JP2015197520A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly detect a temperature of an endless belt, to improve fixing performance.SOLUTION: A fixing apparatus includes: an endless belt (fixing belt 110); a heater arranged inside the endless belt, to generate heat; a first temperature sensor (first thermistor 180) arranged inside the endless belt, to detect a temperature of the endless belt; and a second temperature sensor (second thermistor 210) arranged outside the endless belt, to detect a temperature of the endless belt. The first and second temperature sensors are arranged within a minimum width (minimum sheet width W1) of a recording sheet which can be fixed by the fixing apparatus.

Description

  The present invention relates to a fixing device for thermally fixing a developer image on a recording sheet and an image forming apparatus provided with the fixing device.

  Conventionally, a fixing device including an endless belt, a heater disposed inside the endless belt, and a temperature sensor disposed inside the endless belt and detecting the temperature of the heater is known (see Patent Document 1). .

Japanese Patent Laid-Open No. 03-264976

  However, in the prior art, since the temperature sensor is provided only on the inner side of the endless belt, the temperature of the outer peripheral surface of the endless belt cannot be detected well, and the fixing performance may be deteriorated.

  Accordingly, an object of the present invention is to provide a fixing device and an image forming apparatus that can improve the fixing performance by better detecting the temperature of the endless belt.

In order to solve the above problems, a fixing device according to the present invention includes an endless belt, a heater extending inside the endless belt, a first temperature sensor disposed inside the endless belt, and an outer side of the endless belt. And a second temperature sensor disposed in the.
The first temperature sensor and the second temperature sensor are disposed within a minimum sheet width.

  Here, the “minimum sheet width” refers to the width of the smallest recording sheet among the recording sheets that can be fixed by the fixing device.

  According to this configuration, the temperature within the minimum sheet width is measured from the inside and outside of the endless belt by the first temperature sensor arranged inside the endless belt and the second temperature sensor arranged outside the endless belt. Since it can be detected, the fixing performance can be improved.

  In the above-described configuration, the first temperature sensor and the second temperature sensor may be disposed in a region where the heat generation distribution of the heater is flat.

  According to this, since each temperature sensor is arrange | positioned in the area | region where heat_generation | fever distribution becomes flat, temperature can be detected favorably with each temperature sensor.

  In the above-described configuration, the first temperature sensor is disposed on the opposite side of the second temperature sensor with a plane passing through the recording sheet conveyance center and perpendicular to the width direction of the endless belt. It may be.

  Here, the “conveyance center” refers to the center in the width direction of the recording sheet conveyed by the fixing device.

  According to this, when the user accidentally transports the recording sheet having the minimum width to one side with respect to the transport center (plane), it is on the other side (the side on which the recording sheet does not pass) from the transport center. Since the temperature detected by the temperature sensor increases, it is possible to detect erroneous conveyance of the recording sheet.

  In the above-described configuration, the first temperature sensor and the second temperature sensor may be arranged at the same position in the width direction of the endless belt.

  According to this, since the temperature of the part in the predetermined position in the width direction of the endless belt is detected from the outside and the inside, the fixing performance can be improved.

  The image forming apparatus according to the present invention includes the above-described fixing device and a control unit that controls the fixing device, and the control unit maintains the temperature detected by the first temperature sensor at the fixing temperature. Thus, the basic control for controlling the heater and the auxiliary control for controlling the heater based on the temperature detected by the second temperature sensor can be executed.

  According to the present invention, the temperature of the endless belt can be detected better, so that the fixing performance can be improved.

1 is a cross-sectional view showing a color laser printer according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a fixing device. It is a disassembled perspective view of a halogen lamp, a nip plate, a reflecting plate, a stay, a first thermistor, and a thermostat. It is a perspective view of a stay, a cover member, and a 2nd thermistor. It is the figure (a) which looked at the stay, the cover member, and the 2nd thermistor from the front, and the figure (b) which shows the heat_generation | fever distribution of a halogen lamp. It is a flowchart which shows operation | movement of a control apparatus. It is a figure which shows the positional relationship with the postcard conveyed in the state misaligned and each sensor. It is a figure which shows the modification of arrangement | positioning of each sensor.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, unless otherwise specified, the vertical direction shown in FIG. 1 is up and down, the left side in FIG. 1 is back, the right side is front, the back side of the paper is right, and the front side of the paper is left. Indicates. The direction here is defined with reference to the direction viewed from the person standing in front of the color laser printer 1.

