JP2023086090A - Nip forming unit and image forming apparatus - Google Patents

Abstract

To optimize the interval between a fixing belt and a separating member with a simple configuration.SOLUTION: A nip forming unit has: a rotatable flexible endless belt (fixing belt 20); a nip forming member (heater 22) that is provided contactable with an inner peripheral surface of the endless belt; a pressure member (pressure roller 21) that is in pressure contact with the nip forming member with the endless belt therebetween to form a nip; and guide members (flanges 400) that guide both ends of the endless belt, wherein a body to be conveyed is conveyed through the nip. The nip forming unit includes a separating member (separating plate 310) that separates the body to be conveyed passing through the nip from the endless belt, and the separating member has a non-contact part (leading end 311) that is not in contact with the endless belt, and a contact part 313 that is in contact with the endless belt to maintain the interval between the non-contact part and the endless belt to a predetermined size.SELECTED DRAWING: Figure 9A

Description

The present invention relates to a nip forming unit provided with a separating member for separating a conveyed object that has passed through a nip from an endless belt, and an image forming apparatus provided with the nip forming unit.

2. Description of the Related Art In image forming apparatuses such as copiers and printers, a belt-type fixing device using an endless belt is known as a fixing device for fixing an image formed on a recording medium such as paper (see, for example, Patent Documents 1: See JP-A-2015-011167).

The fixing device disclosed in Japanese Patent Application Laid-Open No. 2002-200012 separates a sheet from the fixing belt with a sheet separation plate arranged close to the fixing belt. When using the paper separation plate in this way, if the gap between the fixing belt and the paper separation plate is too small, the paper separation plate will come into contact with the fixing belt and easily damage the belt, which can cause abnormal images. Become.

Also, if the gap between the fixing belt and the paper separation plate is too large, the paper passes through this large gap and winds around the fixing belt, easily causing a paper jam. Therefore, it is necessary to bring the paper separating plate as close to the fixing belt as possible without contacting the fixing belt.

In the fixing device of Patent Document 1, the separation plate moving mechanism optimizes the above-mentioned spacing, but the separation plate moving mechanism has a problem that the drive unit for driving the separation plate and various sensors make the structure complicated and costly. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to optimize the distance between the endless belt and the separation member with a simple structure, thereby improving the separation of the conveyed object from the endless belt.

In order to solve the above-mentioned problems, the nip forming unit of the present invention includes a rotatable flexible endless belt, a nip forming member provided so as to be in contact with the inner peripheral surface of the endless belt, and a nip forming unit via the endless belt. A nip forming unit that has a pressure member that presses against the nip forming member to form a nip, and a guide member that guides both end portions of the endless belt. wherein the separation member separates the transported object that has passed through the nip from the endless belt, and the separation member includes a non-contact portion that does not contact the endless belt and the non-contact portion that contacts the endless belt. and a contact portion for maintaining a predetermined distance between the portion and the endless belt.

ADVANTAGE OF THE INVENTION According to this invention, the space|interval between an endless belt and a separating member can be optimized, and the separability of a to-be-conveyed object from an endless belt can be improved by this.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention; FIG. 2 is a schematic configuration diagram of a fixing device; FIG. It is a perspective view of a heater, a heater holder, and a guide part. It is a top view of a heater. It is a figure which shows the electric power supply circuit to a heater. 4 is a flow chart showing a heater control operation; 1 is a conceptual diagram of a fixing device having a paper separation mechanism; FIG. 4 is a plan view of the paper separation mechanism; FIG. 4 is a plan view of the paper separation mechanism; FIG. FIG. 4 is a plan view of a deformed separation plate of the paper separation mechanism; FIG. 4 is a perspective view of a deformed separation plate of the paper separation mechanism; FIG. 4 is a plan view of a deformed separation plate of the paper separation mechanism; FIG. 4 is a diagram of tensioning the belt with flanges that hold the ends of the fuser belt. It is a figure which shows the positional relationship of a flange and a heater holder. 4 is a side view of the paper separation mechanism; FIG. FIG. 4 is a side view of the sheet separation mechanism with tension springs; 3 is an exploded perspective view of the paper separation mechanism; FIG. 2 is a side view of a fixing device having a paper separation mechanism; FIG. FIG. 10 is a side view of the fixing device in which a paper jam has occurred; FIG. 3 is a side view of the fixing device showing a state in which paper is pulled out; FIG. 10 is a side view of the fixing device when the fixing belt is moved with pressure removed; FIG. 3 is a plan view of the fixing device for explaining the pressure release amount of the fixing belt; 2 is a perspective view of a fixing device; FIG. 4 is a perspective view of one end cut out from the fixing belt; FIG. 4 is a developed plan view of one end cut out from the fixing belt; FIG. FIG. 4 is a side view showing slackness of the fixing belt; FIG. 4 is a side view showing slackness of the fixing belt; FIG. 5 is a side view showing a method of measuring the sagging rate of the fixing belt; FIG. 5 is a side cross-sectional view showing a schematic configuration of a fixing device according to another embodiment of the invention; It is a perspective view of a heater, a 1st high thermal conductivity member, and a heater holder. It is a top view of a heater which shows arrangement|positioning of a 1st high heat-conduction member. 15 is a side cross-sectional view showing a schematic configuration of a fixing device of an embodiment different from FIG. 14; FIG. It is a perspective view of a heater, a first high thermal conductivity member, a second high thermal conductivity member, and a heater holder. FIG. 4 is a plan view of the heater showing the arrangement of the first high thermal conductivity member and the second high thermal conductivity member; FIG. 16 is a plan view showing a heater in which the arrangement of the second high thermal conductivity member is different from that in FIG. 15; 18 is a side cross-sectional view showing a schematic configuration of a fixing device of an embodiment different from FIGS. 14 and 17; FIG. FIG. 10 is a plan view of the heater showing another example of the arrangement of the first high thermal conductivity member; FIG. 10 is a plan view of the heater showing still another example of the arrangement of the first high thermal conductivity member; FIG. 4 is a plan view of the heater showing an enlarged segmented area; FIG. 4 is a diagram showing a configuration of a fixing device different from that of the embodiment; FIG. 26 is a perspective view of the heater, the first high thermal conductivity member, the second high thermal conductivity member, and the heater holder shown in FIG. 25; It is a top view of a heater which shows arrangement|positioning of a 1st high heat-conductivity member and a 2nd high heat-conductivity member. FIG. 10 is a plan view of the heater showing another example of the arrangement of the first high thermal conductivity member and the second high thermal conductivity member; FIG. 11 is a plan view of the heater showing still another example of the arrangement of the second high thermal conductivity member; FIG. 4 is a diagram showing a configuration of a fixing device different from that of the embodiment; 1 is a diagram showing the atomic crystal structure of graphene; FIG. 1 is a diagram showing the atomic crystal structure of graphite; FIG. FIG. 5 is a side cross-sectional view of a fixing device showing a modification of the thermistor arrangement; FIG. 5 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. FIG. 5 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. FIG. 5 is a side cross-sectional view showing a schematic configuration of a fixing device different from the above. FIG. 2 is a schematic configuration diagram of an image forming apparatus different from FIG. 1; 1 is a side sectional view showing a schematic configuration of a fixing device according to an embodiment of the invention; FIG. 18 is a plan view of a heater in the fixing device of FIG. 17; FIG. It is a perspective view of a heater and a heater holder. It is a perspective view which shows the attachment state of the connector with respect to a heater. It is a figure which shows arrangement|positioning of a thermistor and a thermostat. It is a figure which shows the groove part of a flange.

The present invention will be described below with reference to the accompanying drawings. In addition, in each drawing for explaining the present invention, constituent elements such as members and constituent parts having the same function or shape are denoted by the same reference numerals as much as possible, and once explained, the explanation thereof will be omitted. omitted.

(● Image forming equipment)
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to one embodiment of the present invention. The image forming apparatus 100 shown in FIG. 1 includes four image forming units 1Y, 1M, 1C, and 1Bk detachable from the main body of the image forming apparatus.

Each of the image forming units 1Y, 1M, 1C, and 1Bk has the same configuration except that it contains developers of different colors of yellow, magenta, cyan, and black corresponding to color separation components of a color image. Specifically, each of the image forming units 1Y, 1M, 1C, and 1Bk includes a drum-shaped photoreceptor 2 as an image carrier, a charging device 3 that charges the surface of the photoreceptor 2, and A developing device 4 that supplies toner as a developer to form a toner image and a cleaning device 5 that cleans the surface of the photoreceptor 2 are provided.

The image forming apparatus 100 also includes an exposure device 6 that exposes the surface of each photoreceptor 2 to form an electrostatic latent image, a paper feed device 7 that supplies paper P as a transported body or recording medium, and each photoreceptor. A transfer device 8 for transferring the toner image formed on the body 2 to the paper P, a fixing device 9 as a nip forming unit for fixing the toner image transferred to the paper P, and a paper discharge for discharging the paper P outside the apparatus. an apparatus 10; Recording media include paper P (plain paper), thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, plastic film, prepreg, copper foil, and the like. included.

The transfer device 8 includes an endless intermediate transfer belt 11 as an intermediate transfer body stretched by a plurality of rollers, and four primary transfer members for transferring the toner images on the photoreceptors 2 to the intermediate transfer belt 11. It has a primary transfer roller 12 and a secondary transfer roller 13 as a secondary transfer member for transferring the toner image transferred onto the intermediate transfer belt 11 onto the paper P. Each of the primary transfer rollers 12 is in contact with the photoreceptor 2 via the intermediate transfer belt 11 .

As a result, the intermediate transfer belt 11 and each photoreceptor 2 come into contact with each other, forming a primary transfer nip therebetween. On the other hand, the secondary transfer roller 13 is in contact with one of the rollers that stretch the intermediate transfer belt 11 through the intermediate transfer belt 11 . A secondary transfer nip is thereby formed between the secondary transfer roller 13 and the intermediate transfer belt 11 .

Further, in the image forming apparatus 100, a paper transport path 14 is formed for transporting the paper P fed from the paper feeding device 7. As shown in FIG. A pair of timing rollers 15 are provided on the paper transport path 14 from the paper feeding device 7 to the secondary transfer nip (secondary transfer roller 13).

Next, the printing operation of the image forming apparatus will be described with reference to FIG.

When there is an instruction to start the printing operation, in each of the image forming units 1Y, 1M, 1C, and 1Bk, the photoreceptor 2 is driven to rotate clockwise in FIG. charged to a potential. Next, the exposure device 6 exposes the surface of each photoreceptor 2 based on the image information of the document read by the document reading device or the print information instructed to print from the terminal, and the potential of the exposed portion increases. It lowers to form an electrostatic latent image. Toner is supplied from the developing device 4 to the electrostatic latent image, and a toner image is formed on each photosensitive member 2 .

When the toner image formed on each photoreceptor 2 reaches the primary transfer nip (the position of the primary transfer roller 12) as each photoreceptor 2 rotates, the intermediate transfer belt rotates counterclockwise in FIG. 11 so as to overlap one another. Then, the toner image transferred onto the intermediate transfer belt 11 is conveyed to the secondary transfer nip (the position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates, and is conveyed in the secondary transfer nip. It is transferred to the paper P.

This paper P is supplied from the paper feeding device 7 . The paper P supplied from the paper feeding device 7 is temporarily stopped by the timing roller 15, and then conveyed to the secondary transfer nip at the timing when the toner image on the intermediate transfer belt 11 reaches the secondary transfer nip. Thus, the paper P bears a full-color toner image. After the toner image is transferred, toner remaining on each photosensitive member 2 is removed by each cleaning device 5 .

The paper P onto which the toner image has been transferred is conveyed to the fixing device 9 , and the toner image is fixed on the paper P by the fixing device 9 . After that, the paper P is discharged outside the apparatus by the paper discharging device 10, and a series of printing operations is completed.

