JP2015028506A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus configured to prevent the hand or clothes of a user from being stained even if toner sticks to a non-image area on a recording medium.SOLUTION: The fixing apparatus controls a temperature of a heating area corresponding to the non-image area on the recording medium, on the basis of image information, so as to be lower than a temperature of a heating area corresponding to an image area. The fixing apparatus includes: a cleaning device 35 which removes unfixed toner on a fixed recording medium; and unfixed-toner amount detection means 52 which detects the amount of unfixed toner when the cleaning device 35 removes the unfixed toner. According to a detection result of the unfixed-toner amount detection means 52, a temperature of the heating area corresponding to the non-image area is controlled.

Description

  The present invention relates to a fixing device capable of controlling the temperature of a heating area corresponding to a non-image area on a recording medium to be lower than the temperature of a heating area corresponding to an image area based on image information, and the fixing apparatus The present invention relates to an image forming apparatus.

  In an image forming apparatus such as an electrophotographic system, a fixing device that fixes a toner image on a sheet as a recording medium is provided. The fixing device includes a fixing member heated by a heating unit and a contact member that contacts the fixing member, and the sheet passes through a nip portion formed by the contact between the fixing member and the contact member. Thus, the toner on the paper is heated and melted and fixed.

  In general, the heating unit is configured to heat the fixing member over the entire sheet passing width, and the entire sheet is thereby heated. However, when the image exists only in a partial area of the paper, heat energy is wasted in the non-image area where the image does not exist.

  Therefore, in order to reduce wasteful heat energy consumption in the non-image area, for example, in Patent Document 1 below, the heating area is changed according to the image on the paper, and the image area necessary for fixing is heated. A fixing device that does not heat non-image areas that are not necessary for fixing or controls the heating temperature to be low has been proposed.

  Incidentally, in an image forming apparatus, toner may adhere to a non-image area on a sheet due to an abnormality in a development process or a transfer process. When the toner adheres to the non-image area, in the fixing device in which the non-image area is not heated or the heating temperature is lowered as described above, the toner adhering to the non-image area is not melted after the fixing process and is not yet determined. Residual toner remains on the paper. For this reason, there is a possibility that unfixed toner may fall off from the printed paper, and the user's hand or clothes handling the paper may be soiled.

  In view of such circumstances, the present invention provides a fixing device that does not stain a user's hand or clothes even when toner adheres to a non-image area on a recording medium, and an image including the fixing device. A forming apparatus is to be provided.

  In order to solve the above-described problems, the present invention provides a fixing member, an abutting member that abuts the fixing member to form a nip portion, a heating unit that heats the fixing member, and a heating control that controls the heating unit. The heating means includes a plurality of heating regions that can be independently heated and divided in the width direction of the recording medium, and the heating control means performs recording based on the image information. Cleaning for removing unfixed toner on a recording medium after fixing processing in a fixing device that controls a temperature of a heating area corresponding to a non-image area on the medium to be lower than a temperature of a heating area corresponding to an image area And an unfixed toner amount detecting means for detecting an unfixed toner amount when the cleaning device removes the unfixed toner, and a non-image is detected according to a detection result of the unfixed toner amount detecting means. Characterized by being configured to control the temperature of the heating area corresponding to the frequency.

  According to the present invention, it is possible to grasp the amount of unfixed toner adhering to the non-image area by detecting the amount of unfixed toner when the cleaning device removes the unfixed toner. Then, by controlling the temperature of the heating area corresponding to the non-image area according to the detection result of the unfixed toner amount, it is possible to fix the unfixed toner in the non-image area and prevent the toner from falling off. Accordingly, it is possible to provide a fixing device that does not contaminate the user's hand or clothes.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. 1 is a schematic configuration diagram of a fixing device. It is a perspective view of the fixing device showing the configuration of the heater. It is a top view which shows an image formation pattern. FIG. 7 is a diagram illustrating a heater output and a temperature change of a fixing belt during paper passing. It is a schematic block diagram of a cleaning apparatus. FIG. 6 is a diagram illustrating an example of a temperature control method of the fixing device. FIG. 10 is a diagram illustrating another example of a temperature control method of the fixing device. It is a figure which shows the flow of temperature control. It is a figure which shows the example of another control system. It is a schematic block diagram of the cleaning apparatus which concerns on 2nd Embodiment of this invention. FIG. 6 is a diagram illustrating a state in which toner adheres to a non-image area of a sheet in a streak shape. FIG. 4 is a diagram illustrating a state in which streaky toner is adsorbed on an electrode roller. It is a graph which shows the reflected light intensity at the time of detecting the surface of the electrode roller shown in FIG. 13 with an optical sensor. FIG. 6 is a diagram illustrating an unfixed toner adhesion amount on a sheet after cleaning with a cleaning device. It is a figure for demonstrating the method of resetting a threshold value. It is a figure which shows the toner fall and stripe image which arose on the electrode roller. 1 is a schematic configuration diagram of a color image forming apparatus equipped with a fixing device according to the present invention. It is a schematic block diagram of the other fixing apparatus which can apply this invention. FIG. 6 is a schematic configuration diagram of still another fixing device to which the present invention is applicable.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each of the drawings for explaining the embodiments of the present invention, constituent elements such as members and components having the same function or shape are described once by giving the same reference numerals as much as possible. Then, the explanation is omitted.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention.
The image forming apparatus according to the first embodiment is a monochrome image forming apparatus, and a photosensitive member 2 as an image carrier is disposed in the center of the apparatus main body 1. Around the photosensitive member 2, a charging roller 3 as a charging unit, a light source 4 and a mirror 5 constituting an exposure unit, a developing unit 7 including a developing roller 6, a transfer unit 8, and a cleaning blade 9 are provided. Means 10 and the like are arranged.

  Further, the apparatus main body 1 includes a paper feed tray 11 that stores paper P as a recording medium, a paper feed roller 12 that carries out the paper P from the paper feed tray 11, and foreign matter such as paper dust from the paper P that has been carried out. Removing brush 50 as a foreign matter removing means for removing the toner, a foreign matter collecting unit 51 for collecting the foreign matter removed by the removing brush 50, a pair of registration rollers 13 as a timing roller, and a fixing device for fixing an image on the paper P 14, a cleaning device 35 that removes unfixed toner adhering to the non-image area of the paper P, and an unfixed toner amount detection unit that detects the amount of unfixed toner when the cleaning device 35 removes the unfixed toner. And a paper discharge roller 15 for discharging the paper P to the outside of the apparatus. In addition to plain paper, the recording medium includes cardboard, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, and the like. Although not shown, a manual paper feed mechanism may be provided.

