Fixing device and image forming apparatus

Abstract

The invention discloses a fixing device and an image forming apparatus, the fixing device includes: a fixing belt that rotates while being heated by a heating source; a pressure roller that rotates while forming a nip at a portion in contact with the fixing belt; and a load adjusting mechanism that acquires a belt temperature of the fixing belt and adjusts a load of the nip portion according to a state of the belt temperature with respect to a preset temperature.

Description

Technical Field

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

[0002] A technology is disclosed in Japanese Patent Gazette No. 2005-300986, which provides a fixing device of a belt bite type, in which a fixing belt is driven by a driving component that drives the fixing belt from the outside outside the contact nip area. The fixing device of the belt bite type takes into account both ensuring the gloss of the colorant image by ensuring the pressure in the contact nip area between the fixing belt and the heating roller and stabilizing the belt conveyance by preventing slippage of the belt.

[0003] Japanese Patent Application Laid-Open No. 2007-121407 discloses a technique for reducing the load applied to the fixing member to prevent the life of the fixing member from being shortened by suppressing the forward load applied to the bite forming member when the pressing member moves forward. Summary of the invention

[0004] However, in the fixing device used in the image forming apparatus, a fixing process is performed using a fixing belt to which tension is applied by a plurality of rollers and a pressure roller sandwiching the fixing belt and contacting a pad portion. In this technology, as the temperature of the fixing belt rises, the fixing belt rotates together with the rotation of the pressure roller.

[0005] In this technology, the pressure roller sometimes rotates when the temperature of the fixing belt has not completely risen and the fixing belt is deformed. In this way, when the fixing belt is deformed, the driving torque for rotating the fixing belt increases, and a difference in the rotation speed between the fixing belt and the pressure roller occurs. When a difference in the rotation speed between the fixing belt and the pressure roller occurs, slippage occurs, and the surfaces of the fixing belt and the pressure roller are damaged. In order to suppress this slippage, for example, when a new driving roller is set outside, the fixing device is enlarged and the cost is increased.

[0006] An object of the present invention is to suppress slippage between a fixing belt and a pressure roller and shorten the heating time of the fixing belt without adding a new roller.

[0007] According to a first aspect of the present invention, there is provided a fixing device comprising: a fixing belt, which is heated by a heating source and rotates; a pressure roller, which forms a nip portion at a position in contact with the fixing belt and rotates; and a load adjustment mechanism, which obtains the belt temperature of the fixing belt and adjusts the load of the nip portion according to the state of the belt temperature relative to a preset temperature.

[0008] According to a second aspect of the present invention, in the fixing device of the first aspect, when the belt temperature is equal to or lower than a preset temperature, the load adjustment mechanism makes the load of the nip portion higher than that during printing.

[0009] According to a third aspect of the present invention, in the fixing device of the second aspect, when the belt temperature reaches a predetermined temperature while the load on the nip portion is higher than during printing, the load adjustment mechanism makes the load on the nip portion lower than during printing.

[0010] According to a fourth aspect of the present invention, in the fixing device according to any one of the second or third aspects, when starting printing, the load adjustment mechanism increases the load of the nip portion from a state lower than that during printing to the load during printing.

[0011] According to a fifth aspect of the present invention, in the fixing device of the first aspect, when the belt temperature is equal to or higher than a preset temperature and printing is not being performed, the load adjustment mechanism makes the load of the nip portion lower than that during printing.

[0012] According to a sixth aspect of the present invention, in the fixing device of the fifth aspect, when starting printing, the load adjustment mechanism increases the load of the nip portion from a state lower than that during printing to the load during printing.

[0013] According to a seventh aspect of the present invention, in the fixing device of any one of the first to sixth aspects, the load adjustment mechanism switches the load of the nip portion when the fixing device is activated.

[0014] According to an eighth aspect of the present invention, in the fixing device of any one of the first to seventh aspects, the load of the nip portion is switched from a load larger than the load during printing to a load smaller than the load during printing.

[0015] According to a ninth aspect of the present invention, in the fixing device according to any one of the first to eighth aspects, the preset temperature is a temperature set to alleviate deformation of the fixing belt.

