Fixing device, image forming apparatus

Abstract

To provide a fixing device that extends a usable period without replacement of lubricant.SOLUTION: A fixing device determines, during the circling of a fixing belt, the amount of reduction in the circling speed of the fixing belt and / or fixing temperature of a heating member in accordance with the slide resistance generated between a pad member and the fixing belt, and reduces the circling speed and fixing temperature for a sheet. A motor circuit block 301 and a heater circuit block 302 control a fixing motor 114M and a halogen heater 114H in accordance with the reduced circling speed and fixing temperature to fix an unfixed image transferred to the sheet.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a fixing device that fixes a toner image transferred to a sheet by applying heat and pressure, and to an image forming apparatus equipped with such a fixing device, and in particular to an improved configuration that uses a pad to apply pressure to the sheet. [Background technology]

[0002] A fixing device using a pad for pressing a sheet has the advantage that, while being small and having a low heat capacity, it can ensure a large nip length in the conveying direction and is highly energy efficient. A conventional fixing device using a pad includes a fixing belt heated by a heating means, a pad arranged inside the rotation path of the fixing belt, a pressure member arranged outside the rotation path and pressing the pad via the fixing belt, and a lubricant supplying member that supplies a lubricant to the inner peripheral surface of the fixing belt. In addition to the example of the configuration using the lubricant supplying member, there have also been conventional fixing devices configured to periodically apply a lubricant to the inner peripheral surface of the fixing belt during the manufacturing stage of the fixing device.

[0003] Lubricants are classified into liquid, semi-solid, and solid types. Of these, liquid lubricants are lubricating oils, and semi-solid lubricants are solutions in which grease (composed of raw base oil and thickener) is dissolved in a liquid. Solid lubricants are additives made of molybdenum disulfide, graphite, etc. These reduce the sliding resistance when the fixing belt slides over the pad, allowing the fixing belt to perform stable orbital motion, stabilizing the conveying speed of the sheet passing through the nip and maintaining fixability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-214456 A [Patent Document 2] JP 2008-298935 A [Patent Document 3] JP 2005-202174 A Summary of the Invention [Problem to be solved by the invention]

[0005] In both the fixing device having a lubricant supply member and the fixing device having a lubricant applied to the inner surface of the fixing belt, the lubricant needs to be replaced periodically to maintain the lubricating performance. This is because the lubricant maintains stable lubricating performance if the depletion of the lubricant oil or solvent is periodically replenished. However, if the image forming device is used for a long time, the lubricating performance decreases at an accelerated rate, and the replacement period gradually becomes shorter. This is because, if the image forming device is used for a long time, fine particles of the base material generated by the wear of the fixing belt are mixed into the lubricant, and the lubricant evaporates and the components deteriorate, causing the lubricant to deteriorate rapidly. As described above, the conventional fixing device has a problem that the shortening of the lubricant replacement period when the image forming device is used for a long time increases the burden on the maintenance staff.

[0006] An object of the present disclosure is to provide a fixing device that can extend the replacement cycle of a lubricant even when an image forming apparatus is used for a long period of time. [Means for solving the problem]

[0007] The above problem is solved by a fixing device including a belt heated by a heating means, a pad disposed inside the rotation path of the belt, and a pressure member disposed outside the rotation path and sandwiching the belt and pressing the pad, forming a fixing nip between the belt and the pressure member, a detection means for detecting an index value that indicates a sliding resistance acting on the belt by sliding on the surface of the pad, and a detection means for detecting an index value that indicates a sliding resistance acting on the belt by sliding on the surface of the pad. and a control means for determining whether the index value exceeds a predetermined threshold value, and if it does, determining a combination of the rotation speed and the fixing temperature at which the index value is equal to or less than the threshold value based on dependency data showing that the sliding resistance has speed dependency and temperature dependency, and controlling a driving means and a heating means for the belt using the determined combination. The speed dependency and temperature dependency of the sliding resistance are properties that the lubricating performance of the lubricant applied to the inner peripheral surface of the belt decreases with increasing speed and temperature. The aforementioned problems are solved by a fixing device comprising:

[0008] Here, the speed dependency of the sliding resistance is the rate of decrease in the sliding resistance when the rotating speed is decreased while the fixing temperature is kept constant, and the temperature dependency of the sliding resistance is the rate of decrease in the sliding resistance when the rotating speed is kept constant while the fixing temperature is decreased, and the control means may determine the amount of decrease in the rotating speed and / or the fixing temperature based on the rate of decrease so as to decrease the index value detected by the detection means to below the predetermined threshold value, and may determine the combination of the rotating speed and the fixing temperature by decreasing the rotating speed or the fixing temperature by the amount of decrease in temperature or speed.

[0009] The control means may obtain the amount of reduction in the rotation speed or the fixing temperature by plotting a function whose slope is the rate of reduction in an orthogonal coordinate system in which a first axis represents the rotation speed or the fixing temperature and a second axis represents an index value, and determining the coordinate on the first axis where the value of the function is equal to or less than the predetermined threshold value.

[0010] The detection means may detect the index value multiple times by changing combinations of the fixing temperature and the rotation speed to obtain multiple index values ​​different from each other, and the control means may calculate a rate of reduction indicating the temperature dependency of the sliding resistance from the difference between the index values ​​detected under conditions where the fixing temperature is kept constant and the rotation speed is reduced, and may calculate a rate of reduction indicating the speed dependency of the sliding resistance from the difference between the index values ​​detected under conditions where the fixing temperature is kept constant and the rotation speed is reduced.

[0011] The speed dependency of the sliding resistance is the rate of reduction of the sliding resistance when the rotating speed is reduced while the fixing temperature is kept constant, and the temperature dependency of the sliding resistance is the rate of reduction of the sliding resistance when the rotating speed is kept constant while the fixing temperature is reduced, the dependency data being a table showing multiple amounts of reduction in the rotating speed and / or multiple amounts of reduction in the fixing temperature determined based on the rate of reduction, and the control means may generate the combination by reducing the rotating speed or the fixing temperature based on the amount of reduction shown in the table.

[0012] The table is composed of a threshold table indicating threshold values ​​each indicating a plurality of stages in which the sliding resistance has increased, and a reduction amount table indicating a reduction amount of the rotation speed and / or the fixing temperature required to suppress the sliding resistance that has increased to each stage, The control means may determine the amount of reduction in rotation speed and / or fixing temperature depending on which of a plurality of stages shown in a threshold table the index value detected by the detection means corresponds to.

[0013] The multiple threshold levels in the table may include a first threshold level associated with an amount of decrease in temperature and a second threshold level associated with an amount of decrease in speed, and the second threshold level may be higher than the first threshold level.

[0014] The multiple threshold levels in the table may include a third threshold level associated with an amount of decrease in temperature and an amount of decrease in speed, and the third threshold level may be higher than the second threshold level.

[0015] The fixing nip can accommodate both a standard maximum size sheet and an extended size sheet that is wider than the maximum size, The threshold table includes a first table corresponding to a maximum standard size and a second table corresponding to an extended size, and the threshold to be used for comparison with the detected index value may be selected from either the first table or the second table depending on the size of the sheet passing through the fixing nip.

[0016] A storage means may be provided for storing a user's policy of whether to prioritize speed or quality, and a combination may be generated in which one of the rotation speed and the fixing temperature is fixed and the other is reduced according to the policy set by the user.

[0017] The fixing nip may include a memory means for storing detection conditions in which the detection timing in a non-paper-passing state in which no sheet is passed through the fixing nip and the belt is not rotating is set as the detection timing for an index value, and when the fixing nip and the belt are in a non-paper-passing state, the detection means monitors whether the detection timing indicated in the detection conditions has arrived, and when it has arrived, detects the index value.

[0018] The detection timing may be a time when a predetermined time has elapsed since power is turned on and warm-up by heating by the heating means and rotation of the belt is completed.

[0019] The detection timing may be a time when the heating means is started and the temperature of the belt is raised to a target temperature.

[0020] A reference speed and a reference temperature for fixing the unfixed image to the sheet may further be set according to the width of the sheet, the basis weight of the sheet, or the image content of the unfixed image to be transferred to the sheet, or a combination of these, and a combination of the rotation speed and fixing temperature at which the index value is below a threshold value may be obtained by lowering the reference speed and reference temperature.

[0021] The sheet transported to the nip is a sheet onto which an unfixed toner image has been transferred based on a print job, and the device is provided with a memory means for storing a table indicating the type of sheet according to the print job based on either the width of the sheet, the basis weight, or the image content of the unfixed image transferred to the sheet, or a combination of these, and the detection means may detect the index value when a sheet corresponding to the type passes through the fixing nip.

[0022] The fixing nip may include an update means for updating the usage frequency of the types in the table that have passed through the fixing nip each time a sheet corresponding to the type shown in the table passes through the fixing nip, and the detection means may detect an index value during execution of the job and / or after execution of the job when the fixing nip conveys a sheet corresponding to the type with the highest usage frequency.

[0023] The driving means may be a driving motor, the index value may be a torque acting on a rotating shaft of the driving motor when a driving force is applied to the belt, and the detection means may convert the amount of motor current flowing through the driving motor and use the magnitude of the converted torque as the index value.

[0024] The pressure member may be a roller member, and the rotation of the belt is a driven motion caused by the drive motor rotating the roller member, and the control means may perform feedback control to keep the rotation speed of the belt constant by using the amount of motor current when rotating the roller member.

[0025] The fixing nip may include a counter that counts the passing time of a single sheet from when the leading edge of the sheet that has passed through the fixing nip is detected to when the trailing edge of the sheet is detected, and the index value may be the sheet passing time counted by the counter.

[0026] The above problem is solved by a fixing device including a belt heated by a heating means, a pad disposed inside the rotation path of the belt, and a pressure member disposed outside the rotation path and sandwiching the belt and pressing the pad, forming a fixing nip between the belt and the pressure member, the fixing device including a counter that counts the number of sheets that have passed through the fixing nip, By multiplying the number of sheets counted by the counter by a conversion factor to a detection means for detecting a torque, and determining whether the detected torque exceeds a predetermined threshold value, and if so, The sliding of the pad acts on the belt. Based on the dependency data showing that sliding resistance has speed dependency and temperature dependency, Either or both of the belt rotation speed and the fixing temperature were reduced until the torque indicating the sliding resistance became equal to or lower than a threshold value. The above-mentioned object may also be attained by a fixing device characterized by comprising a control means for determining a combination of a rotation speed and a fixing temperature, and for controlling a driving means and a heating means for the belt using the determined combination.

[0027] The above problem is solved by a fixing device that includes a belt that is heated by a heating means, a pad that is arranged on the inside of the rotation path of the belt, and a pressure member that is arranged on the outside of the rotation path and presses the pad while sandwiching the belt, forming a fixing nip between the belt and the pressure member, and a distance counter that counts the running distance of the belt and a conversion factor that multiplies the running distance counted by the distance counter by a conversion factor. to a detection means for detecting a torque, and determining whether the detected torque exceeds a predetermined threshold value, and if so, The sliding of the pad acts on the belt. Based on the dependency data showing that sliding resistance has speed dependency and temperature dependency, Either or both of the belt rotation speed and the fixing temperature were reduced until the torque indicating the sliding resistance became equal to or lower than a threshold value. The above-mentioned object may also be attained by a fixing device characterized by comprising a control means for determining a combination of a rotation speed and a fixing temperature, and for controlling a driving means and a heating means for the belt using the determined combination.

