JP2010128146A - Fixing device and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a temperature rise in a non-sheet passing area without elongating a conveying time interval between recording sheets, in the case of continuously printing on the recording sheet having a small width. <P>SOLUTION: The temperature rise of a heat roller 31 heated by a halogen lamp 34 is suppressed by air currents formed by first and second temperature rise suppression parts 41 and 42. First, second and third thermal-electric converters 45, 47 and 46 for converting heat generated from the heat roller 31 into electric energy are arranged in order along the axial direction of the heat roller 31, and the first, second and third thermal-electric converters 45, 47 and 46 are cooled by a thermal-electric converter cooling part 43 so that the thermal-electric conversion efficiency thereof may become higher. The first temperature rise suppression part 41, the thermal-electric converter cooling part 43 and the second temperature rise suppression part 42 are separately driven by the output voltage of each of the first, second and third thermal-electric converters 45, 47 and 46. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fixing device that thermally fixes an unfixed image formed on a recording sheet, and an image forming apparatus including the fixing device.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a complex machine of these, a toner image corresponding to the image data is formed and transferred to a recording sheet such as recording paper, and the transferred unfixed toner image is fixed. Thus, the image is fixed on the recording sheet. In the fixing device, for example, a pressure roller is pressed against a heating roller having a heater built in the shaft center portion to form a fixing nip therebetween, and while the recording sheet passes through the fixing nip, The unfixed toner image on the recording sheet is heated to a molten state, and the molten toner image is heated and fixed to the recording sheet by being pressed against the recording sheet.

  In the fixing device having such a configuration, the length of the heating roller in the axial direction is usually the length (sheet width length) of the maximum width direction (direction perpendicular to the conveyance direction) of the recording sheet on which image formation is possible in the image forming apparatus. And is slightly longer than the maximum sheet width. The heating area of the heater built in the axial center of the heating roller is also set to be almost the entire length of the heating roller in the axial direction. Therefore, the heater built in the heating roller is the entire heating roller. It is designed to heat over. For this reason, when a recording sheet having a width direction length smaller than the maximum sheet width length (hereinafter referred to as a small size recording sheet) passes through the fixing nip, it is formed on the roller side portions on both sides in the axial direction of the heating roller. There is a phenomenon in which the recording sheet does not contact and the heat of each roller side portion is not deprived by the recording sheet and is overheated. Such a phenomenon is known as a non-sheet-passing portion overheating, and this causes the following problems.

  1) The heat distribution in the axial direction of the heating roller becomes non-uniform due to an increase in the temperature of the sheet non-passing area. When a recording sheet having a larger sheet width than the small size recording sheet (hereinafter referred to as a large size recording sheet) passes through the fixing nip in such an excessively high temperature state, The heat fixing temperature at each side portion becomes too high, and a so-called high temperature offset occurs in which a part of the toner adheres to the heating roller instead of the recording sheet, and the image quality may be deteriorated.

2) The pressure roller pressed against the heating roller or its surrounding parts may be thermally damaged due to excessive temperature rise in the sheet non-passing area, and the life of the pressure roller and its surrounding parts may be shortened. There is.
3) When the roller side portions on both sides in the axial direction of the pressure roller pressed against the heating roller are thermally expanded and thermally deformed due to the temperature rise in the sheet non-passing area, the peripheral speed of the pressure roller is not uniform in the axial direction. Thus, the pressure roller may not be able to contact the heating roller uniformly. In such a state, there is a possibility that the fixing failure of the toner image may occur due to a conveyance failure or the like in which the recording sheet does not pass through the fixing nip at a constant speed, and wrinkles may occur on the recording sheet.

In order to solve these problems, Patent Document 1 discloses the number of small-sized recording sheets that pass through the fixing nip when a plurality of small-sized recording sheets (recording sheets) pass through the fixing nip continuously. A configuration is disclosed in which when the predetermined value is reached, the temperature increase in the sheet non-passing area is suppressed by increasing the recording paper conveyance time interval.
Patent Document 2 discloses a configuration that suppresses the temperature rise of the non-sheet passing portion by bringing a roller-shaped heat dissipation member into contact with a heating roller (fixing roller) according to the paper size.

In Patent Document 3, when a small-size recording sheet is conveyed, cooling air is blown from a cooling fan to cool the heating roller, and based on the detection result of the temperature detection element that detects the surface temperature of the heating roller. A configuration for controlling the cooling fan is disclosed.
In Patent Document 4, when a small-size recording paper passes through the fixing nip, the opening width of the blower opening that blows cooling air to the sheet non-passing region by the cooling fan is described as the width direction of the recording paper passing through the fixing nip. A configuration for adjusting the length is disclosed.

In Patent Document 5, a sheet passing area heater and a non-sheet passing area heater are provided on the fixing roller, and the sheet is passed based on the temperature detection results of the thermistors provided in each of the sheet passing area and the non-sheet passing area. A configuration for controlling each of the area heater and the non-sheet passing area heater is disclosed.
Patent Document 6 also discloses a configuration in which a plurality of heating elements having a length corresponding to the sheet passing width is provided and each heating element is energized at a different power ratio.
JP-A-6-186875 JP-A-6-11983 Japanese Patent Application Laid-Open No. 60-136779 JP 2003-76209 A JP-A-2-262177 Japanese Patent No. 3647290

  In Patent Document 1, the recording paper continuously passes through the fixing nip at a normal conveyance speed until the predetermined number of small-size recording papers reaches, so the temperature rises in the sheet non-passing area. Will continue. In the case of an image forming apparatus that performs a printing operation at a high speed, a predetermined number of small-size recording sheets pass through the fixing nip at a high speed, so that the temperature of the sheet non-passing area also rapidly increases, adversely affecting the pressure roller and the like. There is a risk of reaching a high temperature exceeding the upper limit temperature (eg, 250 ° C.). When such a high temperature is reached, in order to reduce the temperature of the sheet non-passing area, it is necessary to significantly reduce the recording paper conveyance speed. As a result, a high-speed printing operation cannot be performed, and the printing efficiency is significantly reduced. Further, when the sheet non-passing region becomes a high temperature that is equal to or higher than the upper limit temperature for a long time, there is a possibility that a member such as a pressure roller is adversely affected. In order to prevent such a high temperature state from continuing for a long period of time, it is necessary to perform control for detecting the surface temperature of the heating roller and stopping the heating. In this case, the temperature of the sheet passing area is also reduced. There is a possibility that fixing failure may occur due to the decrease.

With the configuration of Patent Document 2 in which the roller-shaped heat dissipation member is brought into contact, there is a possibility that the temperature rise in the sheet non-passing region cannot be efficiently suppressed. Further, since the heat radiating member itself has a heat capacity, there is a problem that the amount of energy for raising the temperature of the heating roller is increased.
As described in Patent Document 3, in the configuration in which cooling air is blown to the sheet non-passing area of the fixing roller by the cooling fan to cool, a part of the cooling air blown to the sheet non-passing area wraps around the sheet passing area. As a result, the temperature of the sheet passing region may also decrease. It is substantially difficult to perform control to lower the temperature of the sheet non-passing area while maintaining the temperature of the sheet passing area at a temperature suitable for fixing. When small size recording paper passes continuously through the fixing nip, the temperature of the sheet passing area hardly decreases if the number of passing recording paper is as small as about 50, for example. When the number of sheets increases to 50 or more, the temperature drop at the end of the sheet passing area close to the sheet non-passing area becomes significant, and the fixing temperature is lowered due to a decrease in fixing temperature at both ends in the width direction of the recording paper. There is a risk of failure. In the case of an image forming apparatus with an increased printing speed, the amount of cooling air increases, so that a large number of recording sheets pass through the fixing nip, and the temperature drop at the end of the sheet passing area is more remarkable. become.

In the configuration described in Patent Document 4, it is possible to suppress a decrease in the temperature of the sheet passing region by adjusting the opening width of the air blowing port of the cooling fan in accordance with the width direction dimension of the recording paper. However, for this purpose, it is necessary to provide a temperature detection element, a mechanism for adjusting the opening width, a power source for that purpose, and the economy may be impaired.
In the configuration described in Patent Document 5, it is necessary to provide a heater and a thermistor for each of the sheet passing area and the non-sheet passing area, which may complicate the configuration and impair the economy. Further, as described in Patent Document 6, in order to energize a plurality of heating elements with different power ratios, a complicated circuit or the like is required, which may impair economic efficiency.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to extend the conveyance time interval of recording sheets when printing recording sheets such as small-size recording sheets continuously. Another object of the present invention is to provide a fixing device capable of suppressing a temperature rise in a non-passing region of a sheet without performing complicated control, and thus without impairing economy, and an image forming apparatus including the same. Yes.

  In order to achieve the above object, a fixing device according to the present invention includes a heating rotator in which an outer peripheral surface circulates while being heated by a heating unit, and an outer peripheral surface that circulates in a state of being pressed against the outer peripheral surface of the heating rotator. A fixing device that thermally fixes an unfixed image on a recording sheet while the recording sheet passes through a fixing nip formed between the pressure rotating body and the temperature of the heating rotating body is suppressed. A first temperature rise suppression unit that forms an airflow in a direction orthogonal to the circumferential movement direction along the outer peripheral surface of the heating rotator, and sheets on both sides of a sheet passing region through which a recording sheet of a predetermined size passes in the fixing nip. A high-temperature side heat receiving part that faces the outer peripheral surface portions on both sides of the heating rotator that respectively pass through the non-passing region, and a low-temperature side that is located on the opposite side of the heating rotator with respect to each of the high-temperature side heat receiving parts With the heat receiver The first and second thermoelectric converters that generate electrical energy according to the difference in heat receiving temperature between the high temperature side heat receiving part and the low temperature side heat receiving part, and the first and second thermoelectric conversion apparatuses A thermoelectric conversion device cooling section that cools each of the low-temperature side heat receiving sections so that the difference in the heat reception temperature increases, and the first temperature rise by the electric energy output from the first thermoelectric conversion apparatus The suppression unit is driven, and the thermoelectric conversion device cooling unit is driven by electrical energy output from the second thermoelectric conversion device.

  An image forming apparatus according to the present invention is an image forming apparatus that thermally fixes an unfixed image formed on a recording sheet by a fixing unit, and includes the fixing device as the fixing unit. .

  In the fixing device of the present invention, a plurality of small-sized recording sheets continuously pass through the fixing nip between the heating rotator and the pressure rotator, so that the sheet non-passing area on both sides of the sheet passing area. When the temperature rises, the first temperature rise suppression unit and the thermoelectric conversion device cooling unit are driven by the electrical energy output from the first and second thermoelectric conversion devices, and thus are formed by the first temperature rise suppression unit. The temperature rise of the heating rotator is suppressed by the airflow. In this case, since the thermoelectric conversion efficiency of the first and second thermoelectric conversion devices is increased by the cooling air formed by the thermoelectric conversion device cooling unit, the electric energy output from the first and second thermoelectric conversion devices is The temperature increase in the sheet non-passing region by the first temperature rise suppression unit can be further effectively suppressed. As a result, the temperature rise in the sheet non-passing region can be reliably suppressed without extending the recording sheet conveyance time interval and without performing complicated control.

