JP2019128381A - Image heating device and image forming apparatus - Google Patents

Abstract

To provide a technique capable of achieving both quick-start performance at cold starting and power saving performance during continuous printing.SOLUTION: An image heating device C includes: a heater 20 comprising a substrate 201 and heating elements 202 mounted on the substrate 201; a tubular film 25 rotating with its inner surface in contact with the heater 20; a pressing member 26 rotating in contact with an outer surface of the film 25; a holding member 21 holding the heater 20; and a heat conduction member 23 held between the heater 20 and the holding member 21 and making contact with the inner surface of the film 25, the image heating device using the heat of the heater 20 to heat an image T formed on a recording member P held at a nip portion N between the film 25 and the pressing member 26. A contact region between the heater 20 and the heat conduction member 23 does not overlap with the heating elements 202 when projected on a surface of the substrate 201 in the vertical direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a glossiness of a toner image by reheating a fixed toner image on a recording material or a fixing device mounted on an image forming apparatus such as a copying machine or a printer using an electrophotographic method or an electrostatic recording method. The present invention relates to an image heating apparatus such as a gloss imparting apparatus for improving image quality. The present invention also relates to an image forming apparatus including the image heating apparatus.

  A film heating type fixing device, which is a type of fixing device used in an electrophotographic image forming apparatus, can save power and shorten weight time (quick start) because the heater and film have low heat capacity. Has the advantage of In the above-mentioned fixing method, the fixing film of a general film heating method applies heat to the fixing film only from the sliding surface of the heater, while in Patent Document 1, the fixing film fixes heat from other than the sliding surface of the heater. A configuration to convey to is proposed. The configuration proposed in Patent Document 1 is such that the surface opposite to the sliding surface of the heater (hereinafter referred to as the heater back surface) and the surface perpendicular to the sliding surface (hereinafter referred to as the heater side surface) have high thermal conductivity such as aluminum. It is the feature that the member is made to contact. By extending this high thermal conductivity member and placing it in contact with the inner surface of the fixing film, it becomes possible to transfer the heat other than the heater sliding surface to the film. Further, high heat conduction can be realized by bringing the high heat conduction member and the inner surface of the fixing film into contact with each other over a wide range. As a result, the fixing performance can be satisfied while the heater temperature is kept low. With this configuration, even in an image forming apparatus that requires a high printing speed in recent years, the temperature of the member can be kept low (hereinafter referred to as low temperature fixability). If the low-temperature fixability is good, options are widened when selecting materials from the viewpoint of the heat resistance of the member. In addition, deterioration of the heater, the fixing film, and the sliding grease interposed therebetween can be prevented, and there is a merit that the device life can be extended.

JP 2003-257592 A

  However, the configuration of Patent Document 1 has a problem in quick start performance at the time of cold start (when the apparatus is started from a state in which the apparatus is not preheated). In order to satisfy high quick start performance, it is necessary to prevent heat generated by the heater of the heater from warming members other than the recording material (paper) as much as possible. In the above configuration, when the cold start is performed, heat is used to warm the high heat conductive member brought into contact with the back surface of the heater, which may reduce the efficiency of warming the recording material. That is, there is a possibility that the quick start performance is deteriorated due to the heat capacity of the high heat conducting member itself arranged in contact with the heater. On the other hand, at the time of continuous printing, since the high thermal conductivity member is sufficiently heated, it is possible to exert the effect of the low temperature fixability. That is, with the above configuration, it is not easy to achieve both quick start characteristics during cold start and low temperature fixability during continuous printing.

  An object of the present invention is to provide an image heating apparatus capable of satisfying both quick start performance at cold start and low temperature fixability at continuous printing.

In order to achieve the above object, the image heating apparatus of the present invention comprises:
A heater having a substrate and a heating element provided on the substrate; a cylindrical film whose inner surface rotates while being in contact with the heater; a pressure member which rotates while being in contact with the outer surface of the film; and the heater A holding member to be held, and a heat conduction member that is sandwiched between the heater and the holding member and that contacts the inner surface of the film, and a nip portion between the film and the pressure member. In an image heating apparatus for heating an image formed on a nipped recording material using heat of the heater,
The region where the heater and the heat conducting member are in contact with each other does not overlap the heating element when projected in a direction perpendicular to the surface of the substrate.
In order to achieve the above object, an image forming apparatus of the present invention includes:
An image forming unit for forming an image on a recording material;
The image heating apparatus as a fixing unit for fixing an image formed on a recording material to the recording material;
And the like.

  According to the present invention, it is possible to provide an image heating apparatus capable of satisfying both the quick start property at cold start and the low temperature fixability at continuous printing.

FIG. 3 is a cross-sectional view of the image forming apparatus according to the first embodiment. Sectional view of the fixing device according to the first embodiment. FIG. 6 is a schematic cross-sectional view of a fixing nip portion in the fixing device according to the first embodiment. Sectional schematic diagram of fixing nip portion in fixing devices according to Comparative Examples 1 and 2 FIG. 6 is a schematic diagram of the surface and cross section of the heater in the fixing device according to the second embodiment. Surface and cross-sectional schematic view of the fixing nip portion in the fixing device according to the second embodiment. FIG. 6 is a schematic cross-sectional view of a fixing nip portion in the fixing device according to the first embodiment. FIG. 3 is a perspective view of a high heat conductive member in the fixing device according to the first embodiment.

  Hereinafter, with reference to the drawings, modes for carrying out the present invention will be exemplarily described in detail based on examples. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. That is, it is not intended to limit the scope of the present invention to the following embodiments.

