Image forming apparatus

Abstract

In an image forming apparatus, a first fixing member includes a roller. A second fixing member includes a belt that forms a nip portion with the first fixing member. A first motor drives the roller. A pressure modification mechanism modifies the clamping pressure at the nip portion to a selected one of a first clamping pressure and a second clamping pressure that is less than the first clamping pressure. Upon receiving a print command while the clamping pressure is at the second clamping pressure, a controller begins driving the first motor to drive the roller. After the driving operation, the controller modifies the clamping pressure from the second clamping pressure to the first clamping pressure, and fixes a developer image on a sheet while the clamping pressure is at the first clamping pressure.

Description

Technical Field

[0001] The present disclosure relates to an image forming apparatus including a fixing device that fixes a developer image on a sheet. Background Art

[0002] A fixing device known in the art includes a heater and a pressure roller. The heater comprises a belt formed into a loop, a heater, and a nip plate disposed within the belt loop. The pressure roller presses the belt against the nip plate. The heater can be switched between a pressure contact position, where the heater contacts the pressure roller, and a separation position, where the heater and pressure roller are separated.

[0003] However, there is no technology that can reduce the damage to the belt, especially before printing begins. Summary of the Invention

[0004] In view of the foregoing, the present disclosure provides a technique for reducing damage to a tape at the start of printing.

[0005] In order to achieve the above-mentioned and other purposes, the present disclosure provides an image forming device. The image forming device includes an image forming unit, a first fixing member, a second fixing member, a first motor, a pressure modification mechanism and a controller. The image forming unit forms a developer image on a sheet. The first fixing member has a roller. The second fixing member has a belt to form a clamping portion together with the first fixing member. The first motor is configured to drive the roller. The pressure modification mechanism is configured to modify the clamping pressure at the clamping portion to a selected one of a first clamping pressure and a second clamping pressure that is less than the first clamping pressure. The controller is configured to: start driving the first motor to drive the roller when a print command is received in a state where the clamping pressure is the second clamping pressure; after driving, modify the clamping pressure from the second clamping pressure to the first clamping pressure; and fix the developer image on the sheet in a state where the clamping pressure is the first clamping pressure.

[0006] Preferably, the image forming apparatus further includes a second motor and a heater. The second motor is configured to drive the image forming unit. The heater is configured to heat the first fixing member. The controller is further configured to set the mode to a sleep mode in which the heater is turned off. The controller is further configured to: heat the first fixing member in a first case in which a print command is received during the sleep mode; and, after performing the modification in the first case, start driving the second motor to drive the image forming unit.

[0007] Preferably, the image forming apparatus further includes a heater. The heater is configured to heat the first fixing member. The controller is further configured to set the mode to a sleep mode in which the heater is turned off. The controller is further configured to: heat the first fixing member in a first case in which a print command is received during the sleep mode; and start driving the first motor to drive the roller when the temperature of the first fixing member is higher than or equal to a specified temperature in the first case.

[0008] Preferably, the modification is performed after the first motor starts driving and rotating at a constant rotation speed.

[0009] Preferably, the image forming apparatus further includes a heater. The heater is configured to heat the first fixing member. The controller is further configured to set the mode to a preparation mode, in which the temperature of the first fixing member is maintained at a preparation temperature lower than a fixing temperature set when printing is performed. The controller is further configured to: in a second case where a print command is received during the preparation mode: heat the first fixing member so that the temperature of the first fixing member reaches the fixing temperature; and start driving the first motor to drive the roller after starting heating.

[0010] Preferably, the image forming apparatus further includes a heater. The heater is configured to heat the first fixing member. The controller is further configured to set the mode to a preparation mode, in which the temperature of the first fixing member is maintained at a preparation temperature lower than a fixing temperature set during printing. The controller is further configured to: in a second case where a print command is received during the preparation mode: convert the print data included in the print command into raster image data; and start driving the first motor to drive the roller after the conversion is completed.

[0011] Preferably, the image forming device further includes a heater and a second motor. The heater is configured to heat the first fixing member. The second motor is configured to drive the image forming unit. The controller is further configured to set the mode to a preparation mode, in which the temperature of the first fixing member is maintained at a preparation temperature lower than the fixing temperature set when printing. The controller is further configured to: in a second case in which a print command is received during the preparation mode: after the first motor starts driving in the second case but before the clamping pressure is changed from the second clamping pressure to the first clamping pressure, start driving the second motor to drive the image forming unit.

[0012] Preferably, the image forming apparatus further includes a photosensitive member, a developing roller, a third motor, and a first clutch. The developing roller is configured to supply developer to the photosensitive member. The third motor is configured to drive the pressure modifying mechanism. The first clutch is configured to switch between a first transmission state, in which the driving force of the third motor is transmitted to the pressure modifying mechanism, and a first disconnection state, in which the driving force of the third motor is not transmitted to the pressure modifying mechanism.

[0013] Preferably, the pressure modification mechanism includes a cam configured to pivotally move between a first position where the clamping pressure becomes a first clamping pressure and a second position where the clamping pressure becomes a second clamping pressure. Modifying the clamping pressure includes controlling the third motor to switch the first clutch to a first transmission state, thereby pivotally moving the cam from the second position to the first position.

[0014] Preferably, the image forming apparatus further includes a photosensitive member and a developing roller. The developing roller is configured to supply developer to the photosensitive member. The third motor further drives the developing roller.

[0015] Preferably, the image forming apparatus further includes a photosensitive member, a developing roller, a switching mechanism, and a second clutch. The developing roller is configured to supply developer to the photosensitive member. The switching mechanism is configured to switch the developing roller between a contact state in which the developing roller contacts the photosensitive member and a separation state in which the developing roller is separated from the photosensitive member. The second clutch is configured to switch between a second transmission state in which the driving force of the third motor is transmitted to the switching mechanism and a second separation state in which the driving force of the third motor is not transmitted to the switching mechanism.

[0016] Preferably, the pressure modifying mechanism includes a cam configured to pivotally move between a first position in which the clamping pressure becomes a first clamping pressure and a second position in which the clamping pressure becomes a second clamping pressure. Modifying the clamping pressure includes controlling the third motor to rotate when the second clutch is in the second disconnecting state, and then controlling the third motor to switch the first clutch to the first transmitting state, thereby pivotally moving the cam from the second position to the first position.

[0017] Preferably, the cam is pivotally moved from the second position to the first position by forward rotation of the third motor, and the cam is pivotally moved from the first position to the second position by reverse rotation of the third motor. Modifying the clamping pressure includes controlling the third motor to rotate forward.

[0018] Preferably, in a case where the clamping pressure is modified from the second clamping pressure to the first clamping pressure, the third motor rotates at a rotation speed slower than that when printing is performed.

[0019] Preferably, the image forming apparatus further includes a heater configured to heat the first fixing member. The controller is further configured to set a mode between a sleep mode and a standby mode, wherein the heater is turned off in the sleep mode and the temperature of the first fixing member is maintained at a standby temperature lower than a fixing temperature set during printing. In a first case where a print command is received during the sleep mode, driving of the third motor is started after starting driving of the first motor. In a second case where a print command is received in the standby mode, driving of the first motor is started after starting driving of the third motor.

[0020] Preferably, the second fixing member includes an upstream pad and a downstream pad. The upstream pad is configured to clamp the belt together with the first fixing member. The downstream pad is located downstream of the upstream pad in the sheet conveying direction and is configured to clamp the belt together with the first fixing member. When the clamping pressure is a first clamping pressure, both the upstream pad and the downstream pad clamp the belt together with the first fixing member. When the clamping pressure is a second clamping pressure, the upstream pad clamps the belt together with the first fixing member, while the downstream pad does not clamp the belt together with the first fixing member.

[0021] Preferably, the second clamping pressure is a minimum clamping pressure within a range in which the pressure modification mechanism can set the clamping pressure.

[0022] Preferably, the pressure modifying mechanism includes a cam configured to pivotally move between a first position at which the nip pressure becomes a first nip pressure and a second position at which the nip pressure becomes a second nip pressure. The second fixing member moves between the first nip position at which a nip portion is formed between the first fixing member and the second fixing member, and a second nip position at which a distance from the first fixing member to the second fixing member is greater than a distance at the first nip position.

[0023] According to another aspect, the present disclosure provides an image forming device. The image forming device includes an image forming portion, a first fixing member, a second fixing member, and a pressure modification mechanism. The image forming portion forms a developer image on a sheet. The first fixing member has a roller. The second fixing member has a belt to form a clamping portion together with the first fixing member. The pressure modification mechanism is configured to modify the clamping pressure at the clamping portion to a selected one of a first clamping pressure and a second clamping pressure that is smaller than the first clamping pressure. The image forming device is configured to: start driving the roller when a print command is received in a state where the clamping pressure is the second clamping pressure; after the driving is performed, modify the clamping pressure from the second clamping pressure to the first clamping pressure; and fix the developer image on the sheet in a state where the clamping pressure is the first clamping pressure.

[0024] Preferably, the image forming apparatus further includes a heater. The heater is configured to heat the first fixing member. The controller is further configured to set the mode to a sleep mode in which the heater is turned off. The image forming apparatus is further configured to heat the first fixing member in a first case where a print command is received during the sleep mode. The controller is further configured to control the roller to start driving if the temperature of the first fixing member is greater than or equal to a predetermined temperature in the first case. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The specific features and advantages of the present disclosure and other objects will become apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0026] Figure 1 is a sectional view showing a color printer according to an embodiment;

[0027] Figure 2 is a cross-sectional view showing a fixing device of a color printer;

[0028] Figure 3 is an exploded perspective view showing components located within a fixing device with a defined internal space;

[0029] Figure 4 is a perspective view showing a pressure modifying mechanism of a color printer;

[0030] FIG5( a) is a cross-sectional view showing the pressure modification mechanism when the clamping pressure is the maximum clamping pressure;

[0031] FIG5( b) is a cross-sectional view showing the periphery of the configuration of the clamping region when the clamping pressure is the maximum clamping pressure;

[0032] FIG6( a) is a sectional view showing the pressure modification mechanism when the clamping pressure is a second clamping pressure;

[0033] FIG6( b) is a cross-sectional view showing the periphery of the configuration of the clamping region when the clamping pressure is a second clamping pressure;

[0034] Figure 7 is an explanatory diagram showing the relationship between a controller and components controlled by the controller;

[0035] Figure 8 is a flow chart illustrating operations performed by the controller in sleep mode;

[0036] Figure 9 is a timing diagram showing operations performed by the controller in a preparation mode; and

[0037] Figure 10 is a timing diagram illustrating operations performed by the controller in the sleep mode. DETAILED DESCRIPTION

[0038] Next, embodiments of the present disclosure will be described while referring to the accompanying drawings. Figure 1 A color printer 1 is shown as an example of an image forming apparatus. The color printer 1 is provided with a main housing 2, and within the main housing 2 are provided: a sheet feeding section 20 for supplying a sheet S to be printed; an image forming section 30 for forming a toner image on the sheet S supplied by the sheet feeding section 20; a fixing device 80 for fixing the toner image on the sheet S; a paper discharge section 90 for discharging the sheet S from the main housing 2 after the image has been formed and fixed on the sheet S; and a controller 100.

