JP2008112053A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve shortening of warm-up time and improvement of power saving in an image forming apparatus. <P>SOLUTION: The heat roller 52 used for the fixing device of the image forming apparatus includes a base body 31 having cylindrical shape and made of electric insulating synthetic resin, a film type heater 33, and a releasing layer 37 having high releasing property to toner. The film type heater 33 includes: a heat resistant insulating layer 34; a heating element 35 formed on one side surface of the heat resistant insulating layer 34 to have pattern shape comprising a plurality of lines and generating heat by application of voltage; and a heat transfer layer 36 formed in a surface state on the other side surface of the heat resistant insulating layer 34. The film type heater 33 is interposed between the base body 31 and the releasing layer 37, and also the base body 31, the heating element 35, the heat resistant insulating layer 34, the heat transfer layer 36 and the releasing layer 37 are layered in this order outward in a radial direction. Power per unit time given to the film type heater 33 is made to differ between when the heat roller 52 comes into contact with paper and when it does not come into contact therewith. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a configuration of an image forming apparatus using a heat roller for fixing toner on a recording medium.

Patent Document 1 discloses a heat roller fixing type fixing device used in an electrophotographic image forming apparatus. The fixing device of Patent Document 1 has a configuration in which a heat roller and a press roller are pressed against each other to form a nip portion, and the paper passing through the nip portion is heated and pressed to fix the toner onto the paper. . In the configuration of Patent Document 1, the heat roller is formed in a cylindrical shape, and a halogen lamp as a heat source is disposed inside the heat roller.
Japanese Patent Laying-Open No. 2005-257852

  However, the halogen lamp built-in heat roller disclosed in Patent Document 1 has a configuration in which the roller is heated from the inside, and therefore, the time from the start of heating until the roller surface rises to the required temperature. There is room for improvement in terms of shortening the warm-up time. Further, since the heat source is arranged on the inner peripheral side of the cylindrical roller, the roller surface cannot be efficiently heated, and there is room for improvement from the viewpoint of energy saving.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an image forming apparatus capable of shortening the warm-up time and saving power.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to a first aspect of the present invention, an image forming apparatus having the following configuration is provided. That is, a fixing device for fixing the toner on the recording medium is provided. The heat roller used in the fixing device has a columnar shape or a cylindrical shape, and has an electric insulating base body, an electric insulating layer, and a pattern shape including a plurality of lines. A sheet heating element including a heating layer formed on one surface and generating heat upon application of a voltage; and a heat transfer layer formed in a sheet shape on the other surface of the electrical insulating layer; and the toner And a release layer having a high releasability. The planar heating element is interposed between the outer peripheral surface of the base body and the release layer, and the base body, the heating layer, the electrical insulating layer, the heat transfer layer, and the separation layer. The mold layers are laminated in this order outward in the radial direction. Electric power WA per unit time given to the sheet heating element when the recording medium is in contact with the heat roller, and unit given to the sheet heating element when the recording medium is not in contact with the heat roller The power WB per hour is controlled to be different.

  Thereby, since a heat source, that is, a planar heating element is arranged near the roller surface, the temperature of the roller surface can be rapidly increased, and the warm-up time can be remarkably shortened. In addition, since the planar heating element is disposed outside the base body, useless heating of the center portion of the heat roller can be prevented, and power saving is excellent. Furthermore, since the heat generating layer of the planar heat generating element has a pattern shape composed of a plurality of lines, uneven heat generation can be reduced. Further, since the planar heat transfer layer is disposed outside the heat generating layer, the recording medium in contact with the surface of the heat roller can be heated uniformly, and uniform toner fixing can be realized. Further, by switching the amount of electric power applied to the heat roller depending on whether or not the recording medium is in contact with the heat roller, the power consumption of the heat roller can be finely controlled, and power saving is easy. Further, since the temperature of the roller surface can be rapidly raised, even when the power is switched as described above, the roller surface can be reliably raised to the temperature necessary for toner fixing at a desired timing. .

  According to a second aspect of the present invention, an image forming apparatus having the following configuration is provided. That is, a fixing device for fixing the toner on the recording medium is provided. The heat roller used in the fixing device has a columnar shape or a cylindrical shape, and has an electrically insulating base body, an electrically insulating layer laminated on the outer periphery of the base body, and a plurality of the electrically insulating layers on the electrically insulating layer. A sheet heating element including a heating layer that is formed to have a pattern shape composed of a line and generates heat upon application of a voltage, an elastic layer laminated on the sheet heating element, and the elastic body And a release layer which is laminated on the top and has a high release property with respect to the toner. Electric power WA per unit time given to the sheet heating element when the recording medium is in contact with the heat roller, and unit given to the sheet heating element when the recording medium is not in contact with the heat roller The power WB per hour is controlled to be different.

