JP2010097104A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device having such a configuration that the smoking and firing of a transfer material can be prevented, regardless of a simple configuration. <P>SOLUTION: The fixing device heating and fixing a toner image on the transfer material by radiation heat includes: a heating source; a belt for protecting the transfer material rotatably provided so as to surround the heating source; a transfer material conveying belt provided to face the belt for protecting the transfer material; and a cooling means cooling the belt for protecting the transfer material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fixing device that fixes a toner image formed on a transfer material by radiant heat, and includes the fixing device. When the transfer material causes a jam trouble in the fixing device, the transfer material is ignited. The present invention relates to an image forming apparatus configured to prevent the above.

  An image forming apparatus using electrophotography is a method in which a toner image formed on an image carrier by performing charging, exposure, and development processing is directly or directly transferred to an intermediate transfer member and then transferred to a transfer material. In addition, the heat fixing process is performed to fix on the transfer material.

  Further, as a fixing device for performing heat fixing processing, a roller type heat fixing device mainly including a heating roller having a built-in heating source such as a halogen lamp and a pressure roller rotating while being in pressure contact with the heating roller is preferable. Are known.

  The roller-type heat fixing device is useful for reducing the size of the image forming apparatus. However, the roller-type heat fixing device may cause an offset phenomenon that the transfer material is wound around the heating roller due to environmental conditions or the like, or the transfer material may be curled. There is a risk of losing.

  As another heat fixing device, a fixing device in which the transfer material conveyed by the conveying belt is irradiated with a far-infrared lamp as a heating source and the toner image on the transfer material is heated and fixed by the radiant heat is considered. It is done.

  The fixing device using the radiant heat has an advantage that the device configuration is simple.

  The fixing device according to the present invention belongs to the latter using radiant heat.

  However, in the latter case, if the transfer material is jammed (paper jam) in the fixing device or the transfer material comes into contact with a heating source, there is a risk that the transfer material may emit smoke or ignite.

As a countermeasure against such problems, a far-infrared halogen lamp is attached to a predetermined position of the housing, and a protective net formed by wrapping a wire made of a metal wire or a heat-resistant resin is fixed to the opening surface of the housing. A fixing device has been proposed (see, for example, Patent Document 1).
JP-A-6-3986

  The technique disclosed in Patent Document 1 seems to be a useful technique that can reliably prevent the transfer material from entering the housing in which the heating source is disposed.

  However, when the far-infrared halogen lamp is continuously turned on for fixing processing accompanying a series of image forming jobs, the protective net rises to the same temperature as the far-infrared halogen lamp. End up.

  When the transfer material comes into contact with the protection net in such a state, there is a problem that the transfer material is rapidly heated and may cause smoke and ignition.

  The present invention has been made in view of the above problems, and a main object thereof is to provide a fixing device having a configuration that can more reliably prevent smoke and ignition of a transfer material while having a simple configuration.

  Another object is to provide an image forming apparatus provided with the above-described fixing device.

  Another object of the present invention is to provide an image forming apparatus in which the radiant heat of a heating source directed to a transfer material is cut off when the transfer material is jammed in the fixing device.

The present invention can be achieved by the following constitutional requirements.
(1)
In a fixing device for fixing a toner image on a transfer material by heating with radiant heat,
A heating source;
A transfer material protection belt that is rotatably provided around the heating source;
A transfer material transport belt provided opposite to the transfer material protection belt;
Cooling means for cooling the transfer material protection belt;
And a fixing device.
(2)
The fixing device according to (1), wherein a double reflector is attached to the heating source, and an outer reflector is rotatable.
(3)
The fixing device according to (1) or (2), wherein the transfer material protection belt is a wire mesh belt.
(4)
The fixing device according to any one of (1) to (3), wherein the heating source is an infrared heater.
(5)
Image forming means for forming a toner image on a transfer material;
The fixing device according to any one of (1) to (4);
An image forming apparatus comprising:
(6)
A heating source;
A double reflector attached to the heating source;
Of the reflectors, the outer reflector is rotatable,
A transfer material protection belt which is rotatably provided around the heating source;
A transfer material transport belt provided opposite to the transfer material protection belt;
A fixing device having cooling means for cooling the transfer material protection belt;
Image forming means for forming a toner image on a transfer material;
Control means, and
The control means performs drive control so as to block the radiant heat from the heating source by rotating the outer reflector when the transfer material conveyed by the transfer material conveyance belt is jammed. Image forming apparatus.
(7)
The image forming apparatus according to (5) or (6), wherein the transfer material protection belt is a wire mesh belt.
(8)
The image forming apparatus according to any one of (5) to (7), wherein the heating source is a ceramic heater.
(9)
The image forming apparatus according to any one of (5) to (8), wherein linear velocities of the transfer material conveyance belt and the transfer material protection belt are different from each other.