[0028] The sheet conveying device may include a deflection amount sensor disposed near the conveying path of the sheet conveyed toward the nip, for detecting the amount of deflection that occurs in the portion of the sheet passing through the nip that is upstream of the fixing nip in the conveying direction, and the index value may be the detected amount of deflection.

[0030] The belt may further include a lubricant application member for applying a lubricant to the inner peripheral surface of the belt.

[0031] The above-mentioned problems may also be solved by an image forming apparatus that is characterized by including such a fixing device.

[0032] The device may include an accepting means for accepting a setting as to whether to prioritize speed or quality, and the control means may generate a combination in which one of the rotation speed and the fixing temperature is fixed and the other is reduced in accordance with the setting made by the user.

[0033] The receiving means may further receive a setting to achieve both speed and quality, and when the receiving means receives a setting to achieve both speed and quality, the control means may generate a combination in which both the rotation speed and the fixing temperature are reduced.

[0034] The device may further include a reception unit that receives an operation to increase or decrease the predetermined threshold value. Effect of the Invention

[0035] Even if the lubricant applied to the inner circumferential surface of the belt has deteriorated, the combination of rotation speed and fixing temperature is determined based on the dependency data showing that the sliding resistance has speed dependency and temperature dependency. The control means controls the heating means using the fixing temperature of such a combination to restore the viscosity of the lubricant, and the driving means of the belt is controlled using the rotation speed of the combination to eliminate the breakage of the lubricant film formed on the inner circumferential surface of the belt. The lubricating performance can be improved by restoring the viscosity and eliminating the breakage of the film. This makes it possible to extend the replacement cycle of the lubricant while maintaining the fixation performance, thereby reducing the number of visits by maintenance personnel. [Brief description of the drawings]

[0036] [Figure 1] 1 shows the external appearance of an image forming apparatus 1000. [Diagram 2] 2 shows a plurality of mechanism sections for performing electrophotographic image formation. [Diagram 3] Fig. 3(a) shows the configuration of the fuser control block 210. Fig. 3(b) shows the configuration of the motor circuit block 301, and Fig. 3(c) shows the configuration of the heater circuit block 302. [Figure 4] FIG. 4(a) shows the measurement condition table 305, and FIG. 4(b) shows the threshold value table. [Diagram 5] 11 is a flowchart showing a main routine of processing by the fixing unit control block 210. [Figure 6] 10 is a flowchart showing a processing procedure in the case where a rotation speed and a reduction amount of the fixing temperature are determined by giving priority to a change in the fixing temperature. [Figure 7] 7(a) to (d) show a process for determining the rotation speed and the amount of reduction in fixing temperature by giving priority to the change in fixing temperature. [Figure 8]FIG. 8(a) shows the increase in sliding resistance over the course of use, and FIG. 8(b) shows the temperature dependency of sliding resistance. [Figure 9] 9(a) to (c) show the process of determining the combination when the fixing temperature is fixed and the rotation speed is decreased. [Figure 10] A settings screen is shown that includes a tab 700 for setting speed / gloss as one of the options. [Figure 11] Figure 11(a) is a top view of the fixing belt 141, pressure roller 142, heating roller 143, and pad member 146 when A3 paper is being passed through, and Figure 11(b) is a top view of the fixing belt 141, pressure roller 142, heating roller 143, and pad member 146 when SRA3 paper is being passed through. [Figure 12] 8 shows an example of threshold tables 801 to 803 and reduction amount tables 811 to 813. [Figure 13] 13 shows a main routine of the processing procedure of the fixing unit control block 210 according to the second embodiment. [Figure 14] 11 is a flowchart showing a procedure for determining the amount of decrease in rotation speed and fixing temperature using threshold tables 801 to 803 and decrease amount tables 811 to 813. [Figure 15] 1 shows a control system on the main body side of the image forming apparatus 1000. [Figure 16] 9 shows an example of a usage state record table 900. [Figure 17] 13 shows a main routine of the processing procedure of the fixing unit control block 210 according to the third embodiment. [Figure 18] 13 is a flowchart showing a procedure for updating the frequency of use of the usage state record table 900. [Figure 19] 13 shows a setting screen for receiving designation of a usage state in which sliding resistance should be measured. [Figure 20] 10 shows a setting screen displayed on the touch panel display 1001 for level adjustment. [Figure 21] 1 shows a graph showing the relationship between rotation speed and fixing temperature. [Figure 22]A discharge sensor 251 and an actuator 241 provided on the main body side of the image forming apparatus 1000 are shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] [1] First embodiment Hereinafter, a first embodiment of an image forming apparatus according to the present disclosure will be described with reference to the drawings.

[0038] (1-1) Appearance of image forming device FIG. 1 shows the external appearance of an image forming apparatus 1000. As shown in FIG. The image forming apparatus 1000 shown in FIG. 1 is a multifunction peripheral that accepts job settings via a touch panel display 1001, optically reads an original image using a scanner 1004, and forms an image according to the settings on paper fed from paper feed cassettes 1002a, b, c, and d, and discharges the paper onto a discharge tray 1003.

[0039] (1-2) Configuration of Image Forming Apparatus 1000 As shown in FIG. 2, the image forming apparatus 1000 includes a plurality of mechanical parts for performing electrophotographic image formation, including exposure units 110Y, M, C, K that expose photoconductor drums 109Y, M, C, K to light based on an image read by a scanner 1004 to obtain electrostatic latent images, development units 111Y, M, C, K that develop the electrostatic latent images obtained on the photoconductor drums 109Y, M, C, K to obtain toner images, a transport unit 113 that feeds and transports paper from paper feed cassettes 1002a, b, c, d (paper feed cassettes 1002b, c, d are omitted in FIG. 2, and only paper feed cassette 1002a is shown), a transfer unit 112 that transfers the toner image obtained by development to an intermediate transfer belt 112N, transports it to a secondary transfer position 112P, and transfers it onto paper at the secondary transfer position 112P, and a fixing unit 114 that thermocompresses the toner image transferred onto the paper and then discharges it from a discharge port 119. In FIG. 2, photoconductor drums 109Y, M, C, K, exposure units 110Y, M, C, K, development units 111Y, M, C, K, transfer unit 112, and conveyance unit 113 constitute an image forming unit which is the main body of image forming apparatus 1000.

[0040] The fixing unit 114 is composed of a fixing belt 141 , a pressure roller 142 , a heating roller 143 , and a lubricant supplying member 144 .

[0041] The fixing belt 141 is wound around a heating roller 143, a guide member 145, and a pad member 146. The pressure roller 142 forms a wide fixing nip 142N by pressing the pad member 146 through the fixing belt 141. In a state in which the fixing nip 142N is formed, a rotational driving force is applied from the fixing motor 114M, so that the pressure roller 142 rotates in the direction of the arrow C. As the pressure roller 142 rotates, the fixing belt 141 moves in the direction of the arrow B.

[0042] The heating roller 143 is rotated by receiving a rotational driving force from the pressure roller 142 through the fixing belt 141. A halogen heater 114H serving as a heat source is inserted in the heating roller 143. When the halogen heater 114H starts heating, the heating roller 143 is heated by heat conduction through the fixing belt 141. When the generation of heat by the halogen heater 114H and the rotation of the heating roller 143 are repeated, the amount of heat generated by the halogen heater 114H is distributed throughout the circumferential surface of the pressure roller 142, and the temperature of the circumferential surface of the pressure roller 142 increases.

[0043] The lubricant supplying member 144 is a porous material containing a lubricant, and is inserted into a groove portion 145H formed on the back surface of the guide member 145. When the lubricant supplying member 144 comes into contact with the inner surface of the fixing belt 141, the lubricant supplying member 144 elastically deforms, causing the lubricant contained in the lubricant supplying member 144 to seep out, and the lubricant is applied to the inner circumferential surface of the fixing belt 141. When the lubricant is applied abundantly to the inner surface of the fixing belt 141 and a lubricant film with an appropriate thickness is formed on the inner belt surface, the sliding resistance that the fixing belt 141 receives from the guide member 145 and the pad member 146 is reduced, and the fixing belt 141 rotates smoothly.

[0044] [2] Control system of the fixing unit control block 210 The following describes the configuration of a fuser control block, which is a control system for the fuser 114. The fuser control block 210 shown in Fig. 3(a) includes a motor circuit block 301, a heater circuit block 302, and a microcomputer system 303. The fuser control block 210 and the fuser 114 constitute the fixing device.

[0045] (2-1) Motor circuit block 301 The motor circuit block 301 controls the rotation of the fixing motor 114M so that the fixing motor 114M rotates at the same speed as the conveying speed of the paper that passes through the secondary transfer position 112P and is fed into the fixing nip 142N. When the fixing belt 141 rotates, a force (generally called a load torque, hereinafter abbreviated as torque) that tries to stop the rotation acts on the rotating shaft of the fixing motor 114M.

[0046] The motor circuit block 301 includes a PWM waveform circuit 311, a motor control circuit 312, a motor drive circuit 313, and a current detection circuit 314 shown in FIG. 3(b), and performs feedback control to maintain the rotational speed of the fixing belt 141 at the same speed as the paper transport speed, regardless of fluctuations in torque.

[0047] Specifically, a current amount detection circuit 314 detects the amount of current (motor current) flowing through the U-phase, V-phase, and W-phase of the fixing motor 114M, which is a three-phase brushless motor, and feeds back the amount to the motor control circuit 312, which outputs a parameter indicating a current width corresponding to the amount of the motor current to a PWM waveform circuit 311. The PWM waveform circuit 311 generates a PMM waveform with a duty ratio corresponding to the output parameter, and outputs the PWM waveform to a motor drive circuit 313. The motor drive circuit 313 energizes the windings of the fixing motor 114M according to the PWM waveform. Forces that try to stop the rotation shaft include a frictional force acting on the circumferential surface of the pressure roller 142, a frictional force of a paper sheet passing through the fixing nip 142N, and a sliding resistance acting from the pad member 146 to the fixing belt 141.

[0048] There is a linear relationship between the torque acting on the rotation shaft of the fixing motor 114M and the sliding resistance, and as the sliding resistance increases, the torque also increases accordingly. Since such a relationship is recognized, the fixing unit control block 210 outputs the amount of current detected by the current amount detection circuit 314 to the microcomputer system 303.

[0049] Meanwhile, the conversion coefficient for converting the amount of motor current into a torque value is provided by the manufacturer of the fixing motor 114M. If the microcomputer system 303 performs a conversion calculation by multiplying the amount of current detected by the current amount detection circuit 314 by the conversion coefficient, the microcomputer system 303 can calculate the torque acting on the rotating shaft of the fixing motor 114M. This torque calculation serves as an index of the sliding resistance acting on the fixing belt 141 when the pad member 146 slides.

