JP7159708B2 - Fixing device, image forming device - Google Patents

Description

The present invention relates to fixing devices and image forming apparatuses.

Japanese Patent Application Laid-Open No. 2002-200002 describes a fixing device that forms a nip portion for nipping and conveying a recording material carrying an unfixed image together with a sliding member via an endless film. In this fixing device, the second surface of the sliding member opposite to the first surface in contact with the endless film has a higher thermal conductivity in the plane direction perpendicular to the thickness direction than in the thickness direction. A plurality of members having high thermal conductivity anisotropy are laminated.

JP 2015-219510 A

A rotating endless belt, a heating plate that generates heat by contacting the inner peripheral surface of the endless belt and the surface to heat a part of the inner peripheral surface of the endless belt, and a heating plate that contacts the back surface of the heating plate to heat. There is a fixing device provided with a heat transfer portion that transfers heat in the axial direction of an endless belt. Further, the fixing device is provided with a pressure section that forms a nip with the endless belt and presses the recording medium against the outer peripheral surface of the endless belt. Here, the heat transfer section is made of metal and is integrally formed.

In this fixing device, when fixing an image on a recording medium of the smallest size, the heat generated by the heating plate in the portion not facing the recording medium is not absorbed by the recording medium but is absorbed by the heat transfer section. . Furthermore, the heat absorbed by the heat transfer portion flows in the axial direction, and then is transferred to the heat generating plate facing the recording medium. As a result, the temperature of the heating plate becomes uniform in the axial direction. Then, the power switch for the voltage applied to the heat generating plate is turned on and off so that the temperature of the heat generating plate falls within the specified temperature range. In such a configuration, the shorter the time required for the temperature of the heating plate to become uniform in the axial direction, the more the power consumption is suppressed.

SUMMARY OF THE INVENTION An object of the present invention is to reduce power consumption when fixing an image on a recording medium of a minimum size, compared to the case where the heat transfer section is integrally formed of metal.

A fixing device according to a first aspect of the present invention includes an endless belt that rotates in a circumferential direction, and an endless belt that extends in the axial direction of the endless belt. a heat generating plate that generates heat; a detection unit that detects the temperature of the heat generating plate; A pressure portion and a heat transfer portion contacting the rear surface of the heat generating plate and conducting heat of the heat generating plate in the axial direction, the heat transfer portion being arranged in the minimum range in the axial direction at least in which a recording medium having a minimum size passes through. and a first heat transfer section disposed next to the first heat transfer section in the axial direction, and having a thermal conductivity in the axial direction that is greater than the thermal conductivity of the first heat transfer section in the axial direction. and a voltage applied to the heat generating plate so that the temperature of the heat generating plate falls within a predetermined range based on the detection result of the detecting unit. and a control unit that controls the

A fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the thermal conductivity of the second heat transfer portion in the axial direction is the second heat transfer portion in the thickness direction of the heat generating plate. It is characterized by having a high thermal conductivity compared to the heat portion.

A fixing device according to a third aspect of the present invention is the fixing device according to the second aspect, wherein the second heat transfer section is in a state in which a plurality of sheet materials are stacked in the thickness direction. Characterized by

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 the thermal conductivity of the first heat transfer portion in the thickness direction of the heat generating plate is It is characterized by being higher than the thermal conductivity of the second heat transfer portion in the thickness direction.

A fixing device according to a fifth aspect of the present invention is the fixing device according to the fourth aspect, wherein the first heat transfer portion has an anisotropic heat transfer characteristic, The thermal conductivity of the heat portion is higher than the thermal conductivity of the first heat transfer portion in the axial direction.

A fixing device according to a sixth aspect of the present invention is the fixing device according to any one of the first to fifth aspects, wherein the second heat transfer section is divided in the axial direction and has different heat transfer characteristics. It is formed of a plurality of members, and the thermal conductivity of the second heat transfer section in the axial direction increases from the side close to the first heat transfer section toward the side away from the first heat transfer section. It is characterized by

An image forming apparatus according to a seventh aspect of the present invention includes a forming unit that forms an image on a recording medium of a plurality of sizes including a minimum size, and first to sixth aspects that fix the image formed on the recording medium to the recording medium. and a fixing device according to any one aspect of the above.

According to the fixing device of the first aspect of the present invention, power consumption is suppressed when fixing an image on a recording medium of a minimum size, compared to the case where the heat transfer section is integrally formed of metal. be able to.

According to the fixing device of the second aspect of the present invention, compared to the case where the thermal conductivity of the second heat transfer section in the axial direction is the same as the thermal conductivity of the second heat transfer section in the thickness direction, the minimum size power consumption can be suppressed when fixing an image on a recording medium.

According to the fixing device of the third aspect of the present invention, it is possible to form the second heat transfer section having an anisotropic heat transfer characteristic simply by stacking the sheet materials.

According to the fixing device of the fourth aspect of the present invention, compared to the case where the thermal conductivity of the first heat transfer section in the thickness direction is the same as the thermal conductivity of the second heat transfer section in the thickness direction, Power consumption can be suppressed when an image is fixed on a recording medium of minimum size.

According to the fixing device of the fifth aspect of the present invention, the thermal conductivity of the first heat transfer portion in the thickness direction is the lowest compared to the case where the thermal conductivity of the first heat transfer portion in the axial direction is the same. Power consumption can be suppressed when fixing an image on a recording medium of this size.

According to the fixing device of the sixth aspect of the present invention, the thermal conductivity of the second heat transfer portion in the portion away from the first heat transfer portion is Power consumption can be suppressed when fixing an image on a recording medium of the minimum size, compared to the case where the thermal conductivity is the same as that of .