<Schematic configuration of color laser printer>
As shown in FIG. 1, the color laser printer 1 includes a paper supply unit 5 that supplies a sheet 51 as an example of a recording sheet, and an image formation that forms an image on the fed sheet 51 in a main body housing 2. The unit 6 includes a paper discharge unit 7 that discharges the paper 51 on which an image is formed, a control device 300 as an example of a control unit, and a motor 400. The control device 300 will be described later.

  In the lower part of the main body housing 2, the paper feeding unit 5 lifts the paper 51 from the front side from the front side, and the paper feed tray 50 that is attached to and detached from the main body case 2 by a sliding operation. It comprises a transport mechanism M1 that reverses and transports the rear side.

  The transport mechanism M1 includes a pickup roller 52, a separation roller 53, a separation pad 54, and the like provided at the front end portion of the paper feed tray 50, and the paper 51 is separated one by one and sent upward. The paper 51 transported upward is removed in the course of passing between the paper dust removing roller 55 and the pinch roller 56, and then turned backward through the transport path 57, and the transport belt 73. And is conveyed to the fixing device 100.

  The image forming unit 6 includes a scanner unit 61, a process unit 62, a transfer unit 63, and a fixing device 100.

  The scanner unit 61 is provided in the upper part of the main body housing 2 and includes a laser light emitting unit, a polygon mirror, a plurality of lenses, and a reflecting mirror (not shown). In the scanner unit 61, a laser beam emitted from the laser beam emitting unit is scanned at high speed in the left-right direction by a polygon mirror in correspondence with each color of cyan, magenta, yellow, and black, and is passed or reflected by a plurality of lenses and reflecting mirrors. After that, each photosensitive drum 31 is irradiated.

  The process unit 62 is disposed below the scanner unit 61 and above the sheet feeding unit 5, and includes the photosensitive unit 3 that can move in the front-rear direction with respect to the main body housing 2. The photoconductor unit 3 includes four drum subunits 30 provided below the photoconductor unit 3, and a developing cartridge 40 mounted on each drum subunit 30.

The drum subunit 30 includes a photosensitive drum 31, a scorotron charger 32, and the like.
The developing cartridge 40 contains toner as an example of a developer, and includes a supply roller 41, a developing roller 42, a layer thickness regulating blade 43, and the like.

  Such a process unit 62 functions as follows. The toner in the developing cartridge 40 is supplied to the developing roller 42 by the supply roller 41, and at this time, the toner is frictionally charged positively between the supply roller 41 and the developing roller 42. The toner supplied to the developing roller 42 is rubbed by the layer thickness regulating blade 43 as the developing roller 42 rotates, and is carried on the surface of the developing roller 42 as a thin layer having a constant thickness.

  On the other hand, in the drum subunit 30, the scorotron charger 32 uniformly charges the photosensitive drum 31 to positive polarity by corona discharge. The charged photosensitive drum 31 is irradiated with laser from the scanner unit 61, and an electrostatic latent image corresponding to an image to be formed on the paper 51 is formed on the photosensitive drum 31.

  When the photosensitive drum 31 further rotates, the toner carried on the developing roller 42 is transferred by the laser among the electrostatic latent image of the photosensitive drum 31, that is, the surface of the photosensitive drum 31 that is uniformly positively charged. The exposed portion is supplied to the portion where the potential has dropped. As a result, the electrostatic latent image on the photosensitive drum 31 is visualized, and a toner image by reversal development is carried on the surface of the photosensitive drum 31 corresponding to each color toner.

