JP2007047380A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of eliminating moisture-sticking on transfer paper by preventing due condensation on the separation plate, and an image forming apparatus equipped with the fixing device. <P>SOLUTION: The fixing device has a fixing belt (fixing member) 2 which is heated by a halogen lamp (heating means) 7, a pressure roller (pressure member) 5 pressed against the fixing belt (fixing member) 2, a nip part 15 comprising the fixing belt (fixing member) 2 and pressure roller (pressure member) 5, and the separation plate 10 which separates transfer paper, passed through and discharged from the nip part 15, from the fixing belt (fixing member) 2, and is equipped with an MPU (control means) 9 of performing control so as to start paper passing through the nip part 15 when the separation plate 10 is sufficiently warmed up by conducting heat from the fixing belt (fixing member) heated by the halogen lamp (heating means) 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing device that prevents moisture from adhering to transfer paper, and an electrophotographic image forming apparatus such as a printer and a copying machine including the fixing device.

  2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as a printer or a copying machine, an original image is first read by an original reading unit, and then the original reading unit is placed on an electrostatic latent image carrier such as a photosensitive drum of the image forming unit. The electrostatic latent image is formed by performing image exposure corresponding to the original image read in step (b). Further, the electrostatic latent image is developed into a visible toner image, and the toner image is transferred onto a recording sheet or the like conveyed from a recording material supply unit, fixed, and discharged to a paper discharge unit or the like. Take the configuration.

  In the fixing device, a fixing member such as a fixing roller or a fixing belt and a pressure roller pressed against the fixing member are conveyed while sandwiching the paper, and the toner image is fixed on the transfer paper with heat and pressure. Yes.

  Further, there is a known problem that the fixed transfer sheet has an image forming surface wrapped around the fixing member due to the adhesiveness of the toner unless the fixing device is provided with a separation function. Therefore, in order to prevent the transfer paper from being wound, a separation member, for example, a separation claw, is installed so as to be pressed against the surface of the fixing member using a spring. The width of the leading edge of the separation claw in contact with the surface is about 2 mm, and usually about 5 to 6 such narrow separation claws are arranged in the axial direction of the fixing member.

  As described above, since the separation claw is only partially in contact with the surface of the fixing member, a non-uniform pressing force is applied to the surface of the fixing member in the axial direction by the separation claw, and the fixing member wears unevenly. Or scratch the surface. In addition, when the transfer paper is caught by any one of the plurality of separation claws and the transfer paper is wound, the adjacent separation claws receive an abnormal force from the transfer paper and are applied to the fixing member. The fixing member may be strongly pressed or the separation claw may be deformed to cause a large scratch on the surface of the fixing member or cause uneven wear.

Therefore, in recent years, a non-contact type separation plate that does not contact the fixing member is provided as the separation member. As a fixing method using a separation plate, there are those disclosed in Japanese Patent Laid-Open Nos. 2001-83832 and 2003-122175.
JP 2001-83832 A JP 2003-122175 A

  However, in the above-described separation method using the separation plate, for example, even when the preparation for printing immediately after the start of the printer is ready, the separation plate is not sufficiently warmed. For this reason, if the paper is passed immediately after rising, when the transfer paper passes through the nip, the moisture contained in the transfer paper becomes water vapor and condenses on the separation plate. There is a problem that it adheres and stains the transferred image.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fixing device that can prevent condensation on the separation plate and eliminate moisture adhesion to the transfer paper, and an image forming apparatus including the fixing device.

  According to the first aspect of the present invention, there is provided a fixing member heated by a heating means, a pressure member pressed against the fixing member, a nip portion composed of the fixing member and the pressure member, and a passage through the nip portion. And a separation plate for separating the transfer paper discharged from the fixing member from the fixing member, wherein heat is transmitted from the fixing member heated by the heating means and the separation plate is sufficiently warmed. In some cases, the fixing device includes a control unit that controls to start the sheet passing through the nip portion.

  The invention according to claim 2 further includes first temperature detecting means for detecting the temperature of the fixing member, and the control means can fix the temperature of the fixing member by a detection signal of the first temperature detecting means. 2. The fixing device according to claim 1, wherein the fixing device is controlled so as to start passing the paper to the nip portion after a predetermined time has elapsed from the time when the temperature is detected.

