JP2019144493A - Fixation device and image formation apparatus - Google Patents

Abstract

To provide a fixation device and an image formation apparatus which can suppress a local temperature rise of a fixation belt.SOLUTION: A fixation device 1 includes: an endless fixation belt; a base pad 20; and a first thermoelectric transducer. The base pad extends in a width direction DR1 of the fixation belt. The base pad 20 includes an opposite surface 21. The opposite surface 21 is opposite to an inner peripheral surface of the fixation belt. The first thermoelectric transducer is provided on the opposite surface 21. In the fixation belt 10, a regular passage region through which a recording medium regularly passes when fixing a toner image on the recording medium in the width direction DR1, and end regions provided on both ends of the regular passage region in the width direction DR1 are defined. The first thermoelectric transducer is provided in the fixing nip part. The first thermoelectric transducer is arranged so as to face the respective end regions.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a fixing device and an image forming apparatus.

  With respect to conventional fixing devices, techniques for suppressing heat storage in portions related to fixing are disclosed in Japanese Patent Application Laid-Open No. 2015-75567 (Patent Document 1), Japanese Patent Application Laid-Open No. 2015-31841 (Patent Document 2), and Japanese Patent Application Laid-Open No. 4-36283. It is disclosed by the gazette (patent document 3) (patent document 1).

Japanese Patent Laying-Open No. 2015-75567 JP 2015-31841 A JP-A-4-362833

  As disclosed in the above patent document, there is known a fixing device that heats and presses a recording medium such as paper by a fixing belt to fix a toner image on the recording medium. In such a fixing device, when a small size paper such as A6 or A5 is continuously passed, heat transfer from the fixing belt to the paper does not proceed in a portion other than the paper passing area. May rise locally.

  An object of the present invention is to provide a fixing device and an image forming apparatus that can suppress a local temperature rise of the fixing belt.

  A fixing device according to the present disclosure fixes a toner image on a recording medium. The fixing device includes an endless fixing belt, a base pad, a pressure rotator, a heating unit, and a first thermoelectric conversion element. The base pad extends in the width direction of the fixing belt. The base pad includes an opposing surface. The facing surface faces the inner peripheral surface of the fixing belt. The pressure rotator is disposed to face the base pad via the fixing belt. The pressure rotator forms the fixing nip portion with the base pad. The heating unit heats the fixing belt. The first thermoelectric conversion element is provided on the facing surface. In the width direction, the fixing belt always passes through the recording medium when fixing the toner image on the recording medium in the width direction, and end areas provided at both ends of the constant passage area in the width direction. Is prescribed. The first thermoelectric conversion element is provided in the fixing nip portion. The first thermoelectric conversion element is disposed to face each of the end regions.

  According to the above fixing device, it is possible to suppress a deterioration in fixing quality due to temperature unevenness in the end region while suppressing a local temperature increase of the fixing belt.

  In the fixing device, the facing surface has a first region and a second region. The first region extends in the width direction. The second area is provided downstream of the first area in the conveyance direction of the recording medium. In the cross section orthogonal to the width direction, the second region has a shape that extends from the first region toward the downstream side in the transport direction so as to approach the rotation axis of the pressure rotator. The first thermoelectric conversion element is provided in the first region.

  According to the above fixing device, it is possible to prevent deformation and breakage of the first thermoelectric conversion element due to the nip pressure while ensuring good fixing properties.

  In the fixing device, the energization direction and the energization amount to the first thermoelectric conversion element are controlled based on the thermal conductivity of the facing surface and the first thermoelectric conversion element. Thereby, temperature unevenness of the fixing belt can be suppressed.

  In the fixing device, the plurality of first thermoelectric conversion elements are arranged side by side in the width direction in each portion of the facing surface that faces the end region. Thereby, the fixing belt can be efficiently heated or cooled.

  In the fixing device, the arrangement of the plurality of first thermoelectric conversion elements is determined based on various sizes of the recording medium. As a result, it is possible to efficiently cool the region where the temperature rises without the heat being taken away by the recording medium.

  In the above fixing device, the fixing device further includes a temperature detection unit. The temperature detection unit detects the temperatures of the constantly passing region and the end region. When the temperature of the constantly passing region is Tc [° C.] and the temperature of the end region is Te [° C.], depending on the Tc and Te detected by the temperature detecting unit, the first thermoelectric conversion element The energization direction and the energization amount of are controlled. Thereby, the fixing belt can be efficiently cooled.

