JP2019101236A - Fixation device, setting method of fixation device, and image formation device - Google Patents

Abstract

To appropriately correct detection temperature of a fixation member heated by a heat source.SOLUTION: The fixation device comprises a fixation member provided rotatably and heated by a heat source, a pressure member provided rotatably and forming a pressure region by coming into contact with the fixation member, a temperature detection section for detecting inner temperature of the fixation member, a storage section for storing a parameter which indicates characteristics of the temperature detection section, and a control section for correcting the detected inner temperature on the basis of the parameter.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a fixing device for fixing a toner image on a recording medium, a setting method of the fixing device, and an image forming apparatus provided with the fixing device.

  An electrophotographic image forming apparatus such as a copying machine or a printer includes a fixing device for fixing a toner image on a recording medium such as a sheet. The “heat roller method” is widely used as the fixing device from the viewpoint of thermal efficiency and safety. The heat roller method is a method of forming a fixing nip using a pair of rollers and fixing a toner image. In addition, the "heat belt method" has also attracted attention due to demands for shortening warm-up time and energy saving. The heat belt system is a system in which a fixing nip is formed using a fixing belt heated by a heat source to fix a toner image.

  In the fixing device based on the conduction of heat energy as described above, the temperature detection unit (temperature sensor) detects the temperature of the fixing member heated by the heat source, and controls the heat source based on the detection value of the temperature detection unit. Is common.

  For example, the heat fixing device disclosed in Patent Document 1 includes a heating roll having a heat source disposed therein, a pressure roll pressed against the heating roll, a temperature detection unit that detects the surface temperature of the heating roll, and a temperature detection unit. And temperature control means for controlling energization of the heating source based on the detection result of

Unexamined-Japanese-Patent No. 2001-56617

  The temperature responsive element constituting the temperature detection unit has an inherent heat capacity, and the thermal time constant also differs depending on the property of the element. In addition, even if the elements are the same in terms of specifications, the thermal time constant and the heat capacity often differ due to an error or the like at the time of manufacture. In the technique of Patent Document 1, a temperature detection means (thermistor element) having a thermal time constant of 0.8 seconds or less is used, but no particular consideration is given to the variation of the thermal time constant. In order to control the fixing temperature more accurately and improve the energy efficiency, it is preferable to appropriately correct the detection temperature of the fixing member detected by the temperature detection unit and use it for control of the heat source.

  In consideration of the above circumstances, the present invention aims to appropriately correct the detected temperature of a fixing member heated by a heat source.

  The fixing device according to the present invention is provided rotatably, and a fixing member which is heated by a heat source, a pressure member which is rotatably provided and which is in pressure contact with the fixing member to form a pressure area, and the fixing member A temperature detection unit that detects the internal temperature of the storage unit, a storage unit that stores a parameter that indicates the characteristics of the temperature detection unit, and a control unit that corrects the detected internal temperature based on the parameter I assume.

  Preferably, the fixing member is an endless fixing belt, and the temperature detection unit includes a thermistor which is a temperature responsive element, and the thermistor contacts the inner surface of the fixing belt to be in contact with the fixing belt. Detect internal temperature.

  Preferably, the parameters used by the control unit are a nominal thermal time constant which is a nominal value of a thermal time constant of the temperature detection unit and an actual measurement thermal time constant which is an actual measurement value of the thermal time constant of the temperature detection unit. The controller should detect the internal temperature detected based on the measured thermal time constant using the nominal thermal time constant and the measured thermal time constant based on the nominal thermal time constant. Correct to temperature.

  Preferably, in start-up control of the fixing device, the control unit starts an operation preparation state in which a fixing operation by the fixing device is enabled after start of application of a power pulse to the heat source. Correct the internal temperature during the period

In the fixing device setting method according to the present invention, a step of setting a target temperature to be reached by the internal temperature, a step of measuring an initial temperature of the internal temperature, and a step of heating the fixing member by the heat source The time required for the internal temperature to reach a temperature obtained by multiplying the rising temperature, which is the difference between the target temperature and the initial temperature, by (1-e- ¹ ) (e is the base of natural logarithms), the measured heat A step of acquiring as a time constant, and a step of storing the acquired measured thermal time constant in the storage unit are characterized.

  Preferably, the parameter used by the control unit is correlation information indicating a correlation between the surface temperature of the fixing member and the internal temperature, and the control unit determines the internal temperature based on the correlation information. Correct to the corresponding temperature corresponding to the surface temperature.

  Preferably, the control unit corrects the internal temperature during a period after an operation preparation state in which a fixing operation by the fixing device is possible is started.

  In the fixing device setting method according to the present invention, the fixing member is heated by the heat source, the internal temperature is detected by the temperature detection unit, and the non-contact temperature detection unit is not in contact with the fixing member. The method further comprises the steps of: detecting the surface temperature; and storing the detected internal temperature and the surface temperature in the storage unit as the correlation information.

  An image forming apparatus according to the present invention includes the fixing device described in any of the above.

  According to the present invention, the detected internal temperature of the fixing member is appropriately corrected based on the parameter indicating the characteristic of the temperature detection unit.

It is a schematic diagram which shows the outline of a structure of the color printer which concerns on the 1st Embodiment of this invention. FIG. 1 is a cross-sectional view showing a fixing device of a color printer according to a first embodiment of the present invention. FIG. 2 is a plan view showing the arrangement of temperature sensors in the fixing device of the color printer according to the first embodiment of the present invention. FIG. 1 is a block diagram showing a fixing device of a color printer according to a first embodiment of the present invention. 5 is a graph showing temperature control of the fixing device of the color printer according to the first embodiment of the present invention. 5 is a graph showing temperature control of the fixing device of the color printer according to the first embodiment of the present invention. 5 is a flowchart of temperature control of the fixing device of the color printer according to the first embodiment of the present invention. 5 is a graph showing suitable temperature control in the fixing device of the color printer according to the first embodiment of the present invention. 5 is a flowchart for setting parameters of the fixing device of the color printer according to the first embodiment of the present invention. FIG. 6 is a cross-sectional view showing a fixing device of a color printer according to a second embodiment of the present invention. 7 is a table showing correlation information of the fixing device of the color printer according to the first embodiment of the present invention. 5 is a flowchart of temperature control of a fixing device of a color printer according to a second embodiment of the present invention. 6 is a graph showing preferable temperature control in a fixing device of a color printer according to a second embodiment of the present invention. 7 is a flowchart for setting parameters of a fixing device of a color printer according to a second embodiment of the present invention.

