Fixing device and image forming system

Abstract

To provide a fixing device with which, when fixing a toner image on the second side of a recording medium after having fixed a toner image on the first side of the recording medium, it is possible to suppress the uneven gloss of the image due to fusing of the toner on the first side of the recording medium, as compared with the case where the surface of a pressuring member is smooth.SOLUTION: A fixing device 100 comprises: a chain gripper 66 for conveying paper P; a heating roll 130 for heating a toner image T2 carried on the second side PB of the paper P in a contact state; a pressure roll 140 for pressuring the paper P between the heating roll 130 and itself and fixing the toner image T2 carried on the second side PB of the paper P and coming into contact with the toner image T1 fixed to the first side PA of the paper P; and an irregular-shaped part 146 provided on the surface of the pressure roll 140 and shaped to have a plurality of protrusions and recesses, and in which a height difference H1 of the protrusions and recesses is greater than or equal to the height H3 of a toner layer in the solid toner image T3 fixed to the first side PA of the paper P.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a fixing device and an image forming system. [Background technology]

[0002] The following Patent Document 1 discloses a fixing device having a heating roller and a pressure belt, which applies heat and pressure to paper carrying a toner image, melting the toner and fixing it to the paper, in which the pressure belt is made endless from a heat-resistant sheet and its seams are configured so as not to be perpendicular to the direction of belt rotation.

[0003] The following Patent Document 2 discloses a fixing roller and a pressure member arranged in pressure contact with the outer peripheral surface of the fixing roller, and conveys a recording material having an unfixed toner image between the fixing roller and the pressure member. The present invention discloses a fixing device that fixes an unfixed toner image to the recording material by providing a heat-resistant sheet having a glass fiber base between the fixing roller and a pressure member, and transporting the recording material between the fixing roller and the heat-resistant sheet.

[0004] In the following Patent Document 3, a fixing roller is provided with a release layer on the surface and an elastic layer below the release layer, and is heated directly or indirectly by a heat source. The fixing roller is formed of a material having a lower thermal expansion coefficient or lower thermal shrinkage than the layer, and is attached so that wrinkles are generated on the surface when not heated. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-303303 [Patent Document 2] Japanese Patent Application Publication No. 8-241000 [Patent Document 3] JP 2002-139940 A Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to obtain a fixing device and image forming system that, when fixing a toner image on a first surface of a recording medium and then fixing a toner image on a second surface of the recording medium, can suppress uneven gloss of the image caused by melting of the toner on the first surface of the recording medium, compared to when the surface of the pressure member is smooth. [Means for solving the problem]

[0007] The fixing device according to the first aspect includes a transport section that transports a recording medium having a toner image fixed to a first surface thereof by heating and pressurizing and an unfixed toner image retained on a second surface thereof, a heating member that heats, in a contact state, the toner image retained on the second surface of the recording medium transported by the transport section, a pressure member that pressurizes the recording medium between the heating member to fix the toner image retained on the second surface of the recording medium and that comes into contact with the toner image fixed on the first surface of the recording medium, and a concave-convex portion that is provided on the surface of the pressure member and has a shape with a plurality of concaves and convexes, and the difference in height of the concaves and convexes is equal to or greater than the height of the toner layer in a solid toner image fixed on the first surface of the recording medium.

[0008] The fixing device of the second aspect is the fixing device described in the first aspect, further comprising a non-contact heating section that is provided upstream of the heating member in the transport direction of the recording medium and heats the toner image on a second surface of the recording medium in a non-contact state, and the transport section transports the recording medium between the heating member and the pressure member while facing the second surface of the recording medium to the non-contact heating section.

[0009] A fixing device according to a third aspect is the fixing device according to the first aspect, wherein a maximum height roughness Rz corresponding to a difference in height of the projections and recesses is 8 μm or more and 20 μm or less.

[0010] A fixing device according to a fourth aspect is the fixing device according to the third aspect, wherein the uneven portion has an arithmetic mean waviness Wa of 2 μm or more and 5 μm or less.

[0011] A fixing device according to a fifth aspect is the fixing device according to the first aspect, wherein the uneven portion is formed by a woven portion having fibers woven therein, and the pressure member has the woven portion attached to the peripheral surface of a metal base material.

[0012] A fixing device according to a sixth aspect is the fixing device according to the fifth aspect, wherein the fibers are glass fibers.

[0013] A fixing device according to a seventh aspect is the fixing device according to the sixth aspect, wherein the glass fibers are glass fibers impregnated with a release agent.

[0014] A fixing device according to an eighth aspect is the fixing device according to the first aspect, wherein the uneven portion is formed by directly processing a surface of the pressure member.

[0015] The fixing device of the ninth aspect is the fixing device of the first aspect, wherein the pressure member is a pressure cylinder having a concave portion formed on its surface side into which a gripping portion that grips the front end side of the recording medium fits, and the uneven portion is provided on the surface of the pressure cylinder excluding the concave portion.

[0016] An image forming apparatus according to a tenth aspect has an image forming unit that forms a toner image on a recording medium, and a fixing device according to any one of the first to ninth aspects that fixes the toner image formed by the image forming unit to the recording medium.

[0017] An image forming apparatus according to an eleventh aspect has an image forming unit that forms a toner image on a recording medium, a fixing device according to any one of the first to ninth aspects that fixes the toner image formed on a first side of the recording medium by the image forming unit to the recording medium and fixes the toner image formed on a second side of the recording medium by the image forming unit to the recording medium, and an inversion mechanism that inverts the recording medium from the first side to the second side after the toner image is fixed to the first side of the recording medium by the fixing device. Effect of the Invention

[0018] According to the fixing device of the first embodiment, when a toner image on a first surface of a recording medium is fixed and then a toner image on a second surface of the recording medium is fixed, uneven gloss of the image caused by melting of the toner on the first surface of the recording medium can be suppressed compared to when the surface of the pressure member is smooth.

[0019] According to the fixing device of the second aspect, even in a configuration in which the toner image on the second surface of the recording medium is heated in a non-contact manner upstream of the heating member, uneven gloss of the image caused by melting of the toner on the first surface of the recording medium can be suppressed.

[0020] According to the fixing device of the third aspect, gloss unevenness of the image caused by melting of the toner on the first surface of the recording medium can be suppressed compared to when the maximum height roughness Rz corresponding to the height difference of the concaves and convexes is smaller than 8 μm. Also, deformation of the recording medium is suppressed compared to when the maximum height roughness Rz corresponding to the height difference of the concaves and convexes is larger than 20 μm.

[0021] According to the fixing device of the fourth aspect, gloss unevenness of the image caused by melting of the toner on the first surface of the recording medium can be suppressed compared to when the arithmetic mean waviness Wa of the uneven portion is smaller than 2 μm, and deformation of the recording medium is suppressed compared to when the arithmetic mean waviness Wa of the uneven portion is larger than 5 μm.

[0022] According to the fixing device of the fifth aspect, it is easier to set the height difference between the projections and recesses as desired, compared to a case in which the projections and recesses are directly formed on the surface of the pressure member.

[0023] According to the fixing device of the sixth aspect, the toner on the first surface of the recording medium is less likely to adhere to the pressure member, compared to when the fibers are made of resin.

[0024] According to the fixing device of the seventh aspect, the toner on the first surface of the recording medium is less likely to adhere to the pressure member, compared to a case in which glass fibers that are not impregnated with resin are woven into the fixing device.

[0025] According to the fixing device of the eighth aspect, it is possible to reduce the cost of materials compared to a case in which a covering member is attached to the circumferential surface of the base material of the pressure member.

