JP2008052031A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent such troubles that an air applying way is changed or a cooling air loss occurs due to a change in an air flow path being a countermeasure to temperature rise at the end part of a fixing unit. <P>SOLUTION: The fixing device includes fixing members as a pair of rotating bodies forming a fixing region while coming in press-contact with each other with rotation, and then, thermally fixing an unfixed toner image on a transfer material when the transfer material with the unfixed image passes through the fixing region, at least one of the rotating bodies having a heat source. The fixing device also includes: a non-paper-feeding-region cooling duct having an air blow port and a cooling air guide part provided facing the fixing member in order to cool the prescribed region of the fixing member; a cooling device equipped with a cooling fan for sending the cooling air to the non-paper-feeding region cooling duct; and a moving means for moving the cooling device along the prescribed region. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixing device of an electrophotographic image forming apparatus such as a copying machine, a printer, and a facsimile, and in particular, has a heating rotating member and a pressure rotating member that form a fixing region by a pressing region that presses while rotating with respect to each other. And a fixing device that heats and fixes the unfixed toner image when a transfer material on which the unfixed toner image is formed passes through the fixing region.

  Conventionally, as a fixing method for fixing an unfixed toner image on a sheet (transfer material) in the image forming apparatus, heat that heats and melts the unfixed toner image on the sheet to fix it on the sheet from the standpoint of safety and fixability. A fixing method is generally used. In recent years, a belt heating type heating apparatus has been put into practical use from the viewpoint of quick start and energy saving. That is, a heat-resistant resin belt (hereinafter referred to as a fixing belt) as a heating member is sandwiched between, for example, a ceramic heater as a heating body and a pressure roller as a pressure member, and a pressure nip portion (hereinafter referred to as fixing). A recording material on which an unfixed toner image is formed and supported between the fixing belt and the pressure roller of the fixing nip portion, and is conveyed while being held together with the fixing belt. An unfixed toner image is fixed on the surface of the recording material with the pressure of the fixing nip portion while applying heat from the ceramic heater through the fixing belt. This belt heating type heating apparatus does not require energization of the heater in standby, and after the image forming apparatus receives the print signal, the recording material reaches the heating apparatus even if the heater is energized. It is possible to make it heatable. Therefore, from the viewpoint of energy saving, the belt heating type heating device is an excellent heat fixing device that does not waste energy. Furthermore, a fixing method is also proposed in which a pressure member is arranged through a belt so as to face the heating roller. Regardless of which fixing method is used, when the paper is fixed in the fixing region, the surface of the heating roller passing through the paper passing region has a substantially uniform temperature distribution.

  However, when small size paper having a width smaller than the maximum size paper is continuously fixed in the fixing area, the temperature of the surface of the heating roll passing through the non-sheet passing area excessively increases. This is because when small-size paper is continuously passed, heat is partially stored in the non-paper passing area where the paper does not pass, as much as there is no heat removal by the paper. This phenomenon is called the temperature rise at the end of the fixing device or the temperature rise at the non-sheet passing portion. If the temperature rise at the end of the fixing device becomes high, the temperature rise limits of the fixing member components and the pressure roller are exceeded. Lead to damage of the parts.

  In order to prevent the temperature rise of the non-sheet passing portion, a cooling fan is provided in the fixing device, and the temperature rise is suppressed by blowing air to the heating roller and pressure roller of the non-sheet passing portion. It has been. The following is known as a description of the prior art.

In the technique described in this publication, cooling air is selectively blown from the cooling fan arranged in the fixing device to the non-sheet passing area side.

In the technique described in this publication, when cooling air is blown from the cooling fan to the non-sheet passing area side, the length in the width direction of the blower opening according to the width of the paper to be used. By adjusting the temperature, the temperature rise of the non-sheet passing portion is prevented even for paper of different sizes.
JP-A-4-51179 Japanese Patent Laid-Open No. 2003-076209

  However, in the prior art disclosed in Japanese Patent Application Laid-Open No. 2003-076209, paper of various sizes in the width direction is supported by changing the area of the air blowing port that guides the cooling air. The duct shape constituted by the blower opening and the guide portion changes depending on the paper size. The change in the duct shape means that the loss of the cooling air volume generated at the bent portion of the duct, the wind direction, and the like also change. For example, when the shutter member 3 is positioned as shown in FIG. In the case of the position shown in FIG. 7, it is obvious that a change occurs like the streamline X and the streamline Z despite the cooling air flowing through the same position. Therefore, in the above-described configuration, fine tuning is required such that control for increasing the air flow rate of the cooling fan according to the air blowing conditions for various paper sizes is included, or that the air size is ensured by increasing the size of the cooling fan. As a result, the control and configuration of the cooling device are complicated.

