JP2020038302A - Fixing device and image forming apparatus - Google Patents

Abstract

To obtain a fixing device that, when fixing an image to a minimum-size recording medium, can prevent a holding part from melting and being deformed, compared with a case where the holding part is in contact with the entire rear face of a heating plate, and an image forming apparatus.SOLUTION: A resin holding member 90 in contact with a rear face of a heating plate 64 to hold the heating plate 64 is formed with air gaps 96 connecting the rear face of the heating plate 64 with a space 110 opened to the outside, outside a range through which a minimum-size recording medium to be conveyed passes in an axial direction.SELECTED DRAWING: Figure 1

Description

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

  The heating device described in Patent Literature 1 has a flat heating element, a heater holder that supports the heating element on the outer surface, and a pressurization that presses a heat-resistant film against the heating element and conveys a material to be heated introduced into the press-contact portion. And a rotating body. In the portion where the heating element and the heater holder are in contact with each other and receive a force, in the non-sheet passing area in the minimum size of the heatable material that can be passed, and in the range in which the energized heating resistor exists, between the heating element and the heater holder Has a curable resin interposed.

JP 2001-23756 A

  2. Description of the Related Art A fixing device includes a rotating endless belt, and a heat generating plate having a plate-like shape formed with a heat generating portion extending in the axial direction of the endless belt and in contact with the inner peripheral surface of the endless belt at the surface. Furthermore, the fixing device forms a fixing nip between the endless belt and a pressing member that presses the recording medium against the outer peripheral surface of the endless belt, and a resin that contacts the entire back surface of the heat generating plate and holds the heat generating plate. And a holding portion made of a metal.

  In such a fixing device, when an image is fixed on a recording medium having a minimum size, the heat of the heat generating plate generated in a portion not facing the recording medium is not transmitted to the recording medium, and all the heat is applied to the resin. Is transmitted to the holding part. Then, the portion of the holding portion to which the heat has been transmitted may be melted and deformed by the heat.

  An object of the present invention is to suppress melting and deformation of a holding unit when fixing an image on a recording medium having a minimum size, as compared with a case where the holding unit is in contact with the entire back surface of a heating plate. It is.

  The fixing device according to the first aspect of the present invention includes an endless belt that rotates in a circumferential direction, a heating plate that extends in an axial direction of the endless belt, and generates heat by contacting the inner peripheral surface of the endless belt with a surface thereof. A pressurizing unit disposed on the opposite side of the heat generating plate with the endless belt interposed therebetween, for pressing a recording medium to be conveyed against the outer peripheral surface of the endless belt, and contacting the back surface of the heat generating plate with the heat generating plate. A holding portion made of resin to be held, wherein a gap is formed outside the range in which the minimum-sized recording medium to be conveyed passes in the axial direction, connecting the back surface of the heat generating plate and the space opened to the outside. And the above-mentioned holding portion.

  In the fixing device according to a second aspect of the present invention, in the fixing device according to the first aspect, in a cross section that intersects the axial direction, the gap faces the entire back surface of the heating plate. Features.

  In a fixing device according to a third aspect of the present invention, in the fixing device according to the second aspect, in the cross section, the gap faces a side surface of the heating plate.

  A fixing device according to a fourth aspect of the present invention is the fixing device according to any one of the first to third aspects, wherein at least one of the spaces is open to the outside in the axial direction. I do.

  The fixing device according to a fifth aspect of the present invention is the fixing device according to the fourth aspect, wherein the pressing unit rotates, and a driving unit that generates a rotational force that rotates the pressing unit is provided in the axial direction. , And is arranged at one of the pressurizing portions, and in the axial direction, the space is open at least on the other side opposite to the side on which the driving portion is disposed.

  A fixing device according to a sixth aspect of the present invention is the fixing device according to the fourth aspect, wherein both of the space are open to the outside in the axial direction.