(● Fixing device)
Next, an embodiment of a fixing device as a nip forming unit will be described. As shown in FIG. 2, the fixing device 9 according to the present embodiment includes a fixing belt 20 made of an endless belt and a pressing member as a facing member that contacts the outer peripheral surface of the fixing belt 20 to form a fixing nip N. A roller 21 , a heater 22 as a heating member for heating the fixing belt 20 , a heater holder 23 as a holding member for holding the heater 22 , a stay 24 as a support member for supporting the heater holder 23 , and the temperature of the fixing belt 20 is measured. A thermistor 25 or the like is provided as temperature detecting means for detecting.

The fixing belt 20 has, for example, a cylindrical substrate made of polyimide (PI) having an outer diameter of 25 mm and a thickness of 40 to 120 μm. As the outermost layer of the fixing belt 20, a release layer having a thickness of 5 to 50 μm is formed of a fluorine-based resin such as PFA or PTFE in order to increase durability and ensure release properties.

An elastic layer made of rubber or the like having a thickness of 50 to 500 μm may be provided between the substrate and the release layer. Further, the substrate of the fixing belt 20 is not limited to polyimide, and may be a heat-resistant resin such as PEEK, or a metal substrate such as nickel (Ni) or SUS. The inner peripheral surface of the fixing belt 20 may be coated with polyimide, PTFE, or the like as a sliding layer.

The pressure roller 21 has an outer diameter of 25 mm, for example, and comprises a solid iron core 21a, an elastic layer 21b formed on the surface of the core 21a, and a release layer formed on the outer side of the elastic layer 21b. 21c. The elastic layer 21b is made of silicone rubber and has a thickness of 3.5 mm, for example. In order to improve the releasability of the surface of the elastic layer 21b, it is desirable to form a release layer 21c of a fluorine resin layer having a thickness of about 40 μm, for example.

The pressing roller 21 is pressed against the heater 22 via the fixing belt 20 by pressing the pressing roller 21 toward the fixing belt 20 by the pressing means. Thereby, a fixing nip N is formed between the fixing belt 20 and the pressure roller 21 . Further, the pressure roller 21 is configured to be rotationally driven by a driving means, and when the pressure roller 21 rotates in the direction of the arrow in FIG. 2, the fixing belt 20 is driven to rotate accordingly.

The heater 22 is a planar heating member provided longitudinally across the width direction of the fixing belt 20, and includes a plate-like base material 30, a resistance heating element 31 provided on the base material 30, and a resistor. It is composed of an insulating layer 32 covering the heating element 31 and the like. The heater 22 is in contact with the inner peripheral surface of the fixing belt 20 on the insulating layer 32 side, and the heat generated from the resistance heating element 31 is transmitted to the fixing belt 20 via the insulating layer 32 . be.

In this embodiment, the resistance heating element 31 and the insulating layer 32 are provided on the fixing belt 20 side (fixing nip N side) of the base material 30 . may be provided on the heater holder 23 side. In that case, the heat of the resistance heating element 31 is transmitted to the fixing belt 20 through the substrate 30, so the substrate 30 is preferably made of a material with high thermal conductivity such as aluminum nitride. Further, by configuring the base material 30 with a material having good thermal conductivity, the fixing belt 20 can be sufficiently heated even when the resistance heating element 31 is arranged on the opposite side of the base material 30 from the fixing belt 20 side. is possible.

The heater holder 23 and the stay 24 are arranged inside the fixing belt 20 . The stay 24 is made of a metal channel material, and both end portions of the stay 24 are supported by both side plates of the fixing device 9 . Since the heater holder 23 and the heater 22 held by the heater holder 23 are supported by the stay 24 , the pressure roller 21 is pressed against the fixing belt 20 , and the heater 22 reliably presses the pressure roller 21 . The fixing nip N is stably formed by receiving it.

Since the heater holder 23 is likely to reach a high temperature due to the heat of the heater 22, it is desirable to be made of a heat-resistant material. For example, when the heater holder 23 is made of a heat-resistant resin having low thermal conductivity such as LCP, heat transfer from the heater 22 to the heater holder 23 is suppressed, and the fixing belt 20 can be efficiently heated.

Further, in order to reduce the contact area of the heater holder 23 with the heater 22 and reduce the amount of heat transferred from the heater 22 to the heater holder 23, the heater holder 23 is in contact with the base material 30 of the heater 22 via the protrusions 23a. Further, as in the present embodiment, the protrusion 23a of the heater holder 23 is brought into contact with the substrate 30 other than the back side of the location where the resistance heating element 31 is arranged, i.e., avoiding the location where the temperature of the substrate 30 tends to rise. By doing so, the amount of heat transmitted to the heater holder 23 can be further reduced, and the fixing belt 20 can be efficiently heated.

Further, the heater holder 23 is provided with a guide portion 26 for guiding the fixing belt 20 . The guide portions 26 are provided on the upstream side (the lower side of the heater 22 in FIG. 2) and the downstream side (the upper side of the heater 22 in FIG. 2) in the belt rotation direction of the heater 22, respectively.

Further, as shown in FIG. 3, a plurality of guide portions 26 on the upstream side and the downstream side are arranged at intervals in the longitudinal direction (belt width direction) of the heater 22 . Each guide portion 26 is formed in a substantially sector shape, and has an arcuate or convex curved belt facing surface 260 extending in the belt circumferential direction so as to face the inner peripheral surface of the fixing belt 20 (FIG. 2). reference). Further, as shown in FIG. 3, in the present embodiment, the width W of the guide portions 26 arranged at both ends in the longitudinal direction of the heater 22 is formed larger than the width W of the other guide portions 26, and each guide portion 26, the width W, the length in the belt circumferential direction (peripheral length) L, and the height E are formed to be the same.

In the fixing device 9 according to this embodiment, when the printing operation is started, the pressure roller 21 is driven to rotate, and the fixing belt 20 starts to rotate. At this time, the inner peripheral surface of the fixing belt 20 is guided by the belt facing surface 260 of the guide portion 26, so that the fixing belt 20 rotates stably and smoothly.

Further, the fixing belt 20 is heated by supplying electric power to the resistance heating element 31 of the heater 22 . Then, when the temperature of the fixing belt 20 reaches a predetermined target temperature (fixing temperature), the sheet P bearing the unfixed toner image is moved between the fixing belt 20 and the pressure roller 21 as shown in FIG. (fixing nip N), the unfixed toner image is heated and pressurized to be fixed on the paper P. As shown in FIG.

(● Heater configuration)
FIG. 4 is a plan view of the heater according to this embodiment. As shown in FIG. 4, the heater 22 according to this embodiment has a plurality of resistance heating elements 31 spaced apart in the longitudinal direction (belt width direction). In other words, the plurality of resistance heating elements 31 constitute a plurality of heating portions 35 divided in the belt width direction. The heat-generating portion 35 can be divided into at least three or four or more of end heaters that heat both ends and a central heater that heats the central portion.

Each resistance heating element 31 is electrically connected in parallel to a pair of electrode portions 34 provided at both ends in the longitudinal direction of the base material 30 via power supply lines 33 . The power supply line 33 is composed of a conductor having a resistance value smaller than that of the resistance heating element 31 .

From the viewpoint of ensuring insulation between the resistance heating elements 31, the gap between the resistance heating elements 31 adjacent to each other is preferably 0.2 mm or more, more preferably 0.4 mm or more. In addition, if the gap between the resistance heating elements 31 adjacent to each other is too large, the temperature in the gap tends to decrease. Therefore, from the viewpoint of suppressing temperature unevenness in the longitudinal direction, the gap is preferably 5 mm or less, and 1 mm or less. is more preferred.

The resistance heating element 31 is made of a material having a PTC (Positive Temperature Coefficient of Resistance) characteristic, and is characterized by an increase in resistance (a decrease in heater output) as the temperature rises. Due to this feature, for example, when a sheet of paper having a width smaller than the entire width of the heating portion 35 is passed through, the heat of the fixing belt 20 is not taken away by the sheet in the area outside the width of the sheet. The temperature of 31 rises.

Since the voltage applied to the resistance heating element 31 is constant, the temperature of the resistance heating element 31 outside the paper width rises, and when the resistance value rises, the output (calorific value) decreases relatively, and the edge temperature rises. is suppressed. In addition, by electrically connecting the plurality of resistance heating elements 31 in parallel, it is possible to suppress the temperature rise in the non-sheet passing portion while maintaining the printing speed.

It should be noted that the heating element forming the heating portion 35 may be other than the resistance heating element having the PTC characteristic. Also, the heating elements may be arranged in a plurality of rows in the lateral direction of the heater 22 .

The resistance heating element 31 can be formed by, for example, applying a paste prepared by mixing silver palladium (AgPd) or glass powder to the base material 30 by screen printing or the like, and then firing the base material 30. . In this embodiment, the resistance value of the resistance heating element 31 is 80Ω at room temperature.

As the material of the resistance heating element 31, a silver alloy (AgPt) or a resistance material such as ruthenium oxide (RuO2) may be used in addition to the materials described above. Silver (Ag) or silver palladium (AgPd) can be formed by screen printing or the like as the material of the power supply line 33 and the electrode portion 34 .

As the material of the base material 30, ceramics such as alumina and aluminum nitride which are excellent in heat resistance and insulation, and non-metallic materials such as glass and mica are preferable. In this embodiment, an alumina substrate having a short width of 8 mm, a long width of 270 mm, and a thickness of 1.0 mm is used.

Alternatively, the base material 30 may be formed by laminating an insulating material on a conductive material such as metal. As the metal material, aluminum, stainless steel, or the like is preferable because of its low cost. Further, in order to improve the heat uniformity of the heater 22 and improve the image quality, the base material 30 may be made of a material having a high thermal conductivity such as copper, graphite, or graphene.

The insulating layer 32 is made of heat-resistant glass with a thickness of 75 μm, for example. The insulating layer 32 covers the resistance heating element 31 and the power supply line 33 to insulate and protect them, and maintains slidability with the fixing belt 20 .

FIG. 5 is a diagram showing a power supply circuit to the heater according to this embodiment.

As shown in FIG. 5, in this embodiment, a power supply circuit for supplying power to each resistance heating element 31 is configured by electrically connecting an AC power source 200 and the electrode portion 34 of the heater 22. there is The power supply circuit is also provided with a triac 210 that controls the amount of power supplied.

The amount of power supplied to each resistance heating element 31 is controlled by the control unit 220 through the triac 210 based on the temperature detected by the thermistor 25 as temperature detection means. The control unit 220 is composed of a microcomputer including a CPU, ROM, RAM, I/O interface, and the like.

In this embodiment, a thermistor 25 as a temperature detecting means is arranged in the longitudinal central region of the heater 22 within the minimum paper passing width and in one longitudinal end of the heater 22 . Further, a thermostat 27 is arranged at one end in the longitudinal direction of the heater 22 as power cutoff means for cutting off the power supply to the resistance heating element 31 when the temperature of the resistance heating element 31 exceeds a predetermined temperature. ing. The thermistor 25 and the thermostat 27 contact the back surface of the base material 30 (the side opposite to the side where the resistance heating element 31 is arranged) to detect the temperature of the resistance heating element 31 .

Next, the control operation of the heater according to this embodiment will be described with reference to the flowchart of FIG. First, when a printing operation is started in the image forming apparatus (S1 in FIG. 6), power supply from the AC power source 200 to each resistance heating element 31 of the heater 22 is started by the control unit 220 (S2 in FIG. 6). .

As a result, each resistance heating element 31 starts to generate heat, and the fixing belt 20 is heated. At this time, the temperature T4 of the resistance heating element 31 positioned in the central region of the heater 22 is detected by the thermistor (central thermistor) 25 disposed in the longitudinal central region of the heater 22 (S3 in FIG. 6). Then, based on the temperature T4 obtained from the central thermistor 25, the control unit 220 controls the amount of electric power supplied to each resistance heating element 31 by the triac 210 so that each resistance heating element 31 reaches a predetermined temperature ( S4 in FIG. 6).

At the same time, the temperature T8 of the resistance heating element 31 is also detected by the thermistor (end thermistor) 25 arranged at the longitudinal end of the heater 22 (S5 in FIG. 6). Then, it is determined whether or not the temperature T8 detected by the end thermistor 25 is equal to or higher than a predetermined temperature TN (T8≧TN) (S6 in FIG. 6). As a result, the power supply to the heater 22 is cut off (S7 in FIG. 6), and an error display is displayed on the operation panel of the image forming apparatus (S8 in FIG. 6). On the other hand, if the detected temperature T8 is equal to or higher than the predetermined temperature TN, the printing operation is started assuming that there is no abnormally low temperature (S9 in FIG. 6).