According to the image forming apparatus of the seventh aspect of the present invention, it is possible to suppress an increase in running costs compared to the case where the fixing device according to any one of the first to sixth aspects is not provided. .

3 is a plan view showing a heat transfer member and a heat generating plate used in the fixing device according to the first embodiment of the invention; FIG. 3 is a perspective view showing a heat transfer member and a heat generating plate used in the fixing device according to the first exemplary embodiment of the invention; FIG. FIG. 2 is a side view showing a heat transfer member and a heat generating plate used in the fixing device according to the first embodiment of the invention; 1 is a cross-sectional view showing a fixing device according to a first embodiment of the invention; FIG. 1 is a cross-sectional view showing a fixing device according to a first embodiment of the invention; FIG. 3 is a block diagram showing a control system of a control unit provided in the fixing device according to the first embodiment of the invention; FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to a first embodiment of the invention; FIG. FIG. 5 is a side view showing a heat transfer member and a heat generating plate used in a fixing device according to a comparative embodiment of the invention; FIG. 5 is a perspective view showing a heat transfer member and a heat generating plate used in a fixing device according to a comparative embodiment of the invention; FIG. 8 is a side view showing a heat transfer member and a heat generating plate used in a fixing device according to a second embodiment of the invention; FIG. 8 is a perspective view showing a heat transfer member and a heat generating plate used in a fixing device according to a second embodiment of the invention; FIG. 11 is a side view showing a heat transfer member and a heat generating plate used in a fixing device according to a third embodiment of the invention;

<First embodiment>
An example of a fixing device and an image forming apparatus according to a first embodiment of the invention will be described with reference to FIGS. 1 to 9. FIG. An arrow H shown in the drawing indicates the vertical direction of the device, an arrow W indicates the width direction of the device (horizontal direction), and an arrow D indicates the depth direction of the device (horizontal direction).

(overall structure)
As shown in FIG. 7, in the image forming apparatus 10 according to the present embodiment, a storage portion in which a sheet member P as a recording medium is stored extends from the lower side to the upper side in the vertical direction (direction of arrow H). 14, a conveying unit 16 that conveys the sheet member P accommodated in the accommodating unit 14, and an image forming unit 20 that forms an image on the sheet member P conveyed from the accommodating unit 14 by the conveying unit 16, in this order. are provided.

[Accommodating portion 14]
The storage unit 14 is provided with a storage member 26 that can be pulled out from the main body 10A of the image forming apparatus 10 toward the front side in the depth direction of the apparatus. Further, the storage unit 14 is provided with a delivery roll 30 that delivers the sheet members P stacked on the storage member 26 to the transport path 28 that constitutes the transport unit 16 .

[Conveyor 16]
The transport unit 16 is provided with 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, Y, M, C, and K may be omitted when Y, M, C, and K need not be distinguished.

The image forming unit 18 for each color includes an image carrier 36, a charging roll 38 that charges the surface of the image carrier 36, and an exposure device 42 that irradiates the charged image carrier 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 carrier 36 by the exposing device 42 and visualizes it as a toner image. The image forming unit 18 is an example of a forming section.

The image forming unit 20 also has an endless transfer belt 22 that rotates in the direction of arrow A in the drawing, and a primary transfer roll 44 that transfers the toner images formed by the image forming units 18 of each color onto the transfer belt 22 . are provided. Further, the image forming unit 20 includes a secondary transfer roll 46 that transfers the toner image on the transfer belt 22 to the sheet member P, and a fixing device 50 that heats and presses the sheet member P to fix the toner image onto the sheet member P. and are provided. Details of the fixing device 50 will be described later.

(Action of image forming apparatus)
The image forming apparatus 10 forms an image as follows.
First, the charging roll 38 of each color to which a voltage is applied contacts the surface of the image carrier 36 of each color and uniformly negatively charges the surface of the image carrier 36 with a predetermined potential. Subsequently, based on 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.

Thereby, an electrostatic latent image corresponding to the data is formed on the surface of the image carrier 36 for each color. Further, the developing device 40 for each color develops this electrostatic latent image and visualizes it as a toner image. Further, the toner images formed on the surface of the image carrier 36 of each color are transferred onto the transfer belt 22 by the primary transfer roll 44 .

Then, the sheet member P delivered from the storage member 26 to the transport path 28 by the delivery roll 30 is delivered to the transfer position T where the transfer belt 22 and the secondary transfer roll 46 are in contact with each other. At the transfer position T, the toner image on the surface of the transfer belt 22 is transferred to the sheet member P as the sheet member P is sandwiched and conveyed between the transfer belt 22 and the secondary transfer roll 46 .

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

(main part 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. 4, includes a pressure roll 52 and a heating section 60 facing the pressure roll 52 in the width direction of the apparatus. Further, the fixing device 50 includes a control section 102 (see FIG. 6) that controls each section.

[Pressure roll 52]
As shown in FIG. 4, the pressure roll 52 has a metal shaft portion 54 extending in the depth direction of the device, a cylindrical elastic layer 56 into which the shaft portion 54 is inserted, and the elastic layer 56. and a release layer (not shown). The pressure roll 52 is an example of a pressure section.

The shaft portion 54 is made of, for example, a metal material such as steel, stainless steel, or aluminum, the elastic layer 56 is made of, for example, a rubber material, and the release layer is made of, for example, ethylene fluoride-perm. It is made of fluoroalkoxyethylene copolymer (PFA) or the like.

