Patent Publication Number: US-2011076066-A1

Title: Fixing apparatus and image forming apparatus

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to fixing apparatuses and image forming apparatuses that handle electrophotography. 
     2. Related Art 
     A fixing device, in an image forming apparatus, that includes a first fixing unit that fixes an image transferred onto a transfer material, a second fixing unit that carries out fixing after the first fixing, and a bypass transport path in which the transfer material that has passed through the first fixing unit does not pass through the second fixing unit, has been disclosed in the past (see JP-A-2006-308889). 
     However, the image forming apparatus according to JP-A-2006-308889 also includes a curl application means that corrects curls arising due to heat contraction of the toner and the like and a flapper that switches transport paths, leading to an increase in the size and complexity of the apparatus. 
     In addition, there has been a risk that after being discharged from the first fixing unit, the transfer material sags downward in the vertical direction due to the influence of gravity; this causes the printed surface to collide with the second fixing unit, leading to the occurrence of defects in the image. Furthermore, there have been situations where rollers, the flapper, and so on have made contact with the image surface immediately after the fixing, when the image surface is still in a high-temperature state, thus leading to a different glossiness in the areas of the image where the contact was made than in the rest of the image; the quality of the image has thus dropped as a result. 
     SUMMARY 
     An advantage of some aspects of the invention is to provide a fixing apparatus capable of reducing the influence of a second fixing unit on the surface of an image while employing a simple structure, and an image forming apparatus capable of forming a favorable image. 
     A fixing apparatus according to an aspect of the invention includes: a first fixing unit having a first heating unit that applies heat to a transfer material onto which an image has been transferred and a first pressure unit that forms a first nip portion by pressing against the first heating unit; a second fixing unit including a second heating unit that applies heat to the transfer material that has undergone fixing in the first fixing unit and a second pressure unit that forms a second nip portion by pressing against the second heating unit; and a fixing unit suction guide, including a suction surface that sucks the transfer material that has undergone fixing in the first fixing unit upward in the vertical direction with the surface of the transfer material onto which the image has been transferred facing downward in the vertical direction, the end of the suction surface on the side toward the second fixing unit in a transport direction of the transfer material being located higher in the vertical direction than an imaginary line that connects the first nip portion and the second nip portion. 
     An image forming apparatus according to an aspect of the invention includes: a latent image bearing member on which a latent image is formed; a developing unit that develops the latent image on the latent image bearing member using a liquid developer containing toner particles and a carrier liquid; a transfer medium onto which the image developed on the latent image bearing member by the developing unit is transferred; a transfer roller that makes contact with the transfer medium and forms a transfer nip portion therewith, and that transfers the image onto a transfer material; a first fixing unit having a first heating unit that applies heat to the transfer material onto which the image has been transferred and a first pressure unit that forms a first nip portion by pressing against the first heating unit; a second fixing unit having a second heating unit that applies heat to the transfer material that has undergone fixing in the first fixing unit and a second pressure unit that forms a second nip portion by pressing against the second heating unit; and a fixing unit suction guide, having a suction surface that sucks the transfer material that has undergone fixing in the first fixing unit upward in the vertical direction with the surface of the transfer material onto which the image has been transferred facing downward in the vertical direction, the end of the suction surface on the side toward the second fixing unit in a transport direction of the transfer material being located higher in the vertical direction than an imaginary line that connects the first nip portion and the second nip portion. 
     According to another aspect of the invention, the side of the suction surface toward the first fixing unit is parallel or approximately parallel to the imaginary line. 
     According to another aspect of the invention, the first fixing unit is a heating roller in which the first heating unit has an elastic layer, and the first pressure unit is a pressure roller whose surface hardness is the same or approximately the same as the surface hardness of the heating roller. 
     According to another aspect of the invention, the side of the suction surface toward the first fixing unit is sloped downward in the vertical direction beyond the imaginary line. 
     An image forming apparatus according to another aspect of the invention further includes: a transport belt that forms the suction surface and transports the transfer material that has undergone fixing in the first fixing unit; a driving roller, upon which the transport belt is wound, that drives the transport belt; and a slave roller upon which the transport belt is stretched. 
     According to another aspect of the invention, the transport belt has a hole through which air flows. 
     According to the fixing apparatus of the invention, the influence of the second fixing unit on the image surface can be reduced using a simple configuration. Meanwhile, according to the image forming apparatus of the invention, the influence of the second fixing unit on the image surface can be reduced using a simple configuration, thus making it possible to form a favorable image. 
     In addition, because the fixing unit suction guide, in which the end of the suction surface on the side toward the second fixing unit in the transport direction of the transfer material is located higher in the vertical direction than the imaginary line that connects the first nip portion and the second nip portion, is provided, it is possible for the transfer material to move to the nip portion of the second fixing roller pair in a smooth manner. 
     In addition, because the side of the suction surface toward the first fixing unit is parallel or approximately parallel to the imaginary line, the transfer material can move to the fixing unit suction guide in a smooth manner. 
     In addition, because the side of the suction surface toward the first fixing unit is sloped downward in the vertical direction beyond the imaginary line, the transfer material can move to the fixing unit suction guide in a smooth manner. 
     In addition, an image forming apparatus according to an aspect of the invention further includes the transport belt that forms the suction surface and transports the transfer material that has undergone fixing in the first fixing unit, the driving roller, upon which the transport belt is wound, that drives the transport belt, and the slave roller upon which the transport belt is stretched. As a result, the transfer material sticks to the transport belt and the transfer material and transport belt move together, and thus the transfer material can be transported from the first fixing roller pair toward the second fixing roller pair in a stable manner. 
     In addition, because the fixing unit transport belt includes the holes through which air flows, the transfer material can be transported in an even more stable manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a diagram illustrating a first embodiment of an image forming apparatus. 
         FIG. 2  is a diagram illustrating a fixing unit suction guide according to the first embodiment. 
         FIG. 3  is a diagram illustrating a fixing unit suction guide according to a second embodiment. 
         FIG. 4  is a diagram illustrating an enlarged view of a first fixing roller pair according to the second embodiment and a third embodiment. 
         FIG. 5  is a diagram illustrating a fixing unit suction guide according to the third embodiment. 
         FIG. 6  is a diagram illustrating a fixing unit suction guide according to a fourth embodiment. 
         FIG. 7  is a diagram illustrating a fixing unit suction guide according to a fifth embodiment. 
         FIG. 8  is a diagram illustrating an enlarged view of a first fixing roller pair according to the fourth embodiment and the fifth embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Embodiments of the invention will now be described with reference to the drawings. 
       FIG. 1  is a diagram illustrating the primary constituent elements of which an image forming apparatus according to a first embodiment of the invention is configured. Developing units  30 Y,  30 M,  30 C, and  30 K, serving as developing units, are disposed in a lower portion of the image forming apparatus, opposing an intermediate transfer belt  40 , serving as a transfer medium, disposed in a central portion of the image forming apparatus; a secondary transfer unit  60  serving as a transfer unit, a fixing unit  90  serving as a fixing unit, and so on are disposed in an upper portion of the image forming apparatus. In particular, the fixing unit  90  is laid out above the intermediate transfer belt  40 , thereby making it possible to reduce the installation footprint of the image forming apparatus as a whole. 
     First, units surrounding photosensitive members will be described. Photosensitive members  10 Y,  10 M,  10 C, and  10 K, each serving as a latent image bearing member and each configured of a cylindrically-shaped member on the outer circumferential surface of which a photosensitive layer such as an amorphous silicon photosensitive member is formed, are provided, and the following elements are disposed in the respective surrounding areas thereof, following the rotational direction of the outer circumference of the photosensitive members  10 Y,  10 M,  10 C, and  10 K and starting with corona charging units  11 Y,  11 M,  11 C, and  11 K: exposure units  12 Y,  12 M,  12 C, and  12 K; developing rollers  20 Y,  20 M,  20 C, and  20 K serving as developer holding members for the developing units  30 Y,  30 M,  30 C, and  30 K; first photosensitive member squeeze rollers  13 Y,  13 M,  13 C, and  13 K; second photosensitive member squeeze rollers  13 Y′,  13 M′,  13 C′, and  13 K′; primary transfer units  50 Y,  50 M,  50 C, and  50 K; discharge units (not shown); and photosensitive member cleaning blades  18 Y,  18 M,  18 C, and  18 K. Note that in an image formation process, elements disposed earlier in the order from the corona charging units  11 Y,  11 M,  11 C, and  11 K to the photosensitive member cleaning blades  18 Y,  18 M,  18 C, and  18 K are defined as being upstream from elements disposed later in the stated order. 
     With the units surrounding the photosensitive members, first, the photosensitive members  10 Y,  10 M,  10 C, and  10 K are uniformly charged by the corona charging units  11 Y,  11 M,  11 C, and  11 K, which are disposed further upstream in the rotational direction of the photosensitive members  10 Y,  10 M,  10 C, and  10 K than nip portions formed between the photosensitive members  10 Y,  10 M,  10 C, and  10 K and the developing rollers  20 Y,  20 M,  20 C, and  20 K. Then, the exposure units  12 Y,  12 M,  12 C, and  12 K, which are disposed downstream from the corona charging units  11 Y,  11 M,  11 C, and  11 K and upstream from nip portions formed between the photosensitive members  10 Y,  10 M,  10 C, and  10 K and the developing rollers  20 Y,  20 M,  20 C, and  20 K, carry out exposure based on inputted image signals, forming electrostatic latent images by irradiating the surfaces of the charged photosensitive members  10 Y,  10 M,  10 C, and  10 K. 
     Next, the developing units  30 Y,  30 M,  30 C, and  30 K will be described. In the developing units  30 Y,  30 M,  30 C, and  30 K, augers  34 Y,  34 M,  34 C, and  34 K that agitate and transport liquid developers of various colors held within developer reservoirs  31 Y,  31 M,  31 C, and  31 K supply the liquid developers to anilox rollers  32 Y,  32 M,  32 C, and  32 K serving as developer supply members. Next, the anilox rollers  32 Y,  32 M,  32 C, and  32 K apply the liquid developers of the respective colors to the developing rollers  20 Y,  20 M,  20 C, and  20 K, the amount of the liquid developers having been regulated by regulating blades  33 Y,  33 M,  33 C, and  33 K. 
     The liquid developers held on the developing rollers  20 Y,  20 M,  20 C, and  20 K is put into a state of compaction by compaction corona generators  22 Y,  22 M,  22 C, and  22 K, after which the electrostatic latent images formed upon the photosensitive members  10 Y,  10 M,  10 C, and  10 K are developed and toner images formed upon the photosensitive members  10 Y,  10 M,  10 C, and  10 K. Liquid developer that has remained on the developing rollers  20 Y,  20 M,  20 C, and  20 K is cleaned off by developing roller cleaning blades  21 Y,  21 M,  21 C, and  21 K. 
     The liquid developer held in the developer reservoir  31 Y is a non-volatile liquid developer, which is non-volatile at normal temperatures, and which has a high concentration and high viscosity, rather than a volatile liquid developer that uses Isopar (an Exxon brand) as its carrier, which is volatile at normal temperatures, has a low concentration (approximately 1-3 wt %), and that has a low viscosity, as has generally been used in the past. In other words, the liquid developer in the invention is a high-viscosity liquid developer (that is, a viscoelasticity of approximately 30 to 300 mPa/s at a shear rate of 1000 (1/s) at 25° C., measured using a HAAKE RheoStress RS600) with a toner solid content concentration of approximately 15 to 25%, in which solid particles of a colorant such as a pigment having an average particle diameter of 1 μm are dispersed within a thermoplastic resin and are added to a liquid carrier such as an organic carrier, silicon oil, mineral oil, or cooking oil along with a dispersant. 
     The toner images formed upon the photosensitive members  10 Y,  10 M,  10 C, and  10 K are squeezed by the first photosensitive member squeeze rollers  13 Y,  13 M,  13 C, and  13 K and the second photosensitive member squeeze rollers  13 Y′,  13 M′,  13 C′, and  13 K′. 
     The intermediate transfer belt  40  is a belt, formed of a seamless elastic member such as rubber, that is stretched across a belt driving roller  41  and a tension roller  42 ; the intermediate transfer belt  40  is rotationally driven by the belt driving roller  41  while making contact with the photosensitive members  10 Y,  10 M,  10 C, and  10 K at the primary transfer units  50 Y,  50 M,  50 C, and  50 K. The primary transfer units  50 Y,  50 M,  50 C, and  50 K form a full-color toner image by sequentially transferring the developed toner images of the stated colors upon the photosensitive members  10 Y,  10 M,  10 C, and  10 K onto the intermediate transfer belt  40 , thereby superimposing the toner images on one another, using the positions where the intermediate transfer belt  40  makes contact with the photosensitive members  10 Y,  10 M,  10 C, and  10 K located between the photosensitive members  10 Y,  10 M,  10 C, and  10 K and primary transfer rollers  51 Y,  51 M,  51 C, and  51 K as the transfer positions. 
     Liquid developer that has remained on the photosensitive members  10 Y,  10 M,  10 C, and  10 K after passing through the primary transfer units  50 Y,  50 M,  50 C, and  50 K is removed using a discharge unit (not shown), the photosensitive member cleaning blades  18 Y,  18 M,  18 C, and  18 K, and so on. 
     Note that the disposition order of the photosensitive members, the elements of the developing units, and so on with respect to the Y, M, C, and K colors is not limited to the order illustrated in  FIG. 1 , and the order may be set as desired. 
     Next, the transfer of a toner image from the intermediate transfer belt  40  to a transfer material S will be described. 
     The transfer material S is supplied to the image forming apparatus by a paper supply unit. The transfer material S, which has been set in a first paper supply tray  101   a  or a second paper supply tray  101   b,  is transported to a paper supply transport path La at a predetermined timing, one respective sheet at a time, by a first paper supply roller  102   a  or a second paper supply roller  102   b.  Meanwhile, in a transfer material transport path Lab, the transfer material S is transported to a secondary transfer position by a pair of gate rollers  104  and  104 ′ and a transfer material guide  105 . 
     The secondary transfer unit  60  includes a secondary transfer roller  61 , serving as a transfer member, and a secondary transfer roller cleaning blade  85  that cleans the secondary transfer roller  61 . The secondary transfer roller  61  rotates along with the belt driving roller  41  in the direction indicated by the arrow, and a transfer bias is applied thereto. 
     The leading edge of the transfer material S transported by the transfer material guide  105  is caught by a gripper  64 , serving as a transfer material catching unit provided within a concave portion  63  extending in the axial direction of the secondary transfer roller  61 , and a gripper support portion  65 , serving as a transfer material catching unit receiving portion on which the gripper  64  is seated; thus the transfer material S is positioned relative to the secondary transfer roller  61  and moves with certainty toward a transfer nip as the secondary transfer roller  61  rotates. 
     The toner image on the intermediate transfer belt  40  is transferred to the transfer material S, which is paper, film, cloth, or the like, at the transfer nip. When a catching portion of the gripper  64  and the leading edge of the transfer material S pass through the transfer nip, the gripper  64  commences movement in a direction away from a claw seat  65 , and the leading edge of the transfer material S is released as a result. Then, a protruding claw  79  is set to a protruding position as the secondary transfer roller  61  rotates further, and thus the transfer material S separates from the secondary transfer roller  61 . 
     Meanwhile, the transfer material S that was released from the gripper  64  is lightly pressed against the secondary transfer roller  61  by air blown from a blowing unit  400  that expels air, in the direction indicated by an arrow A, from an opening portion  402  in a housing unit  401 , the air being expelled through the operation of an airflow generation unit  405 ; the transfer material S is also pressed in a direction away from the secondary transfer roller  61  by the protruding claw  79 . 
     In this manner, the transfer material S gripped by the nip portion between the belt driving roller  41  and the secondary transfer roller  61  moves to a transfer material transport unit  200 , in order from the leading edge to the following edge, due to further rotation of the belt driving roller  41  and the secondary transfer roller  61 . In other words, the portion of the transfer material S for which transfer is complete separates while the toner image on the intermediate transfer belt  40  undergoes the secondary transfer onto the transfer material S. 
     According to this configuration, it is possible to prevent the following edge of the transfer material S from making contact with the intermediate transfer belt  40  or the like and the image formed thereupon being soiled, when the following edge of the transfer material S is discharged from a secondary transfer nip. Note that the air blowing performed by the blowing unit  400  may be omitted in the case where the transfer material S has a low elastic restitution force and is flimsy. 
     Next, transport of the post-secondary transfer transfer material S will be described. 
     A first suction device  210 , a transfer material transport device  230 , and a second suction device  270  are disposed in that order, as the transfer material transport unit  200 , downstream from the secondary transfer unit  60  in the transfer material transport path Lab, and serve to transport the transfer material S to the fixing unit  90 . 
     The post-secondary transfer transfer material S is held on a suction surface  212  of a housing portion  211 , without falling, as a result of a suction force B from the suction surface  212  that is generated through the operation of an airflow generation unit  215  of the first suction device  210 , and is transported along the suction surface  212 , by the force of a feeding operation, from the side of the secondary transfer unit  60 . 
     As a result of the force of the feeding operation from the side of the secondary transfer unit  60 , the transfer material S transported along the suction surface  212  of the first suction device  210  reaches the side of the transfer material transport device  230 . Next, the transfer material S is held against a transport surface by a suction force C, from a suction surface  232  of a housing portion  231 , that is generated through the operation of an airflow generation unit  235  of the transfer material transport device  230 . Along with this, the transfer material S advances along the transport surface toward the fixing unit  90  as a result of a transfer material transport member  250 , which is wound upon a transfer material transport member driving roller  251  and transfer material transport member support rollers  252  and  253 , performing moving operations due to driving force exerted by the transfer material transport member driving roller  251 . 
     The transfer material S that has been transported along the transport surface of the transfer material transport device  230  is sucked as a result of a suction force D, from a suction surface  272  of a housing portion  271 , generated through operations performed by an airflow generation unit  275  of the second suction device  270 , and is transported thus. 
     Next, fixing of the toner image onto the transfer material S will be described. 
     In the fixing unit  90 , a single-color toner image, a full-color toner image, or the like that has been transferred onto the transfer material S, such as paper or the like, is bonded and fixed to the transfer material S, such as paper or the like. 
     The fixing unit  90  includes a first fixing roller pair  91  serving as a first fixing unit, and a second fixing roller pair  92 , serving as a second fixing unit, located downstream from the first fixing roller pair  91 . The first fixing roller pair  91  includes a first heating roller  91   a,  serving as a first heating unit, that has an internal heater, and a first pressure roller  91   b,  serving as a first pressure unit, that is biased at a predetermined pressure toward the first heating roller  91   a;  the transfer material S enters into a nip formed by these rollers, where a single-color toner image, a full-color toner image, or the like transferred onto the transfer material S is bonded and fixed to the transfer material S, which is paper or the like. Likewise, the second fixing roller pair  92  includes a second heating roller  92   a,  serving as a second heating unit, that has an internal heater, and a second pressure roller  92   b,  serving as a second pressure unit, that is biased at a predetermined pressure toward the second heating roller  92   a;  the transfer material S enters into a nip formed by these rollers, where the single-color toner image, the full-color toner image, or the like transferred into the transfer material S is bonded and fixed with further strength to the transfer material S, which is paper or the like. 
     Furthermore, a fixing unit suction guide  300  is disposed between the first fixing roller pair  91  and the second fixing roller pair  92  of the fixing unit  90 . The fixing unit suction guide  300  includes a housing portion  301 , a fixing unit suction surface  302  disposed on the transfer material transport path Lab side of the housing portion  301 , and an airflow generation unit  305  disposed in the housing portion  301  on the side opposite to the transfer material transport path Lab; the transfer material S is held on the fixing unit suction surface  302  without falling by a suction force E, from the fixing unit suction surface  302  of the housing portion  301 , generated through the operation of the airflow generation unit  305 , and is transported along the fixing unit suction surface  302 , while being held thereon, toward the second fixing roller pair  92  by the force of the feeding operation from the first fixing roller pair  91 . 
     After the fixing, in the case of single-sided printing, the transfer material S is transported along a discharge transport path Lc and is discharged. 
     On the other hand, in the case of double-sided printing, the transfer material S is guided by a first flapper  121 , and is transported to a first double-sided transport path Lb 1 . After this, the transport direction of the transfer material S is inverted in a second double-sided transport path Lb 2  having a first inversion transport roller pair  111  and  111 ′, a second inversion transport roller pair  112  and  112 ′, and a third inversion transport roller pair  113  and  113 ′, after which the transfer material S is guided by a second flapper  122  and transported to a third double-sided transport path Lb 3 . 
     In the third double-sided transport path Lb 3 , the transfer material S passes through a curl application roller pair  114  and  114 ′ serving as a curl application unit, and then passes through a first double-sided transport roller pair  115  and  115 ′, a second double-sided transport roller pair  116  and  116 ′, a third double-sided transport roller pair  117  and  117 ′, and a fourth double-sided transport roller pair  118  and  118 ′. Next, the inverted transfer material S is transported from the pair of gate rollers  104  and  104 ′ and the transfer material guide  105  to the transfer material transport path Lab. After this, the transfer material S passes through the fixing unit  90 , is transported to the discharge transport path Lc, and is discharged. 
     Detailed descriptions of the fixing unit  90  will be given hereinafter. 
     The first heating roller  91   a  and the second heating roller  92   a  of the first embodiment are 60 mm in diameter; the metal cores thereof are 2 mm in thickness, and the material of the metal cores is aluminum, iron, stainless steel, brass, or the like. An elastic layer is formed around the circumference of the respective metal cores. The thickness of the elastic layer is 2 mm, and the material of the elastic layer is silicon rubber, fluorocarbon rubber, urethane rubber, or the like. Furthermore, a delamination layer is formed around the elastic layer. The delamination layer is 30 μm thick, and the material of the delamination layer is PFA, PTFE, FEP, ETFE, or the like. 
     Furthermore, the first pressure roller  91   b  and the second pressure roller  92   b  of the first embodiment are 60 mm in diameter; the metal cores thereof are 2 mm in thickness, and the material of the metal cores is aluminum, iron, stainless steel, brass, or the like. An elastic layer is formed around the circumference of the respective metal cores. The thickness of the elastic layer is 2 mm, and the material of the elastic layer is silicon rubber, fluorocarbon rubber, urethane rubber, or the like. Furthermore, a delamination layer is formed around the elastic layer. The delamination layer is 30 μm thick, and the material of the delamination layer is PFA, PTFE, FEP, ETFE, or the like. 
     In addition, the first heating roller  91   a  and the second heating roller  92   a  are driven by a driving member (not shown), and the first pressure roller  91   b  and the second pressure roller  92   b  rotate as slaves based on the rotation of the first heating roller  91   a  and the second heating roller  92   a,  respectively. 
     Note that in the case where a rigid material such as iron, aluminum, stainless steel, brass, or the like is used for the first pressure roller  91   b  and the second pressure roller  92   b,  and a soft material such a rubber layer made from silicon rubber, urethane rubber, or natural rubber, or a sponge layer made from a silicon sponge, a urethane sponge, or a melamine sponge is provided on the shafts of the first heating roller  91   a  and the second heating roller  92   a,  curling in the direction of the image surface caused by heat can be corrected. In addition, it is not necessary for the second heating roller  92   a  and the second pressure roller  92   b  to separate from each other completely; the rollers may be formed so that the applied pressure is reduced, rather than separating from each other completely. 
     Next, the fixing unit suction guide  300  will de described in detail. The fixing unit suction guide  300  according to this embodiment is disposed so that the side of the fixing unit suction guide  300  toward the second fixing roller pair  92  is higher in the vertical direction relative to an imaginary line H that connects a first nip portion of the first fixing roller pair  91  and a second nip portion of the second fixing roller pair  92 . 
       FIG. 2  is a diagram illustrating the fixing unit suction guide  300  according to the first embodiment. 
     The fixing unit suction guide  300  of the first embodiment includes: the housing portion  301 ; the fixing unit suction surface  302 , disposed in the side of the housing portion  301  toward the transfer material transport path Lab; the airflow generation unit  305  disposed in the side of the housing portion  301  that is opposite to the transfer material transport path Lab; a fixing unit transport belt  310 ; and a driving shaft  311  and a slave shaft  312  around which the fixing unit transport belt  310  is wound. 
     With this fixing unit suction guide  300 , the transfer material S is held on the fixing unit suction surface  302  without dropping as a result of the suction force from the fixing unit suction surface  302  of the housing portion  301  generated through the operation of the airflow generation unit  305 ; the fixing unit transport belt  310  rotates as a result of the driving shaft  311  being driven by a driving unit (not shown), and the transfer material S is transported toward the second fixing roller pair  92  along the fixing unit suction surface  302 . 
     The fixing unit suction guide  300  is disposed so that the side of the fixing unit suction guide  300  toward the second fixing roller pair  92  is higher in the vertical direction relative to the imaginary line H that connects the first nip portion of the first fixing roller pair  91  and the second nip portion of the second fixing roller pair  92 . In the first embodiment, the fixing unit suction guide is sloped by approximately 5° to 30° relative to the horizontal line. 
     Meanwhile, the fixing unit transport belt  310  includes holes through which air passes, and moves along the fixing unit suction surface  302 . 
     By using the fixing unit suction guide  300  in this manner, the amount of moisture contained in the transfer material S is rapidly reduced by subjecting the transfer material S to a large amount of air, thus making it possible to correct curling. Accordingly, it is no longer necessary to provide a curl roller pair as was done in the past, thus making it possible to reduce the size of the image forming apparatus. Furthermore, collisions between the leading edge of the transfer material S and the second heating roller  92   a  can be reduced by sucking the transfer material S using the fixing unit suction guide  300 . 
     Meanwhile, because the fixing unit suction guide  300  is disposed so that the side of the fixing unit suction guide  300  toward the second fixing roller pair  92  is higher in the vertical direction relative to the imaginary line H that connects the first nip portion of the first fixing roller pair  91  and the second nip portion of the second fixing roller pair  92 , even if the transfer material S sags in downward in the vertical direction due to the influence of gravity after being discharged from the fixing unit suction guide  300 , a setting can be made so that the non-printed surface thereof makes contact with the second pressure roller  92   b  instead of the printed surface thereof colliding with the second heating roller  92   a;  this makes it possible to reduce defects in the image. 
       FIG. 3  is a diagram illustrating the fixing unit suction guide  300  according to a second embodiment. 
     The fixing unit suction guide  300  according to the second embodiment includes: a first housing portion  301   a;  a first fixing unit suction surface  302   a  disposed in the first housing portion  301   a  on the side toward the transfer material transport path Lab; a first airflow generation unit  305   a  disposed in the first housing portion  301   a  on the side opposite to the transfer material transport path Lab; a second housing portion  301   b;  a second fixing unit suction surface  302   b  disposed in the second housing portion  301   b  on the side toward the transfer material transport path Lab; a second airflow generation unit  305   b  disposed in the second housing portion  301   b  on the side opposite to the transfer material transport path Lab; the fixing unit transport belt  310 ; the driving shaft  311  and a first slave shaft  312  around which the fixing unit transport belt  310  is wound; and a second slave shaft  313  disposed between the first housing portion  301   a  and the second housing portion  301   b.    
     With this fixing unit suction guide  300 , the transfer material S is held on the first fixing unit suction surface  302   a  and the second fixing unit suction surface  302   b  without dropping as a result of the suction force from the first fixing unit suction surface  302   a  of the first housing portion  301   a  and the second fixing unit suction surface  302   b  of the second housing portion  301   b  generated through the operations of the first airflow generation unit  305   a  and the second airflow generation unit  305   b;  the fixing unit transport belt  310  rotates as a result of the driving shaft  311  being driven by a driving unit (not shown), and the transfer material S is transported toward the second fixing roller pair  92  along the first fixing unit suction surface  302   a  and the second fixing unit suction surface  302   b.    
     The fixing unit suction guide  300  is disposed so that the side of the fixing unit suction guide  300  toward the second fixing roller pair  92  is higher in the vertical direction relative to the imaginary line H that connects the first nip portion of the first fixing roller pair  91  and the second nip portion of the second fixing roller pair  92 . As shown in  FIG. 3 , in the second embodiment, the first fixing unit suction surface  302   a  on the side toward the first fixing roller pair  91  is formed so as to be horizontal, whereas the second fixing unit suction surface  302   b  on the side toward the second fixing roller pair  92  is formed with a slope so as to be higher in the vertical direction. 
     Meanwhile, the fixing unit transport belt  310  includes holes through which air passes, and moves along the fixing unit suction surface  302 . 
     By using the fixing unit suction guide  300  in this manner, the amount of moisture contained in the transfer material S is rapidly reduced by subjecting the transfer material S to a large amount of air, thus making it possible to correct curling. Accordingly, it is no longer necessary to provide a curl roller pair as was done in the past, thus making it possible to reduce the size of the image forming apparatus. Furthermore, collisions between the leading edge of the transfer material S and the second heating roller  92   a  can be reduced by sucking the transfer material S using the fixing unit suction guide  300 . 
     Meanwhile, because the fixing unit suction guide  300  is disposed so that the side of the fixing unit suction guide  300  toward the second fixing roller pair  92  is higher in the vertical direction relative to the imaginary line H that connects the first nip portion of the first fixing roller pair  91  and the second nip portion of the second fixing roller pair  92 , even if the transfer material S sags in downward in the vertical direction due to the influence of gravity after being discharged from the fixing unit suction guide  300 , a setting can be made so that the non-printed surface thereof makes contact with the second pressure roller  92   b  instead of the printed surface thereof colliding with the second heating roller  92   a;  this makes it possible to reduce defects in the image. 
       FIG. 5  is a diagram illustrating the fixing unit suction guide  300  according to a third embodiment. 
     The fixing unit suction guide  300  of the third embodiment includes: the housing portion  301 ; the fixing unit suction surface  302 , disposed in the side of the housing portion  301  toward the transfer material transport path Lab; and the airflow generation unit  305  disposed in the side of the housing portion  301  that is opposite to the transfer material transport path Lab. 
     With this fixing unit suction guide  300 , the transfer material S is held on the fixing unit suction surface  302  without dropping as a result of the suction force from the fixing unit suction surface  302  of the housing portion  301  generated through the operation of the airflow generation unit  305 ; the transfer material S is transported toward the second fixing roller pair  92  along the fixing unit suction surface  302  due to the rotation of the first fixing roller pair  91 . 
     The fixing unit suction guide  300  is disposed so that the side of the fixing unit suction guide  300  toward the second fixing roller pair  92  is higher in the vertical direction relative to the imaginary line H that connects the first nip portion of the first fixing roller pair  91  and the second nip portion of the second fixing roller pair  92 . As shown in  FIG. 5 , in the third embodiment, a first fixing unit suction surface  302  on the side toward the first fixing roller pair  91  is formed so as to be horizontal, whereas a second fixing unit suction surface  302  on the side toward the second fixing roller pair  92  is formed with a slope so as to be higher in the vertical direction, as in the second embodiment. 
     By using the fixing unit suction guide  300  in this manner, the amount of moisture contained in the transfer material S is rapidly reduced by subjecting the transfer material S to a large amount of air, thus making it possible to correct curling. Accordingly, it is no longer necessary to provide a curl roller pair as was done in the past, thus making it possible to reduce the size of the image forming apparatus. Furthermore, collisions between the leading edge of the transfer material S and the second heating roller  92   a  can be reduced by sucking the transfer material S using the fixing unit suction guide  300 . 
     Meanwhile, because the fixing unit suction guide  300  is disposed so that the side of the fixing unit suction guide  300  toward the second fixing roller pair  92  is higher in the vertical direction relative to the imaginary line H that connects the first nip portion of the first fixing roller pair  91  and the second nip portion of the second fixing roller pair  92 , even if the transfer material S sags in downward in the vertical direction due to the influence of gravity after being discharged from the fixing unit suction guide  300 , a setting can be made so that the non-printed surface thereof makes contact with the second pressure roller  92   b  instead of the printed surface thereof colliding with the second heating roller  92   a;  this makes it possible to reduce defects in the image. 
