A and B, that is, a location where both rollers are in a reduced pressure state. In this configuration, the motor 105 is controlled by the control device 104 so that it can rotate forward and backward.

  FIG. 3 is a diagram showing the state of the cam with respect to the angle of the pressure detection sensor flag. In the figure, reference numeral 301 denotes a rotating shaft of the cam 103. In this example, when the angle of the cam 103 with respect to the side plate 101 is at the position A, the pressure roller 210 is free with respect to the cam and is urged by the pressure spring 102 to be in a pressurized state. Further, when the angle of the cam 103 with respect to the side plate 101 is at the position B, the pressure roller 210 is completely pushed down by the cam 103 and is in a separated state. When the angle of the cam 103 with respect to the side plate 101 is at the position C, the pressure roller 210 is slightly pushed down by the cam 103 and is in a reduced pressure state.

  Reference numeral 302 denotes a sensor flag that rotates in conjunction with the cam 103. Reference numeral 303 denotes a photo interrupter that detects the state of the cam 103 by detecting the state of the sensor flag 302.

  The operation at the time of pressurization / decompression / separation will be described with reference to FIG.

  When performing the separation operation, the control device 104 rotates the motor 105 to drive the cam, and when the photo interrupter 303 detects a change from light shielding to transmission by the sensor flag 302, the control device 104 is in the separation state. Stops the motor 105.

  Further, when performing the pressurizing operation, the control device 104 rotates the motor 105 to drive the cam, and when the photo interrupter 303 detects a change from transmission to light shielding by the sensor flag 302, it is in a pressurizing state. The control device 104 stops the motor 105.

  Here, since the sensor flag 302 has only two states of a transmission state and a light shielding state, it cannot directly detect the reduced pressure state. Therefore, after the current cam position is detected using the switching between light shielding and transmission by the sensor flag 302 as a trigger, the cam position is adjusted by rotating a predetermined rotational speed motor, and the pressure is reduced. In this example, when the cam is rotated 1/4 turn from the pressurized state, the pressure is reduced. For example, when the motor 103 rotates eight times, the photo interrupter 303 changes from the transmission to the sensor flag 302 when the cam 103 rotates once. After detecting the change to the light shielding due to, the controller 104 stops the motor 105 because the motor is rotated twice to reduce the pressure.

  FIG. 4 is a view showing a roller state at the time of pressurization / decompression / separation in the present embodiment. In the figure, (a) represents a pressurized state, (b) represents a reduced pressure state, and (c) represents a separated state. As can be seen from the figure, it can be seen that the rubber layer (the outermost layer) of the two rollers is greatly deformed in the pressurized state. Further, it can be seen that the rubber layers of the two rollers are hardly deformed in the reduced pressure state, and that the stress applied to the rubber layer is very small with respect to the pressed state. In addition, since the surfaces of both rollers are in contact with each other with a predetermined width, heat exchange is performed inferior to that in the pressurized state. There are no problems such as paper curl.

  Next, the relationship between the printer state and the pressure state of the roller in this embodiment will be described with reference to FIG.

  As can be seen from the figure, in the printer of this embodiment, the fixing roller and the pressure roller are in a pressurized state only during printing.

  In the warm-up, pre-printing process, post-printing process, standby, and the like, the fixing roller and the pressure roller are in a reduced pressure state.

  For special processing such as power off, jamming, door opening, and sleep, the fixing roller and the pressure roller are separated from each other as in the conventional example.

  The present embodiment has been described by taking as an example a pressurization / decompression separation mechanism in which pressure is applied by a pressure spring and separation is performed by lifting using a cam. However, it is not necessary to be limited to this method, for example, a pressure reducing / depressing separation mechanism of a method in which a roller is directly pressurized by lifting with a cam and separated by releasing a lift-up, or a holding portion of a pressure spring It may be used for any pressurization / decompression separation mechanism such as a pressurization / decompression separation mechanism of a type in which the spring is pushed up by being lifted up and pressurized in accordance therewith and released by releasing the liftup.

  Further, in this embodiment, the case where the fixing roller and the pressure roller are both metal rollers having a thick rubber layer is described as an example, but this is not necessarily the case. The same applies to the case where there is no or a thin metal roller or a film member.

  By using the method as described above, it is possible to reduce the stress on the rubber layer of the roller of the fixing device and provide a fixing device having a longer life.

  In the second embodiment of the present invention, the description of the parts that are the same as those of the first embodiment regarding the configuration of the image forming apparatus and the configuration of the pressure / decompression separating mechanism is omitted, and the configuration unique to the present embodiment is described. Do.

  The automatic pressurizing / depressurizing / separating mechanism, which is a feature of the second embodiment, will be described below with reference to FIG.

  In the figure, components having the same functions as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted. Reference numeral 601 denotes a fixing roller driving motor for rotating the fixing roller, and reference numeral 602 denotes a cam driving motor for driving the cam. The fixing roller driving motor 601 rotates the fixing roller 210 to carry the paper. The cam drive motor 602 rotates the cam 103 of the automatic pressurization / decompression separation mechanism. That is, by making the fixing roller and the cam rotation motor independent of each other, it is possible to pressurize, depressurize, and separate the rollers at any timing in paper conveyance.

  With the configuration described above, it is not necessary to reversely rotate the motor during pressure reduction → pressurization or during pressure → pressure reduction, and it is possible to drive other paper transport systems using the fixing roller drive motor 601. It becomes. For this reason, pressurization is performed immediately before the recording material enters the fixing device, and decompression is performed immediately after the recording material is discharged, so that it is possible to shorten the pressurization time as much as possible. Without affecting, it is possible to reduce the stress on the rubber layer of the roller of the fixing device and provide a fixing device having a longer life.