  Thereby, since the heat source, that is, the planar heating element is arranged near the roller surface, the temperature of the roller surface can be rapidly increased, and the warm-up time can be shortened. In addition, since the planar heating element is disposed outside the base body, useless heating of the center portion of the heat roller can be prevented, and power saving is excellent. Furthermore, since the heat generating layer of the planar heat generating element has a pattern shape composed of a plurality of lines, uneven heat generation can be reduced. In addition, since the elastic layer is disposed between the sheet heating element and the release layer, the toner after fixing can be imparted with appropriate gloss and a glossy image can be formed. Further, by switching the amount of electric power applied to the heat roller depending on whether or not the recording medium is in contact with the heat roller, the power consumption of the heat roller can be finely controlled, and power saving is easy. Further, since the temperature of the roller surface can be rapidly raised, even when the power is switched as described above, the roller surface can be reliably raised to the temperature necessary for toner fixing at a desired timing. .

  In the image forming apparatus, the power WA is preferably larger than the power WB.

  According to this, by supplying the power WA necessary for toner fixing only when necessary, it is possible to save the power consumption and reduce the running cost while reliably fixing the toner on the recording medium.

  In the image forming apparatus, the voltage VA applied to the sheet heating element when the recording medium is in contact with the heat roller, and the sheet heating element when the recording medium is not in contact with the heat roller. It is preferable to control the voltage VB to be different from the voltage VB.

  Thereby, the electric power per unit time can be changed easily.

  In the image forming apparatus, a duty ratio DA that drives the sheet heating element when the recording medium is in contact with the heat roller, and the sheet shape when the recording medium is not in contact with the heat roller. It is preferable to control the duty ratio DB for driving the heating element to be different.

  This also makes it possible to easily change the power per unit time.

  The image forming apparatus is preferably configured as follows. That is, a recording medium detection sensor is provided on the upstream side of the fixing device in the conveyance direction in the conveyance path of the recording medium. Based on the timing when the recording medium detection sensor detects the recording medium, the switching timing of the power per unit time applied to the planar heating element is determined.

  As a result, the power switching timing can be accurately obtained, so that the toner can be reliably fixed to the recording medium, and further power saving can be realized.

  Next, embodiments of the invention will be described. FIG. 1 is an external perspective view of a copy facsimile multifunction peripheral according to an embodiment of the present invention, and FIG. 2 is a front sectional view showing the inside of the main body of the multifunction peripheral.

  As shown in the external perspective view of FIG. 1, a copy facsimile multifunction machine 75 as an image forming apparatus instructs an image reading unit 76 functioning as a flatbed scanner and an auto document feed scanner, the number of copies, a facsimile transmission destination, and the like. An operation panel 77, a main body 78 including an image forming unit for forming an image on a sheet as a recording medium, and a sheet feeding cassette 79 for sequentially supplying the sheet. The main body 78 includes a transmission / reception unit (not shown) for transmitting image data via a communication line.

  The inside of the copy facsimile multifunction machine 75 is shown in FIG. As shown in FIG. 2, a platen glass 82 on which a document to be read is placed is provided on the upper surface of the main body 78. A document table cover 83 is provided above the main body 78, and the document table cover 83 can press and fix the document on the platen glass 82.

  The document table cover 83 is provided with an automatic document feeder (auto document feeder, ADF) 84. The ADF 84 includes a document tray 85 provided above the document table cover 83, and a discharge tray 86 provided below the document tray.

  As shown in FIG. 2, a curved document transport path 87 that connects the document tray 85 and the discharge tray 86 is formed inside the document table cover 83. A separation roller 88 and a plurality of transport rollers 89 are arranged in the document transport path 87. With this configuration, the documents set on the document tray 85 are separated one by one and conveyed along the curved document conveyance path 87, and after passing through the document reading position, are discharged to the discharge tray 86. The

  As shown in FIG. 2, a scanner unit 90 is provided on the upper portion of the main body 78. The scanner unit 90 includes a light source 91 that irradiates light to the original reading position of the platen glass 82 or the ADF 84, reflection mirrors 92, 93, and 94 that reflect light reflected from the original, and converges the reflected light. A condensing lens 95 and a charge coupled device (CCD) 96 that converts the convergent light into an electric signal and outputs the electric signal are provided.

