JP2011232426A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus for preventing air heated by a fixing member in a non-fixing period from reaching a fan motor.SOLUTION: The fixing apparatus for fixing a toner image of a recording material in a nip portion formed by a heated fixing member and a pressurizing member for pressurizing the fixing member includes: a fan; a fan motor having a motor for rotating the fan and a fan control section for controlling the motor; an air nozzle for blowing air sent by the fan motor to the vicinity of the outlet of the nip portion; and control means for controlling the speed of the air discharged from the air nozzle so that the speed in a non-fixing period of the recording medium is decreased to be slower than that in a fixing period thereof.

Description

  The present invention relates to a fixing device that fixes a toner image on a recording material at a nip formed by a fixing member and a pressure member.

  In an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions, a latent image corresponding to an original is formed on a photosensitive member, and toner is applied to the latent image. Then, the visualized toner image is transferred onto the recording paper, and then the toner image transferred onto the recording paper is fixed and discharged.

  As a fixing device for fixing a toner image in this manner, a recording sheet onto which a toner image is transferred is sandwiched between a fixing roller having a built-in halogen heater and a pressure roller that presses the fixing roller. There is a fixing device of a heat roller fixing system that heats and pressurizes while transporting, and such a fixing device is widely used because of its simple configuration.

  In addition, an endless fixing belt is stretched between a heating roller having a halogen heater and the like and a fixing roller, and has a pressure roller that presses the fixing roller through the fixing belt. There is a belt-fixing type fixing device that heats and pressurizes a recording sheet on which a toner image is transferred while nipping and conveying the recording sheet at a nip portion formed by the above. Since such a fixing device separates the functions of heat supply (heating roller) and pressure (fixing roller), a thick rubber layer can be used for the fixing roller to achieve both a wide nip and durability.

  Here, since the toner of the toner image on the recording paper is heated when passing through the nip portion, the toner has adhesive force, and the recording paper passing through the nip portion adheres to the surface of the fixing roller or the fixing belt. There is a risk of jamming due to wrapping and separation. In particular, when a small amount of paper (thin paper) and a small amount of coated paper for printing are used as the recording paper, the separation performance is further deteriorated.

  On the other hand, the speed of the image forming apparatus has been increased, and if the fixing roller is enlarged in order to ensure a sufficiently long nip width, the roller curvature at the fixing nip outlet also becomes small, and the separation performance deteriorates.

  In order to make it easier to separate the recording paper from the fixing member, a heat-resistant resin having high releasability is used on the surface of the fixing member, a release agent such as silicone oil is applied, or the toner is melted by heating in the toner. Various measures have been taken, such as containing wax that functions as a material. However, there are an increasing number of factors that decrease the separation performance, such as the image formation on the coated paper described above and the increase in the toner adhesive force due to the increase in the toner amount due to the addition of the toners of a plurality of colors forming the color image. Separation means for separating is essential.

  Separation means is provided with a separation claw coated with fluororesin having a good releasability on the recording paper discharge side with respect to the nip portion, and its tip is brought into contact with the outer surface of the air blown by a fan. Is separated from the fixing roller or the like.

  However, since the tip of the separation claw is in contact with the surface of the fixing roller or the like, the surface layer formed of a fluororesin or the like covering the surface of the fixing roller or the like is rubbed and the wrinkle is also transferred to the image. There is a problem of end. In particular, in the case of a color image, since a glossy image is required, it tends to be noticeable.

  In order to cope with such a problem, a technique has been developed in which air is blown to the outlet side of the nip portion to separate the recording paper from a fixing roller or the like.

  As an example of this, there is known a fixing device that blows air blown by the rotation of a fan to the nip exit side of the fixing device through an air nozzle to separate the recording paper (see, for example, Patent Documents 1 and 2).

  In the fixing device, when a small-width recording sheet is continuously passed, the non-sheet passing area located at the end of the heating roller is not deprived of heat, and the temperature rises. Thereafter, when a large-sized recording sheet is passed, toner filming or rolling of the recording sheet occurs. Therefore, an image forming apparatus configured to cool a non-sheet passing area by blowing air from a fan is known (see Patent Document 3).

Japanese Patent Laying-Open No. 2005-258035 JP 2006-113173 A Japanese Patent Laying-Open No. 2005-077772

  When the recording paper is separated by the air blown by the fan as described above, the fan consumes power. Therefore, it is desirable to stop the rotation of the fan when printing is not performed, that is, when fixing is not performed.

