JP2017142427A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device which allows continuous printing without varying productivity.SOLUTION: The fixing device has a cylindrical film, a heater 104 in contact with an inside surface of the film, a pressure member forming a nip part with the heater 104 across the film, and a heater support member 106 supporting the heater 104. A graphite sheet (thermal conductive member) 111 (111a to 111d) is provided between the heater 104 and the heater support member 106. The graphite sheet 111 is bonded to the heater 104 by an adhesive and is in contact with a thermistor 112 (112a to 112c) or a thermostat 113 on a side opposite to a side bonded to the heater 104. The heater 104 has a first region where the graphite sheet 111 is fixed, within a transport region for a recording material and has second regions where the heater 104 is in contact with the heater support member 106, at both ends of the first region in a lengthwise direction of the heater 104.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a fixing device as an image heating device used in an image forming apparatus such as a printer, a facsimile, a copying machine, a multi-function printer or the like that employs an image forming process such as an electrophotographic method or an electrostatic recording method. Examples of such a fixing device include a device that heat-fixes an unfixed toner image formed on a recording material (transfer material, printing paper, photosensitive paper, electrostatic recording paper, etc.) as a fixed image. A glossiness increasing device that increases the glossiness of the image by heating the image fixed on the recording material can also be used.

  A film heating and pressing system is generally used as an apparatus that is mounted on an image forming apparatus such as a copying machine, a printer, or a facsimile machine, and that heats and presses an unfixed image transferred onto a transfer material to fix it on the transfer material. The film heating and pressing method uses a film with a small heat capacity, sandwiches and conveys the transfer material between the film and the pressure roller, and heats and adjusts the heater provided on the inner surface of the film to a predetermined fixing temperature, In this method, an unfixed toner image is fixed on a transfer material. A temperature detection member such as a thermistor is in contact with the back surface (non-sheet-passing surface) of the heater to perform temperature control of the heater and abnormal temperature increase detection.

  In this type of fixing device, when small-size paper is continuously printed, a phenomenon occurs in which the temperature of the area where the transfer material does not pass gradually increases in the longitudinal direction of the fixing nip (non-sheet-passing portion temperature rise). In some cases, image defects such as poor fixing and glossy spots may occur.

  In response to this problem, generally, when the temperature detection member detects the temperature rise of the non-sheet passing portion during continuous printing, the productivity is lowered, and heat is released from the temperature rising portion to the surrounding area between the sheets being fed. Measures have been taken to prevent harmful effects. However, in recent years, response to high-speed printing has been desired, and it has been regarded as important to perform continuous printing without deteriorating productivity and without causing image problems.

  As one of the methods corresponding to this, a technique has been proposed in which a high heat conduction member (graphite sheet) is sandwiched between a heater support member and a heater to make the heat distribution uniform (Patent Document 1). More specifically, in the structure of the ceramic heater, the graphite sheet in contact with the ceramic heater, and the temperature detection unit that detects the temperature of the ceramic heater, the temperature detection unit is not provided with a graphite sheet or is made thinner than the thickness other than the temperature detection unit. I am doing so.

JP 2014-102429 A

  However, when the high heat conduction member is sandwiched between the heater and the heater support member and the high heat conduction member is not provided in the place where the temperature detection member is provided or the thickness is thin, the heat uniformity performance of the place is different from other parts. There was a possibility that the productivity during continuous paper feeding could change.

  In order to cope with this, in view of the need to make the heat distribution more uniform than other parts for the part where the temperature rise in the non-sheet-passing part is desired, the desired heat uniformity performance can be obtained even in the part equipped with the temperature detection member. It is necessary to provide the resulting high thermal conductivity member.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device that can perform continuous printing without changing productivity.

  In order to achieve the above object, a fixing device according to the present invention is a fixing device that heats an image while conveying a recording material on which an image is formed at a nip portion, and contacts a cylindrical film and an inner surface of the film. A heater, a pressure member that forms the nip portion together with the heater through the film, a support member that supports the heater, a heat conduction member provided between the heater and the support member, The temperature detection member that contacts the heat conduction member, and the heater include a first region to which the heat conduction member is fixed, and both ends of the first region with respect to the longitudinal direction of the heater in the recording material conveyance region. And a second region where the heater comes into contact with the support member.