Example 1
(Schematic configuration of image forming apparatus)
FIG. 1 is a schematic cross-sectional view of an example of an image forming apparatus according to a first embodiment of the present invention. The image forming apparatus includes an image forming unit A that forms a toner image on a recording material, a recording material feeding unit B that sends the recording material to the image forming unit A, and a toner image on the recording material that is heat-fixed on the recording material. A fixing unit (fixing device) C is provided. The image forming unit A includes a drum-shaped electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1 as an image bearing member. The photosensitive drum 1 is rotatably supported by an image forming apparatus main body (hereinafter referred to as an apparatus main body) M that constitutes a housing of the image forming apparatus. Around the outer peripheral surface of the photosensitive drum 1, a charging roller 2, a laser scanner 3, a developing device 4, a transfer roller 5, and a cleaning device 6 are arranged in this order along the rotation direction. The recording material feeding unit B has a feeding roller 11. The delivery roller 11 is rotated at a predetermined timing in the direction of the arrow by a delivery drive motor (not shown) and delivered to the delivery path of the recording material P loaded and stored in the cassette 7. A transport roller 8, a top sensor 9, a transport guide 10, a fixing device C, a transport roller 12, a discharge roller 13, and a discharge tray 14 are arranged in order along the transport path of the recording material P. .

  The image forming apparatus according to the first exemplary embodiment includes a control unit (control unit 31) that controls the image forming unit A, the recording material feeding unit B, the fixing device C, and the like. The control unit 31 includes a CPU and a memory such as a ROM and a RAM, and the memory stores various programs necessary for image formation. The control unit 31 receives a print signal from an external device such as a host computer and executes a predetermined image formation control sequence based on the print signal. As a result, the drum motor is driven to rotate, and the photosensitive drum 1 rotates in the arrow direction at a predetermined peripheral speed (process speed). The surface of the rotated photosensitive drum 1 is uniformly charged by a charging roller 2 to a predetermined potential having the same polarity as the toner (in this case, a negative polarity). The laser scanner 3 scans the laser beam L on the charged surface of the surface of the photosensitive drum 1 based on the image information to expose the surface of the photosensitive drum 1. By this exposure, the charge at the exposed portion is removed, and an electrostatic latent image is formed on the surface of the photosensitive drum 1.

  The developing device 4 includes a developing roller 41, a toner container 42 for storing toner, and the like. The toner is rubbed by a member such as a urethane blade (not shown) and is charged to a predetermined polarity (negative polarity in the first embodiment). The developing device 4 applies toner to the electrostatic latent image on the surface of the photosensitive drum 1 by applying a negative potential to the developing roller 41 by a developing voltage power supply (not shown), thereby causing toner to adhere to the electrostatic latent image on the surface of the photosensitive drum 1. The latent image is developed as a toner image T. The toner image T formed on the surface of the photosensitive drum 1 is transferred to the recording material P using a potential difference due to the transfer voltage by applying to the transfer roller 5 a positive potential having a polarity opposite to that of the toner. In addition, the conveyance driving motor provided in the recording feeding member B is driven to rotate, and the feeding roller 11 feeds the recording material P from the cassette 7 to the conveying roller 8. The recording material P is conveyed by the conveyance roller 8, passes through the top sensor 9, and is conveyed to the transfer nip portion between the surface of the photosensitive drum 1 and the outer peripheral surface of the transfer roller 5. At this time, the leading edge of the recording material P is detected by the top sensor 9. The recording material P to which the toner image T formed on the surface of the photosensitive drum 1 is transferred is conveyed along a conveyance guide 10 to a fixing device (image heating device) C as a fixing unit (image heating unit). In the fixing device C, the toner image T on the recording material P is heated and pressed to be heat-fixed on the recording material P. The recording material P on which the toner image T has been heat-fixed is transported in the order of the transport roller 12 and the discharge roller 13 and is discharged to the discharge tray 14 on the upper surface of the apparatus main body M. The transfer residual toner remaining on the surface of the photosensitive drum 1 after the toner image is transferred to the recording material P is removed by the cleaning blade 61 of the cleaning device 6 and accumulated in the cleaning device 6. By repeating the above operation, printing is performed sequentially. In the case of the A4 size, the image forming apparatus according to the first exemplary embodiment can perform printing at a printing speed of 70 sheets / minute.

(Configuration of fixing device)
FIG. 2 is a cross-sectional side view of the fixing device of the image forming apparatus according to the first embodiment. The fixing device C according to the first exemplary embodiment includes a ceramic heater 20, a heater holder 21, a metal stay 22, a fixing film 25, and a pressure roller 26 as basic configurations. The heater holder 21 is a holding member that holds the ceramic heater 20 as a heating body. The metal stay 22 is a backup member that applies pressure to the heater holder 21 for backup. The fixing device C holds the recording material P in a nip portion between a cylindrical fixing film 25 as a heating rotating body and a pressure roller 26 as a pressure rotating body (pressure member). The toner image T is heated and fixed to the recording material P by utilizing the heat of (the heating element on the substrate). Power is supplied to the fixing device C from a control circuit 271 as an energization control unit connected to a commercial AC power supply 272.

