JP2007248664A - Belt-fixing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten a warm-up time and to stabilize fixing roller temperature, by efficiently conducting the heat of a heating means disposed in a fixing belt to a nip part between the fixing belt and a pressure roller. <P>SOLUTION: A belt fixing unit has an endless fixing belt 1 is tensed between a fixing roller 2 and a heat roller having a built-in heater 5; a sub heat roller 16 disposed inside the fixing belt 2 across a heater lamp 18, powered to generate heat and heating the fixing roller 2 in contact with the surface of the fixing roller 2 along the length; and the pressure roller pressed against the fixing roller 2 across the fixing belt 1, and performs fixing via transfer paper P, carrying a toner image T to be fixed at the nip part N between the fixing belt 1 and a pressure roller 3. The sub heat roller 16 is arranged to undergo disjunction from the surface of the fixing roller 2, and the fixing unit is equipped with solenoids 25 and 26, which make the sub heat roller 16 undergo disjunction from the surface of the fixing roller 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing belt type fixing device used in an image forming apparatus such as a copying machine or a laser printer.

  In the fixing device for fixing the color toner by passing the transfer paper through the nip portion of the fixing roller and the pressure roller, it is necessary to melt and mix the toner of each color and discharge it without being wound around the fixing roller. Ensuring a sufficient nip width is a problem.

  Therefore, the nip width was obtained by forming the surface layer of the fixing roller and the pressure roller with a thick elastic body. However, when heated by the heater inside the fixing roller, the elastic layer at the core metal boundary has a high temperature. Thus, the elastic body is hardened and liquefied, resulting in a short life.

  As a countermeasure, a thin belt with a low heat capacity is heated by wrapping it around a heating roller with a built-in heat source, and the heated fixing belt is a nip formed by the pressure contact between the fixing roller and the pressure roller. There has been proposed a belt fixing device for fixing by heating and melting.

  However, in such a belt fixing device, since the fixing belt is heated by the heater built in the heating roller, the heat from the heater is transmitted in the order of the heating roller, the fixing belt back surface, and the fixing belt surface. There is a problem that it takes a long time to raise the temperature to a desired temperature, and it takes a long time to warm up the fixing device.

  Therefore, in order to shorten the warm-up time, Japanese Patent Application Laid-Open No. H10-228688 discloses a technique in which a pressure roller is pressed against a fixing roller via an endless fixing belt stretched between a fixing roller and a support roller. It has been proposed to place a heating roller in contact with the outer peripheral surface of the fixing belt upstream in the belt running direction from the nip portion between the belt and the pressure roller.

Further, Patent Document 2 includes an adjustment roller that is a pressure member that applies belt tension based on the detection result of a temperature detection sensor that detects the temperature of the surface of the fixing belt and the like in order to shorten the warm-up time. It has been proposed to adjust the contact range of the fixing belt with the fixing roller having a heat source and the heating roller by adjusting the elastic force of the fixing belt with an adjusting mechanism.
Japanese Patent Laying-Open No. 2005-99104 (see paragraphs 0030 and 0031 and FIG. 2) Japanese Patent Laying-Open No. 2005-257824 (see paragraphs 0023 to 0025, FIGS. 2, 5, and 6)

  However, in the conventional techniques proposed in Patent Document 1 and Patent Document 2 described above, since a load (tension) is applied to the fixing belt itself, a problem occurs in the running performance of the fixing belt, and a separate countermeasure member is provided. There is a problem of increasing the cost.

  The present invention has been made in view of the above-described conventional problems, and shortens the warm-up time by efficiently transferring the heat of the heating means disposed inside the fixing belt to the nip portion between the fixing belt and the pressure roller. And to stabilize (uniformize) the temperature of the fixing roller.

  In order to achieve the above object, the present invention is disposed inside the fixing belt via an endless fixing belt stretched between a fixing roller and a heating roller incorporating a heater, and a heating member that generates heat when energized. A heating unit that heats the fixing roller in contact with the surface of the fixing roller in a longitudinal direction; and a pressure roller that presses against the fixing roller via the fixing belt. In a belt fixing device provided in an electrophotographic image forming apparatus that performs fixing through a transfer paper carrying a fixing toner image in a nip portion, the heating means is disposed so as to be detachable from the surface of the fixing roller, and the heating The image forming apparatus includes a contact / separation unit for separating the unit from the surface of the fixing roller.