  The light source 91 and the reflecting mirror 92 of the scanner unit 90 are configured to be appropriately movable. The original placed on the platen glass 82 is scanned while moving, or moved to the original reading position of the ADF 84, It is possible to scan a document conveyed through the document conveyance path 87.

  The reflected light from the original is guided to the CCD 96 to form an image, and the CCD 96 outputs an electrical signal corresponding to the original. This signal is sent to an image forming unit 11 (to be described later) for printing after appropriate conversion processing, or transmitted to another facsimile apparatus via a communication line by the transmission / reception unit.

  As shown in FIG. 2, a paper feed cassette 79 for supplying paper 100 is provided at the lower part of the main body 78. The paper feed cassette 79 is configured to be pulled out to the front side of the apparatus (the front side of the paper in FIG. 2). An image forming unit 11, a fixing device 51, and a paper discharge tray 80 are provided above the paper feed cassette 79.

  Inside the main body 78, a transport path 24 for transporting the paper 100 from the paper feed cassette 79 to the paper discharge tray 80 is formed. The conveyance path 24 extends upward from one end side of the paper feed cassette 79, then curves in the horizontal direction to reach the image forming unit 11, further extends in the horizontal direction, passes through the fixing device 51, and then is discharged. It is configured to reach the paper tray 80.

  A paper feed roller 21 is disposed above the paper feed cassette 79, and is configured such that the paper feed roller 21 contacts the uppermost paper 100 stacked in the paper feed cassette 79. By driving the paper feed roller 21 in this state, the uppermost sheet 100 is separated and picked up and sent out toward the transport path 24.

  Conveying rollers 22 and 23 are arranged immediately downstream of the paper feed roller 21 in the conveying path 24. The transport rollers 22 and 23 are driven while the paper 100 is nipped between the transport rollers 22 and 23 so as to transport the paper 100 to the image forming unit 11 on the downstream side.

  A paper detection sensor (recording medium detection sensor) 18 is disposed in the vicinity of the conveyance roller 23 in the conveyance path 24. The paper detection sensor 18 is configured to detect the paper 100 conveyed in the conveyance path 24 and output an appropriate signal (paper detection signal).

  As shown in FIG. 2, the image forming unit 11 has a configuration in which a charger 13, an LED head 14, a developing device 15, and a transfer roller 16 are arranged around the photosensitive drum 12.

  The photosensitive drum 12 is configured such that a photoconductive film made of an organic photoreceptor is formed on the surface and is rotated by an electric motor (not shown). The charger 13 is configured in a brush charging system, and the charger 13 uniformly charges the surface of the photosensitive drum 12, for example, negatively.

  The LED head 14 as an exposure device is disposed downstream of the charger 13 (refers to the downstream side in the rotation direction of the photosensitive drum 12; hereinafter, the same applies to the description of the developing device 15 and the transfer roller 16). In this configuration, a large number of light emitting diodes (LEDs) are arranged in the paper width direction. The LED head 14 selectively emits light corresponding to the image data of the facsimile document received via the telephone line or the image data read by the image reading unit 76. As a result, the surface of the photosensitive drum 12 is selectively exposed, and the electrostatic energy is formed by losing the charge energy of the exposed portion.

  The developing device 15 is disposed on the downstream side of the LED head 14. The developing device 15 includes a toner container 26 that stores nonmagnetic one-component toner, and a stirring blade 27 that is rotationally driven inside the toner container 26 for stirring the toner. Further, the developing device 15 is disposed so as to be in contact with the supply roller 28 disposed in the toner container 26, the development roller 29 disposed in contact with the supply roller 28, and the outer peripheral surface of the development roller 29. And a regulating blade 30 to be operated.

  With this configuration, the supply roller 28 and the developing roller 29 are rotationally driven so as to rub the circumferential surfaces in opposite directions. Further, the tip of the regulating blade 30 rubs against the peripheral surface of the developing roller 29 that is driven to rotate. As a result, the toner in the toner container 26 is frictionally charged and adheres to the surface of the developing roller 29 due to a potential difference. The toner on the surface of the developing roller 29 is adjusted by the regulating blade 30 so that the adhesion thickness is uniform, and is sent to the photosensitive drum 12 side by the rotation of the developing roller 29. Thereafter, in the vicinity of the photosensitive drum 12 and the developing roller 29, the toner on the surface of the developing roller 29 is selectively transferred to the surface of the photosensitive drum 12 only in the portion corresponding to the exposed portion of the photosensitive drum 12 by the LED head 14. Moving. As a result, a toner image is formed on the surface of the photosensitive drum 12.