Preferably, the heating rotator and the pressurizing rotator are provided in a housing, and the first temperature rise suppression unit sucks air in the housing and discharges it outside the housing. A fan is provided, and the first blower fan is driven by electric energy output from the first thermoelectric converter.
Preferably, the first blower fan is a second temperature rise suppression unit disposed with the heating rotator interposed therebetween so as to form an airflow in the same direction as the airflow formed by the first temperature rise suppression unit. A high temperature side heat receiving portion that faces an outer peripheral surface portion of the heating rotator that passes through the sheet passing region, and a low temperature side heat receiving portion that is located on the opposite side of the heating rotator with respect to the high temperature side heat receiving portion. A third thermoelectric conversion device that generates electrical energy in accordance with a difference in heat receiving temperature between the high temperature side heat receiving unit and the low temperature side heat receiving unit, wherein the third thermoelectric conversion device is the thermoelectric conversion device cooling unit Is arranged so that the low temperature side heat receiving part of the third thermoelectric converter is cooled, and the generated electric energy is output to the second temperature rise suppressing part, and the second temperature rise suppressing part is It is characterized by being driven.

Preferably, the second temperature rise suppression unit includes a second blower fan that draws air outside the housing into the housing, and the second blower fan is driven by electrical energy output from the third thermoelectric converter. It is characterized by being.
Preferably, each of the first to third thermoelectric conversion devices includes a first substrate constituting the high temperature side heat receiving portion, a second substrate constituting the low temperature side heat receiving portion, the first substrate, and the second substrate. And a plurality of semiconductor elements disposed between the first substrate and the second substrate so that electrical energy is generated by a Seebeck effect based on a temperature difference from the substrate.

Preferably, the thermoelectric conversion device cooling unit cools the second substrate of each of the first to third thermoelectric conversion devices.
Preferably, the thermoelectric conversion device cooling unit blows cooling air along each of the second substrates of the first to third thermoelectric conversion devices.
Preferably, each of the first to third thermoelectric conversion devices has a plurality of P-type semiconductor elements and the same number of N-type semiconductor elements, and each of the P-type semiconductor elements and the N-type semiconductor elements is the first type. Each of the P-type semiconductor elements and each of the N-type semiconductor elements are alternately connected in series between the substrate and the second substrate.

Preferably, each of the first to third thermoelectric conversion devices is characterized in that a heat-absorbing material is provided on a surface of the first substrate facing the heating rotator.
Preferably, the first substrate and the second substrate of the first thermoelectric conversion device are configured to be flat, and the first substrate and the second substrate of the second thermoelectric conversion device have respective areas, The second thermoelectric conversion is formed in a curved state along the outer peripheral surface of the heating rotator so as to be larger than the areas of the first substrate and the second substrate of the first thermoelectric conversion device. The number of the semiconductor elements provided in the device is larger than the number of the semiconductor elements of the first thermoelectric conversion device.

Preferably, the heating means is a heater lamp or a heating wire heater arranged inside the heating rotator.
Preferably, the heating means is arranged to face the outer peripheral surface of the heating rotator so as to heat the outer peripheral surface portion of the heating rotator.
Preferably, each of the first to third thermoelectric conversion devices is provided downstream of the heating means in the rotation direction of the heating rotator.

Preferably, the heating means is an exciting coil that generates heat from a heat generating layer provided in the heating rotating body.
Preferably, the apparatus further includes a temperature detection unit that detects the temperature of the outer peripheral surface of the heating rotator, and a control unit that controls the heating unit based on a detection result by the temperature detection unit.

Preferably, the temperature detecting means is arranged on the opposite side of the heating rotator from a region where an air flow is formed by the first temperature rise suppression unit.
Preferably, when the small-size recording sheet having a length shorter than the length of the fixing nip in the longitudinal direction passes through the plurality of continuous sheets, the control unit includes the plurality of small-size recording sheets. The waiting time for idly rotating the heating rotator and the pressure rotator after the sheet has passed is set in advance according to the number of small-sized recording sheets that pass continuously.

  Preferably, after the plurality of small-sized recording sheets pass through the fixing nip, the control unit passes a recording sheet whose length along the longitudinal direction of the fixing nip is longer than the small-sized recording sheet. In this case, when the recording sheet is not conveyed to the fixing nip, the heating rotator and the pressure rotator are idled for the set waiting time.

  Preferably, the heating rotator is a heating roller, and the pressure rotator is a pressure roller.

<Embodiment 1>
Hereinafter, a fixing device and an image forming apparatus according to Embodiment 1 of the present invention will be described. FIG. 1 is a schematic diagram showing an internal schematic configuration of a printer as an image forming apparatus provided with a fixing device according to an embodiment of the present invention. The printer 1 is a recording sheet such as recording paper or OHP paper. A toner image of a predetermined color is formed on the top. A printer 1 shown in FIG. 1 includes a photosensitive drum 11 that is rotationally driven in a direction indicated by an arrow A. A toner image is printed around a photosensitive drum 11 by an electrophotographic method as a recording sheet as a recording sheet. A charging device 12, an exposure device 13, a developing device 14, and a transfer roller 15 for forming on P are provided in order along the rotation direction of the photosensitive drum 11.

  In the printer 1, image data input from the external host device 54 (see FIG. 7) is converted into a laser diode drive signal by a controller unit (control unit: CPU) 53 (see FIG. 7). The laser diode provided in the exposure device 13 is driven. As a result, the exposure device 13 irradiates the surface of the photosensitive drum 11 with the laser beam L corresponding to the image data. The surface of the photosensitive drum 11 is charged to a predetermined potential in advance by the charging device 12, and an electrostatic latent image is formed on the surface of the photosensitive drum 11 when the laser beam L from the exposure device 13 is exposed. Is done. The electrostatic latent image is developed with toner in the developing device 14 and visualized as a toner image.

  Below the photosensitive drum 11, for example, a recording sheet cassette 17 that can store a plurality of recording sheets P is provided. The recording paper P stored in the recording paper cassette 17 is pressed against the paper feeding roller 18 by being placed on the paper feeding table 17 a biased toward the paper feeding roller 18, and The sheet is fed one by one toward the photosensitive drum 11 by rotation. The recording paper P fed out from the recording paper cassette 17 is conveyed toward the photosensitive drum 11 via the timing roller pair 19. The transfer roller 15 provided on the lower side of the photosensitive drum 11 is rotated in a direction indicated by an arrow B, and the transfer roller 15 and the photosensitive drum 11 are pressed to form a transfer nip therebetween. . The recording paper P fed out from the recording paper cassette 17 is conveyed by the timing roller pair 19 so as to pass through the transfer nip at a predetermined timing synchronized with the rotation of the photosensitive drum 11. When the recording paper P passes through the transfer nip, the toner image formed on the photosensitive drum 11 is transferred onto the recording paper P by the action of the transfer electric field generated by the transfer voltage applied to the transfer roller 15. Is done.

  The recording paper P to which the toner image has been transferred is peeled off from the photosensitive drum 11 and conveyed to the fixing device 30. After the toner image is transferred, the photosensitive drum 11 has its residual charge removed after the toner remaining on the surface is removed by the cleaner 16. The photosensitive drum 11 from which the residual charge has been erased is transferred onto the recording paper P fed out from the recording paper cassette 17 by repeating the same operation as described above according to the next image formation instruction. . As described above, the photosensitive drum 11, the charging device 12, the exposure device 13, the developing device 14, the transfer roller 15, the cleaner 16, the recording paper cassette 17, and the like form an unfixed image on the recording paper P.

  FIG. 2 is a schematic diagram illustrating the configuration of the fixing device 30, and FIG. 3 is a schematic diagram of a cross section taken along line XX in FIG. 2. The heating roller 31 and the pressure roller 32 are not shown in cross section. As shown in FIGS. 2 and 3, the fixing device 30 includes a heating roller 31 and a pressure roller 32 that are pressed against each other in a housing 37, and the pressure roller is disposed on the heating roller 31 disposed on the upper side. 32 is pressed from below. A fixing nip N through which the recording paper P passes is formed between the heating roller 31 and the pressure roller 32 that are pressed against each other. The recording paper P on which the toner image has been transferred is guided by a guide member 33. Then, it is guided into the housing 37 and passes through the fixing nip N between the heating roller 31 and the pressure roller 32 with the surface on which the toner image is transferred as the heating roller 31 side. The toner image transferred onto the recording paper P is heat-fixed on the recording paper P by being heated and pressurized while the recording paper P passes through the fixing nip N. The heat-fixed recording paper P is discharged out of the housing 37 by the paper discharge roller 35.

  A housing 37 of the fixing device 30 is divided into an upper space 37b and a lower space 37c by a partition wall 37a, and a heating roller 31 and a pressure roller 32 are disposed in the lower space 37c. As shown in FIG. 3, the heating roller 31 is rotated in the direction indicated by the arrow M in FIG. 2 by a fixing motor 38 attached to the left side wall 37d of the housing 37 located on the left side in the conveyance direction of the recording paper P. Driven. The heating roller 31 and the pressure roller 32 disposed in the lower space 37c of the housing 37 are configured to have a diameter of, for example, 40 mm, and the fixing nip N is formed by being pressed against each other by a pressure mechanism (not shown). Is formed. The recording paper P conveyed to the fixing device 30 is pressed from above and below by being guided into the fixing nip N between the heating roller 31 and the pressure roller 32. The recording paper P that has passed through the fixing nip N is peeled off from the heating roller 31 by a peeling claw 39 (see FIG. 2), discharged to the outside of the housing 37 by a pair of paper discharge rollers 35, and placed on a paper discharge tray (not shown). Discharged.

  The heating roller 31 is configured by laminating an elastic layer and a release layer on the surface of a metal core made of a metal such as aluminum. A shaft center portion of the core metal is hollow, and a halogen lamp 34 formed linearly along the axial direction of the heating roller 31 is disposed on the shaft center portion. The halogen lamp 34 has a length that extends over substantially the entire length of the heating roller 31 in the axial direction, and heats the heating roller 31 substantially uniformly throughout.