  The invention according to claim 3 further includes second temperature detection means for detecting the temperature of the separation plate, and the control means can fix the temperature of the fixing member by a detection signal of the first temperature detection means. Control is made so that when the temperature is detected and it is detected by the detection signal of the second temperature detection means that the temperature of the separation plate has reached a predetermined temperature, the sheet feeding to the nip portion is started. The fixing device according to claim 2, wherein the fixing device is a fixing device.

  The invention according to claim 4 further includes a displacement means for displacing the position of the separation plate, and the separation plate is disposed at a contact position where the separation plate comes into contact with the fixing member. 4. The fixing device according to claim 1, wherein at the same time, the displacement unit displaces the contact position to a non-contact position that does not contact the fixing member. 5.

  A fifth aspect of the present invention is an image forming apparatus comprising the fixing device according to any one of the first to fourth aspects.

  According to the first aspect of the present invention, the fixing member heated by the heating means, the pressure member pressed against the fixing member, the nip portion composed of the fixing member and the pressure member, and the sheet is passed through the nip portion. And a separation plate for separating the transfer paper discharged from the fixing member, when heat is transmitted from the fixing member heated by the heating means and the separation plate is sufficiently warmed, Since it has a control unit that controls to start the paper feeding, even if moisture is generated from the transfer paper, the separation plate is sufficiently warmed so that the moisture does not condense on the separation plate. Image contamination can be prevented.

  According to a second aspect of the present invention, the fixing device according to the first aspect further comprises first temperature detecting means for detecting the temperature of the fixing member, and the control means is based on a detection signal of the first temperature detecting means. Control is performed so that the passage of paper to the nip portion is started after a predetermined time has elapsed from the time when it is detected that the temperature of the fixing member has reached the fixable temperature. Thereby, since the separation plate is sufficiently warmed, dew condensation on the separation plate can be prevented.

  According to a third aspect of the present invention, the fixing device according to the second aspect further comprises second temperature detecting means for detecting the temperature of the separation plate, and the control means is based on a detection signal of the first temperature detecting means. When it is detected that the temperature of the fixing member has reached the fixable temperature and it is detected by the detection signal of the second temperature detection means that the temperature of the separation plate has reached a predetermined temperature, the sheet is passed through the nip portion. Control to start. Thereby, it is possible to reliably prevent image smearing on the transfer paper. Further, since the temperature of the separation plate can be detected, dew condensation on the separation plate can be prevented. Further, since the sheet passing to the nip portion is started immediately after the separating plate reaches the predetermined temperature, the time required for fixing can be shortened.

  According to a fourth aspect of the present invention, the fixing device according to any one of the first to third aspects further includes a displacement means for displacing the position of the separation plate, and the separation plate is in contact with the fixing member. At the same time as the sheet is fed to the nip portion, the displacement means displaces the contact position to the non-contact position where it does not contact the fixing member, so that wear of the fixing belt can be reduced. Further, since the displacement means is provided, the separation plate can be warmed more quickly when the separation plate is in contact with the fixing member.

  According to the image forming apparatus of the fifth aspect of the present invention, since the fixing device according to any one of the first to fourth aspects is provided, the image forming apparatus having the above-described effects and performing good image formation. An image forming apparatus capable of performing the above can be obtained.

  Embodiments for carrying out the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an image forming apparatus to which the fixing device of the present invention is applied. The image forming apparatus may be any of a copying machine, a facsimile, a printer, and the like. Here, a full color laser printer as a color image forming apparatus is shown. The full-color laser printer has a configuration in which a two-stage sheet feeding unit 42 is disposed below the apparatus main body 41 and an image forming unit 43 is disposed thereon. In this printer, plain paper generally used for copying or the like (hereinafter simply referred to as plain paper), OHP sheet, 90K paper such as card or postcard, thick paper equivalent to a basis weight of about 100 g / m ² or more, envelope, etc. Any so-called special sheet (hereinafter simply referred to as a special sheet) having a heat capacity larger than that of plain paper can be used as the sheet-like medium.

