JP2005292604A - Image heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image heating device in which appropriate fixing temperatures can always be ensured, regardless of the size of an image carrier. <P>SOLUTION: The image heating device includes a rotor 100, having a heat generation layer; a pressure member for forming a nip between the rotor 100 and the pressure member itself; and an excitation means 150 which is accommodated in the rotor 100 and generates an AC magnetic field, in which the heat generation layer generates heat. The image heating device heats the image carrier conveyed, while being held between the rotor 100 and the pressure member. The excitation means 150 comprises a core 151 disposed in the longitudinal direction of the rotor 100, and excitation coil 152 wound around the core 151 in the longitudinal direction of the core 151. The excitation means 150 is constructed, such that the distance of the heat generation layer gradually varies from the longitudinal middle of the rotor 100 towards its both ends. In addition, the excitation means 150 is constructed so as to be rotatable about the longitudinal axis of the rotor 100. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image heating apparatus used in a heating and fixing unit of an image forming apparatus such as a copying machine. More specifically, a rotating body provided with a heat generating layer, a pressure member that forms a nip with the rotating body, Image heating that heats an image carrier that is housed in the rotating body and includes an exciting unit that generates an alternating magnetic field that generates heat from the heat generating layer and is nipped and conveyed between the rotating body and the pressure member. Relates to the device.

  In the image heating apparatus provided with a rotating body having a heat generating layer that generates heat by induction heating, since the heat radiation area is large at the longitudinal end of the rotating body, the temperature drop at the end is larger than the center, A uniform temperature distribution in the longitudinal direction cannot be obtained at the nip. Therefore, even if a sufficient fixing temperature is ensured in the central portion, sufficient heat energy cannot be supplied to the recording paper which is an example of the image carrier and the toner image on the recording paper at the end portion. There was a problem that an offset occurred.

Therefore, by changing the distance between the exciting coil wound in the longitudinal direction of the core arranged along the longitudinal direction of the rotating body and the heat generating layer, the distance between the exciting coil and the rotating body is changed from the central portion to the end portion. A technique for ensuring a uniform temperature distribution at the nip has been proposed by setting the distance closer to the nip.
Japanese Patent No. 3347537

  However, according to the above-described prior art, when narrow recording paper is continuously supplied, the recording paper absorbs heat at the center of the nip, but the recording paper does not pass through the end portion. As a whole, the balance between heat generation and heat dissipation is lost. In this case, if heating is performed so that a sufficient fixing temperature is secured at the center of the nip, the temperature at the end increases excessively, and a high temperature offset occurs at the end when the next wide recording sheet passes. In addition, there is a possibility that the core temperature of the exciting coil exceeds the Curie point.

  If the core temperature exceeds the Curie point, the magnetic flux density of the alternating magnetic field is greatly reduced until the Curie temperature is lowered, so that the heat generating layer cannot be heated and the apparatus cannot be operated during that time.

  On the other hand, when narrow recording paper is continuously fed, if the temperature at the end of the nip is controlled so as not to overheat, the temperature at the center will be lower than the predetermined fixing temperature. There was also a problem that defects occurred.

  In view of the above-described conventional drawbacks, the present invention is to provide an image heating apparatus that can always ensure an appropriate fixing temperature regardless of the size of the image carrier.

  In order to achieve the above-mentioned object, a first characteristic configuration of the image heating apparatus according to the present invention includes a rotating body including a heat generating layer, the rotating body, and the rotating body as described in claim 1 of the claims. A pressure member that forms a nip; and an excitation unit that is housed inside the rotating body and generates an alternating magnetic field that generates heat from the heat generating layer, and is nipped and conveyed between the rotating body and the pressure member. An image heating apparatus for heating an image carrier, wherein the excitation means includes a core disposed along a longitudinal direction of the rotating body and an excitation coil wound in the longitudinal direction of the core. And the distance from the heat generating layer is different from the longitudinal center of the rotating body toward both ends, and is configured to be rotatable around an axis along the longitudinal direction of the rotating body. There is in point.

