Patent Publication Number: US-8971783-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. 2012-191237 filed Aug. 31, 2012. 
     BACKGROUND 
     (i) Technical Field 
     The present invention relates to a fixing device, and an image forming apparatus. 
     (ii) Related Art 
     Fixing devices are known that irradiate a recording medium on which a toner image is formed, to fix toner to a recording medium with laser light. 
     SUMMARY 
     According to an aspect of the invention, there is provided a fixing device including: an irradiation section that irradiates a recording medium with light, the recording medium having thereon an image formed by an image forming material to be fixed by absorbing light and being transported along a transporting path; and a preventing member that is provided with a first hole that allows the light to pass therethrough, and prevents the image forming material irradiated with the light from adhering to the irradiation section. 
    
    
     
       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 the hardware configuration of an image forming apparatus; 
         FIG. 2  is a schematic view when an image forming engine is viewed from one side in a width direction; 
         FIG. 3  is a cross-sectional schematic view when a fixing device related to an exemplary embodiment is viewed from the upstream side in a transporting direction; 
         FIG. 4  is a cross-sectional schematic view when the fixing device related to the exemplary embodiment is viewed from one side in the width direction; 
         FIG. 5  is a cross-sectional schematic view when the fixing device related to Modification Example 1 is viewed from one side in the width direction; and 
         FIG. 6  is a cross-sectional schematic view when the fixing device related to Modification Example 2 is viewed from one side in the width direction. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic view showing the hardware configuration of an image forming apparatus  100  related to one exemplary embodiment of the invention. The image forming apparatus  100  has a controller  1 , a memory  2 , a communication section  3 , a receiver  4 , an image reader  5 , an image processor  6 , a accommodation section  7 , a transporting roller  8 , an image forming section  9 , and a fixing device  10  inside a housing. The controller  1  controls the operation of the respective sections of the image forming apparatus  100 . The controller  1  has a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The memory  2  has a device that stores data and programs to be used by the controller  1 , for example, a HDD (Hard Disk Drive). The communication section  3  is connected with external devices, such as a personal computer or a facsimile, to perform transmission and reception of image data. The receiver  4  receives the input of instructions from a user. The receiver  4  has an operator that allows a user to input instructions to the image forming apparatus  100 . An instruction received by the receiver  4  is sent to the controller  1 , and the controller  1  controls the operation of the image forming apparatus  100  according to the instruction. The image reader  5  optically reads an original document to generate image signals. Specifically, the image reader  5  is equipped with platen glass, a light source, an optical system, and an imaging element. A light source irradiates an original document placed on the platen glass with light, and the reflected light reflected from the original document is decomposed into an R (Red) color, a G (Green) color, and a B (Blue) color via an optical system, and enters the imaging element. The imaging element converts the light that has entered, into image signals, and supplies the image signals to the image processor  6 . The image processor  6  performs A/D conversion of the image signals supplied from the image reader  5 , and performs denoising, gamma correction, conversion of a color space (from R, G, and B to Y (Yellow), M (Magenta), C (Cyan), and K (Black)), screen processing, or the like. In this way, image data showing the gradation of every color and every pixel are generated. 
     The accommodation section  7  accommodates sheet-like paper P (an example of a recording medium). The paper P is a continuous form (also referred to as a continuous business form or continuous paper) that is not cut into a sheet equivalent to one page, and is accommodated in such a form that the paper is wound around a shaft  71 . In addition, in a case where the paper P is delimited page-by-page with perforations, the accommodation section  7  may be configured so as to accommodate the paper in a state where the paper is folded in a zigzag pattern along the perforation face. The transporting roller  8  transports the paper P along a transporting path r. Plural transporting rollers  8  are provided on the transporting path r in addition to the illustrated rollers. The image forming section  9  (an example of a transfer section) has image forming engines  90 Y,  90 M,  90 C, and  90 K. The image forming engines  90 Y,  90 M,  90 C, and  90 K overlappingly transfer toner images in Y color, M color, C color, and K color to the surface of the paper P by an electrophotographic method on the basis of the image data supplied from the image processor  6 , respectively. Since the configurations of the respective image forming engines are common, the respective image forming engines are collectively referred to as image forming engines  90  if these engines do not need to be distinguished from each other in the following. Additionally, notations of Y, M, C, and K are omitted also regarding the constituent elements of the image forming engines  90 . The fixing device  10  fixes the toner images transferred by the image forming section  9  on the paper P. The paper P on which the toner images are fixed is discharged to the outside of the image forming apparatus  100 . The discharged paper P is cut page-by-page, for example, by a cutting device (not shown). In the following, a direction (a direction of arrow A) in which the paper P is transported is simply referred to a “transporting direction”, and a direction (a direction perpendicular to the paper plane of  FIG. 1 ) orthogonal to the transporting direction is referred to as a “width direction”. 