  In the fixing device, when the Tc is smaller than the Te, the first thermoelectric conversion element is energized so as to exhibit a cooling action. Thereby, the temperature rise of an edge part area | region can be suppressed. Therefore, damage to the fixing belt can be suppressed.

  In the fixing device, when the Tc is larger than the Te, the first thermoelectric conversion element is energized so as to exert a heating action. Thereby, temperature unevenness of the fixing belt can be suppressed.

  In the fixing device, the energization amount to the first thermoelectric conversion element is controlled according to the difference between the Tc and the Te. Thereby, the fixing belt can be efficiently heated or cooled.

  In the fixing device, a surface of the first thermoelectric conversion element facing the inner peripheral surface of the fixing belt is smoothly connected to the facing surface. Thereby, it is possible to suppress a change in the nip pressure at the boundary between the nip forming surface and the nip surface.

  The fixing device further includes a sliding member. The sliding member is disposed between the inner peripheral surface of the fixing belt and the first thermoelectric conversion element. Accordingly, it is possible to reduce the influence of a slight step formed at the boundary between the nip forming surface and the nip surface while suppressing wear due to sliding between the opposing surface and the inner peripheral surface of the fixing belt.

  The fixing device further includes a power storage unit. The power storage unit stores electricity using an electromotive force generated by the temperature difference of the first thermoelectric conversion element. Thereby, energy saving performance can be improved.

  In the fixing device, the first thermoelectric conversion element is energized using electricity stored in the power storage unit. Thereby, energy saving performance can be improved.

  The fixing device further includes a second thermoelectric conversion element. The second thermoelectric conversion element is provided on the facing surface. The second thermoelectric conversion element is provided in the fixing nip portion. The second thermoelectric conversion element is disposed to face the constantly passing region. When the temperature Tc [° C.] of the constantly passing region is equal to or lower than the fixing target temperature, the second thermoelectric conversion element is energized so as to exert a heating action. Thereby, the warm-up time can be shortened.

  An image forming apparatus according to the present disclosure includes the fixing device according to any one of the above aspects and a storage unit that stores a recording medium. Accordingly, it is possible to realize an image forming apparatus capable of suppressing a decrease in fixing quality due to temperature unevenness in the end region while suppressing a local temperature increase of the fixing belt.

  According to the present disclosure, it is possible to realize a fixing device and an image forming apparatus that suppress a local temperature increase of the fixing belt.

1 is a schematic diagram of an image forming apparatus according to Embodiment 1. FIG. 1 is a schematic cross-sectional view of a fixing device according to a first embodiment. FIG. 3 is a diagram illustrating an outline of a configuration of a fixing device when viewed from a direction III in FIG. 2. 2 is a schematic perspective view of a base pad according to Embodiment 1. FIG. It is a schematic front view of the base pad when it sees from the V direction in FIG. 2 is a schematic perspective view of a first thermoelectric conversion element according to Embodiment 1. FIG. 6 is a schematic plan view of a base pad according to a second embodiment. FIG. FIG. 6 is a schematic cross-sectional view of a fixing device according to a third embodiment.

  Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

[Embodiment 1]
<Image forming apparatus 100>
FIG. 1 is a schematic diagram of an image forming apparatus 100 according to the first embodiment. The image forming apparatus 100 according to Embodiment 1 is referred to as a tandem color image forming apparatus. The image forming apparatus 100 includes an intermediate transfer belt 3, image forming units 4 Y, M, C, and K, a secondary transfer unit 24, and a fixing device 1 as belt members.

  The intermediate transfer belt 3 rotates counterclockwise (A direction in FIG. 1). Below the intermediate transfer belt 3, four image forming portions 4Y, 4M, 4C, and 4K corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) are intermediate transferred. They are arranged side by side along the belt 3.

  In the following, the configuration relating mainly to yellow (Y) among yellow (Y), magenta (M), cyan (C), and black (K) will be described, but magenta (M), cyan (C), black (K) ) Is the same as that of yellow (Y).

  The image forming unit 4Y includes a photosensitive drum 5Y, a charger 6Y, a print head unit 7Y, a developing unit 8Y, and a primary transfer roller 9Y. The photosensitive drum 5Y rotates clockwise. Around the photosensitive drum 5Y, a charger 6Y, a print head unit 7Y, a developing device 8Y, and a primary transfer roller 9Y are arranged in this order along the rotation direction of the photosensitive drum 5Y. . The primary transfer roller 9Y faces the photosensitive drum 5Y with the intermediate transfer belt 3 interposed therebetween.