The pressure roller 32 has the same configuration as that of a pressure roller used in a fixing device for heat-fixing a toner image in a normal electrophotographic image forming apparatus. Silicone is applied to the surface of a cylindrical cored bar. A surface layer of rubber or the like having good releasability and heat resistance such as rubber and fluororubber is provided.
As shown in FIG. 3, the axial lengths of the heating roller 31 and the pressure roller 32 are the width direction (a direction orthogonal to the conveyance direction of the recording paper P) of the recording paper P having a size printable by the printer 1. The length (sheet width length) is slightly longer than the width L of the maximum recording paper P. The recording paper P guided to the fixing nip N in the fixing device 30 is transported by a so-called center reference in which the center position in the width direction coincides with the center position in the width direction of the transport path even if the sheet widths are different. The fixing device 30 also passes through the fixing nip N based on the center reference along the sheet passing center line CL that is the center position in the axial direction of the heating roller 31 and the pressure roller 32. In the fixing nip N, an area through which the recording sheet P having a minimum sheet width that can be printed by the printer 1 is a sheet passing area N3, and the minimum sheet width length (minimum sheet passing width) is S. Is shown. The left and right areas of the sheet passing area N3 in the fixing nip N are first and second sheet non-passing areas N1 and N2, respectively, through which the minimum size recording paper P does not pass. The lengths along the axial direction are “W1” and “W2” (W1 = W2), respectively. Accordingly, the maximum sheet width length (maximum sheet passing width) L of the recording paper P passing through the fixing nip N is L = S + W1 + W2. In the present embodiment, as the maximum sheet passing width L, the longitudinal dimension of an A4 size recording sheet, that is, the A4 size recording sheet is transported in a state where the longitudinal direction is in a direction perpendicular to the transport direction. It corresponds to the sheet width length in the case of lateral conveyance. Further, the minimum sheet passing width S is set to a sheet width length orthogonal to the longitudinal direction of the A4 size recording sheet, that is, about 70 to 90 mm, and a halogen provided in the axial center portion of the heating roller 31. The axial length of the effective heat generation area of the lamp 34 is the same length as the maximum sheet passing width L or slightly longer than the maximum sheet passing width L.

  As shown in FIG. 2, a thermistor 36 as a temperature detection unit is provided at a position upstream of the heating roller 31 in the recording paper conveyance direction. The thermistor 36 is in contact with the axially central portion of the outer peripheral surface of the heating roller 31 corresponding to the central portion of the effective heat generation area of the halogen lamp 34, and is in contact with the heating roller 31 being rotated. The temperature of the outer peripheral surface of the heating roller 31 is detected. Therefore, the thermistor 36 can accurately and reliably detect the temperature change of the outer peripheral surface of the heating roller 31 even when the recording paper P having a different dimension in the width direction passes through the fixing nip N. As will be described later, the halogen lamp 34 is controlled to have a predetermined fixing temperature based on the outer peripheral surface temperature of the heating roller 31 detected by the thermistor 36.

  FIG. 4 is a perspective view showing a schematic configuration of the fixing device 30, schematically showing a state viewed from the upper right side toward the conveyance direction on the downstream side in the conveyance direction of the recording paper P. As shown in FIGS. 3 and 4, a first temperature increase suppression portion 41 is provided on the right side wall 37e of the housing 37 located on the right side in the conveyance direction of the recording paper P, and the first side wall 37d has a first The 2 temperature rise suppression part 42 is provided in the state facing the 1st temperature rise suppression part 41. As shown in FIG. The first temperature rise suppression unit 41 and the second temperature rise suppression unit 42 are respectively above the discharge port 37h for discharging the recording sheet P and on the right side downstream of the heating roller 31 in the conveyance direction of the recording paper P. It is arrange | positioned at the side and the left side, respectively. The first temperature rise suppression unit 41 sucks air inside the housing 37 and discharges it to the outside of the printer 1. The second temperature rise suppression unit 42 sucks air outside the printer 1 and discharges it into the housing 37. The first temperature rise suppression unit 41 sucks air on the downstream side in the transport direction of the recording paper P around the heating roller 31 in the vicinity of the right side wall 37e, thereby extending the left side wall 37d to the right side wall 37e along the axial direction of the heating roller 31. Forms an airflow that flows toward Further, the second temperature rise suppression unit 42 discharges air to the space downstream of the left side wall 37d in the vicinity of the heating roller 31 in the conveyance direction of the recording paper P, thereby causing the left side wall to extend along the axial direction of the heating roller 31. An airflow that flows from 37d toward the right side wall 37e is formed.

  FIG. 5 is a perspective view for explaining the configuration of the first temperature rise suppression unit 41 and the second temperature rise suppression unit 42, and schematically shows a state viewed from the upper left side on the upstream side in the conveyance direction of the recording paper P. Show. The first temperature rise suppression unit 41 attached to the right side wall 37e of the housing 37 includes a first rotary blade 41a that sucks air inside the housing 37, and a first fan motor 41c that rotationally drives the first rotary blade 41a. And a first duct 41b that guides the air in the housing 37 to the first rotary blade 41a when the first rotary blade 41a is rotationally driven by the first fan motor 41c. Yes. The first duct 41b is provided with a vertically long rectangular air suction port 41d for sucking air in the vicinity of the end of the first rotor blade 41a on the far side. The air suction port 41d is arranged so as to be offset toward the upstream side in the transport direction of the recording paper P. Therefore, the side surface of the first duct 41b located on the downstream side in the transport direction of the recording paper P approaches the air suction port 41d. Accordingly, the recording paper P is inclined in a concavely curved state so as to be positioned upstream in the conveyance direction of the recording paper P.

  Similarly to the first temperature rise suppression unit 41, the second temperature rise suppression unit 42 includes a second blower fan 42e having a second rotary blade 42a and a second fan motor 42c, and a second duct 42b. The second rotary blade 42a is rotationally driven by the second fan motor 42c, thereby sucking air outside the housing 37 and discharging it into the lower space 37c of the housing 37 through the second duct 42b. The second duct 42b includes a discharge port 42d having a vertically long rectangular shape at the far end of the second rotary blade 42a. The discharge port 42d is also arranged so as to be offset toward the upstream side in the conveyance direction of the recording paper P so as to face the air suction port 41d. Accordingly, the side surface of the second duct 42b located on the downstream side in the conveyance direction of the recording paper P is inclined so as to be positioned on the upstream side in the conveyance direction of the recording paper P as it approaches the discharge port 42d. The discharge port 42d has the same vertical length as the air suction port 41d, but the width direction length along the conveyance direction of the recording paper P is the width direction length of the air suction port 41d of the first duct 41b. The opening area of the air suction port 41d is about 20% larger than the opening area of the discharge port 42d.

  Centrifugal fans such as an axial fan and a sirocco fan are used as the first blower fan 41e and the second blower fan 42e. When the first rotary blade 41a of the first blower fan 41e is rotationally driven, air near the end of the heating roller 31 adjacent to the air suction port 41d is sucked into the air suction port 41d of the first duct 41b. And discharged to the outside of the printer 1. As a result, an air flow that flows along the axial direction of the heating roller 31 from the left side wall 37d toward the right side wall 37e is formed on the side of the heating roller 31 on the downstream side in the conveyance direction of the recording paper P. The temperature rise of the outer peripheral surface of the heating roller 31 is suppressed. Further, when the second rotary blade 42 a of the second blower fan 42 e is driven to rotate, air outside the printer 1 is sucked from the discharge port 42 d of the second duct 42 b and discharged into the lower space 37 c of the housing 37. Is done. Thus, the surface of the heating roller 31 is axially moved from the left side wall 37d toward the right side wall 37e along with the airflow formed by the first blower fan 41e on the side of the heating roller 31 on the downstream side in the conveyance direction of the recording paper P. An airflow that flows along the first air blower fan 41e and the second air blower fan 42e is suppressed, and an increase in the temperature of the outer peripheral surface of the heating roller 31 is suppressed.

Since the air flow is formed on the opposite side of the heating roller 31 in the conveyance direction of the recording paper P on which the thermistor 36 is disposed in the heating roller 31, the thermistor 36 has a temperature detected by the air flow. There is no risk of disturbance (noise) and the like, and temperature detection with high accuracy is possible.
As shown in FIGS. 3 and 4, the partition wall 37a of the housing 37 is formed with an opening portion 37g facing substantially the entire length of the heating roller 31 in the axial direction, and the recording paper P of the recording paper P is formed in the opening portion 37g. First, third, and second thermoelectric conversions from the right side to the left side in the conveyance direction, that is, from the leeward to the upwind of the airflow formed by the first temperature rise suppression unit 41 and the second temperature rise suppression unit 42. Devices 45, 46 and 47 are arranged in that order. The first thermoelectric conversion device 45 disposed on the right side in the conveyance direction of the recording paper P is disposed on the heating roller 31 over the entire length W1 in the first sheet non-passing area N1 on the right side (downstream side of the airflow) in the fixing nip N. It arrange | positions so that it may oppose through. The second thermoelectric conversion device 47 disposed on the left side in the conveyance direction of the recording paper P heats the second sheet non-passage region N2 on the left side (windward side of the airflow) in the fixing nip N over the entire length W2. It arrange | positions so that it may oppose through the roller 31. FIG. A third thermoelectric conversion device 46 disposed between the first thermoelectric conversion device 45 and the second thermoelectric conversion device 47 has a heating roller in the sheet passing region N3 in the fixing nip N over the entire length (minimum sheet passing width S). 31 are arranged at positions facing each other.

  FIG. 6A is a perspective view from above of the first thermoelectric conversion device 45, with a part cut away. FIG. 6B is a perspective view of the first thermoelectric conversion device 45 in a state in which the vertical and horizontal directions are inverted. The first thermoelectric conversion device 45 includes a first substrate (high temperature side heat receiving portion) 45a disposed to face the heating roller 31, and a first substrate provided in parallel with the first substrate 45a at an appropriate interval. Two substrates (low temperature side heat receiving portions) 45b are provided, and a plurality of P-type semiconductor elements 45c and the same number of N-type semiconductor elements 45d are provided between the first substrate 45a and the second substrate 45b. A plurality of electrodes 45e are provided on the mutually opposing surfaces of the first substrate 45a and the second substrate 45b, and the P-type semiconductor element 45c and the N-type semiconductor element adjacent to each other are provided by the respective electrodes 45e. 45d are connected in series, and all the P-type semiconductor elements 45c and all the N-type semiconductor elements 45d provided between the first substrate 45a and the second substrate 45b are alternately connected in series. It is connected to the. A P-side lead wire 45f is connected to the electrode 45e connected to the P-type semiconductor element 45c located at one end of the P-type semiconductor element 45c and the N-type semiconductor element 45d connected in series, and located at the other end. An N-side lead wire 45g is connected to the electrode 45e connected to the N-type semiconductor element 45d.

  The first substrate 45a is disposed to face the heating roller 31 with a space therebetween, and the second substrate 45b is disposed on the opposite side of the heating roller 31 with respect to the first substrate 45a. As a result, the heat of the heating roller 31 is caused by the natural convection of air interposed between the heating roller 31 and each of the first, second, and third thermoelectric conversion devices 45, 47, 46. Conducting and conducting by radiation through the air results in a high temperature. On the other hand, since the second substrate 45b does not directly face the heating roller 31, the temperature is lower than that of the first substrate 45a. The P-type semiconductor element 45c and the N-type semiconductor element 45d connected in series with each other use the Seebeck effect to convert the thermal energy generated by the heat receiving temperature difference between the first substrate 45a and the second substrate 45b into electrical energy. The converted electrical energy is output as a voltage from the lead wires 45f and 45g.