  In the fixing device according to (1), the transfer material protection belt is rotatably provided and the transfer material protection belt is cooled by the cooling means, so that the transfer material conveyance performance in the fixing device is improved. In addition, since the transfer material and the heater are not in contact with each other, ignition of the transfer material can be reliably prevented.

  Embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus composed of a digital color copying machine.

  The image forming apparatus shown in the drawing (sometimes referred to as an image forming apparatus main body for convenience) has an automatic document feeder 1 at the top of the apparatus main body, and includes an image reading unit 2, an image forming unit 3, and a belt unit 4 inside. Belt installation section, sheet feeding section 5, fixing device T, reverse sheet discharge / refeed section 6, and ADU 7 serving as a reverse conveying means.

  The automatic document feeder 1 is a device that feeds documents one by one, conveys them to an image reading position, and discharges the document after image reading to a predetermined location.

  The automatic document feeder 1 inverts the front and back sides of the document in the document table 101, the document separation unit 103, the document transport unit 105, the document discharge unit 107, the document discharge table 109, and the duplex copy mode. The document reversing means 111 is composed of a pair of rollers.

  In view of the processing process, a plurality of documents (not shown) placed on the document placing table 101 are separated one by one by the document separating means 103, and the image reading position is passed through the document conveying section 105. It is conveyed toward.

  The document reading position is provided at a lower portion of the document conveying unit 105, where an image of the document is read through the slit 201 constituting the image reading unit 2, and the read document is discharged from the document. The sheet is discharged onto the document discharge table 109 by the means 107.

  In the double-sided copy mode, an original document that has been read and transported on one side is conveyed by the document reversing unit 111 in the direction indicated by the two-dot chain line arrow.

  Then, after the document reversing unit 111 rotates in the reverse direction after being stopped while biting the trailing edge of the document in the advancing direction, the image is again guided to the image reading position via the document conveying unit 105. The document is ejected by the document ejection means 107 onto the document delivery table 109.

  The above process is repeated for the number of documents placed on the document placing table 101.

  The image reading unit 2 includes a first mirror unit 205, a second mirror 217, and a third mirror 219 in which the slit 201, the document irradiation lamp 213, and the first mirror 215 that reflects the reflected light of the document are integrated. The second mirror unit 207 is integrated.

  In addition, an imaging lens 209 that forms an image of reflected light from the third mirror 219 on an imaging device, and a linear imaging that obtains image information by photoelectrically converting a light image formed by the imaging lens 209 An element (hereinafter referred to as a CCD) 211 is included.

  The image information is subjected to appropriate image processing and then temporarily stored in a memory in the control means S described later.

  In the aspect in which the document fed by the automatic document feeder 1 is read by the image reading unit 2, the first mirror unit 205 and the second mirror unit 207 are fixed at positions as shown in the figure.

  The image information for each color read by the image reading unit 2 is sequentially extracted from the memory and input as an electrical signal to the exposure optical system for each color which is an electrostatic charge latent image forming unit.

  The image forming unit 3 forms four sets of image forming means 30 (30Y, 30M, 30C) of yellow (Y), magenta (M), cyan (C), and black (BK) that form a toner image corresponding to a color separation image. , 30BK: hereinafter referred to as an image forming unit).

  Each image forming unit 30 includes a photosensitive drum 310 as an image carrier having a photosensitive layer provided on a drum-shaped metal substrate, a charger 320, an exposure optical system 330 as image writing means, a developing device 340, a transfer device. Means 350 and cleaning means 360 are main components.

  The exposure optical system 330 is an exposure unit composed of a laser optical system.