(heater)
The ceramic heater 20 has a heat resistant heater substrate 201 made of aluminum nitride, alumina or the like. In the first embodiment, as a material of the heater substrate 201, aluminum nitride excellent in thermal conductivity is employed. On the surface of the heater substrate 201, a resistor pattern 202 (hereinafter referred to as a heating element) as an energization heating resistance layer that generates heat due to energization is made orthogonal to the longitudinal direction of the heater substrate 201 (printing material P transport direction) by printing, for example. Direction). In the first embodiment, since aluminum nitride of high thermal conductivity is used for the heater substrate 21, the heat generating element 202 is disposed on the opposite surface to the surface in contact with the inner surface of the fixing film 25. The surface of the heating element 202 is covered with a glass layer 203 as a protective layer. A thermistor 204 as a temperature detection member for detecting the temperature of the heater 20 is disposed on the back surface (the surface opposite to the fixing nip portion N) of the glass layer 203. A sliding glass 205 as a sliding layer is provided on the surface of the heater substrate 21 and the fixing film 25 in contact with each other. Between the sliding glass 205 of the heater 20 and the fixing film 25, sliding grease (not shown) is interposed for the purpose of keeping the rotational torque low. It is desirable that this sliding grease has excellent heat resistance and properties such that the sliding property does not decrease even in long-term use. In Example 1, 400 mg of fluorine grease (hp-300 manufactured by Toray Dow Corning Co., Ltd.) is applied. The heater holder 21 that holds the ceramic heater 20 is made of a heat-resistant resin such as a liquid crystal polymer, a phenol resin, PPS, or PEEK. The heater holder 21 acts as a support member for supporting the heater 20 and also acts as a guide member for guiding the rotation of the fixing film 25. The heater holder 21 is pressed toward the pressure roller 26 by the metal stay 22.

(Pressing roller)
The pressure roller 26 has an elastic layer 262 on the outer periphery of the core shaft portion 261 and has a surface layer 263 on the outer periphery of the elastic layer 262. The outer diameter of the pressure roller 26 is about 25 mm. The core shaft portion 261 is made of a solid or hollow metal material such as aluminum or iron. In Example 1, solid aluminum is used as the core metal material. The elastic layer 262 is made of heat insulating silicone rubber, and is made conductive by adding an electrically conductive material such as carbon. The surface layer 263 in contact with the outer surface of the fixing film 25 is a releasable tube having a thickness of 10 to 80 μm made of a fluororesin such as PFA, PTFE, or FEP. Here, PFA is a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, PTFE is a polytetrafluoroethylene (tetrafluoroethylene), and FEP is an abbreviation for a tetrafluoroethylene / hexafluoropropylene copolymer (4,6 fluoride). It is. In the first embodiment, the surface layer 263 of the pressure roller 26 is a PFA tube with a thickness of 30 μm.

(Fixing film)
The fixing film 25 has a cylindrical shape with a diameter of 24 mm. The fixing film 25 has flexibility and is loosely fitted to the heater holder 21. As shown in the circle of FIG. 2, the layer structure of the fixing film 25 is composed of a multilayer in which a base layer 251, an elastic layer 252, and a surface layer 253 are provided from the inside. As a material for the base layer 251, a heat-resistant resin material having a low heat capacity such as polyimide, polyamideimide, PEEK, or PES is used in many fixing devices. Metals can also be used. The base layer 251 is required to have a heat capacity of 15 μm or more and 150 μm or less because the heat capacity needs to be reduced to satisfy the quick start property and the mechanical strength as well. The base layer 251 of Example 1 was a cylindrical polyimide base layer having a thickness of 70 μm. The elastic layer 252 is made of silicone rubber. By providing the elastic layer 252, it is possible to wrap the toner image T and apply heat uniformly, so it is possible to obtain a high-quality image with high glossiness and no unevenness. Further, since the elastic layer 252 has a low thermal conductivity with silicone rubber alone, 1.2 W / (m · k) can be obtained by adding a thermal conductive filler such as alumina, metal silicon, silicon carbide, or zinc oxide. It is good to secure the above. In Example 1, metal silicone which is a heat conductive filler is added to dimethylpolysiloxane which is a rubber material to elastic layer 252, and the heat conductivity is set to 1.2 W / (m · k). The thickness of the elastic layer 252 is 250 μm. As the release layer, the surface layer 253 is required to have high abrasion resistance and high release property to toner. As the material, fluorine resin such as PFA, PTFE, FEP or the like mentioned above is used. It is formed of a coating layer obtained by firing a resin dispersion, or a tube layer. In some cases, a conductive material such as carbon is added to the fluororesin. The surface layer 253 of Example 1 was made of PFA as a fluorocarbon resin and had a thickness of 15 μm as a coating layer.

(High heat conduction member)
The high heat conduction member 23 which is a characteristic configuration of the first embodiment will be described with reference to FIG. FIG. 3A is a schematic view showing the positional relationship between the heater 20 and the high thermal conductivity member 23 of Example 1 in an enlarged manner, in the longitudinal direction of the heater 20 (direction orthogonal to the conveyance direction of the recording material P). It is typical sectional drawing when it saw.

(Cross sectional shape of high thermal conductivity member)
The fixing device C according to the first embodiment is provided with a high thermal conductive member 23 for conducting heat from the back surface and side surface of the heater 20 to the fixing film 25. The high heat conduction member 23 is divided into two, upstream and downstream, with respect to the recording material conveyance direction indicated by the arrows in the figure. The high heat conduction member 23J is upstream and the high heat conduction member 23K is downstream. is set up. The high thermal conductivity members 23J and 23K are in contact with the back surface of the heater 20 (the upper surface of the glass layer 203) and the side surface of the heater 20 (the side surface of the glass layer 203 and the side surface of the heater substrate 201). As a result, the high heat conductive members 23J and 23K receive the heat generated from the heating element 202 via the glass 203 and the heater substrate 201, and serve to supply heat to the inner surface of the fixing film 25.