[0039] An opening 2A is formed at the top of the main housing 2. An upper cover 3 is pivotally supported on the main housing 2 and opens and closes the opening 2A. The top surface of the upper cover 3 forms a paper discharge tray 4 that collects sheets S discharged from the main housing 2. A plurality of LED mounting members 5 are provided on the bottom surface of the upper cover 3. Each LED mounting member 5 holds an LED unit 40.

[0040] A sheet feeding section 20 is provided in the bottom portion of the main housing 2. The sheet feeding section 20 is provided with a paper tray 21 that is detachably mounted in the main housing 2, and a sheet feeding mechanism 22 that conveys a sheet S from the paper tray 21 toward the image forming section 30. The sheet feeding mechanism 22 includes a pickup roller 23, a separation roller 24, a separation pad 25, and registration rollers 26.

[0041] In the sheet feeding section 20, the pickup roller 23 feeds a sheet S from the paper tray 21. Subsequently, the separation roller 24 and the separation pad 25 separate the sheet S fed by the pickup roller 23, ensuring that each sheet is fed one at a time. Thereafter, the registration rollers 26 straighten the leading edge of the sheet S before conveying it toward the image forming section 30. Specifically, when the sheet S is conveyed to the registration rollers 26, the registration rollers 26 are stopped. When the sheet S contacts the stopped registration rollers 26, the leading edge of the sheet S is aligned with the registration rollers 26, thereby eliminating any skew in the sheet S. Subsequently, the registration rollers 26 begin rotating to convey the sheet S forward.

[0042] The image forming section 30 includes four LED units 40 , four process cartridges 50 , a transfer unit 70 , and a belt cleaner 10 .

[0043] The LED units 40 are coupled to the corresponding LED mounting members 5 so as to be pivotable relative to the LED mounting members 5. Positioning members provided in the main housing 2 support the LED units 40 in place.

[0044] The process cartridges 50 are arranged in parallel in the front-to-rear direction between the upper cover 3 and the sheet feeding portion 20. Each process cartridge 50 is composed of a photosensitive drum 51 as an example of a photosensitive member, a charger 52, a developing roller 53, a toner accommodating chamber 54 for accommodating toner (an example of a developer), and a cleaning roller 55.

[0045] The process cartridges 50 are denoted by symbols 50K, 50Y, 50M, and 50C to indicate the colors of the toners they contain. Thus, the process cartridge 50K contains black (K) toner, the process cartridge 50Y contains yellow (Y) toner, the process cartridge 50M contains magenta (M) toner, and the process cartridge 50C contains cyan (C) toner. The process cartridges 50K, 50Y, 50M, and 50C are arranged in the given order starting from the upstream side in the conveying direction of the sheet S. Note that in the specification and the drawings, the same symbols K, Y, M, and C are also attached to the photosensitive drum 51, the developing roller 53, and the cleaning roller 55 to identify the colors of the toners used with the corresponding components (i.e., black, yellow, magenta, and cyan).

[0046] The photosensitive drum 51 is a member capable of carrying toner. Specifically, each LED unit 40 exposes the surface of the corresponding photosensitive drum 51 so that an electrostatic latent image is formed thereon, and the area of the photosensitive drum 51 on which the electrostatic latent image is formed carries toner. One photosensitive drum 51 is provided in each process cartridge 50. The photosensitive drums 51 are arranged at intervals along the conveyance direction of the sheet S.

[0047] The developing roller 53 is a roller that carries toner and is configured to contact the corresponding photosensitive drum 51 so as to supply toner to the electrostatic latent image formed on the photosensitive drum 51 .

[0048] The developing roller 53 can be brought into contact with or separated from the corresponding photosensitive drum 51. The controller 100 controls the switching mechanism SW (see FIG. Figure 7 ) to switch the developing roller 53 between the pressure contact position and the separation position. Specifically, all of the developing rollers 53K, 53Y, 53M, and 53C are brought into contact with the corresponding photosensitive drums 51K, 51Y, 51M, and 51C in color mode to supply toner to the corresponding photosensitive drums 51K, 51Y, 51M, and 51C. However, only the black developing roller 53K is brought into contact with the photosensitive drum 51K in monochrome mode, while the developing rollers 53Y, 53M, and 53C for the remaining three colors are separated from their corresponding photosensitive drums 51Y, 51M, and 51C. In the cleaning process described later, all of the developing rollers 53K, 53Y, 53M, and 53C are separated from the corresponding photosensitive drums 51K, 51Y, 51M, and 51C.

[0049] The cleaning rollers 55 are members capable of recovering toner from the corresponding photosensitive drums 51. One cleaning roller 55 is provided adjacent to the corresponding photosensitive drum 51.

[0050] The transfer unit 70 is provided between the sheet feeding portion 20 and the process cartridge 50. The transfer unit 70 is provided with a driving roller 71, a driven roller 72, a belt 73, and a transfer roller 74.

[0051] The drive roller 71 and the driven roller 72 are arranged parallel to each other while being separated in the front-to-back direction. The belt 73 is an endless belt stretched around the drive roller 71 and the driven roller 72. The belt 73 is a member for conveying the sheet S. The outer surface of the belt 73 contacts the photosensitive drum 51. Four transfer rollers 74 are provided within the belt 73 at positions opposing the corresponding photosensitive drums 51.

[0052] The belt 73 is interposed between the photosensitive drums 51 and the corresponding transfer rollers 74. The sheet S is conveyed by the belt 73 and the photosensitive drums 51.

[0053] The belt cleaner 10 is a device that slides against the belt 73 to recover toner and other substances that have been deposited on the belt 73. The belt cleaner 10 is provided below the belt 73. Specifically, the belt cleaner 10 is provided with a sliding contact roller 11, a recovery roller 12, a blade 13, and a waste toner container 14.

[0054] The sliding contact roller 11 is provided so as to contact the outer surface of the belt 73. The belt 73 is interposed between the sliding contact roller 11 and the backup roller 15 provided inside the belt 73. The sliding contact roller 11 recovers the substance deposited on the belt 73.

[0055] The recovery roller 12 is a roller that slides in contact with the sliding contact roller 11 to recover the material deposited on the sliding contact roller 11. The blade 13 is provided so as to slide against the recovery roller 12 and scrape off the recovered material on the recovery roller 12. The material scraped off from the recovery roller 12 falls into the waste toner container 14.

[0056] The fixing device 80 is provided with a first fixing member 81 and a second fixing member 82. The structure of the fixing device 80 will be described in more detail later.

[0057] In the image forming unit 30 having the above-described structure, the charger 52 applies a uniform charge to the surface of the photosensitive drum 51. Subsequently, the charged surface of the photosensitive drum 51 is exposed to light by the LED unit 40, forming an electrostatic latent image based on image data on the photosensitive drum 51. Thereafter, toner is supplied from the developing roller 53 to the electrostatic latent image, forming a toner image carried on the photosensitive drum 51.

[0058] As the sheet S passes between the photosensitive drum 51 and the corresponding transfer roller 74 provided inside the belt 73, the toner image formed on each photosensitive drum 51 is transferred to the sheet S carried on the belt 73. As the sheet S passes between the first fixing member 81 and the second fixing member 82, the toner image transferred to the sheet S is thermally fixed to the sheet S.

[0059] The paper discharge section 90 is provided with a discharge side conveying path 91 and a plurality of conveying rollers 92. After the toner image is thermally fixed to the sheet S, the conveying rollers 92 convey the sheet S along the discharge side conveying path 91 and discharge the sheet S from the main casing 2 to be collected in the paper discharge tray 4.

[0060] like Figure 2 As shown, the fixing device 80 is provided with a heater 110 and a pressure modifying mechanism 300 (see FIG. 1 ) described later, in addition to the first fixing member 81 and the second fixing member 82 described above. Figure 4 ). The pressure modifying mechanism 300 described later presses the second fixing member 82 against the first fixing member 81. In the following description, the direction in which the second fixing member 82 presses against the first fixing member 81 and the opposite direction thereof will be referred to as a "prescribed direction". In this embodiment, the prescribed direction is orthogonal to the width direction and the moving direction described later, and is a direction in which the first fixing member 81 and the second fixing member 82 face each other.

[0061] The first fixing member 81 includes a rotatable roller 120. When the second fixing member 82 is positioned against the first fixing member 81, a nip region NP is formed therebetween. The second fixing member 82 includes a belt 130, a nip-forming member N, a retainer 140, a support 200, a belt guide G, and a sliding sheet 150. The belt 130 and the sliding sheet 150 are made of a heat-resistant resin, such as polyimide, having a glass transition temperature greater than or equal to 140 degrees Celsius. In the following description, the width direction of the belt 130 will be referred to simply as the "width direction." The width direction is the direction in which the rotation axis of the rotatable roller 120 extends. Therefore, the width direction is the same as the axial direction of the rotatable roller 120. The width direction is orthogonal to the specified direction.

[0062] The heater 110 is a halogen lamp. When powered, the heater 110 emits light and generates heat. The radiant heat generated by the heater 110 heats the rotatable roller 120. The heater 110 extends through the interior of the rotatable roller 120 along the rotation axis of the rotatable roller 120.

[0063] The rotatable roller 120 is a cylindrical roller elongated in the width direction. The rotatable roller 120 is heated by the heater 110. The rotatable roller 120 has a tubular body 121 formed of metal or the like, and an elastic layer 122 covering the outer surface of the tubular body 121. The elastic layer 122 is formed of rubber (such as silicone rubber). The rotatable roller 120 is rotatably supported on the side frame 83 (see FIG. 1 ) described later. Figure 4 ). The first motor M1 (refer to Figure 7 Description) is provided in the main housing 2. The first motor M1 is an input for driving the rotatable roller 120 in Figure 2 The fixing motor rotates counterclockwise.

[0064] The belt 130 is a long cylindrical member having flexibility. The belt 130 forms a nip region NP together with the first fixing member 81, particularly the rotatable roller 120. Although not shown in the figure, the belt 130 has a base formed of metal, resin, etc., and a release layer covering the outer surface of the base. Due to the friction between the belt 130 and the rotatable roller 120 or the sheet S interposed between the belt 130 and the rotatable roller 120, the belt 130 follows the rotation of the rotatable roller 120. Figure 2 Grease or other lubricant is applied to the inner peripheral surface 131 of the belt 130. The clamp forming member N, the retainer 140, the support 200, the belt guide G and the sliding sheet 150 are all arranged in the inner space defined by the cylindrical belt 130.

[0065] Thus, the nip forming member N, the holder 140 , the stay 200 , the belt guide G, and the sliding sheet 150 are surrounded by the belt 130 .

[0066] like Figure 2 and Figure 3 As shown, the nip forming member N, together with the rotatable roller 120, clamps a portion of the belt 130 to form a nip region NP. The nip forming member N includes an upstream nip forming member N1 and a downstream nip forming member N2.

[0067] The upstream nip forming member N1 includes an upstream pad P1 and an upstream fixing plate B1. The upstream pad P1 is a rectangular parallelepiped member. The upstream pad P1 is formed of rubber (such as silicone rubber). The upstream pad P1 and the rotatable roller 120 sandwich a portion of the belt 130 to form an upstream nip region NP1.

[0068] In the following description, the direction in which the belt 130 moves within the upstream nip region NP1 and the nip region NP will be referred to simply as the "movement direction." In this embodiment, the movement direction is the direction following the outer peripheral surface of the rotatable roller 120. However, since this direction is substantially orthogonal to the specified direction and the width direction within the nip region NP, the movement direction is illustrated in the figures as being orthogonal to both. Note that within the nip region NP, the movement direction is the same as the conveyance direction of the sheet S.

[0069] The upstream pad P1 is fixed to a surface of the upstream fixing plate B1 that is opposite to the rotatable roller 120. The upstream fixing plate B1 is a member formed of metal or other material that is harder than the upstream pad P1.

[0070] The downstream nip forming member N2 is arranged on the downstream side of the upstream nip forming member N1 in the moving direction and is spaced apart from the upstream nip forming member N1. The downstream nip forming member N2 has a downstream pad P2 and a downstream fixing board B2.

[0071] The downstream pad P2 is a rectangular parallelepiped member. It is formed of rubber (such as silicone rubber). Together with the rotatable roller 120, the downstream pad P2 clamps a portion of the belt 130 to form a downstream clamping area NP2. The downstream pad P2 is separated from the upstream pad P1 in the direction of belt 130 rotation.

[0072] Therefore, an intermediate nip region NP3 exists between the upstream nip region NP1 and the downstream nip region NP2, where the second fixing member 82 does not directly apply pressure to the first fixing member 81. Although the belt 130 contacts the rotatable roller 120 in the intermediate nip region NP3, since no members exist on the opposite side of the rotatable roller 120 from the belt 130 in this region, the belt 130 applies little pressure to the rotatable roller 120. Therefore, the sheet S passing through the intermediate nip region NP3 is heated by the rotatable roller 120 but receives little pressure. In this embodiment, the area from the upstream side of the upstream nip region NP1 to the downstream side of the downstream nip region NP2—that is, the entire area on the outer surface of the belt 130 that is in contact with the rotatable roller 120—is referred to as the nip region NP. Therefore, the nip region NP in this embodiment includes an area that receives no pressure from the upstream pad P1 or the downstream pad P2. In other words, the clamping area NP is an area from the upstream end point where the belt 130 is in pressure contact with the rotatable roller 120 in the moving direction to the downstream end point where the belt 130 is in pressure contact with the rotatable roller 120 in the moving direction. The belt 130 and the rotatable roller 120 can be in pressure contact with each other at a single point. In this case, the clamping area is a single clamping point. In addition, actions such as "clamping", "clamping" and "nipping" indicate that two components (such as the first fixing member 81 and the second fixing member 82) are in contact with each other and generate pressure between them. Therefore, the clamping area is an area or point where two components are in contact with each other and at least includes a clamping portion for clamping a sheet by the two components.

[0073] The downstream pad P2 is fixed to the surface of the downstream fixing plate B2 that is opposite to the rotatable roller 120. The downstream fixing plate B2 is a member formed of a metal or the like that is harder than the downstream pad P2.

[0074] Note that the hardness of the upstream pad P1 is greater than the hardness of the elastic layer 122 provided on the rotatable roller 120. Furthermore, the hardness of the downstream pad P2 is greater than the hardness of the upstream pad P1.

[0075] The term "hardness" in this specification refers to the Shore hardness measured using a durometer according to the method specified in ISO 7619-1. Shore hardness is a value based on the depth of indentation when a specified presser foot is pressed into a test piece under specified conditions. For example, in this embodiment, if the Shore hardness of the elastic layer 122 is 5, the Shore hardness of the upstream pad P1 is preferably between 6 and 10, while the Shore hardness of the downstream pad P2 is preferably between 70 and 90.

[0076] The retainer 140 is a member that holds the clamp forming member N. The retainer 140 is formed of a heat-resistant resin or the like. The retainer 140 has a retainer body 141 and two engaging portions 142 and 143 ( Figure 3 ).

[0077] The holder body 141 is a member that holds the nip forming member N. Most of the holder body 141 is provided within the range of the belt 130 in the width direction. The holder body 141 is supported by the support column 200 .

[0078] The engaging portions 142 and 143 extend outward in the width direction from respective ends of the holder body 141. The engaging portions 142 and 143 are located outside the range of the belt 130 in the width direction. The engaging portions 142 and 143 engage with respective width direction ends of the first support 210 described later.

[0079] The support 200 is a member that supports the holder 140. The support 200 is located on the opposite side of the clamp forming member N relative to the holder 140. The support 200 is provided with a first support 210 and a second support 220. The second support 220 is connected to the retainer 140 by a connecting member CM ( Figure 3 ) is connected to the first pillar 210.

[0080] The first support column 210 is a member that supports the holder body 141 of the holder 140. The first support column 210 is formed of metal, etc. The first support column 210 has a base portion 211 and a hem HB that has been bent in a hemming process.

[0081] The base portion 211 has a contact surface Ft along an edge facing the holder 140 for contacting the holder body 141 of the holder 140. The contact surface Ft is a flat surface perpendicular to a prescribed direction.

[0082] The base portion 211 has a load input portion 211A provided on each widthwise end. The load input portion 211A is connected to the pressure modification mechanism 300 (see FIG. Figure 4 ) receiving force. A load input portion 211A is formed in an edge of the base portion 211 on a side opposite to the grip forming member N in a prescribed direction. The load input portion 211A is a concave portion that opens toward a side opposite to the grip forming member N in a prescribed direction.

[0083] The buffer member BF is installed in the load input portion 211A. The buffer member BF is formed of a resin or the like. The buffer member BF suppresses the metal base portion 211 from contacting the metal arm 310 (see FIG. 1 ) described later. Figure 4 Each buffer member BF has a fitting portion BF1 that fits into the corresponding load input portion 211A, and a pair of leg portions BF2 that are respectively provided on the upstream and downstream sides of the outer width direction end of the corresponding base portion 211 in the moving direction.

[0084] The belt guide G is a member that guides the inner peripheral surface 131 of the belt 130. The belt guide G is formed of a heat-resistant resin, etc. The belt guide G has an upstream guide G1 and a downstream guide G2.

[0085] Sliding sheet 150 is a rectangular sheet designed to reduce frictional resistance between belt 130 and pads P1 and P2. Sliding sheet 150 is interposed between inner circumferential surface 131 of belt 130 and pads P1 and P2 within nip region NP. Sliding sheet 150 is formed from an elastically deformable material. While any suitable material may be used for sliding sheet 150, a resin sheet containing polyimide is employed in this embodiment.

[0086] like Figure 2 As shown, the upstream guide G1 , the downstream guide G2 and the first support 210 are fastened together by screws SC.

[0087] like Figure 4 As shown, the fixing device 80 is further provided with a frame FL and a pressure modifying mechanism 300. The frame FL is formed of metal or the like and supports the first fixing member 81 and the second fixing member 82. The frame FL includes two side frames 83, two brackets 84, and a connecting frame 85. The side frames 83 and the brackets 84 are provided at the widthwise ends of the first fixing member 81 and the second fixing member 82. The connecting frame 85 connects the two side frames 83.

[0088] The side frames 83 are frame members that support the first fixing member 81 and the second fixing member 82. Each side frame 83 has a spring engaging portion 83A. One end of a first spring 320 described later is engaged in each spring engaging portion 83A.

[0089] The brackets 84 are fixed to the corresponding side frames 83. The brackets 84 are members that support the second fixing member 82 so that the second fixing member 82 can move in a specified direction. Specifically, each bracket 84 has a first elongated hole 84A that extends in the specified direction. The elongated holes 84A guide the corresponding ends of the first support posts 210 via the engaging portions 142 and 143 of the retainer 140, allowing the first support posts 210 to move in the specified direction.

[0090] The pressure modification mechanism 300 modifies the clamping pressure at the clamping area NP. Figure 4 and 5(a) As shown, the pressure modification mechanism 300 is provided with a pair of arms 310, a first spring 320, a second spring 330 and a cam 340. Each of the arms 310, the first spring 320, the second spring 330 and the cam 340 is provided on the first and second widthwise sides of the frame FL.

[0091] The arm 310 is a member for pressing the first stay 210 via the buffer member BF. The arm 310 supports the second fixing member 82 and is supported by the side frame 83 so as to be pivotally movable.

[0092] Each arm 310 has an arm body 311 and a cam follower 350. The arm body 311 is an L-shaped plate-like member formed of metal or the like.

[0093] Each arm body 311 has a first end 311A pivotally supported on the corresponding side frame 83, a second end 311B coupled to one end of the corresponding first spring 320, and an engagement hole 311C supporting the second fixing member 82. The engagement hole 311C is formed at a position between the first end 311A and the second end 311B and engages with the corresponding buffer member BF.

[0094] The arm body 311 also has a guide protrusion 312 extending toward the cam 340. The guide protrusion 312 is provided between the second end 311B and the engagement hole 311C in a direction from the second end 311B to the engagement hole 311C.

[0095] The cam follower 350 is mounted above the guide protrusion 312 of the arm 311 and is movable relative to the guide protrusion 312 and is capable of contacting the cam 340. The cam follower 350 is formed of a resin or the like. The cam follower 350 includes a cylindrical portion 351 mounted above the guide protrusion 312, a contact portion 352 provided at one end of the cylindrical portion 351, and a flange portion 353 provided at the other end of the cylindrical portion 351.

[0096] The cylindrical portion 351 is supported by the guide protrusion 312 and is movable in the direction in which the guide protrusion 312 extends. The contact portion 352 is a wall that closes an opening formed in the end portion of the cylindrical portion 351 on the cam 340 side. The contact portion 352 is arranged between the cam 340 and the end portion of the guide protrusion 312. A flange portion 353 protrudes from the other end of the cylindrical portion 351 in a direction orthogonal to the moving direction of the cam follower 350.

[0097] The second spring 330 is provided between the cylindrical portion 351 and the arm body 311. With this configuration, the arm body 311 can be pushed by the first spring 320 and the second spring 330.

[0098] The first spring 320 applies a first urging force to the second fixing member 82 , and specifically, applies the first urging force to the second fixing member 82 through the arm body 311 .

[0099] More specifically, the first springs 320 push the upstream pad P1 and the downstream pad P2 toward the rotatable roller 120 via the arm body 311, the buffer member BF, the first support column 210, and the retainer 140. The first springs 320 are tension coil springs formed of metal, etc. One end of each first spring 320 is coupled to the spring engagement portion 83A of the corresponding side frame 83, while the other end is coupled to the second end 311B of the corresponding arm body 311.

[0100] The second spring 330 can apply a second urging force to the second fixing member 82 in a direction opposite to the first urging force, and specifically, can apply the second urging force to the second fixing member 82 through the arm body 311. The second spring 330 is a compression coil spring formed of metal, etc. The second spring 330 is disposed between the corresponding cylindrical portion 351 and the arm body 311, wherein the guide protrusion 312 is inserted into an internal space formed in the compression coil spring 330.

[0101] The cam 340 is a member capable of changing the compression state of the second spring 330 between a first compressed state (in which no second thrust is applied to the second fixing member 82), a second compressed state (in which the second thrust is applied to the second fixing member 82), and a third compressed state (in which the second spring 330 is further compressed from the second compressed state). The cam 340 is supported on the corresponding side frame 83 so as to be pivotally movable (or rotatable) between a first cam position (shown in FIG. 5( a) ), an intermediate cam position (not shown), and a second cam position (see FIG. 6( a) ). The intermediate cam position is pivotally movable (or rotated) approximately 90 degrees clockwise from the first cam position in FIG. 5( a) , and the second cam position is pivotally movable (or rotated) approximately 270 degrees clockwise from the first cam position in FIG. 5( a) .

[0102] The cams 340 are formed of resin, etc. Each cam 340 has a first region 341 , a second region 342 , and a third region 343 . The first region 341 , the second region 342 , and the third region 343 are located along the circumferential surface of the cam 340 .

[0103] The first region 341 is a region located closest to the cam follower 350 when the cam 340 is in the first cam position. When the cam 340 is in the first cam position shown in FIG. 5( a ), the first region 341 is separated from the cam follower 350 .

[0104] The second area 342 is an area on the cam 340 that contacts the cam follower 350 when the cam 340 is in the intermediate cam position. More specifically, when the cam 340 has pivotally moved (or rotated) approximately 90 degrees clockwise in FIG. 5( a) from the first cam position, the second area 342 contacts the cam follower 350. The distance from the second area 342 to the rotation center of the cam 340 is greater than the distance from the first area 341 to the rotation center of the cam 340.

[0105] The third region 343 is the region that contacts the cam follower 350 when the cam 340 is in the second cam position. More specifically, the third region 343 is the region of the cam 340 that contacts the cam follower 350 after the cam 340 has pivotally moved (or rotated) approximately 270 degrees clockwise in FIG. 5( a ) from the first cam position, as shown in FIG. 6( a ), or when the cam 340 has pivotally moved (or rotated) approximately 180 degrees clockwise in FIG. 5( a ) from the intermediate cam position. The distance from the third region 343 to the rotational center of the cam 340 is greater than the distance from the second region 342 to the rotational center of the cam 340.

[0106] When the cam 340 is in the first cam position, the second spring 330 is in the first compressed state because the cam 340 is separated from the cam follower 350. When the cam 340 causes the second spring 330 to be in the first compressed state in this manner, the arm 311 is in the first orientation shown in Figure 5(a).

[0107] Specifically, when the cam 340 has placed the second spring 330 in the first compressed state, the cam 340 is separated from the cam follower 350, so that the second urging force of the second spring 330 is not applied to the second fixing member 82 via the arm body 311, and only the first urging force of the first spring 320 is applied to the second fixing member 82 via the arm body 311. When the first spring 320 applies the first urging force to the second fixing member 82 and the second spring 330 does not apply the second urging force to the second fixing member 82 in this orientation, the clamping pressure is the maximum clamping pressure.

[0108] When the cam 340 pivotally moves (or rotates) from the first cam position shown in FIG5(a) to the intermediate cam position, the cam 340 contacts the cam follower 350 and moves the cam follower 350 a predetermined amount relative to the arm 311. When the cam 340 moves to the intermediate cam position, the compressed state of the second spring 330 is deformed into a second compressed state that is more compressed than the first compressed state.

[0109] Since the cam follower 350 is pressed by the cam 340 when the cam 340 is in the intermediate cam position, the second urging force of the second spring 330 is applied to the second fixing member 82 in the opposite direction to the first urging force via the arm body 311. Therefore, when the first spring 320 applies the first urging force to the second fixing member 82 and the second spring 330 applies the second urging force to the second fixing member 82, the nip pressure becomes an intermediate nip pressure that is smaller than the maximum nip pressure.

[0110] Note that when the cam 340 places the second spring 330 in the second compressed state, the arm 311 maintains the aforementioned first orientation. Here, the downstream pad P2 remains pressed against the rotatable roller 120, so that a load is applied to the downstream pad P2. While the downstream pad P2 is pressed against the rotatable roller 120, i.e., while a load is applied to the downstream pad P2, the shape of the downstream pad P2 remains substantially unchanged, regardless of the magnitude of the load. Because the shape of the downstream pad P2 remains substantially unchanged, the support 200 supporting the downstream pad P2 and the arm 310 supporting the support 200 remain in a substantially fixed position, regardless of the magnitude of the load. Furthermore, since the position of the upstream pad P1 is determined by the position of the downstream pad P2, the position of the upstream pad P1 remains unchanged while the shape and position of the downstream pad P2 remain substantially unchanged. Therefore, the total clamping width (the length from the entrance of the upstream clamping area NP1 to the exit of the downstream clamping area NP2) does not differ between strong clamping (maximum clamping pressure) and weak clamping (intermediate clamping pressure), and thus, the position of the arm 310 remains substantially constant.

[0111] Here, the downstream pad P2 does not deform under these circumstances because it has a sufficiently greater hardness than the upstream pad P1 and the elastic layer 122 of the rotatable roller 120. More specifically, the downstream pad P2 has sufficient hardness to be substantially nondeformed under the clamping pressure required in the downstream nip region NP2, which is within a range from the maximum clamping pressure (downstream clamping pressure in strong clamping) to the intermediate clamping pressure (downstream clamping pressure in weak clamping). In other words, the maximum clamping pressure and the intermediate minimum clamping pressure required for downstream clamping are set to a level within which the downstream pad P2 is substantially nondeformed.

[0112] Here, “the downstream pad P2 hardly undergoes deformation change” allows the downstream pad P2 to undergo some deformation, as long as the amount of change in the clamping width (the clamping length and position in the moving direction of the belt 130) of the downstream clamping area NP2 formed by the downstream pad P2 does not affect the conveying of the sheet and the image quality (that is, the amount of change in the downstream clamping width does not have to be zero).

[0113] In this manner, since the arm body 311 is in the first orientation regardless of whether the compressed state of the second spring 330 is the first compressed state or the second compressed state, the upstream pad P1 and the downstream pad P2 press the belt 130 against the rotatable roller 120 regardless of whether the nip position is the maximum nip pressure or the intermediate nip pressure. Specifically, since the position of the second fixing member 82 relative to the rotatable roller 120 is substantially the same in the maximum and intermediate nip pressure states, the width (length in the moving direction) of the nip area NP is substantially the same for both states.

[0114] Here, the maximum nip pressure or the intermediate nip pressure is a first nip pressure set for printing, particularly for fixing a toner image onto a sheet S. For example, the maximum nip pressure is used when the sheet S has a first thickness, while the intermediate nip pressure is used when the sheet S has a second thickness greater than the first thickness. That is, the first nip pressure is set between the maximum nip pressure and the intermediate nip pressure according to the thickness of the sheet S.

[0115] In addition, the first cam position or the intermediate cam position is a first position where the clamping pressure is the maximum clamping pressure or the intermediate clamping pressure (ie, the first clamping pressure). In addition, the second cam position is a second position where the clamping pressure is the minimum clamping pressure (ie, the second clamping pressure).

[0116] When pivotally moving (or rotating) from the intermediate cam position to the second cam position shown in FIG6( a), the cam 340 first moves the cam follower 350 further toward the arm 311, and then presses the arm 311 through the cam follower 350. As a result, the second spring 330 is deformed to a third compressed state, which is more compressed than the second compressed state, and the arm 311 is pivotally moved from the first orientation to a second orientation different from the first orientation.