In this configuration, the pressure roll 52 is grounded and urged toward the heating section 60 by an urging member (not shown). Further, the pressure roll 52 is rotated in the direction of the arrow R1 in the figure by a rotational force transmitted from a motor 58 (see FIG. 6). As a result, the rotating pressure roller 52 presses the sheet member P having the toner image transferred thereon against the outer peripheral surface of the endless belt 62, which will be described later. In this embodiment, the pressure roll 52 rotates so that the peripheral speed of the outer peripheral surface of the elastic layer 56 is 230 [mm/sec].

[Heating unit 60]
As shown in FIG. 4, the heating unit 60 includes a cylindrical endless belt 62 extending in the depth direction of the apparatus, a heat generating plate 64 that generates heat to heat the endless belt 62, and heat from the heat generating plate 64. and a heat transfer member 92 that transmits heat in the depth direction (the axial direction of the endless belt 62). Further, the heating unit 60 includes a holding member 90 that holds the heat generating plate 64 and the heat transfer member 92, a frame 80 that supports the holding member 90, and a detection member 82 that detects the temperature of the heat generating plate 64 (Fig. 5). The heat transfer member 92 is an example of a heat transfer section.

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

Cylindrical support members (not shown) for supporting the inner peripheral surface of the endless belt 62 are arranged at both ends of the endless belt 62 in the longitudinal direction. Further, the inner peripheral surface of the endless belt 62 is coated with lubricating oil S (an example of a liquid such as silicone oil) in order to reduce the frictional resistance with the heating plate 64 .

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

-Holding member 90-
The holding member 90 is arranged inside the endless belt 62 as shown in FIG. The holding member 90 is made of, for example, a resin material such as LCP (liquid crystal polymer), and extends in the depth direction of the apparatus. A cross section perpendicular to the longitudinal direction of the holding member 90 is U-shaped with an opening on the side opposite to the pressure roll 52 side.

Further, in the portion of the holding member 90 facing the pressure roll 52, a recessed attachment portion 90a is formed to which the heat generating plate 64 and the heat transfer member 92 are attached by an attachment member such as an adhesive (not shown). ing. In addition, as shown in FIG. 5, a through hole 95 in which the detection member 82 is arranged is formed in the holding member 90 at the central portion in the device depth direction.

-Frame 80-
As shown in FIG. 4, the frame 80 is arranged inside the endless belt 62 on the opposite side of the pressure roll 52 with the holding member 90 interposed therebetween. The frame 80 is formed by bending a sheet metal and extends in the depth direction of the apparatus. A cross section perpendicular to the longitudinal direction of the frame 80 is U-shaped with an opening on the side of the holding member 90 .

Furthermore, the frame 80 supports the holding member 90 by attaching the front end portion of the holding member 90 to the front end portion of the U-shaped frame 80 with a mounting member such as an adhesive (not shown). is doing. Both ends of the frame 80 in the longitudinal direction protrude from the endless belt 62, and the protruding portions are fixed to frame members (not shown).

- Heating plate 64 -
As shown in FIG. 4 , the heating plate 64 is arranged 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 its surface. The heating plate 64 is a plate-like member whose plate surface faces the device width direction, and extends from one end side to the other end side of the endless belt 62 in the device depth direction. In this embodiment, the thickness of the heating plate 64 is set to 0.7 [mm] as an example.

When viewed from the plate thickness direction, the heating plate 64 has a rectangular shape extending in the depth direction of the device, as shown in FIG. The heating plate 64 includes an electrically insulating base material 66, an insulating film 68 made of a heat-resistant resin material, a pair of electrodes 72 for voltage application, and a voltage applied to the electrodes 72 to generate an electric current. and a conducting portion 74 through which the current flows. The conductive portion 74 is formed with two resistive heat generating portions 74a (hatched portions in the drawing) that generate heat when current flows. Here, insulating means having an electric conductivity of 1×10 ⁻¹⁰ [S/m] or less.

The base material 66 is a molded body of alumina, which is an electrically insulating ceramic. The heat transfer characteristic of the base material 66 is isotropic, and the heat conductivity of the base material 66 is 41 [W/mK]. Also, the pair of electrodes 72 and the conductive 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 are formed on the front side portion of the substrate 66 in the depth direction of the device, and arranged side by side in the vertical direction. Further, the conductive portion 74 is formed in a U shape extending in the depth direction of the apparatus, and electrodes 72 are arranged at both ends of the conductive portion 74 .

Further, the conducting portion 74 is covered with the insulating film 68, and a resistance heating portion 74a is formed in the linear portion of the conducting portion 74. As shown in FIG. The resistance heating portion 74a is formed so as to include a range in the apparatus depth direction (the width direction of the sheet member P1) through which the conveyed largest sheet member P (P1 in the drawing) passes. Note that the image forming apparatus 10 employs a center registration method in which the sheet members P are brought together from both sides in the width direction and aligned with the center in the width direction as a reference.

-Heat transfer member 92-
As shown in FIG. 4, the heat transfer member 92 is arranged on the back side of the heating plate 64 (the side opposite to the inner peripheral side of the endless belt 62). The heat transfer member 92 is a plate-shaped member whose plate surface faces the width direction of the device, and is stacked on the back surface of the heat generating plate 64 in contact therewith. The thickness of the heat transfer member 92 is, for example, 0.3 [mm]. Here, the heat transfer member 92 is a member that transfers the heat of the heat generating plate 64 in the device depth direction (axial direction). It is higher than the thermal conductivity of the substrate 66 in the device depth direction (axial direction).

As shown in FIGS. 1 and 2, the heat transfer member 92 is divided into three parts in the depth direction of the apparatus. Specifically, the one end side heat transfer section 94, the central side heat transfer section 96, and the other end side heat transfer section 98 are arranged in this order from the front side (left side in the figure) toward the back side in the device depth direction. I'm in. The central heat transfer section 96 is an example of a first heat transfer section, and the one end heat transfer section 94 and the other end heat transfer section 98 are examples of a second heat transfer section. 1 and 2, the thickness of the heat transfer member 92 is increased so that the structure of the heat transfer member 92 can be easily understood.