  The third thermoelectric conversion device 46 and the second thermoelectric conversion device 47 have the same configuration as the first thermoelectric conversion device 45, and a P-type semiconductor is provided between the first substrates 46a and 47a and the second substrates 46b and 47b. Elements 46c and 47c and N-type semiconductor elements 46d and 47d are provided in a state where they are connected by electrodes 46e and 47e, respectively, and lead wires 46f and 47f, 46g and 47g are provided, respectively. The converter 45 and the second thermoelectric converter 47 have the same shape, and therefore the lengths along the axial direction of the heating roller 31 are equal, whereas the third thermoelectric converter 46 is heated. The length along the axial direction of the roller 31 is longer than that of the first thermoelectric conversion device 45 and the second thermoelectric conversion device 47.

As semiconductor materials of the P-type semiconductor elements 45c, 46c, 47c and the N-type semiconductor elements 45d, 46d, 47d, for example, Sb ₂ Te ₃ -Bi ₂ Te ₃ , Bi ₃ Te ₃ -Bi ₂ Se ₃ , Examples include Si—Ge, CoSb ₃ , Fe—Si ₂ , Fe—Al, YbAl ₃ , NaCo ₂ O ₄ , other oxides, and organic substances such as conductive polymers.
The lower surfaces of the first substrates 45a, 46a, 47a facing the heating roller 31 are coated with heat absorbing materials 45h, 46h, 47h, respectively. The heat-absorbing materials 45h, 46h, and 47h efficiently absorb light in the infrared region, and function as heat transfer promotion means that efficiently conducts radiant heat from the heating roller 31 to the first substrates 45a, 46a, and 47a. To do. The heat absorption materials 45h, 46h, and 47h efficiently absorb the radiant heat from the heating roller 31 that is radiated in the form of light, whereby the temperature of the first substrates 45a, 46a, and 47a is increased efficiently.

As the heat absorbing material 45h, 46h, 47h, a paint having a high heat absorption rate is used. Further, since it is disposed opposite the heating roller 31, it is preferable that the heat roller 31 is excellent in heat resistance that can withstand high temperatures near the outer peripheral surface of the heating roller 31. As the heat-absorbing materials 45h, 46h, 47h, Al ₂ O ₃ , AlN, Sb ₂ O ₃ , ZnO, calcium carbonate, iron oxide, SiO, SiO ₂ , SiO ₄ , SiC, TiO, TiO ₂ , TiC, TiB , MgO, MgO ₂ , ZrO ₂ , other ceramic particles, carbon, boron, glass powder, or aluminum, copper, silver, gold, nickel, zinc, iron, cobalt, chromium, titanium, tin, alloys thereof Examples thereof include paints that are contained alone or in combination. Specifically, it has a heat-resistant temperature of 200 ° C. or higher, and preferably has an emissivity of 0.8 or higher in the temperature range. As such a heat-absorbing paint, a trade name “COOLTECH CT-400” (Okitsumo Co., Ltd.).

  As shown in FIGS. 3 and 4, the left side wall 37 d of the housing 37 includes a thermoelectric conversion device cooling unit 43 for cooling the first, second, and third thermoelectric conversion devices 45, 47, 46. It is attached so as to face the upper space 37 b in 37. The thermoelectric conversion device cooling unit 43 includes a third fan 43d in which the third rotor blade 43a is driven by the third fan motor 43c, and the third rotor blade 43a is driven to rotate. By sucking air and discharging it to the upper space 37b, cooling air for cooling the second thermoelectric conversion device 47, the third thermoelectric conversion device 46, and the first thermoelectric conversion device 45 in order is formed. An exhaust port 37f that opens the upper space 37b to the outside is provided in the upper portion of the right side wall 37e of the housing 37. The second thermoelectric conversion device 47, the third thermoelectric conversion device 46, and the first thermoelectric conversion device 45 The cooling air that has cooled the two substrates 47b, 46b, and 45b in order is discharged from the exhaust port 37f and discharged to the outside of the printer 1. As described above, the second substrates 45b, 47b, and 46b of the first, second, and third thermoelectric conversion devices 45, 47, and 46 are cooled by the cooling air, respectively, so that the first, second, and third substrates are cooled. The temperature difference between the second substrates 45b, 47b, 46b of the thermoelectric conversion devices 45, 47, 46 and the first substrates 45a, 47a, 46a becomes large, and the first, second, and third thermoelectric conversion devices. The thermoelectric conversion efficiency of each of 45, 47, and 46 improves, and a high voltage is output.

  The first thermoelectric conversion device 45 disposed so as to face the first sheet non-passing region N1 on the right side in the fixing nip N applies the voltage obtained by the Seebeck effect to the right side wall 37e (downward side of the airflow) of the housing 37. Is output to the first fan motor 41c of the first blower fan 41e in the first temperature rise suppression part 41 attached to the first rotating blade 41a to rotate. The second thermoelectric conversion device 47 disposed on the left side (windward side of the airflow) in the conveyance direction of the recording paper P so as to face the second sheet non-passing region N2 on the left side in the fixing nip N is based on the Seebeck effect. The obtained voltage is output to the third fan motor 43c of the third blower fan 43d in the thermoelectric conversion device cooling section 43 attached to the left side wall 37d of the housing 37 to rotate the third rotary blade 43a. ing. The third thermoelectric conversion device 46 disposed opposite to the central sheet passing region N3 in the fixing nip N is attached with the voltage obtained by the Seebeck effect on the left side wall 37d (windward side of the airflow) of the housing 37. Further, the second fan blade 42a of the second blower fan 42e in the second temperature rise suppression unit 42 is output to rotate the second rotary blade 42a.

  Each of the first, second, and third thermoelectric conversion devices 45, 47, and 46 includes a high temperature side first substrate 45a, 47a, and 46a, and a low temperature side second substrate 45b, 47b, and 46b, respectively. The first, third, and second blowers in the first temperature rise suppression unit 41, the thermoelectric conversion device cooling unit 43, and the second temperature rise suppression unit 42 are increased by the temperature difference of Voltages that can rotate and drive the fans 41e, 43d, and 42e are output, whereby the first rotary blade 41a, the third rotary blade 43a, and the second rotary blade 42a are rotated. Further, the third rotating blade 43a of the thermoelectric conversion device cooling section 43 is driven to rotate, whereby the second substrate 45b on the low temperature side of each of the first, second, and third thermoelectric conversion devices 45, 47, and 46. , 47b, and 46b are formed, whereby the second substrates 45b, 47b, and 46b are cooled, respectively, and the temperature difference from the first substrate 45a, 47a, and 46a on the high temperature side is increased. The thermoelectric conversion efficiency of each of the first, second, and third thermoelectric conversion devices 45, 47, and 46 further increases, and the voltage output from each increases further. By increasing the voltage output from the first, second, and third thermoelectric converters 45, 47, and 46, the rotation speed of each of the first, third, and second blower fans 41e, 43d, and 42e is further increased. And the flow rate of the air flow formed by each increases.

  The first substrates 45a, 47a, and 46a, which are the high temperature sides of the first, second, and third thermoelectric conversion devices 45, 47, and 46, are easily heated to a higher temperature as the gap with the heating roller 31 becomes smaller. However, if the gap is too small, contact with the outer peripheral surface of the heating roller 31 is caused by the rotational vibration of the heating roller 31, and the heating roller 31 or the first, second, and third thermoelectric conversion devices 45, 47 and 46 may be damaged. Therefore, in this embodiment, the minimum gap between the first substrates 45a, 47a, 46a of the first, second, and third thermoelectric converters 45, 47, 46 and the heating roller 31 is set to 3.0 mm. It is set.

  FIG. 7 is a block diagram of a control system of the fixing device 30. The fixing motor 38 and the halogen lamp 34 that rotate the heating roller 31 provided in the fixing device 30 are supplied with voltages supplied from the motor power supply 56 and the heating power supply 57, respectively, by the motor drive circuit 55 and the heating drive. They are supplied in a state adjusted by the circuit 51, the fixing motor 38 is driven, and the halogen lamp 34 is turned on. The motor drive circuit 55 and the heating drive circuit 51 are controlled by the controller unit 53 to adjust the voltage output from each. The controller 53 receives a print instruction signal from a print job from the external host device 54, and an analog signal corresponding to the outer peripheral surface temperature of the heating roller 31 detected by the thermistor 36 is output by the A / D converter 52. Digitally converted and input.

  When the controller 53 receives a print instruction signal from the external host device 54, the controller 53 controls the fixing motor drive circuit 55 to rotate the heating roller 31 at a predetermined rotation speed. When the heating roller 31 rotates, the pressure roller 32 pressed against the heating roller 31 rotates following the heating roller 31. Further, when the controller unit 53 receives a print instruction signal from the external host device 54, the controller unit 53 controls the heating drive circuit 51 to turn on the halogen lamp 34 so that energization to the halogen lamp 34 is started. As a result, the heating roller 31 is rapidly heated throughout the effective heat generation area of the halogen lamp 34. Thereafter, the controller 53 controls the heating drive circuit 51 so that the outer peripheral surface of the heating roller 31 reaches a predetermined fixing temperature based on the detection signal of the thermistor 36 input via the A / D converter 52. To do.

  In the printer 1 of the present embodiment, for example, the process speed is set to 132 mm / sec, the fixing temperature in the fixing device 30 is set to 180 ° C., and the temperature of the outer peripheral surface of the heating roller 31 is 180 ° C. Controlled by temperature. Further, 1.0 sec is set as the conveyance time interval of each recording sheet P when printing on a plurality of recording sheets P, and the printing speed is 18 sheets / min.