  Further, the image forming unit 43 is provided with a transfer belt device that is disposed so as to be inclined so that the paper feed side is on the bottom and the paper discharge side is on the top. A fixing device 55 is provided adjacent to the transfer belt device.

  The transfer belt device includes a plurality of rollers 51, in this example, an endless transfer belt 52 wound around four rollers 51, and one of the rollers 51 is driven by a drive source (not shown). As a result, the transfer belt 52 rotates. Four image forming units 44M, 44C, 44Y, 44BK for magenta (M), cyan (C), yellow (Y), and black (BK) are arranged in parallel on the upper running side of the transfer belt 52 from the bottom. ing.

  Each of the image forming units 44M, 44C, 44Y, 44BK is provided with a photosensitive drum 45 as an image carrier, and the photosensitive drum 45 is driven to rotate clockwise as viewed in the figure by a driving means (not shown). It is supposed to be. Around the photosensitive drum 45, a charging roller 46 as a charging unit, an optical writing unit in which laser beam writing is performed by an optical writing device 48, a developing device 50, and a cleaning device 49 are provided. The developing device 50 is a two-component developing device and is replenished with toner by a later-described toner replenishing / conveying device corresponding to the amount of consumed toner.

  Next, an image forming operation for performing full color printing of the color printer having the above-described configuration will be described using the magenta image forming unit 44M. The photosensitive member 45 charged by the charging roller 46 is driven by an LD (laser diode) (not shown) to irradiate the polygon mirror 48a with laser light, and the reflected light is applied onto the photosensitive member 45 through a cylinder lens or the like. The optical writing device 48 that guides the optical writing of the optical image to be developed with magenta toner. By this writing, an electrostatic latent image is formed on the photosensitive member 45 based on image data sent from a host machine such as a personal computer, and the latent image becomes a visible toner image by the developing device 50.

  On the other hand, a sheet-like medium designated as a transfer material is fed from the paper feeding unit 42, and the fed sheet-like medium is once abutted against a registration roller 53 provided on the upstream side in the conveyance direction of the transfer belt 52. After that, the sheet is fed onto the transfer belt 52 in synchronism with the visible image, and reaches the transfer position facing the photoconductor 45 by the running of the belt. At this transfer position, a visible image of magenta toner is transferred to the sheet-like medium by the action of the transfer roller 54 disposed on the back side of the transfer belt 52.

  In the same manner as described above, in the other image forming units 44C, 44Y, and 44BK, visible images are formed by the respective toners on the surfaces of the respective photoreceptors 45, and these visible images are sheet-like conveyed by the transfer belt 52. Each time the medium arrives at each transfer position, the transfer is overlaid. Therefore, in this color printer, a full-color image is transferred onto a sheet-like medium in a short time that is almost the same as that of monochrome. The sheet-like medium after the transfer is separated from the transfer belt 52 and fixed by the fixing device 55. The sheet-like medium that has been fixed is normally discharged out of the apparatus as it is. At this time, the sheet-like medium is reversed and discharged onto the discharge tray 56 provided on the upper surface of the apparatus main body 41.

  Next, the details of the separation plate type fixing device 55 used in the full color laser printer as the image forming apparatus of the present invention will be described.

  (Basic Configuration of Fixing Device) First, the basic configuration of a separation plate type fixing device will be described with reference to the schematic diagram of FIG. The fixing device shown in FIG. 2 is a device that fixes toner, and transfers toner by pressure and heat by passing a transfer sheet (not shown) through a nip portion 15 that is pressed by a fixing belt 2 and a pressure roller 5. Fix on paper. Further, a heating roller 3 for stretching the fixing belt 2 is provided, and the fixing belt 2 is stretched by the fixing roller 4 and the heating roller 3. A tension roller 6 for attaching tension to the fixing belt 2 is attached. The tension roller 6 is made of a heat insulating felt having an outer shape of 12 mm.

  The fixing roller 4 is a fixing roller having a cored bar part outer diameter φ12 mm, a journal part outer diameter 10 mm, an outer diameter φ30 mm around the cored bar, a length 310 mm, and a material made of silicone sponge. The heating roller 3 is a heating roller having an outer diameter of 30 mm and a length of 310 mm with a thickness of aluminum of 0.6 mm.

