Fixing device and image forming apparatus

Abstract

To suppress influence of image fixation to a recording medium as compared with a case where a distance from a fixing member is different at each end of a rotary member by transmitting rotary driving force to the rotary member.SOLUTION: A fixing device 14 includes: a fixing member 53 which is used for fixing of an image on a recording medium; a rotary member 61 which is pressed on the fixing member, is rotatably provided and forms a pressurization section N by which the recording member is pressurized between the rotary member and the fixing member 53; rotation means which rotates the rotary member 61 by inputting driving force at a position deviated from a shaft core of the rotary member 61; and energization means 83, 84 which energize at least one end of the rotary member 61 in a direction approaching or separating from the fixing member 53.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] For example, Patent Document 1 discloses a fixing device having an endless fixing rotor that heats toner as it rotates and fixes it onto a recording medium, a pressure rotor that sandwiches and pressurizes the toner and recording medium between the fixing rotor, and a support portion that supports the fixing rotor from the inside at a contact portion where the fixing rotor and the pressure rotor come into contact with each other so that the peak pressure on the outlet side of the recording medium is equal to or lower than the peak pressure on the inlet side. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-44257 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, consider a case where a rotating member is pressed against a fixing member used for fixing an image on a recording medium, forming a pressure section between the fixing member and the recording medium where pressure is applied to the recording medium, and the rotating member is rotated by inputting a driving force to a position off the axis. If the distance between each end of the rotating member and the fixing member differs, this affects the fixing of the image on the recording medium. An object of the present invention is to suppress the effect of image fixing on a recording medium, compared to a case in which the distance to the fixing member is different at each end of the rotating member due to a rotational driving force being transmitted to the rotating member. [Means for solving the problem]

[0005] The invention described in claim 1 is a fixing device comprising: a fixing member used to fix an image on a recording medium; a rotating member that is pressed against the fixing member and rotatably arranged, forming a pressure section between the fixing member and the rotating member where pressure is applied to the recording medium; a rotating means that inputs a driving force to a position off the axis of the rotating member to rotate the rotating member; and a biasing means that biases at least one end of the rotating member in a direction toward or away from the fixing member. A second aspect of the present invention is the fixing device according to the first aspect, wherein the biasing means includes a cam member. The invention described in claim 3 is the fixing device described in claim 2, characterized in that the cam member includes one cam member provided at the one end and another cam member provided at the other end opposite the one end, and the urging means is capable of rotating either the one cam member or the other cam member or rotating both. The invention described in claim 4 is the fixing device described in claim 3, characterized in that the one cam member and the other cam member have parts whose contours set relative to the center of rotation of the cams are different from each other. The invention described in claim 5 is the fixing device described in claim 4, characterized in that the one cam member and the other cam member have a common portion in their contours set with respect to the center of rotation. The invention recited in claim 6 is the fixing device recited in claim 3, characterized in that the one cam member and the other cam member are out of phase with each other. A seventh aspect of the present invention is the fixing device according to the first aspect, wherein the biasing means includes a spring member provided at the one end of the rotating member. An eighth aspect of the present invention provides the fixing device according to the first aspect, wherein the biasing means biases the rotating means based on a current value of a driving source that generates the driving force in the rotating means. The invention described in claim 9 is the fixing device described in claim 1, characterized in that the urging means applies urging based on information indicating a relationship between the driving force in the rotating means and the degree of the urging. The invention described in claim 10 is the fixing device described in claim 1, characterized in that a rotating annular member is provided between the fixing member and the rotating member, and the annular member rotates by the driving force of the rotating member. An eleventh aspect of the present invention is an image forming apparatus including the fixing device according to the first aspect. Effect of the Invention

[0006] According to the invention of claim 1, the influence of image fixing on the recording medium can be suppressed compared to a case where the distance from the fixing member to each end of the rotating member is different by transmitting a rotational driving force to the rotating member. According to the invention of claim 2, the biasing means can have a simpler configuration than when the biasing means does not include a configuration including a cam member. According to the invention of claim 3, the cam member includes one cam member provided at one end and another cam member provided at the other end opposite the one end, and the biasing means can simplify control compared to a case in which the biasing means is not configured to be capable of rotating either the one cam member or the other cam member or rotating both. According to the invention of claim 4, the range of correspondence between one cam member and another cam member can be expanded compared to a case in which the contours set relative to the center of rotation of the cam do not have different parts. According to the invention of claim 5, the formation of a pressure applying portion by the rotating member can be performed more smoothly than in a case where one cam member and another cam member do not have a configuration in which the contours set relative to the center of rotation have a common portion. According to the invention of claim 6, the range in which the one cam member and the other cam member can be accommodated can be expanded compared to a case in which the one cam member and the other cam member do not have a configuration in which the phases are different from each other. According to the seventh aspect of the invention, the biasing means can have a simpler configuration than when the biasing means does not include a configuration including a spring member provided at one end of the rotating member. According to the eighth aspect of the present invention, the biasing means can improve accuracy compared to a case where the biasing means does not include a configuration for biasing based on the current value of the drive source that generates the drive force in the rotating means. According to the invention of claim 9, the biasing means can simplify control compared to a case where the biasing means does not have a configuration for biasing based on information indicating the relationship between the driving force in the rotating means and the degree of biasing. According to the invention of claim 10, a rotating annular member is provided between the fixing member and the rotating member, and the annular member can rotate more stably than when the annular member is not configured to rotate by the driving force of the rotating member. According to the invention of claim 11, by transmitting a rotational driving force to the rotating member, the effect of image fixing on the recording medium can be suppressed compared to a case where the distance from the fixing member to each end of the rotating member is different. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating a configuration of a fixing unit according to the present embodiment. [Diagram 3] 2A and 2B are diagrams illustrating a moving mechanism and a drive transmission section included in the fixing unit. [Figure 4] FIG. 2 is a diagram illustrating a fixing unit according to the first embodiment. [Diagram 5] 1 is a graph showing the nip load at one end and the other end of the pressure roll, with the vertical axis representing the nip load, where (a) shows the state before a rotational driving force is input from the drive transmission unit to the pressure roll, (b) shows the state after the rotational driving force is input, and (c) shows the state after adjustment using a spring member. [Figure 6] 4 is a graph showing the relationship between the driving force of a motor and the nip load, in which the vertical axis indicates the nip load fluctuation on one end side of the pressure roll, and the horizontal axis indicates the driving torque. [Figure 7] FIG. 11 is a diagram illustrating a fixing unit according to a second embodiment. [Figure 8] 13A to 13C are diagrams illustrating a cam member used in a fixing unit according to a third embodiment. [Figure 9] 13A to 13C are diagrams illustrating a cam member used in a fixing unit according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing an image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 shown in the figure is an apparatus that forms an image on a sheet of paper P. The image forming apparatus 1 is provided with an image forming section 10, a sheet transport section 20, and a control section 40.