  According to the above-described configuration, the separation distance between the excitation means and the heat generation layer is gradually different from the longitudinal center portion of the rotating body toward both ends, so that the heat generation layer extends from the center portion to both ends. If the separation distance is configured to be longer, the heat generation temperature at both ends can be set lower than the center, and the separation distance from the heat generation layer is decreased from the center to both ends. The heat generation temperature at both ends can be set higher than that at the center. By rotating such excitation means around the axial center along the longitudinal direction of the rotating body, it is possible to switch between an arrangement in which the distance from the heat generating layer becomes longer and a posture in which the distance from the heat generating layer becomes shorter from the center to both ends. Therefore, the nip temperature distribution can be adjusted according to the situation.

  The second characteristic configuration includes a drive mechanism that rotationally drives the excitation means around an axis along the longitudinal direction of the rotating body in addition to the first characteristic configuration described above. The drive mechanism is such that it is driven to rotate so that the excitation means is maintained in a predetermined posture based on the size of the image carrier.

  According to the above configuration, the attitude of the excitation means can be changed according to the size of the image carrier passing through the nip by the drive mechanism, so that the temperature distribution of the nip can always be maintained in an appropriate state and the core is overheated. Such a situation can be prevented in advance.

  As described above, according to the present invention, it is possible to provide an image heating apparatus that can always ensure an appropriate fixing temperature regardless of the size of the image carrier.

  Embodiments of an image processing apparatus according to the present invention will be described below. As shown in FIG. 1, a copying machine 1 as an image processing apparatus performs copying on an upper surface of a main body on which an exposure mechanism 2, a printing mechanism 3, and a recording paper transport mechanism 4 are arranged as image reading means for reading document image information. A contact glass 5 for placing a manuscript (copy original) and an operation display unit 6 are provided. An automatic document feeder 7 is arranged on the contact glass 5 and a paper feed cassette 8 is arranged on one side of the main body. Configured.

  The exposure mechanism 2 includes a first slider 2A including an exposure lamp 21 for exposing and scanning a document placed on the contact glass 5, and a first mirror 22 for reflecting reflected light from the document, and a first mirror. A second slider 2B having second and third mirrors 23 and 24 for guiding the light reflected by the lens 22 to the lens 25, and a CCD for converting the optical information obtained by the condenser lens 25 into an electrical signal. And the like, a control unit 27 to which image information obtained by the solid-state image sensor 26 is input, and a laser unit 28 that converts image data from the control unit 27 into an optical signal.

  The first slider 2A and the second slider 2B are reciprocally driven in the sub operation direction by a scan drive motor (not shown). The second slider 2B is configured to move a distance that is ½ of the moving distance of the first slider 2A at a speed that is 1/2 the scanning moving speed of the first slider 2B.

  The print mechanism 3 includes a photosensitive drum 31 that is driven to rotate in the direction of an arrow by a main drive motor (not shown). The photosensitive drum 31 has a photosensitive drum 31 around the photosensitive drum 31 in the order of the rotation direction. A charger 32 for charging the layer, a developing device 33 for visualizing the electrostatic latent image formed on the photosensitive layer as a toner visible image, and a transfer device for transferring the toner visible image formed on the photosensitive layer to recording paper Discharger 34, separation discharger 35 for separating the recording paper from the photosensitive drum 31, cleaning device 36 for removing toner remaining on the photosensitive drum 31 after transfer, and charge on the surface of the photosensitive drum 31 Each of the static eliminators 37 is disposed to irradiate the photosensitive layer uniformly charged by the charger 32 with the laser beam output from the laser unit 28, thereby forming an electrostatic latent image.

  The recording paper transport mechanism 4 feeds the recording paper in the paper feed cassette 8 and feeds the recording paper sent by the paper feed roller 41 to the photosensitive drum 31 at a predetermined timing. A transport belt 43 is provided for transporting the recording paper on which the toner image formed on the registration roller 42 and the photoconductive drum 31 is transferred and peeled off from the photoconductive drum 31 to the heat fixing unit 44. The transfer paper subjected to the fixing process by the heat fixing unit 44 is discharged onto a discharge tray via a discharge mechanism (not shown).

  As shown in FIG. 2, the heat fixing unit 44 is housed in the rotating body 100 including the heat generating layer 101, a pressure member 104 that forms a nip with the rotating body 100, and the rotating body 100. Excitation means 150 that generates an alternating magnetic field generated by the heat generation layer 101 is provided, and the recording paper on which a toner image is formed as an image carrier that is nipped and conveyed between the rotating body 100 and the pressure member 104 is heated. Is configured to do.

  The rotating body 100 is cylindrical and extends in a horizontal direction perpendicular to the paper transport direction. The rotating body 100 has a heat generating layer 101 on its inner surface, and an elastic layer 102 made of silicon rubber or the like on the inner surface. And a release layer 103.

  The heat generating layer 101 is made of iron, copper, aluminum, stainless steel or the like, and the elastic layer 102 is made of a material having good heat resistance and heat conductivity such as silicon rubber, fluorine rubber or fluorosilicon rubber, and the release layer 103. Is made of a material having good releasability such as fluororesin, silicone resin, fluororesin silicone rubber, fluororubber, silicone rubber, PFA, PTFE, FEP and the like.

  The pressing member 104 is a cylindrical roller that can rotate in the axial direction thereof, and extends in parallel to the rotating body 100. The outer peripheral surface of the pressing member 104 is in contact with the outer peripheral surface of the rotating body 100 with a predetermined pressure. It is in pressure contact and rotates in the direction of the arrow shown in FIG.

  As shown in FIGS. 2, 3, and 4, the exciting unit 150 is disposed along the longitudinal direction of the rotating body 100, is attached to a bobbin 153, and has a core 151 formed in an arc shape, and the core 151. The exciting coil 152 is wound in the longitudinal direction of the rotating body 100, and the separation distance from the heat generating layer 101 is gradually different from the longitudinal center of the rotating body 100 toward both ends. Furthermore, it is configured to be rotatable around a rotation axis 200 along the longitudinal direction of the rotating body 100. 2, 3, and 4 schematically illustrate the configuration of the exciting means 150, and do not limit the number of turns of the exciting coil, for example.

  More specifically, the exciting coil 152 is made of, for example, copper, and is configured such that an eddy current is induced in the heat generating layer 101 by a high-frequency magnetic field generated when a high-frequency current is applied, and is heated by the generated Joule heat. Is done. The closer the distance between the exciting means 150 and the heat generating layer 101 is, the larger the amount of heat generated in the heat generating layer 101 is. The farther the distance between the exciting means 150 and the heat generating layer 101 is, the more heat generated in the heat generating layer 101 is. Get smaller.

  As shown in FIG. 7, the rotation mechanism 500 transmits a motor 501 that rotates a gear, the power of the motor 501 to the excitation unit 150, and a first gear 502 and a second gear 503 that are combined at a predetermined ratio. The excitation unit 150 includes the rotation shaft 200 extending in the longitudinal direction. When the rotation shaft 200 rotates 180 degrees, the excitation unit 150 performs fixing processing on a wide sheet reaching almost the entire nip. The first position, which is the case position, and the second position, which is the position where the narrow sheet passing through a part of the nip is fixed, are switchably positioned.

  The rotation control unit 400 including a part of a control unit including a CPU for controlling the operation of the copying machine 1 is based on a predetermined program based on the sheet size information input from the operation display unit 6 and the rotation mechanism. 500 is driven to control the excitation means 150 to the first position or the second position.

  The rotation control unit 400 controls to switch the position of the excitation unit 150 between the first position and the second position based on the paper size information. Further, the position of the excitation unit 150 may be determined based on temperature information from the temperature information acquisition unit 450 in addition to the paper size information. That is, the temperature information acquisition unit 450 includes a plurality of temperature sensors that measure the temperature distribution in the longitudinal direction of the surface of the rotating body, and is configured to transfer the acquired temperature information to the rotation control unit 400.

  As shown in FIG. 3, in the first position, the excitation unit 150 is configured such that the distance between the excitation unit 150 and the heat generating layer 101 at the center in the longitudinal direction of the rotary body 100 is equal to that of the rotary body 100. The distance between the exciting means 150 and the heat generating layer 101 at both ends in the longitudinal direction is longer.

  FIG. 5 shows the heat distribution characteristics at the first position. The closer the distance between the exciting coil 152 and the heat generating layer 101 is, the larger the amount of heat generated in the heat generating layer 101 is. The longer the distance between the exciting coil 152 and the heat generating layer 101 is, the more heat generated in the heat generating layer 101 is. Get smaller. Accordingly, the amount of heat generated at the center of the rotating body 100 in the longitudinal direction is smaller than the amount of heat generated at both ends of the rotating body 100 in the longitudinal direction. In addition, since the heat dissipation area and the heat dissipation amount at both ends in the longitudinal direction of the rotating body 100 are larger than the central portion in the longitudinal direction of the rotating body 100, the temperature of the rotating body 100 is increased in the longitudinal direction. It is almost constant from the center to both ends. This eliminates the variation in fixing temperature between the center and both ends of the printing paper.