  Furthermore, when the shutter member 3 that adjusts the length of the blower in the width direction is at a position as shown in FIG. 7, the cooling air hits the wall surface of the shutter member 3 vertically, so the cooling air indicated by the streamline Z Thus, the sufficient cooling effect on the non-sheet passing portion could not be obtained. The above situation is the same in the conventional configuration in which cooling air is selectively blown in JP-A-4-51179.

  The present invention has been made in view of the above-mentioned circumstances, and the object of the present invention is to complicate the apparatus and the control, increase the cost, and deteriorate the cooling performance such as cooling air wrapping around the paper passing area. An object of the present invention is to provide a fixing device that efficiently solves the problem.

  At least one of a pair of rotating members that forms a fixing region by a pressure contact region that is pressed against each other while rotating, and that heat-fixes the unfixed toner image when the transfer material on which the unfixed toner image is formed passes through the fixing region. In a fixing device including a fixing member having a heat source on one side, a non-communication in which an air blowing port and a cooling air guide are formed facing the fixing member to cool a predetermined region of the fixing member. A paper area cooling duct, a cooling device having a cooling fan that blows cooling air to the non-paper passing area cooling duct, and a moving unit that allows the cooling device to move along the predetermined area. It is characterized by that.

  According to the present invention, the cooling fan can be moved integrally with the duct provided with the cooling air guide, and the cooling fan and the duct can be moved to predetermined positions according to various paper sizes. Since the blowing condition is not changed even for the transfer material, it is possible to provide a fixing device that realizes simplification of the device configuration and control, cost reduction, and improvement in cooling performance.

  Next, specific examples (examples) of the embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples.

(Embodiment 1)
(Fixing device)
FIG. 1 is a cross-sectional view of the fixing device in this embodiment. The fixing device of this example is a heating device of a fixing belt heating method and a pressure rotating body driving method (tensionless type).

  Reference numeral 20 denotes a fixing belt as a first rotating body (first fixing member), which is a cylindrical member (endless belt-like or sleeve-like) formed by providing an elastic layer on the belt-like member.

  Reference numeral 22 denotes a pressure roller as a second rotating body (second fixing member).

  Reference numeral 17 denotes a heater holder having a heat resistance and rigidity having a substantially semicircular arc shape in cross section as a heating body holding member, and 16 is a fixing heater as a heating body (heat source). It is arranged along. The fixing belt 20 is loosely fitted to the heater holder 17 and is biased at the end by the fixing flange 50 as shown in the perspective view of FIG.

  The pressure roller 22 is formed by forming a silicone rubber layer having a thickness of about 3 mm on a stainless steel core by injection molding and coating a PFA resin tube having a thickness of about 40 μm thereon. The pressure roller 22 is disposed such that both ends of the core bar are rotatably supported by bearings between a side plate (not shown) and a front side plate of the apparatus frame 24. On the upper side of the pressure roller 22, the fixing belt unit composed of the fixing heater 16, the heater holder 17, the fixing belt 20, etc. is arranged in parallel to the pressure roller 22 with the heater 16 facing downward, and both end portions of the heater holder 17. Is biased in the axial direction of the pressure roller 22 by a force of 98 N (10 kgf) on one side and a total pressure of 196 N (20 kgf) by a pressure mechanism (not shown), so that the downward surface of the fixing heater 16 is passed through the fixing belt 20. A fixing nip portion 27 having a predetermined width necessary for heat fixing is formed by pressing the elastic layer of the pressure roller 22 against the elasticity of the elastic layer with a predetermined pressing force. The pressurization mechanism has a pressure release mechanism, and is configured to release the pressurization and remove the recording material P at the time of jam processing or the like.

  Reference numerals 23 and 26 denote an entrance guide and a fixing paper discharge roller assembled to the apparatus frame 24. The entrance guide 23 is a transfer material so that the recording material P that has passed through the secondary transfer nip is accurately guided to the fixing nip portion 27 that is a pressure contact portion between the fixing belt 20 and the pressure roller 22 in the fixing heater 16 portion. To play a leading role. The entrance guide 23 of the present embodiment is formed of polyphenylene sulfide (PPS) resin.