  An image forming apparatus according to a seventh aspect of the present invention, wherein the image forming apparatus forms an image on a recording medium of a plurality of sizes including a minimum size, and the image formed on the recording medium is fixed on the recording medium. And a fixing device according to any one of claims 1 to 3.

  According to the fixing device of the first aspect of the present invention, when the image is fixed on the recording medium having the minimum size, the holding portion is melted compared with the case where the holding portion is in contact with the entire back surface of the heating plate. Deformation can be suppressed.

  According to the fixing device of the second aspect of the present invention, in the cross section that intersects the axial direction, the holding portion is melted and deformed as compared with the case where the gap faces only a part of the back surface of the heat generating plate. Can be suppressed.

  According to the fixing device of the third aspect of the present invention, it is possible to suppress the holding portion from being melted and deformed as compared with the case where the side surface of the heat generating plate is in contact with the holding portion.

  According to the fixing device of the fourth aspect of the present invention, it is possible to suppress the holding portion from being melted and deformed as compared with a case where both of the spaces are closed in the axial direction.

  According to the fixing device of the fifth aspect of the present invention, it is possible to suppress the holding unit from being melted and deformed as compared with the case where only the driving unit side of the space is opened.

  According to the fixing device of the sixth aspect of the present invention, it is possible to suppress the holding portion from being melted and deformed as compared with the case where only one of the spaces is opened to the outside in the axial direction.

  According to the image forming apparatus of the seventh aspect of the present invention, the quality of the output image of the recording medium having the largest size is deteriorated as compared with the case where the fixing device according to any one of the first to sixth aspects is not provided. Can be suppressed.

FIG. 3 is a cross-sectional view illustrating a portion where a gap is formed in the fixing device according to the exemplary embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a portion where a detection member (temperature sensor) is arranged in the fixing device according to the embodiment of the present disclosure. FIG. 1 is a cross-sectional view illustrating a fixing device according to an embodiment of the present disclosure. FIG. 3 is a plan view illustrating a heat generating plate provided in the fixing device according to the embodiment of the present disclosure. FIG. 3 is a perspective view illustrating a holding member and the like provided in the fixing device according to the embodiment of the present disclosure. FIG. 1 is a front view illustrating a fixing device according to an embodiment of the present disclosure. FIG. 3 is a block diagram illustrating a control system of a control unit provided in the fixing device according to the embodiment of the present disclosure. FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present disclosure.

  An example of a fixing device and an image forming apparatus according to an embodiment of the present invention will be described with reference to FIGS. In addition, the arrow H shown in the figure indicates the apparatus vertical direction (vertical direction), the arrow W indicates the apparatus width direction (horizontal direction), and the arrow D indicates the apparatus depth direction (horizontal direction).

(overall structure)
As illustrated in FIG. 8, the image forming apparatus 10 according to the present exemplary embodiment includes a storage unit that stores a sheet member P as a recording medium from a lower side in a vertical direction (the direction of an arrow H) to an upper side. 14, a transport unit 16 that transports the sheet member P stored in the storage unit 14, and an image forming unit 20 that forms an image on the sheet member P transported from the storage unit 14 by the transport unit 16 in this order. Provided.

[Accommodation section 14]
The accommodating portion 14 is provided with an accommodating member 26 that can be pulled out from the apparatus main body 10A of the image forming apparatus 10 to the near side in the apparatus depth direction, and the sheet member P is stacked on the accommodating member 26. Further, the storage unit 14 is provided with a delivery roll 30 that sends out the sheet members P stacked on the storage member 26 to a transport path 28 that configures the transport unit 16.

[Transport section 16]
The transport unit 16 includes a plurality of transport rolls 32 that transport the sheet member P along a predetermined transport path 28.

[Image forming unit 20]
The image forming section 20 includes four image forming units 18Y, 18M, 18C, and 18K for yellow (Y), magenta (M), cyan (C), and black (K). In the following description, when it is not necessary to separately describe Y, M, C, and K, Y, M, C, and K may be omitted.