  According to this configuration, the heating unit can be separated from the surface of the fixing roller as necessary.

  For example, when a temperature detecting means for detecting the temperature of the fixing roller heating part of the heating means detects a temperature equal to or higher than a predetermined temperature, energization to the heat generating member is stopped and the heating means is fixed by the separation / contact means. It is separated from the roller surface.

  According to this, when an abnormality occurs in the fixing temperature control, the heating means moves away from the surface of the fixing roller almost simultaneously with stopping the energization of the heat generating member, so that the abnormally high temperature state of the fixing belt can be released.

  Alternatively, when the image forming operation is not performed for a predetermined time, the energization to the heating member is stopped and the heating unit is separated from the fixing roller surface by the separation / contact unit.

  According to this, the load of the fixing roller can be reduced and the deformation can be prevented because the heating unit is separated from the surface of the fixing roller during standby for the image forming operation.

  Alternatively, when detecting a jam on the transfer paper or when detecting a service man's call, the energization of the heating member is stopped and the heating unit is separated from the surface of the fixing roller by the separation / contact unit.

  According to this, even when the machine main body of the image forming apparatus detects an abnormality, the heating means is separated from the surface of the fixing roller almost simultaneously with the stop of energization of the heat generating member, so that the abnormally high temperature state of the fixing belt can be released.

  A solenoid can be suitably used as the connecting / disconnecting means, and the connecting / disconnecting operation can be surely performed by turning the solenoid ON / OFF, the structure is simplified, and no cost is required.

  According to the present invention, it is possible to reduce the warm-up time and stabilize (uniformize) the surface temperature of the fixing roller at a low cost without applying a load (tension) to the fixing belt itself. It becomes. Further, since the heating means can be separated from the surface of the fixing roller as necessary, the fixing roller can be prevented from being deformed by always leaving the heating means in pressure contact with the surface of the fixing roller. It is possible to extend the service life and ensure safety.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a perspective view illustrating a schematic configuration of a belt fixing device of an image forming apparatus. The belt fixing device generally includes a fixing belt 1, a fixing roller 2, a pressure roller 3, a heating roller 4, and a sub heating roller 16. The fixing roller 2 and the pressure roller 3 are provided in the middle of the conveyance path. The heating roller 4 is provided in parallel with the fixing roller 2 at a substantially horizontal position. The fixing belt 1 is stretched around the fixing roller 2 and the heating roller 4, and is driven to rotate in the direction of the solid arrow A by the fixing roller 2. The fixing belt 1 is an endless belt made of a nickel thin plate having a thickness of 40 μm, and has an outer peripheral surface coated with an offset preventing material such as a silicon rubber film.

  The pressure roller 3 disposed opposite to the fixing roller 2 sandwiches the transfer paper P with the fixing roller 2 and presses (nips) the transfer paper P to the lower running portion of the fixing belt 1. The fixing roller 2 and the pressure roller 3 are rubber rollers having a rubber surface layer on the outer peripheral side of the core metal. The heating roller 4 applies tension to the fixing belt 1. The heating roller 4 is made of a cylindrical aluminum tube having a constant thickness in the axial direction, and shaft portions 4a (see FIG. 2) are formed at both ends by drawing. A rod-shaped heater lamp 5 is disposed in the hollow of the heating roller 4. The heater lamp 5 heats the fixing belt 1 via the heating roller 4.

  Further, the sub-heating roller 16 disposed inside the fixing belt 1 so as to face the fixing roller 2 is upstream in the rotational direction from the nip portion N where the pressure roller 3 is in pressure contact with the fixing belt 1 on the surface of the fixing roller 2. And presses against the fixing roller 2 to rotate following the rotation of the fixing roller 2. A rod-shaped heater lamp 18 is disposed in the hollow of the sub-heating roller 16.

  The sub-heating roller 16 and the heater lamp 18 constitute a heating unit that contacts the surface of the fixing roller 2 in the longitudinal direction and heats the fixing roller 2. That is, the heater lamp 18 heats the surface of the fixing roller 2 via the sub heating roller 16.