[0050] (2-2) Heater circuit block 302 When the paper fed from the secondary transfer position 112P passes through the fixing nip 142N, the heater circuit block 302 melts the toner particles constituting the toner image transferred at the secondary transfer position 112P, and controls the heating of the halogen heater 114H inserted in the heating roller 143 so that the toner image is fixed to the paper. The amount of heat required to melt the toner particles varies depending on the weight per unit area (basis weight) of the paper and the paper conveying speed. Also, each time the paper passes through the fixing nip 142N, part of the heat accumulated in the fixing belt 141 up to that point is lost, so it is necessary to compensate for the amount of heat lost by the passage of the paper.

[0051] 3(c), heater circuit block 302 includes PWM waveform circuit 321, heater control circuit 322, heater drive circuit 323, and temperature sensor 114S, and performs feedback control to compensate for the heat lost by paper passage and maintain the temperature (fixing temperature) required for fixing the toner image. Specifically, temperature sensor 114S detects the temperature at a peripheral position of fixing belt 141 and feeds it back to heater control circuit 322, which outputs a parameter indicating a current width corresponding to the detected temperature to PWM waveform circuit 321. PWM waveform circuit 321 generates a PMM waveform corresponding to the output parameter and energizes halogen heater 114H.

[0052] (2-3) Microcomputer System 303 The microcomputer system 303 is composed of a CPU 303C, a non-volatile memory 303F, a code ROM 303I, and a RAM 303R, and determines whether to reduce the rotational speed of the fixing belt 141 and whether to reduce the fixing temperature at which the halogen heater 114H heats up, based on the torque calculated based on the amount of current detected by the current detection circuit 314.

[0053] The sliding resistance, which is an index of torque, increases with daily use. The CPU 303C of the microcomputer system 303 reads a program from the instruction ROM 303I to the RAM 303R and executes it to calculate the torque under a plurality of conditions with different combinations of rotation speed and fixing temperature.

[0054] If the torque calculated under multiple conditions exceeds a threshold value, a new combination of rotation speed and fixing temperature is determined based on the torque calculated under multiple conditions, and the rotation speed and fixing temperature for that combination are instructed to the motor circuit block 301 and the heater circuit block 302, thereby controlling heating by the heating roller 143 and rotation by the fixing motor 114M.

[0055] A non-volatile memory 303F of the microcomputer system 303 stores a measurement condition table 305 that defines the measurement conditions for the sliding resistance, and a threshold table 306 that indicates threshold values ​​to be compared with the torque calculated from the motor current of the fixing motor 114M.

[0056] (2-4) Measurement condition table 305 The measurement condition table 305 includes a timing condition 305T and a combination condition 305C as shown in FIG.

[0057] Timing condition 305T indicates when to measure the torque acting on fixing motor 114M during the daily operating cycle of image forming apparatus 1000 from the start of work to the end of work. In Fig. 4(a), the measurement timing of the torque acting on the rotating shaft of fixing motor 114M of fixing unit 114 is shown as a point in time when a certain period of time (300 seconds is shown as an example in Fig. 4(a)) has elapsed after the main power of image forming apparatus 1000 is turned on and execution of the first job is completed.

[0058] The combination condition 305C shows a plurality of combinations of the rotation speed of the fixing belt 141 to be set in the motor circuit block 301 and the fixing temperature to be set in the heater circuit block 302. The combination condition 305C in FIG. 4(a) includes, as such a plurality of combinations, a combination 331 of a rotation speed of 330 mm / s, which is the full speed, and 160° C., which is the fixing temperature for plain paper, a combination 332 of the same rotation speed of 330 mm / s and 145° C., which is 15° C. lower than the fixing temperature, a combination 333 of a rotation speed of 165 mm / s, which is half speed, and 160° C., and a combination 334 of the same rotation speed of 165 mm / s and 145° C., which is 15° C. lower than the fixing temperature. The rotation speed of 330 mm / s is the conveying speed of plain paper in the image forming apparatus 1000. 160° C. is the fixing temperature for this plain paper. By calculating the torque for four different combinations of rotation speed and fixing temperature, the relationship between torque and temperature and the relationship between torque and speed are clarified when the rotation speed is increased from half speed to full speed and when the fixing temperature is increased from 145° C. to 160° C. From these relationships, dependency data is generated that shows the speed dependency and temperature dependency of the torque.

[0059] The four combinations 331 to 334 shown in the combination condition 305C are different in the combination of the rotation speed and the fixing temperature, so the torque calculated according to the four combinations 331 to 334 are different from each other. The threshold value table 306 shown in FIG. 4B shows a threshold value that is slightly lower than the torque (1.1 N·m) acting on the rotating shaft of the fixing motor 114M when the durability of the fixing belt 141 reaches the end of its life. Specifically, it shows a torque value of 1.0 N·m obtained by subtracting 0.1 N·m from the torque at the end of its life. By comparing the torque value with the torque value calculated by measuring the sliding resistance four times according to the combination condition 305C of the measurement condition table 305, it is possible to determine whether there is room to recover the lubricating performance of the lubricant due to a decrease in the rotation speed and the fixing temperature, and whether the lubricant needs to be replaced by a service technician.

[0060] [3] Contents of control by the fixing unit 114 The code ROM 303I stores a program that causes the CPU 303C to execute a series of procedures shown in the flowcharts of Figures 5 and 6. The control contents executed by the fixing unit control block 210 will be described below with reference to Figures 5 and 6.

[0061] (3-1) Main routine 5 is started, the process proceeds to a loop consisting of steps S101 and S102. Step S101 is for judging whether or not the time indicated in timing condition 305T of sliding resistance indicated in measurement condition table 305 has arrived, and step S102 is for judging whether or not job data has been accumulated in queue memory (see FIG. 15) on the main body side of image forming apparatus 1000.

[0062] (3-2) Torque measurement according to measurement conditions The timing condition 305T of the sliding resistance shown in the measurement condition table 305 is that after the main power is turned on, the first job data is executed, the fixing of all the toner images transferred to the paper selected by the job data is completed, the rotation of the fixing belt 141 is stopped, and 300 seconds have passed since the fixing nip 142N is in a non-paper passing state where no paper is passing through it. When the measurement timing arrives (Yes in step S101), the torque acting on the fixing motor 114M is calculated according to the combination condition 305C described in the measurement condition table 305. Specifically, the halogen heater 114H is heated and the fixing motor 114M is rotated at a combination of half speed and 145°C and a combination of full speed and 145°C. Thereafter, the halogen heater 114H is heated and the fixing motor 114M is rotated at a combination of full speed and 160°C and a combination of half speed and 160°C. At this time, the torque acting on the rotating shaft of the fixing motor 114M is measured by multiplying the amount of motor current fed back from the motor drive circuit 313 of the motor circuit block 301 to the motor control circuit 312 for PID control of the rotation speed by a conversion coefficient of the roller motor.

[0063] (3-3)Comparing the measured torque with the threshold Next, it is determined whether the torque measured at the combination of half speed and a fixing temperature of 145° C. exceeds the threshold value (1.0 N·m) described in the threshold value table 306 (step S104). If the torque measured at half speed and 145° C. exceeds the threshold value (Yes in step S104), there is no room for improving the rotation speed and fixing temperature. If this state is left as it is, the rotation speed of the fixing belt 141 will be significantly slower than the rotation speed of the pressure roller, and only the pressure roller 142 will rotate, resulting in idling. If the paper fed into the fixing nip 142N slips due to the idling of the pressure roller 142, the paper will bend significantly and cause a paper jam. In addition, the unfixed toner image transferred to the slipped paper will come into contact with the guide plate, causing a toner shift and resulting in a defective image. Therefore, a trouble code related to the fixing belt 141 is displayed on the touch panel display 1001, and a serviceman call is made (step S110).

[0064] If the torque measured at half speed and 145°C is equal to or lower than the threshold value listed in threshold value table 306 (No in step S104), it is determined whether the torque measured at the combination of full speed and 160°C exceeds the threshold value (step S105). If the torque measured at the combination of full speed and 160°C is equal to or lower than the threshold value listed in threshold value table 306 (No in step S105), the process returns to the loop of steps S101 and S102.

[0065] If the torque measured at the combination of full speed and 160°C exceeds the threshold value shown in threshold table 306 (Yes in step S105), the rotation speed and / or the amount of reduction in fixing temperature are calculated so that the torque acting on the rotating shaft of fixing motor 114M is less than or equal to the torque acting on the rotating shaft of fixing motor 114M (step S106).

[0066] (3-4) Interpolation calculation to interpolate measurement points The process of step S106 is shown in detail in the flowchart of FIG. The variable P in the flow chart of FIG. 6 is a variable indicating the extent of the temperature reduction, and increases or decreases within a range from 0 to 10. The variable A is the slope of the interpolation line, and indicates the reduction rate (temperature dependency) of the sliding resistance with respect to the reduction in the fixing temperature. First, the four measurement points measured according to the measurement condition table 305 are plotted on a graph with the horizontal axis representing temperature and the vertical axis representing torque value, and an interpolation formula of an n-th order function that connects the measurement points plotted on the graph is obtained by an interpolation calculation of an n-th order function (step S200). Data indicating such an interpolation formula of an n-th order function is dependency data indicating the temperature dependency of the sliding resistance, and indicates the reduction rate of the sliding resistance when the rotation speed is kept constant and the fixing temperature is reduced. Note that in this explanation, the degree of the n-th order interpolation is set to 1, and the linear function interpolation formula N at full speed, half speed, and 2 / 3 speed is calculated from the torque value at the measurement point. [T] =A [ full speed ] T+C [ full speed ] The slope A of the interpolation equation is calculated by dividing the torque difference (N2-N1) between the torque values ​​N2 and N1 of the two torque data by the difference (T2-T1) between the temperatures T2 and T1 of the two torque data. The intercept C is calculated by subtracting the value T2·A obtained by multiplying the temperature T2 by the slope A from the torque value N2 of torque data 1. In other words, A [ full speed ] =(N [ full speed 160 ℃ ] -N [ full speed 145 ℃ ] ) / (160℃-145℃) C [ full speed ] Since is an intercept, it can be calculated using the following formula:

[0067] C [ full speed ] =N [ full speed 145 ℃ ] -A [ full speed ] ×145℃ Interpolation equation N of linear function at half speed [T] =A [ half speed ] T+C[ half speed ] A [ half speed ] Since is a gradient, it can be calculated from the torque difference and the temperature difference. A [ half speed ] =(N [ half speed 160 ℃ ] -N [ half speed 145 ℃ ] ) / (160℃-145℃) C [ half speed ] Since is an intercept, it can be calculated using the following formula:

[0068] C [ half speed ] =N [ half speed 145 ℃ ] -A [ half speed ] ×145℃ For the measurement points at 2 / 3 speed, the torque value measured at half speed and 160°C was used. The torque values ​​for 2 / 3 speed and 160°C and 2 / 3 speed and 145°C are calculated by proportional allocation to the torque value measured at full speed and 160°C. Expressed as an equation, this is as follows.