  In the figure, only members constituting the yellow image forming unit are provided with reference numerals, and the other image forming units have basically the same configuration, and thus the reference numerals are omitted.

  The developing device 340 contains a two-component developer including a magnetic carrier (hereinafter simply referred to as carrier) and a non-magnetic toner (hereinafter simply referred to as toner).

  The developing device 340 includes a rotatable and non-magnetic cylindrical developer carrier (hereinafter referred to as a developing sleeve or simply a sleeve) in which a plurality of magnets (magnetic poles) are housed in a fixed position along the circumferential direction. And a toner density detecting means (not shown).

  The plurality of magnets magnetically attract and carry the developer on the sleeve and transport the developer to the development region by rotation of the sleeve, and then the developer after the development processing is repelled from above the sleeve. It is arranged so that it can be automatically removed using.

  The developing sleeve in the developing device 340 is applied with a bias voltage having a predetermined polarity (here, a negative polarity DC voltage and an AC voltage superimposed) in an image forming operation. Since it is well known, a detailed explanation is omitted.

  Further, a toner replenishing device is prepared in association with each developing device 340. The toner replenishing device includes a toner bottle mounting portion that rotatably mounts a toner bottle filled with a replenishing toner for each color, and a toner bottle. And a toner storage chamber in which toner discharged from the toner can be stored.

  The transfer unit 350 includes a roller facing a part of the peripheral surface of the photosensitive drum 310 via an intermediate transfer belt 401 described later, and includes a normal transfer electrode including an electrode formed of a discharge wire. It can also be set as the structure of the mode called.

  The cleaning unit 360 removes the toner remaining on the photosensitive drum 310 after the transfer, and the removed toner is lowered through an appropriate pipe (not shown) and installed on the side of the paper tray. The waste toner box DT is accommodated.

  Each of the image forming units 30 is yellow from above along the traveling direction of one flat surface (stretching surface) A of the loop-shaped intermediate transfer belt 401 constituting the belt unit 4 that is long in the vertical direction. (Y), magenta (M), cyan (C), and black (BK) are arranged in this order.

  The intermediate transfer belt 401, the support rollers 405, 406, 407, the backup roller 410, and the like that rotatably suspend the intermediate transfer belt constitute the belt unit 4.

  Further, the backup roller 410 constitutes a secondary transfer means by a transfer roller 510 arranged so as to rotate while pressing the backup roller with the intermediate transfer belt 401 interposed therebetween.

  Image formation by the configuration of the image forming unit 30 and the belt unit 4 is performed as follows.

  With the start of the image forming process, the surface of the photosensitive drum 310 that rotates counterclockwise is charged to a predetermined polarity (here, negative polarity) by the charger 320.

  Next, the exposure optical system 330 performs exposure corresponding to the first color signal, that is, the yellow (Y) image signal, and a latent image corresponding to the yellow (Y) image is formed on the photosensitive drum 310. It is formed.

  The latent image is reversed and developed into a yellow (Y) toner image by contact or non-contact development processing with a developer in the developing device 340 and then transferred onto the intermediate transfer belt 401 by the action of the transfer unit 350. Is done.

  Image formation with other color signals that is sequentially started after a predetermined time from the start of image formation with the first color signal is performed for each of magenta (M), cyan (C), and black (BK) by the same process as described above. This is done by the image forming unit 30.

  Each toner image on the photosensitive drum formed by each image forming unit is sequentially transferred so as to overlap with an image area where the yellow (Y) toner image is present, and is superimposed on the intermediate transfer belt 401. A color toner image is formed.

  On the other hand, the surface of the photosensitive drum 310 after completion of the transfer process is cleaned by the cleaning unit 360, and preparations for new image formation are made.

  The start timing of each image forming process for the photosensitive drum 310 or the intermediate transfer belt 401 is performed as follows.

  That is, a section outside the intermediate transfer belt 401 and from the position where the transfer roller 510 is located to the position where the first set (yellow) image forming unit is provided as viewed in the rotational direction of the intermediate transfer belt. A registration sensor 413 is additionally provided.

  Then, the time is measured from the time when the registration sensor 413 detects the reference mark provided on the intermediate transfer belt 401, and yellow (Y), magenta (M), and cyan (C) are sequentially displayed every predetermined time. , The process related to black (BK) is started.

  Reference numeral S denotes a control means (hereinafter also referred to as a control unit) including a computer, which has a built-in machine operation program and controls all of the control related to a series of image forming processes, paper feed control, toner density control, etc. I do.

  In other words, the control means S includes a CPU that performs calculation control processing, a ROM that stores various operation programs, a RAM that stores calculation result data, and the like.

  And while taking in the output of various sensors to said CPU via an interface, it has the structure which controls drive of a motor or a display means etc. based on the information.

  Reference numerals P1, P2, and P3 are paper trays that can store transfer materials, and are provided at the lower part of the apparatus main body, and can be taken out (drawn) toward the front of the drawing.

  As the transfer material, plain paper or a film sheet can be used.

  DT is a waste toner box as described above, located on the side of the paper trays P1 to P3, and can be taken out (drawn) in the same direction as the paper tray.

  A two-dot chain line surrounding the waste toner box DT and the paper trays P1 to P3 indicates an exterior door 80 that covers the front of the waste toner box DT and a front door 85 that covers the front of the paper tray. .

  The feeding sections of the paper trays P1 to P3 are provided with paper feed rollers 503, 513, and 523, separation rollers 506, 516, and 526, and transport rollers R1 to R3.

  The transfer material P fed out by these rollers is transported along a transport path in which transport rollers R4 to R7 are disposed.

  Reference numeral 59 denotes a registration roller, which is provided downstream of the transport roller R7 and in the vicinity of the secondary transfer portion.

  A fixing device T is provided on the conveyance path and downstream of the secondary transfer portion (position where the transfer roller 510 is located), and is constituted by a heating source, a transfer material conveyance belt, and the like. Will be described later.

  Reference numeral 600 denotes a paper discharge roller, and 650 denotes a paper discharge tray for stacking and storing the discharged paper.

  The sheet conveyance path configuration and conveyance control relating to the reverse sheet discharge / refeed unit 6 and the ADU 7 are well known and are not directly related to the present invention, so the description is omitted.

  Next, a process from when the color toner image formed on the intermediate transfer belt 401 is transferred onto the transfer material P and discharged to the outside of the apparatus will be briefly described with reference to the configuration of the apparatus.

  The transfer material P is fed by the paper feed roller 503 (513, 523) at an appropriate timing corresponding to the image formation on the intermediate transfer belt 401.

  Next, the transfer material P is nipped and conveyed by the separation roller 506 and a plurality of conveyance rollers R1 to R7 provided on the conveyance path, and is directed toward a registration roller 59 provided at a position in front of the transfer portion (transfer area). Be transported.

  The transfer material P to be fed is a sheet material of a size designated / selected on the operation display board 150 on which the number of recordings, a recording start button, or a recording magnification and image density can be set.

  After the leading end of the transfer material P is brought into contact with the registration roller 59, the transfer of the transfer material P is re-feeded at a timing overlapping with the color toner image area on the intermediate transfer belt 401 by resuming the rotation of the registration roller 59. .

  Next, the transfer material P is pressed and clamped together with the intermediate transfer belt by the backup roller 410 and the transfer roller 510 in the secondary transfer portion. During this time, the color toner image on the intermediate transfer belt 401 is transferred to the transfer material P. Transcribed above.

  It is desirable that an appropriate transfer bias voltage is applied to the transfer roller 510 during transfer.

  The transfer material P onto which the toner image has been transferred is separated from the intermediate transfer belt 401, conveyed toward the fixing device T by a conveyance belt (not shown), and is subjected to heat treatment.

  The toner forming the toner image is heated and melted and fixed on the transfer material P.

  After the fixing process by the fixing device T is completed, the transfer material P is conveyed by a paper discharge roller 600 provided downstream thereof, and is discharged onto a paper discharge tray 650 provided outside the apparatus main body.

  On the other hand, the surface of the intermediate transfer belt 401 after the completion of the secondary transfer is cleaned by the cleaning means 40, and preparations for carrying a new toner image are made.

  In the drawing, the illustrated position of the path switching member 601 is a position when the transfer material P is discharged without being inverted after the fixing process.