  In the third embodiment of the present invention, the description of the parts similar to those of the first and second embodiments regarding the configuration of the image forming apparatus and the configuration of the pressure / decompression separating mechanism is omitted, and the configuration unique to the present embodiment is omitted. Give an explanation.

  The automatic pressurizing / depressurizing / separating mechanism, which is a feature of the third embodiment, will be described below with reference to FIG.

  In the figure, components having the same functions as those of the first and second embodiments are denoted by the same reference numerals and description thereof is omitted. Reference numeral 701 denotes a motor for rotating the fixing roller and driving the cam, and reference numeral 702 denotes a cam drive clutch that switches on / off of drive transmission from the motor 701 to the cam 103. The motor 701 rotates the fixing roller 210 to carry the paper. The cam drive clutch 702 transmits the drive of the motor 701 to rotate the cam 103 of the automatic pressurization / decompression separation mechanism. In other words, by providing a dedicated cam drive clutch, it is possible to pressurize, depressurize, and separate the rollers at any timing in paper conveyance.

  By adopting the configuration as described above, it is possible to perform pressure reduction → pressurization and pressurization → pressure reduction at any time without applying a special motor as in the second embodiment. It becomes possible to drive other paper conveyance systems. For this reason, pressurization is performed immediately before the recording material enters the fixing device, and decompression is performed immediately after the recording material is discharged, so that it is possible to shorten the pressurization time as much as possible. Without affecting, it is possible to reduce the stress on the rubber layer of the roller of the fixing device, and to provide a fixing device having a longer life with a lower cost configuration.

The figure explaining the automatic pressurization pressure reduction separation mechanism concerning the 1st example of the present invention. Schematic of a laser beam printer as an image forming apparatus according to the present invention The figure which shows the state of the cam with respect to the angle of the pressurization detection sensor flag concerning 1st Example of this invention. The figure which shows the roller state at the time of pressurization, pressure reduction, and separation concerning the 1st Example of this invention The figure which shows the relationship between the state of the printer concerning the 1st Example of this invention, and the pressurization state of a roller. The figure explaining the automatic pressurization pressure reduction separation mechanism concerning the 2nd example of the present invention. The figure explaining the automatic pressurization pressure reduction separation mechanism concerning the 3rd example of the present invention. Schematic of a general fixing device according to a conventional example of the present invention. The figure explaining the automatic pressure release mechanism of the fixing device concerning the prior art example of this invention. The flowchart explaining the pressurization process concerning the prior art example of this invention The figure which shows the relationship between the state of the printer concerning the prior art example of this invention, and the pressurization state of a roller

Explanation of symbols

102 Pressure Spring 103 Cam 104 Control Device 105 Motor 210 Fixing Roller 211 Pressure Roller 302 Sensor Flag 303 Photointerrupter

Claims (6)

A fixing roller;
An automatic pressurizing / depressing / separating mechanism for pressurizing, depressurizing and separating the roller;
Driving means for driving the roller and the automatic pressure reducing and separating mechanism;
In a fixing device comprising a control means for controlling the driving means,
Press the roller during image fixing,
In certain states of the image forming apparatus including the power off state, the rollers are separated,
A fixing device that decompresses a roller at the time of image fixing and in a case other than the specific state. A fixing roller;
Roller driving means for rotating the roller;
An automatic pressurizing / depressing / separating mechanism for pressurizing, depressurizing and separating the roller;
Mechanism driving means independent of the roller driving means for driving the automatic pressure reducing and separating mechanism;
In a fixing device comprising control means for controlling the roller driving means and the mechanism driving means,
Press the roller during image fixing,
In certain states of the image forming apparatus including the power off state, the rollers are separated,
A fixing device that decompresses a roller at the time of image fixing and in a case other than the specific state. A fixing roller;
Roller driving means for rotating the roller;
An automatic pressurizing / depressing / separating mechanism for pressurizing, depressurizing and separating the roller;
Switching means for driving the automatic pressurization / decompression separation mechanism by switching power transmission of the roller driving means;
In a fixing device comprising control means for controlling the roller driving means and the switching means,
Press the roller during image fixing,
In certain states of the image forming apparatus including the power off state, the rollers are separated,
A fixing device that decompresses a roller at the time of image fixing and in a case other than the specific state. A fixing roller;
An automatic pressurizing / depressing / separating mechanism for pressurizing, depressurizing and separating the roller;
Driving means for driving the roller and the automatic pressure reducing and separating mechanism;
In a fixing device comprising a control means for controlling the driving means,
Press the roller during image fixing,
In certain states of the image forming apparatus including the power off state, the rollers are separated,
An image forming apparatus, wherein the roller is depressurized at the time of image fixing and in a case other than the specific state. A fixing roller;
Roller driving means for rotating the roller;
An automatic pressurizing / depressing / separating mechanism for pressurizing, depressurizing and separating the roller;
Mechanism driving means independent of the roller driving means for driving the automatic pressure reducing and separating mechanism;
In a fixing device comprising control means for controlling the roller driving means and the mechanism driving means,
Press the roller during image fixing,
In certain states of the image forming apparatus including the power off state, the rollers are separated,
An image forming apparatus, wherein the roller is depressurized at the time of image fixing and in a case other than the specific state. A fixing roller;
Roller driving means for rotating the roller;
An automatic pressurizing / depressing / separating mechanism for pressurizing, depressurizing and separating the roller;
Switching means for driving the automatic pressurization / decompression separation mechanism by switching power transmission of the roller driving means;
In a fixing device comprising control means for controlling the roller driving means and the switching means,
Press the roller during image fixing,
In certain states of the image forming apparatus including the power off state, the rollers are separated,
An image forming apparatus, wherein the roller is depressurized at the time of image fixing and in a case other than the specific state.

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