  The first embodiment is characterized by the contact area between the high heat conductive members 23J and 23K and the back surface of the heater 20. The high thermal conductivity members 23J and 23K of the first embodiment are installed at positions where the heating element 202 of the heater 20 is not covered. That is, the regions of the upper RJ and RK of the heating element 202 in FIG. 3A are installed so as not to be covered by the high heat conductive members 23J and 23K. The upper RJ and RK regions of the heating element 202 are areas that overlap the heating element 202 on the back surface (upper surface of the glass layer 203) of the heater substrate 201 when projected in a direction perpendicular to the surface of the heater substrate 201. That is, the high heat conductive members 23J and 23K are installed so as not to overlap the heating element 202 when the projection is performed. At this time, in consideration of variations in the shape and installation position of the high heat conductive member 23, a predetermined clearance X as shown in FIG. 3A is provided between the heat generating body 202 and the high heat conductive members 23J and 23K. It is good to provide. That is, when the above projection is performed, the high heat conductive members 23J and 23K are arranged so that a predetermined clearance X is provided between the heater 202 and the heater substrate 201 in a short direction (a direction perpendicular to the longitudinal direction). It has been installed. Further, since the high heat conductive member 23 is sandwiched between the heater 20 and the heater holder 21, the RJ and RK regions on the back surface (upper surface of the glass layer 203) of the heater substrate 201 and the heater holder by the level difference (thickness) of the high heat conductive member 23. A space (gap) is provided between 21.

The upstream high heat conductive member 23J has a first portion 23J1, a second portion 23J2, and a third portion 23J3, and the shape when viewed in the heater longitudinal direction has a substantially Z-shape. The first portion 23J1 is a portion extending in a direction perpendicular to the surface of the heater substrate 201 that is sandwiched between the heater 20 (the heater substrate 201 and the glass layer 203) on the upstream side in the recording material conveyance direction and the heater holder 21. . The second portion 23J2 is a portion that is sandwiched between the heater holder 21 and the upper surface of the heater 20 (glass layer 203) and extends from the upper end of the first portion 23J1 toward the downstream side in the recording material conveyance direction. The third portion 23J3 is a portion which is sandwiched between the heater holder 21 and the fixing film 25 and extends from the lower end of the first portion 23J1 toward the upstream of the recording material conveyance direction.
The downstream high heat conduction member 23K is also configured in the same manner as the upstream high heat conduction member 23J, and includes a first portion 23K1, a second portion 23K2, and a third portion 23K3, as viewed in the heater longitudinal direction. Has a substantially Z-shape. The first portion 23 </ b> K <b> 1 is a portion extending in a direction perpendicular to the surface of the heater substrate 201 that is sandwiched between the heater 20 (the heater substrate 201 and the glass layer 203) on the downstream side in the recording material conveyance direction and the heater holder 21. . The second portion 23K2 is a portion that is sandwiched between the heater holder 21 and the upper surface of the heater 20 (glass layer 203) and extends from the upper end of the first portion 23K1 toward the upstream in the recording material conveyance direction. The third portion 23K3 is a portion which is sandwiched between the heater holder 21 and the fixing film 25 and which extends from the lower end of the first portion 23K1 toward the downstream in the recording material conveyance direction.

  In addition, the installation position with respect to the back surface of the heater 20 and the size of the clearance X of the high heat conductive members 23J and 23K shown here are merely examples, and the arrangement and number of the heating elements 202, the glass layers 203, and the heater substrate 201 It is appropriately set according to the thickness, material, and the like. In other words, the heating element 202 is appropriately set within a range in which it can be ensured that the heat of the heat generating body 202 is preferentially used (consumed) for heating the recording material P rather than heating the high thermal conductive members 23J and 23K.

(Longitudinal shape of high thermal conductivity member)
FIG. 8A shows the longitudinal shape of the high heat transfer member 23 of the first embodiment. The high heat conductive member 23 is divided in the entire longitudinal direction into the upstream side 23J and the downstream side 23K, and has a symmetrical shape. The longitudinal lengths of the high heat conductive members 23K and 23J are 220 mm, and are installed so as to cover the width of the letter size which is the maximum sheet passing size. In addition, although the shape which divides | segments a high heat conductive member was shown in the present Example 1, the high heat conductive member 23K and the high heat conductive member 23J can also be connected (integrated). FIG. 8B shows an example thereof, in which the high heat conductive member 23K and the high heat conductive member 23J are connected to each other in an end region where image formation is not performed. That is, both ends in the substrate longitudinal direction of the second portion 23K2 of the high thermal conductivity member 23K and the second portion 23J2 of the high thermal conductivity member 23J are respectively connected (portions 23C1 and 23C2). By doing so, the shape and stability during assembly can be increased.

  As a material of the high thermal conductivity members 23K and 23J, it is desirable to be a heat resistant and high strength member having high thermal conductivity. In the first embodiment, an aluminum alloy having a thermal conductivity of 140 W / (m · k) is used, and the thickness is 0.8 mm.

