Patent Publication Number: US-8977180-B2

Title: Fixing device, and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2012-254143 filed Nov. 20, 2012. 
     BACKGROUND 
     (i) Technical Field 
     The present invention relates to a fixing device, and an image forming apparatus. 
     (ii) Related Art 
     A fixing device is known in which a laser light irradiates a recording medium on which a toner image is formed and the toner is fixed on the recording medium. 
     SUMMARY 
     According to an aspect of the invention, there is provided a fixing device including: a curved member that supports a recording medium on which an image is formed by an image forming material that absorbs light and is fixed; and an irradiating portion that irradiates the curved member with light from the recording medium side, wherein the light axis of the light does not intersect with a center axis of the curved member, and is substantially perpendicular to a tangential line in a middle point in a transporting direction of the recording medium in a region of the curved member supporting the recording medium. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a schematic view showing a hardware configuration of an image forming apparatus; 
         FIG. 2  is a schematic view of an image forming processing unit when viewed from one side in a width direction; 
         FIG. 3  is a schematic view when a fixing device according to an exemplary embodiment is taken along a W-W line; 
         FIG. 4  is an enlarged view of an I portion in the fixing device according to the exemplary embodiment; 
         FIG. 5  is a view when a fixing device according to Comparative Example is viewed from one side in a width direction; 
         FIG. 6  is a view showing a distance between a light axis and a rotational axis; 
         FIG. 7  is a schematic view when a fixing device according to a first modification is viewed from one side in a width direction; and 
         FIG. 8  is a schematic view when a fixing device according to a second modification is viewed from one side in a width direction. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic view showing a hardware configuration of an image forming apparatus  100  according to an exemplary embodiment of the invention. The image forming apparatus  100  includes a controller  1 , a memory  2 , a communication portion  3 , a receiving portion  4 , an imaging reading portion  5 , an image processing portion  6 , a storing portion  7 , a transport roll  8 , an image forming portion  9 , and a fixing device  10  in the inner portion of a housing. The controller  1  controls an operation of each portion of the image forming apparatus  100 . The controller  1  includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The memory  2  includes a device that stores data and programs used by the controller  1 , for example, an HDD (Hard Disk Drive). The communication portion  3  is connected to an external device such as a personal computer or a facsimile machine, and sends and receives image data. The receiving portion  4  receives an input of an instruction from a user. The receiving portion  4  includes an operational unit by which the user inputs the instruction to the image forming apparatus  100 . The instruction received through the receiving portion  4  is sent to the controller  1 , and the controller  1  controls the operation of the image forming apparatus  100  in accordance with the instruction. The image reading portion  5  optically reads a document and generates image signals. Specifically, the image reading portion  5  includes a platen glass, a light source, an optical system, and an image device (all not shown). The light source irradiates the light with respect to the document placed on the platen glass, the light reflected by the document is split into red, green, and blue via the optical system, and the split light is incident to the image device. The imaging device converts the incident light into image signals, and the image signals are supplied to the image processing portion  6 . The image processing portion  6  performs an A/D conversion on the image signals that is supplied from the image reading portion  5 , a noise reduction, a gamma correction, a conversion of a color space (from R, G, and B to Y (Yellow), M (Magenta), C (Cyan), and K (Black)), a screen processing, and the like. In this way, the image data representing gradations of every color and every pixel are generated. 