  The transfer roller 16 is disposed on the downstream side of the developing unit 15 and is disposed on the opposite side of the photosensitive drum 12 with the conveyance path 24 interposed therebetween. A predetermined voltage from a power source is applied to the transfer roller 16. Accordingly, the toner image formed on the surface of the photosensitive drum 12 moves so as to approach the transfer roller 16 side by the rotation of the photosensitive drum 12, and is transferred to the paper 100 by the electric field attraction force. The sheet 100 on which the toner image is transferred is sent to the fixing device 51 on the downstream side of the conveyance path 24 by the rotation of the photosensitive drum 12.

  The fixing device 51 includes a heat roller 52 that is rotationally driven, and a press roller 53 that is disposed to face the heat roller 52. The press roller 53 is pressed against the heat roller 52 by an urging spring. The detailed configuration of the heat roller 52 and the press roller 53 will be described later.

  With this configuration, when the paper 100 passes between the heat roller 52 and the press roller 53, the toner of the toner image is melted and fixed to the paper 100 by the heat of the high-temperature heat roller 52 and the pressure by the press roller 53. The fixing device 51 is provided with a separation claw 54 for preventing the paper 100 from being wrapped around the heat roller 52 while being stuck.

  As shown in FIG. 2, a paper discharge roller 25 is provided on the downstream side of the fixing device 51. With this configuration, the sheet 100 sent from the fixing device 51 is nipped between the sheet discharge roller 25 and a driven roller disposed opposite thereto, and is discharged onto the sheet discharge tray 80.

  Next, a detailed configuration of the fixing device 51 will be described. An enlarged cross-sectional view of the fixing device 51 is shown in FIG. 3, and as shown in FIG. 3, the fixing device 51 includes a housing 55 that houses the heat roller 52 and the press roller 53. A heat roller 52 is rotatably supported on the housing 55 via a bearing 56, and a press roller 53 is rotatably supported via a bearing body 57.

  The bearing body 57 is slidably provided with respect to the housing 55, and an urging spring 58 is interposed between the bearing body 57 and the housing 55. The press roller 53 is pressed against the heat roller 52 by the spring force of the urging spring 58, and both are elastically contacted.

  Next, detailed configurations of the heat roller 52 and the press roller 53 will be described with reference to FIG. 4 is an enlarged cross-sectional view of a region (nip portion) indicated by A in FIG. The heat roller 52 includes a base body (heat-resistant carrier) 31, a heat-resistant and heat-insulating layer 32, a film heater (planar heating element) 33, and a release layer 37 as main components.

  The base body 31 has a cylindrical shape, and a film heater 33 is disposed outside the base body 31. The heat conductivity of the base body 31 is smaller than the heat conductivity of the film heater 33 (the heat conductivity of the heat transfer layer 36 described later), and the heat capacity of the base body 31 is the heat capacity of the film heater 33 (heat transfer). The heat capacity of the layer 36).

  The film heater 33 disposed outside the base body 31 includes a heat-resistant insulating layer 34, a heating element (heating layer) 35, and a heat transfer layer (soaking layer) 36.

  The heating element 35 of the film heater 33 can be made of, for example, stainless steel, nickel alloy such as nickel chrome, nickel, or the like. The heating element 35 has a pattern shape in which a plurality of thin lines are arranged in parallel at equal intervals (heater pattern). The thickness of the heating element 35 is preferably 0.1 μm or more and 100 μm or less, for example, and more preferably about 30 μm. Specifically, sputtering, vapor deposition, metal foil etching, pattern printing, blasting, or the like can be used as a method for creating the heater pattern.

  The thickness of the heat-resistant insulating layer 34 of the film heater 33 is, for example, 1 μm to 200 μm, preferably 10 μm to 70 μm. The material of the heat-resistant insulating layer 34 is preferably a polyimide resin, a silicone resin, or the like, but is not limited thereto.

  The heat transfer layer 36 of the film heater 33 is configured to have a thickness of, for example, 1 μm to 50 μm, preferably 10 μm to 30 μm. The heat transfer layer 36 is preferably formed using a material having a higher thermal conductivity than any of the base body 31, the heat generating body 35, the heat resistant insulating layer 34, and the heat resistant heat insulating layer 32 described later. Moreover, it is preferable that the heat conductivity of the heat transfer layer 36 is, for example, 10 W / m · K or more. Examples of the material for the heat transfer layer 36 include metals such as copper and aluminum, and ceramics such as aluminum nitride (AlN) and silicon carbide (SiC).

  A release layer 37 is disposed on the outermost periphery of the heat roller 52. The release layer 37 is made of a material having a high releasability with respect to the toner (a material having a low surface energy and a low intermolecular cohesive force), for example, a fluororesin such as a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, The thickness is, for example, about 30 μm.

