Image forming apparatus

Abstract

To provide an image forming apparatus that can accurately predict deterioration of an elastic layer of a fixing roller when an induction heating type fixing device is used.SOLUTION: An image forming apparatus comprises an image forming unit, a fixing device, a fixing voltage power supply, and a control unit. The fixing device includes an endless fixing belt, a fixing roller that is arranged inside the fixing belt and has a core grid and an elastic layer laminated on an outer peripheral surface of the core grid, a pressure roller that is brought into pressure contact with the fixing roller with the fixing belt therebetween, and an induction heating unit that heats the fixing belt. The control unit calculates a cumulative power introduction time that is a cumulative value of power introduction times when predetermined introduction power is introduced to the induction heating unit, and compares the cumulative power submission time with the lifetime of the fixing roller that is the destruction time y [min] of the elastic layer calculated by substituting the introduction power into damage power x [W] of a life prediction formula (1) and determines the remaining life of the fixing roller.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus equipped with an induction heating type fixing device, such as a copying machine, a printer, a facsimile machine, or a combination machine thereof, and more particularly to a method for predicting the life of a fixing roller. [Background technology]

[0002] In order to fix a toner image on a sheet of paper in an image forming apparatus, a fixing device equipped with a fixing member in which a fixing roller or a fixing belt (a heated rotating body) is pressed against a pressure roller (a pressure rotating body) is widely used. Belt fixing type fixing devices using a fixing belt employ an induction heating method in which the heat generating layer of the fixing belt is heated by electromagnetic induction.

[0003] In an induction heating type fixing device, when the heat generating layer of the fixing belt is heated by the induction heating unit, most of the magnetic flux generated by the induction heating unit is converted into thermal energy in the heat generating layer. However, a small amount of leakage magnetic flux may occur that penetrates the heat generating layer and cause heat generation in the internal components of the fixing device.

[0004] For example, if a fixing roller having a core and an elastic layer is placed inside the fixing belt, when leakage magnetic flux reaches the core of the fixing roller, the core generates slight heat due to surface resistance. As this heat accumulates, the elastic layer exceeds its heat resistance limit and gradually loses its elasticity, leading to deterioration. Furthermore, the period until the elastic layer deteriorates and becomes unusable varies depending on the temperature of the core and the accumulated heat generation time.

[0005] Therefore, a method for suppressing deterioration of the elastic layer due to heat generation from the core of the fixing roller has been proposed. For example, Patent Document 1 discloses a fixing device and an image forming apparatus including a fixing roller having an elastic layer provided on the outer surface of the core, an endless fixing belt fitted around the fixing roller, an IH heater that heats the fixing belt to a controlled temperature, a pressure member that is pressed against the fixing roller via the fixing belt to form a pressure region through which paper with a transferred toner image passes, a temperature detection means that detects the temperature of the end of the core in the rotational axis direction, and a cooling device that cools the end of the core when the temperature detected by the temperature detection means is higher than a predetermined temperature.

[0006] Furthermore, Patent Document 2 discloses an image forming apparatus that includes a fixing unit having an induction heating coil and a detection unit that detects physical quantities related to the heat generation amount of the induction heating coil, and a deterioration estimation unit that classifies the physical quantities sequentially obtained by the detection unit into a plurality of predetermined classes, derives a frequency distribution for each class, derives an index value by weighted addition of the frequencies for each class, and derives an estimated degree of deterioration of the fixing device according to the index value. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-8097 [Patent Document 2] Japanese Patent Publication No. 2023-1981 Summary of the Invention [Problem to be solved by the invention]

[0008] The configuration of Patent Document 1 detects the temperature of the end of the core wire and uses a fan to cool it if the detected temperature is higher than a predetermined temperature. However, the fan is controlled to operate based on a single threshold value, and the cumulative heat received by the elastic layer from the core wire is not taken into account, making it impossible to predict deterioration of the elastic layer.

[0009] In the configuration of Patent Document 2, the deterioration of the elastic layer of the fixing roller is estimated using the cumulative time of input power and the temperature of the core metal, but the deterioration is estimated using a table that defines the relationship between the cumulative time of input power, the temperature of the core metal, and the degree of deterioration. As a result, there is a problem that the prediction accuracy is reduced and the fixing roller cannot be replaced at the appropriate time.