[0009] The image forming section 10 includes an image forming unit 11, an intermediate transfer belt 12, a secondary transfer section 13, and a fixing device 14. In this embodiment, the image forming units 11 include four image forming units 11Y, 11M, 11C, and 11K corresponding to toner of four colors, Y (yellow), M (magenta), C (cyan), and K (black), respectively.

[0010] The image forming units 11Y, 11M, 11C, and 11K are arranged side by side in the moving direction of the intermediate transfer belt 12, and form toner images by electrophotography. Each of the image forming units 11Y, 11M, 11C, and 11K includes a photoconductor drum 111, a charging unit 112, an exposure unit 113, a developing unit 114, and a primary transfer unit 115. Each of the image forming units 11Y, 11M, 11C, and 11K forms a toner image of any one of the colors YMCK, and transfers this toner image onto the intermediate transfer belt 12. As a result, a toner image in which the toner images of the respective colors YMCK are superimposed is formed on the intermediate transfer belt 12.

[0011] The photoconductor drum 111 rotates at a predetermined speed in the direction of the arrow A. Furthermore, an electrostatic latent image is formed on the circumferential surface of the photoconductor drum 111. The charging unit 112 charges the peripheral surface of the photoconductor drum 111 to a predetermined potential. The exposure unit 113 irradiates the charged peripheral surface of the photoconductor drum 111 with light, forming an electrostatic latent image on the peripheral surface of the photoconductor drum 111 . The developing unit 114 deposits toner onto the electrostatic latent image formed on the circumferential surface of the photoconductor drum 111 to form a toner image.

[0012] The primary transfer unit 115 transfers the toner image formed on the circumferential surface of the photosensitive drum 111 onto the intermediate transfer belt 12 . A voltage of a polarity opposite to the charge polarity of the toner is applied to the primary transfer unit 115. As a result, the toner images formed on the circumferential surface of the photoconductor drum 111 are electrostatically attracted in sequence onto the intermediate transfer belt 12, and a single overlapping color toner image is formed on the intermediate transfer belt 12.

[0013] The intermediate transfer belt 12 is supported by a plurality of roll-shaped members. The intermediate transfer belt 12 is formed in an endless shape and circulates in the direction of the arrow B. The intermediate transfer belt 12 has an outer circumferential surface 12a and an inner circumferential surface 12b. The intermediate transfer belt 12 is used to transport a toner image. In this embodiment, a toner image is formed on an outer peripheral surface 12a of the intermediate transfer belt 12, and this toner image is transported to a secondary transfer unit 13 by the movement of the intermediate transfer belt 12.

[0014] In this embodiment, a drive roll 121 that is driven by a motor (not shown) and drives the intermediate transfer belt 12 is provided as a roll-shaped member disposed inside the intermediate transfer belt 12. In addition, an idle roll 123 that supports the intermediate transfer belt 12 and a backup roll 132 are provided as roll-shaped members. These roll-shaped members are rotatably provided and pressed against the inner circumferential surface 12 b of the intermediate transfer belt 12 .

[0015] The paper transport section 20 is provided with a paper storage section 21 in which a plurality of sheets of paper P are stored in a stacked state, and a pick-up roll 22 that picks up and transports the paper P stored in the paper storage section 21. The paper transport section 20 is also provided with a transport roll 23 that transports the paper P picked up by the pickup roll 22 along the paper transport path 30, and a paper guide section 24 that guides the paper P transported by the transport roll 23 to the secondary transfer section 13. Furthermore, the paper transport section 20 is provided with a transport belt 25 that transports the paper P after the secondary transfer to the fixing device 14, and a paper guide section 26 that guides the paper P after the fixing to a paper discharge section 27.