  In the fixing device 30 of the printer 1 having such a configuration, when the printer 1 is turned off at night and the printer 1 is turned on with the fixing device 30 cooled to the same temperature as the ambient temperature (cold start). ), By continuously transporting a plurality of sheets (120 sheets in this case) of A4 size recording paper P in the vertical direction as the minimum size recording paper P, the toner image is thermally fixed to each recording paper P continuously. The case where it is made to explain is demonstrated. Upon receiving the print instruction, the controller 53 controls the motor drive circuit 55 to rotate the fixing motor 38 and controls the heating drive circuit 51 to control the halogen lamp 34 provided inside the heating roller 31. Turn on the light and heat the heating roller 31 until the temperature of the outer peripheral surface of the heating roller 31 reaches a fixing temperature of 180 ° C. When the heating roller 31 is heated, in the first, second, and third thermoelectric conversion devices 45, 47, and 46, the temperatures of the first substrates 45a, 47a, and 46a are increased, and the second substrates 45b, Electric power is generated by increasing the temperature difference between 47 b and 46 b, and a voltage is output to each of the second temperature increase suppression unit 42, the first temperature increase suppression unit 41, and the thermoelectric converter cooling unit 43. Thereafter, when the temperature of the outer peripheral surface of the heating roller 31 gradually increases, the voltages output from the first, second, and third thermoelectric converters 45, 47, and 46 also gradually increase. When the outer peripheral surface temperature of the heating roller 31 reaches a fixing temperature of 180 ° C., the small size recording paper P onto which the unfixed toner image is transferred is conveyed to the fixing device 30, and the heating roller 31, the pressure roller 32, In the fixing nip N between the two. Since the small size recording paper P passes through the fixing nip N so that the center position in the width direction coincides with the paper passing center line CL of the heating roller 31, the first and second side portions on the left and right sides of the heating roller 31 pass. In each of the second sheet non-passing areas N1 and N2, the recording paper P does not pass, and thus the temperature rises (non-sheet passing portion temperature rise). In this case, in each of the first and second sheet non-passing areas N1 and N2, the recording paper P that passes through the fixing nip N only touches a part of its length (W1 and W2). Therefore, the amount of heat taken by the recording paper in each of them is small and the temperature rises rapidly. Thereby, in the 1st and 2nd thermoelectric conversion apparatuses 45 and 47 arrange | positioned facing the outer peripheral surface part of the heating roller 31 which passes 1st and 2nd sheet | seat non-passage area | regions N1 and N2, in the heating roller The temperature rapidly rises in the first substrates 45a and 47a facing the substrate 31, the temperature difference from the second substrates 45b and 47b increases, and a high voltage corresponding to each temperature difference is output by the Seebeck effect.

  The voltage output from the first thermoelectric conversion device 45 is supplied to the fan motor 41 c of the first temperature rise suppression unit 41 attached to the right side wall 37 e of the housing 37, and the output voltage from the first thermoelectric conversion device 45. Exceeds the drive voltage of the first fan motor 41c, the first fan motor 41c is driven and the first rotary blade 41a rotates. By the rotation of the first rotary blade 41a, the air in the vicinity of the first sheet non-passage area N1 whose temperature has risen is sucked and discharged to the outside of the printer 1. Thereby, in the lower space 37c of the housing 37, as indicated by an arrow C in FIG. 4, an air flow is formed along the axial direction of the heating roller 31 from the left side wall 37d of the housing 37 toward the right side wall 37e. And the temperature rise suppression of each 2nd sheet | seat non-passing area | region N1 and N2 is started.

  In this case, the second sheet non-passing region N2 is also from the second thermoelectric conversion device 47 disposed to face the outer peripheral surface portion of the heating roller 31 passing through the second sheet non-passing region N2 close to the left side wall 37d. A high voltage is output due to the high temperature, and the third fan motor 43c of the thermoelectric conversion device cooling unit 43 disposed facing the upper space 37b of the housing 37 is driven to rotate the third rotary blade 43a. . Thereby, the third fan motor 43c sucks air outside the housing 37 and discharges it into the upper space 37b. The air discharged into the upper space 37b is second in each of the second, third, and first thermoelectric converters 47, 46, and 45, as indicated by an arrow D in FIG. Cooling air that flows along the substrates 47b, 46b, and 45b is formed, and the cooling air cools the second substrates 47b, 46b, and 45b in order, and an exhaust port 37f provided on the right side wall 37e of the housing 37 is provided. Then, it is discharged outside the printer 1. In each of the second, third, and first thermoelectric conversion devices 47, 46, and 45, the second substrates 47b, 46b, and 45b are cooled, so that the voltages output from the respective substrates further increase. Thereby, the 1st fan motor 41c of the 1st temperature rising suppression part 41 rotates further at high speed, and the flow volume of the airflow along the axial direction of the heating roller 31 increases.

  The airflow formed by the suction by the first temperature rise suppression unit 41 efficiently suppresses the temperature rise of the first sheet non-passing region N1 in the vicinity of the first temperature rise suppression unit 41, but Since the flow velocity is low on the far windward side, the temperature suppression effect is lower in the second sheet non-passing region N2 than in the first sheet non-passing region N1. However, when the number of sheets of small size recording paper P increases, the temperature rises in the second sheet non-passing area N2 which is on the far side of the first temperature rise suppression unit 41, and this second sheet non-passing area N2 The temperature difference between the first substrate 47a and the second substrate 47b of the second thermoelectric conversion device 47 facing each other increases, and the voltage output from the second thermoelectric conversion device 47 further increases. Thereby, the air volume of the cooling air by the 3rd rotary blade 43a of the 3rd ventilation fan 43d provided in the thermoelectric converter cooling part 43 further increases, and each 1st, 2nd, 3rd thermoelectric converter 45, The second substrates 45b, 47b and 46b in 47 and 46 are further cooled, respectively, and the voltages output from the first, second and third thermoelectric conversion devices 45, 47 and 46 are further increased.

  In this case, the outer peripheral surface portion of the heating roller 31 that passes through the sheet passing region N3 is deprived of heat from the outer peripheral surface portion of the heating roller 31 that passes through the high-temperature second sheet non-passing region N2 located on the windward side. Since the air flow whose temperature has risen flows along the outer peripheral surface of the heating roller 31, the outer peripheral surface portion of the heating roller 31 passing through the sheet passing region N3 is suppressed from being overcooled due to the air flow. As a result, in the third thermoelectric conversion device 46 facing the outer peripheral surface portion of the heating roller 31 passing through the sheet passing region N3, the temperature difference between the first substrate 46a and the second substrate 46b becomes large, and a high voltage is output. The second fan motor 42c of the second blower fan 42e in the second temperature rise suppression part 42 provided on the left side wall 37d of the housing 37, which is the windward side of the airflow, is driven. As a result, the second rotary blade 42a is rotated, and air outside the printer 1 is discharged into the lower space 37c of the housing 37, and in the axial direction of the heating roller 31 from the left side wall 37d of the housing 37 toward the right side wall 37e. A new air flow is formed along. The airflow generated by the discharge from the second temperature rise suppression unit 42 is high speed on the outer peripheral surface portion of the heating roller 31 that passes through the second sheet non-passing region N2 in the vicinity of the second temperature rise suppression unit 42. Moreover, the temperature rise in the second sheet non-passing region N2 is efficiently suppressed. Further, since the air flow discharged from the second temperature rise suppression unit 42 is in the same direction as the air flow generated by the suction of the first temperature rise suppression unit 41, the air flow smoothly along the axial direction of the heating roller 31. It flows, and it is suppressed that a temperature change largely by an airflow in the sheet | seat passage area | region N3. Thereby, the temperature of the outer peripheral surface of the heating roller 31 is made uniform in the axial direction.

  As described above, even when the A4 size recording paper P passes through the fixing nip N continuously in the vertical direction (small size recording paper conveyance), the first and second sheet non-passing areas N1 and N2 Temperature rise is efficiently suppressed. In this case, the second temperature rise suppression unit 42 is driven when the temperature rise of the second sheet non-passing region N2 cannot be suppressed only by the airflow formed by the first temperature rise suppression unit 41, but the heating roller 31 is Since the fixing temperature is controlled to 180 ° C., the electromotive force in the third thermoelectric converter 46 facing the sheet passing region N3 is small, and accordingly, the second rotor blade in the second temperature rise suppression unit 42 The rotational force of 42a is small, and the airflow discharged from the 2nd rotary blade 42a becomes smaller than the flow volume of the airflow formed by the 1st temperature rising suppression part 41. FIG. As a result, there is no possibility that the temperature of the second sheet non-passing region N2 is excessively suppressed, and also in the sheet passing region N3 located on the leeward side, it is suppressed that the temperature greatly changes due to the airflow. . In addition, the air suction port 41d in the first duct 41b of the first temperature rise suppression unit 41 located on the leeward side of the airflow is the discharge port in the second duct 42c of the second temperature rise suppression unit 42 located on the windward side of the airflow. Since the opening area is larger than 42d, the airflow discharged from the second temperature rise suppression unit 42 smoothly flows into the discharge port 42d, and thus the airflow flowing along the heating roller 31 is disturbed. Is reliably suppressed, and the temperature rise of the heating roller 31 can be efficiently and uniformly suppressed along the axial direction.

  In the present embodiment, the first and second sheets on both sides of the heating roller 31 are printed when printing is performed on a small-size recording sheet that continuously conveys 120 A4-sized recording sheets P in the vertical direction. The temperature rise in the non-passing areas N1 and N2 can be reliably suppressed, and the temperature of the heating roller 31 is suppressed to 240 ° C. or less without extending the conveyance time interval of the continuously conveyed recording paper P. I was able to. Since this temperature is lower than the heat resistant temperature of the pressure roller 32 in the fixing device 30 and various members arranged around the fixing device 30, there is no possibility that these members are thermally damaged.

  For comparison, in the fixing device in which the first temperature rise suppression unit 41, the second temperature rise suppression unit 42, and the thermoelectric converter cooling unit 43 are not provided, the same conditions as above (the state where the fixing unit is about room temperature) ), When printing on small size recording paper P by continuously conveying 120 A4 size recording papers in the vertical direction, 45 seconds have passed since the printing operation started. At that time, the temperature of the sheet non-passing region reached a high temperature of 260 ° C. At such a temperature, since it is necessary to extend the conveyance time interval of the recording paper P, the time interval of the recording paper P that is continuously conveyed becomes 1. From 0 sec (printing speed of 18 sheets / min) to 7.0 sec (printing speed of 6 sheets / min), the printing efficiency was significantly reduced.

  In the present embodiment, since the first temperature rise suppression unit 41 sucks air, the first and second sheet non-passing regions N1 and N2 on both sides of the heating roller 31 are suppressed from increasing in temperature. At the beginning of the suction of air by the first temperature rise suppression unit 41, the temperature of the second sheet non-passing region N2 adjacent to the second temperature rise suppression unit 42 tends to increase. For this reason, there is a risk that a difference in thermal expansion between the left and right sides of the heating roller 31 may occur due to the temperature difference between the first sheet non-passing area N1 and the second sheet non-passing area N2. The peripheral speed of the heating roller 31 is changed by the deformation of the left and right sides, but the change is within an allowable range. The recording paper P is poorly conveyed, and the recording paper is heated by the heating roller 31 and the pressure roller 32. There were no problems such as P contacting non-uniformly in the width direction.