The center-side heat transfer section 96 is arranged only in a range (range F02 in FIG. 1) through which the minimum size sheet member P (P2 in the figure) passes in the device depth direction. The end face in the depth direction faces the device depth direction. In this embodiment, the central heat transfer portion 96 is made of aluminum, which is made of metal. The heat transfer characteristic of the central heat transfer portion 96 is isotropic, and the heat conductivity of the central heat transfer portion 96 is 236 [W/mK]. That is, the thermal conductivity of the central heat transfer portion 96 in the device width direction (thickness direction) and the thermal conductivity of the central heat transfer portion 96 in the device depth direction (axial direction) are the same, which is 236 [W /mK].

As described above, the central heat transfer portion 96 has the same heat transfer characteristics in the device width direction (thickness direction) and the device depth direction (axial direction). The portion 96 functions as an isotropic heat transfer means.

Since the one end side heat transfer portion 94 and the other end side heat transfer portion 98 have the same configuration, the one end side heat transfer portion 94 will be described.

The one-end heat transfer portion 94 is formed by stacking three sheets 94a each having an anisotropic heat transfer characteristic and a thickness of 0.1 [mm]. The end face of the heat transfer portion 94 on the one end side in the depth direction of the device faces the depth direction of the device, and is in contact with the end face of the heat transfer portion 96 on the center side in the depth direction of the device. Grease with high thermal conductivity (for example, grease containing silicone as a main component) is applied between the end surface of the one end side heat transfer portion 94 and the end surface of the center side heat transfer portion 96 in consideration of heat transfer. It is

Further, in the present embodiment, a PGS graphite sheet manufactured by Panasonic Corporation is used as an example of the sheet material 94a. The thermal conductivity of the one end heat transfer portion 94 in the device width direction (thickness direction) is 8 [W/mK]. Furthermore, the thermal conductivity of the one end side heat transfer portion 94 in the device depth direction (axial direction) is set to 1000 [W/mK].

Thus, the thermal conductivity of the one end heat transfer portion 94 in the device depth direction (axial direction) is higher than the thermal conductivity of the center side heat transfer portion 96 in the device depth direction (axial direction). . In other words, the one end side heat transfer portion 94 transfers heat faster in the device depth direction than the center side heat transfer portion 96 .

In addition, the one end side heat transfer portion 94 has different heat transfer characteristics in the device width direction (thickness direction) and in the device depth direction (axial direction). Specifically, the thermal conductivity of the one end heat transfer portion 94 in the device depth direction (axial direction) is higher than the thermal conductivity of the one end heat transfer portion 94 in the device width direction (thickness direction). ing. In other words, in the one-end heat transfer portion 94, heat moves faster in the device depth direction (axial direction) than in the device width direction (thickness direction). As described above, the one-end-side heat transfer portion 94 has an anisotropic anisotropic heat transfer characteristic in which heat moves faster in the device depth direction (axial direction) than in the device width direction (thickness direction). It functions as a heat source.

In addition, the thermal conductivity of the one end heat transfer portion 94 in the device width direction (thickness direction) is lower than the thermal conductivity of the central heat transfer portion 96 in the device width direction (thickness direction). . In other words, heat is less likely to move in the width direction of the device in the heat transfer portion 94 on the one end side than in the heat transfer portion 96 on the center side. Furthermore, in other words, heat moves faster in the device width direction in the central heat transfer portion 96 than in the one end heat transfer portion 94 . The same applies to the heat transfer portion 98 on the other end side, and the heat transfer portion 98 on the other end side is formed of three sheet materials 98a.

In this configuration, when the heat generating plate 64 generates heat, the heat transfer member 92 transfers the heat of the heat generating plate 64 in the depth direction of the device, thereby suppressing temperature unevenness of the heat generating plate 64 in the depth direction of the device. That is, by bringing the heat transfer member 92 into contact with the back surface of the heat generating plate 64, the temperature unevenness of the heat generating plate 64 is suppressed as compared with the case where the heat transfer member is not provided. In this manner, the heat transfer member 92 functions as temperature nonuniformity suppressing means.

- Detection member 82 -
As shown in FIG. 5 , the detection member 82 is partially arranged in a through hole 95 formed in the holding member 90 and is in contact with the rear surface of the heat transfer member 92 . Thereby, the detection member 82 detects the temperature of the heating plate 64 via the heat transfer member 92 . Then, the control unit 102 (see FIG. 6) turns the power switch (not shown) on and off so that the temperature of the heating plate 64 detected by the detection member 82 via the heat transfer member 92 falls within a predetermined range. The application of the voltage to the electrode 72 or the application of the voltage is stopped by controlling.

[Control unit 102]
As shown in FIG. 6, the control unit 102 controls the on/off of a power switch (not shown) based on the detection result of the detection member 82 to control the application of voltage to the electrode 72. . The control of each unit by the control unit 102 will be described together with the operation described later.

(action)
Next, the operation of the fixing device 50 will be described in comparison with the fixing device 550 according to the comparative embodiment. First, regarding the configuration of the fixing device 550 according to the comparative embodiment, mainly the portions different from the fixing device 50 will be described. Also, regarding the operation of the fixing device 550, mainly the portions different from those of the fixing device 50 will be described.