[0016] According to a tenth aspect of the present invention, in the fixing device of the first aspect, the nip portion is formed by a pad that presses the paper together with the pressure roller, and the load adjustment mechanism adjusts the load of the nip portion formed by the pad and the pressure roller sandwiching the fixing belt.

[0017] According to the eleventh aspect of the present invention, in the fixing device of the first aspect, there is a temperature sensor for detecting the belt temperature of the fixing belt before entering the nip portion, and the load adjustment mechanism adjusts the load of the nip portion according to the state of the belt temperature detected by the temperature sensor.

[0018] According to the twelfth aspect of the present invention, there is provided an image forming device comprising: a developer which develops an electrostatic latent image on a photosensitive body; a transfer unit which transfers the developed image onto a sheet of paper; and a fixing device which fixes the sheet of paper to which the developed image has been transferred, the fixing device comprising: a fixing belt which is heated by a heating source and rotates; a pressure roller which forms a nip portion at a position in contact with the fixing belt and rotates; and a load adjustment mechanism which obtains the belt temperature of the fixing belt and adjusts the load of the nip portion according to the state of the belt temperature relative to a preset temperature.

[0019] (Effect)

[0020] According to the first aspect, without adding a new roller, it is possible to suppress slippage between the fixing belt and the pressure roller and shorten the heating time of the fixing belt.

[0021] According to the second aspect, slippage between the fixing belt and the pressure roller caused by, for example, the pressure roller rotating in a state where the fixing belt has deformation is suppressed.

[0022] According to the third aspect, the efficiency of heat transfer from the heating source to the belt temperature is improved compared to a case where the load on the nip portion is not reduced compared to that during printing.

[0023] According to the fourth aspect, when printing is started, the load of the nip portion can be adjusted to the load during printing in a state where the efficiency of heat transfer from the heating source to the belt temperature is improved.

[0024] According to the fifth aspect, the preheating time can be shortened while the interlocking width of the interlocking portion is reduced and the efficiency of heat conduction to the belt is improved.

[0025] According to the sixth aspect, printing can be started in a state where the efficiency of heat transfer to the belt is improved.

[0026] According to the seventh aspect, slippage between the fixing belt and the pressure roller can be suppressed when the fixing device is started.

[0027] According to the eighth aspect, after the slip between the fixing belt and the pressure roller is suppressed at the start of the fixing device, the efficiency of heat transfer to the belt can be improved until printing.

[0028] According to the ninth aspect, slippage between the fixing belt and the pressure roller can be suppressed.

[0029] According to the tenth aspect, the load can be stably applied to the pressure roller.

[0030] According to the eleventh aspect, the belt temperature at the nip portion between the fixing belt and the pressure roller can be grasped, and slippage caused by the fixing belt and the pressure roller can be suppressed.

[0031] According to the twelfth aspect, without adding a new roller, it is possible to suppress slippage between the fixing belt and the pressure roller and shorten the heating time of the fixing belt. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A diagram for explaining the image forming apparatus of this embodiment;

[0033] Figure 2 A diagram for explaining the fixing device of this embodiment;

[0034] Figure 3 (a)~ Figure 3 (b) is a diagram for explaining a load adjustment procedure according to the belt temperature state by the load adjustment mechanism. DETAILED DESCRIPTION

[0035] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0036] [Description of image forming apparatus]

[0037] Figure 1 This is a diagram for explaining the image forming apparatus 1 according to the present embodiment.

[0038] The image forming apparatus 1 of the present embodiment includes a paper feeding unit 1A, a printing unit 1B, and a paper discharge unit 1C.

[0039] The paper feeding unit 1A includes first to fourth paper accommodating sections 11 to 14 for accommodating paper P as an example of recording media.

[0040] The paper feeding unit 1A is provided with delivery rollers 15 to 18 which are respectively provided corresponding to the first to fourth paper accommodating sections 11 to 14 and deliver the paper P accommodated in each paper accommodating section to a conveying path connected to the printing unit 1B.