  The pressure roller 22 is driven to rotate at a predetermined peripheral speed in the direction of the arrow by a driving means (not shown). A rotational force acts on the cylindrical fixing belt 20 by the frictional force at the fixing nip portion 27 between the outer surface of the pressure roller 22 and the fixing belt 20 due to the rotation of the pressure roller 22, and the fixing belt 20 While the inner surface of the fixing heater 16 is in close contact with the downward surface and slides, the outer periphery of the heater holder 17 is driven and rotated in the direction of the arrow. Grease is applied to the inner surface of the fixing belt 20 to ensure slidability between the heater holder 17 and the inner surface of the fixing belt 20.

  The pressure roller 22 is rotationally driven, and accordingly, the cylindrical fixing belt 20 is driven and rotated, and the fixing heater 16 is energized. The fixing heater 16 is heated to a predetermined temperature. In the adjusted state, the recording material P carrying an unfixed toner image is guided and introduced along the entrance guide 23 between the fixing belt 20 and the pressure roller 22 of the fixing nip 27, and the fixing nip 27 2, the toner image carrying surface side of the recording material P is in close contact with the outer surface of the fixing belt 20 and is nipped and conveyed together with the fixing belt 20 through the fixing nip portion 27. In this nipping and conveying process, the heat of the fixing heater 16 is applied to the recording material P via the fixing belt 20, and the unfixed toner image t on the recording material P is heated and pressurized on the recording material P and melted and fixed. The The recording material P that has passed through the fixing nip 27 is separated from the fixing belt 20 by the curvature, and is discharged by the fixing discharge roller 26.

(Thermistor)
As shown in FIG. 1, reference numerals 19 and 18 denote main and sub thermistors as first and second temperature detecting means. The main thermistor 19 as the first temperature detecting means is disposed on the fixing heater 16 that is a heating body, and in contact with the back surface of the fixing heater 16 in this embodiment, detects the temperature of the back surface of the fixing heater 16.

  The sub-thermistor is in elastic contact with the inner surface of the fixing belt 20 above the heater holder 17 and detects the temperature of the inner surface of the fixing belt 20.

  The main thermistor 19 is disposed near the longitudinal center of the fixing belt 20, and the sub-thermistor 18 is disposed near the end of the fixing heater 16. The main thermistor 19 is disposed in contact with the back surface of the fixing heater 16 and the inner surface of the fixing belt 20.

  The outputs of the main thermistor 19 and the sub thermistor 18 are respectively connected to a control circuit unit (CPU) 21 via an A / D converter. The control circuit unit 21 is based on the outputs of the main thermistor 19 and the sub thermistor 18. Then, the temperature control content of the fixing heater 16 is determined, and the energization to the fixing heater 16 is controlled by the heater drive circuit unit 28 as a power supply unit (heating means).

(Cooling system)
FIG. 3 is a diagram for explaining the state of the fixing belt, the cooling fan, and the non-sheet passing area cooling duct of the fixing device. In FIG. 3, a cooling fan 1 is provided above the fixing belt, and a non-sheet passing area cooling duct 2 is connected to the cooling fan 1. The cooling fan 1 employs an axial fan that is lower in cost than a sirocco fan or a cross flow fan.

  The non-sheet-passing area cooling duct 2 is a non-sheet-passing area that is a fixing area in which small-size paper (paper having a narrower width than the maximum size paper) passes through the fixing area Q continuously. This is a duct for cooling R.

(Movement mechanism and position detection mechanism)
FIG. 4 shows a moving mechanism of the cooling device and its position detecting mechanism. Basically, the configuration is symmetrical, and only one end is shown in FIG. 4 for simplicity of explanation.

  A cooling frame 8 is disposed at a position facing the belt at the duct outlet on the fixing belt side. A guide groove 100 is carved in the cooling frame 8 along the axial direction of the fixing belt, and a moving wall 3 to which the cooling duct 2 can be attached extends along the guide groove 100 along a drive source (not shown) (pulse motor and drive). It can be moved by a gear or the like. A duct opening 9 is provided in the cooling frame, and cooling air from the air blowing port of the cooling duct 2 attached to the moving wall 3 is configured to hit the fixing belt.

  The position of the cooling duct 2 is detected on the edge 5 determined by the paper size provided on the moving wall 3 by the sensor 5, thereby detecting the position corresponding to each paper size. As a result, the cooling device can be moved to an optimal arrangement for the size of paper to be passed, and air can be blown with the optimal arrangement.

(Cooling fan operation)
Next, the operation of the cooling fan in the present embodiment will be described.

