Image heating device and image forming apparatus

Abstract

An image heating device and an image forming apparatus are disclosed. The image heating device heats an image formed on a recording material, and the device comprises: a heating member provided with a heater having a plurality of heating elements juxtaposed in a direction perpendicular to the conveying direction of the recording material; a roller such that the circumference of the roller increases from a central portion toward an end portion in a direction perpendicular to the conveying direction; and a control unit that independently controls the power supplied to the plurality of heating elements. The control unit sets a control target temperature set to supply power to a heating element corresponding to a non-sheet passing area among the plurality of heating elements to be higher than the lowest control target temperature among the control target temperatures set to supply power to the heating element corresponding to the sheet passing area.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a printer, a copier, etc., which relies on an electrophotographic system. The present invention also relates to an image heating device such as a fixing unit mounted on the image forming apparatus or a gloss imparting device for increasing the gloss value of a toner fixed on a recording material by reheating the toner image. Background Art

[0002] Image heating devices in the form of fixing units or gloss imparting devices used in electrophotographic image forming devices such as copiers or printers include film heating type image heating devices that are excellent in power saving. In such image heating devices, a scheme involving selectively heating the image portion formed on the recording material has also been proposed (Japanese Patent Application Publication No. 2014-059508). In this method, each heating element is selectively thermally controlled depending on the presence or absence of an image on the recording material, so that the energization of the heating element is reduced in the portion without an image on the recording material (hereinafter referred to as the non-image portion), thereby further reducing power consumption. Summary of the invention

[0003] In some cases, the pressure roller in the image heating device may have a so-called concave top shape. The term concave top shape herein refers to a shape in which the outer diameter of the pressure roller gradually increases from the center portion toward the end portion. By relying on this scheme, the recording material is conveyed relatively quickly from the center portion toward the end portion, thereby suppressing the occurrence of wrinkles in the recording material. However, as in Japanese Patent Application Publication No. 2014-059508, in the case where the image portion formed on the recording material is selectively heated, since the image is mainly drawn at the center of the recording material, the thermal expansion of the pressure roller is greater at the end portion than at the center portion, and therefore the wrinkle suppression effect on the recording material caused by the above-mentioned concave top shape is weak. In recent years, with the higher speed of the image forming device, this occurrence has become significant. In addition, it has been found that making the fixing film thinner may cause buckling and fracture of the fixing film in extreme cases.

[0004] An object of the present invention is to provide a technique that allows suppressing the occurrence of wrinkles in a recording material and also saving electric power.

[0005] In order to achieve the above object, an image heating device of the present invention for heating an image formed on a recording material using heat from a heater has:

[0006] a heating member provided with a heater having a plurality of heating elements juxtaposed in a direction perpendicular to a conveying direction of the recording material;

[0007] a roller which forms a nip by being pressed against the heating member and which rotates so that the circumference of the roller increases from a center portion toward an end portion in a direction perpendicular to the conveying direction; and

[0008] a control unit that independently controls power supplied to the plurality of heating elements;

[0009] wherein the image heating device heats an image formed on a recording material using heat from a heater, and wherein a control unit sets a control target temperature for supplying power to heating elements among a plurality of heating elements corresponding to a non-sheet passing area at a clamping portion through which the recording material does not pass, to be higher than a lowest control target temperature among control target temperatures set for supplying power to heating elements corresponding to a sheet passing area at a clamping portion through which the recording material passes.

[0010] The present invention allows suppressing the occurrence of wrinkles while maintaining power saving.

[0011] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention;

[0013] Figure 2 is a cross-sectional view of a heating device of the present invention;

[0014] FIG. 3A to FIG. 3C is a heater configuration diagram of the present invention;

[0015] Figure 4 is a heater control circuit diagram of the present invention;

[0016] Figure 5 is a diagram illustrating the heating area of ​​the present invention;

[0017] Fig. 6A and Figure 6B It is a specific example of the classification of the heating area in the present invention;

[0018] Figure 7 It is a flow chart of the classification of heating areas and determination of control temperature in the present invention;

[0019] FIG. 8A to FIG. 8D are a plurality of specific examples of the classification of the heating area in the present invention; and

[0020] Fig. 9 It is the concave top amount of the pressure roller in Example 1 and the comparative example. DETAILED DESCRIPTION

[0021] Hereinafter, a description of an embodiment (example) of the present invention will be given with reference to the accompanying drawings. However, the size, material, shape, relative arrangement, etc. of the components described in the embodiments may be appropriately changed according to the configuration of the device to which the present invention is applied, various conditions, etc. Therefore, the size, material, shape, relative arrangement, etc. of the components described in the embodiments are not intended to limit the scope of the present invention to the following embodiments.

[0022] Example 1

[0023] 1. Overall structure of the image forming device

[0024] Figure 1 : is a schematic front cross-sectional view of an image forming apparatus. Embodiments of image forming apparatuses to which the present invention can be applied include an electrophotographic system and a copier, a printer, and the like utilizing an electrostatic recording system. Herein, the following example will be described: The present invention is applied to a laser printer that forms an image on a recording material P by relying on an electrophotographic system.