  When the transfer material is reversed and discharged, the passage switching member 601 is rotated by a predetermined amount, and the fixed transfer material P is guided downward along the right side of the passage switching member 601.

  Next, the transfer material P is raised along the left side of the path switching member 601 by the reverse rotation of the roller pair 602 after the rear end is held between the rollers 602, and the paper discharge roller It is discharged through 600.

  Further, in the double-sided copy mode using the ADU 7, the transfer material P after the fixing process on which an image is formed on one side is guided downward along the right side of the path switching member 601, and the rear end of the transfer material P Is stopped while being held by the roller pair 605.

  Next, the roller pair 605 is reversely rotated to raise the transfer material along a guide (not shown), and is guided to the ADU 7 having a plurality of roller pairs 701, 702, 703 and reversed.

  The image forming process for the second surface of the transfer material P is basically the same as described above, and any of the above-described discharge paths after being sent out from the fixing device T is selected.

  In the image forming process described above, the toner density in the developer is detected by the toner density detection sensor, and the output information is taken in and calculated by the control means S and compared with a set threshold value.

  When the control unit S determines that the toner needs to be replenished, the toner conveying unit is driven based on a command from the control unit S, and the necessary toner amount is replenished into the developing device 340.

  On the other hand, the toner removed from the photosensitive drum by the cleaning unit 360 is sent to the waste toner box DT and stored therein.

  FIG. 2 is an explanatory diagram conceptually showing the fixing device.

  The transfer material transport path in FIG. 2 is shown as horizontal for the sake of convenience, but whether or not the transport path has an angle does not affect the present invention.

  The fixing device T has a configuration in which a lower housing 90 and an upper housing 95 are integrally combined. The lower housing 90 includes a transfer material conveyance belt 900 as a transfer material conveyance means. ing.

  The transfer material conveying belt 901 is suspended by rollers 901 and 902 with sprockets and rotated counterclockwise by a driving source M1 connected to the rollers 901.

  A horizontal portion 903 on the upper side of the transfer material conveyance belt 900 constitutes a transfer material conveyance surface (agreement with the conveyance path).

  As shown in FIG. 3, the transfer material conveyance belt 900 in the present embodiment is composed of three belts made of polyimide (PI) bases arranged in parallel with a space therebetween.

  Reference numeral 903 is perforation provided on each belt, and is rotated through engagement (engagement) with sprockets provided on the rollers 901 and 902.

  In the internal space partitioned by the transfer material conveyance belt 900, three cooling means 904 made of a cross flow fan are provided, and the cooling means forms a lower horizontal portion 905. Cool down.

  That is, the air flow generated by the operation of the cooling means 904 flows in the direction indicated by the arrow.

  The air flow that has cooled the transfer material conveyance belt 900 is exhausted from the lower housing to the outside by another fan attached to the exhaust unit 905.

  Heating sources H1 to H5 made of ceramic heaters are built in the upper housing 95. Each heating source extends in a direction perpendicular to the transfer material conveyance direction, and the transfer material conveyance direction. Are arranged in parallel at intervals.

  As a heating source, not only the ceramic heater but also an infrared heater such as a carbon heater or a medium wavelength heater can be used.

  The heating sources H1 to H5 are provided with double reflectors 951 to 955 that cover a part of the circumferential direction on the side opposite to the transfer material conveying surface side.

  The double reflector may be integrated with the heat source or may be a separate body.

  Hereinafter, when one of the paired reflectors is described, the same reference numerals are used, for example, as an inner reflector 951 and an outer reflector 951.

  The double reflector is formed of concentric circles and has a semicircular cross section.

  Further, the position of the inner reflector is fixed, but the outer reflector is configured to be able to rotate 180 degrees.

  A two-dot chain line in the figure indicates a position after the outer reflector is rotated from a predetermined position.

  The rotation of the outer reflector is performed, for example, when the transfer material is jammed on the transfer material conveyance belt 900.

  The outer reflector after the rotation serves to block the radiant heat from the heating sources H1 to H5 from hitting the transfer material, and can prevent the transfer material P from being smoked or ignited.

  Such control includes, for example, sensors S1 and S2 for detecting the transfer material at the inlet and outlet of the fixing device and monitoring based on a timer (not shown) in the control means G. Can be achieved.