  On the other hand, the air blown by the rotation of the fan is generally blown against the nip portion from above via an air nozzle. Further, the fixing roller and the fixing belt are heated for fixing, and are 120 ° C. or more at the nip portion outlet. For this reason, when the rotation of the fan is stopped and the air is not blown, the air heated by the fixing roller and the fixing belt and having water vapor rises in the reverse direction through the flow path of the air nozzle and reaches the fan. The fan is connected to a motor, and a fan control unit including a printed circuit board on which a plurality of electronic components for supplying power to the motor and controlling the motor is mounted. A fan, a motor, and a fan control unit that are integrated into a unit are referred to as a fan motor. When air containing water vapor rises and reaches between a plurality of electronic components of the fan motor and dew condensation occurs, the electronic components may be short-circuited and damaged, and the motor may not operate.

  The present invention has been made in view of such a problem, and is a fixing device that blows air blown by a fan motor to the vicinity of an outlet portion of a nip portion through an air nozzle to separate a recording material from a fixing member. It is an object of the present invention to propose a fixing device configured to prevent air heated by a fixing member during fixing from reaching the fan motor.

  Note that Patent Documents 1 to 3 do not describe the problem that the air heated by the fixing roller or the fixing belt rises through the air nozzle, and does not describe means for solving the problem.

  The above object is achieved by the invention described below.

1. In a fixing device that fixes a toner image of a recording material at a nip formed by a heated fixing member and a pressure member that pressurizes the fixing member.
A fan motor having a fan, a motor for rotating the fan, and a fan control unit for controlling the motor;
An air nozzle that blows air blown by the fan motor to the vicinity of the outlet portion of the nip portion;
Control means for controlling the wind speed of air discharged from the air nozzle to be lower than that at the time of fixing when the recording material is not fixed;
A fixing device comprising:

  2. 2. The fixing device according to claim 1, wherein the control unit performs control so that a voltage lower than a rated voltage is applied to the fan motor when the recording material is not fixed.

  3. 2. The fixing device according to claim 1, wherein the control means controls to repeatedly apply an on / off voltage to the fan motor when the recording material is not fixed.

  4). The temperature sensor is arranged at or near the fan motor, and the control means controls to blow at a wind speed corresponding to the temperature detected by the temperature sensor when the recording material is not fixed. The fixing device according to claim 1.

  5. A temperature sensor is disposed inside an image forming apparatus provided with the fixing device, and the control means controls to blow at a wind speed corresponding to the temperature detected by the temperature sensor when the recording material is not fixed. The fixing device according to any one of 1 to 3 above.

  6). The fixing device according to any one of claims 1 to 3, wherein the control means controls to blow at a wind speed based on print mode information when the recording material is not fixed.

  7). The fixing device according to any one of claims 1 to 3, wherein the control means controls to blow at a wind speed based on print job information when the recording material is not fixed.

  8). An image forming apparatus comprising the fixing device according to any one of 1 to 7 above.

  According to the fixing device and the image forming apparatus provided with the fixing device of the present invention, the recording material is separated from the fixing member by blowing the air blown by the fan motor to the vicinity of the outlet portion of the nip portion through the air nozzle. In addition, when the recording material is not fixed, the air speed of the air discharged from the air nozzle is decreased as compared with the time of fixing, so that air having water vapor heated by the fixing member can be prevented from reaching the fan motor through the air nozzle. Therefore, failure of the fan motor can be prevented.

1 is a configuration diagram of an image forming apparatus. FIG. 3 is a cross-sectional view of a fixing device. It is a block diagram which controls a fan motor. It is sectional drawing of the air nozzle which has an on-off valve.

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

  First, an example of an image forming apparatus using the present invention will be described with reference to the block diagram of FIG.

  The image forming apparatus includes an image forming apparatus main body GH and an image reading apparatus YS.

  The image forming apparatus main body GH is called a tandem type color image forming apparatus. A plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-like intermediate transfer belt 5, a sheet feeding and conveying unit, a fixing device 8, and the like. Consists of.

  An image reading device YS including an automatic document feeder YS1 and a document image scanning exposure device YS2 is installed on the upper portion of the image forming apparatus main body GH. The document d placed on the document table of the automatic document feeder YS1 is transported by a transport means, and an image on one or both sides of the document is scanned and exposed by the optical system of the document image scanning exposure device YS2, and is read into the line image sensor CCD. It is.