[0010] SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an image forming apparatus that can accurately predict the deterioration of the elastic layer of the fixing roller when an induction heating type fixing device is used. [Means for solving the problem]

[0011] To achieve the above object, a first aspect of the present invention is an image forming apparatus including an image forming unit, a fixing device, a fixing voltage power supply, and a control unit. The image forming unit forms a toner image on a recording medium. The fixing device includes an endless fixing belt, a fixing roller disposed inside the fixing belt and having a core and an elastic layer laminated on the outer surface of the core, a pressure roller that is pressed against the fixing roller across the fixing belt to form a fixing nip, and an induction heating unit that heats the fixing belt. The fixing device performs a fixing process in which the toner image is fixed to the recording medium by heating and pressurizing the recording medium passing through the fixing nip. The fixing voltage power supply applies voltage to the induction heating unit. The control unit controls the image forming unit, the fixing device, and the fixing voltage power supply. The control unit calculates the cumulative power input time, which is the cumulative value of the power input time when a predetermined input power is input to the induction heating unit, and determines the remaining life of the fixing roller by comparing the life of the fixing roller with the cumulative power input time, calculating the elastic layer destruction time y [min] by substituting the input power for the damage power x [W] in the following life prediction formula (1). JPEG2025172539000002.jpg18144 [Effects of the Invention]

[0012] According to the first aspect of the present invention, the remaining life of the fixing roller is predicted based on the power actually input from the fixing voltage power supply to the induction heating unit and the cumulative power input time, which allows for more accurate prediction of the remaining life of the fixing roller than the conventional method that uses a pre-stored life prediction table. This makes it possible to prepare a replacement fixing roller in advance and minimize downtime during which printing is not possible. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the internal structure of an image forming apparatus 100 according to an embodiment of the present invention. [Figure 2] A side cross-sectional view of a fixing device 13 mounted in an image forming apparatus 100. [Figure 3] 1 is a plan cross-sectional view of the fixing device 13 cut along the axial direction. [Figure 4] FIG. 1 is a block diagram showing an example of a control path of an image forming apparatus 100. [Figure 5] Graph showing the relationship between printing time and the temperature of the core metal of the fixing roller in the image forming apparatus 100 of this embodiment. [Figure 6] 1 is a flowchart showing an example of life prediction control of a fixing roller in the image forming apparatus 100 of this embodiment. [Figure 7] A flowchart showing an example of control for setting the cumulative waiting time in FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0014] [1. Overall configuration of image forming device] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a schematic cross-sectional view showing the internal structure of an image forming apparatus 100 according to one embodiment of the present invention. Within the main body of the image forming apparatus 100 (here, a color printer), four image forming units Pa, Pb, Pc, and Pd are arranged in this order from the upstream side in the transport direction (the right side in Fig. 1). These image forming units Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow, and black), and sequentially form cyan, magenta, yellow, and black images through the respective processes of charging, exposure, development, and transfer.

[0015] Each of the image forming stations Pa through Pd is provided with photosensitive drums (image carriers) 1a, 1b, 1c, and 1d, which carry visible images (toner images) of each color. An intermediate transfer belt 8, which rotates clockwise in FIG. 1, is provided adjacent to each of the image forming stations Pa through Pd. The toner images formed on the photosensitive drums 1a through 1d are sequentially transferred (primary transfer) onto the intermediate transfer belt 8, which moves while contacting the photosensitive drums 1a through 1d, and then superimposed on each other. The toner images primarily transferred onto the intermediate transfer belt 8 are then secondarily transferred onto a sheet of paper S, an example of a recording medium, by a secondary transfer roller 9. The toner images are then fixed by a fixing device 13, and the sheet of paper S onto which the toner images have been secondarily transferred is then ejected from the image forming apparatus 100 main body. An image formation process is performed on each of the photosensitive drums 1a through 1d while the photosensitive drums 1a through 1d are rotated counterclockwise in FIG. 1 by a main motor 50 (see FIG. 4).

[0016] The paper S onto which the toner image is secondarily transferred is stored in a paper cassette 16 located at the bottom of the main body of the image forming apparatus 100, and is transported via a paper feed roller 12a and a pair of registration rollers 12b to the nip between the secondary transfer roller 9 and the drive roller 11 of the intermediate transfer belt 8. A sheet made of dielectric resin is used for the intermediate transfer belt 8, and a seamless belt is usually used. In addition, a blade-shaped belt cleaner 19 is located downstream of the secondary transfer roller 9 to remove toner and other particles remaining on the surface of the intermediate transfer belt 8.