(Other shapes of high thermal conductivity members)
In the first embodiment, the high thermal conductive members 23K and 23J have a Z shape as shown in FIG. 3 (a), but may have an L shape as shown in FIG. 3 (b). . That is, the upstream high heat conductive member 23J includes the first portion 23J1 and the second portion 23J2, and does not include the third portion 23J3. The downstream high heat conductive member 23K is also configured by the first portion 23K1 and the second portion 23K2, and does not have the third portion 23K3.
Further, as shown in FIG. 3C, it may be formed in an I-shape in contact with only the side surface of the heater 20 and the inner surface of the fixing film 25 without contacting the back surface of the heater 20. That is, the upstream high heat conductive member 23J is configured by only the first portion 23J1, and does not have the second portion 23J2 and the third portion 23J3. The downstream high heat conductive member 23K is also configured by only the first portion 23K1, and does not have the second portion 23K2 and the third portion 23K3.
Further, as shown in FIG. 3D, the heater 20 side surface fixing film 25 can be set to be in contact with the inner surface in an L shape. That is, the upstream high thermal conductive member 23J includes the first portion 23J1 and the third portion 23J3, and does not have the second portion 23J2. The downstream high heat conductive member 23K is also composed of the first portion 23K1 and the third portion 23K3, and does not have the second portion 23K2.
Further, as shown in FIG. 3E, the space (gap) Y is formed between the upper portion of the heating element 202 and the high heat conductive member 23 by connecting the high heat conductive member 23 upstream and downstream and providing a convex shape by drawing or the like. It can also be provided. That is, the space forming portion 23C3 having a convex shape (concave shape with respect to the upper surface of the heater 20 (glass layer 203)) is formed between the second portion 23K2 of the high heat conductive member 23K and the second portion 23J2 of the high heat conductive member 23J. It is a connected configuration. In this case, the example in which the space Y is provided between the heat generating body 202 and the high heat conductive member 23 has been shown, but the same is true even if a member having low heat conductivity is sandwiched between the heat generating body 202 and the high heat conductive member 23. The effect of can be demonstrated. The low thermal conductivity member is preferably a member having a thermal conductivity lower than that of the glass layer 203.
As shown in FIGS. 3C and 3D, in the configuration in which the second portion sandwiched between the upper surface of the heater 20 and the heater guide 21 is not provided in the high thermal conductivity member 23, The opposite portion is provided with a recess 21C for avoiding contact with the RJ and RK portions.

  Further, the contact portions between the high heat conductive members 23K and 23J and the fixing film 25 can take various shapes. As a configuration other than the first embodiment, for example, the configurations shown in FIGS. 7A and 7B can be adopted. In FIG. 7A, a shape 211 that restricts the fixing film 25 from the inner surface (projects downward from the lower surface of the heater 20 (to the pressure roller 26 side)) is provided on the downstream side of the high heat conductive member 23 </ b> K of the heater holder 21. ing. FIG. 7B shows a configuration in which the high heat conduction member 23K is bent and installed at an angle that causes the fixing film 25 to bend toward the pressure roller 26. That is, the first portion 23K1 and the third portion 23K3 are configured to be folded, and a part of the fixing film 25 is bent toward the pressure roller 26 by the bent portion 23K4 of the joint between the first portion 23K1 and the third portion 23K3. . The above configuration is characterized in that the inner surface of the fixing film 25 and the high heat conducting member 23 can be stably brought into contact with each other even when the orbit of the fixing film 25 is not stabilized due to a factor such as a change in the nip width. A similar configuration may be provided in the upstream high heat conduction member 23J.

(Low temperature fixability and quick start property)
FIG. 4 is a schematic diagram illustrating a cross-sectional configuration of a fixing device according to a comparative example. The configuration of Comparative Example 1 is shown in FIG. In Comparative Example 1, the high thermal conductivity member 23 covers the entire back surface of the heater 20. Moreover, the structure of the comparative example 2 is shown in FIG.4 (b). Comparative Example 2 has a configuration in which a space is provided between the upper portion of the heating element 202 in the heater 20 and the heater holder 21 without providing the high heat conductive member 23.

  In Comparative Example 1, the heat transmitted from the back surface and side surface of the heater 20 to the high heat conductive member 23 can be conducted to the inner surface of the fixing film 25 by installing the high heat conductive member 23. As a result, low temperature fixability can be realized during continuous printing. When the low-temperature fixability is realized, the temperature of members such as the heater 20 and the heater holder 21 and the sliding grease can be kept low. In particular, by keeping the temperature of the sliding grease low, it is possible to prevent the grease from deteriorating in durability and to suppress the torque increase. On the other hand, in Comparative Example 1, there is a problem that quick start performance is impaired during a cold start. At the cold start, the high heat conductive member 23 is at a low temperature, and the high heat conductive member itself is warmed by the heat generated by the heating element 202. At this time, heat for warming the high heat conductive member 23 is mainly transmitted through the regions RK and RJ above the heating element 202. As a result, the proportion of the heat generated by the heating element 202 that is transmitted to the recording material via the nip portion N is reduced, and the fixing performance of the toner on the recording material is reduced, so that the quick start property is impaired. From the above, in Comparative Example 1, the quick start property at the cold start was a problem.

  In Comparative Example 2, since a space is provided between the heater 20 and the heater holder 21 in the upper region of the heater 20, the heat generated by the heater 202 can be efficiently transmitted to the recording material, and cold is generated. Quick start performance at the start can be satisfied. On the other hand, Comparative Example 2 has a problem that the low-temperature fixability cannot be satisfied. In Comparative Example 2, the high thermal conductivity member is not installed, and heat exchange between the heater 20 and the fixing film 25 is substantially limited to that in the contact region between the surface of the heater 20 and the inner surface of the fixing film 25. . As a result, the heat of the heater 20 cannot be efficiently transmitted to the film, and thus to the recording material P. Here, in Comparative Example 2, in order to obtain the same fixing property as that provided with the high thermal conductivity member (Example 1 and Comparative Example 1), the temperature of the heater 20 needs to be set 10 ° C. higher. As a result, the temperature of the heater 20, the heater holder 21, and the sliding grease is increased during continuous printing. As described above, when the temperature of the heater 20 is high, there is a problem that a torque increase due to the durability deterioration of the sliding grease occurs.

(Fixing device of Example 1)
The above problem can be solved by using the fixing device of the first embodiment. In the fixing device according to the first exemplary embodiment, the high heat conductive members 23K and 23J are divided into the upstream side and the downstream side in the transport direction so that the upper regions RK and RJ of the heating element 202 are not covered. With this configuration, the heat of the heater 20 can be transferred to the fixing film 25 through the high thermal conductivity members 23K and 23J during continuous printing, and the temperatures of the heater 20, the heater holder 21 and the sliding grease can be kept low. On the other hand, since the high thermal conductivity members 23K and 23J are not in contact with the heater 20 in the upper regions RK and RJ of the heating element 202, the high thermal conductivity members 23J and 23K are not unnecessarily heated at the cold start. Therefore, heat can be efficiently transmitted to the recording material P, and quick start performance can be satisfied.

(Comparison result of the fixing device of Example 1 and the fixing device of the comparative example)
In order to demonstrate the effect of the fixing device of Example 1, the results of a comparative experiment with the fixing devices of Comparative Examples 1 and 2 will be shown. The fixing device according to the first exemplary embodiment has a configuration illustrated in FIG. On the other hand, the fixing devices of Comparative Examples 1 and 2 are configured as shown in FIGS. 4 (a) and 4 (b), respectively. Since other configurations are the same as those of the first embodiment, the description thereof is omitted. The pressing force of Example 1 and Comparative Examples 1 and 2 is 186.2 N (19 kgf), the nip width is 9 mm, and the printing speed of the image forming apparatus is 60 sheets / min. The environment in which the test was performed was an air temperature of 23 ° C. and a humidity of 50%, and Oce RedLabel (A4 size, 80 g / cm 2) was used as the evaluation paper. Under these conditions, evaluation of quick start performance at cold start and low temperature fixability at continuous printing was performed.

  Table 1 is a result table showing quick start performance and energy saving performance in the image forming apparatus using the fixing device of Example 1 and Comparative Examples 1 and 2. A method for determining the level of quick start in Table 1 will be described. The quick start property is a cold start time, which is a time taken for the fixing member to reach a temperature at which the toner image T can be fixed, and the level is determined with “fixing temperature reaching time” as an index. As the fixing temperature reaching time is shorter, the fixing member is heated in a short time, so that the time until the first print job is printed out can be shortened, which indicates that the quick start property is excellent. In the table, ○ indicates that the fixing temperature arrival time is less than 4.0 seconds, and the quick start property is sufficiently excellent. On the other hand, x in the table is 4.0 seconds or more, indicating that the quick start property is poor. For low-temperature fixability, durability is maintained until the torque of the fixing device is increased, and the level is determined based on the number of sheets that can be passed so far. Since the durability is also determined by combining the fixability of the toner, as described above, the temperature of the heater 20 of Comparative Example 2 is controlled by 10 ° C. higher than the temperature of the heater 20 of Example 1 and Comparative Example 2. There is. Further, during the durability, the torque of the fixing device is measured. When the torque value exceeds 5 kgf · cm, it is determined that the torque is increased, and the durability is terminated. In the table, 表 indicates that the number of sheets passed before the torque is increased exceeds 250 k, and the durability is excellent. On the other hand, “X” in the table indicates that the number of sheets passed before the torque is increased is less than 250 k, which is inferior in durability.

表１によれば、比較例１の定着装置においては、トルクアップまでの通紙枚数は満足しているものの、クイックスタート性が不十分であった。また、比較例２の定着装置におい
ては、クイックスタート性は満足しているものの、トルクアップまでの通紙枚数が不十分であった。
一方、実施例１の定着装置を用いることでクイックスタート性とトルクアップまでの通紙枚数を共に満足することができる。その理由は、実施例１の構成により、コールドスタート時は高熱伝導部材２３Ｊ、２３Ｋを温めるための不必要な熱が使われること無く、連続プリント時には高熱伝導部材２３Ｊ、２３Ｋにより、フィルムに効率良く熱伝導が行われるためである。以上のように、実施例１の定着装置を用いれば、比較例１、２には無い作用効果を得ることができる。 (Table 1) Comparative results of Example 1 and Comparative Examples 1 and 2

According to Table 1, in the fixing device of Comparative Example 1, although the number of sheets passed until the torque was increased, the quick start property was insufficient. In the fixing device of Comparative Example 2, although the quick start property was satisfied, the number of sheets to be passed until the torque was increased was insufficient.
On the other hand, by using the fixing device of the first embodiment, both quick start performance and the number of sheets to be passed up to the torque increase can be satisfied. The reason is that, according to the configuration of Example 1, unnecessary heat for warming the high heat conductive members 23J and 23K is not used at the cold start, and the high heat conductive members 23J and 23K are efficiently used for the film at the time of continuous printing. It is because heat conduction is performed. As described above, when the fixing device of Example 1 is used, it is possible to obtain the effects and advantages not found in Comparative Examples 1 and 2.