[0069] N [2 / 3 Fast 160 ℃ ] =N [ half speed 160 ℃ ] +(N [ full speed 160 ℃ ] -N [ half speed 160 ℃ ] )*1 / 3 N [2 / 3 Fast 145 ℃ ] =N [ half speed 145 ℃ ] +(N [ full speed 145 ℃ ] -N [ half speed 145℃ ] )*1 / 3 The following is the same as for full speed and half speed, with slope A. [2 / 3 Fast ] , intercept A [2 / 3 Fast ] Request.

[0070] A [2 / 3 Fast ] =(N [2 / 3 Fast 160 ℃ ] -N [2 / 3 Fast 145 ℃ ] ) / (160℃-145℃) C [2 / 3 Fast ] =N [2 / 3 Fast 145 ℃ ] -A [2 / 3 Fast ] ×145℃ Assume that measurement points 501 to 504 in FIG. 7(a) were obtained by measurements according to the measurement conditions. When the above-mentioned interpolation calculation is performed on these measurement points, these measurement points are connected by interpolation lines 511 and 512 of an n-th order function. Furthermore, torque values ​​of intermediate points 505 and 506 between measurement points 501 and 502 and measurement points 503 and 504 in FIG. 7(b) are obtained by proportional distribution of the torque values ​​shown at the measurement points, and an interpolation equation passing through these intermediate points is obtained. As a result, an interpolation line 513 of an n-th order function passing through intermediate points 505 and 506 is also generated. These interpolation lines 511, 512, and 513 correspond to full speed, half speed, and 2 / 3 speed, respectively.

[0071] Once the rotation speeds at full speed, half speed, and 2 / 3 speed have been calculated in this manner, the following processes are executed in sequence: a process for determining the amount of temperature drop with the rotation speed fixed at full speed (S201-S207), a process for determining the amount of temperature drop with the rotation speed fixed at 2 / 3 speed (S211-S217), and a process for determining the amount of temperature drop with the rotation speed fixed at half speed (S221-S227). Steps S201-S207, steps S211-S217, and steps S221-S227 are all common procedures.

[0072] When used in office applications where productivity is important, it is necessary to maintain the paper transport speed at its maximum. However, if the fixing temperature is lowered too much, the fixing performance will be impaired. Therefore, the interpolation calculation program limits the range in which the fixing temperature can be changed to between 160°C and 150°C, and even if the fixing temperature is set to 150°C, the rotation speed is lowered if the torque value does not exceed the threshold value.

[0073] An interpolation formula based on a fixed rotation speed is set (step S201), the count value P is reset (step S202), the count value P is incremented (step S203), and the value obtained by subtracting the count value P from the fixing temperature (fixing temperature-count value P) is multiplied by the slope A and added with the intercept C (A x (fixing temperature-count value P) + C) to obtain an estimated torque value T(P) (step S204).

[0074] Step S205 is a determination as to whether the torque estimate T(P) is below a threshold value, and step S206 is a determination as to whether the count value P has reached 10. If steps S205 and S206 are No, the process returns to step S203, and the count value P is incremented. As long as steps S205 and S206 are both No, the loop of steps S203 to S206 is repeated.

[0075] By substituting temperatures in increments of unit temperature width ΔT into the interpolation formula of the nth-order function corresponding to the straight line 511 shown in FIG. 7(b), torque estimates 521, 522, 523, 524, 525, 526, and 527 in increments of unit temperature width ΔT are calculated in sequence, as shown in FIG. 7(c).

[0076] If the count value reaches 10 without the estimated value falling below the threshold, step S206 becomes Yes and the process proceeds to step S211, where a 2 / 3 speed interpolation formula is set, and steps S212 to S217 are repeated until the torque estimated value derived from the generated 2 / 3 speed interpolation formula falls below the threshold. If the count value reaches 10 without the estimated value falling below the threshold, step S216 becomes Yes and the process proceeds to step S221, where a half speed interpolation formula is set, and steps S222 to S227 are repeated until the torque estimated value derived from the generated half speed interpolation formula falls below the threshold.

[0077] By substituting the temperature increments of unit temperature width into the interpolation formula of the n-th degree function corresponding to the straight line 513 shown in FIG. 7B, the torque estimates 531, 532, 533, 534, 535, 536, and 537 increments of ΔT are calculated in sequence as shown in FIG. 7D. All of the torque estimates 521 to 527 shown in FIG. 7C exceed the threshold value of 1 N·m. However, among the torque estimates 531 to 537 shown in FIG. 7D, the measurement point 538 is below the threshold value. Therefore, a combination of the rotation speed of 2 / 3 speed corresponding to the interpolation line 512 and the fixing temperature corresponding to the torque estimate 538 is selected, and the reduction amount of the rotation speed of 2 / 3 speed and the reduction amount of the fixing temperature of -8°C are returned to the main routine. In the main routine, the process is resumed from the step immediately after step S106, that is, the loop of steps S101 and S102.

[0078] (3-5) Execution of fixing using the drop amount obtained by the interpolation calculation When the job data is stored in the queue memory on the main body side of the image forming apparatus 1000 (Yes in step S102), it is determined whether there is a reduction in the rotation speed and fixing temperature (step S107), and if there is (Yes in step S107), the rotation speed and fixing temperature are reduced according to the reduction amount (step S108).

[0079] Next, the toner image is fixed (step S109). If the amount of reduction in the rotation speed and fixing temperature has been determined in step S108, the toner image is fixed according to the reduced rotation speed and fixing temperature. On the other hand, if step S108 is not performed and the amount of reduction in the rotation speed and fixing temperature has not been determined (step S107: No), the toner image is fixed according to the original rotation speed and fixing temperature.

[0080] By adjusting the rotation speed of the fixing belt 141 and the fixing temperature by the heating roller 143, the sliding resistance can be reduced and the lubrication performance can be improved. The result is shown in the graph of FIG. 8(a). The graph of FIG. 8(a) shows the relationship between the rotation speed of the fixing belt 141 and the torque value indicating the driving force applied by the fixing motor 114M to the pressure roller 142. Measurement points 401, 402, 403, and 404 in this graph show four torques measured when the image forming apparatus 1000 is in the early durability stage, the fixing temperature is set to 160° C., and the rotation speed is changed to four stages (165 mm / s, 250 mm / s, 290 mm / s, and 330 mm / s). Measurement points 411, 412, 413, and 414 show four torques measured when the image forming apparatus 1000 is in the later durability stage, the fixing temperature is set to 160° C., and the rotation speed is changed to the same four stages. Although the measurements were performed at the same rotation speed, the torque increased at each measurement point. The torque increments 405 and 406 before and after the endurance test are the sliding resistance, which occurs due to evaporation of the solution and contamination of the base material. At measurement points 411 and 412 at full speed (330 mm / s), the change in sliding resistance was large, but at measurement points 413 and 414 at low rotation speeds, the change in sliding resistance was small. This indicates that the sliding resistance is speed-dependent, and that the sliding resistance does not increase at low rotation speeds. In the example of Figure 4(d), the sliding resistance is significantly reduced by reducing the rotation speed from full speed to 2 / 3 speed.

[0081] The graph in FIG. 8(b) includes the measurement points 411, 412, 413, and 414 shown in FIG. 8(a). In addition to the measurement points 411, 412, 413, and 414, FIG. 8(b) also includes four measurement points 421, 422, 423, and 424 measured when the fixing temperature is set high (170° C.), and measurement points 431, 432, 433, and 434 measured when the fixing temperature is set even lower (150° C.). Comparing the torque values ​​at these measurement points, it can be seen that the torque decreases as the fixing temperature is set lower even if the rotation speed is the same. The torque value of the pressure roller 142 increases at high temperatures for the following reasons. The lubricant supplied by the lubricant supply member 144 is interposed between the pad member 146 and the fixing belt 141, and forms a grease film to ensure the original function. When the fixing device 114 becomes hot, the grease film softens. In this state, if the movement of the fixing belt 141 becomes faster, the force of adhesion to the lubricant interface weakens, the film breaks more frequently, the inner circumferential surface of the fixing belt 141 comes into direct contact with the pad member 146, and the friction coefficient increases. However, as the temperature decreases, the viscosity of the lubricant recovers, the film breaks less frequently, and the lubricating performance improves. In the example of Fig. 7(d), it can be seen that the fixing temperature was reduced from 160°C to 152°C, so that the sliding resistance decreased and the lubricating performance of the lubricant recovered to the initial durability stage.

[0082] (3-6) Fixing temperature is fixed and rotation speed is decreased It is also possible to determine a combination of the rotation speed and the fixing temperature at which the torque estimation value is equal to or less than the threshold value by fixing the fixing temperature and lowering the rotation speed. This is because when the rotation speed is lowered, the amount of lubricant conveyed per unit time between the fixing belt 141 and the pad member 146 decreases, resulting in less film breakage and improved lubrication performance. The process of determining this combination is as shown in Figs. 9(a) to 9(c). When the torque value is measured four times according to the measurement condition table 305, the four measurements are plotted on the graph of Fig. 9(a). This graph is a graph in which the X-axis direction is the rotation speed and the Y-axis direction is the torque value, and shows the change in the torque value with respect to the rotation speed. When the measurement points 601, 602, 603, and 604 are plotted on this graph, an interpolation equation of an n-th order function connecting the measurement points is generated as described in the first embodiment. In addition, as shown in Fig. 9(b), intermediate points 605 and 606 of the measurement points are obtained, and an interpolation equation passing through the intermediate points 605 and 606 is generated. As a result, as shown in FIG. 9B, an interpolation line 611 corresponding to a fixing temperature of 160° C., an interpolation line 612 corresponding to a fixing temperature of 145° C., and an interpolation line 613 corresponding to a fixing temperature of 152.5° C., which is an intermediate value, are obtained. The data indicating the interpolation formula thus generated is dependency data indicating the speed dependency of the sliding resistance, and indicates the rate of decrease in the sliding resistance when the fixing temperature is kept constant and the rotation speed is decreased. Thereafter, the rotation speed incremented by unit speed ΔV is substituted into the interpolation formula of the n-th order function of these interpolation lines. The rotation speed incremented by unit speed ΔV is substituted into the interpolation formula corresponding to the fixing temperature of 160° C., thereby obtaining torque estimates 621, 622, 623, 624, 625, 626, 627, 628, and 629. The torque estimate thus obtained is used to fix the paper in an optimal combination that suppresses the decrease in the rotation speed and the fixing temperature as much as possible within a range below the threshold.

[0083] [4] Summary As described above, according to this embodiment, among the combinations of rotation speed and fixing temperature, one of the combinations, the fixing temperature, is gradually decreased, and then the other combination, the rotation speed, is decreased by a unit width, thereby performing a step-by-step adjustment. Therefore, it is possible to determine an optimal combination that minimizes the decrease in rotation speed and fixing temperature within a range in which the load acting on the rotating shaft of fixing motor 114M is below a threshold value.

