Heating device, fixing device, and image forming apparatus

Abstract

A heating device, a fixing device, and an image forming apparatus. The heating device has: a rotating body; a heating body that rotates together with the rotating body while sandwiching a heated material between the rotating body and the heating body to convey the heated material and that heats the heated material; and a contact mechanism that, in a nonexistence state in which the heated material does not exist between the rotating body and the heating body after the heated material passes between the rotating body and the heating body, causes the rotating body to contact the heating body at a central portion in a rotation axis direction while the rotating body rotates together with the heating body and the rotating body is heated, and causes the rotating body to contact the heating body at both end portions in the rotation axis direction with a contact range of the heating body being smaller than a contact range at the central portion in the rotation axis direction, or switches the rotating body between a first contact state and a second contact state in the nonexistence state in which the heated material does not exist between the rotating body and the heating body after the heated material passes between the rotating body and the heating body.

Description

Technical Field

[0001] This invention relates to heating devices, fixing devices, and image forming devices. Background Technology

[0002] Patent Document 1 discloses a fixing device having a heating rotating body heated by a heating element and a pressure rotating body that slides in contact with the heating rotating body and forms a fixing engagement portion between them. Recording paper with an unfixed toner image transferred is heated and pressurized while being engaged and transported by the fixing engagement portion, so that the unfixed toner image is fixed on the surface of the recording paper. The fixing device is characterized by having a heat transfer element that can disengage from either of the rotating bodies.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2004-53674

[0004] When heated materials such as paper pass between the center of a rotating body (such as a pressure roller) and a heating body (such as a heating belt) along the rotation axis, the temperature at the center of the rotating body along the rotation axis is lower than the temperature at both ends along the rotation axis. As a result, uneven temperature distribution along the rotation axis sometimes occurs within the rotating body. Summary of the Invention

[0005] Compared to a structure in which the contact range between the rotating body and the heating body remains the same at the center and both ends of the rotation axis after the heated material passes between the rotating body and the heating body and there is no heated material between the rotating body and the heating body, the present invention reduces the temperature unevenness of the rotating body in the rotation axis direction in a short time after the heated material passes between the rotating body and the center of the rotation axis direction of the heating body.

[0006] The first aspect of the present invention is a heating device comprising: a rotating body; a heating body that, while rotating together with the rotating body, conveys a material to be heated between itself and the rotating body and heats the material to be heated; and a contact mechanism that, in a state where the material to be heated is absent between the rotating body and the heating body after the material to be heated has passed between the rotating body and the heating body, causes the rotating body to contact the heating body, which rotates together with the rotating body and heats the rotating body, at its central portion in the rotational axis direction, such that the contact range between the two ends of the rotating body in the rotational axis direction and the heating body is smaller than the contact range at the central portion in the rotational axis direction.

[0007] According to the second aspect of the heating device of the present invention, in the first aspect described above, the contact mechanism, in the absence of the first aspect, causes the contact width between the rotating body and the heating body in the rotation direction to be smaller at both ends of the rotation axis direction than at the center of the rotation axis direction.

[0008] According to the third-party heating device of the present invention, in the first embodiment described above, the contact mechanism, in the absence state, ensures that the rotating body is not in contact with the heating body at both ends in the direction of the rotation axis.

[0009] The fourth aspect of the present invention is a heating device comprising: a rotating body; a heating body that rotates together with the rotating body while conveying a material to be heated between the rotating body and the heating body, and heating the material to be heated; and a contact mechanism that, in a state where the material to be heated is absent between the rotating body and the heating body after the material to be heated has passed between the rotating body and the heating body, causes the rotating body to contact the heating body at its central portion in the direction of rotation axis, while the heating body rotates together with the rotating body and heats the rotating body, and forms a space between the rotating body and the heating body at both ends in the direction of rotation axis.

[0010] According to the fifth aspect of the heating device of the present invention, in any one of the first to fourth aspects described above, the heating body is formed in a convex shape at the central portion in the direction of rotation axis toward the rotating body side, and compared with the heating state in which the material to be heated is heated between the rotating body and the heating body, the contact mechanism, in the absence of the heating body, moves the rotating body further away from the heating body.

[0011] According to the heating device of the sixth aspect of the present invention, in the fifth aspect described above, the rotating body is a roller with a diameter larger at both ends in the direction of rotation axis than at the center in the direction of rotation axis, and the recessed dimension of the rotating body at the center in the direction of rotation axis is smaller than the protruding dimension of the heating body at the center in the direction of rotation axis toward the rotating body side.

[0012] According to the seventh aspect of the heating device of the present invention, in any one of the first to sixth aspects described above, when the heated material passes between the rotating body and the heating body, and a heated material with a dimension larger than the heated material in the rotation axis direction is being conveyed, in the absence of the heated material between the rotating body and the heating body, the contact mechanism makes the rotating body contact the heating body at its central portion in the rotation axis direction, which rotates together with the rotating body while heating the rotating body, such that the contact range between the two ends of the rotating body in the rotation axis direction and the heating body is smaller than the contact range at the central portion in the rotation axis direction.

[0013] The eighth aspect of the present invention is a fixing device, which is a heating device described in any one of the first to seventh aspects, wherein the rotating body is a pressure roller, and the fixing device pressurizes and heats the recording medium while conveying the recording medium, which is the material to be heated, between the pressure roller and the heating body to fix the image on the recording medium.

[0014] According to the ninth aspect of the fixing apparatus of the present invention, in the eighth aspect described above, the heating element is formed in a convex shape at the center of the rotation axis towards the rotating body side, and the contact mechanism presses the two ends of the pressure roller in the rotation axis direction towards the heating body side in the heating state when the recording medium is heated between the pressure roller and the heating element, so that the pressure roller flexes along the convex shape of the heating element, and in the absence of the heating element, the rotating body is moved away from the heating element.

[0015] The tenth aspect of the present invention is an image forming apparatus comprising: a forming section that forms an image on the recording medium; and a fixing apparatus as described in the eighth or ninth aspect.

[0016] According to the eleventh aspect of the image forming apparatus of the present invention, in the tenth aspect described above, the contact mechanism of the fixing device, in the work room where the non-existent state is, causes the pressure roller to contact a heating element that rotates together with the pressure roller and heats the pressure roller at its central portion in the rotational axis direction, such that the contact range between the two ends of the pressure roller in the rotational axis direction and the heating element is smaller than the contact range at the central portion in the rotational axis direction.

[0017] The twelfth aspect of the present invention is a heating device comprising: a rotating body; a heating body that, while rotating together with the rotating body and conveying a material to be heated between the rotating body and the heating body, heats the material to be heated; and a contact mechanism that, in a state where the material to be heated is absent between the rotating body and the heating body after the material to be heated has passed between the rotating body and the heating body, switches the rotating body between a first contact state and a second contact state. The first contact state is such that the rotating body contacts the heating body, which rotates together with the rotating body and heats the rotating body, at its central portion and one end in the rotational axis direction, and the contact range between the rotating body and the heating body at the other end in the rotational axis direction is smaller than the contact range at the central portion in the rotational axis direction. The second contact state is such that the rotating body contacts the heating body at its central portion and the other end in the rotational axis direction, and the contact range between the rotating body and the heating body at the one end in the rotational axis direction is smaller than the contact range at the central portion in the rotational axis direction.

[0018] According to the heating device of the thirteenth aspect of the present invention, in the twelfth aspect described above, in the first contact state, the contact mechanism makes the contact width between the rotating body and the heating body in the rotation direction smaller at the other end in the rotation axis direction than at the center in the rotation axis direction, thereby making the contact range between the rotating body and the heating body at the other end in the rotation axis direction smaller than the contact range between the rotating body and the heating body at the center in the rotation axis direction. In the second contact state, the contact width between the rotating body and the heating body in the rotation direction is smaller at one end in the rotation axis direction than at the center in the rotation axis direction, thereby making the contact range between the rotating body and the heating body at one end in the rotation axis direction smaller than the contact range between the rotating body and the heating body at the center in the rotation axis direction.

[0019] According to the heating device of the fourteenth aspect of the present invention, in the twelfth aspect described above, the contact mechanism, in the first contact state, prevents the rotating body from contacting the heating body at the other end in the direction of the rotation axis, and in the second contact state, prevents the rotating body from contacting the heating body at one end in the direction of the rotation axis.

[0020] The fifteenth aspect of the present invention is a heating device comprising: a rotating body; a heating body that, while rotating together with the rotating body, conveys a material to be heated between itself and the rotating body and heats the material to be heated; and a contact mechanism that, in a state where the material to be heated is absent between the rotating body and the heating body after the material to be heated has passed between them, switches the rotating body between a first contact state and a second contact state. The first contact state is such that the rotating body contacts the heating body, which rotates together with the rotating body and heats the rotating body, at its central portion and one end in the rotational axis direction, and a space is formed between the rotating body and the heating body at its other end in the rotational axis direction. The second contact state is such that the rotating body contacts the heating body at its central portion and one end in the rotational axis direction, and a space is formed between the rotating body and the heating body at its one end in the rotational axis direction.

[0021] According to the heating device of the sixteenth aspect of the present invention, in any one of the twelfth to fifteenth aspects described above, the contact mechanism comprises: a first cam that contacts a first contacted portion disposed at one end of the rotating body in the direction of the rotation axis, having a major diameter portion and a minor diameter portion; and a second cam that contacts a second contacted portion disposed at the other end of the rotating body in the direction of the rotation axis, having a major diameter portion and a minor diameter portion, wherein the major diameter portion of the first cam contacts the first contacted portion at a first rotational position, the minor diameter portion of the first cam contacts the first contacted portion at a second rotational position, the minor diameter portion of the second cam contacts the second contacted portion at the first rotational position, and the major diameter portion of the second cam contacts the second contacted portion at the second rotational position.

[0022] According to the heating device of the seventeenth aspect of the present invention, in the sixteenth aspect described above, the first cam and the second cam have different shapes.

[0023] According to the heating device of the eighteenth aspect of the present invention, in any one of the twelve to seventeenth aspects described above, the contact mechanism causes the rotating body to rotate multiple times in each of the first contact state and the second contact state, and switches between the first contact state and the second contact state.

[0024] According to the nineteenth aspect of the heating device of the present invention, in the eighteenth aspect described above, the contact mechanism causes the rotating body to rotate at the same rotation speed or the same rotation time in each of the first contact state and the second contact state, and switches between the first contact state and the second contact state.

[0025] According to the heating apparatus of the twentieth aspect of the present invention, in any one of the twelfth to nineteenth aspects described above, when the heated material passes between the rotating body and the heating body, and a heated material with a dimension larger than the heated material in the rotation axis direction is conveyed, the contact mechanism switches the rotating body between the first contact state and the second contact state in the absence of the heated material between the rotating body and the heating body.

[0026] The twenty-first aspect of the present invention is a fixing device, which is a heating device described in any one of the twelfth to twentieth aspects described above, wherein the rotating body is a pressure roller, and the fixing device pressurizes and heats the recording medium while conveying the recording medium, which is the material to be heated, between the pressure roller and the heating body, thereby fixing an image onto the recording medium.

[0027] The twenty-second aspect of the present invention is an image forming apparatus comprising: a fixing apparatus as described in the twenty-first aspect above; and a forming unit that forms an image on the recording medium.

[0028] According to the image forming apparatus of the twenty-third aspect of the present invention, in the aforementioned twenty-second aspect, the contact mechanism of the fixing device switches the pressure roller between a first contact state and a second contact state during a work interval that is in the absence of the aforementioned state.

[0029] According to the structure of the first method, compared with the structure in which the contact range between the rotating body and the heating body is the same in the central part and both ends in the rotation axis direction when the rotating body is not present, the temperature unevenness in the rotation axis direction of the rotating body can be reduced in a short time after the heated material passes between the central part of the rotating body and the heating body in the rotation axis direction.

[0030] According to the structure of the second method, compared with the structure in which the rotating body is not in contact with the heating body at both ends in the direction of the rotation axis when it is not in the state of non-existence, the angle between one of the rotating body and the heating body and the other is not easily changed.

[0031] According to the third structure, compared with the structure in which the rotating body contacts the heating body at both ends in the rotation axis direction when there is no rotating body, the temperature unevenness in the rotation axis direction of the rotating body can be reduced in a short time after the heated material passes between the rotating body and the central part in the rotation axis direction of the heating body.

[0032] According to the structure of the fourth method, compared with the structure in which the rotating body contacts the heating body at both ends in the direction of rotation when there is no rotating body, the temperature unevenness in the direction of rotation of the rotating body can be reduced in a short time after the heated material passes between the rotating body and the central part in the direction of rotation of the heating body.