[0017] Next, the image forming units Pa to Pd will be described. Around and below the rotatably arranged photosensitive drums 1a to 1d, there are provided charging devices 2a, 2b, 2c, and 2d that charge the photosensitive drums 1a to 1d, an exposure device 5 that exposes image information onto each of the photosensitive drums 1a to 1d, developing devices 3a, 3b, 3c, and 3d that form toner images on the photosensitive drums 1a to 1d, and cleaning devices 7a, 7b, 7c, and 7d that remove developer (toner) and the like remaining on the photosensitive drums 1a to 1d.

[0018] When image data is input from a host device such as a personal computer, the charging devices 2a-2d first uniformly charge the surfaces of the photosensitive drums 1a-1d. Next, the exposure device 5 irradiates the photosensitive drums 1a-1d with light in accordance with the image data, forming electrostatic latent images on the photosensitive drums 1a-1d in accordance with the image data. The developing devices 3a-3d are filled with a predetermined amount of two-component developer containing cyan, magenta, yellow, and black toner, respectively. If the toner content in the two-component developer in each developing device 3a-3d falls below a specified value due to the formation of a toner image (described below), toner is replenished from toner containers 4a-4d to each developing device 3a-3d. The toner in the developer is supplied to the photosensitive drums 1a-1d by the developing devices 3a-3d and electrostatically adheres to them. This results in the formation of a toner image corresponding to the electrostatic latent image formed by exposure from the exposure device 5.

[0019] Then, primary transfer rollers 6a-6d apply an electric field at a predetermined transfer voltage between the primary transfer rollers 6a-6d and the photosensitive drums 1a-1d, and the cyan, magenta, yellow, and black toner images on the photosensitive drums 1a-1d are primarily transferred onto the intermediate transfer belt 8. These four color images are formed in a predetermined positional relationship for forming a predetermined full-color image. After that, toner and other substances remaining on the surfaces of the photosensitive drums 1a-1d after the primary transfer are removed by cleaning devices 7a-7d in preparation for the subsequent formation of a new electrostatic latent image.

[0020] The intermediate transfer belt 8 is stretched over a driven roller 10 on the upstream side and a drive roller 11 on the downstream side, and when the intermediate transfer belt 8 starts to rotate clockwise as the drive roller 11 is rotated by a belt drive motor (not shown), the paper S is transported from the registration roller pair 12b to a nip portion (secondary transfer nip portion) between the drive roller 11 and a secondary transfer roller 9 provided adjacent thereto at a predetermined timing, and the full-color image on the intermediate transfer belt 8 is secondarily transferred onto the paper S. The paper S onto which the toner image has been secondarily transferred is transported to a fixing device 13.

[0021] The paper S conveyed to the fixing device 13 is heated and pressurized by the fixing belt 20 and the pressure roller 22 (see FIG. 2), and the toner image is fixed to the surface of the paper S, forming a predetermined full-color image. The paper S on which the full-color image has been formed is then directed to a different conveying direction by the branching section 14, which branches in multiple directions, and is then discharged directly (or after being sent to the double-sided conveying path 18 and having images formed on both sides) onto the discharge tray 17 by the discharge roller pair 15.

[0022] [2. Configuration of the fixing device] Fig. 2 is a side cross-sectional view of fixing device 13 mounted in image forming apparatus 100. Fig. 3 is a plan cross-sectional view (cross-sectional view taken along arrow AA in Fig. 2) of fixing device 13 cut along the axial direction. The upper side of Fig. 2 is the downstream side of the paper insertion direction (conveyance direction) relative to fixing device 13, and the lower side is the upstream side of the paper insertion direction relative to fixing device 13. As shown in Figs. 2 and 3, fixing device 13 includes fixing belt 20, fixing roller 21, pressure roller 22, induction heating unit 23, separation member 25, and fixing temperature sensor 26.

[0023] The fixing belt 20 is supported on a housing (not shown) of the fixing device 13 so as to be rotatable about a horizontal axis. The fixing belt 20 is endless and configured in a cylindrical shape with an outer diameter of, for example, 20 mm to 50 mm, and has approximately the same axial length (widthwise length of the paper S) as the pressure roller 22. The fixing belt 20 rotates in the clockwise direction in FIG. 2 along the insertion direction of the paper S, which is a recording medium. Restricting members 27 that restrict meandering of the fixing belt 20 are arranged adjacent to both axial ends of the fixing belt 20.

[0024] The fixing belt 20 has a laminated structure in which an elastic layer and a release layer are laminated on the outer periphery of a heat generating layer, which is a base layer. The heat generating layer is made of, for example, a 30-50 μm thick metal film made of nickel or the like, or a 50-100 μm thick polyimide film mixed with metal powder such as copper, silver, or aluminum. The elastic layer is made of, for example, silicone rubber or the like, and the thickness is 100-300 μm. The release layer is made of, for example, a 20-30 μm thick fluorine-based resin such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer).

[0025] Fixing roller 21 has a core 21a and an elastic layer 21b. Core 21a is made of a metal such as aluminum. Core 21a is supported by a bearing 28 provided on the housing of fixing device 13 so as to be rotatable about a horizontal axis. Elastic layer 21b is a layer of an elastic material laminated on the outer circumferential surface of core 21a. Elastic layer 21b is, for example, a foamed silicone rubber layer.

[0026] The pressure roller 22 is supported on the housing of the fixing device 13 so as to be rotatable about a horizontal axis. The pressure roller 22 is cylindrical and has approximately the same axial length (widthwise length of the paper S) as the fixing belt 20. A predetermined pressure is applied to the pressure roller 22 toward the fixing belt 20 by a pressure mechanism 30 (see FIG. 4). The outer circumferential surface of the pressure roller 22 presses against the nip forming member 24 via the fixing belt 20, thereby being pressed against the outer circumferential surface of the fixing belt 20 to form a fixing nip N. The pressure roller 22 has a core metal 22a and an elastic layer 22b.

[0027] The pressure roller 22 is connected to a fixing drive motor 45 (see FIG. 3) and rotates counterclockwise in FIG. 2. The pressure roller 22 contacts the outer peripheral surface of the fixing belt 20 with a predetermined pressure, and applies a rotational driving force to the fixing belt 20 in the clockwise direction.

[0028] The pressure roller 22 has a laminated structure in which an elastic layer 22b is laminated on the outer periphery of a core metal 22a, and a release layer (not shown) is laminated on the surface of the elastic layer 22b. The core metal 22a is made of a metal such as aluminum and has a diameter of, for example, about 20 mm. The elastic layer 22b is made of silicone rubber and has a thickness of, for example, about 8 mm. The release layer is made of a fluorine-based resin such as PFA and has a thickness of, for example, about 10 μm to 50 μm.

[0029] Induction heating unit 23 is disposed opposite the outer peripheral surface of fixing belt 20 across a predetermined gap in an area of ​​fixing belt 20 opposite the side where pressure roller 22 is disposed. Induction heating unit 23 extends slightly longer than fixing belt 20 along the axial direction of fixing belt 20 (the width direction of paper S, the direction perpendicular to the plane of the paper in FIG. 2). Induction heating unit 23 heats fixing belt 20 by inductively heating the heat generating layer of fixing belt 20.

[0030] Induction heating unit 23 includes an excitation coil, a holding member, a core (none of which are shown), etc. The excitation coil and core are held in place by the holding member. The excitation coil is made of a litz wire made of multiple conductive wires bundled together, and is wound around to extend along the axial direction of fixing belt 20. The excitation coil is configured in an arc shape along the outer peripheral surface of fixing belt 20 in the circumferential direction of fixing belt 20.

[0031] A separating member 25 is disposed downstream of the fixing nip N in the paper insertion direction (upper side in FIG. 2). The separating member 25 separates the paper S after fixing processing from the surface of the fixing belt 20. The separating member 25 is disposed at a predetermined angle so that its leading edge faces upstream (counter direction) with respect to the rotation direction of the fixing belt 20 and is close to the outer peripheral surface of the fixing belt 20.

[0032] The fixing temperature sensor 26 measures the temperature of the fixing belt 20. The fixing temperature sensor 26 is, for example, a thermistor. The temperature detected by the fixing temperature sensor 26 is used for fixing temperature control. The fixing temperature control is a feedback control that controls the power supplied from the fixing voltage power supply 55 (see FIG. 4) to the induction heating unit 23 by comparing the temperature detected by the fixing temperature sensor 26 with a preset fixing temperature (target temperature).

[0033] A pressure temperature sensor 31 is disposed near the pressure roller 22. The pressure temperature sensor 31 is, for example, a thermistor. The temperature detected by the pressure temperature sensor 31 is used to estimate the temperature of the core metal 21a of the fixing roller 21, which will be described later.

[0034] [3. Control path of image forming device] 4 is a block diagram showing an example of a control path of the image forming apparatus 100. Since various controls are performed on each part of the apparatus when the image forming apparatus 100 is used, the following description will focus on the control path that is necessary for implementing the present invention. Also, a description of parts that have already been described will be omitted.

[0035] Voltage control circuit 51 is connected to charging voltage power supply 52, developing voltage power supply 53, transfer voltage power supply 54, and fixing voltage power supply 55, and activates each of these power supplies in response to an output signal from control unit 90. In response to a control signal from voltage control circuit 51, each of these power supplies applies a predetermined voltage: charging voltage power supply 52 applies a predetermined voltage to charging devices 2a-2d, developing voltage power supply 53 applies a predetermined voltage to developing devices 3a-3d, transfer voltage power supply 54 applies a predetermined voltage to primary transfer rollers 6a-6d and secondary transfer roller 9, and fixing voltage power supply 55 applies a predetermined voltage to induction heating unit 23 in fixing device 13.

[0036] The image input unit 70 is a receiving unit that receives image data transmitted from a personal computer or the like to the image forming apparatus 100. The image signal input from the image input unit 70 is converted into a digital signal and then sent to the temporary storage unit 94.

[0037] The operation unit 80 is provided with a liquid crystal display unit 81 and LEDs 82 that indicate various states, and is configured to indicate the state of the image forming apparatus 100, the image formation status, and the number of copies to be printed. In addition, the type and size of the paper S can be input by specifying the paper cassette 16 or manual paper feed tray (not shown) from which the paper S is to be fed from the operation unit 80. Various settings for the image forming apparatus 100 are made using the printer driver of the computer.

[0038] The control unit 90 includes at least a CPU (Central Processing Unit) 91 as a central processing unit, a ROM (Read Only Memory) 92 as a read-only memory unit, a RAM (Random Access Memory) 93 as a readable and writable memory unit, a temporary memory unit 94 that temporarily stores image data, etc., a timer 95, and multiple (here, two) I / Fs (interfaces) 96 that send control signals to each device within the image forming apparatus 100 and receive input signals from the operation unit 70.

[0039] ROM 92 stores data such as a control program for image forming apparatus 100, numerical values ​​necessary for control, and data that will not be changed while image forming apparatus 100 is in use. RAM 93 stores necessary data that is generated during the control of image forming apparatus 100, data that is temporarily necessary for controlling image forming apparatus 100, and the like.

[0040] The temporary storage unit 94 temporarily stores the image signal that is input from the image input unit 70 and converted into a digital signal. The timer 95 measures the time that the voltage is supplied from the fixing voltage power supply 55 to the induction heating unit 23.

[0041] [4. Fuser Roller Life Prediction Control] Next, a description will be given of the life prediction control of the fixing roller 21 of the fixing device 13 in the image forming apparatus 100 of this embodiment. Fig. 5 is a graph showing the relationship between the printing time and the temperature of the core metal 21a of the fixing roller 21 in the image forming apparatus 100. Fig. 5 shows the temperature transition of the core metal 21a when continuous printing is performed for 65 minutes after starting heating of the fixing belt 20, and then continuous printing is repeated for 10 minutes with a 1-minute interval (a leaving time, the hatched area in Fig. 5) in between.

[0042] 5, the temperature of the metal core 21a gradually increases immediately after the start of heating of the fixing belt 20, and fluctuates between a maximum value (214.2°C) and a minimum value (211.0°C). This is because part of the magnetic flux generated by the induction heating unit 23 penetrates the heat-generating layer of the fixing belt 20 and reaches the metal core 21a of the fixing roller 21.

[0043] Therefore, when continuous printing of a large number of sheets is performed continuously, the core metal 21a of the fixing roller 21 is heated, and the temperature of the core metal 21a is constantly kept high, which may accelerate thermal deterioration (embrittlement) of the elastic layer 21b and lead to breakage of the elastic layer 21b.