[0041] The printing unit 1B includes an image forming section 20 that forms an image on a sheet of paper P. The printing unit 1B is also provided with a control section 21 that controls each section of the image forming apparatus 1 .

[0042] The printing unit 1B also includes an image processing unit 22 . The image processing unit 22 performs image processing on image data sent from the image reading device 4 or a personal computer (PC) 5 .

[0043] The printing unit 1B is also provided with a UI (User Interface) 23 which is composed of a touch panel or the like and which notifies information to the user and receives input of information from the user.

[0044] The image forming section 20 is provided with six image forming units 30T, 30P, 30Y, 30M, 30C, and 30K (hereinafter, sometimes simply referred to as “image forming units 30 ”) arranged in parallel at predetermined intervals.

[0045] Each image forming unit 30 includes: a photosensitive drum 31 that forms an electrostatic latent image while rotating in the direction of arrow A; a charging roller 32 that charges the surface of the photosensitive drum 31; a developer 33 that develops the electrostatic latent image formed on the photosensitive drum 31; and a drum cleaner 34 that removes colorant and the like on the surface of the photosensitive drum 31.

[0046] The image forming section 20 is provided with an exposure device 26 for exposing the photosensitive drum 31 of each image forming unit 30 with a laser beam.

[0047] The exposure device 26 is not limited to the laser beam for exposure of the photosensitive drum 31. For example, a light source such as an LED (Light Emitting Diode) may be provided in each image forming unit 30, and the photosensitive drum 31 may be exposed using light emitted from the light source.

[0048] The image forming units 30 are similarly configured except for the toner stored in the developing device 33. The image forming units 30Y, 30M, 30C, and 30K form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively.

[0049] The image forming units 30T and 30P form toner images using toners corresponding to corporate colors, foaming toners for Braille, fluorescent toners, gloss-enhancing toners, etc. In other words, the image forming units 30T and 30P form toner images using toners of special colors.

[0050] In addition, the image forming section 20 is provided with an intermediate transfer belt 41 to which the toner images of the respective colors formed on the photosensitive drums 31 of the respective image forming units 30 are transferred.

[0051] The image forming section 20 is provided with a primary transfer roller 42 that transfers the color toner images of the image forming units 30 onto the intermediate transfer belt 41 in the primary transfer section P1 .

[0052] In addition, the image forming section 20 is provided with a secondary transfer roller 40 that transfers the toner image transferred onto the intermediate transfer belt 41 onto the paper P at the secondary transfer section P2 .

[0053] Furthermore, the image forming section 20 is provided with a belt cleaner 45 for removing toner and the like on the surface of the intermediate transfer belt 41 , and a fixing device 100 for fixing the image after the secondary transfer to the paper P.

[0054] The image forming section 20 performs an image forming operation based on a control signal from the control section 21 .

[0055] Specifically, in the image forming unit 20 , first, image processing is performed by the image processing unit 22 on image data input from the image reading device 4 or the PC 5 , and the image data after the image processing is supplied to the exposure device 26 .

[0056] Then, for example, in the image forming unit 30M for magenta (M), the surface of the photosensitive drum 31 is charged by the charging roller 32 , and then the photosensitive drum 31 is irradiated with a laser beam modulated according to image data obtained from the image processing section 22 by the exposure device 26 .

[0057] Thus, an electrostatic latent image is formed on the photosensitive drum 31 .

[0058] The formed electrostatic latent image is developed by the developing device 33 , and a magenta toner image is formed on the photosensitive drum 31 .

[0059] Similarly, the image forming units 30Y, 30C, and 30K form toner images of yellow, cyan, and black, and the image forming units 30T and 30P form toner images of special colors.

[0060] The color toner images formed in the image forming units 30 are electrostatically transferred to the image forming units 30 in sequence by the primary transfer rollers 42. Figure 1 On the intermediate transfer belt 41 rotating in the direction of arrow B, overlapping toner images are formed on the intermediate transfer belt 41.