  The image forming unit 18 for each color includes an image holding member 36, a charging roll 38 for charging the surface of the image holding member 36, and an exposure device 42 for irradiating the charged image holding member 36 with exposure light. . Further, the image forming section 20 is provided with a developing device 40 that develops the electrostatic latent image formed by exposing the charged image holding member 36 by the exposure device 42 and visualizes the electrostatic latent image as a toner image.

  The image forming section 20 includes an endless transfer belt 22 that rotates in the direction of arrow A in the figure and a primary transfer roll 44 that transfers the toner images formed by the image forming units 18 of the respective colors to the transfer belt 22. Provided. The image forming section 20 further includes a secondary transfer roll 46 for transferring the toner image on the transfer belt 22 to the sheet member P, and a fixing device 50 for heating and pressing the sheet member P to fix the toner image on the sheet member P. And are provided. The details of the fixing device 50 will be described later. The image forming unit is an example of a forming unit.

(Operation of the image forming apparatus)
In the image forming apparatus 10, an image is formed as follows.
First, the charging rolls 38 of the respective colors to which the voltages are applied come into contact with the surfaces of the image holders 36 of the respective colors, and uniformly negatively charge the surface of the image holder 36 at a predetermined potential. Subsequently, based on the data input from the outside, the exposure device 42 irradiates the surface of the charged image carrier 36 of each color with exposure light to form an electrostatic latent image.

  Thus, an electrostatic latent image corresponding to the data is formed on the surface of the image holder 36 of each color. Further, the developing devices 40 of the respective colors develop the electrostatic latent images and visualize them as toner images. Further, the toner images formed on the surface of the image carrier 36 of each color are transferred to the transfer belt 22 by the primary transfer roll 44.

  Then, the sheet member P sent from the storage member 26 to the transport path 28 by the sending roll 30 is sent to a transfer position T where the transfer belt 22 and the secondary transfer roll 46 are in contact. At the transfer position T, the toner image on the surface of the transfer belt 22 is transferred to the sheet member P by transporting the sheet member P sandwiched between the transfer belt 22 and the secondary transfer roll 46.

  The toner image transferred to the sheet member P is fixed to the sheet member P by the fixing device 50. Then, the sheet member P on which the toner image is fixed is discharged to the outside of the apparatus main body 10A by the transport roll 32.

(Main configuration)
Next, the fixing device 50 will be described.
The fixing device 50 is detachable from the apparatus main body 10A, and as shown in FIG. 3, a pressure roll 52 and a motor 58 (see FIG. 6) for generating a rotational force transmitted to the pressure roll 52. And a heating unit 60 that faces the pressure roll 52 in the apparatus width direction. Further, the fixing device 50 includes a control unit 98 (see FIG. 7) for controlling each unit. The motor 58 is an example of a driving unit.

[Pressing roll 52]
As shown in FIG. 3, the pressure roll 52 covers a metal shaft 54 extending in the depth direction of the device, a cylindrical elastic layer 56 into which the shaft 54 is inserted, and an elastic layer 56. And a release layer (not shown). As shown in FIG. 6, the shaft portion 54 protrudes outward from both ends of the elastic layer 56, and a gear 54a is attached to a protruding portion on the back side (right side in the drawing) in the device depth direction. I have.

  The shaft portion 54 is formed of, for example, a metal material such as steel, stainless steel, or aluminum, the elastic layer 56 is formed of, for example, a rubber material, and the release layer is formed of, for example, ethylene fluoride. It is formed from a fluoroalkoxyethylene copolymer (PFA) or the like. The pressure roll 52 is an example of a pressure unit.

  The pressure roll 52 is grounded and urged toward the heating unit 60 by an urging member (not shown). Thus, the pressure roll 52 presses the sheet member P on which the toner image has been transferred onto an outer peripheral surface of an endless belt 62 described later.