Next, the basic operation of the image forming apparatus according to the present embodiment will be described with reference to FIG.
When the image forming operation is started, the photosensitive member 2 is rotationally driven clockwise by a driving device (not shown), and the surface of the photosensitive member 2 is uniformly charged to a predetermined polarity by the charging roller 3. Next, the exposure light emitted from the light source 4 is scanned through the mirror 5 based on image information from a reading device, a computer, or the like (not shown), and is applied to the charged surface of the photoreceptor 2. As a result, an electrostatic latent image is formed on the surface of the photoreceptor 2. By supplying toner from the developing roller 6 to the electrostatic latent image, the electrostatic latent image is visualized (visualized) as a toner image.

  When the image forming operation is started, the paper feed roller 12 starts to rotate, and the paper P is separated and sent out from the paper feed tray 11 one by one. After the foreign material such as paper dust is removed by the removal brush 50, the fed paper P is temporarily stopped by the registration roller 13 and the deviation of the posture is corrected. Thereafter, the registration roller 13 is driven to rotate in synchronization with the rotation of the photosensitive member 2, and the paper P is conveyed at a timing when the leading end of the toner image on the photosensitive member 2 coincides with a predetermined position at the leading end of the conveying direction of the paper P. Then, the toner image on the photoreceptor 2 is transferred onto the conveyed paper P by the transfer electric field formed by the transfer unit 8. Residual toner remaining on the photoreceptor 2 without being transferred onto the paper P reaches the cleaning blade 9 as the photoreceptor 2 rotates, and is scraped off and removed by the cleaning blade 9. Then, the surface of the photoreceptor 2 is neutralized by a neutralizing unit (not shown) and is prepared for the next image forming process.

  The paper P on which the toner image has been transferred is conveyed to the fixing device 14, and the toner image on the paper P is fixed by the fixing device 14. Subsequently, the paper P is conveyed to the cleaning device 35. At this time, if unfixed toner adheres to the non-image area of the paper P, the unfixed toner on the non-image area is removed by the cleaning device 35. Further, the amount of toner dust generated when the cleaning device 35 is operated is detected by the dust detection sensor 52. When the detected toner dust amount exceeds a preset threshold value, the fixing device 14 is controlled based on the result. A specific control method will be described later. Thereafter, the paper P is discharged out of the apparatus by the paper discharge roller 15.

FIG. 2 is a schematic configuration diagram of the fixing device.
As shown in FIG. 2, the fixing device 14 heats a fixing belt 21 as a fixing member, a pressure roller 22 as an abutting member that contacts the fixing belt 21 to form a nip portion N, and the fixing belt. And a heater 23 as a heating means.

  The fixing belt 21 is composed of an endless belt member (including a film) that is thin and flexible. Specifically, the fixing belt 21 includes a base material 21a made of SUS having an outer diameter of 40 mm and a thickness of 40 μm, an elastic layer 21 b made of silicone rubber having a thickness of 100 μm covering the outer peripheral surface of the base material 21 a, and the elastic layer 21 b. And a release layer 21c made of a fluororesin such as PFA or PTFE having a thickness of 5 to 50 μm covering the outer peripheral surface. The base 21a of the fixing belt 21 may be made of a resin material such as polyimide.

  The pressure roller 22 includes an iron cored bar 22a having an outer diameter of 40 mm and a thickness of 2 mm, and an elastic layer 22b covering the outer peripheral surface of the cored bar 22a. The elastic layer 22b of the pressure roller 22 is made of silicone rubber and has a thickness of 5 mm. Moreover, in order to improve mold release property, you may arrange | position the mold release layer which consists of fluorine resin about 40 micrometers thick in the outer peripheral surface of the elastic layer 22b.

  A nip forming member 24 is disposed at a position facing the pressure roller 22 on the inner peripheral side of the fixing belt 21. The nip forming member 24 is supported by a side plate (not shown) of the fixing device 14 at both ends thereof. When the pressure roller 22 is brought into pressure contact with the nip forming member 24 by a pressure means such as a pressure lever, a nip portion N having a predetermined width is formed at the pressure contact portion between the fixing belt 21 and the pressure roller 22. ing. The fixing member and the abutting member may be simply brought into contact with each other without applying pressure.

  The pressure roller 22 is configured to be rotationally driven in the direction of arrow B in the figure by a drive source such as a motor (not shown). When the pressure roller 22 is rotationally driven, the driving force is transmitted to the fixing belt 21 at the nip portion N, and the fixing belt 21 is driven to rotate in the direction of arrow C in the figure. A belt support member 29 that supports the fixing belt 21 is disposed on the inner peripheral side of the fixing belt 21.

  The heater 23 is composed of a planar or plate-like heating element such as a thermal heater or a ceramic heater. A stay 31 as a support member is disposed on the inner peripheral side of the fixing belt 21, and the stay 31 causes the heater 23 to be upstream of the nip portion N in the sheet conveyance direction A, and the fixing belt 21. It is supported so as to face the inner peripheral surface. Further, a power source 25 is connected to the heater 23 so that power is supplied from the power source 25 to the heater 23. The output of the power source 25 is controlled by the heating control means 26. The heating control means 26 is composed of a microcomputer including a CPU, ROM, RAM, I / O interface and the like.

  The fixing device 14 includes a first thermistor 27 as a heater temperature detecting unit that detects the temperature of the heater 23, and a second thermistor 28 as a belt temperature detecting unit that detects the temperature of the fixing belt 21. The first thermistor 27 is disposed so as to be in direct contact with the heater 23, and the second thermistor 28 is opposed to the outer peripheral surface of the fixing belt 21 on the upstream side in the belt rotation direction C with respect to the heater 23. It is arranged. The temperature information detected by each thermistor 27, 28 is input to the heating control means 26, and the heating control means 26 is configured to control the output of the power source 25 based on this input information. ing.

  A pressing roller 30 as a pressing member that presses the fixing belt 21 from the outer peripheral side is disposed at a position facing the heater 23. The fixing belt 21 is brought into contact with the heater 23 by pressing the fixing belt 21 from the outer peripheral side by the pressing roller 30. The pressing roller 30 has an outer diameter of 15 mm to 30 mm, an iron core metal 30 a having an outer diameter of 8 mm, and an elastic layer 30 b made of silicone rubber having a thickness of 3.5 mm to 11 mm covering the outer peripheral surface of the core metal 30 a. It consists of and. Further, in order to improve the mold release property, a mold release layer made of a fluorine resin having a thickness of about 40 μm may be disposed on the outer peripheral surface of the elastic layer 30b. Here, the pressing roller 30 is pressed against the fixing belt 21 by a pressing means (not shown). However, a configuration in which the pressing roller 30 is simply brought into contact without pressing is also possible.

The basic operation of the fixing device will be described with reference to FIG.
When the power switch of the image forming apparatus main body is turned on, power is supplied from the power source 25 to the heater 23, and the pressure roller 22 starts to rotate in the direction of arrow B in the figure. As a result, the fixing belt 21 is driven to rotate in the direction of arrow C in the figure by the frictional force with the pressure roller 22.