  A signal formed by photoelectric conversion by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit, and then exposure means 3Y, 3M, 3C, 3K. Sent to.

  In the image forming unit 10Y that forms a yellow (Y) image, a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 7Y are arranged around the photosensitive drum 1Y. In the image forming unit 10M that forms a magenta (M) color image, a charging unit 2M, an exposure unit 3M, a developing unit 4M, and a cleaning unit 7M are arranged around the photosensitive drum 1M. In the image forming unit 10C that forms a cyan (C) color image, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a cleaning unit 7C are arranged around the photosensitive drum 1C. In the image forming unit 10K that forms a black (K) image, a charging unit 2K, an exposure unit 3K, a developing unit 4K, and a cleaning unit 7K are arranged around the photosensitive drum 1K. The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure device 3C, and the charging unit 2K and the exposure device 3K constitute a latent image forming unit.

  The developing units 4Y, 4M, 4C, and 4K include a two-component developer composed of a toner having a small particle size of yellow (Y), magenta (M), cyan (C), and black (K) and a carrier. The toner is composed of a pigment or dye serving as a color former, a wax that helps the toner peel from the fixing member after fixing, and a binder resin that holds these.

  The intermediate transfer belt 5 is wound around a plurality of rollers and is rotatably supported.

  The fixing device 8 heats and pressurizes the toner image on the recording paper (recording material) P at a nip portion formed between the heated fixing belt 81 and the pressure roller 83 to fix the toner image.

  Thus, each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred to the rotating intermediate transfer belt 5 by the transfer means 6Y, 6M, 6C, and 6K (primary transfer), and color. A combined toner image is formed. The recording paper P stored in the paper feeding cassette 20 is fed by the paper feeding means 21 and is conveyed to the transfer means 6A through the paper feeding rollers 22A, 22B, 22C, 22D, the registration rollers 23, etc. A color image is transferred to P (secondary transfer). The recording paper P to which the color image has been transferred is heated and pressurized by the fixing device 8 and the color toner image on the recording paper P is fixed. Thereafter, the sheet is sandwiched between the sheet discharge rollers 24 and placed on the sheet discharge tray 25 outside the apparatus.

  On the other hand, after the color image is transferred to the recording paper P by the transfer unit 6A, the residual toner is removed by the cleaning unit 7A from the intermediate transfer belt 5 from which the recording paper P is separated by curvature.

  The image forming apparatus for forming a color image has been described above. However, an image forming apparatus for forming a monochrome image may be used, or an intermediate transfer belt may or may not be used.

  Next, the fixing device 8 will be described based on the cross-sectional view of FIG.

  The fixing belt 81 is formed in an endless shape. For example, an outer peripheral surface of a base having a thickness of 70 μm made of conductive PI (polyimide) is attached to a thickness of 220 μm made of heat-resistant silicon rubber (hardness JIS-A 30 °). It is covered with an elastic layer and further covered with a 30 μm thick tube made of PFA (perfluoroalkoxy) which is a heat resistant resin. The inner diameter is 80 mm, for example.

  The heating roller 82 has a built-in halogen lamp 82A for heating the fixing belt 81. For example, the outer peripheral surface of a cylindrical cored bar 82B made of aluminum or the like is coated with PFA having a thickness of 30 μm. Covered with layer 82C. The outer diameter is 52 mm, for example.

  Further, as the halogen heater 82A, for example, portions of 930 W and 600 W are provided so as to correspond to different paper widths, and the heat generation distribution is different in the axial direction.

  The fixing roller 83 covers a solid core metal 83A formed of a metal such as iron with an elastic layer 83B having a thickness of 7.5 mm made of silicon rubber (hardness JIS-A 10 °) which is a heat-resistant solid rubber. is doing. In addition, an outer diameter dimension is 40 mm, for example. Further, fluorine rubber may be used instead of silicone rubber.

  The pressure roller 84 has a built-in halogen lamp 84A for shortening the temperature rising time immediately after turning on the power to the image output device, and the outer peripheral surface of a cylindrical cored bar 84B made of aluminum or the like and having a thickness of 3 mm. It is covered with a 2 mm thick elastic layer 94C made of heat resistant silicon rubber (hardness JIS-A 20 °), and further covered with a resin layer 84D of a 30 μm thick PFA tube. In addition, an outer diameter dimension is 50 mm, for example.