  Around the fixing belt 1, a pre-fixing guide 50, a post-fixing guide 51, and a pair of conveying rollers 52a and 52b are disposed. The pre-fixing guide 50 is for conveying the transfer paper P conveyed from the image forming unit including the photosensitive drum (not shown) toward the belt fixing unit, that is, in the direction of arrow B. The transfer paper P is pressed against the fixing belt 1 and heated, and the toner image T transferred to the transfer paper P is fixed. The post-fixing guide 51 and the conveyance rollers 52a and 52b are for discharging the transfer paper P after the fixing process to a tray provided outside the image forming apparatus.

  Next, a more detailed configuration of the belt fixing device according to the embodiment of the present invention will be described with reference to FIGS. FIG. 2 is an exploded perspective view showing how the heater unit 11 is attached to the belt fixing device.

  The fixing roller 2 and the heating roller 4 are rotatably supported by fixing device side plates 6 and 7 in which shaft portions 2a and 4a at both ends of the rollers are opposed to each other by bearings 8 and 9, respectively. When the belt fixing device is integrated as a fixing unit, the fixing device side plates 6 and 7 correspond to the side surface portion of the fixing unit casing.

  In the fixing device side plates 6 and 7, rectangular windows 6a and 7a are formed in the substantially central portion of the upper half. From the windows 6a and 7a, the in-belt space 10 faces the outside. The belt inner space 10 is a cavity that extends in the roller axis direction and is open to a plane that borders both side edges of the fixing belt 1.

  The sub-heating roller 16 is supported by bearings 17 on sub-heating roller support plates 14 and 15 that are fixed to the inner surfaces of both ends of the plate-like heater lamp holding member 12. The heater lamp 18 disposed in the hollow of the sub-heating roller 16 is supported by a heater support portion 12 a that protrudes in an arm shape at both ends of the heater lamp holding member 12. Thereby, the heater unit 11 is comprised.

  Here, the interval between the sub-heating roller support plates 14 and 15 is set to be longer than the interval between the fixing device side plates 6 and 7, and the heater unit 11 is moved in the longitudinal direction with the belt fixing device assembled. Further, it can be inserted into the belt inner space 10 through the window 6 a of one fixing device side plate 6 and inserted into the window 7 a of the other side plate 7. The sub heating roller support plates 14 and 15 may be formed integrally with the heater lamp holding member 12.

  The heater lamp holding member 12 is provided with a thermistor 19 for detecting the surface temperature of the sub-heating roller 16 and a thermocut 20 for preventing an excessive temperature rise that disconnects the heater lamp 18 at a certain constant temperature.

  Next, the attachment / detachment structure of the heater unit 11 to the belt fixing device will be described with reference to FIG. The fixing device side plates 6 and 7 are respectively provided with screw holes 6b and 7b for mounting the heater unit mounting members 21 and 22 at positions above the shaft portions 2a of the fixing roller 2 protruding outward.

  In the heater unit mounting members 21 and 22, the mounting portions 21a and 22a for mounting to the fixing device side plates 6 and 7 and the support portions 21b and 22b for supporting the heater unit 11 are opposite to each other. A refracting plate connected to an L-shape, screw holes 21c and 22c are provided in the mounting portions 21a and 22a, respectively, and fulcrums 21d and 22d are provided on the inner surfaces of the support portions 21b and 22b, respectively. ing. And these heater unit attachment members 21 and 22 use screws 23 and 24 in each screw hole 21c and 22c so that each fulcrum 21d and 22d is located on the extension in the roller axial direction above belt inner space 10. The fixing device side plates 6 and 7 are attached to the screw holes 6b and 7b.

  Further, fulcrum holes 14a and 15a for inserting the fulcrums 21d and 22d of the heater unit mounting members 21 and 22 are provided on the upper portions of the sub heating roller support plates 14 and 15, respectively. And 15 are connected to the movable iron cores 25a and 26a (see FIG. 4) of the pull-type solenoids 25 and 26 (see FIG. 4) through the joints 28 and 29 (see FIG. 4), respectively. Oscillating pins 14b and 15b (see FIG. 4) are provided.