  That is, the timer in the control means G is activated according to the transfer material detection information of the sensor S1, and when the transfer material is not detected by the sensor S2 within a predetermined time, the reflector drive means such as a motor is connected via the control means G. This can be accomplished using known techniques to operate.

  Outside the double reflectors, cooling means F1 to F5 including cross flow fans for cooling the reflectors 951 to 955 are provided.

  Reference numeral 960 denotes a transfer material protection belt, which is suspended by four drive rollers 971 to 974 so as to be rotatable in the clockwise direction.

  The transfer material protection belt 960 rotates so that the surface facing the transfer material conveyance belt 900 moves in the same direction as the transfer material conveyance belt 900 at least during the fixing operation and for a predetermined time before and after the fixing operation.

  The transfer material protection belt 960 has a rectangular shape surrounding the heating sources H1 to H5, and the lower horizontal portion 961 faces the transfer material conveyance surface of the transfer material conveyance belt 900 with an appropriate gap. It is arranged.

  The transfer material protection belt 960 in the present embodiment is a single wire mesh belt, and the linear velocity during rotation is configured to be different from the linear velocity of the transfer material conveyance belt 900.

  In other words, when the time taken for the transfer material protection belt to fall into the shadow dropped on the transfer material is integrated over the time the transfer material passes through the fixing device, the integrated value is the same at any position of the transfer material. It is desirable to set.

For example, if the period of the transfer material protection belt in the transfer material conveyance direction is d, the irradiation area length of the fixing device is L, and the speed of the transfer material is vp, the transfer material protection belt speed vb is
vb = vp (1 + nd / L) However, if n is an integer other than 0, the transfer material is uniformly cast into the shadow of the transfer material protection belt at any position.

  When the shadow cast by the transfer material protection belt is sufficiently small with respect to the irradiation area, there is no practical problem even if n is not an integer.

Let r be the mesh line of the transfer material protection belt. The ratio R of the irradiation time (the time not in the shadow) of the area that has entered the shadow and the area that has a little in the shadow is
R = 1 + r / nd
However, when n is an integer, there is no difference in irradiation time depending on the region, so R has no meaning.

  In the examples to be described later, r = 0.3, d = 30, and even if n is 0.5, the dose difference is 2%, and when n is increased, the difference is further reduced.

  Accordingly, the transfer material protection belt speed vb is selected so that n is an integer, or r, d, and vb are selected so that R becomes small.

  If R ≦ 0.05, there is almost no problem in image quality.

  In addition, if the distance between the transfer material protection belt and the transfer material is large, the boundary of the shadow becomes ambiguous, so that even if there is a difference in image quality such as gloss due to the difference in irradiation amount, it is difficult to visually recognize.

  According to the experiment, when the distance between the transfer material protection belt and the transferred transfer material is h, if r / h ≦ 0.05, uneven gloss due to non-uniform irradiation is, for example, Even if the transfer material is driven / conveyed at a moving speed, it is hardly understood with the naked eye.

  In the examples described later, both conditions are satisfied, and no gloss difference due to uneven irradiation is observed.

  For example, the linear velocity of the transfer material protection belt 960 may be slower or faster than the linear velocity of the transfer material conveyance belt 900, and the degree can be determined as appropriate.

  The reason for making the moving speeds different from each other in this way is that the surface of the transfer material is uniformly irradiated with the radiant heat from the heating source.

  An opening 981 is provided in the housing 95 in a region facing the upper horizontal portion 963 of the transfer material protection belt 960, and an exhaust fan (blower fan) 982 is attached to the opening. Yes.

  The exhaust fan 982 and the following opening 983 substantially function as cooling means for cooling the transfer material protection belt 960.

  Reference numeral 983 is an air inflow opening formed in the housing 95.

  With the above-described configuration, when the operation of the fan 982 is controlled, outside air flows in through the opening 983. The inflowing outside air cools the transfer material protection belt 960 located in the horizontal portion 963, and then The air is exhausted through the fan 982.

  The operation of the fixing device having the above-described configuration is summarized as follows.

  When the transfer material P having the toner image transferred by the transfer means is fed into the fixing device, the sensor S1 detects the transfer material P, the information is taken into the control means S, and a timer is started.