The transfer unit 63 includes a driving roller 71, a driven roller 72, a conveyance belt 73, a transfer roller 74, and a cleaning unit 75.
The driving roller 71 and the driven roller 72 are spaced apart in parallel in the front-rear direction, and a conveyance belt 73 formed of an endless belt is wound around them. The outer surface of the conveyance belt 73 is in contact with each photosensitive drum 31. A transfer roller 74 is disposed inside the conveyor belt 73 so as to sandwich the conveyor belt 73 between the photosensitive drums 31. A transfer bias is applied to the transfer roller 74 from a high-pressure substrate (not shown). At the time of image formation, the paper 51 transported by the transport belt 73 is sandwiched between the photosensitive drum 31 and the transfer roller 74, and the toner image on the photosensitive drum 31 is transferred to the paper 51.

  The cleaning unit 75 is disposed below the conveyance belt 73, removes toner adhering to the conveyance belt 73, and drops the removed toner in a toner storage unit 76 disposed below the cleaning belt 75.

  The fixing device 100 is provided behind the transfer unit 63 and thermally fixes the toner image transferred onto the paper 51 onto the paper 51. The fixing device 100 will be described later.

  In the paper discharge unit 7, a paper discharge side conveyance path 91 for the paper 51 is formed so as to extend upward from the exit of the fixing device 100 and reverse to the front side. A plurality of transport rollers 92 that transport the paper 51 are disposed in the middle of the paper discharge side transport path 91. A paper discharge tray 93 for accumulating the printed paper 51 is formed on the upper surface of the main body housing 2, and the paper 51 discharged from the paper discharge side transport path 91 by the transport roller 92 is placed on the paper discharge tray 93. Accumulated.

<Detailed configuration of fixing device>
As shown in FIG. 2, the fixing device 100 includes a heating member 101, a pressure roller 150, a fixing frame 200, and a second thermistor 210 as an example of a second temperature sensor.

  The heating member 101 includes a fixing belt 110 as an example of an endless belt, a halogen lamp 120 as an example of a heater, a nip plate 130, a reflection plate 140, a stay 160, a cover member 170, and a first temperature sensor. As an example, a first thermistor 180 and a thermostat 190 (see FIG. 3) are provided.

  The fixing belt 110 is an endless belt having heat resistance and flexibility, and is configured to rotate by contact with the pressure roller 150 and to move backward in a nip N described later. ing. The fixing belt 110 is configured to rotate around an axis extending in the left-right direction, and has an inner peripheral surface 110A that slides on the nip plate 130 and an outer peripheral surface 110B that slides on the pressure roller 150. . The fixing belt 110 has a metal pipe formed from a metal such as stainless steel. The fixing belt 110 may have a rubber layer that covers the surface of the metal base tube, and may further have a non-metallic release layer such as fluorine coating that covers the surface of the rubber layer.

  The halogen lamp 120 is a heating element configured to generate heat, is configured separately from the nip plate 130, and is configured to extend in the left-right direction. The halogen lamp 120 heats the toner on the paper 51 by heating the nip plate 130 and the fixing belt 110. The halogen lamp 120 is arranged inside the fixing belt 110 at a predetermined distance from the inner surfaces of the fixing belt 110 and the nip plate 130, that is, away from the inner surface of the nip plate 130.

  The nip plate 130 is a plate-like member that receives radiant heat from the halogen lamp 120 and is in contact with the inner peripheral surface 110 </ b> A of the fixing belt 110. The nip plate 130 transmits radiant heat received from the halogen lamp 120 to the toner on the paper 51 via the fixing belt 110. The nip plate 130 is formed of, for example, an aluminum plate having a thermal conductivity higher than that of a steel stay 160 described later, and mainly includes a base portion 131 and a protruding portion 132.

  The base portion 131 is bent so that the central portion 131A in the transport direction is convex toward the pressure roller 150 side from both end portions 131B.

  The protruding portion 132 is formed to protrude rearward from the rear end portion 131R of the base portion 131 along the transport direction. As shown in FIG. 3, a total of two protruding portions 132 are formed, one at a distance from each other at two locations in the center portion of the rear end portion 131R of the base portion 131 in the left-right direction. Specifically, one of the two protrusions 132 is located on the opposite side of the other protrusion 132 with a substantially central position in the left-right direction of the base 131 (refer to a first plane P1: described later). Has been placed.

  As shown in FIG. 2, the reflecting plate 140 reflects the radiant heat from the halogen lamp 120 (radiant heat radiated mainly in the front-rear direction and the upward direction) toward the nip plate 130 (the inner surface of the base portion 131). It is a member, and is arranged at a predetermined interval from the halogen lamp 120 so as to surround the halogen lamp 120 inside the fixing belt 110.