  A fluororesin coat is applied to the outer periphery of the heating roller 3. The heating roller 3 has a hollow shape, and a 1200 W halogen lamp 7 for heating the fixing belt 2 is attached to the center of the heating roller 3 as a heat source. The lighting of the halogen lamp 7 is controlled by a control output from an MPU (microprocessor unit) 9 to which a detection signal of the temperature sensor 8 is supplied, so that the temperature of the fixing belt 2 is controlled to a fixing possible temperature. Is done.

  Further, the fixing belt 2 stretched between the fixing roller 4 and the heating roller 3 is composed of a silicone rubber having a thickness of 200 μm on a polyimide substrate having an outer diameter of φ60 and a thickness of 100 μm, and PFA having a thickness of 30 μm thereon. Fixing belt.

  A temperature sensor 8 such as a thermistor for detecting the temperature of the fixing belt 2 is disposed near the heating roller 3. The pressure roller 5 facing the fixing roller 4 with the fixing belt 2 interposed therebetween is a pressure roller having a silicone rubber having a thickness of 1 mm on a mandrel having a journal portion of 20 mm, a barrel portion of 40 mm, and a length of 310 mm. The pressure roller 5 is in pressure contact with the fixing belt 2 and the fixing roller 4 by a spring (not shown).

  A separation plate 10 for separating the transfer paper passed through the nip portion 15 from the fixing belt 2 is attached at an appropriate position. The separation plate 10 has a shape obtained by bending a flat plate into a substantially “<” shape, and has a width corresponding to the width in the axial direction of the fixing belt 2, that is, the entire width in the direction perpendicular to the paper surface. In addition, resin parts (not shown) for securing a gap between the fixing belt 2 and the leading end of the separation plate 10 are provided at both ends in the width direction of the separation plate 10, and non-image portions (that is, the fixing belt 2). In addition, a gap is provided in contact with the non-sheet-passing region, which is both end regions in the width direction of the fixing belt 2. The gap is set to such a size that the transfer sheet can be peeled off from the fixing belt 2 by the separation plate 10, whereby the separation plate 10 is a non-contact type in which the portion to be peeled does not contact the fixing belt 2. Acts as a separator. Note that such a non-contact type separation plate is disclosed in, for example, the above-mentioned Patent Document 1 (Japanese Patent Laid-Open No. 2001-83832).

  The fixing device having such a basic configuration is mounted as the fixing device 55 of the full-color laser printer shown in FIG. 1, and paper is passed through the nip portion of the fixing device to confirm moisture adhesion to the transfer paper. It was. In addition, A3 plain paper was used as the paper used for paper feeding. As a result, when the sheet was passed immediately after the printer was started up, it was confirmed that moisture was adhered to the transfer sheet up to the seventh sheet.

  (First Embodiment of Fixing Device of the Present Invention) Next, a first embodiment of a fixing device applied to an image forming apparatus of the present invention will be described below. As shown in FIG. 3, the fixing device of the first embodiment has almost the same configuration as the basic configuration of FIG. 2. 2 is different from the basic configuration of FIG. 2 in that the separation plate 10 is not provided with resin parts for securing a gap between the fixing belt 2 and the separation plate 10, and the front end portion of the separation plate 10 is energized. A spring (not shown) as a means is constantly urged to be in a contact position where it contacts the surface of the fixing belt 2, and the separation plate 10 is separated from the fixing belt 2 against the urging force of the spring. Displacement means for providing a non-contact position is provided.

  The displacement means includes an actuator 11 that is driven and controlled by a control output from the MPU 9, a separation plate push-up member 12 that is connected to the actuator 11 and separates the separation plate 10 from the fixing belt 2, and the separated separation plate And a separation plate pressing member 13 for stopping 10 at a predetermined non-contact position.

  Further, for the separation plate 10, a separation plate having a PFA coat applied to the front end portion in contact with the fixing belt 2 is used in order to reduce the frictional force at the time of contact with the fixing belt 2.

  Therefore, the fixing device having the configuration shown in FIG. 3 is mounted as the fixing device 55 of the full-color laser printer shown in FIG. 1, and the separation plate 10 is detached from the fixing belt 2 by the displacing means after a predetermined time has elapsed since the printer was turned on. Is performed by the MPU 9.