[0061] The superimposed toner images formed on the intermediate transfer belt 41 are conveyed to the secondary transfer portion P2 constituted by the secondary transfer roller 40 and the backup roller 49 as the intermediate transfer belt 41 moves.

[0062] On the other hand, the paper P is taken out from the first paper storage unit 11 by, for example, the delivery roller 15 , and then conveyed to the position of the registration roller 74 via the conveyance path.

[0063] When the superimposed toner images are conveyed to the secondary transfer portion P2 , the paper P is supplied from the registration roller 74 to the secondary transfer portion P2 in accordance with the timing.

[0064] Then, in the secondary transfer portion P2 , the superimposed toner images are electrostatically transferred onto the paper P at once by the action of a transfer electric field formed between the secondary transfer roller 40 and the backup roller 49 .

[0065] Thereafter, the paper P to which the superimposed toner images are electrostatically transferred is conveyed to the fixing device 100 .

[0066] In the fixing device 100 , the toner image is fixed to the paper P by applying pressure and heating to the paper P on which the unfixed toner image is formed, under the control of the control unit 21 .

[0067] Then, the paper P subjected to the fixing process passes through a curl correction section 81 provided in the paper discharge unit 1C, and is then conveyed to a paper loading section (not shown).

[0068] [Description of Fixing Device 100]

[0069] Figure 2 is a diagram for explaining the fixing device 100 according to the present embodiment. Figure 1 FIG. 1 is an enlarged view of the fixing device 100 shown in FIG. Figure 2 As shown in FIG. 1 , the fixing device 100 includes: a fixing belt 110 that is heated by a heat source and rotates; a pressure roller 120 that forms a nip portion N at a portion in contact with the fixing belt 110 and presses the paper P; and a load adjustment mechanism 130 that adjusts the load of the nip portion N by moving the pressure roller 120 in the up-down direction. The upward direction is a direction in which the pressure roller 120 approaches the fixing belt 110, and the downward direction is a direction in which the pressure roller 120 moves away from the fixing belt 110.

[0070] Furthermore, the fixing device 100 includes: a pad 140 that sandwiches the fixing belt 110 together with the pressure roller 120 to form a nip N and presses the paper P together with the pressure roller 120; a heating roller 150 that heats the fixing belt 110 as an example of a heat source; and a steering roller 160 that applies tension to the fixing belt 110. In addition, the fixing device 100 includes a temperature sensor 170 that detects the belt temperature T of the fixing belt 110 before entering the nip N.

[0071] The pressure roller 120 is configured to rotate in the same direction as the conveyance direction of the paper P by a motor (not shown). Figure 2 By the rotation of the pressure roller 120 in the C direction, the fixing belt 110 is driven to rotate (in the C direction). Figure 2The pressure roller 120 sequentially conveys the paper P with the unfixed toner image formed thereon to the nip portion N by causing the fixing belt 110 to rotate together with the pressure roller 120. Then, at the nip portion N, the unfixed toner image is fixed to the paper P by the heating of the fixing belt 110 and the pressure of the pressure roller 120 and the pad 140.

[0072] The load adjustment mechanism 130 acquires the belt temperature T from the temperature sensor 170. For example, the belt temperature T is the surface temperature of the fixing belt 110. The load adjustment mechanism 130 is Figure 1 The belt temperature T detected by the temperature sensor 170 is sent to the control unit 21, and the control unit 21 adjusts the load on the nip portion N by the load adjustment mechanism 130 according to the state of the belt temperature T sent.

[0073] The load adjustment mechanism 130 adjusts the load of the nip portion N by moving the pressure roller 120 in the up-down direction. For example, the load adjustment mechanism 130 increases the load of the nip portion N by moving the pressure roller 120 in the direction of approaching the fixing belt 110, that is, in the upward direction, and reduces the load of the nip portion N by moving the pressure roller 120 in the direction of moving the pressure roller 120 away from the fixing belt, that is, in the downward direction. The load adjustment mechanism 130 is configured by combining a motor and an eccentric cam structure, for example.