[0044] Therefore, in the image forming apparatus 100 of this embodiment, the life of the core metal 21a of the fixing roller 21 is predicted based on the power input from the fixing voltage power supply 55 to the induction heating unit 23. Specifically, the life prediction formula (material breakdown formula) shown in the following formula (1) is used to calculate the life time (breakdown time) of the elastic layer 21b of the fixing roller 21 from the input power value (damage power). JPEG2025172539000003.jpg18144However, x; Damage power [W] y: Elastic layer failure time [min] is.

[0045] The calculated lifespan is then compared with the cumulative power input time, which is the cumulative value of the power input time, to determine the remaining lifespan (the time when the roller becomes unusable) of the elastic layer 21b of the fixing roller 21. The determined remaining lifespan is notified to the user. One method of notifying the remaining lifespan is to display it as a gauge on the liquid crystal display 81 (see FIG. 4). Table 1 shows an example of the damage power, the lifespan of the elastic layer 21b (number of printable sheets), the contribution of deterioration due to the damage power to the target lifespan of the elastic layer 21b (here, 600,000 sheets), and the remaining lifespan (gauge display).

[0046] [Table 1] *1: Number of prints at a linear process speed of 70 sheets / min *2: Value when 600k prints is 100%

[0047] As shown in Table 1, the greater the input power (damage power), the shorter the time until elastic layer 21b is destroyed, and the shorter the lifespan (number of printable sheets) of fixing roller 21. When the input power is set to 1417 [W], it can be seen that the lifespan of fixing roller 21 reaches the target lifespan (600,000 sheets).

[0048] According to the above method, the life of the elastic layer 21b of the fixing roller 21 is predicted based on the input power actually applied to the induction heating section 23 from the fixing voltage power supply 55 and the cumulative power input time, so that the life of the fixing roller 21 (elastic layer 21b) can be predicted more accurately than in the conventional method in which prediction is made using a pre-stored life prediction table.

[0049] Here, if the power-on time is 15 minutes or less, such as immediately after the start of heating of the fixing belt 20, the core 21a of the fixing roller 21 does not reach a temperature high enough to accelerate thermal degradation of the elastic layer 21b. In other words, it takes 15 minutes or more after the start of heating for the core 21a to reach a temperature high enough to accelerate thermal degradation of the elastic layer 21b. Therefore, a period of time during which the power-on time is not accumulated (accumulated standby time) is set according to the temperature of the core 21a when the image forming apparatus 100 is turned on or when the image forming apparatus 100 returns from sleep (power saving) mode.

[0050] When estimating the temperature of the metal core 21a of the fixing roller 21, it is preferable to use the temperature of the pressure roller 22 as a substitute. This is because the pressure roller 22 is not a member that is directly heated by the induction heating unit 23, and therefore the temperature detection accuracy is high. Specifically, the correlation between the temperature of the pressure roller 22 and the temperature of the metal core 21a of the fixing roller 21 is compiled into a table in advance and stored in the ROM 92 (or RAM 93). Then, the temperature of the metal core 21a is estimated based on the temperature of the pressure roller 22 measured by the pressure temperature sensor 31.

[0051] For example, when the temperature of the pressure roller 22 is 40° C. or lower, the temperature of the core metal 21a is estimated to be room temperature. Therefore, the input power is not accumulated for 60 minutes after the power is turned on or after returning from sleep (power saving) mode.

[0052] Furthermore, if the temperature of the pressure roller 22 is between 41°C and 80°C, the temperature of the core 21a is estimated to be high (below 130°C). Therefore, the input power is not accumulated for 30 minutes after the power is turned on or the device returns from sleep (power saving) mode. If the temperature of the pressure roller 22 is 81°C or higher, the temperature of the core 21a is estimated to be extremely high (around 200°C). Therefore, the input power is not accumulated for 30 minutes after the power is turned on or the device returns from sleep (power saving) mode.

[0053] By providing such a cumulative standby time, it is possible to prevent the problem of accumulating power supply time that does not contribute to a temperature rise of the core metal 21a. As a result, by accumulating only the power supply time that actually contributes to a temperature rise of the core metal 21a, it is possible to accurately predict the life of the elastic layer 21b.

[0054] 6 is a flowchart showing an example of life prediction control of the fixing roller in the image forming apparatus 100 of this embodiment. The life prediction control of the fixing roller will be described with reference to FIGS. 1 to 5 and FIG. 7, which will be described later, as needed.