[0025] The image forming apparatus 100 is provided with a video controller 120 and a control section 113. As an acquisition section that acquires image information to be formed on a recording material, the video controller 120 receives and processes image information and a print instruction sent from an external device such as a personal computer. The control section 113 connected to the video controller 120 controls each section constituting the image forming apparatus 100 in response to an instruction from the video controller 120. When a print instruction from an external device is received by the video controller 120, image formation is performed according to the following operation.

[0026] When the image forming apparatus 100 receives a print signal, the scanner unit 21 emits laser light modulated according to image information in the received data, and scans the surface of the photosensitive drum 19 charged with a predetermined polarity through the charging roller 16. As a result, an electrostatic latent image becomes formed on the photosensitive drum 19. The electrostatic latent image on the photosensitive drum 19 becomes developed in the form of a toner image by supplying toner from the developing roller 17 to the electrostatic latent image. In addition, the recording material (recording sheet) P loaded in the sheet feeding box 11 is fed sheet by sheet by the pickup roller 12, and is conveyed toward the resist roller pair 14 through the conveying roller pair 13. The recording material P is conveyed from the resist roller pair 14 to the transfer position in accordance with the timing when the toner image on the photosensitive drum 19 reaches the transfer position formed at the photosensitive drum 19 and the transfer roller 20. When the recording material P passes the transfer position, the toner image on the photosensitive drum 19 is transferred to the recording material P. Thereafter, the recording material P is heated by the fixing device (fixing section) 200 as an image heating apparatus (image heating section), and thus the toner image becomes heat-fixed to the recording material P. The recording material P carrying the toner image thus fixed is discharged onto a tray above the image forming apparatus 100 by the conveying roller pair 26, 27. The drum cleaner 18 cleans the toner remaining on the photosensitive drum 19. A sheet feeding tray 28 (manual feeding tray) as a pair of recording material limiting plates whose width can be adjusted according to the size of the recording material P is provided so as to also handle the recording material P having a non-standard size. The pickup roller 29 feeds the recording material P from the sheet feeding tray 28. The image forming apparatus 100 has a motor 30 that drives the fixing device 200 and the like. A heater driving component connected to a commercial AC power source 401 and a control circuit 400 as an energization control section supply power to the fixing device 200. The above-mentioned photosensitive drum 19, charging roller 16, scanner unit 21, developing roller 17 and transfer roller 20 constitute an image forming section that forms an unfixed image on the recording material P. In the present embodiment, the developing unit having the photosensitive drum 19, charging roller 16 and developing roller 17 and the cleaning unit having the drum cleaner 18 are configured to be detachable from the apparatus body of the image forming apparatus 100 in the form of a process cartridge 15.

[0027] The image forming apparatus 100 of this embodiment has a maximum sheet passing width of 216 mm in a direction perpendicular to the conveying direction of the recording material P, and can print 60 copies of the A4-size recording material P per minute, ie, at a conveying speed of 300 mm / sec.

[0028] 2. Configuration of image heating equipment

[0029] Figure 2: is a schematic cross-sectional view of a fixing device 200 as an image heating apparatus of the present embodiment. The fixing device 200 has a fixing film 202 in the form of an endless belt, a heater 300 in contact with the inner surface of the fixing film 202, a pressure roller 208 pressed against the heater 300 across the fixing film 202, and a metal bracket 204. A fixing nip N is formed by pressing the pressure roller 208 against the outer surface of the fixing film 202. The fixing film 202, the heater 300, and various structures disposed inside the fixing film 202 in the present embodiment correspond to the heating member of the present invention.

[0030] The fixing film 202 is a multilayer heat-resistant film formed into a tubular shape and has a base layer of a heat-resistant resin such as polyimide or a metal such as stainless steel. In order to prevent the attachment of the toner and ensure the separability from the recording material P, a release layer is formed on the surface of the fixing film 202 by coating the surface with a heat-resistant resin having excellent release properties such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). In particular, in an apparatus for forming a color image, a heat-resistant rubber such as silicone rubber may be formed as an elastic layer between the base layer and the release layer for the purpose of improving the image quality. In the present embodiment, the outer diameter of the fixing film 202 is 24 mm, the base layer is formed of polyimide with a thickness of 70 μm, the elastic layer is formed of silicone rubber with a thickness of 200 μm, and the release layer is formed of PFA with a thickness of 15 μm.

[0031] The pressure roller 208 has a core metal 209 of a material such as iron, SUS or aluminum and an elastic layer 210 of a material such as silicone rubber. In order to prevent the adhesion of the toner, a release layer 211 is formed on the surface of the pressure roller 208 by coating with a heat-resistant resin having excellent release properties such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). In the present embodiment, the outer diameter of the pressure roller 208 is 25 mm at the center portion of the minimum diameter (minimum circumference), and gradually increases toward both ends until the maximum diameter (maximum circumference) of 25.16 mm. That is, the pressure roller 208 of the present embodiment has a so-called concave top shape. Due to such a shape, a difference in peripheral speed is generated between the center portion and both ends of the pressure roller 208, and as a result, the recording material P clamped in the fixing nip N is subjected to a moderate tension from the center portion in the longitudinal direction perpendicular to the conveying direction of the recording material P toward both ends. By applying a force that stretches the recording material P from the center toward the end in the longitudinal direction, the occurrence of wrinkles in the recording material P can be suppressed and the conveying properties of the recording material P at the fixing nip N can be stabilized. The core metal 209 is formed of SUS and has a constant outer diameter of 17 mm. The elastic layer 210 formed on the outer periphery of the core metal 209 is formed of silicone rubber and has a thickness of 4 mm in the central portion, which gradually increases toward both ends, reaching a value of 4.08 mm at both ends. That is, due to the layer thickness of the elastic layer 210 that varies in the axial direction, the pressure roller 208 is formed in a concave top shape. The release layer 211 formed on the surface of the elastic layer 210 is formed of PFA in this article and has a thickness of 20 μm.