  According to the present invention, it is possible to provide a fixing device capable of continuous printing without changing productivity.

1 is a longitudinal sectional view of an entire printer equipped with a fixing device according to a first embodiment. 1 is a longitudinal sectional view of a fixing device according to a first embodiment. Schematic diagram of film structure in fixing device according to first embodiment 1 is a schematic diagram of a configuration of a pressure roller in a fixing device according to a first embodiment. Schematic diagram of a method for supporting a pressure roller in the fixing device according to the first embodiment. FIG. 3 is a schematic configuration diagram of a heater in the fixing device according to the first embodiment. FIG. 3 is a longitudinal sectional view of a heating unit and a pressure roller in the fixing device according to the first embodiment. Explanatory drawing of the flange attachment part of the heating unit in the fixing device which concerns on 1st Embodiment. Explanatory drawing of the contact / separation operation of the pressure unit in the fixing device according to the first embodiment. 1 is a schematic diagram of a configuration of a graphite sheet in a fixing device according to a first embodiment. Explanatory drawing of the affixing part of the graphite sheet in the fixing device according to the first embodiment. Explanatory drawing of assembly of pressure unit in fixing device according to first embodiment Explanatory drawing of the longitudinal temperature distribution of the heater in the fixing device according to the first embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<< First Embodiment >>
(Image forming device)
A full-color laser beam printer 1 (hereinafter, printer 1), which is an image forming apparatus equipped with a fixing device according to an embodiment of the present invention, will be described with reference to FIG. FIG. 1 is a longitudinal sectional view showing the overall configuration of the printer 1.

  A cassette 2 is housed in a lower portion of the printer 1 so as to be drawable. A manual feed unit 3 is disposed on the right side of the printer 1. A transfer material (recording material) is loaded and accommodated in each of the cassette 2 and the manual feed unit 3, and the transfer materials are separated one by one and fed to the registration roller 4. The printer 1 includes an image forming unit 5 as an image forming unit in which image forming stations 5Y, 5M, 5C, and 5K corresponding to each color of yellow, magenta, cyan, and black are arranged in a horizontal row.

  The image forming unit 5 is provided with photosensitive drums 6Y, 6M, 6C, and 6K (hereinafter unified with the drum 6) that are image carriers, and charging devices 7Y, 7M, 7C, and 7K that uniformly charge the surface of the drum 6. It is done. Also, a scanner unit 8 that irradiates a laser beam based on image information to form an electrostatic latent image on the drum 6, and developing devices 9Y, 9M that attach toner to the electrostatic latent image and develop it as a toner image. 9C and 9K are provided. Further, primary transfer portions 11Y, 11M, 11C, and 11K (hereinafter unified with the primary transfer portion 11) for transferring the toner image on the drum 6 to the electrostatic transfer belt 10 are provided.

  The toner image on the transfer belt 10 onto which the toner image has been transferred by the primary transfer unit 11 is transferred to a transfer material by the secondary transfer unit 12. Thereafter, the transfer image is fixed on the transfer material when passing through the fixing nip portion (nip portion) of the fixing device 100 formed by the heating unit 101 and the pressure roller 102 pressed against the heating unit 101. Thereafter, the conveyance path is switched by the double-sided flapper 13 and conveyed to either the discharge roller pair 14 or the switchback roller pair 15.

  The transfer material conveyed to the switchback roller pair 15 side is reversely conveyed by the switchback roller pair 15 part, and again passes through the registration roller 4, the secondary transfer unit 12, and the fixing device 100, and then the discharge roller pair 14 side. It is conveyed to. After passing through the discharge roller pair 14, the transfer material is discharged to the transfer material stacking unit 16. This completes the description of the full-color laser beam printer equipped with the fixing device of this embodiment.