  Thereafter, when the sheet P carrying the unfixed toner image G through the image forming process is conveyed to the nip portion N between the fixing belt 21 and the pressure roller 22, the sheet P is heated and heated. The toner image G on the paper P is fixed. Then, after the sheet P is carried out from the nip portion N, it is discharged out of the apparatus.

Hereinafter, the configuration of the fixing device according to the present embodiment will be described in more detail.
As shown in FIG. 3, the heater 23 has a plurality of (seven in the figure) heating elements 32 arranged at equal intervals in the width direction of the paper P, and each heating element 32 is independent of each other. It is configured to generate heat. That is, the heater 23 has a plurality of heating regions that can be independently heated and divided in the width direction of the paper P. The heat generation of each heating element 32 is controlled by the heating control means 26.

  Specifically, the heating control unit 26 controls the change of the heating region in the paper width direction by selecting the heating element 32 to generate heat from among the plurality of heating elements 32 and the ON / OFF timing of the heating element 32. Thus, the heating area in the rotation direction can be changed, and the heating amount (heating temperature) can be changed by controlling the heat generation amount of the heating element 32. Note that the amount of heat generated (output) of the heat generating element 32 is controlled by increasing or decreasing the power supplied to the heat generating element 32 or changing the lighting duty (the ratio of the ON time during a predetermined time).

  For example, as shown in FIG. 4A, in the case of the paper P on which the image area a, the non-image area b, and the image area c are formed in order from the leading end side in the paper conveyance direction A, the image area In a and c, fixing is necessary, but in the non-image area c, fixing is not necessary. In such a case, the heating control means 26 determines the temperature of the part of the fixing belt 21 corresponding to the non-image area b based on the image information obtained from the image processing means 33 (see FIG. 2). The heater 23 is controlled to be lower than the temperature of the portion of the fixing belt 21 corresponding to. That is, in this case, the power supply to all the heating elements 32 is normally performed at the locations corresponding to the image areas a and c, but the power supply to all the heating elements 32 is reduced at the locations corresponding to the non-image areas b. Or stop. As described above, in the portion corresponding to the non-image area b, wasteful heat energy consumption to the non-image area b can be reduced by reducing or stopping the power supplied to the heating element 32.

  As shown in FIG. 4B, when the image area d and the non-image area e are mixed in the width direction of the paper P, it corresponds to the non-image area e among the plurality of heating elements 32. The power supply to the heating element 32 at the position (right side in the figure) is reduced or stopped. Thereby, useless heat energy consumption to the non-image area e can be reduced.

  In the example shown in FIG. 4C, the image area and the non-image area are mixed in the width direction and the conveyance direction of the paper P. In this case, the power supply to the heating element 32 is reduced or stopped in correspondence with the non-image area formed in the portion where the range of the symbol g and the range of the symbol i in the figure overlap with each other. Similarly, useless heat energy consumption to non-image areas can be reduced.

  FIG. 5 is a diagram illustrating the output of the heater and the temperature change of the fixing belt when the sheet illustrated in FIG. 4A is passed. Hereinafter, the temperature control of the fixing belt will be described with reference to FIG.

  As shown in FIG. 5, at the timings Ta and Tc when the image areas a and c on the paper pass through the nip portion, the temperature of the fixing belt is set to a predetermined first target temperature Q1 necessary for fixing. Controls the power supplied to the heating element. Specifically, the first target temperature Q1 is set to 140 ° C., for example, in order to reliably fix the toner on the image areas a and c. On the other hand, at the timing Tb when the non-image area b passes through the nip portion, power supply to the heating element is reduced to control the second target temperature Q2 that is lower than the first target temperature Q1, which is wasteful. Reduce energy consumption. Here, in the times Tb, T1, and T2 when the image areas a and c do not pass through the nip portion, the power supply to the heating element may be stopped completely. Alternatively, the temperature rise corresponding to the first image area may not be in time. Therefore, as in the example shown in FIG. 5, the output W2 smaller than the output W1 for the first target temperature Q1 is set as the output of the heating element, and the non-passing times Tb, T1, T2 of the image area It is desirable to perform control so as to maintain the second target temperature Q2 that is lower than the first target temperature Q1 but higher than room temperature by heating with a small output W2. Specifically, it is desirable that the second target temperature Q2 is 80 ° C. or higher. In the present embodiment, the second target temperature Q2 is set to 100 ° C.

  In general, it takes a certain time for the temperature of the fixing belt to reach the target temperature after the heating of the fixing belt is started. Accordingly, when the rise at the output W1 for the first target temperature Q1 is started when the leading edge of the image area a reaches the nip portion, the temperature rise to the first target temperature Q1 is not in time. Therefore, as in the example shown in FIG. 5, in consideration of the heating time of the fixing belt, the output is performed for a predetermined time Tx from the timing before the leading ends of the image areas a and c reach the nip portion. It is desirable to perform preheating with W1. However, from the viewpoint of energy saving, it is desirable that the preheating time Tx is as short as possible. In addition, the temperature increase time of the fixing belt varies depending on the heat transfer coefficient of the fixing belt itself, the heat generation length in the rotation direction, and the like, and therefore it is preferable to specify the temperature beforehand by experiments.

  In the example shown in FIG. 5, the fixing temperatures of the image areas a and c are set to the same first target temperature Q1, but the target temperatures may be varied depending on the image areas.

  For example, when the image type of each image area is different for characters, photographs, drawings, etc., the target temperature corresponding to each image area may be varied depending on the image type. In particular, when the image is a photograph, it may be necessary to increase the glossiness of the image. Therefore, a desired glossiness can be obtained by setting a high target temperature for the image area of the photograph.

  Also, if the image pattern of each image area is different for solid images, halftone images, line images, character images, etc., or if the image pattern processing method is different for dither method, error diffusion method, etc., the image pattern and processing The target temperature corresponding to each image region may be varied depending on the method. It is known that the degree of isolation or density of toner particles differs depending on various image patterns, and the toner is more easily peeled off when it is isolated than when it is dense. Therefore, for image patterns with isolated toner, the target temperature is raised to make it difficult to peel off. On the other hand, for image patterns with dense toner, reducing the target temperature reduces energy consumption. Is possible.

  In addition, when the toner adhesion amount of each image area is different, the temperature required for fixing is different, so the toner adhesion amount is grasped based on the image information, and the target temperature is different for each image area accordingly. It may be allowed. Usually, in an image with a large amount of toner adhesion, a large amount of heat is required for melting the toner, and thus it is necessary to raise the target temperature. On the contrary, for an image with a small amount of toner, the target temperature can be lowered to reduce energy consumption.