[0032] The degree of the concave top shape of the pressing roller 208 is defined as the concave top amount as follows.

[0033] (Concave top amount) = (outer diameter of the pressure roller 208 at both end portions) - (outer diameter of the pressure roller 208 at the center portion)

[0034] The pressure roller 208 expands and deforms due to the heat from the heater 300; herein, considering that the temperature is easily increased at both ends in the longitudinal direction in particular, the amount of concave top tends to increase as heating proceeds. From the viewpoint of suppressing the adverse effects of the temperature increase at the ends or from the viewpoint of energy saving, it is possible to rely on control for keeping the control temperature at the ends of the fixing nip N low. Due to this control, the heating at the ends of the pressure roller 208 is suppressed, and the amount of concave top required for ensuring the conveying shape of the recording material may not be ensured in some cases.

[0035] The heater 300 is held in a heater holding member 201 made of a heat-resistant resin so that the fixing film 202 passes through a heating area A provided in the fixing nip N. 1 To A7 (described in detail below). The heater holding member 201 also has a guiding function of guiding the rotation of the fixing film 202. On the side opposite to the side of the fixing nip N, an electrode E is provided on the heater 300, wherein power is supplied to the electrode E through the electrical contact C. The metal bracket 204 receives a pressing force not shown, thereby pushing the heater holding member 201 toward the pressure roller 208. As a result, the pressure roller 208 is pressed against the fixing film 202 as a part of the heating member, thereby forming a fixing nip. A safety element 212 such as a thermal switch or a thermal fuse that cuts off the power supply to the heater 300 when triggered by abnormal heat generated by the heater 300 is directly or indirectly in contact with the heater 300 via the heater holding member 201. The heater 300, the heater holding member 201 and the metal bracket 204 constitute a heater unit 311. Other components such as a heat transfer component can be inserted between the fixing film 202 and the heater 300.

[0036] The pressure roller 208 receives power from the motor 30 and rotates in the direction of the arrow R1. Due to the rotation of the pressure roller 208, the fixing film 202 is driven to rotate in the direction of the arrow R2. When the recording material P is nipped and conveyed at the fixing nip N, the unfixed toner image on the recording material P is fixed to the fixing film 202 by the application of heat. In order to ensure the sliding property of the fixing film 202 and realize a stable driven rotation state, a highly heat-resistant sliding grease is inserted between the heater 300 and the fixing film 202.

[0037] 3. Heater configuration

[0038] Reference FIG. 3A to FIG. 3C The configuration of the heater 300 in this embodiment will be described. Figure 3A is a cross-sectional view of the heater 300, Figure 3B is a plan view of the layers of the heater 300, and Figure 3C 3 is a diagram for explaining a method for connecting the electric contact C to the heater 300 . Figure 3B The conveyance reference position X of the recording material P in the image forming apparatus 100 of this embodiment is illustrated. The term conveyance reference in this embodiment is a center reference where the recording material P is conveyed such that its center line in a direction perpendicular to the conveyance direction runs along the conveyance reference position X. Figure 3A 3 is a cross-sectional view of the heater 300 at the transport reference position X.

[0039] The heater 300 is composed of a ceramic substrate 305, a back surface layer 1 arranged on the substrate 305, a back surface layer 2 covering the back surface layer 1, a sliding surface layer 1 arranged on the substrate 305 on the side opposite to the back surface layer 1, and a sliding surface layer 2 covering the sliding surface layer 1.

[0040] The back surface layer 1 has a conductor 301 (301a, 301b) arranged along the longitudinal direction of the heater 300. The conductor 301 is divided into a conductor 301a and a conductor 301b, and the conductor 301b is arranged downstream of the conductor 301a in the conveying direction of the recording material P. In addition, the back surface layer 1 has a conductor 303 (303-1 to 303-7) arranged in parallel with the conductors 301a and 301b. The conductor 303 is arranged between the conductor 301a and the conductor 301b in the longitudinal direction of the heater 300.

[0041] The back surface layer 1 has heating elements 302a (302a-1 to 302a-7) and heating elements 302b (302b-1 to 302b-7) as heating resistors that generate heat by energizing. The heating element 302a is provided between the conductor 301a and the conductor 303, and generates heat by supplying power via the conductor 301a and the conductor 303. The heating element 302b is provided between the conductor 301b and the conductor 303, and generates heat by supplying power via the conductor 301b and the conductor 303.