  The halogen heater 84A is 700 W, for example.

  The pressing roller 84 presses the fixing belt 81 against the fixing roller 83 by an urging means (not shown).

  The resin layers 82C and 84D may be formed by covering or coating PTFE (polytetrafluoroethylene) tubes.

  Further, any heating means may be used as the heating means for heating the fixing belt 81. For example, an induction heating heating element using an excitation coil may be used. Further, the heating means is not necessarily arranged in the heating roller 82 or the like, and may be arranged anywhere.

  Further, a fixing device provided with a tension roller for pressing the fixing belt may be used.

  In the above configuration, when the fixing roller 83 is rotated clockwise by a driving unit (not shown), the fixing belt 81 and the heating roller 82 are also rotated clockwise, and the pressure roller 84 is rotated counterclockwise. Note that the pressure roller 84 may be driven. The heating roller 82 is heated by the halogen heater 82A, and the fixing belt 81 in contact with the heating roller 82 is also heated. Since the pressure roller 84 is urged in the direction of the fixing roller 83 by an urging means (not shown), a nip portion N between the fixing belt 81 wound around the fixing roller 83 and the pressure roller 84. Thus, the fed recording paper P is heated and pressurized, and the toner image on the recording paper P is fixed.

  In the fixing device 8 as described above, if the fixed recording material P is ejected from the nip portion N and then attached to the fixing belt 81 and wound, there is a risk of jamming. It is necessary to ensure separation from

  Therefore, in the present fixing device 8, an air nozzle 101 is provided in the vicinity of the exit side of the nip portion N as the separating means. The air nozzle 101 discharges air blown by a fan motor 102 arranged to blow in a substantially vertical direction. The air nozzle 101 is formed so that its cross-sectional area decreases toward the tip. The leading end of the air nozzle 101 faces the tangential direction of the fixing belt 81 stretched around the fixing roller 83. In this way, air is continuously blown onto the recording paper P that has passed through the nip portion N so as not to adhere to the fixing belt 81. The air nozzle 101 is made of a heat resistant resin or the like.

  The fan motor 102 is electrically connected to the fan 102A, the motor 102B that rotationally drives the fan 102A, and the motor 102B, and transmits electric power input from an external power source via a switch (not shown) to the motor 102B and controls the motor 102B. The printed circuit board 102C as a fan control unit on which electronic components to be mounted are mounted.

  The motor 102B is a direct current motor. The fan 102A may be an axial fan, a sirocco fan, a cross flow fan, a blower, or the like. For example, the fan motor 102 having a rated voltage of 24 V and a static pressure of 125 Pa is used. In short, the fan motor 102 only needs to have a wind pressure and an air volume capable of separating the recording paper P from the fixing belt 81.

  Here, when printing is not performed on the recording paper P, that is, when no fixing is performed, it is not necessary to perform blowing for separation. Therefore, it is conceivable to stop the rotation of the fan motor 102 in order to prevent power consumption. However, air heated by the fixing belt 81 and air having water vapor rises, so that part of the air passes through the flow path of the air nozzle 101 and reaches the fan motor 102. If air containing water vapor hits the printed circuit board 102C of the fan motor 102 and is dewed, the electronic components may be short-circuited and damaged, and the fan motor 102 may not operate.

  Therefore, the fan motor 102 is rotated and air is blown from the air nozzle 101 even during non-fixing, but the wind speed during non-fixing is made lower than the wind speed during fixing. If air is blown from the air nozzle 101 even at a low speed, the air heated by the fixing belt 81 and naturally rising does not enter the flow path of the air nozzle 101, and the above-described problem of the fan motor 102 does not occur. In addition, for example, the applied voltage may be lowered to blow at low speed, so that power consumption is significantly reduced as compared to the case of always blowing.

  As a specific example, when the A3 recording paper can be fixed, the fan motors 102 having a rated voltage of 24 VDC and a static pressure of 125 Pa are arranged at three locations in the center and both ends in the width direction of the recording paper. A 24V rated voltage is applied to the fan motor 102 during fixing, and a voltage of about 8V corresponding to 1/3 of the rated voltage is applied during non-fixing. The wind speed from the discharge port 101A of the air nozzle 101 is proportional to the applied voltage if the size of the discharge port 101A is constant. Therefore, if the discharge port 101A of the air nozzle is 3 mm in length and 300 mm in width, the wind speed from the discharge port is about 18 m / s at the time of fixing, whereas it is about 6 m / s at the time of non-fixing.