[0117] Specifically, in the initial stage of the process for pivotally moving (or rotating) the cam 340 from the intermediate cam position to the second cam position, the cam follower 350 moves relative to the arm 311, causing the contact portion 352 of the cam follower 350 to approach the distal end of the guide protrusion 312. When the contact portion 352 contacts the distal end of the guide protrusion 312, the compressed state of the second spring 330 is in the third compressed state. When the cam 340 thus causes the second spring 330 to be in the third compressed state, the contact portion 352, which constitutes a portion of the cam follower 350, is interposed between the cam 340 and the guide protrusion 312. In other words, the contact portion 352 contacts both the cam 340 and the guide protrusion 312. Thereafter, as the cam 340 further pivotally moves (or rotates), the cam 340 presses against the guide protrusion 312 via the contact portion 352, causing the arm 311 to pivotally move from the first orientation to the second orientation against the urging force of the first spring 320.

[0118] When the arm body 311 is placed in the second orientation by this operation, the second fixing member 82 is positioned farther away from the rotatable roller 120 (the position in Figure 6 (b)) than when the arm body 311 is in the first orientation (the position in Figure 5 (b)). The position of the second fixing member 82 when the arm body 311 is in the first orientation will be referred to as the "first clamping position", and the position of the second fixing member 82 when the arm body 311 is in the second orientation will be referred to as the "second clamping position". In the second clamping position, the distance between the first fixing member 81 and the second fixing member 82 is greater than the distance in the first clamping position. As the cam 340 pivotally moves (or rotates), the second fixing member 82 moves between the first clamping position and the second clamping position, in which the second fixing member 82 is farther away from the rotatable roller 120 than in the first clamping position. When the second fixing member 81 is in the second clamping position shown in Figure 6 (b), the rotatable roller 120 is in pressure contact with the belt 130 corresponding to the downstream portion of the upstream pad P1. Therefore, in this case, the nip region NP is the area between the rotatable roller 120 and the belt 130 corresponding to the downstream portion of the upstream pad P1. In this case, although the rotatable roller 120 is in contact with the belt 130 in the area downstream of the upstream pad P1, little nip pressure is generated in this area. Therefore, the nip region NP does not include the area downstream of the upstream pad P1. Although in this example, the rotatable roller 120 is in contact with a portion of the belt 130 in the area downstream of the upstream pad P1, when the second fixing member 81 is in the second nip position, the rotatable roller 120 can separate from the portion of the belt 130 in the area downstream of the upstream pad P1.

[0119] When the cam 340 moves to the second cam position, causing the arm 311 to switch to the second orientation, the position of the second fixing member 82 relative to the rotatable roller 120 changes so that the width of the clamping area NP is smaller than the width when the arm 311 is in the first orientation, and the clamping pressure is a minimum clamping pressure that is smaller than the intermediate clamping pressure. In other words, by changing the orientation of the arm 310 and the cam 340, the clamping pressure and the clamping width can be modified. Specifically, when the arm 310 is in the second orientation, the belt 130 is only clamped between the upstream pad P1 and the rotatable roller 120, and not between the downstream pad P2 and the rotatable roller 120. Therefore, when the arm 310 is in the second orientation, the upstream clamping pressure and the upstream clamping width generated in the upstream clamping area NP1 are both reduced, while the downstream clamping pressure generated in the upstream clamping area NP2 is eliminated. In other words, when the arm 310 is in the second orientation, the upstream clamping region NP1 is the only region that generates clamping pressure, whereas when the arm 310 is in the first orientation, both the upstream clamping region NP1 and the downstream clamping region NP2 are regions that generate clamping pressure. Therefore, when the arm 310 is in the second orientation, the size of all regions that generate clamping pressure is smaller than when the arm is in the first orientation.

[0120] The minimum clamping pressure is when printing is not performed, especially when the first motor M1 (see Figure 7 ) is set for the non-printing time when the printing is stopped. The minimum clamping pressure is also the minimum clamping pressure within the range of clamping pressures that can be modified by the pressure modification mechanism 300. The maximum clamping pressure is the maximum clamping pressure within the same range.

[0121] In this embodiment, when the clamping pressure is set to the minimum clamping pressure, the belt 130 is clamped between the upstream pad P1 and the rotatable roller 120, but the present disclosure is not limited to this configuration. For example, when the clamping pressure is the minimum clamping pressure, the belt 130 does not need to be clamped between the upstream pad P1 and the rotatable roller 120. In this case, the minimum clamping pressure is 0.

[0122] In the present embodiment, when the rotatable roller 120 is rotated while the nip pressure is the minimum nip pressure, the belt 130 rotates by following the rotation of the rotatable roller 120 .

[0123] like Figure 7 As shown, the color printer 1 is further provided with a first motor M1, a second motor M2, a third motor M3, a fourth motor M4, a first clutch C1, a second clutch C2, a sheet sensor SE1, a fixed sheet sensor SE2, a position sensor SE3 and a temperature sensor SE4.

[0124] The third motor M3 is a developing motor or a pressure modifying motor. The third motor M3 is configured to rotate in both forward and reverse directions and is primarily configured to drive each developing roller 53 to rotate. In this embodiment, the rotation direction of the third motor M3 during printing will be referred to as the forward direction. The third motor M3 is coupled to the developing roller 53 via a gear and a clutch (not shown) to rotate the developing roller 53. The third motor M3 is also coupled to the switching mechanism SW via a second clutch C2 and a gear (not shown). The third motor M3 is also coupled to the cam 340 of the pressure modifying mechanism 300 via a first clutch C1 and a gear (not shown).

[0125] The first motor M1 is provided to drive the rotatable roller 120 to rotate.

[0126] The second motor M2 is a process motor provided for applying a driving force to components in the image forming section 30. Specifically, the second motor M2 drives the photosensitive drum 51 and the like to rotate.

[0127] The fourth motor M4 is a conveying motor provided to apply a driving force to a conveying roller that conveys the sheet S. Specifically, the fourth motor M4 drives the pickup roller 23 , the separation roller 24 , the registration roller 26 , and the like to rotate.

[0128] The second clutch C2 is, for example, an electromagnetic clutch and is a developing clutch that can be switched between a second transmission state in which the driving force of the third motor M3 is transmitted to the switching mechanism SW and a second disconnection state in which the driving force of the third motor M3 is not transmitted to the switching mechanism SW.

[0129] The switching mechanism SW is configured to switch the state of the developing roller 53 between a pressure-contact state in which the developing roller 53 is pressed against the photosensitive drum 51 and a separated state in which the developing roller 53 is separated from the photosensitive drum 51. When the second clutch C2 is set to the second transmission state under the conditions that the developing roller 53 is in the separated state and the third motor M3 is rotating in the forward direction, the switching mechanism SW switches the developing roller 53 from the separated state to the pressure-contact state. When the second clutch C2 is set to the second transmission state under the conditions that the developing roller 53 is in the pressure-contact state and the third motor M3 is rotating in the forward direction, the switching mechanism SW switches the developing roller 53 from the pressure-contact state to the separated state.

[0130] For example, the first clutch C1 is an electromagnetic clutch. The first clutch C1 is a pressure modifying clutch capable of switching between a first transmission state, in which the driving force of the third motor M3 is transmitted to the cam 340 of the pressure modifying mechanism 300, and a first disconnection state, in which the driving force of the third motor M3 is not transmitted to the cam 340. When the first clutch C1 is placed in the first transmission state with the cam 340 in the second cam position and the third motor M3 rotating in the forward direction, the cam 340 pivotally moves (or rotates) counterclockwise from the second cam position shown in FIG. 6( a ) to the first cam position shown in FIG. 5( a ). When the first clutch C1 is placed in the first transmission state with the cam 340 in the first cam position and the third motor M3 rotating in the reverse direction, the cam 340 pivotally moves (or rotates) clockwise from the first cam position shown in FIG. 5 toward the second cam position shown in FIG. 6( a ).

[0131] The sheet sensor SE1 and the fixed sheet sensor SE2 function to detect the presence or absence of a sheet S. Each of the sheet sensors SE1 and SE2 is provided with a pivot lever that pivots when pressed by a sheet S being conveyed in the conveying direction, and a photosensor that detects the pivoting of the pivot lever. In this embodiment, the sheet sensors SE1 and SE2 are set to ON when a sheet S passes (i.e., when the pivot lever is pushed past by the sheet S), and are set to OFF when a sheet S does not pass (i.e., when the pivot lever is not pushed past by the sheet S). However, the relationship between the orientation of the pivot lever and the ON / OFF signals from the sheet sensors SE1 and SE2 may be reversed.

[0132] In this specification, the expression "sensor for detecting a prescribed event" refers to a sensor for outputting a signal that enables the controller 100 to determine whether a prescribed event has occurred. For example, the above-mentioned "sensor for detecting the presence or absence of a sheet S" refers to a sensor that outputs a signal by which the controller 100 can determine the presence or absence of the sheet S.

[0133] In this embodiment, when the sheet sensor SE1 or SE2 is ON, the controller 100 determines that a sheet S exists at the position of the sheet sensor SE1 or SE2. When the sheet sensor SE1 or SE2 is OFF, the controller 100 determines that a sheet S does not exist at the corresponding position of the sheet sensor SE1 or SE2.

[0134] The sheet sensor SE1 is provided upstream of the fixing device 80 in the conveying direction of the sheet S. Specifically, the sheet sensor SE1 is provided downstream of the registration roller 26 and upstream of the image forming section 30 in the conveying direction of the sheet S.

[0135] The fixing sheet sensor SE2 is provided to detect when the trailing edge of the sheet S has passed through the nip region NP. By determining whether the fixing sheet sensor SE2 has been switched from ON to OFF, the controller 100 can determine whether the trailing edge of the sheet S has passed through the nip region NP. The fixing sheet sensor SE2 is provided in the fixing device 80. The fixing sheet sensor SE2 is provided downstream of the nip region NP in the conveying direction of the sheet S.

[0136] The position sensor SE3 is provided to detect the position of the second fixing member 82. Specifically, the position sensor SE3 is provided near the second clamping position and detects the second fixing member 82 when the second fixing member 82 approaches the second clamping position. FIG5(a) shows an example in which the position sensor SE3 is provided at a position capable of detecting the pivoting of the arm body 311. However, the position sensor SE3 may be provided at any position capable of detecting a member that moves in association with the movement of the second fixing member 82.