  A schematic operation of the image forming apparatus 100 will be described. The image forming apparatus 100 further includes a control unit 70. The control unit 70 includes an image signal processing unit (not shown). When an image signal is input from an external device (for example, a personal computer), the image signal processing unit creates a digital image signal obtained by color-converting the image signal into yellow, cyan, magenta, and black. Based on the digital image signal, the control unit 70 causes the print head unit 7Y to emit light and exposes the photosensitive drum 5Y. Thereby, an electrostatic latent image is formed on the photosensitive drum 5Y. The electrostatic latent image is developed by the developing device 8Y to become a toner image.

  The respective color toner images developed by the developing devices 8Y, 8M, 8C, 8K are sequentially superimposed on the intermediate transfer belt 3 that moves in the direction of arrow A by the action of the primary transfer rollers 9Y, 9M, 9C, and 9K. In addition, primary transfer is performed. The toner images of the respective colors primarily transferred to the intermediate transfer belt 3 are transported to the secondary transfer unit 24 along the transport path 23.

  The image forming apparatus 100 further includes a detachable container 2, a paper feed roller 2a, and a registration roller 2b. The storage unit 2 stores a recording medium. In the embodiment, the recording medium is plain paper P. The plain paper P stacked and accommodated in the storage unit 2 is conveyed one by one toward the registration roller 2b by the rotation of the paper supply roller 2a, and from the registration roller 2b along the conveyance path 23, the secondary transfer unit 24. To be transported.

  In the secondary transfer unit 24, the color toner images that are primarily transferred and superimposed on the intermediate transfer belt 3 are transferred to the plain paper P conveyed from the storage unit 2 (secondary transfer). The plain paper P on which each color toner image is secondarily transferred is conveyed to the fixing device 1.

  The image forming apparatus 100 further includes a cleaning unit 27. The cleaning unit 27 removes the toner remaining on the intermediate transfer belt 3 after the respective color toner images are transferred to the plain paper P in the secondary transfer unit 24.

  The fixing device 1 is disposed on the downstream side of the conveyance path 23 with respect to the secondary transfer unit 24. The fixing device 1 heats and pressurizes the toner image secondarily transferred onto the plain paper P to fix it on the plain paper P. The plain paper P on which the toner image is fixed is discharged to the paper discharge tray 26 via the paper discharge roller 25.

(Fixing device 1)
FIG. 2 is a schematic cross-sectional view of the fixing device 1 according to the first embodiment. FIG. 3 is a diagram showing an outline of the configuration of the fixing device 1 when viewed from the III direction in FIG. The fixing device 1 will be described with reference to FIGS. 2 and 3.

  The fixing device 1 includes an endless fixing belt 10, a base pad 20, a fixing member 35, a pressure rotating body, and a heating unit 32. A base pad 20, a fixing member 35, and a heating unit 32 are disposed on the inner peripheral side of the fixing belt 10.

  The heating unit 32 includes a heating roller 33 and a halogen lamp 51 as a heating source. A halogen lamp 51 is provided on the inner peripheral side of the heating roller 33. The halogen lamp 51 heats the fixing belt 10 via the heating roller 33.

  During the fixing operation, the control unit 70 automatically controls the surface temperature of the fixing belt 10 to be the fixing target temperature by heating the fixing belt 10 with the halogen lamp 51. In a state where the temperature of the fixing belt 10 reaches the fixing target temperature, the plain paper P carrying an unfixed toner image is introduced into the fixing nip portion N.

  In the embodiment, the pressure rotating body is a pressure roller 30. The pressure roller 30 is disposed to face the base pad 20 through the fixing belt 10. The pressure roller 30 forms the base pad 20 and the fixing nip portion N. The pressure roller 30 is pressed against the base pad 20 with a predetermined pressure by a pressure mechanism (not shown) using a spring or the like. The pressure roller 30 is driven to rotate by a driving device such as a motor (not shown). The pressure roller 30 has a rotating shaft 30a and an outer peripheral portion 30b that covers the rotating shaft 30a. At least a part of the outer peripheral portion 30b is made of an elastic body. As the rotary shaft 30a rotates about the rotation center C, the entire pressure roller 30 rotates.

  A double-headed arrow shown in FIG. 3 indicates the width direction DR1. The width direction DR1 is a direction orthogonal to the conveyance direction of the plain paper P (the direction of arrow A in FIG. 2), and is the width direction of the fixing belt 10. The width direction DR1 is the left-right direction in FIG. The width direction DR1 direction is substantially parallel to the axial direction of the pressure roller 30.