[0016] The secondary transfer section 13 is provided with a secondary transfer roll 134 arranged in contact with the outer peripheral surface 12a of the intermediate transfer belt 12, and a backup roll 132 arranged on the inner peripheral surface 12b side of the intermediate transfer belt 12 and serving as an opposing electrode to the secondary transfer roll 134. In this embodiment, a metallic power supply roll 133 that applies a secondary transfer bias to the backup roll 132 is provided. The secondary transfer unit 13 thus configured transfers the toner image, which has been conveyed to the secondary transfer unit 13 by the intermediate transfer belt 12, onto the paper P which has also been conveyed thereto.

[0017] The fixing unit 14 is disposed downstream of the secondary transfer unit 13 in the transport direction of the paper P. The fixing unit 14 includes a fixing belt module 50 having a heat source, and a pressure roll 61 disposed opposite the fixing belt module 50. When the paper P that has passed through the secondary transfer unit 13 is transported between the fixing belt module 50 and the pressure roll 61, the unfixed toner image on the paper P is melted and then fixed onto the paper P. As a result, an image made of the toner image is formed on the paper P.

[0018] FIG. 2 is a diagram illustrating the configuration of the fixing unit 14 according to the present embodiment. As shown in the figure, the fixing device 14 according to the present embodiment includes the above-mentioned fixing belt module 50 having the fixing belt 51, and the above-mentioned pressure roll 61 that contacts the outer surface of the fixing belt 51.

[0019] The fixing belt module 50 includes the above-mentioned fixing belt 51 that moves in a direction of the arrow C, and a first tension roll 52 that stretches the fixing belt 51 from the inside of the fixing belt 51. The fixing belt module 50 also includes a second tension roll 55 that stretches the fixing belt 51 from the inside, upstream of the first tension roll 52 in the direction of the arrow C. The fixing belt module 50 also includes a pressing unit 53 that is located downstream of the first tension roll 52 in the direction of the arrow C and has a pad portion 53a for pressing the fixing belt 51 against the pressure roll 61 to form a nip portion N.

[0020] In the fixing device 14, a part of the outer circumferential surface 61a of the pressure roll 61 is pressed against the outer circumferential surface 51a of the fixing belt 51, which is in contact with the pressing portion 53, from the side opposite to the pressing portion 53, thereby forming a nip portion N. The nip portion N, where the outer circumferential surface 61a of the pressure roll 61 and the fixing belt 51 are in contact with each other, is a passage portion through which the paper P on which the toner image is formed passes while being pressurized and heated.

[0021] The paper P that enters the nip portion N has a toner image forming surface on which a toner image is formed, but in this embodiment, the paper P enters the nip portion N with the toner image forming surface facing upward. As a result, in this embodiment, the toner image forming surface side of the paper P comes into contact with the fixing belt 51.

[0022] In the present embodiment, the pressure roll 61 is rotated by a motor 62, and the fixing belt 51 moves in a circular motion following the pressure roll 61. That is, the fixing belt 51 receives a driving force from the rotating pressure roll 61 and moves in a circular motion (circulation) in the direction of arrow C. More specifically, the rotational driving force of the motor 62 is transmitted to the pressure roll 61 via a drive transmission unit 90. The motor 62 is controlled by the control unit 40.

[0023] The first tension roll 52 and the second tension roll 55 are supported rotatably, and the fixing belt 51 is wound around them at positions spaced apart from each other, thereby supporting the fixing belt 51 so as to be capable of rotating. The pressing unit 53 is disposed at a position facing the pressure roll 61 with the fixing belt 51 sandwiched therebetween, and presses the fixing belt 51 against the pressure roll 61 without rotating. The pressure roll 61 has an elastically deformable layer on the outer circumferential surface side, and the pressing unit 53 comes into contact with the pressure roll 61 via the fixing belt 51, causing the pressure roll 61 to assume a recessed shape at the nip portion N. In this embodiment, the paper P is sandwiched from both sides by the pressure roll 61 and the pressing unit 53, and pressure is applied to the paper P.

[0024] A heater 52a is provided inside the first tension roll 52. A heater 55a is provided inside the second tension roll 55. These heaters 52a and 55a are, for example, halogen heaters. The first tension roll 52 is heated by the heat of the heater 52a, and the second tension roll 55 is heated by the heat of the heater 55a. The fixing belt 51 is heated by the heat from the first tension roll 52 and the second tension roll 55. 2, the fixing belt 51 is wound around the outer circumferential surface of the first tension roll 52 in a section that is about a quarter of the circumference, and the fixing belt 51 is wound around the outer circumferential surface 55b in a section that is about half or more of the circumference. This allows the amount of heat from the heaters 52a and 55a to be imparted to the fixing belt 51.

[0025] The fixing belt module 50 includes a liquid applicator 54 between the first tension roll 52 and the second tension roll 55, which applies oil to the inner surface of the fixing belt 51. The liquid applicator 54 includes an oil-impregnated member 541 that contacts the inner surface of the fixing belt 51, a housing 542 that holds the oil-impregnated member 541, and a support member 543 that supports a portion of the oil-impregnated member 541 including its tip from the side opposite the fixing belt 51.

[0026] The oil-impregnated member 541 is a nonwoven fabric made of heat-resistant fibers impregnated with oil. For example, PTFE (polytetrafluoroethylene) is used as the heat-resistant fiber. The oil applied to the inner circumferential surface 51b of the fixing belt 51 by the oil-impregnated member 541 reduces the coefficient of friction between the pressing portion 53 and the fixing belt 51, and suppresses wear of the fixing belt 51.

[0027] The fixing belt module 50 includes an upstream cleaning roll 71 as a component for cleaning the outer peripheral surface 51 a of the fixing belt 51 . The upstream cleaning roll 71 is a cleaning member for cleaning the outer peripheral surface 51a of the fixing belt 51, and more specifically, removes any attached matter or the like that has adhered to the outer peripheral surface 51a of the fixing belt 51 after passing through the nip portion N.

[0028] The upstream cleaning roll 71 is provided at a position upstream of the second tension roll 55 and at a position where the fixing belt 51 is sandwiched between the upstream cleaning roll 71 and the second tension roll 55. In other words, the upstream cleaning roll 71 is disposed so as to press a portion of the fixing belt 51 away from the second tension roll 55 at the entrance of the second tension roll 55 against the second tension roll 55.

[0029] The surface of the upstream cleaning roll 71 according to the present embodiment is formed of a nonwoven fabric, a felt material, or a porous material. The upstream cleaning roll 71 according to the present embodiment is a driven roll that rotates by contacting with the circulating fixing belt 51.

[0030] 2, the fixing belt 51 that has passed through the nip portion N is sandwiched between the upstream cleaning roll 71 and the second tension roll 55, and is deformed into a so-called S-shape. That is, the fixing belt 51 is deformed into a shape in which an inner peripheral surface side protrusion 51c that is protruding toward the inner peripheral surface 51b of the fixing belt 51 along the upstream cleaning roll 71 and an outer peripheral surface side protrusion 51d that is protruding toward the outer peripheral surface 51a of the fixing belt 51 along the second tension roll 55 are continuous. The inner peripheral surface convex portion 51 c is a deformation caused by the pressure of the upstream cleaning roll 71 at the entrance portion of the fixing belt 51 to the second tension roll 55 . Such S-shaped deformation is formed by the path of the fixing belt 51 caused by the pressure of the upstream cleaning roll 71 at the entrance portion of the fixing belt 51 relative to the second tension roll 55 .

[0031] FIG. 3 is a diagram illustrating a moving mechanism 80 and a drive transmission section 90 included in the fixing device 14. As shown in FIG. 3, the fixing device 14 includes a moving mechanism 80 capable of moving the pressure roll 61 in a direction toward and away from the fixing belt module 50. The fixing device 14 also includes the aforementioned drive transmission unit 90 that transmits the rotational driving force of the motor 62 to the pressure roll 61. The moving mechanism 80 and the drive transmission unit 90 will be described below. The fixing belt module 50 of the fixing unit 14 has a configuration common to that shown in FIG. 2, and therefore the description thereof may be omitted.

[0032] (Moving mechanism 80) As shown in FIG. 3, the moving mechanism 80 includes a main body portion 81, a rotating shaft portion 82, a cam member 83, and a spring member 84.

[0033] The main body 81 rotatably supports the rotation shafts 61b at both ends of the pressure roll 61. Moreover, the main body 81 is movable relative to the device main body of the fixing device 14. More specifically, the main body 81 is rotatable about a rotation shaft 82. The rotation shaft 82 does not move relative to the fixing belt module 50. Therefore, the pressure roll 61 supported by the main body 81 can move in accordance with the movement of the main body 81 in the direction of arrow D. That is, the pressure roll 61 can advance and retreat with respect to the fixing belt module 50 or the pressing unit 53.

[0034] The cam member 83 is a disk-shaped part having a cam surface 831 whose distance from its own rotation axis varies depending on the circumferential position, and is driven by a motor (not shown) and its circumferential position is controlled. As the motor (not shown), a stepping motor capable of positioning control can be used.

[0035] More specifically, the cam member 83 is located below the main body portion 81. A portion of the main body portion 81 is in contact with the cam surface 831, and moves up and down around the rotation shaft portion 82 as the cam member 83 rotates. As a result, the pressure roll 61 supported by the main body 81 can be displaced from a position in contact with the fixing belt module 50, indicated by a solid line, to a position (not shown) away from the fixing belt module 50, and also in the reverse direction. Therefore, the pressure roll 61 can be moved in the forward and backward directions relative to the fixing belt module 50 by the cam member 83.

[0036] The spring member 84 is attached by connecting the main body of the fixing device 14 and the main body 81 of the moving mechanism 80. The spring member 84 acts in a direction in which the pressure roll 61 is pressed against the fixing belt module 50, and maintains a nip load, which is the load of the nip portion N.

[0037] (Drive transmission part 90) 3, the drive transmission unit 90 includes a drive gear 91 to which the rotational drive force of the motor 62 (see FIG. 2) is input, a driven gear 92 that meshes with the drive gear 91, and a gear 93 at the end of the pressure roll 61 that meshes with the driven gear 92. The drive gear 91, the driven gear 92, and the gear 93 are provided in the main body 81 of the movement mechanism 80. As a result, the driving force of the motor 62 is transmitted to the gear 93 at the end of the pressure roll 61, causing the pressure roll 61 to rotate.

[0038] More specifically, in the drive transmission unit 90, the position where the driven gear 92 coaxial with the rotating shaft unit 82 meshes with the gear 93 at the end of the pressure roll 61 is a position away from the axis of the pressure roll 61, where a moment can be generated relative to the moving mechanism 80. Due to this gear meshing, a driving force is input to the pressure roll 61, causing it to rotate. On the other hand, due to a driving reaction force generated by the input of the driving force, the movement mechanism 80 moves in the direction of the arrow D, causing the nip load to fluctuate.