[0042] The heat generating portion composed of the conductor 301, the conductor 303, the heating element 302a and the heating element 302b is divided into seven heat generating blocks (HB) in the longitudinal direction of the heater 300. 1 To HB 7 ). That is, the heating element 302a is divided into seven regions of heating elements 302a-1 to 302a-7 in the longitudinal direction of the heater 300. In addition, the heating element 302b is divided into seven regions of heating elements 302b-1 to 302b-7 in the longitudinal direction of the heater 300. The conductor 303 is divided into seven regions of conductors 303-1 to 303-7 according to the division positions of the heating elements 302a, 302b. The seven heating blocks (HB) are independently controlled by controlling the amount of current flowing through the heating resistor in each block. 1 To HB 7 ) in each.

[0043] The heating range in this embodiment is from the heating block HB in the figure. 1 The left end of the heating block HB in the figure 7 The right end of the range, the total length is 220mm. Herein, the length of each heating block in the longitudinal direction is the same, about 31mm, but the length of the block can be different.

[0044] The back surface layer 1 has electrodes E (E1 to E7 plus E8-1 and E8-2). The electrodes E1 to E7 respectively provided in the regions of the conductors 303-1 to 303-7 are used to supply heat to the heat generating block HB via the conductors 303-1 to 303-7, respectively. 1 To HB7 Electrodes E8-1 and E8-2 are provided at the ends of the heater 300 in the longitudinal direction to be connected to the conductor 301 and are used to supply power to the heat generating block HB via the conductor 301. 1 To HB 7 Electrodes for supplying power. In the present embodiment, the electrodes E8-1 and E8-2 are provided at both ends of the heater 300 in the longitudinal direction, but for example, only the electrode E8-1 may be provided on one side. Power is supplied to the conductors 301a and 301b through a common electrode, but a separate electrode may be provided for each of the conductors 301a and 301b to supply power to the corresponding conductor.

[0045] The back surface layer 2 is made of a surface protection layer 307 (in this embodiment, glass) having insulating properties and covers the conductor 301, the conductor 303 and the heating elements 302a, 302b. The surface protection layer 307 is formed outside the position of the electrode E so that the electric contact C can be connected to the electrode E from the back surface layer 2 side of the heater.

[0046] The sliding surface layer 1 is provided on the surface of the substrate 305 on the opposite side to the surface on which the back surface layer 1 is provided, and has a structure for detecting each of the heating blocks HB. 1 To HB 7 The thermistor TH (TH1-1 to TH1-4 and TH2-5 to TH2-7) of the temperature detection component. The thermistor TH is composed of a material having a PTC characteristic or an NTC characteristic (NTC characteristic in this embodiment), so that the temperature of all heating blocks can be detected by detecting the resistance value of the thermistor TH.

[0047] For the purpose of energizing the thermistor TH and detecting its resistance value, the sliding surface layer 1 has conductors ET (ET1-1 to ET1-4 and ET2-5 to ET2-7) and conductors EG (EG1, EG2). The conductors ET1-1 to ET1-4 are connected to the thermistors TH1-1 to TH1-4, respectively. The conductors ET2-5 to ET2-7 are connected to the thermistors TH2-5 to TH2-7, respectively. The conductor EG1 is connected to the four thermistors TH1-1 to TH1-4, thereby forming a common conductive path therewith. The conductor EG2 is connected to the three thermistors TH2-5 to TH2-7, thereby forming a common conductive path therewith. The conductor ET and the conductor EG are formed along the length of the heater 300 until the end in the longitudinal direction thereof, and are connected to the control circuit 400 at the end in the longitudinal direction of the heater via various electrical contacts not shown.

[0048] The sliding surface layer 2 made of a surface protection layer 308 (in this embodiment, glass) having slidability and insulating properties covers the thermistor TH, the conductor ET, and the conductor EG to ensure slidability with the inner surface of the fixing film 202. The surface protection layer 308 is formed outside the two longitudinal direction end portions of the heater 300 for the purpose of providing electrical contact with the conductor ET and the conductor EG.

[0049] Next, a method for connecting the electric contacts C to the respective electrodes E will be described. Figure 3C 2 is a plan view of the manner in which the electrical contacts C are connected to the respective electrodes E as viewed from the heater holding member 201 side. The heater holding member 201 is provided with through holes at positions corresponding to the electrodes E (E1 to E7 plus E8-1 and E8-2). The electrical contacts C (C1 to C7 plus C8-1 and C8-2) are electrically connected to the electrodes E (E1 to E7 plus E8-1 and E8-2) at the respective through hole positions according to a method such as spring push or welding. The electrical contacts C are connected to the control circuit 400 described later of the heater 300 via an unillustrated conductive material provided between the metal bracket 204 and the heater holding member 201.

[0050] 4. Configuration of heater control circuit

[0051] Figure 4 A circuit diagram of a control circuit 400 of the heater 300 of Embodiment 1 is illustrated. Reference symbol 401 denotes a commercial AC power source connected to the image forming apparatus 100. Power control of the heater 300 is performed by turning on / off the bidirectional thyristors 411 to 417. The bidirectional thyristors 411 to 417 operate according to respective FUSER1 to FUSER7 signals from the CPU 420. The driving circuit of the bidirectional thyristors 411 to 417 is not depicted. The control circuit 400 of the heater 300 has a structure whereby seven heating blocks HB can be independently controlled respectively by seven bidirectional thyristors 411 to 417. 1 To HB 7 The zero-crossing detection section 421 is a circuit that detects the zero-crossing of the AC power source 401, and outputs a ZEROX signal to the CPU 420. For example, the ZEROX signal is used to detect the timing of the phase control and the wave number control of the bidirectional thyristors 411 to 417.