In the unlikely event that temperature control based on detection by the central thermistor 25 becomes impossible due to breakage or disconnection of the resistance heating elements 31, the other resistance heating elements 31 including the resistance heating elements 31 at the ends in the longitudinal direction An abnormally high temperature may occur. In that case, the thermostat 27 operates to cut off the power supply to the resistance heating element 31 when the temperature of the resistance heating element 31 exceeds a predetermined temperature, thereby preventing the resistance heating element 31 from becoming abnormally hot. .

(Paper separation mechanism)
FIG. 7A is a conceptual diagram of a fixing device provided with a paper separating mechanism 300 that separates the paper that has passed through the fixing nip from the fixing belt 20. FIG. The paper separation mechanism 300 has a separation plate 310 as a paper separation member, and the separation plate 310 separates the paper from the fixing belt 20 . The separation plate 310 is arranged so as to be movable toward and away from the fixing belt 20 as will be described later.

The heater 22 and the heater holder 23 as nip forming members move between the approach position where the fixing nip is pressed by the pressure roller 21 with respect to the pressure roller 21 and the separated position where the fixing nip is released. It is disposed so as to be movable in the horizontal direction in FIG. 7A. The heater 22 and the heater holder 23 are configured to be movable to the separated position while the separation plate 310 is restricted in rotation by a first restriction portion of a rotation restriction hole 321, which will be described later.

The separation plate 310 extends parallel to the axial direction of the fixing belt 20 and has contact portions 313 at both ends in the longitudinal direction thereof, the contact portions 313 coming into contact with the outer peripheral surface of the fixing belt 20 . The contact portions 313 contact the outer circumferential surfaces of both ends of the fixing belt 20 in the axial direction, thereby regulating the gap between the separation plate 310 and the fixing belt 20 to a predetermined size.

The fixing belt 20 is slidably supported at both ends in the axial direction by flanges 400 as guide members. The flanges 400 are ring-shaped, and are slidably fitted to the inner circumferences of both ends of the fixing belt 20 in the axial direction. Thereby, the rotation of the fixing belt 20 is guided by the flange 400 .

As shown in FIG. 7B, a gap (backlash) C is generally formed between the inner peripheral surface of both ends of the fixing belt 20 in the axial direction and the outer peripheral surface of the flange 400 . The presence of this gap C enables the fixing belt 20 to smoothly run around.

However, if the fixing belt 20 and the pressure roller 21 are out of parallel, the fixing belt 20 may follow the pressure roller 21 and be inclined with respect to the flange 400 . As a result, the revolving running performance of the fixing belt 20 becomes unstable, which may cause a paper jam.

In the embodiment of the present invention, at least one of the contact portions 313 at both ends in the longitudinal direction of the separation plate 310 is brought into contact with the outer peripheral surface of at least one end of the fixing belt 20 as shown in FIGS. Inclination (parallelism deviation) of the fixing belt 20 is suppressed, and circulation running performance of the fixing belt 20 is stabilized. The position of the contact portion 313 can be a position facing the flange 400 in the radial direction of the fixing belt 20 as shown in FIGS. 7Ba and 7Bb. By doing so, the rattling amount of the fixing belt 20 can be minimized.

Specifically, in FIG. 7B, the separation plate 310 is positioned relatively apart from the fixing belt 20 or the flange 400 . Therefore, one (left) contact portion 313 of the separation plate 310 is in contact with the outer peripheral surface of the end portion of the fixing belt 20 , but the opposite contact portion 313 is separated from the outer peripheral surface of the end portion of the fixing belt 20 . ing.

Therefore, a relatively large gap is generated between the outer peripheral surface of the fixing belt 20 and the tip portion 311 of the separating plate 310 as a non-contact portion that does not contact the fixing belt 20 . If there is such a large gap, the paper passes through the gap and winds around the fixing belt 20, which easily causes a paper jam.

Therefore, the separation plate 310 is brought closer to the fixing belt 20 as shown in FIG. As a result, the contact portions 313 at both ends of the separation plate 310 approach the left and right flanges 400 while being in contact with the outer peripheral surfaces at both ends of the fixing belt 20 .

In FIG. 7B , the backlash C between the flange 400 and the fixing belt 20 increases the inclination (parallelism deviation) of the fixing belt 20 with respect to the axis of the flange 400 , destabilizing the circular running performance of the fixing belt 20 . However, when the contact portions 313 at both ends of the separation plate 310 are brought closer to the left and right flanges 400 as shown in FIG. can do.

In the state of FIG. 7Bb, a relatively large play C is formed on the lower side of the left and right flanges 400, but since the contact portions 313 at both ends of the separation plate 310 are close to the left and right flanges 400, backlash C is small. Therefore, the inclination (parallelism deviation) of the fixing belt 20 does not become large and the circular running performance of the fixing belt 20 does not become unstable.

Next, deformation (elastic deformation) of the separation plate 310 will be described with reference to FIGS. 7Bc to 7Be. Although the separation plate 310 is made of a heat-resistant metal such as stainless steel, it is easily deformed due to its thin plate thickness. Therefore, when the separation plate 310 is brought closer to the fixing belt 20 as shown in FIGS. may be displaced to the downstream side in the rotation direction (back side of the paper surface).

Further, even if the separation plate 310 is not brought closer to the fixing belt 20 as shown in FIG. Similarly, one of the left and right contact portions 313 may be dragged by the rotation of the fixing belt 20 and displaced to the downstream side in the rotation direction (back side of the paper surface of FIG. 7Bc). As a result, the separation plate 310 is twisted in the longitudinal direction or buckled (elastic buckling) in the lateral direction, as shown at T in FIGS. 7Bc and 7Bd.

However, even if the separation plate 310 deforms (elastic deformation) in this way, the left and right contact portions 313 of the separation plate 310 contact the fixing belt 20 as shown in FIG. It is possible to maintain a constant “small gap” with the outer peripheral surface of the fixing belt 20 . The size of this "small gap" is always constant in the axial direction of the fixing belt 20 even if the size of the backlash C on the left and right sides of the fixing belt 20 fluctuates, so paper jams can be effectively prevented. .

Section T in FIG. 7Be corresponds to section T in FIGS. 7Bc and 7Bd. In this T portion, the backlash C (small) between the flange 400 and the fixing belt 20 is approximately the same as the backlash C (small) on the opposite side in the illustrated example, but the contact portion 313 of the separation plate 310 is the contact portion of the fixing belt 20 . By pushing the end, the backlash C on the upper side is further reduced and the backlash C on the opposite side is increased. As a result, the inclination of the fixing belt 20 is reduced, and an effect that damage to the end portion of the belt due to the belt shift in the axial direction is less likely to occur can be obtained.

It is known that increasing the curvature of the fixing belt 20 on the fixing nip exit side is effective in improving the separability of the paper from the fixing belt 20 . Therefore, as shown in FIG. 7C, the nip forming member NF holding the heater is made shorter than the length of the fixing belt 20 in the axial direction, and the flange 400 is moved away from the fixing nip as indicated by the arrow to pull the fixing belt 20 . As a result, the curvature of the fixing belt 20 increases on the fixing nip outlet side and the fixing nip inlet side over the entire length of the fixing belt 20 in the axial direction, and the sheet separation property is improved.

On the other hand, as shown in FIG. 7D, when the nip forming member SH including the planar heater is longer than the axial length of the fixing belt 20 and protrudes from both ends of the fixing belt 20 in the axial direction, the flange 400 is separated from the fixing nip. If you try to pull the fixing belt 20, the fixing belt 20 may be over tensioned. If the tension is applied to the fixing belt 20 too much, the inner surface of the fixing belt 20 may be worn, or the fixing belt 20 may slip due to an increase in the sliding load, resulting in poor paper transport.

In addition, if the fixing belt 20 is excessively tensioned, a problem also arises in the ease of assembly of the fixing unit. Therefore, the radial size of the flange 400 and the nip forming member SH is set to be small so that the inner surface of the fixing belt 20 has play. As a result, there is a limit to increasing the curvature of the fixing belt 20 on the exit side of the fixing nip, and there remains a problem in improving the paper separability. According to the embodiments of the present invention, such problems can also be solved.

FIG. 8A shows a specific embodiment of the sheet separation mechanism 300 and the separation plate 310. FIG. In this embodiment, the separation plate 310 is rotatably arranged around the support shaft 322 . That is, the separation plate 310 is arranged so that the leading end portion 311 of the separation plate 310 can rotate in a direction toward and away from the fixing belt 20 as shown in FIG. 9A.

The support shafts 322 protrude from the inner surfaces facing each other of the pair of side plates 320 (only one of which is shown) as shown in FIG. 8C. The support shafts 322 are rotatably fitted in shaft holes 315 formed at both ends of the separation plate 310 .

The side plate 320 has a U-shaped notch 324 for rotatably supporting both end shaft portions of the pressure roller 21 . At a position above and adjacent to the notch 324 of the side plate 320, a rotation restricting hole 321 as a fan-shaped movement restricting hole centered on the support shaft 322 is formed. The rotational range (movement position) of the separation plate 310 is regulated by the rotational regulation hole 321 .

As shown in FIG. 8C, the separation plate 310 has rotation restriction pieces 312 as movement restriction pieces projecting in the longitudinal direction at both ends in the longitudinal direction. is inserted in the The movement restricting means or rotation restricting means of the separation plate 310 is constituted by the rotation restricting piece 312 and the rotation restricting hole 321 .

That is, one end (the left end in FIG. 8C) of the rotation restricting hole 321 determines the movement position or the rotation position of the separation plate 310 in the direction in which the leading end 311 of the separation plate 310 approaches the fixing belt 20 . 1 constitutes a regulation section. Also, the other end portion (the right end portion in FIG. 8C) of the rotation restricting hole 321 determines the movement position or rotation position of the separation plate 310 in the direction in which the leading end portion 311 of the separation plate 310 moves away from the fixing belt 20 . Construct the regulatory department. In addition, since an appropriate clearance is provided between the surface (arc-shaped surface) of the regulation hole 321 other than the first regulation portion and the second regulation portion and the rotation regulation piece 312, the arc-shaped surface will not interfere with the rotation restricting piece 312 to hinder the rotation of the separation plate 310 .

When the leading end portion 311 of the separation plate 310 rotates in a direction approaching the fixing belt 20, the desired distance between the leading end portion 311 and the fixing belt 20 is 0.6 to 1.2 mm or 0.6 to 1.3 mm. . If the gap between the fixing belt 20 and the separation plate 310 is too small, the separation plate 310 contacts the fixing belt 20 and easily scratches the belt, which causes abnormal images. With the above-mentioned 0.6 mm interval, it is possible to prevent the fixing belt 20 from being damaged.

If the gap between the fixing belt 20 and the separation plate 310 is too large, the paper passes through this large gap and winds around the fixing belt 20, easily causing a paper jam. If the interval is 1.2 mm or 1.3 mm or less as described above, it is possible to prevent the paper from winding around the fixing belt 20 and causing a paper jam. Note that the relationship between the rotation restricting piece 312 and the rotation restricting hole 321 can be reversed, and it is also possible to provide the rotation restricting hole on the separation plate 310 side and the rotation restricting piece on the side plate 320 side. is.

L-shaped contact portions 313 are formed at both ends of the separation plate 310 in the longitudinal direction and at the lower end in the lateral direction. This contact portion 313 is arranged at a position facing the flange 400 in the radial direction of the fixing belt 20 in order to suppress the amount of backlash of the fixing belt 20 .

A tension spring 330 is bridged between the spring engaging portions 314 at both ends of the separation plate 310 and the spring engaging portions 323 at the upper ends of the side plates. The tension spring 330 urges the separation plate 310 clockwise around the support shaft 322 in FIGS. 8B and 8C.

This rotational biasing direction is the direction in which the leading end portion 311 of the separating plate 310 approaches the fixing belt 20 . Since the separation plate 310 is easily deformed as described above, it is desirable to attach tension springs 330 to both ends of the separation plate 310 in order to ensure that the separation plate 310 is biased to rotate.