-Structure of Fixing Device 550-
The fixing device 550 differs from the fixing device 50 only in the heat transfer member 592 . As shown in FIGS. 8 and 9, the heat transfer member 592 of the fixing device 550 is integrally made of metal. Specifically, the thickness of the heat transfer member 592 is 0.3 [mm], and the heat transfer member 592 is made of aluminum. The heat transfer characteristic of the heat transfer member 592 is isotropic, and the heat conductivity of the heat transfer member 592 is 236 [W/mK].

-Function of Fixing Device 50, 550-
Before the fixing device 50 starts to operate as shown in FIG. 4, voltage application to the electrode 72 (see FIG. 3) is stopped, and the pressure roll 52 is stopped.

When the toner image transferred to the sheet member P is fixed on the sheet member P, the control unit 102 (see FIG. 6) controls the motor 58 to transmit the rotational force to the pressure roll 52 . Then, the pressure roller 52 shown in FIG. 4 rotates in the arrow R1 direction in the figure. As a result, the endless belt 62 in contact with the pressure roll 52 is driven by the rotating pressure roll 52 and rotates in the arrow R2 direction in the figure.

When the endless belt 62 rotates, the controller 102 turns on a power switch (not shown) to start applying voltage to the electrodes 72 . As a result, heat is generated in the resistance heating portion 74a (see FIG. 3), and the heating plate 64 generates heat. Furthermore, the heating plate 64 heats the rotating endless belt 62 from the inner peripheral surface. Further, when the heat generating plate 64 generates heat, the heat transfer member 92 transfers the heat of the heat generating plate 64 in the depth direction of the device, thereby suppressing temperature unevenness of the heat generating plate 64 in the depth direction of the device.

Then, when the temperature detected by the detection member 82 (see FIG. 5) reaches, for example, 200[° C.], the heating mode (startup mode) for heating the endless belt 62 ends, and the toner image is transferred to the sheet member. Then, the mode is shifted to the fixing mode for fixing to P.

In the fixing mode, the toner image is fixed on the sheet member P by sandwiching and conveying the sheet member P with the toner image transferred between the heating unit 60 and the pressure roll 52 . In addition, the heating portion 60 and the pressure roll 52 sandwich and convey the sheet member P onto which the toner image has been transferred, so that the sheet member P absorbs the heat of the heating plate 64 in the portion through which the sheet member P passes. As a result, the temperature of the heating plate 64 is lowered. Therefore, the control unit 102 controls on/off of a power switch (not shown) so that the temperature of the heating plate 64 is 190° C. or higher and 220° C. or lower, for example.

For example, when fixing a toner image on a sheet member P2 of the smallest size, as shown in FIG. exist. In other words, there is heat that is not directly used for fixing the sheet member P2. In other words, there is heat that is not lost to the sheet member P.

Here, in the fixing device 550, the heat of the heating plate 64 generated in the area F01 that is not directly used for fixing the sheet member P2 is transferred to the heat transfer member 592 in the area F01 as shown in FIG. See arrow G01 in the figure). The heat transferred to the heat transfer member 592 in the range F01 is the temperature difference between the heat transfer member 592 in the range F01 and the heat transfer member 592 in the range through which the sheet member P2 passes (range F02 in the figure). is transmitted to the heat transfer member 592 in the range F02 (see arrow G02 in the drawing).

Further, the heat transmitted to the heat transfer member 592 in the range F02 is transmitted to the heating plate 64 in the range F02 (see arrow G03 in the figure). Then, the temperature of the heating plate 64 becomes uniform.

On the other hand, in the fixing device 50, the heat of the heating plate 64 generated in the area F01 that is not directly used for fixing the sheet member P2 is transferred to the one end side heat transfer portion 94 and the other end side heat transfer portion 94 as shown in FIG. It is transmitted to the heat transfer portion 98 (see arrow G11 in the drawing). The heat transferred to the one end heat transfer portion 94 and the other end heat transfer portion 98 is adjusted so that the temperature difference between the one end heat transfer portion 94 and the other end heat transfer portion 98 and the central heat transfer portion 96 becomes small. Then, the heat is transmitted to the central heat transfer portion 96 (see arrow G12 in the figure).

Further, the heat transmitted to the central heat transfer portion 96 is transmitted to the heat generating plate 64 in the range F02 (see arrow G13 in the drawing). Then, the temperature of the heating plate 64 becomes uniform.

As described above, the thermal conductivity of the one end side heat transfer portion 94 and the other end side heat transfer portion 98 in the device depth direction (axial direction) is equal to that of the central side heat transfer portion 96 in the device depth direction (axial direction). higher than the rate. In other words, the one end side heat transfer portion 94 and the other end side heat transfer portion 98 move heat faster in the device depth direction than the central side heat transfer portion 96 . In the fixing device 50, the speed at which heat is transferred to the central heat transfer portion 96 (arrow G12 in FIG. 1) is the same as the speed at which heat is transferred to the heat transfer member 592 in the range F02 in the fixing device 550 (arrow G02 in FIG. 8). ) speed relative to speed. Therefore, the time required for the temperature of the heating plate 64 of the fixing device 50 to become uniform is shorter than the time required for the temperature of the heating plate 64 of the fixing device 550 to become uniform. In other words, the temperature of the central heat transfer section 96 rises faster.

In addition, as described above, the thermal conductivity of the one end side heat transfer portion 94 and the other end side heat transfer portion 98 in the device depth direction (axial direction) is It is higher than the device width row direction (thickness direction). In other words, in the one end side heat transfer portion 94 and the other end side heat transfer portion 98, heat moves faster in the device depth direction (axial direction) than in the device width direction (thickness direction). ing.