  A heat-resistant and heat-insulating layer 32 is interposed between the film heater 33 and the base body 31. The heat resistant heat insulating layer 32 is configured to have a thickness of 0.1 mm to 0.5 mm, for example. The material of the heat-resistant and heat-insulating layer 32 is preferably a material having a lower thermal conductivity than any of the heat generating body 35, the heat-resistant insulating layer 34, the heat transfer layer 36, and the base body 31, for example, a mat mainly composed of ceramic fibers. It is conceivable to use glass fiber, foamed resin, porous ceramics and the like.

  The film heater 33 can be formed by the following method, for example. That is, the thing which bonded copper foil to the surface of one side of the polyimide film as a base material is prepared. This polyimide film corresponds to the heat-resistant insulating layer 34, and the copper foil corresponds to the heat transfer layer 36. Then, a stainless steel foil having a thickness of 25 μm is heat-pressed with a heat-resistant adhesive such as polyimide or silicone on the surface of the polyimide film opposite to the copper foil. This heat-resistant adhesive can be applied by a known method such as screen printing. Next, the stainless steel foil is processed into a pattern shape having a plurality of lines by a known method such as wet etching. As a result, a heater pattern-shaped heating element (heating layer) 35 made of stainless steel foil is formed, and a film-like heater 33 having good flexibility is obtained.

  As a method for forming the heat transfer layer 36, a copper foil may be separately attached to a single polyimide film with a heat-resistant adhesive such as polyimide or silicone. Further, as a method of forming the heating element 35, the foil-shaped material may be processed in advance into a predetermined heater pattern shape by a method such as wet etching, dry etching, or blasting and then attached to a polyimide film. Alternatively, a wire-shaped material previously processed into a heater pattern shape may be separately attached to a polyimide film with a heat-resistant adhesive such as polyimide or silicone. Further, the foil body may be formed by using a thin film process such as sputtering or vapor deposition, or the heater pattern may be directly formed by a thin film process.

  Next, a base body 31 is prepared in which a resin having electrical insulating properties, for example, polyphenylene sulfide (PPS) resin is formed into a cylindrical shape. Next, a ceramic mat mainly composed of alumina-silica is heat-pressed to the outer peripheral surface of the base body 31 with a heat-resistant adhesive such as polyimide or silicone. Thereby, the heat-resistant and heat-insulating layer 32 is formed on the surface of the base body 31. The heat-resistant adhesive can be applied by a known method such as screen printing.

  Thereafter, the film heater 33 obtained by the above procedure is arranged so that the surface on the side of the heating element 35 faces the outer peripheral surface of the base body 31 (the heat-resistant and heat-insulating layer 32), and heat resistant such as silicone and polyimide. Heat-press with an adhesive. The heat-resistant adhesive can be applied by a known method such as screen printing. As a result, the adhesive layer 38 is interposed between the film heater 33 and the base body 31 (between the film heater 33 and the heat-resistant heat insulating layer 32).

  Further, a fluororesin layer such as a tetrafluoroethylene / perfluoroalkylvinyl copolymer is formed on the outer peripheral surface of the film heater 33 to form a release layer 37. The heat roller 52 can be manufactured by the above process.

  However, the heat roller 52x may be modified as shown in FIG. The heat roller 52x includes a cylindrical base body 31, a film heater 133, an elastic layer 39, and a release layer 37 as main components.

  In the present modification, the film heater 133 includes a heat-resistant insulating layer 34 and a heating element (heating layer) 35. Specifically, a heating element 35 having a heater pattern shape is formed on one surface of the heat-resistant insulating layer 34 in the same manner as the heat roller 52 described with reference to FIG. However, the heat transfer layer 36 provided in the heat roller 52 is not provided in the present modification.

  The elastic layer 39 is a layer having appropriate elasticity, and in the example of FIG. 5, it is a silicon rubber layer, specifically, a foamed silicone layer. The thickness of the elastic layer 39 is preferably 0.1 mm or more and 0.5 mm or less.

  A release layer 37 is disposed on the outermost periphery of the heat roller 52x. The release layer 37 can be made of, for example, a fluororesin such as a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, similarly to the heat roller 52 described in FIG.

  Compared with the heat roller 52 described with reference to FIG. 4, the heat roller 52x can cause the fixing toner to be glossy by the elastic layer 39, so that an image having a glossy and high-class feeling can be obtained. This effect is particularly effective when images such as photographs are formed.