[0074] The nip width of the nip portion N is the contact area between the pressure roller 120 and the fixing belt 110, and is the width that expands in the conveying direction of the paper P at the portion where the pad 140 is provided. The surface shape of the pressure roller 120 is composed of an elastic layer, and the nip width changes according to the load of the nip portion N. For example, when the load adjustment mechanism 130 moves the pressure roller 120 in the direction of approaching the fixing belt 110, that is, in the upward direction, to increase the load of the nip portion N, the nip width of the nip portion N becomes wider. In addition, for example, when the load adjustment mechanism 130 moves the pressure roller 120 in the direction of moving the pressure roller 120 away from the fixing belt, that is, in the downward direction, to reduce the load of the nip portion N, the nip width of the nip portion N becomes narrower.

[0075] [Load Adjustment of Load Adjustment Mechanism 130 Corresponding to State of Belt Temperature T]

[0076] Next, refer to Figure 3 (a) and Figure 3 (b) describes the load adjustment of the load adjustment mechanism 130 corresponding to the state of the belt temperature T.

[0077] Figure 3 (a) and Figure 3 (b) is a diagram for explaining the procedure of load adjustment corresponding to the state of the belt temperature T by the load adjustment mechanism 130 of the present embodiment. Figure 3 (a) is a diagram showing the change of the load based on the load adjustment mechanism 130, Figure 3 (b) is a graph showing the temperature change of the belt temperature T.

[0078] Figure 3 The vertical axis of (a) represents the load of the bite portion N adjusted by the load adjustment mechanism 130, and the horizontal axis represents time. In addition, N1 to N3 recorded on the vertical axis represent the preset load of the bite portion N. The time on the horizontal axis shows the startup time from the power supply being turned on to the start of the first print, the printing time for the first print from the startup time, the subsequent standby time for waiting for printing, the next print time, and the next standby time. The startup time is divided into a first startup time (1) and a second startup time (2). The first startup time (1) is the period from the start of the rotation of the pressure roller 120 and the driven rotation of the fixing belt 110, and the second startup time (2) is the period from the startup time (1) to the first print. It should be noted that in Figure 3 (a) shows the state after a certain time has passed since the first startup (1).

[0079] In addition, among N1 to N3 recorded on the vertical axis, N1 is a relatively low load set to suppress the temperature drop without hindering the temperature rise of the fixing belt 110. In addition, N2 is a load set to fix the unfixed colorant image to the paper P. In addition, N3 is a load set to increase the clamping force of the pressure roller 120 on the fixing belt 110. By increasing the clamping force by using the load of N3, the slip of the fixing belt 110 and the pressure roller 120 is suppressed. When considering the load when the unfixed colorant image is actually fixed, that is, N2, as the center, N1 can be set to a load of about 1 / 4 to 2 / 3 times that of N2, and N3 can be set to a load of about 5 / 4 to 2 times. As the actual loads of N1 to N3, for example, N1 can be selected as 30 Newtons (30N), N2 as 50 Newtons (50N), N3 as 80 Newtons (80N), etc.

[0080] Figure 3 In (b), the vertical axis represents the belt temperature T, and the horizontal axis represents time. Figure 3 The startup, printing and standby described in (b) are respectively Figure 3(a) corresponds to the state of the belt temperature T. T1 to T3 recorded on the vertical axis represent the state of the belt temperature T. T1 represents the belt temperature after a certain period of time has passed from the room temperature, i.e., the initial temperature, at the first start (1). T2 is a predetermined temperature, i.e., a set temperature, which represents the temperature when switching from the first start (1) to the second start (2). The set temperature is a temperature that is predetermined in order to alleviate the deformation of the fixing belt 110. If the belt temperature T becomes T2, the influence of slippage caused by the deformation of the fixing belt 110 can be eliminated or reduced, and it is a temperature that can give priority to the increase in the belt temperature. Then, the control unit 21 recognizes that the belt temperature T becomes T2, and reduces the load of the nip portion N from N3 to N1 through the load adjustment mechanism 130. The load of the nip portion N is reduced, so that heat dissipation is suppressed and the start-up time is shortened. T3 is the heating temperature when fixing the unfixed colorant image on the paper P, which represents the temperature during printing. The temperature T3 during printing is, for example, 150° C. to 200° C., and T2 can be set to about 1 / 2 times of T3 , for example, 100° C.

[0081] Next, refer to Figure 3 (a) and Figure 3 (b) describes the adjustment of the load corresponding to the state of the belt temperature T by the load adjustment mechanism 130.

[0082] First, the first startup (1) is described. Figure 3 As shown in (b), the first start (1) is a state where the belt temperature T is below the set temperature T2. In this first start (1), the deformation of the belt is not alleviated. When the belt temperature T is below the set temperature T2, Figure 2 The load adjustment mechanism 130 described in the above increases the load of the nip portion N by moving the pressure roller 120 upward. Figure 3 As shown in (a), at the first start (1), the load of the nip portion N is N3, which is higher than the load N2 during printing. The load of the nip portion N becomes N3, so that the clamping force of the pressure roller 120 on the fixing belt 110 increases. In this way, even in a state where the deformation of the belt is not relaxed, the slip between the fixing belt 110 and the pressure roller 120 can be suppressed.

[0083] The transition from the first startup (1) to the second startup (2) is described below. Figure 3 As shown in (b), if the belt temperature T further rises from the first start (1), the belt temperature T becomes the set temperature T2. The set temperature T2 is a temperature pre-set as a temperature for relieving the deformation of the fixing belt 110. By making the belt temperature T reach the set temperature T2, Figure 2 The load adjustment mechanism 130 described above moves the pressure roller 120 downward to reduce the load on the nip portion N. Figure 3As shown in (a), the load of the nip portion N changes from N3 to N1, which is lower than the load N2 during printing. In this way, in the present embodiment, the load of the nip portion N is switched when the fixing device 100 is started.

[0084] The second start (2) is described. The second start (2) is the preheating time for the belt temperature T to rise from T2 to the temperature T3 at which printing is possible. At the second start (2), the load of the bite portion N is reduced from N3 to N1 through the load adjustment mechanism 130, that is, the load is switched from N3, which is a load larger than the load N2 during printing, to N1, which is a load smaller than the load N2 during printing. As a result, the bite width of the bite portion N becomes narrower than that of the first start (1), and at the second start (2), the heat conduction efficiency of the belt temperature T is improved compared to the first start (1). That is, at the second start (2), heat dissipation is suppressed from T2 to the temperature T3 at which printing is possible, making it easier to increase the belt temperature T, thereby shortening the start time.

[0085] Next, the transition from the second start-up (2) to the printing time is described. In the second start-up (2), the belt temperature T rises to T3, and the printing of the paper P starts accordingly. In addition, when the transition from the second start-up (2) to the printing time is Figure 2 The load adjustment mechanism 130 described in the above makes the pressure roller 120 move upward, increasing the load of the nip portion N until it reaches the load during printing. Figure 3 As shown in (a), the load of the bite portion N is increased from N1 to N2, which is the load during printing. Figure 3 (a) and Figure 3 In (b), the state of the belt temperature T and the load of the nip portion N transitions from the start-up to the printing. During printing, the belt temperature T is maintained at T3, and the load of the nip portion N is maintained at N2.

[0086] Next, we will explain the standby mode. Figure 3 As shown in (b), the belt temperature T is above the set temperature T2. During this standby period, the load adjustment mechanism 130 moves the pressure roller 120 downward to make the load of the nip portion N lower than that during printing. Figure 3 As shown in (a), when migrating from printing to standby, the load of the bite portion N is reduced from the load during printing, that is, N2, to N1. In this way, by reducing the load of the bite portion N, the state of improved heat conduction efficiency with temperature T can be maintained during standby until the next printing.

[0087] During the next printing, the load adjustment mechanism 130 moves the pressure roller 120 upward to increase the load of the nip portion N from a lower state than during printing to a load equal to that during printing. Figure 3As shown in (a), the load of the bite portion N is increased from N1 to N2, which is the load during printing.