[0026] According to the fixing device of the ninth aspect, even when the pressure member is a pressure cylinder having a recessed portion into which the gripping portion that grips the front end side of the recording medium fits, uneven gloss of the image caused by melting of the toner on the first surface of the recording medium can be suppressed.

[0027] According to the image forming device of the tenth aspect, when a toner image on a first surface of a recording medium is fixed and then a toner image on a second surface of the recording medium is fixed, uneven gloss of the image caused by melting of the toner on the first surface of the recording medium can be suppressed compared to when the surface of the pressure member is smooth.

[0028] According to the image forming device of the eleventh aspect, when a toner image on a first surface of a recording medium is fixed and then a toner image on a second surface of the recording medium is fixed, uneven gloss of the image caused by melting of the toner on the first surface of the recording medium can be suppressed compared to when the surface of the pressure member is smooth. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus including a fixing device according to a first embodiment. [Diagram 2] 1 is a schematic diagram illustrating a toner image forming unit of an image forming apparatus including a fixing device according to a first embodiment. [Diagram 3] FIG. 2 is a configuration diagram showing a fixing device according to the first embodiment. [Figure 4] FIG. 2 is a configuration diagram showing a part of a heating unit of the fixing device according to the first embodiment. [Diagram 5] FIG. 1A is a diagram showing a toner image fixed on a first surface of a sheet of paper and a toner image held on a second surface of the sheet of paper, and FIG. 1B is an enlarged cross-sectional view showing the substrate and jacket of a pressure roll used in the fixing device of the first embodiment. [Figure 6] 2 is an enlarged view showing a jacket of a pressure roll used in the fixing device of the first embodiment. FIG. [Figure 7] FIG. 4 is an enlarged cross-sectional view showing a base material and a jacket of a pressure roll used in a fixing device of a comparative example. [Figure 8] 4 is a graph showing the measurement results of surface roughness of a jacket according to the first embodiment and a jacket according to a comparative example. [Figure 9] FIG. 4 is a diagram showing an example in which a measured cross-sectional curve of the jacket of the first embodiment is converted into a waviness curve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] An example of an embodiment of the present invention will be described below with reference to the drawings. Note that the arrow H shown in each drawing indicates the vertical direction, i.e., the up-down direction of the device, the arrow W indicates the horizontal direction, i.e., the width direction of the device, and the arrow D indicates the front-rear direction of the device (depth direction of the device).

[0031] First Embodiment First, a description will be given of the configuration of an image forming apparatus 10 including a fixing device 100 according to the first embodiment. Fig. 1 is a schematic diagram showing the configuration of an image forming apparatus 10 according to the first embodiment.

[0032] (Image forming apparatus 10) The image forming apparatus 10 shown in Fig. 1 is an example of an image forming system that forms an image on a recording medium. Specifically, the image forming apparatus 10 is an electrophotographic image forming apparatus that forms a toner image on paper P, which is an example of a recording medium. More specifically, the image forming apparatus 10 has a storage section 50, a discharge section 52, an image forming section 12, a conveying mechanism 60, a reversing mechanism 80, a fixing device 100, and a cooling section 90, as shown in Fig. 1.

[0033] (Storage section 50) The storage section 50 shown in FIG. 1 has a function of storing paper P. In the image forming apparatus 10, a plurality of storage sections 50 (for example, two) are provided. The configuration is such that paper P is selectively sent out from the plurality of storage sections 50. As the paper P as an example of a recording medium, a sheet of paper (cut paper) having a predetermined size is used. The paper P has a first side PA (see FIG. 5) as one side and a second side PB (see FIG. 5) as the other side. In the first embodiment, the first side PA is the front side of the paper P, and is the side on which the toner image T1 is first held. The second side PB is the back side of the paper P, and is the side on which the toner image T2 is held after the toner image T1 on the first side PA is fixed.

[0034] (Discharge section 52) 1 is a portion where the paper P on which an image has been formed is discharged. Specifically, after the image has been fixed by the fixing device 100, the paper P cooled by the cooling section 90 is discharged to the discharge section 52.

[0035] (Image forming unit 12) The image forming unit 12 shown in Fig. 1 is an example of an image forming unit that forms an image on a recording medium. Specifically, the image forming unit 12 has a function of forming a toner image on a sheet of paper P by an electrophotographic method. More specifically, as shown in Fig. 1, the image forming unit 12 has a toner image forming unit 20 that forms a toner image, and a transfer device 30 that transfers the toner image formed by the toner image forming unit 20 onto the sheet of paper P.

[0036] [Toner image forming unit 20] A plurality of toner image forming units 20 are provided so as to form a toner image for each color. The image forming device 10 is provided with toner image forming units 20 for a total of four colors: yellow (Y), magenta (M), cyan (C), and black (K). (Y), (M), (C), and (K) shown in FIG. 1 indicate components corresponding to the above-mentioned colors.

[0037] The toner image forming units 20 for each color are basically configured in the same way except for the toner used. Specifically, as shown in Fig. 2, the toner image forming units 20 for each color have a photoconductor drum 21 (photoconductor) that rotates in the direction of the arrow A in Fig. 2, and a charger 22 that charges the photoconductor drum 21. Furthermore, the toner image forming units 20 for each color have an exposure device 23 that exposes the photoconductor drum 21 charged by the charger 22 to form an electrostatic latent image on the photoconductor drum 21, and a developing device 24 that develops the electrostatic latent image formed on the photoconductor drum 21 by the exposure device 23 to form a toner image.

[0038] [Transfer device 30] 1 has a function of primarily transferring the toner images of the photoconductor drums 21 of each color in a superimposed manner onto an intermediate transfer body, and then secondarily transferring the superimposed toner images onto paper P. Specifically, as shown in FIG. 1, the transfer device 30 includes a transfer belt 31 as an intermediate transfer body, a primary transfer roll 33, and a transfer section 35.

[0039] The primary transfer roll 33 has the function of transferring the toner image formed on the photosensitive drum 21 onto the transfer belt 31 at a primary transfer position T (see Figure 2) between the photosensitive drum 21 and the primary transfer roll 33.

[0040] 1, the transfer belt 31 is endless and has a determined position by being wound around a plurality of rolls 32. When at least one of the rolls 32 is driven to rotate, the transfer belt 31 rotates in the direction of arrow B, and transports the primarily transferred image to the secondary transfer position NT.

[0041] The transfer unit 35 has a function of transferring the toner image transferred onto the transfer belt 31 onto the paper P. The transfer unit 35 specifically includes a secondary transfer unit 34 and an opposing roll 36.

[0042] The opposing roll 36 is disposed below the transfer belt 31 so as to face the transfer belt 31. The secondary transfer unit 34 is disposed inside the transfer belt 31 so that the transfer belt 31 is disposed between the opposing roll 36 and the secondary transfer unit 34, as shown in FIG. 1. The secondary transfer unit 34 is specifically composed of a corotron. In the transfer unit 35, the toner image transferred onto the transfer belt 31 is transferred onto the paper P passing through the secondary transfer position NT by electrostatic force generated by discharge of the secondary transfer unit 34.

[0043] (Transport mechanism 60) 1 is a mechanism for transporting paper P. Specifically, the transport mechanism 60 has a function of transporting paper P stored in the storage section 50 to a secondary transfer position NT. Furthermore, the transport mechanism 60 has a function of transporting paper P from the secondary transfer position NT to a fixing unit 120 (a heating roll 130 and a pressure roll 140, which will be described later) which will be described later. In other words, the transport mechanism 60 has a function of transporting paper P, to which a toner image has been transferred, through the fixing device 100.

[0044] 1, the transport mechanism 60 has a feed roll 62, multiple transport rolls 64, and a chain gripper 66. The feed roll 62 is a roll that feeds out the paper P stored in the storage section 50. The multiple transport rolls 64 are rolls that transport the paper P sent out by the feed roll 62 to the chain gripper 66.