[Motor 58]
As shown in FIG. 6, the motor 58 is disposed on the back side in the apparatus depth direction with respect to the pressure roll 52. The gear 58a attached to the motor 58 meshes with the gear 54a. In this configuration, the motor 58 rotates while generating heat. Then, the pressing roller 52 shown in FIG. 3 is rotated in the direction of the arrow R1 (clockwise) in FIG. In the present embodiment, the pressure roll 52 rotates so that the outer peripheral surface of the elastic layer 56 has a peripheral speed of 230 [mm / sec].

[Heating section 60]
As shown in FIG. 3, the heating unit 60 holds the cylindrical endless belt 62 extending in the apparatus depth direction, a heating plate 64 that generates heat to heat the endless belt 62, and a heating plate 64. Holding member 90. Further, the heating unit 60 includes a frame 80 that supports the holding member 90, a detection member 82 (see FIG. 2) that detects the temperature of the heat generating plate 64, and a thermostat 84 (see FIG. 1). The holding member 90 is an example of a holding unit.

-Endless belt 62-
The endless belt 62 is in contact with the pressure roll 52 on the outer peripheral surface as shown in FIG. In the present embodiment, for example, the endless belt 62 is formed of a polyimide resin having a surface coated with fluorine, and the thickness of the endless belt 62 is 100 [μm].

  At both ends in the longitudinal direction of the endless belt 62, cylindrical support members (not shown) for supporting the inner peripheral surface of the endless belt 62 are arranged. Further, a lubricating oil S (an example of a liquid, for example, silicone oil) is applied to an inner peripheral surface of the endless belt 62 in order to reduce frictional resistance with the heat generating plate 64.

  In this configuration, the endless belt 62 rotates (circulates) in the direction of the arrow R2 (counterclockwise) in the figure following the rotating pressure roll 52 while maintaining the circular shape.

-Heat plate 64-
As shown in FIG. 3, the heat generating plate 64 is disposed on the opposite side of the pressure roll 52 with the endless belt 62 interposed therebetween, and is in contact with the inner peripheral surface of the endless belt 62 at the surface. The heat generating plate 64 is a plate-shaped member whose surface faces in the width direction of the apparatus, and extends from one end side of the endless belt 62 in the apparatus depth direction to the other end side. When viewed from the plate thickness direction, the heat generating plate 64 has a rectangular shape extending in the device depth direction as shown in FIG.

  The heat generating plate 64 has an electrically insulating base material 66, an insulating film 68 formed of a heat-resistant resin material, and a heat transfer layer 70 (see FIG. 3) for transmitting heat in a depth direction of the device. . Further, the heating plate 64 has a pair of electrodes 72 for applying a voltage, and a conduction portion 74 through which a current flows when a voltage is applied to the electrodes 72. The conductive portion 74 is formed with two resistance heating portions 74a (hatched portions in the drawing) that generate heat when a current flows. Here, the insulating property means that the electric conductivity is 1 × 10 −10 [S / m] or less.

  The base material 66 is a molded body of an electrically insulating ceramic. Further, the pair of electrodes 72 and the conducting portion 74 are formed on the surface of the base material 66 (the surface on the inner peripheral surface side of the endless belt 62). Specifically, the pair of electrodes 72 is formed on a portion of the base material 66 on the near side in the device depth direction, and is arranged in a vertical direction. Further, the conduction portion 74 is formed in a U-shape extending in the device depth direction, and electrodes 72 are arranged at both ends of the conduction portion 74. In addition, the conductive portion 74 is covered with an insulating film 68.

  Further, a resistance heating portion 74a is formed in a linear portion of the conduction portion 74. The resistance heating portion 74a is formed so as to cover the range in which the largest conveyed sheet member P (P1 in the drawing) passes in the apparatus depth direction (the width direction of the sheet member P1).

  Further, as shown in FIG. 3, the heat transfer layer 70 is formed on the back surface of the base 66, and is formed of a material having a higher thermal conductivity than the base 66. The heat transfer layer 70 is formed of, for example, copper or aluminum.