     The storing portion  7  stores sheet-like paper P. The paper P is a continuous paper (referred to as “continuous form” or “continuous form paper”) that is not cut into single pages, and is stored in a state of being wound around a shaft  71 . In addition, when the paper P is divided at perforations for each page, the storing portion  7  may be configured so that the paper is stored in a state of being folded in a zigzag manner along the perforated surfaces. The transport roll  8  (an example of a transport member) transports the paper P along a transport path r. In addition to the shown one, plural transport rolls  8  are provided on the transport path r. The image forming portion  9  (an example of the transfer portion) includes image forming processing units  90 Y,  90 M,  90 C, and  90 K. The image forming processing units  90 Y,  90 M,  90 C, and  90 K repeatedly transfer the toner image of each of yellow, magenta, cyan, and black to the surface of the paper P according to an electrographic method based on the image data supplied from the image processing portion  6 . Hereinafter, the surface of the paper P to which the toner image is transferred is referred to as a “front surface” and the surface to which the toner image is not transferred is referred to as a “rear surface”. Since the configuration of each of the image forming processing units is common, hereinafter, when it is not necessary to distinguish each of the image forming processing units, the image forming processing units are collectively referred to as the image forming processing unit  90 . In addition, also with respect to the component of the image forming processing unit  90 , the notation such as Y, M, C, and K is omitted. The fixing device  10  fixes the toner image transferred by the image forming portion  9  to the paper P. The paper P on which the toner image is fixed is discharged to the outside of the image forming apparatus  100 . For example, the discharged paper P is cut for each page by a cutting device (not shown). Hereinafter, the direction (direction of an arrow A) in which the paper P is transported is simply referred to as a “transporting direction” (an example of a first direction), and a direction (direction perpendicular to a paper surface of  FIG. 1 ) perpendicular to the transporting direction is referred to as a “width direction” 
       FIG. 2  is a schematic view of the image forming processing unit  90  when viewed from one side in the width direction. The image forming processing unit  90  includes a photoconductor drum  91 , a charging device  92 , an exposure device  93 , a developing device  94 , a transfer device  95 , and a cleaner  96 . The photoconductor drum  91  is a cylindrical member in which a photoconductor film is laminated around the outer circumferential surface thereof, and is supported so as to rotate in a direction of an arrow B with the center of the cylinder as an axis. For example, the charging device  92  may be a scorotron charger and charge the photoconductive film of the photoconductor drum  91  to a potential which is predetermined. The exposure device  93  exposes the photoconductor drum  91  charged by the charging device  92  and forms an electrostatic latent image. Specifically, laser light corresponding to the gradation of each pixel representing the image data, which are supplied from the image processing portion  6 , is generated, and the laser light scans the photoconductive film of the photoconductor drum  91  in the width direction. The photoconductor drum  91  rotates in the direction of the arrow B, and writing of the electrostatic latent image at a scan line unit in the width direction is repeated in the transporting direction. 
     The developing device  94  develops the electrostatic latent image formed on the photoconductor drum  91 . The developing device  94  includes a development roller  941  that is provided so as to be opposite to the outer circumferential surface of the photoconductor drum  91 . A two-component developer including the toner and a carrier is accommodated in the inner portion of the developing device  94 . The toner is one in which powder made of resin is colored with any one color material of yellow, magenta, cyan, and black. The carrier is a powder that is manufactured by a magnetic material. The two-component developer is attached to the outer circumferential surface of the development roller  941 , which is driven to rotate, through a magnetic force. A developing bias having a reverse polarity to the electrostatic latent image is applied to the development roller  941 . If the toner is charged so as to have a reverse polarity to the electrostatic latent image by the developing bias, the toner moves on the electrostatic latent image and the toner image is formed. The transfer device  95  is a cylindrical member that is opposite to the photoconductor drum  91  while interposing the transport path r. A transfer bias having a reverse polarity to the toner image is applied to the transfer device  95 . If the paper P is charged so as to have a reverse polarity to the toner image by the transfer bias, the toner image is transferred to the paper P. If the paper P passes through the image forming processing units  90 K,  90 C,  90 M, and  90 Y, the toner image is repeatedly transferred. The cleaner  96  removes the toner remaining on the surface of the photoconductor drum  91  after the toner image is transferred. 
       FIG. 3  is a schematic view when the fixing device  10  according to an exemplary embodiment of the invention is taken along a W-W line of  FIG. 1 .  FIG. 4  is an enlarged view of an I portion shown by a two-dotted chain line of  FIG. 1  in the fixing device  10 . The fixing device  10  includes an irradiating portion  101 , an optical member  102 , a reflection member  103 , a partition member  104 , and a rotating body (support roller)  105 . 
     The irradiating portion  101  (an example of a first irradiating portion) irradiates the laser light LB on the paper P that is transferred through the transport roll  8 . The irradiating portion  101  includes plural light sources  1011  that generate the laser light LB. A light axis a 1  is the light axis of the laser light LB. The light sources  1011  are lined up at intervals g along the width direction. The interval g is determined so that the laser light LB irradiates the entire region on which the toner image of the paper P is formed. In the example shown in  FIG. 3 , the irradiating portion  101  includes four light sources  1011 . A wavelength of the laser light LB may be any wavelength if applying sufficient energy to melt the toner to the toner. For example, infrared ray is used for the laser light LB. In this case, toner to which a material absorbing the infrared rays is mixed is used in the developing device  94 . 