  By collecting the radiant heat from the halogen lamp 120 on the nip plate 130 by such a reflector 140, the radiant heat from the halogen lamp 120 can be used efficiently, and the nip plate 130 and the fixing belt 110 can be heated quickly. Can do.

  The reflection plate 140 is formed by curving an aluminum plate or the like in a substantially U shape in cross section, for example, having a high infrared and far infrared reflectance. More specifically, the reflecting plate 140 mainly includes a reflecting portion 141 having a curved shape (substantially U-shaped in cross section) and a flange portion 142 extending from both ends of the reflecting portion 141 along the outer side in the front-rear direction. . In order to increase the thermal reflectance, the reflection plate 140 may be formed using a mirror-finished aluminum plate or the like.

  The stay 160 is a member that secures the rigidity of the nip plate 130 by supporting both end portions 131B of the base portion 131 of the nip plate 130 in the front-rear direction via the flange portion 142 of the reflection plate 140, and covers the reflection plate 140. Are arranged as follows. More specifically, the stay 160 is formed in a U shape in a sectional view by an upper wall 160A, a front wall 160B extending downward from the front end of the upper wall 160A, and a rear wall 160C extending downward from the rear end of the upper wall 160A. Yes.

  As shown in FIG. 3, the stay 160 has two notches 161 for arranging the first thermistor 180 and the thermostat 190 on the rear wall 160C. More specifically, the notch 161 is formed at a position corresponding to the two protrusions 132 of the nip plate 130 so as to have a gap that does not contact the first thermistor 180 and the like.

  As shown in FIGS. 4A and 4B, the cover member 170 is disposed so as to cover the upper wall 160 </ b> A and the front wall 160 </ b> B of the stay 160, and extends downward from the upper wall 171 and the front end of the upper wall 171. It is comprised from the front side wall 172 extended in this. A rib 173 is provided on the front surface of the front side wall 172.

  A plurality of ribs 173 are arranged on the front surface of the front side wall 172 at intervals in the left-right direction, specifically seven in total, and are formed so as to protrude forward from the front surface of the rib 173. Each rib 173 is formed in a substantially square shape, and the front surface thereof is a guide surface 173A configured to guide the inner peripheral surface 110A of the fixing belt 110. Among the ribs 173, the third rib 173 from the right is opposed to the second thermistor 210 with the fixing belt 110 interposed therebetween.

  As shown in FIGS. 2 and 3, the first thermistor 180 is a contact type thermistor and is arranged so as to detect the temperature of the nip plate 130. In other words, the first thermistor 180 is configured to detect the temperature of the fixing belt 110 via the nip plate 130.

  Specifically, the first thermistor 180 is located inside the fixing belt 110 and within the minimum sheet width W1 as an example of the minimum sheet width (see FIG. 5A), and is provided at the top. The fixing rib 183 is fixed to the rear wall 160C of the stay 160 with screws 189. Here, the minimum paper width W1 refers to the width of the minimum paper 51 that can be printed by the color laser printer 1 (fixable by the fixing device 100). The first thermistor 180 is disposed so as to face the upper surface of the protruding portion 132 of the nip plate 130, and the temperature detection surface 181 is in contact with the upper surface of the protruding portion 132. The first thermistor 180 may be a non-contact thermistor disposed away from the nip plate 130 or an infrared sensor.

  Here, the “minimum paper width W” is the minimum paper width that can be set by the driver of the image forming apparatus or the like, or the minimum paper width that can be set by a regulating member that regulates the end face of the paper in the paper feed tray. Point to. The minimum paper width W may be 69.9 mm (= OrganizerJ width), 76.0 mm (= Monarch width), or 100 mm (Japanese public postcard width). It may be 81 mm (C7 paper width) or 105 mm (A6 paper width).