[0033] According to the structure of the fifth method, the contact range between the rotating body and the heating body at the center in the direction of the rotation axis can be adjusted by the distance of the rotating body away from the heating body.

[0034] According to the structure of the sixth method, compared with the structure in which the concave size is larger than the protruding size, in the absence of the structure, it is easy to make the contact range between the rotating body and the heating body at both ends in the direction of rotation axis smaller than the contact range at the center in the direction of rotation axis.

[0035] According to the structure of the seventh method, when the heated material passes between the rotating body and the heating body, and a heated material with a dimension larger than the heated material in the rotation axis direction is transported, in the absence of a state between the heated materials, the effect of suppressing wrinkles of the transported heated material is better compared to a structure in which the contact range between the rotating body and the heating body is the same in the central part and both ends in the rotation axis direction.

[0036] According to the structure of the eighth method, compared with the structure in which the contact range between the pressure roller and the heating body is the same in the central part and both ends in the direction of rotation axis when the pressure roller is not present, it is possible to suppress the uneven fixing of the image.

[0037] According to the ninth method, compared with the structure that maintains the pressure roller along the rotation axis, the structure in which the heating body is formed in a convex shape at the center of the rotation axis toward the rotating body side can suppress the uneven fixing of the image under heating.

[0038] According to the tenth method, compared with the structure in which the contact range between the pressure roller and the heating body is the same in the central part and both ends in the direction of rotation axis when the pressure roller is not present, image defects can be suppressed.

[0039] According to the structure of the eleventh method, compared with the structure in which the contact range between the pressure roller and the heating element in the work area is the same in the central part and both ends in the direction of rotation axis, it is possible to suppress image defects.

[0040] According to the structure of the twelfth method, compared with the structure in which the rotating body and the heating body continue to contact each other from one end to the other end in the direction of rotation in the absence of a state, the temperature unevenness in the direction of rotation of the rotating body can be reduced in a short time after the heated material passes between the rotating body and the heating body at the center in the direction of rotation.

[0041] According to the structure of the thirteenth method, compared with the structure in which the rotating body is not in contact with the heating body at both ends in the direction of the rotation axis when it is not in the state of non-existence, the angle between the rotating body and the heating body relative to the other is not easily changed.

[0042] According to the structure of the fourteenth method, compared with the structure in which one end of the rotating body in the rotation axis direction and the other end in the rotation axis direction are simultaneously in contact with the heating body in the absence of the rotating body, the temperature unevenness in the rotation axis direction of the rotating body can be reduced in a short time after the heated material passes between the rotating body and the heating body in the central part of the rotation axis direction.

[0043] According to the fifteenth method, compared with the structure in which one end of the rotating body in the rotation axis direction and the other end in the rotation axis direction are simultaneously in contact with the heating body in the absence of the rotating body, the temperature unevenness in the rotation axis direction of the rotating body can be reduced in a short time after the heated material passes between the rotating body and the heating body at the center of the rotation axis direction.

[0044] According to the structure of the sixteenth method, by rotating the first cam and the second cam between the first rotation position and the second rotation position, the rotating body can be switched between the first contact state and the second contact state.

[0045] According to the structure of the seventeenth method, compared with the structure used to change the phase of a pair of cams of the same shape, the degree of freedom in adjusting the positional relationship between the rotating body and the heating body in the first contact state and the second contact state is high.

[0046] According to the structure of the eighteenth method, compared with the structure in which the rotating body rotates less than two revolutions in each of the first and second contact states, the temperature unevenness in the rotation direction of the rotating body can be reduced.

[0047] According to the structure of the nineteenth method, compared with the structure in which the rotating body rotates at different speeds or different rotation times in the first contact state and the second contact state, the temperature unevenness in the direction of the rotation axis of the rotating body can be reduced.

[0048] According to the structure of the twentieth embodiment, in the case where heated materials are transported after the heated material has passed between the rotating body and the heating body, and the heated material is larger than the heated material in the direction of the rotation axis, the structure in which the heated materials do not exist, compared with the structure in which the rotating body and the heating body continue to contact each other from one end to the other in the direction of the rotation axis, has a better effect in suppressing wrinkles of the transported heated material.

[0049] According to the structure of the twenty-first method, compared with the structure in which the pressure roller and the heating body continue to be in contact from one end to the other end in the direction of rotation in the absence of the structure, it is possible to suppress the uneven fixing of the image.

[0050] According to the structure of the twenty-second method, compared with the structure in which the pressure roller and the heating element continue to contact each other from one end to the other end in the direction of the rotation axis in the absence of the structure, image defects can be suppressed.

[0051] According to the structure of the twenty-third method, compared with the structure in which the pressure roller and the heating element continue to contact each other from one end to the other in the direction of rotation in the work area, image defects can be suppressed. Attached Figure Description

[0052] Figure 1 This is a schematic diagram showing the structure of the image forming apparatus according to the first and fourth embodiments.

[0053] Figure 2 This is a schematic diagram showing the structure of the heating belt in the first and fourth embodiments.

[0054] Figure 3 This is a schematic diagram showing the structure of the pressure roller in the first and fourth embodiments.

[0055] Figure 4 This is a schematic diagram showing the state of the pressure roller in the engagement position in the first and fourth embodiments.

[0056] Figure 5 This is a schematic diagram showing the state of the pressure roller in the first embodiment at the central contact position.

[0057] Figure 6 This is a schematic diagram showing the state of the pressure roller in the separation position according to the first embodiment.

[0058] Figure 7 This is a front view showing the structure of the contact mechanism according to the first embodiment.

[0059] Figure 8 This is a perspective view showing the structure of the contact mechanism according to the first embodiment.

[0060] Figure 9 This is a schematic diagram showing the structure of the cam according to the first embodiment.

[0061] Figure 10 It is a graph showing the relationship between the rotational position of the cam in the first embodiment and the amount of pressure applied to the cam follower.

[0062] Figure 11 This is a block diagram illustrating the hardware structure of the control device in the first and fourth embodiments.

[0063] Figure 12 This is a block diagram illustrating an example of the functional structure of the control device in the first and fourth embodiments.

[0064] Figure 13 This diagram illustrates the concepts of preceding operations, subsequent operations, and the relationships between operations when the image forming apparatus of the first and fourth embodiments performs multiple operations.

[0065] Figure 14 It is a graph showing the relationship between the axial position of the pressure roller in the first embodiment and the temperature.

[0066] Figure 15 This is a schematic diagram showing the contact state of the pressure roller with the heating belt at both ends of the axial direction when the pressure roller is in the central contact position in the second embodiment.

[0067] Figure 16 This is a schematic diagram showing the contact state between the pressure roller and the heating belt at the axial center when the pressure roller is in the central contact position in the second embodiment.

[0068] Figure 17 This is a schematic diagram illustrating the size difference between the recording media of the preceding and subsequent operations in the image forming apparatus of the third and sixth embodiments.

[0069] Figure 18A This is a schematic diagram showing the state of the pressure roller in the first contact position according to the fourth embodiment.

[0070] Figure 18B This is a schematic diagram showing the state of the pressure roller in the second contact position according to the fourth embodiment.

[0071] Figure 19 This is a front view showing the structure of the contact mechanism according to the fourth embodiment.

[0072] Figure 20 This is a perspective view showing the structure of the contact mechanism according to the fourth embodiment.

[0073] Figure 21 This is a schematic diagram showing the structure of the cam according to the fourth embodiment.

[0074] Figure 22 This is a graph showing the relationship between the rotational position of the cam and the amount of pressure applied to the cam follower in the fourth embodiment.

[0075] Figure 23 This is a graph showing the relationship between the axial position of the pressure roller and the temperature in the fourth embodiment.

[0076] Figure 24 This is a graph showing the relationship between the axial position of the pressure roller and the temperature when the pressure roller of the fourth embodiment is in the first contact position.

[0077] Figure 25 This is a graph showing the relationship between the axial position of the pressure roller and the temperature when the pressure roller of the fourth embodiment is in the second contact position.

[0078] Figure 26 This is a schematic diagram showing the contact state of the pressure roller with the heating belt at the axial end when the pressure roller of the fifth embodiment is in the first contact position and the second contact position.

[0079] Figure 27 This is a schematic diagram showing the contact state between the pressure roller and the heating belt at the axial center when the pressure roller of the fifth embodiment is in the first contact position and the second contact position.

[0080] Label Explanation

[0081] 10: Image forming apparatus; 14: Forming section; 16: Fixing apparatus (an example of a heating apparatus); 40: Pressure roller (an example of a rotating body); 46: Space; 60: Heating belt (an example of a heating body); 70: Contact mechanism; P2: Recording medium (an example of a heated material); 71: First cam; 72: Second cam. Detailed Implementation

[0082] Hereinafter, an example of an embodiment of the present invention will be described with reference to the accompanying drawings.

[0083] First Implementation Method

[0084] (Image forming apparatus 10)

[0085] First, the structure of the image forming apparatus 10 of this embodiment will be described. Figure 1 This is a schematic diagram showing the structure of the image forming apparatus 10 of this embodiment.

[0086] like Figure 1 As shown, the image forming apparatus 10 includes a first transport section 11, a second transport section 12, a forming section 14, and a fixing device 16. The first transport section 11 has the function of transporting the recording medium P1. Specifically, as... Figure 1 As shown, the first conveying unit 11 has an unwinding roller 22, a winding roller 24, and a wrap roller 26.

[0087] A recording medium P1 is pre-wound on the take-up roller 22. The take-up roller 22 rotates to unwind the wound recording medium P1. A winding roller 26 winds the recording medium P1 between the take-up roller 22 and the take-up roller 24. This determines the transport path of the recording medium P1 from the take-up roller 22 to the take-up roller 24. The take-up roller 24 is a roller that winds up the recording medium P1. This take-up roller 24 is driven to rotate by a drive unit (not shown). Thus, the take-up roller 24 winds up the recording medium P1, and the take-up roller 22 unwinds the recording medium P1. Thus, the recording medium P1 is transported from the take-up roller 22 to the take-up roller 24. Additionally, as an example of the recording medium P1, a heat-pressed foil is used.

[0088] The forming section 14 has the function of forming an image on the recording medium P1. Specifically, the forming section 14 is an ejection section that ejects droplets. More specifically, the forming section 14 is composed of a nozzle that serves as an ejection section, which ejects ink droplets as droplets.

[0089] The second transport section 12 has the function of transporting a recording medium P2, which is an example of a heated material. This second transport section 12 includes, for example, a pair of transport rollers 13. In the second transport section 12, the recording medium P2 is transported to the fixing device 16 (specifically, the contact area 50S described later) at the same time as the image formed on the recording medium P1 is transported. For example, paper is used as a recording medium P2. Here, the recording medium P1 is roll paper, but the recording medium P2 is cut paper. Furthermore, the recording medium P1 has almost no effect on the temperature of the fixing device 16 (specifically, the temperature of the pressure roller 40), and the temperature drop of the fixing device 16 due to the heated material depends primarily on the recording medium P2.

[0090] The fixing device 16 transfers and fixes the image formed on the recording medium P1 onto the recording medium P2. The specific structure of the fixing device 16 will be described later.

[0091] Alternatively, the forming unit 14 can also be an electrophotographic image forming unit that forms a toner image as an image. In an electrophotographic image forming unit, a toner image is formed on the recording medium P2 through processes such as charging, exposure, development, and transfer.

[0092] Alternatively, the forming unit 14 can also directly form an image on the recording medium P2. In this case, for example, the fixing device 16 fixes the image formed on the recording medium P2 onto the recording medium P2.

[0093] (Fixing device 16)

[0094] Figure 1 The fixing device 16 shown is an example of a heating device. For example... Figure 1 As shown, the fixing device 16 has a pressure roller 40 and a heating belt 60. The fixing device 16 pressurizes and heats the recording medium P1 and the recording medium P2 while conveying them between the pressure roller 40 and the heating belt 60, thereby fixing the image of the recording medium P1 onto the recording medium P2.

[0095] Thus, the fixing unit 16 functions as a heating device, which heats the recording medium P2, one example of the material to be heated. More specifically, in addition to the pressure roller 40 and the heating belt 60, the fixing unit 16 also has a contact mechanism 70 (see reference). Figure 7 ) and control device 50 (refer to Figure 7 The specific structure of each part of the fixing device 16 will be described below.

[0096] (Pressure roller 40 and heating belt 60)

[0097] Figure 1 The heating band 60 shown is an example of a heating element. Figure 1 The pressure roller 40 shown is an example of a rotating body. The pressure roller 40 and the heating belt 60 are arranged opposite each other. In this embodiment, as... Figure 1 As shown, for example, the heating belt 60 is positioned on the lower side relative to the pressure roller 40.

[0098] The heating band 60 is formed in a ring shape, specifically a seamless shape. A heating element (not shown) for heating the heating band 60 is provided on at least one of its inner and outer circumferential sides. This heating element may be, for example, a heating element that heats the heating band 60 using a heating body that generates Joule heat due to internal resistance, or a heating element that heats the heating band 60 using radiant heat, such as a lamp.

[0099] like Figure 1 As shown, a pad 66 serving as a support is provided on the side of the pressure roller 40 on the inner circumference of the heating belt 60. Figure 2 As shown, the pad 66 has a length along the width direction of the heating belt 60. The pad 66 has a support surface 66A facing the pressure roller 40 (i.e., the upper side). This support surface 66A supports the inner circumferential surface of the heating belt 60. Furthermore, the pad 66 is convex towards the pressure roller 40 at its central portion in the width direction. Thus, the heating belt 60 as a whole is convex towards the pressure roller 40 (i.e., the upper side) at its central portion in the width direction.

[0100] Furthermore, the bandwidth direction is the direction that intersects (specifically, the direction perpendicular to) the rotation direction of the heating belt 60. This bandwidth direction can also be described as the direction along the rotation axis of the pressure roller 40 (hereinafter referred to as the axial direction).

[0101] like Figure 3 As shown, the pressure roller 40 is a roller with a larger diameter at both ends in the axial direction than at the center. Specifically, the outer diameter of the pressure roller 40 gradually increases from the center in the axial direction toward both ends. Furthermore, the outer diameter of the pressure roller 40 continuously increases from the center in the axial direction toward both ends. In this way, by making the diameters at both ends of the pressure roller 40 larger than those at the center, the conveying speed of the pressure roller 40 to the recording medium P2 is faster at both ends in the width direction than at the center. As a result, tension acts from the center of the recording medium P2 in the width direction toward both ends, thereby suppressing wrinkles in the recording medium P2.

[0102] Furthermore, the size of the recess at the axial center of the pressure roller 40 (refer to...) Figure 3 The protrusion dimension towards the pressure roller 40 at the axial center of the heating belt 60 is smaller than (refer to...) Figure 2 The recess dimension of the pressure roller 40 is the radial dimension from the outer peripheral surface of the axial end of the pressure roller 40 to the outer peripheral surface of the axial center (see reference). Figure 3 In other words, the recessed dimension of the pressure roller 40 is the radius difference between the maximum and minimum radii of the pressure roller 40. The protruding dimension of the heating belt 60 is the radial dimension from the outer peripheral surface of the end of the heating belt 60 in the bandwidth direction to the outer peripheral surface of the center portion in the bandwidth direction. This protruding dimension of the heating belt 60 can also be understood as the height difference between the end of the heating belt 60 and the center portion in the bandwidth direction at the support surface 66A of the pad 66.

[0103] like Figure 1 and Figure 4 As shown, the pressure roller 40 is pressed onto the heating belt 60. This forms a contact area 50S (i.e., fixing engagement) where the heating belt 60 contacts the pressure roller 40. In other words, the contact area 50S is the area formed between the heating belt 60 and the pressure roller 40.

[0104] Additionally, as described later, the pressure roller 40 is contacted by the contact mechanism 70. Figure 1 and Figure 4 The contact position shown (hereinafter referred to as the occlusal position) Figure 5 The contact position shown (hereinafter referred to as the center contact position) and Figure 6 The pressure roller 40 moves between the indicated separation positions. Figure 4 The indicated engagement position is pressed onto the heating band 60.

[0105] Furthermore, the pressure roller 40 is driven by the drive unit 42 (see reference). Figure 7 The heating belt 60 is driven to rotate. The heating belt 60 rotates driven by the pressure roller 40. Thus, the heating belt 60 rotates together with the pressure roller 40 and conveys the recording medium P2 between the pressure roller 40 and the recording medium P2 while heating it.

[0106] That is, in the fixing device 16, the recording medium P2, which is introduced into the contact area 50S, is pressurized and conveyed while being clamped by the heating belt 60 and the pressure roller 40. The image of the recording medium P1 is fixed onto the recording medium P2 by the pressure and the heat generated by the heating belt 60. Thus, in this embodiment, the recording medium P2 passes through the contact area 50S (i.e., between the heating belt 60 and the pressure roller 40), thereby fixing the image of the recording medium P1.

[0107] Furthermore, the axial center of the pressure roller 40 is approximately aligned with the center of the width direction of the heating belt 60. The recording medium P2 is conveyed by the heating belt 60 and the pressure roller 40 with its width direction center approximately aligned with the axial center of the pressure roller 40 and the center of the width direction of the heating belt 60 (i.e., center alignment).

[0108] (Contact Mechanism 70)

[0109] Figure 7 and Figure 8 The contact mechanism 70 shown is a mechanism that brings the pressure roller 40 into contact with the heating belt 60. Specifically, the contact mechanism 70 brings the pressure roller 40 into contact with the heating belt 60. Figure 1 , Figure 4 , Figure 7 as well as Figure 8 The bite position shown Figure 5 The central contact position shown and Figure 6Move between the shown separation positions.

[0110] More specifically, such as Figure 7 and Figure 8 As shown, the contact mechanism 70 has a pair of levers 80, a pair of cams 72, a camshaft 74, a camshaft gear 76, a transmission gear 78, and a drive unit 79 (see reference). Figure 7 Additionally, in Figure 7 and Figure 8 The image shows one of a pair of levers 80 and one of a pair of cams 72.

[0111] A pair of rods 80 are displacement parts that shift the pressure roller 40. These rods 80 are respectively disposed on one end and the other end of the pressure roller 40 along its axial direction. Specifically, as... Figure 7 As shown, each rod 80 has a rod 82, a support member 84, a spring 86, and a cam follower 88.

[0112] The rod 82 is supported on the main body of the fixing device 16 at one end, which is rotatable by means of a fulcrum 82A, which is positioned upstream of the pressure roller 40 in the conveying direction. Figure 7 (The right side of the middle).

[0113] The rod 82 extends from the fulcrum 82A towards the downstream side in the conveying direction. Figure 7 Extending obliquely upward from the left side of the middle, and buckling above the pressure roller 40, from this buckled portion 82B downstream in the conveying direction ( Figure 7 (Extending to the left of the middle). The cam follower 88 is formed in the shape of a roller and is rotatably mounted on the bent portion 82B of the rod 82.

[0114] The support member 84 supports the pressure roller 40 so that it can rotate. This support member 84 allows the pressure roller 40 to move within a predetermined range in an approach direction relative to the heating belt 60. Figure 7 (below) and its opposite direction ( Figure 7 The way the rod moves (above) is set at the other end of the rod 82.

[0115] The spring section 86, which is composed of a helical spring, is disposed between the rod 82 and the support member 84. The spring section 86 uses its elastic force to press the support member 84 in the approach direction.

[0116] The camshaft 74 is a rotating shaft that extends axially along the pressure roller 40 on the upper side of the pressure roller 40 and the rod 82. The camshaft 74 is rotatably supported on the main body of the fixing device 16.

[0117] A pair of cams 72 are respectively fixed to one end and the other end of the camshaft 74 along its axial direction. For example... Figure 9As shown, each of the cams 72 has: a short diameter portion 90; a first long diameter portion 91, the radial length of which from the camshaft 74 (i.e., the center of rotation) is longer than that of the short diameter portion 90; and a second long diameter portion 92, the radial length of which from the camshaft 74 is longer than that of the short diameter portion 90 and shorter than that of the first long diameter portion 91.

[0118] like Figure 7 As shown, each cam 72 contacts each cam follower 88, and the contact position between the cam 72 and the cam follower 88 changes according to the rotation angle of the camshaft 74. In addition, a pair of cams 72 are identical in shape.

[0119] The camshaft gear 76 is fixed to one axial end of the camshaft 74. The transmission gear 78 is rotatably supported on the main body of the fixing device 16 in a state of meshing with the camshaft gear 76.

[0120] The drive unit 79 drives the transmission gear 78 to rotate. Specifically, as an example, the drive unit 79 is composed of a stepper motor that causes the transmission gear 78 to rotate forward and backward.

[0121] Furthermore, in the contact mechanism 70, the drive unit 79 rotates the transmission gear 78 (specifically, forward and reverse rotation), thereby transmitting the driving force to the camshaft 74 via the camshaft gear 76, thus causing the camshaft 74 and the cam 72 to rotate.

[0122] As the cam 72 rotates, the contact position with the cam follower 88 varies between the short diameter portion 90, the first long diameter portion 91, and the second long diameter portion 92. The pressure roller 40 is positioned such that the short diameter portion 90 of the cam 72 contacts the cam follower 88. Figure 6 The separation position is shown. In the separation position, the pressure roller 40 is not in contact with the heating belt 60 from one axial end to the other axial end.

[0123] Furthermore, when the short diameter portion 90 of the cam 72 contacts the cam follower 88, such as Figure 10 As shown, the amount of pressure A of cam 72 relative to cam follower 88 is the minimum.

[0124] When cam 72 rotates and its first long axis portion 91 contacts cam follower 88, rod 82 rotates around fulcrum 82A, and pressure roller 40 moves to... Figure 4 The engagement position is shown. In the engagement position, both axial ends of the pressure roller 40 are pressed towards the heating belt 60 due to the elastic force of the spring portion 86. As a result, the pressure roller 40 flexes along the convex shape of the heating belt 60. Consequently, in the engagement position, the pressure roller 40 contacts the heating belt 60 from one axial end to the other axial end, forming a contact area 50S.

[0125] Furthermore, when the first long diameter portion 91 of the cam 72 contacts the cam follower 88, such as Figure 10 As shown, the indentation C of cam 72 relative to cam follower 88 is at its maximum.

[0126] As the cam 72 rotates further and the second long diameter portion 92 of the cam 72 contacts the cam follower 88, the rod 82 rotates around the fulcrum 82A, and the pressure roller 40 moves to... Figure 5 The central contact position is shown. At the central contact position, the pressure roller 40 contacts the heating belt 60 at its axial center, while the contact range between the pressure roller 40 and the heating belt 60 at each of its axial ends is smaller than the contact range at the axial center. Specifically, at the central contact position, the pressure roller 40 contacts the heating belt 60 at its axial center, but does not contact the heating belt 60 at its axial ends.

[0127] In other words, at the central contact position, the pressure roller 40 contacts the heating belt 60 at the axial center, forming a space 46 between the two axial ends of the pressure roller 40 and the heating belt 60.

[0128] Furthermore, when the second long diameter portion 92 of the cam 72 contacts the cam follower 88, such as Figure 10 As shown, the pressing amount B of cam 72 relative to cam follower 88 is the intermediate value between the pressing amount A and the pressing amount C mentioned above. Therefore, the pressure roller 40 is farther from the heating belt 60 at the central contact position than at the engagement position and closer to it than at the disengagement position.

[0129] Furthermore, the structure in which the contact range between the two ends of the axial direction and the heating band 60 is smaller than the contact range at the central part of the axial direction includes the concept of a structure with a contact range of 0 (zero) as described above.

[0130] As described above, the contact mechanism 70 causes the pressure roller 40 to contact and separate from the heating belt 60. In other words, the contact mechanism 70 can also be described as a mechanism that shifts the pressure roller 40 to change the distance between the rotation axis of the pressure roller 40 and the rotation axis of the heating belt 60.

[0131] (Control device 50)

[0132] The control device 50 is a device in the fixing device 16 that controls the operation of each part, including the drive unit 79. In this embodiment, the control device 50 is configured to control the operation of each part of the image forming apparatus 10. Furthermore, the control device 50 can be configured to at least control the operation of the drive unit 79. Figure 11 This is a block diagram showing the hardware structure of the control device 50.

[0133] like Figure 11As shown, the control device 50 functions as a computer and includes a CPU (Central Processing Unit) 51, ROM (Read Only Memory) 52, RAM (Random Access Memory) 53, memory 54, user interface 55, communication interface 56, and I / O unit 57. The various parts of the control device 50 are communicatively connected to each other via a bus 59.