Therefore, in the fixing device 50, the speed at which heat is transferred to the central heat transfer portion 96 (arrow G12 in FIG. 1) is the same as the speed at which heat is transferred to the heat transfer member 592 in the range F02 in the fixing device 550 (see FIG. 8). arrow G02) becomes faster than the speed. As a result, the time required for the temperature of the heating plate 64 of the fixing device 50 to become uniform is shorter than the time required for the temperature of the heating plate 64 of the fixing device 550 to become uniform.

In addition, the thermal conductivity in the device width direction (thickness direction) of the one end side heat transfer portion 94 and the other end side heat transfer portion 98 is the thermal conductivity of the central side heat transfer portion 96 in the device width direction (thickness direction). is low compared to In other words, in the heat transfer portion 96 on the center side, heat moves faster in the width direction of the device than in the heat transfer portion 94 on the one end side. Therefore, compared to the case where the heat conductivity of the central heat transfer portion 96 in the device width direction is the same as the heat conductivity of the one end heat transfer portion 94 in the device width direction, the range F02 from the central heat transfer portion 96 The heat transfer to the heat generating plate 64 at the portion of . As a result, the time required for the temperature of the heat generating plate 64 of the fixing device 50 to become uniform is that the heat conductivity of the central heat transfer portion 96 in the device width direction is equal to the heat of the one end heat transfer portion 94 in the device width direction. It is shorter than in the case of conductivity.

Therefore, the control unit 102 sets the time (timing) for turning off the power switch when the temperature of the heating plate 64 reaches a specified temperature (for example, 220[deg.] C.) as compared with the case where the fixing device 550 is used. get faster.

(summary)
As described above, in the fixing device 50 , the thermal conductivity of the one end heat transfer portion 94 and the other end heat transfer portion 98 in the device depth direction (axial direction) is the same as that of the central heat transfer portion 96 . It is high compared to Therefore, the time required for the temperature of the heating plate 64 of the fixing device 50 to become uniform is shorter than the time required for the temperature of the heating plate 64 of the fixing device 550 to become uniform. As a result, compared with the case where the fixing device 550 including the heat transfer member 592 integrally made of metal is used, the power consumption is suppressed when fixing the toner image on the sheet member P of the minimum size. be.

Further, in the fixing device 50 , the thermal conductivity of the one end heat transfer portion 94 and the other end heat transfer portion 98 in the device depth direction (axial direction) is It is higher than the thermal conductivity in the device width direction (thickness direction). Therefore, the time required for the temperature of the heating plate 64 of the fixing device 50 to become uniform is shorter than the time required for the temperature of the heating plate 64 of the fixing device 550 to become uniform. As a result, compared to the case of using the fixing device 550 having the heat transfer member 592 whose thermal conductivity in the device depth direction is the same as that in the device width direction, a toner image is formed on the minimum size sheet member P. Power consumption is suppressed when fixing.

Further, in the fixing device 50, the one end side heat transfer portion 94 and the other end side heat transfer portion 98 are formed by stacking sheet materials 94a in the device width direction. By simply stacking the sheet materials 94a in this manner, the one end side heat transfer portion 94 and the other end side heat transfer portion 98 having anisotropic heat transfer characteristics are formed.

Further, in the fixing device 50 , the thermal conductivity in the device width direction (thickness direction) of the one end side heat transfer portion 94 and the other end side heat transfer portion 98 is ) is lower than the thermal conductivity of In other words, heat moves faster in the device width direction in the central heat transfer portion 96 than in the one end heat transfer portion 94 and the other end heat transfer portion 98 . Therefore, compared to the case where the heat conductivity of the central heat transfer portion 96 in the device width direction is the same as the heat conductivity of the one end heat transfer portion 94 in the device width direction, the range F02 from the central heat transfer portion 96 The heat transfer to the heat generating plate 64 at the portion of . As a result, compared to the case where the central heat transfer portion 96 in the device width direction has the same heat conductivity as the one end side heat transfer portion 94 in the device width direction, a toner image is formed on the sheet member P of the minimum size. power consumption is suppressed when fixing

In addition, since the image forming apparatus 10 includes the fixing device 50 , an increase in running costs can be suppressed compared to when the fixing device 550 is included.

<Second embodiment>
An example of a fixing device and an image forming apparatus according to a second embodiment of the invention will be described with reference to FIGS. 10 and 11. FIG. In addition, about 2nd Embodiment, a different part from 1st Embodiment is mainly demonstrated. A fixing device 150 according to the second embodiment differs from the fixing device 50 only in a heat transfer member 192 .

(Heat transfer member 192)
As shown in FIGS. 10 and 11, the heat transfer member 192 is divided into three parts in the depth direction of the apparatus. Specifically, the one end side heat transfer section 94, the center side heat transfer section 196, and the other end side heat transfer section 98 are arranged in this order from the front side (left side in the figure) toward the back side in the device depth direction. I'm in. The central heat transfer section 196 is an example of a first heat transfer section.

The central heat transfer portion 196 is arranged in a range in which the minimum size sheet member P2 passes in the depth direction of the device, and the end surface of the central heat transfer portion 196 in the depth direction of the device faces the depth direction of the device. The center-side heat transfer portion 196 is formed by stacking a plurality of strip-shaped sheet materials 196a having a thickness of 0.1 [mm] and having anisotropic heat transfer characteristics in the device depth direction (axial direction). . In consideration of heat transfer, grease with high thermal conductivity (for example, Grease containing silicone as the main ingredient) is applied.

Further, in the present embodiment, a PGS graphite sheet manufactured by Matsushita Electric Industrial Co., Ltd. is used as an example of the sheet material 196a. The thermal conductivity of the central heat transfer portion 196 in the device width direction (thickness direction) is 1000 [W/mK]. Furthermore, the thermal conductivity of the central heat transfer portion 196 in the device depth direction (axial direction) is 8 [W/mK].