  The fixing belt 10 is stretched by the heating roller 33 and the base pad 20. The fixing belt 10 is driven to rotate with the rotation of the pressure roller 30 due to the pressure frictional force with the pressure roller 30 at the fixing nip portion N.

  The fixing belt 10 is defined with a constantly passing region 12 and an end region 11 in the width direction DR1. The constantly passing area 12 is an area through which the recording medium always passes when the toner image on the recording medium is fixed. The length of the constantly passing region 12 in the width direction DR1 is the width direction DR1 of the recording medium (minimum recording medium S) having the minimum length in the width direction DR1 among the recording media on which the toner image is fixed by the fixing device 1. Is the same as the length in. The end regions 11 are provided at both ends of the constantly passing region 12 in the width direction DR1. The end region 11 is a region through which the minimum recording medium S does not pass.

  As shown in FIG. 2, the fixing device 1 further includes a temperature detection unit 75. The temperature detection unit 75 is disposed to face the outer peripheral surface of the fixing belt 10. The temperature detector 75 detects the temperature of the fixing belt 10 heated by the halogen lamp 51 and the heating roller 33. The temperature detector 75 detects the temperatures of the constantly passing area 12 and the end area 11. The temperature control of the fixing belt 10 is performed by the control unit 70.

(Base pad 20)
FIG. 4 is a schematic perspective view of the base pad 20 according to the first embodiment. The base pad 20 will be described with reference to FIGS. 2 and 4. The base pad 20 has a shape extending in the width direction DR1. The base pad 20 has a facing surface 21 and a fixed surface 22 provided on the opposite side of the facing surface 21. The fixing surface 22 is in contact with the fixing member 35. A fixing member 35 is disposed on the fixing surface 22 side of the base pad 20, and the base pad 20 is fixed by the fixing member 35. The fixing member 35 serves as a heat sink.

  The facing surface 21 faces the inner peripheral surface of the fixing belt 10. In the first embodiment, the facing surface 21 is in contact with the inner peripheral surface of the fixing belt 10. In the first embodiment, the facing surface 21 slides with the fixing belt 10.

  The facing surface 21 has a nip forming surface 21c. The nip forming surface 21 c is a portion of the facing surface 21 where the fixing nip portion N is formed. The nip forming surface 21c has a first region 21a and a second region 21b continuous with the first region 21a. The first region 21a extends in the width direction DR1. The first region 21a has a substantially smooth shape. The first region 21a has a shape extending substantially straight in a cross section perpendicular to the width direction DR1 (cross section in FIG. 2; hereinafter, cross section Z).

  The second region 21b extends in the width direction DR1. The second area 21b is provided downstream of the first area 21a in the conveyance direction of the plain paper P (the direction of arrow A in FIG. 2). In the cross section Z, the second region 21b approaches the rotation center C of the pressure roller 30 as it goes downstream from the first region 21a in the transport direction of the plain paper P (bites into the outer peripheral portion 30b of the pressure roller 30). It has a shape that extends like this. The second region 21 b has a shape that protrudes toward the pressure roller 30. The second region 21b has a concave shape. The second region 21 b has a shape that is recessed toward the fixed surface 22. The second region 21 b is curved so as to bite into the outer peripheral portion 30 b of the pressure roller 30. The maximum elastic deformation amount of the outer peripheral portion 30b in the second region 21b is larger than the maximum elastic deformation amount of the outer peripheral portion 30b in the first region 21a. The nip pressure in the second region 21b is larger than the nip pressure in the first region 21a.

(First thermoelectric conversion element)
FIG. 5 is a schematic front view of the base pad 20 when viewed from the V direction in FIG. 4. FIG. 6 is a schematic perspective view of the first thermoelectric conversion element of the first embodiment. The first thermoelectric conversion element will be described with reference to FIGS.

  The fixing device 1 further includes a first thermoelectric conversion element. In the embodiment, the first thermoelectric conversion element is a Peltier element 40. A plurality of Peltier elements 40a, 40b, 40c, 40d, 40e, and 40f are arranged side by side in the width direction DR1. Hereinafter, when the Peltier elements 40a, 40b, 40c, 40d, 40e, and 40f are not particularly distinguished from each other, they will be referred to as Peltier elements 40.

  The Peltier element 40 has a substantially rectangular parallelepiped shape. The Peltier element 40 is a semiconductor element that can freely control the temperature of cooling and heating with a direct current. When the Peltier element 40 is energized by the controller 70, one surface becomes a cooling surface and the other surface becomes a heating surface, and when the energizing direction is reversed, the cooling surface and the heating surface are reversed (Peltier effect). . The amount of heat generated by the Peltier device 40 can be changed in accordance with the amount of energization.