[0045] 3, the chain gripper 66 is an example of a conveying section that holds the front end side (leading end side) of the paper sheet P and conveys the paper sheet P. Specifically, the chain gripper 66 includes a pair of chains 72 and a gripper 76 as an example of a gripping section (holding section).

[0046] The pair of chains 72 are formed in a loop as shown in Fig. 1. The pair of chains 72 are arranged at an interval in the front-rear direction of the device (direction D in Fig. 1) (see Fig. 4). The pair of chains 72 are wound around a pair of sprockets (not shown) arranged at one end and the other end in the axial direction of the counter roll 36 and the pressure roll 140 described below, respectively, and a pair of sprockets 74 arranged at an interval in the front-rear direction of the device. When one of the pair of sprockets rotates, the chain 72 goes around in the direction of arrow C (see Fig. 1).

[0047] An attachment member 75 (see FIG. 4) to which a gripper 76 is attached is hung between the pair of chains 72 in the front-rear direction of the device. A plurality of attachment members 75 are fixed to the pair of chains 72 at predetermined intervals along the circumferential direction (circumferential direction) of the chains 72. In each drawing, the components of the chain 72 are shown in blocks in order to simplify the illustration of the chain 72.

[0048] A plurality of grippers 76 are attached to the attachment member 75 at predetermined intervals along the front-rear direction of the device (see FIG. 3). The gripper 76 has a function of holding (grasping) the front end of the paper P. By holding the front end of the paper P, the position of the paper P in the paper transport direction is easily determined, and alignment (registration) between the paper P and the image in the transfer unit 35 is easy. Specifically, as shown in FIG. 3 and FIG. 4, the gripper 76 has a claw 76A and a claw base 76B. The gripper 76 is configured to hold the paper P by pinching the front end of the paper P between the claw 76A and the claw base 76B. For example, the gripper 76 has a claw 76A pressed against the claw base 76B by a spring or the like, and the claw 76A opens and closes with respect to the claw base 76B by the action of a cam or the like.

[0049] In the chain gripper 66, the chain 72 rotates in the direction of the arrow C while the gripper 76 holds the leading end of the paper P, thereby transporting the paper P. The chain gripper 66 transports the paper P to the secondary transfer position NT while the first surface PA faces upward, and then transports the paper P to a fixing unit 120, which will be described later, after passing through a heating section 102 described later. In this manner, the chain gripper 66 is a part that has the function of holding the paper P and passing it through the heating section 102, and transporting it from the heating section 102 to the fixing unit 120, and also serves as the fixing device 100. Note that a part of the transport path along which the paper P is transported in the transport mechanism 60 is indicated by a dashed line in FIG. 1.

[0050] (Reversing mechanism 80) The reversing mechanism 80 shown in Fig. 1 is an example of a reversing mechanism that reverses the front and back of a recording medium on which an image has been fixed by the fixing device 100. Specifically, the reversing mechanism 80 is a mechanism that reverses the front and back of a sheet of paper P on which a toner image has been fixed by the fixing device 100 (i.e., a first side PA and a second side PB of the sheet of paper P). More specifically, as shown in Fig. 1, the reversing mechanism 80 has a plurality of (e.g., two) transport rolls 82, a reversing device 84, and a plurality of (e.g., seven) transport rolls 86.

[0051] The plurality of transport rolls 82 are rolls that transport the paper P sent from the fixing device 100 to the reversing device 84 .

[0052] As an example, the inversion device 84 is a device that twists the paper P like a Moebius strip by transporting the paper P while curving it multiple times so that the transport direction of the paper P changes, for example, by 90 degrees at a time, thereby inverting the front and back of the paper P (i.e., the first side PA and second side PB of the paper P).

[0053] The multiple transport rolls 86 are rolls that transport the paper P whose front and back sides (i.e., the first surface PA and second surface PB of the paper P) have been inverted by the inverting device 84 to the chain gripper 66. In other words, the multiple transport rolls 86 have a function of delivering the paper P whose front and back sides (i.e., the first surface PA and second surface PB of the paper P) have been inverted to the chain gripper 66.

[0054] In this way, the inversion mechanism 80 inverts the paper P (i.e., the first side PA and second side PB of the paper P) and hands it over to the chain gripper 66, so that the chain gripper 66 transports the paper P that has been handed over to it as a paper P having a fixed toner image (image) T1 on the first side PA.

[0055] 1, a part of the transport path along which the paper sheet P is transported in the reversing mechanism 80 is indicated by a dashed line. Also, the reversing mechanism 80 may be a mechanism that reverses the paper sheet P by switching it back.

[0056] (Fixing device 100) 3 is an example of a fixing device that fixes an image formed by an image forming unit onto a recording medium. Specifically, the fixing device 100 is a device that fixes a toner image transferred by the transfer device 30 onto a sheet of paper P.

[0057] 1, the fixing device 100 is disposed downstream of the secondary transfer position NT in the transport direction of the paper P. As shown in FIG. 3, the fixing device 100 includes a heating section 102, the chain gripper 66, a blower 160, a ventilation plate 180, and a fixing unit 120 (fixing section).

[0058] [Heating section 102] The heating section 102 shown in Fig. 3 is an example of a non-contact heating section that heats the surface of a recording medium without contact. Specifically, the heating section 102 has a function of non-contact heating the surface of the paper P transported by the chain gripper 66 that faces the heating section 102 (for example, the second surface PB when the paper P is turned over). Here, the surface of the paper P that faces the heating section 102 is the first surface PA, or the second surface PB when the paper P is turned over as shown in Fig. 3.

[0059] The heating section 102 is disposed downstream of the secondary transfer position NT (see FIG. 1) in the transport direction of the paper P and faces the first side PA of the paper P transported by the chain gripper 66, or the second side PB when the paper P is inverted as shown in FIG. 3. Specifically, the heating section 102 includes a reflecting plate 104, a plurality of heaters 106 (heat sources), and a wire mesh 112.

[0060] The reflector 104 has a function of reflecting infrared rays from the heater 106 to the lower side of the device (the side of the paper P transported by the chain gripper 66). The reflector 104 is formed using a metal plate such as an aluminum plate. The reflector 104 is formed in a box shape with the lower side of the device open. Specifically, the reflector 104 has an upper reflector 1040 that covers the upper side of the heater 106 of the heating unit 102, an upstream reflector 1042 that extends from the upper reflector 1040 downward to cover the upstream side of the heater 106 on the upstream side of the reflector 104 in the transport direction of the paper P, and a downstream reflector 1044 that extends from the upper reflector 1040 downward to cover the downstream side of the heater 106 on the downstream side of the reflector 104 in the transport direction of the paper P. Furthermore, although not shown, the reflector 104 is composed of a pair of side reflectors that extend from the upper reflector 1040 downward from the device at both end portions of the reflector 104 in a direction intersecting the transport direction of the paper P and cover both side surfaces of the heater 106.

[0061] The heater 106 is a cylindrical infrared heater having a length in the front-rear direction of the device. A plurality of heaters 106 (e.g., 40 heaters) are arranged inside the reflector 104 along the width direction of the device. The heater 106 includes, for example, a carbon filament 109 and a cylindrical quartz tube 108 in which the carbon filament 109 is housed. The surface temperature of the heater 106 of the heating unit 102 is set to a predetermined temperature, for example, between 300° C. and 1175° C.

[0062] The wire mesh 112 is fixed to the edge of the opening on the lower side of the reflector 104. As a result, the wire mesh 112 separates the inside of the reflector 104 from the outside of the reflector 104. The wire mesh 112 also prevents the heater 106 from contacting the paper P being transported by the chain gripper 66.