  In a color image forming apparatus using a plurality of color toners, the amount of heat required for fixing may differ depending on the color of the toner. In this case, the target temperature may be varied depending on the color of the toner. For example, black toner often requires less heat than other color toners, such as yellow, cyan, and magenta. Therefore, in an image area where only black toner is used, the target temperature By reducing the value, energy consumption can be reduced.

FIG. 6 is a schematic configuration diagram of the cleaning device.
As shown in FIG. 6, the cleaning device 35 of the present embodiment includes a cleaning brush 36 as a removing member that removes unfixed toner on the paper P after the fixing process, and a counter member as a counter member that faces the cleaning brush 36. A roller 38 and a case 39 for housing the cleaning brush 36 are provided.

  The cleaning brush 36 is a brush roller including a cored bar 36a and a large number of brush fibers 36b provided on the outer peripheral surface of the cored bar 36a. The cleaning brush 36 is disposed on the image forming surface side of the conveyed paper P, and the opposing roller 38 is disposed on the surface opposite to the image forming surface of the paper P.

As shown in FIG. 6, when the paper P after the fixing process enters between the cleaning brush 36 and the opposing roller 38, the cleaning brush 36 that rotates in the direction of arrow D and the opposing roller 38 that rotates in the direction of arrow E P is conveyed in the direction of arrow A. Here, the sheet P is fixed, but as described above, the heating area corresponding to the non-image area is heated at a low temperature, so that by any chance toner adheres to the non-image area on the sheet P. The toner on the non-image area exists as unfixed toner. In FIG. 6, unfixed toner on the non-image area is indicated by a symbol i, and fixed toner on the image area is indicated by a symbol j. When the sheet P to which such unfixed toner i adheres enters between the cleaning brush 36 and the opposing roller 38, the unfixed toner i is mechanically scraped off by the rotating cleaning brush 36, and the sheet P is removed from above the sheet P. Removed.

When the unfixed toner i on the paper P is scraped off by the cleaning brush 36, dust of the unfixed toner is generated by the scraping operation at this time. The unfixed toner that has become dust is detected by the dust detection sensor 52. The dust detection sensor 52 includes, for example, DISTTRK AEROSOL MONITOR 8520 manufactured by TIS, but other dust detection sensors may be used. Instead of the cleaning brush 36, a means for removing unfixed toner by blowing air onto the paper may be used to detect the amount of toner dust generated at that time.

  The toner dust amount detected by the dust detection sensor 52 is related to the adhesion amount of unfixed toner in the non-image area. That is, as the amount of unfixed toner adhering to the non-image area increases, the amount of toner dust detected by the dust detection sensor 52 increases. Therefore, the detection result of the dust detection sensor 52 serves as an index representing an abnormality in which toner adheres to the non-image area.

  As described above, in this embodiment, the unfixed toner on the paper is removed by the cleaning brush 36. However, it is not yet determined depending on the amount of unfixed toner attached, the removal ability of the cleaning brush 36, and various other factors. In some cases, the toner contact may not be completely removed. In that case, since unfixed toner remains on the paper, the user's hand or clothes may be stained by the unfixed toner. Therefore, in the present embodiment, the heating control means 26 (see FIG. 2) controls the temperature of the heating area corresponding to the non-image area according to the toner dust amount (unfixed toner amount) detected by the dust detection sensor 52. Like to do.

Hereinafter, the temperature control method will be described in detail.
In the present embodiment, in addition to the first target temperature Q1 and the second target temperature Q2 that is lower than the first target temperature Q1, the second target temperature Q2 is lower than the first target temperature Q1. A higher third target temperature Q3 is set (Q1>Q3> Q2). As described above, the first target temperature Q1 is the temperature of the heating area corresponding to the image area, and is set to 140 ° C. in this embodiment in order to reliably fix the toner on the image area. On the other hand, the second target temperature Q2 is the temperature of the heating area corresponding to the non-image area, and is set to 100 ° C. in order to reduce wasteful heat energy consumption to the non-image area. In the present embodiment, the third target temperature Q3 is set to 120 ° C., which is lower than the first target temperature Q1 (140 ° C.) and higher than the second target temperature Q2 (100 ° C.). . This temperature of 120 ° C. is a temperature at which the toner adhering to the non-image area on the paper can be fixed to the extent that it does not fall off the paper. More specifically, it is a fixing temperature at which a sufficient fixing property can be obtained at a toner adhesion amount of 50% of a monochromatic solid image, and the fixing property was evaluated using a smear method.

  In the present embodiment, normally, the temperature of the fixing belt becomes the first target temperature Q1 at the timings Ta and Tc when the image area on the sheet passes through the nip portion as in the temperature control indicated by the one-dot chain line in FIG. At the timing Tb when the non-image area on the paper passes through the nip portion, the temperature of the fixing belt is controlled to be the second target temperature Q2. However, when the amount of toner dust detected by the dust detection sensor 52 exceeds a preset threshold, unfixed toner is attached to the non-image area to the extent that the user's hand or clothes may be stained. Then, as shown by the solid line in FIG. 7, the temperature of the heating area corresponding to the non-image area is controlled to be the third target temperature Q3 higher than the second target temperature Q2. Note that the temperature of the heating area corresponding to the image area is controlled to be the first target temperature Q1 as described above.

  As described above, when the toner dust amount detected by the dust detection sensor 52 exceeds the threshold value, the temperature of the heating area corresponding to the non-image area is changed from the second target temperature Q2 to the third target temperature Q3. Thus, it is possible to fix the toner on the non-image area on the paper discharged thereafter. As a result, it is possible to prevent the user's hand, clothes, and the like from being soiled by unfixed toner.

  However, when a paper with a lot of paper dust is conveyed, there is a possibility that the dust detection sensor 52 detects the paper dust on the paper and erroneously detects that the dust of the unfixed toner is detected. Therefore, in order to prevent such erroneous detection, in this embodiment, as shown in FIG. 2, a removal brush that removes foreign matters such as paper dust on the paper upstream of the fixing device 14 in the paper conveyance direction. 50 is provided. Thereby, since paper dust etc. can be removed beforehand by the removal brush 50, the erroneous detection by the dust detection sensor 52 detecting paper dust can be prevented.

  In the example shown in FIG. 7, the third target temperature Q3 is set to a temperature lower than the first target temperature Q1, but the third target temperature Q3 is set to the first target temperature Q1 as in the example shown in FIG. Simple control may be performed by setting the same temperature as the target temperature Q1. On the other hand, as shown in FIG. 7, when the third target temperature Q3 is set to a temperature lower than the first target temperature Q1, wasteful heat energy consumption can be reduced. In particular, when printing a color image, since a plurality of color toners overlap, the temperature sufficient for fixing becomes higher than when printing a monochrome image. Therefore, the third target temperature Q3 is set to the first target temperature Q1. By setting the temperature lower than that, a greater energy saving effect can be expected. For this reason, the third target temperature Q3 is set lower than the first target temperature Q1 (Q1> Q3> Q2) only when forming a color image, and the third target temperature Q3 is set to be the first when forming a monochrome image. It is also possible to set the same as the target temperature Q1 of 1 and perform simple control (Q1 = Q3> Q2).