[0039] Here, the paper P is an example of a recording medium, the pressing portion 53 is an example of a fixing member, the pressure roll 61 is an example of a rotating member, the nip portion N is an example of a pressure portion, the fixing belt 51 is an example of an annular member, and the fixing device 14 is an example of a fixing device. The motor 62 and the drive transmission unit 90 are an example of a rotating means. The cam member 83 is an example of a biasing means, and the spring member 84 is an example of a biasing means.

[0040] Here, in this embodiment, the pressing part 53 (see FIG. 2) is fixed in order to form the nip part N in the fixing device 14 (see FIG. 2) and to ensure the running stability of the paper P (see FIG. 1). In addition, in order to keep the nip load against the fixed pressing part 53 at a predetermined value, for example, it is necessary to press the pressure roll 61 (see FIG. 2) with a spring. In order to efficiently generate the nip load with the pressure roll 61 and move in the direction of the arrow D (see FIG. 3, for example), which is the direction of moving toward and away from the fixed pressing part 53, the position of the rotation shaft part 82 (see FIG. 3, for example) in the moving mechanism 80 described later needs to be on the upstream side or downstream side of the conveying direction of the paper P with respect to the pressure roll 61. Furthermore, when the fixed pressing part 53 is adopted, it is necessary to drive the fixing belt 51 by the pressure roll 61. Furthermore, when the pressure roll 61 moves by a latch operation, in order to maintain the precision of the gears' axes, it is preferable to adopt a configuration in which the driving force of the motor 62 (see FIG. 2) is input to the gears rotating around the rotation shaft part 82.

[0041] However, when a configuration is adopted in which a driving force is input to a position off the axis at one end of the pressure roll 61 to rotate the pressure roll 61, a difference occurs between the nip load at one end of the pressure roll 61 and the nip load at the other end due to the driving reaction force at one end of the pressure roll 61. In other words, the distance between the pressing portion 53 at one end of the pressure roll 61 and the distance between the pressing portion 53 at the other end of the pressure roll 61 become different from each other, which adversely affects image fixing to the paper P. Therefore, in this embodiment, a configuration is adopted in which the influence of image fixing on the paper P is suppressed by reducing the difference in distance between one end of the pressure roll 61 and the pressing portion 53 at the other end. The first, second, third and fourth embodiments will be described below.

[0042] <First embodiment> FIG. 4 is a diagram for explaining the fixing unit 14 according to the first embodiment, and is a perspective view in which the length of the pressure roll 61 can be visually confirmed. 4, the fixing device 14 of the first embodiment includes, as the above-mentioned spring member 84, spring members 84a and 84b at different positions in the depth direction E. The depth direction E here is the direction perpendicular to the paper surface of the above-mentioned FIG.

[0043] More specifically, the spring member 84a is located on one end 61c side of the pressure roll 61 in the axial direction, and the spring member 84b is located on the other end 61d side of the pressure roll 61. The drive transmission unit 90 described above is disposed on the one end 61c side of the pressure roll 61.

[0044] The spring member 84a is a member that presses one end 61c of the pressure roll 61 upward, and the degree of pressing can be changed by the driving force of the motor 141. More specifically, the spring member 84a includes a torsion coil spring and a screw that changes the length of the torsion coil spring, and the spring length is changed by moving the screw in the length direction by the driving force of the motor 141. The spring member 84a biases the one end 61c side of the pressure roll 61 in a direction F to approach or in a direction G to move the one end 61c side of the pressure roll 61 toward or away from the pressing portion 53 (see FIG. 2) by adjusting the driving force of the motor 141. This makes it possible to change the distance of the one end 61c of the pressure roll 61 from the pressing portion 53 (see FIG. 2), and therefore makes it possible to change the nip load on the one end 61c side.

[0045] The spring member 84b is a member that presses the other end 61d of the pressure roll 61 upward, and the degree of pressing can be changed by the driving force of the motor 142. The spring member 84b has the same configuration as the above-mentioned spring member 84a. The spring member 84b biases the other end 61d side of the pressure roll 61 in a direction F to approach the pressing portion 53 (see FIG. 2) or in a direction G to move the other end 61d side away from the pressing portion 53 (see FIG. 2) by adjusting the driving force of the motor 142. This makes it possible to change the distance of the other end 61d of the pressure roll 61 from the pressing portion 53 (see FIG. 2), and therefore makes it possible to change the nip load on the other end 61d side.

[0046] In addition, there is a relationship between the change in distance of each end 61c, 61d of the pressure roll 61 from the pressing portion 53 (see FIG. 2) and the change in the nip load at each end 61c, 61d, such that as the distance decreases, the nip load increases, and as the distance increases, the nip load decreases. When each end 61c, 61d of the pressure roll 61 is biased in a direction F that brings it closer to the pressing portion 53, the nip load increases, whereas when it is biased in a direction G that moves it away from the pressing portion 53, the nip load decreases.

[0047] More specifically, the motor 141 that drives the spring member 84a and the motor 142 that drives the spring member 84b operate independently. Therefore, it is possible to change the nip load at either one of the end portion 61c and the other end portion 61d of the pressure roll 61. It is possible to use stepping motors as the motors 141 and 142.

[0048] In addition, the fixing device 14 of the first embodiment is equipped with a motor 141 provided on the spring member 84a on one end 61c side of the pressure roll 61, and a motor 142 provided on the spring member 84b on the other end 61d side, but it is also possible to adopt a configuration that only includes the motor 142 on the other end 61d side.