  Next, a procedure for attaching the heater unit 11 to the belt fixing device will be described with reference to FIG. First, as shown by the one-dot chain line arrow C, in a state where the belt fixing device is assembled, the heater unit 11 is inserted in the belt inner space 10 from the window 6a of the fixing device side plate 6 in the longitudinal direction. The sub-heating roller support plates 14 and 15 are held through the windows 7a and exposed to the outside of the belt fixing unit from the windows 6a and 7a. Then, as indicated by the dashed line arrow D, the fulcrums 21d and 22d of the heater unit mounting members 21 and 22 are inserted into the fulcrum holes 14a and 15a of the sub-heating roller support plates 14 and 15, respectively. As described above, the screw holes 21 c and 22 c of the heater unit mounting members 21 and 22 and the screw holes 6 b and 7 b of the fixing device side plates 6 and 7 are fastened using screws 23 and 24. Thus, the heater unit 11 is attached to the belt fixing device so as to be swingable around the fulcrum holes 14a and 15a of the sub-heating roller support plates 14 and 15. Finally, the sub heating roller support plates 14 and 15 are connected to the movable iron cores 25a and 26a (see FIG. 4) of the pull type solenoids 25 and 26 (see FIG. 4) via the joints 28 and 29 (see FIG. 4). It connects with each rocking pin 14b and 15b (refer FIG. 4) of (refer FIG. 4).

  As shown in FIG. 3, the heater unit 11 attached in this way has heater unit attachment members 21 and 22 in an angle range corresponding to the strokes of the movable iron cores 25 a and 26 b by ON / OFF operation of the solenoids 25 and 26. The fulcrum 21d and 22d are swingable. If this is seen with respect to the sub-heating roller 16, as shown in FIG. 5, the sub-heating roller 16 is moved from the position (a) in contact with the surface of the fixing roller 2 by the ON / OFF operation of the solenoids 25 and 26 or from the surface of the fixing roller 2. It can be separated from the surface of the fixing roller 2 so that the posture can be changed between the separated position (b).

  Next, an operation example of the heater unit 11 will be described with reference to FIGS. FIG. 3 is a side view of the belt fixing device showing the position of the heater unit 11 when the pull type solenoids 25 and 26 are ON (a) or OFF (b), and FIG. 4 is built in the sub-heating roller 16. FIG. 5 is a sectional view passing through the roller shafts of the fixing roller 2 and the heating roller 4 of the belt fixing device showing the control system of the heater lamp 18 and the solenoids 25 and 26, and FIG. 5 corresponds to FIGS. 3 (a) and 3 (b). FIG. 5 is a side sectional view of the belt fixing device showing a position (a) where the sub heating roller 16 is in contact with the surface of the fixing roller 2 and a position (b) where the sub heating roller 16 is in contact with the surface of the fixing roller 2 as the heater unit swings.

  As shown in FIG. 4, the ON / OFF operation of the heater lamp 18 incorporated in the sub-heating roller 16 is controlled by switching the driving of the driver 31 that energizes the heater lamp 18. The ON / OFF operation of the solenoids 25 and 26 is controlled by switching ON / OFF of the driver 32 that energizes the solenoids 25 and 26. The main body control unit 30 controls driving of the drivers 31 and 32 based on detection signals from the power switch 33, the timer 34, the serviceman call detection unit 35, the jam detection unit 36, and the like of the image shape generation apparatus.

  In this configuration, when the power switch 33 of the image forming apparatus is turned on, the heating roller 4 is rotationally driven by a driving unit (not shown), so that the fixing roller 2 and the fixing belt 1 stretched over the heating roller 4 are shown in FIG. In the direction of arrow A. At the same time, the driver 31 is turned on, the heater lamp 18 is energized and the heater lamp 18 generates heat, and the driver 32 is turned on and the solenoids 25 and 26 are energized. As shown in FIG. 5 and 26, the heater unit 11 is swung clockwise and attracted to the fixing roller 2 side, and the fixing roller 2 is positioned at a position where the sub-heating roller 16 contacts the surface of the fixing roller 2 as shown in FIG. Heat. When the thermistor 19 detects a predetermined temperature or more, the driver 31 is turned off to stop energization of the heater lamp 18, and the driver 32 is turned off to stop energization of the solenoids 25 and 26. As shown in FIG. 3B, the heater unit 11 is swung counterclockwise by releasing the suction force of the solenoids 25 and 26, and as shown in FIG. 5B, the sub-heating roller 16 becomes the fixing roller. 2. Heating of the fixing roller 2 is stopped at a position separating from the surface.