FIG. 9 shows a flow of temperature control.
Hereinafter, a normal control mode in which temperature control is performed using the second target temperature Q2 is referred to as a “first control mode”, and a control mode at the time of occurrence of an abnormality in which temperature control is performed using the third target temperature Q3. This will be described as “second control mode”.

  In this embodiment, the first control mode is initially set. As shown in FIG. 9, when printing is started, the first sheet is first fixed in the first control mode. . Thereafter, cleaning is performed by the cleaning device 35, and the amount of toner dust generated at that time is detected by the dust detection sensor 52. If the detected amount of toner dust is less than or equal to the threshold value, it is determined that there is no abnormality, and control in the first control mode is maintained. Thereafter, when printing is continued, the fixing process, the cleaning process, and the toner dust amount detection in the first control mode are performed for each sheet in the same manner as described above.

  On the other hand, if the amount of toner dust detected on the first sheet or subsequent sheets exceeds the threshold, it is determined that there is an abnormality, and the control mode is changed from the first control mode to the second control mode. The When the mode is changed to the second control mode, the fixing process is performed in the second control mode for the paper to be printed thereafter.

  Here, the above-mentioned abnormality, that is, the phenomenon in which unfixed toner adheres to the non-image area to the extent that the user's hand or clothes may become dirty, is mainly due to the life of the image forming unit. Even when the replacement time has passed and the image forming unit is still used. For this reason, once an abnormal image with unfixed toner attached to the non-image area is output, the same abnormal image tends to be output continuously. Therefore, in this embodiment, when the mode is once changed to the second control mode, even if the detection result by the dust detection sensor 52 becomes equal to or lower than the threshold value, the first control mode is used regardless of the detection result. However, the second control mode is maintained. By controlling in this way, it becomes possible to stably control without repeatedly increasing or decreasing the fixing temperature.

  However, when the image forming unit is replaced with a new one, the above-described abnormalities are resolved, so that the unit replacement detecting means 53 (see FIG. 2) detects that the image forming unit has been replaced. Returns to the first control mode. As the unit replacement detection means 53, a device that reads and detects information of an ID chip provided in the image forming unit, a device that detects with a mechanical configuration, and the like can be adopted.

  When the image forming unit is exchanged, the cover of the apparatus main body is generally opened and closed. For this reason, as shown in FIG. 10, instead of the unit replacement detecting means 53, a cover closing detecting means 54 may be provided. When the cover closing detection means 54 detects the closing of the cover of the apparatus main body, the fixing temperature control is returned from the second control mode to the first control mode on the assumption that the image forming unit may be replaced. However, in this method, if the image forming unit is replaced when the power of the apparatus main body is turned off, the cover closing detection unit 54 may not be able to detect the cover closing. Therefore, as shown in FIG. 10, a power-on detection means 55 for detecting power-on of the apparatus main body is provided, and when power-on of the apparatus main body is detected, control can be performed so as to return to the first control mode. desirable.

The configuration of the second embodiment of the present invention will be described below.
In the second embodiment of the present invention, compared with the first embodiment, the cleaning device 35 mainly removes the unfixed toner on the paper after the fixing process, and the cleaning device 35 removes the unfixed toner. The configuration of the unfixed toner amount detecting means for detecting the unfixed toner amount at this time is different. Otherwise, the configuration is basically the same as in the first embodiment.

  As shown in FIG. 11, the cleaning device 35 according to the second embodiment includes a cleaning brush 36 and a counter roller 38 as in the first embodiment, but the metal core 36 a of the cleaning brush 36 includes A predetermined voltage is applied from the cleaning brush power supply 40.

  Here, if the cleaning brush 36 is a first removal member that removes unfixed toner from the paper, in the second embodiment, a second removal that removes unfixed toner adhering to the first removal member is performed. As a member, an electrode roller 41 that contacts the cleaning brush 36 is provided. The electrode roller 41 includes a conductive metal core 41a and an insulating surface layer 41b that covers the outer peripheral surface of the metal core 41a. A predetermined voltage is applied to the core metal 41 a of the electrode roller 41 from the electrode roller power supply 43.

  Furthermore, the cleaning device 35 according to the second embodiment includes a scraper 42 as a third removal member that removes unfixed toner adhering to the second removal member (electrode roller 41). The scraper 42 is disposed in contact with the surface of the electrode roller 41.

  In the second embodiment, an optical sensor 44 is used as unfixed toner amount detection means. The optical sensor 44 is disposed so as to face the electrode roller 41, and irradiates the electrode roller 41 with light to detect the intensity of reflected light. Here, the optical sensor 44 irradiates the surface of the electrode roller 41 with light from the position where the surface of the electrode roller 41 comes into contact with the cleaning brush 36 to the contact position with the scraper 42, and the reflected light thereof. Detect intensity. At this time, if unfixed toner is attached on the electrode roller 41, a part of the light emitted from the optical sensor 44 is absorbed by the unfixed toner on the electrode roller 41, and the reflected light intensity is reduced. Therefore, by detecting the intensity of reflected light from the electrode roller 41, it is possible to detect the amount of unfixed toner adhering to the electrode roller 41. In the present embodiment, the optical sensor 44 detects the reflected light intensity over the entire axial direction of the electrode roller 41. As the optical sensor 44, for example, a line sensor (WD6R305X manufactured by Mitsubishi Electric Corporation) or the like can be used.

As shown in FIG. 11, when the paper P after the fixing process enters between the cleaning brush 36 and the opposing roller 38, the cleaning brush 36 that rotates in the arrow D direction and the arrow E direction as in the first embodiment. The sheet P is conveyed in the direction of arrow A by the counter roller 38 that rotates in the direction of A. A predetermined voltage is applied to the cleaning brush 36 from the cleaning brush power supply 40 so that the potential of the cleaning brush 36 is opposite to the toner charging polarity with respect to the potential of the counter roller 38. For example, when the charging polarity of the toner is negative, a positive voltage is applied to the cleaning brush 36 so that the cleaning brush 36 has a positive potential with respect to the installation potential (0 V) of the opposing roller 38. . As a result, an electrostatic force that moves the toner toward the cleaning brush 36 is generated between the cleaning brush 36 and the opposing roller 38. For this reason, the paper P to which the unfixed toner i adheres is removed from the cleaning brush 36 and the opposing roller 3
8, the unfixed toner on the paper P is transferred to the cleaning brush 36 by the electrostatic force and is adsorbed by the brush fibers 36b of the cleaning brush 36. As a result, unfixed toner is removed from the non-image area.