  In this configuration, when a voltage is applied to the pair of electrodes 72, heat is generated in the resistance heating portion 74a, and the heating plate 64 generates heat. Further, the heat transfer layer 70 transmits the heat generated in the resistance heating portion 74a in the device depth direction, and suppresses the temperature unevenness of the heat generating plate 64 in the device depth direction.

-Holding member 90-
As shown in FIG. 3, the holding member 90 is disposed inside the endless belt 62 and on the opposite side of the pressure roll 52 with the heating plate 64 interposed therebetween. The holding member 90 is formed of, for example, a resin material such as LCP (liquid crystal polymer) and extends in the depth direction of the device. The cross section orthogonal to the longitudinal direction of the holding member 90 has a U-shape that is open on the side opposite to the pressure roll 52 side. Further, a space 110 in the U-shaped holding member 90 is open to the outside in the apparatus depth direction. Here, the space 110 is a space inside the endless belt 62, and being open to the outside means that the entire space 110 is closed at an end of the holding member 90 as shown in FIG. A member (lid member) is not provided, and the space 110 is continuously connected to an external space with respect to the fixing device 50 in the device depth direction. The outside of the fixing device 50 is a region that is not surrounded by the inner peripheral surface of the endless belt 62.

  Further, as shown in FIG. 3, the holding member 90 has a contact surface 92 that contacts the back surface of the heating plate 64 and a pair of contact surfaces 94 that contacts the side surface of the heating plate 64.

  Further, a through hole 95 that opens a part of the back surface of the heat generating plate 64 to the space 110 is formed in a portion of the holding member 90 on the center side in the device depth direction, as shown in FIG.

  Also, as shown in FIGS. 1 and 4, a holding member at a portion outside a range through which a sheet member P of the smallest size to be conveyed (P2 in the drawing) passes in the apparatus depth direction (the axial direction of the endless belt 62). The space 90 is formed with a space 96 that opens the back surface of the heat generating plate 64 to the space 110. Specifically, the gaps 96 are formed in the depth direction of the apparatus, on the rear side and the front side, respectively, in a range where the sheet member P2 of the minimum size to be conveyed passes. Each gap 96 is arranged at a position overlapping a part of the resistance heating portion 74a in the apparatus depth direction. Note that the image forming apparatus 10 employs a so-called center register (a recording sheet is urged from both sides in the width direction and the positions are aligned with respect to the center in the width direction).

  As shown in FIGS. 4 and 5, the gap 96 has a rectangular shape when viewed from the width direction of the device, and is formed by penetrating a portion of the holding member 90 that supports the heat generating plate 64 in the width direction of the device. ing. Then, in the holding member 90 where the gap 96 is formed, as shown in FIG. 1, the entire back surface of the heating plate 64 and a pair of side surfaces of the heating plate 64 are connected to the space 110 via the gap 96. ing. In other words, in the cross section that intersects the device depth direction, the gap 96 faces the entire back surface of the heating plate 64 and a pair of side surfaces of the heating plate 64.

  As described above, the gap 96 connects a part of the heat generating plate 64 to the space 110. That is, the gap 96 functions as an opening unit that opens a part of the heat generating plate 64 to the space 110.

  Further, the gap 96 is arranged at a position overlapping a part of the resistance heating portion 74a in the device depth direction. As described above, since the gap 96 overlaps a part of the resistance heating portion 74a, heat generated by the resistance heating portion 74a in a portion overlapping the gap 96 is released from the heating plate 64 to the space 110 through the gap 96. It is supposed to be. That is, the gap 96 functions as a release unit that releases heat to the space 110.

  Regarding the gap 96, from the viewpoint of releasing heat generated in a portion outside the range where the minimum size sheet member P2 passes to the space 110 when fixing the toner image on the minimum size sheet member P2, A wider one is preferred. On the other hand, when fixing the toner image on the sheet member P1 having the maximum size, the gap 96 is preferably narrow from the viewpoint of fixing the toner image on the sheet member P1 having the maximum size.