  As a result, the heat of the sub-heating roller 16 including the heater lamp 18 disposed inside the fixing belt 1 is efficiently transmitted to the nip portion between the fixing belt 1 and the pressure roller 3, thereby applying a load (tension) to the fixing belt 1 itself. ), The warm-up time can be shortened and the surface temperature of the fixing roller 2 can be stabilized (uniformized) at a low cost. Further, when an abnormality occurs in the fixing temperature control, the sub-heating roller 16 is moved away from the surface of the fixing roller 2 almost simultaneously with the stop of energization of the heater lamp 18, so that the abnormally high temperature state of the fixing belt 1 can be released.

  Note that the timing for switching on / off the energization of the heater lamp 18 and the solenoids 25 and 26 is not limited to being performed during warm-up.

  For example, when the timer 34 detects that the image forming operation has not been performed for a predetermined time, the power supply to the heater lamp 18 and the solenoids 25 and 26 may be turned off.

  According to this, the load of the fixing roller 2 can be reduced and the deformation can be prevented because the heating unit is separated from the surface of the fixing roller 2 during the standby for the image forming operation.

  Alternatively, when the jam detection unit 36 detects a jam of the transfer paper P or when the serviceman call detection unit 35 detects a serviceman call, the heater lamp 18 and the solenoids 25 and 26 are turned off. Good.

  According to this, even when the machine body of the image forming apparatus detects an abnormality, the sub-heating roller 16 moves away from the surface of the fixing roller 2 almost simultaneously with the stop of energization of the heater lamp 18, so that the fixing belt 1 The abnormally high temperature can be released.

  In addition, this invention is not limited to said embodiment, It is possible to add and implement various changes.

  For example, as shown in FIG. 6, a heating means composed of one planar heating element (resistance heating element) 37 inserted through the belt inner space 10 is supported on a support plate similar to the above, and It is also possible to adopt a configuration in which contact and separation are made from the surface of the fixing roller 2 by the same separation and contact means.

  According to this configuration. Since the planar heating element 37 is disposed in a hollow portion formed inside the fixing belt 1, an increase in the size of the apparatus can be prevented. Further, since a roller, a belt, and the like are not required, a belt fixing device having a simple configuration is obtained, and the cost can be suppressed.

  Further, as shown in FIG. 7, a heating means composed of two planar heating elements (resistance heating elements) 38 and 39 disposed through the belt inner space 10 is supported on a support plate similar to the above. It is also possible to adopt a configuration in which the same contact / separation means as described above is used to separate from the surface of the fixing roller 2.

  According to this configuration. The heat transmitted from the sheet heating elements 38 and 39 to the surface of the fixing roller 2 is transmitted to the fixing belt 1. Therefore, the belt fixing device is effective even when a larger amount of heat is required.

  Further, as shown in FIG. 8, a belt heater (heating) comprising a heating belt 40, an internal heating roller 41, an internal heater lamp 42, and an internal roller 43, which is inserted through the belt inner space 10. (Means) may be supported on a support plate similar to the above and may be separated from the surface of the fixing roller 2 by a separation / contact means similar to the above.

  According to this configuration, the contact area between the fixing roller 2 and the heating belt 40 can be increased, so that the belt fixing device that can efficiently supply the amount of heat necessary for fixing.

  Further, as shown in FIG. 9, the heating belt 40 is inserted through the belt inner space 10, and includes an internal heating roller 41, an internal heater lamp 42, an internal heating roller 44, and an internal heater lamp 45. A belt heater (heating means) may be supported on a support plate similar to the above and may be separated from the surface of the fixing roller 2 by a separation / contact means similar to the above.

  According to the above configuration, the contact area between the fixing roller 2 and the heating belt 40 can be increased, so that the belt fixing device can efficiently supply the amount of heat necessary for fixing.

