JP2005201917A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing apparatus and an image forming apparatus of high reliability wherein the permanent deformation of a heating member and a pressure member can be surely suppressed with a comparatively simple constitution, irrespective of image forming apparatus operating states by a user. <P>SOLUTION: Regarding the fixing apparatus for transporting and inserting a recording medium P with an image T carried in between the heating member 21 and the pressure member 24, and then, fixing the image T on the recording medium P, the apparatus is provided with attachment/detachment adjusting means 27 to 31 and 41 for performing the press contact of the heating member 21 and the pressure member 24 and releasing the press contact state. When a job signal related to the image formation is not inputted to the image forming apparatus body 40, the press contact state of the heating member 21 and the pressure member 24 is released by the attachment/detachment adjusting means 27 to 31 and 41. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile, or a multifunction machine thereof, and a fixing device installed therein.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a fixing device using a heat roller system is often used (for example, see Patent Document 1).

Specifically, the fixing device is mainly composed of a fixing roller as a heating member and a pressure roller as a pressure member in pressure contact with the fixing roller.
On the other hand, an image (toner image) is transferred onto the surface of a recording medium that moves along the conveyance path of the image forming apparatus. Then, the recording medium carrying the unfixed image further moves along the transport path and reaches the fixing device. The recording medium that has reached the fixing device is fed between the fixing roller and the pressure roller (a nip), and the image is fixed by heat received from the fixing roller and pressure received from both rollers. The recording medium on which the image is fixed is delivered from between the fixing roller and the pressure roller and then discharged from the image forming apparatus.

  In such a fixing device, it is known that when the fixing roller and the pressure roller are pressed against each other for a long period of time, the elastic layer of the fixing roller and the pressure roller is permanently deformed to cause problems such as fixing failure. (For example, refer to Patent Document 1).

  In order to solve such a problem, Patent Document 1 and the like disclose a technique in which a pressure release mechanism (contact / separation adjusting means) for releasing the pressure contact state of the fixing roller and the pressure roller is installed in the fixing device. . That is, when there is no print job for a certain time or longer, the pressure release mechanism is operated to release the pressure contact state between the fixing roller and the pressure roller.

JP 11-125985 A

  The conventional technology described above may not be able to reliably prevent permanent deformation of the fixing roller and the pressure roller depending on the mode of operation of the image forming apparatus by the user.

  As described above, in the fixing device using the heat roller system, permanent deformation due to long-term pressure contact between the fixing roller and the pressure roller is a problem. That is, when the fixing device is not operated for a long period of time, the contact portions of the fixing roller and the pressure roller always receive a load, and both the rollers are crushed in the radial direction or bent in an arc shape in the axial direction. In such a case, a gap is formed at the contact portion (nip) of both rollers, and fixing failure occurs in the image on the recording medium. Furthermore, abnormal images such as image blur due to conveyance failure by both rollers, abnormal noise due to driving of the deformed roller, and the like may occur.

  In particular, in recent fixing devices, a fixing roller composed of a thin cylindrical body is used for the purpose of reducing power consumption, and a desired nip can be obtained even with a low pressing force corresponding to a thin cylindrical fixing roller having a low strength. A pressure roller made of foamable silicone rubber that can be formed is used. A pressure roller using such a foamable silicone rubber as an elastic layer is relatively easy to be permanently deformed against long-term pressure contact, and thus the above-mentioned problems cannot be ignored.

  On the other hand, in the technique of the above-mentioned Patent Document 1, a pressure release mechanism that releases the pressure contact state of the fixing roller and the pressure roller is installed in the fixing device, and the pressure release is performed when there is no print job for a certain time or more. The mechanism is operated to release the pressure contact state between the fixing roller and the pressure roller. Therefore, the time during which the fixing roller and the pressure roller are in contact with each other is reduced, and a certain effect of preventing the both rollers from being permanently deformed can be expected.

  However, in the above-described control, the contact state between the fixing roller and the pressure roller is maintained when the user turns off the power switch of the image forming apparatus before the fixed time elapses until the pressure release mechanism operates. It will be done. In this case, since the contact state of the fixing roller and the pressure roller is maintained until the power switch of the image forming apparatus is turned on again, there is a high possibility that both rollers are deformed.

  Japanese Patent Application Laid-Open No. 2004-228561 describes that the contact state between the fixing roller and the pressure roller is released when the power switch is turned off, but there is no description about a specific method. Here, even when the power switch is turned off before the lapse of a certain time as described above, the auxiliary power source for operating the pressure release mechanism is used to release the contact state between the fixing roller and the pressure roller. It is also possible to install it separately from the power supply related to the above. However, in that case, the cost and installation space for installing the auxiliary power supply are required.

  The present invention has been made in order to solve the above-described problems. When the user turns off the power switch of the image forming apparatus immediately after the job related to image formation is completed, the image by the user is provided. It is an object of the present invention to provide a highly reliable fixing device and image forming apparatus in which permanent deformation of a heating member and a pressure member is reliably suppressed with a relatively simple configuration regardless of the operation mode of the forming apparatus.

  In the fixing device according to the first aspect of the present invention, a recording medium carrying an image is fed between a heating member and a pressure member pressed against the heating member, and the image is placed on the recording medium. A fixing device for fixing, comprising contact / separation adjusting means for pressing and releasing the heating member and the pressure member, and the contact / separation adjusting means includes a job signal related to image formation in the image forming apparatus main body. When no is input, the pressure contact between the heating member and the pressure member is released.

  The fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the contact / separation adjusting unit is configured to perform the heating when a job signal related to image formation is input to the image forming apparatus main body. The member and the pressure member are pressed against each other.

  According to a third aspect of the present invention, in the fixing device according to the second aspect, the contact / separation adjusting means is a recording medium related to the job signal between the heating member and the pressure member. When a job signal following the job signal is not input to the image forming apparatus main body when the image is sent, the pressure member is released from the pressure contact, and the heating member and the pressure member are released. When the recording medium related to the job signal is sent from between and the job signal following the job signal is input to the image forming apparatus main body, the press contact between the heating member and the pressure member is maintained. To do.

  According to a fourth aspect of the present invention, there is provided a fixing device according to the third aspect of the invention, further comprising a detecting unit that detects a recording medium sent from between the heating member and the pressure member, The time when the detection means detects the passage of the recording medium is when the recording medium is delivered from between the heating member and the pressure member.

  A fixing device according to a fifth aspect of the invention is the fixing device according to the fourth aspect, wherein the detecting means is a reflective or transmissive photosensor that detects a recording medium in a non-contact state. is there.

  According to a sixth aspect of the present invention, there is provided a fixing device according to the fourth or fifth aspect, wherein the detecting means is a photo provided with a filler that swings in conjunction with contact with a recording medium. It is a sensor.

  A fixing device according to a seventh aspect of the invention is the fixing device according to any one of the fourth to sixth aspects, wherein the detection means is a jam detection means for detecting a jam position of a recording medium. It is.

  An image forming apparatus according to an eighth aspect of the present invention includes the fixing device according to any one of the first to seventh aspects in the main body of the image forming apparatus.

  According to the present invention, the heating member and the pressure member of the fixing device are instantaneously contacted and separated in conjunction with the presence or absence of a job signal input to the image forming apparatus main body. As a result, the permanent deformation of the heating member and the pressure member is relatively small regardless of the mode of operation of the image forming apparatus by the user, such as when the power switch of the image forming apparatus is turned off immediately after the job is completed. It is possible to provide a highly reliable fixing device and image forming apparatus that are reliably suppressed with a simple configuration.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
The first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes an apparatus main body of a copying machine as an image forming apparatus, 2 an original reading unit that optically reads image information of an original D, and 3 an exposure light L based on image information read by the original reading unit 2. Is exposed to the photosensitive drum 5, 4 is an image forming unit that forms an image (toner image) on the photosensitive drum 5, and 7 is an image formed on the photosensitive drum 5 that is transferred to the recording medium P. The transfer unit 10 is a document transport unit (ADF) that transports a set document D to the document reading unit 2, 12 to 14 is a paper feed unit that stores a recording medium P such as transfer paper, and 20 is a recording medium P. A fixing device for fixing the unfixed image above, 21 is a fixing roller as a heating member installed in the fixing device 20, and 24 is a pressure roller as a pressure member installed in the fixing device 20.