(Fixing device)
Next, the detailed configuration and operation of the fixing device 100 of the printer 1 will be described with reference to FIGS. FIG. 2 is a cross-sectional view of the fixing device 100. In the fixing device 100, 101 is a heating unit, and 102 is a pressure roller (nip portion forming member) as a pressure rotator (pressure member). The heating unit 101 includes a tubular film (moving body, rotating body) 103 and a heater (heating body) 104 that comes into contact with the inner surface of the film 103. A nip portion N is formed with the pressure roller 102.

  As shown in FIG. 3, the film 103 includes an endless base layer 103a, a primer layer 103b provided on the outer periphery of the base layer 103a, an elastic layer 103c provided on the outer periphery of the primer layer 103b, and an outer periphery of the elastic layer 103c. And a release layer 103d. The material of the base layer 103a which is the base layer of the film 103 is a heat resistant resin made of polyimide. The primer layer 103b is formed by applying a conductive primer having an appropriate amount of conductive particles such as carbon dispersed on the base layer 103a to a thickness of about 5 μm.

  The primer layer 103b can wrap the toner image carried on the transfer material by the elasticity of the elastic layer 103c, and can realize uniform heat and pressure fixing. The release layer 103d is coated with a PFA resin having a thickness of about 20 μm as a fluororesin having excellent release properties and high heat resistance in order to prevent adhesion of toner and paper powder and to ensure separation performance of the transfer material from the film 103. It is formed by doing.

  As shown in FIG. 4, the pressure roller 102 includes a metallic (steel) core metal 102a, an elastic layer 102b formed of silicon rubber on the outer side of the core metal 102a, and a release covering the surface of the elastic layer 102b. And a mold layer 102c. As shown in FIG. 5, both ends of the core metal 102a are rotatably supported by the side plate pair 105 (105a, 105b). As the elastic layer 102b, a solid rubber layer formed of silicon rubber is used. The release layer 102c is a fluorine-based resin of PFA and covers the tube.

  As shown in FIG. 6, the heater 104 includes a ceramic heater substrate 104a and resistance heating provided on the heater substrate 104a along the substrate longitudinal direction (first direction orthogonal to the transfer material conveyance direction). It has a body 104b. The resistance heating element 104b is covered with an insulating (glass in this embodiment) surface protective layer 104c. Moreover, the both ends have contact portions 104d for supplying power from the outside.

  Here, as shown in FIG. 7, the heater support member 106 that supports the heater 104 is formed of a heat-resistant resin made of a liquid crystal polymer and having a heat resistance and a sliding property so as to have a substantially semicircular cross section. . Such a heater support member 106 also has a guide function for guiding the rotation of the film 103.

  In FIG. 7, reference numeral 107 denotes a metallic stay for applying pressure to the heater support member 106. The stay 107 has a U-shaped cross section, and is a member that is long in the longitudinal direction (first direction) of the film 103. The role of the stay 107 is to increase the bending rigidity of the film unit 101 in the fixing device 100 and also serves as a positioning reference with the heater support member 106.

  As shown in FIG. 8, both end portions of the film 103 are rotatably held on the outer periphery of the pair of sleeve flanges 108. Further, both end portions of the heater support member 106 are also held by the sleeve flange 108. Then, the heater 104 and the film 103 supported by the heater support member 106 are applied to the pressure roller 102 via the sleeve flange 108 and the stay 107 with a predetermined pressure F (FIG. 9A) by the pressure spring 109. Press contact. The pressing force F does not act on the thermistor 112 described later because the stay 107 and the heater support member 106 are in contact with each other (a biasing force such as a leaf spring described later acts on the thermistor 112).

  As shown in FIG. 9A, the pressing force F is obtained when the pressure spring 109 presses the separation plate 110 and the separation plate 110 presses the sleeve flange 108. A nip portion (fixing nip portion) N is formed between the film 103 and the pressure roller 102 by the applied pressure F.

(Non-paper passing part temperature rise)
When power is supplied to the heater 104 and the resistance heating element 104b generates heat, if the transfer material having a width smaller than that of the transfer material having the maximum width that can be passed through the nip portion N is passed, the pressure roller 102 is As shown in FIG. 13, there is a possibility that the non-sheet passing portion temperature rises. That is, there is a possibility that the temperature of the non-sheet passing portion region at the end portion is excessively increased (a portion higher than other portions in the heat distribution of the heater is generated at the end portion).