[0137] For example, the position sensor SE3 can be constructed by a photoelectric sensor having a light-emitting unit and a light-receiving unit. As shown in FIG5( a), when the second fixing member 82 is in the first clamping position (when the arm body 311 is in the first orientation), the light emitted from the light-emitting unit is not blocked by the arm body 311 and is received by the light-receiving unit. As shown in FIG6( a), when the second fixing member 82 is in the second clamping position (when the arm body 311 is in the second orientation), the light emitted from the light-emitting unit is blocked by the arm body 311 and is therefore not received by the light-receiving unit. The position sensor SE3 constructed in this manner can detect when the second fixing member 82 approaches the second clamping position.

[0138] The temperature sensor SE4 is provided to detect the temperature of the first fixing member 81 or the second fixing member 82. In the present embodiment, the temperature sensor SE4 detects the temperature of the rotatable roller 120 configuring the first fixing member 81.

[0139] Figure 7 The controller 100 shown is provided with a CPU, RAM, ROM, nonvolatile memory, ASIC, input / output circuits, etc. The controller 100 executes various processes by performing calculation operations based on print commands output from an external computer, signals output from sensors SE1-SE4, and programs and data stored in the ROM, etc.

[0140] The controller 100 has the following functions: first, it drives the first motor M1, and then, upon receiving a print command, it changes the clamping pressure at the clamping area NP from the second clamping pressure to the first clamping pressure (maximum clamping pressure or intermediate clamping pressure). After printing is completed, the controller 100 executes a process to change the clamping pressure from the first clamping pressure (maximum clamping pressure or intermediate clamping pressure) to the second clamping pressure, and executes a process to change the state of the developing roller 53 from the pressure contact state to the separation state. Therefore, whenever the printing operation is started, the clamping pressure is always at the second clamping pressure, and the state of the developing roller 53 is always in the separation state.

[0141] Specifically, upon receiving a print command, the controller 100 starts driving the first motor M1. After the rotational speed of the first motor M1 becomes constant, the controller 100 changes the clamping pressure from the second clamping pressure to the first clamping pressure. In the case where the controller 100 changes the clamping pressure from the second clamping pressure to the first clamping pressure upon receiving a print command, the controller 100 first rotates the third motor M3 in the forward direction while the second clutch C2 is in the second disconnected state, and then switches the first clutch C1 to the first transmission state so that the cam 340 pivotally moves (or rotates) from the second position toward the first position. In addition, in the case where the controller 100 pivotally moves (or rotates) the cam 340 from the second position toward the first position, the controller 100 sets the rotational speed of the third motor M3 to a speed slower than the rotational speed used during printing.

[0142] After printing is completed, the controller 100 can enter a preparation mode and a sleep mode. In the preparation mode, the temperature of the rotatable roller 120 is maintained at a preparation temperature lower than the temperature used for printing, and in the sleep mode, the heater 110 is set to the OFF state. Specifically, the controller 100 executes the preparation mode within a first prescribed time interval after printing is completed. After a second prescribed time interval longer than the first prescribed time interval has passed since the end of printing, the controller 100 enters the sleep mode. Since after printing is completed, the controller 100 executes a process of changing the clamping pressure from the first clamping pressure (maximum clamping pressure or intermediate clamping pressure) to the second clamping pressure, and executes a process of changing the state of the developing roller 53 from the pressure contact state to the separated state, in the preparation mode and the sleep mode, the clamping pressure is the second clamping pressure and the developing roller 53 is in the separated state. In the following description, the temperature during printing will be referred to as the "fixing temperature T3", and the preparation temperature will be referred to as the "preparation temperature T2". When a print command is received, the sleep mode and the preparation mode end.

[0143] When a print command is received during the sleep mode, the controller 100 first changes the clamping pressure from the second clamping pressure to the first clamping pressure, and then drives the second motor M2. Conversely, when a print command is received during the preparation mode, the controller 100 starts driving the first motor M1, and then starts driving the second motor M2 before the process of changing the clamping pressure from the second clamping pressure to the first clamping pressure is completed.

[0144] In the case where a print command is received during the sleep mode, the controller 100 drives the first motor M1 when the temperature of the rotatable roller 120 becomes greater than or equal to a prescribed value. On the other hand, in the case where a print command is received during the preparation mode, the controller 100 performs a conversion process to convert the print data received by the print command into raster image data that can be used by the color printer 1, and then drives the first motor M1 regardless of the temperature of the rotatable roller 120. Here, for example, the raster image data is used to expose the photosensitive drum 51, and is data written in a page description language, bitmap image data, or vector data. The prescribed value represents a temperature for determining whether to start driving the first motor M1 during the sleep mode. In the following description, the prescribed value will be the "fixing drive start temperature T1". The fixing drive start temperature T1 is set to a value lower than the preparation temperature T2.

[0145] When a print command is received during the sleep mode, the controller 100 first drives the first motor M1 and then the third motor M3. On the other hand, when a print command is received during the preparation mode, the controller 100 first drives the third motor M3 and then the first motor M1.

[0146] Next, the operation of the controller 100 will be described in more detail. When a print command is received during the sleep mode, the controller 100 Figure 8 In the following description, setting the clutch C1 or C2 to the transmission state will be simply referred to as turning the clutch C1 or C2 ON, and setting the clutch C1 or C2 to the disconnection state will be simply referred to as turning the clutch C1 or C2 OFF.

[0147] exist Figure 8In S1 of the processing shown, the controller 100 first determines whether a preheating command has been received. When a print command is received, the preheating command in this specification is output, and this preheating command is a command to turn the heater 110 to ON. Specifically, the controller 100 has a print command receiving unit and a heater control unit. When the print command receiving unit receives a print command, this unit outputs the preheating command to the heater control unit. When the preheating command is received, the heater control unit turns the heater 110 to ON. When the preheating command has not been received (S1: No), the controller 100 repeats the determination in S1.

[0148] When the controller 100 determines that the preheating command has been received (S1: Yes), in S2, the controller 100 sets the target temperature Tth of the rotatable roller 120 to the fixing drive start temperature T1 and turns the heater 110 to ON. In S2, the controller 100 also performs a conversion process on the print data in the received print command. In S2, the controller 100 can set the first clamping pressure to either the maximum clamping pressure or the intermediate clamping pressure based on the thickness of the sheet to be printed specified in the print command.

[0149] In S3, the controller 100 determines whether the detected temperature T detected by the temperature sensor SE4 has risen to the fixing drive start temperature T1 or higher. When T < T1 (S3: No), the controller 100 continues to repeat the determination in S3. In the case where the controller 100 determines that T ≥ T1 (S3: Yes), in S4, the controller 100 starts driving the first motor M1. When the first motor M1 is driven, the first fixing member 81 and the belt 130 circulate, and the heat from the rotatable roller 120 is absorbed by the belt 130, causing the detected temperature T to drop below the fixing drive start temperature T1.

[0150] In S5, the controller 100 determines whether the detected temperature T is the developing drive start temperature T0 or higher, and repeats the determination when T < T0 (S5: No). Here, the developing drive start temperature T0 is the temperature for determining the moment to start driving the third motor M3, and is set to a value lower than the fixing drive start temperature T1.

[0151] When the controller 100 determines that T≥T0 (S5: Yes), in S6, the controller 100 drives the third motor M3 forward at a rotational speed (low speed) lower than the rotational speed (high speed) used during printing. In S7, the controller 100 determines whether the rotational speeds of the third motor M3 and the first motor M1 have stabilized, that is, whether their rotational speeds have become constant. For example, this determination can be made by determining whether at least a specified time has elapsed since the third motor M3 and the first motor M1 started rotating. When the rotational speeds of the third motor M3 and the first motor M1 have not yet stabilized (S7: No), the controller 100 repeats the determination in S7.

[0152] Once the controller 100 determines that the rotational speeds of the third motor M3 and the first motor M1 have stabilized (S7: Yes), in S8, the controller 100 turns the first clutch C1 to ON, and more specifically, changes the clamping pressure from the second clamping pressure to the first clamping pressure. In addition, after the clamping pressure in the fixing device 80 has been modified to the first clamping pressure in S8, the controller 100 switches the rotational speed of the third motor M3 from low speed to high speed.

[0153] After the process of S8 has been executed, in S9, the controller 100 determines whether the process for converting print data is completed. When the controller 100 determines that the developing process has been completed (S9: Yes), in S10, the controller 100 sets the target temperature Tth to the fixing temperature T3.

[0154] In S11, the controller 100 determines whether the detected temperature T has risen to the process drive start temperature Tp or higher. Here, the process drive start temperature Tp is the temperature for determining the moment to start driving the second motor M2. The process drive start temperature Tp is set to a temperature higher than the preparation temperature T2 and lower than the fixing temperature T3. When T < Tp (S11: No), the controller 100 continues to repeat the determination in S11.

[0155] When the controller 100 determines that T≥Tp (S11: Yes), in S12, the controller 100 drives the second motor M2. Specifically, in S12, the controller 100 first drives the second motor M2, and then drives the fourth motor M4.

[0156] After the process of S12 has been executed, in S13, the controller 100 turns the second clutch C2 to ON to switch the developing roller 53 to the pressure contact state. Specifically, in S13, the controller 100 sets all the developing rollers 53 to the pressure contact state during the color mode, and only sets the developing roller 53K for black to the pressure contact state in the monochrome mode.

[0157] In S14, the controller 100 determines whether the detected temperature T has risen to the sheet supply start temperature Ts or higher. Here, the sheet supply start temperature Ts is the temperature for determining the timing to start feeding the sheet S. The sheet supply start temperature Ts is set to a temperature higher than the processing drive start temperature Tp and lower than the fixing temperature T3.

[0158] The relationship between the magnitudes of all the above temperatures can be summarized as follows.

[0159] T0 < T1 < T2 < Tp < Ts < T3

[0160] T0: Developing drive start temperature, T1: Fixing drive start temperature, T2: Preparation temperature, Tp: Processing drive start temperature, Ts: Sheet supply start temperature, T3: Fixing temperature

[0161] When the controller 100 determines that T < Ts (S14: No), the determination in S14 is repeated. When the controller 100 determines that T ≥ Ts (S14: Yes), in S15, the controller 100 performs the process of feeding the sheet S, and in S16, performs the printing process on the sheet S. In S17, the controller 100 performs post-printing processing (such as cleaning processing), and then ends Figure 8 the process. In S17, the controller 100 can perform the process of changing the clamping pressure from the first clamping pressure (maximum clamping pressure or intermediate clamping pressure) to the second clamping pressure, and perform the process of changing the state of the developing roller 53 from the pressure contact state to the separated state.