       FIG. 2  is a schematic view when an image forming engine  90  is viewed from one side in the width direction. The x-axis represents the width direction, the y-axis represents the transporting direction, and the z-axis represents a height direction. The image forming engine  90  has 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 , which is a cylindrical member that has a photoconductive layer laminated on the outer peripheral surface thereof, is supported so as to rotate in a direction of arrow B around the center of the cylinder. The charging device  92 , which is, for example, a scorotron charger, charges the photoconductive layer of the photoconductor drum  91  with predetermined potential. The exposure device  93  exposes the photoconductor drum  91  charged by the charging device  92  to form an electrostatic latent image. Specifically, laser light corresponding to the gradation of each pixel expressed by the image data supplied from the image processor  6  is generated, and the photoconductive layer of the photoconductor drum  91  is scanned in the width direction with the laser light. As the photoconductor drum  91  rotates in the direction of arrow B, the writing of the electrostatic latent image in units of scanning lines 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  has a developing roller  941  that has an outer peripheral surface provided so as to face the photoconductor drum  91 . Two-component developer including toner and carrier is contained within the developing device  94 . The toner is obtained by coloring powder made of resin with a color material in any of Y color, M color, C color, and K color. The carrier is powder produced from magnetic substance. The two-component developer adheres to the outer peripheral surface of the rotationally driven developing roller  941  by a magnetic force. Developing bias having a polarity reverse to the electrostatic latent image is applied to the developing roller  941 . If the toner is charged with a polarity reverse to the electrostatic latent image by the developing bias, the toner moves onto the electrostatic latent image to form a toner image. The transfer device  95  is a cylindrical member that faces the photoconductor drum  91  across the transporting path r. Transfer bias having a polarity reverse to the toner image is applied to the transfer device  95 . If the paper P is charged with a polarity reverse to the toner image, the toner image is transferred to the paper P by the transfer bias. If the paper P passes through the image forming engines  90 K,  90 C,  90 M, and  90 Y, toner images are overlappingly transferred. The cleaner  96  removes the toner that remains on the surface of the photoconductor drum  91  after the toner image is transferred. 
       FIG. 3  is a cross-sectional schematic view when the fixing device  10  related to one exemplary embodiment of the invention is viewed from the upstream side in the transporting direction.  FIG. 4  is a cross-sectional schematic view when the fixing device  10  is viewed from one side in the width direction. The fixing device  10  has an irradiation section  101 , optical members  102 , a reflective member  103 , a preventing member  104 , a supporting roller  105 , and a blower  106 . 
     The irradiation section  101  irradiates the paper P transported by the transporting roller  8  with laser light LB. A region, which is irradiated with the laser light LB, on the transporting path r is referred to as irradiation region D 1 . The irradiation section  101  has plural light sources  1011  that generate the laser light LB. An optical axis a 1  is the optical axis of the laser light LB. The optical axis a 1 , as shown in  FIG. 4 , inclines to the downstream side with respect to the transporting path r. Inclining to the downstream side with respect to the transporting path r means that the irradiation section  101  is further toward the downstream side of the transporting path r than the irradiation region D 1  as viewed from the height direction. The light sources  1011 , as shown in  FIG. 3 , are located at intervals g along the width direction. The intervals g are determined so that the overall region where the toner image of the paper P may be formed is irradiated with the laser light LB. In the example shown in  FIG. 3 , the irradiation section  101  has four light sources  1011 . The wavelength of the laser light LB may be arbitrary wavelengths as long as the energy that is enough to melt the toner is imparted to the toner. As the laser light LB, for example, infrared rays are used. In this case, in the developing device  94 , toner in which a material that absorbs infrared rays is mixed is used. 
     The optical member  102  is a member that controls a direction in which laser light LB irradiated from a light source propagates, for example, a lens. One optical member  102  is provided for one light source  1011 . In the example shown in  FIG. 3 , four optical members  102  are provided to correspond to four light sources  1011 , respectively. The laser light LB radiated from the light source  1011  propagates toward the optical member  102 . The optical member  102 , as shown in  FIG. 4 , forms a convex shape in a cross-section viewed from the width direction, and converges the laser light LB in the transporting direction. The optical member  102  converges the laser light LB so that the irradiation width in the transporting direction falls within a predetermined range (for example, 1.0±0.1 mm). Additionally, the optical member  102 , as shown in  FIG. 3 , is rectangular in a cross-section viewed from the transporting direction, and transmits the laser light LB without refracting the laser light LB in the width direction. If the laser light LB is transmitted through the optical member  102 , the laser light propagates toward the reflective member  103 . 