  For this reason, in the device depth direction, it is preferable that the gap 96 overlaps with 60% or more and 98% or less of the resistance heating portion 74a outside the range where the sheet member P2 of the minimum size passes. It is more preferable that they overlap 70% or more and 95% or less, and it is particularly preferable that they overlap 80% or more and 90% or less.

  In this configuration, when the heat generating plate 64 generates heat, heat in the portion of the heat generating plate 64 where the gap 96 is formed is released to the space 110 via the gap 96 without being transmitted to the holding member 90. Further, since the space 110 is open to the outside in the device depth direction, the air in the space 110 flows in the device depth direction.

-Frame 80-
As shown in FIG. 3, the frame 80 is disposed inside the endless belt 62 and on the opposite side of the heating plate 64 with the holding member 90 interposed therebetween. The frame 80 is formed by bending a sheet metal and extends in the apparatus depth direction. The cross section of the frame 80 perpendicular to the longitudinal direction has a U-shape with the holding member 90 side opened.

  Furthermore, the frame 80 supports the holding member 90 by attaching the front-side portion of the holding member 90 to an end portion of the U-shaped frame 80 with a mounting member such as an adhesive (not shown). are doing. The area surrounded by the frame 80 and the holding member 90 is the space 110 described above.

  Further, both ends in the longitudinal direction of the frame 80 protrude outside from the endless belt 62, and the protruding portions are fixed to a skeleton member (not shown).

-Detection member 82-
As shown in FIG. 2, the detection member 82 is partially disposed in a through hole 95 formed in the holding member 90, and is in contact with the back surface of the heat generating plate 64. As a result, the detecting member 82 detects the temperature of the heat generating plate 64. Then, the control unit 98 controls on / off of a power switch (not shown) to apply a voltage to the electrode 72 so that the temperature of the heat generating plate 64 detected by the detecting member 82 falls within a predetermined range. Alternatively, the application is stopped.

-Thermostat 84-
As shown in FIG. 1, the thermostat 84 is provided in a pair, and is arranged so as to be in contact with the back surface of the heat generating plate 64 in the portion arranged in the gap 96. When the temperature of the heating plate 64 detected by the thermostat 84 reaches the threshold temperature, the thermostat 84 stops applying voltage to the electrode 72.

[Control unit 98]
As shown in FIG. 7, the control unit 98 controls on / off of a power switch (not shown) based on a detection result of the detection member 82 to control application of a voltage to the electrode 72. . The control of each unit by the control unit 98 will be described together with the operation described later.

(Action)
Next, the operation of the fixing device 50 will be described. Before the operation of the fixing device 50 illustrated in FIG. 3, the application of the voltage to the electrode 72 (see FIG. 4) is stopped, and the pressure roller 52 is stopped.

  When fixing the toner image transferred to the sheet member P to the sheet member P, the control section 98 (see FIG. 7) controls the motor 58 to transmit the rotational force to the pressure roll 52. Then, the pressure roll 52 shown in FIG. 3 rotates in the direction of the arrow R1 in the figure. Accordingly, the endless belt 62 that comes into contact with the pressure roll 52 rotates in the direction of the arrow R2 in the drawing following the rotating pressure roller 52.

  When the endless belt 62 rotates, the control unit 98 turns on a power switch (not shown) and starts applying a voltage to the electrode 72. As a result, heat is generated in the resistance heating portion 74a, and the heating plate 64 generates heat. Further, the heating plate 64 heats the rotating endless belt 62 from the inner peripheral surface.

  When the temperature of the heat generating plate 64 detected by the detecting member 82 (see FIG. 2) reaches 200 ° C., the heating mode (rising mode) for heating the endless belt 62 ends, and the toner image is transferred to the sheet member P. Then, the mode shifts to the fixing mode where the image is fixed.