  As shown in FIG. 3, the thermostat 190 is a temperature detection element using bimetal or the like, and is arranged to detect the temperature of the nip plate 130. Specifically, the thermostat 190 is located on the inner side of the fixing belt 110 and on the inner side in the left-right direction of the minimum sheet width W1 (see FIG. 5A), and a fixing rib 193 provided on the upper portion stays on the stay. 160 is fixed to the rear wall 160C of the screw 160 by a screw 199.

  The thermostat 190 is disposed so as to face the upper surface of the protruding portion 132 of the nip plate 130, and the temperature detection surface 191 is in contact with the upper surface of the protruding portion 132. The thermostat 190 is provided on a circuit that supplies power to the halogen lamp 120, and cuts off the energization of the halogen lamp 120 when a temperature equal to or higher than a predetermined value is detected. Thereby, it is possible to prevent the temperature of the fixing device 100 from rising excessively.

  As shown in FIG. 2, the pressure roller 150 is a member that contacts the outer peripheral surface 110 </ b> B of the fixing belt 110 and forms a nip N with the fixing belt 110. The pressure roller 150 is disposed below the nip plate 130 and sandwiches the fixing belt 110 with the nip plate 130.

  The fixing frame 200 is arranged to cover the heating member 101 above and in front of the heating member 101, and a second thermistor 210 is provided on the front wall 201 in front of the heating member 101.

  The second thermistor 210 is a non-contact thermistor, and is disposed outside the fixing belt 110, and fixing ribs 213 provided on the upper portion are fixed to the front wall 201 of the fixing frame 200 with screws 219. The second thermistor 210 is arranged so that the temperature detection surface 211 provided on the rear surface faces the outer peripheral surface 110B of the fixing belt 110 with a slight gap (a gap that allows temperature detection).

  More specifically, in the second thermistor 210, the temperature detection surface 211 is disposed on the front side with respect to the nip N, that is, on the upstream side in the moving direction of the fixing belt 110 at the nip N. Further, as shown in FIGS. 5A and 5B, the second thermistor 210 is disposed within the minimum sheet width W1. That is, the first thermistor 180 and the second thermistor 210 are both disposed within the minimum sheet width W1. In other words, the first thermistor 180 and the second thermistor 210 pass through the left end of the sheet 51 having the minimum sheet width W1 and are orthogonal to the left and right direction (width direction of the fixing belt 110) and the minimum sheet. It is disposed between the third plane P3 passing through the right end of the paper 51 having the width W1 and orthogonal to the left-right direction.

  As a result, the temperature of the portion of the fixing belt 110 within the minimum paper width W1 is set to the inside by the first thermistor 180 disposed inside the fixing belt 110 and the second thermistor 210 disposed outside the fixing belt 110. Therefore, it is possible to improve the fixing performance.

  Further, the first thermistor 180 and the second thermistor 210 are arranged in a region W2 where the heat generation distribution of the halogen lamp 120 is flat. As a result, the thermistors 180 and 210 can improve the temperature of the fixing belt 110 and the nip plate 130 in a region where the temperature distribution is substantially constant (a portion heated substantially uniformly in the flat region W2 of the halogen lamp 120). It is possible to detect.

  Further, the first thermistor 180 is disposed on the opposite side of the second thermistor 210 across the first plane P1 that passes through the transport center of the paper 51 and is orthogonal to the left-right direction. Here, the transport center refers to the center in the width direction of the paper 51 transported by the fixing device 100.

  According to this, as will be described in detail later, when the user mistakenly conveys the paper 51 having the minimum paper width W1 biased to one side with respect to the conveyance center (first plane P1) (see FIG. 7). ) Since the temperature detected by the thermistor on the other side (the side on which the paper 51 does not pass) becomes higher than the transport center, the erroneous transport of the paper 51 can be detected.

  In the present embodiment, the paper 51 is transported in such a way that the paper 51 is transported so that the transport center of the paper 51 is aligned with the approximate center of the nip plate 130 in the left-right direction. However, the present invention is not limited to this. Instead, for example, a method may be employed in which the edge of the sheet in the left-right direction is moved toward the one end side in the left-right direction of the nip plate.

  The second thermistor 210 may be a contact thermistor that contacts the fixing belt 110 or an infrared sensor. Further, the second thermistor 210 and the first thermistor 180 may generate analog values according to temperature, or may generate digital values based on the analog values. These analog values or digital values are transmitted to the control device 300 as signals.