     The reflective member  103 , as shown in  FIG. 3 , forms a rectangular shape in a cross-section viewed from the transporting direction, and as shown in  FIG. 4 , forms an arch shape in a cross-section viewed from the width direction. The reflective member  103  has a hole  1031 , an opening portion  1032 , and a reflecting surface  1033 . A hole  1031  (an example of a second hole) allows the laser light LB irradiated from the light sources  1011  to pass therethrough. The opening portion  1032  faces the transporting path r, and allows the laser light LB, which has propagated through the reflective member  103 , to pass therethrough. The laser light LB that has passed through the opening portion  1032  is irradiated to the irradiation region D 1  on the transporting path r. If toner T transferred to the surface of the paper P passes through the irradiation region D 1  as shown in  FIG. 4 , the toner melts, and is fixed on the paper P. If the paper P is irradiated with the laser light LB, the laser light LB is reflected in the region of the surface of the paper P to which toner particles do not adhere. Since specular reflection and diffuse reflection occur on the surface of the paper P, reflection in all directions may occur. Additionally, the opening portion  1032  allows the reflected light reflected by the paper P to pass therethrough. The reflecting surface  1033  is the inner surface of the reflective member  103  that faces the transporting path r. The reflecting surface  1033  reflects the reflected light, which has passed through the opening portion  1032 , to the paper P. The reflecting surface  1033  is subjected to processing for reflecting the laser light LB. For example, the reflective member  103  may be made of metals, such as aluminum, the reflecting surface  1033  may be ground into a mirror surface, and the reflecting surface  1033  may be plated with silver or the like. By reflecting the reflected light on the reflecting surface  1033 , a portion of the reflected light is absorbed by the toner particles and the remainder is again reflected on the surface of the paper P. Thus, if the reflection of the laser light LB is repeated on the surface of the paper P and on the reflecting surface  1033  of the reflective member  103 , a portion of the laser light LB reflected on the reflecting surface  1033  is absorbed by the toner, and heating and melting of the toner are promoted. 
     A portion of the toner irradiated with and heated by the laser light LB may sublimate into gas, and this gas may be cooled to generate powder dust. The preventing member  104  prevents powder dust from adhering to the irradiation section  101 . Specifically, the preventing member  104  partitions off the irradiation section  101  and the transporting path r so that the powder dust does not enter the inside of the reflective member  103 . The preventing member  104 , which is a rectangular and plate-shaped member having short sides and long sides, is formed by materials that transmit light, for example, quartz glass. The preventing member  104  is supported by the reflective member  103  so that, in the opening portion  1032 , the short sides run along the transporting direction and the long sides run along the width direction. The preventing member  104  has a hole  1041  (an example of a first hole). The hole  1041  allows the laser light LB to pass therethrough. Here, the “allowing the laser light LB to pass therethrough” means that the laser light LB passes through the hole  1041  without intersecting the preventing member  104 . The hole  1041  is provided from one side toward the other side in the width direction. If the hole  1041  is provided in the preventing member  104 , the powder dust adhering to the reflective member  104  is prevented from being irradiated with the laser light LB and the preventing member  104  is prevented from being heated. 
     The supporting roller  105  rotates in the transporting direction around a rotation axis a 2  with the transport of the paper P by the transporting roller  8 , and supports the paper P. The supporting roller  105  is provided so that the lateral face thereof may face the opening portion  1032 . The laser light LB is irradiated to the lateral face of the supporting roller  105  from the paper P side. 
     The blower  106  (an example of a blowing unit) sends the wind for preventing powder dust from passing through the hole  1041 . The blower  106  is provided outside the reflective member  103 , and sends wind into a space, which is surrounded by the reflective member  103  and the preventing member  104 , via the hole  1031 . If wind is sent into the space surrounded by the reflective member  103  and the preventing member  104 , the pressure within the space becomes higher than the pressure outside the space. Therefore, the wind that is directed to the outside of the space from the inside of the space surrounded by the reflective member  103  and the preventing member  104  is sent via the hole  1041 . 
     As described above, the optical axis a 1  of the laser light LB inclines to the downstream side with respect to the transporting path r. If the optical axis a 1  of the laser light LB inclines to the downstream side with respect to the transporting path r, the position of the irradiation region D 1  is located further toward the upstream side than the hole  1041 . Therefore, the toner T in a region where the wind passed through the hole  1041  touches the surface of the paper P is fixed on the paper P. Accordingly, compared with a case where the optical axis a 1  of the laser light LB inclines to the upstream side with respect to the transporting path r, a toner image is kept from being disturbed by the wind passed through the hole  1041 . 