  In the fixing mode, the toner image is fixed to the sheet member P by the heating unit 60 and the pressure roll 52 sandwiching and conveying the sheet member P to which the toner image has been transferred. Further, when the heating unit 60 and the pressure roll 52 sandwich and convey the sheet member P on which the toner image has been transferred, the heat of the heat generating plate 64 where the sheet member P passes is taken away. As a result, the temperature of the heating plate 64 decreases. Therefore, as an example, the control unit 98 controls on / off of a power switch (not shown) so that the temperature of the heat generating plate 64 becomes 190 ° C. or more and 230 ° C. or less.

  Here, for example, when the toner image is fixed on the sheet member P2 of the minimum size, as shown in FIG. 4, a region where the sheet member P2 does not pass in the resistance heating portion 74a where heat is generated (region in the drawing) F01) exists.

  Since the heat generated in the region F01 in the resistance heating portion 74a is not deprived by the sheet member P2, when the holding member 90 is in contact with the entire back surface of the heating plate 64, the heating plate in the region F01 is not used. It is conceivable that the temperature of the holding member 90 in the area F <b> 01 may be melted and deformed in the area F <b> 01.

  However, as described above, the holding member 90 has the gap 96 that connects the back surface of the heating plate 64 and the space 110. Therefore, the heat generated in the region F01 is released to the space 110 through the gap 96. In other words, the space 96 suppresses a temperature rise of the heat generating plate 64 in the region F01.

  On the other hand, when an unexpected situation occurs and the temperature of the heating plate 64 detected by the thermostat 84 reaches a threshold temperature (for example, 250 ° C.), the thermostat 84 stops applying a voltage to the electrode 72. .

(Summary)
As described above, in the fixing device 50, the gap 96 that connects the back surface of the heat generating plate 64 and the space 110 is formed in the portion of the holding member 90 outside the range where the conveyed minimum-sized sheet member P2 passes. ing. As described above, the gap 96 suppresses a temperature rise of the heating plate 64 in the region F01. For this reason, when the toner image is fixed on the sheet member P2 having the minimum size, the resin holding member 90 melts and deforms as compared with the case where the holding member is in contact with the entire back surface of the heat generating plate. Is suppressed.

  In the fixing device 50, the entire back surface of the heat generating plate 64 is connected to the space 110 via the gap 96 at the portion where the gap 96 is formed. For this reason, for example, compared with the case where a part of the back surface of the heat generating plate is covered with the holding member, the amount of heat released from the heat generating plate 64 to the space 110 via the gap 96 is increased, and the resin Melting and deformation of the holding member 90 are suppressed.

  In the fixing device 50, a pair of side surfaces of the heat generating plate 64 are connected to the space 110 via the gap 96 at a portion where the gap 96 is formed. Therefore, for example, as compared with the case where the side surface of the heat generating plate is in contact with the holding member, the amount of heat released from the heat generating plate 64 to the space 110 via the gap 96 is increased, so that the resin holding member 90 is formed. Is prevented from melting and deforming.

  In the fixing device 50, at least one of the spaces 110 is open to the outside in the depth direction of the device. For this reason, compared with the case where both of the space in the device depth direction are closed, the air in the space 110 from which heat has been released flows in the device depth direction and is discharged to the outside without changing the flow direction. As a result, the amount of heat released from the heat generating plate 64 to the space 110 via the space 96 increases, so that the resin holding member 90 is melted compared to the case where both the space in the apparatus depth direction are closed. Deformation is suppressed.

  In the fixing device 50, both of the spaces 110 are open to the outside in the depth direction of the device. For this reason, as compared with the case where only one of the spaces in the device depth direction is open to the outside, the flow rate of air flowing in the device depth direction increases, and the air is discharged from the heat generating plate to the space 110 through the gap 96. Increase the amount of heat generated. This suppresses the resin holding member 90 from being melted and deformed as compared with the case where only one of the spaces in the apparatus depth direction is open to the outside.

  Further, in the image forming apparatus 10, when the sheet member P2 having the minimum size is used, the resin holding member 90 is suppressed from being melted and deformed as compared with the case where the fixing device 50 is not provided. In addition, the deterioration of the quality of the output image of the sheet member P having the maximum size is suppressed.