As described above, the central heat transfer portion 196 has different heat transfer characteristics in the device width direction (thickness direction) and in the device depth direction (axial direction). Specifically, the thermal conductivity of the central heat transfer portion 196 in the device width direction is higher than the thermal conductivity of the central heat transfer portion 196 in the device depth direction. That is, the central heat transfer portion 196 functions as an anisotropic heat transfer means having an anisotropic heat transfer characteristic in which heat moves faster in the width direction of the device than in the depth direction of the device.

In this configuration, when fixing a toner image on the sheet member P2 of the minimum size, the heat of the heating plate 64 generated in the range F01 that is not directly used for fixing the sheet member P2 is, as shown in FIG. It is transmitted to the one end side heat transfer portion 94 and the other end side heat transfer portion 98 (see arrow G31 in the figure). The heat transferred to the one end heat transfer portion 94 and the other end heat transfer portion 98 is adjusted so that the temperature difference between the one end heat transfer portion 94 and the other end heat transfer portion 98 and the central heat transfer portion 196 becomes small. Then, the heat is transmitted to the central heat transfer portion 196 (arrow G32 in the figure).

Furthermore, the heat transmitted to the central heat transfer portion 196 is transmitted to the heat generating plate 64 in the area F02 (see arrow G33 in the figure). Then, the temperature of the heating plate 64 becomes uniform.

As described above, the thermal conductivity of the central heat transfer portion 196 in the device width direction (thickness direction) is higher than the thermal conductivity in the device depth direction (axial direction). In other words, in the central heat transfer portion 196, heat moves faster in the device width direction than in the device depth direction. Therefore, compared to the case where the thermal conductivity of the central heat transfer portion in the device width direction is the same as the thermal conductivity of the central heat transfer portion in the device depth direction, the image can be fixed on the smallest size recording medium. power consumption is reduced.

<Third Embodiment>
An example of a fixing device and an image forming apparatus according to the third embodiment of the invention will be described with reference to FIG. In addition, about 3rd Embodiment, a different part from 1st Embodiment is mainly demonstrated. A fixing device 250 according to the third embodiment differs from the fixing device 50 only in a heat transfer member 292 .

(Heat transfer member 292)
As shown in FIG. 12, the heat transfer member 292 is divided into five parts in the device depth direction. Specifically, the one end side heat transfer section 294, the central side heat transfer section 96, and the other end side heat transfer section 298 are arranged in this order from the front side (left side in the figure) toward the back side in the device depth direction. I'm in. The one end side heat transfer section 294 and the other end side heat transfer section 298 are examples of a second heat transfer section.

Since the one end side heat transfer portion 294 and the other end side heat transfer portion 298 have the same configuration, the one end side heat transfer portion 294 will be described.

The one-end-side heat transfer section 294 is divided into two parts in the device depth direction, and is formed of a first heat transfer body 294a and a second heat transfer body 294b. The length of the first heat transfer body 294a and the length of the second heat transfer body 294b in the depth direction of the device are the same, and the first heat transfer body 294a and the second heat transfer body 294b They are arranged in this order from the side close to the portion 96 . Also, in consideration of heat transfer, grease with high thermal conductivity (for example, grease containing silicone as a main component) is applied to the end face with which each heat conductor contacts.

In this embodiment, the first heat transfer body 294a is integrally formed of gold, and the thickness of the first heat transfer body 294a is 0.3 [mm]. The heat transfer characteristic of the first heat transfer member 294a is isotropic, and the thermal conductivity of the first heat transfer member 294a is 319 [W/mK].

The second heat transfer body 294b is integrally formed of silver, and the thickness of the second heat transfer body 294b is 0.3 [mm]. The heat transfer characteristics of the second heat transfer member 294b are isotropic, and the thermal conductivity of the second heat transfer member 294b is 428 [W/mK].

Thus, the thermal conductivity of the second heat conductor 294b is higher than that of the first heat conductor 294a. In other words, the one-end heat transfer portion 294 increases in height from the side close to the center heat transfer portion 96 toward the side away from the center heat transfer portion 96 . The other end side heat transfer section 298 has a similar configuration, and the other end side heat transfer section 298 is formed of a first heat transfer body 298a and a second heat transfer body 298b.

In this configuration, when a toner image is fixed on the sheet member P2 of the minimum size, the heat of the heat generating plate 64 generated in the area F01 is transferred to the one end side heat transfer portion 294 and the other end side heat transfer portion 294 as shown in FIG. It is transmitted to the first heat transfer bodies 294a, 298a or the second heat transfer bodies 294b, 298b of the heat transfer section 298 (see arrow G41 in the figure).

Also, the heat transmitted to the second heat conductors 294b and 298b is transmitted to the first heat conductors 294a and 298a (arrow G42 in the drawing). Furthermore, the heat transmitted from the second heat conductors 294b, 298b to the first heat conductors 294a, 298a and the heat transmitted from the heating plate 64 to the first heat conductors 294a, 298a are The heat is transmitted to the central heat transfer portion 96 so that the temperature difference between the other end heat transfer portion 298 and the central heat transfer portion 96 is reduced (arrow G43 in the drawing).

Furthermore, the heat transmitted to the central heat transfer portion 96 is transmitted to the heat generating plate 64 in the area F02 (see arrow G44 in the drawing). Then, the temperature of the heating plate 64 becomes uniform.

As described above, the thermal conductivity of the second heat conductors 294b, 298b is higher than that of the first heat conductors 294a, 294a. For this reason, compared to the case where the thermal conductivity of the second heat conductor is the same as the thermal conductivity of the first heat conductor, the second heat conductors 294b and 298b apart from the central heat conductor 96 are The speed at which heat is transferred to the central heat transfer portion 96 increases.