[0049] FIG. 5 is a graph showing the nip load at one end 61c and the other end 61d of the pressure roll 61, with the vertical axis representing the nip load, in which (a) shows the state before a rotational driving force is input from the drive transmission unit 90 to the pressure roll 61, (b) shows the state after the rotational driving force is input, and (c) shows the state after adjustment by the spring member 84b. As shown in FIG. 5(a), before a rotational driving force is input from the drive transmission unit 90 to the pressure roll 61, the nip loads at both the one end 61c and the other end 61d are N1.

[0050] Then, when a rotational driving force is input from the drive transmission unit 90 to the pressure roll 61, the nip load at one end 61c increases by an increment Δ1 to N2, as shown in FIG. 5(b). Meanwhile, the nip load at the other end 61d is N1. A difference in nip load occurs between the one end 61c and the other end 61d. This difference in nip load is due to the difference in distance from the pressing unit 53 (see FIG. 2) between the one end 61c and the other end 61d of the pressure roll 61.

[0051] When the motor 142 (see FIG. 4) is operated to increase the nip load at the other end 61d, the nip load on the other end 61d side increases by an adjustment amount Δ2 to N2, as shown in FIG. 5(c). This reduces the difference between the nip load at one end 61c and the nip load at the other end 61d. In order to suppress the difference between the nip load at one end 61c and the nip load at the other end 61d, the nip load at the other end 61d is adjusted to be larger, but this is not limited to the above. For example, the nip load at one end 61c may be adjusted to be smaller in response to the increase Δ1. Also, the nip load at one end 61c may be adjusted to be smaller and the nip load at the other end 61d may be adjusted to be larger.

[0052] To explain further, it is possible to detect the difference from the torque reference value of the motor 62 (see FIG. 2) by a sensor or the like. Also, such difference may be calculated by measuring the motor current. That is, the motor 62 is energized by the adjustment amount Δ2 based on the current value of the motor 62. It is possible to perform such energization by the adjustment amount Δ2 during a preparatory operation performed before the paper P (see FIG. 1) is transported to the fixing device 14. In addition, the difference may be calculated from a value predicted by an experiment. That is, the adjustment amount Δ2 is applied based on information indicating the relationship between the driving force of the motor 62 and the nip load.

[0053] 6 is a graph showing the relationship between the driving force of the motor 62 and the nip load, where the vertical axis shows the nip load fluctuation on one end 61c side of the pressure roll 61, and the horizontal axis shows the driving torque. Note that the driving torque shown on the horizontal axis is the difference between the current value and the target value. As shown in Fig. 6, the difference ΔT between the current value and the target value of the driving torque on the horizontal axis is calculated, and the nip load fluctuation ΔN on the one end 61c side of the vertical axis is obtained from the difference ΔT. Then, the spring length corresponding to the nip load fluctuation ΔN is obtained, and the motor 142 (see Fig. 4) is operated so that the spring member 84b (see Fig. 4) has that spring length. This allows the spring member 84b to perform a bias of an adjustment amount Δ2 (see Fig. 5(c)).

[0054] <Second embodiment> FIG. 7 is a diagram illustrating a fixing unit 14 according to the second embodiment, and corresponds to FIG. 4 illustrating the first embodiment. As shown in FIG. 6, the fixing unit 14 of the second embodiment includes cam members 83a and 83b at different positions in the depth direction E as the above-mentioned cam member 83.

[0055] More specifically, the cam member 83a is located on one end 61c side of the pressure roll 61 in the axial direction, and the cam member 83b is located on the other end 61d side of the pressure roll 61. In the second embodiment, as in the first embodiment, the drive transmission unit 90 (see FIG. 3) is disposed on one end 61c side of the pressure roll 61.

[0056] The cam members 83a and 83b have the same cam shape. Cam member 83 a contacts body portion 81 at cam surface 831 , and cam member 83 b contacts body portion 81 at cam surface 831 .

[0057] The cam member 83a is rotatable by the driving force of the motor 131. The cam member 83a biases one end 61c of the pressure roll 61 in a direction F to approach or in a direction G to move away from the pressing portion 53 (see FIG. 2) depending on the contact position of the cam surface 831. The cam member 83b can rotate by the driving force of the motor 132. The cam member 83b biases the other end 61d of the pressure roll 61 in a direction F to move it closer to or in a direction G to move it away from the pressing portion 53 (see FIG. 2) depending on the contact position of the cam surface 831. The cam member 83a is an example of one cam member, and the cam member 83b is an example of the other cam member.

[0058] More specifically, the motor 131 that rotates the cam member 83a and the motor 132 that rotates the cam member 83b operate independently, and the lifting amount can be changed between one end 61c and the other end 61d of the pressure roll 61. That is, the relative positional relationship between the cam member 83a and the cam member 83b around the rotation axis can be changed. For example, it is possible to control the cam member 83a to rotate while the cam member 83b is not rotated. Therefore, the distance between one end 61c of the pressure roll 61 and the pressing portion 53 (see FIG. 2) and the distance between the other end 61d of the pressure roll 61 and the pressing portion 53 can be made different from each other.

[0059] In this way, it is possible to change the distance between one end 61c and the other end 61d of the pressure roll 61 and the pressing portion 53 (see Figure 2), and it is also possible to make one distance different from the other distance. It is possible to use stepping motors as the motors 131 and 122.