  Although the present invention has been described in detail with respect to a specific embodiment, the present invention is not limited to such an embodiment, and various other embodiments can be taken within the scope of the present invention. That will be apparent to those skilled in the art. For example, although not particularly described in the above embodiment, when only one of the spaces 110 in the apparatus depth direction is open to the outside, the opposite side to the side where the motor 58 shown in FIG. It is better to open the other. As a result, compared to the case where only the motor 58 side of the space is open, the heating of the air in the space 110 by the heat of the motor 58 is suppressed, and the resin holding member 90 is melted and deformed. Is suppressed.

  Although not particularly described in the above embodiment, the length of the gap 96 on the side where the motor 58 that generates heat when operated is arranged in the apparatus depth direction is the length of the gap 96 on the opposite side in the apparatus depth direction. Alternatively, it may be longer. By doing so, the length of the gap 96 on the side where the motor 58 is disposed in the device depth direction is shorter than the case where the length of the gap 96 on the opposite side is shortened in the device depth direction. A decrease in the amount of heat released from the heat generating plate to the space 110 through the gap 96 on the motor 58 side by the heat of the motor 58 is suppressed.

  Although not particularly described in the above embodiment, the length of the gap 96 on the side where the motor 58 that generates heat when operated is arranged in the vertical direction of the device is the length of the gap 96 on the opposite side in the vertical direction of the device. Alternatively, it may be longer. By doing so, the length of the gap 96 on the side where the motor 58 is disposed in the vertical direction of the device is shorter than the length of the gap 96 on the opposite side in the vertical direction of the device. A decrease in the amount of heat released from the heat generating plate to the space 110 through the gap 96 on the motor 58 side by the heat of the motor 58 is suppressed.

  Although not particularly described in the above-described embodiment, the gap 96 may be divided. As a result, a crosspiece that partitions the divided gap is formed, and the heating plate is supported by the crosspiece.

  In the above embodiment, the gap 96 faces the side surface of the heating plate 64, but the gap does not have to face the side surface of the heating plate. In this case, there is no effect caused by the gap facing the side surface of the heat generating plate.

10 Image forming apparatus 18 Image forming unit (an example of a forming unit)
50 fixing device 52 pressure roll (an example of a pressure unit)
58 Motor (Example of drive unit)
62 Endless belt 64 Heating plate 90 Holding member (an example of a holding portion)
96 void 110 space

Claims (7)

An endless belt that rotates in the circumferential direction,
A heating plate that extends in the axial direction of the endless belt and that generates heat by contacting the inner peripheral surface and the surface of the endless belt,
A pressurizing unit disposed on the opposite side of the heat generating plate with the endless belt interposed therebetween, and pressing a recording medium to be conveyed to an outer peripheral surface of the endless belt;
A resin holding portion that contacts the rear surface of the heat generating plate and holds the heat generating plate. The holding portion in which a gap connecting the space opened to the outside is formed,
A fixing device comprising:   2. The fixing device according to claim 1, wherein in the cross section that intersects with the axial direction, the gap faces the entire back surface of the heating plate. 3.   The fixing device according to claim 2, wherein in the cross section, the gap faces a side surface of the heating plate.   The fixing device according to claim 1, wherein at least one of the spaces is open to the outside in the axial direction. The pressurizing section rotates,
A driving unit that generates a rotational force that rotates the pressurizing unit is disposed on one of the pressurizing units in the axial direction,
5. The fixing device according to claim 4, wherein in the axial direction, at least the other side of the space opposite to the side on which the driving unit is disposed is opened.   The fixing device according to claim 4, wherein both of the spaces are open to the outside in the axial direction. A forming unit that forms an image on a recording medium of a plurality of sizes including a minimum size,
A fixing device according to any one of claims 1 to 6, which fixes an image formed on the recording medium to the recording medium,
An image forming apparatus comprising: