Patent Publication Number: US-10331063-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. 2017-146676 filed Jul. 28, 2017. 
     BACKGROUND 
     Technical Field 
     The present invention relates to a fixing device and an image forming apparatus. 
     SUMMARY 
     According to an aspect of the invention, there is provided a fixing device including: a rotary member; a heating member provided inside the rotary member; supply parts that supply power to the heating member; cover parts that cover the supply parts; and fixing members that fix the rotary member in an axial direction. The cover parts have a restriction part that restricts movement of the rotary member in the axial direction. 
    
    
     
       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 vertical sectional view of an image forming apparatus according to first to third exemplary embodiments; 
         FIG. 2  is a vertical sectional view of a fixing device according to the first to third exemplary embodiments; 
         FIG. 3A  is a sectional view of a heating unit,  FIG. 3B  is a sectional view showing a state in which a heating roller of the heating unit has moved, and  FIG. 3C  is an enlarged view of a part IIIC in  FIG. 3B ; 
         FIG. 4A  is a partial sectional view showing a detailed configuration of a gear-side portion of the heating unit,  FIG. 4B  is a sectional view of the heating unit, as viewed from the other end, and  FIG. 4C  is a sectional view showing a state in which the heating roller of the heating unit has moved; 
         FIG. 5A  is a sectional view of the heating unit in which a cover part does not have a restriction part, and  FIG. 5B  is a sectional view showing a state in which the heating roller has moved; 
         FIG. 6A  is a partial sectional view of the heating unit according to a modification of the first exemplary embodiment,  FIG. 6B  is a partial sectional view of the heating unit according to the second exemplary embodiment, and  FIG. 6C  is a partial sectional view showing a modification of the second exemplary embodiment; and 
         FIG. 7A  is a partial sectional view of the heating unit according to the third exemplary embodiment, and  FIG. 7B  is a partial sectional view showing a state in which the cover part and a projecting portion are separated. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of the present invention will be described below with reference to the drawings. Note that the exemplary embodiments described below show, as examples, a fixing device and an image forming apparatus for embodying the technical idea of the present invention and are not intended for limiting the present invention thereto. The present invention can be equally applicable to other exemplary embodiments included in the scope of the claims. 
     First Exemplary Embodiment 
     Referring to  FIGS. 1 to 4 , an image forming apparatus  10  according to a first exemplary embodiment will be described. As shown in  FIG. 1 , the image forming apparatus  10  according to the first exemplary embodiment includes an image forming apparatus body  12 , and at least one sheet feed unit  18 , an image forming unit  14 , and a fixing device  36 , which are accommodated in the image forming apparatus body  12 . The image forming apparatus body  12  has a discharge port  34  at the top. A transport path  32  along which a recording medium  140 , such as a recording sheet, serving as a medium to which an image is transferred, is transported is provided so as to communicate between the above-described components. The configurations of these components will be described below. 
     The sheet feed units  18  each include a sheet feed unit body  20 , a sheet feed cassette  22  that accommodates the recording media  140 , a pickup roller  24  that picks up the recording media  140  stacked in the sheet feed cassette  22 , and a feed roller  28  and a retard roller  26  that feed the recording media  140  while separating them into individual media. As the pickup roller  24 , the feed roller  28 , and the retard roller  26  rotate, the recording media  140  in the sheet feed cassette  22  are transported along the transport path  32  to registration rollers  38  (described below). The sheet feed cassette  22  is removably attached to the sheet feed unit body  20 . Although there are two sheet feed units  18  in the first exemplary embodiment, as shown in  FIG. 1 , the number of the sheet feed units  18  may be one, or more than two. 