  Next, after the continuous printing of a plurality of small-sized recording papers P in the fixing device 30 is finished, the controller unit 53 performs printing on the recording paper P having a longer length in the width direction than the small-sized recording papers. The operation of the fixing device 30 when instructed to will be described. Immediately after the small size recording paper P passes through the fixing nip N, the temperatures of the first and second sheet non-passing areas N1 and N2 on both sides of the heating roller 31 are higher than the temperature of the sheet passing area N3. In this state, when the recording paper P having a size longer in the width direction than that of the small size recording paper passes through the fixing nip N, the both sides of the recording paper P in the width direction in the image area have a high temperature. There is a possibility that an image is deteriorated due to an offset. Therefore, after the continuous printing of the small-sized recording paper P is completed, the controller unit 53 has a waiting time (wait time) during which the heating roller 31 and the pressure roller 32 are idly rotated to lower the temperature. The heating roller 31 and the pressure roller are set in advance according to the number of small-sized recording sheets P that have passed through the nip N, and the recording sheet P does not pass through the fixing nip N during the set waiting time. 32 is idly rotated. The wait time is stored in the controller unit 53 as a time table as shown in FIG. In the time table shown in FIG. 8, the first and second sheet non-passing areas N1 and N2 on both sides of the heating roller 31 are related to the usage environment of the printer 1, the size of the recording paper P, the type of the recording paper P, and the like. Instead, the wait time is set in accordance with the number of small-sized recording sheets P that have passed through the fixing nip N continuously so that the temperature decreases to 200 ° C. or less, which is a temperature at which no high temperature offset occurs. In the time table shown in FIG. 8, when the number of small-size recording sheets P on which toner images are continuously fixed in the fixing device 30 is less than 5, the wait time is set to 0 seconds (sec). Therefore, the printing operation of the large-size recording paper P is performed continuously with the continuous printing operation of the small-size recording paper P without particularly rotating the heating roller 31 and the pressure roller 32 idle. When the number of small-sized recording sheets P that have passed through the fixing nip N is 5 to less than 10 sheets, the wait time is set to 3 seconds (sec). Less than 5 seconds (sec), 18 to less than 25 sheets, 7 seconds (sec), 25 to less than 36 sheets, 15 seconds (sec), 36 to less than 54 sheets 20 seconds (sec), 54 to less than 80 sheets, 25 seconds (sec), 80 to less than 110 sheets, 30 seconds (sec), 110 to less than 140 sheets The wait time is set to 45 seconds (sec), 75 seconds (sec) for 140 to less than 160 sheets, and 105 seconds (sec) for 160 sheets or more.

  The controller unit 53 is instructed by the external host device 54 to continuously print a plurality of small-size recording sheets, and when there is an instruction to print a large-size recording sheet thereafter, the stored time Based on the table, the wait time corresponding to the designated number of prints is read out and set, and when the designated number of continuous print operations is completed, the halogen lamp 34 is turned off and the heating is performed over the set wait time. The roller 31 and the pressure roller 32 are idled. As a result, even if the sheet non-passing areas N1 and N2 in the fixing nip N are in a high temperature state, the temperature can be quickly reduced to a temperature of 200 ° C. or less, and a high temperature offset is applied to the fixed image on the large size recording paper P. It is possible to prevent image degradation due to.

  For example, the controller unit 53 performs a print instruction for performing a printing operation of a small size recording sheet for conveying 120 A4 size recording sheets P in the vertical direction, and then, for example, conveys an A4 size recording sheet in the horizontal direction. When a print instruction for performing a print operation is received from the external host device 54, a wait time of 45 seconds is set based on the time table shown in FIG. When the operation was completed, the heating roller 31 and the pressure roller 32 were idled for 45 seconds, and then a printing operation was carried out by conveying A4 size recording paper in the horizontal direction. In this case, the toner image on the large size recording paper P did not cause image deterioration due to high temperature offset, and a good image could be obtained.

  The wait time shown in FIG. 8 is set to an optimum time (shortest time) according to the width direction size of the recording sheet, the material, the environment around the printer 1, and the like. Further, immediately after the continuous fixing operation of the small size recording paper P, not only the configuration in which the wait time is set when the fixing operation of the large size recording paper P is performed immediately after the continuous fixing operation of the small size recording paper P is performed. Even when the printing operation is stopped, the wait time may be set.

  Next, a case where a continuous print operation is performed by conveying a maximum width, for example, A4 size recording paper in the horizontal direction will be described. In this case, since the A4 size recording paper in the lateral direction passes through the entire first and second sheet non-passing areas N1 and N2 and the sheet passing area N3 in the nip N, the first and second sheets Heat is lost in all of the sheet non-passing areas N1 and N2 and the sheet passing area N3. Therefore, even if the large size recording paper P passes through the fixing nip N in a state where the heating roller 31 is uniformly controlled at a fixing temperature of 180 ° C. in the axial direction, the heating roller 31 remains in the axial direction. The temperature rises almost uniformly, and the temperature in the upper space 37b of the housing 37 rises with this temperature rise. Accordingly, in each of the first, second, and third thermoelectric conversion devices 45, 47, and 46, the temperature difference between the first substrate 45a, 47a, and 46a and the second substrate 45b, 47b, and 46b does not increase. Furthermore, the electric power generated in each of the first, second, and third thermoelectric conversion devices 45, 47, 46 is small, and the first temperature rise suppression unit 41, the second temperature rise suppression unit 42, and the thermoelectric conversion device cooling unit 43 Each is never driven. In this embodiment, A4 size recording paper is conveyed in the horizontal direction and printed continuously over 200 sheets. However, the temperature rise in the heating roller 31 is small, and the first temperature rise suppression unit 41, the second temperature rise suppression unit 42, The thermoelectric converter cooling unit 43 was not driven.

  In addition, when continuously printing the recording paper P having an intermediate size between the large size and the small size (for example, when conveying a B4 size recording paper in the vertical direction), the sheet non-passing area on both sides of the heating roller 31 is used. Since the axial length at which the recording paper P at N1 and N2 does not contact is shorter than when the A4-sized recording paper P is transported in the vertical direction, the temperature of the region where the recording paper P does not contact at the fixing nip N However, it rises more slowly than in the case of vertical conveyance of A4 size recording paper. Accordingly, the voltages output from the first and second thermoelectric conversion devices 45 and 47 disposed opposite to the first and second sheet non-passing regions N1 and N2 on both sides of the heating roller 31 also gradually increase. To do. For this reason, the timing at which the first temperature rise suppression unit 41 and the thermoelectric conversion device cooling unit 43 connected to the first and second thermoelectric conversion devices 45 and 47 are driven is the A4 size recording paper vertical transport. In the first and second sheet non-passing areas N1 and N2, the temperature of the portion where the B4 size recording paper does not come in contact is higher than that in the case of the vertical conveyance of the A4 size recording paper. However, when the first temperature rise suppression unit 41 and the thermoelectric converter cooling unit 43 are driven by the temperature rise in each region where the recording paper P does not contact, thereafter, during the continuous printing operation by the vertical conveyance of the A4 size recording paper In the same manner as described above, a high voltage is output from each of the first, second, and third thermoelectric converters 45, 47, and 46, and then the second temperature rise suppression unit 42 is also driven. Thus, the temperature rise of the heating roller 31 can be suppressed to the same level as in the case of continuous printing by vertical conveyance. In the present embodiment, when 120 B4-size recording sheets are continuously conveyed and printed in the vertical direction, the driving of the first temperature rise suppression unit 41 and the thermoelectric converter cooling unit 43 is delayed, Although the heating roller 31 temporarily reached 250 ° C., it could be suppressed to a temperature (240 ° C.) that does not affect the peripheral members of the fixing device 30 after that.

  Next, a description will be given of the case where the printer 1 receives a print instruction for conveying 120 sheets of A4 size recording paper in the vertical direction from a standby state (standby state) without performing a printing operation for 3 hours with the power on. To do. In this case, the fixing device 30 idles the heating roller 31 and the pressure roller 32 during the waiting time of 3 hours (however, the peripheral speeds are lower than the peripheral speeds during the fixing operation). The temperature of the outer peripheral surface of the heating roller 31 is controlled to 150 ° C. For example, when the output voltage from the heating drive circuit 51 is 100, the output voltage from the heating drive circuit 51 is about half (55%) of the cold start. A method for controlling the halogen lamp 34 is adopted. Of course, other control methods may be used. Thereby, in the standby state, the power consumption of the halogen lamp 34 can be reduced.

  When the temperature of the outer peripheral surface of the heating roller 31 is maintained at 150 ° C. and the apparatus is on standby for a long time, the heat from the halogen lamp 34 spreads over the entire fixing device 30, and thus the lower space 37 c of the housing 37. Not only the temperature around the heating roller 31 but also the temperature in the upper space 37b of the housing 37 rises to about 55% to 75% with respect to the temperature 150 ° of the outer peripheral surface of the heating roller 31. From this state, when the heating roller 31 is heated to 180 ° C., the A4 size recording paper P is continuously conveyed in the vertical direction and passed through the fixing nip N in the fixing device 30. Therefore, the fixing temperature can be maintained at 180 ° C. with a small amount of power. Therefore, the temperature rises gently in the area where the recording paper P does not contact on both sides of the heating roller 31, and the upper space of the housing 37 increases with the gradual temperature rise in the area where the recording paper P does not contact the heating roller 31. The temperature gradually rises in 37b. As a result, the voltage output from each of the first and second thermoelectric conversion devices 45 and 47 also gradually increases, and the timing at which the first temperature rise suppression unit 41 and the thermoelectric conversion device cooling unit 43 are driven is delayed. As in the case of the intermediate size, there is a possibility that the temperature of about 250 ° C. may be temporarily reached in the region where the recording paper P is not in contact with the heating roller 31. However, when each region of the heating roller 31 that does not contact the recording paper P becomes high temperature, when the first temperature rise suppression unit 41 and the thermoelectric conversion device cooling unit 43 are driven, the surrounding members are thermally heated thereafter. The temperature can be lowered to such an extent that there is no risk of damage (about 240 ° C.).

  Note that when the continuous printing is performed by the vertical conveyance of the B4-sized recording paper P in which the timing at which the first temperature rise suppression unit 41 and the thermoelectric converter cooling unit 43 are driven is further delayed, the temperature of the heating roller 31 is Although the temperature has temporarily reached 254 ° C., when the first temperature rise suppression unit 41 and the thermoelectric converter cooling unit 43 are driven, thereafter, the same as in the case of continuous printing by the vertical conveyance of the A4 size recording paper P is performed. In addition, the peripheral members of the fixing device 30 could be suppressed to a temperature (240 ° C. or less) that does not affect the thermal degradation. In the standby state, since the temperature of the outer peripheral surface of the heating roller 31 is maintained at 150 ° C., the temperature rise when the temperature rises to the fixing temperature of 180 ° C. is more gradual than the cold start, As a result, overheating can be prevented.

  As described above, in the first embodiment, the fixing nip N of the fixing device 30 is not subjected to complicated control when continuously printing recording sheets such as recording paper having a small width in the length direction. The temperature rise in each area where the recording paper does not come into contact with the recording paper can be reliably suppressed without extending the recording paper conveyance time interval, and therefore the image is continuously fixed to a plurality of recording papers. Therefore, there is no possibility that the time required for the fixing is extended, and as a result, it is possible to prevent the fixing efficiency from being lowered.