If the contact portion 313 were not provided, the biasing force of the tension spring 330 would allow the tip portion 311 of the separation plate 310 to come into contact with the outer peripheral surface of the fixing belt 20 as shown in FIG. 9A. In this state, the rotation restricting piece 312 is provided at a position where one side end (left end) of the rotation restricting hole 321 abuts against the rotation restricting piece 321a. Therefore, even if the contact portion 313 becomes non-functional for some reason, the separating plate 310 cannot rotate further clockwise from the state shown in FIG. 9A.

(● Dealing with paper jams)
As shown in FIG. 9B, when a paper jam occurs and the paper P is wrapped around the fixing belt 20, the separation plate 310 rotates counterclockwise so as to escape from the paper P to avoid collision with the paper P. can be done. Thereby, the paper P can be prevented from being damaged. Further, when the paper P wound around the fixing belt 20 is pulled downward from the fixing nip as shown in FIG. can be pulled out without

Even if the separation plate 310 improves the paper separability, if an image with toner on the front edge of the paper P is to be fixed, for example, if the print settings are incorrect, the separation plate 310 and the fixing belt 20 will not be able to hold the image. The paper P slips into the fixing belt 20 and the paper P may wind around the fixing belt 20 . If the paper P is wrapped around the fixing belt 20 in a plurality of layers, or if the paper P is greatly wrinkled, the separation plate 310 is strongly brought into contact with the separation plate 310 when the paper P is pulled out, and the separation plate 310 is deformed or the fixing belt 20 is damaged. may occur.

Therefore, in this embodiment, the tension spring 330 is configured to press the separation plate 310 . With this configuration, the separation plate 310 is released against the tension spring 330 when the sheet P is pulled out, so deformation and damage of the separation plate 310 can be suppressed. In addition, since the force required to pull out the paper P can be reduced, operability is improved.

In order to reduce the pulling force, the opening amount of the separation plate 310, that is, the clearance between the rotation regulating piece 312 of the separation plate 310 and the rotation regulating hole 321 of the side plate 320 should be adjusted to the pressure release at the fixing nip pressure release. It is effective to make it larger than the amount. As shown in FIG. 10, the pressure release amount at the fixing nip pressure release is determined by measuring the distance GAP between the metal core M of the pressure roller 21 and the nip forming member SH using a vernier caliper or the like. It can be obtained by measuring and subtracting.

However, if the opening amount of the rotation restricting hole 321 is too large, the tip portion 311 of the separation plate 310 may contact the pressure roller 21 or the pressure roller 21 may be damaged by the contact. Therefore, it is preferable to set the size of the rotation restriction hole 321 so that the rotation of the separation plate 310 stops at a position before the front end portion 311 of the separation plate 310 contacts the pressure roller 21 . That is, when the separation plate 310 rotates in the direction to widen the distance between the tip end portion 311 and the fixing belt 20 , the second restriction opening of the rotation restriction hole 321 occurs before the separation plate 310 contacts the pressure roller 21 . Rotation is regulated at the other end (the right end in FIG. 8C) as a portion.

As another method of preventing contact with the pressure roller 21 , the position of the support shaft 322 of the separation plate 310 may be devised so that the layout does not come into contact with the pressure roller 21 . To this end, it is effective to make the diameter of the pressure roller 21 smaller than that of the fixing belt 20, or to shift the center of the pressure roller 21 away from the separation plate 310 from the center of the fixing belt 20 (downward in FIG. 9D). is.

(Composition of pressurization and depressurization of fixing nip)

Two pressure configurations, first and second, are possible for the pressure configuration of the fuser nip. A first pressure configuration is a configuration in which the fixing belt 20 side (heater holder 23 ) is fixed, the pressure roller 21 can be brought into contact with and separated from the fixing belt 20 , and the fixing belt 20 side is biased. In the second pressure structure, the pressure roller 21 side (the metal core of the pressure roller 21) is fixed, and the fixing belt 20 side can be brought into contact with and separated from the pressure roller 21. It is a configuration for biasing.

The latter second pressurizing configuration is preferable because it can further reduce the force for pulling out the paper P when dealing with a paper jam. That is, in the second pressure configuration, when the pressure is released, the fixing belt 20 and the pressure roller 21 are separated, and the fixing belt 20 and the separation plate 310 are also separated. Therefore, the displacement of the tension spring 330 is reduced, and the force for pulling out the paper P can be further reduced.

In addition, by setting the clearance in the biasing direction of the rotation restricting hole 321 to be smaller than the pressure release amount, the separation plate 310 is restricted from rotating clockwise in FIG. Since the distance between the plate 310 and the leading end portion 311 is widened, it becomes easier to pull out the paper P.

Further, in the event of a paper jam, it is difficult for the user to pull out the paper P unless the paper is sufficiently visible from the fixing nip. If the distance between the fixing belt 20 and the leading end portion 311 of the separation plate 310 can be widened, the pressure roller 21 and the fixing belt 20 can be easily reversely rotated, and the paper P is moved to the upstream side of the fixing nip (FIG. 9B). down) to a sufficient length.

On the other hand, the trajectory of the fixing belt 20 changes between forward rotation and reverse rotation of the fixing belt 20 during paper jam handling. Therefore, it is preferable to adopt the second pressure configuration in which the fixing belt 20 and the tip portion 311 of the separation plate 310 do not come into contact with each other even if the trajectory of the fixing belt 20 changes.

(Use rate of inner circumference)
The inner circumference usage rate of the fixing belt 20 (see JP-A-2019-082733) is preferably 95 to 99.8%. The inner circumference usage rate can be calculated by the following formula using the overlapping amount W in FIG. can be done.
Inner circumference usage rate=[(peripheral length of fixing belt 20−overlapping amount W)/peripheral length of fixing belt 20 L]×100%
The circumferential length L of the fixing belt 20 is the total length of the cut out shaded portion as shown in FIG. 11C.

The inner circumference usage rate simply indicates the ratio of the length of the circumference of the guide portion to the circumference L of the fixing belt 20, and serves as an indicator of ease of assembly (fitting). There is room for improvement as an index of separability. 12A and 12B, the sag in the width direction of the fixing nip differs depending on the rigidity of the fixing belt 20, the width of the fixing nip, and the shape of the flange 400, even if the usage rate of the inner periphery is the same. Specifically, the higher the rigidity of the fixing belt 20, the narrower the width of the fixing nip, and the farther the guide shape of the flange 400 is from a perfect circle, the smaller the slack.

Therefore, it is preferable to define the sag rate by directly measuring the sag on the downstream side of the fixing nip with a height gauge. A method for measuring the sagging rate will be described with reference to FIG.

The fixing unit is oriented as shown in FIG. 13 and fixed. With the pressure roller 21 pressing the fixing nip, the pressure roller 21 is rotated more than once and then stopped. At that time, the height coordinate of the vertex of the fixing belt 20 in the region where the flange 400 is present in the axial direction of the fixing belt 20 is measured with a height gauge as shown in FIG. 13(a).

Next, the height coordinates are measured when the position where the vertex coordinates are measured is pressed against the flange as shown in FIG. 13(b). The difference in height before and after pressing is taken as the sag amount, and the sag ratio is calculated by the following formula.
Sag rate = [sag amount/belt diameter] x 100%

If the slack rate is too small, it is difficult to assemble, and there is a problem that the fixing belt 20 is worn due to friction between the flange 400 and the fixing belt 20 . If the slack rate is too large, the fixing belt 20 tends to tilt, and the curvature of the exit of the fixing nip becomes small, resulting in poor separation performance and difficulty in arranging the separation plate 310 . Therefore, the sagging rate is preferably 0.1 to 10%, more preferably 0.5 to 5%.
(Placement of high thermal conductivity materials)
Next, an embodiment in which a high thermal conductivity member is arranged in the heater holder 23 described above will be described with reference to FIGS. 14 to 32. FIG. As shown in FIG. 14, the fixing device 9 according to this embodiment includes a fixing belt 20 as a rotating member or a fixing member, a pressure roller 21 as a counter rotating member or a pressure member, and a heater 22 as a heating member. , a heater holder 23 as a holding member, a stay 24 as a support member, a thermistor 25 as a temperature detection member, a first high heat conduction member 28, and the like.

The fixing belt 20 is an endless belt. The pressure roller 21 contacts the outer peripheral surface of the fixing belt 20 to form a fixing nip N with the fixing belt 20 . A heater 22 heats the fixing belt 20 . A heater holder 23 holds the heater 22 . The stay 24 supports the heater holder 23 .

The thermistor 25 detects the temperature of the first high heat conduction member 28 . The direction perpendicular to the paper surface of FIG. 14 is the longitudinal direction of the fixing belt 20, pressure roller 21, heater 22, heater holder 23, stay 24, first high heat conductive member 28, etc. Hereinafter, this direction is simply referred to as the longitudinal direction. . The longitudinal direction is also the width direction of the sheet to be conveyed, the width direction of the fixing belt 20 , and the axial direction of the pressure roller 21 .

In the present embodiment, the above-described first high heat conductive member 28 is provided in order to suppress the temperature drop in the interval and suppress the temperature unevenness in the alignment direction of the fixing belt 20 . The first high thermal conductivity member 28 will be described in more detail below.

As shown in FIG. 14, the first high thermal conductivity member 28 is arranged between the heater 22 and the stay 24 in the horizontal direction of FIG. That is, the first high thermal conductivity member 28 has one surface in contact with the back surface of the base material 30 and the other surface in contact with the heater holder 23 .

The stay 24 supports the heater holder 23 , the first high heat conductive member 28 , and the heater 22 by bringing the contact surfaces 24 a 1 of the two vertical portions 24 a extending in the thickness direction of the heater 22 and the like into contact with the heater holder 23 . The contact surface 24a1 is provided outside the range in which the resistance heating elements 31 are provided in the arrangement cross direction (vertical direction in FIG. 14). Accordingly, heat transfer from the heater 22 to the stay 24 can be suppressed, and the heater 22 can efficiently heat the fixing belt 20 .

As shown in FIG. 15, the first high thermal conductivity member 28 is made of a plate material having a thickness of 0.3 mm, a length of 222 mm in the arrangement direction, and a width of 10 mm in the arrangement cross direction. Although the first high thermal conductivity member 28 is made of a single plate material in this embodiment, it may be made of a plurality of members. 15, illustration of the guide portion 26 of FIG. 14 is omitted.

The first high thermal conductivity member 28 is fitted into the recessed portion 23b of the heater holder 23, and the heater 22 is mounted thereon, so that the first high heat conductive member 28 is sandwiched and held between the heater holder 23 and the heater 22. As shown in FIG. In the present embodiment, the width of the first high thermal conductivity member 28 in the arrangement direction is substantially the same as the width of the heater 22 in the arrangement direction.

The first high thermal conductivity member 28 and the heater 22 are restricted from moving in the arrangement direction by the arrangement direction side walls (arrangement direction regulation portions) 23b1 forming the recess 23b. In this way, by restricting the positional deviation of the first high heat conductive member 28 in the fixing device 9 in the arrangement direction, it is possible to improve the heat conduction efficiency in the target range in the arrangement direction. Further, the movement of the first high thermal conductivity member 28 and the heater 22 in the cross-array direction is restricted by the cross-array direction side walls (array cross-direction restricting portions) 23b2 that form the recess 23b.

The range of the arrangement direction in which the first high thermal conductivity members 28 are provided is not limited to the above. For example, as shown in FIG. 16, the first high thermal conductivity member 28 may be provided only in the range corresponding to the heat generating portions 35 in the arrangement direction (see the hatched portion in FIG. 16).

Due to the pressing force of the pressure roller 21, the first high heat conductive member 28 is sandwiched between the heater 22 and the heater holder 23 and adheres to these members. The contact of the first high thermal conductive member 28 with the heater 22 improves the heat transfer efficiency in the arrangement direction of the heater 22 .