1. First Embodiment 1-1. Overall Configuration of Color Printer The overall configuration of a color printer 1 (image forming apparatus) according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic view (front view) showing the color printer 1.

  The color printer 1 is provided with a box-shaped printer main body 2, a paper feed cassette 3 for containing paper is detachably provided in the lower part of the printer main body 2, and a paper discharge tray 4 is provided in the upper part of the printer main body 2 .

  At a central portion of the printer main body 2, an intermediate transfer belt 6 is bridged between a plurality of rollers, and below the intermediate transfer belt 6, an exposure device 7 formed of a laser scanning unit (LSU) is disposed. Below the intermediate transfer belt 6, four image forming portions 8 are provided for each toner (developer) color (for example, four colors of cyan, magenta, yellow and black). The photosensitive drum 9 is rotatably provided in each of the image forming units 8, and around the photosensitive drum 9, the charger 10, the developing unit 11, the primary transfer unit 12, the cleaning device 13, and the static eliminator 14 are primary. Arranged in order of process of transcription. A toner container 15 corresponding to each image forming unit 8 is provided above the developing device 11 for each toner color (for example, four colors of cyan, magenta, yellow and black).

  A sheet conveyance path 16 is provided on one side of the printer body 2 (right side in FIG. 1). A paper feed unit 17 is provided at the upstream end of the conveyance path 16, and a secondary transfer unit 18 is provided at one end of the intermediate transfer belt 6 in the middle of the conveyance path 16. Is provided, and the discharge port 20 is provided at the downstream end of the conveyance path 16.

1-2. Outline of Image Forming Operation Next, an image forming operation of the color printer 1 having the above configuration will be schematically described. The color printer 1 executes an image forming operation as follows when image data is input from an external computer or the like connected via a network or the like and a print start instruction is issued.

  First, the charger 10 charges the surface of the photosensitive drum 9. The exposure device 7 emits a laser beam (arrow P) corresponding to the image data to form an electrostatic latent image on the surface of the photosensitive drum 9. The developing device 11 uses the toner supplied from the toner container 15 to develop the electrostatic latent image carried on the photosensitive drum 9 into a toner image. The primary transfer portion 12 primarily transfers the toner image to the surface of the intermediate transfer belt 6. A full-color toner image is formed on the intermediate transfer belt 6 as each image forming unit 8 sequentially repeats the above operation. The toner remaining on the photosensitive drum 9 is removed by the cleaning device 13, and the electrification remaining on the photosensitive drum 9 is removed by the charge removing device 14.

  On the other hand, the sheet taken out of the sheet feeding cassette 3 or the manual feed tray (not shown) by the sheet feeding section 17 is conveyed to the secondary transfer section 18 in synchronization with the image forming operation described above. The secondary transfer unit 18 secondarily transfers the full-color toner image on the intermediate transfer belt 6 to a sheet. The sheet on which the toner image has been secondarily transferred is conveyed to the downstream side of the conveyance path 16 and enters the fixing device 19. The fixing device 19 fixes the toner image on the sheet, and the sheet on which the toner image is fixed is discharged from the sheet discharge port 20 to the sheet discharge tray 4.

1-3. Configuration of Fixing Device Next, the configuration of the fixing device 19 according to the first embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a cross-sectional view of the fixing device 19, and FIG. 3 is a plan view of the fixing device 19. The front side of the sheet in FIG. 2 is the front side (front side) of the fixing device 19, and the front side of the sheet in FIG. 3 is the upper side of the fixing device 19.

  As shown in FIG. 2, the fixing device 19 includes a fixing belt 21 (fixing member), a pressure roller 22 (pressure member), an IH fixing unit 23, a support member 24, a pressing pad 25, and a temperature sensor 26 (temperature detection unit). ), The magnetic shielding plate 27 and the guide plate 28.

  In FIG. 2, a pressure roller 22 is provided on the right side of the fixing belt 21, an IH fixing unit 23 is provided on the left side of the fixing belt 21, and a support member 24 is provided inside the fixing belt 21. Further, inside the fixing belt 21, the pressing pad 25 is provided on the right side of the support member 24, the temperature sensor 26 is provided on the left side of the support member 24, and the magnetic shielding plate 27 is provided on the left side of the temperature sensor 26. A guide plate 28 is provided on the left side of the shield plate 27.

  As shown in FIG. 2, the fixing belt 21 is an endless belt, and has a substantially cylindrical shape which is long in the front-rear direction. Further, as shown in FIG. 2, the fixing belt 21 is configured to rotate in a counterclockwise direction in a front view.

  The fixing belt 21 has, for example, a three-layer structure of a base material layer, an elastic layer laminated on the outer periphery of the base material layer, and a release layer covering the elastic layer. The base material layer is formed, for example, by plating or rolling a metal such as nickel or copper. The elastic layer is formed of, for example, silicone rubber. The release layer is formed of, for example, a fluorine-based resin such as PFA. In each of the drawings, the layers (base layer, elastic layer, release layer) of the fixing belt 21 are displayed without being particularly distinguished.

  As shown in FIG. 2, a first area R 1 is formed on the left side of the fixing belt 21, and a second area R 2 is formed on the lower side of the fixing belt 21.

  As shown in FIGS. 2 and 3, the pressure roller 22 has a substantially cylindrical shape that is long in the front-rear direction. As shown in FIG. 2, the pressure roller 22 is in pressure contact with the fixing belt 21 to form a fixing nip 30 (pressure area) with the fixing belt 21. A first area R1 is formed on the opposite side of the fixing nip 30 (left side of the fixing belt 21), and a second area R2 is formed on the upstream side of the fixing nip 30 in the rotational direction (lower side of the fixing belt 21).

  The pressure roller 22 has, for example, a three-layer structure of a cylindrical core 31, an elastic layer 32 laminated around the core 31, and a release layer (not shown) covering the elastic layer 32. . The core material 31 is formed of, for example, a metal such as stainless steel or aluminum. The elastic layer 32 is formed of, for example, silicone rubber or silicone sponge. The release layer is formed of, for example, a fluorine-based resin such as PFA. As shown in FIG. 2, the pressure roller 22 is configured to rotate clockwise in a front view. The pressure roller 22 is rotationally driven by a drive motor 73. By the rotation of the pressure roller 22, the fixing belt 21 is driven to rotate.

  As shown in FIG. 2, the IH fixing unit 23 includes an IH (Induction Heating) coil 35 (heat source) provided in an arc along the outer periphery of the fixing belt 21 and an arch core 36 provided along the outer periphery of the IH coil 35. And That is, the fixing device of the present embodiment adopts the induction heating method (IH method).

  The IH coil 35 is disposed outside the fixing belt 21. As shown in FIG. 2, the first region R <b> 1 of the fixing belt 21 is opposed to the IH coil 35. The first region R1 of the fixing belt 21 is configured to generate heat by the magnetic field generated by the IH coil 35. On the other hand, the second region R2 of the fixing belt 21 does not face the IH coil 35 and is separated from the IH coil 35.

  As shown in FIG. 2, the support member 24 is formed by bending a single sheet metal and has a substantially rectangular cross-sectional shape. The pressing pad support plate 55 is fixed to the lower surface (outer surface) of the lower wall portion of the support member 24. The right end of the pressing pad support plate 55 protrudes to the right from the support member 24.

  As shown in FIG. 2, the pressing pad 25 has a substantially vertically elongated rectangular shape in a front view. The pressing pad 25 has a long shape in the front-rear direction. The pressing pad 25 is fixed to the right surface (outer surface) of the side wall portion of the support member 24. The pressing pad 25 is sandwiched from above and below by the projection 41 provided on the side wall of the support member 24 and the pressing pad support plate 55. The right side surface of the pressing pad 25 contacts the inner circumferential surface of the fixing belt 21 and presses the fixing belt 21 to the pressure roller 22 side (right side in the present embodiment). When the fixing belt 21 rotates, the fixing belt 21 slides on the pressing pad 25. That is, the fixing device 19 of the present embodiment is a “sliding belt system”. The pressing pad 25 contacts only the right side portion (the portion on the fixing nip 30 side) of the inner peripheral surface of the fixing belt 21.

  As shown in FIG. 2, the temperature sensor 26 is disposed inside the fixing belt 21. The temperature sensor 26 is attached to the base portion 65, a leaf spring 66 having a first end attached to the base portion 65, a sponge 67 (elastic member) attached to a second end of the leaf spring 66, and the sponge 67 And a thermistor 68. The thermistor 68 is a temperature responsive element, and its electrical resistance value changes according to the temperature.

  The thermistor 68 of the temperature sensor 26 is in contact with the inner surface (inner surface) of the second region R 2 of the fixing belt 21. Therefore, the temperature sensor 26 can detect the temperature of the inner surface of the second region R2 of the fixing belt 21 (the internal temperature of the fixing belt 21). The thermistor 68 of the temperature sensor 26 is disposed near the entrance of the fixing nip 30 (the upstream end of the fixing nip 30 in the rotational direction). The thermistor 68 of the temperature sensor 26 is disposed in the vicinity of the pressing pad 25.

  As shown in FIG. 3, the thermistor 68 of the temperature sensor 26 is in contact with the inner surface of a substantially central portion in the front-rear direction (axial direction) of the fixing belt 21. Therefore, the temperature sensor 26 can detect the internal temperature near the center of the fixing belt 21 in the front-rear direction.

  As shown in FIG. 2, the magnetic shielding plate 27 includes a side plate 60 that covers the left side of the support member 24 and upper and lower plates 61 a and 61 b that are bent from the upper and lower ends of the side plate 60 toward the right. The magnetic shielding plate 27 is fixed to the support member 24. The magnetic shielding plate 27 is formed using, for example, a nonmagnetic and highly conductive material such as oxygen free copper. The magnetic shielding plate 27 prevents the magnetic field generated by the IH coil 35 from penetrating the support member 24.

  As shown in FIG. 2, the guide plate 28 is provided to cover the magnetic shielding plate 27. The guide plate 28 is formed of, for example, a magnetic material, generates heat by the action of the magnetic field generated by the IH coil 35, and heats the fixing belt 21. The guide plate 28 includes an upper attachment portion 62 attached to the upper plate 61 a of the magnetic shield plate 27, a lower attachment portion 63 attached to the lower plate 61 b of the magnetic shield plate 27, an upper attachment portion 62 and a lower attachment portion 63. And a curved portion 64 curving in an arc shape toward the left side. The curved portion 64 is disposed along the left side portion of the inner peripheral surface of the fixing belt 21 and guides (stretches) the fixing belt 21 from the inside.

1-4. Control System Next, the configuration of the control system of the fixing device 19 will be described with reference to FIG.

  The fixing device 19 is provided with a control unit 71 mainly composed of a CPU (Central Processing Unit). The control unit 71 is connected to a storage unit 72 configured of a storage device such as a ROM and a RAM. The control unit 71 is configured to execute control of each unit of the fixing device 19 based on the control program and control data stored in the storage unit 72. The storage unit 72 also stores parameters indicating the characteristics of the temperature sensor 26. Details of the parameters will be described later.

  The controller 71 is connected to the temperature sensor 26. When the temperature sensor 26 detects the temperature of the second region R 2 of the fixing belt 21, a signal indicating the detected value is output to the control unit 71.

  The control unit 71 is connected to the IH coil 35. When power is supplied to the IH coil 35 based on a signal from the control unit 71, the IH coil 35 generates a magnetic field, and the first region R1 of the fixing belt 21 and the guide plate 28 generate heat due to the action of the magnetic field. Configured as. That is, the control unit 71 controls the heating of the fixing belt 21 by the IH coil 35.

  The control unit 71 is connected to the drive motor 73, and the drive motor 73 is connected to the pressure roller 22 via the drive gear 34. The drive motor 73 rotationally drives the pressure roller 22 based on a signal from the control unit 71.

  Control unit 71 is connected to operation panel 74. Various instruction signals are transmitted to the control unit 71 when the operation panel 74 is operated by the user. The control unit 71 executes various controls in accordance with the instruction signal.

1-5. Temperature control 1-5-1. Design Temperature Control The design temperature control of the fixing device 19 will be described with reference to FIG. Here, the designed temperature control is temperature control performed according to the nominal value of each member (in particular, the nominal thermal time constant τ _{N of the} thermistor 68). In FIG. 5, the solid line indicates the input power W, and the dashed-dotted line indicates the temperature T indicated by the temperature sensor 26 (thermistor 68).

  A period P50 in FIG. 5 is a period before start-up of the fixing device 19 (before start of temperature control). In period P50, the electric power W is not supplied to the IH coil 35, and the temperature T indicated by the temperature sensor 26 (thermistor 68) indicates the initial temperature Ti (for example, 25 ° C. which is a normal temperature).

  When start-up of the fixing device 19 is started with power on of the color printer 1 or the like, the control unit 71 transitions to a period P51 which is a first heating control period. In period P51, control unit 71 executes control such that the power pulse of first power W1 (for example, 1300 W) is applied to IH coil 35. When the power pulse is applied, the first region R1 of the fixing belt 21 generates heat due to the magnetic field generated by the IH coil 35, and the temperature T indicated by the temperature sensor 26 (thermistor 68) rises sharply. When the temperature T indicated by the temperature sensor 26 reaches the secondary heating control switching temperature Tm (for example, 100 ° C.), the control unit 71 transitions to a period P52, which is a secondary heating control period.

  In period P52, control unit 71 performs control such that second electric power W2 (for example, 800 W) lower than first electric power W1 is supplied to IH coil 35. In period P52, the temperature T indicated by the temperature sensor 26 (thermistor 68) continues to increase, but as the input power W decreases, the rate of temperature increase is lower than in the period P51. When the temperature T indicated by the temperature sensor 26 reaches the ready control switching temperature Tf (for example, 140 ° C.), the control unit 71 transitions to a period P53, which is a ready control period.

  In period P53, control unit 71 executes feedback control so that the ready state is maintained. That is, in period P53, control unit 71 adjusts input power W input to IH coil 35 such that the temperature indicated by temperature sensor 26 (thermistor 68) maintains ready temperature Tr (eg, 150 ° C.) Keep doing. When the temperature indicated by the temperature sensor 26 is stabilized at the ready temperature Tr, the fixing device 19 transitions to the ready state (operation preparation state) in which the fixing operation is possible.

1-5-2. Variations of the Thermistor and Actual Temperature Control As described above, the thermistor 68 provided in the temperature sensor 26 is a temperature responsive element, and the temperature response is indicated by a parameter such as a thermal time constant. Generally, when changing the ambient temperature of the thermistor from the initial temperature Ti to the target temperature Tf, the following relational expression (1) is established between the elapsed time t (seconds) and the thermistor temperature T. (Tau) in Formula (1) is a thermal time constant.
T = (Tf-Ti) (1-exp (-t / τ)) + Ti (1)

Assuming that τ = t in the above equation (1), the following equation (2) is established.
T = (1-e- ¹ ) (Tf-Ti) + Ti (2)
As understood from the equation (2), the thermal time constant τ is such that the thermistor temperature T reaches a temperature obtained by multiplying the temperature difference (T2−T1) by 1−e ⁻¹ (≒ 0.632). It's time.

The thermistor supplier (manufacturer) announces the nominal value (nominal thermal time constant τ _N ) of the thermal time constant τ of the thermistor provided by the person. On the other hand, the thermal time constant τ possessed by an actual thermistor varies not only due to manufacturing errors but also changes according to the use conditions such as the contact condition (contact width and contact angle). Therefore, the nominal thermal time constant τ _N and the actual thermal time constant τ are often different.

  In the present embodiment, since the contact width and the contact angle when the thermistor 68 contacts the fixing belt 21 differ according to the specification of the fixing belt 21, the thermal time constant τ of the thermistor 68 also changes. The thermal time constant τ of the thermistor 68 is also affected by the contact pressure between the fixing belt 21 and the pressure roller 22.

As described above, the thermal time constant τ of the thermistor 68 fluctuates due to various factors. When the thermal time constant τ of the thermistor is larger than the nominal thermal time constant τ _N , if the same temperature control as described above with reference to FIG. 5 is performed, the heating time becomes excessive and the stable state is transitioned. Time will be longer than the design time. Specifically, this is as described below with reference to FIG. In FIG. 6, a solid line and an alternate long and short dash line respectively indicate the design applied power W and temperature T described in FIG. 5, and a dotted line and an alternate long and two short dashed line respectively indicate the actual applied power W and temperature T.

A period P60 in FIG. 6 is a period before the fixing device 19 is started. When start-up of fixing device 19 is started in period P61, a power pulse of first power W1 is applied to IH coil 35 under the control of control unit 71. Example thermal time constant tau of the thermistor 68 in the FIG. 6, if (hereinafter, referred to as the thermal time constant tau ₆₎ nominal value as during the time equal length and period P51, the first power W1 is the IH coil 35 It is thrown in. However, since the thermal time constant tau ₆ of the present embodiment is greater than the nominal thermal time constant tau _N, a temperature sensor 26 the time required for the temperature T shown (thermistor 68) reaches the secondary heating control switching temperature Tm Is longer than the required time (the length of time of the period P51) in the example of FIG. Therefore, the first electric power W1 is supplied to the IH coil 35 during a period P61 which is longer than the period P51.

  When the temperature T indicated by the temperature sensor 26 reaches the secondary heating control switching temperature Tm and the control unit 71 transitions to the period P62, the second power W2 is input to the IH coil 35 by the control of the control unit 71. As described above, the time required for the temperature T indicated by the temperature sensor 26 to reach the ready control switching temperature Tf is longer than the required time (the time length of the period P52) in the example of FIG. Therefore, the second power W2 is supplied to the IH coil 35 for a period P62 which is longer than the period P52.