     The optical member  102  is a member that controls a direction in which the laser light LB irradiated from the light source  1011  propagates, and for example is a lens. The optical member  102  is provided to the light source  1011  in a one-to-one correspondence. In the example of  FIG. 3 , four optical members  102  are provided so as to correspond to each of four light sources  1011 . The laser light LB irradiated from the light sources  1011  propagates toward the optical member  102 . As shown in  FIG. 4 , in the optical member  102 , the cross-section when is viewed from the width direction is formed in an approximately convex shape, and the optical member  102  converges the laser light LB in the transporting direction. The optical member  102  converges the laser light LB so that an irradiation width in the transporting direction is within a determined range (for example, 1.0±0.1 mm). Moreover, as shown in  FIG. 3 , in the optical member  102 , the cross-section when viewed from the transporting direction is an approximately rectangular shape, and transmits the laser light LB without refracting the laser light LB in the width direction. If the laser light LB transmits the optical member  102 , the laser light propagates toward the reflection member  103 . 
     In the reflection member  103 , as shown in  FIG. 3 , the cross-section when viewed from the transporting direction is formed in an approximately rectangular shape, and as shown in  FIG. 4 , the cross-section when viewed from the width direction is formed in an approximately arch shape. The reflection member  103  includes holes  1031 , an opening  1032 , and a reflection surface  1033 . The laser light LB that is irradiated from the light sources  1011  passes through holes  1031 . The opening  1032  is opposite to the transport path r, and the laser light LB propagating the inner portion of the reflection member  103  passes through the opening  1032 . The laser light LB passing through the opening  1032  is irradiated to an irradiation region D 1  that extends in the width direction on the transport path r. If the laser light LB is irradiated to the paper P, the laser light LB is reflected at a region of the front surface of the paper P on which toner particles are not attached. Since not only a mirror reflection but also a diffusion reflection are generated on the surface of the paper P, reflection in all directions may be generated. Moreover, the reflected light that is reflected by the paper P passes through the opening  1032 . The reflection surface  1033  is a surface that is opposite to the transport path r in the inside of the reflection member  103 . The reflection surface  1033  reflects the reflected light passing through the opening  1032  to the paper P. A processing for reflecting the laser light LB is performed on the reflection surface  1033 . For example, the reflection member  103  is made of a metal such as aluminum, the reflection surface  1033  may be polished to a mirror surface, and plating such as silver may be performed on the reflection surface  1033 . The reflected light is reflected at the reflection surface  1033 , and thus, a portion of the reflected light is absorbed by the toner particles and the remainder is reflected at the surface of the paper P again. In this way, if the reflection of the laser light LB is repeated at the surface of the paper P and the reflection surface  1033  of the reflection member  103 , a portion of the laser light LB reflected at the reflection surface  1033  is absorbed by the toner and promotes the heating and melting of the toner. 
     A portion of the toner heated by the laser light LB is sublimated and becomes a gas, and the gas is cooled and dust may be generated. The partition member  104  partitions between the irradiation portion  101  and the transport path r so that dust does not enter a space that is surrounded by the reflection member  103 . The partition member  104  is an approximately rectangular plate-shaped member that includes a short side and a long side, and is formed of a material through which light transmits, for example, quartz glass. The partition member  104  is supported by the reflection member  103  so that the short side is along the transporting direction and the long side is along the width direction in the opening  1032 . 
     The support roller  105  that is an example of a curved member rotates about a rotational axis a 2  (an example of a center axis) in the transporting direction according to the transport of the paper P by the transport roll  8 , and supports the paper P. The support roller  105  is provided so that the side surface faces the opening  1032 . Therefore, the laser light LB of the irradiating portion  101  is irradiated from the paper P side toward the support roller  105 . In  FIG. 4 , the light axis a 1  intersects with the support roller  105 . In addition, in the example shown in  FIG. 4 , an angle θ, in which the light axis a 1  forms a tangential line in a point q that is a center of the region of the side surface of the support roller  105  supporting the paper P, is 90°. 