By providing the first high thermal conductivity member 28 at a position corresponding to the space B between the heaters 22 in the arrangement direction, the heat conduction efficiency in the space B can be improved, and the heat transfer efficiency can be improved to the position of the space B in the arrangement direction. It is possible to increase the amount of heat transferred and raise the temperature at the interval B in the arrangement direction. Therefore, temperature unevenness in the arrangement direction of the heaters 22 can be suppressed.

Thereby, temperature unevenness in the alignment direction of the fixing belt 20 can be suppressed. Therefore, it is possible to suppress fixing unevenness and glossiness unevenness of the image fixed on the paper.

Alternatively, in order to ensure sufficient fixing performance at intervals, the need for extra heating by the heater 22 is eliminated, and energy saving of the fixing device 9 can be realized. In addition, by providing the first high heat conduction member 28 over the entire area of the heat generating portion 35 in the arrangement direction, the heat transfer efficiency of the heater 22 can be increased over the entire main heating area (that is, the image forming area of the paper to be passed) by the heater 22. It is possible to suppress temperature unevenness in the arrangement direction of the heater 22 and thus the fixing belt 20 .

In particular, in this embodiment, the combination of the configuration of the first high thermal conductivity member 28 and the resistance heating element 31 having the PTC characteristic described above effectively prevents excessive temperature rise in the non-paper-passing area when small-size paper is passing. can be suppressed to In other words, the PTC characteristic can suppress the amount of heat generated by the resistance heating element 31 in the non-paper-passing area, and can efficiently transmit the heat of the non-paper-passing area whose temperature has increased to the side of the non-paper-passing area. Excessive temperature rise in the paper area can be effectively suppressed.

In addition, since the amount of heat generated in the space B is small, the temperature in the vicinity of the space B is also small, so it is preferable to dispose the first high thermal conductive member 28 . Especially in this embodiment, the first high thermal conductivity member 28 is provided over the entire area of the heat generating portion 35 in the arrangement direction. Thereby, temperature unevenness in the arrangement direction of the heater 22 (fixing belt 20) can be further suppressed.

Next, different embodiments of fixing devices will be described. As shown in FIG. 17 , the fixing device 9 of this embodiment has a second high heat conductive member 36 between the heater holder 23 and the first high heat conductive member 28 . The second high heat conductive member 36 is provided at a different position from the first high heat conductive member 28 in the stacking direction (horizontal direction in FIG. 17) of members such as the heater holder 23, the stay 24, and the first high heat conductive member 28.

More specifically, the second high thermal conductivity member 36 is provided so as to overlap the first high thermal conductivity member 28 . Note that FIG. 17 shows a cross section in which the second high thermal conductivity member 36 in the arrangement direction is arranged and the thermistor 25 is not arranged, unlike FIG. 2 .

The second high thermal conductivity member 36 is made of a member having higher thermal conductivity than the base material 30, such as graphene or graphite. In this embodiment, the second high thermal conductivity member 36 is made of a graphite sheet with a thickness of 1 mm. However, the second high thermal conductivity member 36 may be made of a plate material such as aluminum, copper, or silver.

As shown in FIG. 18, a plurality of second high thermal conductivity members 36 partially provided in the arrangement direction are arranged in the arrangement direction. The portion of the recess 23b of the heater holder 23 where the second high thermal conductivity member 36 is provided is one step deeper than the other portions.

The second high thermal conductivity member 36 is provided with a gap between it and the heater holder 23 on both sides in the arrangement direction. As a result, the heat transfer from the second high heat conductive member 36 to the heater holder 23 is suppressed, and the heater 22 can efficiently heat the fixing belt 20 . 18, the illustration of the guide portion 26 of FIG. 17 is omitted.

As shown in FIG. 19, the second high thermal conductivity member 36 (see the hatched portion) is provided at a position corresponding to the interval B in the arrangement direction and at a position overlapping at least a portion of the adjacent resistance heating elements 31. In this embodiment, it is provided over the entire interval B. However, although FIG. 19 (and FIG. 20 to be described later) shows the case where the first high thermal conductivity member 28 is provided only in the region corresponding to the heat generating portion 35 in the arrangement direction, it is not limited to this as described above.

As in the present embodiment, in addition to the first high thermal conductivity member 28, a second high thermal conductivity member 36 is provided at a position corresponding to the interval B in the arrangement direction and overlapping at least a portion of the adjacent resistance heating elements 31. As a result, the heat transfer efficiency in the arrangement direction at the interval B can be particularly improved, and the temperature unevenness in the arrangement direction of the heaters 22 can be further suppressed. Most preferably, as shown in FIG. 28, which will be described later, the first high heat conduction member 89 and the second high heat conduction member 90 can be provided only over the entire area of the position corresponding to the interval B. As a result, the heat transfer efficiency can be particularly improved at the position corresponding to the interval B as compared with other regions.

In a different embodiment of the present invention, the first high thermal conductivity member 28 and the second high thermal conductivity member 36 are composed of the graphene sheets. Thereby, the first high thermal conductivity member 28 and the second high thermal conductivity member 36 having high thermal conductivity can be formed in a predetermined direction along the plane of the graphene, that is, in the arrangement direction rather than the thickness direction. Therefore, temperature unevenness in the arrangement direction of the heater 22 and the fixing belt 20 can be effectively suppressed.

Graphene is a flaky powder. Graphene consists of a planar hexagonal lattice structure of carbon atoms, as shown in FIG. 31 described later. A graphene sheet is sheet-like graphene, and is usually a single layer. Impurities may be included in the single layer of carbon.

Graphene may also have a fullerene structure. A fullerene structure is generally recognized as a compound composed of five-membered and six-membered rings of equal numbers of carbon atoms forming a cage-condensed polycyclic ring, such as C60, C70 and C80 fullerenes. or other closed cage structures with tricoordinated carbon atoms.

Graphene sheets are man-made and can be made, for example, by chemical vapor deposition (CVD) methods. A commercial item can be used for the graphene sheet. The size and thickness of the graphene sheet, or the number of layers of the graphite sheet, which will be described later, are measured by, for example, a transmission electron microscope (TEM).

Graphite obtained by multilayering graphene has a large thermal conductivity anisotropy. Graphite, as shown in FIG. 32, which will be described later, has a crystal structure in which layers of condensed six-membered rings of carbon atoms extend in a planar manner, and these layers are stacked many times.

Adjacent carbon atoms in a layer form a covalent bond between carbon atoms in this crystal structure, and carbon atoms between layers form a van der Waals bond. A covalent bond has a greater bonding strength than a van der Waals bond, and a bond within a layer and a bond between layers have a large anisotropy.

In other words, by configuring the first high thermal conductive member 28 or the second high thermal conductive member 36 from graphite, the heat transfer efficiency in the arrangement direction of the first high thermal conductive member 28 or the second high thermal conductive member 36 increases in the thickness direction (that is, the thickness of the member). stacking direction), and heat transfer to the heater holder 23 can be suppressed. Therefore, it is possible to efficiently suppress the temperature unevenness in the arrangement direction of the heaters 22 and to minimize the heat flowing out to the heater holder 23 side. Further, by forming the first high heat conductive member 28 or the second high heat conductive member 36 from graphite, the first high heat conductive member 28 or the second high heat conductive member 36 has excellent heat resistance that does not oxidize up to about 700 degrees. can be done.

The physical properties and dimensions of the graphite sheet can be appropriately changed according to the functions required of the first high heat conductive member 28 or the second high heat conductive member 36 . For example, the anisotropy of heat conduction can be enhanced by using high-purity graphite or single-crystal graphite, or by increasing the thickness of the graphite sheet.

Further, in order to increase the speed of the fixing device 9, the heat capacity of the fixing device 9 may be reduced by using a thin graphite sheet. If the width of the fixing nip N or the heater 22 is large, the width of the first high heat conductive member 28 or the second high heat conductive member 36 may be increased accordingly.

From the viewpoint of increasing the mechanical strength, the number of layers of graphite sheets is preferably 11 or more. Graphite sheets may also partially include single-layer and multilayer portions.

The second high thermal conductivity member 36 may be provided at a position corresponding to the interval B (further region C) in the arrangement direction and at a position overlapping at least a part of the adjacent resistance heating elements 31, and is limited to the arrangement shown in FIG. do not have. For example, as shown in FIG. 20, the second high thermal conductivity member 36A is provided so as to protrude from the substrate 30 to both sides in the crossing direction of the array.

Also, the second high thermal conductivity member 36B is provided in a range in which the resistance heating elements 31 are provided in the arrangement cross direction. 36 C of 2nd high heat-conduction members are provided in a part of space|interval B. As shown in FIG.

Further, as shown in FIG. 21, in the present embodiment, a gap (relief portion 23c) is provided between the first high heat conductive member 28 and the heater holder 23 in the thickness direction (horizontal direction in FIG. 21). That is, a partial area of the recess 23b (see FIG. 18) for arranging the heater 22 of the heater holder 23, the first high heat conductive member 28, and the second high heat conductive member 36, and the second high heat conductive member in the arrangement direction In a portion other than the portion where the 36 is provided, a relief portion 23c as a heat insulating layer is provided in a partial region in the array crossing direction so that the depth of the recess 23b is deeper than the other portion that receives the first high heat conduction member 28. prepare.

Thereby, the contact area between the heater holder 23 and the first high thermal conductivity member 28 can be minimized. Therefore, the heat transfer from the first high heat conductive member 28 to the heater holder 23 is suppressed, and the heater 22 can efficiently heat the fixing belt 20 . In addition, in the cross section where the second high heat conductive member 36 is provided in the arrangement direction, the second high heat conductive member 36 contacts the heater holder 23 as shown in FIG. 17 of the above-described embodiment.

Moreover, particularly in the present embodiment, the relief portion 23c is provided over the entire range in which the resistance heating elements 31 are provided in the arrangement cross direction (vertical direction in FIG. 21). As a result, heat transfer from the first high heat conductive member 28 to the heater holder 23 is particularly suppressed, and the heater 22 can efficiently heat the fixing belt 20 . As the heat insulating layer, in addition to the configuration in which a space is provided like the relief portion 23c, a configuration in which a heat insulating member having a lower thermal conductivity than the heater holder 23 may be provided.

Furthermore, in the above description, the second high thermal conductivity member 36 is provided as a member different from the first high thermal conductivity member 28, but the present invention is not limited to this. For example, the portion corresponding to the interval B of the first high thermal conductivity member 28 may be thicker than the other portions.

FIG. 22 is a plan view of a heater showing another example of the arrangement of the first high thermal conductivity member. As shown in FIG. 22, it is also possible to provide the first high thermal conductivity member 89 only over the entire area at the position corresponding to the interval B in the arrangement direction. In FIG. 22, the resistance heating element 56 and the first high heat conductive member 89 are shown shifted in the vertical direction of FIG. 22 for the sake of convenience, but they are arranged at substantially the same position in the arrangement cross direction. However, the present invention is not limited to this, and the first high thermal conductivity member 89 may be provided in a part of the resistance heating element 56 in the crossing direction of the arrangement, or may be provided so as to cover the entirety in the crossing direction of the arrangement as shown in FIG. You can have it.

Furthermore, as shown in FIG. 23, in addition to the position corresponding to the space B in the arrangement direction, the first high thermal conductivity member 89 can be provided so as to straddle the resistance heating elements 56 on both sides of the space B therebetween. . The phrase "provided across the resistance heating elements 56 on both sides" means that the first high thermal conductive member 89 at least partially overlaps the resistance heating elements 56 on both sides in the arrangement direction.

The first high thermal conductivity member 89 may be provided corresponding to all intervals B of the heater 22, or the first high thermal conductivity member 89 may be provided only at a position corresponding to one interval B as shown in FIG. As shown, the first high thermal conductivity member 89 may be provided only at a position corresponding to a part of the gap B. Here, providing at a position corresponding to the interval B in the arrangement direction means that at least a part of the interval B overlaps in the arrangement direction.

Here, in the heater 63 of this embodiment, a plurality of resistance heating elements 56 are arranged at intervals in the longitudinal direction of the heater 63 in the same manner as the resistance heating element 31 of the heater shown in FIG. 39 which will be described later. ing. However, in a configuration in which a plurality of resistance heating elements 56 are arranged at intervals, the temperature of the heater 63 in the divided region B in FIG. It tends to be lower than the part where Therefore, in the divided area B, the temperature of the fixing belt 61 is also lowered, and there is a possibility that the temperature of the fixing belt 21 becomes uneven over the longitudinal direction.