[0088] As described above, in the present embodiment, the load of the nip portion N is adjusted according to the state of the belt temperature T, thereby suppressing slippage between the fixing belt and the pressure roller at the time of startup, thereby shortening the heating time of the fixing belt.

[0089] Although the present embodiment has been described above, the present invention is not limited to these embodiments. For example, the load on the nipple N may be increased by moving the pad 140 in the vertical direction. In addition, the adjustment of the load on the nipple N may be set in more detail.

[0090] <Note>

[0091] (((1)))A fixing device, characterized by comprising:

[0092] a fixing belt which is heated by a heating source and rotates;

[0093] a pressure roller, the pressure roller forming a nip portion at a position in contact with the fixing belt and rotating;

[0094] A load adjustment mechanism is provided for obtaining a belt temperature of the fixing belt and adjusting a load of the nip portion according to a state of the belt temperature relative to a preset temperature.

[0095] (((2)))The fixing device according to (((1))), characterized in that:

[0096] When the belt temperature is lower than a preset temperature, the load adjustment mechanism increases the load on the nip portion compared to that during printing.

[0097] (((3)))The fixing device according to (((2))), characterized in that:

[0098] The load adjustment mechanism reduces the load on the nip portion compared to that during printing when the belt temperature reaches a predetermined temperature in a state where the load on the nip portion is higher than that during printing.

[0099] (((4))) The fixing device according to any one of (((2))) or (((3))), characterized in that:

[0100] When printing starts, the load adjustment mechanism increases the load of the nip portion from a state lower than that during printing to the load during printing.

[0101] (((5)))The fixing device according to (((1))), characterized in that:

[0102] When the belt temperature is equal to or higher than a preset temperature and printing is not being performed, the load adjustment mechanism reduces the load on the nip portion compared to that during printing.

[0103] (((6)))The fixing device according to (((5))), characterized in that:

[0104] When printing starts, the load adjustment mechanism increases the load of the nip portion from a state lower than that during printing to the load during printing.

[0105] (((7))) The fixing device according to any one of (((1))) to (((6))), characterized in that:

[0106] The load adjustment mechanism switches the load of the nip portion when the fixing device is activated.

[0107] (((8))) The fixing device according to any one of (((1))) to (((7))), characterized in that:

[0108] The switching of the load at the nip portion is switching from a load greater than the load during printing to a load smaller than the load during printing.

[0109] (((9))) The fixing device according to any one of (((1))) to (((8))), characterized in that:

[0110] The preset temperature is a temperature set to alleviate deformation of the fixing belt.

[0111] (((10)))The fixing device according to (((1))) is characterized in that:

[0112] The nip portion is formed by a pad that presses the paper together with the pressure roller.

[0113] The load adjustment mechanism adjusts a load of the nip portion formed by the pad and the pressure roller sandwiching the fixing belt.

[0114] (((11)))The fixing device according to (((1))) is characterized in that:

[0115] A temperature sensor is provided for detecting the temperature of the fixing belt before the fixing belt enters the nip portion.

[0116] The load adjustment mechanism adjusts the load of the nip portion according to the state of the belt temperature detected by the temperature sensor.

[0117] (((12)))An image forming apparatus, comprising:

[0118] A developer that develops the electrostatic latent image on the photoreceptor;

[0119] a transfer unit that transfers the developed image to paper; and

[0120] A fixing device for fixing the paper to which the developer is transferred, the fixing device comprising:

[0121] A fixing belt that is heated by a heat source and rotates;

[0122] A pressure roller that rotates while forming a nip portion at a portion in contact with the fixing belt; and

[0123] A load adjustment mechanism acquires a belt temperature of the fixing belt and adjusts the load of the nip portion according to a state of the belt temperature relative to a preset temperature.

[0124] According to (((1))), without adding a new roller, it is possible to suppress slippage between the fixing belt and the pressure roller and shorten the heating time of the fixing belt.

[0125] According to (((2))), slippage between the fixing belt and the pressure roller caused by, for example, the pressure roller rotating in a state where the fixing belt has a deformation is suppressed.