[0084] [5] Second embodiment In the first embodiment, after the first job is executed every morning, torque values ​​are calculated for multiple combinations of rotation speed and fixing temperature to reduce the rotation speed and fixing temperature. In contrast, in the second embodiment, the fixing conditions are dynamically changed according to the differences in paper and the printing policy of each user.

[0085] (5-1) Use of SRA3 form The reason for implementing such dynamic changes is that the applications of image forming devices have expanded in recent years. In other words, they are increasingly being used not only for office printing, which requires high productivity, but also for design printing such as creating posters, pamphlets, and color booklets. For design printing, posters are made using a special paper called SRA3, which requires special handling.

[0086] When printing pamphlets or color booklets, if you use A3 size paper, the edges are not printed and become blank, which doesn't look good. On the other hand, if you use SRA3 paper, you can print without borders. Since SRA3 paper is larger than A3 paper (320mm x 450mm), as long as the gloss after printing is ensured, you can achieve printed images that are comparable to posters printed with production printing.

[0087] To use SRA3 paper, the paper feed cassettes 1002a, b, c, and d according to the second embodiment store SRA3 paper in addition to standard paper of A3 size or smaller. When the user selects image / density settings, the touch panel display 1001 displays the setting screen shown in FIG. 10. The setting screen in FIG. 10 includes a tab 700 for setting speed / gloss as one of the selection items. The fixing setting tab includes a button 701 for receiving a designation that prioritizes productivity, a button 702 for receiving a designation that prioritizes gloss, and a button 703 for requesting automatic adjustment of productivity and gloss. This is because, in poster printing using SRA3 paper, the gloss of the image is often prioritized, and it is necessary to confirm the user's intention.

[0088] 10, policy information is written to the non-volatile memory 303F. The policy information indicates the user's policy of whether to prioritize speed (productivity), quality (fixability), or both.

[0089] On the other hand, it is important to note that the use of SRA3 paper may hinder the rotational movement of the fixing belt 141 more than standard paper of A3 or smaller. The reason for this will be explained below with reference to Figures 11(a) and 11(b). Figures 11(a) and 11(b) are top views of the fixing belt 141, pressure roller 142, heating roller 143, and pad member 146.

[0090] The pressure roller 142 has a metal core on which an elastic layer made of rubber or the like is laminated, and further, a release layer is laminated on the surface of the elastic layer except for both axial ends 142E, 142F to make it easier for the paper to separate from the roller surface. The reason that no release layer is provided on both ends 142E, 142F of the pressure roller 142 is that the frequency of use of SRA3 paper other than standard paper is generally quite low.

[0091] The coefficient of friction at both ends 142E, 142F is higher than that at the center portion having the release layer, and the driving force of the pressure roller 142 is easily transmitted to the fixing belt 141. Even when an A3 size paper is passed through as shown in Fig. 11(a), both ends 142E, 142F are in pressure contact with the fixing belt 141. For this reason, when a standard size paper 1020A of A3 or smaller is passed through as shown in Fig. 11(a), a driving force is applied to the fixing belt 141 through contact at both ends 142E, F.

[0092] However, as shown in FIG. 11(b), SRA3 paper is wider than standard paper, so when SRA3 paper 1020B passes through fixing nip 142N as shown in FIG. 11(b), it hits both ends 142E, F of pressure roller 142 and is significantly dented (see 142S), reducing the area of ​​contact portion 142T between fixing belt 141 and pressure roller 142, and the driving force transmitted directly to fixing belt 141 is less than that for A3 or smaller paper.

[0093] Generally, the coefficient of friction is higher on the surface of pressure roller 142 than on paper. Therefore, when SRA3 paper is passed through, the area of ​​direct contact between fixing belt 141 and pressure roller 142 is smaller, and a load is more likely to act on fixing belt 141, which becomes a sliding resistance between fixing belt 141 and pad member 146. Due to this reason, for SRA3 size paper, a threshold value that is slightly smaller than the threshold value for A3 size or smaller paper is prepared, making it easier to adjust the fixing temperature and rotation speed as described above than when standard size paper of A3 or smaller is passed through.

[0094] (5-2) Improvements in the Fixing Unit Control Block 210 The improvements of the fuser control block 210 in the second embodiment are as follows.

[0095] In the second embodiment, instead of the threshold table 306, a set of a threshold table 801 and a reduction amount table 811, a set of a threshold table 802 and a reduction amount table 812, and a set of a threshold table 803 and a reduction amount table 813 are provided in the non-volatile memory 303F as shown in Fig. 12. These sets of tables are reference tables indicating a plurality of reduction amounts of the rotation speed and a plurality of reduction amounts of the fixing temperature, which are determined based on the reduction rate of the interpolation formula shown in the first embodiment.

[0096] Threshold tables 801, 802, and 803 indicate a plurality of thresholds (first to third thresholds) that indicate a plurality of stages of increase in sliding resistance.

[0097] The reduction amount tables 811, 812, and 813 indicate the reduction amount of the rotation speed and / or the fixing temperature required to suppress the sliding resistance that has increased to each stage.

[0098] 10, and indicates three thresholds to be referenced when A3 or smaller paper and SRA3 or smaller paper pass through the fixing nip 142N. The three thresholds for A3 or smaller paper consist of a first threshold of 1.1 N·m, a second threshold of 1.2 N·m, and a third threshold of 1.4 N·m. On the other hand, the three thresholds for SRA3 paper consist of first to third thresholds (first threshold of 1.0 N·m, second threshold of 1.05 N·m, and third threshold of 1.1 N·m) that are set to lower values ​​because the contact area at both ends 142E and F is small and rotation of the fixing belt 141 is hindered.

[0099] 10, and indicates two-stage thresholds to be referenced when A3 or smaller paper and SRA3 or smaller paper pass through the fixing nip 142N. The two-stage thresholds for A3 or smaller paper consist of a first threshold of 1.1 N·m and a second threshold of 1.2 N·m. On the other hand, the two-stage thresholds for SRA3 paper consist of a first threshold of 1.0 N·m and a second threshold of 1.05 N·m.

[0100] 10, and indicates three threshold levels to be referenced when A3 or smaller paper and SRA3 or smaller paper pass through the fixing nip 142N. The three threshold levels for A3 paper are made up of a first threshold level of 1.1 N·m, a second threshold level of 1.15 N·m, and a third threshold level of 1.2 N·m. On the other hand, the three threshold levels for SRA3 or smaller paper are made up of a first threshold level of 1 N·m, a second threshold level of 1.02 N·m, and a third threshold level of 1.01 N·m.

[0101] The reduction amount tables 811, 812, and 813 indicate the reduction amount of the rotation speed and / or the fixing temperature required to suppress the sliding resistance that has increased to each stage indicated by the first, second, and third thresholds in the threshold tables 801, 802, and 803. Each reduction amount table will be described below. The reduction amount table 811 pre-stores the reduction amount of the fixing temperature (-8°C) described in the first embodiment in association with the torque range that exceeds the first threshold and is equal to or less than the second threshold. Also, the reduction amount of the rotation speed (2 / 3 speed) described in the first embodiment in association with the torque range that exceeds the second threshold and is equal to or less than the third threshold. Furthermore, the reduction amount of the fixing temperature (-8°C) and the reduction amount of the rotation speed (2 / 3 speed) described in the first embodiment in association with the torque range that exceeds the third threshold are pre-stored. If the user selects a policy of prioritizing productivity on the setting screen of FIG. 10, the rotation speed and fixing temperature can be gradually decreased in the order of -8°C -> 2 / 3 speed -> -8°C and 2 / 3 speed depending on which torque range in reduction amount table 811 the torque measured according to the measurement conditions falls into.

[0102] In the reduction amount table 812, the reduction amount of the rotation speed (2 / 3 speed) described in the first embodiment is stored in advance in association with the torque range exceeding the first threshold and not exceeding the second threshold. Also, the reduction amount of the rotation speed (half speed) described in the first embodiment is stored in advance in association with the torque range exceeding the second threshold. When the user selects a policy of prioritizing gloss on the setting screen of FIG. 10, the rotation speed can be gradually reduced in the order of full speed -> 2 / 3 speed -> half speed depending on which torque range in the reduction amount table 812 the torque measured according to the measurement conditions belongs to.

[0103] In the reduction amount table 813, the reduction amount of the fixing temperature (-5°C) described in the first embodiment is previously recorded in association with the torque range exceeding the first threshold and not exceeding the second threshold. Also, the reduction amount of the fixing temperature (-5°C) and the reduction amount of the rotation speed (2 / 3 speed) are previously recorded in association with the torque range exceeding the second threshold and not exceeding the third threshold. Furthermore, the reduction amount of the fixing temperature (-10°C) and the reduction amount of the rotation speed (1 / 2 speed) are previously recorded in association with the torque range exceeding the third threshold. In the setting screen of FIG. 10, if the user selects a policy of achieving both productivity and gloss, the rotation speed and the fixing temperature can be gradually reduced in the order of -5°C -> -5°C and 2 / 3 speed -> -10°C and half speed depending on which torque range in the reduction amount table 813 the torque measured according to the measurement conditions belongs to.

[0104] (5-3) Contents of the program executed in the second embodiment Fig. 13 shows a main routine of the processing procedure of the fixing unit control block 210 according to the second embodiment. The flowchart in this figure is based on the flowchart in Fig. 5, and the same steps as in Fig. 5 are given the same reference numerals as in Fig. 5. The operation of the image forming apparatus 1000 according to the second embodiment will be described with reference to this flowchart.

[0105] 13, it is determined whether job data has been stored in the queue memory (step S102), and whether the user has performed an operation to select image quality / gloss setting (step S112). When image quality / gloss tab 700 is displayed on touch panel display 1001 and the user has performed an operation to select either productivity priority, gloss priority, or productivity / gloss compatibility, step S112 becomes Yes, and the process proceeds to step S113, where the result is written to non-volatile memory 303F of microcomputer system 303.

[0106] If job data is stored in the queue memory (Yes in step S102), it is determined whether the stored job data is job data that selects A3 or smaller paper and is the first job to be executed after the main power is turned on (step S114). If not (No in step S114), it is determined whether the stored job data is job data that selects SRA3 paper and is the first job to be executed after the main power is turned on (step S115). If either of these applies, the process proceeds to step S116. In step S116, the toner image is fixed according to the rotation speed and fixing temperature, and the motor current flowing through the fixing motor 114M during this fixing is converted to measure the torque when the fixing is being performed in the fixing nip 142N (step S116). Thereafter, the amount of reduction corresponding to the measured torque is determined using threshold tables 801, 802, 803 and reduction amount tables 811, 812, 813 (step S117).

[0107] The procedure for determining the reduction amount of the rotation speed and the fixing temperature in step S117 is shown in detail in the flowchart of Fig. 14. The procedure for adjusting the rotation speed and the fixing temperature will be described below with reference to the flowchart of Fig. 14. The first, second and third threshold values ​​corresponding to the paper width are read out from the threshold table corresponding to the selection of productivity priority, fixing quality priority, or compatibility between productivity and fixing quality among threshold tables 801, 802 and 803 (step S303).