  The unfixed toner adsorbed by the cleaning brush 36 is electrostatically adsorbed and collected by the electrode roller 41 rotating in the arrow F direction. Specifically, cleaning is performed by applying a predetermined voltage from the electrode roller power supply 43 to the electrode roller 41 such that the potential of the electrode roller 41 is opposite to the charging polarity of the toner with respect to the potential of the cleaning brush 36. An electrostatic force that moves unfixed toner from the brush 36 to the electrode roller 41 is generated. For example, as described above, when the charge polarity of the toner is negative and when a positive voltage is applied to the cleaning brush 36, a higher positive electrode is applied so that the electrode roller 41 has a positive potential. Apply a positive voltage. Thereby, the unfixed toner adhering to the cleaning brush 36 is electrostatically removed by the electrode roller 41.

  Then, the reflected light intensity from the electrode roller 41 is detected by the optical sensor 44 from the position where the surface of the electrode roller 41 comes into contact with the cleaning brush 36 to the contact position with the scraper 42. If the reflected light intensity detected at this time falls below a predetermined value, that is, if the amount of unfixed toner on the electrode roller 41 exceeds a threshold value, the user's hand or clothes may be stained in the non-image area. It is determined that unfixed toner is attached to such a degree that the temperature is high, and the temperature of the heating area corresponding to the non-image area is higher than the second target temperature Q2 as in the first embodiment. It controls so that it may become temperature Q3. The detailed contents of the temperature control in the second embodiment are basically the same as the temperature control in the first embodiment (contents shown in FIGS. 7 to 10), and thus the description thereof is omitted.

  In the second embodiment, the unfixed toner on the electrode roller 41 passes through a position facing the optical sensor 44 and is then scraped off and mechanically removed by the scraper 42. Unfixed toner scraped off by the scraper 42 is accumulated in a collecting mechanism (not shown).

FIG. 12 is a diagram illustrating a state in which toner adheres in a streaky manner to a non-image area of a sheet.
In the example shown in FIG. 12, a halftone line having a line thickness of 0.5 pt (point), a halftone line of 1.0 pt, a solid line of 0.5 pt, and a solid line of 1.0 pt are formed in order from the left of the figure. Has been. These streaky abnormal images (unfixed toner) are removed from the sheet P by the cleaning brush 36 and then adsorbed onto the electrode roller 41.

  FIG. 13 is a diagram illustrating a state where the streaky abnormal image (unfixed toner) is adsorbed on the electrode roller 41. In this manner, streaky abnormal images are adsorbed on the electrode roller 41 in the rotation direction of the electrode roller 41.

FIG. 14 is a graph showing the reflected light intensity when the surface of the electrode roller 41 shown in FIG. 13 is detected by the optical sensor 44.
As shown in FIG. 14A, the reflected light intensity is reduced at the halftone line and the solid line. In particular, a solid line with a large amount of toner adhesion has a lower reflected light intensity than a halftone line with a small amount of toner adhesion. In each of the halftone line and the solid line, the reflected light intensity is lower for the thicker 1.0 pt than for the thinner 0.5 pt.

  The reflected light intensity indicated by the dotted line H in FIG. 14A is a threshold value that serves as a reference for abnormal image determination. Here, the reflected light intensity of a halftone line of 0.5 pt is set as the threshold value. Even if the halftone line of 0.5 pt is output in an unfixed state without being cleaned, smear measurement (scraping the unfixed toner on the paper with a white cotton cloth, and the ID (toner density) attached to the white cotton cloth) As a result of the test), the toner adhesion amount is such that the user's hand is not soiled. Therefore, when the reflected light intensity detected is lower than the reflected light intensity H of the halftone line of 0.5 pt, it is determined that the user's hand may become dirty. In this case, the temperature of the heating area corresponding to the non-image area is raised to the third target temperature Q3, and the unfixed toner on the non-image area is fixed and output.

  If the amount of toner adhering to the electrode roller 41 decreases for some reason despite the occurrence of black streaks exceeding 0.5 pt, the reflected light intensity is the above-mentioned threshold reflected light intensity H. It is detected as described above, and there is a possibility of erroneous detection that no abnormal image has occurred. However, in the present embodiment, as shown in FIG. 15, even if a 1.0 pt solid line occurs, the unfixed toner is removed to some extent by the cleaning device 35, so that the user's hand is not soiled (smear ID allowable This is not a problem because it can be suppressed to an unfixed toner adhesion amount (smear ID) below the line).

FIG. 14B shows the result of detecting the surface of the electrode roller 41 shown in FIG. 13 by the optical sensor 44 as in FIG. 14A. In this case, the optical for the electrode roller 41 is shown. The position of the sensor 44 is set at a position farther from the case of (a).
Even if the toner adhesion amount on the electrode roller 41 is the same, if the position of the optical sensor 44 with respect to the electrode roller 41 is separated, the sensitivity of the optical sensor 44 is lowered. Therefore, as shown in FIG. The drop in reflection intensity between the line and the solid line is smaller than that shown in FIG. If noise occurs in the reflected light intensity at the background portion of the electrode roller 41 when the position of the optical sensor 44 is separated, the difference in reflected light intensity between the background portion and the toner adhering portion becomes small, causing false detection. There is a possibility that. Therefore, it is desirable to increase the sensitivity of the optical sensor 44 by arranging the optical sensor 44 as close to the electrode roller 41 as possible. Furthermore, in order to make a difference in the reflected light intensity between the toner adhering portion and the background portion, the background portion of the electrode roller 41 may be processed into white or a color close thereto so that the reflected light intensity is increased.

  Similarly to the first embodiment, also in the second embodiment, when the image forming unit is replaced after shifting from the first control mode to the second control mode, the cause of the abnormal image may be generated. Returning to the first control mode again as improved. However, when a predetermined amount or more of unfixed toner adheres to the electrode roller 41 when returning to the first control mode, the mode immediately shifts to the second control mode based on the detection result of the optical sensor 44. As a method for avoiding this, there is a method in which the unfixed toner on the electrode roller 41 is removed by the scraper 42, but it is also conceivable that the unfixed toner cannot be completely removed.

  Therefore, in this embodiment, the electrode roller 41 is rotated for a predetermined time when the image forming unit is replaced (when the image forming unit replacement is detected, when the main body cover is closed, or when power is detected), and the electrode roller 41 is rotated by the scraper 42. After the unfixed toner on the upper side is removed, the intensity of reflected light from the electrode roller 41 is detected by the optical sensor 44, and the detection result at that time is set as a new reference value. Then, based on this reference value, a threshold value for determining an abnormal image is reset. Hereinafter, a method of resetting the threshold will be described.