  The Peltier element 40 is provided in the fixing nip portion N. The Peltier element 40 is provided on the facing surface 21 (nip forming surface 21c). The Peltier element 40 is provided in the first region 21a. The Peltier element 40 is disposed to face each end region 11. In the first embodiment, the Peltier element 40 is not disposed so as to face the constantly passing region 12 but is disposed so as to face only the end region 11.

  The Peltier elements 40a, 40b, and 40c are arranged to face one end region 11. The Peltier elements 40d, 40e, and 40f are arranged to face the other end region 11.

  The Peltier element 40 has a nip surface 40x and a back surface 40y opposite to the nip surface 40x. The nip surface 40 x is a surface facing the inner peripheral surface of the fixing belt 10. When the Peltier element 40 is energized, for example, the nip surface 40x becomes a cooling surface and the back surface 40y becomes a heating surface. The nip surface 40x is smoothly connected to the facing surface 21 (nip forming surface 21c). The thermal conductivity of the Peltier element 40 is larger than the thermal conductivity of the base pad 20 (opposing surface 21).

  The arrangement of the Peltier elements 40a, 40b, 40c, 40d, 40e, and 40f is determined based on various sizes of the recording medium. An area between the Peltier element 40c and the Peltier element 40d (area E in FIGS. 4 and 5) is, for example, an area corresponding to (opposed to) an area through which A6 size plain paper is passed through the fixing belt 10. . When the A6 size plain paper is the minimum recording medium S, the area E is an area corresponding to (opposing to) the constantly passing area 12 (see FIG. 3). The Peltier element 40c and the Peltier element 40d are provided at both ends of the region E in the width direction DR1. The Peltier element 40c and the Peltier element 40d are disposed so as to face a region of the fixing belt 10 where A6 size plain paper (minimum recording medium S) does not pass. At both ends of the region E in the width direction DR1, regions (regions H in FIGS. 3, 4 and 5) corresponding to (facing) the end region 11 are provided.

  An area between the Peltier element 40b and the Peltier element 40e (area F in FIG. 5) is, for example, an area corresponding to (opposed to) an area through which A5 size plain paper is passed through the fixing belt 10. The Peltier element 40b and the Peltier element 40e are provided at both ends of the region F in the width direction DR1. The Peltier element 40b and the Peltier element 40e are disposed so as to face a region of the fixing belt 10 through which A5 size plain paper does not pass.

  An area between the Peltier element 40a and the Peltier element 40f (area G in FIG. 5) is an area corresponding to (opposed to) an area through which, for example, A4-size plain paper in the fixing belt 10 is passed. The Peltier element 40a and the Peltier element 40f are provided at both ends of the region G in the width direction DR1. The Peltier element 40a and the Peltier element 40f are disposed so as to face a region of the fixing belt 10 through which A4 size plain paper does not pass.

  The fixing device 1 further includes a power supply unit 60 and a power storage unit 90. The power supply unit 60 supplies power to the control unit 70. The controller 70 controls the energization direction and the energization amount to the Peltier elements 40a, 40b, 40c, 40d, 40e, and 40f.

  When a temperature difference occurs between the nip surface 40x and the back surface 40y of the Peltier element 40, an electromotive force proportional to the magnitude of the temperature difference is generated in the Peltier element 40 due to the Seebeck effect. When heating and cooling using the Peltier effect are not necessary (for example, at the end of the fixing operation), the power storage unit 90 can store power using the electromotive force obtained by the Seebeck effect. The power stored in the power storage unit 90 can be used when utilizing the Peltier effect.

(Temperature control of fixing belt 10)
The temperature detector 75 detects the temperature Tc [° C.] of the constantly passing region 12 in the fixing belt 10 and the temperature Te [° C.] of the end region 11 of the fixing belt 10. In accordance with Tc and Te detected by the temperature detection unit 75, the control unit 70 controls the energization direction and the energization amount to the Peltier element 40.

  When Tc is smaller than Te (Tc−Te <0), the control unit 70 controls to energize the nip surface 40x in the cooling direction. Thereby, the edge part area | region 11 is cooled. When Tc is larger than Te (Tc−Te> 0), the control unit 70 controls to energize the nip surface 40x in the heating direction. Thereby, the edge part area | region 11 is heated.