With reference to FIG. 1, an operation during normal image formation in the image forming apparatus will be described.
First, the document D is conveyed from the document table in the direction of the arrow in the drawing by the conveyance roller of the document conveyance unit 10 and passes over the document reading unit 2. At this time, the document reading unit 2 optically reads the image information of the document D passing above.
Then, the optical image information read by the document reading unit 2 is converted into an electric signal and then transmitted to the exposure unit 3 (writing unit). Then, exposure light L such as laser light based on the image information of the electrical signal is emitted from the exposure unit 3 toward the photosensitive drum 5 of the image forming unit 4.

On the other hand, in the image forming unit 4, the photosensitive drum 5 is rotated in the clockwise direction in the drawing, and image information is transferred onto the photosensitive drum 5 through a predetermined image forming process (charging process, exposure process, development process). An image (toner image) corresponding to is formed.
Thereafter, the image formed on the photosensitive drum 5 is transferred by the transfer unit 7 onto the recording medium P conveyed by the registration roller.

On the other hand, the recording medium P conveyed to the transfer unit 7 operates as follows.
First, one of the plurality of paper feeding units 12, 13, and 14 of the image forming apparatus main body 1 is automatically or manually selected (for example, the uppermost paper feeding unit 12 is selected). To do.)
Then, the uppermost sheet of the recording medium P stored in the paper feeding unit 12 is transported toward the position of the transport path K.

  Thereafter, the recording medium P passes through the conveyance path K and reaches the position of the registration roller. Then, the recording medium P that has reached the position of the registration roller is conveyed toward the transfer unit 7 at the same timing in order to align with the image formed on the photosensitive drum 5.

After the transfer process, the recording medium P passes through the position of the transfer unit 7 and then reaches the fixing device 20 through the conveyance path. The recording medium P that has reached the fixing device 20 is fed between the fixing roller 21 and the pressure roller 24, and the image is fixed by the heat received from the fixing roller 21 and the pressure received from both rollers 21, 24. The The recording medium P on which the image is fixed is delivered from between the fixing roller 21 and the pressure roller 24 and then discharged from the image forming apparatus main body 1.
Thus, a series of image forming processes is completed.

Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIGS.
As shown in FIG. 2, the fixing device 20 mainly includes a fixing roller 21, a pressure roller 24, a thermistor 37, a separation claw 38, and contact / separation adjusting means 27 to 31.

  Here, the fixing roller 21 as a heating member includes a thin cylindrical body that rotates in the direction of the arrow in FIG. 2 and a heater 22 fixed inside the cylindrical body. The surface of the cylindrical body of the fixing roller 21 is processed with a fluororesin so as to ensure releasability (peelability) from the toner T. The heater 22 of the fixing roller 21 is a rod-shaped heater having a heating wire inside, and both ends thereof are fixed to the side plate of the fixing device 20. Then, the cylindrical body is heated by the heater 22 whose output is controlled by the control unit 40 of the apparatus main body 1, and heat is applied to the toner T on the recording medium from the surface of the cylindrical body. The output control of the heater 22 is performed based on the detection result of the roller surface temperature by the thermistor 37 that contacts the surface of the fixing roller 21.

  As shown in FIG. 2, a separation claw 38 that is swingably supported is disposed on the outer peripheral side of the fixing roller 21. The separation claw 38 has a tip abutting against the outer peripheral surface of the fixing roller 21, and the recording medium P sent from between the fixing roller 21 and the pressure roller 24 moves along the rotation of the fixing roller 21. The trouble which winds around 21 is suppressed.