[0052] Next, the temperature detection method of the heater 300 is described. The temperature of the heater 300 is detected by the thermistors TH (TH1-1 to TH1-4 and TH2-5 to TH2-7). The divided voltage between the thermistors TH1-1 to TH1-4 and the resistors 451 to 454 is detected by the CPU 420 in the form of Th1-1 to Th1-4 signals, and then converted into temperature in the CPU 420. Similarly, the divided voltage between the thermistors TH2-5 to TH2-7 and the resistors 465 to 467 is detected by the CPU 420 in the form of Th2-5 to Th2-7 signals, and then converted into temperature in the CPU 420.

[0053] In the internal processing of the CPU 420, based on the control temperature (control target temperature) TGT of each heat generating block described later, i The power to be supplied is calculated based on the temperature detected by each thermistor, for example, by PI control (proportional integral control). In addition, the power to be supplied is converted into a control level of a phase angle (phase control) and a wave number (wave number control) corresponding to the power, so that the bidirectional thyristors 411 to 417 are controlled according to these control conditions. As a control unit and an acquisition unit in the present invention, the CPU 420 performs various calculations and power-on control related to the temperature control of the heater 300, for example.

[0054] In the case where the heater 300 is overheated due to a malfunction or the like, the relay 430 and the relay 440 are used as a component for cutting off the power to the heater 300. Next, the circuit operation of the relay 430 and the relay 440 will be described. When the RLON signal is in a high state, the transistor 433 is turned on, the secondary coil of the relay 430 is energized by the power supply voltage Vcc, and the primary contact of the relay 430 is connected. When the RLON signal is in a low state, the transistor 433 is turned off, the current flowing from the power supply voltage Vcc to the secondary coil of the relay 430 is cut off, and the primary contact of the relay 430 is disconnected. When the RLON signal is in a high state, the transistor 443 is turned on, the secondary coil of the relay 440 is energized by the power supply voltage Vcc, and the primary contact of the relay 440 is connected. When the RLON signal is in a low state, the transistor 443 is turned off, the current flowing from the power supply voltage Vcc to the secondary coil of the relay 440 is cut off, and the primary contact of the relay 440 is disconnected. Resistor 434 and resistor 444 are current limiting resistors.

[0055] Next, the operation of the safety circuit using the relay 430 and the relay 440 is described. When any one of the temperatures detected by thermistors TH1-1 to TH1-4 exceeds the respectively set predetermined values, the comparison unit 431 operates the latch unit 432, and the latch unit 432 latches the RLOFF1 signal to a low state. When the RLOFF1 signal is in a low state, even if the RLON signal is set to a high state by the CPU 420, the transistor 433 remains disconnected, so the relay 430 can remain disconnected (safe state). In the non-latched state, the latch unit 432 sets the RLOFF1 signal to an open state output. Similarly, when any one of the temperatures detected by thermistors TH2-5 to TH2-7 exceeds the respectively set predetermined values, the comparison unit 441 operates the latch unit 442, and the latch unit 442 latches the RLOFF2 signal to a low state. When the RLOFF2 signal is in a low state, the transistor 443 remains off even if the RLON signal is set to a high state by the CPU 420, so the relay 440 can remain off (safe state). Similarly, in the non-latched state, the latch unit 442 sets the RLOFF2 signal to an open state output.

[0056] 5. Setting of heating area

[0057] Figure 5 The heating area A in this embodiment is shown in FIG. 1 To A 7 In the figure, the heating area is depicted compared to the sheet width of a letter size sheet. Heating Area A 1 To A 7 The heating block HB is arranged in the fixing nip N. 1 To HB 7 At the corresponding position, heating area A i (i=1 to 7) is due to the corresponding heating block HB i (i = 1 to 7) is heated by the heat generated by the heating block HB. 1 To HB 7 (Multiple heating elements) correspondingly form heating area A 1 To A 7 . Heating area A 1 To A 7 The total length of the substrate is 220 mm, and each region is the result of dividing the total length into seven equal parts (L=31.4 mm).

[0058] Next, we will refer to Fig. 6A and Figure 6B Description Heating Zone A i In this example, the recording material P passes through the heating area A. 2 To heating area A 6The recording material P and the image exist in Fig. 6A In addition, reference symbol PE denotes both edge portions of the recording material P in the longitudinal direction. Figure 6B Heating area A is shown i Based on the image data (image information) and the recording material information (recording material size), the image range (the range of the image present on the recording material) passes through the heating area A. 3 , A 4 , A 5 , therefore, these are classified as image area AI. In contrast, the image range does not pass through the heating area A 2 , A 6 , therefore, these are classified as non-image areas AP. In addition, the recording material P does not pass through the heating area A 1 , A 7 , therefore, these are all classified as non-sheet passing areas AN.

[0059] 6. Overview of heater control methods

[0060] Next, the heater control method of this embodiment, that is, the method for controlling the heating block HB, will be described. i (i = 1 to 7) of the heat generation method. The heating block HB i The heat generated is supplied to the heating block HB i The power of the heating block HB i The heat generated by the heat supply to the heating block HB i The increase of power increases, and the heating block HB i The heat generated by the heating block HB i Based on the control temperature TGT selected for each heating block i (i=1 to 7) and calculates the power supplied to the heat generating block HB based on the temperature detected by the thermistor. i In this embodiment, the supplied power is calculated by PI control (proportional integral control) so that the detected temperature of each thermistor becomes equal to the control temperature TGT of each heating block. i .