  This is because when the small size transfer material is continuously printed, heat is not taken away by the transfer material in the non-sheet passing portion region at the end of the nip portion N, and is partially stored. If the temperature rise at the non-sheet passing portion is excessively large, image adverse effects such as hot offset and glossy spots are caused.

  In order to prevent image damage due to the temperature rise of the non-sheet passing portion, thermistors 112a and 112c as temperature detecting means are installed in the non-sheet passing portion temperature rising region as shown in FIG. Control the input power to suppress the temperature rise of the non-sheet passing part. In addition, by controlling so as to lengthen the interval between sheets during continuous printing, the non-sheet-passing portion temperature rise can be suppressed by promoting heat dispersion from the place where the temperature increase of the non-sheet-passing portion of the pressure roller 102 occurs. It is also possible to do.

  Here, in the present embodiment, a graphite sheet having a uniform thickness (including substantially uniform) shown in FIG. 10A (a sheet-like member with thermal conductivity anisotropy) is provided between the heater support member 106 and the heater 104. , Heat conduction anisotropic member) 111 (111a to 111d). Here, the heat conduction anisotropy means that the heat conduction is higher in the longitudinal direction of the heater 104 than in the direction orthogonal to the longitudinal direction of the heater 104. The graphite sheet 111 is sandwiched between the heater 104 and the heater support member 106 biased by the pressure F applied by the pressure spring 109.

  Such a graphite sheet 111 serves as a first fixing means to the heater 104 so as not to be displaced with respect to the heater 104 on the non-sheet passing surface side of the heater 104 (surface opposite to the surface in contact with the inner surface of the film 103). Glued with adhesive. As shown in FIG. 11, the thermistor (first temperature detecting means) 112 (112a to 112c) is in contact with the graphite sheet 111 on the opposite side (the surface opposite to the surface bonded to the heater 104).

  In addition, on the non-sheet passing surface side of the heater 104, a thermostat (second temperature detecting means) 113 such as a thermo switch or a temperature fuse that operates when the heater 104 is abnormally heated and shuts off the power supply line to the heat generating area is also used. It touches.

  The graphite sheets 111a and 111d of the present embodiment are arranged in an area larger than the area where the thermistors 112a and 112c are in contact with the heater 104 at the positions of the thermistors 112a and 112c. The thermal conductivity of the graphite sheet 111 is high in the longitudinal direction, and the graphite sheets 111a and 111d are provided so as to extend in the longitudinal direction.

  Here, the thermistor 112 and the thermostat 113 are pressed against the graphite sheet 111 by a leaf spring (not shown) or the like (provided between the stay 107 and the thermistor 112). In this way, the thermistor 112 is biased by the heater 104 to which the graphite sheet 111 is bonded in order to obtain stable response performance.

  FIG. 10B shows a state viewed from a direction (upward direction) orthogonal to the longitudinal direction, and the arrangement configuration in each region in the longitudinal direction (first direction) will be described below. Here, in the present embodiment, the heater 104 includes the first region in which the graphite sheet 111 is fixed and the heater 104 at both ends of the first region in the longitudinal direction of the heater 104 within the recording material conveyance region. And a second region in contact with the heater support member 106. This will be specifically described below.

  In the present embodiment, a graphite sheet 111a is provided in a region (first region) in a region Qa provided between two regions P in the longitudinal direction (first direction), and a region Ra in the region Qa. A thermistor 112a is provided inside. The region Ra is a region of an insertion opening for the thermistor 112a provided in the heater support member 106.

  In a region (second region) P as a plurality of fixed portions including both ends in the longitudinal direction (first direction), a pressing force F by the pressure spring 109 acts between the heater support member 106 and the stay 107. To do. Here, the heater support member 106 and the heater 104 are bonded with an adhesive as a second fixing means.

  In the region Qa, the thermistor 112a is biased to the heater 104 (the graphite sheet 111a is bonded) by the above-described unillustrated leaf spring or the like provided between the stay 107 and the thermistor 112a.