  When small-size paper having a width smaller than the above-mentioned maximum-size paper is continuously fixed during image formation, the temperature of the non-sheet passing area R rises. At this time, the sub-thermistor as the second temperature detecting means detects the temperature of the inner surface of the fixing belt 20, and when the sub-thermistor detects a temperature higher than a predetermined temperature, the cooling fan 1 operates. Start and suppress the temperature rise in the non-paper passing area. And it cools with the cooling air of a cooling fan, and when the temperature of a sub thermistor falls to a certain temperature, operation | movement of a cooling fan is stopped.

  The ON / OFF temperature range based on the detected temperature of the sub-thermistor of the cooling fan is controlled to change depending on the operation status of the cooling fan.

  The cooling fan in this embodiment has an ON-OFF temperature range. When 100 sheets of B4 size paper are continuously passed and the number of sheets to be passed is 0 to 30, the operation start temperature of the cooling fan is set to the sub-temperature. When the detected temperature of the thermistor reaches 200 ° C, the cooling fan is stopped when the detected temperature of the sub-thermistor reaches 190 ° C. The operation is started at 205 ° C. and stopped at 195 ° C., and thereafter the start temperature and stop temperature of the cooling fan are increased by 5 ° C. every 30 sheets.

(Cooling state explanation)
5 and 6 are cross-sectional views illustrating a state in which the cooling air generated from the cooling fan cools the non-sheet passing area of the fixing belt. FIG. 5 shows the arrangement of the cooling fans when the maximum size paper P ′ is continuously passed, and FIG. 6 shows the arrangement of the cooling fans when the small size paper P is continuously passed.

  As the order of operations to reach the cooling state, the moving device of the cooling device integrates the cooling fan 1 and the cooling duct 2 in accordance with the paper size set before passing the paper, and is symmetric with respect to the center of the paper. Move to the position of left and right respectively. Therefore, at this time, when the paper size is the maximum size width, the cooling fan 1 moves to the left and right arrangement as shown in FIG. 5, and when the paper size is smaller than the large size, FIG. Thus, the cooling fan 1 moves to an arrangement in which the interval between the cooling fans 1 is narrowed.

  As described above, although the cooling devices are arranged differently depending on the size of paper to be passed, the arrangement and positional relationship between the cooling fan 1 and the cooling duct 2 and the arrangement and positional relationship between the cooling duct 2 and the fixing belt 20 are as shown in FIG. It can be seen that there is no change at all as shown in FIG. Therefore, it can be seen that there is no change in the cooling stream line Z between when the maximum size sheet is passed and when the small size sheet is passed, and it is not necessary to perform fine tuning or the like according to the blowing conditions for various paper sizes.

  As described above, it can be seen that by adopting the configuration of this embodiment, simplification is possible without changing the control and configuration of the cooling device in accordance with various paper sizes. In addition, since it is possible to optimize the air blowing conditions without worrying about the arrangement of the cooling fan 1, it is understood that the loss of cooling air can be reduced and efficient cooling is possible.

Sectional view of the fixing device in the embodiment The perspective view of the fixing device in the embodiment Top view of cooling device in embodiment The perspective view of the cooling device moving mechanism and position detection mechanism in an Example Sectional drawing which shows the cooling state at the time of large size paper passing in an Example Sectional drawing which shows the cooling state at the time of small size paper passing in an Example Sectional view of the configuration when a conventional large-size sheet is passed Sectional view of the configuration when passing through a conventional small size paper

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cooling fan 2 Non-sheet-passing area cooling duct 3 Shutter 4 Edge position 5 Sensor 8 Shutter frame 9 Duct opening 16 Fixing heater 17 Heater holder 18 Sub thermistor 19 Main thermistor 20 Fixing belt 22 Pressure roller
P Recording material
Q Fixing area
R Non-paper passing area
X streamline
Y streamline
Z streamline

Claims (3)

At least one of a pair of rotating members that forms a fixing region by a pressure contact region that is pressed against each other while rotating, and that heat-fixes the unfixed toner image when the transfer material on which the unfixed toner image is formed passes through the fixing region. In a fixing device provided with a fixing member having a heat source on one side,
A non-sheet-passing area cooling duct in which a blowing port and a guide for cooling air are formed facing the fixing member to cool a predetermined region of the fixing member;
A cooling device having a cooling fan for blowing cooling air to the non-sheet-passing area cooling duct, and a moving means for moving the cooling device along the predetermined area;
A fixing device comprising:   The fixing device according to claim 1, wherein the moving unit is a moving unit that allows the non-sheet-passing area cooling duct and the cooling device to move together. The fixing device includes a recognition unit that recognizes the width of the transfer material that passes through the fixing region,
The fixing device according to claim 2, wherein the moving unit is a unit that moves the cooling device to a predetermined position in accordance with the width of the transfer material recognized by the recognition unit.

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