  The pressure roller 24 as a pressure member mainly includes a cored bar and a plurality of elastic layers formed on the outer peripheral surface of the cored bar via an adhesive layer. The elastic body layer of the pressure roller 24 has a layer thickness of 1 to 10 mm, and a material such as fluorine rubber, silicone rubber, or foamable silicone rubber is used. A thin release layer having a layer thickness of 300 μm or less (preferably 40 μm or less) is provided on the surface layer of the elastic layer. As the material of the release layer, a single layer film of heat-resistant resin such as polyimide, polyetherimide, PES (polyether sulfide), PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin), or a film having a thickness of 20 μm The composite layer film etc. which gave the release coat layer which added the electrically conductive material to fluororesins, such as PTFE (tetrafluoroethylene resin) and PFA, in the surface layer side of 10-30 micrometers can be used. The pressure roller 24 configured in this manner is excellent in elasticity, heat resistance, releasability, and durability.

  Here, the shaft 24 a at both ends of the pressure roller 24 is inserted into a long hole provided in the side plate of the fixing device 20. Referring to FIG. 2, pressure levers 27 are engaged with shaft portions 24a at both ends of pressure roller 24, respectively. One end side of the pressure lever 27 is supported by the support shaft 30, and a tension spring 29 is installed on the other end side. With such a configuration, the pressure roller 24 is pushed up by the pressure lever 27 that rotates about the support shaft 30 by the urging force of the tension spring 29 and presses the fixing roller 21.

  Further, a shaft portion is provided at the lower end of the pressure lever 27 so as to stand upright in the direction perpendicular to the paper surface of FIG. 2, and a bearing 28 is inserted into the shaft portion. The bearing 28 of the pressure lever 27 is configured to be able to engage with an eccentric cam 31 that rotates in the direction of the arrow Y <b> 1 by the drive unit 41.

Referring to FIG. 3, the drive unit 41 that rotationally drives the eccentric cam 31 includes a drive motor 42 such as a stepping motor or a DC motor, and a plurality of gears 44 to 49.
Specifically, after the control unit 40 of the apparatus main body 1 determines whether or not a job signal is input, an operation signal is transmitted from the control unit 40 to the drive motor 42. When the drive motor 42 is driven, the driving force is transmitted to an idle gear 45a that meshes with a gear 44 connected to the motor shaft. Further, the drive is transmitted to the worm wheel 46a meshing with the worm gear 45b integrated with the idle gear 45a, and the idle gear 46b integrated with the worm wheel 46a is passed through the two-stage idle gears 47a, 47b and the idle gear 48. Finally, the drive is transmitted to the gear 49 integrated with the eccentric cam 31. Thus, the eccentric cam 31 is rotationally driven in the direction of the arrow Y1 in FIG. 3 at a predetermined timing.

  Then, as shown in FIG. 4, the eccentric cam 31 is rotationally driven, and the top dead center of the eccentric cam 31 (the position on the circumferential surface where the distance from the rotation center is the longest) is engaged with the bearing 28. Thus, the pressure lever 27 is pushed down in the direction of the arrow Y2, and the pressure roller 24 is moved in the direction of the arrow Y3, so that the pressure contact between the fixing roller 21 and the pressure roller 24 is released.

  Further, the eccentric cam 31 is driven to rotate, and the bottom dead center of the eccentric cam 31 (the position on the circumferential surface where the distance from the rotation center is the shortest) is opposed to the bearing 28, whereby the eccentric cam 31 The pressure lever 27 is released and the urging force of the tension spring 29 moves the pressure lever 27 and the pressure roller 24 to the positions shown in FIG. 2 so that the fixing roller 21 and the pressure roller 24 are pressed against each other. In the pressure contact state shown in FIG. 2, the eccentric cam 31 and the bearing 28 are not in contact with each other, and therefore the pressure contact force of the fixing roller 21 and the pressure roller 24 is determined by the urging force of the tension spring 29.