[0063] As described above, the chain gripper 66 transports the paper P while the first side PA or the second side PB of the paper P faces the heater 106 of the heating unit 102, by rotating the chain 72 in the direction of the arrow C with the gripper 76 holding the leading end of the paper P. In other words, the chain gripper 66 is an example of a transport unit that transports the paper P while the first side PA or the second side PB (see FIG. 3) of the paper P faces the heating unit 102. Note that when transported by the chain gripper 66, the trailing end side of the paper P is not held and is in a free state.

[0064] Furthermore, the chain gripper 66 has a function of transporting the paper P from the heating section 102 to the fixing unit 120. In this manner, the chain gripper 66 functions as an example of a transport section of the fixing device 100 in a portion having a function of passing the paper P through the heating region of the heating section 102 and transporting the paper P from the heating section 102 to the fixing unit 120.

[0065] [Blower 160] The blower 160 shown in Fig. 3 is an example of a blower that blows air to the side of the recording medium conveyed by the conveying unit opposite the heating unit 102 (the second side PB, or the first side PA when the paper P is inverted as shown in Fig. 3). This blower 160 is disposed inside (on the inner periphery side) of the chain 72 as viewed in the front-rear direction of the device, below the heating unit 102. As shown in Fig. 3, the multiple blowers 160 are disposed two-dimensionally (in a matrix) along the conveying direction of the paper P and the front-rear direction of the device.

[0066] As shown in Fig. 3, the blower 160 faces upward and is configured to blow air upward. That is, the blower 160 is configured to blow air in the thickness direction of the paper P only to the lower surface (second surface PB, or first surface PA when the paper P is inverted as shown in Fig. 3) of the paper P conveyed by the chain gripper 66 while facing the heating unit 102.

[0067] An axial flow fan that blows air in an axial direction is used as the fan 160, for example. Note that a centrifugal fan that blows air in a centrifugal direction, such as a multi-blade fan (for example, a sirocco fan), may also be used as the fan 160.

[0068] The blower 160 blows air to the lower surface (e.g., the first surface PA shown in FIG. 3) of the paper sheet P being transported by the chain gripper 66, thereby lifting the paper sheet P. As a result, the lower surface (e.g., the first surface PA) of the paper sheet P is in a non-contact state. Therefore, the blower 160 has a function of maintaining the non-contact state so that the paper sheet P is transported by the chain gripper 66 with the lower surface (e.g., the first surface PA) of the paper sheet P in a non-contact state. In addition, the blower 160 supplies air only to the lower surface (e.g., the first surface PA) of the paper sheet P, thereby suppressing cooling of the toner transferred to the upper surface (e.g., the second surface PB shown in FIG. 3) of the paper sheet P.

[0069] [Ventilation board 180] 3 is an example of a ventilation section having a plurality of ventilation holes that allow air to pass through when it is blown from the blower section toward the back surface of the recording medium. Specifically, the ventilation plate 180 is configured as a plate having a plurality of ventilation holes 182 formed therein that allow air to pass through when it is blown from the blower 160 toward the lower surface (e.g., the first surface PA) of the paper P.

[0070] This ventilation plate 180 is disposed on the inside (inner circumference side) of the chain 72 when viewed in the front-rear direction of the device, below the heating unit 102 and above the blower 160, with the thickness direction being the vertical direction of the device. That is, it is disposed on the blowing direction side of the blower 160 so as to cover the blower 160.

[0071] Each ventilation hole 182 penetrates the ventilation plate 180 in the thickness direction. The ventilation holes 182 are arranged, for example, two-dimensionally (in a matrix) along the transport direction of the paper P and the front-rear direction of the device.

[0072] This ventilation plate 180 is configured so that air blown from the blower 160 passes through a plurality of ventilation holes 182 and hits the lower surface (e.g., the first surface PA) of the paper P transported by the chain gripper 66.

[0073] [Fixing unit 120] 3 is a fixing section that fixes an image on paper P to paper P. Specifically, the fixing unit 120 has a function of fixing a toner image on paper P by contacting with paper P and applying heat and pressure to paper P.

[0074] 3, the fixing unit 120 is disposed downstream of the heating section 102 in the transport direction of the paper P. Specifically, the fixing unit 120 has a heating roll 130, a pressure roll 140, and a driven roll 150.

[0075] [Heating Roll 130] The heating roll 130 shown in Fig. 3 is an example of a heating member that heats the toner image held on the paper P in a contact state. Specifically, the heating roll 130 is disposed downstream of the heating section 102 in the transport direction, and has a function of contacting and heating the paper P. The heating roll 130 is disposed with its axial direction aligned in the front-rear direction of the apparatus so as to contact the upper surface of the paper P (first surface PA, or second surface PB when the paper P is inverted as shown in Fig. 3). In Fig. 3, the heating roll 130 heats the toner image held on the second surface PB of the paper P in a contact state.

[0076] The heating roll 130 has a cylindrical substrate 132, a rubber layer 134 formed on the outer periphery of the substrate 132, a release layer 136 formed on the outer periphery of the rubber layer 134, and a heater 138 (heat source) housed inside the substrate 132. The heater 138 is composed of, for example, a single or multiple halogen lamps.

[0077] [Driven roll 150] The driven roll 150 shown in Fig. 3 is disposed with its axis extending in the front-rear direction of the apparatus so as to contact the outer peripheral surface of the heating roll 130 in an area other than the contact area with the paper P. The driven roll 150 has a cylindrical base material 152 and a heater 154 (heat source) housed inside the base material 152. The driven roll 150 rotates following the heating roll 130, and heats the heating roll 130. Since the heating roll 130 is heated by the driven roll 150 and the heating roll 130 itself has the heater 138, the surface temperature of the heating roll 130 becomes a predetermined temperature of 180°C or more and 200°C or less.

[0078] [Pressure Roll 140] 3 is an example of a pressure member that pressurizes a recording medium between itself and the heating roll 130. Specifically, the pressure roll 140 has a function of pressing paper P by nipping the paper P between itself and the heating roll 130. The pressure roll 140 is disposed below the heating roll 130 with the front-rear direction of the apparatus as its axial direction.

[0079] The circumferential length of the pressure roll 140 is the same as the interval at which grippers 76, which are an example of a gripping portion, are arranged on the chain 72. As shown in Fig. 4, a recessed portion 148 extending in the front-rear direction of the device is formed on the outer circumferential surface of the pressure roll 140. The gripper 76, which holds the front end side of the paper P, is configured to enter the recessed portion 148 when passing between the pressure roll 140 and the heating roll 130. The pressure roll 140 is an example of a pressure cylinder with the recessed portion 148 formed on the surface side.

[0080] The pressure roll 140 includes a cylindrical substrate 142 and a jacket 144 attached to the outer periphery of the substrate 142 .

[0081] 4, in the first embodiment, a recess 148 is formed on the surface of the substrate 142, and the jacket 144 is attached to the surface of the substrate 142 excluding the recess 148. Although not shown, support pieces extend from both ends of the jacket 144 in the width direction (i.e., both ends in the front-rear direction of the device). The support pieces of the jacket 144 are brought into contact with both ends of the substrate 142 in the axial direction, and the support pieces are fixed to the substrate 142 by fixtures, whereby the jacket 144 is attached to the substrate 142. As an example, the substrate 142 is made of metal.