  By setting the energization amount to the Peltier element 40 based on the temperature difference (ΔT = | Tc−Te |) of the detected temperature, the control unit 70 can control the heat generation amount or the heat absorption amount of the Peltier element 40. . The greater the amount of current supplied to the Peltier element 40, the greater the amount of heat generated or absorbed by the Peltier element 40.

  The Peltier element 40 to be energized is set based on the size of the recording medium to be passed. For example, when an A4 size plain paper P is passed, an area facing the area where the A4 size plain paper P does not pass through the fixing belt 10 (the outer side in the width direction DR1 than the Peltier element 40b and the Peltier element 40e). The Peltier element 40a and the Peltier element 40f arranged in the region are controlled to be energized only. When A6 size plain paper is passed, Peltier elements 40a, 40b, 40c, 40d, which are arranged in a region facing the region (edge region 11) where the A6 size plain paper P does not pass through the fixing belt 10; 40e and 40f are controlled to be energized.

(Function and effect)
When a relatively small recording medium is continuously printed, the fixing belt in the constantly passing area is deprived of heat by the recording medium. Therefore, the fixing belt is heated by the heating unit so as to maintain the temperature of the constantly passing region. However, since the fixing belt in the end region is not easily deprived of heat by the recording medium, the temperature in the end region increases and the fixing belt may be damaged.

  As shown in FIGS. 3 and 4, the Peltier element 40 is disposed so as to face the two end regions 11, and the Peltier element 40 is energized so that the nip surface 40 x exhibits a cooling action. Thereby, the temperature rise of the edge part area | region 11 can be suppressed. Thereby, the local temperature rise of the fixing belt 10 can be suppressed. Therefore, damage to the fixing belt 10 can be suppressed.

  Further, by providing the Peltier element 40 on the nip forming surface 21c, a local temperature rise of the fixing belt 10 can be suppressed without providing a cooling roller, a cooling fan, or the like. Thereby, the fixing device 1 can be configured compactly.

  Furthermore, by arranging the Peltier element 40 at a position close to the fixing belt 10 (nip forming surface 21c), good adhesion to the fixing belt 10 can be secured. Thereby, the fixing belt 10 can be efficiently heated or cooled.

  When a relatively small recording medium is continuously printed after a relatively small recording medium is printed, temperature unevenness may occur in the width direction of the fixing belt due to the temperature increase of the fixing belt in the end region. . Due to the temperature unevenness, fixing quality may be deteriorated due to occurrence of fixing failure, bending of the recording medium to be printed, wrinkling of the recording medium, or the like.

  As described above, the Peltier element 40 is disposed so as to face the two end regions 11, and the Peltier element 40 is energized so that the nip surface 40x exhibits a cooling action. In addition to suppressing the local temperature increase of 10, it is possible to suppress deterioration in fixing quality due to temperature unevenness in the end region 11.

  As shown in FIGS. 2 and 4, the nip forming surface 21c has a first region 21a having a low nip pressure and a second region 21b having a high nip pressure. In the first area 21a, the toner image on the recording medium is heated to melt the toner. In the second area 21b, the melted toner is pushed into the recording medium to fix the toner. In the second area 21b, the toner is fixed. Improves sex. As described above, by separating the functions on the nip forming surface 21c (mainly toner melting in the first area 21a and mainly toner fixing in the second area 21b), good fixability can be secured.

  The Peltier element 40 is provided in the first region 21a having a small nip pressure. Thereby, deformation and breakage of the Peltier element 40 due to the nip pressure can be suppressed.

  The Peltier element 40 has a thermal conductivity larger than that of the base pad 20 (opposing surface 21). As a result, the fixing belt 10 is likely to be deprived of heat at a portion facing the Peltier element 40, and thus temperature unevenness may occur in the fixing belt 10 in the width direction DR1.

  Therefore, the control unit 70 controls the energization direction and the energization amount to the Peltier element 40 based on the thermal conductivity of the facing surface 21 and the Peltier element 40. Thereby, temperature unevenness of the fixing belt 10 can be suppressed, and fixing quality can be ensured.

  A plurality of Peltier elements 40 (Peltier elements 40a, 40b, 40c, 40d, 40e, 40f) are arranged side by side in the width direction DR1. Thereby, the fixing belt 10 can be efficiently heated or cooled.

  The positions of the plurality of Peltier elements 40 are determined based on various sizes of the recording medium. By disposing the Peltier element 40 at a position corresponding to various recording media, it is possible to reliably cool an area through which the recording medium does not pass. As a result, it is possible to efficiently cool the region where the temperature rises without the heat being taken away by the recording medium.