  As shown in FIG. 4, the press roller 53 elastically contacted with the heat roller 52 (52x) in the fixing device 51 has a cylindrical sponge body 62 around a roller shaft 61 formed of metal such as stainless steel. The release layer 63 is arranged on the outer peripheral surface of the sponge body 62 and fixed.

  Next, the electrical configuration of the copy facsimile multifunction machine 75 will be described with reference to the block diagram of FIG. The multi-function device 75 includes a power supply unit 65, a control unit 66 that controls each unit, and a calculation unit 67 that performs various calculations. The control unit 66 is connected to the power supply unit 65, and the heat roller 52 of the fixing device 51 generates heat upon receiving power supply from the power supply unit 65.

  A temperature detector 68 made of, for example, a thermistor is disposed in the housing 55 of the fixing device 51 (see also FIG. 3). The temperature detector 68 is disposed opposite to the outer peripheral surface of the heat roller 52 and is configured to measure the surface temperature of the heat roller 52.

  As shown in FIG. 6, the temperature signal detected by the temperature detector 68 is sent to a thermometer circuit 69, and the thermometer circuit outputs a signal of the surface temperature of the heat roller 52 to the calculation unit 67. When the calculation unit 67 performs various calculations on this signal, the control unit 66 recognizes the temperature of the heat roller 52 and controls the power supplied to the film heater 33 based on this.

  As described above, the paper detection sensor 18 is installed in the middle of the transport path 24 through which the paper 100 is transported in the multifunction device 75. The sheet detection sensor 18 is disposed upstream of the fixing device 51 in the sheet conveyance direction, detects the sheet 100 being conveyed, and transmits a sheet detection signal to the control unit 66.

  The control unit 66, the calculation unit 67, and the like are stored in hardware such as a CPU (calculation unit), a ROM, a RAM (storage unit), a timer circuit (time measurement unit), and the like included in the multi-function device 75 and the ROM. It is constructed by combining with control software.

  Consider the case where a print command is given to the multi-function device 75 with the above configuration. Immediately after the print command, the drive of each unit such as the paper feed roller 21 and the image forming unit 11 is started, and the paper 100 is conveyed through the conveyance path 24 and image formation is performed. However, at the time immediately after the start of printing, the control unit 66 performs control so that no voltage is applied to the film heater 33.

  When the printing process advances and the top of the paper 100 reaches the detection area of the paper detection sensor 18, the paper detection sensor 18 transmits a paper detection signal to the control unit 66. The control unit 66 that has received the paper detection signal starts applying a voltage to the film heater 33 of the heat roller 52 after a predetermined delay time has elapsed from the signal reception timing. This delay time is set in advance as the time from when the leading edge of the paper 100 passes through the paper detection sensor 18 until it contacts the heat roller 52.

  As a result, power is supplied to the film-like heater 33 at the timing when the paper 100 comes into contact with the heat roller 52 in the fixing device 51. Then, the paper 100 is pressed while being in contact with the surface of the heat roller 52 whose temperature has been increased, and the toner image is fixed on the surface of the paper 100.

  Further, the control unit 66 applies the voltage to the film heater 33 after the delay time elapses from the timing when the paper detection signal is not received (that is, the timing when the trailing edge of the paper 100 passes the paper detection sensor 18). The voltage is set to 0V again. Accordingly, the heating of the heat roller 52 is stopped at the timing when the paper 100 has completed the passage of the heat roller 52 and is no longer in contact with the heat roller 52.

  In this way, by switching the supply / stop of power supply to the film heater 33 between the state in which the paper 100 is not in contact with the heat roller 52, only when it is necessary for fixing the toner on the paper 100. The heat roller 52 can be heated, and power consumption can be saved.

  As described above, the heat roller 52 of the present embodiment includes the base body 31 having a cylindrical shape and electrical insulation, the film heater 33, and the release layer 37 having a high releasability with respect to the toner. And comprising. The film-like heater 33 is formed on one surface of the heat-resistant insulating layer 34 so as to have a pattern shape composed of a plurality of wires, and a heating element 35 that generates heat upon application of voltage, A heat transfer layer 36 formed in a planar shape on the other surface of the heat-resistant insulating layer 34. A film heater 33 is interposed between the outer peripheral surface of the base body 31 and the release layer 37, and the base body 31, the heating element 35, the heat-resistant insulating layer 34, the heat transfer layer 36, and the release layer 37. The mold layer 37 is laminated in this order outward in the radial direction. Further, the power WA per unit time given to the film heater 33 when the paper 100 is in contact with the heat roller 52 and the unit time per unit time given to the film heater 33 when the paper 100 is not in contact with the heat roller 52. The power WB is controlled so as to be different.