     When the laser light LB is irradiated and fixes the toner image on the paper P, it is considered that the laser light is focused to some extent by the optical system and irradiated. In this case, since the paper P moves up and down and thus, variation in the intensity of the irradiated laser occurs, it is necessary to suppress flapping of the paper P. Here, the paper P is transported along the surface of the curved member, and it may be expected that the flapping is suppressed. However, if laser light is irradiated to the top of the curved member, the primary reflected light is returned to the light source, and thus, the light source may be damaged. In the exemplary embodiment, when the laser light is irradiated to the paper P that is transported using the curved member as described above, the primary reflected light is suppressed to be returned to the light source. Moreover, “suppressing the primary reflected light returning to the light source” does not mean that the primary reflected light is not at all returned to the light source. When the curved member or the paper P does not perform a mirror reflection, it is sufficiently expected that scattered light is returned to the light source. In the exemplary embodiment of the invention, when it is assumed that the laser light LB performs a mirror reflection on the surface of the curved member, the light source may be physically provided so as to avoid the irradiation region of the primary reflected light. 
       FIG. 5  is a view when a fixing device  11  according to Comparative Example is viewed from one side of the width direction. In Comparative Example, a light source  1011  and a support roller  105  are disposed so that the light axis a 1  intersects with the rotational axis a 2 . “The light axis a 1  and the rotational axis a 2  intersecting with each other” means that a distance between the light axis a 1  and the rotational axis a 2  becomes less than or equal to a determined value. For example, the determined value is a value that is determined according to a diameter  2 R of the support roller  105 . An arrow b indicates a propagation direction of the laser light LB that is mirror-reflected in the irradiation region D 1 . When the light axis a 1  and the rotational axis a 2  intersect with each other, the laser light LB that is mirror-reflected at the surface of the paper P passes through the hole  1031  and reaches the light source  1011 . In this case, the light source  1011  may be broken down. 
     Refer to  FIG. 4  again, in the fixing device  10  according to the exemplary embodiment of the invention, the light source  1011  and the support roller  105  are disposed so that the light axis a 1  does not intersect with the rotational axis a 2 . “The light axis a 1  being not intersecting with the rotational axis a 2 ” means that the distance between the light axis a 1  and the rotational axis a 2  is more than the determined value. When the light axis a 1  and the rotational axis a 2  do not intersect with each other, the laser light LB that is mirror-reflected at the irradiation region D 1  reaches the reflection surface  1033  without passing through the hole  1031 . Therefore, compared to the case where the light axis a 1  intersects with the rotational axis a 2 , the possibility that the light source  1011  may be broken down by the laser light LB reflected at the irradiation region D 1  is suppressed. 
       FIG. 6  is a view showing the distance d between the light axis a 1  and the rotational axis a 2  in the fixing device  10 . In the fixing device  10 , for example, the light source  1011  and the support roller  105  are disposed so that the distance d between the light axis a 1  and the rotational axis a 2  is less than or equal to ¼ (R/2) of a diameter (here, the diameter  2 R of the support roller  105 ) that perpendicularly crosses the light axis a 1  of the support roller  105 . 
     Modification 
     The present invention is not limited to the above-described exemplary embodiment, and various modifications may be performed. Hereinafter, some modifications will be described. Among the modifications described below, two or more may be combined and be used. In addition, a first modification and a second modification are not included in the present invention. 
     (1) First Modification 
     The angle θ, in which the light axis a 1  forms a tangential line in the point q of the side surface of the support roller  105 , is not limited to the case of 90°. The angle θ may be less than 90°. 
       FIG. 7  is a schematic view when a fixing device  12  according to the first modification is viewed from one side in a width direction. In the fixing device  12 , the light source  1011  is disposed so that the angle θ is less than 90°. Moreover, similar to the fixing device  10  in the exemplary embodiment, the light source  1011  and the support roller  105  are disposed so that the light axis a 1  does not intersect with the rotational axis a 2 . Moreover, in the example of  FIG. 7 , the point q is included in the irradiation region D 1 . 