[0162] On the other hand, when the controller 100 determines in S9 that the conversion process is not completed (S9: No), in S18, the controller 100 determines whether a timeout has occurred. Specifically, the controller 100 determines whether the specified waiting time for waiting for the conversion process to complete has passed. When the controller 100 determines that a timeout has not occurred, that is, the waiting time has not passed (S18: No), the controller 100 returns to S9 and determines again whether the conversion process is completed. However, if the controller 100 determines that a timeout has occurred, that is, the waiting time has passed (S18: Yes), then in S19, the controller 100 performs the process of turning off the heater 110 and changing the clamping pressure from the first clamping pressure to the second clamping pressure, changing the state of the developing roller 53 from the pressure contact state to the separated state, and performing the stop process of stopping various rotating members. Subsequently, the controller 100 ends Figure 8 the process.

[0163] In the preparation mode, the controller 100 performs various processing steps according to Figure 9 the timing chart shown. Figure 9 The example in

[0164] During the preparation mode (e.g., see time t0), the controller 100 controls the heater 110 to maintain the temperature of the rotatable roller 120 at the preparation temperature T2. When a print command is received during the preparation mode (time t1), the controller 100 performs a data conversion process and controls the heater 110 to increase the temperature of the rotatable roller 120 to the fixing temperature T3.

[0165] When the switching process is completed (time t2), the controller 100 drives the third motor M3 at a rotation speed (low speed) slower than the rotation speed for printing (time t3). Subsequently, the controller 100 starts driving the first motor M1 in the forward direction while setting the rotation speed to low speed (time t4).

[0166] After driving the motors M1 and M2, the controller 100 waits until the rotational speeds of the motors M1 and M2 stabilize. Once the rotational speeds have stabilized (become constant), the controller 100 turns ON the first clutch C1 (time t5).

[0167] When the first clutch C1 is turned ON at time t5, the cam 340 pivotally moves (or rotates) from the second position toward the first position. Therefore, the clamping pressure gradually changes from the second clamping pressure to the first clamping pressure.

[0168] After turning the first clutch C1 ON but before the clamping pressure has completely changed to the first clamping pressure, the controller 100 begins driving the second motor M2 (time t6). In other words, the controller 100 begins driving the second motor M2 (time t6) between the point at which driving the first motor M1 begins and the point at which the process of changing the clamping pressure from the second clamping pressure to the first clamping pressure is completed (between times t4 and t8). Furthermore, after driving the second motor M2 and before the clamping pressure has completely changed from the second clamping pressure to the first clamping pressure, the controller 100 begins driving the fourth motor M4 (time t7).

[0169] When the clamping pressure has completely changed from the second clamping pressure to the first clamping pressure, the controller 100 turns OFF the first clutch C1 (time t8). After turning OFF the first clutch C1, the controller 100 switches the rotation speed of the third motor M3 from low speed to high speed (time t9).

[0170] The controller 100 waits from time t9 until the rotational speed of the third motor M3 stabilizes. Once the rotational speed stabilizes, the controller 100 turns on the second clutch C2 (time t10). As a result, each developing roller 53 sequentially switches from a disengaged state to a press-contact state (times t11, t12, t13, and t14). After all developing rollers 53 are in press-contact, the controller 100 turns off the second clutch C2 (time t16).

[0171] In addition, the controller 100 turns on a feed clutch (not shown) at a predetermined timing during the period in which the developing roller 53 is sequentially switched from the separated state to the press-contact state, so as to start feeding the sheet S (time t15). The feed clutch is a clutch for starting to feed the sheet S, and is provided on a driving force transmission path along which the driving force from the fourth motor M4 for driving the pickup roller 23 is transmitted to the pickup roller 23.

[0172] When a print command for monochrome printing is received in the preparation mode, the controller 100 performs a process similar to the above to start the print process for printing in the monochrome mode. In the monochrome mode, the pressure contact state and separation state of the developing roller 53 and other aspects are the same as those in the preparation mode. Figure 9 The examples in the example are different, but the timing of the steps performed on the various components is the same Figure 9 The examples are essentially the same as those in .

[0173] Next, we will refer to Figure 10 An example of an operation performed by the controller 100 in the sleep mode is described. Figure 10 An example is shown in which printing is started when the temperature of the rotatable roller 120 has dropped to a relatively low temperature (eg, ambient temperature).

[0174] When a print command is received during the sleep mode (time t31), the controller 100 performs a data conversion process and turns ON the heater 110 to increase the temperature of the rotatable roller 120 to the fixing drive start temperature T1. Figure 10 In the example shown in FIG. 1 , the switching process is completed before the temperature of the rotatable roller 120 reaches the fixing drive start temperature T1 .

[0175] When the temperature of the rotatable roller 120 reaches the fixing drive start temperature T1, the controller 100 starts driving the first motor M1 (time t32). When the first motor M1 is driven, the rotatable roller 120 and the belt 130 begin to rotate. As a result, the heat in the rotatable roller 120 is absorbed by the belt 130, causing the temperature of the rotatable roller 120 (detected temperature T) to drop.

[0176] When the temperature of the rotatable roller 120 subsequently reaches the development drive start temperature T0, the controller 100 starts driving the third motor M3 in the forward direction while setting the rotation speed to a low speed (time t33). The controller 100 waits from time t33 until the rotation speeds of the third motor M3 and the first motor M1 stabilize. Once the rotation speeds stabilize, the controller 100 turns on the first clutch C1 (time t34).

[0177] By turning the first clutch C1 ON at time t34, the cam 340 pivotally moves (or rotates) from the second position toward the first position. Therefore, the clamping pressure gradually changes from the second clamping pressure to the first clamping pressure.

[0178] After the clamping pressure has completely changed to the first clamping pressure, the controller 100 turns OFF the first clutch C1 (time t35). After closing the first clutch C1, the controller 100 switches the rotation speed of the third motor M3 from low speed to high speed (time t36).

[0179] When the temperature of the rotatable roller 120 reaches the process drive start temperature Tp after time t36, the controller 100 starts driving the second motor M2 (time t37). Subsequently, the controller 100 starts driving the fourth motor M4 (time t38). Thereafter, the controller 100 turns on the second clutch C2 (time t39).

[0180] As a result, each developing roller 53 is sequentially switched from the separated state to the press-contact state. Once all the developing rollers 53 are in the press-contact state, the controller 100 turns OFF the second clutch C2 (timing t41).

[0181] Furthermore, the controller 100 turns on a feed clutch (not shown) at a predetermined time during the period in which the developing roller 53 sequentially switches from a separated state to a press-contact state to start feeding the sheet S (time t40). Specifically, the controller 100 turns on the feed clutch when the temperature of the rotatable roller 120 reaches the sheet supply start temperature Ts. Similar to the standby mode, when a print command for monochrome printing is received in sleep mode, the controller 100 performs a process similar to that described above to start printing in monochrome mode.

[0182] Through the above process, the following effects can be achieved in this embodiment. In this embodiment, when a print command is received, the first motor M1 is driven before the clamping pressure is changed. Therefore, before the first fixing member 81 is firmly pressed against the belt 130, the belt 130 rotates in conjunction with the rotation of the first fixing member 81. Compared to a conceivable configuration in which the first motor (fixing motor) is driven after the clamping pressure is changed from the second clamping pressure to the first clamping pressure upon receiving a print command, this configuration can better suppress damage caused by the belt 130.

[0183] When the controller 100 receives a print command during the sleep mode, the controller 100 first changes the clamping pressure from the second clamping pressure to the first clamping pressure before driving the second motor M2. This configuration can better suppress wear on components in the image forming unit 30 (e.g., the photosensitive drum 51) compared to a conceivable configuration in which the second motor (process motor) is driven before changing the clamping pressure from the second clamping pressure to the first clamping pressure.

[0184] In the case where the controller 100 receives a print command during the preparation mode, the controller 100 starts driving the second motor (process motor) after starting driving the first motor M1, thereby suppressing wear on components in the image forming section 30. In addition, in the case where the controller 100 receives a print command during the preparation mode, the controller 100 starts driving the second motor M2 before completing the process of modifying the nip pressure, thereby shortening the time required to complete printing after receiving the print command.

[0185] Since the driving force of the third motor M3 is used both for switching the developing roller 53 between the press-contact state and the separated state and for modifying the nip pressure, this embodiment can reduce costs.

[0186] When the nip pressure is modified, the rotation speed of the third motor M3 is set to a slower speed than the rotation speed used during printing, thereby reducing noise that may occur when the cam 340 is driven.

[0187] The second clamping pressure is set to a second clamping pressure that is the minimum clamping pressure within the modification range of the pressure modification mechanism 300, thereby suppressing wear caused by sliding friction between the belt 130 and the clamping forming member N, which rotates by following the rotation of the first fixing member 81 and supports the belt 130 from the side opposite to the first fixing member 81.

[0188] When a print command is received during sleep mode, after the first motor M1 starts driving, the third motor M3 is not driven and the nip pressure is not modified until the temperature of the rotatable roller 120 reaches the development drive start temperature T0. This method reduces the time during which the rotatable roller 120 slides against the belt 130 under high nip pressure, and can better suppress wear on the belt 130 compared to, for example, a conceivable configuration in which the developing motor is driven immediately after the fixing motor starts driving and the nip pressure is modified.

[0189] While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that many changes and modifications can be made therein without departing from the scope of the invention.

[0190] In the above embodiment, when the nip pressure is the second nip pressure, the belt 130 interposed between the rotatable roller 120 and the upstream pad P1 rotates by following the rotation of the rotatable roller 120. However, when the nip pressure is set to the second nip pressure, the belt 130 does not need to be configured to rotate by following the rotation of the rotatable roller 120. However, if the heater 110 is turned on upon receiving a print command in this case, since the belt 130 does not rotate along with the rotatable roller 120, the heat applied by the rotatable roller 120 will be concentrated in a portion of the belt 130. Therefore, the nip pressure can be changed from the second nip pressure to the first nip pressure immediately after starting to drive the first motor M1, so that the belt 130 will rotate by following the rotation of the rotatable roller 120.

[0191] Although the photosensitive member of the present disclosure is described as the photosensitive drum 51 in the present embodiment, for example, a belt-shaped photosensitive member may be used instead.