  The high heat conduction member 23 according to the first embodiment may be configured to have only the high heat conduction member 23J on the upstream side or the high heat conduction member 23K on the downstream side. Further, different shapes may be used on the upstream side and the downstream side. For example, the upstream side may be arbitrarily selected as Z-shaped and the downstream side may be L-shaped. In the first embodiment, the heater 20 is configured to generate heat on the back side, but the same effect can be obtained also in the case of a configuration to generate heat on the surface of the substrate with the heat generating body 202 on the sliding surface side with the fixing film 25. Can get

Example 2
A second embodiment of the present invention will be described. The difference between the second embodiment and the first embodiment is only the heater 20 and the high heat conduction member 23, and the other configurations are the same as those of the first embodiment, so that the description thereof is omitted. The heater 20 of the second embodiment is characterized in that the heating element 202 is divided in the longitudinal direction. The merit of this is that the temperature rise of the non-sheet passing portion and the non-image portion can be suppressed by changing the heat generation amount of the heating element 202 according to the paper size (recording material size) and the image pattern.

  The configuration of the heater 20 according to the second embodiment will be described with reference to FIG. 5A is a cross-sectional view of the heater 20, FIG. 5B is a plan view of each layer of the heater 20, and FIG. 3C is a view for explaining a method of connecting the electrical contacts C to the heater 20. FIG. 5B shows the conveyance reference position X of the recording material P in the image forming apparatus according to the second embodiment. The conveyance standard in the second embodiment is the central standard, and the recording material P is conveyed such that the center in the width direction is along the conveyance standard position X. FIG. 5A is a cross-sectional view of the heater 20 at the transport reference position X.

  The heater 20 was provided on the surface of the ceramic substrate 201, the back surface layer 1 provided on the substrate 201, the back surface layer 2 covering the back surface layer 1, and the surface opposite to the back surface layer 1 on the substrate 201. The sliding surface layer 1 and the sliding surface layer 2 covering the sliding surface layer 1 are configured. The back surface layer 1 has the conductor 206 (206a, 206b) provided along the longitudinal direction of the heater 20. The conductor 206 is separated into the conductor 206a and the conductor 206b, and the conductor 206b is disposed downstream of the conductor 206a in the conveyance direction of the recording material P. Further, the back surface layer 1 includes conductors 207 (207-1 to 207-7) provided in parallel with the conductors 206a and 206b. The conductor 207 is provided along the longitudinal direction of the heater 20 between the conductor 206a and the conductor 206b. Furthermore, the back surface layer 1 includes a heating element 202a (202a-1 to 202a-7) and a heating element 202b (202b-1 to 202b-7). The heating element 202b is provided between the conductor 206a and the conductor 207, and generates heat when electric power is supplied through the conductor 206a and the conductor 207.

A heat generating portion formed of the conductor 206, the conductor 207, and the heat generating body 202 is divided into seven heat generating blocks (HB1 to HB7) in the longitudinal direction of the heater 300. That is, the heating element 202a is divided into seven regions of heating elements 202a-1 to 202a-7 with respect to the longitudinal direction of the heater 20. The heating element 202b is divided into seven regions of heating elements 202b-1 to 202b-7 with respect to the longitudinal direction of the heater 20. Furthermore, the conductor 207 is divided into seven regions of the conductors 207-1 to 207-7 in accordance with the division positions of the heating elements 202 a and 202 b. The heat generation range (heating area) of the second embodiment is a range from the left end in the drawing of the heat generation block HB1 to the right end in the drawing of the heat generation block HB7, and its total length is 220 mm. Moreover, the longitudinal direction length of each heat generation block is all the same about 31 mm. In the second embodiment, although the length is set as described above, the length of the heat generation block may be set to be different. At this time, it is also possible to set so that both ends of a fixed small-size paper (for example, A5 size) and heat generation block ends (for example, HB2 and HB6) are matched.

  Moreover, the back surface layer 1 has the electrode E (E1-E7 and E8-1, E8-2). The electrodes E1 to E7 are provided in the regions of the conductors 207-1 to 207-7, respectively, for supplying power to the heat generating blocks HB1 to HB7 via the conductors 207-1 to 207-7, respectively. It is an electrode. Electrodes E8-1 and E8-2 are provided at the end of the heater 20 in the longitudinal direction so as to be connected to the conductor 206, and are electrodes for supplying power to the heat generating blocks HB1 to HB7 via the conductor 206. . Although the electrodes E8-1 and E8-2 are provided at both ends in the longitudinal direction of the heater 20 in the second embodiment, for example, only the electrode E8-1 may be provided on one side. In addition, power is supplied to the conductors 206a and 206b with a common electrode, but power may be supplied by providing individual electrodes for the conductor 206a and the conductor 206b.

  The back surface layer 2 is composed of a glass layer 203 as a protective layer having an insulating property, and covers the conductor 206, the conductor 207, and the heating elements 202a and 202b. Moreover, the glass layer 203 is formed except for the part of the electrode E, and has a configuration in which the electrical contact C can be connected to the electrode E from the back surface layer 2 side of the heater.

  The sliding surface layer 1 provided on the surface opposite to the back surface layer 1 on the substrate 201 is a thermistor TH (TH1-1 to TH1) as a temperature detecting element for detecting the temperature of each of the heat generating blocks HB1 to HB7. -4, and TH2-5 to TH2-7). The thermistor TH is made of a material (PTC characteristic or NTC characteristic) having a temperature dependence characteristic of resistance value, and the temperature of all the heat generation blocks can be detected by detecting the resistance value. Further, the sliding surface layer 1 energizes the thermistor TH and detects its resistance value, so that the conductor ET (ET1-1 to ET1-4 and ET2-5 to ET2-7) and the conductor EG (EG1, EG1, EG2). The conductors ET1-1 to ET1-4 are respectively connected to the thermistors TH1-1 to TH1-4. Conductors WT2-5 to ET2-7 are connected to thermistors TH2-5 to 2-7, respectively. The conductor EG1 is connected to the four thermistors TH1-1 to TH1-4 to form a common conductive path. The conductor EG2 is connected to the three thermistors TH2-5 to TH2-7 to form a common conductive path. Conductor ET and conductor EG are formed along the length of heater 20 to the longitudinal end, and are connected to the control circuit at the heater longitudinal end via an electrical contact (not shown).