[0082] Here, an example of double-sided printing in which an image is formed on the first side PA of the paper P and then an image is formed on the second side PB of the paper P will be described. In this example, the pressure roll 140 pressurizes the paper P between itself and the heating roll 130, fixing the toner image T2 (see FIG. 5(A)) held on the second side PB of the paper P, and also comes into contact with the toner image T1 (see FIG. 5(B)) fixed on the first side PA of the paper P. Specifically, the toner image T1 fixed on the first side PA of the paper P comes into contact with the jacket 144 of the pressure roll 140.

[0083] 5(B), the surface of the jacket 144 is formed with an uneven portion 146 having a shape with a plurality of projections and recesses. Specifically, the uneven portion 146 has a plurality of recesses 146A and a plurality of projections 146B. The difference in height between the projections and recesses of the uneven portion 146 (i.e., the peak-to-peak value of the projections and recesses) H1 is set to be equal to or greater than the height H3 of the toner layer in the solid toner image T3 fixed on the first surface PA of the paper P. Here, the solid toner image T3 is a toner image in which the toner concentration in the fixed image on the paper P is 100%.

[0084] 6, the jacket 144 is, for example, configured with a woven member 203 as an example of a woven portion into which the fibers 202 are woven. As a result, the uneven shape portion 146 is formed by the surface of the woven member 203 into which the fibers 202 are woven. For example, the fibers 202 are glass fibers. For example, the glass fibers are glass fibers impregnated with a release agent.

[0085] The jacket 144 may be made of, for example, a member in which the fibers 202 are woven, and the uneven portion 146 may be formed of a woven portion in which the fibers 202 are woven.

[0086] 8 shows the results of measuring the surface roughness of the uneven portion 146 on the surface of the jacket 144. The surface roughness of the uneven portion 146 is a value measured by a surface roughness measuring device (Surfcom, manufactured by Tokyo Seimitsu Co., Ltd.) described later.

[0087] 8, the pitch P1 of the weave of the jacket 144 (i.e., the pitch of the convex portions 146B) is preferably 0.8 mm or less, more preferably 0.7 mm or less, and even more preferably 0.6 mm or less. The pitch P1 of the weave of the jacket 144 is equal to the pitch of the convex portions 146B of the uneven portion 146 of the jacket 144. If the pitch P1 of the weave of the jacket 144 is greater than 0.8 mm, uneven melting of the toner image T1 on the first surface PA of the paper P is likely to occur. Also, if the pitch P1 of the weave of the jacket 144 is greater than 0.8 mm, deformation of the paper P is likely to occur when the paper P is a coated paper with a basis weight of 64 gsm.

[0088] As shown in FIG. 8, the peak-to-peak value of the unevenness of uneven portion 146, that is, the difference H1 in height between the unevennesses, is preferably 8 μm to 20 μm, more preferably 9 μm to 18 μm, and even more preferably 10 μm to 16 μm.

[0089] Here, the peak-to-peak value of the unevenness of the uneven portion 146, i.e., the height difference H1 between the unevenness, can be expressed by the maximum height roughness Rz. In other words, the maximum height roughness Rz is the surface roughness corresponding to the height difference H1 between the unevenness. The maximum height roughness Rz is measured as follows. The outer peripheral surface of the pressure roll is scanned in the axial direction from one edge to a position 5 mm toward the center in the axial direction to measure the surface shape (roughness curve). The axial scanning is performed every 10° in the circumferential direction, a total of 36 times. The measurement is performed using a surface roughness measuring instrument (Surfcom, manufactured by Tokyo Seimitsu) under conditions of a measurement length of 2.5 mm, a cutoff wavelength of 0.8 mm, and a measurement speed of 0.60 mm / s. The maximum height roughness Rz is calculated based on the roughness curve obtained by the above scanning. The maximum height roughness Rz is calculated by finding the "sum of the maximum peak height and the maximum valley depth" from the roughness curve above. In other words, if the highest point within the reference length is the maximum peak height Zp and the lowest point is the maximum valley depth Zv, the difference between them is the maximum height roughness Rz (= Zp-Zv).

[0090] The upper limit of the height difference H1 between the projections and recesses of the uneven portion 146 (i.e., the maximum height roughness Rz corresponding to the height difference H1 between the projections and recesses) of 20 μm is a value stipulated by the height of the fixed image. If the height difference H1 between the projections and recesses of the uneven portion 146 is greater than 20 μm, deformation of the paper P is likely to occur. For example, if the height difference H1 between the projections and recesses of the uneven portion 146 is greater than 20 μm, deformation of the paper P occurs when coated paper having a basis weight of 64 gsm is used as the paper P.

[0091] The arithmetic mean waviness Wa of the uneven portion 146 is preferably 2 μm to 5 μm, more preferably 2.5 μm to 4.5 μm, and even more preferably 3 μm to 4 μm. When the paper P is a thin film with a thickness of 100 μm, if the arithmetic mean waviness Wa of the uneven portion 146 is greater than 5 μm, the change in shape of the paper P becomes noticeable. The arithmetic mean waviness Wa is obtained by extracting a portion of a roughness curve measured with a surface roughness measuring device (described later) over a reference length and expressing the uneven state of that section as an average value.

[0092] Here, the arithmetic mean waviness Wa is the average of the absolute values ​​of the height of the waviness curve over a reference length as defined in JIS B0601 (2013), and is a value measured using a surface roughness measuring instrument (Surfcom, manufactured by Tokyo Seimitsu Co., Ltd.).

[0093] The arithmetic mean waviness Wa is measured as follows. The outer peripheral surface of the pressure roll is scanned from one end to the other end in the axial direction to measure the surface shape (cross-sectional curve). Note that scanning in the axial direction is performed every 10° in the circumferential direction, a total of 36 times. The measurement is performed using a surface roughness measuring device (Surfcom, manufactured by Tokyo Seimitsu) under the conditions of measurement length: 4 mm, cutoff wavelength λc: 0.8 mm, and measurement speed: 0.60 mm / s. The arithmetic mean waviness Wa is calculated based on the measured profile curve obtained by the above scanning.

[0094] 9, the waviness curve 404 is obtained by removing short wavelength shapes from the measured profile curve 402 measured by a surface roughness measuring device (SURFCOM, manufactured by Tokyo Seimitsu Co., Ltd.), and the extent to which short wavelengths are removed is determined by the cutoff wavelength λc. For example, if λc is 0.8 mm, shapes with wavelengths shorter than 0.8 mm are ignored.

[0095] As described above, the jacket 144 is attached to the surface of the base material 142 excluding the recessed portion 148 , and the uneven portion 146 is provided on the surface of the pressure roll 140 excluding the recessed portion 148 .

[0096] In the fixing unit 120, the pressure roll 140 is rotated by a drive unit (not shown), the heating roll 130 rotates following the pressure roll 140, and the driven roll 150 rotates following the heating roll 130.

[0097] (Cooling section 90) 1, the cooling section 90 is disposed downstream of the fixing unit 120 in the transport direction of the paper P. The cooling section 90 also includes a plurality of (for example, two) cooling rolls 92 arranged in the device width direction.

[0098] The cooling roll 92 is configured as a cylindrical roll made of metal etc. The cooling roll 92 is configured to cool the paper P by air cooling (heat exchange with the air) by circulating air inside the cooling roll 92.

[0099] (Operation of image forming device) Next, the operation of the image forming apparatus 10 will be described.

[0100] 1, the paper P is conveyed by a plurality of conveying rolls 64 and handed over to the chain gripper 66. The paper P handed over to the chain gripper 66 is conveyed by the chain gripper 66 to the secondary transfer position NT with the front end held by the gripper 76, and the toner image is transferred from the transfer belt 31 to the first surface PA. The paper P to which the toner image has been transferred is conveyed by the chain gripper 66 with the first surface PA facing the heater 106 of the heating unit 102, as shown in FIG. 3, and the toner image is heated.