[0134] The CPU 51 is the central processing unit, which executes various programs and controls various parts. That is, the CPU 51 reads the program from the ROM 52 or the memory 54 and uses the RAM 53 as the working area to execute the program. The CPU 51 performs control and various arithmetic processing of various parts of the image forming apparatus 10 according to the program recorded in the ROM 52 or the memory 54.

[0135] ROM 52 stores various programs and data. RAM 53 serves as a working area to temporarily store programs or data. Memory 54 consists of storage units such as HDD (Hard Disk Drive) or SSD (Solid State Drive), storing various programs including the operating system, as well as various data.

[0136] The user interface 55 is the interface through which a user uses the image forming apparatus 10. The user interface 55 may include, for example, input sections such as buttons or touch panels and display sections such as liquid crystal displays. The user is the one instructing others to perform tasks.

[0137] Communication interface 56 is an interface used for communication with user terminals such as personal computers. The communication method of communication interface 56 can be wired or wireless. The communication standard of communication interface 56 can be, for example, Ethernet (registered trademark), FDDI, Wi-Fi (registered trademark), etc. I / O unit 57 connects CPU 51 to various parts of image forming apparatus 10.

[0138] When executing the above procedure, the control device 50 uses the aforementioned hardware resources to implement various functions. The functional configuration implemented by the control device 50 will be described below. Figure 12 This is a block diagram illustrating an example of the functional structure of the control device 50.

[0139] like Figure 12 As shown, the control device 50 has an acquisition unit 50A and a control unit 50B as its functional structure. Each functional structure is implemented by the CPU 51 reading and executing the control program stored in the ROM 52 or the memory 54.

[0140] The acquisition unit 50A acquires the execution instruction for the job and job information related to the job. The acquisition unit 50A acquires information such as the size of the recording medium P2 (specifically, the size in the transport direction and width direction), the number of sheets, and the transport speed specified in the job, as job-related information. Furthermore, a job refers to a processing unit of image forming action executed according to a single instruction from the instructor. The instructor specifies the size of the recording medium P2, the number of sheets, and the transport speed, etc., in the job.

[0141] Alternatively, as an example, the job execution instruction can be input via a user terminal capable of communication using the communication interface 56, and the acquisition unit 50A can acquire the job execution instruction. Alternatively, a job can be generated by reading the original document using a reading device (specifically a scanner), and the acquisition unit 50A can acquire the job execution instruction.

[0142] When the acquisition unit 50A receives the operation execution instruction, the control unit 50B controls each part of the image forming apparatus 10, including the fixing unit 16, to execute the operation. At this time, for each part of the fixing unit 16, including the drive unit 42, the control unit 50B controls the heating belt 60 to heat and the pressure roller 40 to rotate. Furthermore, for the drive unit 79 of the contact mechanism 70 in the fixing unit 16 (see reference...) Figure 7 The control unit 50B controls the pressure roller 40 to be in the engagement position (see reference). Figure 4 ).

[0143] Furthermore, upon completion of the operation, the control unit 50B controls the drive unit 79 to drive the pressure roller 40 to the separated position. At this time, the control unit 50B controls each part of the fixing device 16, including the drive unit 42, to stop the heating of the heating belt 60 and the rotation of the pressure roller 40.

[0144] Furthermore, when the acquisition unit 50A continuously acquires multiple jobs, the control unit 50B controls the drive unit 79 between jobs, so that the pressure roller 40 is located at the central contact position (see reference). Figure 5 At this time, the control unit 50B controls each part of the fixing device 16, including the drive unit 42, in the work area to maintain the heating of the heating belt 60 and the rotation of the pressure roller 40.

[0145] Furthermore, the scenario of continuously fetching jobs is equivalent to fetching another job before completing the execution of the first job. Additionally, as... Figure 13 As shown, the job executed first among multiple jobs continuously acquired by the acquisition unit 50A is called the preceding job, and the job executed immediately after the preceding job is called the subsequent job. Furthermore, the period between the preceding job and the subsequent job is called the job interval.

[0146] Here, the working area is in a state where there is no recording medium P2 in the contact area 50S. That is, in the state where there is no recording medium P2 between the pressure roller 40 and the heating belt 60 after the recording medium P2 has passed between the pressure roller 40 and the heating belt 60 (hereinafter referred to as the absence state), the control unit 50B controls the drive unit 79 to position the pressure roller 40 at the central contact position.

[0147] (The function of the first embodiment)

[0148] Next, the function of the first embodiment will be explained.

[0149] According to the image forming apparatus 10 of the first embodiment, when the acquisition unit 50A acquires the operation execution command, the control unit 50B of the control device 50 (see reference) Figure 12 The image forming apparatus 10 is controlled to perform operations. At this time, the control unit 50B controls each part of the fixing apparatus 16, including the drive unit 42, to heat the heating belt 60 and rotate the pressure roller 40. Furthermore, the control unit 50B controls the drive unit 79 of the contact mechanism 70 in the fixing apparatus 16 to position the pressure roller 40 in the engagement position (see reference). Figure 4 ).

[0150] Therefore, the contact mechanism 70 moves the pressure roller 40 from the disengaged position to the engaged position. As a result, both axial ends of the pressure roller 40 are pressed towards the heating belt 60, causing the pressure roller 40 to flex along the convex shape of the heating belt 60. Thus, a contact area 50S is formed between the pressure roller 40 and the heating belt 60.

[0151] Furthermore, the forming part 14 is aimed at Figure 1 The recording medium P1 conveyed by the first conveying unit 11 forms an image. The recording medium P1 with the image formed is conveyed by the first conveying unit 11 to the contact area 50S.

[0152] Recording medium P2 is transported to contact area 50S by second transport unit 12 at the same time as the image formed on recording medium P1 is transported to contact area 50S.

[0153] Then, the fixing device 16 pressurizes and heats the recording media P1 and P2 while conveying them between the pressure roller 40 and the heating belt 60, thereby fixing the image of the recording media P1 onto the recording media P2.

[0154] Furthermore, when the recording medium P2 is heated between the pressure roller 40 and the heating belt 60, the pressure roller 40 maintains contact with the heating belt 60 while remaining in a state of convex flexing along the heating belt 60. That is, in this embodiment, when the recording medium P2 is heated between the pressure roller 40 and the heating belt 60, the contact mechanism 70 applies pressure to both axial ends of the pressure roller 40 towards the heating belt 60, causing the pressure roller 40 to flex along the convex shape of the heating belt 60.

[0155] Furthermore, in this embodiment, when the acquisition unit 50A continuously acquires multiple jobs, the control unit 50B controls the drive unit 79 of the contact mechanism 70 between the preceding job and the subsequent job, so that the pressure roller 40 is located at the central contact position (see reference). Figure 5 At this time, the control unit 50B controls each part of the fixing device 16, including the drive unit 42, in the work area to maintain the heating of the heating belt 60 and the rotation of the pressure roller 40.

[0156] Thus, when the contact mechanism 70 is not in use, the pressure roller 40 contacts the heating band 60 that heats the pressure roller 40 at its axial center, while the pressure roller 40 is not in contact with the heating band 60 at its axial ends (hereinafter referred to as the recovery action). As a result, the axial center of the pressure roller 40 is heated by the heating band 60, while the axial ends of the pressure roller 40 are not heated.

[0157] Here, in the case of multiple consecutive operations, the following situation is considered: In the preceding operation, a recording medium P2 (hereinafter referred to as the small-sized recording medium P2) with a width dimension smaller than the bandwidth dimension of the contact area 50S is used; in the subsequent operation, a recording medium P2 (hereinafter referred to as the large-sized recording medium P2) with a width dimension larger than the width dimension of the recording medium P2 used in the preceding operation is used (see reference). Figure 17 As an example, the width dimension of the recording medium P2 used in subsequent operations is equal to the bandwidth dimension of the contact area 50S (specifically, a slightly smaller dimension than the bandwidth dimension of the contact area 50S).

[0158] In the initial operation, when the small recording medium P2 passes through the contact area 50S, the heat from the heating belt 60 is transferred to the pressure roller 40 via the recording medium P2 at the center of the belt width direction. On the other hand, at both ends of the heating belt 60 in the belt width direction, the heat from the heating belt 60 is not transferred to the pressure roller 40 via the recording medium P2. Therefore, as... Figure 14 As shown by the dashed line, the temperature becomes lower at the axial center of the pressure roller 40 than at the two axial ends.

[0159] Furthermore, in the absence of a state (i.e., in the work area), with the contact range between the pressure roller 40 and the heating belt 60 being the same at the axial center and both axial ends (hereinafter referred to as the first structure), the temperature is maintained in subsequent operations at a lower axial center than at the axial ends of the pressure roller 40. Figure 14 (The state indicated by the dashed line).

[0160] Thus, due to the uneven temperature generated along the axial direction of the pressure roller 40, the difference in outer diameter between the two ends of the pressure roller 40 and the axial center increases due to thermal expansion at the two ends of the pressure roller 40. As a result, in subsequent operations, when the large-sized recording medium P2 passes through the contact area 50S, the conveying speed of the recording medium P2 is too fast compared to the two ends in the width direction of the center, sometimes causing wrinkles on the recording medium P2.

[0161] In addition, due to the uneven temperature generated in the axial direction of the pressure roller 40, uneven fixing of the image may occur in the width direction of the recording medium P2 during subsequent operations.

[0162] In contrast, during the recovery operation of this embodiment, the axial central portion of the pressure roller 40 is heated by the heating belt 60 in the work area, while the axial ends of the pressure roller 40 are not heated. Therefore, after the recording medium P2 passes between the axial central portion of the pressure roller 40 and the heating belt 60, the axial temperature unevenness of the pressure roller decreases in a short time compared to the first structure. That is, the temperature recovers to normal within a short time. Figure 14 The solid line represents the temperature distribution.

[0163] Thus, according to the structure of this embodiment, the axial temperature unevenness of the pressure roller decreases rapidly. Therefore, compared to the first structure, wrinkles in the recording medium P2 caused by the difference in outer diameter between the two axial ends and the axial center of the pressure roller 40 can be suppressed in subsequent operations. Furthermore, according to the structure of this embodiment, compared to the first structure, image fixing unevenness generated in the width direction of the recording medium P2 is suppressed in subsequent operations. Therefore, according to the structure of this embodiment, compared to the first structure, image defects formed on the recording medium P2 are suppressed in subsequent operations.

[0164] In particular, during the recovery operation of this embodiment, the pressure roller 40 is not in contact with the heating belt 60 at both ends of the axial direction in the working chamber. Therefore, compared with the structure in which the pressure roller 40 is in contact with the heating belt 60 in the working chamber (hereinafter referred to as the second structure), the axial temperature unevenness of the pressure roller is reduced in a short time after the recording medium P2 passes between the pressure roller 40 and the axial center of the heating belt 60.

[0165] Furthermore, in the recovery operation of this embodiment, a space 46 is formed between the two axial ends of the pressure roller 40 and the heating belt 60 in the work area (see reference). Figure 5 Therefore, compared to the second structure, air can more easily flow between the two axial ends of the pressure roller 40 and the heating belt 60, and after the recording medium P2 passes between the axial center of the pressure roller 40 and the heating belt 60, the axial temperature unevenness of the pressure roller decreases in a short time.

[0166] Furthermore, in this embodiment, the entire heating belt 60 is convex towards the pressure roller 40 (i.e., the upper side) at its central portion in the bandwidth direction. The pressure roller 40 is far from the engagement position relative to the heating belt 60 at its central contact position, thereby maintaining contact with the heating belt 60 at its axial central portion while not contacting the heating belt 60 at its two axial ends.

[0167] Thus, in this embodiment, the heating belt 60 is convex towards the pressure roller 40 at its central portion in the bandwidth direction. Therefore, the contact range between the pressure roller 40 and the heating belt 60 at its axial central portion can be adjusted by moving the pressure roller 40 away from the heating belt 60.

[0168] Furthermore, in this embodiment, the recess size at the axial center of the pressure roller 40 (refer to...) Figure 3 The protrusion dimension of the heating belt 60 towards the pressure roller 40 is smaller than the axial center portion (refer to...). Figure 2 Therefore, compared to a structure where the recessed size is larger than the protruding size, in the work area, it is easier to make the contact range between the two axial ends of the pressure roller 40 and the heating belt 60 smaller than the contact range at the axial center.

[0169] In addition, in this embodiment, when the recording medium P2 is heated between the pressure roller 40 and the heating belt 60, the contact mechanism 70 presses the two axial ends of the pressure roller 40 toward the heating belt 60, causing the pressure roller 40 to flex along the convex shape of the heating belt 60.