     (2) Second Modification 
     The light source  1011  is not limited to a single light source in the transporting direction. Plural light sources  1011  may be lined up in the transporting direction. In this case, the light source  1011  and the support roller  105  are disposed so that the light axis a 1  of each of the light sources  1011  lined up in the transporting direction does not intersect with the rotational axis a 2 . 
       FIG. 8  is a schematic view when a fixing device  13  according to the second modification is viewed from one side in a width direction. In the second modification, the fixing device  13  includes an irradiating portion  101   a  and an irradiating portion  101   b  (an example of a second irradiating portion). The irradiating portion  101   a  and the irradiating portion  101   b  irradiate the laser light LB from the paper P side toward the support roller  105 . The irradiating portion  101   a  includes plural light sources  1011   a , and the irradiating portion  101   b  includes plural light sources  1011   b . The light sources  1011   a  are light sources of the upstream side in the transporting direction, and the light sources  1011   b  are light sources of the downstream side in transporting direction. The light sources  1011   a  and the light sources  1001   b  are lined up at intervals g along the width direction. The light sources  1011   a  and the light sources  1011   b  are disposed so that a light axis a 11  of each light source  1011   a  and a light axis a 12  of each light source  1011   b  do not intersect with the rotational axis a 2 . Moreover, the light sources  1011   a  and the light sources  1011   b  are disposed so that the light axis a 11  and the light axis a 12  cross to each other at the irradiation region D 1 . In the second modification, for example, the distance between the light axis a 11  and the light axis a 12  and the rotational axis a 2  is less than or equal to ¼ (R/2) of the diameter  2 R of the support roller  105 . 
     In addition, the light sources  1011   a  (or light sources  1011   b ) are disposed at a position in which the laser light LB that is mirror-reflected at the irradiation region D 1  does not reach the light sources  1011   b  (or light source  1011   a ). Specifically, the light sources  1011   a  and the light sources  1011   b  are disposed so that an angle φ 1  in which the light axis all of each light source  1011   a  is incident with respect to a surface S including the irradiation region D 1  and an angle φ 2  in which the light axis a 12  of each light source  1011   b  is incident with respect to the surface S are different from each other. 
     (3) Third Modification 
     In the above-described exemplary embodiment, the example in which the support roller  105  which is an example of the rotating body supports the paper P is described. Here, if the rotating body contacts the paper P, the rotating body may not support the paper P. For example, the rotating body may contact the rear surface of the paper P that is transported in the height direction. As another example, the rotating body may contact the rear surface of the paper P from the upper side in the height direction with respect to the transport path r. In this case, the irradiating portion  101  irradiates the laser light LB to the front surface of the paper P from the lower side in the height direction with respect to the transport path r. 
     (4) Fourth Modification 
     The structures of the fixing device are not limited to those described in the exemplary embodiment. For example, the optical member  102  may diffuse the laser light LB in the width direction. In this case, a lens, in which the cross-section when viewed from the transporting direction is an approximately concave shape, is used for the optical member  102 . As another example, a lens that diffuses the laser light LB in the width direction and a lens that converges the laser light LB in the transporting direction may be provided with respect to a single light source  1011 . As still another example, a single optical member  102  that extends along the width direction may be provided so as to correspond to plural light sources  1011  that are lined up along the width direction. 
     (5) Fifth Modification 
     In the above-described exemplary embodiment, the rotating body (support roller  105 ) is exemplified as an example of the curved member. However, it is needless to say that the curved member is not limited to this. For example, an aspect, in which a recording medium is slidably transported on a fixed member having an approximately curved shape, is also included in the invention. Moreover, the center axis of the curved member indicates an axis that physically reflects the primary reflected light of the light irradiated on the surface of the curved member to the light source when the light axis of the laser light LB irradiated from the light source intersects with the center axis. For example, when the cross-section of the curved member is a column having complete roundness, the axis of the column corresponds to the center axis. 
     (6) Other Modifications 
     In the exemplary embodiment, the example where the paper P is the continuous paper is shown. However, the paper P may be one that is cut for each page according to the determined size. In the exemplary embodiment, an example of the image forming material is a toner. However, ink may be the image forming material. In this case, the ink is irradiated by light and dried, and thus, the image is fixed to the paper P. 
     The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.