Therefore, in this embodiment, the first high thermal conductivity member 89 is provided in order to suppress the temperature drop in the divided area B and suppress the temperature unevenness in the longitudinal direction of the fixing belt 61 . The first high thermal conductivity member 89 will be described in more detail below.

As shown in FIG. 25, the first high thermal conductivity member 89 is arranged between the heater 63 and the stay 65 in the lateral direction of the drawing, and particularly sandwiched between the heater 63 and the heater holder 64 . That is, one surface of the first high thermal conductivity member 89 is in contact with the back surface of the base material 55 of the heater 63, and the other surface (the surface opposite to the one surface) of the first high thermal conductivity member 89 is the heater holder. 64.

The stay 65 supports the heater holder 64 , the first high heat conductive member 89 , and the heater 63 by bringing the contact surfaces 65 a 1 of the two vertical portions 65 a extending in the thickness direction of the heater 63 and the like into contact with the heater holder 64 . The contact surface 65a1 is provided outside the range in which the resistance heating element 56 is provided in the longitudinal cross direction (vertical direction in FIG. 25). As a result, heat transfer from the heater 63 to the stay 65 can be suppressed, and the heater 63 can heat the fixing belt 61 efficiently.

As shown in FIG. 26, the first high thermal conductivity member 89 is a plate-shaped member having a certain thickness, for example, the thickness is 0.3 mm, the length in the longitudinal direction is 222 mm, and the length in the crossing direction is 0.3 mm. Width is set to 10 mm. In the present embodiment, the first high thermal conductivity member 89 is composed of a single plate material, but may be composed of a plurality of members. 26, the guide member 66 shown in FIG. 25 is omitted.

The first high thermal conductivity member 89 is fitted into the recessed portion 64 b of the heater holder 64 , and the heater 63 is mounted thereon, so that the first high heat conductive member 89 is sandwiched and held between the heater holder 64 and the heater 63 . In this embodiment, the longitudinal width of the first high thermal conductivity member 89 is set substantially equal to the longitudinal width of the heater 63 .

The first high thermal conductivity member 89 and the heater 63 are restricted from moving in the longitudinal direction by side walls (longitudinal direction restricting portions) 64b1 arranged in a direction intersecting the longitudinal direction of the recess 64b. In this way, by restricting the positional displacement of the first high thermal conductivity member 89 in the fixing device 60 in the longitudinal direction, it is possible to improve the heat transfer efficiency in the target range in the longitudinal direction. Further, the movement of the first high thermal conductivity member 89 and the heater 63 in the cross-longitudinal direction is restricted by both side walls (arrangement cross-direction restricting portions) 64b2 arranged in the longitudinal direction of the recess 64b.

The range in the longitudinal direction (arrow X direction) where the first high thermal conductivity member 89 is arranged is not limited to the range shown in FIG. For example, as shown in FIG. 29, the first high thermal conductivity member 89 may be arranged only in the longitudinal range where the resistance heating element 56 is arranged (see hatching in FIG. 29).

Also, as in the example shown in FIG. 22, the first high thermal conductivity member 89 can be arranged only in the entire area at the position corresponding to the interval (divided area) B in the longitudinal direction (arrow X direction). In FIG. 22, the resistance heating element 56 and the first high thermal conductivity member 89 are shown shifted vertically in FIG. placed.

Also, the first high thermal conductivity member 89 may be arranged over a part of the resistance heating element 56 in the longitudinal crossing direction (arrow Y direction), or as in the example shown in FIG. The member 89 may be arranged over the entire lengthwise crossing direction (arrow Y direction) of the resistance heating element 56 . Furthermore, as shown in FIG. 23, in addition to the position corresponding to the space B in the longitudinal direction, the first high thermal conductivity member 89 is placed across the resistance heating elements 56 on both sides of the space B. can also

The phrase "arranging the first high thermal conductivity member 89 across the resistance heating elements 56 on both sides" means that the first high thermal conductivity member 89 overlaps the resistance heating elements 56 on both sides at least partially in the longitudinal direction. do. Also, the first high thermal conductivity member 89 may be arranged at a position corresponding to the entire interval B of the heater 63, or as in the example shown in FIG. may be arranged only at positions corresponding to . Here, "the first high heat conductive member 89 is arranged at a position corresponding to the space B" means that the space B and at least a part of the first high heat conductive member 89 overlap in the longitudinal direction.

Due to the pressing force of the pressure roller 62, the first high heat conductive member 89 is sandwiched between the heater 63 and the heater holder 64 and adheres to these members. The contact of the first high thermal conductivity member 89 with the heater 63 improves the heat conduction efficiency of the heater 63 in the longitudinal direction. By arranging the first high thermal conductivity member 89 at a position corresponding to the space B between the heaters 63 in the longitudinal direction, the heat conduction efficiency in the space B can be improved, and the amount of heat transferred to the space B can be increased to increase the temperature in interval B.

Thereby, temperature unevenness in the longitudinal direction of the heater 63 can be suppressed, and temperature unevenness in the longitudinal direction of the fixing belt 61 can be suppressed. As a result, it is possible to suppress fixing unevenness and glossiness unevenness of the image fixed on the paper.

Further, it is not necessary to increase the amount of heat generated by the heater 63 in order to ensure sufficient fixing performance at the interval B, and energy saving of the fixing device can be realized. In particular, when the first high thermal conductivity member 89 is arranged over the entire lengthwise area where the resistance heating element 56 is arranged, the main heating area by the heater 63 (that is, the image forming area of the paper to be passed) , the heat transfer efficiency of the heater 63 can be improved, and temperature unevenness in the longitudinal direction of the heater 63 and thus the fixing belt 61 can be suppressed.

Furthermore, the combination of the first high thermal conductivity member 89 and the resistance heating element 56 having the PTC characteristic can more effectively suppress excessive temperature rise in the non-sheet-passing area when small-size sheets are being passed. The PTC characteristic is a characteristic in which the resistance value increases as the temperature increases (the heater output decreases when a constant voltage is applied). That is, since the resistance heating element 56 has the PTC characteristic, it is possible to effectively suppress the amount of heat generated by the resistance heating element 56 in the non-sheet passing area, Since the amount of heat in the paper-passing area can be efficiently transferred to the paper-passing area, the synergistic effect of these can effectively suppress excessive temperature rise in the non-paper-passing area.

Moreover, since the amount of heat generated at the interval B is small around the interval B, the temperature of the heater 63 is lowered, so it is preferable to dispose the first high heat conductive member 89 . For example, by arranging the first high thermal conductivity member 89 at a position corresponding to the enlarged divided area C including the area around the interval B shown in FIG. The temperature unevenness in the longitudinal direction of the heater 63 can be suppressed more effectively. In addition, when the first high thermal conductivity member 89 is arranged over the entire longitudinal direction of the region where all the resistance heating elements 56 are arranged, the temperature unevenness in the longitudinal direction of the heater 63 (fixing belt 61) can be further reduced. can be suppressed with certainty.

Next, still another embodiment of the fixing device will be described. The fixing device 60 shown in FIG. 25 has a second high thermal conductivity member 90 between the heater holder 64 and the first high thermal conductivity member 89 . The second high heat conductive member 90 is provided at a different position from the first high heat conductive member 89 in the stacking direction (horizontal direction in FIG. 25) of members such as the heater holder 64, the stay 65, and the first high heat conductive member 89.

More specifically, the second high thermal conductivity member 90 is provided so as to overlap the first high thermal conductivity member 89 . 14, a temperature sensor (thermistor) 67 is provided in this embodiment, but FIG. 25 shows a cross section in which the temperature sensor 67 is not arranged. there is

The second high thermal conductivity member 90 is made of a member having higher thermal conductivity than the base material 55, such as graphene or graphite. In this embodiment, the second high thermal conductivity member 90 is composed of a graphite sheet with a thickness of 1 mm. Also, the second high thermal conductivity member 90 may be made of a plate material such as aluminum, copper, or silver.

As shown in FIG. 26, a plurality of second high heat conduction members 90 are arranged in the recessed portion 64b of the heater holder 64, and longitudinal intervals are interposed between the second high heat conduction members 90. As shown in FIG. A portion of the heater holder 64 where the second high thermal conductivity member 90 is provided has a recess that is one step deeper than the other portions.

The second high thermal conductivity member 90 has a gap between it and the heater holder 64 on both sides in the longitudinal direction. As a result, heat transfer from the second high thermal conductivity member 90 to the heater holder 64 is suppressed, and the fixing belt 61 is efficiently heated by the heater 63 . 26, the guide member 66 shown in FIG. 25 is omitted.

As shown in FIG. 27, the second high thermal conductivity member 90 (see the hatched portion) overlaps at least a portion of the adjacent resistance heating elements 56 at a position corresponding to the interval B in the longitudinal direction (arrow X direction). placed in position. In particular, in this embodiment, the second high thermal conductivity member 90 is arranged over the entire interval B. As shown in FIG. Note that FIG. 27 (and FIG. 29 to be described later) shows the case where the first high thermal conductivity member 89 is arranged over the entire longitudinal direction of the region where all the resistance heating elements 56 are arranged. , the arrangement range of the first high thermal conductivity member 89 is not limited to this.

As in the present embodiment, in addition to the first high thermal conductivity member 89, a second high thermal conductivity member 90 is arranged at a position corresponding to the longitudinal interval B and overlapping at least a portion of the adjacent resistance heating elements 56. As a result, the heat transfer efficiency in the longitudinal direction at the interval B can be further improved, and the temperature unevenness in the longitudinal direction of the heater 63 can be suppressed more effectively. Most preferably, as shown in FIG. 28, the first high thermal conductivity member 89 and the second high thermal conductivity member 90 are provided only over the entire area of the position corresponding to the interval B. FIG.

Thereby, at the position corresponding to the interval B, the heat transfer efficiency can be particularly improved compared to other regions. In FIG. 28, for the sake of convenience, the resistance heating element 56, the first high thermal conductivity member 89 and the second high thermal conductivity member 90 are shown shifted in the vertical direction of the figure, but they are shown in the longitudinal cross direction (arrow Y direction) are arranged at substantially the same position. However, the present invention is not limited to this, and the first high thermal conductivity member 89 and the second high thermal conductivity member 90 may be arranged in a part of the resistance heating element 56 in the longitudinal cross direction, or may be arranged in the whole longitudinal cross direction. You may arrange|position so that it may cover.

Also, both the first high thermal conductivity member 89 and the second high thermal conductivity member 90 may be composed of the graphene sheet. In this case, the first high thermal conductivity member 89 and the second high thermal conductivity member 90 can be formed with high thermal conductivity in a predetermined direction along the plane of graphene, that is, not in the thickness direction but in the longitudinal direction. Therefore, temperature unevenness in the longitudinal direction of the heater 63 and the fixing belt 61 can be effectively suppressed.

Graphene is a flaky powder. Graphene consists of a planar hexagonal lattice structure of carbon atoms, as shown in FIG. A graphene sheet is sheet-like graphene, and is usually a single layer.

Further, the graphene sheet may contain impurities in a single layer of carbon, or may have a fullerene structure. Fullerene structures are generally recognized as compounds composed of equal numbers of carbon atoms forming a cage-fused polycyclic ring with five- and six-membered rings, such as C60, C70 and C80 fullerenes. or other closed cage structures with tricoordinated carbon atoms.

Graphene sheets are man-made and can be made, for example, by chemical vapor deposition (CVD) methods. A commercial item can be used for the graphene sheet. The size and thickness of the graphene sheet, or the number of layers of the graphite sheet, which will be described later, are measured by, for example, a transmission electron microscope (TEM).

Graphite obtained by multilayering graphene has a large thermal conductivity anisotropy. Graphite, as shown in FIG. 32, has a crystal structure in which layers of condensed six-membered ring layers of carbon atoms extend in a plane, and these layers are stacked many times.