[0101] The paper sheet P on which the toner image has been heated in the heating section 102 is further transported by the chain gripper 66 to the fixing unit 120, where it is pressed and heated while being sandwiched between the heating roll 130 and the pressure roll 140. This causes the toner image to be fixed onto the first surface PA of the paper sheet P. When an image is formed only on the first surface PA of the paper sheet P, the paper sheet P on which the toner image has been fixed is cooled by the cooling roll 92 of the cooling section 90, and then discharged to the discharge section 52.

[0102] When forming images on both sides of the paper P (i.e., double-sided printing), the paper P with the images fixed on the first side PA is reversed between the first side PA and the second side PB by a reversing mechanism 80 shown in Fig. 1, and then handed over to the chain gripper 66 again. The paper P handed over to the chain gripper 66 is transported to the secondary transfer position NT as the paper P having the fixed toner image (image) T1 on the first side PA, and the toner image T2 is transferred from the transfer belt 31 to the second side PB (see Fig. 5(A)). The chain gripper 66 transports the paper P with the toner image T1 fixed on the first side PA by heat and pressure and the unfixed toner image T2 transferred (i.e., held) on the second side PB to the fixing device 100.

[0103] As described above, the paper P with the toner image T2 transferred to its second surface PB is heated in the heating section 102, and then sandwiched between the heating roll 130 and the pressure roll 140 and pressurized and heated, so that the toner image T2 is fixed to the paper P. At this time, in the heating section 102, the blower 160 blows air toward the first surface PA of the paper P transported by the chain gripper 66, thereby maintaining the blower 160 in a non-contact state so that the paper P is transported without contacting the first surface PA of the paper P.

[0104] The paper P on which the toner image T2 has been fixed is cooled by a cooling roll 92 in a cooling section 90, and then discharged to a discharge section 52.

[0105] (Fixing device of comparative example) Next, before specifically describing the operation of the first embodiment, a fixing device of a comparative example will be described.

[0106] Fig. 7 is an enlarged cross-sectional view showing a fixing roll 502 used in a fixing device of a comparative example. As shown in Fig. 7, the fixing roll 502 includes a base material 504 and a jacket 506 attached to the outer periphery of the base material 504. The jacket 506 is attached to the base material 504 by a mounting fixture (not shown).

[0107] The jacket 506 includes a woven portion 510 in which the fibers 202 are woven, resin layers 512 formed on both sides of the woven portion 510 in the thickness direction, and a coating layer 514 that coats the surface of the resin layer 512. The resin layer 512 is made of, for example, a fluororesin. The coating layer 514 is formed by coating the surface of the resin layer 512 with a film having releasability, such as polytetrafluoroethylene.

[0108] The surface of the covering layer 514 in the jacket 506 is smoother than the surface of the woven portion 510. Fig. 8 shows the measurement results of the surface roughness of the jacket 506. As shown in Fig. 8, the difference in height between the projections and recesses of the covering layer 514 in the jacket 506 (i.e., the peak-to-peak value) is, for example, 3.5 µm or less. The other configurations of the fixing device of the comparative example are similar to those of the fixing device 100 of the first embodiment.

[0109] In the fixing device of the comparative example, in double-sided printing, the toner image T1 on the first surface PA of the paper P is fixed by heating and pressurization, and then the toner image T2 on the second surface PB of the paper P is fixed. When the toner image T2 on the second surface PB of the paper P is fixed, the toner image T1 on the first surface PA of the paper P is heated to a high temperature by the heating section 102 (see FIG. 1) and melts slightly. Furthermore, in the fixing unit 120 (see FIG. 1) downstream of the heating section 102 in the conveying direction, when the toner image T2 on the second surface PB of the paper P is fixed, the toner image T1 on the first surface PA of the paper P comes into contact with the fixing roll 502. When the paper P passes between the fixing roll 502 and the heating roll 130 (see FIG. 1) in this state, the toner image T1 on the first surface PA of the paper P is likely to melt and become uneven. For this reason, the toner on the first surface PA of the paper P may melt, resulting in uneven gloss of the image. Here, the gloss unevenness of an image caused by melting of toner on the first side PA of the paper P refers to the gloss unevenness between the first side PA and the second side PB of a single sheet of paper P. Gloss means luster.

[0110] (Operation of the first embodiment) Next, the operation of the first embodiment will be described.

[0111] 5(A), in double-sided printing, the fixing device 100 fixes a toner image T1 on a first surface PA of a sheet P by applying heat and pressure, and then fixes a toner image T2 on a second surface PB of the sheet P. The fixing device 100 conveys the sheet P on which a toner image has been fixed on its first surface PA by applying heat and pressure using a chain gripper 66 and on which an unfixed toner image is held on its second surface PB.

[0112] In the fixing device 100, the heating roll 130 heats the toner image T2 held on the second surface PB of the paper P in a contact state. Furthermore, the paper P is pressed between the heating roll 130 and the pressure roll 140 to fix the toner image T2 held on the second surface PB of the paper P. At this time, the pressure roll 140 comes into contact with the toner image T1 fixed on the first surface PA of the paper P, and passes between the heating roll 130 and the pressure roll 140.

[0113] In the fixing device 100, an uneven portion 146 having a shape with a plurality of projections and recesses is provided on the surface of the pressure roll 140. A difference H1 in height between the projections and recesses in the uneven portion 146 is set to be equal to or greater than a height H3 of the toner layer in the solid toner image T3 fixed on the first surface PA of the paper P.

[0114] As a result, even if the toner image T1 on the first surface PA of the paper P comes into contact with the pressure roll 140, the thermal conductivity can be reduced by reducing the contact area between the toner image T1 on the first surface PA of the paper P and the pressure roll 140. This prevents the toner image T1 on the first surface PA of the paper P from melting.

[0115] Therefore, in the fixing device 100, when fixing the toner image T1 on the first surface PA of the paper P and then fixing the toner image T2 on the second surface PB of the paper P, uneven gloss of the image caused by melting of the toner on the first surface PA of the paper P can be suppressed compared to when the surface of the pressure roll is smooth.

[0116] Furthermore, in the fixing device 100, a heating section 102 that heats the toner image on the second surface PB of the paper P in a non-contact state is provided upstream of the heating roll 130 in the transport direction of the paper P. Furthermore, in the fixing device 100, a chain gripper 66 that transports the paper P between the heating roll 130 and the pressure roll 140 while the second surface PB of the paper P faces the heating section 102 is provided. Therefore, in the fixing device 100, even in the configuration in which the toner image T2 on the second surface PB of the paper P is heated in a non-contact state upstream of the heating roll 130, it is possible to suppress uneven gloss of the image due to melting of the toner on the first surface PA of the paper P.

[0117] In the fixing device 100, the maximum height roughness Rz corresponding to the height difference H1 between the convex and concave portions of the concave and convex portion 146 in the pressure roll 140 is 8 μm or more and 20 μm or less. Therefore, in the fixing device 100, gloss unevenness of the image caused by melting of the toner on the first surface PA of the paper P can be suppressed compared to when the maximum height roughness Rz corresponding to the height difference H1 between the convex and concave portions is smaller than 8 μm. Also, deformation of the paper P can be suppressed compared to when the maximum height roughness Rz corresponding to the height difference H1 between the convex and concave portions of the concave and convex portion is larger than 20 μm.

[0118] In addition, in the fixing device 100, the arithmetic mean waviness Wa of the uneven portion 146 of the pressure roll 140 is 2 μm or more and 5 μm or less. Therefore, in the fixing device 100, it is possible to suppress uneven gloss of the image caused by melting of the toner on the first surface PA of the paper P, compared to when the arithmetic mean waviness Wa of the uneven portion 146 is smaller than 2 μm. Also, it is possible to suppress deformation of the paper P, compared to when the arithmetic mean waviness Wa of the uneven portion 146 is larger than 5 μm.