  In the above-described embodiment, the description has been given using the belt fixing device that conveys the paper in the substantially horizontal direction, but the present invention can be similarly applied to the belt fixing device that conveys the paper in the substantially vertical direction. As the separating / connecting means, an eccentric cam mechanism and a gear mechanism can be used in addition to the solenoid.

  The present invention can be used in an image forming apparatus such as a copying machine or a laser printer.

These are sectional drawings which show schematic structure of the belt fixing device periphery which concerns on embodiment of this invention. These are exploded perspective views showing how to attach the heater unit to the belt fixing device. These are side views of the belt fixing device showing the position of the heater unit when the pull solenoid is ON (a) or OFF (b). These are sectional drawings which pass along the roller axis | shaft of the fixing roller of a belt fixing device, and a heating roller which shows the control system of the heater lamp and solenoid incorporated in the sub-heating roller. FIG. 3 shows a position (a) where the sub-heating roller is in contact with the surface of the fixing roller and a position (b) where it is separated from the surface of the fixing roller, corresponding to FIGS. 3 (a) and 3 (b). It is a sectional side view of a belt fixing device. These are sectional views of a belt fixing device showing an example in which one sheet heating element is provided as heating means for the fixing roller. These are sectional views of a belt fixing device showing an example in which two planar heating elements are provided as heating means for the fixing roller. These are sectional views of a belt fixing device showing an example in which a belt heater (single internal heating roller type) is provided as heating means for the fixing roller. These are sectional views of a belt fixing device showing an example in which a belt heater (double internal heating roller type) is provided as heating means for the fixing roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing belt 2 Fixing roller 2a Shaft part 3 Pressure roller 4 Heating roller 4a Shaft part 5 Heater lamps 6 and 7 Fixer side plate 8 Bearing 10 Belt inner space 11 Heater unit 12 Heater lamp holding member 12a Heater support parts 14 and 15 Sub Heating roller support plates 14a, 15a Support hole 14b, 14c Swing pin 16 Sub heating roller 17 Bearing 18 Heater lamp 19 Thermistor 20 Thermo cut 21 Heater unit mounting member 21d Support point 23, 24 Screws 25, 26 Pull type solenoid 25a Movable iron core 28, 29 Joint 30 Controller 31 Driver 32 Driver 33 Power switch 34 Timer 35 Serviceman call detection means 36 Jam detection means 37, 38, 39 Planar heating element 40 Heating belt 41 Internal heating roller 42 Internal heater lamp 43 Internal roller 4 Internal heating roller 45 inside the heater lamp 50 before fixing guide 51 post-fixing guides 52a, 52b conveying roller N nip P transfer sheet T toner image

Claims (5)

  An endless fixing belt stretched between a fixing roller and a heating roller having a built-in heater, and a heating member that generates heat when energized, is disposed inside the fixing belt and is in contact with the surface of the fixing roller in the longitudinal direction. Transfer paper having heating means for heating the fixing roller, and a pressure roller that is pressed against the fixing roller via the fixing belt, and carrying a fixing toner image at a nip portion between the fixing belt and the pressure roller In a belt fixing device provided in an electrophotographic image forming apparatus that performs fixing through the heating unit, the heating unit is arranged to be detachable from the surface of the fixing roller, and the heating unit is separated from the surface of the fixing roller. A belt fixing device comprising a contact means.   A temperature detection unit that detects a temperature of a fixing roller heating portion of the heating unit; when the temperature detection unit detects a temperature equal to or higher than a predetermined temperature, power supply to the heating member is stopped and the heating / disconnection unit performs the heating. 2. The belt fixing device according to claim 1, wherein the means is separated from the surface of the fixing roller.   3. The belt according to claim 1, wherein when the image forming operation is not performed for a predetermined time, energization to the heating member is stopped and the heating unit is separated from the surface of the fixing roller. Fixer.   4. When detecting a jam on a transfer sheet or when detecting a service man's call, the energization of the heat generating member is stopped and the heating unit is separated from or brought into contact with the fixing roller surface by the separation / contact unit. The belt fixing device according to any one of the above.   The belt fixing device according to claim 1, wherein the separation / contact means is a solenoid.

Images