Adjacent carbon atoms in a layer form a covalent bond between carbon atoms in this crystal structure, and carbon atoms between layers form a van der Waals bond. A covalent bond has a greater bonding strength than a van der Waals bond, and a bond within a layer and a bond between layers have a large anisotropy. In other words, by forming the first high heat conductive member 89 or the second high heat conductive member 90 from graphite, the heat transfer efficiency in the longitudinal direction of the first high heat conductive member 89 or the second high heat conductive member 90 increases in the thickness direction (that is, the thickness of the member). stacking direction), and heat transfer to the heater holder 64 can be suppressed.

Therefore, it is possible to efficiently suppress the temperature unevenness in the longitudinal direction of the heater 63 and to minimize the heat flowing out to the heater holder 64 side. Further, by forming the first high heat conductive member 89 or the second high heat conductive member 90 from graphite, the first high heat conductive member 89 or the second high heat conductive member 90 has excellent heat resistance that does not oxidize up to about 700 degrees. can be done.

The physical properties and dimensions of the graphite sheet can be changed as appropriate according to the functions required of the first high heat conductive member 89 or the second high heat conductive member 90 . For example, the anisotropy of heat conduction can be enhanced by using high-purity graphite or single-crystal graphite, or by increasing the thickness of the graphite sheet.

Further, in order to increase the speed of the fixing device, a graphite sheet having a small thickness may be used to reduce the heat capacity of the fixing device. Also, if the widths of the fixing nip N and the heater 63 are large, the longitudinal width of the first high thermal conductivity member 89 or the second high thermal conductivity member 90 may be increased accordingly.

From the viewpoint of increasing the mechanical strength, the number of layers of graphite sheets is preferably 11 or more. Graphite sheets may also partially include single-layer and multilayer portions.

The second high thermal conductivity member 90 may be provided at a position corresponding to the interval B (further, the enlarged divided region C) in the longitudinal direction and at a position overlapping at least a part of the adjacent resistance heating elements 56. The arrangement shown in FIG. is not limited to For example, as in the example shown in FIG. 29, the second high thermal conductivity member 90A may protrude from the substrate 55 to both sides in the longitudinal crossing direction (arrow Y direction).

Also, the second high thermal conductivity member 90B may be provided in a range in which the resistance heating element 56 is provided in the longitudinal cross direction. Also, the second high thermal conductivity member 90C may be provided in part of the interval B. As shown in FIG.

In another embodiment shown in FIG. 30, a gap is provided in the thickness direction (horizontal direction in FIG. 30) between the first high thermal conductivity member 89 and the heater holder 64. As shown in FIG. That is, a relief portion 64c as a heat insulating layer is provided in a partial region of the recess 64b (see FIG. 26) of the heater holder 64 in which the heater 63, the first high heat conductive member 89, and the second high heat conductive member 90 are arranged. ing.

The relief portion 64c is provided in a partial region in the longitudinal direction other than the portion where the second high thermal conductivity member 90 (not shown in FIG. 30) is provided. The escape portion 64c is formed by making the depth of the recessed portion 64b of the heater holder 64 deeper than the other portions.

As a result, since the contact area between the heater holder 64 and the first high heat conductive member 89 can be minimized, the heat transfer from the first high heat conductive member 89 to the heater holder 64 is suppressed, and the fixing belt 61 is heated by the heater 63. Allows for efficient heating. In addition, in the cross section where the second high heat conduction member 90 is provided in the longitudinal direction, the second high heat conduction member 90 contacts the heater holder 64 as in the embodiment shown in FIG.

Further, in the present embodiment, the relief portion 64c is provided over the entire range in which the resistance heating element 56 is provided in the longitudinal cross direction (vertical direction in FIG. 30). As a result, the heat transfer from the first high heat conductive member 89 to the heater holder 64 is effectively suppressed, and the heating efficiency of the fixing belt 61 by the heater 63 is improved. In addition to the configuration in which a space is provided as the heat insulating layer like the escape portion 64c, a configuration in which a heat insulating member having a lower thermal conductivity than the heater holder 64 may be provided.

Moreover, in the present embodiment, the second high thermal conductivity member 90 is provided as a member different from the first high thermal conductivity member 89, but the present invention is not limited to this. For example, by making the portion corresponding to the interval B of the first high heat conductive member 89 thicker than the other portions, the first high heat conductive member 89 may also function as the second high heat conductive member 90. good.

In the above description, the case where the present invention is applied to a fixing device, which is an example of a belt-type heating device (rotary body driving device), has been described as an example. However, the present invention is not limited to the fixing device, but also includes a drying device for drying liquid such as ink applied to paper, a laminator for thermally pressing a film as a coating member to the surface of a sheet such as paper, and a sealing portion of packaging material. A heating device such as a heat sealer for thermocompression bonding may also be used. Moreover, the present invention can also be applied to a rotating body driving device that does not have a heat source such as a heater.

(● Modified embodiment of the fixing device)
Next, modified embodiments of the fixing device 9 will be described with reference to FIGS. 33 to 43. FIG. FIG. 33 shows a modified arrangement of the thermistors.

In this embodiment, the thermistor 25 is provided on the upstream side in the rotation direction of the fixing belt 20 with respect to the central position NA of the fixing nip N, in other words, on the inlet side of the fixing nip N in the arrangement cross direction. Since the inlet side of the fixing nip N is a region that is particularly susceptible to heat loss by the paper P, the thermistor 25 detects the temperature of this portion, thereby ensuring the fixing performance of the fixing device 9 and effectively reducing the fixing offset. can be suppressed to

In the fixing device 9 shown in FIG. 34, the pressure roller 44 is arranged on the opposite side of the fixing belt 20 from the pressure roller 21 side. The pressing roller 44 is a counter rotating member that rotates facing the fixing belt 20 as a rotating member. The pressure roller 44 and the heater 22 are configured to sandwich the fixing belt 20 and heat it.

On the other hand, a nip forming member 45 is arranged on the inner periphery of the fixing belt 20 on the pressure roller 21 side. The nip forming member 45 is supported by the stay 24 . A fixing nip N is formed by the nip forming member 45 and the pressure roller 21 with the fixing belt 20 interposed therebetween.

Next, in the fixing device 9 shown in FIG. 35, the pressure roller 44 described above is omitted. is formed in an arc shape. Otherwise, the configuration is the same as that of the fixing device 9 shown in FIG.

Finally, the fixing device 9 shown in FIG. 36 will be described. The fixing device 9 comprises a heating assembly 92, a fixing roller 93 as a fixing member, and a pressure assembly 94 as a facing member.

The heating assembly 92 includes the heater 22, the heater holder 23, the stay 24, the heating belt 120 as a rotating member, and the like, which have been described in the previous embodiment. The fixing roller 93 is a counter rotating member that rotates facing the heating belt 120 as a rotating member. The fixing roller 93 is composed of a solid iron core 93a, an elastic layer 93b formed on the surface of the core 93a, and a release layer 93c formed outside the elastic layer 93b. .

A pressure assembly 94 is provided on the opposite side of the fixing roller 93 from the heating assembly 92 side. The pressure assembly 94 has a nip forming member 95 and a stay 96 arranged therein, and a pressure belt 97 rotatably arranged to enclose the nip forming member 95 and stay 96 . Then, the paper P is passed through the fixing nip N2 between the pressure belt 97 and the fixing roller 93 and heated and pressed to fix the image.

34 to 36 as well, the amount of heat generated by the heater 22 is reduced in the divided region B between the resistance heating elements 31 of the heater 22. As shown in FIG. Therefore, by providing the temperature detection element of the temperature detection member at a position corresponding to the divided area B of the heater 22, the portion corresponding to the divided area of the rotating member can be sufficiently heated as in the above-described embodiment. . As a result, the fixability of the image can be sufficiently ensured, and problems such as fixation offset can be prevented.

Further, the present invention is not limited to the fixing device as described in the above embodiment, but may also be applied to a drying device for drying ink applied to paper, and a film as a coating member that is heated on the surface of a sheet such as paper. The present invention can also be applied to a heating device such as a laminator that presses and a heat sealer that thermally presses the sealed portion of the packaging material. By applying the present invention to such a device, the portions corresponding to the divided regions of the rotating member can be sufficiently heated.

The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, but may be a monochrome image forming apparatus, a copying machine, a printer, a facsimile machine, or a multi-function machine of these. For example, as shown in FIG. 37, the image forming apparatus 100 of this embodiment includes an image forming unit 50 including a photosensitive drum and the like, a sheet conveying section including a pair of timing rollers 15 and the like, a sheet feeding device 7, a fixing A device 9 , a paper ejection device 10 , and a reading unit 51 are provided. The paper feed device 7 has a plurality of paper feed trays, and each paper feed tray accommodates sheets of different sizes.

The reading unit 51 reads the image of the document Q. As shown in FIG. The reading unit 51 generates image data from the read image. The paper feeder 7 accommodates a plurality of papers P and sends out the papers P to the transport path. The timing roller 15 conveys the paper P on the conveying path to the image forming means 50 .

The image forming means 50 forms a toner image on the paper P. As shown in FIG. Specifically, the image forming means 50 includes a photosensitive drum, a charging roller, an exposure device, a developing device, a replenishing device, a transfer roller, a cleaning device, and a neutralizing device. The toner image indicates the image of the document Q, for example.

The fixing device 9 fixes the toner image on the paper P by heating and pressing the toner image. The paper P on which the toner image is fixed is conveyed to the paper discharge device 10 by a conveying roller or the like. The paper discharge device 10 discharges the paper P to the outside of the image forming apparatus 100 .

Next, the fixing device 9 of this embodiment will be described. The description of the configuration common to the fixing device of the above embodiment will be omitted as appropriate.

As shown in FIG. 38, the fixing device 9 includes a fixing belt 20, a pressure roller 21, a heater 22, a heater holder 23, a stay 24, a thermistor 25, and the like. A fixing nip N is formed between the fixing belt 20 and the pressure roller 21 . The fixing nip N has a nip width of 10 mm, and the linear speed of the fixing device 9 is 240 mm/s.

The fixing belt 20 has a polyimide substrate and a release layer, and does not have an elastic layer. The release layer is made of a heat-resistant film material made of, for example, fluororesin. The fixing belt 20 has an outer diameter of about 24 mm.

The pressure roller 21 includes a metal core 21a, an elastic layer 21b, and a release layer 21c. The pressure roller 21 has an outer diameter of 24 to 30 mm, and the elastic layer 21b has a thickness of 3 to 4 mm.

The heater 22 includes a base material, a heat insulating layer, a conductor layer including a resistance heating element and the like, and an insulating layer, and has an overall thickness of 1 mm. Moreover, the width Y of the heater 22 in the array crossing direction is 13 mm.

As shown in FIG. 39, the conductor layer of the heater 22 includes a plurality of resistance heating elements 31, power supply lines 33, and electrode portions 34A-34C. Also in this embodiment, as shown in the enlarged view of FIG. 39, divided regions B are formed in which a plurality of resistance heating elements 31 are divided in the arrangement direction (however, in FIG. Although B is shown in the figure, divided regions are actually provided between all the resistance heating elements 31).

The resistance heating element 31 constitutes three heating portions 35A to 35C. By energizing the electrode portions 34A and 34B, the heat generating portions 35A and 35C generate heat. By energizing the electrode portions 34A and 34C, the heat generating portion 35B generates heat. For example, the heat-generating portion 35B can be caused to generate heat when performing the fixing operation on small-sized paper, and all the heat-generating portions can generate heat when performing the fixing operation on large-sized paper.

As shown in FIG. 40, the heater holder 23 holds the heater 22 in its recess 23b. The recess 23 b is provided on the heater holder 23 on the heater 22 side. The concave portion 23b is provided inside the heater holder 23 on both sides (or one side) in the arrangement direction of the heater holder 23, and a surface 23b3 that is concave on the stay 24 side from the other surface of the heater 22 and is substantially parallel to the base material 30. and wall portions 23b2 provided inside the heater holder 23 on both sides in the arrangement cross direction.

The heater holder 23 has a guide portion 26 . The heater holder 23 is made of LCP (liquid crystal polymer).