[0055] The control unit 90 determines whether a print command has been input from a host device such as a personal computer (step S1). If a print command has not been input (No in step S1), the printing standby state continues. If a print command has been input (Yes in step S1), the pressure temperature sensor 31 measures the temperature Tp of the pressure roller 22 (step S2). Next, the control unit 90 sets the cumulative standby time for the input power (step S3).

[0056] 7 is a flowchart showing an example of control for setting the accumulated standby time in FIG. 6. When setting the accumulated standby time (step S3), the control unit 90 determines whether the temperature Tp of the pressure roller 22 measured in step S2 is 40° C. or less (step S31). If Tp≦40° C. (Yes in step S31), it is estimated that the core 21a of the fixing roller 21 is at room temperature (cold start). Therefore, the input power is not accumulated for 60 minutes after the power is turned on (step S32). That is, the accumulated standby time is set to 60 minutes.

[0057] If Tp>40°C (No in step S31), the control unit 90 determines whether the temperature Tp of the pressure roller 22 is 81°C or higher (step S33). If 40≦Tp≦80°C (No in step S31), it is estimated that the core metal 21a of the fixing roller 21 is at a high temperature (130°C or lower). Therefore, the input power is not accumulated for 30 minutes after the power is turned on (step S34). That is, the accumulated standby time is set to 30 minutes.

[0058] If Tp≧81°C (Yes in step S31), it is estimated that the core metal 21a of the fixing roller 21 is at an extremely high temperature (around 200°C). Therefore, the input power is not accumulated for 15 minutes after the power is turned on (step S35). In other words, the accumulated standby time is set to 15 minutes.

[0059] Thereafter, the control unit 90 turns on the fixing voltage power supply 55 (step S4). Then, when the fixing temperature sensor 26 confirms that the temperature of the fixing belt 20 has reached a predetermined fixing temperature, printing starts (step S5).

[0060] After turning on the fixing voltage power supply 55 in step S4, the control unit 90 determines whether the cumulative standby time set in step S3 has elapsed (step S6). If the cumulative standby time has elapsed (Yes in step S6), the control unit 90 starts accumulating the input power (step S7). The control unit 90 calculates the life of the fixing roller 21 (elastic layer 21b) using equation (1) based on the input power (step S8). The control unit 90 then compares the calculated life of the elastic layer 21b with the cumulative power input time to predict the remaining life of the fixing roller 21 and displays it as a gauge on the LCD display unit 81 (step S9).

[0061] If the cumulative waiting time has not elapsed in step S6 (No in step S6), the process proceeds to step S9 without accumulating the input power, and the remaining life of the fixing roller 21 based on the cumulative power input time up to that point is displayed as a gauge on the liquid crystal display unit 81 (step S9).

[0062] Thereafter, it is determined whether printing has finished (step S10), and if printing is continuing (No in step S10), the process returns to step S6, where it determines whether the cumulative standby time has elapsed, accumulates the input power, calculates the life of the fixing roller, and displays the remaining life (steps S6 to S9).If printing has finished (Yes in step S10), the process ends.

[0063] According to the control examples shown in Figures 6 and 7, the life of elastic layer 21b of fixing roller 21 can be accurately predicted based on the input power value applied to induction heating section 23 from fixing voltage power supply 55 and the accumulated power input time.

[0064] In addition, by providing a cumulative standby time to exclude the power input time that does not contribute to the temperature rise of the core metal 21a, and by accumulating only the input power that actually contributes to the temperature rise of the core metal 21a, the accuracy of predicting the life of the fixing roller 21 can be further improved.

[0065] Furthermore, by displaying the remaining life of the fixing roller 21 as a gauge on the liquid crystal display unit 81, the user can easily recognize the remaining life of the fixing roller 21. This allows a replacement fixing roller 21 to be prepared in advance, minimizing the occurrence of downtime during which printing is not possible.

[0066] Furthermore, the present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the spirit of the present invention. For example, in the above-described embodiment, the fixing device 13 is of a uniaxial belt type in which the fixing belt 20 is wound around the fixing roller 21, but the present invention is also applicable to a fixing device of a biaxial belt type in which the fixing belt 20 is stretched between the fixing roller 13 and another roller.

[0067] Furthermore, the present invention is not limited to a vertical conveying type fixing device 13 in which the paper S passes through the fixing nip portion N from bottom to top as shown in the above embodiment, but can also be applied to a horizontal conveying type fixing device in which the paper S passes through the fixing nip portion N horizontally.