  Such control of the fan motor 102 will be described with reference to the block diagram of FIG.

  As shown in FIG. 1, a position sensor 702 composed of a photo sensor or the like is disposed upstream of the registration roller 23. Since the fixing is performed when the position sensor 702 detects that the recording paper P has been fed, the control means 701 including a CPU or the like controls the voltage control circuit 703 to apply a rated voltage of 24V to the fan motor 102. After the position sensor 702 detects that the recording paper P has been fed, if the position sensor 702 does not detect the recording paper P even after a predetermined time measured by the timer 704 has passed, the recording paper P is fed. Since it has not been done, it is not fixed. Therefore, the control unit 701 controls the voltage control circuit 703 to apply a rated voltage of, for example, 8V to the fan motor 102.

  Regarding the operation of the fan motor 102, there is a time lag from when the motor 102B is energized until the maximum number of rotations is reached, so the motor 102B is turned on immediately after detecting that the recording paper P has been fed by the paper feeding means 21. It is desirable to start rotation.

  Further, instead of changing the voltage applied to the fan motor 102, the application time may be changed. That is, if the voltage is continuously applied during fixing and discontinuously applied during non-fixing, the wind speed during non-fixing can be made lower than the wind speed during fixing.

  As a specific example, during non-fixing, a voltage of 24 V is applied for a time of 1 s, and an on / off state in which no voltage is applied for the subsequent time of 2 s is repeated. Thereby, the wind speed at the time of non-fixing becomes 1/3 of the wind speed at the time of fixing.

  Further, if the fan motor is compatible with PWM (pulse width modulation) control, on / off control can be performed with a finer period.

  As a specific example, after a voltage is applied for 1 ms during non-fixing, an on / off state in which no voltage is applied for 2 ms is repeated.

  When the above-described 1s on and 2s off are repeated, the rise time from the voltage application to the stabilization of the fan motor needs to be about 1 s. Therefore, the rotation speed of the fan motor, that is, the wind speed fluctuates periodically. However, since PWM control can be performed at a high frequency, there is an advantage that the rotation speed of the fan motor, that is, the wind speed is stabilized.

  In this case, in the block diagram of FIG. 3, the control unit 701 controls the voltage control circuit 703 based on the information of the timer 704 to turn the fan motor 102 on and off during non-fixing.

  Further, a temperature sensor may be arranged in the fan motor 102 or in the vicinity thereof, and the air may be blown at a wind speed corresponding to the temperature detected by the temperature sensor during non-fixing. A thermocouple or thermistor can be used as the temperature sensor. The temperature sensor is preferably located near the printed circuit board 102C of the fan motor 102, but the air temperature in the air nozzle 101 or the temperature of the air nozzle 101 may be detected.

  As a specific example, the temperature is detected by a temperature sensor during non-fixing, and the voltage applied to the fan motor 101 is changed according to the temperature. For example, no voltage is applied when the detected temperature is 40 ° C. or lower. When the detected temperature exceeds 40 ° C. and is 50 ° C. or lower, a voltage of 30% of the rated voltage (about 8V in the case of 24V) is applied. When the detected temperature exceeds 50 ° C., 50% of the rated voltage (12 V in the case of 24 V) is applied.

  Instead of changing the applied voltage, the on / off time of the application time may be changed as described above.

  In this case, in the block diagram of FIG. 3, the control unit 701 controls the voltage control circuit 703 based on the temperature detected by the temperature sensor 705 and applies a voltage lower than the rated voltage to the fan motor 102 during non-fixing.

  In addition, a temperature sensor may be arranged in an image forming apparatus provided with a fixing device, and air may be blown at a wind speed corresponding to the temperature detected by the temperature sensor during non-fixing. That is, when the environmental temperature is high, the influence on the fan motor 102 becomes larger, so the wind speed is set to a high speed. Note that the temperature detected by the temperature sensor is made to correspond to the temperature of the recording paper, and it is desirable to dispose the temperature sensor in a place away from the high-temperature fixing device.