[0170] Therefore, compared with the structure in which the pressure roller 40 is kept in a state along the axial direction, the structure in which the heating belt 60 is formed in a convex shape at the axial center towards the pressure roller 40 can suppress uneven fixing of the image to the recording medium under heating.

[0171] Second Implementation Method

[0172] Next, the second embodiment will be described. Furthermore, parts that are identically constructed to those in the first embodiment will be labeled with the same reference numerals, and descriptions will be omitted where appropriate.

[0173] In the first embodiment, the pressure roller 40 is in the central contact position (see reference). Figure 5In the second embodiment, the heating element is in contact with the heating band 60 at its central axial position and not in contact with the heating band 60 at its two axial ends.

[0174] That is, in the second embodiment, the pressure roller 40 contacts the heating belt 60 at the central axial contact position, and at both axial ends, the contact range with the heating belt 60 is smaller than the contact range at the central axial position. Specifically, at the central contact position, the contact width W1 at both axial ends of the pressure roller 40 in the rotational direction (i.e., circumferential direction) of the heating belt 60 is (refer to...) Figure 15 The contact width W2 at the axial center is less than the contact width at the axial center (refer to...). Figure 16 ).

[0175] The function of the second embodiment will be explained below.

[0176] In this embodiment, when the acquisition unit 50A continuously acquires multiple jobs, the control unit 50B controls the drive unit 79 of the contact mechanism 70 in the job room, so that the pressure roller 40 is in the central contact position. At this time, the control unit 50B controls each part of the fixing device 16, including the drive unit 42, in the job room to maintain the heating of the heating belt 60 and the rotation of the pressure roller 40.

[0177] Therefore, when the contact mechanism 70 is not in use, the pressure roller 40 contacts the heating belt 60 that heats the pressure roller 40 at its axial center, and the contact width between the pressure roller 40 and the heating belt 60 in the rotational direction is smaller at both axial ends than at the axial center.

[0178] Therefore, the amount of heating at both ends of the pressure roller 40 in the axial direction is less than the amount of heating at the center of the pressure roller 40 in the axial direction.

[0179] Therefore, after the recording medium P2 passes between the pressure roller 40 and the axial center of the heating belt 60, the axial temperature unevenness of the pressure roller is reduced in a short time compared to the first structure described above.

[0180] Thus, according to the structure of this embodiment, the axial temperature unevenness of the pressure roller is reduced in a short time. Therefore, compared with the first structure, wrinkles in the recording medium P2 caused by the difference in outer diameter between the two ends and the center of the axial direction of the pressure roller 40 are suppressed in subsequent operations. Furthermore, according to the structure of this embodiment, compared with the first structure, image fixing unevenness generated in the width direction of the recording medium P2 is suppressed in subsequent operations. Therefore, according to the structure of this embodiment, image defects formed on the recording medium P2 are suppressed in subsequent operations compared with the first structure.

[0181] Furthermore, during the recovery operation in this embodiment, the pressure roller 40 is in contact with the heating belt 60 at its central portion and both ends in the axial direction during the work area. Therefore, one of the pressure roller 40 and the heating belt 60 is supported by the other. Thus, compared to a structure where the pressure roller 40 is not in contact with the heating belt 60 at both ends in the axial direction during the work area, the angle between the pressure roller 40 and the heating belt 60 and the other is less likely to change.

[0182] Furthermore, in the recovery operation of this embodiment, the pressure roller 40 is in contact with the heating belt 60 at its central part and both ends in the axial direction during the work area. Therefore, compared with the structure in which the pressure roller 40 is not in contact with the heating belt 60 at both ends in the axial direction during the work area, the heating belt 60 can be stably driven by the pressure roller 40 to rotate.

[0183] Third Implementation Method

[0184] Next, the third embodiment will be described. Furthermore, parts that are identically constructed to those in the first embodiment will be labeled with the same reference numerals, and descriptions will be omitted where appropriate.

[0185] As described above, in the first embodiment, when the acquisition unit 50A continuously acquires multiple jobs, the control unit 50B controls the drive unit 79 between jobs so that the pressure roller 40 is located at the central contact position. In contrast, in the third embodiment, it is configured as follows.

[0186] That is, in the third embodiment, when the acquisition unit 50B continuously acquires multiple jobs, such as... Figure 17 As shown, in the case where the width dimension of the recording medium P2 used in the subsequent operation is larger than the width dimension of the recording medium P2 used in the preceding operation (hereinafter referred to as "the case where the size of the subsequent medium is larger"), the drive unit 79 is controlled so that the pressure roller 40 is located at the central contact position.

[0187] In other words, after the recording medium P2 has passed through the contact area for 50 seconds, a recovery operation is performed when a recording medium P2 with a width dimension larger than the recording medium P2 is transported, which is in a state where the recording medium P2 is not present.

[0188] Therefore, in this non-contact state, the contact mechanism 70 causes the pressure roller 40 to contact the heating band 60 that heats the pressure roller 40 at its axial center, while preventing the pressure roller 40 from contacting the heating band 60 at its axial ends. Thus, the axial center of the pressure roller 40 is heated by the heating band 60, while the axial ends of the pressure roller 40 are not heated.

[0189] Furthermore, in this embodiment, if the width dimension of the recording medium P2 used in a subsequent operation is smaller than the width dimension of the recording medium P2 used in a previous operation, a recovery operation is not performed between operations. Specifically, for example, the control unit 50B controls the drive unit 79 so that the pressure roller 40 is in the separation position.

[0190] Additionally, the control unit 50B may, for example, determine the width dimension of the recording medium P2 as operational information. Alternatively, the control unit 50B may determine the width dimension of the recording medium P2 based on detection results from sensors or other detection units.

[0191] Here, when the size of the subsequent medium is large, the pressure roller 40 contacts the recording medium P2 at both axial ends in subsequent operations compared to the initial operations. Therefore, when the difference in outer diameter between the axial ends and the axial center of the pressure roller 40 increases due to thermal expansion at both axial ends, the conveying speed of the recording medium P2 tends to be faster at the ends in the width direction than at the center.

[0192] Therefore, when the size of the subsequent medium is large, compared to the structure in which the contact range between the pressure roller 40 and the heating belt 60 is the same in the axial center and at both ends, in the structure that controls the pressure roller 40 to be in the central contact position (hereinafter referred to as the third structure), the recording medium P2 is prone to wrinkling in subsequent operations.

[0193] In contrast, in this embodiment, when the size of the subsequent medium is large, the drive unit 79 is controlled so that the pressure roller 40 is in the central contact position. Therefore, compared with the third structure, the effect of suppressing wrinkles of the conveyed recording medium P2 is better.

[0194] In the third embodiment described above, a recovery operation is performed when the size of the subsequent medium is large, but this is not a limitation. For example, a structure can be adopted in which the recovery operation is performed when the temperature difference between the axial center portion and at least one of the two ends of the pressure roller 40 is above a predetermined threshold as a result of the preliminary operation. In this case, the recovery operation is performed, for example, based on information obtained by a detection unit such as a temperature sensor measuring the temperature of the axial center portion and the two ends of the pressure roller 40. Alternatively, the temperature difference of the pressure roller 40 can be predicted based on the number of recording media P2 sheets processed in the preliminary operation, and the recovery operation can be performed based on this information.

[0195] Fourth Implementation Method

[0196] Next, the fourth embodiment will be described. The image forming apparatus 10, fixing apparatus 16, and heating belt 6 are configured the same as in the first embodiment, so descriptions will be omitted. Furthermore, as described later, the pressure roller 40 is moved by the contact mechanism 70... Figure 1 and Figure 4 The contact position shown (hereinafter referred to as the occlusal position) Figure 18A The first contact position shown Figure 18B The second contact position shown and Figure 6 The separation positions shown can be moved between, but otherwise the structure is the same as in the first embodiment.

[0197] (Contact Mechanism 70)

[0198] Figure 7 and Figure 20 The contact mechanism 70 shown is a mechanism that brings the pressure roller 40 into contact with the heating belt 60. Specifically, the contact mechanism 70 brings the pressure roller 40 into contact with the heating belt 60. Figure 1 , Figure 4 , Figure 7 as well as Figure 20 The bite position shown Figure 18A The first contact position shown Figure 18B The second contact position shown and Figure 6 Move between the shown separation positions.

[0199] More specifically, such as Figure 7 and Figure 20 As shown, the contact mechanism 70 has a pair of levers 80, a first cam 71A, a second cam 72A, a camshaft 74, a camshaft gear 76, a transmission gear 78, and a drive unit 79 (see reference). Figure 7 Additionally, in Figure 7 and Figure 20 The image shows one of a pair of levers 80, and also shows the first cam 71A of the first cam 71A and the second cam 72A.

[0200] A pair of rods 80 are displacement parts that shift the pressure roller 40. These rods 80 are respectively disposed on one end side and the other end side of the pressure roller 40 along its axial direction. Specifically, as... Figure 7 As shown, each rod 80 has a rod 82, a support member 84, a spring 86, and a cam follower 88.

[0201] Rod 82 can be positioned at one end on the upstream side of the conveying direction relative to pressure roller 40 ( Figure 7 The fulcrum 82A (on the right side of the image) is rotated and supported on the main body of the fixing device 16.

[0202] The rod 82 extends from the fulcrum 82A towards the downstream side in the conveying direction. Figure 7Extending obliquely upward from the left side of the middle, and buckling above the pressure roller 40, from this buckled portion 82B downstream in the conveying direction ( Figure 7 (Extending to the left of the middle). The cam follower 88 is formed in the shape of a roller and is rotatably mounted on the bent portion 82B of the rod 82.

[0203] The support member 84 supports the pressure roller 40 so that it can rotate. This support member 84 allows the pressure roller 40 to move within a predetermined range in an approach direction relative to the heating belt 60. Figure 7 (below) and its opposite direction ( Figure 7 The upper part of the rod is positioned at the other end of the rod 82.

[0204] The spring section 86, which is composed of a helical spring, is disposed between the rod 82 and the support member 84. The spring section 86 uses its elastic force to press the support member 84 in the approach direction.

[0205] The camshaft 74 is a rotating shaft that extends axially along the pressure roller 40 on the upper side of the pressure roller 40 and the rod 82. The camshaft 74 is rotatably supported on the main body of the fixing device 16.

[0206] Figure 21 The first cam 71A shown is fixed to one end of the camshaft 74 in the axial direction. Figure 22 The second cam 72A shown is fixed to the other end of the camshaft 74 in the axial direction. The first cam 71A and the second cam 72A respectively contact each other with a cam follower 88. Specifically, the first cam 71A contacts the cam follower 88 (hereinafter sometimes referred to as cam follower 881) disposed at one end of the pressure roller 40 in the axial direction, and the second cam 72A contacts the cam follower 88 (hereinafter sometimes referred to as cam follower 882) disposed at the other end of the pressure roller 40 in the axial direction. In addition, the cam follower 881 is an example of the first contacted part. The cam follower 882 is an example of the second contacted part.

[0207] like Figure 21 and Figure 22 As shown, the first cam 71A and the second cam 72A each have a first contact portion 91A, a second contact portion 92A, a third contact portion 93A, and a fourth contact portion 94A. The radial lengths (hereinafter referred to as radial lengths) of the first contact portion 91A, the second contact portion 92A, the third contact portion 93A, and the fourth contact portion 94A from the camshaft 74 (i.e., the center of rotation) increase sequentially. Furthermore, the second contact portion 92A is an example of a short-diameter portion. Furthermore, the third contact portion 93A is an example of a long-diameter portion.

[0208] In the first cam 71A, with the first contact portion 91A as the reference, along Figure 21The first contact portion 91A, the second contact portion 92A, the fourth contact portion 94A, and the third contact portion 93A are arranged sequentially in a clockwise direction. On the other hand, in the second cam 72A, the first contact portion 91A is used as a reference along... Figure 22 The first contact portion 91A, the third contact portion 93A, the fourth contact portion 94A, and the second contact portion 92A are arranged sequentially in a clockwise direction. Thus, in the second cam 72A, along... Figure 22 When viewed clockwise, the third contact portion 93A is positioned between the first contact portion 91A and the fourth contact portion 94A, and the second contact portion 92A is positioned between the fourth contact portion 94A and the first contact portion 91A. Therefore, compared to a structure where both the third contact portion 93A and the second contact portion 92A are positioned between the first contact portion 91A and the fourth contact portion 94A, the variation in the outer diameter of the second cam 72A from the first contact portion 91A to the fourth contact portion 94A and from the fourth contact portion 94A to the first contact portion 91A can be minimized. Furthermore, in the first cam 71A, along... Figure 21 When viewed clockwise, the second contact portion 92A is positioned between the first contact portion 91A and the fourth contact portion 94A, and the third contact portion 93A is positioned between the fourth contact portion 94A and the first contact portion 91A. Therefore, compared to a structure where both the third contact portion 93A and the second contact portion 92A are positioned between the first contact portion 91A and the fourth contact portion 94A, the variation in the outer diameter of the first cam 71A from the first contact portion 91A to the fourth contact portion 94A and from the fourth contact portion 94A to the first contact portion 91A can be minimized. Consequently, the movement of the pressure roller 40 between the engagement and disengagement positions becomes smoother.

[0209] The first contact portion 91A of the first cam 71A and the first contact portion 91A of the second cam 72A are positioned at the same location in the circumferential direction of the camshaft 74. Furthermore, the third contact portion 93A of the first cam 71A and the second contact portion 92A of the second cam 72A are positioned at the same location in the circumferential direction of the camshaft 74. Additionally, the fourth contact portion 94A of the first cam 71A and the fourth contact portion 94A of the second cam 72A are positioned at the same location in the circumferential direction of the camshaft 74.

[0210] As described above, the first contact portion 91A, the second contact portion 92A, the third contact portion 93A and the fourth contact portion 94A are configured differently in the first cam 71A and the second cam 72A, thereby the shapes of the first cam 71A and the second cam 72A are different.

[0211] Furthermore, based on the rotational position of the camshaft 74, the contact positions of the first cam 71A and the second cam 72A relative to their respective cam followers 88 are switched. Specifically, the first cam 71A and the second cam 72A are each at a predetermined reference rotational position ( Figure 21 and Figure 22 Position A), their first contact portion 91A contacts each cam follower 88. Additionally, the first cam 71A, after rotating a predetermined angle from its reference rotational position, reaches its first rotational position (…). Figure 21 Position B), its third contact portion 93A contacts the cam follower 881. Additionally, the first cam 71A rotates to a second rotational position after rotating a predetermined angle from the first rotational position (…). Figure 21 At position C), its second contact portion 92A contacts the cam follower 881. Furthermore, the first cam 71A, after rotating a predetermined angle from the second rotational position, reaches a third rotational position (…). Figure 21 Position D), its fourth contact part 94A contacts the cam follower 881.

[0212] On the other hand, the second cam 72A in the first rotational position ( Figure 22 At position B), its second contact portion 92A contacts the cam follower 882. Additionally, the second cam 72A at the second rotational position ( Figure 22 At position C), its third contact portion 93A contacts the cam follower 882. Furthermore, the second cam 72A is in the third rotational position ( Figure 22 Position D), its fourth contact part 94A contacts the cam follower 882.

[0213] The camshaft gear 76 is fixed to one axial end of the camshaft 74. The transmission gear 78 is rotatably supported on the main body of the fixing device 16 in a state of meshing with the camshaft gear 76.

[0214] The drive unit 79 drives the transmission gear 78 to rotate. Specifically, as an example, the drive unit 79 is composed of a stepper motor that causes the transmission gear 78 to rotate forward and backward.

[0215] Furthermore, in the contact mechanism 70, the drive unit 79 rotates the transmission gear 78 (specifically, forward and reverse rotation), thereby transmitting the driving force to the camshaft 74 via the camshaft gear 76, thus causing the camshaft 74 to rotate.

[0216] As described above, by rotating the camshaft 74, the contact positions of the first cam 71A and the second cam 72A relative to the respective cam followers 88 vary between the first contact portion 91A, the second contact portion 92A, the third contact portion 93A, and the fourth contact portion 94A. The pressure roller 40 is positioned such that the first contact portion 91A of each of the first cam 71A and the second cam 72A contacts the respective cam followers 88. Figure 6 The separation position is shown. In the separation position, the pressure roller 40 is not in contact with the heating belt 60 from one axial end to the other axial end.

[0217] When the camshaft 74 rotates and the fourth contact portion 94A of the first cam 71A and the second cam 72A respectively contacts the respective cam follower 88, the rod 82 rotates around the fulcrum 82A, and the pressure roller 40 moves to... Figure 4 The engagement position is shown. In the engagement position, the two axial ends of the pressure roller 40 are pressed towards the heating belt 60 by the elastic force of the spring portion 86. As a result, the pressure roller 40 flexes along the convex shape of the heating belt 60. As a result, the pressure roller 40 contacts the heating belt 60 from one axial end to the other axial end in the engagement position, forming a contact area 50S.

[0218] Furthermore, when the fourth contact portion 94A of the first cam 71A and the second cam 72A respectively contacts the respective cam follower 88, the pressing amount of the first cam 71A and the second cam 72A relative to the respective cam follower 88 is at its maximum.

[0219] When the camshaft 74 rotates further and the third contact portion 93A of the first cam 71A and the second contact portion 92A of the second cam 72A respectively contact the respective cam followers 88, the rod 82 rotates around the fulcrum 82A, and the pressure roller 40 moves to... Figure 18A The first contact position is shown. At the first contact position, the pressure roller 40 contacts the heating belt 60 at one end and the center in the axial direction, and the contact range at the other end in the axial direction is smaller than the contact range at the center in the axial direction. Specifically, at the first contact position, the pressure roller 40 contacts the heating belt 60 at one end and the center in the axial direction, and does not contact the heating belt 60 at the other end in the axial direction.

[0220] In other words, the pressure roller 40 contacts the heating belt 60 at one end and the center of the first contact position in the axial direction, and forms a space 46 between the pressure roller 40 and the heating belt 60 at the other end in the axial direction.

[0221] Furthermore, when the camshaft 74 rotates and the second contact portion 92A of the first cam 71A and the third contact portion 93A of the second cam 72A respectively contact the respective cam followers 88, the rod 82 rotates around the fulcrum 82A, and the pressure roller 40 moves to... Figure 18BThe second contact position is shown. At the second contact position, the pressure roller 40 contacts the heating belt 60 at its other axial end and central portion, and the contact range at one axial end with the heating belt 60 is smaller than the contact range at the central portion. Specifically, at the second contact position, the pressure roller 40 contacts the heating belt 60 at its other axial end and central portion, and does not contact the heating belt 60 at one axial end.

[0222] In other words, the pressure roller 40 contacts the heating belt 60 at the other end and the center of the second contact position in the axial direction, and a space 46 is formed between the pressure roller 40 and the heating belt 60 at one end in the axial direction.

[0223] Furthermore, as described above, the structure in which the contact range between the axial end and the heating band 60 is smaller than the contact range at the axial center is a concept that includes a structure with a contact range of 0 (zero).

[0224] As described above, the contact mechanism 70 causes the pressure roller 40 to contact and separate from the heating belt 60. In other words, the contact mechanism 70 can also be described as a mechanism that shifts the pressure roller 40 to change the distance between the rotation axis of the pressure roller 40 and the rotation axis of the heating belt 60.

[0225] (Control device 50)

[0226] Regarding the control device 50, descriptions of points identical to those described in the first embodiment are omitted. When the acquisition unit 50A continuously acquires multiple jobs, the control unit 50B controls the drive unit 79 between jobs, causing the pressure roller 40 to alternately occupy the first contact position (see reference). Figure 18A ) and second contact position (refer to Figure 18B ).

[0227] Furthermore, the scenario of continuously fetching jobs is equivalent to fetching another job before completing the execution of the first job. Additionally, as... Figure 13 As shown, the job executed first among multiple jobs continuously acquired by the acquisition unit 50A is called the preceding job, and the job executed immediately after the preceding job is called the subsequent job. Furthermore, the period between the preceding job and the subsequent job is called the job interval.

[0228] Here, the working area is in a state where there is no recording medium P2 in the contact area 50S. That is, in the state where there is no recording medium P2 between the pressure roller 40 and the heating belt 60 after the recording medium P2 has passed between the pressure roller 40 and the heating belt 60 (hereinafter referred to as the absence state), the control unit 50B controls the drive unit 79 so that the pressure roller 40 alternately lies in the first contact position (refer to...). Figure 18A ) and second contact position (refer to Figure 18BSpecifically, the control unit 50B controls the drive unit 79 to control the pressure roller 40 in the state of the first contact position and the state of the second contact position (see reference). Figure 18B The pressure roller is rotated more than 40 times in each of the various states.

[0229] More specifically, the control unit 50B controls the drive unit 79 so that the pressure roller 40 is in the first contact position and in the second contact position (see reference). Figure 18B In each state of the pressure roller 40, the rotation time is the same. Additionally, the control unit 50B can also control the drive of the drive unit 79, so that the pressure roller 40 rotates for the same amount of time in both the first contact position and the second contact position (see reference 79). Figure 18B In each state of the heating band 60, the heating band 60 is rotated at the same speed.

[0230] (Function of the fourth implementation method)

[0231] Next, the function of the fourth embodiment will be explained.

[0232] According to the image forming apparatus 10 of the fourth embodiment, when the acquisition unit 50A acquires an execution instruction for a job, the control unit 50B of the control device 50 (see reference) Figure 12 The control unit 50B controls each part of the image forming apparatus 10 to perform the operation. At this time, the control unit 50B controls each part of the fixing apparatus 16, including the drive unit 42, to heat the heating belt 60 and rotate the pressure roller 40. Furthermore, the control unit 50B controls the drive unit 79 of the contact mechanism 70 in the fixing apparatus 16, so that the pressure roller 40 is in the engagement position (see reference). Figure 4 ).

[0233] Therefore, the contact mechanism 70 moves the pressure roller 40 from the disengaged position to the engaged position. As a result, both axial ends of the pressure roller 40 are pressed towards the heating belt 60, causing the pressure roller 40 to flex along the convex shape of the heating belt 60. Thus, a contact area 50S is formed between the pressure roller 40 and the heating belt 60.

[0234] Furthermore, forming part 14 pairs Figure 1 The recording medium P1 conveyed by the first conveying unit 11 forms an image. The recording medium P1 with the image formed is conveyed by the first conveying unit 11 to the contact area 50S.

[0235] Recording medium P2 is transported to contact area 50S via second transport unit 12 at the same time as the image formed on recording medium P1 is transported to contact area 50S.

[0236] Then, the fixing device 16 pressurizes and heats the recording media P1 and P2 while conveying them between the pressure roller 40 and the heating belt 60, thereby fixing the image of the recording media P1 onto the recording media P2.

[0237] Furthermore, when the recording medium P2 is heated between the pressure roller 40 and the heating belt 60, the pressure roller 40 maintains contact with the heating belt 60 while remaining in a convex flexed state along the heating belt 60. That is, in this embodiment, during the heating state where the recording medium P2 is heated between the pressure roller 40 and the heating belt 60, the contact mechanism 70 presses the two axial ends of the pressure roller 40 toward the heating belt 60, causing the pressure roller 40 to flex along the convex flex of the heating belt 60.

[0238] Furthermore, in this embodiment, when the acquisition unit 50A continuously acquires multiple jobs, the control unit 50B controls the drive unit 79 of the contact mechanism 70 between the preceding job and the subsequent job, causing the pressure roller 40 to alternately occupy the first contact position (see reference). Figure 18A ) and second contact position (refer to Figure 18B At this time, the control unit 50B controls each part of the fixing device 16, including the drive unit 42, in the work area to maintain the heating of the heating belt 60 and the rotation of the pressure roller 40.

[0239] Therefore, when the contact mechanism 70 is not in operation, it switches the pressure roller 40 to the following first contact state (see reference). Figure 18A ) and the following second contact state (refer to Figure 18B (Hereinafter referred to as the recovery action). The first contact state is as follows: the pressure roller 40 is in contact with the heating belt 60, which rotates with the pressure roller 40 and heats it while being in contact with its axial center and one axial end, such that the contact range between the pressure roller 40 and the heating belt 60 at the other axial end of the pressure roller 40 is smaller than the contact range at the axial center. Specifically, in the first contact state, the pressure roller 40 is not in contact with the heating belt 60 at its other axial end.

[0240] The second contact state is such that the pressure roller 40 contacts the heating belt 60, which rotates with the pressure roller 40 while heating it, at its axial central portion and at the other axial end, such that the contact range between the pressure roller 40 and the heating belt 60 at one axial end is smaller than the contact range at the axial central portion. Specifically, in the second contact state, the pressure roller 40 is not in contact with the heating belt 60 at one axial end. Thus, by switching the heating belt 60 to the first contact state (refer to...), Figure 18A ) and second contact state (refer to Figure 18BThe amount of heat at both ends of the pressure roller 40 is less than the amount of heat at the center of the pressure roller 40.