  With the above configuration, since the heat source, that is, the film heater 33 is disposed near the roller surface, the temperature of the roller surface can be rapidly increased as compared with the halogen roller built-in type heat roller disclosed in Patent Document 1, and the warm Uptime can be significantly reduced. In addition, since the film heater 33 is disposed outside the base body 31, unnecessary heating of the center portion of the heat roller 52 can be prevented and power can be saved. Further, since the heat transfer layer 36 is disposed radially outward from the heating element 35, the paper 100 in contact with the surface of the heat roller 52 can be heated uniformly, and uniform toner fixing can be realized and image quality can be improved. It can contribute to improvement. Further, by switching the magnitude of the power applied to the heat roller 52 depending on whether or not the paper 100 is in contact with the heat roller 52, the power consumption of the heat roller 52 can be finely controlled, and power saving is easy. Furthermore, since the temperature responsiveness of the roller surface is excellent as described above, even when the power is switched as described above, the roller surface is reliably raised to the temperature necessary for toner fixing at a desired timing. Can do. Therefore, even when a plurality of sheets of paper 100 pass through the fixing device 51 one after another at high speed, toner supply to each sheet 100 can be reliably fixed while changing the supply power in a short time between the sheets 100. Can be done.

  In the present embodiment, the power WA per unit time given to the film heater 33 when the paper 100 is in contact with the heat roller 52 is applied to the film heater 33 when the paper 100 is not in contact with the heat roller 52. It is set larger than the given power WB per unit time.

  Accordingly, since the sheet 100 can be efficiently heated when it is in contact with the heat roller 52, further power saving can be realized while reliably fixing the toner on the sheet 100.

  Further, in the present embodiment, the power per unit time is changed by changing the voltage applied to the film heater 33.

  Thereby, the electric power per unit time can be changed easily.

  However, the change of the power per unit time supplied to the film heater 33 is not limited to the change of the voltage, and can be performed by changing the duty ratio, for example.

  This also makes it possible to easily change the power per unit time.

  In the present embodiment, the sheet detection sensor 18 is provided on the conveyance path 24 upstream of the fixing device 51 in the sheet conveyance direction. Based on the timing at which the paper detection sensor 18 detects the paper 100, the switching timing of the power per unit time given to the film heater 33 is determined.

  As a result, it is possible to accurately obtain the switching timing of the power applied to the film heater 33, so that the toner can be reliably fixed to the paper 100 and further power saving can be realized.

  The effect of the configuration of the heat roller 52 is supported by the following experiment conducted by the inventors of the present application.

  That is, a configuration in which a non-woven fabric made of glass fiber is laminated as a heat-resistant and heat-insulating layer 32 on the outer peripheral surface of a base body 31 formed into a cylindrical shape using polyphenylene sulfide resin, and a film-like heater 33 is spirally wound around it. The heat roller 52 was prepared. In the film heater 33, a nickel chromium alloy was used as the heating element 35, a polyimide film was used as the heat-resistant insulating layer 34, and a copper foil was used as the heat transfer layer 36.

  A predetermined voltage was applied to the heat roller 52 having this configuration, and the time until the surface of the heat roller rose from room temperature to 180 ° C. was measured as a warm-up time. Then, it was found that the warm-up time of the heat roller 52 of this embodiment is shortened to about 1/7 as compared with the heat roller with a built-in halogen heater disclosed in Patent Document 1. Specifically, the warm-up time of the conventional heat roller was about 30 seconds, whereas the warm-up time of the heat roller 52 configured as described above was less than 4 seconds. Even when stainless steel was used as the heating element 35, good results similar to the above were obtained.

  6 illustrates the heat roller 52 having the configuration shown in FIG. 4 as an example. However, the configuration shown in FIG. 6 can be similarly applied to the heat roller 52x described with reference to FIG. Needless to say, is obtained.

  Although the preferred embodiments and modifications of the present invention have been described above, the above configuration can be further modified as follows.

  In the above embodiment, when the sheet 100 is not in contact with the heat roller 52, the voltage is set to 0 V (that is, the power per unit time is zero). The power can be changed to give power per unit time.

  The base body 31 can be formed in a columnar shape instead of being formed in a hollow cylindrical shape. Further, the material of the base body 31 is not limited to PPS, and heat resistant resins such as glass epoxy, and inorganic materials such as alumina, mullite, zirconia, and glass ceramics can be employed.