As shown in FIG. 2, guide plates 35 for guiding the conveyance of the recording medium P are disposed on the entrance side and the exit side of the contact portion between the fixing roller 21 and the pressure roller 24, respectively. The guide plate 35 is fixed to the side plate of the fixing device 20.
A photo sensor 51 as a detecting means is installed on the guide plate on the outlet side. The photosensor 51 includes a light emitting element 51 a such as a light emitting diode and a light receiving element 51 b such as a phototransistor, and detects the recording medium P sent from between the fixing roller 21 and the pressure roller 24 in a non-contact state. That is, when the light emitted from the light emitting element 51a does not reach the light receiving element 51b, it is identified that the recording medium P exists at the position of the photosensor 51.

The fixing device 20 configured as described above operates under the following control.
First, when the power switch (not shown) of the apparatus main body 1 is not turned on, the state where the eccentric cam 31 is engaged with the bearing 28 of the pressure lever 27 is maintained. That is, the pressure contact between the fixing roller 21 and the pressure roller 24 is released (the state shown in FIG. 4). This pressure-release state is maintained even when the power switch of the apparatus main body 1 is turned on.

  When the power switch of the apparatus main body 1 is turned on and the operation unit 55 is operated by the user (for example, when the copy start button is pressed), a job signal related to image formation is sent from the operation unit 55 to the control unit 40. When transmitted, an operation signal is transmitted from the control unit 40 to the drive unit 41. Thereby, the contact / separation adjusting means by the pressure lever 27, the eccentric cam 31, the drive unit 41 and the like described above operates, and the pressure contact between the fixing roller 21 and the pressure roller 24 is performed (the state shown in FIG. 2). . Further, rotation driving of the fixing roller 21 and the pressure roller 24 in the direction of the arrow in FIG. 2 is started.

  At the same time, based on the input of the job signal, the recording medium P is fed from the paper feeding units 12 to 14, and an unfixed image is carried on the recording medium P by the image forming unit 4. The recording medium P carrying the unfixed image T is conveyed in the direction of the arrow Y10 in FIG. 2 and fed into the nip portion between the fixing roller 21 and the pressure roller 24 that are in a pressure contact state. Then, the image T is fixed on the surface of the recording medium P by the heating by the fixing roller 21 and the pressing force of the fixing roller 21 and the pressure roller 24.

  Thereafter, the recording medium P sent out from the nip portion by the rotating fixing roller 21 and the pressure roller 24 is conveyed in the direction of the arrow Y11. At this time, the sent recording medium P is detected by the photosensor 51. More specifically, the leading end of the recording medium P sent out when the light receiving element 51b of the photosensor 51 is blocked is detected, and the recording sent out when the light receiving blocking of the light receiving element 51b is released. The rear end of the medium P is detected. When the rear end of the recording medium P is detected (when the passage of the recording medium P is detected), the recording medium P is sent from the fixing roller 21 and the pressure roller 24 and the fixing process is completed. And the presence or absence of a job signal in the control unit 40 at that time is identified.

That is, when the control unit 40 changes the output value transmitted from the light receiving element 51a (when the rear end of the recording medium P is detected), the presence / absence of a job signal related to image formation in the next process is determined. Identified.
As a result, when it is determined that the input of a job signal following the previous job is detected when the trailing edge of the recording medium P is detected, the pressure contact state of the fixing roller 21 and the pressure roller 24 is maintained. Then, the above-described fixing process and control are performed again on the recording medium P related to the next job.
On the other hand, when it is determined that the job signal following the previous job is not input when the trailing edge of the recording medium P is detected, the pressure contact state of the fixing roller 21 and the pressure roller 24 is released. . Then, the pressure release state is maintained until a job signal is input again via the operation unit 55.