     The image forming unit  14  uses an electrophotographic system and includes: an image carrier  44 , which is formed of a photoconductor; a charging device  56  that is formed of, for example, a charging roller and uniformly charges the image carrier  44 ; a photo-writing device  58  that writes, with light, a latent image on the image carrier  44  charged by the charging device  56 ; a developing device  60  having a developing roller that develops the latent image formed on the image carrier  44  by the photo-writing device  58  into a visible image using toner; a transfer device  42  that is formed of, for example, a transfer roller for transferring the toner image formed by the developing device  60  to a recording medium  140 ; a cleaning device  62  for cleaning the residual toner on the image carrier  44 ; and a fixing device  36  that fixes the toner image transferred to the recording medium  140  by the transfer device  42  to the recording medium  140 . 
     The photo-writing device  58  is formed of, for example, a scanning laser exposure device that forms a latent image on the image carrier  44  through a process cartridge  64  (described below). In other exemplary embodiments, the photo-writing device  58  may alternatively be an LED, a surface emitting laser, or the like. 
     The process cartridge  64  includes the image carrier  44 , the charging device  56 , the developing device  60 , and the cleaning device  62 , which are integrated together, and is replaceable. 
     The transport path  32  is a path for the recording media  140  and is continuous from the pickup roller  24  of the sheet feed unit  18  at the bottom of the image forming apparatus body  12  to the discharge port  34  at the top of the image forming apparatus body  12 . The transport path  32  is located inside the image forming apparatus body  12  and has a substantially vertical portion extending from the pickup roller  24  of the sheet feed unit  18  at the bottom to the fixing device  36 . 
     On the transport path  32 , the transfer device  42  and the image carrier  44  are located upstream of the fixing device  36 , and the registration rollers  38  are located upstream of the transfer device  42  and the image carrier  44 . Furthermore, discharge rollers  40  are provided on the transport path  32 , near the discharge port  34 . 
     Recording media  140  fed from the sheet feed cassette  22  in the sheet feed unit  18  by the pickup roller  24  are separated into individual media by the retard roller  26  and the feed roller  28 . Then, each of the separated media is guided to the transport path  32 , is temporarily stopped by the registration rollers  38 , and is then caused to pass between the transfer device  42  and the image carrier  44  at a certain timing, during which a developer image is transferred to the medium. The transferred developer image is fixed to the medium by the fixing device  36 , and the medium is discharged from the discharge port  34  to the discharge portion  16  by the discharge rollers  40 . 
     Furthermore, as shown in  FIG. 2 , the fixing device  36  includes: a heating unit  66 ; an endless belt  72 , serving as an endless belt body; guide members  74  that guide the endless belt  72  so as to allow rotation thereof; and a pressure part  70  that is disposed in the endless belt  72  and is pressed toward the heating roller  68 , together with the endless belt  72 . 
     As shown in  FIGS. 2 and 3A , the heating unit  66  includes: a heating roller  68 , which is a tubular rotary member capable of rotation; heaters  86 , serving as heating members and disposed inside the heating roller  68 ; gear  124 , serving as a transmitting member, that transmits a driving force for rotating the heating roller  68  from a driving-force source (not shown); a pair of bearing members  128   a  and  128   b  that support the heating roller  68  so as to allow rotation thereof; and a pair of fixing members  122   a  and  122   b  fixed to the heating roller  68  to keep the heating roller  68  in a predetermined rotation position. 
     In the first exemplary embodiment, the bearing member located at one end, which is an end closer to a cover part  116   a  (described below) having a restriction part  120 , is the bearing member  128   a , and the bearing member located at the other end, which is an end closer to a cover part  116   b  having no restriction part, is the bearing member  128   b . Similarly, the fixing member located at one end is the fixing member  122   a , and the fixing member located at the other end is the fixing member  122   b . The fixing members  122   a  and  122   b  may be collectively referred to as the fixing members  122 , and the bearing members  128   a  and  128   b  may be collectively referred to as the bearing members  128 . 
     The heating roller  68  is a so-called hard roller, which does not have an elastic layer, and is formed of a cylindrical roller portion  84  and a releasing layer  90  covering or applied to the roller portion  84 . The heating roller  68  is supported by the bearing members  128  at both ends so as to be capable of rotation in a direction of arrow A (see  FIG. 2 ). 
     The roller portion  84  is made of metal, such as iron, stainless steel, or aluminum. The releasing layer  90  is formed of an insulating and highly releasable material, such as PFA. A separation member  92  is in contact with the heating roller  68 . 
     As shown in  FIGS. 4A and 4B , the heating roller  68  has a groove extending in the longitudinal direction from one end. This groove serves as a key groove  110  to mesh with the gear  124  (described below). The depth of the key groove  110  is substantially half the thickness of the roller portion  84 . 
     The gear  124  provided at one end of the heating roller  68  transmits, to the heating roller  68 , a rotational driving force exerted by a driving part, such as a motor, provided inside the image forming apparatus body  12 . The gear  124  is, for example, a cylindrical helical gear, which has a helical tooth trace. 
     Furthermore, the gear  124  has a projecting portion  126  on the inner circumference, that is, on the circumference closer to the heating roller  68  (see  FIGS. 4A and 4B ). The projecting portion  126  enters the key groove  110  formed in the heating roller  68  so as to extend in the axial direction, thus meshing together the gear  124  and the heating roller  68 , thereby allowing the driving force to be more smoothly transmitted. 
     The fixing members  122 , which are, for example, C rings, are attached to both ends of the heating roller  68 , at predetermined positions, to keep the rotation position of the heating roller  68  within a predetermined position. The fixing members  122  are each provided at the corresponding end of the heating roller  68  in the longitudinal direction. In the first exemplary embodiment, the fixing member  122   b  at the other end is attached on the outer side of the gear  124 , and the fixing member  122   a  at one end is provided on the outer side of the bearing member  128   a , which is provided opposite from the gear  124 . When a large displacement of the rotating heating roller  68  from the predetermined rotation position is likely to occur, the fixing member  122   a  and the bearing member  128   a  at one end come into contact with each other, or the gear  124  and the bearing member  128   b  at the other end come into contact with each other, reducing the displacement of the heating roller  68  from the rotation position and keeping the heating roller  68  at the predetermined position. 
     The heaters  86  are disposed inside the heating roller  68  and include, for example, two lamp heaters. A thermostat  94  is provided on the opposite side of the heating roller  68  from the endless belt  72  so as to face the heating roller  68 . The heaters  86  may be known heaters, such as halogen lamp heaters or carbon lamp heaters. 
     The heaters  86  have, at one end and the other end in the axial direction (the longitudinal direction), supply parts  112   a  and  112   b  to which power is supplied through lead wires  114  connected to the inside of the image forming apparatus body  12 . The supply parts  112   a  and  112   b  are covered, together with portions of the lead wires  114 , by cover parts  116   a  and  116   b.    
     The cover part at one end, which is a cover part having a restriction part  120  (described below) is the cover part  116   a , and the cover part at the other end, which is a cover part having no restriction part  120  is the cover part  116   b . Similarly, the supply part at one end is the supply part  112   a , and the supply part at the other end is the supply part  112   b . The supply parts  112   a  and  112   b  may be collectively referred to as the supply parts  112 , and the cover parts  116   a  and  116   b  may be collectively referred to as the cover parts  116 . 
     The cover parts  116  are so-called insulators covering the supply parts  112  so as to be integral therewith. The cover parts  116  are formed of a strong, heat-proof material, such as ceramics. 
     The cover parts  116  at both ends have different shapes. The cover part  116   a  at one end, that is, the cover part  116   a  located opposite from the gear  124  when assembled into the heating unit  66  in the first exemplary embodiment, has the restriction part  120 . The cover part  116   b  opposite from the cover part  116   a  having the restriction part  120  does not have the restriction part. 
     The cover part  116   a  according to the first exemplary embodiment has a projecting portion  118  projecting, together with the lead wires  114 , in a direction intersecting the longitudinal direction of the heaters  86  (e.g., the vertical direction) and thus has an L shape. A surface of the projecting portion  118  of the cover part  116   a  facing the heating roller  68  serves as the restriction part  120 . 
     The projecting portion  118  extends to, at least, a position at substantially the same height as the roller portion  84  of the heating roller  68 . More specifically, the projecting portion  118  projects to a position at which the restriction part  120  of the projecting portion  118  comes into contact with the end of the heating roller  68  when the heating roller  68  has moved in the rotation-axis direction. The projecting portion  118  may be higher than the heating roller  68 . The restriction part  120  formed on the cover part  116   a  will be described in detail below. 
     As shown in  FIG. 2 , the pressure part  70  includes a carrier  100  disposed on the inner side the endless belt  72 , a pressure member  108  attached to the carrier  100 , and frames  78  and  79  that support the carrier  100 . An impregnation pad  80  for supplying lubricant is provided on the inner side of the endless belt  72 . 
     When the pressure part  70  is pressed against the heating roller  68 , a pressure area  102  is formed by the pressure member  108  attached to the carrier  100 . The pressure part  70  presses the pressure member  108  toward the heating roller  68 , in cooperation with the carrier  100  and the frames  78  and  79 . 
     The carrier  100  is formed of a resin material, such as a heat-resistant liquid crystal polymer (LCP). As shown in  FIG. 2 , the carrier  100  has, on the side facing the heating roller  68 , a surface  106  to which the pressure member  108 , which forms the pressure area  102 , is attached. 
     The pressure member  108  has substantially the same length as the carrier  100  in the longitudinal direction and is formed in a substantially rectangular-parallelepiped shape from a heat-resistant resin material, such as silicone rubber. 
     As shown in  FIG. 2 , the guide members  74  are disposed at both ends of the endless belt  72  and the pressure part  70 , and the pressure part  70  is supported by the guide members  74 . 
     As shown in  FIG. 2 , the frames  78  and  79  support the carrier  100 . The ends of the frames  78  and  79  are supported by the guide members  74 , and the carrier  100  is urged toward the heating roller  68 . 
     The endless belt  72  is provided between the heating roller  68  and the pressure part  70  and travels in the direction of arrow C so as to follow the rotation of the heating roller  68  (see  FIG. 2 ). The pressure part  70  presses the endless belt  72  toward the heating roller  68 , forming the pressure area  102 , where a toner image is fixed to a recording medium  140 . The endless belt  72  is formed in a belt-like shape from a synthetic resin, such as polyimide, and has a releasing layer, formed of PFA or the like, on the surface thereof. 
     An inlet chute  96  is provided upstream of the pressure area  102 . A recording medium  140  transported in the direction of arrow B is guided into the inlet chute  96 , and the distal end of the recording medium  140  is guided to the pressure area  102  (see  FIG. 2 ). An outlet chute  98  is provided downstream of the pressure area  102 . 
     Next, the restriction part  120  provided on the cover part  116   a  of the heating unit  66  in the fixing device  36  according to the first exemplary embodiment will be described. 
     As shown in  FIG. 3A , the heating roller  68  of the heating unit  66  in the fixing device  36  according to the first exemplary embodiment has the fixing members  122   a  and  122   b  on the outer circumference thereof, on the outer side of the bearing member  128   a  and on the outer side of the gear  124 , respectively, to reduce a large displacement of the heating roller  68  from the predetermined rotation position. 
     If the fixing member  122   b  near the gear  124  falls off while the image forming apparatus  10  is used, that is, while the heating roller  68  is rotating, the rotating heating roller  68  moves away from the fixing member  122   b , that is, away from the gear  124 . When the gear  124  is a helical gear, the heating roller  68  easily moves due to a thrust force (a force in the axial direction) along the shape of the obliquely extending (helical) teeth. 
     In this case, if the fixing member  122   b  comes off from the heating roller  68  when a cover part  116   a ′ does not have the restriction part  120  as in a heating unit  66 ′ of a fixing device  36 ′ shown in  FIG. 5A , a large displacement of the heating roller  68  from a predetermined position may occur, as shown in  FIG. 5B . 
     In contrast, as in the heating unit  66  according to the first exemplary embodiment shown in  FIG. 3A , when the cover part  116   a  of the supply part  112   a  of the heaters  86  has the restriction part  120 , as shown in  FIGS. 3B and 3C , even if the heating roller  68  moves, it comes into contact with the restriction part  120 , and the movement of the heating roller  68  is restricted. Hence, even if the fixing member  122   b  comes off, the movement of the heating roller  68  restricted. 
     Furthermore, because the movement of the heating roller  68  is restricted by the restriction part  120  of the projecting portion  118 , contact with the lead wires  114  extending and guided from the supply part  112   a  is reduced. 
     When the fixing member  122   a  on the opposite side of the heating roller  68  from the gear  124  comes off, the projecting portion  126  formed on the inner circumference of the gear  124  engages with the end of the key groove  110  formed in the heating roller  68 , reducing the movement of the heating roller  68  toward the gear  124  (see  FIG. 4C ). 
     Furthermore, although the cover parts  116  are provided at both ends of the heating unit  66  in the longitudinal direction of the heaters  86 , the restriction part  120  is provided only on one of the cover parts  116 . Thus, the cover part opposite from the cover part having the restriction part does not have the restriction part. 
     As shown in  FIG. 3A , in the first exemplary embodiment, the restriction part  120  formed on the cover part  116   a  is located at one end of the heaters  86 , that is, on the opposite side from the gear  124  provided on the heating roller  68 . Thus, the restriction part is not formed on the cover part  116   b  provided near the gear  124 . Because the restriction part  120  is provided only on the cover part  116   a , it is possible to easily insert the heaters  86  into the heating roller  68 , thus making assembly easy. 
     Modification 
     In the first exemplary embodiment, although the projecting portion  118  of the cover part  116   a  having the restriction part  120  is provided so as to project only in the direction in which the lead wires  114  extend, it is also possible to form another projecting portion  118 A projecting in the direction opposite to the direction in which the lead wires  114  extend and are guided, thus forming a T shape, as in a cover part  116 Aa of a heating unit  66 A shown in  FIG. 6A . 
     With this configuration, the projecting portions  118  and  118 A projecting at both sides of the cover part  116 Aa covering the supply part  112 Aa respectively have the restriction parts  120  and  120 A for restricting the movement of the heating roller  68 . Hence, even the heating roller  68  that has moved can be stably rotated. Furthermore, by increasing the number of the restriction parts  120  and  120 A with which the heating roller  68  comes into contact, damage to the cover part  116 Aa is reduced. 
     The number of projecting portions formed on the cover part may be three or more, or the projecting portion may have a circular shape so as to surround the cover part. 
     Second Exemplary Embodiment 
     In the first exemplary embodiment, the restriction part  120  is provided on the cover part  116   a  that covers the supply part  112   a  having the projecting portion  118  projecting with the lead wires  114 . In the second exemplary embodiment, a cover part  116 Ba of a heating unit  66 B has a projecting portion  119 B projecting in a direction different from the direction in which the lead wires  114  extending from a supply part  112 Ba are guided, and a restriction part  120 B is provided in the projecting portion  119 B. The configurations the same as those in the first exemplary embodiment will be denoted by the same reference signs, and detailed descriptions thereof will be omitted. 
     For example, the lead wires  114  extend and are guided from the supply part  112 Ba in the longitudinal direction of the heaters  86  (see  FIG. 6B ). The projecting portion  119 B is formed on the cover part  116 Ba that covers the supply part  112 Ba to which the lead wires  114  are guided. 