[0061] Figure 7 FIG. 4 is a flow chart of the classification of the heating areas and the determination of the control temperature in this embodiment. Figure 7 As shown in the figure, heating area A i The heating area A is classified based on image information (image data) and recording material information (recording material size) sent from an external device (not shown) such as a host computer. i .

[0062] Each heating area A is determined according to the recording material information (recording material size) i Is it the scope of recorded materials? Figure 7 : S1001). In the case of recording material range, next, the heating area A is determined based on the image information (image data). i Is it an image range? Figure 7 :S1002). In the case of the image range, heating area A i Classified as image area AI ( Figure 7 :S1003); otherwise, heating area A i Classified as non-image area AP( Figure 7 :S1004). In heating area A i When the image area AI is classified, each control temperature TGT i Set as TGT i =T AI ( Figure 7 :S1006). In this article, T AI is the image area temperature and is set to an appropriate temperature so as to fix the unfixed image onto the recording material P. In S1002, the area A is heated. i When the area is classified as a non-image area AP, each control temperature TGT i Set as TGT i =T AP ( Figure 7 :S1007). In this article, T AP is the non-image area temperature. AP Set to the image area temperature T AI The low temperature makes the heat generating block HB in the non-image area AP i The heating area A is smaller than the heating area A1, and power is saved in the fixing device 200. In S1001, the heating area A is heated. i When the recording material is not within the range, the heating area A i The area classified as the non-sheet passing area AN ( Figure 7 :S1005). In addition, each control temperature TGT i Set as TGT i =T AN ( Figure 7 :S1008). In this article, T AP is the temperature of the non-sheet passing area. AP Set to a temperature T lower than the non-image area AP The high temperature makes the non-sheet material pass through the heating block HB at the area AN.i The heat generated in the image area is greater than the heat generated in the non-image area AP to maintain the concave top shape of the pressure roller 208.

[0063] FIG. 8A to FIG. 8D Heating area A is shown i (i = 1 to 7) various classification modes. Fig. 8A In the heating area A 4 Classified as image area AI, heating area A 2 , A 3 , A 5 , A 6 are classified as non-image area AP, and heating area A 1 , A 7 It is classified as the non-sheet passing area AN. Figure 8B In the heating area A 2 , A 3 , A 4 , A 5 Classified as image area AI, heating area A 6 is classified as a non-image area AP, and the heating area A 1 , A 7 All are classified as non-sheet passing area AN. 2 As in , even if an image area exists in a part of the heating area, the heating area is regarded as the image area AI. Figure 8C In the heating area A 2 , A 3 , A 4 , A 5 Classified as image area AI, and heating area A 1 , A 6 , A 7 All are classified as non-image areas AP. 1 , A 7 As in , even in the case where there is a non-sheet passing area in a part of the heating area and the heating area is not an image area, the heating area is regarded as a non-image area AP. Fig.8D In the heating area A 1 , A 2 , A 3 , A 4 , A 5 , A 6 Classified as image area AI, and heating area A 7 It is classified as non-image area AP. 1 As in , when the image area exists even in a part of the heated area, the heated area is regarded as the image area AI.

[0064] 7. Details of heater control method

[0065] Next, the image area temperature T described in detail in the previous section is explained. AI , non-image area temperature T AP and non-sheet passing area temperature T AN and the relationship between the concave top amount of the pressure roller 208. Fig. 8A In the case of recording material P of the mode (sheet width 155 mm, sheet length 297 mm, image width 31 mm, basis weight 60 g / m 2 ), each heating area is classified as follows based on the image information and the recording material information. Specifically, the heating area A 4 Classified as image area AI, heating area A 2 , A 3 , A 5 , A 6 The heating areas A1 and A7 are classified as the non-image area AP, and the heating areas A1 and A7 are both classified as the non-sheet passing area AN.

[0066] Table 1 shows the control temperature of each heating area in this embodiment and the control temperature in the comparative example. Fig. 9 The center difference of the outer diameter as the concave top amount of the pressure roller 208 when the control temperature is set is shown in the figure. Fig. 9 In FIG. 1 , the solid line is the setting in Example 1, the dashed line is the setting in Comparative Example 1, and the dotted line is the setting in Comparative Example 2. As in Comparative Example 1, the non-image area temperature T AP The higher the temperature T , the greater the concave top amount of the pressure roller 208, and the more significant the effect of suppressing wrinkles in the recording material P; however, the power consumption of the fixing device 200 is conversely higher. In contrast, as in Comparative Example 2, the non-image area temperature T AP The lower the value, the smaller the power consumption of the fixing device 200. However, the amount of concave top of the pressure roller 208 is also smaller, so the effect of suppressing wrinkles in the recording material P is weaker.