[0126] According to (((3))), the efficiency of heat conduction from the heating source to the belt temperature is improved compared to the case where the load on the nip portion is not lowered compared to the case of printing.

[0127] According to (((4))), when starting printing, the load of the nip portion can be adjusted to the load during printing in a state where the efficiency of heat transfer from the heating source to the belt temperature is improved.

[0128] According to (((5))), the preheating time can be shortened while reducing the interlocking width of the interlocking portion and improving the efficiency of heat conduction to the belt.

[0129] According to (((6))), printing can be started in a state where the efficiency of heat conduction to the belt is improved.

[0130] According to (((7))), it is possible to suppress slippage between the fixing belt and the pressure roller when starting the fixing device.

[0131] According to (((8))), after the slip between the fixing belt and the pressure roller is suppressed when the fixing device is started, the efficiency of heat transfer to the belt can be improved until printing.

[0132] According to (((9))), slippage between the fixing belt and the pressure roller can be suppressed.

[0133] According to (((10))), it is possible to stably apply a load to the pressure roller.

[0134] According to (((11))), the belt temperature at the nip portion between the fixing belt and the pressure roller can be grasped, and slippage caused by the fixing belt and the pressure roller can be suppressed.

[0135] According to the image forming apparatus of (((12))), without adding a new roller, it is possible to suppress slippage between the fixing belt and the pressure roller and shorten the heating time of the fixing belt.

Claims

1. A fixing device, characterized in that: have: a fixing belt which is heated by a heating source and rotates; a pressure roller that forms a nip portion at a portion in contact with the fixing belt and rotates; and A load adjustment mechanism is provided for obtaining a belt temperature of the fixing belt and adjusting a load of the nip portion according to a state of the belt temperature relative to a preset temperature.

2. The fixing device according to claim 1, wherein: When the belt temperature is lower than a preset temperature, the load adjustment mechanism increases the load on the nip portion compared to that during printing.

3. The fixing device according to claim 2, wherein: The load adjustment mechanism reduces the load on the nip portion compared to that during printing when the belt temperature reaches a predetermined temperature in a state where the load on the nip portion is higher than that during printing.

4. The fixing device according to claim 2 or 3, wherein: When printing starts, the load adjustment mechanism increases the load of the nip portion from a state lower than that during printing to the load during printing.

5. The fixing device according to claim 1, wherein: When the belt temperature is equal to or higher than a preset temperature and printing is not being performed, the load adjustment mechanism reduces the load on the nip portion compared to that during printing.

6. The fixing device according to claim 5, wherein: When printing starts, the load adjustment mechanism increases the load of the nip portion from a state lower than that during printing to the load during printing.

7. The fixing device according to any one of claims 1 to 6, wherein: The load adjustment mechanism switches the load of the nip portion when the fixing device is activated.

8. The fixing device according to any one of claims 1 to 7, wherein: The switching of the load at the nip portion is switching from a load greater than the load during printing to a load smaller than the load during printing.

9. The fixing device according to any one of claims 1 to 8, wherein: The preset temperature is a temperature set to alleviate deformation of the fixing belt.

10. The fixing device according to claim 1, wherein The nip portion is formed by a pad that presses the paper together with the pressure roller. The load adjustment mechanism adjusts a load of the nip portion formed by the pad and the pressure roller sandwiching the fixing belt.

11. The fixing device according to claim 1, wherein: A temperature sensor is provided for detecting the temperature of the fixing belt before the fixing belt enters the nip portion. The load adjustment mechanism adjusts the load of the nip portion according to the state of the belt temperature detected by the temperature sensor.

12. An image forming device, characterized in that: have: A developer that develops the electrostatic latent image on the photoreceptor; a transfer unit that transfers the developed image to paper; and A fixing device for fixing the paper to which the developer is transferred, the fixing device comprising: A fixing belt that is heated by a heat source and rotates; A pressure roller that rotates while forming a nip portion at a portion in contact with the fixing belt; and A load adjustment mechanism acquires a belt temperature of the fixing belt and adjusts the load of the nip portion according to a state of the belt temperature relative to a preset temperature.

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