  As a specific example, the voltage applied to the fan motor 102 during non-fixing is set to 30% of the rated voltage (wind speed is also reduced to 30%) in a 20 ° C environment, and 40% of the rated voltage in a 30 ° C environment ( The wind speed is also reduced to 40%). Further, since condensation tends to occur on the printed circuit board 102C of the fan motor 102 at low temperatures, it is desirable to increase the applied voltage and set the wind speed at a high speed. Therefore, in a 10 ° C. environment, it is set to 40% of the rated voltage (wind speed is also reduced to 40%).

  In this case, in the block diagram of FIG. 3, the control unit 701 controls the voltage control circuit 703 based on the temperature detected by the temperature sensor 706 during non-fixing, and applies a voltage lower than the rated voltage to the fan motor 102.

  Further, the fixing temperature may be improved by changing the set temperature of the fixing member based on the print mode. In such a case, the air may be blown at a wind speed based on the print mode at the time of non-fixing. That is, at the time of non-fixing, the voltage applied to the fan motor 102 is changed, and the wind speed from the air nozzle 101 is changed. Specific examples are shown below. The discharge port of the air nozzle 101 is 3 mm long and 300 mm wide.

  In the color mode, when the set temperature of the fixing member is increased by 10 ° C. than in the monochrome mode, the voltage applied to the fan motor 102 is increased by 10%, and the wind speed is set about 2 m / s faster.

  In the case of the double-sided mode, when the set temperature of the fixing member is lowered by 10 ° C. on the second side than the first side, the voltage applied to the fan motor 102 is lowered by 10% and the wind speed is set slower by about 2 m / s.

  In the high gloss mode, when the set temperature of the fixing member is increased by 10 ° C. compared to the normal mode, the voltage applied to the fan motor 102 is increased by 10% and the wind speed is set to be about 2 m / s faster.

  The high gloss mode is a mode for forming a high-quality image as compared to the normal mode, and is a mode for forming a high-quality image or a photographic image, for example.

  In the thick paper mode and the coated paper mode, when the set temperature of the fixing member is increased by 10 ° C. compared to the plain paper mode, the voltage applied to the fan motor 102 is increased by 10% and the wind speed is set to be about 2 m / s faster. .

  In this case, in the block diagram of FIG. 3, the control unit 701 controls the voltage control circuit 703 based on the set print mode information 707 and applies a voltage to the fan motor 101 during non-fixing.

  Further, at the time of non-fixing, the air may be blown at a wind speed based on the print job information. That is, at the time of non-fixing, the voltage applied to the fan motor 102 may be changed to change the wind speed from the air nozzle 101.

  For example, since the temperature of the fixing belt 81 is likely to increase after the continuous sheet passing, the wind speed to the fan motor 102 is set to be high. As a specific example, at the time of non-fixing after continuously passing and fixing less than 30 recording papers, a voltage of 30% of the rated voltage (about 8V in the case of 24V) is applied, and 30 or more recording papers are applied. At the time of non-fixing after the paper is continuously fed and fixed, a voltage of 40% to 50% of the rated voltage (about 10V to 12V in the case of 24V) is applied.

Further, when the image density, that is, the toner adhesion amount on the recording paper is large, the set temperature of the fixing member may be increased. In this case, the wind speed to the fan motor 102 is set to be high. For example, if the set temperature of the fixing member is set higher by 10 ° C. when the toner adhesion amount is changed from 5 to 8 g / m ² to 10 to 15 g / m ² , the voltage applied to the fan motor 102 is increased by 10%. The wind speed is set about 2 m / s faster.

  In this case, in the block diagram of FIG. 3, the control unit 701 controls the voltage control circuit 703 based on the set job mode information 708 and applies a voltage to the fan motor 101 during non-fixing.

  When the control unit 701 controls based on the detected temperature, the print mode information, and the print job information when the recording material is not fixed, the control unit 701 does not control the voltage applied to the fan motor 102 to be lowered. In this manner, the on / off voltage may be repeatedly applied.

  In the above configuration, the fan motor 102 may be heated to a predetermined temperature or more as the temperature of the fixing belt 81 rises. If there is such a possibility, an on-off valve for opening and closing the flow path of the air nozzle 101 may be provided as shown in FIG.

  As shown in FIG. 4, the on-off valve 111 is supported by a support shaft 112 and is configured to be rotatable about the support shaft 112. A spring (not shown) is engaged with the support shaft 112, and the spring biases the on-off valve 111 counterclockwise. That is, the on-off valve 111 is urged in a direction to close the flow path of the air nozzle 101.