<Control device>
Next, the control device 300 will be described in detail.
The control device 300 includes, for example, a storage unit including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and signals from the first thermistor 180 and the second thermistor 210. The control of the halogen lamp 120, the pickup roller 52, the motor 400, and the like is executed by performing arithmetic processing based on a program prepared in advance. The signal may be the temperature itself acquired by the first thermistor 180 and the second thermistor 210. Note that the ROM stores instructions for executing various control processes described later as programs. The CPU reads commands from the ROM and executes various control processes.

  The control device 300 controls the halogen lamp 120 based on the signal from the first thermistor 180. Specifically, the control device 300 controls the output of the halogen lamp 120 to be basically constant until the first temperature acquired from the first thermistor 180 reaches a predetermined fixing temperature, and the first temperature is the fixing temperature. After that, the basic control for controlling the halogen lamp 120 can be executed so that the first temperature is maintained at the fixing temperature. The fixing temperature is a temperature within a range where satisfactory fixing can be performed, and can be appropriately set by experiment, simulation, or the like. In this embodiment, the fixing temperature is 180 ° C. The fixing temperature may be any value within the range of 160 to 240 ° C. or any value within the range of 175 to 200 ° C. depending on the characteristics of the fixing device 100. Good.

  The control device 300 can execute auxiliary control for controlling the halogen lamp 120 based on a signal from the second thermistor 210. Specifically, when the difference between the first temperature detected by the first thermistor 180 and the second temperature detected by the second thermistor 210 is greater than a predetermined threshold A, the control device 300 outputs the output of the halogen lamp 120. Control is performed to increase the value to a value higher than the current value. Here, the threshold value A may be appropriately determined by experiment, simulation, or the like.

  In addition, when the difference between the temperatures detected by the thermistors 180 and 210 is larger than the threshold value B having a value larger than the threshold value A, the control device 300 executes control for stopping the printing control. Here, the threshold value B is a temperature difference that occurs when the user mistakenly conveys the paper 51 having the minimum paper width W1 toward the one side with respect to the conveyance center (first plane P1). It can be determined as appropriate.

In detail, the control apparatus 300 performs control according to the flowchart shown in FIG.
As shown in FIG. 6, the control device 300 first determines whether or not there is a print command (S1). If it is determined in step S1 that there is no print command (No), the control device 300 ends this control.

  If it is determined in step S1 that a print command has been issued (Yes), the control device 300 turns on the halogen lamp 120 (S2). After step S2, control device 300 determines whether or not the first temperature detected by first thermistor 180 is equal to or higher than the fixing temperature (S3).

  If it is determined in step S3 that the first temperature is lower than the fixing temperature (No), the control device 300 turns on the halogen lamp 120 (S4). Specifically, in step S4, the control device 300 continues the ON state when the halogen lamp 120 is already in the ON state, and turns on the halogen lamp 120 when the halogen lamp 120 is in the OFF state.

  If it is determined in step S3 that the first temperature is equal to or higher than the fixing temperature (Yes), the control device 300 turns off the halogen lamp 120 (S5). After steps S4 and S5, the control device 300 determines whether or not the difference between the temperatures detected by the thermistors 180 and 210 is greater than the threshold A (S6).

  If it is determined in step S6 that the temperature difference is greater than the threshold A (Yes), the control device 300 subsequently determines whether or not the temperature difference is greater than the threshold B (S7). If it is determined in step S7 that the temperature difference is equal to or less than the threshold value B (No), the control device 300 increases the output of the halogen lamp 120 to a value higher than the current value (S8).

  After step S8 or when determining No in step S6, the control device 300 determines whether or not the print control is completed (S9). If it is determined in step S9 that the print control has not been completed (No), the control device 300 returns to the process of step S3. If it is determined in step S9 that the print control has been completed (Yes), the control device 300 turns off the halogen lamp 120 (S10) and ends this control.