  As described above, in the example of FIG. 6, the first region R1 of the fixing belt 21 is heated for a long time than the temperature control case of the example of FIG. 5 (in other words, than the preferable heating time in design). . Therefore, more power than the required input power for design is consumed. Further, as compared with the example of FIG. 5, in the example of FIG. 6 (period P63), it takes longer time for the overshooting temperature T to be cooled and to be stabilized at the ready temperature Tr.

1-5-3. Temperature Control with Correction Process Based on Thermal Time Constant In view of the above circumstances, in the fixing device 19 of the present embodiment, the measured values of the nominal thermal time constant τ _N of the thermistor 68 and the thermal time constant τ of the thermistor 68 in it using measured thermal time constant tau _a, the internal temperature of the fixing belt 21 detected based on the measured thermal time constant tau _a, to correct the temperature to be detected on the basis of the nominal thermal time constant tau _N. The nominal thermal time constant τ _N and the measured thermal time constant τ _A are parameters that are stored in the storage unit 72 and indicate the characteristics of the temperature sensor 26 (thermistor 68).

First, temperature control accompanied by correction processing will be described with reference to FIGS. 7 and 8, and the measurement procedure (FIG. 9) of the measured thermal time constant τ _A will be described later. FIG. 7 is a flowchart showing start-up temperature control processing of the present embodiment, and FIG. 8 is a graph showing time-series temperature changes due to the temperature control processing of the present embodiment. In FIG. 8, the solid line indicates the supplied electric power W, the dotted line indicates the (measured) internal temperature T before correction, and the dashed-dotted line indicates the corrected internal temperature (correction temperature T ′).

  A period P80 is a period before startup of the fixing device 19 (before start of temperature control) (FIG. 8). When start-up control of fixing device 19 is started with power on of color printer 1 or the like, control unit 71 transits to period P81, which is a first heating control period, and starts the temperature control process shown in FIG. Do.

  First, the control unit 71 sets the target temperature Tf and stores the target temperature Tf in the storage unit 72 (step S10). The target temperature Tf is, for example, a ready control switching temperature (for example, 140 ° C.). Next, the control unit 71 reads the output from the temperature sensor 26 (thermistor 68) and stores it as the initial temperature Ti in the storage unit 72 (step S20). Steps S10 and S20 may be performed in the reverse order, or may be performed in parallel.

  Next, the control unit 71 starts primary heat treatment (step S30). More specifically, the control unit 71 executes control such that a power pulse of the first power W1 (for example, 1300 W) is input to the IH coil 35 (heat source).

After the step S30, in a state where the application of the power pulse of the first power W1 is continued, the control unit 71 reads the output from the temperature sensor 26 (thermistor 68) to acquire the current internal temperature T. The elapsed time t from the start of the primary heating (power pulse input start) is acquired from a timer (not shown), and both are stored in the storage unit 72 (step S40). Here, the internal temperature T is detected temperatures based on the measured thermal time constant tau _A.

After step S40, the control unit 71 uses the nominal thermal time constant τ _N and the actual thermal time constant τ _A to determine the internal temperature T detected based on the actual thermal time constant τ _A as the nominal thermal time constant τ. _The temperature to be detected (corrected temperature T ') is corrected based on _N (step S50). Here, “the temperature to be detected based on the nominal thermal time constant τ _N ” is the temperature that would be detected when the thermistor 68 of the temperature sensor 26 has the nominal thermal time constant τ _N It is.

More specifically, the correction temperature T 'is calculated as follows. Let α be a correction coefficient by which the internal temperature T is multiplied to obtain the correction temperature T ′.
The internal temperature T at the elapsed time t is expressed by the following equation (3).
T = (Tf-Ti) ( 1-exp (-t / τ A)) + Ti ...... (3)
On the other hand, the theoretical (calculated) detected temperature T _{0 at} the elapsed time t when the nominal thermal time constant τ _N is used is expressed by the following equation (4).
T ₀ = (Tf−Ti) (1−exp (−t / τ _N )) + Ti (4)

Here, when the correction coefficient α is used, the relationship between T ₀ and T is expressed as the following equation (5).
T ₀ = α × T (5)
By transforming equation (5), the following equation (6) is obtained.
α = T ₀ / T ...... (6)
Since the value on the right side of Equation (3) indicating T and each value on the right side of Equation (4) indicating T ₀ are all known, the correction coefficient α can be calculated by Equation (6).

The corrected temperature T ′ is calculated by the following equation (7) using the correction coefficient α obtained as described above.
T '= α × T (7)

  After step S50, the control unit 71 determines whether or not the correction temperature T 'has reached the second heating control switching temperature Tm (for example, 100 ° C.) (step S60). The secondary heating control switching temperature Tm may be stored in advance in the storage unit 72 or may be set together with the target temperature Tf in step S10.

  If it is determined that the correction temperature T ′ has not reached the second heating control switching temperature Tm (S60: NO), the control unit 71 increments the timer (t = t + 1), and steps S40 to S60 described above are performed. Execute the process of. On the other hand, when it is determined that the correction temperature T 'has reached the secondary heating control switching temperature Tm (S60: YES), the control unit 71 advances the process to step S70.

  The control unit 71 transitions to a period P82 which is a second heating control period (FIG. 8), and starts the second heating process (step S70). More specifically, the control unit 71 executes control such that the second power W2 (for example, 800 W) lower than the first power W1 is input to the IH coil 35 (heat source).

  After the step S70, in a state where the supply of the second electric power W2 is continued, the control unit 71 reads the output from the temperature sensor 26 (thermistor 68) and outputs the current internal temperature T as in the case of step S40. While acquiring, an elapsed time t from the start of the first heating (power pulse input start) is acquired from a timer (not shown), and both are stored in the storage unit 72 (step S80).

After step S80, the control unit 71 uses the nominal thermal time constant τ _N and the actual thermal time constant τ _A based on the equations (3) to (7) as in step S50, and uses the actual thermal time constant. The internal temperature T detected based on τ _A is corrected to the temperature to be detected (corrected temperature T ′) based on the nominal thermal time constant τ _N (step S90).