  The transfer material P is adsorbed by the transfer material conveyance belt 900 and conveyed in a predetermined direction. After being exposed to radiant heat from the heating sources H1 to H5, the transfer material P is discharged out of the fixing device and the fixing process is completed.

  When the transfer material P is detected by the sensor S2 on the outlet side immediately before the discharge, the information of the sensor S2 is taken into the control means S and the timer is reset.

  In the fixing region, since the linear speeds of the transfer material conveyance belt 900 and the transfer material protection belt 960 are different, uniform radiant heat is applied to the entire surface of the transfer material P, and the toner is satisfactorily fixed.

  In such an operation, the transfer material conveying belt 900 is cooled by the air flow generated by the operation of the cooling means 904, and the transfer material protection belt 960 is generated by the operation of the exhaust fan 982. It is cooled by.

  Since the cooled airflow is exhausted outside the apparatus, the temperature in the fixing device is always kept within a predetermined range.

  Next, a case where the transfer material is jammed in the fixing device will be described as follows.

  When the transfer material P having the toner image transferred by the transfer means is fed into the fixing device, the sensor S1 detects the transfer material P, the information is taken into the control means S, and a timer is started.

  If the transfer material P is not detected by the sensor S2 within the set predetermined time, the determination means in the control means S determines that a trouble has occurred, and the control means S drives the reflector drive means via the drive circuit, The reflector is rotated 180 degrees.

  At the same time, the power supply of the heating source is stopped.

  The rotation of the outer reflectors (951 to 955) prevents radiant heat from the heating sources (H1 to H5) from being applied to the transfer material conveyance surface, so that smoke and ignition of the transfer material P are prevented. .

  Further, since the outer reflector is cooled by the cooling means F1 to F5, when the transfer material transport belt is rotated and shielded from the heating source, the reflector itself can prevent the transfer material from being heated as much as possible.

  It should be noted that the controller S resets the sensor S2 by using a pull-out signal when the fixing device is pulled out, or after the jammed transfer material P is removed, and a return signal to a predetermined position of the fixing device. Then, the count of the number of formed images is corrected.

  Furthermore, after the control necessary for performing the function as the fixing device is performed, such as returning the reflector to the initial position or restarting the power supply to the heating source in accordance with the return of the fixing device to the initial position. Then, image formation based on the image formation process is resumed.

  As described above, the fixing device according to the present invention makes the transfer material protection belt rotatable, and prevents the temperature of the transfer material protection belt from reaching the ignition point (about 300 ° C.) of the transfer material. It is characterized by a structure that is cooled by a cooling means, and is highly versatile.

  In addition, for the cooling of the transfer material protection belt, a space is formed above the reflector 990 shown horizontally on the outside of the reflector, and another cooling fan is additionally arranged there, and the transfer material protection belt is attached. It can also be configured to cool from the inside.

  This also has the advantage of cooling the aforementioned outer reflector.

  Furthermore, although the transfer material protection belt has been described as a wire mesh belt, the mesh does not have to be a woven mesh, and may have a mesh shape by etching or the like.

  In this case, it is desirable to configure the belt so that the base material forming the mesh is inclined with respect to the moving direction of the belt.

  An example of the mesh shape is shown in FIG.

  The belt may not be in the form of a mesh. For example, a number of wires are integrally formed so as to be parallel to each other, and as described above, the wires are inclined with respect to the moving direction of the belt. A configured belt may also be used.

  Furthermore, a belt formed of a base material itself corresponding to the wire may be used, and the shape and the like are not restricted as long as the intended purpose can be achieved.

  A fixing device having the following configuration was incorporated in a color copier similar to the image forming apparatus shown in FIG. 1, and an experiment for confirming the fixing property and the temperature rise state of the transfer material protection belt was conducted.

  Heat source: Ceramic heater 350 mm x 60 mm (single surface area) x 5 sheets (5 kW), surface layer is black painted and controlled at around 700 ° C.

  Reflector for ceramic heater: The outer reflector diameter was 85 mm, the inner reflector diameter was 70 mm and the thickness was 1 mm, and each inner surface was mirror finished.