     The first heating roller  91   a  and the first pressure roller  91   b  of the second embodiment and the third embodiment are 60 mm in diameter; the metal cores thereof are 2 mm in thickness, and the material of the metal cores is aluminum, iron, stainless steel, brass, or the like. An elastic layer is formed around the circumference of the respective metal cores. The thickness of the elastic layer is 2 mm, and the material of the elastic layer is silicon rubber, fluorocarbon rubber, urethane rubber, or the like. Furthermore, a delamination layer is formed around the elastic layer. The delamination layer is 30 μm thick, and the material of the delamination layer is PFA, PTFE, FEP, ETFE, or the like. The roller hardness is the Asker type C measurement of 20 points. 
     Meanwhile, the first heating roller  91   a  and the first pressure roller  91   b  have the same or approximately the same hardness, and thus the first nip portion formed by the first heating roller  91   a  and the first pressure roller  91   b  configures a horizontal nip that is essentially perpendicular to a line C that connects the centerlines of the first heating roller  91   a  and the first pressure roller  91   b,  as shown in  FIG. 4 . Note that the distance between a line extending from the horizontal nip and the fixing unit suction surface  302  is set to approximately 0 to 5 mm. The first heating roller  91   a  and the first pressure roller  91   b  apply pressure at a loading of 10 to 80 kgf. Here, “the same or approximately the same hardness” refers to ±5 points in the same Asker type C hardness. 
       FIG. 6  is a diagram illustrating the fixing unit suction guide  300  according to a fourth embodiment. 
     The fixing unit suction guide  300  according to the fourth embodiment includes: the first housing portion  301   a;  the first fixing unit suction surface  302   a  disposed in the first housing portion  301   a  on the side toward the transfer material transport path Lab; the first airflow generation unit  305   a  disposed in the first housing portion  301   a  on the side opposite to the transfer material transport path Lab; the second housing portion  301   b;  the second fixing unit suction surface  302   b  disposed in the second housing portion  301   b  on the side toward the transfer material transport path Lab; the second airflow generation unit  305   b  disposed in the second housing portion  301   b  on the side opposite to the transfer material transport path Lab; the fixing unit transport belt  310 ; the driving shaft  311  and the first slave shaft  312  around which the fixing unit transport belt  310  is wound; and the second slave shaft  313  disposed between the first housing portion  301   a  and the second housing portion  301   b.    
     With this fixing unit suction guide  300 , the transfer material S is held on the first fixing unit suction surface  302   a  and the second fixing unit suction surface  302   b  without dropping as a result of the suction force from the first fixing unit suction surface  302   a  of the first housing portion  301   a  and the second fixing unit suction surface  302   b  of the second housing portion  301   b  generated through the operations of the first airflow generation unit  305   a  and the second airflow generation unit  305   b;  the fixing unit transport belt  310  rotates as a result of the driving shaft  311  being driven by a driving unit (not shown), and the transfer material S is transported toward the second fixing roller pair  92  along the first fixing unit suction surface  302   a  and the second fixing unit suction surface  302   b.    
     The fixing unit suction guide  300  is disposed so that the side of the fixing unit suction guide  300  toward the second fixing roller pair  92  is higher in the vertical direction relative to the imaginary line H that connects the first nip portion of the first fixing roller pair  91  and the second nip portion of the second fixing roller pair  92 . In the fourth embodiment, the first fixing unit suction surface  302   a  on the side toward the first fixing roller pair  91  is formed so as to slope toward the printed surface and thus be lower in the vertical direction, whereas the second fixing unit suction surface  302   b  on the side toward the second fixing roller pair  92  is formed so as to slope away from the printed surface and thus be higher in the vertical direction. 
     Meanwhile, the fixing unit transport belt  310  includes holes through which air passes, and moves along the fixing unit suction surface  302 . 
     By using the fixing unit suction guide  300  in this manner, the amount of moisture contained in the transfer material S is rapidly reduced by subjecting the transfer material S to a large amount of air, thus making it possible to correct curling. Accordingly, it is no longer necessary to provide a curl roller pair as was done in the past, thus making it possible to reduce the size of the image forming apparatus. Furthermore, collisions between the leading edge of the transfer material S and the second heating roller  92   a  can be reduced by sucking the transfer material S using the fixing unit suction guide  300 . 
     Meanwhile, because the fixing unit suction guide  300  is disposed so that the side of the fixing unit suction guide  300  toward the second fixing roller pair  92  is higher in the vertical direction relative to the imaginary line H that connects the first nip portion of the first fixing roller pair  91  and the second nip portion of the second fixing roller pair  92 , even if the transfer material S sags in downward in the vertical direction due to the influence of gravity after being discharged from the fixing unit suction guide  300 , a setting can be made so that the non-printed surface thereof makes contact with the second pressure roller  92   b  instead of the printed surface thereof colliding with the second heating roller  92   a;  this makes it possible to reduce defects in the image. 
       FIG. 7  is a diagram illustrating the fixing unit suction guide  300  according to a fifth embodiment. 
     The fixing unit suction guide  300  of the fifth embodiment includes: the housing portion  301 ; the fixing unit suction surface  302 , disposed in the side of the housing portion  301  toward the transfer material transport path Lab; and the airflow generation unit  305  disposed in the side of the housing portion  301  that is opposite to the transfer material transport path Lab. 