  After step S90, the control unit 71 determines whether the correction temperature T 'has reached the target temperature Tf (for example, the ready control switching temperature) (step S100). If it is determined that the correction temperature T ′ has not reached the target temperature Tf (S100: NO), the control unit 71 increments the timer (t = t + 1), and executes the above-described steps S80 to S100 again. Do. On the other hand, when it is determined that the correction temperature T 'has reached the target temperature Tf (S100: YES), the control unit 71 advances the process to step S110.

  The control unit 71 transitions to a period P83 which is a ready control period, ends the above-described correction of the internal temperature T, and executes feedback control so that the ready state is maintained (step S110). With feedback control, for example, the input power W input to the IH coil 35 is continuously adjusted so that the temperature indicated by the temperature sensor 26 (thermistor 68) maintains the ready temperature Tr (for example, 150 ° C.) is there.

  As described above, at the time of start-up control of fixing device 19, control unit 71 is ready so that the fixing operation by fixing device 19 can be performed after the start of power pulse input to IH coil 35 serving as the heat source. The internal temperature T is corrected in a period (a period in which the period P81 and the period P82 are combined) until the state (operation preparation state) starts.

1-6. Setting of Fixing Device The nominal thermal time constant τ _N and the actual thermal time constant τ _A stored in the storage unit 72 are used to execute the temperature control accompanied by the correction process described above. These parameters can be set arbitrarily. For example, since the nominal thermal time constant τ _N is a value presented by the manufacturer of the thermistor 68, the fixing device 19 is manufactured or shipped, or the color printer 1 incorporating the fixing device 19 is manufactured or shipped It may be set.

On the other hand, the measured thermal time constant τ _A is determined by actually measuring the thermal time constant τ of the thermistor 68. For example, when the fixing device 19 is manufactured or shipped, or when the color printer 1 incorporating the fixing device 19 is manufactured or shipped, it is preferable that the measured thermal time constant τ _A is set according to the flowchart of FIG.

  First, the control unit 71 sets the target temperature Tf to be reached for the internal temperature T indicated by the temperature sensor 26 (thermistor 68), stores the target temperature Tf in the storage unit 72 (step S120), and detects the current internal temperature T. The initial temperature Ti is stored in the storage unit 72 (step S130). Steps S120 and S130 may be performed in the reverse order, or may be performed in parallel. In the subsequent processing, the difference (Tf−Ti) between the target temperature Tf and the initial temperature Ti is referred to as a rising temperature.

The thermal time constant τ is a time t until the internal temperature T of the thermistor 68 reaches a temperature Tc obtained by multiplying the rising temperature by (1-e ⁻¹ ) (≒ 0.632) from the initial temperature Tf. . The thermal time constant τ is measured by the following steps S140 to S180.

  The controller 71 starts heating the fixing belt 21 by the IH coil 35 (step S140). More specifically, the control unit 71 performs control such that a predetermined power (for example, the same power as the first power W1 input during the above-described first heating control) is input to the IH coil 35. Do. Then, the control unit 71 reads the output from the temperature sensor 26 (thermistor 68) to acquire the current internal temperature T, acquires the elapsed time t from the start of heating from the timer (not shown), and obtains both. It memorize | stores in the memory | storage part 72 (step S150).

  After step S150, the control unit 71 determines whether the internal temperature T has reached the temperature Tc (step S160). If it is determined that the internal temperature T has not reached the temperature Tc (S160: NO), the control unit 71 increments the timer (t = t + 1), and executes the above-mentioned processing of step S150 and step S160 again. . While the loop of step S150 and step S160 is repeated, input power to the IH coil 35 is maintained. On the other hand, when it is determined that internal temperature T has reached temperature Tc (S160: YES), control unit 71 advances the process to step S170.

Control unit 71 executes control such that power input to IH coil 35 is stopped (step S170). Then, the control unit 71 refers to the storage unit 72, acquires the time until the internal temperature T of the thermistor 68 reaches the initial temperature Ti to the temperature Tc as the measured thermal time constant τ _A , and the storage unit 72 (Step S180).

It is preferable that the measured thermal time constant τ _A stored in the storage unit 72 as described above be used for actual temperature control (from step S10 to step S110). The above-described setting of the measured thermal time constant τ _A may be performed based on an instruction from the user via the operation panel 74 at the time of maintenance.

1-7. As described above, according to the configuration of the present embodiment, the internal temperature T of the fixing belt 21 detected by the temperature sensor 26 as the temperature detection unit is a parameter (nominal indicating the characteristics of the temperature sensor 26) The correction is appropriately made based on the thermal time constant τ _N and the measured thermal time constant τ _A ).

  In particular, according to the configuration in which the temperature sensor 26 has the thermistor 68 and the thermistor 68 contacts the inner surface of the endless fixing belt 21 to detect the internal temperature T, the internal temperature T is detected with high sensitivity. It is possible.

Also, in particular, using the nominal thermal time constant τ _N and the actual thermal time constant τ _A , the internal temperature T detected based on the actual thermal time constant τ _A is detected based on the nominal thermal time constant τ _N According to the configuration in which the temperature is corrected, the variation in the temperature response of the temperature sensor 26 (thermistor 68) is compensated, so that the accuracy of the temperature control is improved and the improvement of the energy efficiency is also realized.

  Further, in particular, according to the configuration in which the correction of the internal temperature T is executed during the start-up control of the fixing device 19 during the start-up control of the fixing device 19 and the start of the ready period, the thermal time constant becomes power efficiency. The accuracy of temperature control is improved at the time of start-up, which has a large influence, and the improvement of energy efficiency is also realized.

In particular, the step of heating the fixing belt 21 by the IH coil 35 and the thermistor 68 at the initial temperature Ti raise (1-e- ¹ ) to the rising temperature which is the difference between the target temperature Tf and the initial temperature Ti. According to the setting method including the step of acquiring the time to reach the multiplied temperature Tc as the measured thermal time constant τ _A , the thermistor 68 to be measured is actually heated to acquire the thermal time constant Therefore, a more accurate thermal time constant can be obtained, which in turn improves the accuracy of temperature control.

  Further, according to the configuration of the present embodiment described above, a color printer 1 (image forming apparatus) including the above-described fixing device 19 is realized.