  In the above description, the maximum length in the width direction of the recording sheet being conveyed is the length in the longitudinal direction of the A4 size recording sheet, and the minimum length in the width direction of the recording sheet being conveyed is the length of the A4 size recording sheet. Although the length in the width direction is described, it is not limited to such a configuration. Further, the second blower fan 42e is driven with a delay from the first blower fan 41e, but the second blower fan 42e is a fan driven at a low voltage so as to be driven almost simultaneously. Also good. Further, the first air fan 41e and the third air fan 43d may be configured so that the fan is operated by the temperature increase of the heating roller 31 during the printing operation to cool the sheet non-passing region so as to prevent an excessive temperature increase. If the excessive temperature rise can be suppressed only by this, the second thermoelectric converter 47 and the second blower fan 42e may be omitted.

<Embodiment 2>
FIG. 9 is a schematic diagram illustrating a configuration of the fixing device 30 according to the second exemplary embodiment. FIG. 10 is a cross-sectional view taken along line YY in FIG. In the fixing device 30 according to the second embodiment, the configuration of the second thermoelectric conversion device 47 ′ disposed to face the second sheet non-passing area N2 on the left side of the heating roller 31 is the same as that of the fixing device 30 according to the first embodiment. The configuration is the same except that it is different from the two thermoelectric conversion device 47. In the second thermoelectric conversion device 47 ′ of the second embodiment, the areas of the first substrate 47a ′ and the second substrate 47b ′ are the same as those of the first substrate 47a and the second substrate 47b of the second thermoelectric conversion device 47 of the first embodiment. The number of P-type semiconductor elements 47c ′ and N-type semiconductor elements 47d ′ arranged between the first substrate 47a ′ and the second substrate 47b ′ so as to be larger than the area is determined as the second thermoelectric element of the first embodiment. By increasing the number of P-type semiconductor elements 47c and N-type semiconductor elements 47d in the conversion device 47, the thermoelectric conversion efficiency of the second thermoelectric conversion device 47 ′ is increased. Thereby, the thermoelectric conversion efficiency of 2nd thermoelectric conversion apparatus 47 'is higher than the thermoelectric conversion efficiency of the 1st thermoelectric conversion apparatus 45 arrange | positioned facing the 1st sheet | seat non-passing area | region N1. In the second thermoelectric conversion device 47 ′ of the present embodiment, the first substrate 47 a ′ and the second substrate 47 b ′ respectively protrude upward along the outer peripheral surface of the heating roller 31 as shown in FIG. 9. And is disposed in an opening 37g formed in the partition wall 37a of the housing 37. Accordingly, the gap between the second substrate 47b ′ and the outer peripheral surface of the heating roller 31 becomes substantially constant, and the second substrate 47b ′ is uniformly heated by the heating roller 31, so that the thermoelectric power of the second thermoelectric conversion device 47 ′ can be obtained. The conversion efficiency is further increased.

  The second thermoelectric conversion device 47 ′ has such a configuration, thereby improving the thermoelectric conversion efficiency and increasing the output voltage even if the temperature difference between the first substrate 47a ′ and the second substrate 47b ′ is small. be able to. Therefore, the drive timing of the thermoelectric converter cooling unit 43 can be advanced. As a result, for example, when continuous printing is performed on the A4 size recording paper P in the vertical direction (width direction small size recording paper), the second thermoelectric conversion device 47 ′ is first in a high-voltage output state and thermoelectric conversion is performed. The device cooling unit 43 is driven. Thereby, the timing which the 2nd board | substrate 45b, 47b ', 46b of 1st, 2nd, 3rd thermoelectric conversion apparatus 45, 47', 46 is cooled also becomes early, and from 1st thermoelectric conversion apparatus 45 after that, The first temperature rise suppression unit 41 is driven by the output voltage, and then the second temperature rise suppression unit 42 is driven by the voltage output from the second thermoelectric converter 45. The timing at which the suppression unit 42 is driven is faster than in the first embodiment. Thereby, the temperature rise in the 1st and 2nd sheet | seat non-passage area | regions N1 and N2 of the both sides in the heating roller 31 can be suppressed efficiently and more reliably.

  In the fixing device 30 according to the second embodiment, the standby state in which the heating roller 31 and the pressure roller 32 are idled and controlled to a temperature of 150 ° C. continues for three hours, and then 120 sheets of A4 size recording paper P are printed. When the printing is continuously performed in the vertical conveyance, the heating roller 31 temporarily reaches a temperature of 240 ° C., which is lower than 254 ° C. in the first embodiment, and the thermoelectric conversion device. Since the timing at which the cooling unit 43 is driven is advanced, the subsequent temperature rise in the sheet non-passing region can be effectively suppressed.

  Even in the case of the cold start described above, the temperature at which the temperature of the heating roller 31 reaches temporarily can be lowered to 223 ° C. because the timing at which the thermoelectric conversion device cooling unit 43 is driven becomes earlier. In addition, in the first and second sheet non-passing regions N1 and N2 on both sides of the heating roller 31 in the fixing device 30, the temperature of the heating roller 31 is effective so as not to affect the fixability of the toner image. It was possible to suppress the temperature rise.

<Embodiment 3>
FIG. 11 is a cross-sectional view illustrating a schematic configuration of the fixing device 30 according to the third exemplary embodiment of the present invention. In the fixing device 30, an unfixed toner image on the recording paper passing through the fixing nip N is heated by an electromagnetic induction heating type heating unit. For this purpose, for example, the heating roller 31 is provided with an iron heating layer having a thickness of about 1 mm to several tens of mm on the surface of the core metal, and a release layer such as a fluororesin is formed on the surface. The diameter is 40 mm. The heat generating layer is not limited to iron, but may be stainless steel, aluminum, a composite material of stainless steel and aluminum, or the like. The pressure roller 32 has the same configuration as that of the first embodiment, and has a diameter of 40 mm like the heating roller 31. The pressure roller 32 is pressed against the heating roller 31 by a pressure mechanism (not shown), and the heating roller 31 is rotationally driven. Thereby, it follows the heating roller 31 and rotates.

  On the upper side of the heating roller 31, a magnetic field generator 60 that constitutes a heating means of an electromagnetic induction heating system is provided in a curved state along the upper outer peripheral surface of the heating roller 31. The magnetic field generator 60 includes a pair of excitation coils 61, for example. Each exciting coil 61 is formed by coating a copper wire having a diameter of 0.5 mm with a heat-resistant polyamide imide, and, for example, litz wire obtained by bundling 16 coated copper wires in an insulated state. It is comprised by the air-core coil formed in the coil, without using a core member.

  A high frequency current is applied to each excitation coil 61 from an excitation circuit (inverter circuit) (not shown). When the high frequency current is applied, a magnetic flux is generated from each excitation coil 61, and the heating roller 31. Magnetic flux and eddy current are generated in the portion of the heat generating layer facing each exciting coil 61 so as to prevent the change of the magnetic field, and this eddy current causes the heat generating layer in the heating roller 31 to follow the axial direction of the heating roller 31. Joule heat is generated. As described above, only the portion of the heating roller 31 facing each excitation coil 61 is heated. However, when the heating roller 31 rotates, the heat generating layer portion facing each excitation coil 61 continuously changes in the circumferential direction. Thus, the heating roller 31 is heated over the entire circumferential direction. The current for the excitation circuit is supplied via a thermostat (not shown) that is a temperature fuse pressed against the surface of the heating roller 31. The thermostat cuts off the supply of current to the excitation circuit when the surface temperature of the heating roller 31 reaches a predetermined abnormal temperature set in advance.

  In the present embodiment, the exciting coil 61 is set so as to supply a high frequency current having a frequency of 30 kHz and an output of 1000 W, the fixing temperature is set to 200 ° C., and the temperature of the outer peripheral surface of the heating roller 31 is set to the thermistor. The temperature of the outer peripheral surface of the heating roller 31 is feedback-controlled so as to be 200 ° C. detected by 36, and the printing operation is started when the temperature of the surface of the heating roller 31 becomes 200 ° C. In the standby state until the printing operation is started, the heating roller 31 and the pressure roller 32 are idly rotated without the recording paper P being conveyed so that the surface of the heating roller 31 is uniformly heated. Has been.

  Also in the fixing device 30 according to the third embodiment, similarly to the fixing device 30 according to the first embodiment, the first temperature increase suppression unit 41, the second temperature increase suppression unit 42, the thermoelectric conversion device cooling unit 43, and the first and first 2 and the third thermoelectric converters 45, 47, and 46 are provided. The first temperature rise suppression unit 41 and the second temperature rise suppression unit 42 are arranged above the paper discharge roller 35 as in the first embodiment. The first, second, and third thermoelectric conversion devices 45, 47, and 46 and the thermoelectric conversion device cooling unit 43 are provided, whereas the recording paper P is provided on the right and left sides in the conveyance direction. The position is different from that of the fixing device 30 of the first embodiment. That is, the first, second, and third thermoelectric conversion devices 45, 47, and 46 are located downstream of the magnetic field generator 60 in the rotation direction of the heating roller 31 and upstream of the thermistor 36 in the rotation direction. The first substrates 45a, 46a, 47a are arranged in a state of facing the first sheet non-passing area N1, the sheet passing area N3, and the left second sheet passing area N2 on the heating roller 31, respectively. The second substrates 45b, 47b, and 46b of the first, second, and third thermoelectric conversion devices 45, 47, and 46 are provided above the upstream side in the conveyance direction of the recording paper P in the housing 37 of the fixing device 30. It arrange | positions in the cooling space 37s. The thermoelectric conversion device cooling section 43 is formed on the left side of the cooling space 37s along the second substrates 47b, 46b, and 45b of the second, third, and first thermoelectric conversion devices 47, 46, and 45b. It arrange | positions so that a cooling wind may be ventilated. Other configurations are the same as those of the fixing device 30 of the first embodiment.

  Similarly to the fixing device 30 of the first embodiment, the fixing device 30 having such a configuration also suppresses the first temperature rise by the voltages generated in the first, second, and third thermoelectric conversion devices 45, 47, and 46. Since each of the unit 41, the second temperature rise suppression unit 42, and the thermoelectric converter cooling unit 43 is driven, the recording paper P having a small size in the width direction is continuously printed (for example, In the case of printing by vertical conveyance of A4 size recording paper), the temperature rise in the first and second sheet non-passing areas N1 and N2 on both sides of the heating roller 31 can be reliably suppressed. In particular, the fixing device 30 of the present embodiment has a configuration in which the exciting coil 61 partially heats the peripheral surface portion of the opposing heating roller 31, and the heating roller 31 is rotated by one rotation of the heating roller 31. Although heated over the entire circumference, each of the first, second, and third thermoelectric conversion devices 45, 47, 46 is downstream of the outer peripheral surface portion of the heating roller 31 that is heated by the exciting coil 61 and in the rotational direction. By being positioned upstream of the fixing nip, the first substrates 45a, 47a, 46a of the first, second, and third thermoelectric converters 45, 47, 46 are heated immediately after being heated. The roller 31 is heated quickly. Thereby, each of the 1st temperature rising suppression part 41, the 2nd temperature rising suppression part 42, and the thermoelectric converter cooling part 43 is driven rapidly, and each 1st and 2nd sheet | seat non-passing area | region N1 of the heating roller 31 and The start timing of the control for suppressing the temperature increase of N2 is accelerated, and each temperature increase can be reliably suppressed.