As a result, compared to the case where the thermal conductivity of the second heat conductor is the same as the thermal conductivity of the first heat conductor, power consumption is suppressed when fixing an image on a minimum size recording medium.

Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to such embodiments, and various other embodiments are possible within the scope of the present invention. It is clear to those skilled in the art. For example, in the above-described embodiment, the central heat transfer sections 96 and 196 are arranged in the range (range F02) through which the sheet member P2 passes in the device depth direction, but the central heat transfer section is arranged in the device depth direction ( (axis direction), it may be arranged in a range through which at least the sheet member P2 passes, and may be larger than the range F02. However, from the viewpoint of suppressing power consumption when fixing an image on the sheet member P of the minimum size, if the length of the range F02 in the depth direction of the apparatus is set to 10, the center in the depth direction of the apparatus is aligned (center allocation d), the length of the central heat transfer portion in the device depth direction is preferably 16 or less, more preferably 14 or less, and particularly preferably 12 or less.

Moreover, although not specifically described in the first and third embodiments, the central heat transfer portion 96 may be integrally formed of a metal material other than aluminum. For example, the central heat transfer section may be made of copper. In this case, the thermal conductivity of the central heat transfer portion is 403 [W/mK].

Further, in the first and second embodiments, the heat transfer characteristics of the one end side heat transfer portion 94 and the other end side heat transfer portion 98 were anisotropic, but the heat transfer characteristics were isotropic. good too. It is sufficient that the thermal conductivity of the one end heat transfer portion and the other end heat transfer portion in the depth direction of the device is higher than the heat conductivity of the central heat transfer portions 96 and 196 in the depth direction of the device. However, in this case, the effect of the anisotropic heat transfer characteristics of the one end heat transfer portion 94 and the other end heat transfer portion 98 is not exhibited.

In addition, in the third embodiment, the first heat conductors 294a and 298a are integrally formed of gold, and the second heat conductors 294b and 298b are integrally formed of silver. A member formed by laminating PGS graphite sheets in the thickness direction may be used as the body, and a member formed by laminating carbon nanotube sheet materials in the thickness direction may be used as the second heat transfer member.

Further, in the above-described third embodiment, the one end side heat transfer section 294 and the other end side heat transfer section 298 are divided into two in the device depth direction, but may be divided into three or more. It is sufficient that the heat conductivity in the device depth direction increases from the side close to the central heat transfer section 96 toward the side away from the central heat transfer section 96 .

Further, in the above embodiment, the detection member 82 detects the temperature of the heating plate 64 via the heat transfer member 92, but the detection member is brought into direct contact with the heating plate so that the detection member directly detects the temperature of the heating plate. You may

Further, in the above embodiment, the center registration method has been described as an example, but a side registration method using one end of the sheet member P in the width direction as a reference may also be used.

10 image forming device 18 image forming unit (an example of a forming unit)
50 fixing device 52 pressure roll (an example of a pressure unit)
62 endless belt 64 heating plate 82 detection member 92 heat transfer member (an example of a heat transfer section)
94 One end side heat transfer section (second heat transfer section)
94a Sheet material 96 Central side heat transfer section (first heat transfer section)
98 other end side heat transfer section (second heat transfer section)
102 control unit
150 fixing device 192 heat transfer member (an example of heat transfer section)
196 central heat transfer section (first heat transfer section)
250 fixing device 292 heat transfer member (an example of heat transfer section)
294 one end side heat transfer section (second heat transfer section)
298 other end side heat transfer section (second heat transfer section)
F02 range (minimum range)

Claims (5)

an endless belt that rotates in the circumferential direction;
a heating plate that extends in the axial direction of the endless belt and that is in contact with the inner peripheral surface of the endless belt and generates heat when a voltage is applied;
a detection unit that detects the temperature of the heating plate;
a pressure unit disposed on the opposite side of the heat generating plate with the endless belt interposed therebetween for pressing the conveyed recording medium against the outer peripheral surface of the endless belt;
A first heat transfer portion that is in contact with the back surface of the heat generating plate and transfers heat of the heat generating plate in the axial direction, the first heat transfer portion being arranged in a minimum range in which at least a minimum size recording medium passes in the axial direction. a second heat transfer portion which is arranged next to the first heat transfer portion in the axial direction and has a higher thermal conductivity in the axial direction than the first heat transfer portion in the axial direction; the heat transfer section having a heat transfer section;
a control unit that controls the voltage applied to the heating plate so that the temperature of the heating plate falls within a predetermined range based on the detection result of the detection unit ;
The thermal conductivity of the first heat transfer portion in the thickness direction of the heat generating plate is higher than the thermal conductivity of the second heat transfer portion in the thickness direction,
The first heat transfer part has an anisotropic heat transfer characteristic,
The fixing device , wherein the heat conductivity of the first heat transfer portion in the thickness direction is higher than the heat conductivity of the first heat transfer portion in the axial direction . 2. The fixing device according to claim 1, wherein the heat conductivity of the second heat transfer portion in the axial direction is higher than the heat conductivity of the second heat transfer portion in the thickness direction of the heat generating plate. 3. The fixing device according to claim 2, wherein the second heat transfer section is formed by stacking a plurality of sheet materials in the thickness direction. The second heat transfer section is divided in the axial direction and formed of a plurality of members having different heat transfer characteristics,
4. The thermal conductivity of the second heat transfer portion in the axial direction increases from a side close to the first heat transfer portion toward a side away from the first heat transfer portion. 1. The fixing device according to claim 1. 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 4 , which fixes an image formed on a recording medium to the recording medium;
image forming apparatus.

Images