[0108] Then, the process proceeds to a series of judgment steps including steps S304, S305, S306, S307, and S308. Step S304 is a judgment as to whether the torque value exceeds the first threshold value and belongs to a torque range equal to or less than the second threshold value. Step S305 is a judgment as to whether the selected threshold value table has a third threshold value. Step S306 is a judgment as to whether the torque value exceeds the second threshold value and belongs to a torque range equal to or less than the third threshold value if the selected threshold value table has a third threshold value. Step S307 is a judgment as to whether the torque value exceeds the third threshold value. Step S308 is a judgment as to whether the torque value exceeds the second threshold value if the selected threshold value table does not have a third threshold value.

[0109] If the torque value exceeds the first threshold and belongs to a torque range equal to or less than the second threshold (Yes in step S304), the reduction amount corresponding to the torque range equal to or less than the first threshold and the second threshold is read from the reduction amount table of the selected threshold table (step S311).

[0110] If the selected threshold table has a third threshold and the torque value exceeds the second threshold and belongs to a torque range equal to or less than the third threshold (Yes in step S305, Yes in step S306), the reduction amount corresponding to the torque range equal to or less than the third threshold and exceeding the second threshold is read from the reduction amount table of the selected threshold table (step S313).

[0111] If the selected threshold table contains a third threshold and the torque value belongs to a torque range exceeding the third threshold (Yes in step S305, Yes in step S307), the reduction amount corresponding to the torque range exceeding the third threshold is read from the reduction amount table of the selected threshold table (step S314).

[0112] If the torque falls within a range equal to or less than the first threshold and the second threshold exists in the threshold table, step S304 becomes No, step S305 becomes Yes, and steps S306 and S307 become No, and the process returns to the main routine.

[0113] If the selected threshold table does not have a third threshold and the torque value belongs to a torque range exceeding the second threshold (No in step S305, Yes in step S308), the reduction amount corresponding to the torque range exceeding the second threshold is read from the reduction amount table of the selected threshold table (step S315).

[0114] If the torque falls within the torque range equal to or less than the first threshold and the second threshold does not exist in the threshold table, step S304 becomes No, step S305 becomes No, and step S308 becomes No, and the process returns to the main routine. After returning to the main routine, the process returns to the loop of step S102.

[0115] If both steps S114 and S115 are No, the sliding resistance is not measured, and the rotation speed and fixing temperature are reduced according to the reduction amount already obtained when the sliding resistance was measured, and the toner image is fixed according to the reduced rotation speed and fixing temperature (steps S107 to S109).If the reduction amount of the rotation speed and fixing temperature has not been determined (step S107 is No), the toner image is fixed according to the original rotation speed and fixing temperature (step S109).

[0116] [6] Summary As described above, according to this embodiment, the torque value calculated by converting the motor current flowing through the fixing motor 114M is compared with the first, second, and third thresholds listed in the threshold table, and depending on which torque range the calculated torque value falls into, the rotation speed and fixing temperature are reduced using the reduction amount listed in the reduction amount table. This makes it possible to adjust the rotation speed and fixing temperature with processing that is simpler than that of the first embodiment, which can contribute to reducing the cost of the image forming apparatus 1000.

[0117] [7] Third embodiment In the second embodiment, the rotation speed and fixing temperature are changed according to the difference in paper and the policy of each user regarding printing. In contrast, in the third embodiment, the usage state performed by the job is tallied, and the sliding resistance is measured while the transported paper passes through the fixing nip 142N (during paper passing).

[0118] (7-1) Control system on the main body side of the image forming apparatus 1000 The configuration of the control system on the main body side of image forming apparatus 1000 is shown in Fig. 15. As shown in this figure, the control system of image forming apparatus 1000 includes a screen control LSI 201 that displays a setting screen on touch panel display 1001 and generates job data including image data read by scanner 1004 in accordance with a user's operation, a communication control LSI 202 that receives job data issued by terminal 1011, a queue memory 203 in which job data is accumulated, a CPU 204 that interprets and executes the job data, an image processing LSI 205, an exposure unit control block 206 that controls exposure unit 110, a developer control block 207 that controls developer 111, a transfer unit control block 208 that controls transfer unit 112, a transport unit control block 209 that controls transport unit 113, and a fixing unit control block 210.

[0119] The image processing LSI 205 determines whether the image data, which is included in the job data and is to be the target of image formation, is mainly text or mainly solid images, and notifies the fixing unit control block 210 of the determination result.

[0120] The paper width sensor 209W is a component of the transport control block 209, and detects the width of the paper placed in the paper feed cassette 1002a from the amount of movement of the alignment plate 1021 in the paper feed cassette 1002a in the width direction. The paper widths that can be detected include A3 portrait (A3T), A3 landscape (A3Y), A4 portrait (A4T), and A4 landscape (A4Y).

[0121] Basis weight sensor 209L is located before timing roller 123 and has light emitting units 231R, G, B arranged on both sides of transport path 113P shown in FIG. 2 and light receiving unit 231P arranged on one side, and irradiates light from the light emitting units toward the paper transported on transport path 113P and receives the light that passes through the paper. Basis weight is detected based on the amount of received light. The user may manually input the basis weight of the paper via touch panel display 1001.

[0122] (7-2) Improvement of the Fixing Unit Control Block 210 The configuration of the fixing unit control block 210 in the third embodiment will be described below. The fixing unit control block 210 according to the third embodiment includes a usage state record table 900 shown in FIG. 16 as a new component not included in the second embodiment.

[0123] 16, the print condition table 900 is data in a variable-length format in which any number of common format record units 911, 912, 913, 914, 915, 916, 917, 918, and 919 are arranged, and the record units consist of paper width 901, grammage 902, image content 903, and total number of sheets 904. Paper width 901 indicates the paper width (A4T, A4Y) determined by the standard size category and portrait / landscape orientation, and grammage 902 is 60 to 70 g / m 2 , 70~90g / m 2 , 90~105g / m 2 The image content 903 indicates whether the image to be printed is mainly text or includes solid color portions.

[0124] In the third embodiment, the fixing operation is performed according to the flowcharts in Fig. 17 and Fig. 18. The process of the fixing unit control block 210 according to the third embodiment will be described with reference to the flowcharts in Fig. 17 and Fig. 18. When the fixing unit control block 210 is started, the flowchart in Fig. 17 is based on the flowchart in Fig. 13, and the same reference numerals are used for the processes common to Fig. 13. When this flowchart is started, it is determined whether job data has been accumulated in the queue memory 203. When job data has been accumulated (Yes in step S102), the rotation speed and fixing temperature are set based on the paper width detected by the paper width sensor 209W, the basis weight detected by the basis weight sensor 209L, and the image content notified from the image processing LSI 205 (step S121). Specifically, the fixing conditions for plain paper, which are a rotation speed of 330 mm / s and a fixing temperature of 160° C., are adjusted according to the paper width detected by the paper width sensor 209W, the basis weight detected by the basis weight sensor 209L, and the image content notified by the image processing LSI 205.

[0125] Next, the most frequently used state is selected from among the use states shown in the use state record table 900 (step S122), and it is determined whether the job data stored in the queue memory 203 matches the selected print state and the fixing nip 142N has passed a sheet corresponding to the most frequently used type (step S123). If it matches, fixing of the toner image is performed under the fixing conditions, and the torque is calculated at the timing when the paper selected by the job data passes through the fixing nip 142N of the fixing unit 114 (step S115). A reduction amount that matches the calculated torque is obtained (step S116). The process returns to the loop of step S102.

[0126] If the usage state of the job data stored in the queue memory 203 does not match the usage state determined to be frequently used (No in step S123), the rotation speed and fixing temperature are reduced according to the determined reduction amount (steps S107, S108), and the toner image is fixed according to the reduced rotation speed and fixing temperature (step S109).On the other hand, if step S108 is not performed and the reduction amount of the rotation speed and fixing temperature has not been determined (No in step S107), the toner image is fixed according to the original rotation speed and fixing temperature.

[0127] After a sheet corresponding to a printing state shown in the usage state record table 900 passes through the fixing nip 142N, the usage frequency of the printing states in the usage state record table 900 that have passed through the fixing nip 142N is updated (step S125).

[0128] The procedure for updating the usage frequency for the usage status record table is shown in the flowchart of Fig. 18. In this diagram, N is a variable for storing a status number that indicates each record unit in the usage status record table. First, the variable N is initialized to 1 (step S401), and then the process proceeds to the judgment step sequence of steps S402 and S403.

[0129] Step S402 is a judgment as to whether the paper is A4 landscape, step S403 is a judgment as to whether the paper is A4 portrait, and step S405 is a judgment as to whether the paper has a basis weight of 60 to 70 g / m2 In step S406, it is determined whether the paper weight is within the range of 70 to 90 g / m 2 In step S407, it is determined whether the paper weight is within the range of 90 to 105 g / m 2 In step S411, it is determined whether the image content is text.

[0130] A4 portrait with a basis weight of 60-70g / m 2 If the image content is in the range and mainly consists of text, step S402 becomes No and step S403 becomes Yes, and 6 is added to N (step S404). After that, step S405 becomes Yes, and 1 is added to N indicating the state number (step S408). Since N becomes 7, the total number of prints in record 917 in the 7th row of usage state table 332 is increased by the number of prints commanded by the job data (step S413).

[0131] A4 landscape with a basis weight of 60-70g / m 2 If the image content is in the range and the image content is mainly a solid image, step S402 becomes Yes, step S405 becomes Yes, and the variable N indicating the state number is incremented by 1 (step S408). If the image content is mainly a solid image, step S411 becomes No, and the variable N is incremented (step S412). This makes the state number 2. Since the state number is now 2, in the usage state table 332, the total number of prints in record 912 on the second line is incremented by the number of prints commanded by the job data (step S413). Thereafter, the processing in FIG. 17 is resumed from step S102.

[0132] [8] Summary As described above, according to this embodiment, the type of print content frequently used by various users is collected, and when job data of the frequently used print content is executed, the sliding resistance is measured, so that the fixing conditions can be adjusted according to the usage tendency of the user. As a result, even if the image forming device is used for a long time, stable fixing can be performed on the paper, and the print quality can be improved.

[0133] [9] Variations Although the present invention has been described above based on the embodiment, the present invention is of course not limited to the above-described embodiment, and the following modifications are possible.

[0134] (1) In the first to third embodiments, a setting screen for the usage state in which the sliding resistance should be measured as shown in FIG. 19 may be displayed to accept the setting of the printing state in which the sliding resistance should be measured. The setting screen accepts designations 711, 712, 713, 714 of the paper contained in the paper feed cassettes 1002a, b, c, d, and designations 715, 716 of the difference between text and solid image as the image content. According to these designations, the print content is specified from the paper width and basis weight of the paper contained in the paper feed cassettes 1002a, b, c, d, and the image content. Thereafter, it is determined whether the job data stored in the queue memory 203 corresponds to the print content thus specified, and if so, the sliding resistance is measured at the timing when the paper selected by the job data passes through the fixing nip 142N of the fixing unit 114.