[0067] It was found experimentally that in the configuration of this embodiment, when the concave top amount of the pressure roller 208 is less than 100 μm, wrinkles appear in the recording material P. In the case of Comparative Example 2, A as the edge of the sheet passing area of ​​the recording material P 2 and A 6 The amount of concave tops in the recording material P was less than 100 μm, and wrinkles occurred in the recording material P. In contrast, in the case of the setting of Comparative Example 1, A as the edge of the sheet passing area of ​​the recording material P was 2 and A 6The amount of concave tops in the recording material P is 100 μm or more, and wrinkles do not occur in the recording material P, but the power consumption of the fixing device 200 does increase. In this embodiment, in view of the above considerations, by focusing on the non-sheet passing area temperature T AN To achieve both wrinkle suppression and power saving in the recording material P. Specifically, as shown in Table 1, the non-sheet passing area temperature T AN is set to 260°C, which is higher than the image area temperature T AI , while the non-image area temperature T AP is set to 100°C. According to such temperature control, the concave top amount of the pressure roller 208 is Fig. 9 The solid line of the concave top is A, and the edge of the sheet passing through the area 2 and A 6 The concave top amount in the recording material P is 100 μm or more, and wrinkles in the recording material P are suppressed. The heating area A is set to 260°C. 1 , A 7 It is the non-sheet passing area, so it comes from the heating block HB 1 and HB 7 The heat is not taken away by the recording material P, and since the power consumption is not significantly increased, the power saving is maintained.

[0068] Table 1

[0069] Control temperature in Example 1 and Comparative Examples 1 and 2

[0070]

[0071] 8. Effects of the Invention

[0072] As a comparative experiment, the control temperatures of Example 1 and Comparative Examples 1 and 2 given in Table 1 were Fig. 8A The corresponding 60 print copies of recording material P (sheet width 155 mm, sheet length 297 mm, basis weight 60 g / m 2 ); the frequency of occurrence of sheet wrinkles at this time is given in Table 2. Table 2 reveals that in the configuration of Comparative Example 2, wrinkles in the recording material P are less likely to occur in 30 of 60 print copies, while in the configuration of Embodiment 1, wrinkles do not occur in the recording material P. In Embodiment 1, by heating the heating area A as the non-sheet passing area AN, 1 , A 7The force transmitted by the pressure roller 208 and causing the recording material P to be stretched from the central area toward the edge portion PE is maintained; as a result, the occurrence of wrinkles in the recording material P can be suppressed. Table 2 further lists the power when the sheet is passed by comparison with Comparative Example 1. Similar to Example 1, wrinkles did not occur in the recording material P in Comparative Example 1; however, in Example 1, the power was reduced by 7%. The reason for this is that the heating area A as the non-image area AP 2 , A 3 , A 5 , A 6 The above comparison reveals that setting the non-sheet passing area temperature to be higher than the non-image area temperature, which is a feature of the present embodiment, results in both effects of suppressing wrinkles in the recording material and saving electric power.

[0073] Table 2

[0074] Wrinkle Occurrence Frequency and Power Saving in Example 1 and Comparative Examples 1 and 2

[0075]

[0076] Example 2

[0077] Next, we will explain how to follow Fig. 6A and Figure 6B The recording material P of the mode (sheet width 155 mm, sheet length 297 mm, image width 93 mm, basis weight 60 g / m 2 ) is an example of this embodiment. Table 3 lists the controlled temperature of each heating zone in this embodiment. In the comparative example, the temperature T of the non-sheet passing zone AN Relative to T in the embodiment AN The temperature was changed by ±20°C, and all non-sheet passing area temperatures were set higher than the non-image area temperature.

[0078] Table 3

[0079] Control temperature in Example 2 and Comparative Examples 3 and 4

[0080]

[0081] Table 4 shows the recording material P (sheet width 155 mm, sheet length 297 mm, image width 93 mm, basis weight 60 g / m2) when traveling 60 copies. 2 ) is the frequency of sheet wrinkles.

[0082] Table 4

[0083] Corrugation frequency and power saving in Example 2 and Comparative Examples 3 and 4

[0084]

[0085] In this embodiment, the temperature of the non-sheet passing area T AN is set to 240°C, which is higher than T in Example 1 and Comparative Example 3. AN However, no wrinkles occurred in the recording material P. This is because in this embodiment, the image area AI is wider and the non-image area AP is narrower than in the case of Embodiment 1, so it is easy to maintain the concave top amount of the pressure roller 208. In the setting of Comparative Example 4, the non-sheet passing area temperature T AN Further decreasing by 20°C, however, the power decreased, but the recording material P showed slight wrinkles in 5 of 60 prints. This revealed that the non-sheet passing area temperature T AN It is necessary to set according to the image area and the non-image area in order to suppress the occurrence of wrinkles and maximize power saving. Therefore, in order to suppress the occurrence of wrinkles and maximize power saving, it is preferable to appropriately change the non-sheet passing area temperature T depending on other sheet passing conditions. AN In the case where, for example, a recording material P having a large basis weight and thus not prone to wrinkles travels, the non-sheet passing area temperature T AN can be lowered; on the contrary, for example, in the case where wrinkles may occur, such as in a high humidity environment, the non-sheet passing area temperature T AN The non-sheet passing region temperature T may be changed according to the cumulative use state of the pressure roller 208 and the sheet passing interval of the recording material P. AN .

[0086] Therefore, in the present embodiment, for the purpose of maximizing wrinkle suppression in the recording material and maximizing power saving, it has been described that the non-sheet passing area temperature T is appropriately set according to the sheet passing condition. AN needs.