  As described above, in the first embodiment, when the job is not executed, the fixing roller 21 and the pressure roller 24 are released from the pressure contact state, and when the job is actually executed, the fixing roller 21 is set. The pressure roller 24 is brought into a pressure contact state. Further, when the subsequent fixing process is not performed, immediately after the fixing process in the fixing device 20 is completed, the fixing roller 21 and the pressure roller 24 are brought into a pressure contact released state. As a result, the responsiveness of the contact / separation operation of the fixing roller 21 and the pressure roller 24 is improved, so that immediately after the recording medium P is discharged from the apparatus main body 1, the user can turn off the power switch or execute the job. Even when the user turns off the power switch while waiting for a job, the pressure contact between the fixing roller 21 and the pressure roller 24 is surely released. That is, permanent deformation of the fixing roller 21 and the pressure roller 24 is suppressed with a relatively simple configuration, and problems such as fixing failure are prevented.

Embodiment 2. FIG.
The second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 5 is a configuration diagram illustrating the fixing device 20 according to the second embodiment, and corresponds to FIG. 2 of the first embodiment. The second embodiment is different from the first embodiment using a transmissive photosensor in that a reflective photosensor 51 is used as detection means.

  As shown in FIG. 5, a photo sensor 51 as a detection unit is installed on the guide plate on the outlet side so as to be close to the fixing roller 21 and the pressure roller 24. In the photosensor 51, the light emitting element and the light receiving element are disposed in the same plane. Further, the light emitting element and the light receiving element of the photosensor 51 are disposed so as to face the roller surface of the fixing roller 21.

  The photosensor 51 configured in this manner detects the recording medium P sent from between the fixing roller 21 and the pressure roller 24 in a non-contact state, as in the first embodiment. That is, the amount of light received by the light receiving element when the light emitted from the light emitting element is reflected by the surface of the fixing roller 21, the amount of light received by the light receiving element when the light emitted from the light emitting element is reflected by the back surface of the recording medium P, The presence or absence of the recording medium P is identified by the difference in the amount of reflected light. In order to improve the above-described identification accuracy, it is preferable that the surface of the fixing roller 21 is black considering that the back surface of the recording medium P is usually white.

  As described above, in the second embodiment, by using the non-contact reflection type photo sensor 51, the photo sensor 51 can be disposed between the fixing roller 21 and the pressure roller 24. it can. Accordingly, since the trailing end of the recording medium P immediately after being sent from between the fixing roller 21 and the pressure roller 24 can be detected, the contact / separation operation of the fixing roller 21 and the pressure roller 24 is responsive. Is further increased, and the pressure contact between the fixing roller 21 and the pressure roller 24 is reliably released.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 6 is a configuration diagram illustrating the fixing device 20 according to the third embodiment, and corresponds to FIG. 2 of the first embodiment. The third embodiment is different from the first embodiment in that a photosensor 51 including a filler 52 is used as a detection unit and that the photosensor 51 is also used as a jam detection unit. .

  As shown in FIG. 6, a photo sensor 51 having a filler 52 as a detecting means is installed on the guide plate on the outlet side. The filler 52 is disposed at a position where one end can contact the sent recording medium P, and the other end is disposed between the light emitting element and the light receiving element of the photosensor 51.

The photosensor 51 configured as described above detects the recording medium P sent from between the fixing roller 21 and the pressure roller 24 in a contact state with the filler 52.
That is, when one end of the filler 52 comes into contact with the recording medium P, the other end moves to a position where light projection from the light emitting element to the light receiving element of the photosensor 51 is blocked in conjunction with the operation of one end of the filler 52. (This is the counterclockwise rotational movement of the arrow Y21 in the figure.)
On the other hand, when one end of the filler 52 is released from contact with the recording medium P, the other end is projected from the light emitting element of the photosensor 51 to the light receiving element in conjunction with the operation of one end of the filler 52. It moves to a position where it releases light (this is a clockwise rotational movement of the arrow Y21 in the figure).

Furthermore, the photosensor 51 of the third embodiment also functions as a jam detection unit (remaining paper sensor) that detects the jam position of the recording medium P. In other words, jam detection means are arranged in several places on the conveyance path K of the image forming apparatus main body 1 in addition to the photosensor 51 shown in FIG. If a jam (paper jam) occurs in the recording medium P being transported at any position in the transport path K, the jam position is displayed on the display unit 60 to notify the user. When a jam occurs at the position of the fixing device 20 or the recording medium P remains as remaining paper, the information is transmitted to the display unit 60 via the control unit 40 by the photosensor 51 shown in FIG. The
When the photo sensor 51 detects a jam in the fixing unit 20, the control unit 40 controls the contact / separation adjusting units 27 to 31 and 41 to release the pressure contact between the fixing roller 21 and the pressure roller 24. It is preferable to do this. This simplifies the user's jam removal operation at the fixing device 20 position.