[0068] Furthermore, image forming apparatus 100 is not limited to a tandem color printer as shown in Fig. 1, but can be applied to various image forming apparatuses equipped with a fixing device, such as monochrome copying machines, digital multifunction machines, facsimiles, laser printers, etc. The effects of the present invention will be described more specifically below with reference to examples. [Example]

[0069] 1, the remaining life display of the fixing roller 21 when a certain input power (damaging power) is applied to the induction heating section 23 of the fixing device 13 to heat the fixing belt 20 will be described. The cumulative time of input power is calculated by accumulating the average integrated power for the most recent 15 minutes every minute.

[0070] The process linear speed of image forming apparatus 100 is set to 70 sheets / min, and the target life (number of printable sheets) is set to 600 k sheets. In this case, the time required to print 600 k sheets is 600,000 / 70 ≒ 8571 minutes. Substituting this time into equation (1), x ≒ 1417 W. When image forming apparatus 100 is operated with a constant input power (damage power) of 1417 W, the gauge displays for the cumulative input power [W·min], cumulative number of prints [k sheets], and remaining life of fixing roller 21 are as shown in Table 2.

[0071] [Table 2]

[0072] As shown in Table 2, as the cumulative number of printed sheets increases, the cumulative input power increases and the remaining life (gauge display) of the fuser roller 21 decreases. The cumulative input power when printing 600,000 sheets is 1417 [W] × 8571 [min] = 12,145,107 [W·min], and when this value is reached, the remaining life of the fuser roller 21 becomes 0 [%]. Here, the remaining life [%] of the fuser roller 21 is displayed on the gauge every minute, so it is possible to accurately predict when the fuser roller 21 will reach the end of its life. [Industrial Applicability]

[0073] The present invention can be applied to an image forming apparatus equipped with an induction heating fixing device, and can provide an image forming apparatus that can accurately predict deterioration of the elastic layer of the fixing roller when using an induction heating fixing device. [Explanation of symbols]

[0074] Pa~Pd Image forming section 13 Fixing device 20 Fixing belt 21 Fixing roller 21a Core metal (fixing roller) 21b Elastic layer (fixing roller) 22 Pressure roller 23 Induction heating section 26 Fixing temperature sensor 30 Pressure Mechanism 31 Pressurized temperature sensor 80 Control section 81 LCD display section 90 Control Unit 95 Timer 100 Image forming device N Fixing nip S Paper (recording medium)

Claims

1. an image forming unit that forms a toner image on a recording medium; an endless fixing belt; a fixing roller disposed inside the fixing belt and having a core metal and an elastic layer laminated on an outer peripheral surface of the core metal; a pressure roller that is pressed against the fixing roller with the fixing belt sandwiched therebetween to form a fixing nip portion; an induction heating unit that heats the fixing belt; a fixing device that performs a fixing process of fixing the toner image onto the recording medium by applying heat and pressure to the recording medium that passes through the fixing nip portion; a fixing voltage power supply that applies a voltage to the induction heating unit; a control unit that controls the image forming unit, the fixing device, and the fixing voltage power supply; In an image forming apparatus comprising: The control unit calculates an accumulated power input time, which is an accumulated value of a power input time when a predetermined input power is input to the induction heating unit, and The breakdown time y [min] of the elastic layer calculated by substituting the input power for the damage power x [W] in the following life prediction formula (1) is defined as the life of the fixing roller, an image forming apparatus, characterized in that the remaining life of the fixing roller is determined by comparing the life of the fixing roller with the cumulative power-on time;

2. 2. The image forming apparatus according to claim 1, wherein the control unit sets a cumulative waiting time that does not accumulate the power supply time based on the temperature of the core metal when the supply of the power to the induction heating unit is started.

3. a pressure temperature sensor that detects the temperature of the pressure roller; a storage unit that stores a correlation between the temperature of the pressure roller and the temperature of the core metal; Equipped with 3. The image forming apparatus according to claim 2, wherein the control unit estimates the temperature of the core metal based on the temperature of the pressure roller detected by the pressure temperature sensor and the correlation stored in the memory unit.

4. 4. The image forming apparatus according to claim 1, further comprising a notification unit that notifies the user of the remaining life of the fixing roller.

5. 5. The image forming apparatus according to claim 4, wherein the notification unit is a liquid crystal display unit that displays the remaining life of the fixing roller with a gauge.

Images