The present embodiment is not limited to the electromagnetic induction heating type fixing device, and a fixing device that partially heats one or both of the heating roller 31 and the pressure roller 32, for example, the heating roller 31. It can also be applied to a fixing device provided with a second heating roller that auxiliaryly heats the heating roller 31 by a halogen lamp or the like.
<Modification>
In each of the above embodiments, the configuration using the halogen lamp and the fixing roller as the fixing device has been described. However, the present invention is not limited to such a configuration. For example, a heating having a cylindrical fixing film and a heating resistance layer provided on the inner surface of the fixing film and provided on the outer peripheral surface of a glass (ceramic, heat resistant plastic) or other substrate (thickness of about 0.1 mm to 2.0 mm). As a film heating type fixing device that includes a body and a holder that supports the heating body, and presses the heating body against the pressure roller via the fixing film to secure a nip between the fixing film and the pressure roller. Good. In such a fixing device having a small heat capacity, it is possible to increase the temperature at high speed. In particular, since the temperature increase in the sheet non-passing region is rapid, the present invention can be suitably implemented.

  In the fixing device according to each of the above embodiments, either one or both of the heating roller 31 and the pressure roller 32 may be a belt. Further, the image forming apparatus to which the fixing device according to each of the above embodiments is applied is not limited to the mono-color printer shown in FIG. 1, and four image forming units are arranged facing the circumferential movement area of the intermediate transfer belt. Tandem color digital printer, so-called four-cycle image, in which four developing devices are arranged around the rotation axis, and these four developing devices are sequentially opposed to the electrostatic latent image carrier to form a full-color image. It may be a forming device or the like. Further, the present invention can be applied not only to a printer but also to a copying machine, a FAX, an MFP (Multiple Function Printer), and the like.

  The present invention provides a fixing device that heats and pressurizes an unfixed image to fix the temperature in a sheet non-passing area when continuously printing recording sheets such as a recording paper having a small width. In addition, the recording sheet conveyance time interval can be reliably suppressed without being extended.

1 is a schematic diagram illustrating an overall schematic configuration of a printer in which a fixing device according to an embodiment of the present invention is mounted as a fixing unit. FIG. 2 is a schematic diagram illustrating a configuration of a fixing device according to an embodiment of the present invention provided in the printer. It is a schematic diagram of the cross section along the XX line of FIG. FIG. 4 is a perspective view schematically illustrating a state in which the fixing device is viewed from the upper right side in the conveyance direction on the downstream side in the conveyance direction of the recording paper P. It is a schematic diagram for demonstrating the structure of the 1st temperature rising suppression part and the 2nd temperature rising suppression part provided in the fixing device. (A) is the perspective view of the state which looked at the 1st thermoelectric conversion device from the upper part, and is notched and shown. (B) is the perspective view of the state which reversed the 1st thermoelectric conversion apparatus in the up-down direction and the left-right direction, respectively. 2 is a block diagram of a control system of a fixing device. FIG. 6 is a table showing an example of a time table stored in a controller unit of the fixing device. FIG. 6 is a schematic diagram illustrating a configuration of a fixing device according to a second exemplary embodiment of the present invention. It is a schematic diagram of the cross section along the YY line of FIG. FIG. 6 is a schematic cross-sectional view illustrating a configuration of a fixing device according to Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 30 Fixing device 31 Heating roller 32 Pressure roller 34 Halogen lamp 36 Thermistor 37 Housing 37a Partition wall 37b Upper space 37c Lower space 41 1st temperature rising suppression part 41a 1st rotary blade 41b 1st duct 41c 1st fan motor 41d Air suction port 41e 1st ventilation fan 42 2nd temperature rising suppression part 42a 2nd rotary blade 42b 2nd duct 42c 2nd fan motor 42d discharge port 42e 2nd ventilation fan 43 thermoelectric conversion device cooling part 43a 3rd rotary blade 43c 3rd fan motor 43d 3rd ventilation fan 45 1st thermoelectric converter 45a 1st board | substrate 45b 2nd board | substrate 45c P-type semiconductor element 45d N-type semiconductor element 45h Heat-absorbing material 46 3rd thermoelectric converter 46a 1st board | substrate 46b 2nd board | substrate 46cP Type semiconductor element 46d N type semiconductor element 47, 4 'The second thermoelectric conversion device 47a, 47a' first substrate 47b, 47b 'of the second substrate 47c, 47c' P-type semiconductor element 47d, 47d 'N-type semiconductor element 60 the magnetic field generator 61 exciting coil

Claims (20)

A fixing nip formed between a heating rotator whose outer peripheral surface circulates while being heated by the heating means and a pressure rotator whose outer peripheral surface circulates while being pressed against the outer peripheral surface of the heating rotator. A fixing device for thermally fixing an unfixed image on a recording sheet while the recording sheet passes,
A first temperature rise suppression unit that forms an air flow that suppresses the temperature rise of the heating rotator in a direction orthogonal to the direction of circumferential movement along the outer peripheral surface of the heating rotator;
A high-temperature-side heat-receiving portion respectively facing the outer peripheral surface portions on both sides of the heating rotator that respectively pass through sheet non-passage areas on both sides of a sheet-passing area through which a recording sheet of a predetermined size passes in the fixing nip; A low-temperature side heat receiving part located on the opposite side of the heating rotator with respect to each of the parts, and generates electric energy according to a difference in heat-receiving temperature between the high-temperature side heat receiving part and the low-temperature side heat receiving part , First and second thermoelectric conversion devices;
A thermoelectric conversion device cooling section that cools each of the low-temperature side heat receiving sections so that the difference between the heat receiving temperature increases in each of the first and second thermoelectric conversion apparatuses,
The first temperature rise suppression unit is driven by electrical energy output from the first thermoelectric conversion device, and the thermoelectric conversion device cooling unit is driven by electrical energy output from the second thermoelectric conversion device. A fixing device. The heating rotator and the pressure rotator are provided in a housing,
The first temperature rise suppression unit includes a first blower fan that sucks air in the housing and discharges the air out of the housing, and the first blower fan uses electric energy output from the first thermoelectric converter. The fixing device according to claim 1, wherein the fixing device is driven. The first blower fan is a second temperature rise suppression unit arranged with the heating rotator interposed therebetween so as to form an airflow in the same direction as the airflow formed by the first temperature rise suppression unit,
A high temperature side heat receiving portion facing the outer peripheral surface portion of the heating rotator passing through the sheet passing region, and a low temperature side heat receiving portion located on the opposite side of the heating rotator with respect to the high temperature side heat receiving portion. A third thermoelectric conversion device that generates electrical energy according to a difference in heat receiving temperature between the high temperature side heat receiving portion and the low temperature side heat receiving portion,
The third thermoelectric conversion device is arranged such that the low temperature side heat receiving unit of the third thermoelectric conversion device is cooled by the thermoelectric conversion device cooling unit, and the generated electric energy is suppressed to the second temperature rise. The fixing device according to claim 2, wherein the second temperature rise suppression unit is driven by outputting to the unit.   The second temperature rise suppression unit includes a second blower fan that draws air outside the housing into the housing, and the second blower fan is driven by electric energy output from the third thermoelectric converter. The fixing device according to claim 3. Each of the first to third thermoelectric converters is
A first substrate constituting the high temperature side heat receiving part;
A second substrate constituting the low temperature side heat receiving part;
A plurality of semiconductor elements disposed between the first substrate and the second substrate so that electrical energy is generated by a Seebeck effect based on a temperature difference between the first substrate and the second substrate;
The fixing device according to claim 3, further comprising:   The fixing device according to claim 5, wherein the thermoelectric conversion device cooling unit cools the second substrate of each of the first to third thermoelectric conversion devices.   The fixing device according to claim 6, wherein the thermoelectric conversion device cooling unit blows cooling air along the second substrate of each of the first to third thermoelectric conversion devices. Each of the first to third thermoelectric conversion devices has a plurality of P-type semiconductor elements and the same number of N-type semiconductor elements,
Each of the P-type semiconductor element and each of the N-type semiconductor element are alternately connected in series between each of the P-type semiconductor element and the N-type semiconductor element between the first substrate and the second substrate. The fixing device according to claim 5, wherein   Each of the first to third thermoelectric conversion devices is provided with a heat-absorbing material on a surface of the first substrate facing the heating rotator. The fixing device according to one item. The first substrate and the second substrate of the first thermoelectric conversion device are configured to be flat,
The areas of the first substrate and the second substrate of the second thermoelectric conversion device are larger than the areas of the first substrate and the second substrate of the first thermoelectric conversion device, respectively. The number of the semiconductor elements formed in the curved state along the outer peripheral surface of the heating rotator and provided in the second thermoelectric conversion device is larger than the number of the semiconductor elements of the first thermoelectric conversion device. The fixing device according to claim 8, wherein the fixing device is increased.   The fixing device according to claim 1, wherein the heating unit is a heater lamp or a heating wire heater disposed inside the heating rotator.   The heating means is arranged to face the outer peripheral surface of the heating rotator so as to heat the outer peripheral surface portion of the heating rotator. The fixing device described.   13. The fixing device according to claim 12, wherein each of the first to third thermoelectric conversion devices is provided downstream of the heating unit in a rotation direction of the heating rotator.   The fixing device according to claim 12, wherein the heating unit is an exciting coil that generates heat from a heat generating layer provided in the heating rotating body. Temperature detecting means for detecting the temperature of the outer peripheral surface of the heating rotating body;
A control unit for controlling the heating unit based on a detection result by the temperature detection unit;
The fixing device according to claim 1, further comprising:   The fixing device according to claim 15, wherein the temperature detection unit is disposed on an opposite side of the heating rotator from a region where an air flow is formed by the first temperature increase suppression unit.   When the small-size recording sheet having a length shorter than the length of the fixing nip in the longitudinal direction passes continuously over the plurality of sheets, the plurality of small-size recording sheets have passed through the control unit. The standby time for idly rotating the heating rotator and the pressure rotator later is set in advance according to the number of the small-sized recording sheets that pass continuously. The fixing device according to 1.   The control unit, when the plurality of small-sized recording sheets pass through the fixing nip and then a recording sheet having a longer length along the longitudinal direction of the fixing nip passes than the small-sized recording sheet; 18. The fixing device according to claim 17, wherein when the recording sheet is not conveyed to the fixing nip, the heating rotator and the pressure rotator are idly rotated over the set waiting time.   The fixing device according to claim 1, wherein the heating rotator is a heating roller, and the pressure rotator is a pressure roller. An image forming apparatus for thermally fixing an unfixed image formed on a recording sheet by a fixing unit,
An image forming apparatus comprising the fixing device according to claim 1 as the fixing unit.

Images