[0087] Example 3

[0088] Next, we will explain how to follow Figure 8B The recording material P of the mode (sheet width 155 mm, sheet length 297 mm, image width 108 mm, basis weight 60 g / m 2 ) is an example of this embodiment. Table 5 lists the controlled temperature of each heating zone in this embodiment. 2 The image pattern in this embodiment is the same as that in Embodiment 2 (Table 3), except for the image area AI in this context. 2 The control temperature is set as the image area temperature T AI The heating area A is 250℃. 1 The control temperature was set to 220 °C.

[0089] Table 5

[0090] Temperature Control in Example 3

[0091]

[0092] In heating area A 1 In Comparative Example 4 (Table 3) where the control temperature is the same as that in Example 3, the frequency of sheet wrinkling is 5 out of 60 sheets (Table 4). In contrast, in the present embodiment, in 60 printed copies of the recording material P (sheet width 155 mm, sheet length 108 mm, image width 93 mm, basis weight 60 g / m 2 ) The frequency of sheet wrinkles during the running is 0 out of 60 sheets. This is because in Comparative Example 4, the heating area A 2 is the non-image area AP, and in this embodiment, the heating area A 2 is the image area AI. Specifically, the above results are derived from the following facts: the image area temperature T AI high, 250°C, so even if the adjacent heating area A 1 The temperature is as low as 220° C., and the concave top of the pressure roller 208 can be easily maintained.

[0093] The surface temperature of the fixing film 202 at this time is listed in Table 6. The surface temperature of the fixing film 202 was measured from the outside using a non-contact temperature detection device.

[0094] Table 6

[0095] The surface temperature of the fixing film in Example 3

[0096]

[0097] Table 6 reveals that the heating area A as the non-sheet passing area of ​​the recording material P 1 and A 7 The fixing film temperature in the heating area A is higher than the heating area A where the sheet of recording material P passes. 2 , A 3 , A 4 , A 5 , A 6 The fixing film temperature is 20°C or more higher. It is found that since the high temperature of the end of the fixing film 202 acts on the pressure roller 208 by direct face-to-face contact with the pressure roller 208, the pressure roller 208 is also successfully concave-topped by these. Heating area A 1 and heating area A 7have the same fixing film temperature. This indicates that the amount of thermal expansion at the end of the pressure roller 208 is balanced. It was found that, as a result, the force that stretches the recording material P from the center area toward the edge portion PE also acts evenly on the left and right sides, which leads to the suppression of wrinkles. On the other hand, as described in Examples 1 and 2, in the heating area A 1 and A 7 In the non-sheet passing area, the heat from the heat generating block is not taken away by the recording material P, so that the power saving can be maintained without causing a significant increase in power consumption.

[0098] As described above, in the present embodiment, the effect of suppressing wrinkles in the recording material is caused by controlling so that the temperature of the non-sheet passing region of the recording material in the fixing film is higher than the temperature in the sheet passing region of the recording material.

[0099] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An image heating device, comprising: a heating member provided with a heater having a plurality of heating elements juxtaposed in a direction perpendicular to a conveying direction of the recording material; a roller which forms a nip by being pressed against a heating member and which rotates so that a circumference of the roller increases from a center portion toward an end portion in a direction perpendicular to the conveying direction; and a control unit that independently controls power supplied to the plurality of heating elements; wherein the image heating device heats the image formed on the recording material using heat from the heater, and In which the control unit will set a control target temperature for supplying power to a heating element among the multiple heating elements corresponding to a non-sheet passing area where the recording material does not pass over the entire width of the heating element at the clamping portion to be higher than the lowest control target temperature among the control target temperatures set to supply power to a heating element corresponding to a sheet passing area where the recording material passes at the clamping portion.

2. The image heating device according to claim 1, in, The sheet passing region corresponding to the heating element for which the lowest control target temperature is set is a non-image region through which a region on the recording material where no image is formed passes.

3. The image heating device according to claim 1, in, The sheet passing region corresponding to the heating element for which the lowest control target temperature is set is a sheet passing region adjacent to the non-sheet passing region.

4. The image heating device according to claim 1, 2 or 3, in, The heating member has a tubular film with a heater disposed inside, a nip is formed by the heater and the roller across the film, and an image on a recording material is heated via the film.

5. An image forming device, comprising: an image forming section in which an image is formed on a recording material; as well as a fixing section that fixes the image formed on the recording material to the recording material, The fixing unit has: a heating member provided with a heater having a plurality of heating elements juxtaposed in a direction perpendicular to a conveying direction of the recording material; a roller which forms a nip by being pressed against a heating member and which rotates so that a circumference of the roller increases from a center portion toward an end portion in a direction perpendicular to the conveying direction; and a control unit that independently controls power supplied to the plurality of heating elements; The fixing unit heats the image formed on the recording material using heat from the heater, and In which the control unit will set a control target temperature for supplying power to a heating element among the multiple heating elements corresponding to a non-sheet passing area where the recording material does not pass over the entire width of the heating element at the clamping portion to be higher than the lowest control target temperature among the control target temperatures set to supply power to a heating element corresponding to a sheet passing area where the recording material passes at the clamping portion.

Images