     Specifically, as shown in  FIG. 6B , the cover part  116 Ba of the heating unit  66 B according to the second exemplary embodiment covers the supply part  112 Ba to which the lead wires  114  extending in the longitudinal direction of the heaters  86  are guided. The cover part  116 Ba has the projecting portion  119 B projecting in a direction different from the direction in which the lead wires  114  extend, which direction intersects the longitudinal direction of the heaters  86 , that is, for example, the vertical direction. A surface of the projecting portion  119 B facing the heating roller  68  constitutes the restriction part  120 B. 
     With this configuration, it is possible to freely set the direction in which the lead wires  114  are guided, even when the projecting portion  119 B is formed on the cover part  116 Ba. 
     Modification 
     Although the cover part  116 Ba according to the second exemplary embodiment has one projecting portion  119 B projecting in a direction intersecting the longitudinal direction of the heaters  86 , as in a cover part  116 Ca of a heating unit  66 C shown in  FIG. 6C , a projecting portion  119 C may be formed so as to project in a direction different from the direction in which the lead wires  114  extending from the supply part  112 Ca are guided, that is, for example, in a direction intersecting the lead wires  114  guided in the longitudinal direction of the heaters  86 , in addition to the projecting portion  119 B according to the second exemplary embodiment, and the projecting portions  119 B and  119 C may respectively have restriction parts  120 B and  120 C. 
     With this configuration, the projecting portions  119 B and  119 C projecting at both sides of the cover part  116 Ca have the restriction parts  120 B and  120 C that restrict the movement of the heating roller  68 . Thus, even the heating roller  68  that has moved can be stably rotated. Furthermore, by increasing the number of the restriction parts  120 B and  120 C with which the heating roller  68  comes into contact, damage to the cover part  116 Ca is reduced. 
     The number of projecting portions formed on the cover part may be three or more, or the projecting portion may have a circular shape so as to surround the cover part. 
     Third Exemplary Embodiment 
     In the first exemplary embodiment and the modification of the first exemplary embodiment, the projecting portions  118  and  118 A are formed integrally with the cover parts  116   a  and  116 Aa, and in the second exemplary embodiment and the modification of the second exemplary embodiment, the projecting portions  119 B and  119 C are formed integrally with the cover parts  116 Ba and  116 Ca. The present invention is not limited to such configurations. As shown in  FIGS. 7A and 7B , it is also possible that a separately formed projecting portion  130  is attached to a cover part  116 Da. The configurations the same as those in the first exemplary embodiment will be denoted by the same reference signs, and detailed descriptions thereof will be omitted. 
     Specifically, in the third exemplary embodiment, as shown in  FIG. 7B , the cover part  116 Da that covers a supply part  112 Da of the heating unit  66 D has a projection  132  on which the projecting portion  130  is attached, and the projecting portion  130  has a hole  134  into which the projection  132  formed on the cover part  116 Da is inserted. 
     By fitting the hole  134  in the projecting portion  130  onto the projection  132  of the cover part  116 Da, the projecting portion  130  is attached to the cover part  116 Da. At this time, a surface of the projecting portion  130  facing the heating roller  68  constitutes a restriction part  120 D. 
     In the third exemplary embodiment, although the cover part  116 Da has the projection  132 , and the projecting portion  130  has the hole  134 , the cover part may have a hole, and the projecting portion may have a projection. 
     In this configuration, compared with a case where the cover part and the projecting portion that form the restriction part are not formed of different members, the shape of the cover part is simple, and thus, manufacturing is easy. 
     The cover part  116 Da and the projecting portion  130  do not necessarily have to be joined together by using the projection  132  and the hole  134  and may be joined together by another joining method, such as screwing, welding, or the like. 
     In the third exemplary embodiment, although one projecting portion  130  is attached to the cover part  116 Da, multiple projecting portions may be attached to the cover part  116 Da. 
     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.