2. Second Embodiment Next, a color printer 1 provided with a fixing device 19 according to a second embodiment will be described with reference to FIGS. 10 to 13. In the following description, the same components as those in the first embodiment may be assigned the same reference numerals and descriptions thereof may be omitted.

In the first embodiment, the nominal thermal time constant τ _N and the measured thermal time constant τ _A are used for temperature control as parameters indicating the characteristics of the temperature sensor 26 (thermistor 68). In the second embodiment, correlation information C indicating the correlation between the internal temperature T of the fixing belt 21 and the surface temperature Ts is used as a parameter for temperature control.

2-1. Configuration of Fixing Device With reference to FIG. 10, the configuration of the fixing device 89 of the second embodiment will be described. FIG. 10 is a cross-sectional view of the fixing device 89. As shown in FIG.

  In FIG. 10, a fixing belt 21 (fixing member), a pressure roller 22 (pressure member), an IH fixing unit 23, a support member 24, a pressing pad 25, a temperature sensor 26 (temperature detection unit), a magnetic shielding plate 27 and a guide The plate 28 is the same as the fixing device 19 of the first embodiment (FIG. 2).

  The fixing device 89 includes a thermopile 91 which is a noncontact temperature detection unit. In FIG. 10, the thermopile 91 is provided below the fixing belt 21. Further, the thermopile 91 is provided to face the second region R2 formed in the lower portion of the fixing belt 21.

  The thermopile 91 is an element that is configured using a thermocouple, receives thermal energy radiated from the surface of the opposing object (fixing belt 21), and outputs a signal indicating a temperature corresponding to the received thermal energy. That is, the thermopile 91 can measure the surface temperature Ts of the fixing belt 21. The thermopile 91 is connected to the control unit 71, and the signal output from the thermopile 91 is supplied to the control unit 71.

2-2. Temperature Control with Correction Processing Based on Correlation Information The correlation information C of the present embodiment will be described with reference to FIG. The correlation information C is stored in the storage unit 72. The correlation information C is a table representing the correlation between the internal temperature T of the fixing belt 21 detected by the temperature sensor 26 (thermistor 68) and the surface temperature Ts of the fixing belt 21 detected by the thermopile 91. The control unit 71 can convert the internal temperature T acquired from the output of the temperature sensor 26 (thermistor 68) into the corresponding temperature Tcr corresponding to the surface temperature Ts by referring to the correlation information C. That is, based on the correlation information C, the control unit 71 can correct the internal temperature T to the corresponding temperature Tcr corresponding to the surface temperature Ts.

  The temperature control accompanied by the correction process will be described with reference to FIGS. 12 and 13. FIG. 12 is a flowchart showing the temperature control process of the present embodiment, and FIG. 13 is a graph showing time-series temperature changes due to the temperature control process of the present embodiment. In FIG. 13, the solid line indicates the internal temperature T, the dashed-dotted line indicates the corresponding temperature Tcr, and the dashed-dotted line indicates the surface temperature Ts.

  First, the control unit 71 sets a target temperature Tf and stores the target temperature Tf in the storage unit 72 (step S200). The target temperature Tf is, for example, 150 ° C. Next, the control unit 71 reads the output from the temperature sensor 26 (thermistor 68) and stores it as an initial temperature Ti in the storage unit (step S210). Steps S200 and S210 may be performed in the reverse order, or may be performed in parallel.

  Next, the control unit 71 starts heating the fixing belt 21 by the IH coil 35 (step S220). More specifically, the control unit 71 performs control such that a predetermined power (for example, the same power as the first power W1 input during the above-described first heating control) is input to the IH coil 35. Do. Then, the control unit 71 reads the output from the temperature sensor 26 (thermistor 68) to obtain the current internal temperature T, reads the output from the thermopile 91 to obtain the current surface temperature Ts, and starts heating The elapsed time t is acquired from a timer (not shown), and the above values are stored in the storage unit 72 (step S230).

  After step S230, the control unit 71 corrects the internal temperature T to the corresponding temperature Tcr corresponding to the surface temperature Ts based on the correlation information C (that is, referring to the correlation information C) (step S240).

  After step S240, the control unit 71 determines whether the corresponding temperature Tcr has reached the target temperature Tf (step S250). If it is determined that the corresponding temperature Tcr has not reached the target temperature Tf (S250: NO), the control unit 71 increments the timer (t = t + 1), and executes the above-mentioned steps S230 to S250 again. .

  On the other hand, when it is determined that the corresponding temperature Tcr has reached the target temperature Tf (S250: YES), the control unit 71 executes control such that power input to the IH coil 35 is stopped (step S260).

  The above temperature control can be performed at any timing. For example, the above temperature control may be performed at the time of start-up control, or the above temperature control may be performed in a period (period P83) after the ready state (operation preparation state) of the first embodiment is started. Good.

2-3. Setting of Fixing Device The correlation information C stored in the storage unit 72 is used to execute the temperature control accompanied by the correction process described above. The correlation information C can be set arbitrarily. It may be set when manufacturing or shipping the fixing device 89, or when manufacturing or shipping the color printer 1 incorporating the fixing device 89. Further, instead of or in addition to the above timings, the correlation information C may be set after the installation of the color printer 1. The correlation information C is preferably set according to the flowchart of FIG. 14 below.

  First, the control unit 71 sets the target temperature Tf and stores the target temperature Tf in the storage unit 72 (step S270). Then, the control unit 71 starts heating of the fixing belt 21 by the IH coil 35 (step S280).

  Next, the control unit 71 reads the output from the temperature sensor 26 (thermistor 68) to obtain the current internal temperature T, and reads the output from the thermopile 91 to obtain the current surface temperature Ts. Then, the control unit 71 determines the corresponding temperature Tcr based on the internal temperature T and the surface temperature Ts, associates these temperature values, and stores them in the correlation information C in the storage unit 72 (step S290).

  The corresponding temperature Tcr can be determined by any method. For example, the combination of the internal temperature (standard internal temperature) and the surface temperature (standard surface temperature) in a standard fixing belt is stored in advance in the storage unit 72, and the deviation from the above standard value is compensated. Preferably, the temperature Tcr is determined. The surface temperature Ts and the corresponding temperature Tcr may be equal.