[0241] Here, in the case of multiple consecutive operations, the following situation is considered: In the preceding operation, a recording medium P2 with a width dimension smaller than the bandwidth dimension of the contact area 50S (hereinafter referred to as the small-size recording medium P2) is used; in the subsequent operation, a recording medium P2 with a width dimension larger than the width dimension of the recording medium P2 used in the preceding operation (hereinafter referred to as the large-size recording medium P2) is used (see reference). Figure 17 As an example, the width dimension of the recording medium P2 used in subsequent operations is equal to the bandwidth dimension of the contact area 50S (specifically, slightly smaller than the bandwidth dimension of the contact area 50S).

[0242] In the initial operation, when the small recording medium P2 passes through the contact area 50S, the heat from the heating belt 60 is transferred to the pressure roller 40 via the recording medium P2 at the center of the belt width direction. On the other hand, at both ends of the heating belt 60 in the belt width direction, the heat from the heating belt 60 is not transferred to the pressure roller 40 via the recording medium P2. Therefore, as... Figure 23 As shown by the dashed line, the temperature is lower in the axial center of the pressure roller 40 than at both ends.

[0243] Furthermore, in the structure where the pressure roller 40 and the heating belt 60 are in continuous contact from one end of the axial direction to the other (hereinafter referred to as the first structure) in a non-existent state (i.e., in the work area), the temperature is maintained at a lower level in the axial central part of the pressure roller 40 than at both ends of the axial direction during subsequent operations. Figure 23 (The state indicated by the dashed line).

[0244] Thus, due to the uneven temperature generated along the axial direction of the pressure roller 40, the difference in outer diameter between the two axial ends and the axial center of the pressure roller 40 increases due to thermal expansion at the two axial ends. As a result, in subsequent operations, when the large-sized recording medium P2 passes through the contact area 50S, the conveying speed of the recording medium P2 is too fast compared to the two ends in the width direction of the center, and therefore, wrinkles sometimes occur on the recording medium P2 in subsequent operations.

[0245] In addition, due to the uneven temperature generated in the axial direction of the pressure roller 40, uneven fixing of the image sometimes occurs in the width direction of the recording medium P2 during subsequent operations.

[0246] In contrast, during the recovery operation of this embodiment, the pressure roller 40 is switched between a first contact state and a second contact state. In the first contact state, the axial central portion and one axial end of the pressure roller 40 are heated by the heating belt 60, while the other axial end of the pressure roller 40 is not heated. Therefore, as Figure 24 As shown, the temperature rises at the axial center of the pressure roller 40 and decreases at the other axial end of the pressure roller 40.

[0247] Furthermore, in the second contact state, the axial central portion and the other axial end of the pressure roller 40 are heated by the heating belt 60, while one axial end of the pressure roller 40 is not heated. Therefore, as Figure 25 As shown, the temperature rises at the axial center of the pressure roller 40 and decreases at one axial end of the pressure roller 40.

[0248] Therefore, after the recording medium P2 passes between the axial center of the pressure roller 40 and the heating belt 60, the axial temperature unevenness of the pressure roller is reduced in a short time compared to the first structure.

[0249] Thus, according to the structure of this embodiment, since the temperature unevenness in the axial direction of the pressure roller decreases in a short time, wrinkles in the recording medium P2 caused by the difference in outer diameter between the two ends and the center of the axial direction of the pressure roller 40 are suppressed in subsequent operations, compared to the first structure. Furthermore, according to the structure of this embodiment, compared to the first structure, image fixing unevenness generated in the width direction of the recording medium P2 is suppressed in subsequent operations. Therefore, according to the structure of this embodiment, compared to the first structure, image defects formed on the recording medium P2 are suppressed in subsequent operations.

[0250] In particular, during the recovery operation of this embodiment, the other axial end and one axial end of the pressure roller 40 alternately do not contact the heating belt 60 in the work area. Therefore, compared with the structure in which the other axial end and one axial end of the pressure roller 40 are in contact with the heating belt 60 simultaneously in the work area (hereinafter referred to as the second structure), the axial temperature unevenness of the pressure roller is reduced in a short time after the recording medium P2 passes between the pressure roller 40 and the axial center of the heating belt 60.

[0251] Furthermore, in the recovery operation of this embodiment, spaces 46 are alternately formed between the other axial end and one axial end of the pressure roller 40 and the heating belt 60 in the work area. Therefore, compared with the second structure, air can easily flow in the spaces 46 between the pressure roller 40 and the heating belt 60 at the other axial end and one axial end, and after the recording medium P2 passes between the pressure roller 40 and the heating belt 60 at the axial center, the axial temperature unevenness of the pressure roller decreases in a short time.

[0252] In this embodiment, the control unit 50B controls the drive unit 79, causing the pressure roller 40 to be in the state of the first contact position and the state of the second contact position (see reference). Figure 18B The pressure roller 40 rotates multiple times in each of the first and second contact states. As a result, the contact mechanism 70 causes the pressure roller 40 to switch between the first and second contact states while rotating multiple times in each of the first and second contact states.

[0253] Therefore, compared with the structure where the heating belt 60 rotates less than two revolutions in each of the first and second contact states, the temperature unevenness in the rotation direction of the pressure roller 40 is reduced.

[0254] Furthermore, in this embodiment, the control unit 50B controls the drive unit 79, causing the pressure roller 40 to be in the state of being in the first contact position and in the state of being in the second contact position (see reference). Figure 18B The rotation time is the same in each state of the state.

[0255] Thus, the contact mechanism 70 causes the pressure roller 40 to switch between the first contact state and the second contact state while rotating for the same amount of time in each of the first contact state and the second contact state.

[0256] Therefore, compared to the structure where the heating belt 60 rotates for different times in the first and second contact states, the temperature unevenness in the rotation direction of the pressure roller 40 is reduced.

[0257] Furthermore, in this embodiment, the first cam 71A and the second cam 72A have different shapes. Therefore, compared to a structure that uses a pair of cams with the same shape to change their phases, the adjustment of the positional relationship between the pressure roller 40 and the heating belt 60 in the first contact state and the second contact state has a higher degree of freedom.

[0258] In addition, in this embodiment, when the recording medium P2 is heated between the pressure roller 40 and the heating belt 60, the contact mechanism 70 presses the two axial ends of the pressure roller 40 toward the heating belt 60, causing the pressure roller 40 to flex along the convex shape of the heating belt 60.

[0259] Therefore, compared to the structure in which the pressure roller 40 is kept in an axial state, the structure in which the heating belt 60 is formed in a convex shape at the axial center towards the pressure roller 40 suppresses the uneven fixing of the image onto the recording medium under heating conditions.

[0260] Fifth Implementation Method

[0261] Next, the fifth embodiment will be described. Furthermore, parts that are identical in construction to those in the fourth embodiment will be labeled with the same reference numerals, and descriptions will be omitted as appropriate.

[0262] In the fourth embodiment, the pressure roller 40 is at the first contact position (refer to...) Figure 18A The pressure roller 40 contacts the heating belt 60 at one end and the center in the axial direction, and does not contact the heating belt 60 at the other end in the axial direction. Additionally, the pressure roller 40 is in the second contact position (see reference...). Figure 18B The heating band 60 is in contact at the other end and the center of the axial direction, and not in contact at one end of the axial direction. In contrast, the fifth embodiment is configured as follows.

[0263] That is, in the fifth embodiment, the pressure roller 40 contacts the heating belt 60 at one end and the center of the first contact position in the axial direction, and contacts the heating belt 60 at the other end in the axial direction in a manner that the contact range with the heating belt 60 is smaller than the contact range at the center of the axial direction. Specifically, the contact width W1 of the pressure roller 40 at the other end in the axial direction (i.e., circumferential direction) of the heating belt 60 at the first contact position (refer to...) Figure 26 The contact width W2 at the axial center is less than the contact width at the axial center (refer to...). Figure 27 ).

[0264] Furthermore, the pressure roller 40 contacts the heating belt 60 at its other end and central portion in the second contact position, and contacts the heating belt 60 at one end in the axial direction such that the contact range with the heating belt 60 is smaller than the contact range at the central portion in the axial direction. Specifically, the contact width W1 of the pressure roller 40 at one end in the axial direction (i.e., circumferential direction) of the heating belt 60 in the second contact position is (refer to...) Figure 26 The contact width W2 at the axial center is less than the contact width at the axial center (refer to...). Figure 27 ).

[0265] The function of the fifth embodiment will be explained below.

[0266] In this embodiment, when the acquisition unit 50A continuously acquires multiple jobs, the control unit 50B controls the drive unit 79 of the contact mechanism 70 in the job room, causing the pressure roller 40 to alternately occupy the first contact position and the second contact position. At this time, the control unit 50B controls each part of the fixing device 16, including the drive unit 42, in the job room to maintain the heating of the heating belt 60 and the rotation of the pressure roller 40.

[0267] Therefore, in the absence of a contact state, the contact mechanism 70 switches the pressure roller 40 between a first contact state and a second contact state (hereinafter referred to as a recovery operation). The first contact state is such that the pressure roller 40 is in contact with the heating belt 60, which rotates with the pressure roller 40 and heats it while being in contact with the axial center and one axial end, such that the contact range between the pressure roller 40 and the heating belt 60 at the other axial end is smaller than the contact range at the axial center. Specifically, in the first contact state, the pressure roller 40 is not in contact with the heating belt 60 at the other axial end.

[0268] The second contact state is as follows: the pressure roller 40 is in contact with the heating belt 60, which rotates with the pressure roller 40 while heating it, at its axial central portion and at the other axial end, such that the contact range between the pressure roller 40 and the heating belt 60 at one axial end is smaller than the contact range at the axial central portion. Specifically, in the second contact state, the pressure roller 40 is not in contact with the heating belt 60 at one axial end. Thus, by adjusting the heating belt 60 in the first contact state (refer to...), the heating belt 60... Figure 18A ) and second contact state (refer to Figure 18B The heating amount at both ends of the pressure roller 40 is less than the heating amount at the center of the pressure roller 40.

[0269] Therefore, after the recording medium P2 passes between the pressure roller 40 and the heating belt 60 at the axial center, the axial temperature unevenness of the pressure roller is reduced in a short time compared to the first structure described above.

[0270] Thus, according to the structure of this embodiment, since the temperature unevenness in the axial direction of the pressure roller decreases in a short time, wrinkles in the recording medium P2 caused by the difference in outer diameter between the two ends and the center of the axial direction of the pressure roller 40 are suppressed in subsequent operations, compared to the first structure. Furthermore, according to the structure of this embodiment, compared to the first structure, image fixing unevenness generated in the width direction of the recording medium P2 is suppressed in subsequent operations. Therefore, according to the structure of this embodiment, compared to the first structure, image defects formed on the recording medium P2 are suppressed in subsequent operations.

[0271] Furthermore, during the recovery operation in this embodiment, the pressure roller 40 is in contact with the heating belt 60 at its central portion and both ends in the axial direction during the work area. Therefore, one of the pressure roller 40 and the heating belt 60 is supported by the other. Thus, compared to a structure where the pressure roller 40 is not in contact with the heating belt 60 at both ends in the axial direction during the work area, the angle between the pressure roller 40 and the heating belt 60 and the other is less likely to change.

[0272] Furthermore, in the recovery operation of this embodiment, in the work area, the pressure roller 40 is in contact with the heating belt 60 at its central part and both ends in the axial direction. Therefore, compared with the structure in which the pressure roller 40 is not in contact with the heating belt 60 at both ends in the axial direction in the work area, the heating belt 60 is stably driven by the pressure roller 40 to rotate.

[0273] The Sixth Implementation Method

[0274] Next, the sixth embodiment will be described. Furthermore, parts that are identical in construction to those in the fourth embodiment will be labeled with the same reference numerals, and descriptions will be omitted as appropriate.

[0275] As described above, in the fourth embodiment, when the acquisition unit 50A continuously acquires multiple jobs, the control unit 50B controls the drive unit 79 between jobs so that the pressure roller 40 is in the second contact position. In contrast, the sixth embodiment is configured as follows.

[0276] That is, in the sixth embodiment, when the acquisition unit 50B continuously acquires multiple jobs, such as... Figure 17 As shown, in the case where the width dimension of the recording medium P2 used in subsequent operations is larger than the width dimension of the recording medium P2 used in the preceding operations (hereinafter referred to as "the case where the size of the subsequent medium is larger"), the drive unit 79 is controlled so that the pressure roller 40 is alternately located at the first contact position (see reference). Figure 18A ) and second contact position (refer to Figure 18B ).