  That is, when the power is turned on, the fixing device 55 starts operating, and the fixing belt 2 rotates while the separation plate 10 is in contact. After the power is turned on, the MPU 9 detects that the temperature of the fixing belt 2 heated by the lighting of the halogen lamp 7 has reached a fixable temperature (for example, 160 ° C.) by the detection signal of the temperature sensor 8.

  Next, when the MPU 9 determines that a predetermined time (for example, 30 seconds) has elapsed from the time when the fixable temperature is reached by counting up the built-in timer, the MPU 9 issues a command to start passing the transfer paper to the nip portion 15. At the same time, the control signal is supplied to the actuator 11 to drive the actuator 11. As a result, the separation plate push-up member 12 connected to the actuator 11 moves to the separation plate 10 side to disengage the separation plate 10 from the fixing belt 2, and the separation plate pushing member 13 is moved to the separation plate pushing member 13 as shown in FIG. It pushes up to the predetermined non-contact position which contacts. As a result, the separation plate 10 is held at the non-contact position where the above-mentioned gap is formed between the separation plate 10 and the fixing belt 2 as described in the basic configuration of FIG.

  As described above, until the fixing belt 2 is heated up to the fixing temperature after the power is turned on and a predetermined time (for example, 30 seconds) elapses, the leading end of the separation plate 10 contacts the surface of the fixing belt 2 to be heated. Therefore, since the heat is transmitted from the fixing belt 2, the separation plate 10 is warmed faster than before. The reason why the separation plate 10 is detached from the fixing belt 2 after a predetermined time has elapsed is that if the separation plate 10 is kept in contact with the fixing belt 2, the surface of the fixing belt 2 is quickly worn out. Therefore, after the power supply to the fixing device is turned on and the fixing belt 2 reaches a fixing possible temperature of 160 ° C., only for a predetermined time (for example, 30 seconds) (in other words, until the separation plate 10 is sufficiently warmed). 10 is in contact with the fixing belt 2.

  Then, in the full-color laser printer of FIG. 1 equipped with the fixing device having the configuration of FIG. 3, paper is passed through the nip portion of the fixing device under the same conditions as when the fixing device having the configuration of FIG. When water adhesion to the transfer paper was confirmed, water adhesion to the transfer paper was not confirmed. This is because the fixing device rotates while the separation plate 10 is in contact with the fixing belt 2 until the fixing belt 2 reaches a fixing possible temperature of 160 ° C. and a predetermined time (for example, 30 seconds) elapses. This is because the separation plate 10 warms up quickly.

  (Second Embodiment of Fixing Device of the Present Invention) Next, a second embodiment of the fixing device applied to the image forming apparatus of the present invention will be described below. As shown in FIG. 5, the fixing device of the second embodiment has almost the same configuration as the configuration example 1 of FIG. The difference from the configuration example 1 in FIG. 3 is that a temperature sensor 14 for detecting the temperature of the separation plate 10 is further provided at the center of the separation plate 10.

  Therefore, the fixing device having the configuration shown in FIG. 5 is mounted as the fixing device 55 of the full-color laser printer of FIG. 1, and after the printer is turned on, the temperature of the fixing belt 2 reaches a fixing possible temperature (for example, 160 ° C.) When the temperature of the separation plate 10 reaches a predetermined temperature (for example, 90 ° C.), the MPU 9 performs control for detaching the separation plate 10 from the fixing belt 2 by the displacing means.

  That is, when the power is turned on, the fixing device 55 starts operating, and the fixing belt 2 rotates while the separation plate 10 is in contact. The MPU 9 monitors the temperature of the fixing belt 2 and the separation plate 10 with the detection signals of the temperature sensors 8 and 14 after the power is turned on.