[0135] (2) The threshold level may be adjusted in conjunction with the touch panel display 1001. A setting screen displayed on the touch panel display 1001 for level adjustment is shown in FIG. 20. The setting screen in this figure includes a message 720 inquiring about the presence or absence of image rubbing, which indicates a decrease in glossiness, and a level adjustment gauge 721 for adjusting the speed and temperature. The threshold value written in the threshold table 306 is increased or decreased in increments of 0.1 N·m in response to touching a plus button 722 or a minus button 723 on the level adjustment gauge 721. Instead of the message inquiring about the presence or absence of image rubbing, a message requesting confirmation of the paper transport state may be displayed on the menu screen.

[0136] (3) In the first embodiment, the torque estimation value is calculated from the rotation speed and the fixing temperature, and the rotation speed and the fixing temperature are adjusted so that the torque estimation value is equal to or less than a threshold value. However, this is not limited to this. Data showing the relationship between the rotation speed and the fixing temperature as shown in the graph of FIG. 21 may be stored, and the rotation speed of the fixing belt 141 and the fixing temperature of the halogen heater 114H may be adjusted according to the graph. Specifically, when only the fixing temperature is to be lowered, the fixing temperature is lowered along the perpendicular line 551. When only the rotation speed is to be lowered, the rotation speed is lowered along the parallel line 552. When both the rotation speed and the fixing temperature are to be lowered, both the fixing temperature and the rotation speed are lowered along the oblique line 553.

[0137] (4) In the first embodiment, the degree of the n-th order function is 1, but it may be 2 or more, and measurement points may be interpolated using a quadratic or cubic function. Also, two measurement points are used and a straight line is used to connect the two measurement points, but this is not limited to this. The slope A of the linear function may be calculated and stored in advance, and the linear function may be calculated from one measurement point using the slope.

[0138] (5) In the third embodiment, the paper width, the basis weight, and the image content (whether the image is mainly text or mainly solid images) are used as the usage state, but this is not limited to this. The usage frequency may be calculated based on any one of the paper width, the basis weight, and the image content, or any combination of these may be used as the usage state.

[0139] (6) In the first embodiment, the torque is measured by converting the motor current flowing through the fixing motor 114M, but this is not limiting. The torque may be measured based on the count value of the discharge sensor 251 provided near the discharge port 119 of the image forming apparatus 1000 in FIG. 22. The discharge sensor 251 is used to measure the time from when the leading edge of the paper is detected during paper passing to when the trailing edge of the paper is detected. The measured time indicates the passing time of one sheet of paper. When the sliding resistance of the fixing belt 141 increases and the paper starts to slip against the fixing belt, the passing time becomes longer by an amount corresponding to the amount of slip compared to when there is no normal slip. Therefore, there is a certain correlation between the sliding resistance and the passing time. The magnitude of the sliding resistance may be determined by obtaining this correlation in advance through an experiment or the like.

[0140] (7) In the first embodiment, the torque is measured by converting the motor current flowing through the fixing motor 114M, but this is not limited to the above. The torque indicating the load acting on the fixing motor 114M may be obtained by converting the count value of a counter that counts the number of sheets of paper that have passed through the fixing nip 142N. As the number of sheets of paper that have passed through the fixing nip 142N increases, the sliding resistance of the fixing belt 141 increases. A conversion coefficient that defines the relationship between the number of sheets of paper and the torque may be calculated in advance, and the torque may be calculated by multiplying the number of sheets of paper that have passed through the fixing nip 142N by the conversion coefficient. In addition, since the value of the number of sheets of paper that have passed is an index value that indicates the sliding resistance, the number of sheets of paper can be set as the threshold value instead of the torque threshold value.

[0141] (8) In the first embodiment, the torque is measured by converting the motor current flowing through the fixing motor 114M, but this is not limited to the above. A distance counter that counts the running distance of the fixing belt may be provided in the fixing unit 114, and the torque may be obtained by converting the total running distance, which is the count value of the distance counter. As the running distance of the fixing belt 141 increases, the sliding resistance of the fixing belt 141 increases. A conversion coefficient that defines the relationship between the running distance and the torque may be calculated in advance, and the torque may be calculated by multiplying the number of sheets of paper that have passed through the fixing nip 142N by the conversion coefficient. Alternatively, the total running distance may be used as an index value of the sliding resistance, and a threshold value for the total running distance may be set instead of the threshold value for the torque.

[0142] (9) In the first embodiment, the torque was measured by converting the motor current flowing through the fixing motor 114M, but this is not limited to this. The torque may be obtained by converting the detection value of a deflection sensor that detects the deflection of the paper that occurs at the end of the paper upstream of the nip in the transport direction while the paper is passing through the fixing nip 142N. The deflection sensor includes an actuator 241 that is provided near the transport path 113P between the transfer position 112P where the toner image is transferred to the paper and the fixing nip 142N. When the amount of deflection of the paper is small, the tip of the actuator 241 contacts the paper, but when the amount of deflection becomes large, the paper swells greatly in the direction away from the tip of the actuator 241 and no longer contacts the tip of the actuator 241. There is a relationship that the number of contacts between the paper and the actuator 241 decreases as the amount of deflection increases. There is also a relationship that the deflection increases due to slippage that occurs between the paper and the fixing belt 141 when the sliding resistance increases. Therefore, the torque may be obtained by converting the number of contacts counted by the counter of the deflection sensor per unit time using a linear function conversion formula using a counter that counts the number of contacts of the paper when the paper passes through the fixing nip 142N. Also, the amount of deflection may be used as an index value of the sliding resistance, and the amount of deflection may be set instead of the torque threshold value.

[0143] (10) The fixing device 114 may be an induction heating fixing device. In an induction heating fixing device, the fixing belt also functions as a heating element. The fixing belt in an induction heating fixing device is an endless belt with a multi-layer structure including a base layer made of polyimide or the like, a heat generating layer made of metal such as nickel or silver, an elastic layer made of silicone rubber or the like, and a release layer made of a fluorine compound or the like, and the release layer of the fixing belt maintains the release property for the toner image, and the fixing belt is supported by two rollers (heating roller, fixing roller). An electromagnetic induction heating device is disposed at a distance from the outer periphery of the fixing belt. It includes an excitation coil, a core, and a coil guide, and heats the fixing belt and the heating roller by performing electromagnetic induction heating. This heat is transferred to the fixing roller via the fixing belt.

[0144] (11) In the second embodiment, the threshold tables 801-803 and the reduction amount tables 811-813 are three types of tables corresponding to three policies, namely, speed priority, quality priority, and both speed and quality, but the present invention is not limited to this. One, two, or four or more types of threshold tables and tables may be provided. For example, a threshold table and an adjustment table may be provided for each number of years that the image forming apparatus 1000 has been in use. The threshold table and the reduction amount table may be combined into one table, and a correspondence may be established between the threshold value, which is torque, and the rotation speed or the fixing temperature.

[0145] Also, the threshold tables 801-803 are provided with thresholds for A3 paper and smaller, and SRA3 paper, but are not limited to this. They may show one type of paper, or may show thresholds for three or more types of paper. Furthermore, the threshold tables 801-803 are described as showing three levels of thresholds, the first to third thresholds, but are not limited to this. They may show only the first threshold, or only the first and second thresholds, or may clearly show three or more thresholds.

[0146] (12) Although the torque measurement is performed during execution of a job that is one of the printing states recorded in the state record table 900 and is frequently used, this is not limited to the above. The torque measurement may be performed 300 seconds after a job that is one of the printing states recorded in the print state record table 900 and is frequently used is executed.

[0147] (13) In the first embodiment, the torque measurement is performed 300 seconds after the main power is turned on and the first printing is performed in order to reduce the measurement variation when the warm-up state of the fixing unit 114 to be measured is constant and the torque is measured every day. If the warm-up state is constant in this way, the measurement timing is not limited to the above, and other measurement timing may be specified in the timing condition 305T of the measurement condition table 305, and the sliding resistance may be measured according to this timing condition 305T. For example, the torque measurement may be performed 300 seconds after the main power is turned on and the warm-up is performed, or the measurement may be performed before the first printing operation goes into sleep mode. Furthermore, the measurement may be performed not at the first printing operation but at the second or subsequent printing operations, and the waiting time is not limited to 300 seconds and may be increased or decreased.

[0148] (14) In the above embodiment, the semi-solid lubricant has been described as the target, but the present invention is not limited to this. The lubricant supplying member 144 may apply a liquid lubricant to the inner circumferential surface of the fixing belt 141. In addition, the amount of reduction in the rotation speed and fixing temperature based on the temperature dependency and speed dependency of the liquid lubricant may be determined, and the toner image may be fixed using the rotation speed and fixing temperature reduced by the determined amount of reduction. Furthermore, even if a solid lubricant is used, one having the same temperature dependency and speed dependency as a semi-solid lubricant may be used.

[0149] (15) In the above embodiment, the fixing unit 114 is provided in an image forming apparatus that is an MFP, but this is not limited thereto. It may be provided in a production print device. It may also be provided in a single-function copier or a single-function peripheral device (printer) of a personal computer. It may also be provided in a label printer, a postcard printer, or a ticket issuing machine. Also, the fixing motor 114M is a three-phase brushless motor, but this is not limited thereto. Other motors such as a stepping motor may also be used. [Industrial Applicability]

[0150] The present invention can extend the replacement cycle of the lubricant in the fixing unit 114, thereby reducing the burden on maintenance personnel, and therefore has the potential to be used in a wide variety of industrial fields, including the office automation equipment and information equipment industries, as well as retail, rental, real estate, advertising, transportation, publishing, and other industries. [Explanation of symbols]

[0151] 141 Fixing belt 142 Pressure roller 143 Heated Roller 144 Lubricant supply member 145 Guide member 146 Pad material 210 Fuser control block 301 Motor circuit block 302 Heater circuit block 303 Microcomputer System 305 Measurement Condition Table 306 Threshold Table 900 Printing status record table 1000 Image forming device 1001 Touch Panel Display 1002a, b, c, d Paper Cassettes 1004 Scanner 1011 Terminal

Claims

1. A fixing device including a belt heated by a heating means, a pad disposed inside a rotation path of the belt, and a pressure member disposed outside the rotation path and sandwiching the belt to press the pad, forming a fixing nip between the belt and the pressure member, A detection means for detecting an index value indicating a sliding resistance acting on the belt as the belt slides on the surface of the pad; a control means for determining whether the detected index value exceeds a predetermined threshold value, and if so, determining a combination of rotation speed and fixing temperature at which the index value is equal to or less than the threshold value based on dependency data indicating that the sliding resistance has speed dependency and temperature dependency, and controlling a driving means and a heating means for the belt using the determined combination; The speed dependency and temperature dependency of the sliding resistance are the properties that the lubricating performance of the lubricant applied to the inner peripheral surface of the belt decreases with increasing speed and temperature. A fixing device comprising:

2. A fixing device including a belt heated by a heating means, a pad disposed inside a rotation path of the belt, and a pressure member disposed outside the rotation path and sandwiching the belt to press the pad, forming a fixing nip between the belt and the pressure member, A detection means for detecting an index value indicating a sliding resistance acting on the belt as the belt slides on the surface of the pad; a control means for determining whether the detected index value exceeds a predetermined threshold value, and if so, determining a combination of rotation speed and fixing temperature at which the index value is equal to or less than the threshold value based on dependency data indicating that the sliding resistance has speed dependency and temperature dependency, and controlling a driving means and a heating means for the belt using the determined combination; The speed dependency of the sliding resistance is the rate of decrease in the sliding resistance when the rotation speed is decreased while the fixing temperature is kept constant, and The temperature dependency of the sliding resistance is the rate of decrease in the sliding resistance when the rotation speed is kept constant and the fixing temperature is decreased, The control means determines an amount of reduction in rotation speed and / or fixing temperature that can reduce the index value detected by the detection means to below the predetermined threshold based on the reduction rate, and determines a combination of the rotation speed and fixing temperature by reducing the rotation speed or fixing temperature by the amount of reduction in temperature or speed. The fixing device according to claim 1,

3. The control means obtains the amount of reduction in the rotation speed or the fixing temperature by plotting a function having a slope representing the rate of reduction in an orthogonal coordinate system in which a first axis represents the rotation speed or the fixing temperature and a second axis represents an index value, and determining a coordinate on the first axis where the value of the function is equal to or less than the predetermined threshold value.