  A solenoid 114 is provided outside the air nozzle 101, and a plunger 114 </ b> A of the solenoid 114 passes through the side wall of the air nozzle 101 and engages with the on-off valve 111. At the time of fixing, when the solenoid 114 is energized, the rear end of the plunger 114A is retracted into the solenoid 114 as shown in FIG. Become. Therefore, the air blown to the fan motor 102 is discharged to the outlet side of the nip portion N.

  On the other hand, if the solenoid 114 is not energized at the time of non-fixing, the plunger 114A protrudes by a spring (not shown) provided inside the solenoid 114 as shown in FIG. It rotates in the clockwise direction, and the tip abuts against the inner wall of the air nozzle 101 to close the flow path of the air nozzle 101. As a result, since the air heated by the fixing belt 81 does not reach the fan motor 102, the electronic component mounted on the printed circuit board 102C is not damaged. In addition, since the exhaust port 101A is provided on the side wall of the air nozzle 101, the air heated by the fixing belt 81 and entering the air nozzle 101 passes through the exhaust port 101A and rises.

  Further, at the time of fixing, the on-off valve 111 closes the exhaust port 101A, so that part of the air blown from the fan motor 102 escapes and is not wasted.

  However, in the configuration of FIG. 4B, since the space between the fan motor 102 and the on-off valve 111 is a sealed space, an exhaust port may be provided in this space. However, it is desirable to provide this exhaust port in a portion where air blown from the fan motor 102 at the time of fixing is difficult to escape. Cold air blown by the fan motor 102 easily flows through this exhaust port.

  In addition, when the fan motor 102 is arranged at three locations in the center and both ends in the width direction of the recording paper, when feeding and fixing a small width recording paper, only the fan motor 102 arranged at the center is used. May be driven. In addition, when recording paper of a small width is continuously fed, heat is absorbed in the central portion of the fixing belt 81 due to the contact of the recording paper and the temperature is lowered, and the recording paper is not in contact at both ends. Does not drop in temperature. As a result, since a temperature difference occurs in the axial direction, it is desirable to make the wind speed of the fan motors 102 arranged at both ends higher than the wind speed of the fan motor 102 arranged in the central part at the time of non-fixing.

  Further, although the above embodiment has been described as a belt fixing device, the present invention can also be applied to a heat roller fixing device.

DESCRIPTION OF SYMBOLS 8 Fixing device 81 Fixing belt 101 Air nozzle 102 Fan motor 102A Fan 102B Motor 102C Print circuit board 111 Open / close valve 114 Solenoid 114A Plunger 701 Control means 702 Position sensor 703 Voltage control circuit 704 Timer 705, 706 Temperature sensor 707 Print mode information 708 Print job Information N Nip part P Recording paper

Claims (8)

In a fixing device that fixes a toner image of a recording material at a nip formed by a heated fixing member and a pressure member that pressurizes the fixing member.
A fan motor having a fan, a motor for rotating the fan, and a fan control unit for controlling the motor;
An air nozzle that blows air blown by the fan motor to the vicinity of the outlet portion of the nip portion;
Control means for controlling the wind speed of air discharged from the air nozzle to be lower than that at the time of fixing when the recording material is not fixed;
A fixing device comprising:   The fixing device according to claim 1, wherein the control unit controls to apply a voltage lower than a rated voltage to the fan motor when the recording material is not fixed.   The fixing device according to claim 1, wherein the control unit controls to repeatedly apply an on / off voltage to the fan motor when the recording material is not fixed.   4. A temperature sensor is disposed at or near the fan motor, and the control means controls to blow at a wind speed corresponding to the temperature detected by the temperature sensor when the recording material is not fixed. The fixing device according to any one of the above.   A temperature sensor is disposed inside an image forming apparatus provided with the fixing device, and the control means controls to blow at a wind speed corresponding to the temperature detected by the temperature sensor when the recording material is not fixed. The fixing device according to claim 1.   The fixing device according to any one of claims 1 to 3, wherein the control unit controls to blow at a wind speed based on print mode information when the recording material is not fixed.   The fixing device according to any one of claims 1 to 3, wherein the control unit controls to blow at a wind speed based on print job information when the recording material is not fixed.   An image forming apparatus comprising the fixing device according to claim 1.

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