  If it is determined in step S7 that the temperature difference is larger than the threshold value B (Yes), the control device 300 stops printing control by turning off the halogen lamp 120 (S11), and a buzzer or the like. An error is notified to the user by the notification means (S12), and this control is terminated. Here, for example, as shown in FIG. 7, when the postcard 51A having the minimum sheet width W1 is mistakenly conveyed to the right side of the first plane P1 (conveyance center) as shown in FIG. The portion on the left side of the one plane P1 is not deprived of heat by the postcard 51A, and the temperature rises excessively.

  As a result, the first temperature detected by the first thermistor 180 disposed on the left side of the first plane P1 becomes abnormally high, and the difference between the temperatures detected by the thermistors 180 and 210 becomes abnormally large. B is exceeded. In this embodiment, in such a case, it is determined as Yes in step S7, and the printing control is stopped, so that it is possible to prompt the user to carry the postcard 51A incorrectly.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of this invention. In the following description, components that are substantially the same as those in the above embodiment are given the same reference numerals and description thereof is omitted.

  In the embodiment, the first thermistor 180 and the second thermistor 210 are arranged at different positions in the left-right direction, but the present invention is not limited to this, and for example, as shown in FIG. 8, the first thermistor 180 and the second thermistor 210 may be arranged at the same position in the left-right direction. According to this, since the temperature of the part at a predetermined position in the left-right direction of the fixing belt 110 is detected from the outside and the inside, the fixing performance can be improved.

  In the above embodiment, the first thermistor 180 is configured to detect the temperature of the fixing belt 110 via the nip plate 130. However, the present invention is not limited to this, and the first thermistor directly detects the temperature of the fixing belt. You may make it do.

  In the above embodiment, the halogen lamp 120 is illustrated as an example of the heater, but the present invention is not limited to this, and the heater may be, for example, a ceramic heater or a carbon heater.

  In the above-described embodiment, the paper 51 such as thick paper, postcard, and thin paper is exemplified as the recording sheet. However, the present invention is not limited to this, and may be, for example, an OHP sheet.

  In the above embodiment, the present invention is applied to the color laser printer 1, but the present invention is not limited to this, and the present invention may be applied to other image forming apparatuses such as a copying machine and a multifunction machine.

  In the embodiment, the control device 300 has one CPU configured to execute the processing of FIG. 6, but the present invention is not limited to this. For example, the control device may include a plurality of CPUs configured to execute the process of FIG. 6, or an ASIC (Application Specific Integrated Circuit) configured to execute the process of FIG. You may have the hard circuit. Further, the control device may include a CPU and a hardware circuit configured to execute the process of FIG.

  Note that the fixing belt may be a resin film containing polyimide as a main component. In this case, the fixing belt is covered with a fluororesin such as PTFE on the surface layer.

51 Paper 100 Fixing device 110 Fixing belt 120 Halogen lamp 180 First thermistor 210 Second thermistor W1 Minimum paper width

Claims (10)

Endless belt,
A heater extending inside the endless belt;
A first temperature sensor disposed inside the endless belt;
A second temperature sensor disposed outside the endless belt,
The fixing device, wherein the first temperature sensor and the second temperature sensor are disposed within a minimum sheet width.   2. The fixing device according to claim 1, wherein the first temperature sensor and the second temperature sensor are arranged in a region where the heat generation distribution of the heater is flat.   The first temperature sensor is disposed on a side opposite to the second temperature sensor across a plane that passes through the recording sheet conveyance center and is orthogonal to the width direction of the endless belt. The fixing device according to claim 1 or 2.   The fixing device according to claim 1, wherein the first temperature sensor and the second temperature sensor are arranged at the same position in a width direction of the endless belt.   The fixing device according to claim 1, wherein the minimum sheet width is 69.9 mm.   The fixing device according to claim 1, wherein the minimum sheet width is 76.0 mm.   The fixing device according to claim 1, wherein the minimum sheet width is 100 mm.   The fixing device according to claim 1, wherein the minimum sheet width is 81 mm.   The fixing device according to claim 1, wherein the minimum sheet width is 105 mm. A fixing device according to any one of claims 1 to 9,
An image forming apparatus comprising: a control unit that controls the fixing device;
The control unit controls the heater so that the temperature detected by the first temperature sensor is maintained at the fixing temperature, and assists to control the heater based on the temperature detected by the second temperature sensor. An image forming apparatus configured to execute control.

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