  As described above, in the third embodiment, the photosensor 51 as the detection unit that determines the operation timing of the contact / separation adjustment units 27 to 31 and 41 is also used as the jam detection unit, thereby forming an image. An increase in the cost of the entire apparatus can be prevented. Further, similarly to each of the above-described embodiments, since the rear end of the recording medium P immediately after being sent from between the fixing roller 21 and the pressure roller 24 can be detected, the fixing roller 21 and the pressure roller The responsiveness of the contact / separation operation 24 is improved, and the pressure contact between the fixing roller 21 and the pressure roller 24 is surely released.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the above-described embodiments can be modified as appropriate in addition to those suggested in the above-described embodiments. Is clear. Further, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiments, and the number, position, shape, and the like that are suitable for implementing the present invention can be used.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a configuration diagram illustrating a fixing device installed in the image forming apparatus of FIG. 1. FIG. 3 is a configuration diagram illustrating a driving unit of contact / separation adjusting means in the fixing device of FIG. 2. FIG. 3 is a schematic diagram illustrating a state in which the contact between the fixing roller and the pressure roller is released in the fixing device of FIG. 2. It is a block diagram which shows the fixing device in Embodiment 2 of this invention. It is a block diagram which shows the fixing device in Embodiment 3 of this invention.

Explanation of symbols

1 image forming apparatus body (apparatus body),
2 Document reading section, 3 Exposure section, 4 Image forming section, 7 Transfer section,
10 Document transport section, 12-14 Paper feed section,
20 fixing device, 21 fixing roller (heating member), 22 heater,
24 pressure roller (pressure member), 27 pressure lever, 28 bearing,
29 tension spring, 30 spindle, 31 eccentric cam,
40 control unit, 41 drive unit, 51 photosensor (detection means),
52 Filler, P recording medium, K transport path.

Claims (8)

A fixing device for feeding a recording medium carrying an image between a heating member and a pressure member pressed against the heating member and fixing the image on the recording medium,
A contact / separation adjusting means for performing pressure contact between the heating member and the pressure member and releasing the pressure member,
The fixing device is characterized in that the contact / separation adjusting unit releases the pressure contact between the heating member and the pressure member when a job signal relating to image formation is not input to the image forming apparatus main body. The fixing according to claim 1, wherein the contact / separation adjusting unit performs pressure contact between the heating member and the pressure member when a job signal related to image formation is input to the main body of the image forming apparatus. apparatus. The contact / separation adjusting unit is configured such that when a recording medium related to the job signal is sent from between the heating member and the pressure member, a job signal following the job signal is not input to the image forming apparatus main body. When the recording medium relating to the job signal is sent from between the heating member and the pressure member, the pressure contact between the heating member and the pressure member is released, and the job is applied to the image forming apparatus main body. The fixing device according to claim 2, wherein when the job signal following the signal is input, the press contact between the heating member and the pressure member is maintained. A detecting means for detecting a recording medium sent from between the heating member and the pressure member;
The fixing device according to claim 3, wherein the detection unit detects the passage of the recording medium when the recording medium is delivered from between the heating member and the pressure member. The fixing device according to claim 4, wherein the detection unit is a reflection type or transmission type photosensor that detects a recording medium in a non-contact state. The fixing device according to claim 4, wherein the detection unit is a photosensor provided with a filler that swings in conjunction with contact with a recording medium. The fixing device according to claim 4, wherein the detection unit is a jam detection unit that detects a jam position of a recording medium. An image forming apparatus comprising the fixing device according to claim 1 in the main body of the image forming apparatus.

Images