  After step S290, the control unit 71 determines whether the internal temperature T has reached the target temperature Tf (step S300). If it is determined that the internal temperature T has not reached the target temperature Tf (S300: NO), the control unit 71 executes the processing from step S280 to step S300 described above again.

  On the other hand, when it is determined that the internal temperature T has reached the target temperature Tf (S300: YES), the control unit 71 executes control so that the power supply to the IH coil 35 is stopped (step S310). Then, the control unit 71 stores the correlation information C including a plurality of combinations of the internal temperature T, the surface temperature Ts, and the corresponding temperature Tcr in the storage unit 72 (step S320).

2-4. As described above, according to the configuration of the present embodiment, the internal temperature T of the fixing belt 21 detected by the temperature sensor 26 as the temperature detection unit is a parameter (correlation indicating the characteristics of the temperature sensor 26) Corrected appropriately based on the information C). In particular, according to the configuration in which the internal temperature T is corrected to the corresponding temperature Tcr corresponding to the surface temperature Ts based on the correlation information C, the correction corresponding to the surface temperature Ts of the fixing belt 21 is performed. It will improve and realize energy efficiency improvement.

  In addition, according to the configuration in which the internal temperature T is corrected particularly in the period after the ready state (operation preparation state) starts, it is possible to execute temperature control accurately even in the ready state after start-up control .

  Further, in particular, the internal temperature T is detected by the temperature sensor 26 (thermistor 68), and the surface temperature Ts is detected without contacting the fixing belt 21 by the thermopile 91, and the detected internal temperature T and surface temperature According to the setting method including the step of associating Ts with Ts and storing it in the storage unit 72 as the correlation information C, more accurate correlation information C is obtained, and as a result, the accuracy of temperature control is improved.

  Further, according to the configuration of the present embodiment described above, the color printer 1 (image forming apparatus) provided with the fixing device 89 described above is realized.

3. Modifications The above embodiments can be variously modified. The aspect of a specific deformation | transformation is illustrated below. Two or more aspects arbitrarily selected from the above embodiments and the following exemplifications may be appropriately combined as long as they do not contradict each other.

  In the above embodiment, the second region R <b> 2 of the fixing member 21 is formed on the upstream side of the fixing nip 30. In another different embodiment, the second region R2 of the fixing member 21 may be formed on the downstream side of the fixing nip 30.

  In the above embodiment, the IH coil 35 has a function of heating the fixing belt 21. In another different embodiment, the fixing belt 21 may be heated by a heater using radiant heat such as a halogen heater. That is, the type and arrangement of the heat sources can be changed as appropriate. When a heater is used as a heat source, the guide plate 28 may not have the function of heating the fixing member 21.

  In the second embodiment, the fixing device 89 includes a thermopile 91. In another different embodiment, the fixing device 89 does not include the thermopile 91, and the correlation information C is acquired using the thermopile present outside the device (production line) in the manufacturing process, and stored in the storage unit 72 of the fixing device 89. Ru.

  In the above embodiment, the drive motor 73 connected to the pressure roller 22 rotationally drives the pressure roller 22. In another different embodiment, the drive motor 73 may be connected to the fixing belt 21 to drive the fixing belt 21 to rotate.

  In the present embodiment, the case where the configuration of the present invention is applied to the color printer 1 has been described, but in another different embodiment, the present invention is applied to another image forming apparatus such as a monochrome printer, a copier, a facsimile, and a multifunction machine. The configuration may be applied.

1 Color printer (image forming device)
19 fixing device 21 fixing belt (fixing member)
22 Pressure roller (pressure member)
26 Temperature sensor (temperature detector)
30 Fixing nip (pressure area)
35 IH coil (heat source)
68 thermistor 71 control unit 72 storage unit

Claims (9)

A fixing member rotatably provided and heated by a heat source;
A pressure member provided rotatably and forming a pressure area in pressure contact with the fixing member;
A temperature detection unit that detects an internal temperature of the fixing member;
A storage unit that stores parameters indicating characteristics of the temperature detection unit;
A control unit configured to correct the detected internal temperature based on the parameter. The fixing member is an endless fixing belt,
The fixing device according to claim 1, wherein the temperature detection unit includes a thermistor that is a temperature responsive element, and the thermistor contacts the inner surface of the fixing belt to detect the internal temperature. The parameters used by the control unit are a nominal thermal time constant which is a nominal value of the thermal time constant of the temperature detection unit, and an actual measurement thermal time constant which is an actual measurement value of the thermal time constant of the temperature detection unit.
The control unit uses the nominal thermal time constant and the actual thermal time constant to detect the internal temperature detected based on the actual thermal time constant based on the nominal thermal time constant. The fixing device according to claim 1, wherein the correction is made to   The control unit performs a start control of the fixing device during a period from when the application of the power pulse to the heat source is started to when an operation preparation state in which the fixing device can perform the fixing operation is started. The fixing device according to claim 3, wherein the internal temperature is corrected. 5. The fixing device setting method according to claim 3, wherein
Setting a target temperature to be reached by the internal temperature;
Measuring an initial temperature of the internal temperature;
Heating the fixing member with the heat source;
The time required for the internal temperature to reach a temperature obtained by multiplying the rising temperature, which is the difference between the target temperature and the initial temperature, by (1-e- ¹ ) (e is the base of natural logarithms), the measured heat Acquiring as a time constant,
Storing the acquired measured thermal time constant in the storage unit. The parameter used by the control unit is correlation information indicating a correlation between the surface temperature of the fixing member and the internal temperature,
The fixing device according to claim 1, wherein the control unit corrects the internal temperature to a corresponding temperature corresponding to the surface temperature based on the correlation information.   The fixing device according to claim 6, wherein the control unit corrects the internal temperature during a period after an operation preparation state in which a fixing operation by the fixing device is possible is started. The fixing device setting method according to claim 6 or 7,
Heating the fixing member with the heat source;
Detecting the internal temperature by the temperature detection unit, and detecting the surface temperature without contacting the fixing member by a non-contact temperature detection unit;
Setting the detected internal temperature and the surface temperature in association with each other and storing the correlation information as the correlation information.   An image forming apparatus comprising the fixing device according to any one of claims 1 to 4 or 6 to 8.

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