  Transfer material protection belt: made of 18-8 stainless steel having a width of 400 mm, a belt diameter of φ350 mm, and a wire diameter of 0.3 mm, a mesh area of 30 mm × 30 mm, a moving linear velocity of 300 mm / sec, and the mesh has an angle with respect to the moving direction. Constitution.

  Driving roller for the transfer material protection belt (four): an aluminum pipe having an outer diameter of 40 mm and a thickness of 3 mm.

Capacity of cooling means (blower fan) for transfer material protection belt: 2.7 m ³ / min
Transfer material conveying belt: belt width 80 mm × 3, belt diameter φ500 mm, PI base belt, no rubber layer, with perforation, moving linear velocity 400 mm / sec.

  Suspension roller (2) for transfer material conveying belt: 400mm wide, 40mm outer diameter, made of aluminum (surface gloss treatment), with sprocket.

Distance between transfer material protection belt and transfer material transport belt: 50 mm
Transfer material transport belt cooling means (cross flow fan): 3 units, length 400 mm x width 60 mm
Reflector cooling means (cross flow fan): 3 units, length 400 mm x width 60 mm
Transfer material: 200 to 250 g / m ² coated paper.

  In the experiment, a full-color toner image continuously formed by the image forming means is transferred to a transfer material, adsorbed on a transfer material conveyance belt having a linear velocity of 400 mm / sec, and conveniently 1000 sheets by a heat source that is continuously energized. Fixing treatment was performed on the transfer material.

  As a result, the transfer material protection belt was rotatable, and no transfer material jam occurred.

  The fixing state of the toner image was good, and the temperature of the transfer material protection belt using the contact type temperature detection sensor could be kept at 250 ° C. or lower.

  This is a temperature at which there is no fear of igniting even if a transfer material that has caused jamming contacts.

  For example, even when a jam occurs, the transfer material conveyance belt is continuously driven to forcibly discharge the transfer material, the heating source is stopped simultaneously with the rotation of the reflector, or a combination of these is adopted. As a result, the safety at the time of jam can be further enhanced.

1 is a schematic diagram illustrating a configuration of an image forming apparatus including a digital color copying machine. FIG. 2 is an explanatory diagram conceptually showing a fixing device. It is a conceptual diagram which shows the structure of a transfer material conveyance belt. It is a figure which shows an example of a mesh shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Automatic document feeder 2 Image reading part 3 Image forming part 4 Belt unit 5 Paper feed part 6 Reverse discharge / re-feed part 900 Transfer material conveyance belt 904 Cooling means 951,952,953,954,955 Reflector 960 Transfer material Protective belt 982 Exhaust fan F1, F2, F3, F4, F5 Cooling means H1, H2, H3, H4, H5 Heat source

Claims (9)

In a fixing device for fixing a toner image on a transfer material by heating with radiant heat,
A heating source;
A transfer material protection belt that is rotatably provided around the heating source;
A transfer material transport belt provided opposite to the transfer material protection belt;
Cooling means for cooling the transfer material protection belt;
And a fixing device. The fixing device according to claim 1, wherein a double reflector is attached to the heating source, and an outer reflector is rotatable. The fixing device according to claim 1, wherein the transfer material protection belt is a wire mesh belt. The fixing device according to claim 1, wherein the heating source is an infrared heater. Image forming means for forming a toner image on a transfer material;
A fixing device according to any one of claims 1 to 4,
An image forming apparatus comprising: A heating source;
A double reflector attached to the heating source;
Of the reflectors, the outer reflector is rotatable,
A transfer material protection belt which is rotatably provided around the heating source;
A transfer material transport belt provided opposite to the transfer material protection belt;
A fixing device having cooling means for cooling the transfer material protection belt;
Image forming means for forming a toner image on a transfer material;
Control means, and
The control means performs drive control so as to block the radiant heat from the heating source by rotating the outer reflector when the transfer material conveyed by the transfer material conveyance belt is jammed. Image forming apparatus. The image forming apparatus according to claim 5, wherein the transfer material protection belt is a wire mesh belt. The image forming apparatus according to claim 5, wherein the heat source is a ceramic heater. 9. The image forming apparatus according to claim 5, wherein linear velocities of the transfer material conveyance belt and the transfer material protection belt are different from each other.

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