[0277] In other words, after the recording medium P2 has passed through the contact area for 50 seconds, a recovery operation is performed when a recording medium P2 with a width dimension larger than the recording medium P2 is transported, which is in a state where the recording medium P2 is not present.

[0278] Furthermore, in this embodiment, if the width dimension of the recording medium P2 used in a subsequent operation is smaller than the width dimension of the recording medium P2 used in a previous operation, a recovery operation is not performed between operations. Specifically, for example, the control unit 50B controls the drive unit 79 so that the pressure roller 40 is in the separation position.

[0279] Additionally, the control unit 50B may, for example, determine the width dimension of the recording medium P2 as operational information. Alternatively, the control unit 50B may determine the width dimension of the recording medium P2 based on detection results from sensors or other detection units.

[0280] Here, when the size of the subsequent medium is large, the pressure roller 40 contacts the recording medium P2 at both ends of the axial direction in subsequent operations compared to the previous operation. Therefore, when the difference in outer diameter between the two ends of the axial direction and the center of the pressure roller 40 increases due to thermal expansion at the two ends of the axial direction, the conveying speed of the recording medium P2 tends to be faster at the two ends in the width direction than at the center.

[0281] Therefore, when the size of the subsequent medium is large, in the structure where the pressure roller 40 and the heating belt 60 continue to contact each other from one end of the axial direction to the other end (hereinafter referred to as the third structure), the recording medium P2 is prone to wrinkling during subsequent operations.

[0282] In contrast, in this embodiment, since the recovery operation is performed in the work area when the size of the subsequent medium is large, the effect of suppressing wrinkles of the transported recording medium P2 is better than that of the third structure.

[0283] In the sixth embodiment described above, a recovery operation is performed when the size of the subsequent medium is large, but this is not limited to this. For example, a structure can be adopted in which the recovery operation is performed when the temperature difference between at least one of the axial center portion and both ends of the pressure roller 40 is above a predetermined threshold as a result of the preliminary operation. In this case, for example, the recovery operation is performed based on information obtained by a detection unit such as a temperature sensor measuring the temperature of the axial center portion and both ends of the pressure roller 40. Alternatively, the temperature difference of the pressure roller 40 can be predicted based on the number of recording media P2 sheets used in the preliminary operation, and the recovery operation can be performed based on this information.

[0284] (Other implementation methods)

[0285] In embodiments 1 to 3 described above, when multiple operations are performed, the pressure roller 40 is positioned at the central contact position (see reference 70) between operations via the contact mechanism 70. Figure 5 The recovery action can be performed using the contact mechanism 70, but is not limited to this. For example, the following structure can be used: when performing a single task, after the recovery action is performed after the task is completed, the contact mechanism 70 moves the pressure roller 40 to the separated position. In this structure, when performing a task immediately after the completion of the single task, the effect of uneven temperature in the axial direction of the pressure roller is suppressed.

[0286] In embodiments 4 to 6 described above, a recovery action is performed between operations when multiple operations are being performed, but this is not a limitation. For example, a structure can be adopted where, when performing a single operation, after the recovery action is performed after the operation is completed, the contact mechanism 70 positions the pressure roller 40 in a separated position. In this structure, when an operation is performed immediately after the completion of the single operation, the effect of uneven temperature in the axial direction of the pressure roller is suppressed.

[0287] Alternatively, the following structure can be adopted: if a task is executed immediately after the task has just been completed, a recovery action can be performed before executing the task.

[0288] Alternatively, the following structure can be adopted: the recovery operation can be performed between recording media P2 in a single job.

[0289] In the above embodiment, a pressure roller 40 was used as an example of a rotating body, but it is not limited to this. For example, a pressure belt or the like could also be used as a rotating body.

[0290] Furthermore, in the above embodiment, a heating belt 60 was used as an example of a heating element, but it is not limited to this. For example, a heating roller or the like could also be used as a heating element.

[0291] This invention is not limited to the embodiments described above, and various modifications, alterations, and improvements can be made without departing from its spirit. For example, the modifications shown above can also be appropriately combined to form a complete system.

Claims

1. A heating device comprising: Solid of revolution; A heating element, which rotates together with the rotating body while conveying the material to be heated between itself and the rotating body, heats the material to be heated; and The contact mechanism, in a state where the heated material is absent between the rotating body and the heating body after the rotating body has passed between them, and there is no heated material between them, causes the rotating body to contact the heating body at its central portion in the rotational axis direction. The heating body rotates with the rotating body while heating it, and the contact range between the two ends of the rotating body and the heating body in the rotational axis direction is smaller than the contact range at the central portion in the rotational axis direction. In the absence of the contact mechanism, the rotating body is kept out of contact with the heating body at both ends in the direction of the rotation axis.

2. The heating device according to claim 1, wherein, In the absence of the contact mechanism, the contact width between the rotating body and the heating body in the rotation direction is smaller at both ends of the rotation axis direction than at the center of the rotation axis direction.

3. A heating device, comprising: Solid of revolution; A heating element, which rotates together with the rotating body while conveying the material to be heated between itself and the rotating body, heats the material to be heated; and A contact mechanism that, in a state where the heated material is absent between the rotating body and the heating body after the heated material has passed between the rotating body and the heating body, makes the rotating body contact the heating body at its central part in the direction of rotation axis, while the rotating body rotates together with the rotating body and heats the rotating body, and forms a space between the rotating body and the heating body at both ends in the direction of rotation axis.

4. The heating device according to any one of claims 1 to 3, wherein, The heating element is convex in the central portion of the rotating axis towards the rotating body side. Compared to the heating state in which the material to be heated is heated between the rotating body and the heating body, in the absence of the contact mechanism, the rotating body is moved further away from the heating body.

5. The heating device according to claim 4, wherein, The rotating body is a roller with a diameter larger at both ends in the direction of the rotation axis than at the center in the direction of the rotation axis. The recessed dimension of the rotating body at the center in the direction of the rotation axis is smaller than the protruding dimension of the heating body at the center in the direction of the rotation axis toward the rotating body.

6. The heating device according to any one of claims 1 to 3, wherein, After the heated material passes between the rotating body and the heating body, when a heated material with a dimension larger than the heated material in the rotation axis direction is being transported, and in the absence of the heated material between the rotating body and the heating body, the contact mechanism causes the rotating body to contact the heating body at its central portion in the rotation axis direction, while the rotating body rotates together with the rotating body and heats the rotating body, such that the contact range between the two ends of the rotating body in the rotation axis direction and the heating body is smaller than the contact range at the central portion in the rotation axis direction.

7. A fixing device, comprising the heating device according to any one of claims 1 to 6, wherein, The rotating body is a pressure roller. The fixing device pressurizes and heats the recording medium, which is the material to be heated, while conveying it between the pressure roller and the heating element, thereby fixing the image onto the recording medium.

8. The fixing apparatus according to claim 7, wherein, The heating element is convex in the central portion of the rotating axis towards the rotating body side. In the heated state where the recording medium is heated between the pressure roller and the heating element, the contact mechanism applies pressure to both ends of the pressure roller in the direction of its rotation axis toward the heating element, causing the pressure roller to flex along the convex shape of the heating element. In the absence of the aforementioned state, the rotating body is moved away from the heating body.

9. An image forming apparatus comprising: Forming section, which forms an image on the recording medium; and The fixing device according to claim 7 or 8.

10. The image forming apparatus according to claim 9, wherein, In the working chamber where the fixing device is in a non-existent state, the contact mechanism causes the pressure roller to contact the heating element, which rotates together with the pressure roller and heats it, at the center of the rotation axis direction, such that the contact range between the two ends of the pressure roller and the heating element in the rotation axis direction is smaller than the contact range at the center of the rotation axis direction.

11. A heating device comprising: Solid of revolution; A heating element, which rotates together with the rotating body while conveying the material to be heated between itself and the rotating body, heats the material to be heated; and The contact mechanism switches the rotating body between a first contact state and a second contact state after the heated material has passed between the rotating body and the heating body, when the heated material is no longer present between the rotating body and the heating body. The first contact state is as follows: the rotating body is in contact with a heating element that rotates with the rotating body and heats it at its central portion and one end portion in the rotation axis direction, and the contact range between the rotating body and the heating element at the other end portion in the rotation axis direction is smaller than the contact range at the central portion in the rotation axis direction. The second contact state is as follows: the rotating body is in contact with the heating body at its central portion and at its other end in the direction of the rotation axis, such that the contact area at one end in the direction of the rotation axis is smaller than the contact area at the central portion in the direction of the rotation axis. After the heated material passes between the rotating body and the heating body, when a heated material with a dimension larger than the heated material in the direction of the rotation axis is being transported, the contact mechanism switches the rotating body between the first contact state and the second contact state when there is no heated material between the rotating body and the heating body.

12. The heating device according to claim 11, wherein, In the first contact state, the contact mechanism makes the contact width between the rotating body and the heating body in the rotational direction smaller at the other end in the rotational axis direction than at the center in the rotational axis direction. This results in the contact range between the rotating body and the heating body at the other end in the rotational axis direction being smaller than the contact range at the center in the rotational axis direction. In the second contact state, the contact mechanism makes the contact width between the rotating body and the heating body in the rotation direction smaller at one end in the rotation axis direction than at the center in the rotation axis direction, thereby making the contact range between the rotating body and the heating body at one end in the rotation axis direction smaller than the contact range between the rotating body and the heating body at the center in the rotation axis direction.

13. The heating device according to claim 11, wherein, In the first contact state, the contact mechanism ensures that the other end of the rotating body in the direction of the rotation axis is not in contact with the heating body. In the second contact state, the contact mechanism ensures that one end of the rotating body in the direction of the rotation axis is not in contact with the heating body.

14. A heating device comprising: Solid of revolution; A heating element, which rotates together with the rotating body while conveying the material to be heated between itself and the rotating body, heats the material to be heated; and The contact mechanism switches the rotating body between a first contact state and a second contact state after the heated material has passed between the rotating body and the heating body, when the heated material is no longer present between the rotating body and the heating body. The first contact state is as follows: the rotating body is in contact with a heating element that rotates together with the rotating body and heats the rotating body at its central portion and one end in the rotation axis direction, and a space is formed between the rotating body and the heating element at the other end in the rotation axis direction. The second contact state is as follows: the rotating body is in contact with the heating body at its central portion and at its other end in the direction of the rotation axis, and a space is formed between the rotating body and the heating body at one end in the direction of the rotation axis. After the heated material passes between the rotating body and the heating body, when a heated material with a dimension larger than the heated material in the direction of the rotation axis is being transported, the contact mechanism switches the rotating body between the first contact state and the second contact state when there is no heated material between the rotating body and the heating body.

15. The heating device according to any one of claims 11 to 14, wherein, The contact mechanism has: The first cam, which contacts a first contacted portion disposed at one end of the rotating body in the direction of the rotation axis, has a long diameter portion and a short diameter portion; as well as The second cam, which contacts the second contact portion disposed at the other end of the rotating body in the direction of the rotation axis, has a long diameter portion and a short diameter portion. The long-diameter portion of the first cam contacts the first contacted portion at a first rotational position, and the short-diameter portion of the first cam contacts the first contacted portion at a second rotational position. The short diameter portion of the second cam contacts the second contacted portion in the first rotational position, and the long diameter portion of the second cam contacts the second contacted portion in the second rotational position.

16. The heating device according to claim 15, wherein, The first cam and the second cam have different shapes.

17. The heating device according to any one of claims 11 to 14, wherein, The contact mechanism causes the rotating body to rotate multiple times in each of the first contact state and the second contact state, and switches between the first contact state and the second contact state.

18. The heating device according to claim 17, wherein, The contact mechanism causes the rotating body to rotate at the same speed or for the same rotation time in each of the first contact state and the second contact state, and switches between the first contact state and the second contact state.

19. A fixing device, comprising the heating device according to any one of claims 11 to 18, wherein, The rotating body is a pressure roller. The fixing device pressurizes and heats the recording medium, which is the material to be heated, while conveying it between the pressure roller and the heating element, thereby fixing the image onto the recording medium.

20. An image forming apparatus comprising: The fixing device according to claim 19; and A forming section that forms an image on the recording medium.

21. The image forming apparatus according to claim 20, wherein, The contact mechanism of the fixing device switches the pressure roller between a first contact state and a second contact state in the work area, which is in the non-contact state.

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