3. The fixing device according to claim 2,

4. The detection means includes: The index value is detected multiple times while changing the combination of the fixing temperature and the rotation speed to obtain multiple index values ​​that are different from each other. The control means A rate of decrease in the sliding resistance, which indicates the temperature dependency of the sliding resistance, is calculated from a difference between the index values ​​detected under the condition of keeping the rotation speed constant and decreasing the fixing temperature. The rate of decrease, which indicates the speed dependency of sliding resistance, is calculated from the difference in the index values ​​detected under the condition of keeping the fixing temperature constant and decreasing the rotation speed.

4. The fixing device according to claim 2, wherein the fixing member is a fixing member having a fixing roller.

5. A fixing device including a belt heated by a heating means, a pad disposed inside a rotation path of the belt, and a pressure member disposed outside the rotation path and sandwiching the belt to press the pad, forming a fixing nip between the belt and the pressure member, A detection means for detecting an index value indicating a sliding resistance acting on the belt as the belt slides on the surface of the pad; a control means for determining whether the detected index value exceeds a predetermined threshold value, and if so, determining a combination of rotation speed and fixing temperature at which the index value is equal to or less than the threshold value based on dependency data indicating that the sliding resistance has speed dependency and temperature dependency, and controlling a driving means and a heating means for the belt using the determined combination; The speed dependency of the sliding resistance is the rate of decrease in the sliding resistance when the rotation speed is decreased while the fixing temperature is kept constant, and The temperature dependency of the sliding resistance is the rate of decrease in the sliding resistance when the rotation speed is kept constant and the fixing temperature is decreased, the dependency data is a table indicating a plurality of reduction amounts of the rotation speed and / or a plurality of reduction amounts of the fixing temperature determined based on the reduction rate, The control means generates the combination by decreasing the rotation speed or the fixing temperature based on the decrease amount shown in the table. A fixing device comprising:

6. The table is composed of a threshold table indicating threshold values ​​each indicating a plurality of stages in which the sliding resistance has increased, and a reduction amount table indicating a reduction amount of the rotation speed and / or the fixing temperature required to suppress the sliding resistance that has increased to each stage, The control means determines the amount of reduction in rotation speed and / or fixing temperature depending on which of a plurality of stages shown in a threshold table the index value detected by the detection means corresponds to.

6. The fixing device according to claim 5,

7. The multiple threshold levels in the table include a first threshold level associated with an amount of decrease in temperature and a second threshold level associated with an amount of decrease in speed, The second threshold is higher than the first threshold.

7. The fixing device according to claim 6,

8. The multiple threshold levels in the table include a third threshold level associated with a temperature decrease amount and a speed decrease amount, The third threshold is higher than the second threshold.

8. The fixing device according to claim 7,

9. The fixing nip can accommodate both a standard maximum size sheet and an extended size sheet that is wider than the maximum size, The threshold table includes a first table corresponding to a maximum size of a standard form and a second table corresponding to an extended size, A threshold value to be used for comparison with the detected index value is selected from either a first table or a second table according to the size of the sheet passing through the fixing nip.

9. The fixing device according to claim 6, wherein the fixing device is a fixing unit.

10. a storage means for storing a user's policy of whether to prioritize speed or quality; According to the user's policy, a combination is generated in which one of the rotation speed and the fixing temperature is fixed and the other is decreased.

10. The fixing device according to claim 1, wherein the fixing device is a fixing unit.

11. a storage unit that stores a detection condition in which a detection timing in a non-paper passing state in which no sheet is passed through the fixing nip and the belt is not rotating is set as a detection timing of the index value; When the fixing nip and the belt are in a non-paper passing state, the detection means monitors whether or not a detection timing indicated in the detection condition has arrived, and when the timing arrives, detects the index value.

11. The fixing device according to claim 1, wherein the fixing device is a fixing unit.

12. The detection timing is a time when a predetermined time has elapsed since power is turned on and warm-up by heating by the heating means and rotation of the belt is completed. The fixing device according to claim 11 .

13. The detection timing is the time when the heating means is started and the temperature of the belt is raised to the target temperature. The fixing device according to claim 11 .

14. Further setting a reference speed and a reference temperature for fixing the unfixed image to the sheet in accordance with any one of the width of the sheet, the basis weight of the sheet, and the image content of the unfixed image to be transferred to the sheet, or a combination thereof; The combination of the rotation speed and the fixing temperature at which the index value is equal to or less than the threshold value is obtained by lowering the reference speed and the reference temperature.

10. The fixing device according to claim 9,

15. The sheet conveyed to the fixing nip is a sheet onto which an unfixed toner image has been transferred based on a print job, a storage unit for storing a table indicating a type of sheet according to the print job based on any one of the width of the sheet, the basis weight, and the image content of an unfixed image to be transferred to the sheet, or a combination thereof; The detection means detects the index value when a sheet corresponding to the type passes through a fixing nip. The fixing device according to claim 14 .

16. an updating unit that updates a usage frequency of a type in the table that has passed through the fixing nip every time a sheet corresponding to the type shown in the table passes through the fixing nip; The detection unit detects an index value when a sheet corresponding to a type with a highest usage frequency is conveyed to the fixing nip, during execution of the print job, and / or after execution of the print job. The fixing device according to claim 15 .

17. the drive means is a drive motor; the index value is a torque acting on a rotation shaft of a drive motor when a driving force is applied to the belt, The detection means converts the amount of motor current flowing through the drive motor, and sets the converted torque magnitude as the index value.

17. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image.

18. the pressure member is a roller member, the rotation of the belt is a driven motion caused by the drive motor rotating a roller member, The control means performs feedback control to keep the rotational speed of the belt constant by using the amount of motor current when rotating the roller member. The fixing device according to claim 17 .

19. A fixing device including a belt heated by a heating means, a pad disposed inside a rotation path of the belt, and a pressure member disposed outside the rotation path and sandwiching the belt to press the pad, forming a fixing nip between the belt and the pressure member, A detection means for detecting an index value indicating a sliding resistance acting on the belt as the belt slides on the surface of the pad; a control means for determining whether the detected index value exceeds a predetermined threshold value, and if so, determining a combination of a rotation speed and a fixing temperature at which the index value is equal to or less than the threshold value based on dependency data indicating that the sliding resistance has speed dependency and temperature dependency, and controlling a driving means and a heating means for the belt using the determined combination; a counter that counts the passing time of one sheet from when the leading edge of the sheet that has passed through the fixing nip is detected to when the trailing edge of the sheet is detected, The index value is the sheet passing time counted by the counter. A fixing device comprising:

20. A fixing device including a belt heated by a heating means, a pad disposed inside a rotation path of the belt, and a pressure member disposed outside the rotation path and sandwiching the belt to press the pad, forming a fixing nip between the belt and the pressure member, a counter for counting the number of sheets that have passed through the fixing nip; a detection means for detecting a torque by multiplying the number of sheets counted by the counter by a conversion factor; a control means for determining whether the detected torque exceeds a predetermined threshold value, and if so, determining a combination of a rotation speed and a fixing temperature in which either or both of the rotation speed and the fixing temperature of the belt are lowered until the torque indicating the sliding resistance becomes equal to or lower than the threshold value based on dependency data indicating that the sliding resistance acting on the belt due to the sliding of the pad has speed dependency and temperature dependency, and controlling a driving means and a heating means for the belt using the determined combination; A fixing device comprising:

21. A fixing device including a belt heated by a heating means, a pad disposed inside a rotation path of the belt, and a pressure member disposed outside the rotation path and sandwiching the belt to press the pad, forming a fixing nip between the belt and the pressure member, a distance counter for counting the travel distance of the belt; a detection means for detecting torque by multiplying a travel distance counted by the distance counter by a conversion factor; a control means for determining whether the detected torque exceeds a predetermined threshold value, and if so, determining a combination of a rotation speed and a fixing temperature in which either or both of the rotation speed and the fixing temperature of the belt are lowered until the torque indicating the sliding resistance becomes equal to or lower than the threshold value based on dependency data indicating that the sliding resistance acting on the belt due to the sliding of the pad has speed dependency and temperature dependency, and controlling a driving means and a heating means for the belt using the determined combination; A fixing device comprising:

22. A fixing device including a belt heated by a heating means, a pad disposed inside a rotation path of the belt, and a pressure member disposed outside the rotation path and sandwiching the belt to press the pad, forming a fixing nip between the belt and the pressure member, A detection means for detecting an index value indicating a sliding resistance acting on the belt as the belt slides on the surface of the pad; a control means for determining whether the detected index value exceeds a predetermined threshold value, and if so, determining a combination of rotation speed and fixing temperature at which the index value is equal to or less than the threshold value based on dependency data showing that the sliding resistance has speed dependency and temperature dependency, and controlling a driving means and a heating means for the belt using the determined combination; a deflection amount sensor disposed near a conveyance path of the sheet conveyed toward the fixing nip and detecting a deflection amount generated in a portion of the sheet passing through the nip upstream of the fixing nip in a conveyance direction, the index value being the detected deflection amount. A fixing device comprising:

23. A lubricant application member for applying a lubricant to the inner peripheral surface of the belt.

23. The fixing device according to claim 1, further comprising:

24. An image forming apparatus comprising the fixing device according to any one of claims 1 to 23.

25. A reception means is provided for receiving a setting as to whether to prioritize speed or quality, The control means generates a combination in which one of the rotation speed and the fixing temperature is fixed and the other is reduced according to the settings made by the user.

25. The image forming apparatus according to claim 24.

26. The receiving means further receives a setting to achieve both speed and quality; When the receiving means receives a setting to achieve both speed and quality, the control means generates a combination in which both the rotation speed and the fixing temperature are reduced.

26. The image forming apparatus according to claim 25.

27. A reception unit is provided for receiving an operation to increase or decrease the predetermined threshold value.

25. The image forming apparatus according to claim 24.

Images