[0060] Here, the adjustment of the nip load using the cam members 83a, 83b is the same as that described for the spring members 84a, 84b in the first embodiment with reference to FIG. 5, and therefore the description thereof will be omitted. In addition, when adjusting the nip load, in addition to using both cam members 83a, 83b, it is also possible to reduce the difference in nip load by using only one of them, for example, the cam member 83b located at the other end 61d of the pressure roll 61.

[0061] In the second embodiment, the cam members 83a and 83b can rotate independently, thereby realizing a difference in the lift amount between the cam members 83a and 83b. By utilizing this difference in the lift amount, the difference in the nip load between the one end 61c of the pressure roll 61 and the other end 61d of the pressure roll 61 is suppressed.

[0062] <Third embodiment> 8 is a diagram for explaining cam members 83a and 83b used in a fixing device 14 according to the third embodiment, and shows the cam members 83a and 83b as viewed from the direction of the rotation axis. Note that the fixing device 14 according to the third embodiment has the same configuration as the second embodiment except for the cam members 83a and 83b, and therefore illustrations and descriptions thereof will be omitted.

[0063] In the third embodiment, the cam members 83a and 83b have different cam shapes. In the third embodiment, the cam members 83a and 83b rotate synchronously around the rotation center 832. That is, it is not the case that only one of the cam members 83a and 83b rotates. More specifically, when the cam members 83a and 83b rotate, the relative positional relationship between the cam members 83a and 83b is maintained as shown in FIG. 8, and they rotate around the rotation center 832. For this reason, in the third embodiment, it is possible to adopt a configuration including only one of the motors 131 and 122 (see FIG. 7) in the second embodiment.

[0064] To explain further, cam members 83a, 83b have a common portion 833 where the contours of cam surface 831 set with respect to rotation center 832 are the same, and also have a unique portion 834 where the contours are different. Common portion 833 is an example of a portion where the contours are in common, and unique portion 834 is an example of a portion where the contours are different. In the third embodiment, the common part 833 and the unique part 834 are provided, but the present invention is not limited to this, and it is also possible to adopt a configuration that does not include the common part 833.

[0065] Information on the adjustment distance corresponding to a predetermined position in each unique portion 834 of the cam members 83a and 83b is stored. Then, when adjustment of the nip load due to the driving reaction force is required, the amount of rotation of the cam members 83a and 83b is calculated based on the adjustment distance required for the adjustment.

[0066] Comparing the inherent portion 834 of the cam member 83a with the inherent portion 834 of the cam member 83b, the distance from the rotation center 832 of the cam member 83b is longer than that of the cam member 83a. In other words, the cam member 83b enables greater adjustment on the one end 61c side of the pressure roll 61 where the drive transmission unit 90 (see FIG. 3) is disposed.

[0067] When the cam members 83a and 83b rotate, the relative positional relationship between one end 61c and the other end 61d (see FIG. 7) of the pressure roll 61 does not change when the main body 81 supporting the pressure roll 61 comes into contact with the common portion 833. To explain further, when the relative positional relationship does not change, the nip load does not change, and the outer peripheral surface 61a (see FIG. 3) of the pressure roll 61 can be made to conform to the nip portion N, and the formation of the nip portion N becomes smooth.

[0068] In the third embodiment, the cam shapes of the cam members 83a and 83b are changed, thereby realizing a difference in the lift amount between the cam members 83a and 83b. By utilizing this difference in the lift amount, the difference in the nip load between one end 61c (see FIG. 7, for example) of the pressure roll 61 and the other end 61d (see the same figure) is suppressed.

[0069] <Fourth embodiment> Fig. 9 is a diagram for explaining cam members 83a, 83b used in a fixing unit 14 according to a fourth embodiment, and shows the cam members 83a, 83b as viewed from the direction of the rotation axis. Fig. 9 corresponds to Fig. 8 for explaining the third embodiment. As in the third embodiment, the fixing unit 14 according to the fourth embodiment has the same configuration as the second embodiment except for the cam members 83a, 83b, and therefore illustrations and descriptions thereof will be omitted.

[0070] In the fourth embodiment, the cam members 83a, 83b have the same cam shape, and in this respect, the fourth embodiment is the same as the second embodiment, but different from the third embodiment. On the other hand, in the fourth embodiment, the cam members 83a and 83b rotate synchronously around the rotation center 832. In this respect, the fourth embodiment is the same as the third embodiment, but is different from the second embodiment. Therefore, the fourth embodiment may be configured to include only one of the motors 131 and 122 (see FIG. 7) in the second embodiment.

[0071] In the fourth embodiment, the phases of the cam members 83a and 83b are changed, thereby realizing a difference in the lift amount between the cam members 83a and 83b. By utilizing this difference in the lift amount, the difference in the nip load between the one end 61c (see FIG. 7 for example) of the pressure roll 61 and the other end 61d (see the same figure) is suppressed. In the fourth embodiment, the cam members 83a, 83b have the same cam shape, but the phases are shifted so that the lift amounts of the cam members 83a, 83b are increased.