  When the temperature of the constantly passing region 12 is Tc [° C.] and the temperature of the end region 11 is Te [° C.], the control unit 70 moves to the Peltier element 40 according to Tc and Te detected by the temperature detecting unit 75. The energizing direction and energizing amount are controlled. Thereby, the fixing belt 10 can be efficiently cooled.

  When Tc is smaller than Te, the Peltier element 40 is energized so as to exert a cooling action. Thereby, the temperature rise of the edge part area | region 11 can be suppressed. Therefore, damage to the fixing belt 10 can be suppressed.

  When Tc is larger than Te, the Peltier element 40 is energized so as to exert a heating action. Thereby, temperature unevenness of the fixing belt 10 can be suppressed. Accordingly, it is possible to suppress a decrease in fixing quality.

  The energization amount to the Peltier element 40 is controlled according to the difference between Tc and Te (ΔT = | Tc−Te |). The control unit 70 controls to increase the energization amount when ΔT is large and to decrease the energization amount when ΔT is small. Thereby, the fixing belt 10 can be efficiently heated or cooled.

  The nip surface 40x of the Peltier element 40 is disposed on substantially the same plane as the nip forming surface 21c. The nip surface 40x and the nip forming surface 21c are connected smoothly. Thereby, it is possible to suppress a change in the nip pressure at the boundary between the nip forming surface 21c and the nip surface 40x. Accordingly, it is possible to suppress image defects.

  As shown in FIG. 5, the power storage unit 90 stores electricity using an electromotive force generated by the temperature difference of the Peltier element 40. Thereby, energy saving performance can be improved.

  The Peltier element 40 is energized using the electricity stored in the power storage unit 90. The fixing belt 10 is heated or cooled by reusing the stored electric power. Thereby, energy saving performance can be improved.

[Embodiment 2]
FIG. 7 is a schematic plan view of the base pad 20 of the second embodiment. The fixing device 1 further includes a second thermoelectric conversion element. The second thermoelectric conversion element of the second embodiment is a Peltier element 50. The configuration of the Peltier element 50 alone is the same as that of the Peltier element 40 of the first embodiment.

  Unlike the first embodiment, in the fixing device 1 according to the second embodiment, in addition to the Peltier element 40 disposed to face the end region 11, the second device is always disposed to face the passing region 12. A thermoelectric conversion element (Peltier element 50) is provided. A region E in FIG. 7 is a region corresponding to (opposing to) the always-passing region 12 as in the fixing device 1 of the first embodiment. The Peltier element 50 is provided on the facing surface 21. The Peltier element 50 is provided in the fixing nip portion N. The Peltier element 50 is provided on the nip forming surface 21c.

  When the temperature Tc [° C.] of the fixing belt 10 in the constantly passing region 12 is equal to or lower than the fixing target temperature, the Peltier element 50 is energized so that the Peltier element 50 exhibits a heating action. Thereby, the warm-up time can be shortened.

[Embodiment 3]
FIG. 8 is a schematic cross-sectional view of the fixing device 1 according to the third embodiment. Unlike the first embodiment, the fixing device 1 according to the third embodiment has a uniaxial belt configuration in which the fixing belt 10 is not stretched. The fixing device 1 according to the third embodiment further includes a sheet-like sliding member 80. The sliding member 80 is disposed between the facing surface 21 and the inner peripheral surface of the fixing belt 10. The sliding member 80 is disposed between the Peltier element 40 and the inner peripheral surface of the fixing belt 10. The sliding member 80 is in contact with the opposing surface 21 and the inner peripheral surface of the fixing belt 10.

  By providing the sliding member 80, it is possible to suppress wear due to rubbing between the facing surface 21 and the inner peripheral surface of the fixing belt 10. Furthermore, the influence of a slight step formed at the boundary between the nip forming surface 21c of the opposing surface 21 and the nip surface 40x of the Peltier element 40 can be reduced. Thereby, it is possible to suppress a decrease in fixing quality.

(Other)
In the embodiment, the image forming apparatus 100 that forms a color image has been described. However, the image forming apparatus 100 may form a monochrome image.

  In the embodiment, the fixing device 1 includes the power storage unit 90 and the power supply unit 60. However, the image forming apparatus 100 may include the power storage unit 90 and the power supply unit 60.