  In FIG. 4, the excitation means 150 in the second position is such that the distance between the excitation means 150 and the heat generating layer 101 in the longitudinal center of the rotating body 100 is in the longitudinal direction of the rotating body 100. It is configured to be closer than the distance between the exciting means 150 and the heat generating layer 101 at both ends.

  FIG. 6 shows the heat distribution characteristics at the second position. The amount of heat generated at the center of the rotating body 100 in the longitudinal direction is larger than the amount of heat generated at both ends of the rotating body 100 in the longitudinal direction. When small size paper passes through the nip, heat is dissipated for fixing at the portion where the small size paper in the center passes, and no heat is given to the paper because the paper does not pass at both ends. . This prevents abnormal high temperature heat treatment at both ends where the sheet does not pass while heating to a sufficient fixing temperature at the center, and preferably the temperature of the rotating body 100 is changed from the center in the longitudinal direction to both ends. It becomes almost constant over the part.

  If the selected paper size is a wide paper such as A3 portrait or A4 landscape, for example, the excitation mechanism 150 is set to the first position by the rotation mechanism 500 and printing is performed. If the selected paper size is a narrow paper such as A4 portrait or B5 landscape, for example, the excitation mechanism 150 is set to the second position by the rotation mechanism 500 and printing is performed.

  Another embodiment of the present invention will be described below. In the embodiment described above, the heat fixing unit 44 is configured to heat the recording paper on which the toner image is formed by the pressure roller. However, as shown in FIG. 8, an endless belt-shaped fixing film is used. You may comprise by the used film fixing system (film heating system). The fixing film 1000 is stretched between a driving roller 1100 on the left side, a driven roller 1200 on the right side, and a pressing member 104 fixedly disposed below the rollers 1100 and 1200. The driven roller is fixed. It also serves as a tension roller that applies tension in the direction of stretching the film outward.

  In the above-described embodiment, the shape of the excitation means 150 is such that the distance from the heat generating layer 101 from the longitudinal center of the rotating body 100 toward both ends is as shown in FIGS. However, the present invention is not limited to this, and the separation distance from the heat generating layer 101 varies stepwise from the longitudinal center of the rotating body 100 toward both ends. It may be configured. Moreover, how to make these separation distances different is determined suitably based on experimental data etc., and is not specifically limited.

Block diagram of the image forming apparatus Explanatory drawing of heat fixing unit Explanatory drawing of shape of excitation means Explanatory drawing of shape of excitation means Explanatory drawing showing heat distribution at the first position Explanatory drawing showing heat distribution at the second position Block diagram showing the main parts around the rotating mechanism Explanatory drawing of the heat fixing part in another embodiment

Explanation of symbols

1: Copier 6: Operation display unit 44: Heat fixing unit 100: Rotating body 101: Heat generation layer 102: Elastic layer 103: Release layer 104: Pressure member 150: Excitation means 151: Core 152: Excitation coil 200: Rotation Shaft 400: Rotation control means 500: Rotation mechanism

Claims (2)

A rotating body including a heat generating layer; a pressure member that forms a nip with the rotating body; and an excitation unit that is housed in the rotating body and generates an alternating magnetic field that generates heat from the heat generating layer. An image heating apparatus for heating an image carrier that is nipped and conveyed between a body and the pressure member,
The excitation means is composed of a core disposed along the longitudinal direction of the rotating body and an excitation coil wound in the longitudinal direction of the core, and both end portions from the longitudinal center of the rotating body. The image heating apparatus is configured so that the distance from the heat generating layer is different toward the heat generating layer and is rotatable about an axis along the longitudinal direction of the rotating body. A drive mechanism for rotating the excitation means around an axis along the longitudinal direction of the rotating body, the drive mechanism being configured so that the excitation means is maintained in a predetermined posture based on the size of the image carrier; 2. The image heating apparatus according to claim 1, wherein the image heating apparatus is rotationally driven.

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