  As shown in FIG. 16A, since no unfixed toner is attached to the electrode roller 41 at first, the reflected light intensity X of the ground portion of the electrode roller 41 is a uniform linear shape in the axial direction. become. A threshold U serving as a reference for abnormal image determination is set using the reflected light intensity X of the background portion as a reference value. Specifically, assuming that the amount of decrease in reflected light intensity when unfixed toner that is determined to be an abnormal image is attached is S, a value that is lower than the reference value X by the amount of decrease S is set as the threshold value U. Thus, since the threshold value U that is initially set is set to a value that is lower than the linear reference value X by a certain amount S, the threshold value U is a uniform value in the axial direction of the electrode roller 41.

  On the other hand, as shown in FIG. 16B, the reference value X newly set when the image forming unit is replaced has a certain amount of unfixed toner remaining on the electrode roller 41. The reflected light intensity is reduced at the location where the light is adhered, and the value becomes variable. Then, the reset threshold value U is set to a value that is lower than the new reference value X by a certain amount S similar to the above, and thus is set to a value that partially decreases in the axial direction of the electrode roller 41. .

  In addition, as shown in FIG. 17, when an abnormal image such as a toner drop where the toner adheres to a part of the electrode roller 41 in the circumferential direction is detected, a streaky abnormal image continuous in the circumferential direction is detected. Unlike the case, the reflected light intensity decreases at a certain position in the circumferential direction. In this case, since the reflected light intensity varies even in the circumferential direction, the new reference value is set even in the circumferential direction. Therefore, the threshold value is reset not only in the axial direction of the electrode roller 41 but also in the circumferential direction based on the new reference value.

  As a result of detecting the reflected light intensity by the optical sensor 44 based on the reset threshold value, if the reflected light intensity falls below at least one point in the circumferential direction and the axial direction with respect to the threshold value, an abnormal image is generated. Is determined, and the control mode is changed to the second control mode. Thereafter, when the image forming unit is replaced again, the reference value and the threshold value are reset as described above, and this is repeated thereafter.

  However, in the method of repeatedly resetting the reference value and threshold value, the reset reference value and threshold value gradually decrease as the amount of toner remaining on the electrode roller 41 gradually increases. When the amount of toner adhering to a certain portion on the electrode roller 41 approaches the limit value of the adsorbable toner amount, the portion further adsorbs an unfixed toner amount enough to detect the occurrence of an abnormal image. become unable. In other words, if the reference value Xn (the minimum value among them) reset n times falls below a certain value, even if an abnormal image occurs, the reflected light intensity of the electrode roller 41 does not fall below the threshold value Un, and an abnormal image is generated. Misdetection that misses.

  Therefore, in this embodiment, when the value of the reference value exceeds a predetermined value (when it falls below), the life of the electrode roller 41 is determined and the electrode roller 41 is replaced. Thereby, the erroneous detection as described above can be prevented.

  As described above, according to the present invention, it is possible to grasp the amount of unfixed toner adhering to the non-image area by detecting the amount of unfixed toner when the cleaning device removes the unfixed toner. It is. Then, by controlling the temperature of the heating area corresponding to the non-image area according to the detection result of the unfixed toner amount, it is possible to fix the unfixed toner in the non-image area and prevent the toner from falling off. Accordingly, it is possible to provide a fixing device that does not contaminate the user's hand or clothes.

  The image forming apparatus according to the present invention is not limited to the monochrome image forming apparatus as described above, but may be a printer, a copier, a facsimile, or a complex machine of these as other image forming apparatuses.

FIG. 18 is a schematic configuration diagram of a color image forming apparatus equipped with a fixing device according to the present invention.
The color image forming apparatus shown in FIG. 18 includes four process units 20Y, 20M, 20C, and 20K that are detachable from the apparatus main body 1. Each process unit 20Y, 20M, 20C, and 20K contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. The configuration is the same except that. Specifically, each of the process units 20Y, 20M, 20C, and 20K includes a photosensitive member 2, a charging roller 3 that charges the surface of the photosensitive member 2, a developing unit 7 that includes a developing roller 6, and a surface of the photosensitive member 2. A cleaning means 10 for cleaning is provided.

  Above each process unit 20Y, 20M, 20C, 20K, an intermediate transfer belt 16, a plurality of primary transfer rollers 17, and a secondary transfer roller 18 are provided as transfer means 8. An exposure device 19 is provided below each process unit 20Y, 20M, 20C, 20K.

  The image forming apparatus shown in FIG. 18 includes a reverse conveyance path R2 that conveys a sheet for duplex printing. The reverse conveyance path R2 branches from the conveyance path R1 on the downstream side in the sheet conveyance direction of the fixing device 14, and joins the conveyance path R1 on the upstream side in the sheet conveyance direction of the registration roller 13.

The basic image forming operation of the color image forming apparatus shown in FIG. 18 will be described below.
When the image forming operation is started, each photoconductor 2 in each process unit 20Y, 20M, 20C, 20K is rotationally driven, and the surface of each photoconductor 2 is uniformly charged to a predetermined polarity by the charging roller 3. . An electrostatic latent image is formed on the surface of each charged photoreceptor 2 by irradiating laser light from the exposure device 19. At this time, the image information to be exposed on each photoconductor 2 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. The electrostatic latent images formed on the respective photoreceptors 2 in this way are supplied with toner by the developing means 7 so that the electrostatic latent images are visualized (visualized) as toner images. .

  When the image forming operation is started, the intermediate transfer belt 16 is rotationally driven in the direction indicated by the arrow in the drawing. When each toner image of each color on the photoconductor 2 reaches the position of each primary transfer roller 17 with the rotation of each photoconductor 2, the transfer formed between the primary transfer roller 17 and the photoconductor 2. The toner images on the respective photoreceptors 2 are sequentially superimposed and transferred onto the intermediate transfer belt 16 by the electric field. Thus, a full-color toner image is carried on the surface of the intermediate transfer belt 16. Further, the surface of each photoconductor 2 after the transfer is cleaned by the cleaning means 10 and then discharged by a charge removal device (not shown).

  In the lower part of the apparatus main body 1, the paper feed roller 12 starts to rotate, and the paper P is sent out from the paper feed tray 11 to the transport path R1. The paper P sent to the transport path R1 is transported between the secondary transfer roller 18 and the intermediate transfer belt 16 at a predetermined timing after the transport is temporarily stopped by the registration roller 13. The toner images on the intermediate transfer belt 16 are collectively transferred onto the paper P by a transfer electric field formed between the secondary transfer roller 18 and the intermediate transfer belt 16. Thereafter, the paper P is conveyed to the fixing device 14, and after the toner image on the paper P is fixed to the paper P by the fixing device 14, the paper P is discharged out of the device by the paper discharge roller 15.