  In addition, the base body 31 can be made of a material having high thermal conductivity. For example, a material such as AlN or SiC, or a metal such as aluminum can be used. However, from the viewpoint of power saving, the base body 31 is preferably made of a material having low thermal conductivity. When the base body 31 is made of a material having high heat conductivity as described above, it is extremely preferable to form the heat-resistant and heat-insulating layer 32 on the outer peripheral surface.

  Moreover, the base body 31 is not limited to the case where the whole has electrical insulation, and only the outer peripheral surface may have electrical insulation. For example, when the base body 31 is made of aluminum, it is conceivable that an appropriate electrical insulating layer is formed on the outer peripheral surface and the film heater 33 is disposed outside the electrical insulating layer.

  The configuration of the present invention can be applied to various electrophotographic image forming apparatuses such as a copy, a facsimile, and a printer, as well as a copy facsimile multifunction peripheral.

1 is an external perspective view of a copy facsimile multifunction peripheral according to an embodiment of the present invention. FIG. 3 is a front cross-sectional view showing the inside of the main body of the multifunction machine. FIG. 3 is an enlarged cross-sectional view showing a state of the fixing device. The cross-sectional enlarged view which shows the part of A of FIG. 3 in detail. The cross-sectional enlarged view which shows the modification of a heat roller. 1 is a block diagram showing an electrical configuration of a copy facsimile multifunction peripheral.

Explanation of symbols

18 Paper detection sensor (recording medium detection sensor)
24 Conveyance path 31 Base body 32 Heat-resistant and heat-insulating layer (heat-insulating layer)
33 Film heater (planar heating element)
34 Heat-resistant insulation layer (electrical insulation layer)
35 Heating element (heating layer)
36 Heat Transfer Layer 37 Release Layer 38 Adhesive Layer 39 Elastic Layer 51 Fixing Device 52 Heat Roller 53 Press Roller 65 Power Supply Unit 66 Control Unit 67 Calculation Unit 75 Copy Facsimile Multifunction Machine (Image Forming Apparatus)
100 paper (recording medium)

Claims (6)

In an image forming apparatus including a fixing device for fixing toner on a recording medium,
The heat roller used in the fixing device is
A base body having a columnar shape or a cylindrical shape and having electrical insulation;
An electric insulating layer, a heat generating layer formed on one surface of the electric insulating layer so as to have a pattern shape composed of a plurality of lines and generating heat upon application of a voltage, and the other surface of the electric insulating layer A sheet heating element including a heat transfer layer formed in a sheet shape;
A release layer having high releasability to the toner;
Including
The planar heating element is interposed between the outer peripheral surface of the base body and the release layer, and the base body, the heating layer, the electrical insulating layer, the heat transfer layer, and the separation layer. The mold layers are laminated in this order outward in the radial direction,
Electric power WA per unit time given to the sheet heating element when the recording medium is in contact with the heat roller, and unit given to the sheet heating element when the recording medium is not in contact with the heat roller An image forming apparatus, wherein power WB per hour is controlled to be different. In an image forming apparatus including a fixing device for fixing toner on a recording medium,
The heat roller used in the fixing device is
A base body having a columnar shape or a cylindrical shape and having electrical insulation;
A surface including an electrical insulation layer laminated on the outer periphery of the base body, and a heat generation layer formed on the electrical insulation layer so as to have a pattern shape composed of a plurality of lines and generating heat upon application of voltage. A heating element,
An elastic layer laminated on the planar heating element;
A release layer laminated on the elastic body and having high releasability with respect to the toner;
Including
Electric power WA per unit time given to the sheet heating element when the recording medium is in contact with the heat roller, and unit given to the sheet heating element when the recording medium is not in contact with the heat roller An image forming apparatus, wherein power WB per hour is controlled to be different. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the power WA is larger than the power WB. An image forming apparatus according to any one of claims 1 to 3,
A voltage VA applied to the sheet heating element when the recording medium is in contact with the heat roller, and a voltage VB applied to the sheet heating element when the recording medium is not in contact with the heat roller. An image forming apparatus that is controlled to be different. An image forming apparatus according to any one of claims 1 to 3,
A duty ratio DA for driving the sheet heating element when the recording medium is in contact with the heat roller, and a duty ratio for driving the sheet heating element when the recording medium is not in contact with the heat roller. An image forming apparatus that controls a DB so as to be different. An image forming apparatus according to any one of claims 1 to 5,
In the recording medium conveyance path, a recording medium detection sensor is provided upstream of the fixing device in the conveyance direction;
An image forming apparatus characterized in that a switching timing of electric power per unit time applied to the planar heating element is determined based on a timing at which the recording medium detection sensor detects a recording medium.

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