[0192] In this embodiment, the pressure modifying mechanism 300 is configured to modify the clamping pressure in the clamping region NP between a maximum clamping pressure, an intermediate clamping pressure, and a minimum clamping pressure. However, the pressure modifying mechanism should be capable of modifying the clamping pressure in the clamping region between at least a first clamping pressure and a second clamping pressure. Thus, the pressure modifying mechanism may be configured to modify the clamping pressure between two, four, or more pressure values.

[0193] The pressure modification mechanism is not limited to the configuration described in the embodiment. For example, the pressure modification mechanism may be configured similarly to that shown in FIG5(a), but, for example, without the cam follower 350 and the second spring 330. In other words, the cam 340 may be configured to contact the arm body 311.

[0194] In this embodiment, the fixed film sensor SE2 ( Figure 7) is provided downstream of the nip region NP, but for example the fixed web sensor may instead be provided upstream of the nip region.

[0195] Although the present disclosure is applied to the color printer 1 in the present embodiment, the present disclosure may instead be applied to another image forming apparatus such as a monochrome printer, a copier, or a multifunction peripheral.

[0196] Although a halogen lamp is used as an example of the heater in this embodiment, the heater may be a carbon heater or the like.

[0197] Although the first fixing member in this embodiment is configured with a built-in heater, the second fixing member may alternatively be configured with a built-in heater. For example, the second fixing member may be provided with a belt, and a heater and a clamping forming member disposed in a space defined by the belt, while the first fixing member may be a pressure roller that clamps the belt and the clamping forming member of the second fixing member together. In this case, the first fixing member does not have a heater. Alternatively, the heater may be disposed outside the first fixing member, and an external heating system or an induction heating system may be employed to heat the circumferential surface of the first fixing member. Alternatively, both the first and second fixing members may be provided with a built-in heater.

[0198] Furthermore, the first fixing member may be formed of a belt wrapped around the heater, that is, a nip region may be formed between the belt of the first fixing member and the belt of the second fixing member.

[0199] Although the pressure modifying mechanism 300 is provided in the fixing device 80 in this embodiment, the pressure modifying mechanism may be provided in the main housing instead. Alternatively, a portion of the pressure modifying mechanism may be provided in the fixing device and the remaining portion may be provided in the main housing.

[0200] The technical elements and variations thereof described above in this embodiment may be used in any suitable combination.

Claims

1. An image forming apparatus, characterized in that: include: an image forming section that forms a developer image on a sheet; a first fixing member having a roller; a second fixing member having a belt to form a nip portion with the first fixing member; a first motor configured to drive the roller; a second motor configured to drive the image forming portion; a heater configured to heat the first fixing member; a pressure modifying mechanism configured to modify a clamping pressure at the clamping portion to a selected one of a first clamping pressure and a second clamping pressure that is smaller than the first clamping pressure; and A controller configured to: starting driving the first motor to drive the roller when a print command is received in a state where the clamping pressure is the second clamping pressure; After the driving is performed, the clamping pressure is modified from the second clamping pressure to the first clamping pressure; and fixing the developer image on the sheet in a state where the nip pressure is the first nip pressure, wherein the controller is further configured to set a mode between a sleep mode in which the heater is turned off and a standby mode in which the temperature of the first fixing member is maintained at a standby temperature lower than a fixing temperature set when printing is performed, The controller is configured to further: heating the first fixing member in a first case where the print command is received during the sleep mode; and starting driving the second motor to drive the image forming section after performing the modification in the first case, the modification being a modification of the nip pressure from the second nip pressure to the first nip pressure, In a second case where the print command is received during the preparation mode, after the first motor starts driving in the second case but before the clamping pressure is changed from the second clamping pressure to the first clamping pressure, the second motor starts driving to drive the image forming portion.

2. The image forming apparatus according to claim 1, wherein Further including: The controller is configured to further: heating the first fixing member in a first case where the print command is received during the sleep mode; When the temperature of the first fixing member is higher than or equal to a prescribed temperature in the first condition, driving of the first motor is started to drive the roller.

3. The image forming apparatus according to claim 1, wherein in, The modification is performed after the first motor starts driving and rotating at a constant rotation speed.

4. The image forming apparatus according to claim 1, wherein Further including: The controller is configured to further: In a second case where the print command is received during the preparation mode: heating the first fixing member so that the temperature of the first fixing member increases to the fixing temperature; and The driving of the first motor to drive the roller is started after the heating is started.

5. The image forming apparatus according to any one of claims 1 to 3, wherein: Further including: The controller is configured to further: In a second case where the print command is received during the preparation mode: converting the print data included in the print command into raster image data; and The first motor starts to be driven to drive the roller after the switching is completed.

6. The image forming apparatus according to any one of claims 1 to 3, wherein: Further including: photosensitive member; a developing roller configured to supply a developer to the photosensitive member; a third motor configured to drive the pressure modifying mechanism; and A first clutch, the first clutch is configured to change between a first transmission state and a first disconnection state, in which the driving force of the third motor is transmitted to the pressure modification mechanism, and in which the driving force of the third motor is not transmitted to the pressure modification mechanism.

7. The image forming apparatus according to claim 6, wherein: in, The pressure modification mechanism includes a cam configured to pivotally move between a first position where the clamping pressure becomes the first clamping pressure and a second position where the clamping pressure becomes the second clamping pressure, Wherein modifying the clamping pressure includes controlling the third motor to switch the first clutch to the first transmitting state, thereby pivotally moving the cam from the second position to the first position.

8. The image forming apparatus according to claim 6, wherein Further including: photosensitive member; and a developing roller configured to supply a developer to the photosensitive member; Wherein, the third motor further drives the developing roller.

9. The image forming apparatus according to claim 6, wherein Further including: photosensitive member; a developing roller configured to supply a developer to the photosensitive member; a switching mechanism configured to switch a state of the developing roller between a contact state in which the developing roller is in contact with the photosensitive member and a separation state in which the developing roller is separated from the photosensitive member; and The second clutch is configured to change between a second transmission state and a second disconnection state, in which the driving force of the third motor is transmitted to the switching mechanism, and in which the driving force of the third motor is not transmitted to the switching mechanism.

10. The image forming apparatus according to claim 9, wherein in, The pressure modification mechanism includes a cam configured to pivotally move between a first position where the clamping pressure becomes the first clamping pressure and a second position where the clamping pressure becomes the second clamping pressure, Wherein, modifying the clamping pressure includes controlling the third motor to rotate when the second clutch is in the second disconnected state, and then controlling the third motor to switch the first clutch to the first transmission state, thereby pivotally moving the cam from the second position to the first position.

11. The image forming apparatus according to claim 10, wherein in, The cam is pivotally moved from the second position to the first position by forward rotation of the third motor, and the cam is pivotally moved from the first position to the second position by reverse rotation of the third motor. Wherein, modifying the clamping pressure includes controlling the third motor to rotate in a forward direction.

12. The image forming apparatus according to claim 6, wherein in, When the nip pressure is modified from the second nip pressure to the first nip pressure, the third motor rotates at a slower rotation speed than when printing is performed.

13. The image forming apparatus according to claim 6, wherein Further including: a heater configured to heat the first fixing member; wherein, in a first case where the print command is received during the sleep mode, driving the third motor is started after starting to drive the first motor; In the second case where the print command is received in the preparation mode, the starting of driving the first motor is performed after the starting of driving the third motor is performed.

14. The image forming apparatus according to any one of claims 1 to 3, wherein: in, The second fixing member includes: an upstream pad configured to clamp the belt together with the first fixing member; and a downstream pad located downstream of the upstream pad in the conveying direction of the sheet, the downstream pad being configured to nip the belt together with the first fixing member, wherein, when the clamping pressure is the first clamping pressure, the upstream pad and the downstream pad both clamp the belt together with the first fixing member, Here, when the nip pressure is the second nip pressure, the upstream pad and the first fixing member nip the belt together, while the downstream pad and the first fixing member do not nip the belt together.

15. The image forming apparatus according to any one of claims 1 to 3, wherein: in, The second clamping pressure is a minimum clamping pressure within a range in which the pressure modification mechanism can set the clamping pressure.

16. The image forming apparatus according to claim 1, wherein in, The pressure modification mechanism includes a cam configured to pivotally move between a first position where the clamping pressure becomes the first clamping pressure and a second position where the clamping pressure becomes the second clamping pressure, Wherein, the second fixing member moves between a first clamping position and a second clamping position, in which at the first clamping position, the clamping portion is formed between the first fixing member and the second fixing member, and in the second clamping position, the distance between the first fixing member and the second fixing member is greater than the distance at the first clamping position.

17. An image forming apparatus, characterized in that: include: an image forming section that forms a developer image on a sheet; a first fixing member having a roller; a second fixing member having a belt to form a nip portion with the first fixing member; a pressure modifying mechanism configured to modify a clamping pressure at the clamping portion to a selected one of a first clamping pressure and a second clamping pressure that is smaller than the first clamping pressure; photosensitive member; a developing roller configured to supply a developer to the photosensitive member; a switching mechanism configured to switch a state of the developing roller between a contact state in which the developing roller is in contact with the photosensitive member and a separation state in which the developing roller is separated from the photosensitive member; a first motor configured to drive the roller; a third motor configured to drive the pressure modifying mechanism and the developing roller; a first clutch configured to change between a first transmission state in which the driving force of the third motor is transmitted to the pressure modification mechanism and a first disconnection state in which the driving force of the third motor is not transmitted to the pressure modification mechanism; and a second clutch configured to change between a second transmission state in which the driving force of the third motor is transmitted to the switching mechanism and a second disconnection state in which the driving force of the third motor is not transmitted to the switching mechanism; The image forming device is configured to: When a print command is received while the clamping pressure is the second clamping pressure, starting to drive the roller; After the driving is performed, the clamping pressure is modified from the second clamping pressure to the first clamping pressure; and The developer image is fixed on the sheet in a state where the nip pressure is the first nip pressure.

18. The image forming apparatus according to claim 17, wherein Further including: a heater configured to heat the first fixing member, The image forming apparatus is further configured to have a sleep mode in which the heater is turned off. Wherein, the image forming apparatus is configured to further perform: heating the first fixing member in a first case where the print command is received during the sleep mode; When the temperature of the first fixing member is higher than or equal to a prescribed temperature in the first condition, control is performed to start driving the roller.

Images