  Similarly, in the region Qb, the thermistor 112b is biased to the heater 104 (the graphite sheet 111b is bonded) by the above-described unillustrated leaf spring or the like provided between the stay 107 and the thermistor 112b.

(Assembly)
As shown in FIG. 12A, the heater support member 106 (further, the heater 104, the graphite sheet 111 attached to the heater 104, the thermistor 112, and the thermostat 113) is assembled with the metal stay 107. The thermistor 112 (112c) contacts the heater 104 as shown in the sectional view of FIG. Similarly, the thermostat 113 contacts the heater 104. As described above, the thermistor 112 and the thermostat 113 are pressed against the graphite sheet 111 by a leaf spring (not shown) or the like.

  The fixing device takes a contact position during operation, but takes a separated position when the power is turned off or a jam occurs. Switching between the contact position and the separation position is performed by rotating the cam 114 and operating the separation plate 110 as shown in FIG. At the time of contact, the cam 114 and the separation plate 110 are not in contact, but the cam 114 is rotated 180 ° by a cam drive motor (not shown) when the power is turned off or JAM is generated.

  By this rotation operation, the separation plate 110 is lifted in the direction of the arrow with the hole 110a as the center of rotation. At this time, the sleeve flange 108 is also lifted in the same direction and separated from the fixing nip portion N. Therefore, when taking the separated position, the heater 104 is bonded to the heater support member 106 so that the heater 104 does not move away from the heater support member 106 due to pressurization of the thermistor 112 and the graphite sheet 111.

  Thereby, the heater 104 is bonded to the heater support member 106 in both the separated position and the contact position. Since the graphite sheet 111 is bonded to the heater 104 as described above, the position does not shift with respect to the heater 104. The above is the configuration of the fixing device 100. Subsequently, the operation will be described.

(Fixing device operation)
A heater drive control circuit as a control unit of the fixing device according to the present embodiment includes a power supply device, a CPU that controls the power supply device, and the like. This heater drive control circuit energizes and heats the heating resistor 104b of the heater 104 when the CPU inputs a print signal and performs on / off control of the power feeding device. The heater 104 is rapidly heated by energization heating of the heating resistor 104b.

  The temperature of the heater 104 is detected by a thermistor 112 as temperature detecting means provided on the back surface of the heater 104 (surface opposite to the nip portion N). Based on the detected temperature, the heater 104 is temperature-controlled to a predetermined target set temperature, and the film 103 is heated to that temperature.

  Based on the detected temperature of the thermistor 112 and the set temperature of the heater 104, for example, based on the difference, the power to be supplied is calculated by PI control that continuously performs feedback control on the input power so that the heater 104 reaches the target temperature. . Furthermore, it is converted into a control level of phase angle (phase control) and wave number (wave number control) corresponding to the power to be supplied, and the triac is controlled according to the control conditions.

  For example, when the heating unit 101 enters a heat generation state that exceeds the steady state due to a failure of the power control unit, such as a short circuit of the triac, the thermostat 113 operates to cut off the power supply to the heater 104. When the thermistor detection temperature (TH signal) detects a predetermined temperature or higher, the relay is turned off and the power supply to the heater 104 is cut off.

  The pressure roller 102 receives power from a motor (not shown) and rotates in the A direction indicated by the arrow in FIG. As the pressure roller 102 rotates, the film 103 is driven to rotate in the B direction indicated by the arrow. The transfer material carrying the unfixed toner image is introduced into the nip portion N from the transfer material conveyance direction indicated by the arrow X direction, and the transfer material is nipped and conveyed by the nip portion N.

  During this conveyance process, the heat of the heater 104 is applied to the transfer material via the film 103. The unfixed toner image is fixed on the transfer material by the heat of the heater 104 and the nip pressure. The transfer material that has exited the nip N is separated from the surface of the film 103 by the curvature, and is conveyed to the paper discharge roller pair 14 or the switchback roller pair 15 as described above.