  In the embodiment, the second region 21b has a curved shape, but may have a shape that extends straight.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Fixing device, 2 Accommodating part, 2a Paper feed roller, 2b Registration roller, 3 Intermediate transfer belt, 4Y, C, K, M Image forming part, 5Y Photosensitive drum, 6Y Charger, 7Y Print head part, 8Y, C , K, M Developer, 9Y, C, K, M Secondary transfer roller, 10 fixing belt, 11 end area, 12 constantly passing area, 20 base pad, 21 facing surface, 21a first area, 21b second area, 21c Nip forming surface, 22 fixed surface, 23 transport path, 24th transfer unit, 25 paper discharge roller, 26 paper discharge tray, 27 cleaning unit, 30 pressure roller, 30a rotating shaft, 30b outer periphery, 32 heating unit, 33 Heating roller, 35 fixing member, 40, 40a, 40b, 40c, 40d, 40e, 40f, 50 Peltier element, 40x nip surface, 40 Backside, 51 halogen lamp, 60 power supply unit, 70 control unit, 75 temperature detection unit, 80 sliding member, 90 storage unit, 100 image forming apparatus, DR1 width direction, P plain paper, S minimum recording medium.

Claims (15)

A fixing device for fixing a toner image on a recording medium,
An endless fixing belt,
A base pad including a facing surface facing the inner peripheral surface of the fixing belt and extending in a width direction of the fixing belt;
A pressure rotator which is disposed to face the base pad via the fixing belt and forms a fixing nip portion with the base pad;
A heating unit for heating the fixing belt;
A first thermoelectric conversion element provided on the facing surface,
In the width direction, the fixing belt always passes through the recording medium when the toner image on the recording medium is fixed, and end areas provided at both ends of the constant-pass area in the width direction. And is prescribed,
The first thermoelectric conversion element is provided in the fixing nip portion,
The first thermoelectric conversion element is a fixing device arranged to face each of the end regions. The opposed surface has a first region extending in the width direction, and a second region provided downstream of the first region in the conveyance direction of the recording medium,
In the cross section orthogonal to the width direction, the second region has a shape extending so as to approach the rotation center of the pressurizing rotating body from the first region toward the downstream side in the transport direction,
The fixing device according to claim 1, wherein the first thermoelectric conversion element is provided in the first region.   3. The fixing device according to claim 1, wherein an energization direction and an energization amount to the first thermoelectric conversion element are controlled based on thermal conductivity of the opposing surface and the first thermoelectric conversion element.   4. The device according to claim 1, wherein a plurality of the first thermoelectric conversion elements are arranged side by side in the width direction in each of the portions facing the end region of the facing surface. The fixing device according to 1.   The fixing device according to claim 4, wherein an arrangement of the plurality of first thermoelectric conversion elements is determined based on various sizes of the recording medium. A temperature detection unit for detecting the temperature of each of the constantly passing region and the end region;
When the temperature of the constantly passing region is Tc [° C.] and the temperature of the end region is Te [° C.], depending on the Tc and Te detected by the temperature detecting unit, the first thermoelectric conversion element The fixing device according to any one of claims 1 to 5, wherein an energization direction and an energization amount are controlled.   The fixing device according to claim 6, wherein when the Tc is smaller than the Te, the first thermoelectric conversion element is energized so as to exhibit a cooling action.   The fixing device according to claim 6, wherein when the Tc is larger than the Te, the first thermoelectric conversion element is energized so as to exert a heating action.   The fixing device according to any one of claims 6 to 8, wherein an energization amount to the first thermoelectric conversion element is controlled in accordance with a difference between the Tc and the Te.   10. The fixing according to claim 1, wherein a surface of the first thermoelectric conversion element facing the inner peripheral surface of the fixing belt is smoothly connected to the facing surface. apparatus.   The fixing device according to any one of claims 1 to 10, wherein a sheet-like sliding member is disposed between an inner peripheral surface of the fixing belt and the first thermoelectric conversion element.   The fixing device according to claim 1, further comprising a power storage unit that stores electricity using an electromotive force generated by a temperature difference of the first thermoelectric conversion element.   The fixing device according to claim 12, wherein the first thermoelectric conversion element is energized using electricity stored in the power storage unit. A second thermoelectric conversion element provided on the facing surface;
The second thermoelectric conversion element is provided in the fixing nip portion,
The second thermoelectric conversion element is disposed to face the constantly passing region,
14. The device according to claim 1, wherein when the temperature Tc [° C.] of the constantly passing region is equal to or lower than a fixing target temperature, the second thermoelectric conversion element is energized so as to exert a heating action. The fixing device described. A fixing device according to any one of claims 1 to 14,
An image forming apparatus comprising: a storage unit that stores the recording medium.