  The sliding surface layer 2 is composed of a glass sliding layer 205 having slidability and insulating properties, and covers the thermistor TH, the conductor ET, and the conductor EG, and has slidability with the inner surface of the fixing film 25. I have secured. Further, the glass sliding layer 205 is formed except for the longitudinal ends of the heater 20 in order to provide electrical contacts to the conductor ET and the conductor EG.

  Then, the connection method of the electrical contact C to each electrode E is demonstrated. FIG. 5C is a plan view of the state in which the electrical contacts C are connected to the electrodes E as viewed from the heater holder 21 side. The heater holder 21 is provided with through holes at positions corresponding to the electrodes E (E1 to E7, and E8-1 and E8-2). At each through hole position, the electrical contacts C (C1 to C7 and C8-1 and C8-2) are biased by a spring to the electrodes E (E1 to E7 and E8-1 and E8-2). They are electrically connected by a technique such as welding. Electric power is supplied to the heating element 202 via the electrical contact C.

  The configuration of the high heat conductive member 23 of the second embodiment will be described with reference to FIG. FIG. 6A is a schematic plan view of the heater 20 and the high heat conductive member 23 of the second embodiment, and a schematic cross-sectional view at the transport reference position X. The high thermal conductive member 23 is in contact with the back layer 2 on the back surface of the heater 20 and is not in contact with the back layer 1, but in order to clarify the positional relationship between the high thermal conductive member 23 and the heating element 202, The positional relationship will be described with reference to a schematic diagram. As shown in FIG. 6A, the high thermal conductivity members 23J and 23K of the second embodiment are installed so as not to cover the upper and lower heat generating members 202a and 202b. Then, by bringing the high thermal conductivity member 23 into contact with the side surface of the heater 20 and the inner surface of the fixing film 25, the heat generated by the heater heating element 202 can be transferred to the fixing film with high efficiency as in the first embodiment. Therefore, even when the heating element 202 of the heater 20 is divided in the longitudinal direction as in the second embodiment, the same effect as that of the first embodiment can be obtained.

  FIG. 6B is a schematic plan view of a heater 20 and a high heat conductive member 23 according to a modification of the second embodiment, and a schematic cross-sectional view at the conveyance reference position X. Moreover, as shown in FIG.6 (b), it can also be set as the shape where the high heat conductive members 23J and 23K are connected in the area | region (for example, edge part area | region) where the heat generating body 202 does not exist. Further, the high heat conductive member 23 can be arbitrarily installed in an area that does not cover the heating element 202. For example, it is also possible to install a high heat conduction member between the heating element 202a-1 and the heating element 202a-2 in FIG. At this time, electrode contacts can be stably formed by providing predetermined clearances with the electrodes E1 to 7 and E8-1 and E8-2.

  The above embodiments can be combined with each other as much as possible.

  C: fixing device, 20: heater, 21: heater holder, 23: high heat conducting member, 25: film, 26: pressure roller

Claims (11)

A heater having a substrate and a heating element provided on the substrate; a cylindrical film whose inner surface rotates while being in contact with the heater; a pressure member which rotates while being in contact with the outer surface of the film; and the heater A holding member to be held, and a heat conduction member that is sandwiched between the heater and the holding member and that contacts the inner surface of the film, and a nip portion between the film and the pressure member. In an image heating apparatus for heating an image formed on a nipped recording material using heat of the heater,
An image heating apparatus according to claim 1, wherein a region where the heater and the heat conducting member are in contact with each other does not overlap the heating element when projected in a direction perpendicular to the surface of the substrate.   A space is formed between the heater and the holding member in a region overlapping the heating element when projected in a direction perpendicular to the surface of the substrate. Image heating device.   The image heating apparatus according to claim 2, wherein the space is formed by a thickness of the heat conducting member sandwiched between the heater and the holding member.   The said heat conductive member is divided | segmented and arrange | positioned with respect to the said heat generating body in the upstream and downstream in the conveyance direction of a recording material, The one of Claims 1-3 characterized by the above-mentioned. Image heating device.   The heat conduction member has a portion disposed on the upstream side and a portion disposed on the downstream side in the recording material conveyance direction with respect to the heating element. An image heating apparatus according to item 1.   The portion disposed on the upstream side and the portion disposed on the downstream side of the heat conducting member are connected in a region that does not overlap the heating element when projected in a direction perpendicular to the surface of the substrate. The image heating apparatus according to claim 5.   The image according to any one of claims 1 to 3, wherein the heat conducting member is disposed on either the upstream side or the downstream side in the recording material conveyance direction with respect to the heating element. Heating device.   The image heating apparatus according to claim 1, wherein a region where the heater and the heat conducting member are in contact is only a side surface of the heater.   The image heating apparatus according to claim 1, wherein a protective layer that covers the heating element is formed on a surface of the substrate on which the heating element is provided.   The image heating apparatus according to any one of claims 1 to 9, wherein the heating element is provided on the substrate so as to be divided in the longitudinal direction of the substrate. An image forming unit for forming an image on a recording material;
The image heating apparatus according to any one of claims 1 to 10, as a fixing unit that fixes an image formed on the recording material to the recording material,
An image forming apparatus comprising:

Images