As shown in FIG. 41, the connector 160 includes a housing made of resin (for example, LCP) and a plurality of contact terminals provided in the housing. The connector 160 is attached so as to sandwich the heater 22 and the heater holder 23 together from the front side and the back side.

In this state, each contact terminal is brought into contact (pressure contact) with each electrode portion of the heater 22 , thereby electrically connecting the heat generating portion 35 and the power source provided in the image forming apparatus through the connector 160 . As a result, power can be supplied from the power supply to the heating unit 35 . At least a portion of each electrode portion 34 is not covered with the insulating layer and is exposed in order to ensure connection with the connector 160 .

The flanges 53 are provided on both sides in the alignment direction of the fixing belt 20 and hold both ends of the fixing belt 20 from the inside of the belt. The flange 53 is fixed to the housing of the fixing device 9 . The flanges 53 are inserted into both ends of the stay 24 (see arrow directions from the flanges 53 in FIG. 41).

The direction in which the connector 160 is attached to the heater 22 and the heater holder 23 is the heater array intersecting direction (see the arrow direction from the connector 160 in FIG. 41). When the connector 160 is attached to the heater holder 23, the protrusion provided on one of the connector 160 and the heater holder 23 may be engaged with the recess provided on the other so that the protrusion relatively moves within the recess. Further, the connector 160 is attached to the heater 22 and the heater holder 23 on one side in the arrangement direction, which is opposite to the side on which the drive motor of the pressure roller 21 is provided.

As shown in FIG. 42 , thermistors 25 are provided on the inner peripheral surface of the fixing belt 20 so as to face the center and end portions of the fixing belt 20 in the alignment direction. The heater 22 is controlled based on the temperatures detected by the thermistor 25 at the central side and the end side of the fixing belt 20 in the arrangement direction. One of these thermistors 25 is provided at a position corresponding to the divided area between the resistance heating elements of the heater 22, as in the above-described embodiment.

Thermostats 27 are provided on the center side and the end side of the fixing belt 20 in the arrangement direction so as to face the inner peripheral surface of the fixing belt 20 . When the temperature of the fixing belt 20 detected by the thermostat 27 exceeds a predetermined threshold value, power supply to the heater 22 is stopped.

Flanges 53 that hold the ends of the fixing belt 20 are provided at both ends of the fixing belt 20 in the arrangement direction. The flange 53 is made of LCP (liquid crystal polymer).

As shown in FIG. 43, the flange 53 is provided with a slide groove 53a. The slide groove 53 a extends in the contact/separation direction of the fixing belt 20 with respect to the pressure roller 21 . An engaging portion of the housing of the fixing device 9 is engaged with the slide groove 53a. The fixing belt 20 can move toward and away from the pressure roller 21 by relatively moving the engaging portion within the slide groove 53a.

In the above-described fixing device 9 as well, by providing the temperature detection element of the thermistor 25 at a position corresponding to the divided area B of the heater 22, the portion corresponding to the divided area of the fixing belt 20 can be sufficiently heated. As a result, the fixability of the image can be sufficiently ensured, and problems such as fixation offset can be prevented.

In particular, in the case of an image forming apparatus that performs an image forming operation using a single color toner, hot offset is relatively less likely to occur than an image forming apparatus that performs an image forming operation using a plurality of color toners. Therefore, even if the heating member is controlled based on the detection result of the temperature detection element arranged at the position corresponding to the divided area as in the present invention, the hot offset is relative to the image forming apparatus using the single color toner. It has the advantage that it is less likely to occur

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above-described embodiments and can be modified in various ways. For example, the separation plate 310 can be disposed so as to move toward and away from the fixing belt 20. In addition to the separation plate 310 being rotatable as in the above-described embodiment, the heater holder 23 and The fixing belt 20 may be configured to move in parallel in the direction of approaching and separating from the fixing belt 20 while maintaining the parallel state.

Moreover, the separation plate 310 may be arranged in a fixed position so as not to move. That is, the separation plate 310 has a leading end portion 311 that can contact the sheet P as a conveyed body and does not contact the fixing belt 20 , and a leading end portion 311 that contacts the fixing belt 20 to separate the fixing belt 20 from the leading end portion 311 . It is sufficient that it has a contact portion 313 that maintains the interval at a predetermined size.

Further, although the fixing belt 20 of the fixing device 60 has been described as an example of the endless belt in the above embodiment, the endless belt may be a photosensitive belt. That is, in an image forming apparatus that transfers a toner image carried on a photoreceptor belt as an image carrier onto a recording medium as a conveyed body, the recording medium is separated from the photoreceptor belt by the aforementioned separation plate.

Also, the endless belt may be the intermediate transfer belt 11 of FIG. 1 as an image bearing member. That is, the recording medium conveyed through the nip between the intermediate transfer belt 11 and the secondary transfer roller 13 is separated from the intermediate transfer belt 11 by the separation plate described above. Similarly, the endless belt may be an intermediate transfer belt used in an inkjet image forming apparatus. In addition, in other inkjet image forming apparatuses, when the pressurizing member forms a nip by being pressed against a nip forming member via an endless belt, and the object to be transported passes through the nip to be transported. Also, the object to be conveyed after passing through the nip can be separated from the endless belt by the separation plate described above.

<Appendix>
Preferred embodiments of the present invention are described below.
<First aspect>
a rotatable flexible endless belt;
a nip forming member provided so as to be in contact with the inner peripheral surface of the endless belt;
a pressing member that presses against the nip forming member via the endless belt to form a nip;
and a guide member that guides both ends of the endless belt,
In a nip forming unit in which an object to be transported passes through the nip and is transported,
A separating member that separates the conveyed object that has passed through the nip from the endless belt, the separating member includes a non-contact portion that does not contact the endless belt, and a non-contact portion that contacts the endless belt. and a contact portion that maintains a predetermined distance from the endless belt.
<Second aspect>
The separation member is arranged so as to be movable in a direction toward and away from the endless belt, and a first regulating portion that determines a moving position in the approaching direction and a second regulating portion that determines a moving position in the moving away direction. The nip forming unit according to the first mode, characterized in that a movement restricting means is provided.
<Third aspect>
The nip forming unit according to the second aspect, wherein the separating member is biased by biasing means in the approaching direction.
<Fourth Aspect>
The nip forming member is disposed movably with respect to the pressing member between an approaching position where the nip is pressed by the pressing member and a separated position where the nip is released. The nip forming unit according to the third aspect, wherein the nip forming member is movable to the separated position while the separating member is restricted in movement by the first restricting portion.
<Fifth aspect>
Any one of the second aspect to the fourth aspect, wherein when the separating member moves in the moving away direction, the movement is restricted by the second restricting portion before coming into contact with the pressing member. Embodiment nip forming unit.
<Sixth Aspect>
The separation member is constituted by a separation plate movably supported between a pair of left and right side plates, and the movement restricting means is disposed between the separation plate and the side plate. The nip forming unit of any one of the five aspects.
<Seventh Aspect>
The movement restricting means includes a movement restricting piece formed at an end of the separation plate and a movement restricting hole formed in the side plate, and one end of the movement restricting hole constitutes the first restricting portion. The nip forming unit according to the sixth mode, wherein the other end portion of the movement restricting hole constitutes the second restricting portion.
<Eighth aspect>
The nip forming unit according to any one of the first to seventh aspects, wherein the contact portion is provided outside the passage area of the transported object.
<Ninth Aspect>
The heater disposed in the nip forming member for heating the endless belt is divided into at least three heaters, ie, an end heater for heating both ends of the endless belt and a center heater for heating a central portion of the endless belt. The nip forming unit according to any one of the first to eighth aspects, characterized by:
<Tenth Aspect>
An image forming apparatus comprising the nip forming unit according to any one of the first to ninth aspects.

1Y, 1M, 1C, 1Bk: Image forming unit 2: Photoreceptor 3: Charging device 4: Developing device 5: Cleaning device 6: Exposure device 7: Paper feeding device 8: Transfer device 9: Fixing device 10: Paper discharging device 11 : Intermediate transfer belt 12: Primary transfer roller 13: Secondary transfer roller 13: Secondary transfer nip 14: Paper transport path 15: Timing roller 20: Fixing belt 21: Pressure roller 21: Fixing belt 21a: Metal core 21b: Elasticity Layer 21c: release layer 22: heater 23: heater holder 23: heater holder 23a: protrusion 23b: recess 23b1 to 23b3: wall 23c: relief 24: stay 24a: vertical portion 24a1: contact surface 25: thermistor 26: guide Part 27: thermostat 30: base material 31: resistance heating element 31: back surface (resistance heating element 32: insulating layer 33: power supply line 34: electrode 34: electrode parts 34A, 34B: electrode parts 34A, 34C: electrode parts 34A to 34C : Electrode portion 35: Heat generating portions 35A, 35C: Heat generating portions 35A to 35C: Heat generating portion 35B: Heat generating portion 44: Pressing roller 45: Nip forming member 50: Image forming means 51: Reading portion 53: Flange 53a: Slide groove 55: Substrate 56: Resistance heating element 60: Fixing device 60: Connector 61: Fixing belt 62: Pressure roller 63: Heater 64: Heater holder 64b: Concave portions 64b1, 64b2: Both side walls 64c: Escape portion 65: Stay 65a: Vertical portion 65a1 : Contact surface 66: Guide member 67: Temperature sensor 92: Heating assembly 93: Fixing roller 93a: Metal core 93b: Elastic layer 93c: Release layer 94: Pressure assembly 95: Nip forming member 96: Stay 97: Pressure Belt 100: Image forming apparatus 120: Heating belt 160: Connector 200: AC power supply 210: Triac 220: Control unit 260: Belt facing surface 300: Paper separation mechanism 310: Separation plate (separation member) 311: Tip part 312: Wrap around Motion restriction piece 313: Contact portion 314: Spring engagement portion 315: Shaft hole 320: Side plate 321: Rotation restriction hole 322: Support shaft 323: Spring engagement portion 324: Notch 330: Extension spring 400: Flange (guide member )

JP 2015-011167 A

Claims (10)

a rotatable flexible endless belt;
a nip forming member provided so as to be in contact with the inner peripheral surface of the endless belt;
a pressing member that presses against the nip forming member via the endless belt to form a nip; and a guide member that guides both ends of the endless belt,
In a nip forming unit in which an object to be transported passes through the nip and is transported,
A separating member that separates the conveyed object that has passed through the nip from the endless belt, the separating member includes a non-contact portion that does not contact the endless belt, and a non-contact portion that contacts the endless belt. and a contact portion that maintains a predetermined distance from the endless belt. The separation member is arranged so as to be movable in a direction toward and away from the endless belt, and a first regulating portion that determines a moving position in the approaching direction and a second regulating portion that determines a moving position in the moving away direction. 2. A nip forming unit according to claim 1, further comprising: a movement restricting means. 3. A nip forming unit according to claim 2, wherein said separating member is biased in said approaching direction by biasing means. The nip forming member is disposed movably with respect to the pressing member between an approaching position where the nip is pressed by the pressing member and a separated position where the nip is released. 4. The nip forming unit according to claim 3, wherein the nip forming member is movable to the separated position while the separation member is restricted in movement by the first restricting portion. 5. The nip according to any one of claims 2 to 4, characterized in that when the separating member moves in the separating direction, the movement is restricted by the second restricting portion before coming into contact with the pressing member. forming unit. 5. The separation member is composed of a separation plate movably supported between a pair of left and right side plates, and the movement restricting means is disposed between the separation plate and the side plate. The nip forming unit of any one of Claims. The movement restricting means includes a movement restricting piece formed at an end of the separation plate and a movement restricting hole formed in the side plate, and one end of the movement restricting hole constitutes the first restricting portion. 7. The nip forming unit according to claim 6, wherein the other end portion of the movement restricting hole constitutes the second restricting portion. 5. The nip forming unit according to any one of claims 1 to 4, wherein the contact portion is provided outside the passage area of the transported object. The heater disposed in the nip forming member for heating the endless belt is divided into at least three heaters, ie, an end heater for heating both ends of the endless belt and a central heater for heating a central portion of the endless belt. A nip forming unit according to any one of claims 1 to 4, characterized in that: An image forming apparatus comprising the nip forming unit according to any one of claims 1 to 4.

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