  In the case of duplex printing, the paper discharge roller 15 is rotated in the reverse direction, and the paper P discharged from the fixing device 14 (the paper with the image fixed on one side) is conveyed to the reverse conveyance path R2. Then, the sheet P passes through the reverse conveyance path R2 and is conveyed again to the conveyance path R1, so that the sheet P is supplied to the secondary transfer nip in a state where the paper is reversed. Thereafter, in the same manner as described above, after the toner image is transferred and fixed on the back surface of the paper P, the paper P is discharged out of the apparatus.

  The above description is an image forming operation when a full-color image is formed on a sheet, but a single color image is formed using any one of the four process units 20Y, 20M, 20C, and 20K. It is also possible to form a two-color or three-color image using two or three image forming units.

  Also in the color image forming apparatus configured as described above, by applying the configuration of the present invention, when toner adheres to the non-image area of the paper, the temperature of the non-image area is raised as in the above embodiment. Unfixed toner can be fixed. As a result, it is possible to prevent the user's hand or costume from being stained with toner.

The fixing device to which the present invention is applied is not limited to the one shown in FIG.
For example, like the fixing device 14 shown in FIG. 19, the heater 23 may be disposed at a position facing the pressure roller 22 so that the heater 23 also functions as the nip forming member 24 shown in FIG.

  Further, as shown in FIG. 20, the fixing roller 60 may be used as the fixing member, and the heater 23 may be disposed on the outer peripheral side of the fixing roller 60. The fixing roller 60 shown in FIG. 20 includes an aluminum core bar 60a having an outer diameter of 40 mm and a thickness of 1 mm, a heat insulating layer 60b covering the outer peripheral surface of the core metal 60a, and heat covering the outer peripheral surface of the heat insulating layer 60b. The conductive layer 60c and the release layer 60d covering the outer peripheral surface of the heat conductive layer 60c are configured.

  The heat insulation layer 60b is made of, for example, silicone rubber and has a thickness of 3 mm. Further, in order to further enhance the heat insulating function of the heat insulating layer 60b, the heat insulating layer 60b may be formed of a foamed silicone rubber with little heat escape.

  The heat conductive layer 60c is made of nickel, for example. However, the material of the heat conductive layer 60c is not limited to nickel, and may be any material having higher heat conductivity than that of the heat insulating layer 60b, such as an iron-based alloy such as stainless steel, a metal-based material such as aluminum or copper, or a graphite sheet. . By providing such a heat conductive layer 60c with good heat conductivity, local temperature variations in the surface temperature of the fixing roller 60 due to uneven heat generation of the heater 23 can be reduced. Further, since the temperature can be raised in a region slightly wider than the region where the heater 23 is provided by the heat conductive layer 60c, there is also an advantage that a deviation from the image can be compensated. Thereby, the freedom degree of setting of the magnitude | size, space | interval, etc. of the several heat generating body which comprises the heater 23 spreads.

  The release layer 60c is made of, for example, a fluorine-based resin such as PTF or PTFE, and has a thickness of 5 to 30 μm.

  20 includes a power supply 25 that supplies power to the heater 23, a heating control unit 26 that controls the heater 23 based on information obtained from the image processing unit 33, and the heater 23. A first thermistor 27 for detecting the temperature, a second thermistor 28 for detecting the temperature of the fixing member (fixing roller 60), and the like are provided.

  In addition, the heater 23 is not limited to the one that contacts the fixing member, and may be a non-contact type heating unit using an IH method using a coil and an inverter. In the case of the IH method, a plurality of heating coils are arranged in the width direction of the paper, or a plurality of members for canceling the magnetic flux are arranged in the axial direction of the paper, so that image information is obtained. It is possible to control the heating region and the heating amount according to the above.

14 Fixing device 21 Fixing belt (fixing member)
22 Pressure roller (contact member)
23 Heater (heating means)
26 Heating control means 35 Cleaning device 44 Optical sensor (unfixed toner amount detecting means)
50 Removal brush (foreign matter removal means)
52 Dust detection sensor (unfixed toner amount detection means)
60 Fixing roller (fixing member)
N Nip part

JP 2001-343860 A

Claims (10)

A fixing member; a contact member that contacts the fixing member to form a nip portion; a heating unit that heats the fixing member; and a heating control unit that controls the heating unit. A plurality of heating areas that can be independently heated and divided in the width direction of the recording medium, and the heating control means corresponds to a non-image area on the recording medium based on image information; In the fixing device that controls the temperature of the heater to be lower than the temperature of the heating area corresponding to the image area,
A cleaning device for removing unfixed toner on the recording medium after the fixing process;
An unfixed toner amount detecting means for detecting an unfixed toner amount when the cleaning device removes the unfixed toner;
A fixing device configured to control a temperature of a heating region corresponding to a non-image region in accordance with a detection result of the unfixed toner amount detection unit.   2. The fixing device according to claim 1, wherein the unfixed toner amount detection unit detects an amount of toner dust generated when the cleaning device scrapes and removes the unfixed toner.   The fixing device according to claim 1, wherein the unfixed toner amount detection unit detects a toner amount collected when the cleaning device removes the unfixed toner.   Corresponding to the non-image area when the temperature of the heating area corresponding to the image area is Q1, the unfixed toner amount is not detected by the unfixed toner amount detecting means, or the detected unfixed toner quantity is equal to or less than the threshold value. When the temperature of the heating region is Q2, and the temperature of the heating region corresponding to the non-image region when the unfixed toner amount detected by the unfixed toner amount detection unit exceeds the threshold is Q3, the relationship of Q1 ≧ Q3> Q2 The fixing device according to claim 1, wherein the fixing device is controlled so that   When the unfixed toner amount detected by the unfixed toner amount detection means exceeds a threshold value, the temperature of the heating area corresponding to the non-image area to be fixed thereafter is determined by the subsequent unfixed toner amount detection means. The fixing device according to claim 4, wherein the fixing device is controlled so as to be Q3 irrespective of the detection result. If the image forming unit mounted on the image forming device has been replaced,
The fixing device according to claim 5, wherein the temperature of the heating area corresponding to the non-image area to be fixed thereafter is controlled to return from Q3 to Q2. When the cover provided on the image forming apparatus is closed or when the image forming apparatus is turned on,
The fixing device according to claim 5, wherein the temperature of the heating area corresponding to the non-image area to be fixed thereafter is controlled to return from Q3 to Q2.   When returning the temperature of the heating area corresponding to the non-image area from Q3 to Q2, the detection operation of the unfixed toner amount detection means is performed before starting the fixing process, and the detection result at that time is used as a reference value. The fixing device according to claim 6, wherein the threshold value is set based on a reference value.   An image forming apparatus comprising the fixing device according to claim 1.   The image forming apparatus according to claim 9, further comprising a foreign matter removing unit that removes foreign matter on the recording medium upstream of the fixing device in the recording medium conveyance direction.

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