[0119] Furthermore, in the fixing device 100, the uneven portion 146 is formed by a woven member 203 into which fibers 202 are woven, and the pressure roll 140 has the woven member 203 attached to the peripheral surface of the metal substrate 142. Therefore, in the fixing device 100, it is easier to set the height difference H1 between the unevenness of the uneven portion 146 as desired, compared to a case in which the uneven portion is directly formed on the surface of the pressure roll.

[0120] In addition, in the fixing device 100, the fibers 202 are glass fibers. Therefore, in the fixing device 100, the toner on the first surface PA of the paper P is less likely to adhere to the pressure roll 140 compared to when the fibers are made of resin.

[0121] In addition, in the fixing device 100, the glass fibers are glass fibers impregnated with a release agent. Therefore, in the fixing device 100, the toner on the first surface PA of the paper P is less likely to adhere to the pressure roll 140 compared to a case where glass fibers not impregnated with resin are woven.

[0122] Furthermore, in the fixing device 100, the pressure roll 140 is a pressure cylinder having a recess 148 formed on the surface side into which the gripper 76 that grips the leading end of the paper P enters, and an uneven portion 146 is provided on the surface of the pressure cylinder excluding the recess 148. Therefore, in the fixing device 100, even when the pressure roll 140 is a pressure cylinder having a recess 148 formed therein into which the gripper 76 that grips the leading end of the paper P enters, it is possible to suppress uneven gloss of the image caused by melting of the toner on the first side PA of the paper P.

[0123] The image forming apparatus 10 also includes an image forming section 12 that forms a toner image on the paper P, and a fixing device 100 that fixes the toner image T1 formed on the first side PA of the paper P by the image forming section 12 to the paper P, and fixes the toner image formed on the second side PB of the paper P by the image forming section 12 to the paper P. The image forming apparatus 10 also includes a reversing mechanism that reverses the paper P from the first side PA to the second side PB after the toner image T1 is fixed on the first side PA of the paper P by the fixing device 100. Therefore, in the image forming apparatus 10, when fixing the toner image T2 on the second side PB of the paper P after fixing the toner image T1 on the first side PA of the paper P, gloss unevenness of the image caused by melting of the toner on the first side PA of the paper P can be suppressed compared to the case where the surface of the pressure roll is smooth.

[0124] <First Modification> In the fixing device 100 of the first embodiment, the pressure roll 140 has the jacket 144 attached to the surface of the base material 142, but the present disclosure is not limited to this configuration.

[0125] Although not shown in the drawings, the fixing device of the first modified example may be configured so that the uneven portion 146 is formed by directly processing the surface of the pressure roll. For example, the surface of the pressure roll may be configured with a resin layer, and the uneven portion 146 may be formed by directly processing the surface of the resin layer. In this configuration, it is possible to reduce the cost of materials compared to the case where a covering member is attached to the peripheral surface of the base material of the pressure roll.

[0126] <Second Modification> The image forming apparatus 10 of the first embodiment is provided with an inversion mechanism 80 that inverts the paper P from the first side PA to the second side PB after the toner image T1 is fixed to the first side PA of the paper P by the fixing device 100, but the present disclosure is not limited to this configuration.

[0127] The image forming apparatus of the second modified example may be configured without the reversing mechanism 80 shown in Fig. 1. Specifically, the image forming apparatus includes an image forming unit 12 that forms a toner image on paper P, and a fixing device 100 that fixes the toner image formed by the image forming unit 12 onto paper P, and does not include a reversing mechanism that reverses paper P.

[0128] In this image forming apparatus, after the toner image T1 is fixed to the first surface PA of the paper P by the fixing device 100, the paper P is discharged to the discharge section. As a result, the paper P is stacked vertically in the discharge section with the first surface PA of the paper P facing upward. After that, the stacked paper P is turned upside down by an external inversion device (not shown) or manually, so that the paper P is stacked so that the second surface PB is on the upper side. Then, in the image forming apparatus, the paper P with the second surface PB facing upward is stored in the storage section 50, a toner image T2 is formed on the second surface PB of the paper P, and the toner image T2 on the second surface PB of the paper P is fixed by the fixing device 100.

[0129] In the image forming apparatus of the second variant, when the toner image T1 on the first surface PA of the paper P is fixed and then the toner image T2 on the second surface PB of the paper P is fixed, uneven gloss of the image caused by melting of the toner on the first surface PA of the paper P can be suppressed compared to when the surface of the pressure roll is smooth.

[0130] <Other Modifications> In the above embodiment, paper P is used as an example of a recording medium, but this is not limited to this. An example of a recording medium may be, for example, a film, and an example of a recording medium may be a sheet material formed into a sheet shape (paper shape, film shape) other than paper P.

[0131] In the above embodiment, the chain gripper 66 as an example of a transport section transports the paper P to the secondary transfer position NT, and then transports the paper P to the fixing unit 120 after passing through the heating section 102, but this is not limited to the above. Another example of the transport section may be a transport section such as a chain gripper to which the paper P that has passed through the secondary transfer position NT is handed over, and the paper P is transported to the fixing unit 120 after passing through the heating section 102. In this case, the paper P is transported to the secondary transfer position NT by another transport section (for example, transport rolls).

[0132] In the above embodiment, the jacket 144 is formed of the woven member 203 into which the fibers 202 are woven, but the present disclosure is not limited to this configuration. For example, a resin sheet on which the uneven portion 146 is formed may be attached to a base material. In addition, when using the woven member 203 in which the fibers 202 are woven, the fibers 202 may be made of a resin other than glass fiber. For example, a woven portion in which fibers made of fluororesin having releasability are woven may be used.

[0133] Although the present disclosure has been described in detail with respect to a specific embodiment, the present disclosure is not limited to such embodiment, and it will be apparent to those skilled in the art that various other embodiments are possible within the scope of the present disclosure.

[0134] <Preferred aspects of the present disclosure> Preferred aspects of the present disclosure will be described below.

[0135] (((1))) a conveying section that conveys a recording medium having a toner image fixed on a first surface thereof by application of heat and pressure and an unfixed toner image held on a second surface thereof; a heating member that heats, in contact with the toner image held on the second surface of the recording medium transported by the transport unit; a pressure member that presses the recording medium between the heating member and the recording medium to fix the toner image held on the second surface of the recording medium and that comes into contact with the toner image fixed on the first surface of the recording medium; a concave-convex portion provided on a surface of the pressing member, the concave-convex portion having a shape with a plurality of concaves and convexes, the height difference between the concaves and convexes being equal to or greater than the height of a toner layer in a solid toner image fixed on a first surface of the recording medium; A fixing device having the same.

[0136] (((2))) a non-contact heating unit that is provided upstream of the heating member in a conveying direction of the recording medium and that heats the toner image on the second surface of the recording medium in a non-contact state; The fixing device according to (((1))), wherein the transport section transports the recording medium between the heating member and the pressure member while the second surface of the recording medium faces the non-contact heating section.

[0137] (((3))) The fixing device according to ((1))) or (((2))), wherein a maximum height roughness Rz corresponding to a difference in height of the concaves and convexes is 8 μm or more and 20 μm or less.

[0138] (((4))) The fixing device according to any one of ((1))) to (((3))), wherein the arithmetic mean waviness Wa of the uneven portion is 2 μm or more and 5 μm or less.

[0139] (((5))) The uneven portion is formed by a woven portion in which fibers are woven, The fixing device according to any one of ((1))) to (((4))), wherein the pressure member has the woven portion attached to a peripheral surface of a metal base material.