(Effect of this embodiment)
In the present embodiment, the graphite sheets 111 a and 111 d are arranged at the non-sheet-passing portion temperature rising portions, and the graphite sheets 111 a and 111 d are bonded to the heater 104. Thereby, the position of the graphite sheets 111a and 111d with respect to the heater 104 is not shifted. Then, the graphite sheets 111 a and 111 d are brought into close contact with the heater 104 by adhesion, whereby heat is efficiently transferred from the heater 104. This makes it possible to prevent image defects such as poor fixing and glossy spots by further distributing the heat of the non-sheet passing portion temperature rising portion to the surroundings, rather than dealing with a longer paper interval.

  Further, the heater 104 and the heater support member 106 are bonded, and the graphite sheet 111 is disposed between the bonding positions, thereby providing the following advantages over the case where the heater 104 and the heater support member 106 are not bonded. is there. In other words, it is possible to prevent the graphite sheet 111 from climbing onto the heater support member 106 due to the force that urges the graphite sheet 111 toward the heater 104 to lift the heater 104 from the heater support member 106.

(Modification)
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

(Modification 1)
In the above-described embodiment, the heater 104 and the graphite sheet 111 are bonded with the adhesive as the first fixing means. However, the double-sided tape (both surfaces are double-sided) that can be attached with a more uniform thickness as the first fixing means. An affixing surface) can also be used.

(Modification 2)
At least a part of the graphite sheet 111 fixed to the heater 104 with the adhesive or double-sided tape as the fixing means described above may be provided in contact with the heater support member 106. In this case, the graphite sheet 111 is fixed to the heater 104 in a state of being biased to the heater support member 106, and a more stable arrangement can be achieved.

(Modification 3)
In the embodiment described above, the graphite sheet 111 is used as the heat conducting member. However, the graphite sheet may be a flexible one having a thickness of 100 μm or less. Further, as the material of the heat conducting member, a metal such as aluminum, copper, silver, etc. having higher heat conductivity than the material of the heater substrate can be used.

(Modification 4)
In the embodiment described above, the heater 104 and the heater support member 106 are fixed in the second regions at both ends of the first region in which the graphite sheet 111 is fixed to the heater 104 in the longitudinal direction of the heater 104. The present invention is not limited to this. That is, in the second region, the heater 104 and the heater support member 106 may be pressed and contacted by the pressure member.

(Modification 5)
The fixing device according to the above-described embodiment is applied to a full-color laser beam printer having a plurality of photosensitive drums. However, the fixing device can be applied to a monochrome copying machine and printer having a single photosensitive drum. it can.

102 ..Pressure roller, 103 ..Film, 104 ..Heater, 106 ..Heater support member, 107 ..Metal stay, 111 ..Graphite sheet, 112 ..Thermistor

Claims (12)

In the fixing device that heats the image while conveying the recording material on which the image is formed at the nip portion,
A tubular film,
A heater in contact with the inner surface of the film;
A pressure member that forms the nip portion together with the heater through the film;
A support member for supporting the heater;
A heat conducting member provided between the heater and the support member;
A temperature sensing member in contact with the heat conducting member;
The heater is in contact with the support member at a first area where the heat conducting member is fixed and at both ends of the first area in the longitudinal direction of the heater in the recording material conveyance area. And a second region.   The fixing device according to claim 1, wherein the heater and the support member are fixed or pressed in the second region.   The fixing device according to claim 1, wherein the heater and the heat conducting member are fixed by a first fixing unit in the first region.   The fixing device according to claim 3, wherein the first fixing unit is an adhesive or a double-sided tape.   The fixing device according to claim 2, wherein the heater and the support member are fixed by a second fixing unit in the second region.   The fixing device according to claim 5, wherein the second fixing unit is an adhesive.   The fixing device according to claim 1, further comprising a separation unit that separates the film from the pressure member.   The fixing device according to claim 1, wherein the heat conducting member is provided at a position higher than other portions in the heat distribution of the heater.   The fixing device according to claim 1, wherein the heat conduction member has higher heat conduction in a longitudinal direction of the heater than in a direction orthogonal to the longitudinal direction of the heater.   The fixing device according to claim 1, wherein the heat conducting member is a graphite sheet.   The fixing device according to claim 1, wherein a material of the heat conducting member is aluminum.   The fixing device according to claim 1, wherein at least a part of the heat conducting member is in contact with the support member.