     With this fixing unit suction guide  300 , the transfer material S is held on the fixing unit suction surface  302  without dropping as a result of the suction force from the fixing unit suction surface  302  of the housing portion  301  generated through the operation of the airflow generation unit  305 ; the transfer material S is transported toward the second fixing roller pair  92  along the fixing unit suction surface  302  due to the rotation of the first fixing roller pair  91 . 
     The fixing unit suction guide  300  is disposed so that the side of the fixing unit suction guide  300  toward the second fixing roller pair  92  is higher in the vertical direction relative to the imaginary line H that connects the first nip portion of the first fixing roller pair  91  and the second nip portion of the second fixing roller pair  92 . In the fifth embodiment, the first fixing unit suction surface  302   a  on the side toward the first fixing roller pair  91  is formed so as to slope toward the printed surface and thus be lower in the vertical direction, whereas the second fixing unit suction surface  302   b  on the side toward the second fixing roller pair  92  is formed so as to slope away from the printed surface and thus be higher in the vertical direction. 
     By using the fixing unit suction guide  300  in this manner, the amount of moisture contained in the transfer material S is rapidly reduced by subjecting the transfer material S to a large amount of air, thus making it possible to correct curling. Accordingly, it is no longer necessary to provide a curl roller pair as was done in the past, thus making it possible to reduce the size of the image forming apparatus. Furthermore, collisions between the leading edge of the transfer material S and the second heating roller  92   a  can be reduced by sucking the transfer material S using the fixing unit suction guide  300 . 
     Meanwhile, because the fixing unit suction guide  300  is disposed so that the side of the fixing unit suction guide  300  toward the second fixing roller pair  92  is higher in the vertical direction relative to the imaginary line H that connects the first nip portion of the first fixing roller pair  91  and the second nip portion of the second fixing roller pair  92 , even if the transfer material S sags in downward in the vertical direction due to the influence of gravity after being discharged from the fixing unit suction guide  300 , a setting can be made so that the non-printed surface thereof makes contact with the second pressure roller  92   b  instead of the printed surface thereof colliding with the second heating roller  92   a;  this makes it possible to reduce defects in the image. 
     The first heating roller  91   a  of the fourth embodiment and the fifth embodiment is 60 mm in diameter; the metal core thereof is 2 mm in thickness, and the material of the metal core is aluminum, iron, stainless steel, brass, or the like. An elastic layer is formed around the circumference of the metal core. The thickness of the elastic layer is 2 mm, and the material of the elastic layer is silicon rubber, fluorocarbon rubber, urethane rubber, or the like. Furthermore, a delamination layer is formed around the elastic layer. The delamination layer is 30 μm thick, and the material of the delamination layer is PFA, PTFE, FEP, ETFE, or the like. The roller hardness is the Asker type C measurement of 20 points. 
     The first pressure roller  91   b  of the fourth embodiment and the fifth embodiment has an elastic layer thickness of 5 mm, but the rest of the specifications are the same as those of the first heating roller  91   a.    
     Meanwhile, in the case where the roller hardness of the first heating roller  91   a  is greater than the roller hardness of the first pressure roller  91   b,  as in the fourth embodiment and the fifth embodiment, the first nip portion formed by the first heating roller  91   a  and the first pressure roller  91   b  takes on a convex shape in the upward direction, as shown in  FIG. 8 . Note that the first fixing unit suction surface  302   a  is disposed parallel or approximately parallel to a line of contact at the nip exit of the first heating roller  91   a.  The distance between the line of contact and the fixing unit suction surface  302  is set to approximately 0 to 5 mm. The first heating roller  91   a  and the first pressure roller  91   b  apply pressure at a loading of 10 to 80 kgf. 
     In this manner, according to the fixing unit  90  of the embodiments, the influence of the second fixing roller pair  92  on the image surface can be reduced using a simple configuration. In addition, according to the image forming apparatus of these embodiments, the influence of the second fixing roller pair  92  on the image surface can be reduced using a simple configuration, thus making it possible to form a favorable image. 
     In addition, the fixing unit suction guide  300 , in which the end of the suction surface  302  on the side toward the second fixing unit in the transport direction of the transfer material S is located higher in the vertical direction than an imaginary line that connects the first nip portion and the second nip portion, is provided, and thus the transfer material S can move to the second nip portion of the second fixing roller pair  92  in a smooth manner. 
     In addition, because the side of the suction surface  302  toward the first fixing unit is parallel or approximately parallel to the imaginary line, the transfer material S can move to the fixing unit suction guide  300  in a smooth manner. 
     In addition, because the side of the suction surface  302  toward the first fixing unit is sloped downward in the vertical direction beyond the imaginary line, the transfer material S can move to the fixing unit suction guide  300  in a smooth manner. 
     In addition, because the fixing unit transport belt  310  that forms the suction surface  302  and transports the transfer material S that has undergone fixing in the first fixing unit, the driving shaft  311  upon which the fixing unit transport belt  310  is stretched and that drives the fixing unit transport belt  310 , and the slave shaft  312  upon which the fixing unit transport belt  310  is stretched are provided, the transfer material S sticks to the fixing unit transport belt  310  and the transfer material S and fixing unit transport belt  310  move together; as a result, the transfer material S can be transported from the first fixing roller pair  91  toward the second fixing roller pair  92  in a stable manner. 
     Furthermore, because the fixing unit transport belt  310  includes the holes  310   a  through which air flows, the transfer material S can be transported in an even more stable manner. 
     The entire disclosure of Japanese Patent Application No: 2009-226425, filed Sep. 30, 2009 is expressly incorporated by reference herein.