  When the MPU 9 determines that the temperature of the fixing belt 2 has reached a fixable temperature (for example, 160 ° C.) and the temperature of the separation plate 10 has reached a predetermined temperature (for example, 90 ° C.), the MPU 9 moves to the nip portion 15 of the transfer paper. At the same time as sending a command signal for instructing the start of paper feeding, a control output is supplied to the actuator 11 to drive the actuator 11. As a result, the separation plate push-up member 12 connected to the actuator 11 moves to the separation plate 10 side, disengages the separation plate 10 from the fixing belt 2, and as shown in FIG. It pushes up to the predetermined non-contact position which contacts. As a result, the separation plate 10 is held at the non-contact position where the above-mentioned gap is formed between the separation plate 10 and the fixing belt 2 as described in the basic configuration of FIG.

  As described above, after the power is turned on, until the temperature of the fixing belt 2 reaches a fixable temperature (for example, 160 ° C.) and the temperature of the separation plate 10 reaches a predetermined temperature (for example, 90 ° C.) Since the portion is in contact with the surface of the fixing belt 2 to be heated, the separation plate 10 is warmed faster than before.

  Then, in the full-color laser printer of FIG. 1 equipped with the fixing device having the configuration of FIG. 3, paper is passed through the nip portion of the fixing device under the same conditions as when the fixing device having the configuration of FIG. When water adhesion to the transfer paper was confirmed, water adhesion to the transfer paper was not confirmed in this case as well. The time when the fixing of the first sheet was started was 8 seconds, the waiting time required for the temperature of the separation plate 10 to reach 90 ° C. from the time when the fixing belt 2 reached 160 ° C.

  Therefore, the fixing device according to the second embodiment can shorten the fixing start time by 22 seconds as compared with the fixing device according to the first embodiment. This is because by attaching the temperature sensor 14 to the separation plate 10, sheet feeding and fixing are started as soon as the separation plate 10 reaches a predetermined temperature.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various deformation | transformation and application are possible.

1 is a schematic configuration diagram of an image forming apparatus to which a fixing device of the present invention is applied. FIG. 2 is a schematic configuration diagram illustrating a basic configuration of a separation plate type fixing device. 1 is a schematic configuration diagram illustrating a first embodiment of a fixing device of the present invention applied in an image forming apparatus. It is a figure explaining operation | movement of the fixing device of FIG. It is a schematic block diagram which shows 2nd Embodiment of the fixing device of this invention applied with an image forming apparatus. It is a figure explaining operation | movement of the fixing device of FIG.

Explanation of symbols

2 Fixing belt (fixing member)
5 Pressure roller (Pressure member)
7 Halogen lamp (heating means)
8 Temperature sensor (first temperature detection means)
9 MPU (control means)
10 Separation plate 11 Actuator (part of displacement means)
12 Separating plate push-up member (part of displacement means)
13 Separating plate pressing member (part of displacement means)
14 Temperature sensor (second temperature detection means)
15 Nip part

Claims (5)

A fixing member that is heated by a heating unit; a pressure member that is in pressure contact with the fixing member; a nip portion that includes the fixing member and the pressure member; and a transfer sheet that passes through the nip portion and is discharged. A fixing device having a separating plate for separating the fixing member from the fixing member,
Control means is provided for controlling to start passing the paper through the nip portion when heat is transmitted from the fixing member heated by the heating means and the separation plate is sufficiently warmed. Fixing device. A first temperature detecting means for detecting the temperature of the fixing member;
The control means starts paper passage to the nip portion after a predetermined time has elapsed from the time when it is detected by the detection signal of the first temperature detection means that the temperature of the fixing member has reached a fixable temperature. The fixing device according to claim 1, wherein the fixing device is controlled as follows. A second temperature detecting means for detecting the temperature of the separation plate;
The control means detects that the temperature of the fixing member has reached a fixable temperature based on the detection signal of the first temperature detection means, and the temperature of the separation plate is detected based on the detection signal of the second temperature detection means. 3. The fixing device according to claim 2, wherein when the temperature reaches a predetermined temperature, the fixing device is controlled so as to start passing the paper to the nip portion. Displacement means for displacing the position of the separation plate is further provided,
The separation plate is disposed at a contact position that contacts the fixing member, and is displaced from the contact position to a non-contact position that does not contact the fixing member by the displacing means at the same time as the paper passage to the nip portion is started. The fixing device according to any one of claims 1 to 3, wherein the fixing device is any one of the above. An image forming apparatus comprising the fixing device according to claim 1.

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