[0072] <Additional Notes> (((1))) a fixing member used to fix an image on a recording medium; a rotating member that is pressed against the fixing member and rotatably provided, and that forms a pressure section between the fixing member and the rotating member, where a recording medium is pressed; a rotation means for inputting a driving force to a position off the axis of the rotation member to rotate the rotation member; a biasing means for biasing at least one end of the rotating member in a direction toward or away from the fixing member; A fixing device comprising: (((2))) The biasing means includes a cam member. The fixing device according to (((1))) above. (((3))) the cam member includes one cam member provided at the one end and another cam member provided at the other end opposite to the one end, the biasing means is operable to rotate either one of the one cam member and the other cam member, or to rotate both of them; The fixing device according to (((2))) above. (((4))) The one cam member and the other cam member have portions whose contours are set with respect to a rotation center of the cams and which are different from each other. The fixing device according to (((3))) above. (((5))) the one cam member and the other cam member have a common portion of a contour set with respect to the rotation center, The fixing device according to (((4))) above. (((6))) The one cam member and the other cam member are out of phase with each other. The fixing device according to any one of ((3))) to (((5))) above. (((7))) The biasing means includes a spring member provided at the one end of the rotating member. The fixing device according to (((1))) above. (((8))) the biasing means biases the rotating means based on a current value of a driving source that generates the driving force of the rotating means. 4. The fixing device according to claim 1, wherein the fixing device is a fixing device having a fixing member. (((9))) The biasing means biases the rotating member based on information indicating a relationship between the driving force of the rotating member and the degree of bias. 4. The fixing device according to claim 1, wherein the fixing device is a fixing device having a fixing member. (((10))) a rotating annular member is provided between the fixing member and the rotating member, The annular member rotates by the driving force of the rotating member. 4. The fixing device according to claim 1, wherein the fixing device is a fixing device having a fixing member. (((11))) An image forming apparatus including the fixing device described in (((1))).

[0073] According to the invention (((1))), by transmitting a rotational driving force to the rotating member, the effect of image fixing on the recording medium can be suppressed compared to a case where the distance from the fixing member to each end of the rotating member is different. According to the invention (((2))), the biasing means can have a simpler configuration than when the biasing means does not include a configuration including a cam member. According to the invention (((3))), the cam member includes one cam member provided at one end and another cam member provided at the other end opposite the one end, and the biasing means can simplify control compared to a case in which the biasing means is not configured to be capable of rotating either the one cam member or the other cam member or both. According to the invention (((4))), the range of correspondence between one cam member and another cam member can be expanded compared to a case in which the cam members do not have a configuration in which the contours set relative to the center of rotation of the cams have different portions. According to the invention (((5))), the formation of a pressure section by a rotating member can be carried out more smoothly than in a case where one cam member and another cam member do not have a configuration in which the contours set relative to the center of rotation have a common portion. According to the invention (((6))), the range in which one cam member and another cam member can correspond to each other can be expanded compared to a case in which the cam members do not have a configuration in which they are out of phase with each other. According to the invention (((7))), the biasing means can have a simpler configuration than when it does not include a configuration including a spring member provided at one end of the rotating member. According to the invention (((8))), the biasing means can improve accuracy compared to a case in which the biasing means is not provided with a configuration for biasing based on the current value of the drive source that generates the drive force in the rotating means. According to the invention (((9))), the biasing means can simplify control compared to a case in which the biasing means is not provided with a configuration for biasing based on information indicating the relationship between the driving force in the rotating means and the degree of biasing. According to the invention of (((10))), a rotating annular member is provided between the fixing member and the rotating member, and the annular member can rotate more stably than when the annular member is not configured to rotate by the driving force of the rotating member. According to the invention of (((11))), by transmitting a rotational driving force to the rotating member, the effect of image fixing on the recording medium can be suppressed compared to a case where the distance from the fixing member to each end of the rotating member is different. [Explanation of symbols]

[0074] 1... image forming apparatus, 14... fixing unit, 51... fixing belt, 53... pressing portion, 61... pressure roll, 83, 83a, 83b... cam members, 84... spring member, 90... drive transmission portion, N... nip portion

Claims

1. a fixing member used to fix an image on a recording medium; a rotating member that is pressed against the fixing member and rotatably provided, and that forms a pressure section between the fixing member and the rotating member, where a recording medium is pressed; a rotation means for inputting a driving force to a position off the axis of the rotation member to rotate the rotation member; a biasing means for biasing at least one end of the rotating member in a direction toward or away from the fixing member; A fixing device comprising:

2. The biasing means includes a cam member.

2. The fixing device according to claim 1,

3. the cam member includes one cam member provided at the one end and another cam member provided at the other end opposite to the one end, the biasing means is operable to rotate either one of the one cam member and the other cam member, or to rotate both of them; 3. The fixing device according to claim 2,

4. The one cam member and the other cam member have portions whose contours are set with respect to a rotation center of the cams and which are different from each other.

4. The fixing device according to claim 3.

5. the one cam member and the other cam member have a common portion of a contour set with respect to the rotation center, 5. The fixing device according to claim 4.

6. The one cam member and the other cam member are out of phase with each other.

4. The fixing device according to claim 3.

7. The biasing means includes a spring member provided at the one end of the rotating member.

2. The fixing device according to claim 1,

8. the biasing means biases the rotating means based on a current value of a driving source that generates the driving force of the rotating means.

2. The fixing device according to claim 1,

9. The biasing means biases the rotating member based on information indicating a relationship between the driving force of the rotating member and the degree of bias.

2. The fixing device according to claim 1,

10. a rotating annular member is provided between the fixing member and the rotating member, The annular member rotates by the driving force of the rotating member.

2. The fixing device according to claim 1,

11. An image forming apparatus comprising the fixing device according to claim 1 .

Images