[0140] (((6))) The fixing device according to (((5))), wherein the fibers are glass fibers.

[0141] (((7))) The fixing device according to (((6))), wherein the glass fibers are glass fibers impregnated with a release agent.

[0142] (((8))) The fixing device according to any one of ((1))) to (((4))), wherein the uneven portion is formed by directly processing a surface of the pressure member.

[0143] (((9))) the pressure member is a pressure cylinder having a concave portion formed on a surface side thereof into which a gripping portion that grips a front end side of the recording medium is inserted, The fixing device according to any one of ((1)) to ((8)) above, wherein the uneven portion is provided on a surface of the pressure cylinder excluding the concave portion.

[0144] (((10))) an image forming unit that forms a toner image on a recording medium; a fixing device according to any one of ((1)) to ((9)) above, which fixes a toner image formed by the image forming unit onto the recording medium; An image forming system comprising:

[0145] (((11))) an image forming unit that forms a toner image on a recording medium; a fixing device according to any one of ((1))) to (((9))) that fixes a toner image formed on a first surface of the recording medium by the image forming unit onto the recording medium and fixes a toner image formed on a second surface of the recording medium by the image forming unit onto the recording medium; a reversing mechanism that reverses the recording medium from the first surface to a second surface after the toner image is fixed to the first surface of the recording medium by the fixing device; An image forming system comprising:

[0146] According to the fixing device described in (((1))), when a toner image on a first surface of a recording medium is fixed and then a toner image on a second surface of the recording medium is fixed, uneven gloss of the image caused by melting of the toner on the first surface of the recording medium can be suppressed compared to when the surface of the pressure member is smooth.

[0147] According to the fixing device described in (((2))), even in a configuration in which the toner image on the second surface of the recording medium is heated in a non-contact manner upstream of the heating member, uneven gloss of the image caused by melting of the toner on the first surface of the recording medium can be suppressed.

[0148] According to the fixing device described in (((3))), gloss unevenness of the image caused by melting of the toner on the first surface of the recording medium can be suppressed, compared to when the maximum height roughness Rz corresponding to the difference in height of the concaves and convexes is less than 8 μm. Also, deformation of the recording medium is suppressed, compared to when the maximum height roughness Rz corresponding to the difference in height of the concaves and convexes is more than 20 μm.

[0149] According to the fixing device described in (((4))), gloss unevenness of an image caused by melting of toner on the first surface of a recording medium can be suppressed compared to when the arithmetic mean waviness Wa of the uneven portion is smaller than 2 μm. Also, deformation of the recording medium is suppressed compared to when the arithmetic mean waviness Wa of the uneven portion is larger than 5 μm.

[0150] According to the fixing device described in (((5))), it is easier to set the height difference between the projections and recesses as desired, compared to a case in which the projections and recesses are directly formed on the surface of the pressure member.

[0151] According to the fixing device described in (((6))), the toner on the first surface of the recording medium is less likely to adhere to the pressure member, compared to when the fibers are made of resin.

[0152] According to the fixing device described in (((7))), the toner on the first surface of the recording medium is less likely to adhere to the pressure member, compared to when glass fibers that are not impregnated with resin are woven into the fixing device.

[0153] According to the fixing device described in (((8))), it is possible to reduce the cost of materials compared to a case in which a covering member is attached to the peripheral surface of the base material of the pressure member.

[0154] According to the fixing device described in (((9))), even when the pressure member is a pressure cylinder having a recessed portion into which the gripping portion that grips the front end side of the recording medium fits, uneven gloss of the image caused by melting of the toner on the first surface of the recording medium can be suppressed.

[0155] According to the image forming apparatus described in (((10))), when a toner image on a first surface of a recording medium is fixed and then a toner image on a second surface of the recording medium is fixed, uneven gloss of the image caused by melting of the toner on the first surface of the recording medium can be suppressed compared to when the surface of the pressure member is smooth.

[0156] According to the image forming apparatus described in (((11))), when a toner image on a first surface of a recording medium is fixed and then a toner image on a second surface of the recording medium is fixed, uneven gloss of the image caused by melting of the toner on the first surface of the recording medium can be suppressed compared to when the surface of the pressure member is smooth. [Explanation of symbols]

[0157] 10 Image forming device (an example of an image forming system) 12 Image forming unit (an example of an image forming unit) 66 Chain gripper (an example of a conveying unit) 76 Gripper (an example of a gripping part) 80 Reversal mechanism 100 Fixing device 102 Heating section (an example of a non-contact heating section) 130 Heating roll (an example of a heating member) 140 Pressure roll (an example of a pressure member) 142 Base material 144 Jacket 146 Uneven shape part 146A Concave (an example of concave and convex) 146B Convex part (example of concave and convex part) 148 Concave part 202 Textiles 203 Woven material (an example of a woven part) H1 Height difference between the bumps P Paper (an example of a recording medium) PA front page PB second side T1 Toner Image T2 Toner image T3 solid toner image

Claims

1. a conveying section that conveys a recording medium having a toner image fixed on a first surface thereof by application of heat and pressure and an unfixed toner image held on a second surface thereof; a heating member that heats, in contact with the toner image held on the second surface of the recording medium transported by the transport unit; a pressure member that presses the recording medium between the heating member and the recording medium to fix the toner image held on the second surface of the recording medium and that comes into contact with the toner image fixed on the first surface of the recording medium; a concave-convex portion provided on a surface of the pressing member, the concave-convex portion having a shape with a plurality of concaves and convexes, the height difference between the concaves and convexes being equal to or greater than the height of a toner layer in a solid toner image fixed on a first surface of the recording medium; A fixing device having the same.

2. a non-contact heating unit that is provided upstream of the heating member in a conveying direction of the recording medium and that heats the toner image on the second surface of the recording medium in a non-contact state; The fixing device according to claim 1 , wherein the transport section transports the recording medium between the heating member and the pressure member while the second surface of the recording medium faces the non-contact heating section.

3. 2. The fixing device according to claim 1, wherein a maximum height roughness Rz corresponding to a difference in height of the projections and recesses is 8 [mu]m or more and 20 [mu]m or less.

4. 4. The fixing device according to claim 3, wherein the arithmetic mean waviness Wa of the uneven portion is 2 [mu]m or more and 5 [mu]m or less.

5. The uneven portion is formed by a woven portion in which fibers are woven, The fixing device according to claim 1 , wherein the pressure member has the woven portion attached to a peripheral surface of a metal base material.

6. 6. The fixing device according to claim 5, wherein the fibers are glass fibers.

7. 7. The fixing device according to claim 6, wherein the glass fibers are glass fibers impregnated with a release agent.

8. The fixing device according to claim 1 , wherein the uneven portion is formed by directly processing a surface of the pressure member.

9. the pressure member is a pressure cylinder having a concave portion formed on a surface side thereof into which a gripping portion that grips a front end side of the recording medium is inserted, The fixing device according to claim 1 , wherein the uneven portion is provided on a surface of the pressure cylinder excluding the concave portion.

10. an image forming unit that forms a toner image on a recording medium; a fixing device according to claim 1 , which fixes a toner image formed by the image forming unit onto the recording medium; An image forming system comprising:

11. an image forming unit that forms a toner image on a recording medium; a fixing device according to any one of claims 1 to 9, which fixes a toner image formed on a first surface of the recording medium by the image forming unit onto the recording medium, and fixes a toner image formed on a second surface of the recording medium by the image forming unit onto the recording medium; a reversing mechanism that reverses the recording medium from the first surface to a second surface after the toner image is fixed to the first surface of the recording medium by the fixing device; An image forming system comprising:

Images