     MODIFICATION EXAMPLE 
     The invention is not limited to the above-described exemplary embodiment and various modifications may be made. Some modification examples will be described below. Two or more of modification examples to be described below may be used in combination. 
     (1) Modification Example 1 
     In the above-described exemplary embodiment, a case where the blower  106  sends the wind that passes through the hole  1041  and goes to the transporting path r is described. In this regard, the path of the wind sent by the blower  106  is not limited to passing through the hole  1041 . The blower  106  may send wind along the transporting path r, for example. 
       FIG. 5  is a cross-sectional schematic view when the fixing device  11  related to Modification Example 1 is viewed from one side in the width direction. In the fixing device  11 , the blower  106  sends the wind that goes from the upstream side of the transporting path r to the downstream side. Additionally, in the fixing device  11 , the light source  1011  is arranged so that the optical axis a 1  of the laser light LB inclines to the upstream side with respect to the transporting path r. If the optical axis a 1  of the laser light LB inclines to the upstream side with respect to the transporting path r, the position of the irradiation region D 1  is located further toward the downstream side than the hole  1041 . Therefore, compared with a case where the optical axis a 1  of the laser light LB inclines to the downstream side with respect to the transporting path r, powder dust is kept from passing through the hole  1041 . 
     (2) Modification Example 2 
     The configuration of the fixing device is not limited to one described to the exemplary embodiment. The fixing device may not have, for example, the reflective member  103 . 
       FIG. 6  is a cross-sectional schematic view when a fixing device  12  related to Modification Example 2 is viewed from one side in the width direction. The fixing device  12  is different from the fixing device  10  in that the fixing device does not have the reflective member  103 . In  FIG. 6 , the blower  106 , similarly to the exemplary embodiment, sends the wind that passes through the hole  1041  and goes to the transporting path r. Additionally, the optical axis a 1  of the laser light LB inclines to the downstream side with respect to the transporting path r. In addition, in a case where the reflective member  103  is not used, the preventing member  104  may not be formed by a material that transmits light. Additionally, the preventing member  104  is not limited to a case where the preventing member is flat-plate-shaped, and may have, for example, a shape that is curved with respect to the transporting path r. 
     (3) Modification Example 3 
     The path along which the blower  106  sends wind into the space surrounded by the reflective member  103  and the preventing member  104  is not limited to a path through the hole  1031 . The blower  106  may also send wind into the space from a hole separate from the hole  1031  provided in the reflective member  103 . 
     (4) Modification Example 4 
     In the above-described exemplary embodiment, a case where one light source  1011  is provided in the transporting direction is described. In this regard, plural light sources  1011  may be provided in the transporting direction. In this case, the hole  1041  allows the laser light LB generated by the plural light sources  1011  aligned in the transporting direction to pass therethrough. In addition, in a case where the plural light sources  1011  are provided in the transporting direction, a hole that allows the laser light LB by one light source  1011  in the transporting direction to pass therethrough and a hole that allows the laser light LB by the other light source  1011  may be separately provided in the preventing member  104 . 
     (5) Modification Example 5 
     The optical member  102  is not limited to the lens that converges the laser light LB in the transporting direction. For example, the optical member  102  may diffuse the laser light LB in the width direction. In this case, a lens that is concave in a cross-section viewed in the transporting direction is used as the optical member  102 . In another example, one light source  1011  may be provided with 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. In still another example, one optical member  102  that extends along the width direction may be provided so as to correspond to plural light sources  1011  aligned along the width direction. 
     (6) Modification Example 6 
     Although the exemplary embodiment has showed a case where the paper P is a continuous form, the paper P may be cut page-by-page with a predetermined dimension. In this case, a transporting belt may be used instead of the supporting roller  105 . The transporting belt, which is an endless belt-like member, transports plural sheets of paper P sequentially along the transporting path r. 
     (7) Modification Example 7 
     The direction in which the optical axis a 1  of the laser light LB inclines with respect to the transporting path r is not limited to the direction shown in  FIG. 4  or  5 . In  FIG. 4 , the optical axis a 1  of the laser light LB may incline to the upstream side with respect to the transporting path r. Moreover, in  FIG. 5 , the optical axis a 1  of the laser light LB may incline to the downstream side with respect to the transporting path r. 
     (8) Other Modification Examples 
     Although the exemplary embodiment has shown the toner as an example of an image forming material, the image forming material may be ink. In this case, as the ink is irradiated and dried with light, an image is fixed on the paper P. 
     In the exemplary embodiment, the image forming apparatus  100  forms a color image. However, the image forming apparatus  100  may form a monochrome image. In this case, the image forming apparatus  100  may has the image forming engine  90 K among the image forming engines  90 Y,  90 M,  90 C, and  90 K. 
     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.